Chongqing, China
Chongqing, China

Chongqing University is a key national university located in Chongqing, China,and a member of the "Excellence League". Chongqing University is also one of the "Project 211 and Project 985” universities with full support in the construction and development from the central government and the Chongqing Municipal Government. Among its various departments, Chongqing University is especially highly ranked in the Built Environment, Engineering, Technology, and Business disciplines. Wikipedia.

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Chongqing University, Chongqing University of Science and Technology | Date: 2016-09-22

A method of using a device for conducting a vascular hemodynamic bionic cell experiment is provided, the method comprises: firstly, experiment preparation; and secondly, experiment operation, namely, switching on a peristaltic pump, pumping a circulation liquid from a collection bottle into an independently corresponding shunting chamber of a corresponding shunting bottle through a collection bottle sampling tube of an independent chamber of a collection bottle, after shunting by the shunting chamber of the shunting bottle, the circulation liquid flowing out of a branch shunting tube flows to a corresponding flow chamber on the 1-3 flow chamber platforms placed side by side, and then converging the circulation liquid to a corresponding independent chamber of the collection bottle through respective sampling tubes of the flow chamber platforms. The method provided by the present disclosure has the technical characteristics of strong practicability and low manufacturing cost, and can perform a vascular hemodynamic bionic cell experiment under multiple conditions with multiple parameters when used in combination with different models of shunting bottles and flow chamber platforms.

Disclosed are a point contact gear based on conjugate curves, a meshing pair, and a machining tool therefor. The point contact gear comprises a convex gear and a concave gear which mesh with each other in one-point or multi-point contact, and a contact curve composed of meshing points on tooth surfaces of the convex gear and a contact curve composed of the meshing points on the concave gear are the conjugate curves. Further disclosed is a point contact gear meshing pair based on conjugate curves, a meshing method of the meshing pair is making both a convex gear tooth surface and a concave gear tooth surface in one-point or multi-point contact, and a contact track of the contact points on each of the tooth surfaces is a smooth space curve. The meshing characteristics of the conjugate curves are inherited; in addition, point contact tooth profiles are high in contact strength, high in load capacity, high in transmission efficiency and low in lubricating oil temperature rise, the sliding ratio is greatly lowered, and abrasion is low.

Ma G.,Chongqing University | Andrews-Speed P.,National University of Singapore | Zhang J.,Chongqing University
Energy Policy | Year: 2013

Energy saving is now an important component of China's energy policy. This paper reports the findings of a survey carried out in 2009 and 2010 of 246 citizens at different locations in the municipality of Chongqing in order to reveal information about attitudes towards energy and energy saving in the context of household electrical appliances. This study shows that citizens in Chongqing receive relatively little information and guidance on how to save energy in the home and that their stated level of knowledge on this subject is also rather limited. Respondents showed some willingness to save energy as long as this did not reduce their comfort and convenience, and they appeared likely to respond to economic incentives, such as high electricity prices or discounts on appliances. But they seemed to be unaware of the potential for information to help them save energy. The survey also demonstrated a high degree of heterogeneity across society with respect to sources of information and trust in those sources and with respect to attitudes to energy saving at home. These results show that the government needs to substantially adjust its strategies for promoting household energy saving. © 2013 Elsevier Ltd.

Sun J.,Sichuan University of Arts and Science | Mei H.,Chongqing University
Chemical Biology and Drug Design | Year: 2012

Docking studies of pyrrolidine derivatives indicated that Trp178, Arg371, and Tyr406 were the key residues in the active pocket of influenza neuraminidase (NA). Hydrogen bond and electrostatic factors mainly influenced interactions between pyrrolidine derivatives and NA. Moreover, there was a significant correlation between binding affinity (total scores) and the experimental pIC 50. Meanwhile, 3D-QSAR models of 87 pyrrolidine derivatives were developed to understand chemical-biological interactions governing their activities toward NA. Furthermore, R 2, Q 2, , and of the models were from 0.731 to 0.830, from 0.560 to 0.611, from 0.762 to 0.875, and from 0.649 to 0.856, respectively. QSAR modeling results elucidated that hydrogen bonds and electrostatic factors highly contributed to inhibitory activity, which was unanimous in the docking results. © 2012 John Wiley & Sons A/S.

Qin D.,Chongqing University
Jixie Gongcheng Xuebao/Journal of Mechanical Engineering | Year: 2011

Starting and shifting states of clutch in automatic transmission are identified on the basis of the motion states of driven plates of the clutch. Unified dynamic model is set up for the starting control of clutches in both automatic mechanical transmission (AMT) and dual clutch transmission (DCT). The linear quadratic optimal control method is used to achieve the optimum starting control of the clutches, in which the jerk is converted to one of the restrain conditions, and the minimization of sliding friction work of the clutches is set as optimal target in control. Universal optimal starting control of AMT and DCT clutches is realized through selection of state variables, setting of parameters and modifying of restrain conditions in the unified model for clutch starting of AMT, single and dual clutch starting of DCT. Simulation is carried out and then verified by experiment. The research results lay the foundation for the construction of universal development platform of the AMT and DCT automatic transmissions. © 2011 Journal of Mechanical Engineering.

Hu Y.,Georgia Institute of Technology | Hu Y.,Peking University | Yang J.,Georgia Institute of Technology | Yang J.,Chongqing University | And 4 more authors.
ACS Nano | Year: 2014

The recently introduced triboelectric nanogenerator (TENG) and the traditional electromagnetic induction generator (EMIG) are coherently integrated in one structure for energy harvesting and vibration sensing/isolation. The suspended structure is based on two oppositely oriented magnets that are enclosed by hollow cubes surrounded with coils, which oscillates in response to external disturbance and harvests mechanical energy simultaneously from triboelectrification and electromagnetic induction. It extends the previous definition of hybrid cell to harvest the same type of energy with multiple approaches. Both the sliding-mode TENG and contact-mode TENG can be achieved in the same structure. In order to make the TENG and EMIG work together, transformers are used to match the output impedance between these two power sources with very different characteristics. The maximum output power of 7.7 and 1.9 mW on the same load of 5 kΩ was obtained for the TENG and EMIG, respectively, after impedance matching. Benefiting from the rational design, the output signal from the TENG and the EMIG are in phase. They can be added up directly to get an output voltage of 4.6 V and an output current of 2.2 mA in parallel connection. A power management circuit was connected to the hybrid cell, and a regulated voltage of 3.3 V with constant current was achieved. For the first time, a logic operation was carried out on a half-adder circuit by using the hybrid cell working as both the power source and the input digit signals. We also demonstrated that the hybrid cell can serve as a vibration isolator. Further applications as vibration dampers, triggers, and sensors are all promising. © 2014 American Chemical Society.

Yu Y.,Chongqing University | Lui H.-S.,Chalmers University of Technology | Niow C.H.,National University of Singapore | Hui H.T.,National University of Singapore
IEEE Transactions on Wireless Communications | Year: 2011

An experimental study is performed to investigate the improvement of direction-of-arrival (DOA) estimation using the recently proposed receiving mutual impedances for mutual coupling compensation. A seven-monopole antenna array is constructed and used in DOA estimation employing the MUSIC algorithm. Comparisons are made with the case of using the conventional mutual impedances for mutual coupling compensation. All experiments are carried out inside an anechoic chamber. Results are obtained for one- and two-source experiments which indicate that the performance of DOA estimation in the presence of mutual coupling can be significantly improved when the mutual coupling effect is compensated by using the receiving mutual impedances. © 2011 IEEE.

Chen D.G.,Hong Kong University of Science and Technology | Tang F.,Chongqing University | Law M.-K.,University of Macau | Bermak A.,Hong Kong University of Science and Technology
IEEE Journal of Solid-State Circuits | Year: 2014

Analog-to-information converters (AICs) take advantage of the limited information bandwidth in high-frequency signals to improve the energy efficiency of front-end data converters. High-resolution image sensors often convey limited information due to the spatial redundancy between neighboring pixels. This paper proposes a mixed-signal AIC which compresses each nonoverlapping 4 × 4 pixel block in a 816 × 640 pixel prototype active-pixel sensor (APS) imager. It combines an energy-efficient charge-pump bit-image processor (BIP) with an area-efficient successive-approximation-register-single-slope (SAR-SS) hybrid analog-to-digital converter (ADC) via a charge-transfer- amplifier (CTA). The AIC is fully dynamic and consumes no static power. The ADC's capacitor array doubles as a computational device for parts of the compression algorithm which reduces its sampling rate by a factor of four. The compressed data contains direct edge information and can be decoded by a very simple receiver. The fabricated prototype consumes 12 pJ per pixel at 111 fps in the image compression mode and 48 pJ per pixel at 28.7 fps in raw data mode (9 b per pixel) under the same clock rate. To the best of our knowledge, this is the most energy-efficient compressive CMOS image sensor ever reported in the literature, thanks to the proposed AIC. © 1966-2012 IEEE.

Su X.,Chongqing University | Wu L.,Harbin Institute of Technology | Shi P.,University of Adelaide | Shi P.,Victoria University of Melbourne | Song Y.-D.,Chongqing University
Automatica | Year: 2014

This paper investigates the problem of Hankel-norm output feedback controller design for a class of T-S fuzzy stochastic systems. The full-order output feedback controller design technique with the Hankel-norm performance is proposed by the fuzzy-basis-dependent Lyapunov function approach and the conversion on the Hankel-norm controller parameters. Sufficient conditions are established to design the controllers such that the resulting closed-loop system is stochastically stable and satisfies a prescribed performance. The desired output feedback controller can be obtained by solving a convex optimization problem, which can be efficiently solved by standard numerical algorithms. Finally, a Henon map system is used to illustrate the effectiveness of the proposed techniques. © 2014 Elsevier Ltd. All rights reserved.

Kucukkoc I.,University of Exeter | Kucukkoc I.,Balikesir University | Zhang D.Z.,University of Exeter | Zhang D.Z.,Chongqing University
International Journal of Production Economics | Year: 2014

One of the key factors of a successfully implemented mixed-model line system is considering model sequencing problem as well as the line balancing problem. In the literature, there are many studies, which consider these two tightly interrelated problems individually. However, we integrate the model sequencing problem in the line balancing procedure to obtain a more efficient solution for the problem of Simultaneous Balancing and Sequencing of Mixed-Model Parallel Two-Sided Assembly Lines. A mathematical model is developed to present the problem and a novel agent based ant colony optimisation approach is proposed as the solution method. Different agents interact with each other to find a near optimal solution for the problem. Each ant selects a random behaviour from a predefined list of heuristics and builds a solution using this behaviour as a local search rule along with the pheromone value. Different cycle times are allowed for different two-sided lines located in parallel to each other and this yields a complex problem where different production cycles need to be considered to build a feasible solution. The performance of the proposed approach is tested through a set of test cases. Experimental results indicate that considering model sequencing problem with the line balancing problem together helps minimise line length and total number of required workstations. Also, it is found that the proposed approach outperforms other three heuristics tested. © 2014 Elsevier B.V. All rights reserved.

Sun C.,National University of Singapore | Ren C.,National University of Singapore | Wei Y.,Chongqing University | Qin B.,Chongqing University | Zeng H.,National University of Singapore
Chemical Communications | Year: 2013

A stimuli-responsive hexameric oligophenol host undergoes amine-induced co-operative folding from a more fluorescent, more linear structure into less fluorescent, more curved or helically folded states, enabling easy identification and classification of the bound amine guests. This journal is © The Royal Society of Chemistry 2013.

Su X.,Key Laboratory of Dependable Service Computing | Su X.,Chongqing University | Wu L.,Harbin Institute of Technology | Shi P.,Harbin Engineering University | And 3 more authors.
IEEE Transactions on Fuzzy Systems | Year: 2015

In this paper, the model approximation problem is investigated for a Takagi-Sugeno fuzzy switched system with stochastic disturbance. For a high-order considered system, our attention is focused on the construction of a reduced-order model, which not only approximates the original system well with a Hankel-norm performance but translates it into a lower dimensional fuzzy switched system as well. By using the average dwell time approach and the piecewise Lyapunov function technique, a sufficient condition is first proposed to guarantee the mean-square exponential stability with a Hankel-norm error performance for the error system. The model approximation is then converted into a convex optimization problem by using a linearization procedure. Finally, simulations are provided to illustrate the effectiveness of the proposed theory. © 2014 IEEE.

Azam A.,Dar Al Uloom University | Qiang F.,Chongqing University
International Journal of Electronic Business | Year: 2014

Some of the most electrifying advances in our economy right away are in the realm of electronic commerce. However, many issues associated with online world still pose serious challenges to the growth of electronic commerce and affect consumer behaviour to purchase online. In this study, we test constructs from behavioural study (decomposed theory of planned behaviour (DTPB)) and online retailer ethics (consumers' perception of online retailing ethics (CPEOR)) in an integrated theoretical framework of online consumer behaviour. Exclusively, we examine how attitude, subjective norms, perceived behavioural control (PBC) and CPEOR influence online consumers' intention to purchase online and actual purchase behaviour. An empirical investigation of online consumers' behaviour in China was conducted. Forward logistic regression was used for data analysis and results showed substantial support for most of the hypotheses proposed. Managerial implications and contributions of the study were also discussed. © 2014 Inderscience Enterprises Ltd.

Jiang Y.,Zhejiang Normal University | Jiang Y.,Chongqing University | Tang B.,Chongqing University | Qin Y.,Chongqing University | Liu W.,Chongqing University
Renewable Energy | Year: 2011

Analyzing the vibration signals of wind turbine usually requires feature extraction. However, in many cases, to extract feature components becomes challenging and the applicability of information drops down due to the large amount of noise. In this paper, a new denoising method based on adaptive Morlet wavelet and singular value decomposition (SVD) is applied to feature extraction for wind turbine vibration signals. Modified Shannon wavelet entropy is utilized to optimize central frequency and bandwidth parameter of the Morlet wavelet so as to achieve optimal match with the impulsive components. The time-frequency resolution can be adapted to different signals of interest. Then, an improved matrix construction method is used to construct matrix of the wavelet coefficient, and the scale periodical exponential (SPE) spectrum is obtained by SVD for selecting the appropriate transform scale. Experimental analysis and application into signal denoising indicate that the proposed method has better denoising performance than other wavelet transforms. The results of the experimental analysis in rolling bearing and the application in planetary gearbox show that the proposed method is an effective approach to detecting the impulsive feature components hidden in vibration signals and performs well for wind turbine fault diagnosis. © 2011 Elsevier Ltd.

Sun W.,Princeton University | Chen Z.,Peking University | Gou X.,Chongqing University | Ju Y.,Princeton University
Combustion and Flame | Year: 2010

A direct path flux analysis (PFA) method for kinetic mechanism reduction is proposed and validated by using high temperature ignition, perfect stirred reactors, and steady and unsteady flame propagations of n-heptane and n-decane/air mixtures. The formation and consumption fluxes of each species at multiple reaction path generations are analyzed and used to identify the important reaction pathways and the associated species. The formation and consumption path fluxes used in this method retain flux conservation information and are used to define the path indexes for the first and the second generation reaction paths related to a targeted species. Based on the indexes of each reaction path for the first and second generations, different sized reduced chemical mechanisms which contain different number of species are generated. The reduced mechanisms of n-heptane and n-decane obtained by using the present method are compared to those generated by the direct relation graph (DRG) method. The reaction path analysis for n-decane is conducted to demonstrate the validity of the present method. The comparisons of the ignition delay times, flame propagation speeds, flame structures, and unsteady spherical flame propagation processes showed that with either the same or significantly less number of species, the reduced mechanisms generated by the present PFA are more accurate than that of DRG in a broad range of initial pressures and temperatures. The method is also integrated with the dynamic multi-timescale method and a further increase of computation efficiency is achieved. © 2010 The Combustion Institute.

Fan Z.,National University of Singapore | Fan Z.,University of California at Berkeley | Sun K.,Chongqing University | Wang J.,National University of Singapore
Journal of Materials Chemistry A | Year: 2015

Over the past few years, very interestingly, two subclasses of perovskites - organic-inorganic halide perovskites and ferroelectric oxide perovskites, have simultaneously become the hotspots in the research field of photovoltaics. Organic-inorganic halide perovskites have launched a new era of low-cost, high-efficiency solar cells, due to their easy solution processability and superior optical and electrical properties for the photovoltaic effect. More recently, a so-called giant switchable photovoltaic effect has been demonstrated in organic-inorganic halide perovskites, thus promising a new memristive functionality. On the other hand, the recent renaissance of ferroelectric oxide perovskites for photovoltaics is caused by their fundamentally new photovoltaic mechanisms, which can produce a photovoltage far beyond the bandgap and may even lead to a boost of energy conversion efficiency. In addition, the combination of photovoltaic properties with the ferroic orders may create many novel functionalities for ferroelectric oxide perovskites. Toward the common goals of developing high-efficiency photovoltaics and novel opto-electronic functional devices, these two different subclasses of perovskites shall be brought together into a combined review. In this context, we review both organic-inorganic halide perovskites and ferroelectric oxide perovskites for photovoltaics, focusing on the material nature and the photovoltaic mechanisms. We also discuss their respective unresolved issues, along with useful suggestions for future research. © The Royal Society of Chemistry.

Sun Y.,University of Texas at Tyler | Sun Y.,Pennsylvania State University | Sundell J.,Tsinghua University | Sundell J.,Chongqing University
Science of the Total Environment | Year: 2011

A high prevalence and racial disparities in asthma and allergy have been observed in American children. This study aimed to identify risk factors for asthma and allergy among children, and their contribution to racial disparities in allergy prevalence. A population-based cross-sectional study was carried out among children aged 1-8. years in Northeast Texas 2008-2009. The health conditions, life style and home environment of 3766 children were surveyed by parental questionnaires through e.g. daycares, elementary school, and medical clinics. Among participants who indicated their ethnicity, 255 were Mexican-Americans, 178 Afro-Americans and 969 Caucasians. Afro-American children had a significantly higher prevalence of asthma and eczema. Caucasian had the highest prevalence of rhinitis. Compared to Mexican-American children, Afro-American and Caucasian children were breast fed shorter time, more often went to day care center, had pets and environmental tobacco smoke exposure at home more often. For all children, being at a day care center, being exposed to dampness and environmental tobacco smoke at home were strong risk factors for asthma and allergy. Central air conditioning system was associated with an increased prevalence of wheeze among Mexican-American children, while pets were associated with an increased risk of rhinitis among Afro-American and Caucasian children. Caucasian children were generally not healthier than relatively poor Mexican-American children. Differences in the prevalence of asthma and allergy between races cannot be explained by socioeconomic status only. Life style and home environmental exposures are important risk factors for asthma and allergy in Northeast Texas children. © 2011 Elsevier B.V.

Zhao H.,Chongqing University | Shang Z.,Chongqing University | Tang Y.Y.,Chongqing University | Tang Y.Y.,University of Macau | Fang B.,Chongqing University
Pattern Recognition | Year: 2013

The effective measurement of pixel's sharpness is a key factor in multi-focus image fusion. In this paper, a gray image is considered as a two-dimensional surface, and the neighbor distance deduced from the oriented distance in differential geometry is used as a measure of pixel's sharpness, where the smooth image surface is restored by kernel regression. Based on the deduced neighbor distance filter, we construct a multi-scale image analysis framework, and propose a multi-focus image fusion method based on the neighbor distance. The experiments demonstrate that the proposed method is superior to the conventional image fusion methods in terms of some objective evaluation indexes, such as spatial frequency, standard deviation, average gradient, etc. © 2012 Elsevier Ltd.

Zhu X.,Chongqing University | Liao Q.,Chongqing University | Sui P.C.,University of Victoria | Djilali N.,University of Victoria
Journal of Power Sources | Year: 2010

The sensitivity of liquid water to geometry of cathode gas microchannel in low-temperature fuel cells is investigated numerically. The two-phase flow is resolved using 3D CFD simulations with the volume-of-fluid (VOF) method. Simulations for microchannels with different cross-sections, including rectangle with aspect ratios in a range of 0.1-2, trapezoid, upside-down trapezoid, triangle, rectangle with a curved bottom wall, and semicircle are compared. The 0.5 aspect ratio rectangle yields the longest detachment time and the largest detachment diameter, whereas the longest removal time occurs for the 0.25 aspect ratio case. With decreasing aspect ratio for the rectangle the pressure drop increases and the coverage ratio decreases. The 0.1 and 2 aspect ratios rectangles have the largest water saturation. For microchannels with different cross-sections, the detachment time, detachment diameter, and removal time of the water droplet are found to be in this order: triangle < trapezoid < rectangle with a curved bottom wall < rectangle < upside-down trapezoid. The friction coefficient increases by a factor of 2-4 in the presence of water. The upside-down trapezoid yields the maximum coverage ratio and water saturation, while the rectangle with a curved bottom wall results in the minimum values. © 2009 Elsevier B.V. All rights reserved.

Yong J.,Chongqing University | Chen L.,Chongqing University | Nassif A.B.,Hydro One Networks Inc. | Xu W.,University of Alberta
IEEE Transactions on Power Delivery | Year: 2010

Compact fluorescent lamps (CFLs) are gaining widespread acceptance due to energy conservation concerns. The CFL is a significant harmonic source since its current total harmonic distortion can exceed 100%. Although each CFL consumes only a small amount of power, mass-deployed CFLs could become a significant harmonic source. This paper presents a frequency-domain harmonic model for the CFL. This model is suitable for assessing the collective impact of a large number of CFLs since it includes the impact of supply-voltage harmonics on the harmonic currents produced by the CFLs. The model is subsequently simplified and two variations are proposed. The model and its variations are verified by comparing their results with the measurements taken from various CFLs. Furthermore, the attenuation characteristics of CFLs are investigated. The results reveal the conditions in which the simplified models can be applied with acceptable errors. © 2010 IEEE.

Lin P.,Chongqing University | Lin P.,Beijing University of Posts and Telecommunications | Ren W.,University of California at Riverside
IEEE Transactions on Automatic Control | Year: 2014

In this note, a constrained consensus problem is studied for multi-agent systems in unbalanced networks in the presence of communication delays. Here each agent needs to lie in a closed convex constraint set while reaching a consensus. The communication graphs are directed, dynamically changing, and not necessarily balanced and only the union of the graphs is assumed to be strongly connected among each time interval of a certain bounded length. The analysis is performed based on an undelayed equivalent system that is composed of a linear main body and an error auxiliary. To tackle the loss of symmetry caused by unbalanced graphs and communication delays, a novel approach is proposed. The idea is to estimate the distance from each agent to the intersection set of all agents' constraint sets based on the properties of the projection on convex sets so as to show consensus convergence by contradiction. It is shown that the error auxiliary vanishes as time evolves and the linear main body converges to a vector with an exponential rate as a separate system. It is also shown that the communication delays do not affect the consensus stability and constrained consensus is reached even if the communication delays are arbitrarily bounded. Finally, a numerical example is included to illustrate the obtained theoretical results. © 2013 IEEE.

Li Q.,Chongqing University | Li Q.,University of Adelaide | Iqbal A.,Chongqing University | Chen M.,Chongqing University | Abbott D.,Chongqing University
New Journal of Physics | Year: 2012

In this paper, quantum strategies are introduced within evolutionary games in order to investigate the evolution of quantum and classical strategies on networks in the public goods game. Comparing the results of evolution on a scale-free network and a square lattice, we find that a quantum strategy outperforms the classical strategies, regardless of the network. Moreover, a quantum strategy dominates the population earlier in group interactions than it does in pairwise interactions. In particular, if the hub node in a scale-free network is occupied by a cooperator initially, the strategy of cooperation will prevail in the population. However, in other situations, a quantum strategy can defeat the classical ones and finally becomes the dominant strategy in the population. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Yang F.-Q.,Chongqing University | Zhao J.,University of Macau | Li S.-P.,University of Macau
Electrophoresis | Year: 2010

Although there are many publications related to technological or methodological developments of CEC, few focus on the analysis of natural products, especially phytochemical bioactive compounds. This review summarized the application of CEC in the analysis of phytochemical bioactive components, including flavonoids, nucleosides, steroids, lignans, quinones and coumarins, as well as fingerprint analysis of herbs. The strategies for optimization of CEC conditions and detection were also discussed. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA.

Ogawa Y.,Kyushu University | Hu B.,Kyushu University | Hu B.,Chongqing University | Orofeo C.M.,Kyushu University | And 5 more authors.
Journal of Physical Chemistry Letters | Year: 2012

Size, orientation, and boundary of graphene domains are the current focus of chemical vapor deposition (CVD) growth because they are closely related to graphenes physical properties. Here, we study the domain structure of single-layer graphene grown by ambient pressure CVD over heteroepitaxial Cu(111) and Cu(100) films. Low energy electron microscope measurements reveal that the Cu(111) film gives uniform single-layer graphene whose orientation is consistent with the underlying Cu lattice for areas over 1 mm 2. On the other hand, single-layer graphene grown on Cu(100) film exhibits clear multidomain structure with two main orientations rotated by 30°. Moreover, a weak Raman D-band is observed along the domain boundaries for the graphene grown on the Cu(100). Our results give new insights into the growth mechanism of CVD-grown graphene over Cu metals and offer a new direction for the realization of single-crystalline graphene. © 2011 American Chemical Society.

Gou X.,Chongqing University | Chen Z.,Peking University | Sun W.,Princeton University | Ju Y.,Princeton University
Combustion and Flame | Year: 2013

A new error controlled dynamic adaptive chemistry (EC-DAC) scheme is developed and validated for ignition and combustion modeling with large, detailed, and comprehensively reduced n-heptane and n-decane mechanisms. A fuel oxidation progress variable is introduced to determine the local model reduction threshold by using the mass fraction of oxygen. An initial threshold database for error control is created according to the progress variable in a homogeneous ignition system using a detailed mechanism. The threshold database tabulated by the fuel oxidation progress variable is used to generate a dynamically reduced mechanism with a specified error bound by using the Path Flux Analysis (PFA) method. The method leads to an error-controlled kinetic model reduction according to the local mixture reactivity and improves the computation efficiency. Numerical simulations of the homogeneous ignition of n-heptane/air and n-decane/air mixtures at different initial conditions are conducted with one detailed and one comprehensively reduced mechanism involving 1034 and 121 species, respectively. The results show that the present algorithm of error-controlled adaptive chemistry scheme is accurate. The computation efficiency is improved by more than one-order for both mechanisms. Moreover, unsteady simulations of outwardly propagating spherical n-heptane/air premixed flames demonstrate that the method is rigorous even when transport is included. The successful validation in both ignition and unsteady flame propagation for both detailed and reduced mechanisms demonstrates that this method can be efficiently used in the direct numerical simulation of reactive flow for large kinetic mechanisms. © 2012 The Combustion Institute.

Deng F.-G.,Beijing Normal University | Li X.-H.,Chongqing University | Zhou H.-Y.,Beijing Normal University
Quantum Information and Computation | Year: 2011

We propose a passively self-error-rejecting single-qubit transmission scheme for an arbi-trary polarization state of a single qubit over a collective-noise channel, without resorting to additional qubits and entanglement. By splitting a single qubit into some wavepack-ets with some Mach-Zehnder interferometers, we can obtain an uncorrupted state with a success probability approaching 100% via postselection in different time bins, inde-pendent of the parameters of collective noise. It is simpler and more flexible than the schemes utilizing decoherence-free subspace and those with additional qubits. One can directly apply this scheme to almost all quantum communication protocols based on single photons or entangled photon systems against a collective noise. © Rinton Press.

Li D.,Chongqing University
Advanced Materials Research | Year: 2012

The contaminated site remediation is an important content of site management. Plans for the introduction of measures and requirements to prevent and remediate soil contamination, particularly through the development of inventories of contaminated sites and the definition of targets for prioritization of remediation actions, are expected to have important consequences for site management practice and national site policies. Nowadays contaminated soil and groundwater treatment technologies can be sorted as three categories, that is bioremediation, chemical treatment and physical treatment. Biodegradation generally refers to the breakdown of organic compounds by living organism eventually resulting in the formation of carbon dioxide and water or methane. Chemical remediation is a kind of method that chemical reagent, chemical reaction and chemistry principles are used to reduce the mobility, organisms use ratio of heavy metals and decrease the heavy metals in the soil so as to remediate and repair the soil. Physical treatments in the remediation of contaminated site contains revising methods, capping methods, stabilization methods, electrokinetic methods and so on.

Su X.,Harbin Institute of Technology | Shi P.,University of South Wales | Shi P.,Victoria University of Melbourne | Shi P.,University of Adelaide | And 2 more authors.
IEEE Transactions on Fuzzy Systems | Year: 2013

This paper focuses on analyzing a new model transformation of discrete-time Takagi-Sugeno (T-S) fuzzy systems with time-varying delays and applying it to dynamic output feedback (DOF) controller design. A new comparison model is proposed by employing a new approximation for time-varying delay state, and then, a delay partitioning method is used to analyze the scaled small gain of this comparison model. A sufficient condition on discrete-time T-S fuzzy systems with time-varying delays, which guarantees the corresponding closed-loop system to be asymptotically stable and has an induced ℓ2 disturbance attenuation performance, is derived by employing the scaled small-gain theorem. Then, the solvability condition for the induced ℓ2 DOF control is also established, by which the DOF controller can be solved as linear matrix inequality optimization problems. Finally, examples are provided to illustrate the effectiveness of the proposed approaches. © 1993-2012 IEEE.

Liao J.-Y.,National University of Singapore | Shao P.-L.,National University of Singapore | Shao P.-L.,Chongqing University | Zhao Y.,National University of Singapore
Journal of the American Chemical Society | Year: 2015

The cyclization of allenoates with activated isocyanides was reported for the first time. While Ag catalysis led to an unprecedented enantioselective synthesis of 3H pyrroles, a simple procedure using PPh3 produced a wide range of polysubstituted 1H pyrroles with high efficiency. © 2015 American Chemical Society.

Ju Y.,Princeton University | Sun W.,Princeton University | Burke M.P.,Princeton University | Gou X.,Chongqing University | Chen Z.,Peking University
Proceedings of the Combustion Institute | Year: 2011

The flame regimes of ignition and flame propagation as well as transitions between different flame regimes of n-heptane-air mixtures in a one-dimensional, cylindrical, spark assisted homogeneously charged compression ignition (HCCI) reactor are numerically modeled using a multi-timescale method with reduced kinetic mechanism. It is found that the initial mixture temperature and pressure have a dramatic impact on flame dynamics. Depending on the initial temperature gradient, there exist at least six different combustion regimes, an initial single flame front propagation regime, a coupled low temperature and high temperature double-flame regime, a decoupled low temperature and high temperature double-flame regime, a low temperature ignition regime, a single high temperature flame regime, and a hot ignition regime. The results show that the low temperature and high temperature flames have distinct kinetic and transport properties as well as flame speeds, and are strongly influenced by the low temperature chemistry. The pressure and heat release rates are affected by the appearance of different flame regimes and the transitions between them. Furthermore, it is found that the critical temperature gradient for ignition and acoustic wave coupling becomes singular at the negative temperature coefficient (NTC) region. The results show that both the NTC effect and the acoustic wave propagation in a closed reactor have a dramatic impact on the ignition front and acoustic interaction. © 2010 Published by Elsevier Inc. on behalf of The Combustion Institute. All rights reserved.

Lin Y.,University of South Carolina | Tang Y.Y.,University of Macau | Fang B.,Chongqing University | Shang Z.,Chongqing University | And 2 more authors.
IEEE Transactions on Pattern Analysis and Machine Intelligence | Year: 2013

This paper introduces a new computational visual-attention model for static and dynamic saliency maps. First, we use the Earth Mover's Distance (EMD) to measure the center-surround difference in the receptive field, instead of using the Difference-of-Gaussian filter that is widely used in many previous visual-attention models. Second, we propose to take two steps of biologically inspired nonlinear operations for combining different features: combining subsets of basic features into a set of super features using the Lm-norm and then combining the super features using the Winner-Take-All mechanism. Third, we extend the proposed model to construct dynamic saliency maps from videos by using EMD for computing the center-surround difference in the spatiotemporal receptive field. We evaluate the performance of the proposed model on both static image data and video data. Comparison results show that the proposed model outperforms several existing models under a unified evaluation setting. © 2012 IEEE.

Chongqing University | Date: 2013-11-27

A system for harvesting rainwater for use in a skirt building. The skirt building includes a main building and a podium supporting the main building. The system includes: a standpipe; a buffer channel; a filter channel; and a green roof. The green roof includes a vegetation region including a baffled diversion corridor, and a bottom filtering layer including a drainage pipe. The standpipe is arranged on the main building and is connected to the buffer channel where the energy of rainwater flowing out of the standpipe is dissipated. The buffer channel, the filter channel, and the green roof are arranged on the podium, and the buffer channel communicates with the filter channel. The filter channel is connected to the green roof. The filter channel is divided into a plurality of sections respectively filled with different matrix materials.

Cheng T.,Chongqing University | Li W.,Chongqing University | Fang D.,Peking University
AIAA Journal | Year: 2013

A model of thermal stress field from literature with temperature-dependent thermophysical properties is updated using an appropriate expression of thermal strain due to free thermal expansion. The thermal shock resistance of the ultra-high-temperature ceramic plate under aerodynamic thermal environments is then studied by combining the proposed analytical method of heat for thermal shock. The numerical simulation is conducted to examine the theoretical model. The results from the model agree well with those from the simulation. The study shows that for the given material and thermal shock initial temperature the same heat transfer condition (product of surface heat flux and plate thickness) results in the same critical failure temperature difference. The critical failure time is inversely proportional to the square of the surface heat flux and is proportional to the square of the plate thickness, that is, the ultra-high-temperature ceramic plate has the same critical failure dimensionless time. The thermal shock resistance of ultra-high-temperature ceramics decreases as the heat transfer condition increases. The critical heat transfer condition is introduced to characterize the thermal shock resistance of ultra-high-temperature ceramics similar to using the strength in representing the fracture-resistance ability of the materials. © 2012 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

Yu Y.,Chongqing University | Hui H.T.,National University of Singapore
IEEE Transactions on Microwave Theory and Techniques | Year: 2011

The design of a new mutual coupling compensation network for a small and compact-size receiving monopole array is presented. This is the first example for the experimental realization of mutual coupling compensation in a receiving array by using the receiving mutual impedances. The compensation network is designed on a printed circuit board substrate using only passive circuit components to minimize the additional circuit noise. Its output voltages are carefully measured and verified to satisfy the requirements. Its compensation function is experimentally demonstrated with a two-element monopole array in a directional-of-arrival estimation example using the MUSIC algorithm. The experimental results confirm the effectiveness and accuracy of using the receiving mutual impedances in mutual coupling analysis. © 2011 IEEE.

Huang Y.,Chongqing University | Huang Y.,CAS Institute of Physics | Fang Y.,Chalmers University of Technology | Zhang Z.,Institute of Photonic Technology | And 4 more authors.
Light: Science and Applications | Year: 2014

Due to its amazing ability to manipulate light at the nanoscale, plasmonics has become one of the most interesting topics in the field of light-matter interaction. As a promising application of plasmonics, surface-enhanced Raman scattering (SERS) has been widely used in scientific investigations and material analysis. The large enhanced Raman signals are mainly caused by the extremely enhanced electromagnetic field that results from localized surface plasmon polaritons. Recently, a novel SERS technology called remote SERS has been reported, combining both localized surface plasmon polaritons and propagating surface plasmon polaritons (PSPPs, or called plasmonic waveguide), which may be found in prominent applications in special circumstances compared to traditional local SERS. In this article, we review the mechanism of remote SERS and its development since it was first reported in 2009. Various remote metal systems based on plasmonic waveguides, such as nanoparticle-nanowire systems, single nanowire systems, crossed nanowire systems and nanowire dimer systems, are introduced, and recent novel applications, such as sensors, plasmon-driven surface-catalyzed reactions and Raman optical activity, are also presented. Furthermore, studies of remote SERS in dielectric and organic systems based on dielectric waveguides remind us that this useful technology has additional, tremendous application prospects that have not been realized in metal systems.© 2014 CIOMP. All rights reserved 2047-7538/14.

Su L.,University of Connecticut | Jia W.,University of Connecticut | Hou C.,Chongqing University | Lei Y.,University of Connecticut
Biosensors and Bioelectronics | Year: 2011

A microbial biosensor is an analytical device which integrates microorganism(s) with a physical transducer to generate a measurable signal proportional to the concentration of analytes. In recent years, a large number of microbial biosensors have been developed for environmental, food, and biomedical applications. Starting with the discussion of various sensing techniques commonly used in microbial biosensing, this review article concentrates on the summarization of the recent progress in the fabrication and application of microbial biosensors based on amperometry, potentiometry, conductometry, voltammetry, microbial fuel cell, fluorescence, bioluminescence, and colorimetry, respectively. Prospective strategies for the design of future microbial biosensors will also be discussed. © 2010 .

Yan X.,Dongguan University of Technology | Ji Y.,Zhejiang Agriculture And forestry University | Wang Y.,Chongqing University
International Journal of Production Economics | Year: 2012

We consider the problem of a retailer that is served by multiple suppliers, where any given supplier, who leads to random yield in orders, is defined to be unreliable. We examine how random yield affects the outcome of supplier selection and the retailers profit in two cases: independent random yields (IRY) and correlated random yields (CRY). For the IRY, we show that the wholesale price generally takes precedence over reliability in the retailers supplier selection, that is, a given supplier will be selected only if all less-expensive suppliers are selected, regardless of the given suppliers reliability level. For the CRY, we show that the results may be totally different from results obtained in the IRY. That is, a given supplier is selected but not all less-expensive suppliers are selected. Moreover, we examine the impacts of yield uncertainty on the retailers profit. We show that the retailer might be better off under unreliable suppliers than under completely reliable suppliers. © 2010 Elsevier B.V. All rights reserved.

Zhang P.,University of Connecticut | Li W.,BC Hydro | Li S.,University of Connecticut | Wang Y.,University of Connecticut | And 2 more authors.
Applied Energy | Year: 2013

Quantitative reliability assessment of photovoltaic (PV) power system is an indispensable technology to assure reliable and utility-friendly integration of PV generation. This paper reviews the state-of-the-art technologies for evaluating the reliability of large-scale PV systems and the effect of PV interconnection on the reliability of local distribution system. The discussions are extended to emerging research topics including time varying and ambient-condition-dependent failure rates of critical PV system components, accurate operating models of PV generators in both interconnected and islanded modes, and the reliability evaluation of active distribution networks with PV penetration and transmission level Giga-PV system. A vision for the future research is presented, with a focus on the cyber-physical perspective of the PV reliability, modeling of PV voltage control scheme for reliability assessment, reliability assessment for PV systems under extreme events and PV reliability assessment considering cybersecurity. © 2012 Elsevier Ltd.

Liu Q.,Chongqing University of Posts and Telecommunications | Wang L.,Chongqing University of Posts and Telecommunications | Liao X.,Chongqing University
Information Sciences | Year: 2012

This paper investigates the collective behavior of a general swarm model with communication time delays under different environment profiles, and the complex dynamic behavior of the delayed swarm model along a plane and a quadratic attractant/repellent profile are analyzed respectively too. It turns out that the swarm members can eventually converge to a finite region under certain conditions and the time delay plays an important role in the dynamic behavior of swarms. Finally numerical simulation results indicate that our theoretical analysis is correct. © 2010 Elsevier Inc. All rights reserved.

