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Beijing Institute of Technology , is a co-educational public university, located in Beijing, China. Established in 1940 in Yan'an, the university is now under the direct administration of the Ministry of Industry and Information Technology.As a member university of National Key Universities, “Project 211” and “Project 985”, it has been given priority for development from the Chinese government, the Commission of Science, Technology and Industry for National Defense, the Ministry of Education and the Beijing Government. Wikipedia.

Zhang X.,CAS Institute of Mechanics | Yu Y.,Beijing Institute of Technology
Combustion and Flame | Year: 2011

The three-dimensional effects of flame spread over thin solid materials were experimentally studied using a natural-convection-suppressing horizontal narrow-channel. In a sufficiently wide narrow-channel, the variation of flame spread against the width of the material sample showed different trends for different gas flow speeds and oxygen concentrations. The extent of three-dimensional effects was inversely proportional to the gas flow speed or its square. Near quenching extinction limits, the effects were significant because weak combustion is sensitive to a slight variation of heat loss and oxygen concentration. The effects may be due to different factors such as side heat loss, side oxygen diffusion, or both. Far away from quenching extinction limits, the effects were weak because vigorous combustion is insensitive to a small variation of oxygen concentration and heat loss. In all tests, the effects were limited to the samples of width less than 10 times of the diffusion length. Moreover, a higher oxygen concentration suppressed the effects at a lower gas flow speed. For sufficiently wide samples, in the most range of gas flow speeds, the channel width had almost no effect on flame spread. However, near extinction limits, the flame spread rate decreased with the increasing channel width. © 2010 The Combustion Institute.

Wang Z.-M.,Huaihai Institute of Technology | Yu X.,Guangxi University of Technology | Yu X.,Beijing Institute of Technology
Proceedings of the Institution of Mechanical Engineers, Part O: Journal of Risk and Reliability | Year: 2013

Two non-homogeneous Poisson processes including the power law process and the log-linear process with reliability improvement or deterioration are analyzed. Based on Akaike information criterion and Bayesian information criterion, the best model of failure data is presented. The point maximum likelihood and interval estimators of the parameters, as well as seven reliability indices of the log-linear process model, such as cumulative mean time between failures, cumulative number of failures, reliability at a given time, and warranty time given reliability are given. In tests for failure time trends, both the graphical methods, including the cumulative failures versus time plot and the total-time-on-test plot, and the analytical methods including the Laplace, the Military Handbook, and the Lewis-Robinson tests are used. Three real cases for failure data with failure truncation and time truncation of multiple numerically controlled machine tools are given to illustrate the use of the proposed models. © 2012 IMechE.

Chen S.-L.,Chung Yuan Christian University | Wang J.-G.,Beijing Institute of Technology
Electronics Letters | Year: 2013

An efficient VLSI architecture of a lossless ECG encoding circuit is proposed for wireless healthcare monitoring applications. To reduce the transmission and storage data, a novel lossless compression algorithm is proposed for ECG signal compression. It consists of a novel adaptive rending predictor and a novel two-stage entropy encoder based on two Huffman coding tables. The proposed lossless ECG encoder design was implemented using only simple arithmetic units. To improve the performance, the proposed ECG encoder was designed by pipeline technology and implemented the two-stage entropy encoder by the architecture of a look-up table. The VLSI architecture of this work contains 3.55 K gate counts and its core area is 45987 μm2 synthesised by a 0.18 μm CMOS process. It can operate at 100 MHz processing rate with only 36.4 μW. The data compression rate reaches an average value 2.43 for the MIT-BIH Arrhythmia Database. Compared with the previous low-complexity and high performance techniques, this work achieves lower hardware cost, lower power consumption, and a better compression rate than other lossless ECG encoder designs. © The Institution of Engineering and Technology 2013.

Chen H.,Peking University | Long H.,Peking University | Long H.,Beijing Institute of Technology | Cui X.,Peking University | And 3 more authors.
Journal of the American Chemical Society | Year: 2014

Four putative G-quadruplex sequences (PGSs) in the HIF1α promoter and the 5′UTR were evaluated for their G-quadruplex-forming potential using ESI-MS, CD, FRET, DMS footprinting, and a polymerase stop assay. An important G-quadruplex (S1) has been proven to inhibit HIF1α transcription by blocking AP2 binding. A benzo[c]phenanthridine derivative was found to target the S1 G-quadruplex and induce its conformational conversion from antiparallel to parallel orientation. The transcriptional suppression of HIF1α by this compound was demonstrated using western blotting, Q-RT-PCR, luciferase assay, and ChIP. Our new findings provided a novel strategy for HIF1α regulation and potential insight for cancer therapy. © 2014 American Chemical Society.

Mahmoud M.S.,King Fahd University of Petroleum and Minerals | Xia Y.,Beijing Institute of Technology
Asian Journal of Control | Year: 2012

The objective of this paper is to propose a generalized approach to stabilization of systems which are composed of linear time-delay subsystems coupled by linear time-varying interconnections. The proposed algorithms, which are formulated within the convex optimization framework, provide decentralized solutions to the problem of delay-dependent asymptotic stability with strict dissipativity. It is established that the new methodology can reproduce earlier results on passivity, positive realness and disturbance attenuation. Then a decentralized structure of dissipative state-feedback controllers is designed to render the closed-loop interconnected system delay-dependent asymptotically stable with strict dissipativity. Numerical examples are presented to illustrate the applicability of the design method. © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society.

Zhang B.,Beijing Institute of Technology | Ng H.D.,Concordia University at Montreal | Lee J.H.S.,McGill University
Shock Waves | Year: 2012

In this study, effective energy from spark discharge for direct blast initiation of spherical gaseous detonations is investigated. In the experiment, direct initiation of detonation is achieved via a spark discharge from a high-voltage and low-inductance capacitor bank and the spark energy is estimated from the analysis of the current output. To determine the blast wave energy from the powerful spark, the time-of-arrival of the blast wave in air is measured at different radii using a piezoelectric pressure transducer. Good agreement is found in the scaled blast trajectories, i. e., scaled time c o·t/R o where c o is the ambient sound speed, as a function of blast radius R s/R o between the numerical simulation of a spherical blast wave from a point energy source and the experimental results where the explosion length scale R o is computed using the equivalent spark energy from the first 1/4 current discharge cycle. Alternatively, by fitting the experimental trajectories data, the blast energy estimated from the numerical simulation appears also in good agreement with that obtained experimentally using the 1/4 cycle criterion. Using the 1/4 cycle of spark discharge for the effective energy, direct initiation experiments of spherical gaseous detonations are carried out to determine the critical initiation energy in C 2H 2-2.5O 2 mixtures with 70 and 0% argon dilution. The experimental results obtained from the 1/4 cycle of spark discharge agree well with the prediction from two initiation models, namely, the Lee's surface energy model and a simplified work done model. The main source of discrepancy in the comparison can be explained by the uncertainty of cell size measurement which is needed for both the semi-empirical models. © 2011 Springer-Verlag.

Yu Y.,Beijing Institute of Technology
Beijing Ligong Daxue Xuebao/Transaction of Beijing Institute of Technology | Year: 2013

In this paper, according to basic fluid dynamics theory and interacting shear flows (ISF) theory, following conclusion can be proved. There exists the best computational mesh in simulation of free shear flows. The best mesh design are orthogonal grid which grid line are parallel to the direction of ISF viscous shear thin layer streamline, in addition, the grid must be refined in the thin layer along normal. As for no optimal mesh, it will be difficult to capture the physics viscous effect in ISF viscous thin shear layer as the result of much more refined grid and viscous effect will be numerical. The conclusion were validated by simulation of an uncompressible free shear layer laminar flow.