Zhang Y.,Chongqing University | Xiao D.,Chongqing University | Wen W.,Jiangxi University of Finance and Economics | Liu H.,Chongqing University | Liu H.,Chongqing University of Posts and Telecommunications
Optics Letters | Year: 2013

We demonstrate a new approach to chosen-plaintext attack on a general encryption model based on scrambling preprocessing operation and double random phase encoding (DRPE). With this attack, an opponent can access both the scrambling key and two random phase keys. We hope that our work motivates further security analysis of the optical encryption scheme combining the scrambling techniques and DRPE. © 2013 Optical Society of America.

Liu Y.,University of Washington | Clark M.,University of Washington | Clark M.,University of British Columbia | Zhang Q.,University of Washington | And 5 more authors.
Advanced Energy Materials | Year: 2011

Nanostructured V 2O 5 thin films have been prepared by means of cathodic deposition from an aqueous solution made from V 2O 5 and H 2O 2 directly on fluorine-doped tin oxide coated (FTO) glasses followed by annealing at 500 °C in air, and studied as film electrodes for lithium ion batteries. XPS results show that the as-deposited films contained 15% V 4+, however after annealing all the vanadium is oxidized to V 5+. The crystallinity, surface morphology, and microstructures of the films have been investigated by means of XRD, SEM, and AFM. The V 2O 5 thin film electrodes show excellent electrochemical properties as cathodes for lithium ion intercalation: a high initial discharge capacity of 402 mA h g -1 and 240 mA h g -1 is retained after over 200 cycles with a discharging rate of 200 mA g -1 (1.3 C). The specific energy density is calculated as 900 W h kg -1 for the 1 st cycle and 723 W h kg -1 for the 180 th cycle when the films are tested at 200 mA g -1 (1.3 C). When discharge/charge is carried out at a high current density of 10.5 A g -1 (70 C), the thin film electrodes retain a good discharge capacity of 120 mA h g -1, and the specific power density is over 28 kW kg -1. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Huang Y.,Chongqing University | Huang Y.,CAS Institute of Physics | Fang Y.,CAS Institute of Physics | Sun M.,CAS Institute of Physics
Journal of Physical Chemistry C | Year: 2011

In this paper, remote excitation of surface-enhanced Raman scattering (SERS) based on propagating surface plasmon polariton (SPP) on single well-defined crystal Au nanowire with quasi-spherical termini has been reported. Considering the terminal shape dependence of propagating SPP on nanowires, we first study the relationship between polarization of incident laser and emission induced by propagating SPP to acquire best Raman signal at quasi-spherical terminus. This result is confirmed by simulation using finite-difference time-domain method. And then, remote excitation of SERS is achieved when polarization of incident laser was parallel to Au nanowire. © 2011 American Chemical Society.

Yu J.,Chongqing University of Posts and Telecommunications | Hu H.,Hubei University | Zhou S.,Chongqing University | Lin X.,Chongqing University
Automatica | Year: 2013

In this paper, the stability of multi-variable fractional order nonlinear dynamic system is investigated. We propose the definition of generalized Mittag-Leffler stability with multi-variable and introduce the fractional Lyapunov direct method with multi-variable. Meanwhile, a novel approach is suggested to study generalized Mittag-Leffler stability in multi-variable fractional order nonlinear dynamic systems. An interesting multi-variable fractional order Lotka-Volterra predator-prey model is used to illustrate the proposed method and its effectiveness. © 2013 Elsevier Ltd. All rights reserved.

Li H.,Chongqing University | Liao X.,Chongqing University | Lei X.,Chongqing University | Huang T.,Qatar University | Zhu W.,Chongqing University of Posts and Telecommunications
IEEE Transactions on Circuits and Systems I: Regular Papers | Year: 2013

This paper discusses the second-order local consensus problem for multi-agent systems with nonlinear dynamics over dynamically switching random directed networks. By applying the orthogonal decomposition method, the state vector of resulted error dynamical system can be decomposed as two transversal components, one of which evolves along the consensus manifold and the other evolves transversally with the consensus manifold. Several sufficient conditions for reaching almost surely second-order local consensus are derived for the cases of time-delay-free coupling and time-delay coupling, respectively. For the case of time-delay-free coupling, we find that if there exists one directed spanning tree in the network which corresponds to the fixed time-averaged topology and the switching rate of the dynamic network is not more than a critical value which is also estimated analytically, then second-order dynamical consensus can be guaranteed for the choice of suitable parameters. For the case of time-delay coupling, we not only prove that under some assumptions, the second-order consensus can be reached exponentially, but also give an analytical estimation of the upper bounds of convergence rate and the switching rate. Finally, numerical simulations are provided to illustrate the feasibility and effectiveness of the obtained theoretical results. © 2004-2012 IEEE.

Xiang D.,Chongqing University | Ran L.,Durham University | Tavner P.,Durham University | Yang S.,University of Warwick | And 2 more authors.
IEEE Transactions on Power Electronics | Year: 2012

Condition monitoring power semiconductor devices can inform converter maintenance and reduce damage. This paper presents a method to monitor solder fatigue in a voltage source inverter insulated gate bipolar transistor power module by detecting the change of an inverter output harmonic. It is shown that low-order harmonics, caused by nonideal switching, are affected by the device junction temperature, which in turn depends upon module solder condition. To improve the detection accuracy of the phenomenon, the inverter controller is set to cause harmonic resonance at the target harmonic frequency. The would-be resonance is suppressed by an outer control loop where the control action can be used as the condition monitoring signal. Simulation and experiment are presented to validate the method and evaluate its performance in operation. © 2011 IEEE.

Ma H.-H.,Chongqing University | Wu X.-G.,Chongqing University | Ma Y.,Chongqing University | Brodsky S.J.,SLAC | Mojaza M.,KTH Royal Institute of Technology
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

A key problem in making precise perturbative QCD (pQCD) predictions is how to set the renormalization scale of the running coupling unambiguously at each finite order. The elimination of the uncertainty in setting the renormalization scale in pQCD will greatly increase the precision of collider tests of the Standard Model and the sensitivity to new phenomena. Renormalization group invariance requires that predictions for observables must also be independent on the choice of the renormalization scheme. The well-known Brodsky-Lepage-Mackenzie (BLM) approach cannot be easily extended beyond next-to-next-to-leading order of pQCD. Several suggestions have been proposed to extend the BLM approach to all orders. In this paper we discuss two distinct methods. One is based on the "Principle of Maximum Conformality" (PMC), which provides a systematic all-orders method to eliminate the scale and scheme ambiguities of pQCD. The PMC extends the BLM procedure to all orders using renormalization group methods; as an outcome, it significantly improves the pQCD convergence by eliminating renormalon divergences. An alternative method is the "sequential extended BLM" (seBLM) approach, which has been primarily designed to improve the convergence of pQCD series. The seBLM, as originally proposed, introduces auxiliary fields and follows the pattern of the β0-expansion to fix the renormalization scale. However, the seBLM requires a recomputation of pQCD amplitudes including the auxiliary fields; due to the limited availability of calculations using these auxiliary fields, the seBLM has only been applied to a few processes at low orders. In order to avoid the complications of adding extra fields, we propose a modified version of seBLM which allows us to apply this method to higher orders. We then perform detailed numerical comparisons of the two alternative scale-setting approaches by investigating their predictions for the annihilation cross section ratio Re+e- at four-loop order in pQCD. © 2015 American Physical Society.

Liao W.,Chongqing University | Wang Y.,Shanghai JiaoTong University | Pan E.,Shanghai JiaoTong University
International Journal of Advanced Manufacturing Technology | Year: 2012

As an increasing number of manufacturers are beginning to realize the importance of maintaining throughput, many maintenance models have been developed to enable machines to achieve near-zero downtime. However, previous maintenance models usually ignore machine's deterioration process. Therefore, this paper develops a novel data-driven machinery prognostic approach for machine performance assessment and prediction. With this prognostic information, a predictive maintenance model is proposed for a repairable deteriorating machine. As machine performance can be assessed, once it reaches the maintenance threshold, a maintenance operation is performed to restore the machine. Moreover, an operational cost is introduced to meet real manufacturing process. In this predictive maintenance model, the optimal maintenance threshold and maintenance cycle number are obtained with the aim to minimize the long-term average cost. Finally, a case study is presented. The computational results show the efficiency of this proposed predictive maintenance model. © 2012 Springer-Verlag London Limited.

Li Y.,University of Electronic Science and Technology of China | Li Y.,Chongqing University | Celebi H.,Stevens Institute of Technology | Daneshmand M.,University of Electronic Science and Technology of China | And 2 more authors.
IEEE Wireless Communications | Year: 2013

As a promising technique for next-generation wireless networks, femtocells expand the coverage of cellular networks, provide high data rate for users, decrease the transmission power of user equipments, and increase the spectrum efficiency. In a few years, the number of deployed femtocell base stations (FBSs) will reach hundreds of millions. This huge deployment will bring a lot of challenges in terms of interference management, resource scheduling, and energy consumption. In recent years, more and more attention has been paid to energy-efficient communications. The huge number of deployed FBSs will aggravate energy consumption. In this article, we comprehensively survey the related work on energy efficiency issues in femtocell networks, including energy efficiency metrics, energy consumption models, deployments of femtocells, and energy-efficient schemes. Then a simple sleeping scheme, fixed time sleeping, is presented as a case study for saving the energy of FBSs. Some interesting results are also presented to show that fixed time sleeping makes a good trade-off among energy efficiency, actual waiting time, and call loss. © 2013 IEEE.

Zhang T.J.,Chongqing University | Zhang T.J.,Key Laboratory of Micro Nano Materials Engineering and Technology
Applied Mechanics and Materials | Year: 2013

In order to produce required free-cutting steel billets for auto industry, it is necessary to provide steel with correct content of sulfur. Effective, controlled method adding sulfur is very important in the production of sulfur free-cutting steel of consistent microstructure and hence mechanical properties and machinability. Because traditional methods of adding sulfur in steel can not provide stable results and always cause environmental pollution problems,the sulfur cored wire injection process was introduced. Stable results were obtained, and effects of parameters such as feeding rate, etc on sulfur recovery are investigated. The experimental results show that the mean recovery of sulfur was 80%, the treatment time of adding sulfur was about 2 minutes, and the melting period was shortened. Favorable metallurgical achievements and economical benefits were gained. © (2013) Trans Tech Publications, Switzerland.

Wang Y.,Chongqing University of Posts and Telecommunications | Wang Y.,City University of Hong Kong | Wong K.-W.,City University of Hong Kong | Liao X.,Chongqing University | Chen G.,City University of Hong Kong
Applied Soft Computing Journal | Year: 2011

In recent years, various image encryption algorithms based on the permutation-diffusion architecture have been proposed where, however, permutation and diffusion are considered as two separate stages, both requiring image-scanning to obtain pixel values. If these two stages are combined, the duplicated scanning effort can be reduced and the encryption can be accelerated. In this paper, a fast image encryption algorithm with combined permutation and diffusion is proposed. First, the image is partitioned into blocks of pixels. Then, spatiotemporal chaos is employed to shuffle the blocks and, at the same time, to change the pixel values. Meanwhile, an efficient method for generating pseudorandom numbers from spatiotemporal chaos is suggested, which further increases the encryption speed. Theoretical analyses and computer simulations both confirm that the new algorithm has high security and is very fast for practical image encryption. © 2010 Elsevier B.V. All rights reserved.

Li L.,Tongji University | Li L.,University of California at Berkeley | Gao N.,Tongji University | Deng Y.,Montclair State University | And 2 more authors.
Water Research | Year: 2012

Algae organic matters (AOM), including intracellular organic matters (IOM) and extracellular organic matters (EOM), are causing numerous water quality issues, among which formation of disinfection byproducts (DBPs) and odor & taste (O&T) compounds are of particular concern. In this study, physiochemical properties of IOM and EOM of Microcystic aeruginosa under an exponential growth phase (2.01×10 11/L) were comprehensively characterized. Moreover, the yields of DBPs during AOM disinfection and O&T-causing compounds were quantified. Hydrophilic organic matters accounted for 86% and 63% of DOC in IOM and EOM, respectively. Molecular weight (MW) fractions of IOM in <1kDa, 40-800kDa, and >800kDa were 27%, 42%, and 31% of DOC, respectively, while EOM primarily contained 1-100kDa molecules. Besides, a low SUVA (0.84L/mgm) and the specific fluorescence spectra suggested that AOM (especially IOM) was principally comprised of protein-like substances, instead of humic-like matters. The formation potentials of chloroform, chloroacetic acid, and nitrosodimethylamine were 21.46, 68.29 and 0.0096μg/mgC for IOM, and 32.44, 54.58 and 0.0189μg/mgC for EOM, respectively. Furthermore, the dominant O&T compound produced from EOM and IOM were 2-MIB (68.75ng/mgC) and β-cyclocitral (367.59ng/mgC), respectively. Of note, dimethyltrisulfide became the prevailing O & T compound following anaerobic cultivation. © 2011 Elsevier Ltd.

Liu H.,Chongqing University of Posts and Telecommunications | Nan H.,Chongqing University
Optics and Laser Technology | Year: 2013

In this paper, a color image encryption algorithm is designed by use of chaos-based cyclic shift and multiple-order discrete fractional cosine transform (MODFrCT). The RGB components of the color image are vertically combined and then simultaneously scrambled by chaos-based cyclic shift to make these three components affect each other. The scrambled RGB components are separately transformed with the MODFrCT, whose orders are determined by the Chirikov standard chaotic map. Based on chaotic inherent properties, the corresponding keys are highly sensitive. At the same time, the transmission of the cipher image is very fast since the DFrCT is a reality preserving transform. Simulation results proved the validity of the proposed algorithm. © 2013 Elsevier Ltd.

Yan X.,Dongguan University of Technology | Wang Y.,Chongqing University
International Journal of Production Research | Year: 2014

We study a newsvendor problem with capital constraint and demand forecast update. The newsvendor has two instants to order from a supplier prior to a single selling season. While the demand is uncertain, the newsvendor can improve the forecast by utilizing the market signal observed between the first and second instants. We analyze the newsvendors optimal ordering policy in two cases: risk-neutrality and risk-aversion. Our analysis suggests that the optimal policy in each case is characterized by a critical value: A target safety capital. Under this policy, part of capital is left to use at instant 2 if and only if the initial capital is above the target safety capital. When this happens, the order quantity at instant 1 decreases as the initial capital increases. We further analyze the effect of information update on the newsvendors ordering policy. Our results indicate that more capital should be left to use at instant 2 when the correlation coefficient between market information and demand becomes large or when the newsvendor is more risk-averse. © 2014 Taylor & Francis.

Dong T.,Chongqing University | Dong T.,Chongqing University of Posts and Telecommunications | Liao X.,Chongqing University | Huang T.,Texas A&M University at Qatar
Nonlinear Analysis: Real World Applications | Year: 2013

In this paper, a congestion control algorithm with heterogeneous delays in a wireless access network is considered. We regard the communication time delay as a bifurcating parameter to study the dynamical behaviors, i.e., local asymptotical stability, Hopf bifurcation and resonant codimension-two bifurcation. By analyzing the associated characteristic equation, the Hopf bifurcation occurs when the delay passes through a sequence of critical value. Furthermore, the direction and stability of the bifurcating periodic solutions are derived by applying the normal form theory and the center manifold theorem. In the meantime, the resonant codimension-two bifurcation is also found in this model. Some numerical examples are finally performed to verify the theoretical results. © 2012 Published by Elsevier Ltd.

Huang Y.,CAS Institute of Physics | Huang Y.,Chongqing University | Fang Y.,CAS Institute of Physics | Yang Z.,Xiamen University | Sun M.,CAS Institute of Physics
Journal of Physical Chemistry C | Year: 2010

In this study, we attempt to experimentally address the question of whether p,p′-dimercaptoazobisbenzene (DMAB) can be produced from p-aminothiophenol (PATP) by surface photochemistry reaction in the junctions of a Ag nanoparticle-molecule-Ag (or Au) film. First, utilizing surface-enhanced Raman scattering (SERS) spectra, we provide experimental and theoretical evidence that DMAB can be produced from PATP by surface photochemistry reaction in the junctions of a Ag nanoparticle-molecule-Ag film. Second, we investigate the SERS spectra utilizing both experimental and theoretical approaches, ultimately revealing that DMAB cannot be produced from PATP in the junctions of a Ag nanoparticle-molecule-Au film. The electromagnetic enhancements are estimated with three-dimensional finite-difference time domain methods, which are about 9 × 105 times in the junctions of Ag nanoparticle-PATP-Ag/Au films. © 2010 American Chemical Society.

Zhao W.,Chongqing University | Leeftink R.B.,Decistor bv | Rotter V.S.,TU Berlin
Resources, Conservation and Recycling | Year: 2010

In the recycling chain of construction and demolition waste, it is impossible to guarantee a certain quality of recycled products and to recycle a large amount of materials in recycling centers without mechanical sorting facilities. This counts even more when the produced materials have a low economic value, as is the case with crushed and cleaned debris, also called aggregates. In order to assess if recycling can be done effectively, a feasibility study of the recycling of construction and demolition (C&D) waste is necessary. In the paper, the economic feasibility of recycling facilities for C&D waste in China's Chongqing city was assessed. Investigations on the current situation of C&D waste recycling in Chongqing showed that there were a large quantity of waste and an enormous demand for recycled materials due to the busy ongoing construction activities, which generated a large market potential and also brought a challenge to the strengthening of the recycling sector. However, a full cost calculation and an investment analysis showed that, under current market conditions, operating C&D waste recycling centers in Chongqing might face high investment risks. Thus, the regulations and economic instruments like tax that can support the economic feasibility of recycling are discussed, and the recommendations for the choice of instruments are provided. © 2009 Elsevier B.V. All rights reserved.

Zhu H.,Chongqing University | Zhu H.,University of Calgary | Zhu H.,Chongqing University of Posts and Telecommunications | Leung H.,University of Calgary | He Z.,Chongqing University
Information Sciences | Year: 2013

In this paper, a robust sensor fusion method is proposed where the measurement noise is modeled by a Student-t distribution. The Student-t distribution has a heavy tail compared to the Gaussian distribution and is robust to outliers. We formulate sensor fusion as a state space estimation problem in the Bayesian framework. Both batch and recursive variational Bayesian (VB) algorithms are developed to perform this non-Gaussian state space estimation problem to obtain the fusion results. Computer simulations show that the proposed approach has an improved fusion performance and a lower computation cost compared to methods based on Gaussian and finite Gaussian mixture models. © 2012 Elsevier Inc. All rights reserved.

Li H.,Chongqing University | Liao X.,Chongqing University | Luo M.,Chongqing University of Posts and Telecommunications
Nonlinear Dynamics | Year: 2012

In this paper, we construct a novel four dimensional fractional-order chaotic system. Compared with all the proposed chaotic systems until now, the biggest difference and most attractive place is that there exists no equilibrium point in this system. Those rigorous approaches, i.e., Melnikov's and Shilnikov's methods, fail to mathematically prove the existence of chaos in this kind of system under some parameters. To reconcile this awkward situation, we resort to circuit simulation experiment to accomplish this task. Before this, we use improved version of the Adams-Bashforth-Moulton numerical algorithm to calculate this fractional-order chaotic system and show that the proposed fractional-order system with the order as low as 3.28 exhibits a chaotic attractor. Then an electronic circuit is designed for order q=0.9, from which we can observe that chaotic attractor does exist in this fractional-order system. Furthermore, based on the final value theorem of the Laplace transformation, synchronization of two novel fractional-order chaotic systems with the help of one-way coupling method is realized for order q=0.9. An electronic circuit is designed for hardware implementation to synchronize two novel fractional-order chaotic systems for the same order. The results for numerical simulations and circuit experiments are in very good agreement with each other, thus proving that chaos exists indeed in the proposed fractional-order system and the one-way coupling synchronization method is very effective to this system. © 2011 Springer Science+Business Media B.V.

Zhao B.,Chongqing University | An Q.,Chongqing University | He Y.L.,Shanghai JiaoTong University | Guo J.S.,Chongqing University
Bioresource Technology | Year: 2012

A heterotrophic nitrifier, strain NR, was isolated from a membrane bioreactor. Strain NR was identified as Alcaligenes faecalis by Auto-Microbic system and16S rRNA gene sequence analysis. A. faecalis strain NR shows a capability of heterotrophic nitrification and N 2O and N 2 production as well under the aerobic condition. Further tests demonstrated that neither nitrite nor nitrate could be denitrified aerobically by strain NR. However, when hydroxylamine was used as the sole nitrogen source, nitrogenous gases were detected. With an enzyme assay, a 0.063U activity of hydroxylamine oxidase was observed, while nitrate reductase and nitrite reductase were undetectable. Thus, nitrogenous gas was speculated to be produced via hydroxylamine. Therefore, two different metabolic pathways might exist in A. faecalis NR. One is heterotrophic nitrification by oxidizing ammonium to nitrite and nitrate. The other is oxidizing ammonium to nitrogenous gas directly via hydroxylamine. © 2012 Elsevier Ltd.

Duan P.,Chongqing University | Xie K.-G.,Chongqing University | Zhang L.,University of Leeds | Rong X.,Dongfang Hitachi CD Electrical Control Equipments Co.
IEEE Transactions on Power Electronics | Year: 2011

Microgrid is becoming more and more popular in the west and north of China, where there is abundant wind energy. For the microgrid, the faults in the wind generation system usually result in the power accidents. The open switch fault of wind power converter is one of the faults, and many diagnosing methods have been developed. To avoid the disadvantages of current open-switch fault diagnosing methods for a doubly fed wind power converter, an anti-false-alarm method, which can detect one or two open switch faults is proposed in the paper, which is based on the investigation of the characteristics of current signals. Simulations were carried out to test the method presented in the paper, and results indicate the diagnosing method cannot only detect one open switch fault, also two open switch faults at the same time. In addition, the false alarm caused by the open switch fault at the rotor side can be avoided. Finally, a system reconfiguration topology was designed to keep the doubly fed induction generator (DFIG) continue running after the open switch faults. Simulation results show that the method can detect the locations and styles of open switch faults precisely, and the system reconfiguration strategy can restart the DFIG rapidly. © 2010 IEEE.

Peng X.,Shanghai JiaoTong University | Guo Z.,Chongqing University | Du T.,Shanghai JiaoTong University | Yu W.-R.,Seoul National University
Composites Part B: Engineering | Year: 2013

A simple hyperelastic constitutive model is developed to characterize the anisotropic and large deformation behavior of textile fabrics. In the model, the strain energy function is decomposed into two parts representing fiber stretches and fiber-fiber interaction (cross-over shearing) between weft and warp yarns. The proposed constitutive model is demonstrated on a balanced plain woven fabric. The actual forms of the strain energy functions are determined by fitting uni-axial tensile and picture-frame shear tests of the woven fabrics. The developed model is validated by comparing numerical results with experimental bias extension data, and then applied to simulation of a benchmark double dome forming, demonstrating that the proposed anisotropic hyperelastic constitutive model is highly suitable to predict the large deformation behavior of textile fabrics. © 2013 Elsevier Ltd. All rights reserved.

Pan E.,Shanghai JiaoTong University | Liao W.,Chongqing University | Xi L.,Shanghai JiaoTong University
International Journal of Advanced Manufacturing Technology | Year: 2012

As increasingly diverse tasks are being processed on single multi-functional machine, production scheduling has become a critical issue in the planning and management of manufacturing processes. However, the majority of production scheduling literature ignores machine availability and assumes that machine is available all the time. In reality, machines physically deteriorate with increased usage and time. Thus, there is an intense need for manufacturing industries to reduce unexpected breakdowns and remain competitive, and motivating maintenance operations should be integrated into production scheduling models. With the advancements in sensor and prognostic technologies, machine's condition can be monitored and assessed over time through conducting predictive maintenance. Hence, based on this scheme, this study proposes a single-machine-based scheduling model incorporating production scheduling and predictive maintenance. A machine's effective age and remaining maintenance life are introduced to describe machine degradation. Finally, a numerical example is given; the computational results show that this integrated scheduling model has better performance than those existing models, which proves its efficiency. © 2011 Springer-Verlag.

Hu A.,Chongqing University | Li L.,Chongqing University | Uddin R.,University of Illinois at Urbana - Champaign
Journal of Computational Physics | Year: 2015

Single component pseudo-potential lattice Boltzmann models have been widely studied due to their simplicity and stability in multiphase simulations. While numerous models have been proposed, comparative analysis and advantages and disadvantages of different force schemes are often lacking. A pseudo-potential model to simulate large density ratios proposed by Kupershtokh et al. [1] is analyzed in detail in this work. Several common used force schemes are utilized and results compared. Based on the numerical results, the relatively most accurate force scheme proposed by Guo et al. [2] is selected and applied to improve the accuracy of Kupershtokh et al.'s model. Results obtained using the modified Kupershtokh et al.'s model [1] for different value of τ are compared with those obtained using Li et al.'s model [3]. Effect of relaxation time τ on the accuracy of the results is reported. Moreover, it is noted that the error in the density ratio predicted by the model is directly correlated with the magnitude of the spurious velocities on (curved) interfaces. Simulation results show that, the accuracy of Kupershtokh et al.'s model can be improved with Guo et al.'s force scheme [2]. However, the errors and τ's effects are still noticeable when density ratios are large. To improve the accuracy of the pseudo-potential model and to reduce the effects of τ, two possible methods were discussed in the present work. Both, a rescaling of the equation of state and multi-relaxation time, are applied and are shown to improve the prediction of the density ratios. © 2015 Elsevier Inc.

Jiang L.,Chongqing University | Wang Y.,Chongqing University | Yan X.,Dongguan University of Technology
Computers and Industrial Engineering | Year: 2014

This paper investigates decision and coordination in a supply-chain-wide system consisting of a manufacturer, a third-party logistics (3PL) provider, and two competing retailers. The product distribution functions may be implemented by the 3PL provider or the two retailers who face a decision problem that whether the 3PL provider should be introduced. The advantage of introducing the 3PL provider lies in his/her lower logistics cost. The drawback lies in the 3PL provider's profit margin which leads to classic double marginalization. A new insight provided by this paper is that whether or not introducing the 3PL provider depends on the balance of these two effects. This paper reveals the conditions of the balance and explores the effect of retail competition on this balance. Furthermore, we discuss the dominant retailer model where one retailer is a price leader, and the other is a price follower. Whether the 3PL provider should be introduced under the dominant retailer model is also analyzed. Finally, three contracts: a spanning revenue-sharing contract, a quantity discount contract and a two-part tariffs contract are devised to effectively coordinate the decentralized system involving the 3PL provider. © 2014 Elsevier Ltd. All rights reserved.

News Article | November 25, 2015

Abstract: Cryptography is the approach to protect data secrecy in public environment. Certain cryptographic communications require not only the security of the transmitted message against eavesdropping from an outside adversary, but also the communicators' individual privacy against each other. Symmetrically private information retrieval (SPIR), which deals with the problem of private user queries to a database, is an example of such communication protocols. In a SPIR protocol Alice can obtain one item (i.e. one secret) from Bob's secret database in such a manner that Bob does not know which item Alice has obtained and, simultaneously, Alice cannot get additional items except the one she wanted in the database. With the advantage of unconditional security, as we know, quantum cryptography has attracted a great deal of attention now. Quantum private query (QPQ) is the quantum scheme for SPIR problem. Since the first QPQ protocol was proposed by Vittorio Giovannetti et al in 2008, quite a few scholars have participated in the study of this interesting and important field. The original QPQ protocols are based on oracle operations. Though those protocols have significant advantages in theory, they are difficult to implement since the dimension of the oracle operation would be exceedingly high when a large database is concerned. In 2011, to overcome the above drawback, scholars proposed a new type of QPQ, i.e. quantum-key-distribution (QKD)-based QPQ. Based on the mature technology of QKD, this new kind of QPQ has some important advantages such as being easy to realize and loss-tolerant. Therefore, as a practical model, QKD-based QPQ is overwhelmingly attractive and soon becomes a research hotspot. However, QKD-based QPQ seems somewhat unreliable in the sense that all the existing protocols would fail with a non-zero probability. Besides, the database would generally reveal some additional secrets to the honest user. Even worse, to reduce the failure probability, one must increase the expectation of the number of the revealed secrets, while to protect the security of the database better, the protocol would be more likely to fail. It seems incompatible to improve the above two disadvantages of the present QKD-based QPQ. Fortunately, based on a differential phase-shift (DPS) QKD protocol, researchers have tactfully and perfectly removed these two obstacles. The DPS-QKD protocol mentioned above was proposed by Toshihiko Sasaki et al. in the famous journal Nature in 2014. In this QKD protocol participants need not to monitor signal disturbance anymore. It can tolerate up to 50% bit error rate by setting a parameter large enough, while the generally used BB84 protocol can only tolerate 11% at most. Besides, the DPS-QKD protocol is naturally immune to the photon-number-splitting attack, where the adversary utilizes the imperfection of the photon source in practice to attack. As is seen, the technology of DPS has greatly promoted the development of QKD and captured lots of attention. Recently, researchers find that DPS is also beneficial for QKD-based QPQ. Based on the DPS-QKD, a new QPQ protocol was proposed by Bin Liu, Fei Gao, Wei Huang and Qiaoyan Wen, scientists at the State Key Laboratory of Networking and Switching Technology, Beijing University of Posts and Telecommunications, in the Chinese city of Beijing (See Figure 1). "It maintains the advantages of the QKD-based QPQ, i.e., easy to implement and loss tolerant" according to the four scholars. In an article connected with College of Computer Science, Chongqing University, in the Chinese city of Chongqing, they revealed in the study, which was published in Science China-Physics, Mechanics & Astronomy, that it is the randomness in the dilution of the oblivious key, one of the main processes in such protocols, that caused the possible failure of previous QKD-based QPQ. And utilizing the features of DPS, their protocol successfully avoids the process of dilution. Without the process of dilution, this new protocol becomes more reliable and reasonable, compared with the previous QKD-based QPQ protocols. Just as the scholars stated in their article: "Different from the situations in the previous QKD-based QPQ protocols, in our protocol, the number of the items an honest user will obtain is always one and the failure probability is always zero." They also calculated an upper bound for the leaked information of the database in theory, and claimed that when the number of the database items "become larger, the advantage of our protocol's bound would be highlighted comparing with the other QKD-based QPQ protocols". What's more, just like the DPS-QKD, the QKD-based QPQ protocol proposed by the four scholars is also naturally immune to the photon-number-splitting attacks. While other QKD-based QPQ protocols would leak more secrets of the database than expected to both the outside adversaries and the dishonest users provided the photon source were not perfect. At the end of this article, these four scholars summarized "the proposed protocol is the first QKD-based QPQ protocol without the process of the oblivious key dilution, and, therefore, it is the first QKD-based one with no failure probability and no information reveal for the database when the user is honest", and they believed that "the proposed protocol initiates a new branch of QKD-based QPQ". ### This research was funded by the National Natural Science Foundation of China (Grant Nos. 61272057 and 61170270). For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

News Article | December 1, 2015

Researchers have built a prototype biosensor that could make it cheaper to detect a common class of toxic pesticides on food and in the environment (J. Ag. Food Chem., DOI: 10.1021/acs.jafc.5b03971). Organophosphate pesticides represent nearly 40% of pesticides used on crops worldwide, and are highly neurotoxic. Scientists are developing sensitive, portable biosensors that can detect the low limits of these pesticides set by regulatory agencies, or uncover illegal uses of banned compounds. Organophosphates inhibit acetylcholinesterase—the mechanism of their toxicity in humans—and many current biosensors monitor this reaction. But this enzyme is expensive because it needs to be extracted from animal tissue. So some researchers have considered using a cheaper alternative, plant esterase. Changjun Hou of Chongqing University and Yu Lei of the University of Connecticut and their colleagues designed a plant-esterase-based biosensor for organophosphates that boosts performance by including nanomaterials used in previous acetylcholinesterase-based biosensors (Anal. Chem. 2012, DOI:10.1021/ac300545p). The new sensor incorporates gold nanoparticles to ease electron transfer, graphene nanosheets to improve conductivity, and chitosan, a hydrophilic polysaccharide derived from shrimp and insect shells, to stabilize the enzyme. To make the biosensor, the team started with a solution of gold nanoparticles and graphene nanosheets, which they deposited onto the surface of glassy carbon electrodes. Then they extracted and purified plant esterase from wheat flour, and mixed it with chitosan. They applied the solution of plant esterase and chitosan onto the surface of the nanocomponents and let it dry. When the system is placed in a buffer solution containing 1-naphthyl acetate, a carboxylic ester, plant esterase hydrolyzes the ester to produce an electroactive product, 1-naphthol. Organophosphate pesticides inhibit this reaction, so the researchers can determine their concentration in a solution by monitoring the decrease in electrochemical current in the electrodes. The team used the biosensor to measure concentrations of two organophosphate pesticides, methyl parathion and malathion, in solution at up to 500 ppb. It has detection limits of 50 ppt and 0.5 ppb for these compounds, respectively, comparable to or more sensitive than most previous acetylcholinesterase-based methods and below the maximum limits set by the EPA (2 ppb for methyl parathion). It also accurately quantified spikes of these pesticides on ground up samples of carrots and apples with an average error of 4%. Though the team’s concept is not unique, it could have potential for food analysis, says Omowunmi A. Sadik, a chemist who develops environmental biosensors at Binghamton University, SUNY. She adds that both the NSF and USDA are stressing the development of less expensive detection methods for food safety. Because these organophosphate compounds are nerve agents, the method could also be used in defense, she says. Still, she says the team must make the prototype portable and robust enough to perform in the “dirty” conditions of the real environment, and that the use of nanomaterials will raise its cost.

Zhang G.,China Agricultural University | Liang Y.,Chongqing University
Archives of Microbiology | Year: 2013

Cordyceps militaris is a heterothallic ascomycetous fungus that has been cultivated as a medicinal mushroom. This study was conducted to improve fruiting body production by PCR assessment. Based on single-ascospore isolates selected from wild and cultivated populations, the conserved sequences of α-BOX in MAT1-1 and HMG-BOX in MAT1-2 were used as markers for the detection of mating types by PCR. PCR results indicated that the ratio of mating types is consistent with a theoretical ratio of 1:1 (MAT1-1:MAT1-2) in wild (66:70) and cultivated (71:60) populations. Cross-mating between the opposite mating types produced over fivefold more well-developed fruiting bodies than self- or cross-mating between strains within the same mating type. This study may serve as a valuable reference for artificial culturing of C. militaris and other edible and medicinal mushrooms and may be useful to develop an efficient process for the selection, domestication, and management of strains for industrial-scale production. © 2013 Springer-Verlag Berlin Heidelberg.

Li R.,Nanjing Southeast University | Wei H.,Chongqing University
International Journal of Machine Learning and Cybernetics | Year: 2016

This paper is concerned with the sampled-data synchronization issues for delayed memristive neural networks with Markovian jumping and reaction–diffusion terms. In the frame work of inequality techniques and a useful Lyapunov functional, some new testable algebraic criteria are obtained to ensure the stability of the error system, and thus, the master system can synchronize with the slave system. Finally, an illustrative example is exploited to demonstrate the performance and effectiveness of the developed approach. © 2015, Springer-Verlag Berlin Heidelberg.

Tang B.,Chongqing University | Song T.,Chongqing University | Li F.,Sichuan University | Deng L.,Chongqing University
Renewable Energy | Year: 2014

Fault diagnosis for wind turbine transmission systems is an important task for reducing their maintenance cost. However, the non-stationary dynamic operating conditions of wind turbines pose a challenge to fault diagnosis for wind turbine transmission systems. In this paper, a novel fault diagnosis method based on manifold learning and Shannon wavelet support vector machine is proposed for wind turbine transmission systems. Firstly, mixed-domain features are extracted to construct a high-dimensional feature set characterizing the properties of non-stationary vibration signals from wind turbine transmission systems. Moreover, an effective manifold learning algorithm with non-linear dimensionality reduction capability, orthogonal neighborhood preserving embedding (ONPE), is applied to compress the high-dimensional feature set into low-dimensional eigenvectors. Finally, the low-dimensional eigenvectors are inputted into a Shannon wavelet support vector machine (SWSVM) to recognize faults. The performance of the proposed method was proved by successful fault diagnosis application in a wind turbine's gearbox. The application results indicated that the proposed method improved the accuracy of fault diagnosis. © 2013 Elsevier Ltd.

Huang Y.,Chongqing University | Huang Y.,National Center for Nanosciences and Technology of China | He S.,Chongqing University | Cao W.,National Center for Nanosciences and Technology of China | And 2 more authors.
Nanoscale | Year: 2012

To date, even though various kinds of nanomaterials have been evaluated over the years in order to develop effective cancer therapy, there is still significant challenges in the improvement of the capabilities of nano-carriers. Developing a new theranostic nanomedicine platform for imaging-guided, visualized cancer therapy is currently a promising way to enhance therapeutic efficiency and reduce side effects. Firstly, conventional imaging technologies are reviewed with their advantages and disadvantages, respectively. Then, advanced biomedical materials for multimodal imaging are illustrated in detail, including representative examples for various dual-modalities and triple-modalities. Besides conventional cancer treatment (chemotherapy, radiotherapy), current biomaterials are also summarized for novel cancer therapy based on hyperthermia, photothermal, photodynamic effects, and clinical imaging-guided surgery. In conclusion, biomedical materials for imaging-guided therapy are becoming one of the mainstream treatments for cancer in the future. It is hoped that this review might provide new impetus to understand nanotechnology and nanomaterials employed for imaging-guided cancer therapy. This journal is © 2012 The Royal Society of Chemistry.

Xiao L.,Chongqing University | Cao Y.,Florida InternationalUniversity
Journal of Enhanced Heat Transfer | Year: 2012

The pulsating/oscillating heat pipe (PHP/OHP) is a relatively new, efficient, two-phase heat-Transfer device, which has attracted considerable interest due to its unique features in comparison with other types of heat pipes. In this paper, the most recent experimental and theoretical research work on the PHP and its derivatives is discussed and summarized. Many important features, parameters, significant conclusions, and comments of the subjects are presented in a tabular form. The effects of the main parameters on the thermal performance of the PHP and its derivatives are analyzed in depth. Although a complete theoretical understanding of the operational characteristics of the PHP is not yet achieved, there are many emerging niche applications of the PHP which are thoroughly reviewed. Finally, some directions and suggestions for PHP development in the future are given. © 2012 by Begell House, Inc.

Yang T.,Stevens Institute of Technology | Chen G.,Chongqing University | Tian C.,Stevens Institute of Technology | Martini R.,Stevens Institute of Technology
Optics Letters | Year: 2013

The excitationwavelength for all-optical modulation of a 10.6 μmmid-infrared (MIR) quantumcascade laser (QCL)was varied in order to obtain maximum modulation depth. Both amplitude and wavelength modulation experiments were conducted at 820 nm and 1550 nm excitation respectively, whereby the latter matches the interband transition in the QCL active region. Experimental results show that for continuous-wave mode-operated QCL, the efficiency of free carrier generation is doubled under 1550 nm excitation compared with 820 nm excitation, resulting in an increase of the amplitude modulation index from 19% to 36%. At the same time, the maximum wavelength shift is more than doubled from 1.05 nm to 2.80 nm. Furthermore, for the first time to our knowledge, we demonstrated the optical switching of a QCL operated in pulse mode by simple variation of the excitation wavelength. © 2013 Optical Society of America.