Xu B.,Beijing Research Institute of Chemical Defense | Hou S.,China University of Mining and Technology | Cao G.,Beijing Research Institute of Chemical Defense | Wu F.,Beijing Institute of Technology | Yang Y.,Beijing Research Institute of Chemical Defense
Journal of Materials Chemistry | Year: 2012

Gelatin, a renewable animal derivative composed of various proteins, was used as a precursor for nitrogen-doped porous carbon with high surface areas for supercapacitors for the first time. The preparation procedure is very simple, including the carbonization of gelatin under inert atmosphere, followed by NaOH activation of the carbonized char at 600 °C for 1 h. The porosity and surface chemistry of the carbon depend strongly on the weight ratio of NaOH/char, with the specific surface area and nitrogen content varying between 323 and 3012 m 2 g -1 and between 0.88 and 9.26 at%, respectively. The unique microstructure and nitrogen functionalities enable the carbon to exhibit a high capacitance of up to 385 F g -1 in 6 mol L -1 KOH aqueous electrolytes, attributed to the co-contribution of double layer capacitance and pseudo-capacitance. It also shows excellent rate capability (235 F g -1 remained at 50 A g -1) and cycle durability, making it a promising electrode material for supercapacitors. This journal is © The Royal Society of Chemistry.

Zhang J.,Beijing Institute of Technology
Acta Mechanica Sinica/Lixue Xuebao | Year: 2010

Studied in this paper are the attitude control law design and the output torque estimation problem of micro control moment gyros (MCMGs) for the agile satellites executing rapid attitude maneuver mission. An algorithm is proposed for estimating the output torques and the gimbal angular rates of MCMGs, which can help engineers to choose reasonable size for actuators so that the cost of satellite can be decreased. According to some special maneuver missions, a numerical example of attitude control system for a small satellite with MCMGs in pyramid configuration is studied, and the simulation results validate the proposed estimation algorithm. © 2009 The Chinese Society of Theoretical and Applied Mechanics and Springer-Verlag GmbH.

Xiao F.,Beijing Institute of Technology | Xiao F.,University of Alberta | Wang L.,Peking University | Chen T.,University of Alberta
Automatica | Year: 2012

This paper proposes a new connectivity-preserving protocol in terms of rectangle-like regions. The protocol consists of a set of distributed control rules; their working together guarantees the network connectivity as well as rendezvous of a discrete-time multi-agent system. It is assumed that all agents share a common minimum sensing radius, but the information exchange may suffer from link failure and recovery. Consequently, the interaction topology is in fact directed and time-varying. By rigorous mathematical arguments, we show the effectiveness and robustness of the protocol in the presence of alignment errors in local coordinate orientations of agents and measurement errors in relative positions of neighbors. We also present simulations to demonstrate the effectiveness of the theoretical results. © 2011 Elsevier Ltd. All rights reserved.

Gao L.,Beijing Institute of Technology | Lemarchand R.,Ecole Centrale Marseille | Lequime M.,Ecole Centrale Marseille
Journal of the European Optical Society | Year: 2013

In this paper we use spectrophotometric measurements and a Clustering Global Optimization procedure to determine the complex refractive index of SiO2 layer from 250 nm to 1250 nm. A special commercial optical module allows the reflection and transmission measurements to be made under exactly the same illumination and measurement conditions. We compare the index determination results obtained from two different single layer SiO2 samples, with high and low index glass substrates, respectively. We then determine the refractive index of SiO2 for a bi-layer design in which the first deposited layer is Ta2O5. The corresponding solutions are discussed and we show that the real part of the complex refractive index obtained for a bi-layer is slightly different to that found for a single layer investigation. When SiO2 is included inside a thin film stack, we propose the use of an index determination method in which a bi-layer is used for the real part of the complex refractive index, and single layer determination is used for the imaginary part of the refractive index in the UV range.

Sun B.,Beijing Institute of Technology
Transactions of the Institute of Measurement and Control | Year: 2013

In this work, an optimal distributed control problem of the viscous generalized Camassa-Holm equation is considered. By the Dubovitskii and Milyutin functional analytical approach, we prove the Pontryagin maximum principle of the investigational system. The necessary condition for optimality is established for the controlled object in the fixed final horizon case and, subsequently, a remark on how to apply the obtained results is made as an illustration. © The Author(s) 2012.

Li Z.,Peking University | Ren W.,University of California at Riverside | Liu X.,Beijing Institute of Technology | Xie L.,Nanyang Technological University
Automatica | Year: 2013

This paper considers the distributed consensus problem of multi-agent systems with general continuous-time linear dynamics for both the cases without and with a leader whose control input might be nonzero and time varying. For the case without a leader, based on the relative output information of neighboring agents, two types of distributed adaptive dynamic consensus protocols are proposed, namely, the edge-based adaptive protocol which assigns a time-varying coupling weight to each edge in the communication graph and the node-based adaptive protocol which uses a time-varying coupling weight for each node. These two adaptive protocols are designed to ensure that consensus is reached in a fully distributed fashion for all undirected connected communication graphs. It is shown that the edge-based adaptive consensus protocol is applicable to arbitrary switching connected graphs. For the case where there exists a leader whose control input is possibly nonzero and bounded, a distributed continuous adaptive protocol is designed to guarantee the ultimate boundedness of the consensus error with respect to any communication graph which contains a directed spanning tree with the leader as the root and whose subgraph associated with the followers is undirected, requiring neither global information of the communication graph nor the upper bound of the leader's control input. A distributed discontinuous protocol is also discussed as a special case. Simulation examples are finally given to illustrate the theoretical results. © 2013 Published by Elsevier Ltd.

Ji B.,Beijing Institute of Technology
European Physical Journal: Special Topics | Year: 2014

Commentary on the contribution by Falko Ziebert and Igor S. Aranson [1] in this special issue. © 2014 EDP Sciences and Springer.

Xu Z.,Massachusetts Institute of Technology | Xue K.,Tsinghua University | Xue K.,Beijing Institute of Technology
Nanotechnology | Year: 2010

Graphene epoxide, with oxygen atoms lining up on pristine graphene sheets, is investigated theoretically here using first-principles calculations. Two distinct phases - metastable clamped and stable unzipped structures - are observed consistent with experimental observations. In the clamped structure, oxygen atoms form a regular lattice on the graphene sheet. In the unzipped phase, an epoxy group breaks the lower sp2 bond and modifies the mechanical and electronic properties of graphene remarkably. The foldable epoxy ring structure reduces its Young's modulus by 42.4%, while leaving the tensile strength almost unchanged. The perturbation of epoxidation on the band structures depends on the density and symmetry of oxidation. These results pave the way for oxidation-based engineering of graphene-related materials. © 2010 IOP Publishing Ltd.

We demonstrate applications of a novel setup which is used for measuring the relative phase difference between S and P polarization at an oblique incidence point in optically denser medium by analyzing the relative frequency shift of adjacent axial modes of S and P resonances of a monolithic folded Fabry-Perot cavity (MFC). The relative frequency shift of adjacent axial modes of S and P resonances of an MFC is around 1.030 GHz for a confocal MFC cavity and 0.3869 GHz for a parallel MFC cavity. The relative phase difference at a reflection point A in an optically denser medium is inferred to be around -167.4° for a confocal cavity and -201.1° for a parallel cavity. This scheme can be used to measure relative phase differences in optically denser media which are out of the measuring range of ellipsometry. © 2013 Astro Ltd.

Wang Z.,Beijing Forestry University | Huang K.,Beijing Forestry University | Yang S.,Hunan Academy of Social Science | Yu Y.,Beijing Institute of Technology
Journal of Cleaner Production | Year: 2013

Water is scarce in Beijing, China, and rapid economic and societal development, as well as the dense population, causes severe pressure on local water resources. This paper involves the "water footprint", defined as the volume of water needed to produce the goods and services consumed, which quantifies the environmental impact of consumption. By combining an input-output model with intersectoral water flows, this paper describes a modified input-output model to calculate the direct, indirect and gross water footprint intensity and the gross water footprint of different sectors in Beijing in 2002 and 2007. The results show declines in the agricultural and industrial water footprints for these years. The grey water footprint, which reflects environmental pollution caused by human production and consumption, was also calculated and suggests that the shortage of water resources, rather than water pollution, is the main problem in Beijing. Evaluation of the virtual water trade, along with water savings in the various sectors, verified that Beijing is a net virtual water importer. Furthermore, the water footprint shows that Beijing is advanced in water use efficiency compared to other provinces in China. Finally, adjustments in the industrial structure, along with virtual water importing, should be prioritized as water-saving strategies for Beijing. © 2012 Elsevier Ltd. All rights reserved.