Qin Y.,Chongqing University | Qin Y.,Sichuan University | Mao Y.,Chongqing University | Tang B.,Chongqing University
Journal of Sound and Vibration | Year: 2013

Using different transform basis, the vibration signal components, such as impulses, harmonics and modulated components, can be effectively separated by basis pursuit. For multicomponent vibration signals, this paper proposes a new vibration signal component separation approach by iteratively using basis pursuit. The signal is firstly denoised by basis pursuit denoising and the impulsive component can be separated by using identity matrix and redundant Fourier basis. Then signal components with different frequency ranges can be separated by using short-time Fourier transform basis with different window lengths, and the components with high frequency are separated after each iteration. To choose the best basis from the dictionary, the separation coefficient is proposed for evaluating the separating performance of the transform basis. The proposed approach, empirical mode decomposition (EMD) and matching pursuit are respectively applied to analyzing a simulated faulty vibration and a simulated faulty gear vibration signal. The comparison results demonstrate its superiority to EMD and matching pursuit in separation accuracy. Finally, the proposed approach is used for detecting the faults of a rotor and rolling bearings. The results further show that this proposed method can be effectively applied to mechanical fault diagnosis. © 2013 Elsevier Ltd.

Hong T.,Beihang University | Yu Y.,Chongqing University
Journal of Electromagnetic Waves and Applications | Year: 2011

Strong mutual coupling between closely spaced elements in compact antenna arrays may cause significant system performance degradation. Decoupling networks can be used to compensate for the mutual coupling effect. In this paper, a new compact network structure is proposed to enhance the port isolation between three closely spaced antennas. This 6-port network consists of only a microstrip ring. Transmission lines are used to connect the output ports of the network to the terminals of the three-element array. Open stubs match the input ports of the network to the system impedance. A three-monopole array with the proposed decoupling and matching network was fabricated. The experimental results show that port isolation is achieved for this compact three-monopole array. © 2011 VSP.

Dai J.,Kunming University of Science and Technology | Meng W.,Chongqing University
International Journal of Production Economics | Year: 2015

In this paper we analyze a single-period inventory model where a risk-averse newsvendor makes a joint decision on ordering, pricing and marketing under the CVaR risk measure criterion. The newsvendor can exert marketing effort to enhance market demand. We assume that the newsvendor's marketing effort affects the scale of the demand distribution and hence to model the marketing-dependent demand as a multiplicative form. We characterize sufficient conditions that guarantee existence and uniqueness of the optimal solutions under some mild assumptions on demand distribution, expected demand function and marketing effort cost, which are widely used in the related literature. We show that the optimal order quantity increases in the newsvendor's marketing effort, but the optimal price remains unchanged whether the demand is marketing-dependent or not. Additionally, we explore impact of exogenous parameters, such as unit order cost, salvage value and the newsvendor's risk aversion coefficient, on the optimal decision variables, and find that the optimal marketing effort always keeps the same changing direction with the optimal marketing-independent order quantity as the exogenous parameters change. This suggests that impact of the parameters on the optimal order quantity gets strengthened in the case of marketing-dependent demand. © 2014 Elsevier B.V. All rights reserved.

Wu S.,Chongqing University | Wu S.,Beihang University | Wang C.,Beihang University | Cui Y.,Beijing Solar Energy Research Institute Co.
Applied Surface Science | Year: 2014

Bismuth oxychloride (BiOCl) granular and flake-like films with specific {0 0 1} crystal facets are synthesized by a facile hydrolysis route. The percentage of reactive {0 0 1} facets is up to 97.36% in granular film and 91.69% in flake-like film, respectively. It is found that the synthesized granular film is composed by the nano grains with average size around 5-10 nm, but the flake-like film contains the flakes originated from the large nano crystals. The percentage of the {0 0 1} reactive facets and morphology of the BiOCl film can be tuned by adjusting the concentration or the pH value of the solution during the synthesis process, companied with the appearance of the (1 0 1), (1 0 2), and (1 1 0) facets. The formation mechanism of {0 0 1}-preferential orientation has been rationally explained in terms of crystal growth habit and dynamics. Photocatalytic degradation of RhB dye has been observed under UV light, representing that the flake-like film with {0 0 1} facets preferred orientation exhibits excellent photoactivity. © 2013 Elsevier B.V.

Ren F.,Hong Kong University of Science and Technology | Leng Y.,Hong Kong University of Science and Technology | Xin R.,Chongqing University | Ge X.,Hong Kong University of Science and Technology
Acta Biomaterialia | Year: 2010

The substitution of magnesium in hydroxyapatite (HA) was examined in HA nano-crystals synthesized by the wet-chemical precipitation method at 90 °C. Comprehensive characterization techniques, including X-ray diffraction, X-ray fluorescence, field emission scanning electron microscopy, high-resolution transmission electron microscopy, thermogravimetric analysis and Rietveld refinement, provided experimental evidence of the effects of Mg substitution on the phase, crystallinity, chemical composition, crystal size, morphology, thermal stability and crystal lattice structure of HA. A computational study using ab initio generalized gradient approximation density functional theory was performed to reveal changes in lattice parameters and preferential calcium sites for Mg substitution in HA. The experimental results showed that a limited amount of Mg (Mg/(Mg + Ca) between 5 and 7 mol.%) could successfully substitute for Ca in HA. HA crystallites became smaller and more irregular, and they formed greater agglomerates with Mg substitution. Mg substitution resulted in decreases in the crystallinity and thermal stability of HA. The lattice constants, α and c, decreased with increasing Mg substitution. The simulation results revealed that the Ca(1) sites in HA lattices were energetically favored sites for Mg substitution. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Xie T.,State Key Laboratory of Coal Mine Disaster Dynamics and Control | Xu L.,State Key Laboratory of Coal Mine Disaster Dynamics and Control | Liu C.,Chongqing University | Wang Y.,Chongqing University
Applied Surface Science | Year: 2013

One-step chemical coprecipitation with high-temperature sintering method was employed for preparing magnetic composite ZnFe2O 4/SrFe12O19 including a hard-magnetic phase (SrFe12O19) and a soft-magnetic phase (ZnFe 2O4). The magnetic composite was characterized by FTIR, XRD, SEM, BET, XPS, VSM, and UV-vis. The testing results showed that the saturation magnetization (Ms), remanent magnetization (M r), and coercivity (Hc) were 34.95 emu/g, 18.31 emu/g, and 2254.54 G, respectively, indicating that the composite possessed excellent magnetic properties and a greater capacity for anti-demagnetize. The properties of the composite were favourable to its separation, recycling, and reuse after reaction. The photocatalytic performance of the composite was studied by the degradation reaction of methylene blue under visible light irradiation. The experimental results revealed that the degradation rate was still more than 70% when the composite was reused for four times. In addition, this research was expected to provide a promising method to prepare various composite materials with multi-functional components. Crown Copyright © 2013 Published by Elsevier B.V. All rights reserved.

Xie T.,State Key Laboratory of Coal Mine Disaster Dynamics and Control | Xu L.,State Key Laboratory of Coal Mine Disaster Dynamics and Control | Liu C.,Chongqing University
Powder Technology | Year: 2012

The composites SrCo xFe 12-xO 19(x=0-0.3) were prepared by coprecipitation high-temperature sintering method with low-cost reagents. The structures and properties of SrCo xFe 12-xO 19 were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) techniques. There were hard magnetic phase (SrFe 12O 19) and soft magnetic phase (CoFe 2O 4) in SrCo xFe 12-xO 19(x=0.05-0.3). The saturation magnetization of SrCo xFe 12-xO 19(x=0.3) was larger than those of SrCo xFe 12-xO 19(x≤0.2). The synthesized composites were fit to act as good magnetic substrate of catalysts. © 2012.

Xin R.,Chongqing University | Ren F.,Hong Kong University of Science and Technology | Leng Y.,Hong Kong University of Science and Technology
Materials and Design | Year: 2010

This study aims to prepare the biologically important hydroxyapatite (HA), dicalcium phosphate dihydrate (DCPD) and dicalcium phosphate anhydrous (DCPA) phases in simple EDTA - assisted hydrothermal method. X-ray diffraction results showed that pure DCPD, DCPA and HA nano-crystals were obtained in the Ca-EDTA/PO4 solutions at 120 °C, 180 °C and 210 °C, respectively. Thermal gravimetric analysis of the DCPD precipitates revealed that phase transformations of DCPD to DCPA and DCPA to HA occurred at 139 °C and 195 °C, respectively, which resulted in the different Ca-P phases during hydrothermal synthesis at different temperature ranges. © 2009 Elsevier Ltd. All rights reserved.

Li F.,Sichuan University | Tang B.,Chongqing University | Yang R.,Sichuan University
Measurement: Journal of the International Measurement Confederation | Year: 2013

A novel fault diagnosis method using dimension reduction with linear local tangent space alignment is proposed in this paper. With this method, the mixed-domain feature set is first constructed to completely characterize the property of each fault by combining Empirical Mode Decomposition (EMD) with the Autoregression (AR) model coefficients. Then, Linear Local Tangent Space Alignment (LLTSA) is used to automatically compress the high-dimensional eigenvectors of training and test samples into the low-dimensional eigenvectors which have better discrimination. By using the tangent space in the neighborhood of a data point to represent the local geometry, and aligning those local tangent spaces in the low-dimensional space (which is linearly mapped from the raw high-dimensional space), LLTSA can not only gain a perfect approximation of low-dimensional intrinsic geometric structure within the high-dimensional observation data, but can also enhance local within-class relations. Finally, the Littlewoods-Paley wavelet support vector machine (LPWSVM) is proposed to perform fault classification with the obtained low-dimensional eigenvectors. Compared with the existing methods, the proposed approach has improved the fault diagnosis precision. The experiments on deep groove ball bearings fault diagnosis demonstrated the advantage and effectiveness of the proposed fault diagnosis approach. © 2013 Elsevier Ltd. All rights reserved.

Huang M.,Chongqing University | Huang M.,Ulsan National Institute of Science and Technology | Zhao X.L.,Chongqing University | Li F.,Chongqing University | And 2 more authors.
Journal of Power Sources | Year: 2015

Ultrathin MnO2 nanosheets arrays on Ni foam have been fabricated by a facile hydrothermal approach and further investigated as the binder-free electrode for high-performance supercapacitors. This unique well-designed binder-free electrode exhibits a high specific capacitance (595.2 F g-1 at a current density of 0.5 A g-1), good rate capability (64.1% retention), and excellent cycling stability (89% capacitance retention after 3000 cycles). Moreover, an asymmetric supercapacitor is constructed using the as-prepared MnO2 nanosheets arrays as the positive electrode and activated microwave exfoliated graphite oxide (MEGO) as the negative electrode. The optimized asymmetric supercapacitor displays excellent electrochemical performance with an energy density of 25.8 Wh kg-1 and a maximum power density of 223.2 kW kg-1. These impressive performances suggest that the MnO2 nanosheet array is a promising electrode material for supercapacitors. © 2014 Elsevier B.V.

Zhang H.,Kunming University of Science and Technology | Wang R.,Chongqing University
Physica B: Condensed Matter | Year: 2011

By using the first-principles calculations based on the density-functional theory (DFT), we study the stability and the nonlinear elasticity of two-dimensional (2D) hexagonal structures of Si and Ge. The reproduced structure optimization and phonondispersion curves demonstrate that Si and Ge can form stable 2D hexagonal lattices with low-buckled structures, and provide a good agreement with the previous DFT calculations. The second- and third-order elastic constants are calculated by using the method of homogeneous deformation. The present results of the linear elastic moduli agree well with the previous results. In comparison with the linear approach, the nonlinear effects really matter while strain is larger than approximately 3.5%. The forcedisplacement behaviors and the breaking strength of 2D hexagonal Si and Ge are discussed using the nonlinear stressstrain relationship. By using the available results of graphene, we reasonably demonstrate that the radius of the atom increases and breaking strength of this element decreases for 2D hexagonal structures of group IV-elements. © 2011 Elsevier B.V. All Rights Reserved.

Tian H.,Jilin University | Yuan R.,Chongqing University | Zhao Y.,Chongqing University
Dianwang Jishu/Power System Technology | Year: 2013

To improve the reliability evaluation efficiency of distribution network containing distributed generation (DG), a network partition-based fault recovery strategy is proposed. Considering the influence of DG on distribution network reliability, a probability distribution model for the reliability of distribution network containing DG and corresponding algorithm are put forward, thus the defect of traditional expectation indices that measure system risk only in the meaning of probabilistic mean values is remedied. Based on the thinking of partitioning of distribution network, the reliability indices of distribution network are characterized by random function in system level and nodal hierarchies, and combining with non-parametric kernel density estimation the probability distribution calculation of random function expression for reliability indices is implemented. Simulation results of RBTS-BUS6 system show that the proposed method is effective.

Roy B.,Florida State University | Hu Z.-X.,Chongqing University | Hu Z.-X.,Princeton University | Yang K.,Florida State University
Physical Review B - Condensed Matter and Materials Physics | Year: 2013

We show through both theoretical arguments and numerical calculations that graphene discerns an unconventional sequence of quantized Hall conductivity, when subject to both magnetic fields (B) and strain. The latter produces time-reversal symmetric pseudo/axial magnetic fields (b). The single-electron spectrum is composed of two interpenetrating sets of Landau levels (LLs), located at ±√2n|b±B|, n=0,1,2,⋯. For b>B, these two sets of LLs have opposite chiralities, resulting in oscillating Hall conductivity between 0 and ∓2e2/h in electron and hole doped systems, respectively, when the chemical potential is tuned in the vicinity of the neutrality point. The electron-electron interactions stabilize various correlated ground states, e.g., spin-polarized, quantum spin Hall insulators at and near the neutrality point, and possibly the anomalous Hall insulating phase at incommensurate filling ∼B. Such broken-symmetry ground states have similarities as well as significant differences from their counterparts in the absence of strain. For realistic strength of magnetic fields and interactions, we present scaling of the interaction-induced gap for various Hall states within the zeroth Landau level. © 2013 American Physical Society.

Zhang H.-F.,Military School of Engineering | Sun Z.,Chongqing University | Sang W.-L.,Southwest University | Sang W.-L.,CAS Institute of Theoretical Physics | Li R.,Xi'an Jiaotong University
Physical Review Letters | Year: 2015

With the recent LHCb data on ηc production and based on heavy quark spin symmetry, we obtain the long-distance matrix elements for both ηc and J/ψ productions, among which, the color-singlet one for ηc is obtained directly by the fit of experiment for the first time. Using our long-distance matrix elements, we can provide good description of the ηc and J/ψ hadroproduction measurements. Our predictions on J/ψ polarization are in good agreement with the LHCb data, explain most of the CMS data, and pass through the two sets of CDF measurements in the medium pt region. Considering all the possible uncertainties carefully, we obtained quite narrow bands of the J/ψ polarization curves. © 2015 American Physical Society.

Su X.,Harbin Institute of Technology | Wu L.,Harbin Institute of Technology | Shi P.,University of South Wales | Shi P.,Victoria University of Melbourne | And 2 more authors.
IEEE Transactions on Systems, Man, and Cybernetics, Part B: Cybernetics | Year: 2012

This paper is concerned with the problem of H∞ model reduction for Takagi-Sugeno (T-S) fuzzy stochastic systems. For a given mean-square stable T-S fuzzy stochastic system, our attention is focused on the construction of a reduced-order model, which not only approximates the original system well with an H∞ performance but also translates it into a linear lower dimensional system. Then, the model reduction is converted into a convex optimization problem by using a linearization procedure, and a projection approach is also presented, which casts the model reduction into a sequential minimization problem subject to linear matrix inequality constraints by employing the cone complementary linearization algorithm. Finally, two numerical examples are provided to illustrate the effectiveness of the proposed methods. © 1996-2012 IEEE.

Zhang C.,Sun Yat Sen University | Huang L.,Chongqing University
Physica A: Statistical Mechanics and its Applications | Year: 2010

Beginning with several basic hypotheses of quantum mechanics, we give a new quantum model in econophysics. In this model, we define wave functions and operators of the stock market to establish the Schrdinger equation for stock price. Based on this theoretical framework, an example of a driven infinite quantum well is considered, in which we use a cosine distribution to simulate the state of stock price in equilibrium. After adding an external field into the Hamiltonian to analytically calculate the wave function, the distribution and the average value of the rate of return are shown. © 2010 Elsevier B.V. All rights reserved.

Wang M.-H.,Chongqing University | Li Y.-F.,Chongqing University | Wang W.-H.,Chongqing University | Zhou J.,Chongqing University | Chiba A.,Tohoku University
Materials and Design | Year: 2013

In this study, the constitutive equation and DRX(Dynamic recrystallization) model of Nuclear Pressure Vessel Material 20MnNiMo steel were established to study the work hardening and dynamic softening behavior based on the flow behavior, which was investigated by hot compression experiment at temperature of 950°C, 1050°C, 1150°C and 1250°C with strain rate of 0.01s-1, 0.1s-1 and 10s-1 on a thermo-mechanical simulator THE RMECMASTOR-Z. The critical conditions for the occurence of dynamic recrystallization were determined based on the strain hardening rate curves of 20MnNiMo steel. Then the model of volume fraction of DRX was established to analyze the DRX behavior based on flow curves. At last, the strain rate sensitivity and activation volume V* of 20MnNiMo steel were calculated to discuss the mechanisms of work hardening and dynamic softening during the hot forming process. The results show that the volume fraction of DRX is lower with the higher value of Z (Zener-Hollomon parameter), which indicated that the DRX fraction curves can accurately predicte the DRX behavior of 20MnNiMo steel. The storage and annihilation of dislocation at off-equilibrium saturation situation is the main reason that the strain has significant effects on SRS(Strain rate sensitivity) at the low strain rate of 0.01s-1 and 0.1s-1. While, the effects of temperature on the SRS are caused by the uniformity of microstructure distribution. And the cross-slip caused by dislocation piled up which beyond the grain boundaries or obstacles is related to the low activation volume under the high Z deformation conditions. Otherwise, the coarsening of DRX grains is the main reason for the high activation volume at low Z under the same strain conditions. © 2012 Elsevier Ltd.

Huang J.,Nanyang Technological University | Wen C.,Nanyang Technological University | Wang W.,Tsinghua University | Song Y.-D.,Chongqing University
Automatica | Year: 2015

In this paper we consider finite-time leaderless consensus control of multi-agent systems consisting of a group of nonlinear mechanical systems with parametric uncertainties. New adaptive finite time continuous distributed control algorithms are proposed for the multi-agent systems. It is shown that the states of the mechanical systems can reach a consensus within finite time under an undirected graph. Transient performances in terms of convergence rates and time are also analyzed. Finally simulation results illustrate and verify the effectiveness of the proposed schemes. © 2014 Elsevier Ltd. All rights reserved.

Guan X.-W.,CAS Wuhan Institute of Physics and Mathematics | Guan X.-W.,Australian National University | Batchelor M.T.,Australian National University | Batchelor M.T.,Chongqing University | And 2 more authors.
Reviews of Modern Physics | Year: 2013

This article reviews theoretical and experimental developments for one-dimensional Fermi gases. Specifically, the experimentally realized two-component delta-function interacting Fermi gas - the Gaudin-Yang model - and its generalizations to multicomponent Fermi systems with larger spin symmetries is discussed. The exact results obtained for Bethe ansatz integrable models of this kind enable the study of the nature and microscopic origin of a wide range of quantum many-body phenomena driven by spin population imbalance, dynamical interactions, and magnetic fields. This physics includes Bardeen-Cooper- Schrieffer-like pairing, Tomonaga-Luttinger liquids, spin-charge separation, Fulde-Ferrel-Larkin-Ovchinnikov-like pair correlations, quantum criticality and scaling, polarons, and the few-body physics of the trimer state (trions). The fascinating interplay between exactly solved models and experimental developments in one dimension promises to yield further insight into the exciting and fundamental physics of interacting Fermi systems. © 2013 American Physical Society.

Mojaza M.,University of Southern Denmark | Mojaza M.,SLAC | Brodsky S.J.,SLAC | Wu X.-G.,Chongqing University
Physical Review Letters | Year: 2013

We introduce a generalization of the conventional renormalization schemes used in dimensional regularization, which illuminates the renormalization scheme and scale ambiguities of perturbative QCD predictions, exposes the general pattern of nonconformal {βi} terms, and reveals a special degeneracy of the terms in the perturbative coefficients. It allows us to systematically determine the argument of the running coupling order by order in perturbative QCD in a form which can be readily automatized. The new method satisfies all of the principles of the renormalization group and eliminates an unnecessary source of systematic error. © 2013 American Physical Society.

Chen X.H.,CAS Shenyang Institute of Metal Research | Chen X.H.,Chongqing University | Lu L.,CAS Shenyang Institute of Metal Research | Lu K.,CAS Shenyang Institute of Metal Research
Scripta Materialia | Year: 2011

We investigate the grain size dependence of tensile behaviors of nanotwinned Cu with fixed twin thickness. With an increased grain size, ductility and work hardening of nanotwinned Cu are effectively promoted, but strength is not sacrificed to any notable degree. This may be attributed to the highly anisotropic plastic deformation of nanoscale twins. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Li J.,Chongqing University | Ma H.,Chongqing University | Lin K.,University of Sao Paulo
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

Using the WKB approximation, massless and massive Dirac quasinormal modes (QNMs) are studied in spherically symmetric regular spacetimes. We analyze the relationships between QNM frequencies and the parameters (angular momentum number l, magnetic monopole charge β, and the mass of the field m) and discuss the extreme charge of magnetic monopole βe for spherically symmetric regular black holes. Furthermore, we apply an expansion method to expand QNMs in inverse powers of L=l+1/2 and confirm good precision with l>n. Finally, we improve the traditional finite difference method to be available in the massive Dirac case and illuminate the dynamical evolution of the massive Dirac field. © 2013 American Physical Society.

Chern R.-L.,National Taiwan University | Han D.,Chongqing University
Optics Express | Year: 2014

Based on the effective medium model, nonlocal optical properties in periodic lattice of graphene layers with the period much less than the wavelength are investigated. Strong nonlocal effects are found in a broad frequency range for TM polarization, where the effective permittivity tensor exhibits the Lorentzian resonance. The resonance frequency varies with the wave vector and coincides well with the polaritonicmode. Nonlocal features are manifest on the emergence of additional wave and the occurrence of negative refraction. By examining the characters of the eigenmode, the nonlocal optical properties are attributed to the excitation of plasmons on the graphene surfaces. © 2014 Optical Society of America.

Brodsky S.J.,SLAC | Wu X.-G.,SLAC | Wu X.-G.,Chongqing University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

A key problem in making precise perturbative QCD predictions is to set the proper renormalization scale of the running coupling. The extended renormalization group equations, which express the invariance of the physical observables under both the renormalization scale- and scheme-parameter transformations, provide a convenient way for estimating the scale- and scheme-dependence of the physical process. In this paper, we present a solution for the scale equation of the extended renormalization group equations at the four-loop level. Using the principle of maximum conformality (PMC)/Brodsky-Lepage-Mackenzie (BLM) scale-setting method, all nonconformal {β i} terms in the perturbative expansion series can be summed into the running coupling, and the resulting scale-fixed predictions are independent of the renormalization scheme. The PMC/BLM scales can be fixed order-by-order. As a useful reference, we present a systematic and scheme-independent procedure for setting PMC/BLM scales up to next-to-next-to-leading order. An explicit application for determining the scale setting of R e+e-(Q) up to four loops is presented. By using the world average αsMS̄(M Z)=0. 1184±0.0007, we obtain the asymptotic scale for the 't Hooft scheme associated with the MS̄ scheme, ΛMS̄′tH=245-10+9MeV, and the asymptotic scale for the conventional MS̄ scheme, Λ MS̄=213-8+19MeV. © 2012 American Physical Society.

Brodsky S.J.,SLAC | Wu X.-G.,SLAC | Wu X.-G.,Chongqing University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

A major contribution to the uncertainty of finite-order perturbative QCD predictions is the perceived ambiguity in setting the renormalization scale μ r. For example, by using the conventional way of setting μ r∈[m t/2,2m t], one obtains the total tt̄ production cross section σ tt̄ with the uncertainty Δσ tt̄/σ tt̄∼ (+3%-4%) at the Tevatron and LHC even for the present next-to next-to-leading-order level. The principle of maximum conformality (PMC) eliminates the renormalization scale ambiguity in precision tests of Abelian QED and non-Abelian QCD theories. By using the PMC, all nonconformal {β i} terms in the perturbative expansion series are summed into the running coupling constant, and the resulting scale-fixed predictions are independent of the renormalization scheme. The correct scale displacement between the arguments of different renormalization schemes is automatically set, and the number of active flavors n f in the {β i} function is correctly determined. The PMC is consistent with the renormalization group property that a physical result is independent of the renormalization scheme and the choice of the initial renormalization scale μrinit. The PMC scale μrPMC is unambiguous at finite order. Any residual dependence on μrinit for a finite-order calculation will be highly suppressed since the unknown higher-order {β i} terms will be absorbed into the PMC scales' higher-order perturbative terms. We find that such renormalization group invariance can be satisfied to high accuracy for σ tt̄ at the next-to next-to-leading-order level. In this paper we apply PMC scale setting to predict the tt̄ cross section σ tt̄ at the Tevatron and LHC colliders. It is found that σ tt̄ remains almost unchanged by varying μrinit within the region of [m t/4,4m t]. The convergence of the expansion series is greatly improved. For the (qq̄) channel, which is dominant at the Tevatron, its next-to-leading-order (NLO) PMC scale is much smaller than the top-quark mass in the small x region, and thus its NLO cross section is increased by about a factor of 2. In the case of the (gg) channel, which is dominant at the LHC, its NLO PMC scale slightly increases with the subprocess collision energy √s, but it is still smaller than m t for √s≲1TeV, and the resulting NLO cross section is increased by ∼20%. As a result, a larger σ tt̄ is obtained in comparison to the conventional scale setting method, which agrees well with the present Tevatron and LHC data. More explicitly, by setting m t=172.9±1.1GeV, we predict σ Tevatron,1.96TeV=7.626-0.257+0.265pb, σ LHC,7TeV=171.8-5.6+5.8pb and σ LHC,14TeV=941.3-26. 5+28.4pb. © 2012 American Physical Society.

Brodsky S.J.,SLAC | Wu X.-G.,SLAC | Wu X.-G.,Chongqing University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

In conventional treatments, predictions from fixed-order perturbative QCD calculations cannot be fixed with certainty because of ambiguities in the choice of the renormalization scale as well as the renormalization scheme. In this paper we present a general discussion of the constraints of the renormalization group (RG) invariance on the choice of the renormalization scale. We adopt the RG-based equations, which incorporate the scheme parameters, for a general exposition of RG invariance, since they simultaneously express the invariance of physical observables under both the variation of the renormalization scale and the renormalization scheme parameters. We then discuss the self-consistency requirements of the RG, such as reflexivity, symmetry, and transitivity, which must be satisfied by the scale-setting method. The principle of minimal sensitivity requires the slope of the approximant of an observable to vanish at the renormalization point. This criterion provides a scheme-independent estimation, but it violates the symmetry and transitivity properties of the RG and does not reproduce the Gell-Mann-Low scale for QED observables. The principle of maximum conformality (PMC) satisfies all of the deductions of the RG invariance-reflectivity, symmetry, and transitivity. Using the PMC, all nonconformal {βiR} terms (R stands for an arbitrary renormalization scheme) in the perturbative expansion series are summed into the running coupling, and one obtains a unique, scale-fixed, scheme-independent prediction at any finite order. The PMC scales and the resulting finite-order PMC predictions are both to high accuracy independent of the choice of initial renormalization scale, consistent with RG invariance. Moreover, after PMC scale setting, the residual initial scale dependence at fixed order owing to unknown higher-order {β i} terms can be substantially suppressed. The PMC thus eliminates a serious systematic scale error in perturbative quantum chromodynamics predictions, greatly improving the precision of tests of the Standard Model and the sensitivity to new physics at collider and other experiments. © 2012 American Physical Society.

Su X.,Harbin Institute of Technology | Shi P.,University of South Wales | Shi P.,Victoria University of Melbourne | Shi P.,University of South Australia | And 2 more authors.
IEEE Transactions on Fuzzy Systems | Year: 2012

In this paper, the problem of l2-l? filtering for a class of discrete-time Takagi-Sugeno (T-S) fuzzy time-varying delay systems is studied. Our attention is focused on the design of full-and reduced-order filters that guarantee the filtering error system to be asymptotically stable with a prescribed H? performance. Sufficient conditions for the obtained filtering error system are proposed by applying an input-output approach and a two-term approximation method, which is employed to approximate the time-varying delay. The corresponding full-and reduced-order filter design is cast into a convex optimization problem, which can be efficiently solved by standard numerical algorithms. Finally, simulation examples are provided to illustrate the effectiveness of the proposed approaches. © 2012 IEEE.

Brodsky S.J.,SLAC | Wu X.-G.,SLAC | Wu X.-G.,Chongqing University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

The renormalization scale uncertainty can be eliminated by the principle of maximum conformality (PMC) in a systematic, scheme-independent way. Applying the PMC for the tt̄-pair hadroproduction at the next-to-next-to-leading- order level, we have found that the total cross sections σ tt̄ at both the Tevatron and LHC remain almost unchanged when taking very disparate initial scales μRinit equal to m t, 10m t, 20m t and √s, which is consistent with renormalization group invariance. As an important new application, we apply PMC scale setting to study the top quark forward-backward asymmetry. We observe that the more convergent perturbative series after PMC scale-setting leads to a more accurate top quark forward-backward asymmetry. The resulting PMC prediction on the asymmetry is also free from the initial renormalization scale dependence. Because the next-to-leading-order PMC scale has a dip behavior for the (qq̄) channel at small subprocess collision energies, the importance of this channel to the asymmetry is increased. We observe that the asymmetries AFBtt̄ and AFBpp̄ at the Tevatron will be increased by 42% in comparison to the previous estimates obtained by using conventional scale setting; i.e., we obtain AFBtt̄,PMC12.5% and AFBpp̄,PMC8.28%. Moreover, we obtain AFBtt̄,PMC(M tt̄>450GeV)35.0%. These predictions have a 1σ deviation from the present CDF and D0 measurements; the large discrepancies of the top quark forward-backward asymmetry between the standard model estimate and the CDF and D0 data are thus greatly reduced. © 2012 American Physical Society.

Zhang X.,City University of Hong Kong | Wu Y.,Zhejiang University | Shen L.,Chongqing University | Skitmore M.,Queensland University of Technology
International Journal of Project Management | Year: 2014

There is a worldwide demand for an increasingly sustainable built environment. This has resulted in the need for a more accurate evaluation of the level of sustainability of construction projects. To do this it involves the development of better measurement and benchmarking methods. One approach is to use a theoretical model to assess construction projects in terms of their sustainable development value (SDV) and sustainable development ability (SDA) for implementation in the project life cycle, where SDA measures the contribution of a project to development sustainability and as a major criterion for assessing its feasibility.This paper develops an improved SDA prototype model that incorporates the effects of dynamical factors on project sustainability. This involves the introduction of two major factors concerning technological advancement and changes in people's perceptions. A case study is used to demonstrate the procedures involved in simulation and modeling, one outcome of which is to demonstrate the greater influence of technological advancement on project sustainability than changes in perception. © 2013 Elsevier Ltd and IPMA.

Zhou X.,University of Sichuan | Xiao T.,University of Sichuan | Iwama Y.,Tohoku University | Qin Y.,University of Sichuan | Qin Y.,Chongqing University
Angewandte Chemie - International Edition | Year: 2012

Challenging: (+)-gelsemine was synthesized from (R,R)-aziridine 1 in 25 steps with approximately 1% overall yield. A multistep, one-pot enol-oxonium cyclization cascade was used to construct, simultaneously, the E ring, F ring, C3 stereocenter, and C7 quaternary stereocenter. This synthesis using the enol-oxonium cyclization reaction as a key step to make the cage structure has demonstrated the proposed biosynthetic pathway of the gelsemine family. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Huang B.,Tsinghua University | Li C.,Tsinghua University | Yin C.,Chongqing University | Zhao X.,NDTech Co.
International Journal of Advanced Manufacturing Technology | Year: 2013

In order to address the key problems faced by small- and medium-sized enterprises (SMEs), existing solutions and shortcomings were analyzed. The possibilities by using the new emerged technologies and theories (e.g., cloud computing, internet of things, service-oriented technology) to solve the bottlenecks faced by SMEs are investigated. The idea of manufacturing resource and capability sharing based on cloud computing for SME is discussed, and an SME-oriented cloud manufacturing service platform (SME-CMfgSP) is introduced. The architecture of SME-CMfgSP is proposed, and the key technologies for implementing SME-CMfgSP are introduced in details. The challenges for implementing cloud manufacturing service platform for SMEs were discussed. A case study is described to illustrate the application of the proposed SME-CMfgSP. © 2012 Springer-Verlag London Limited.

Luo J.R.,Tsinghua University | Godfrey A.,Tsinghua University | Liu W.,Tsinghua University | Liu Q.,Chongqing University
Acta Materialia | Year: 2012

The twinning behavior of a strongly basal textured magnesium alloy AZ31 plate during warm rolling to a reduction of 9% has been investigated. Analysis of the twin types and twin variants was carried out based on orientation data collected using electron backscatter diffraction. Double twins (corresponding to contraction twinning followed by extension twinning) were the most commonly observed twin type, with more than 70% of the grains examined containing this type of twin. The double twin variant with a 38° misorientation to the original grain orientation was the most frequently observed, with the 30° variant being the next most frequently observed. The twinning variant selection was analyzed using both a modified Schmid factor for rolling and by use of normal strain maps, used to show the compatibility between the normal strains due to twinning and the applied rolling deformation. It was found that the 38° and 30° misorientation double twin variants provide normal strains that are similarly compatible with the applied deformation, with a slight advantage for the 30° variant. Overall, the results show that for rolling deformation external strain accommodation, rather than self-strain accommodation, is the dominant factor in determining the variant types of the double twins formed during warm rolling. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Bian L.,Chongqing University | Bian L.,CAS Institute of Theoretical Physics | Chen N.,Anhui University of Science and Technology | Liu D.,CAS Institute of Theoretical Physics | And 2 more authors.
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2016

We explain the recent diphoton excesses around 750 GeV by both ATLAS and CMS as a singlet scalar Φ which couples to SM gluon and neutral gauge bosons only through higher-dimensional operators. A natural explanation is that Φ is a pseudo-Nambu-Goldstone boson (pNGB) which receives parity violation through anomaly if there exists a hidden strong dynamics. The singlet and other light pNGBs will decay into two SM gauge bosons and even serves as the metastable colored states which can be probed in the future. By accurately measuring their relative decay and the total production rate in the future, we will learn the underlying strong dynamics parameter. The lightest baryon in this confining theory could serve as a viable dark matter candidate. © 2016 American Physical Society.

Brodsky S.J.,SLAC | Wu X.-G.,SLAC | Wu X.-G.,Chongqing University
Physical Review Letters | Year: 2012

It is conventional to choose a typical momentum transfer of the process as the renormalization scale and take an arbitrary range to estimate the uncertainty in the QCD prediction. However, predictions using this procedure depend on the renormalization scheme, leave a nonconvergent renormalon perturbative series, and moreover, one obtains incorrect results when applied to QED processes. In contrast, if one fixes the renormalization scale using the principle of maximum conformality (PMC), all nonconformal {β i} terms in the perturbative expansion series are summed into the running coupling, and one obtains a unique, scale-fixed, scheme-independent prediction at any finite order. The PMC scale μRPMC and the resulting finite-order PMC prediction are both to high accuracy independent of the choice of initial renormalization scale μRinit, consistent with renormalization group invariance. As an application, we apply the PMC procedure to obtain next-to-next-to-leading-order (NNLO) predictions for the tt̄-pair production at the Tevatron and LHC colliders. The PMC prediction for the total cross section σ tt̄ agrees well with the present Tevatron and LHC data. We also verify that the initial scale independence of the PMC prediction is satisfied to high accuracy at the NNLO level: the total cross section remains almost unchanged even when taking very disparate initial scales μRinit equal to m t, 20m t, and √s. Moreover, after PMC scale setting, we obtain AFBtt̄ 12.5%, AFBpp̄ 8.28% and AFBtt̄(M tt̄>450GeV) 35.0%. These predictions have a 1σ deviation from the present CDF and D0 measurements; the large discrepancy of the top quark forward-backward asymmetry between the standard model estimate and the data are, thus, greatly reduced. © 2012 American Physical Society.

Peng G.H.,University of Science and Arts of Iran | Peng G.H.,Chongqing University | Sun D.H.,Chongqing University
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2010

An improved multiple car-following (MCF) model is proposed, based on the full velocity difference (FVD) model, but taking into consideration multiple information inputs from preceding vehicles. The linear stability condition of the model is obtained by using the linear stability theory. Through nonlinear analysis, the modified Korteweg-de Vries (mKdV) equation is derived to describe the traffic behavior near the critical point. Numerical simulation shows that the proposed model is theoretically an improvement over others, while retaining many strong points in the previous ones by adjusting the information of the multiple leading vehicles. © 2010 Elsevier B.V. All rights reserved.

Yang X.-H.,Chinese Academy of Sciences | Yang X.-H.,Chongqing University | Yuan F.,Chinese Academy of Sciences | Ohsuga K.,Japan National Astronomical Observatory | Bu D.-F.,Chinese Academy of Sciences
Astrophysical Journal | Year: 2014

We study the dynamics of super-Eddington accretion flows by performing two-dimensional radiation-hydrodynamic simulations. Compared with previous works, in this paper we include the T θφ component of the viscous stress and consider various values of the viscous parameter α. We find that when T θφ is included, the rotational speed of the high-latitude flow decreases, while the density increases and decreases at the high and low latitudes, respectively. We calculate the radial profiles of inflow and outflow rates. We find that the inflow rate decreases inward, following a power law form of . The value of s depends on the magnitude of α and is within the range of ∼0.4-1.0. Correspondingly, the radial profile of density becomes flatter compared with the case of a constant . We find that the density profile can be described by ρ(r)∝r -p and the value of p is almost same for a wide range of α ranging from α = 0.1 to 0.005. The inward decrease of inflow accretion rate is very similar to hot accretion flows, which is attributed to the mass loss in outflows. To study the origin of outflow, we analyze the convective stability of the slim disk. We find that depending on the value of α, the flow is marginally stable (when α is small) or unstable (when α is large). This is different from the case of hydrodynamical hot accretion flow, where radiation is dynamically unimportant and the flow is always convectively unstable. We speculate that the reason for the difference is because radiation can stabilize convection. The origin of outflow is thus likely because of the joint function of convection and radiation, but further investigation is required. © 2014. The American Astronomical Society. All rights reserved.

Feng G.,amician Delluniversita | Gou Q.,amician Delluniversita | Evangelisti L.,amician Delluniversita | Xia Z.,Chongqing University | Caminati W.,amician Delluniversita
Physical Chemistry Chemical Physics | Year: 2013

The bimolecule acrylic acid-formic acid has been investigated by pulsed jet Fourier transform microwave spectroscopy. The complex adopts two different conformational shapes, according to the cis or trans forms of the acrylic acid moiety. The measurements have been extended to four deuterated and to four 13C (natural abundance) species, and their combinations, for each conformer. These data allowed us to determine the carbon skeleton structures and to size quantitatively the structural effect caused by the OH → OD isotopic substitutions (the Ubbelohde effect).© 2013 the Owner Societies.

Huang M.,Chongqing University | Zhang Y.,Chongqing University | Li F.,Chongqing University | Zhang L.,Institute of Chemical and Engineering Sciences, Singapore | And 2 more authors.
Journal of Power Sources | Year: 2014

Hierarchical Co3O4@MnO2 core-shell arrays on Ni foam have been fabricated by a facile hydrothermal approach and further investigated as the electrode for high-performance supercapacitors. Owing to the high conductivity of the well-defined mesoporous Co3O4 nanowire arrays in combination with the large surface area provided by the ultrathin MnO2 nanosheets, the unique designed Co3O 4@MnO2 core-shell arrays on Ni foam have exhibited a high specific capacitance (560 F g-1 at a current density of 0.2 A g -1), good rate capability, and excellent cycling stability (95% capacitance retention after 5000 cycles). An asymmetric supercapacitor with Co3O4@MnO2 core-shell nanostructure as the positive electrode and activated microwave exfoliated graphite oxide activated graphene (MEGO) as the negative electrode yielded an energy density of 17.7 Wh kg-1 and a maximum power density of 158 kW kg-1. The rational design of the unique core-shell array architectures demonstrated in this work provides a new and facile approach to fabricate high-performance electrode for supercapacitors. © 2013 Elsevier B.V. All rights reserved.

Huang X.,Tsinghua University | Zhang W.,Tsinghua University | Wang J.,Chongqing University | Wei W.,Chongqing University
Journal of Alloys and Compounds | Year: 2012

A high number of dislocations have been observed in an as-cast high-damping Mg-3Cu-1Mn-2Zn-1Y (wt.%) alloy using transmission electron microscope (TEM). The majority of dislocations are distributed in parallel and uniform rows. Mg 2Cu particles in the matrix are often found to be associated with a number of parallel dislocations. Twins containing stacking faults are also frequently observed. The formation of eutectic phases occurring during casting is followed by precipitation of secondary intermetallic phases in supersaturated α-Mg with alloying elements upon annealing. The observed defect structures provide useful experimental evidence supporting the previously proposed damping mechanism for Mg alloys. © 2011 Elsevier B.V. All rights reserved.

Brodsky S.J.,SLAC | Mojaza M.,SLAC | Mojaza M.,University of Southern Denmark | Wu X.-G.,Chongqing University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

We present in detail a new systematic method which can be used to automatically eliminate the renormalization scheme and scale ambiguities in perturbative QCD predictions at all orders. We show that all of the nonconformal β-dependent terms in a QCD perturbative series can be readily identified by generalizing the conventional renormalization schemes based on dimensional regularization. We then demonstrate that the nonconformal series of pQCD at any order can be resummed systematically into the scale of the QCD coupling in a unique and unambiguous way due to a special degeneracy of the β terms in the series. The resummation follows from the principal of maximum conformality (PMC) and assigns a unique scale for the running coupling at each perturbative order. The final result is independent of the initial choices of renormalization scheme and scale, in accordance with the principles of the renormalization group, and thus eliminates an unnecessary source of systematic error in physical predictions. We exhibit several examples known to order αs4; i.e. (i) the electron-positron annihilation into hadrons, (ii) the tau-lepton decay to hadrons, (iii) the Bjorken and Gross-Llewellyn Smith (GLS) sum rules, and (iv) the static quark potential. We show that the final series of the first three cases are all given in terms of the anomalous dimension of the photon field in SU(N), in accordance with conformality, and with all nonconformal properties encoded in the running coupling. The final expressions for the Bjorken and GLS sum rules directly lead to the generalized Crewther relations, exposing another relevant feature of conformality. The static quark potential shows that PMC scale-setting in the Abelian limit is to all orders consistent with QED scale-setting. Finally, we demonstrate that the method applies to any renormalization scheme and can be used to derive commensurate scale relations between measurable effective charges, which provide nontrivial tests of QCD to high precision. This work extends Brodsky-Lepage-Mackenzie (BLM) scale-setting to any perturbative order, with no ambiguities in identifying β terms in pQCD, demonstrating that BLM scale-setting follows from a principle of maximum conformality. © 2014 American Physical Society.

Wang S.-Q.,Chongqing University | Wu X.-G.,Chongqing University | Brodsky S.J.,SLAC
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

A complete calculation of the O(αs4) perturbative quantum chromodynamics (pQCD) corrections to the hadronic decay width of the Z boson has recently been performed by Baikov et al. [Phys. Rev. Lett. 108, 222003 (2012)]. In their analysis, Baikov et al. relied on the conventional practice of simply guessing the renormalization scale and taking an arbitrary range to estimate the pQCD uncertainties. This procedure inevitably introduces an arbitrary, scheme-dependent theoretical systematic error in the predictions. In this paper, we show that the renormalization scale uncertainties for hadronic Z decays can be greatly reduced by applying the principle of maximum conformality (PMC), a rigorous extension of the Brodsky-Lepage-Mackenzie method. The PMC prediction is independent of the choice of renormalization scheme; i.e., it respects renormalization group invariance, and thus it provides an optimal and theoretically rigorous method for setting the renormalization scale. We show that the convergence of the pQCD prediction for the Z hadronic width is greatly improved using the PMC since the divergent renormalon series does not appear. The magnitude of the high-order corrections quickly approach a steady point. The PMC predictions also have the property that any residual dependence on the choice of initial scale is highly suppressed, even for low-order predictions. Thus, one obtains optimal fixed-order predictions for the Z-boson hadronic decay rates thus enabling high precision tests of the Standard Model. © 2014 American Physical Society.

Wang X.-Y.,Chongqing University | Wu X.-G.,Chongqing University | Wu X.-G.,SLAC
Computer Physics Communications | Year: 2012

In the present paper, we provide an addendum to improve the efficiency of generating unweighted events within PYTHIA environment for the generator BCVEGPY2.1 [C.H. Chang, J.X. Wang, X.G. Wu, Comput. Phys. Commun. 174 (2006) 241]. This trick is helpful for experimental simulation. Moreover, the BCVEGPY output has also been improved, i.e. one Les Houches Event common block has been added so as to generate a standard Les Houches Event file that contains the information of the generated Bc meson and the accompanying partons, which can be more conveniently used for further simulation. © 2011 Elsevier B.V. All rights reserved.

Zhong J.,Chongqing University | Li X.,Queensland University of Technology
Expert Systems with Applications | Year: 2010

Collaborative filtering (CF) has been studied extensively in the literature and is demonstrated successfully in many different types of personalized recommender systems. In this paper, we propose a unified method combining the latent and external features of users and items for accurate recommendation. A mapping scheme for collaborative filtering problem to text analysis problem is introduced, and the probabilistic latent semantic analysis was used to calculate the latent features based on the historical rating data. The main advantages of this technique over standard memory-based methods are the higher accuracy, constant time prediction, and an explicit and compact model representation. The experimental evaluation shows that substantial improvements in accuracy over existing methods can be obtained. © 2010 Elsevier Ltd. All rights reserved.

Wang M.,Queensland University of Technology | Hu N.,Chongqing University | Zhou L.,Hong Kong Polytechnic University | Yan C.,Queensland University of Technology
Carbon | Year: 2015

Thermal transport in graphene-polymer nanocomposite is complicated and has not been well understood. The interfacial thermal transport between graphene nanofiller and polymer matrix is expected to play a key role in controlling the overall thermal performance of graphene-polymer nanocomposite. In this work, we investigated the thermal transport across graphene-polymer interfaces functionalized with end-grafted polymer chains using molecular dynamics simulations. The effects of grafting density, chain length and initial morphology on the interfacial thermal transport were systematically investigated. It was found that end-grafted polymer chains could significantly enhance interfacial thermal transport and the underlying mechanism was considered to be the enhanced vibration coupling between graphene and polymer. In addition, a theoretical model based on effective medium theory was established to predict the thermal conductivity in graphene-polymer nanocomposites. © 2015 Elsevier Ltd. All rights reserved.

Zeng W.,Chongqing University | Liu T.,Chongqing University | Wang Z.,Tohoku University
Sensors and Actuators, B: Chemical | Year: 2012

Using a simple hydrothermal method, the pristine and Nb doped TiO 2 is prepared, and their microstructures and gas-sensing responses to the harmful volatile organic compounds are investigated with a special focus on the impact of Nb additive. We find that the gas response of TiO 2 is enhanced significantly by doping Nb, which is understood in theory upon proposed adsorption models. Combining experimental measurements with first-principles calculations, the working mechanism underlying such improvement in gas-sensing functions by the Nb additive is discussed. © 2012 Elsevier B.V. All rights reserved.

Li X.,Chongqing University | Li X.,CAS Institute of High Energy Physics | Li X.,CAS Institute of Theoretical Physics | Chang Z.,CAS Institute of High Energy Physics | Chang Z.,CAS Institute of Theoretical Physics
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

We suggest that the vacuum field equation in Finsler spacetime is equivalent to the vanishing of the Ricci scalar. The Schwarzschild metric can be deduced from a solution of our field equation if the spacetime preserves spherical symmetry. Supposing that the spacetime preserves the symmetry of the "Finslerian sphere," we find a non-Riemannian exact solution of the Finslerian vacuum field equation. The solution is similar to the Schwarzschild metric. It reduces to the Schwarzschild metric as the Finslerian parameter ε vanishes. It is proven that the Finslerian covariant derivative of the geometrical part of the gravitational field equation is conserved. The interior solution is also given. We get solutions of the geodesic equation in such a Schwarzschild-like spacetime, and show that the geodesic equation returns to its counterpart in Newtonian gravity in the weak-field approximation. Celestial observations give a constraint on the Finslerian parameter ε<10-4, and the recent Michelson-Morley experiment requires ε<10-16. A counterpart of Birkhoff's theorem exists in the Finslerian vacuum. This shows that the Finslerian gravitational field with the symmetry of the "Finslerian sphere" in vacuum must be static. © 2014 American Physical Society.

Luo S.,Chongqing University | Luo S.,University of Science and Arts of Iran
Chaos | Year: 2014

This paper is concerned with the problem of adaptive fuzzy dynamic surface control (DSC) for the permanent magnet synchronous motor (PMSM) system with chaotic behavior, disturbance and unknown control gain and parameters. Nussbaum gain is adopted to cope with the situation that the control gain is unknown. And the unknown items can be estimated by fuzzy logic system. The proposed controller guarantees that all the signals in the closed-loop system are bounded and the system output eventually converges to a small neighborhood of the desired reference signal. Finally, the numerical simulations indicate that the proposed scheme can suppress the chaos of PMSM and show the effectiveness and robustness of the proposed method. © 2014 AIP Publishing LLC.

Zeng W.,Chongqing University | Liu T.,Chongqing University | Wang Z.,Tohoku University
Journal of Materials Chemistry | Year: 2012

We report synthesis of hierarchical nanostructures of SnO 2 nanosphere functionalized TiO 2 nanobelts as a novel sensing material by a simple hydrothermal technique. A systematic comparison study reveals an enhanced gas sensing performance for the sensor made of SnO 2 and TiO 2 toward volatile organic compounds of several species over that of the commonly applied undecorated TiO 2 nanobelts. The improved gas sensing properties are attributed to the pronounced electron transfer between the hierarchical nanostructures and the absorbed oxygen species as well as to the heterojunctions of the SnO 2 nanospheres to the TiO 2 nanobelts which provide additional reaction rooms. The results represent an advance of hierarchical nanostructures in further enhancing the functionality of gas sensors, and this facile method could be applicable to many sensing materials. © 2012 The Royal Society of Chemistry.

Wu X.-G.,Chongqing University | Brodsky S.J.,SLAC | Mojaza M.,SLAC | Mojaza M.,University of Southern Denmark
Progress in Particle and Nuclear Physics | Year: 2013

A key problem in making precise perturbative QCD predictions is to set the proper renormalization scale of the running coupling. The conventional scale-setting procedure assigns an arbitrary range and an arbitrary systematic error to fixed-order pQCD predictions. In fact, this ad hoc procedure gives results which depend on the choice of the renormalization scheme, and it is in conflict with the standard scale-setting procedure used in QED. Predictions for physical results should be independent of the choice of the scheme or other theoretical conventions. We review current ideas and points of view on how to deal with the renormalization scale ambiguity and show how to obtain renormalization scheme- and scale-independent estimates. We begin by introducing the renormalization group (RG) equation and an extended version, which expresses the invariance of physical observables under both the renormalization scheme and scale-parameter transformations. The RG equation provides a convenient way for estimating the scheme- and scale-dependence of a physical process. We then discuss self-consistency requirements of the RG equations, such as reflexivity, symmetry, and transitivity, which must be satisfied by a scale-setting method. Four typical scale setting methods suggested in the literature, i.e., the Fastest Apparent Convergence (FAC) criterion, the Principle of Minimum Sensitivity (PMS), the Brodsky-Lepage-Mackenzie method (BLM), and the Principle of Maximum Conformality (PMC), are introduced. Basic properties and their applications are discussed. We pay particular attention to the PMC, which satisfies all of the requirements of RG invariance. Using the PMC, all non-conformal terms associated with the β-function in the perturbative series are summed into the running coupling, and one obtains a unique, scale-fixed, scheme-independent prediction at any finite order. The PMC provides the principle underlying the BLM method, since it gives the general rule for extending BLM up to any perturbative order; in fact, they are equivalent to each other through the PMC-BLM correspondence principle. Thus, all the features previously observed in the BLM literature are also adaptable to the PMC. The PMC scales and the resulting finite-order PMC predictions are to high accuracy independent of the choice of the initial renormalization scale, and thus consistent with RG invariance. The PMC is also consistent with the renormalization scale-setting procedure for QED in the zero-color limit. The use of the PMC thus eliminates a serious systematic scale error in perturbative QCD predictions, greatly improving the precision of empirical tests of the Standard Model and their sensitivity to new physics. © 2013 Elsevier B.V. All rights reserved.

Tao Z.,Chongqing University | Zhang S.,Chongqing University | Li W.,CAS Qingdao Institute of Oceanology | Hou B.,CAS Qingdao Institute of Oceanology
Industrial and Engineering Chemistry Research | Year: 2011

The triazole-acetate derivative TMCA was synthesized and its inhibiting action on the corrosion of mild steel in sulphuric acid was investigated by means of weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and scanning electronic microscope (SEM). The potentiodynamic polarization measurements show that the TMCA acts essentially as a mixed-type inhibitor, and EIS confirmed that changes in the impedance parameters were due to surface adsorption. The inhibition efficiencies (IE%) obtained from weight loss measurement and electrochemical tests were in good agreement. Substitutional inhibition mechanism of mild steel was established according to the fitted results at different temperatures. The number of water molecules (X) replaced by a molecule of organic adsorbate was determined from the different substitutional adsorption isotherms applied to the data obtained from weight loss experiments. © 2011 American Chemical Society.

Zhu J.,Rice University | Cao L.,Rice University | Cao L.,Chongqing University | Wu Y.,Rice University | And 10 more authors.
Nano Letters | Year: 2013

Various two-dimensional (2D) materials have recently attracted great attention owing to their unique properties and wide application potential in electronics, catalysis, energy storage, and conversion. However, large-scale production of ultrathin sheets and functional nanosheets remains a scientific and engineering challenge. Here we demonstrate an efficient approach for large-scale production of V2O5 nanosheets having a thickness of 4 nm and utilization as building blocks for constructing 3D architectures via a freeze-drying process. The resulting highly flexible V 2O5 structures possess a surface area of 133 m2 g-1, ultrathin walls, and multilevel pores. Such unique features are favorable for providing easy access of the electrolyte to the structure when they are used as a supercapacitor electrode, and they also provide a large electroactive surface that advantageous in energy storage applications. As a consequence, a high specific capacitance of 451 F g-1 is achieved in a neutral aqueous Na2SO4 electrolyte as the 3D architectures are utilized for energy storage. Remarkably, the capacitance retention after 4000 cycles is more than 90%, and the energy density is up to 107 W·h·kg-1 at a high power density of 9.4 kW kg -1. © 2013 American Chemical Society.

Zhang X.,Tsinghua University | Zhang X.,Technical University of Denmark | Godfrey A.,Tsinghua University | Huang X.,Technical University of Denmark | And 2 more authors.
Acta Materialia | Year: 2011

Strengthening mechanisms and strength-structure relationships have been analyzed in a cold-drawn pearlitic steel with a structural scale in the nanometer range and a flow stress of about 3.5 GPa. The wires have been drawn up to a strain of 3.7 and the structures analyzed and quantified by transmission electron microscopy and high resolution electron microscopy. The mechanical properties have been determined by tensile testing. It is found that the interlamellar spacing and the thickness of the cementite lamellae are reduced in accordance with the changes in wire diameter up to a strain of 2.5. At a higher strain enhanced thinning of the cementite lamellae points to decomposition of the cementite and carbon enrichment of the ferrite lamellae. Dislocations are stored in the interior of the ferrite lamellae and their density increases to about 2 × 1016 m-2. A high dislocation density is also observed at the ferrite/cementite interface. Three strengthening mechanisms have been analyzed: (i) boundary strengthening, (ii) dislocation strengthening and (iii) solid solution hardening. The individual and combined contributions, based on an assumption of linear additivity, of these mechanisms to the wire strength have been estimated. Good agreement has been found between the estimated and the measured flow stresses, which is followed up by a discussion of structure and strengthening mechanisms with a view to extrapolation to larger strains, finer structures and larger stresses. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Yuan L.,Chongqing University | Yuan L.,Tohoku University | Sakamoto N.,Kawasaki University of Medical Welfare | Song G.,Chongqing University | Sato M.,Tohoku University
Stem Cells and Development | Year: 2013

Mesenchymal stem cells (MSCs) are able to home and migrate into damaged tissues and are thus, considered an optimal therapeutic strategy for clinical use. We previously demonstrated that higher shear stress (>2 Pa) hindered human MSC (hMSC) migration, whereas lower shear stress (0.2 Pa) induced cell migration through mitogen-activated protein kinase (MAPK) pathways. Here the mechanisms underlying shear stress-induced hMSC migration have been studied further. An MSC monolayer was mechanically wounded and subsequently exposed to low-level shear stress of 0.2 Pa. Image analysis was performed to quantify cell migration speeds under both flow and static conditions. hMSCs along both upstream- and downstream edges of the wound migrated at a similar speed to cover the wounded area under static conditions, whereas shear stress induced cells along the downstream edge of the wound to migrate significantly faster than those along the upstream edge. We also found that shear stress upregulated the secretion of stromal-derived factor-1 (SDF-1), which stimulated its receptor CXCR4 expression in hMSCs until the cells covered the wounded area. A CXCR4 antagonist repressed both cell migration and activation of c-Jun N-terminal kinase (JNK) and p38 MAPK but did not affect extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation. When MAPK activation in upstream- and downstream hMSCs was evaluated separately, ERK1/2 was activated earlier in downstream than in upstream cells. These results indicate that the SDF-1/CXCR4 axis mediates shear stress-induced hMSC migration through JNK and p38 MAPK pathways and that the difference in migration speeds between upstream- and downstream cells may be due to ERK1/2 activation. © Mary Ann Liebert, Inc.

Li J.,Chongqing University | Jiang T.,Chongqing University | Wang C.,Wayne State University | Cheng C.,Chongqing University
IEEE Transactions on Antennas and Propagation | Year: 2012

Partial discharge (PD) online monitoring is an effective tool of inspecting insulation defects and identifying potential faults in power transformers. Ultra-high-frequency (UHF) approaches have caught increasing attention recently and been considered as a promising technology for online monitoring PD signals. The size of a UHF sensor for PD online monitoring of transformer is a critical factor for practical installation inside transformer. This communication presents a compact fourth order UHF Hilbert fractal antenna with desired performance and suitable size for easy installation. Actual PD experiments were carried out for four typical artificial insulation defect models while the antenna was used for PD measurements. The experimental results show that the proposed Hilbert fractal antenna is suitable and effective for UHF online monitoring of PDs in transformers. © 2012 IEEE.

Huang M.,Chongqing University | Li F.,Chongqing University | Dong F.,Chongqing Technology and Business University | Zhang Y.X.,Chongqing University | Zhang L.L.,Institute of Chemical and Engineering Sciences, Singapore
Journal of Materials Chemistry A | Year: 2015

MnO2-based materials have been intensively investigated for use in pseudocapacitors due to their high theoretical specific capacitance, good chemical and thermal stability, natural abundance, environmental benignity and low cost. In this review, several main factors that affect the electrochemical properties of MnO2-based electrodes are presented. Various strategic design and synthetic methods of MnO2-based electrode materials for enhanced electrochemical performance are highlighted and summarized. Finally, the challenges and future directions toward the development of MnO2-based nanostructured electrode materials for high performance supercapacitors (SCs) are discussed. © The Royal Society of Chemistry 2015.

News Article | December 7, 2015

« ContiTech develops first polyamide strut mount for Cadillac chassis vibration control; 25% lighter | Main | UCLA–UC Berkeley paper outlines how CA can boost biofuel production to cut pollution and help the economy » Researchers at Fudan University, with colleagues at the University of Jinan and Chongqing University, have developed alkali- and sulfur-resistant tungsten-based catalysts for SCR NO emissions control. A paper on their work is published in the ACS journal Environmental Science & Technology. Alkali metals and sulfur oxides are two kinds of the well-known poisons of catalysts used in the selective catalytic reduction (SCR) of NO with NH from both stationary and mobile sources. At the 2015 AIChE Annual Meeting in Houston last month, Yasser Jangjou and William Epling presented a paper on sulfur poisoning of the SCR reaction, noting that sulfur is a common automotive catalyst poison even for the newer metal-exchanged small pore zeolite selective catalytic reduction (SCR) catalysts. In 2013, a team from NREL, Oak Ridge National Laboratory, Ford, MECA (Manufacturers of Emission Controls Association) and the University of Tennessee - Knoxville published an SAE paper investigating the impact of alkali (e.g., Na and K) and alkaline earth metals impurities in a light-duty application. They found that alkali metals are volatile at temperatures typically seen in diesel exhaust, allowing them to migrate into the catalyst washcoat leading to catalyst deactivation. However, they also found that there was sufficient unaltered catalyst volume to maintain mandated NO emission levels on the dynamometer after the simulated equivalent of 150,000 miles of exposure. I.e., by loading enough catalyst into the system, the deactivation problem can be managed. In the new work out of China, the researchers note that: Catalysts with acidic V O as an active component are proven to have an excellent resistance against SO poisoning than other “basic” metal oxides such as M O , CuO, CeO , and so on, although the vanadium-based catalysts are prone to poisoning by alkalis due largely to their strong acidity. … In this work, we develop a V O /HWO catalyst with strong resistance simultaneously to alkalis and SO poisoning. Two acidic oxides with strong resistance to SO poisoning, V O and HWO, are designed as an active component and a support, respectively. The HWO have rich size-suitable alkali-trapping sites with high specificity, and can professionally trap alkalis in the presence of high-concentration SO , even though alkalis are initially accumulated on the V O surfaces under normal SCR conditions. Testing showed that the V O /HWO catalyst exhibited strong resistance to alkali poisoning, and the catalysts with high K+ loading of 350 μmol g−1 did not decrease their high SCR activity even in the presence of the high-concentration SO , whereas conventional V O /WO −TiO catalysts almost completely lost SCR activity under the same conditions. The experimental results coupled with theoretical calculations demonstrated that the strong resistance of the V2O5/HWO catalysts to alkali and sulfur poisoning mainly originated from the specific alkali- trapping sites of the HWO. Alkalis accumulated on the catalytically active surface sites of the V O /HWO catalysts could spontaneously migrate into the HWO tunnels during the SCR reactions, and arrived at a separate state from the catalytically active sites, thus leading to simultaneous resistance to alkalis and SO poisoning. Therefore, the V O /HWO catalysts with a hexagonal structure of WO are promising candidates for controlling NO emissions from the stationary source and the mobile source against alkali and sulfur poisoning.

News Article | September 20, 2016

A piece of fabric woven with special strands of material that harvest electricity from the sun and motion. A fabric designed to power wearable devices by harvesting energy from both sunlight and body movements can be produced on a standard industrial weaving machine, according to a new study. Scientists in China and the United States have demonstrated how a glove-size piece of the "smart textile" could continuously power an electronic watch or charge a mobile phone using ambient sunlight and gentle body movements. The fabric is based on low-cost, lightweight polymer fibers coated with metals and semiconductors that allow the material to harvest energy. These fibers are then woven together along with wool on high-throughput commercial weaving equipment to create a textile just 0.01 inches (0.32 millimeters) thick. [Top 10 Inventions that Changed the World] "It is highly deformable, breathable and adaptive to human surface curves and biomechanical movement," said Xing Fan, one of the fabric's inventors and an associate professor of chemical engineering at Chongqing University in China. "And this approach enables the power textile to be easily integrated with other functional fibers or electronic devices to form a flexible, self-powered system." In a paper published online Sept. 12 in the journal Nature Energy, the researchers described how they used a layer-by-layer process similar to those employed in the semiconductor industry. Using this method, they coated polymer fibers with various materials to create cable-like solar cells that generate electricity   from sunlight and also  so-called triboelectric nanogenerators (TENG). The TENGs rely on the triboelectric effect, by which certain materials become electrically charged when rubbed against another type of material. When the materials are in contact, electrons flow from one to the other, but when the materials are separated, the one receiving electrons will hold a charge, Fan said. If these two materials are then connected by a circuit, a small current will flow to equalize the charges. By continuously repeating the process, an alternating electrical current can be produced to generate power, Fan added. By tweaking the patterns and configurations of the textile, the researchers found they could tune the power output and customize it for specific applications by aligning the TENGs with the direction of body movements so that they can capture as much energy as possible, or by using different patterns for high-light and low-light environments. "This is very important. Different applications have different requirements. For example, the voltage requirement of a cellphone is different from that of an electronic watch," Fan told Live Science. "Also, people walking between buildings in London may have less sunshine than those running on the beach in California." [Gallery: Futuristic 'Smart Textiles' Merge Fashion with Tech] The team has yet to conduct long-term durability tests, but after 500 cycles of bending, there was no drop in performance, Fan said. However, the study noted that electrical output of the TENG did gradually drop to 73.5 percent of its original performance when relative humidity was increased from 10 percent to 90 percent. Still, the fabric's full performance can be recovered if the device is dried out, Fan said. He added that encapsulating the textile in an inert material using a common heat-wrapping process should counteract the issue. Juan Hinestroza, an associate professor of fiber science at Cornell University in Ithaca, New York, who was not involved in the research, said combining two sources of electrical power in a single device was impressive. But even more exciting was the researchers' use of traditional textile techniques to fabricate the device, he said. "I believe that this is a fantastic proof of concept that could eventually be escalated to other forms of mass production for textile surfaces," he told Live Science. "This amazing system approach taken by the research team validates my personal belief that everything can be a textile and that everything will eventually become a textile system — from fiber-based airplane structures and space station inflatable modules to wearable power generators such as the one described in this article." In addition to wearable devices, the material could be used to create larger energy-generating structures, like curtains or tents, the researchers said. The fabrication process should also allow the energy-generating materials to be combined with other fiber-based functional devices, like sensors, Fan added. Next, the researchers plan to focus on improving the efficiency, durability and power management of the textile while optimizing the weaving and encapsulation processes to enable industrial-scale production, they said. Copyright 2016 LiveScience, a Purch company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Feng Y.,Harbin Institute of Technology | Feng Y.,Chongqing University | Han F.,RMIT University | Yu X.,RMIT University
Automatica | Year: 2014

In conventional sliding-mode control systems, the sliding-mode motion is of reduced order. Two main problems hindering the application of the sliding-mode control are the singularity in terminal sliding-mode control systems and the chattering in both the conventional linear sliding-mode and the terminal sliding-mode control systems. This paper proposes a chattering-free full-order terminal-sliding-mode control scheme. Since the derivatives of terms with fractional powers do not appear in the control law, the control singularities are avoided. A continuous control strategy is developed to achieve the chattering free sliding-mode control. During the ideal sliding-mode motion, the systems behave as a desirable full-order dynamics rather than a desirable reduced-order dynamics. A systematic design method of full-order sliding-mode control for nonlinear systems is presented, which allows both the chattering and singularity problems to be resolved. Simulations validate the proposed chattering free full-order sliding-mode control. © 2014 Elsevier Ltd. All rights reserved.

Guo S.,Chongqing University | Guo S.,State University of New York at Stony Brook | Wang C.,Chongqing University | Wang C.,State University of New York at Stony Brook | And 2 more authors.
Proceedings - IEEE INFOCOM | Year: 2013

The emerging wireless energy transfer technology enables charging sensor batteries in a wireless sensor network (WSN) and maintaining perpetual operation of the network. Recent breakthrough in this area has opened up a new dimension to the design of sensor network protocols. In the meanwhile, mobile data gathering has been considered as an efficient alternative to data relaying in WSNs. However, time variation of recharging rates in wireless rechargeable sensor networks imposes a great challenge in obtaining an optimal data gathering strategy. In this paper, we propose a framework of joint Wireless Energy Replenishment and anchor-point based Mobile Data Gathering (WerMDG) in WSNs by considering various sources of energy consumption and time-varying nature of energy replenishment. To that end, we first determine the anchor point selection and the sequence to visit the anchor points. We then formulate the WerMDG problem into a network utility maximization problem which is constrained by flow conversation, energy balance, link and battery capacity and the bounded sojourn time of the mobile collector. Furthermore, we present a distributed algorithm composed of cross-layer data control, scheduling and routing subalgorithms for each sensor node, and sojourn time allocation subalgorithm for the mobile collector at different anchor points. Finally, we give extensive numerical results to verify the convergence of the proposed algorithm and the impact of utility weight on network performance. © 2013 IEEE.

Lee J.,Chongqing University | Imai K.,Hiroshima University | Zhu Q.-S.,Chongqing University
Information Sciences | Year: 2012

A number-conserving cellular automaton (NCCA) is a cellular automaton in which the states of cells are denoted by integers, and the sum of all of the numbers in a configuration is conserved throughout its evolution. NCCAs have been widely used to model physical systems that are ruled by conservation laws of mass or energy. Imai et al. [13] showed that the local transition function of NCCA can be effectively translated into the sum of a binary flow function over pairs of neighboring cells. In this paper, we explore the computability of NCCAs in which the pairwise number flows are performed at fully asynchronous timings. Despite the randomness that is associated with asynchronous transitions, useful computation still can be accomplished efficiently in the cellular automata through the active exploitation of fluctuations [18]. Specifically, certain numbers may flow randomly fluctuating between forward and backward directions in the cellular space, as if they were subject to Brownian motion. Because random fluctuations promise a powerful resource for searching through a computational state space, the Brownian-like flow of the numbers allows for efficient embedding of logic circuits into our novel asynchronous NCCA. © 2011 Elsevier Inc. All rights reserved.

Jin X.,Chongqing University | Zhao G.,Georgia Institute of Technology | Gao K.,Chongqing Science and Technology Commission | Ju W.,Chongqing University
Renewable and Sustainable Energy Reviews | Year: 2014

Horizontal axis wind turbines (HAWTs) are the mainstream of wind power industry in the world; however, as turbines are becoming bigger, the maintenance of equipments grows more complex and costs much higher. Compared with HAWTs, Darrieus vertical axis wind turbines (VAWTs) have more technological advantages, providing an alternative for the wind power technology; hence Darrieus VAWTs are catching more eyes. Nevertheless, the majority of wind turbine design currently focuses on HAWTs, researches on Darrieus VAWTs have lagged significantly behind those on HAWTs, which have greatly hindered the development of VAWTs. Accordingly, this paper reviews the main basic research methods and their corresponding applications in Darrieus VAWTs, aiming to let more experts know the current research status and also provide some guidance for relevant researches. © 2014 Elsevier Ltd. All rights reserved.

Zhao X.,Pusan National University | Zhao X.,Chongqing University | Kim S.-Y.,National Academy of Agricultural science NAAS | Park K.-Y.,Pusan National University
Journal of Medicinal Food | Year: 2013

Bamboo salt is a traditional food widely used in Korea. The in vitro anticancer effects of this salt were evaluated in HCT-116 human colon cancer cells using a 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide (MTT) assay. A 1% salt concentration of bamboo salt baked nine times (9×) inhibited the growth of HCT-116 cells by 53%, which was higher than salt baked three times (3×) or once (1×; 44% and 41%, respectively) and much higher than solar sea salt (Korean sea salt) and purified salt (22% and 18%, respectively). To elucidate the inhibitory mechanisms underlying the anticancer effect of the salt samples in cancer cells, expression of genes associated with apoptosis, inflammation, and metastasis was measured with reverse transcription-polymerase chain reaction and Western blotting. Bamboo salt (9×) significantly induced apoptosis in cancer cells (P<.05) by upregulating Bax, caspase-9, and caspase-3, and downregulating Bcl-2. The expression of genes associated with inflammation (NF-κB, iNOS, and COX-2) was significantly downregulated (P<.05) by 9× bamboo salt, demonstrating its anti-inflammatory properties. The 9× bamboo salt also exerted a greater anti-metastatic effect on cancer cells than the other salts as demonstrated by decreased mRNA expression of MMP genes and increased expression of tissue inhibitors of metalloproteinases, which was confirmed by the inhibition of tumor metastasis induced in colon 26-M3.1 cells in BALB/c mice. In contrast, purified and solar salts increased metastasis in the mice. Our results demonstrated that 9× bamboo salt had the most potent in vitro anticancer effect, induced apoptosis, had anti-inflammatory activities, and exerted in vivo anti-metastatic effects. Additionally, the anticancer, anti-inflammatory, and anti-metastatic effects of the 1× and 3× bamboo salts were stronger than those of the purified and solar salts. © Copyright 2013, Mary Ann Liebert, Inc. and Korean Society of Food Science and Nutrition.

Zhang X.,Hong Kong Polytechnic University | Shen L.,Chongqing University | Zhang L.,Harbin Institute of Technology
Renewable and Sustainable Energy Reviews | Year: 2013

The generation of significant amount of emissions from building construction process has led the promotion of controlling emissions as an important strategy for implementing sustainable development principles in the built environment. The emissions incurred during various stages include carbon dioxide, methane, nitrous oxide, sulphur dioxide, carbon monoxide, nitrogen oxide, non methane volatile organic compounds and particulate matter. This paper conducts the life cycle assessment of the air emissions by using a particular case to examine emissions during construction stage. This study examines the emissions sources in each of the six stages and presents an inventory analysis method to measure air emissions to quantify the air emissions during the six life cycle stages for buildings. This method can help evaluating the impacts of implementing a building on the air quality, thus actions can be taken in early stages to reduce the environmental impacts during building life cycle. A case study is presented to demonstrate the practical application of the method with reference to the building practices for all life cycle stages in Hong Kong. © 2012 Elsevier Ltd.

Zhang S.,Chongqing University | Zhang S.,University of Florida | Xia Y.,Chongqing University | Keyhani N.O.,University of Florida
Applied and Environmental Microbiology | Year: 2011

Beauveria bassiana is a mycoinsecticide alternative to chemicals for use in biological pest control. The fungus-insect interaction is also an emerging model system to examine unique aspects of the development, pathogenesis, and diversity of fungal lifestyles. The glycoside hydrolase 72 (GH72) family includes β-1,3-glucanosyltransferases that are glycosylphosphatidylinositol (GPI)-anchored cell wall-modeling enzymes affecting fungal physiology. A putative B. bassiana GPI-anchored β-1,3-glucanosyltransferase (Bbgas1) was isolated and characterized. B. bassiana targeted gene knockouts lacking Bbgas1 were affected in Congo red and salt sensitivity but displayed minor growth defects in the presence of sorbitol, SDS, or calcofluor white. Lectin and antibody mapping of surface carbohydrates revealed increased exposure of carbohydrate epitopes, including β-1,3-glucans, in the ΔBbgas1 strain. Transmission electron micrographs revealed localized destabilization of the cell wall in ΔBbgas1 conidia, in which fraying of the outer cell wall was apparent. Heat shock temperature sensitivity profiling showed that in contrast to the wild-type parent, ΔBbgas1 conidial spores displayed decreased germination after 1 to 4 h of heat shock at temperatures >40°C, and propidium iodide exclusion assays revealed decreased membrane stability in the knockout strain at temperatures >50°C. The ΔBbgas1 knockout showed reduced virulence in Galleria mellonella insect bioassays in both topical and intrahemocoelinjection assays. B. bassiana ΔBbgas1 strains complemented with the complete Bbgas1 open reading frame were indistinguishable from the wild-type parent in all phenotypes examined. The Bbgas1 gene did not complement the phenotype of a Saccharomyces cerevisiae β-1,3-glucanosyltransferase Δgas1 mutant, indicating that this family of enzymes likely posses discrete cellular functions. © 2011, American Society for Microbiology.

Hu Y.,Chongqing University | Cai K.,Chongqing University | Luo Z.,Chongqing University | Jandt K.D.,Friedrich - Schiller University of Jena
Advanced Materials | Year: 2010

Drug-loading mesoporous silica nanoparticles that serve as a nanoreservoirtype drug-delivery system are successfully attached to titanium substrates via the layer-by-layer assembly technique (see scheme). The obtained structure demonstrates great potential for regulating the biological behaviors of osteoblasts/ steoclasts in order to maintain bone homeostasis. The approach we present here may have wide applications in implant technology, tissue engineering, and regenerative medicine. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zhang S.,Chongqing University | Zhang S.,University of Florida | Xia Y.X.,Chongqing University | Kim B.,Martin Martin Inc. | Keyhani N.O.,University of Florida
Molecular Microbiology | Year: 2011

The entomogenous filamentous fungus, Beauveria bassiana expresses two hydrophobin genes, hyd1 and hyd2, hypothesized to be involved in cell surface hydrophobicity, adhesion, virulence, and to constitute the protective spore coat structure known as the rodlet layer. Targeted gene inactivation of hyd1 resulted in seemingly 'bald' conidia that contained significantly altered surface fascicles or bundles. These cells displayed decreased spore hydrophobicity, loss of water mediated dispersal, changes in surface carbohydrate epitopes and β-1,3-glucan distribution, lowered virulence in insect bioassays, but no effect on adhesion. In contrast, Δhyd2 mutants retained distorted surface bundles, but truncated/incomplete rodlets could be seen within the bundles. Δhyd2 conidia displayed both decreased cell surface hydrophobicity and adhesion, but the mutant was unaffected in virulence. The double Δhyd1Δhyd2 mutant was distinct from the single mutants, lacking both bundles and rodlets, and displaying additively decreased cell surface hydrophobicity, reduced cell attachment and lowered virulence than the Δhyd1 mutant. Epitope tagged constructs of the proteins were used to examine the expression and distribution of the proteins and to demonstrate the continued presence of Hyd2 in the Δhyd1 strain and vice versa. The implications of our results with respect to fascicle and rodlet assembly on the spore surface are discussed. © 2011 Blackwell Publishing Ltd.

Raval C.M.,University of Bath | Zhong J.L.,Chongqing University | Mitchell S.A.,University of Bath | Tyrrell R.M.,University of Bath
Free Radical Biology and Medicine | Year: 2012

Up-regulation of heme oxygenase 1 (HO-1) by ultraviolet A (UVA; 320-380 nm) irradiation of human skin cells protects them against oxidative stress. The role of Nrf2 in up-regulation of HO-1 and other phase II genes is well established. The mechanism underlying Bach1-mediated HO-1 repression is less well understood although cellular localization seems to be crucial. Because prolonged HO-1 overexpression is likely to be detrimental, it is crucial that activation of the gene is transient. We now show that UVA irradiation of cultured human skin fibroblasts enhances accumulation of Bach1 mRNA and protein severalfold. Endogenous Bach1 protein accumulates in the nucleus after 8 h and may occupy MARE sites after HO-1 activation thus providing a compensatory mechanism to control HO-1 overexpression. Overexpression of Bach1, together with MafK, represses basal and UVA-mediated HO-1 protein expression, whereas silencing of the Bach1 gene by Bach1-specific siRNAs causes robust enhancement of constitutive HO-1 levels. UVA treatment of cells in which Bach1 has been silenced leads to higher levels of induction of the HO-1 protein. Although Bach1 protein is exported from the nucleus 12 h after UVA irradiation, the release of free cellular heme from microsomal heme-containing proteins is immediate rather than delayed. Although heme does promote the export of Bach1 via the Crm1/exportin 1 pathway and is involved in the delayed UVA-mediated export of the protein, it is not clear how this occurs. © 2011 Elsevier Inc.

Hu J.,Chongqing University | Yan B.,Chongqing University | Zhou S.,Test Institute | Zhang H.,Sichuan Electric Power Research Institute
IEEE Transactions on Power Delivery | Year: 2012

The aerodynamic coefficients of each subconductor in an iced quad bundle conductor covered with crescent-shaped and sector-shaped cross-sections were determined by the wind tunnel test. A cable element with torsional degree of freedom used to simulate the iced conductor is obtained in ABAQUS software by releasing the two bending degrees of freedom and setting the material to be incompressible. The aerodynamic loads varying with the angle of attack during moving of the bundle conductor are applied on the cable elements used to discretize the iced subconductors through the user-defined element subroutine UEL in ABAQUS. The numerical method verified by two examples is employed to investigate galloping of iced quad bundle conductors at different wind speed, initial angle of attack, ice thickness, ice shape, and span length, and the results reflect the influences of these parameters on the galloping behavior of the quad bundle conductor, which is important for the development of anti-galloping technology. © 2012 IEEE.

Guo S.,Chongqing University | Guo S.,State University of New York at Stony Brook | Yang Y.,Chongqing University | Yang Y.,State University of New York at Stony Brook
Proceedings - IEEE INFOCOM | Year: 2012

In this paper, we consider mobile data gathering in wireless sensor networks (WSNs) by using a mobile collector with multiple antennas. By taking into account the elastic nature of wireless link capacity and the power control for each sensor, we first propose a data gathering cost minimization (DaGCM) framework with concurrent data uploading, which is constrained by flow conservation, energy consumption, link capacity, compatibility among sensors and the bound on total sojourn time of the mobile collector at all anchor points. One of the main features of this framework is that it allows concurrent data uploading from sensors to the mobile collector to sharply shorten data gathering latency and significantly reduce energy consumption due to the use of multiple antennas and space-division multiple access technique. We then relax the DaGCM problem with Lagrangian dualization and solve it with the subgradient iteration algorithm. Furthermore, we present a distributed algorithm composed of cross-layer data control, routing, power control and compatibility determination subalgorithms with explicit message passing. We also give the subalgorithm for finding the optimal sojourn time of the mobile collector at different anchor points. Finally, we provide numerical results to show the convergence of the proposed DaGCM algorithm and its advantages over the algorithm without concurrent data uploading and power control in terms of data gathering latency and energy consumption. © 2012 IEEE.

Wang Z.,Harbin Institute of Technology | Zhang X.,Harbin Institute of Technology | Zhang X.,Chongqing University | Nie L.,Harbin Institute of Technology | And 2 more authors.
Applied Energy | Year: 2014

To solve the water flooding problem of micro passive direct methanol fuel cell (DMFC), plasma electrolytic oxidation (PEO) was adopted to prepare a superhydrophilic coating on the surface of an aluminum-based cathode current collector which contacts with air. Results data show that liquid water spreads quickly as a plane on the surface of the porous PEO coating that is composed of Al2SiO3 and Al2O3. As a result, water droplet can be prevented from accumulating along the air-breathing channels of the PEO-treated cathode current collector, and thus the water flooding problem of the micro passive DMFC is effectively solved. The cell fabricated with the novel cathode structure gives excellent stability. © 2014 Elsevier Ltd.

State Grid Corporation of China, Chongqing Electric Power Research Institute and Chongqing University | Date: 2014-03-04

The application discloses a method for acquiring parameters of a dynamic signal, including: selecting a dynamic sample signal sequence of a power grid to constitute an autocorrelation matrix; determining an effective rank of the autocorrelation matrix and the number of frequency components of the dynamic sample signal sequence; establishing an AR model, and solving a model parameter of the AR model; determining an expression and a complex sequence of the dynamic sample signal sequence by using a Prony algorithm, wherein the dynamic sample signal sequence is represented by the complex sequence with a minimum square error; and substituting a root of a characteristic polynomial corresponding to the model parameter into the complex sequence and solving various parameters of the dynamic sample signal sequence. In the application, with the idea of AR parameter model, a current signal is considered to be a linear combination of signals at previous time points.

Wang Q.,Chongqing University | Wang Q.,Nanchang University | Liu F.,Chongqing University | Li C.,Chongqing University
Journal of Cleaner Production | Year: 2013

Increasing pressures from energy price and environmental directive force the manufacturing enterprises to consider and initiate the implementation of energy assessment and energy quota practices to improve both their economic benefit and environmental performance. Against this background this paper presents an integrated method to evaluate energy efficiency in machining workshop. The integrated features of the assessing method are reflected in three aspects: (1) In this evaluation system, the energy profile of machining workshop is viewed from the machine tool layer, manufacturing unit layer, task layer and workshop layer to reveal the energy performance inside the workshop completely. (2) The assessing indexes for each layer include both effective energy indicator and Specific Energy Consumption (SEC) indicator. (3) An integrated calculation method of energy indexes is introduced, which combines off-line experiments with theoretical formulas. To verify its feasibility and validity, the assessment method is applied to a small machining workshop. The assessing results showed that the assessment method is helpful in providing support for machining scheme selection, energy saving discovery and energy quota allocation in plant, which has significance in practice. © 2013 Elsevier Ltd. All rights reserved.

Li X.,Wilfrid Laurier University | Li X.,Chongqing University | Ghose S.,Wilfrid Laurier University | Ghose S.,University of Waterloo
Laser Physics Letters | Year: 2014

We present a hyperconcentration scheme for nonlocal N-photon hyperentangled Greenberger-Horne-Zeilinger states. The maximally hyperentangled state, in which N particles are entangled simultaneously in the polarization and the spatial mode, can be obtained with a certain probability from two partially hyperentangled states. The hyperconcentration scheme is based on one polarization parity check measurement, one spatial mode parity check measurement and N - 2 single-photon two-qubit measurements. The concentration only requires linear optical elements, which makes it feasible and practical with current technology. © 2014 Astro Ltd.

Li X.-H.,Chongqing University | Li X.-H.,Wilfrid Laurier University | Ghose S.,Wilfrid Laurier University | Ghose S.,University of Waterloo
Optics Express | Year: 2015

We propose two schemes for concentration of hyperentanglement of nonlocal multipartite states which are simultaneously entangled in the polarization and spatial modes. One scheme uses an auxiliary singlephoton state prepared according to the parameters of the less-entangled states. The other scheme uses two less-entangled states with unknown parameters to distill the maximal hyperentanglement. The procrustean concentration is realized by two parity check measurements in both the two degrees of freedom. Nondestructive quantum nondemolition detectors based on cross-Kerr nonlinearity are used to implement the parity check, which makes the unsuccessful instances reusable in the next concentration round. The success probabilities in both schemes can be made to approach unity by iteration. Moreover, in both schemes only one of the N parties has to perform the parity check measurements. Our schemes are efficient and useful for quantum information processing involving hyperentanglement. © 2015 Optical Society of America.

Wang X.,Nanchang University | Wang Z.,Chongqing University
Tetrahedron | Year: 2014

A novel silver-catalyzed tandem reaction of 2-alkynylbenzaldoximes with H-phosphinate esters, and H-phosphine oxides has been developed, providing a general and powerful tool for the synthesis of various 1-phosphorylated isoquinolins in moderate to excellent yield. This reaction proceeded smoothly to construct C-N and C-P bonds in one-pot with good functional group tolerance under mild conditions. © 2014 Elsevier Ltd. All rights reserved.

Harrison P.,University of Glasgow | Abdiwi F.,University of Glasgow | Guo Z.,Chongqing University | Potluri P.,University of Manchester | Yu W.R.,Seoul National University
Composites Part A: Applied Science and Manufacturing | Year: 2012

Modelling the forming process for engineering fabrics and textile composites using a mechanical approach, such as the finite element method, requires characterisation of the materials behaviour under large shear deformation. For woven engineering fabrics, a coupling between in-plane tension and both shear compliance and the onset of wrinkling is to be expected. This paper focuses on a novel testing technique, the biaxial bias extension test, as a means to investigate this shear-tension coupling and fabric wrinkling. Novel methods of determining the wrinkling behaviour are demonstrated. The main difficulty with the technique lies in extracting the material contribution to the recorded signal. To do this, an experimental method is proposed and demonstrated using a plain weave glass fabric. Biaxial bias extension test results are compared against picture frame and uniaxial bias extension results. © 2012 Published by Elsevier Ltd. All rights reserved.

Li X.-H.,Chongqing University | Li X.-H.,Wilfrid Laurier University | Ghose S.,Wilfrid Laurier University | Ghose S.,University of Waterloo
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2015

We present two hyperentanglement concentration schemes for two-photon states that are partially entangled in the polarization and time-bin degrees of freedom. The first scheme distills a maximally hyperentangled state from two identical less-entangled states with unknown parameters via the Schmidt projection method. The other scheme can be used to concentrate an initial state with known parameters and requires only one copy of the initial state for the concentration process. Both these two protocols can be generalized to concentrate N-photon hyperentangled Greenberger-Horne-Zeilinger states that are simultaneously entangled in the polarization and time-bin degrees of freedom. Our schemes require only linear optics and are feasible with current technology. Using the time-bin degree of freedom rather than the spatial-mode degree of freedom can provide savings in quantum resources, which makes our schemes practical and useful for long-distance quantum communication. © 2015 American Physical Society.

Li X.-H.,Chongqing University | Li X.-H.,Wilfrid Laurier University | Ghose S.,Wilfrid Laurier University | Ghose S.,University of Waterloo
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2015

We quantitatively analyze and evaluate the controller's power in N-qubit controlled teleportation schemes. We calculate the minimum control power required to ensure the controller's authority such that the teleportation fidelity without the controller's permission is no more than the classical bound. We revisit several typical controlled teleportation schemes from the controller's point of view and evaluate the control power in these schemes. We find that for teleporting arbitrary N-qubit states, each controller should control at least N bits of useful information to ensure his or her authority over the protocol. We also discuss the general rules that must be satisfied by controlled teleportation schemes to ensure both teleportation fidelity and control power. © 2015 American Physical Society.

Wang X.,Nanchang University | Wang Z.,Chongqing University
Tetrahedron | Year: 2014

A tandem reaction of 2-alkynylbenzaldoximes with cyclic ethers co-catalyzed by silver(I) triflate and copper(II) acetate is developed, affording 1-substituted isoquinolines in moderate to good yields. The transformation proceeds efficiently through C-H activation. © 2014 Elsevier Ltd. All rights reserved.

Wang X.,Nanchang University | Xue L.,Chongqing University | Wang Z.,Chongqing University
Organic Letters | Year: 2014

A three-component reaction of triethoxysilanes, sulfur dioxide, and hydrazines catalyzed by copper(II) acetate is reported, leading to N-aminosulfonamides in good yields. Not only triethoxy(aryl)silanes but also triethoxy(alkyl)silanes are compatible during the process of insertion of sulfur dioxide. Additionally, diethoxydiarylsilanes are suitable under the conditions as well. © 2014 American Chemical Society.

Li X.-H.,Wilfrid Laurier University | Li X.-H.,Chongqing University | Ghose S.,Wilfrid Laurier University | Ghose S.,University of Waterloo
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2014

We analyze and evaluate perfect controlled teleportation via three-qubit entangled channels from the point of view of the controller. The key idea in controlled teleportation is that the teleportation is performed only with the participation of the controller. We calculate a quantitative measure of the controller's power and establish a lower bound on the control power required for controlled teleportation. We show that the maximally entangled Greenberger-Horne-Zeilinger state is a suitable channel for controlled teleportation of arbitrary single qubits - the controller's power meets the bound and the teleportation fidelity without the controller's permission is no better than the fidelity of a classical channel. We also construct partially entangled channels that exceed the bound for controlled teleportation of a restricted set of states called the equatorial states. We calculate the minimum entanglement required in these channels to exceed the bound. Moreover, we find that in these restricted controlled teleportation schemes, the partially entangled channels can outperform maximally entangled channels with respect to the controller's power. Our results provide an alternative perspective on controlled teleportation schemes and are of practical interest since we propose useful partially entangled channels. © 2014 American Physical Society.

Deng D.,Chongqing University | Kiyoshima S.,Computational Mechanics Inc
Nuclear Engineering and Design | Year: 2010

With the development of computer hardware and software, numerical simulation technology has been widely used to predict welding temperature field, residual stresses and distortion. However, till now the influences of initial stresses induced by the manufacturing process before welding on the welding-induced residual stresses are rarely investigated experimentally and numerically. In the present work, we have developed a computational approach based on thermal elastic plastic FEM to clarify how the initial stresses due to heat treatment affect the welding-induced residual stresses in an austenitic stainless steel pipe. A heat treatment process, which is similar to solution heat treatment, is employed to produce initial stresses in the pipe before welding. After the heat treatment, the laser beam welding is used to perform a girth weld in the middle of the pipe. Through comparing the residual stress distributions after heat treatment and laser beam welding, we have investigated the influence of the initial residual stresses on the welding-induced residual stresses. The numerical results suggest that the initial residual stresses prior to welding have significant effects on the residual stresses after welding in the pipe model. © 2009 Elsevier B.V. All rights reserved.

Deng D.,Chongqing University | Kiyoshima S.,Computational Mechanics Inc
Computational Materials Science | Year: 2010

A finite element approach based on Quick Welder software is developed to simulate welding temperature field and welding residual stress distribution in a 3D multi-pass girth-welded pipe model. The characteristics of welding residual stress distributions in a SUS304 stainless steel pipe induced by heating with a tungsten inert gas arc welding torch are investigated numerically. Meanwhile, an emphasis is focused on examining the welding residual stress distributions in and near the weld start/end location. Moreover, the residual stresses predicted by the present computational approach are compared with the measured data; and the comparison suggests that the numerical simulation method has basically captured the feature of welding residual stress distribution near the weld start/end region. The numerical simulation results show that both the hoop and the axial residual stresses near the weld start/end region have sharp gradients and are significantly different from those in the steady range. © 2010 Elsevier B.V. All rights reserved.

Deng D.,Chongqing University | Kiyoshima S.,Computational Mechanics Inc
Computational Materials Science | Year: 2012

To increase productivity, welding process with large heat input such as electro slag welding (ESW) process has been used to connect the joints between the diaphragm and the column plate in high-rise steel building. However, the heat input of ESW is much higher than those of the other welding processes, and the high heat input not only largely alters the properties of steel but also results in large residual stresses. Consequently, the changes of steel properties and residual stresses induced by ESW have significantly effects on the safety of a structure. In this study, a three dimension (3-D) finite element model with considering moving heat source was developed to simulate the welding temperature field, Δt 8/5 time, welding residual stress and distortion in a typical thick plate joint performed by ESW. The thermal cycles computed by finite element model were compared with experimental measurements. Meanwhile, the features of welding residual stress and distortion distributions in the ESW joint were investigated numerically. In addition, the influences of heat input on the size of heat affected-zone (HAZ), Δt 8/5 time welding residual stress and distortion were examined. The thermal cycle curve and simulated by FEM model can be used to deduce the micro-structure as well as toughness of weld zone and HAZ, while the welding residual stress distribution estimated by numerical model can be helpful to assess the structural integrity. © 2012 Elsevier B.V. All rights reserved.

Lei G.,Chongqing University | Shixiang L.,Wuhan University
Journal of Convergence Information Technology | Year: 2012

In the study,support vector regression with improved quantum-behaved particle swarm optimization(IQPSO-SVR) is applied to evaluate coal resources demand,and improved quantum-behaved particle swarm optimization(IQPSO) is used to choose the suitable parameters of support vector regression. Firstly,the dimensions of the input vector in the the training sample sets need to be determined and the training sample sets are created.Then, the different IQPSO-SVR models trained by the different training sample sets are generated. The experimental resuts indicate that the IQPSO-SVR model trained by the training sample sets with 4 dimensional input vector has the best evaluation results and the comparison results of the validation and prediction results for coal resources demand between the IQPSO-SVR model and the SVR model show that the evaluation results of the IQPSO-SVR model have better than those of the SVR model.

Lei Y.,Xi'an Jiaotong University | Lei Y.,Chongqing University | Han D.,Xi'an Jiaotong University | Lin J.,Xi'an Jiaotong University | He Z.,Xi'an Jiaotong University
Mechanical Systems and Signal Processing | Year: 2013

Planetary gearboxes are widely used in aerospace, automotive and heavy industry applications due to their large transmission ratio, strong load-bearing capacity and high transmission efficiency. The tough operation conditions of heavy duty and intensive impact load may cause gear tooth damage such as fatigue crack and teeth missed etc. The challenging issues in fault diagnosis of planetary gearboxes include selection of sensitive measurement locations, investigation of vibration transmission paths and weak feature extraction. One of them is how to effectively discover the weak characteristics from noisy signals of faulty components in planetary gearboxes. To address the issue in fault diagnosis of planetary gearboxes, an adaptive stochastic resonance (ASR) method is proposed in this paper. The ASR method utilizes the optimization ability of ant colony algorithms and adaptively realizes the optimal stochastic resonance system matching input signals. Using the ASR method, the noise may be weakened and weak characteristics highlighted, and therefore the faults can be diagnosed accurately. A planetary gearbox test rig is established and experiments with sun gear faults including a chipped tooth and a missing tooth are conducted. And the vibration signals are collected under the loaded condition and various motor speeds. The proposed method is used to process the collected signals and the results of feature extraction and fault diagnosis demonstrate its effectiveness. © 2012 Elsevier Ltd.

Wang Y.,Albany Research Center | Coleman-Derr D.,U.S. Department of Agriculture | Chen G.,Chongqing University | Gu Y.Q.,U.S. Department of Agriculture
Nucleic acids research | Year: 2015

Genome wide analysis of orthologous clusters is an important component of comparative genomics studies. Identifying the overlap among orthologous clusters can enable us to elucidate the function and evolution of proteins across multiple species. Here, we report a web platform named OrthoVenn that is useful for genome wide comparisons and visualization of orthologous clusters. OrthoVenn provides coverage of vertebrates, metazoa, protists, fungi, plants and bacteria for the comparison of orthologous clusters and also supports uploading of customized protein sequences from user-defined species. An interactive Venn diagram, summary counts, and functional summaries of the disjunction and intersection of clusters shared between species are displayed as part of the OrthoVenn result. OrthoVenn also includes in-depth views of the clusters using various sequence analysis tools. Furthermore, OrthoVenn identifies orthologous clusters of single copy genes and allows for a customized search of clusters of specific genes through key words or BLAST. OrthoVenn is an efficient and user-friendly web server freely accessible at or © The Author(s) 2015. Published by Oxford University Press on behalf of Nucleic Acids Research.

Li X.-Y.,Southwest Jiaotong University | Wu F.,Southwest Jiaotong University | Jin X.,Chongqing University | Chen W.-Q.,Zhejiang University
Journal of the Mechanics and Physics of Solids | Year: 2015

The present paper is concerned with three-dimensional (3D) coupled field in a transversely isotropic magneto-electro-elastic half space punched by a rigid flat-ended elliptic indenter. Closed form solutions and corresponding numerical results are presented in this work, in a systematic manner. The material in question is transversely isotropic with the axis of symmetry normal to the surface of the half space. The indenter is assumed to be either electrically and magnetically conducting or insulating. Corresponding boundary integral equations (BIEs), to indenter with different magneto-electric properties, are solved by virtue of the method of generalized potential theory. For all four physical cases, corresponding coupled magneto-electro-elastic fields in the half space are obtained. The present analytical solutions indicate that the indentation forces and stiffness may be written as intrinsic combinations of a physical factor and a geometrical factor. The present study is an extension of the previous work on circular punch, and may find applications in guiding future indentation experiments. © 2014 Elsevier Ltd.

Song F.H.,Chongqing University | Song F.H.,Xi'an Jiaotong University | Li B.Q.,University of Michigan | Liu C.,Chongqing University
Langmuir | Year: 2013

Molecular dynamics (MD) simulations are performed for the spreading of a nanosized water droplet on a solid substrate subject to a parallel electric field. A combined electrostatic and Lennard-Jones potential is employed to represent the intermolecular interactions. Results show that in response to the applied field, polar water molecules realign themselves and this microscopic reorientation of molecular dipoles combines with the intermolecular forces to produce a macroscopic deformation of a free spherical water droplet into an ellipsoid. The applied field has a strong effect on the spreading of the water droplet on a solid substrate. For a weaker parallel field, the droplet spreading is asymmetric with the leading contact angle being greater than the trailing contact angle. With an increase in field strength, this asymmetry continues to increase, culminates, and then decreases until it disappears. The symmetric spreading remains with a further increase in the field strength until the saturation point is reached. This transition from the asymmetric to symmetric spreading is a manifestation of the interaction of the electric field with polar water molecules and the intermolecular forces within the droplet and between the water and solid; the interaction also leads to a change in hydrogen bonds along the droplet surface. The dynamics of the droplet spreading is entailed by the electrically induced motion of molecules along the liquid surface toward the solid substrate and is controlled by a competing mechanism among the electric, water-water, and water-solid intermolecular forces. © 2013 American Chemical Society.

Yang B.,Princeton University | Hu Z.-X.,Princeton University | Hu Z.-X.,Chongqing University | Papic Z.,Princeton University | Haldane F.D.M.,Princeton University
Physical Review Letters | Year: 2012

We construct model wave functions for the collective modes of fractional quantum Hall systems. The wave functions are expressed in terms of symmetric polynomials characterized by a root partition that defines a "squeezed" basis, and show excellent agreement with exact diagonalization results for finite systems. In the long wavelength limit, we prove that the model wave functions are identical to those predicted by the single-mode approximation, leading to intriguing interpretations of the collective modes from the perspective of the ground-state guiding-center metric. © 2012 American Physical Society.

Zhou P.,University of Electronic Science and Technology of China | Wang C.,University of Electronic Science and Technology of China | Ren Y.,Chongqing University | Yang C.,University of Electronic Science and Technology of China | Tian F.,Southwest Jiaotong University
Current Medicinal Chemistry | Year: 2013

The recent focus on protein-protein interaction networks has increasingly been shifted towards the disruption of protein complexes, which either are mediated by the binding of a globular domain in one protein to a short peptide stretch in another, or involve flat, large, and hydrophobic interfaces that classical small-molecule agents are not always ideally suited. Rational design of therapeutic peptides with high affinity targeting such interactions has emerged as a new and promising tool in discovery of potential drug candidates against associated diseases. The design is commonly based on bioinformatics methods or molecular modeling techniques, indirectly exploiting structure-activity relationship at the level of peptide sequence or directly deriving lead entities from protein complex architecture. Here, a newly rising subfield called computational peptidology that focuses on the use of computational and theoretical approaches to treat peptiderelated problems is comprehensively reviewed on the design and discovery of peptide agents targeting protein-protein interactions. We address a systematic discussion on several representative cases in which the computational peptidology is successfully employed to develop peptide therapeutics. Besides, some problems and pitfalls accompanied with the current use of computational methods in peptide modeling and design are also present. © 2013 Bentham Science Publishers.

Miranda O.R.,University of Massachusetts Amherst | Chen H.-T.,University of Massachusetts Amherst | You C.-C.,University of Massachusetts Amherst | Mortenson D.E.,University of Massachusetts Amherst | And 3 more authors.
Journal of the American Chemical Society | Year: 2010

We have developed an enzyme-nanoparticle sensor array where the sensitivity is amplified through enzymatic catalysis. In this approach cationic gold nanoparticles are electrostatically bound to an enzyme (β-galactosidase, β-Gal), inhibiting enzyme activity. Analyte proteins release the β-Gal, restoring activity and providing an amplified readout of the binding event. Using this strategy we have been able to identify proteins in buffer at a concentration of 1 nM, substantially lower than current strategies for array-based protein sensing. Moreover, we have obtained identical sensitivity in studies where the proteins are spiked into the complex protein matrix provided by desalted human urine (∼1.5 μM total protein; spiked protein concentrations were 0.067% of the overall protein concentration), demonstrating the potential of the method for diagnostic applications. © 2010 American Chemical Society.

Deng D.,Chongqing University | Kiyoshima S.,Computational Mechanics Inc
Computational Materials Science | Year: 2011

Residual stresses in a welded structure often reached to or even over the yield strengths of base metal and weld metal. Tensile residual stress is a main factor resulting in stress corrosion cracking, fatigue damage and brittle fracture. Generally, welding cracking and flaw frequently occurs at the weld start/end location. Therefore, it is necessary to investigate the feature of welding residual stress distribution near the weld start/end location. In the present work, both numerical simulation technology and experimental method were used to study welding residual stress distribution in a thick plate joint with a special groove. Meanwhile, an emphasis was played on examining the characteristics of welding residual stress distribution near the weld start/end location. Moreover, the influence of deposition sequence and direction on the welding residual stress distribution was clarified by means of numerical simulation method. © 2011 Elsevier B.V. All rights reserved.

Liu J.,Wuhan University | Liu Q.,Wuhan University | Yi H.,Wuhan University | Qin C.,Wuhan University | And 6 more authors.
Angewandte Chemie - International Edition | Year: 2014

Photochemistry has ushered in a new era in the development of chemistry, and photoredox catalysis has become a hot topic, especially over the last five years, with the combination of visible-light photoredox catalysis and radical reactions. A novel, simple, and efficient radical oxidative decarboxylative coupling with the assistant of the photocatalyst [Ru(phen)3]Cl 2 is described. Various functional groups are well-tolerated in this reaction and thus provides a new approach to developing advanced methods for aerobic oxidative decarboxylation. The preliminary mechanistic studies revealed that: 1)an SET process between [Ru(phen)3]2+* and aniline play an important role; 2)O2 activation might be the rate-determining step; and 3)the decarboxylation step is an irreversible and fast process. Bring to light: A new approach to oxidative decarboxylation under visible light using O2 as the oxidant has been developed. A variety of functional groups were well-tolerated in this reaction and insights into the mechanism were investigated with the assistance of EPR spectroscopy, cyclic voltammetry, and theoretical studies. © 2014 WILEY-VCH Verlag GmbH.

Zhou L.,Hubei University | Tang S.,Hubei University | Qi X.,Chongqing University | Lin C.,Hubei University | And 4 more authors.
Organic Letters | Year: 2014

A transition-metal-assisted oxidative C(sp3)-H/N-H cross-coupling reaction of N-alkoxyamides with aliphatic hydrocarbons is described. During the reaction, nitrogen radicals were generated from the oxidation of N-alkoxyamides. Experiments and DFT calculations revealed that transition-metal catalyst could lower the reactivity of the generated nitrogen radical by the coordination of the transition metal, which allowed the selective radical/radical cross-coupling with the transient sp3 carbon radical to construct C(sp3) - N bonds. Various C(sp3)-H bonds could be transformed into C(sp3)-N bonds through this radical amidation strategy. © 2014 American Chemical Society.

Wang D.,Henan Polytechnic University | Wei J.,Henan Polytechnic University | Yin G.,Chongqing University
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2012

According to experimental investigation on permeability property of coal containing gas, the change rule of permeability of coal containing gas is analyzed systematically under complex stress paths. Quantitative and qualitative relations of the permeability of coal containing gas with axial pressure, confining pressure, gas pressure, loading-unloading of confining pressure and complete stress-strain process are established respectively. The controlling mechanism and change law of permeability of coal containing gas under different stress paths are discussed. The results show that the stress path has an important impact on the permeability of coal containing gas: (1) The permeability of coal containing gas decreases with the increase of axial pressure and confining pressure, while increases with the increase of gas pressure. (2) The relationships of permeability of coal containing gas with axial pressure, confining pressure and gas pressure obey approximately an exponential law. (3) During the loading-unloading process of confining pressure, the permeability of coal containing gas is damaged to a certain extent and this damage can be represented by the maximal damage rate and damage rate of permeability. At the same time, the results show that the second-compacting effect of coal containing gas will happen under the condition of triaxial compression. (4) During the complete stress-strain a test process under triaxial compression, the change trend of permeability of coal containing gas versus strain curve is V-shaped approximately. The permeability of coal sample decreases first, then increases with strain, and reaches its maximum finally. The increasing amplitude is less than the decreasing amplitude.

Li B.,University of Nevada, Reno | Zhang X.Y.,Chongqing University
Scripta Materialia | Year: 2016

It is generally believed that the . 101-2101-1- twinning shear in magnesium equals 0.129 and twin growth is mediated by twinning dislocations. Starting from these notions, we analyze, in great detail, the lattice transformation from parent to twin, and prove that the twinning shear cannot be any finite value but zero. Thus, no twinning dislocations should be involved in this twinning mode and the lattice transformation is solely accomplished by atomic shuffling. Atomistic simulations and high resolution transmission electron microscopy observations unambiguously confirm our conclusion. © 2016 Elsevier B.V.

Liu W.,Xuzhou Normal University | Liu W.,Chongqing University | Tang B.,Chongqing University
Expert Systems with Applications | Year: 2011

In this paper, a hybrid time-frequency method (HTM) based on the improved Morlet wavelet and auto terms window (ATW) is presented. The Morlet wavelet, for its shape is similar to the mechanical shock signals, is added two parameters which decide the shape of the mother wavelet. The added parameters and the appropriate scale parameter for continuous wavelet transformation (CWT) are calculated using the cross validation method (CVM) and the minimum Shannon entropy method. The useless noise in the original signal can be filtered by the CWT filter de-noising process. An ATW based on the Smoothed Pseudo Wigner-Ville Distribution (SPWVD) spectrum is designed as a window function to suppress the cross terms in Wigner-Ville Distribution (WVD). The gear fault diagnosis experiment results show that the proposed method has a good de-nosing performance and is effective in removing the cross terms and extracting fault feature. © 2010 Elsevier Ltd. All rights reserved.

Berglund S.P.,University of Texas at Austin | He H.,University of Texas at Austin | He H.,Chongqing University | Chemelewski W.D.,University of Texas at Austin | And 3 more authors.
Journal of the American Chemical Society | Year: 2014

p-Si/W2C photocathodes are synthesized by evaporating tungsten metal in an ambient of ethylene gas to form tungsten semicarbide (W 2C) thin films on top of p-type silicon (p-Si) substrates. As deposited the thin films contain crystalline W2C with a bulk W:C atomic ratio of approximately 2:1. The W2C films demonstrate catalytic activity for the hydrogen evolution reaction (HER), and p-Si/W 2C photocathodes produce cathodic photocurrent at potentials more positive than 0.0 V vs RHE while bare p-Si photocathodes do not. The W 2C films are an effective support for Pt nanoparticles allowing for a considerable reduction in Pt loading. p-Si/W2C/Pt photocathodes with Pt nanoparticles achieve photocurrent onset potentials and limiting photocurrent densities that are comparable to p-Si/Pt photocathodes with Pt loading nine times higher. This makes W2C an earth abundant alternative to pure Pt for use as an electrocatalyst on photocathodes for the HER. © 2014 American Chemical Society.

Luo Z.,Chongqing University | Cai K.,Chongqing University | Hu Y.,Chongqing University | Zhao L.,China National Center for Biotechnology Development | And 3 more authors.
Angewandte Chemie - International Edition | Year: 2011

If the cap fits: Attachment of collagen (Col) to silica nanoparticles (MSN) by a disulfide linker, followed by introduction of lactobionic acid (LA, a cell-specific targeting moiety), results in a redox-responsive system for cell-specific intracellular drug delivery and efficient endocytosis (see picture). Controlled release of a model drug (fluorescein isothiocyanate, FITC) was achieved by cleavage of the disufide bonds. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rowlinson S.,Chongqing University | Rowlinson S.,University of Hong Kong | Jia Y.A.,University of Hong Kong
Annals of Occupational Hygiene | Year: 2014

Existing heat stress risk management guidelines recommended by international standards are not practical for the construction industry which needs site supervision staff to make instant managerial decisions to mitigate heat risks. The ability of the predicted heat strain (PHS) model [ISO 7933 (2004). Ergonomics of the thermal environment analytical determination and interpretation of heat stress using calculation of the predicted heat strain. Geneva: International Standard Organisation] to predict maximum allowable exposure time (Dlim) has now enabled development of localized, action-Triggering and threshold-based guidelines for implementation by lay frontline staff on construction sites. This article presents a protocol for development of two heat stress management tools by applying the PHS model to its full potential. One of the tools is developed to facilitate managerial decisions on an optimized work-rest regimen for paced work. The other tool is developed to enable workers' self-regulation during self-paced work. © 2013 © The Author 2013. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.

Liu X.-M.,Luoyang Normal University | Gao W.-L.,Chongqing University
Materials and Manufacturing Processes | Year: 2012

Nickel ferrite (NiFe 2O 4) nanoparticles have been synthesized by modified Pechini method in the presence of surfactant and certain amount of concentrated nitric acid. The obtained foamed gel precursors were characterized by thermogravimetry-differential thermal analysis (TG-DTA) to determine the thermal decomposition and subsequently calcined at different temperatures in the range of 500 -800C for 2h to obtain NiFe 2O 4 nanoparticles, which were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron micrograph (TEM), and vibrating sample magnetometer (VSM). The results showed that Ni ferrite nanoparticles obtained by modified Pechini method exhibited good dispersibility, uniform distribution, and good crystallinity, and the particle diameter of NiFe 2O 4 calcined at 500C is almost 80nm. Its saturation magnetization was 50.5emu/g at the maximum magnetic field of 10kOe at room temperature. The particle size, saturation magnetization, and coercivity of NiFe 2O 4 increased with the increase of the calcination temperature. © Taylor and Francis Group, LLC.

Li M.,Chongqing University | Guyenne P.,University of Delaware | Li F.,Rensselaer Polytechnic Institute | Xu L.,Chongqing University
Journal of Computational Physics | Year: 2013

In this paper, we consider a one-dimensional fully nonlinear weakly dispersive Green-Naghdi model for shallow water waves over variable bottom topographies. Such model describes a large spectrum of shallow water waves, and it is thus of great importance to design accurate and robust numerical methods for solving it. The governing equations contain mixed spatial and temporal derivatives of the unknowns. They also have still-water stationary solutions which should be preserved in stable numerical simulations. In our numerical approach, we first reformulate the Green-Naghdi equations into balance laws coupled with an elliptic equation. We then propose a family of high order numerical methods which discretize the balance laws with well-balanced central discontinuous Galerkin methods and the elliptic part with continuous finite element methods. Linear dispersion analysis for both the (reformulated) Green-Naghdi system and versions of the proposed numerical scheme is performed when the bottom topography is flat. Numerical tests are presented to illustrate the accuracy and stability of the proposed schemes as well as the capability of the Green-Naghdi model to describe a wide range of shallow water wave phenomena. © 2013 Elsevier Inc.

Zhang X.Y.,Chongqing University | Li B.,University of Nevada, Reno | Liu Q.,Chongqing University
Acta Materialia | Year: 2015

Transmission electron microscopy (TEM) studies were performed to investigate non-equilibrium basal stacking faults (SFs) in deformed hexagonal, close-packed (HCP) metals, i.e., magnesium (Mg), cobalt (Co), titanium (Ti) and a Mg AZ31 alloy. These SFs present a width that is two to three orders of magnitude wider than the equilibrium width of the basal SFs created by partial dislocations. The non-equilibrium basal SFs are often generated inside deformation twins, and in conventional TEM the SFs present a morphology of straight lines well aligned with the trace of the basal planes, and may cross a whole twin. To investigate the mechanism of the formation of the SFs, we performed atomistic simulations. The simulation results show that the formation of the non-equilibrium basal SFs is closely associated with incoherent twin boundary (TB) migration. When the structure of the initial TB is incoherent, basal SFs are nucleated with one end being anchored at the moving TB. SFs subsequently grow along with the moving TB, resulting in SFs with a large width that may cross the whole twin. No Shockley or Frank partial dislocations are involved in the nucleation and the growth of SFs. When the structure of the initial TB is coherent or nearly coherent, no SFs are generated. The non-equilibrium basal SFs interact with prismatic and pyramidal slips, and impede the dislocation slip. © 2015 Acta Materialia Inc.

Liu X.M.,Luoyang Normal University | Gao W.L.,Chongqing University
Advanced Materials Research | Year: 2011

Spinel-perovskite multiferroics of NiFe2O4/BiFeO 3 nanoparticles were prepared by modified Pechini method. The structure and morphology of the composites were examined by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the composites consisted of spinel NiFe2O4 and perovskite BiFeO3 after annealed at 700°C for 2h, and the particle size ranges from 40 to 100nm. VSM and ME results indicated that the nanocomposites exhibited both tuning magnetic properties and a ME effect. The ME effect of the nanocomposites strongly depended on the magnetic bias and magnetic field frequency. © (2011) Trans Tech Publications.

Huang Q.,Chongqing University | Fang L.,Chongqing University | Chen X.,Chongqing University of Technology | Saleem M.,Chongqing University
Journal of Alloys and Compounds | Year: 2011

A series of oriented hexagonal wurtzite ZnO nanorod-array films were grown on fluorine-doped tin oxide (FTO) coated glass substrates by chemical process. The effect of polyethyleneimine (PEI) on the structure and micro-morphology of ZnO nanorod array films, as well as the photoelectric conversion properties in dye-sensitized solar cells (DSSCs) was analyzed. It was found that with the addition of PEI in growth solution, the ZnO nanorods became smaller in diameter and longer in length and hence the dye absorption and the photovoltaic performance of DSSCs were improved. A power conversion efficiency of 2.30% had been achieved on a DSSC based on a 7.9 μm-long nanorod array film prepared by a growth solution containing the PEI. © 2011 Elsevier B.V.

Yang M.,Chongqing University of Technology | Yang M.,Chongqing University | Pan F.,Chongqing University
Materials and Design | Year: 2010

The effects of Sn addition on the as-cast microstructure, mechanical properties and casting fluidity of the ZA84 magnesium alloy are investigated. The results indicate that adding 0.5-2.0 wt.%Sn to the ZA84 alloy not only can result in the formation of Mg2Sn phase but also can refine the Mg32(Al, Zn)49 phase and suppress the formation of Mg32(Al, Zn)49 phase, and with the increase of Sn amount from 0.5 wt.% to 2.0 wt.%, the morphology of Mg32(Al, Zn)49 phase gradually changes from coarse continuous and/or quasi-continuous net to relatively fine quasi-continuous and/or disconnected shapes. In addition, adding 0.5-2.0 wt.%Sn to the ZA84 alloy can improve the tensile and creep properties, and casting fluidity of the alloy. Among the Sn-containing ZA84 alloys, the ZA84 alloy added 1.0 wt.%Sn exhibits the best ultimate tensile strength, elongation and casting fluidity while the ZA84 alloy added 2.0 wt.%Sn has the best yield strength and creep properties. © 2009 Elsevier Ltd. All rights reserved.

Wei J.,Dalian University of Technology | Zhang G.,Chongqing University
International Journal of Advanced Manufacturing Technology | Year: 2010

Aiming at the high precision machining of screw rotors, a new grinding method for screw rotors using cubic boron nitride (CBN) grinding wheel is presented in this paper. Small electroplated CBN grinding wheel is firstly used to grind screw rotors. The mathematical model for the axial profiles of CBN grinding wheel is developed based on gear engagement theory. Taking the backlash of screw rotors and the coating thickness of CBN layer into consideration, the modification of the base body of the wheel shape is introduced into the design of the CBN grinding wheel. Wire cut electrical discharge machining low speed (WEDM-LS) was used to machine the base body of the CBN grinding wheel. The formed turning tools of the base body of CBN grinding wheel using WEDM-LS and the wheel shapes of CBN grinding wheel using the formed turning tool were performed. The CBN grinding wheels for the screw rotors were made to verify the validity and effectiveness of the presented method. The electroplated CBN grinding wheels were used to machine the screw rotors, and the machining experiments were performed. The data obtained in the experiments reach the fifth class of Chinese Standard GB10095-88. © 2009 Springer-Verlag London Limited.

Gao M.,Chongqing University | Liu K.,University of Reading | Wu Z.,Chongqing University
Information Systems Frontiers | Year: 2010

Recently, personalised search engines and recommendation systems have been widely adopted by users who require assistance in searching, classifying, and filtering information. This paper presents an overview of the field of personalisation systems and describes current state-of-the-art methods and techniques. It reviews approaches for (1) user profiling, including behaviour, preference, and intention modelling; (2) content modelling, comprising content representation, analysis, and classification; and (3) filtering methods for recommendation, classified into four main categories: rule-based, content-based, collaborative, and hybrid filtering. The paper also discusses personalisation systems in different domains, and various techniques and their limitations. Finally, it identifies several issues and possible directions for further research that can improve recommendation capabilities and enhance personalised systems. © 2009 Springer Science+Business Media, LLC.

Li B.,Chongqing Three Gorges University | Li B.,Chongqing University | Yao R.,University of Reading
Building Research and Information | Year: 2012

Rapid urbanization in China has resulted in great demands for energy, resources and pressure on the environment. The progress in China's development is considered in the context of energy efficiency in the built environment, including policy, technology and implementation. The key research challenges and opportunities are identified for delivering a low-carbon built environment. The barriers include the existing traditional sequential design process, the lack of integrated approaches and insufficient socio-technical knowledge. A proposed conceptual systemic model of an integrated approach identifies research opportunities. The organization of research activities should be initiated, operated and managed in a collaborative way among policy-makers, professionals, researchers and stakeholders. More emphasis is needed on integrating social, economic and environmental impacts in the short, medium and long terms. An ideal opportunity exists for China to develop its own expertise, not merely in a technical sense but in terms of vision and intellectual leadership in order to flourish in global collaborations. © 2012 Taylor & Francis.

Tang M.-C.,University of Electronic Science and Technology of China | Tang M.-C.,University of Arizona | Tang M.-C.,Chongqing University | Ziolkowski R.W.,University of Arizona
IEEE Transactions on Antennas and Propagation | Year: 2013

The designs and performance characteristics of several electrically small antennas based on complementary split ring resonators (CSRRs) are reported. A coaxial-fed monopole is first integrated with a CSRR that is cut from a grounded finite copper disc. The presence of the electrically small CSRR element facilitates a nearly complete impedance match to the source, a nearly broadside radiation pattern, and a high radiation efficiency. The addition of a circular top-hat to the monopole then achieves an ultra-low profile (0. 005λ0) design and an improved broadside pattern, while maintaining all other desirable features. Finally, to enrich their potential usefulness, two additional enhancements of these designs were accomplished. One is a further miniaturization (ka < 0.5) that is achieved by introducing a more complex CSRR element, while maintaining a high, 82%, radiation efficiency. The second is a further enhancement of the directivity and front-to-back ratio through the introduction of a slot-modified parasitic disc, while maintaining the original impedance matching, low-profile and electrically small properties. These designs were consummated and their performance characteristics evaluated with the frequency domain ANSYS-ANSOFT High Frequency Structure Simulator (HFSS) and were confirmed independently using the time domain CST Microwave Studio (MWS) simulator. A prototype of the basic system was fabricated and tested; the agreement between the simulated and measured results validates the design principles. © 1963-2012 IEEE.

Zhao H.-B.,China University of Mining and Technology | Yin G.-Z.,Chongqing University
Yantu Lixue/Rock and Soil Mechanics | Year: 2011

Mechanical properties and acoustic emission characteristics of briquette samples are studied under fixed gas pressure and confining pressure. The results show: mechanical properties discreteness of coal containing gas is decreased because of gas existing; triaxial strength is decreased and Young's modulus is increased compared with coal; acoustic emission events are comparatively well distributed in process of triaxial compression of coal containing gas; the concentrated regions only appear at near damage regions; the distribution of AE events amplitude shows three peaks mode, energy of AE events is increased as deformation increasing; AE events parameters lag behind triaxial compression curve.

Duan D.-W.,Chongqing University | Rao Y.-J.,Chongqing University | Rao Y.-J.,University of Electronic Science and Technology of China | Hou Y.-S.,Chongqing University | Zhu T.,Chongqing University
Applied Optics | Year: 2012

We demonstrate an all-fiber optical Fabry-Perot interferometer (FPI) strain sensor whose cavity is a microscopic air bubble. The bubble is formed by fusion splicing together two sections of single-mode fibers (SMFs) with cleaved flat tip and arc fusion induced hemispherical tip, respectively. The fabricated interferometers are with bubble diameters of typically ∼100 μm. Strain and temperature sensitivities of fabricated interferometers are studied experimentally; a strain sensitivity of over 4 Pm/με and a thermal sensitivity of less than 0.9 Pm/°C is obtained. © 2012 Optical Society of America.

Wu S.,Chongqing University | Li C.,Chongqing University | Liao X.,Chongqing University | Duan S.,Southwest University
Neurocomputing | Year: 2012

This paper investigates exponential stability of the equilibrium point of discrete-time delayed dynamic systems with impulsive effects. Firstly, some Razumikhin-type theorems considering stabilizing effects of impulses are introduced. These results show that even the impulse-free component of the original system is unstable; impulses may compensate the deviating trend. Then, we apply the theoretical results to a class of recurrent neural networks under stochastic perturbations and derive several stability preservation criteria; the applicable region of the impulsive strength is also estimated. Some numerical examples are provided to illustrate the efficiency of the results at the end. © 2012 Elsevier B.V..

Zou J.,Southwest University | Zou J.,Chongqing University | Gao J.,Chongqing University
Journal of Hazardous Materials | Year: 2011

TiO2/SiO2 composite photocatalysts were prepared by depositing of TiO2 onto nano-SiO2 particles. X-ray diffraction (XRD), transmission electron micrograph (TEM), Raman spectrometer, UV-Vis diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy (FT-IR) were employed to characterize the properties of the synthesized TiO2/SiO2 composites. These results indicated that the products without calcination were amorphous, and calcination could enhance the crystallinity of TiO2. Increases in the amount of TiO2 would decrease the dispersion in the composites. H2O2-sensitized TiO2/SiO2 composite photocatalysts could absorb visible light at wavelength below 550nm. The photocatalytic activity of as-prepared catalysts was characterized by methyl-orange degradation. The results showed the uncalcined composite photocatalysts with amorphous TiO2 exhibited higher photocatalytic activity under visible light, and the activity of catalysts with TiO2 content over 30% decreased with increasing of TiO2 content. Increases in the calcination temperature and TiO2 content promote the formation of bulk TiO2 and result in a decrease in activity. © 2010.

Dang Z.-M.,University of Science and Technology Beijing | Dang Z.-M.,Beijing University of Chemical Technology | Dang Z.-M.,Chongqing University | Yuan J.-K.,Beijing University of Chemical Technology | And 2 more authors.
Advanced Materials | Year: 2013

Study of flexible nanodielectric materials (FNDMs) with high permittivity is one of the most active academic research areas in advanced functional materials. FNDMs with excellent dielectric properties are demonstrated to show great promise as energy-storage dielectric layers in high-performance capacitors. These materials, in common, consist of nanoscale particles dispersed into a flexible polymer matrix so that both the physical/chemical characteristics of the nanoparticles and the interaction between the nanoparticles and the polymers have crucial effects on the microstructures and final properties. This review first outlines the crucial issues in the nanodielectric field and then focuses on recent remarkable research developments in the fabrication of FNDMs with special constitutents, molecular structures, and microstructures. Possible reasons for several persistent issues are analyzed and the general strategies to realize FNDMs with excellent integral properties are summarized. The review further highlights some exciting examples of these FNDMs for power-energy-storage applications. Recent progress in the development of flexible nanodielectric materials (FNDMs) with high dielectric permittivity is highlighted. Particular focus is given to increasing the energy density of various FNDMs. Key issuses in the synthesis, structure, and dielectric properties of nanodielectrics are reviewed. Some long-standing problems and topics that warrant further investigation are also addressed. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Sun W.,Chongqing University | Shen Y.-H.,Southwest University | Han M.-J.,Chongqing University | Cao Y.-F.,Southwest University | Zhang Z.,Chongqing University
Molecular Biology and Evolution | Year: 2014

Although there are many studies to show a key role of transposable elements (TEs) in adaptive evolution of higher organisms, little is known about the molecular mechanisms. In this study, we found that a partial TE (Taguchi) inserted in the cis-regulatory region of the silkworm ecdysone oxidase (EO) gene, which encodes a crucial enzyme to reduce the titer of molting hormone (20-hydroxyecdysone, 20E). The TE insertion occurred during domestication of silkworm and the frequency of the TE insertion in the domesticated silkworm (Bombyx mori) is high, 54.24%. The linkage disequilibrium in the TE inserted strains of the domesticated silkworm was elevated. Molecular population genetics analyses suggest that this TE insertion is adaptive for the domesticated silkworm. Luminescent reporter assay shows that the TE inserted in the cis-regulatory region of the EO gene functions as a 20E-induced enhancer of the gene expression. Further, phenotypic bioassay indicates that the silkworm with the TE insertion exhibited more stable developmental phenotype than the silkworm without the TE insertion when suffering from food shortage. Thus, the inserted TE in the cis-regulatory region of the EO gene increased developmental uniformity of silkworm individuals through regulating 20E metabolism, partially explaining transformation of a domestication developmental trait in the domesticated silkworm. Our results emphasize the exceptional role of gene expression regulation in developmental transition of domesticated animals. © The Author 2014. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Guo N.,Southwest University | Guo N.,Chongqing University | Luan B.,Chongqing University | Liu Q.,Chongqing University
Materials and Design | Year: 2013

The influences of pre-torsion deformation on microstructures, tensile strength and microhardness of cold drawing pearlitic steel wires have been investigated in this study by twisting the wires to different number of revolutions. The results indicated that the tensile strength is very sensitive to torsion deformation and reduced distinctly after pre-torsion. Microhardness in the center layer and surface layer displayed different evoluting process with increasing number of the pre-torsion revolutions. Boundary strengthening reduced by fragmentation of cementite lamellae and work hardening enhanced by strain gradient induced by the pre-torsion were discussed to reveal the changes of the tensile strength and microhardness. © 2013 Elsevier Ltd.

Zhu Y.,Chongqing University | Zhu Y.,Southwest University of Political Science and Law
Advance Journal of Food Science and Technology | Year: 2013

The law of resource industries and resource-based urban development is that the resource-based cities will inevitably experience the process of construction, prosperity, recession, restructuring and revitalization, or extinction. This studies takes the Wansheng district of Chinese Chongqing as an example, starting from the basic conditions of agriculture to analyze the basis for developing the modern agriculture transformation in resources exhausted cities, analyzing the current situation of developing the modern agriculture transformation in the Wansheng district from the agricultural elements, the agricultural conditions and agricultural functions and reaching the conclusions that the scientific planning, overall planning, relying on the government, implementing the policy, adding to the financial and social investment, increasing the investment intensity of infrastructure construction in resource-based cities and strengthening the basic research about the harm to the geological structure, groundwater caused by the deep goaf and extra large pit, increasing the construction about the industrialization of agriculture, agro-processing and agricultural standardization, implementing the development of the modern agriculture's transformation strategy about the modern agriculture mechanism of company, professional cooperatives and farmers in resource-exhausted cities. © Maxwell Scientific Organization, 2013.

Zhu Y.,Chongqing University | Zhu Y.,Southwest University of Political Science and Law
Advance Journal of Food Science and Technology | Year: 2013

Agricultural modernization is organically integrated with the development of industrialization and urbanization. Agricultural modernization is the key and difficult point in the simultaneous development with Chinese characteristics industrialization, informatization and urbanization. This study takes Tongnan county as an example and analyzes the measures and strategies to step up agricultural modernization from perspectives of organizational leadership and assessment, spatial layout and base industries, creative demonstration and scientific popularization, information circulation system, policy support and incentive mechanism and innovation of Financial insurance cooperation organization, with aiming to accelerate agricultural modernization, enhance the fast increase in farmers' income, improve rural living condition and promote the synchronous development of industrialization, informationization, urbanization and agricultural modernization.

Zhu Y.,Chongqing University | Zhu Y.,Southwest University of Political Science and Law
Advance Journal of Food Science and Technology | Year: 2013

In order to study the causes of weak agricultural base in China, the income gap between urban and rural residents, agriculture and the obvious insufficiency in agriculture, rural areas and farmers, we analyze focal and difficult points in the simultaneous development between Chinese industrialization, informatization, urbanization and agricultural modernization and seek for ways and strategies to promote the modernization of agriculture process. This study takes Qijiang district of Chongqing as an example, from five aspects to discuss the ways and strategies of advancing the process of agricultural modernization; they are the development of the profitable agriculture, the reform of rural property rights, management rights and land ticket, rural circulation and financing, government investment and support and the improvement of the production and living conditions in rural areas. We hope these can accelerate the construction of agricultural modernization, promote sustained and rapid growth in farmers' income, constantly improve the production and living conditions in rural areas and promote the simultaneous development of industrialization, informatization, urbanization and agricultural modernization. © Maxwell Scientific Organization, 2013.

Liu J.,University of Reading | Yao R.,University of Reading | Wang J.,Chongqing University | Li B.,Chongqing University
Applied Thermal Engineering | Year: 2012

Occupants' behaviour when improving the indoor environment plays a significant role in saving energy in buildings. Therefore the key step to reducing energy consumption and carbon emissions from buildings is to understand how occupants interact with the environment they are exposed to in terms of achieving thermal comfort and well-being; though such interaction is complex. This paper presents a dynamic process of occupant behaviours involving technological, personal and psychological adaptations in response to varied thermal conditions based on the data covering four seasons gathered from the field study in Chongqing, China. It demonstrates that occupants are active players in environmental control and their adaptive responses are driven strongly by ambient thermal stimuli and vary from season to season and from time to time, even on the same day. Positive, dynamic, behavioural adaptation will help save energy used in heating and cooling buildings. However, when environmental parameters cannot fully satisfy occupants' requirements, negative behaviours could conflict with energy saving. The survey revealed that about 23% of windows are partly open for fresh air when air-conditioners are in operation in summer. This paper addresses the issues how the building and environmental systems should be designed, operated and managed in a way that meets the requirements of energy efficiency without compromising wellbeing and productivity. © 2011 Elsevier Ltd. All rights reserved.

Duan D.W.,Chongqing University | Rao Y-J.,Chongqing University | Rao Y-J.,University of Electronic Science and Technology of China | Zhu T.,Chongqing University
Journal of the Optical Society of America B: Optical Physics | Year: 2012

A compact, all-fiber, open-cavity Fabry-Perot interferometer gas refractometer formed by fusion splicing a short section of single-mode fiber (SMF) between two sections of SMFs with a large lateral offset is proposed. Only simple fabrication steps including cleaving and fusion splicing are involved, so the fabrication is easy, safe, and cost effective. Such fabricated sensors have been successfully demonstrated as gas refractometers having a refractive index response of high sensitivity (~1540nm/RIU), good linearity, and high repeatability. Temperature evaluations also show that this kind of interferometer has a very low thermal sensitivity. © 2012 Optical Society of America.

Li B.L.,Southwest University | Luo H.Q.,Southwest University | Lei J.L.,Chongqing University | Li N.B.,Southwest University
RSC Advances | Year: 2014

Hemin-functionalized MoS2 nanosheets (hemin/MoS2-NSs) are first obtained via van der Waals interactions between few-layered MoS 2 nanosheets (MoS2-NSs) and hemin molecules. It is demonstrated that a portion of MoS2-NSs undergoes a phase transition from semiconducting to metallic phase under the influence of hemin, which shows the coexistence of semiconducting and metallic phases in the crystal structure of hemin/MoS2-NSs. MoS2-NSs prepared from sonication-induced exfoliation of bulk MoS2 crystals in aqueous surfactant solution exhibit intrinsic peroxidase-like activity for the oxidation of 3,3,5,5-tetramethylbenzidine in the presence of H2O2, which is further improved by the functionalization of hemin. Significantly, MoS2-NSs are presented as a new support of hemin, and when compared to MoS2-NSs, hemin/MoS2-NSs exhibit better dispersity in aqueous solution, which is used in the development of H2O2 sensor based on the enhanced peroxidase-like activity. © The Royal Society of Chemistry 2014.

Xu G.,Chongqing University | Xu G.,Southwest University of Political Science and Law | Dan B.,Chongqing University | Zhang X.,Chongqing University | Liu C.,Chongqing University
International Journal of Production Economics | Year: 2014

This paper investigates the impact of establishing a dual-channel supply chain coordinating contract when the supply chain agents are risk aversion under a mean-variance model. We present an analytical framework for marking price decisions in a centralized and a decentralized dual-channel supply chain with risk-averse, and we analyze the impact of risk tolerance on the manufacturer and retailer's pricing decisions. The results show that the price set by a risk-averse dual-channel supply chain is lower than the one set by a risk-neutral dual-channel supply chain. Furthermore, compared with a centralized system, the vertical and horizontal competition in a decentralized system tends to result in channel inefficiency. To achieve channel coordination, we propose a contract the two-way revenue sharing contract that we demonstrate by coordinating the dual-channel supply chain with risk-averse, and we analyze that how the risk attitude changes the parameters of the coordinating contract. In addition, it is found that the manufacturer can prompt the retailer to cooperate by providing such a contract, which not only coordinates the dual-channel supply chain but also ensures that both supply chain members achieve a win-win situation. © 2013 Elsevier B.V.

He X.,Southwest University | Li C.,Southwest University | Huang T.,Texas A&M University at Qatar | Li C.,University of Ballarat | Huang J.,Chongqing University
IEEE Transactions on Neural Networks and Learning Systems | Year: 2014

In this brief, based on the method of penalty functions, a recurrent neural network (NN) modeled by means of a differential inclusion is proposed for solving the bilevel linear programming problem (BLPP). Compared with the existing NNs for BLPP, the model has the least number of state variables and simple structure. Using nonsmooth analysis, the theory of differential inclusions, and Lyapunov-like method, the equilibrium point sequence of the proposed NNs can approximately converge to an optimal solution of BLPP under certain conditions. Finally, the numerical simulations of a supply chain distribution model have shown excellent performance of the proposed recurrent NNs. © 2013 IEEE.

Zhou J.,Southwest University | Zhou J.,Chongqing University | Mu C.,Chongqing University
Nonlinear Analysis: Real World Applications | Year: 2011

In this paper, we investigate the existence, stability, permanence, and global attractor of positive solutions for the following three species food chain model with diffusion and BeddingtonDeangelis functional response -Δu1=u1(r-u1)-a1u1u2e1+u1+u2inΩ,-Δu2=m1u1u2e1+u1+u2-b1u2- a2u2u3e2+u2+u3inΩ,-Δu3=m2u2u3e2+u2+u3-b2u3inΩ, k1∂u1∂ν+u1=k2∂u2∂ν+u2=k3∂u3∂ν+u3= 0on∂Ω, where Ω is a bounded domain of RN, N<1, with boundary ∂Ω of class C2+α for some α∈(0,1), ν is the outward unit vector on ∂Ω, the parameters r,ai,bi,ei,mi(i=1,2) are strictly positive, and ki<0(i=1,2,3), ui(i=1,2,3) are the respective densities of prey, predator, and top predator. © 2010 Elsevier Ltd. All rights reserved.

Yang S.,China West Normal University | Lin K.,University of Electronic Science and Technology of China | Li J.,Chongqing University
International Journal of Theoretical Physics | Year: 2014

The Hawking radiation of black hole in Einstein-Proca theory is discussed in this paper. The Einstein-Proca black hole is more general than Reissner-Nordström black hole, because Proca field is massive vector field. We calculate several quantum perturbations in this spacetime, and obtain the Hawking radiation at the horizon in Einstein-Proca theory. © 2014 Springer Science+Business Media New York.

Yang L.-X.,Chongqing University | Yang X.,Chongqing University | Yang X.,Southwest University
Physica A: Statistical Mechanics and its Applications | Year: 2014

Due to the high dimensionality of an epidemic model of computer viruses over a general scale-free network, it is difficult to make a close study of its dynamics. In particular, it is extremely difficult, if not impossible, to prove the global stability of its viral equilibrium, if any. To overcome this difficulty, we suggest to simplify a general scale-free network by partitioning all of its nodes into two classes: higher-degree nodes and lower-degree nodes, and then equating the degrees of all higher-degree nodes and all lower-degree nodes, respectively, yielding a reduced scale-free network. We then propose an epidemic model of computer viruses over a reduced scale-free network. A theoretical analysis reveals that the proposed model is bound to have a globally stable viral equilibrium, implying that any attempt to eradicate network viruses would prove unavailing. As a result, the next best thing we can do is to restrain virus prevalence. Based on an analysis of the impact of different model parameters on virus prevalence, some practicable measures are recommended to contain virus spreading. The work in this paper adequately justifies the idea of reduced scale-free networks. © 2013 Elsevier B.V. All rights reserved.

Wang Y.,Chongqing University | Li W.,British Columbia Transmission Corporation | Lu J.,Chongqing University
IEEE Transactions on Power Delivery | Year: 2010

As a key technology in smart grid, the wide-area measurement system (WAMS) will gradually become an important guarantee for security and stability of future power systems. This paper presents a quantified reliability evaluation method for the backbone communication network in WAMS and the overall WAMS from a hardware reliability viewpoint. The whole WAMS is modeled using a hierarchical structure. Markov modeling and state enumeration techniques are combined to perform the reliability evaluation. The WAMS in the IEEE 14bus system is used as an example to demonstrate the application of the presented method in reliability assessment of overall WAMS. © 2010 IEEE.

Xu K.,University of Electronic Science and Technology of China | Liu H.,Chongqing University | Zhang Z.,Sichuan Solid State Circuit Research Institute SISC
Applied Optics | Year: 2015

In this paper, we discuss the emission of visible light by a monolithically integrated silicon gate-controlled diode with the p-n junction reverse-biased. Since the MOS-like diode utilizes the field effect to modulate the optical output, the modulation speed will benefit from this mechanism. Hence, a silicon gate-controlled diode structure for optical modulation analyzed its modulation principle, its dynamic characteristics are presented, and the bandwidth of the device is considered to approach GHz in theory due to the field-induced emission mechanism. The prototype MOS-like diode opens up the design of multiterminal silicon light emitting devices (LEDs), where gate electrodes with more than one gate contact overlap several junctions with different junction intersection geometries. The device appears as a good candidate for optical modulation within silicon technology. © 2015 Optical Society of America.

Yin J.,University of Missouri | Zhu G.,University of Missouri | Zhu G.,Chongqing University | Deng B.,University of Missouri
Journal of Membrane Science | Year: 2013

Due to the carbon nanotubes' unique one-dimensional tubular structure and superior mechanical and chemical properties, it has been used as a filler to prepare high performance flat sheet membranes. In this study, we explored if the incorporation of oxidized multi-walled carbon nanotubes (MWNTs) into polysulfone (PSU) hollow fiber membranes could enhance the membrane performance. Polyvinylpyrrolidone (PVP) was used as porogen and 1-methyl-2-pyrrolidinone (NMP) as the solvent in the phase inversion spinning process, and deionized water was used as bore fluid and coagulant. Purified and oxidized MWNTs in the mixed acid solution (H2SO4/HNO3=3/1 in volume) were used as fillers at concentrations ranging from 0 to 1wt%. Results indicated that at three different PSU concentrations (15, 18, and 20wt%), the pure water flux of all membranes increased first and then gradually decreased with increasing nanotube concentration. The optimized mixed matrix membranes showed a significant increase in pure water flux (60% to 100%) while maintaining a similar capability for solute rejection, and also an improved resistance to protein fouling. The water contact angle of the membrane decreased with increasing filler concentration, suggesting an increase in the membrane surface hydrophilicity that might have contributed to the improved membrane performance. © 2013 Elsevier B.V.

Yang L.-X.,Southwest University | Yang L.-X.,Chongqing University | Yang X.,Southwest University
Physica A: Statistical Mechanics and its Applications | Year: 2013

Inevitably, there exist infected computers outside of the Internet. This paper aims to understand how infected external computers affect the spread of computer viruses. For that purpose, a new virus-antivirus spreading model, which takes into account the effect of infected/immune external computers, is established. A systematic study shows that, unlike most previous models, the proposed model admits no virus-free equilibrium and admits a globally asymptotically stable viral equilibrium. This result implies that it would be practically impossible to eradicate viruses on the Internet. As a result, inhibiting the virus prevalence to below an acceptable level would be the next best thing. A theoretical study reveals the effect of different parameters on the steady virus prevalence. On this basis, a number of suggestions are made so as to contain virus spreading. © 2013 Elsevier B.V. All rights reserved.

Yu L.,University of Cardiff | Yu L.,Chongqing University
Habitat International | Year: 2014

Chinese urbanisation is occurring rapidly but faces great challenges due to its large population, the continuing level of rural-urban migration, the shortage of resources to support the present development and the urbanisation model. One result is that China is the world's largest carbon emitter. The application of low carbon eco-city development should be contribute to the solution in addressing these challenges. This paper attempts to explore the low carbon eco-city initiatives in China. By analysing critically the problems which impact upon such an environmentally friendly development model, including government policy, social value and delivery mechanisms, this paper suggests that despite problems in implementing such a model, the low carbon eco-city model must be the mainstream approach to Chinese urbanisation and industrialisation. © 2014 Elsevier Ltd.

Zhang H.J.,Chongqing University | Zhang D.F.,Chongqing University | Ma C.H.,Chongqing University | Guo S.F.,Southwest University
Materials Letters | Year: 2013

The current work presents the room-temperature mechanical properties and the corrosion resistance in 3.5% NaCl solution of conventional casting and rapidly solidified Mg-6Zn-Mn (ZM61) magnesium alloys. It is found that the mechanical properties of rapidly solidified ZM61 alloy are dramatically enhanced, with the ultimate strength increased from 335 MPa to 460 MPa (37% increment), which can be attributed to the formation of the refined dendrite microstructure and the strengthening MgZn2 phase distributed within the matrix. Furthermore, the rapidly solidified ZM61 alloy performs better in corrosion resistance than the extruded ZK60 and pure Mg alloys, suggesting that the rapid-solidification technique is a promising way to improve the strength and corrosion resistance of magnesium alloy for the structural and corrosive media utilization. © 2012 Elsevier B.V.

Sun Z.,Chongqing University | Arentze T.,TU Eindhoven | Timmermans H.,TU Eindhoven
Transportation Research Part C: Emerging Technologies | Year: 2012

Travel information plays a central role in reducing uncertainty and persuading travelers to act in particular ways. It may result in activity-travel rescheduling decisions. The modeling of such behavior is relatively complex as it goes beyond simple route/link choice. Moreover, it involves multiple uncertain events that may appear at different points in the future. In addition, travelers may differ in their attitudes toward risk and the decision heuristics they apply. This paper develops a decision model that incorporates these aspects and reports the results of an interactive computer experiment which was developed to collect data on activity-travel rescheduling under multiple uncertain events and information acquisition. The results of the model estimation suggest that the model performed well. © 2012 Elsevier Ltd.

Chen F.,Chinese University of Hong Kong | Wong K.-W.,City University of Hong Kong | Liao X.,Southwest University | Liao X.,Chongqing University | Xiang T.,Chongqing University
IEEE Transactions on Information Theory | Year: 2013

The Arnold cat map is employed in various applications where chaos is utilized, especially chaos-based cryptography and watermarking. In this paper, we study the problem of period distribution of the generalized discrete Arnold cat map over the Galois ring BBZ 2 e. Full knowledge of the period distribution is obtained analytically by adopting the Hensel lift approach. Our results have impact on both chaos theory and its applications as they not only provide design strategy in applications where special periods are required, but also help to identify unstable periodic orbits of the original chaotic cat map. The method in our paper also shows some ideas how to handle problems over the Galois ring BBZ 2e. © 1963-2012 IEEE.

Huang T.,Texas A&M University at Qatar | Li C.,Chongqing University | Duan S.,Southwest University | Starzyk J.A.,Ohio University | Starzyk J.A.,Rzeszow University of Technology
IEEE Transactions on Neural Networks and Learning Systems | Year: 2012

This paper focuses on the hybrid effects of parameter uncertainty, stochastic perturbation, and impulses on global stability of delayed neural networks. By using the Ito formula, Lyapunov function, and Halanay inequality, we established several mean-square stability criteria from which we can estimate the feasible bounds of impulses, provided that parameter uncertainty and stochastic perturbations are well-constrained. Moreover, the present method can also be applied to general differential systems with stochastic perturbation and impulses. © 2012 IEEE.

Hu C.,Chongqing University | Hu C.,George Washington University | Liao X.,Chongqing University | Cheng X.,George Washington University
Theoretical Computer Science | Year: 2012

In verifiable multi-secret sharing schemes (VMSSs), many secrets can be shared but only one share is kept by each user and this share is verifiable by others. In this paper, we propose two secure, efficient, and verifiable (t,n) multi-secret sharing schemes, namely Scheme-I and Scheme-II. Scheme-I is based on the Lagrange interpolating polynomial and the LFSR-based public key cryptosystem. The Lagrange interpolating polynomial is used to split and reconstruct the secrets and the LFSR-based public key cryptosystem is employed to verify the validity of the data. Scheme-II is designed according to the LFSR sequence and the LFSR-based public key cryptosystem. We compare our schemes with the state-of-the-art in terms of attack resistance, computation complexity, and so on, and conclude that our schemes have better performance and incur less computation overhead. Our schemes can effectively detect a variety of forgery or cheating actions to ensure that the recovery of the secrets is secure and creditable, and the length of the private key is only one third of that of others for the same security level. © 2012 Elsevier B.V. All rights reserved.

Xiao J.,Chongqing University | Hu R.,University of Science and Technology of China | Qian Y.,Chongqing University | Gong L.,University of Electronic Science and Technology of China | Wang B.,Huawei
IEEE Wireless Communications | Year: 2013

Wireless data traffic is growing extraordinarily, with new wireless devices such as smartphones and bandwidth-demanding wireless applications such as video streaming becoming increasingly popular and widely adopted. Correspondingly, we have also witnessed the phenomenal wireless technology evolutions to support higher system capacities from generation to generation. Long Term Evolution has been developed as a 4G wireless technology that can support next generation multimedia applications with high capacity and high mobility needs. However, the peak data rate from 3G UMTS to 4G LTE-Advanced only increases 55 percent annually, while global mobile traffic has increased 66 times with an annual growth rate of 131 percent between 2008 and 2013. Clearly, there is a huge gap between the growth rate of the new air interface and the growth rate of customers¿ needs. A promising way to alleviate the contention between the actual traffic demands and the actual system capacity growth is to exploit more available spectrum resources. Recently, cognitive radio technology has been under extensive research and study. It aims to provide abundant new spectrum opportunities by exploiting underutilized or unutilized spectrum opportunistically. In this article, we discuss the technical solutions to expand LTE spectrum with CR technology (LTE-CR), and survey the advances in LTE-CR from both research and implementation aspects. We present detailed key technologies that enable LTE-CR in the TV white space (TVWS), and related standards and regulation progresses. To demonstrate the feasibility of deploying LTECR in TVWS, we have conducted extensive system-level simulations and also developed a LTE-CR prototype. Both simulation and laboratory testing results show that applying LTECR in TVWS can achieve satisfactory performance. © 2002-2012 IEEE.

Xie K.,Chongqing University | Jiang Z.,Chongqing University | Li W.,British Columbia Transmission Corporation
IEEE Transactions on Energy Conversion | Year: 2012

Wind turbine power converter system (WTPCS) is a crucial device in a wind energy conversion system. This paper presents the new failure rate models and a reliability evaluation technique for the (WTPCS) considering effects of wind speeds, which can be named by the multistate probability analysis method. The case studies on the WTPCS of a 2 MW wind turbine with a permanent magnet synchronous generator are conducted using wind speed data at Lauwersoog and Valkenburg wind sites in Holland. The results indicate that reliability of the WTPCS is affected significantly by variations of wind speed and the rated wind speed of wind turbine. The effectiveness of the proposed method is demonstrated by examples. © 2011 IEEE.

Li H.,Chongqing University | Liao Sr. X.,Chongqing University | Liao Sr. X.,Southwest University | Huang T.,Texas A&M University at Qatar
IEEE Transactions on Systems, Man, and Cybernetics: Systems | Year: 2013

This paper is mainly concerned with the analysis of the second-order locally dynamical consensus of multiagent systems with nonlinear dynamics in the directed networks with arbitrarily fast switching topologies. In our designed framework, the time-varying network topology is constant in each time interval and then randomly jumps to another topology when certain occasional events occur at some random moments. In addition, we further assume that the dwell time of each topology is unknown in advance and the corresponding adjacency weighted matrix is not necessarily nonnegative due to the probable existence of deteriorated communication channels in the underlying interaction network. By the orthogonal decomposition method, the state vector of the resultant error dynamical system can be further decomposed as two transversal components, one of which evolves along the consensus manifold and the other evolves transversally with the consensus manifold. Then, by introducing the generalized matrix measure and by applying the tools of contraction and circle analysis, the second-order locally dynamical consensus of multiagent systems with arbitrarily fast switching directed topologies is theoretically investigated in detail, and some easily verified sufficient conditions are also presented. It is shown that, under sufficiently large coupling strengths, the random switchings can be effectively tolerated and the consensus can be achieved for all agents in the network. Finally, numerical simulation examples are also provided to demonstrate the feasibility and effectiveness of the obtained theoretical results. © 2013 IEEE.

Zhu Y.,Southwest University of Political Science and Law | Zhu Y.,Chongqing University
ICIC Express Letters, Part B: Applications | Year: 2014

We design the electronic commerce practice teaching simulation platform in order to adapt to the development of E-commerce practice teaching. Through simulating the E-commerce activities mainly including three kinds of transaction mode of electronic business activities such as B2C, B2B, C2C, supplementing with E-business environment of virtual bank, teaching center, the CA certificate and EDI electronic data interchange, the E-commerce teaching simulation platform allows students to experience and understand the macro E-commerce environment and micro E-commerce applications in simulation practice. It finishes the acknowledgement of practical teaching and the verification experiment tasks as student-oriented. The design and implementation of the platform help students to understand basic knowledge of E-commerce, and to enhance students' abilities of mastering and operating E-commerce software. It is helpful to enhance the students' understanding of E-commerce, which fully reflects the application of IT in practice teaching process. © 2014 ICIC International.

Liu M.,Chongqing University | Li B.,Chongqing University | Yao R.,Chongqing University | Yao R.,University of Reading
Energy and Buildings | Year: 2010

A generic model of Exergy Assessment is proposed for the Environmental Impact of the Building Lifecycle, with a special focus on the natural environment. Three environmental impacts: energy consumption, resource consumption and pollutant discharge have been analyzed with reference to energy-embodied exergy, resource chemical exergy and abatement exergy, respectively. The generic model of Exergy Assessment of the Environmental Impact of the Building Lifecycle thus formulated contains two submodels, one from the aspect of building energy utilization and the other from building materials use. Combined with theories by ecologists such as Odum, the paper evaluates a building's environmental sustainability through its exergy footprint and environmental impacts. A case study from Chongqing, China illustrates the application of this method. From the case study, it was found that energy consumption constitutes 70-80% of the total environmental impact during a 50-year building lifecycle, in which the operation phase accounts for 80% of the total environmental impact, the building material production phase 15% and 5% for the other phases. © 2010 Elsevier B.V.

Chung C.Y.,Chongqing University | Chung C.Y.,Hong Kong Polytechnic University | Yan W.,Chongqing University | Liu F.,Chongqing Shapingba Power Supply Bureau
IEEE Transactions on Power Systems | Year: 2011

In this paper, a decomposed predictor-corrector interior point method (DPCIPM) is proposed for solving the dynamic optimal power flow (DOPF) problem, which is a large-scale nonlinear optimization problem. The Karush-Kuhn-Tucker (KKT) system in DPCIPM is decomposed into many subsystems based on its special block structure, where the size of each subsystem depends on the network size only. In the iterative process, slack variables and Lagrange multipliers of dynamic constraints are first predicted and corrected, and then other variables in each time interval are predicted and corrected. The parameters, such as step length and barrier parameter, are independently estimated in each subsystem. Besides, an inequality iteration strategy is introduced to avoid unnecessary computation. Implementation of the proposed DPCIPM is described in detail. The effectiveness of the proposed method has been demonstrated on the IEEE 14-bus and IEEE 118-bus systems with up to 24 time intervals. It has been found that compared with a decomposed pure primal dual interior point method (DIPM), the proposed DPCIPM is more attractive, especially when dynamic constraints become active. © 2011 IEEE.

Li W.,Shandong Academy of Sciences | Hu L.,Chongqing University | Zhang S.,Chongqing University | Hou B.,Shandong Academy of Sciences
Corrosion Science | Year: 2011

Effects of two fungicides (myclobutanil and hexaconazole) on the corrosion resistance of copper in 3.5% NaCl solution under various conditions were evaluated via weight loss, electrochemical techniques, SEM and EDS. Results show that these compounds act as mixed-type inhibitors, suppressing the charge transfer process by the adsorption on copper surface. Chemisorption between inhibitors and copper is accordance with the Langmuir adsorption isotherm. The corrosion resistance of copper with inhibitors under near neutral conditions is better than that under acidic or alkaline conditions. Good inhibition performances at different temperatures and during a long time of immersion are also observed. © 2010 Elsevier Ltd.

Wang D.H.,Chongqing University | Liao W.H.,Chinese University of Hong Kong
Smart Materials and Structures | Year: 2011

Due to the inherent nonlinear nature of magnetorheological (MR) dampers, one of the challenging aspects for developing and utilizing these devices to achieve high performance is the development of models that can accurately describe their unique characteristics. In this review, the characteristics of MR dampers are summarized according to the measured responses under different conditions. On these bases, the considerations and methods of the parametric dynamic modelling for MR dampers are given and the state-of-the-art parametric dynamic modelling, identification and validation techniques for MR dampers are reviewed. In the past two decades, the models for MR dampers have been focused on how to improve the modelling accuracy. Although the force-displacement behaviour is well represented by most of the proposed dynamic models for MR dampers, no simple parametric models with high accuracy for MR dampers can be found. In addition, the parametric dynamic models for MR dampers with on-line updating ability and the inverse parametric models for MR dampers are scarcely explored. Moreover, whether one dynamic model for MR dampers can portray the force-displacement and force-velocity behaviour is not only determined by the dynamic model itself but also determined by the identification method.

Zhang W.,Henan Institute of Science and Technology | Wang M.,Chongqing University | Zhao W.,Henan Institute of Science and Technology | Wang B.,Henan Institute of Science and Technology
Dalton Transactions | Year: 2013

Magnetic composite ZnFe2O4/BiVO4 was successfully synthesized by the one-step chemical coprecipitation method. The photocatalytic activity of BiVO4 was improved by doping ZnFe 2O4 that possessed a narrow band gap, which enabled the ZnFe2O4/BiVO4 composite to show increased visible-light absorption and further generate more photo-produced electrons than pure BiVO4. The experimental results showed that the photocatalytic ability of the composite was better than that of pure BiVO4 under visible light irradiation. The n-type ZnFe2O4 nanoparticles were uniformly distributed on the surface of n-type BiVO 4, leading to the formation of n-n-type heterogeneous structures in the composite system. Since CB and VB potentials of ZnFe2O 4 and BiVO4 were differential, the photo-produced electrons and holes would migrate to a position at a relatively positive potential and a relatively negative potential, respectively, which enhanced the separation efficiency between photo-produced electrons and holes and thus further contributed to the enhancement of photocatalytic activity. © 2013 The Royal Society of Chemistry.

Wang D.H.,Chongqing University | Bai X.X.,Chongqing University | Liao W.H.,Chinese University of Hong Kong
Smart Materials and Structures | Year: 2010

In this paper, an integrated relative displacement self-sensing magnetorheological damper (IRDSMRD) and the corresponding electronic system to realize the integrated relative displacement sensing and controllable damping, including the relative displacement modulator/demodulator, circuit for superposing the carrier signal for the integrated relative displacement sensor (IRDS) on the exciting current from the controllable current driver for the controllable damping and controllable current driver are developed and tested. In the developed IRDSMRD, the exciting coil is energized by the current from the controllable current driver, on which the carrier signal for the IRDS is superposed by the superposition circuit. The amplitude modulation of the carrier signal for the IRDS by the relative displacement between the piston and cylinder of the IRDSMRD and the magnetization of the MR fluid are realized through the frequency division multiplexing of the exciting coil for both the IRDS and the MR damper and the relative displacement is accessed by demodulating the induced harmonic voltage from the induction coil of the IRDSMRD by the demodulator. The characteristics of the developed IRDSMRD, including the linearity, sensitivity and hysteresis error of the IRDS and the controllable damping force are tested on the established experimental setup based on the MTS 849 shock absorber test system and the real time simulation system. The testing results indicate that the developed IRDSMRD can not only achieve the integration of the relative displacement sensing capability but also possesses good performance of the relative displacement sensing of the IRDS and the large controllable damping force range. In addition, the performance of the IRDS will not be affected by the exciting current within a certain range and the damping force will not be degraded by the carrier signal for the IRDS. The realized principle and technology of the IRDSMRD lay a foundation for reducing the commercializing cost of MR dampers. © 2010 IOP Publishing Ltd.

Zhang Y.,Chongqing University | Xiao D.,Chongqing University | Wen W.,Jiangxi University of Finance and Economics | Tian Y.,Chongqing University
Optics and Laser Technology | Year: 2013

In some special multimedia applications, only the regions with semantic information should be provided better protection whereas the other smooth regions can be free of encryption. However, most of the existing multimedia security schemes only consider bits and pixels rather than semantic information during their encryption. Motivated by this, we propose an edge-based lightweight image encryption scheme using chaos-based reversible hidden transform and multiple-order discrete fractional cosine transform. An image is first carried out by the edge detection based on advanced CNN structure with adaptive thresholds to assess data significance in the image. The detection output is a binary image, in which a "1" reflects the detected pixel whereas a "0" is opposite. Both the detected image and the original image are divided into non-overlapping pixel blocks in the same way, respectively. Whether each block is encrypted or not depends on the significance judged by the corresponding detected block. The significant block is performed by reversible hidden transform followed by multiple-order discrete fractional cosine transform parameters and orders of these two transforms are determined by a two dimensional cross chaotic map. Experiment results show the significant contour features of an image that have been largely hidden only by encrypting about half pixels in the average sense. The keys are extremely sensitive and the proposed scheme can resist noise attack to some extent. © 2013 Elsevier Ltd.

Gong Y.,CAS Fujian Institute of Research on the Structure of Matter | Gong Y.,Chongqing University | Li J.,Chongqing University | Qin J.,Chongqing University | And 2 more authors.
Crystal Growth and Design | Year: 2011

Using bis-pyridyl-bis-amide ligands N,N'-bis-(4-pyridyl)phthalamide (L1), N,N'-bis-(4-pyridyl)iso-phthalamide (L2), hexanedioic acid bis-pyridin-4-ylamide (L3), and carboxylates, six metal(II) complexes formulated as Cd2(1, 4-chdc)(L1)2 · 4H2O (1,4-H2chdc = 1,4-cyclohexanedicarboxylic acid) (1), Cd2(L1)2(in) 4 · 3DMF (Hin = isonicotinic acid) (2), Zn(L1)(1,4-bdc) (1,4-H2bdc = 1,4-benzenedicarboxylic acid) (3), Cd(L2)(1,4-chdc) (4), Zn2(L2)2(tdc)2 · DMF (H2tdc = thiophene-2,5-dicarboxylic acid) (5), and Zn(2,6-ndc)0.5- (L3) 0.5(SO4) · (CH3NHCH3) (2,6-H2ndc = 2,6-naphthalenedicarboxylic acid) (6) have been hydro(solvo)thermally synthesized and structurally characterized by single-crystal X-ray diffraction. Complex 1 is a uninodal 6-connected noninterpenetrated three-dimensional (3D) network with {44.6 10.8}-mab topology, complex 2 exhibits a uninodal 6-connected 2-fold interpenetrated 3D framework with {412.63}-pcu topology, complex 3 shows a uninodal 8-fold interpenetrated 3D diamondoid framework, complexes 4 and 5 possess similar uninodal 2D layer with 44-sql topology, and complex 6 shows a framework of 2D → 3D inclined polycatenation based on 44-sql layer. The six complexes show different thermal stability and photoluminescence properties. The emission band of complex 1 becomes strong after dehydration, and water can reduce the emission intensities of the six complexes to some extents. © 2011 American Chemical Society.

Qin H.,Chongqing University | Qin H.,McGill University | Jonas J.J.,McGill University
Acta Materialia | Year: 2014

Three generations of twins were identified by electron backscatter diffraction techniques in pure titanium subjected to uniaxial compression at room temperature. Many primary contraction twins were observed as the initial texture was favourable for their formation. Numerous secondary extension twins formed within the primary contraction twins and some tertiary contraction twins within the secondary extension twins. The orientations of these three generations of twins were determined and their associated Schmid factors (SFs) were calculated. The formation of the twin variants selected in each generation and the absence of certain potential variants are explained by rotating the twinning displacement gradient tensor expressed in the twin system reference frame into the crystal reference frame of the relevant neighbouring grain. The presence of the observed secondary and tertiary twins is accounted for in terms of the ease of imposing the required accommodation strains on their neighbours. The results show that secondary twins can form even with low SFs as long as their accommodation takes place by prismatic or basal glide. However, the formation of certain second and third generation potential high SF twins was impeded when this would have required accommodation by the most difficult deformation mode: pyramidal glide. © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Zhou S.,Chongqing Normal University | Mu C.,Chongqing University
Journal of Nonlinear Science | Year: 2013

This paper deals with the Cauchy problem for a shallow water equation with high-order nonlinearities, y t +u m+1 y x +bu m u x y=0, where b is a constant, m∈ N, and we have the notation y:= (1-∂x 2) u, which includes the famous Camassa-Holm equation, the Degasperis-Procesi equation, and the Novikov equation as special cases. The local well-posedness of strong solutions for the equation in each of the Sobolev spaces Hs(R) with s>3/2 is obtained, and persistence properties of the strong solutions are studied. Furthermore, although the H1(R)-norm of the solution to the nonlinear model does not remain constant, the existence of its weak solutions in each of the low order Sobolev spaces Hs(R) with 1

Ma W.,Chongqing University | Wang M.,Chongqing University | Li C.,Hebei Electric Power Research Institute
Nonlinear Dynamics | Year: 2012

One-cycle controlled Cuk converter is a piecewise smooth nonlinear system. In this paper, sampled-data model is applied to analyze the dynamics of this converter. The results show that the four eigenvalues of the converter can be two pairs of complex conjugates, and that one pair may move out of the unit circle as some parameters are varied. This causes occurrence of slow-scale oscillation as a result of the Neimark-Sacker bifurcation in the input stage of the converter. Bifurcation may jeopardize the performance of the converter by decreasing the efficiency. A washout filter is used to control the bifurcation so as to stabilize the converter, and the effects of parameters of the filter on the stability of the converter are analyzed. Experimental measurements are provided to verify the analytical results. © 2011 Springer Science+Business Media B.V.

Zhou X.,Chongqing University | Qian Q.,Chongqing University | Qian Q.,PLA University of Science and Technology
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2013

Rock masses without pre-existing macrocracks are considered as granular materials with only microcracks. During excavation of tunnels, microcracks may nucleate, grow and propagate through rock matrix;secondary micrcracks may appear, and discontinuous and incompatible deformation of rock masses may occur. The classical continuum elastoplastic theory is not suitable for analyzing discontinuous and incompatible deformation of rock masses any more. A new non-Euclidean model is established based on free energy density, the equilibrium equation and the deformation incompatibility condition, where effects of the half length and density of microcracks on scalar curvature and the self-equilibrated stresses in deep rock mass are investigated. Stress fields in the surrounding rock masses around a deep circular tunnel are determined, which are the sum of elastic stresses and the self-equilibrated stresses determined by the scalar curvature. Due to the self-equilibrated stresses, the distribution of stresses in the surrounding rock masses around deep tunnels is obviously fluctuant or wave-like when the half length and density of microcracks are large, while the distribution of stresses in the surrounding rock masses around deep tunnels is not obviously fluctuant or wave-like when the half length and density of microcracks are small. The stress concentration at the tips of microcracks located in vicinity of stress wave crest is comparatively large, which may lead to the unstable growth and coalescence of secondary microcracks, and consequently the occurrence of fractured zones. On the other hand, the stress concentration at the tips of microcracks located around stress wave trough is relatively small, which may lead to arrest of microcracks, and thus to the non-fractured zones. The alternative appearance of stress wave crest and stress trough thus may induce the alternative occurrence of fractured and non-fractured zones in deep rock masses. The influences of the density and half length of microcracks on zonal disintegration and self-equilibrated stresses are investigated in detail by using numerical simulation.

Zhang X.-Z.,Chongqing University | Huang P.-K.,China Aerospace Science and Technology Corporation
Xi Tong Gong Cheng Yu Dian Zi Ji Shu/Systems Engineering and Electronics | Year: 2013

A new approach is developed for synthetic aperture radar (SAR) automatic target recognition based on Bayesian compressive sensing (BCS). Firstly SAR images are segmented into image data of target zones by constant false alarm rate. Then based on the BCS model, the sensing matrix is constructed by all training sets. The sparse coefficient vectors corresponding to the test samples are solved. Recognition is performed according to the L2 norm corresponding to each of training types of samples in the sensing matrix. Experimental results with the moving and stationary target acquisition and recognition public dataset show that the proposed approach has good recognition effects.

Chen C.R.,Chongqing University | Li M.H.,Northwest University, China
Numerical Functional Analysis and Optimization | Year: 2014

In this article, using the nonlinear scalarization approach by virtue of the nonlinear scalarization function, commonly known as the Gerstewitz function in the theory of vector optimization, Hölder continuity of solution mappings for both set-valued and single-valued cases to parametric vector equilibrium problems is studied. The nonlinear scalarization function is a powerful tool that plays a key role in the proofs, and its main properties (such as sublinearity, continuity, convexity) are fully employed. Especially, its locally and globally Lipschitz properties are provided and the Lipschitz property is first exploited to investigate the Hölder continuity of solutions. © 2014 Copyright Taylor & Francis Group, LLC.

Wang X.,Chongqing University | Niu Y.,Chongqing Normal University
Neurocomputing | Year: 2013

The optimal separating hyperplane with maximum margin plays a central role in the support vector machine (SVM) classifiers, but is exclusively determined by the support vectors that does not take any structure information into account, especially in the one-versus-all (OVA) SVM for the multi-class classification application where the positive samples and negative ones are usually unbalanced. To address this intra-inter class imbalance problem, a new OVA SVM method is proposed by extending manifold regularization and enhancing the relative maximum margin. It aims to minimize the scatter of nearby intra-class point pairs while penalize that of nearby inter-class point pairs not being arbitrarily large through the constraints of marginal separation and manifold regularization. This objective is transformed into a constrained optimization problem that overcomes both the classical SVM's weakness of ignoring the data underlying structure, and the Laplacian SVM's weakness of abandoning class label information and class separation of manifolds. It also takes the positive and negative samples into different consideration according to their unbalanced distribution. Additionally, risk bounds are derived for the proposed formulation based on the theory of Rademacher complexity and the improvement on the bounds of standard SVM is proven. The comparative experiments for multi-class classification, face recognition, and natural image segmentation on several synthetic and benchmark data sets validate the effectiveness of the proposed method and indicate the consideration of both preserving intrinsic within-class manifold structure and bounding the local relative margin between class is helpful to improve the OVA SVM classification performance. © 2013 Elsevier B.V.

Chen P.S.,CAS National Astronomical Observatories | Yang X.H.,Chongqing University
Astronomical Journal | Year: 2012

We collected almost all of the Galactic infrared carbon stars (IRCSs) from literature published up to the present to organize a catalog of 974 Galactic IRCSs in this paper. Some of their photometric properties in the near-, mid-, and far-infrared are discussed. © 2012. The American Astronomical Society. All rights reserved.

Chen P.S.,CAS National Astronomical Observatories | Yang X.H.,Chongqing University
Astronomical Journal | Year: 2012

Sources with infrared spectra in Group P of the IRAS/LRS database all show polycyclic aromatic hydrocarbon features. They are often planetary nebulae, H II regions, reflection/dark nebulae, Wolf-Rayet stars, or external galaxies. However, we noted that some carbon stars are also included in this group. We searched for and investigated all infrared spectra in Group P of the IRAS/LRS database. Finally, we found 11 previously known carbon stars and identified 8 new candidate carbon stars in Group P. Infrared spectra of these stars may present the 11.2 μm SiC emission features indicative of their carbon-rich properties. © © 2012. The American Astronomical Society. All rights reserved.

He Y.,Chongqing University | Liu B.,Chongqing University | Zhang X.,University of Science and Technology Beijing | Gao H.,Chongqing Machine Tools Group Co. | Liu X.,IBM
Journal of Cleaner Production | Year: 2012

Machining tasks are performed on machine tools with enormous amount of energy consumption in manufacturing system. Understanding and characterizing task-oriented energy consumption is significantly essential to explore the potential on energy-saving in production management. To achieve it, this paper proposes a modeling method of task-oriented energy consumption for machining manufacturing system. The energy consumption characteristics driven by task flow in machining manufacturing system are analyzed, which describes that energy consumption dynamically depends on the flexibility and variability of task flow in production processes. Based on the task-oriented energy consumption characteristics, an event graph methodology has been exploited to model the energy consumption driven by tasks in production processes of machining manufacturing system. The proposed modeling method is solved in Simulink simulation environment, and applied to select the flexible processes of tasks for optimizing energy consumption. The results show a valuable insight of energy consumption in machining manufacturing system so as to make robust decisions on the potential for improving energy efficiency. © 2011 Elsevier Ltd. All rights reserved.

Huang Q.,Fudan University | Huang Q.,Chongqing University | Zhou G.,Fudan University | Fang L.,Chongqing University | And 2 more authors.
Energy and Environmental Science | Year: 2011

A series of oriented rutile TiO2 nanorod-array films are in-situ grown on fluorine-doped tin oxide (FTO) coated glass substrates from a mixed acid solution containing titanium tetraisopropoxide (TTIP), hydrochloric acid (HCl), acetic acid (HOAc), and water (H2O) by means of hydrothermal reaction at 150°C. The effect of HOAc in the titania growth solution on the structure and micro-morphology of TiO2 nanorod array films, as well as the photoelectric conversion properties in dye-sensitized solar cells (DSSCs) has been fully investigated. It is found that HOAc can facilitate the formation of uniform, dense, and vertically oriented TiO2 nanorods and hence improves the dye adsorption, electron diffusion coefficient, and the photovoltaic performance of DSSCs, typically in short-circuit photocurrent and power conversion efficiency. A power conversion efficiency of 4.03% has been achieved on a DSSC based on a 2.3 m-long nanorod array film obtained from a mixed acid solution with the TTIP:HCl:HOAc:H2O ratio of 0.8:4:8:8 by volume. © 2011 The Royal Society of Chemistry.

Tu W.,University of Toronto | Tu W.,Chongqing University | Chin Y.-H.,University of Toronto
Journal of Catalysis | Year: 2014

Rate measurements, carried out after elimination of transport corruptions, show that CH3OH partial oxidation on Pt clusters proceeds via three distinctly different kinetic regimes defined by the operating oxidant-to-reductant (O2-to-CH3OH) ratio. These kinetic regimes, each with unique rate dependencies for HCHO, HCOOCH3, and CO2 formation, arise from a dynamic shift in the identity and coverages of reactive intermediates on Pt cluster surfaces from saturated with chemisorbed oxygen, to uncovered, and then to partially covered with methanol derived species as the oxygen chemical potential at cluster surfaces decreases with decreasing O2-to-CH3OH ratio. HCHO formation rates first remain insensitive to O2 on Pt cluster surfaces saturated with chemisorbed oxygen (O*), then increase proportionally with O2 as cluster surfaces depleted of oxygen and as unoccupied Pt sites become the most abundant surface intermediates, and eventually increase more than linearly with O2 on Pt surfaces predominantly covered with CH3OH derived intermediates. The transition in rate dependence on O2 is accompanied by a concomitant transition on CH3OH dependence: HCHO formation rates are linearly proportional to, then independent of, and eventually inhibited by CH3OH as the O2-to-CH 3OH ratio decreases. Similar transition in reaction orders is also found for HCOOCH3 and CO2 formation. The first-order rate coefficient for CH3OH oxidation is a single-valued function of the operating O2-to-CH3OH ratio, because the ratio determines the oxygen chemical potential at Pt cluster surfaces via the kinetic coupling of O2 and CH3OH activation steps and, in turn, the identity and coverage of reactive intermediates, the nature and availability of active sites, and the identity of kinetically-relevant steps. © 2014 Elsevier Inc. All rights reserved.

Zhang Y.,Henan University of Technology | Liu C.,Henan University of Technology | Song Y.,Chongqing University
Journal of the Franklin Institute | Year: 2013

This paper investigates the problem of finite-time H∞ filtering for one class of discrete-time Markovian jump systems with time-varying norm-bounded disturbance. Firstly, the filtering error dynamic system is constructed based on an H∞ filter with or without the control input. Then, an H∞ filtering is designed to ensure stochastic finite-time boundedness of the resulting filtering error system and satisfying a prescribed H∞ attenuation level for the filtering error system in the given finite-time interval. Sufficient criteria on the stochastic H∞ finite-time boundedness are established in terms of linear matrix inequalities with a fixed parameter. As an auxiliary result, we also tackle the problem of finite-time H∞ filtering for discrete-time Markovian jump systems without the control input and provide sufficient conditions on finite-time H∞ filtering for the family of discrete-time Markovian jump systems. Finally, numerical examples are presented to show the validity of the developed techniques. © 2013 The Franklin Institute.

Zhou X.P.,Chongqing University | Bi J.,Chongqing University | Qian Q.H.,Chongqing University | Qian Q.H.,PLA University of Science and Technology
Rock Mechanics and Rock Engineering | Year: 2015

A novel meshless numerical method, called general particle dynamics (GPD), is proposed to simulate samples of rock-like brittle heterogeneous material containing four preexisting flaws under uniaxial compressive loads. Numerical simulations are conducted to investigate the initiation, growth, and coalescence of cracks using a GPD code. An elasto-brittle damage model based on an extension of the Hoek–Brown strength criterion is applied to reflect crack initiation, growth, and coalescence and the macrofailure of the rock-like material. The preexisting flaws are simulated by empty particles. The particle is killed when its stresses satisfy the Hoek–Brown strength criterion, and the growth path of cracks is captured through the sequence of such damaged particles. A statistical approach is applied to model the heterogeneity of the rock-like material. It is found from the numerical results that samples containing four preexisting flaws may produce five types of cracks at or near the tips of preexisting flaws including wing, coplanar or quasi-coplanar secondary, oblique secondary, out-of-plane tensile, and out-of-plane shear cracks. Four coalescence modes are observed from the numerical results: tensile (T), compression (C), shear (S), and mixed tension/shear (TS). A higher load is required to induce crack coalescence in the shear mode (S) than the tensile (T) or mixed (TS) mode. It is concluded from the numerical results that crack coalescence occurs following the weakest coalescence path among all possible paths between any two flaws. The numerical results are in good agreement with reported experimental observations. © 2014, Springer-Verlag Wien.

Zhou X.P.,Chongqing University | Chen G.,Chongqing University | Qian Q.H.,PLA University of Science and Technology
Theoretical and Applied Fracture Mechanics | Year: 2012

The zonal disintegration phenomenon is investigated for cross-anisotropic rock around a deep circular tunnel under hydrostatic pressure condition as well as the total elastic stress-field distributions. The number and size of fractured and non-fractured zones is determined by using the Mohr-Coulomb criterion. Effects of cross-anisotropic elastic parameters of deep rock mass on the zonal disintegration phenomenon are investigated. Numerical computations are carried out. It is shown from numerical results that the number and size of fractured and non-fractured zones significantly depend on to cross-anisotropic elastic parameters of deep rock mass. © 2011 Elsevier Ltd.

Zhang S.,Chongqing University | Zhang S.,Chongqing Normal University | Zhu J.,Chongqing University
Engineering Analysis with Boundary Elements | Year: 2012

The boundary element-linear complementarity method for solving the Laplacian Signorini problem is presented in this paper. Both Greens formula and the fundamental solution of the Laplace equation have been used to solve the boundary integral equation. By imposing the Signorini constraints of the potential and its normal derivative on the boundary, the discrete integral equation can be written into a standard linear complementarity problem (LCP). In the LCP, the unique variable to be affected by the Signorini boundary constraints is the boundary potential variable. A projected successive over-relaxation (PSOR) iterative method is employed to solve the LCP, and some numerical results are presented to illustrate the efficiency of this method. © 2011 Elsevier Ltd. All rights reserved.

Zhang S.,Chongqing University | Zhang S.,Chongqing Normal University | Zhu J.,Chongqing University
Engineering Analysis with Boundary Elements | Year: 2013

We propose a projection iterative algorithm based on a fixed point equation for solving a certain class of Signorini problem. The satisfaction of the Signorini boundary conditions is verified in a projection iterative manner, and at each iterative step, an elliptic mixed boundary value problem is solved by a boundary element method which is suitable for any domain. We prove the convergence of the algorithm by the property of projection. The advantage of this algorithm is that it is easy to be implemented and converge quickly. Some numerical results show the accuracy and effectiveness of the algorithm. © 2012 Elsevier Ltd.

Zheng L.,Chongqing University | Lu S.,Chongqing Municipal Power Corporation
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2013

A discrete model of Boost PFC converter is built, the stroboscopic map of its inductor current is obtained and its phase-plane trajectory is applied to reveal the relationship between input voltage and inductor current stability. The small parametric perturbation method and the double integral sliding mode method are respectively adopted to avoid bifurcations. Simulative results show that, the later, with better robustness and higher power factor does not need to exert external disturbance, effectively avoids the bifurcations caused by input voltage variation and has better fast-scale bifurcation control effect.

Yu S.,CAS Dalian Institute of Chemical Physics | Liu S.,Chongqing University | Lan Y.,Chongqing University | Wan B.,CAS Dalian Institute of Chemical Physics | Li X.,CAS Dalian Institute of Chemical Physics
Journal of the American Chemical Society | Year: 2015

Rh(III)-catalyzed C-H activation assisted by an oxidizing directing group has evolved to a mild and redox-economic strategy for the construction of heterocycles. Despite the success, these coupling systems are currently limited to cleavage of an oxidizing N-O or N-N bond. Cleavage of an oxidizing C-N bond, which allows for complementary carbocycle synthesis, is unprecedented. In this article, α-ammonium acetophenones with an oxidizing C-N bond have been designed as substrates for Rh(III)-catalyzed C-H activation under redox-neutral conditions. The coupling with α-diazo esters afforded benzocyclopentanones, and the coupling with unactivated alkenes such as styrenes and aliphatic olefins gave ortho-olefinated acetophenoes. In both systems the reactions proceeded with a broad scope, high efficiency, and functional group tolerance. Moreover, efficient one-pot coupling of diazo esters has been realized starting from α-bromoacetophenones and triethylamine. The reaction mechanism for the coupling with diazo esters has been studied by a combination of experimental and theoretical methods. In particular, three distinct mechanistic pathways have been scrutinized by DFT studies, which revealed that the C-H activation occurs via a C-bound enolate-assisted concerted metalation-deprotonation mechanism and is rate-limiting. In subsequent C-C formation steps, the lowest energy pathway involves two rhodium carbene species as key intermediates. © 2015 American Chemical Society.

Zhong S.,Chongqing Normal University | Zhongshi H.E.,Chongqing University
Journal of Software | Year: 2012

Grid task scheduling is a NP-hard problem. Inthis paper, an optimization algorithm of grid taskscheduling is brought forward by using classificationstrategies to improve particle swarm algorithm. The particleswarm is divided into accurate subgroups for local slowsearch, commonness subgroups for the cloning strategyprocessing and inferior subgroups for changing intoaccurate subgroups to operate the positive and reverseclouds. The experimental results show that the schedulingalgorithm effectively achieves the load balancing ofresources and preferably avoids falling into local optimalsolution and the selection pressure of genetic algorithm andelementary particle swarm algorithm. This algorithm hasthe high accuracy and convergence speed and so on. © 2012 ACADEMY PUBLISHER.

Wang L.,Chongqing University | Mu C.,Chongqing University | Zhou S.,Chongqing Normal University
Zeitschrift fur Angewandte Mathematik und Physik | Year: 2013

This paper deals with the global existence and boundedness of the solutions for the quasilinear chemotaxis system (Formula presented.) under homogeneous Neumann boundary conditions in a convex smooth bounded domain Ω ⊂ Rn, with nonnegative initial data (Formula presented.) (for some θ > n) and (Formula presented.). The given functions (Formula presented.) and f(s) are supposed to be sufficiently smooth for all s ≥ 0 and such that f(0) = 0. This model describes the motion of the cells (e.g., bacteria) under the effect of gradients of the concentration of the oxygen that is consumed by the cells. It is proved that the corresponding initial boundary value problem possesses a unique global classical solution that is uniformly bounded in (Formula presented.) provided that some technical conditions are fulfilled. © 2013, Springer Basel.

Qian Q.,Chongqing University | Zhou X.,PLA University of Science and Technology
Journal of Mining Science | Year: 2011

A non-Euclidean continuum model for the descriptions of the elastic stress-field distributions and fractured zones in the surrounding rock masses around the deep circular tunnels subjected to nonhydrostatic pressure are established. In the non-Euclidean continuum model, the elastic stress-field distribution of the deep surrounding rock induced by compatible deformation of non-fractured zones and incompatible deformation of fractured zones is determined. The wavy behavior of the stress components based on the non-Euclidean model are obviously different from that of the stress components which have extrema on the working contour and tend monotonically to the value of the in-situ stress at infinity in rock masses within the framework of the classical model. Mohr-Coulomb criterion is applied to research the occurrence of disintegration zones. Disintegration zones appear when the stresses in deep rock masses reach a certain critical value. It is found from the numerical results that the magnitude and site of fractured zones depend on the value of in-situ stress and non-Euclideanness parameters. © 2011 Pleiades Publishing, Ltd.

Chu Z.,Chongqing University | Yang Y.,Tongji University
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2011

In order to improve the sound source identification performance of near-field beamforming and the calculation accuracy of maximum sound pressure contribution on the array plane, the influence of array microphone signal amplitude correction to acoustical imaging and sound source identification was analyzed by using the cross-spectra beamforming algorithm with auto-spectra exclusion based on the assumption of spherical wave. The results indicated that the calculation accuracy of the maximum sound pressure contribution on the array plane was improved, and some shortages such as the increase of the maximum side-lobe level and the reduction of the dynamic range were come out in the meantime. Ulteriorly, the improved near-field beamforming algorithm for the calculation of the sound pressure contribution on the array plane was put forward. Both results of simulation and the experiments showed that the improved algorithm could calculate the maximum sound pressure contribution accurately, and the dynamic range was increased 1.0-1.6 dB. Finally, the acoustical sealed performance test for a car was carried out by using the improved algorithm. The weak positions of the acoustical seal were identified precisely.

Chen G.,Chongqing University | Lewis F.L.,University of Texas at Arlington
Asian Journal of Control | Year: 2012

This paper investigates the distributed tracking control problems for a group of networked mechanical systems. We describe three scenarios that motivate these problems. Firstly, under the conditions that the desired time-varying trajectory is available to a portion of the networked mechanical systems and that the available signals from the neighboring mechanical systems include the position and velocity information, a distributed tracking control strategy is proposed. Next, we remove the requirement for the neighboring mechanical system's velocity information and propose a control method so that the coupling signals among the networked mechanical systems can be only position information. In the third scenario, we assume that only positions are measured for each mechanical system. Distributed nonlinear observers are proposed to estimate the local mechanical system's velocity and acceleration. Based on the estimated states, the distributed controllers are designed to achieve the tracking control. Simulation results are provided to show the effectiveness of the proposed control laws. © 2012 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society.

Shen L.,Chongqing University | Zhou J.,Chongqing University | Zhou J.,Shandong Jianzhu University
Habitat International | Year: 2014

The Chinese government is a promoting sustainable urbanization process to develop future cities, and various indicator systems have been introduced for guiding the sustainable urbanization practice. This paper examines the effectiveness of these existing indicator systems introduced in China. Nine sample indicator systems were collected and compared. Principal criteria selected to analyze the effectiveness of the nine samples was based on a literature review. This study reveals that the existing indicator systems have limitations for guiding sustainable urbanization practice and the differences between the various indicator systems present barriers for their effective application. It is found that no official department in China supervises the application of these indicators. The lack of a systematic method for establishing indicators is considered as a major reason for contributing to the limited effectiveness of these established indicators. There is a need to develop an effective method to supervise decision makers to establish and select effective indicators. © 2014 Elsevier Ltd.

Chen G.,Chongqing University | Lewis F.L.,University of Texas at Arlington
IFAC Proceedings Volumes (IFAC-PapersOnline) | Year: 2011

The binary control protocols are proposed for synchronization of networked Lagrangian systems with/without tracking. These protocols are inspired by the observed behavior in animal groups, where relative motion is determined not by full time-signal measurements, but by coarse estimates of relative heading differences between neighbors. The signum protocol does not require explicit measurement of time signals from neighbors, and hence it has the potential to significantly reduce the requirements for both computation and sensing. In the case that there exists a time-varying control node in the networked Lagrangian systems, the finite-time tracking control is achieved by using the signum protocol. Numerical examples are given to illustrate the theoretical results. © 2011 IFAC.

Lin M.,ChongqingUniversity | Chen S.,Chongqing University
IEEE Transactions on Consumer Electronics | Year: 2013

Because NAND flash memory provides the outof-place update scheme to address its erase-before-write hardware constraint, garbage collection policy is included in the flash-aware file systems and flash translation layer (FTL) to reclaim garbage and obtain free space. In this paper, an efficient and intelligent garbage collection policy is proposed for NAND flash-based consumer electronics, which is called EIGC. EIGC introduces an efficient grey prediction model for forecasting the future I/O workload during the next garbage collection operation execution time interval and determines the number of victim blocks that should be selected for evicting according to the predicted I/O workload. In order to reduce the cleaning cost in terms of the cost for copying the valid pages to the free space of NAND flash memory and improve the degree of wear leveling, an efficient victim block selection scheme is included in the proposed EIGC policy. Trace-driven simulations show that the proposed EIGC policy is superior to the state-of-the-art policies in terms of the number of copy operations, the number of erase operations, and the degree of wear leveling. © 2013 IEEE.

Wang W.,Chongqing University | Kodur V.,Michigan State University | Yang X.,Chongqing University | Li G.,Tongji University
Thin-Walled Structures | Year: 2014

There are few design provisions in codes and standards on local buckling of steel columns under fire conditions. To examine the local stability of steel stub columns at elevated temperatures, 12 stub columns were tested under simultaneous application of load and fire conditions. The test variables included Grade (type) of steel, buckling resistance, temperature and load levels. During fire tests, cross sectional temperatures, axial displacement, buckling deflection, and local buckling failure modes of flange and web of stub columns were recorded at various temperatures. Data from the tests is utilized to evaluate buckling resistance of flange and web both at room and elevated temperatures by applying the ultimate strain method and curve inflexion point method. Results from fire tests are utilized to validate a finite element model developed for tracing local buckling of steel columns at elevated temperatures. Results from fire tests and finite element analysis show that failure mode of columns at room and elevated temperatures follow similar pattern but the load bearing capacity of Q460 steel columns degrade much more rapidly under fire conditions than that of Q235 steel columns. Further, Eurocode 3 provisions for local buckling produce non-conservative results in certain situations. © 2014 Elsevier Ltd.

Chen L.,Chongqing University | Xu Z.,Chongqing University | Dai H.,Nantong University | Zhang S.,Chongqing University
Journal of Alloys and Compounds | Year: 2010

A facile route for the production of high quality monodisperse Fe3O4/silica nanocomposite microspheres (NMs) with embedded structures has been successfully established by employing a solution-based route via direct decomposition of tetraethyl ortho-silicate (TEOS) in solution under the presence of freshly synthesized Fe3O4 nanoparticles (NPs). This method is based on a two-step process, involving: (i) synthesis of Fe3O4 NPs by coprecipitaiton of Fe2+ and Fe3+ with NH3·H2O in solution at room temperature; (ii) formation of Fe3O4/silica NMs by direct decomposition of TEOS in the presence of dispersed Fe3O4 NPs of (i) under mechanical stirring at room temperature. The effects of the concentration of TEOS and pH value have been investigated in detail to optimize the synthetic conditions. XRD, XPS, FTIR, EDS, SEM, and TEM were used for the characterization of the synthesized products. It is found that the synthesized Fe3O4/silica NMs with as typical values average diameters of 0.25-4 μm obtained under the optimized conditions were nearly monodisperse, superparamagnetic with a relatively high saturation magnetization value, which implies potentially promising applications in engineering and biomedicine areas. Moreover, a possible formation mechanism of NMs was also proposed. Meanwhile, this general approach could be extended to prepare other metal oxide/silica NMs. © 2010 Elsevier B.V.

Chen G.,Chongqing University | Lewis F.L.,University of Texas at Arlington
International Journal of Robust and Nonlinear Control | Year: 2011

In this paper, we consider the exponential second-order consensus problem of a network of inertial agents with time-varying coupling delays and variable balanced topologies. The passive decomposition approach is employed to incorporate the agents' inertial effect into the distributed control design. The sufficient conditions for the exponential second-order consensus are provided, both when the topology is switched arbitrarily (without dwell time between consecutive switches) and when it is switched with average dwell time. The results present conditions that must be satisfied by the controller design parameters and performance requirements. Furthermore, an approach to the design of consensus protocol is presented, which is robust to the time delays and the dynamically changing interaction topologies. Numerical examples are given to illustrate our theoretical results. © 2010 John Wiley & Sons, Ltd.

Chen G.,Chongqing University | Lewis F.L.,University of Texas at Arlington
International Journal of Robust and Nonlinear Control | Year: 2011

This paper investigates distributed controller design problem for a leader-follower network in the presence of communication delays. Two main contributions are made in this work. First, the second-order controlled consensus scheme for the weakly connected communication graph topology is proposed. A necessary and sufficient condition is given under which the exponential consensus is achieved. Meanwhile, the relationship among the agents' inertias, the allowable delay bound, the communication topology, the consensus convergence rate, and the control gains is unveiled. Second, the robustness performances of the distributed control scheme with respect to the communication failures and delays are provided. It is shown that if the communication failure rate and the topology switching frequency, respectively, satisfy the given bounds, the exponential second-order controlled consensus can be achieved under a bounded delay. Numerical examples are given to illustrate the theoretical results. © 2010 John Wiley & Sons, Ltd.

Wang Y.,Chongqing University | Song Y.,Chongqing University | Lewis F.L.,University of Texas at Arlington
IEEE Transactions on Industrial Electronics | Year: 2015

This paper studies the distributed consensus problem of multiagent systems (MASs) in the presence of nonidentical unknown nonlinear dynamics and undetectable actuation failures. Of particular interest is the development of a robust adaptive fault-tolerant consensus protocol capable of compensating uncertain dynamics/disturbances and time-varying yet unpredictable actuation failures simultaneously. By introducing the virtual parameter estimation error into the artfully chosen Lyapunov function, the consensus problem is solved with a robust adaptive fault-tolerant control scheme based upon local (neighboring) agent state information. It is shown that the proposed method is user friendly in that there is no need for detail dynamic information of the agent or costly detection/diagnosis of the actuation faults in control design and implementation, resulting in a structurally simple and computationally inexpensive solution for the leaderless consensus problem of MAS. Simulation results illustrate and verify the benefits and effectiveness of the proposed scheme. © 2015 IEEE.

Bi H.,Chongqing University | Bi H.,Changzhou University | Si H.,Chongqing University
Safety Science | Year: 2012

A novel method for dynamic risk assessment of oil spill accidents based on numerical simulation was presented in this paper. The dynamic risk assessment model was developed consisting of a comprehensive list of caused consequences like environmental damage, asset loss, health impact and social effect as well as emergency actions preventing these losses. Contributing events in the Mater Logic Diagram (MLD) of the dynamic risk assessment model were valued based on the simulated evolvement of oil contaminants under spill scenario on quasi-static fluid, which was obtained by coupling an oil spill model with hydrodynamic module in Jialing river of Three Gorges Reservoir in China after the impoundment of the reservoir to 175. m water level in 2010. Calculated result of dynamic risk as grade IV indicated that the assessed oil spill was not as catastrophic as we thought because of the slow transport of oil fractions on water surface and absence of dispersed oil in water body due to the quasi-static fluid, very gentle wind and effective emergency actions, as well as by the reason that rare agriculture or industrial crops exist in spill adjacent area. © 2011 Elsevier Ltd.

Hongjun L.,Henan University | Hongjun L.,AGplus Technologies Pte Ltd | Zang Z.,Chongqing University | Tang X.,Chongqing University
Optical Materials Express | Year: 2014

Photoluminescent ZnO nanoparticles have wide applications in biolabeling. A dual phase hydrothermal method has been developed in this paper to synthesize nanoflower-shaped ZnO nanoparticles. Hydrogen peroxide was identified as a unique oxygenic source to promote the formation of ZnO nanoflowers from the organic zinc precursor. The reaction mechanism for the formation of ZnO nanoflowers was proposed and studied by Fourier transform infrared (FTIR). The as-prepared hydrophobic colloidal ZnO nanoparticles could be subsequently modified to water-soluble ZnO nanoflowers via a ligand exchange process with aminethanethiol HCl. The structure and optical properties of the ZnO nanoparticles were studied by transmission electron microscopy, X-ray diffraction, and photoluminescence measurement (PL). Both types of ZnO nanoflowers demonstrated good photoluminescent properties which could have wide applications. © 2014 Optical Society of America.

Chen G.,Chongqing University | Lewis F.L.,University of Texas at Arlington | Xie L.,Nanyang Technological University
Automatica | Year: 2011

This paper investigates the finite-time distributed consensus problem for multi-agent systems using a binary consensus protocol and the pinning control scheme. Compared with other consensus algorithms which need the complete state or output information of neighbors, the proposed algorithm only requires sign information of the relative state measurements, that is, the differences between a node's state and that of its neighbors. This corresponds to only requiring a single-bit quantization error relative to each neighbor. This signum protocol is realistic in terms of observed behavior in animal groups, where relative motion is determined not by full time-signal measurements, but by coarse estimates of relative heading differences between neighbors. The signum protocol does not require explicit measurement of time signals from neighbors, and hence has the potential to significantly reduce the requirements for both computation and sensing. Analysis of discontinuous dynamical systems is used, including the Filippov solutions and set-valued Lie derivative. Based on the second-order information on the evolution of Lyapunov functions, the conditions that guarantee the finite-time consensus for the systems are identified. Numerical examples are given to illustrate the theoretical results. © 2011 Elsevier Ltd. All rights reserved.

Zhao W.,Chongqing University | Ren H.,Chongqing University | Rotter V.S.,TU Berlin
Resources, Conservation and Recycling | Year: 2011

This paper presents a system dynamics computer model to evaluate alternative type of recycling center under different policy and economy environments through comparison on the economic feasibility of recycling centers and ratio of savings to costs in C&D waste management. A case study for the City of Chongqing, China is selected. Simulated results show three key factors can contribute to the economic feasibility of recycling and the ratio of savings to costs in C&D waste management: (a) profit; (b) unit recycling cost; (c) extra revenue from location advantage (It was assumed that the mobile centers can attain extra revenue from the location advantage compared with fixed recycling centers). The sensitive analysis and comparison on ratios between public and private sector indicate that to achieve the optimum ratio of savings to costs, design of recycling centers and selection of governmental instruments are determined by the priority list: (1) low extra revenue from location advantage; (2) low profit; (3) low unit recycling cost. Meanwhile, the fluctuation of the three factors must be prior to achieve economic feasibility of corresponding recycling centers. Crown Copyright © 2011 Published by Elsevier B.V. All rights reserved.

Chen G.,Chongqing University | Lewis F.L.,University of Texas at Arlington
IEEE Transactions on Systems, Man, and Cybernetics, Part B: Cybernetics | Year: 2011

This paper investigates the cooperative tracking control problem for a group of Lagrangian vehicle systems with directed communication graph topology. All the vehicles can have different dynamics. A design method for a distributed adaptive protocol is given which guarantees that all the networked systems synchronize to the motion of a target system. The dynamics of the networked systems, as well as the target system, are all assumed unknown. A neural network (NN) is used at each node to approximate the distributed dynamics. The resulting protocol consists of a simple decentralized proportional-plus- derivative term and a nonlinear term with distributed adaptive tuning laws at each node. The case with nonconstant NN approximation error is considered. There, a robust term is added to suppress the external disturbances and the approximation errors of the NNs. Simulation examples are included to demonstrate the effectiveness of the proposed algorithms. © 2010 IEEE.

Zhang Z.,Chongqing University | Qian J.,Chongqing University | You C.,Chongqing University | Hu C.,Sichuan CFBC Demonstration Power Co.
Construction and Building Materials | Year: 2012

Circulating fluidized bed combustion (CFBC) fly ash and slag are wastes from CFBC power plant, and have such a high sulfur content (usually more than 5% SO 3 by weight) that would result in a great risk of destructive expansion when used in building materials, which are produced in normal temperature. This work investigated the preparation conditions of autoclaved brick with CFBC fly ash and slag, and compared the long-term volume stability and the hydration products between the autoclaved brick and adobe one. It is shown that the autoclaved brick could be made up of 77% CFBC fly ash, 20% CFBC slag and 3% cement by weight, and exhibited good long-term volume stability, and achieved the compressive strength of up to 14.3 MPa, and that there was no dihydrate gypsum and ettringite formation in the autoclaved brick so that the destructive expansion could be avoided. This work has carried out practical production and application of the autoclaved brick. It is concluded that CFBC fly ash and slag can be used to make high-quality brick as long as it is autoclaved. © 2012 Elsevier Ltd. All rights reserved.

Zhang Y.-Y.,Chongqing University | Chen Q.-H.,Zhejiang University | Chen Q.-H.,Nanjing University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2015

The generalized rotating-wave approximation (GRWA) is presented for the two-qubit quantum Rabi model. The analytical expressions in the zeroth-order approximation recover the previous adiabatic ones. The counter-rotating-wave terms can be eliminated by performing the first-order corrections. An effective solvable Hamiltonian with the same form as the ordinary RWA one is then obtained, giving very accurate eigenvalues and eigenstates. Energy levels in the present GRWA are in accordance with the numerical exact diagonalization ones in a wide range of coupling strengths. The population dynamics in the GRWA are in quantitative agreement with the numerical results and exhibit the absence of collapses clearly, revealing the effects of the counter-rotating wave. © 2015 American Physical Society.

Xi Y.,West Virginia University | Su Y.,West Virginia University | Yu Z.,Chongqing University | Dong B.,West Virginia University | And 3 more authors.
Angewandte Chemie - International Edition | Year: 2014

The chemoselective addition of arenes and 1,3-diketones to α-aryldiazoesters was achieved through ligand-controlled gold catalysis. Unlike a dirhodium catalyst (which promotes C sp 3-H insertion and cyclopropanation) and a copper catalyst (which catalyzes O-H and N-H insertions), the gold catalyst with an electron-deficient phosphite as the ancillary ligand exclusively gave the carbophilic addition product, thus representing a new and efficient approach to form "carbophilic carbocations", which selectively react with carbon nucleophiles. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chen G.,Chongqing University | Lewis F.L.,University of Texas at Arlington
International Journal of Systems Science | Year: 2012

It is well known that achieving consensus among a group of multi-vehicle systems by local distributed control is feasible if and only if all nodes in the communication digraph are reachable from a single (root) node. In this article, we take into account a more general case that the communication digraph of the networked multi-vehicle systems is weakly connected and has two or more zero-in-degree and strongly connected subgraphs, i.e. there are two or more leader groups. Based on the pinning control strategy, the feasibility problem of achieving second-order controlled consensus is studied. At first, a necessary and sufficient condition is given when the topology is fixed. Then the method to design the controller and the rule to choose the pinned vehicles are discussed. The proposed approach allows us to extend several existing results for undirected graphs to directed balanced graphs. A sufficient condition is proposed in the case where the coupling topology is variable. As an illustrative example, a second-order controlled consensus scheme is applied to coordinate the movement of networked multiple mobile robots. © 2011 Copyright Taylor and Francis Group, LLC.

Lei M.-X.,University of Southern California | Lei M.-X.,Chongqing University | Chuong C.-M.,University of Southern California | Widelitz R.B.,University of Southern California
Journal of Investigative Dermatology | Year: 2013

Activation of β-catenin was shown to be of central importance for hair development and cycling. Recent progress brought more understanding to how Wnt signaling is regulated during hair follicle generation and regeneration, telogen-anagen reentry, and extra-follicular macro-environmental modulation. This new understanding presents multiple possibilities to fine tune Wnt signaling for desired hair growth. © 2013 The Society for Investigative Dermatology.

Li B.,Mississippi State University | Zhang X.Y.,Chongqing University
Scripta Materialia | Year: 2014

Recent experimental observations have revealed that {101̄2} <101̄1̄> twinning involves zero shear, confirming this twinning mode is dominated by shuffling rather than shear. This raises the question: how is global strain generated by shuffling in hexagonal close-packed metals without involving shear? This paper addresses this important question. We demonstrate that although shuffling does not contribute to the twinning shear, it generates a normal strain along the c-axis due to the misfit between the parent and the twin lattice. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Huang T.,CAS Institute of High Energy Physics | Zhong T.,CAS Institute of High Energy Physics | Wu X.-G.,Chongqing University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

Currently, not enough is known to determine the hadron distribution amplitudes (DAs) - which are universal physical quantities in the high-energy processes involving hadrons - in order to apply perturbative QCD to exclusive processes. Even for the simplest pion, one cannot discriminate between different DA models. Conversely, one expects that processes involving pions can in principle provide strong constraints on the pion DA. For example, the pion-photon transition form factor (TFF) can get accurate information about the pion wave function or DA due to the single pion in this process. However, the data from Belle and BABAR show a big difference regarding this TFF in high-Q2 regions; at present, they are unable to determine the pion DA. In the present paper, we think it is still possible to determine the pion DA as long as we perform a combined analysis of the existing data of the processes involving pions, such as π→μν̄, π0→γγ, B→πlν, D→πlν, etc. Based on the revised light-cone harmonic oscillator model, a convenient DA model is suggested, whose parameter B - which dominates its longitudinal behavior for φπ(x,μ2) - can be determined in a definite range by these processes. A light-cone sum rule analysis of the semileptonic processes B→πlν and D→πlν leads to a narrow region B=[0.01,0.14], which indicates a slight deviation from the asymptotic DA. Then, one can predict the behavior of the pion-photon TFF in high-Q2 regions which can be tested in future experiments. This method provides the possibility that the pion DA will be finally determined by a global fit. © 2013 American Physical Society.

Yang B.,Chongqing University | Yang B.,Nanyang Technological University | Tan K.H.,Nanyang Technological University
Engineering Structures | Year: 2013

Several structural collapse incidents indicate that failure usually started from beam-column joints when exposed to abnormal loads. If the connections are sufficiently robust and there is adequate axial restraint from adjoining structures, catenary action usually forms and gives rise to alternate load paths when. affected columns are severely damaged, resulting in large deformations in adjoining beams and slabs. This paper presents seven experimental tests of the performance of common types of bolted steel beam-column joints under a central-column-removal scenario. The joint types including web cleat, top and seat angle, top and seat with web angle (TSWA) (8. mm angle), fin plate, flush end plate, extended end plate and TSWA(12. mm angle) are studied under the central-column-removal scenario. This study provides the behaviour and failure modes of different connections, including their abilities to deform in catenary mode. The test results indicate that the web cleat connection has the best performance in the development of catenary action, and the flush end plate, fin plate and TSWA connections could also deform in a ductile manner and develop catenary action prior to failure. It is worthy to note that tensile capacities of beam-column joints after undergoing large rotations usually control the failure mode and the formation of catenary action. A new tying resistance expression is proposed to consider the effect of large rotation. If large rotation is not considered in the design stage, the joints with poor rotation capacities would fail to achieve the design tying resistances. The test results also demonstrate that the rotation capacities of beam-column joints based on the experimental results in this study were much higher than the recommended values. © 2013 Elsevier Ltd.

Li J.,Chongqing University | Cheng C.,Chongqing University | Jiang T.,Chongqing University | Grzybowski S.,Mississippi State University
IEEE Transactions on Dielectrics and Electrical Insulation | Year: 2012

Wavelet shrinkage is efficient for de-noising the partial discharge (PD) detection. An improved wavelet de-noising approach for PD online measurement is presented. The wavelet de-noising approach is based on a genetic adaptive threshold estimation (GATE) scheme. The thresholding functions with continuous derivatives are used for the GATE scheme. A genetic algorithm is used to obtain global optimum thresholds of the GATE, and to improve the robustness and computation speed of the adaptive threshold estimation. De-noising experiments of simulative high-frequency PD signals, actual PD ultra-high-frequency (UHF) signals, and a field detected PD signal are presented. The GATE generates significantly smaller waveform distortion and magnitude errors than the Donoho's soft threshold estimation. © 2012 IEEE.

Yang B.,Chongqing University | Yang B.,Nanyang Technological University | Tan K.H.,Nanyang Technological University
Journal of Structural Engineering (United States) | Year: 2013

Several structural collapse incidents indicate that failure usually starts from beam-column joints exposed to abnormal loads, especially for steel and composite structures. If the connections are sufficiently robust and there is adequate axial restraint from adjoining structures, catenary action forms in the beams and slabs, causing alternate load paths when affected columns are severely damaged, and resulting in large deformations in the beams and slabs. This paper presents experimental results of bolted-angle beam-column joints under a middle column-removal scenario. Three types of connections - including (1) web cleat, (2) top and seat angle, and (3) top and seat with web angle connections - were investigated, and three angle thicknesses (8, 10, and 12 mm) were tested. The results of the nine experimental tests conducted demonstrate the ductility and load-carrying capacities of these three connection types with different angle thicknesses in catenary action mode. When the angle thickness increases, the failure mode changes from angle fracture to bolt fracture. A component-based model is also developed to predict the behavior of bolted-angle beam-column joints up to total failure. The validation study indicates that the proposed models can represent the key responses of bolted-angle beam-column joints under a middle column-removal scenario, including the formation of flexural action at small deformation stage, the development of catenary action at large deformation stage, and fractures of the connection components at the last stage. Based on the proposed joint model, frame analyses are conducted. The analytical results of the frame models demonstrate that the conducted joint tests could represent the behavior of prototype steel frames against progressive collapse. The effect of horizontal restraint stiffness, which is critical to the development of catenary action, is also investigated. © 2013 American Society of Civil Engineers.

Wang R.,Nanyang Technological University | Xu C.,Chongqing University | Lee J.-M.,Nanyang Technological University
Nano Energy | Year: 2016

NiOOH nanosheet/graphene hydrogels (H-NiOOH/GS), with mesoporous NiOOH nanosheets uniformly dispersed within the highly interconnected 3D graphene network, are constructed and studied for the first time by a mixed solvothermal and hydrothermal reaction. The effect of solvent composition on the morphology, phase, dispersibility of nanocrystal and hydrogel strength is systematically studied. As binder-free electrodes of supercapacitors, H-NiOOH/GS delivers high capacitance of 1162 Fg-1 at 1 Ag-1 with excellent rate capability (981 Fg-1 at 20 Ag-1). The charge-storage mechanisms of H-NiOOH/GS are in-depth investigated by quantifying the kinetics of charge storage, which reveals that NiOOH exhibits both capacitive effects and diffusion-controlled battery-type behavior during charge storage. Additionally, solvothermal-induced pure graphene hydrogels (H-GS) are also prepared and used as the negative electrode for the first time, which show an impressive specific capacitance of 425 and 368 Fg-1 at 5 and 40 mV s-1, respectively. Benefitting from the synergistic contribution of both positive and negative electrodes, the assembled H-NiOOH/GS//H-GS asymmetric supercapacitors achieve a remarkable energy density of 66.8 W h kg-1 at a power density of 800 W kg-1, and excellent cycling stability with 85.3% capacitance retention after 8000 cycles, holding great promise for energy storage applications. © 2015 Elsevier Ltd.

Wang X.,Nanyang Technological University | Sun L.,Chongqing University | Zhang S.,Nanyang Technological University
ACS Applied Materials and Interfaces | Year: 2014

An optimized two-step anodization is developed to fabricate ultralong, small-diameter TiO2 nanotubes, that is, with tube length of up to 31 μm and pore diameter of about 35 nm in this work. This overcomes the length limitation of small diameter tubes that usually presents in conventional one-step anodization. The small tubes with lengths of 23 μm yield a conversion efficiency of 5.02% in dye-sensitized solar cells under nonoptimized conditions. © 2014 American Chemical Society.

Huang R.,Chengdu University of Technology | Huang D.,Chengdu University of Technology | Huang D.,Chongqing University
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2010

The mechanical properties of rocks are obviously affected by initial stress state and unloading rates that are caused by excavation. Based on triaxial unloading and scanning electron microscopy(SEM) analysis, the deformation, breakage, and strength features of marble samples of the Jinping First Hydropower Station under different unloading rates and geostress conditions are studied. With unloading rates vu and initial confining pressure σ3 0 increasing, the brittle rupture and tensile characteristics of rock are more obvious. There are annular tensile cracks in secondary unloading direction when the rock samples are unloaded in two directions; and the meso-shapes of the tensile fracture surface under SEM consequently are presented with branch-tension, and multilayer biscuit-lancinated and slippery plane-ejected shapes. The axial strain compression increment Δε1 is gradually reduced, but the confining expansion stress Δε3 is increased during the process of unloading. The influence of unloading rate vu on deformation modulus E is different at the different deformation stages during process of unloading. The deformation modulus E is gradually increased before peak strength, but it gradually increases firstly and rapidly decreases afterward with vu enhanced. The Poisson s ratio μ is gradually increased during process of unloading, and it is more distinct with vu and σ3 0 enhancing, especially after peak strength. Relative to data of traditional triaxial loading test, the rock cohesion c is remarkably reduced but inner friction angle ψ is a little increased under unloading test. The faster the vu is, the more c is reduced, and the less the ψ increases.

Farzana S.,Chongqing University | Liu M.,Chongqing University | Baldwin A.,Chongqing University | Hossain M.U.,Hong Kong Polytechnic University
Energy and Buildings | Year: 2014

Energy simulation and prediction plays a vital role in energy policy and decision making. This study has been conducted to predict the future energy demand in the urban residential buildings of Chongqing a city in south west China. The comparative study adopts and compares the results of different demand models to improve estimation efficiency for future projections. A structured questionnaire survey was undertaken to collect primary household energy consumption data for inclusion in the annual energy consumption simulation model. An ANN model, two Grey models, a Regression model, a Polynomial model and a Polynomial regression model were used to forecast and compare demand. The precision of the models have been used statistical methods. The predicted results show that the total residential building energy and electricity consumption in urban areas of Chongqing is increasing rapidly. Based on MRPE (%) and the statistical tests, the study concluded that an ANN model is the most acceptable forecasting method of the six models. Hence, based on ANN model, urban residential building energy consumption will be at 1005 × 10 4 SCE and electricity consumption will be at 264.81 × 10 8 kW h in 2025 which is about three times and four times higher than that of the 2012, respectively. © 2014 Elsevier B.V.

Liao R.,Chongqing University | Zheng H.,Chongqing University | Grzybowski S.,Mississippi State University | Yang L.,Chongqing University
Electric Power Systems Research | Year: 2011

This paper presents a forecasting model based upon least squares support vector machine (LS-SVM) regression and particle swarm optimization (PSO) algorithm on dissolved gases in oil-filled power transformers. First, the LS-SVM regression model, with radial basis function (RBF) kernel, is established to facilitate the forecasting model. Then a global optimizer, PSO is employed to optimize the hyper-parameters needed in LS-SVM regression. Afterward, a procedure is put forward to serve as an effective tool for forecasting of gas contents in transformer oil. The application of the proposed model on actual transformer gas data has given promising results. Moreover, four other forecasting models, derived from back propagation neural network (BPNN), radial basis function neural network (RBFNN), generalized regression neural network (GRNN) and support vector regression (SVR), are selected for comparisons. The experimental results further demonstrate that the proposed model achieves better forecasting performance than its counterparts under the circumstances of limited samples. © 2011 Elsevier B.V. All rights reserved.

Zhang L.,Chongqing University | Zhang L.,Hong Kong Polytechnic University | Tian F.-C.,Chongqing University
Analytica Chimica Acta | Year: 2014

Electronic nose (e-Nose) technology based on metal oxide semiconductor gas sensor array is widely studied for detection of gas components. This paper proposes a new discriminant analysis framework (NDA) for dimension reduction and e-Nose recognition. In a NDA, the between-class and the within-class Laplacian scatter matrix are designed from sample to sample, respectively, to characterize the between-class separability and the within-class compactness by seeking for discriminant matrix to simultaneously maximize the between-class Laplacian scatter and minimize the within-class Laplacian scatter. In terms of the linear separability in high dimensional kernel mapping space and the dimension reduction of principal component analysis (PCA), an effective kernel PCA plus NDA method (KNDA) is proposed for rapid detection of gas mixture components by an e-Nose. The NDA framework is derived in this paper as well as the specific implementations of the proposed KNDA method in training and recognition process. The KNDA is examined on the e-Nose datasets of six kinds of gas components, and compared with state of the art e-Nose classification methods. Experimental results demonstrate that the proposed KNDA method shows the best performance with average recognition rate and total recognition rate as 94.14% and 95.06% which leads to a promising feature extraction and multi-class recognition in e-Nose. © 2014 Elsevier B.V.

Wu X.-G.,Chongqing University | Huang T.,CAS Institute of High Energy Physics
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010

The new BABAR data on the pion-photon transition form factor arouses people's interest for the determination of the pion distribution amplitude. To explain the data, we take both the leading valence quark state's and the nonvalence quark state's contributions into consideration, where the valence quark part up to next-to-leading order is presented and the nonvalence quark part is estimated by a phenomenological model based on its limiting behavior at both Q2→0 and Q2→. Our results show that to be consistent with the new BABAR data at the large Q2 region, a broader amplitude other than the asymptoticlike pion distribution amplitude should be adopted. The broadness of the pion distribution amplitude is controlled by a parameter B. It has been found that the new BABAR data at low and high energy regions can be explained simultaneously by setting B to be around 0.60, in which the pion distribution amplitude is closed to the Chernyak-Zhitnitsky form.

Wu X.-G.,Chongqing University | Huang T.,CAS Institute of High Energy Physics
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

The meson-photon transition form factors γγ*→P (P stands for π, η and η′) provide strong constraints on the distribution amplitudes of the pseudoscalar mesons. In this paper, these transition form factors are calculated under the light-cone perturbative QCD approach, in which both the valence and nonvalence quarks' contributions have been taken into consideration. To be consistent, a unified wave function model is adopted to analyze these form factors. It is shown that with the proper charm component fη′c∼-30MeV and a moderate DA with B∼0.30, the experimental data on Q2Fηγ(Q2) and Q2F η′γ(Q2) in the whole Q2 region can be explained simultaneously. Furthermore, a detailed discussion on the form factors' uncertainties caused by the constituent quark masses mq and m s, the parameter B, the mixing angle, and fη′c are presented. It is found that, by adjusting these parameters within their reasonable regions, one can improve the form factor to a certain degree but cannot solve the puzzle for Q2Fπγ(Q2), especially to explain the behavior of the π-γ form factor within the whole Q2 region consistently. We hope further experimental data on these form factors in the large Q2 region can clarify the present situation. © 2011 American Physical Society.

Wang Z.,Northeastern University China | Yang D.,Northeastern University China | Ma T.,Chongqing University | Sun N.,Jilin Electrical Power Co.
Nonlinear Dynamics | Year: 2014

This work constructs a theoretical framework for the stability analysis of nonlinear fractional-order systems. A new definition, the generalized Caputo fractional derivative, is proposed for the first time. Based on that, the comparison principles for scalar and vector fractional-order systems are constructed, respectively. Furthermore, a sufficient theorem for stability analysis is proved, and how to use this theorem in stabilization is also discussed. Three examples have been presented to illustrate how to use the developed theory to analyze the stability and to design stabilization controllers. With the proposed method, the problems of stabilization and synchronization of the fractional-order chaotic fractional-order systems can be easily solved with linear feedback control. © 2013 Springer Science+Business Media Dordrecht.

Zhang L.,Chongqing University | Zhang L.,Hong Kong Polytechnic University | Tian F.,Chongqing University
IEEE Transactions on Instrumentation and Measurement | Year: 2014

Nonselective gas sensor array has different sensitivities to different chemicals in which each gas sensor will also produce different voltage signals when exposed to an analyte with different concentrations. Therefore, the characteristics of cross sensitivities and broad spectrum of nonselective chemical sensors promote the fast development of portable and low-cost electronic nose (E-nose). Simultaneous concentration estimation of multiple kinds of chemicals is always a challengeable task in E-nose. Multilayer perceptron (MLP) neural network, as one of the most popular pattern recognition algorithms in E-nose, has been studied further in this paper. Two structures of single multiple inputs multiple outputs (SMIMO) and multiple multiple inputs single output (MMISO)-based MLP with parameters optimization in neural network learning processing using eight computational intelligence optimization algorithms are presented in this paper for detection of six kinds of indoor air contaminants. Experiments prove that the performance in accuracy and convergence of MMISO structure-based MLP are much better than SMIMO structure in concentration estimation for more general use of E-nose. © 1963-2012 IEEE.

Li X.-H.,Chongqing University | Li X.-H.,Wilfrid Laurier University
Wuli Xuebao/Acta Physica Sinica | Year: 2015

Quantum secure direct communication (QSDC) is one of the most important branches of quantum communication. In contrast to the quantum key distribution (QKD) which distributes a secure key between distant parties, QSDC directly transmits secret message instead of sharing key in advance. To establish a secure QSDC protocol, on the one hand, the security of the quantum channel should be confirmed before the exchange of the secret message. On the other hand, the quantum state should be transmitted in a quantum data block since the security of QSDC is based on the error rate analysis in the theories on statistics. Compared with the deterministic quantum key distribution (DQKD) which can also be used to transmit deterministic information, QSDC schemes do not need extra classical bits to read the secret message except for public discussion. In this article, we introduce the basic principles of QSDC and review the development in this field by introducing typical QSDC protocols chronologically. The first QSDC protocol was proposed by Long and Liu, which can be used to establish a common key between distant parties. In their scheme, the method for transmitting quantum states in a block by block way and in multiple steps was proposed and the information leakage before eavesdropping detection was solved. Subsequently, Deng et al. presented two pioneering QSDC schemes, an entangled-state-based two-step QSDC scheme and a single-photon-state-based quantum one-time pad scheme, in which the basic principle and criteria for QSDC were pointed out. From then on, many interesting QSDC schemes have been proposed, including the high-dimension QSDC scheme based on quantum superdense coding, multi-step QSDC scheme based on Greenberger-Horne-Zeilinger states, QSDC scheme based on quantum encryption with practical non-maximally entangled quantum channel, and so on. We also introduce the anti-noise QSDC schemes which were designed for coping with the collective-dephasing noise and the collective-rotation noise, respectively. In 2011, Wang et al. presented the first QSDC which exploited the hyperentangled state as the information carrier and several QSDC schemes based on the spatial degree of freedom (DOF) of photon, single-photon multi-DOF state and hyperentanglement were proposed subsequently. In addition to the point-to-point QSDC schemes, we also review the QSDC networks. Finally, a perspective of QSDC research is given in the last section. ©, 2015, Chinese Physical Society. All right reserved.

Huang Z.,Chongqing University | Leng J.,Edith Cowan University
ICCET 2010 - 2010 International Conference on Computer Engineering and Technology, Proceedings | Year: 2010

Moment invariants have been widely applied to image pattern recognition in a variety of applications due to its invariant features on image translation, scaling and rotation. The moments are strictly invariant for the continuous function. However, in practical applications images are discrete. Consequently, the moment invariants may change over image geometric transformation. To address this research problem, an analysis with respect to the variation of moment invariants on image geometric transformation is presented, so as to analyze the effect of image's scaling and rotation. Finally, the guidance is also provided for minimizing the fluctuation of moment invariants. © 2010 IEEE.

Shao Y.,Chongqing University | Liu J.,Chongqing University | Mechefske C.K.,Queen's University
Engineering Failure Analysis | Year: 2011

One of the key components in a mining dump truck is the drive axle housing. Failure of this component during normal use is unacceptable. Recently, early fatigue fracture became a problem during the normal working process of these machines. However, it is difficult to calculate exactly the fatigue failure life of the drive axle housing based on bench testing or pure computer simulation due to the differences between practical road conditions (such as slope and roughness) and simplified boundary conditions. To increase the reliability of analysis results a new analysis method based on dynamic strain measurement from practical mine road surface conditions combined with finite element analysis is proposed in this paper. The dynamic strain and stress on the drive axle housing is obtained by strain measurements while the truck travels over normal mine road surface conditions. The dynamic stress was analyzed using the rain-flow counting method, which can determine the amplitudes and mean values of counted cycles. The influence of the stress mean value was taken into consideration with the Morrow's model. According to the assumption of a linear Palmgren-Miner hypothesis of damage accumulation and using typical fatigue characteristics of the material, the fatigue failure life was calculated. Analysis of the measurements showed that the dynamic stress experienced by the axle housing was far greater than expected. In order to find the factors affecting the dynamic stress of the drive axle housing, the slope of the road surface, any uneven loading and eccentricities were analyzed using the finite element method. This paper shows that the new analysis methods described are valuable tools for analyzing the reasons behind the failure of these truck axle housings. © 2011 Elsevier Ltd.

Deng M.,Chongqing University | Liu D.,Chongqing University | Li D.,Beijing Jiaotong University
Sensors and Actuators, A: Physical | Year: 2014

We report an optical fiber magnetic field sensor by merging the advantages of magnetic fluid and a core-cladding-mode interferometer which is directly fabricated on a standard single-mode fiber by using an arc fusion splicing machine. The sensing performances of the sensors are controllable by designing the parameters of the asymmetric-tapered structure. Experimental results show that the sensor with axial offset of 168 μm and taper waist diameter of 45 μm not only has good optical properties but also a relatively high magnetic-field sensitivity of ∼162.06 pm/mT ranging from 0 to 21.4 mT. The proposed sensors would find potential applications in weak magnetic sensing fields. © 2014 Elsevier B.V.

Yang B.,Chongqing University | Yang B.,Nanyang Technological University | Tan K.H.,Nanyang Technological University
Journal of Structural Engineering (United States) | Year: 2014

A series of experiments has been conducted to investigate the failure modes and ductility of composite beam-column joints in a middle-column-removal scenario. Composite web cleat and flush end plate connections were studied. The research included two types of tests: namely, middle joints under a sagging moment and side joints under a hogging moment. Five composite beam-column joints with reentrant steel profile decking were tested. The contributions from two types of mechanisms (namely, flexural action and catenary action) have been identified. The main objective of the experimental program is to study the behavior of composite joints in a middle-column-removal scenario. The test results demonstrate the ductility and load resistances of these five specimens in catenary action mode, and indicate that at the initial loading stage, the applied load was resisted by flexural action, while at the large deformation stage, the load was resisted by catenary action. It is also found that composite slabs could increase the load-carrying capacities of beam-column joints at both the flexural action and catenary action stages. The strengthened web cleat connection has a much higher load-carrying capacity than the normal web cleat connection because the former could sustain greater deformation. © 2013 American Society of Civil Engineers.

Deng M.,Chongqing University | Sun X.,Chongqing University | Han M.,Chongqing University | Li D.,Beijing Jiaotong University
Applied Optics | Year: 2013

We report a magnetic-field sensor by merging the advantages of optical fiber Michelson interferometers with that of magnetic fluid. Compact and low-cost optical fiber Michelson interferometers were first fabricated by a high-frequency CO2 laser, and then they were inserted into glass capillaries with water-based Fe3O4 magnetic fluid as sensing elements. The sensing characteristics have been investigated and the experimental results show that the reflective spectrum of the fiber-magnetic sensor linearly shifted with the change of the magnetic-field strength that is perpendicular to the axial of the devices. The fiber-magnetic sensor with interference arm's diameter of 50 μm is most sensitive to the external magnetic field, and the sensitivity is up to 64.9 pm/mT, which is 20 times higher than that of 125 μm diameter. © 2013 Optical Society of America.

Huang D.,Chongqing University | Huang D.,Chengdu University of Technology | Huang R.,Chengdu University of Technology | Zhang Y.,Chongqing University
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2012

Loading rate has an important influence on rock mechanical properties. The influence degree is closely related to the microstructure of rock, loading and unloading paths and states, etc.. Based on the uniaxial compression tests of coarse crystal grain marble with nine strain rate levels in range of static loading rate, the influences of loading strain rate on stress-strain curve, failure pattern, strength, elastic modulus, deformation modulus and strain energy dissipation and release of the marble are investigated; and the energy mechanism of rock damage evolution is discussed. The initial cracking stress and critical dilatancy stress of rock specimens under different loading rates can be obtained by the relations of total volumetric strain and crack volumetric strain with initial cracking stress and critical dilatancy stress. The loading strain rate of about 1×10 -3 s -1 is the dividing point. When the strain rate is less than the value, a certain plastic yield or flowing section near the peak of stress-strain curve is still present; but when the strain rate is more than the value, the fold line type near the peak of stress-strain curve is present. The fracture pattern of rock specimen changes from tension-shear to tensile rip and even rip-ejection with the increase of loading strain rate. Generally, the initial cracking stress, critical dilatancy stress, and uniaxial compressive strength increase with the loading strain rate; and the initial cracking stress and critical dilatancy stress are more closer to the peak strength. But when the loading strain rate is 1×10 -4-1×10 -3 s -1, a relative low value area is present for all values mentioned above, which is related to the microstructure of coarse crystal grain marble. The correlations between the initial cracking stress, critical dilatancy stress, elastic modulus and deformation modulus and the uniaxial compressive strength are linear. Under uniaxial compression, the more the energy dissipation before peak strength is, the higher the strength is; and the more the energy release after the peak strength is, the stronger the tensile through fracture characteristic is, and the more the fractured blocks are. The energy dissipation makes rock damage and the strength loss; and the energy release makes the macrofracture surface be run-through, inducing integral damage.

Song Q.,Beijing Jiaotong University | Song Y.D.,Beijing Jiaotong University | Song Y.D.,Chongqing University
Systems and Control Letters | Year: 2014

This work deals with the tracking control problem of a class of unknown nonaffine dynamic systems that involve unpredictable sensor and actuation failures. As the control inputs enter into and influence the dynamic behavior of the nonaffine system through a nonlinear and implicit way, control design for such system becomes quite challenging. The underlying problem becomes even more complex if the system dynamics are unavailable for control design yet involving unanticipated sensor and/or actuator faults. In this work, a structurally simple and computationally inexpensive control scheme is proposed to achieve uniformly ultimately bounded (UUB) stable tracking control of a class of nonaffine systems. The proposed control is of a generalized PI form and is able to accommodate both sensor and actuator faults. The effectiveness of the proposed control strategy is confirmed by theoretical analysis and numerical simulations. © 2013 Elsevier B.V. All rights reserved.

Wu Z.,Hong Kong Polytechnic University | Yu A.T.W.,Hong Kong Polytechnic University | Shen L.,Chongqing University | Liu G.,Chongqing University
Waste Management | Year: 2014

Quantifying construction and demolition (C&D) waste generation is regarded as a prerequisite for the implementation of successful waste management. In literature, various methods have been employed to quantify the C&D waste generation at both regional and project levels. However, an integrated review that systemically describes and analyses all the existing methods has yet to be conducted. To bridge this research gap, an analytical review is conducted. Fifty-seven papers are retrieved based on a set of rigorous procedures. The characteristics of the selected papers are classified according to the following criteria - waste generation activity, estimation level and quantification methodology. Six categories of existing C&D waste quantification methodologies are identified, including site visit method, waste generation rate method, lifetime analysis method, classification system accumulation method, variables modelling method and other particular methods. A critical comparison of the identified methods is given according to their characteristics and implementation constraints. Moreover, a decision tree is proposed for aiding the selection of the most appropriate quantification method in different scenarios. Based on the analytical review, limitations of previous studies and recommendations of potential future research directions are further suggested. © 2014 Elsevier Ltd.

Yang J.,Georgia Institute of Technology | Yang J.,Chongqing University | Chen J.,Georgia Institute of Technology | Liu Y.,Georgia Institute of Technology | And 4 more authors.
ACS Nano | Year: 2014

As a vastly available energy source in our daily life, acoustic vibrations are usually taken as noise pollution with little use as a power source. In this work, we have developed a triboelectrification-based thin-film nanogenerator for harvesting acoustic energy from ambient environment. Structured using a polytetrafluoroethylene thin film and a holey aluminum film electrode under carefully designed straining conditions, the nanogenerator is capable of converting acoustic energy into electric energy via triboelectric transduction. With an acoustic sensitivity of 9.54 V Pa-1 in a pressure range from 70 to 110 dB and a directivity angle of 52°, the nanogenerator produced a maximum electric power density of 60.2 mW m-2, which directly lit 17 commercial light-emitting diodes (LEDs). Furthermore, the nanogenerator can also act as a self-powered active sensor for automatically detecting the location of an acoustic source with an error less than 7 cm. In addition, an array of devices with varying resonance frequencies was employed to widen the overall bandwidth from 10 to 1700 Hz, so that the nanogenerator was used as a superior self-powered microphone for sound recording. Our approach presents an adaptable, mobile, and cost-effective technology for harvesting acoustic energy from ambient environment, with applications in infrastructure monitoring, sensor networks, military surveillance, and environmental noise reduction. © 2014 American Chemical Society.

Hu Y.,Georgia Institute of Technology | Yang J.,Georgia Institute of Technology | Yang J.,Chongqing University | Jing Q.,Georgia Institute of Technology | And 4 more authors.
ACS Nano | Year: 2013

An unstable mechanical structure that can self-balance when perturbed is a superior choice for vibration energy harvesting and vibration detection. In this work, a suspended 3D spiral structure is integrated with a triboelectric nanogenerator (TENG) for energy harvesting and sensor applications. The newly designed vertical contact-separation mode TENG has a wide working bandwidth of 30 Hz in low-frequency range with a maximum output power density of 2.76 W/m2 on a load of 6 MΩ. The position of an in-plane vibration source was identified by placing TENGs at multiple positions as multichannel, self-powered active sensors, and the location of the vibration source was determined with an error less than 6%. The magnitude of the vibration is also measured by the output voltage and current signal of the TENG. By integrating the TENG inside a buoy ball, wave energy harvesting at water surface has been demonstrated and used for lighting illumination light, which shows great potential applications in marine science and environmental/infrastructure monitoring. © 2013 American Chemical Society.

Wen L.,Chongqing University | Bi X.T.,University of British Columbia
Powder Technology | Year: 2011

A method has been developed to deduce a "breakup" force in a packed bed based on measured pressure drop and internal cavity size hysteresis data in a conical spouted bed. The pressure drop over the vertical jet is estimated by the Eulerian-Eulerian two-fluid model using the commercial Fluent software. The pressure drop over the packed bed is extracted from the measured total pressure drop following a flow rate descending process in the spouted bed, while the "breakup" force is determined from the combination of measured total pressure drop and internal jet height following the flow ascending process, the simulated pressure drop over the gas jet and the pressure drop over the loosely packed upper bed section. Such a proposed method can be applied in the future to develop a generalized expression for the "breakup" force in spouted beds and other packed bed systems where a vertical fluid jet is issued into the packed particles. © 2010 Elsevier B.V.

Hou P.-K.,Chongqing University | Hou P.-K.,Northwestern University | Kawashima S.,Northwestern University | Wang K.-J.,Iowa State University | And 3 more authors.
Cement and Concrete Composites | Year: 2013

The present study is aimed at investigating the combined effects of colloidal nanosilica (CNS) and fly ash on the properties of cement-based materials. The fresh and hardened properties of mixtures with CNS of 10 nm size and two Class F fly ashes were evaluated. Results revealed that CNS accelerates the setting of fly ash-cement systems by accelerating cement hydration, while fly ash can offset the reduction in fluidity caused by CNS. The early-age strength gain (before 7 d) of fly ash-cement systems was improved by CNS. However, the strength gain of mixtures with CNS diminished at later ages (after 28 d), where strength was eventually comparable to or exceeded by mixtures without CNS. Results showed that lack of Ca(OH)2, which results from the high pozzolanic reactivity of CNS at early ages, and the hydration hindrance effect of CNS on cement at later ages can be the critical reasons. © 2012 Elsevier Ltd. All rights reserved.