Liu P.,Beijing Institute of Technology
2012 3rd International Conference on System Science, Engineering Design and Manufacturing Informatization, ICSEM 2012 | Year: 2012

This paper is aimed at putting forward design and use strategies of the corresponding design symbols based on the physiological and psychological characteristics of vulnerable groups in the decoding process, so that the vulnerable groups are able to enjoy the convenience brought for life by the design symbol on equal terms with the mainstream. Based on Donald A. Norman's design hierarchy frame of Visceral-Behavioral-Reflective model, analyze the three design factors functions of design symbols, design context based on Universal Design (UD) and mental model of decoding of vulnerable groups, and on this basis, put forward the design and use strategies of the design symbols meeting the demands of the vulnerable groups, including: using similar symbols to ensure the appearance of products and the purpose easy to understand, using indicatory symbols to indicate the operational approach and process, and using symbolic symbols to extend the psychological life of the appearance of products. These strategies can ensure the vulnerable groups to have better exchange with products and improve the life satisfaction. © 2012 IEEE.

Miao C.,Changchun University | Ge W.,Beijing Institute of Technology
Mathematical Methods in the Applied Sciences | Year: 2015

In this paper, we study the existence of positive solutions for singular impulsive differential equations with integral boundary conditions u′′(t) + q(t)f(t,u(t),u′(t)) = 0,t ∈ J′, Δu(tk) = Ik(u(tk),u′(tk)),k = 1,2,p, Δu′(tk) = -Lk(u(tk),u′(tk)),k = 1,2,p, u(0) =∫01g(t)u(t)dt,u′(1) = 0, where the nonlinearity f(t,u,v) may be singular at u-=-0 and v-=-0. The proof is based on the theory of Leray-Schauder degree, together with a truncation technique. Some recent results in the literature are generalized and improved. Copyright © 2014 John Wiley & Sons, Ltd.

Wang J.-M.,Beijing Institute of Technology | Krstic M.,University of California at San Diego
ESAIM - Control, Optimisation and Calculus of Variations | Year: 2015

We study the stability of an interconnected system of Euler-Bernoulli beam and heat equation with boundary coupling, where the boundary temperature of the heat equation is fed as the boundary moment of the Euler-Bernoulli beam and, in turn, the boundary angular velocity of the Euler-Bernoulli beam is fed into the boundary heat flux of the heat equation. We show that the spectrum of the closed-loop system consists only of two branches: one along the real axis and the another along two parabolas symmetric to the real axis and open to the imaginary axis. The asymptotic expressions of both eigenvalues and eigenfunctions are obtained. With a careful estimate for the resolvent operator, the completeness of the root subspaces of the system is verified. The Riesz basis property and exponential stability of the system are then proved. Finally we show that the semigroup, generated by the system operator, is of Gevrey class δ > 2. © EDP Sciences, SMAI, 2015.

Yu H.,Wuhan Naval University of Engineering | Huang G.,Wuhan Naval University of Engineering | Gao J.,Wuhan Naval University of Engineering | Liu B.,Beijing Institute of Technology
IEEE Transactions on Wireless Communications | Year: 2012

In this paper, by utilizing the time difference of arrival (TDOA) and frequency difference of arrival (FDOA) measurements of a signal received at a number of receivers, an efficient constrained weighted least-squares (CWLS) algorithm for estimating the position and velocity of a moving source is proposed, which exploits the known relation between the intermediate variable and the source location coordinates explicitly. On basis of Newton's method, a numerical iterative solution can be obtained allowing real-time implementation and ensuring global convergence. Simulation results show that the proposed estimator achieves remarkably better performance than the two-step weighted least squares (WLS) approach, which makes the Cramr-Rao lower bound (CRLB) at a sufficiently high noise level before the threshold effect occurs. © 2012 IEEE.

Fan T.,Beijing Institute of Technology
Lixue Xuebao/Chinese Journal of Theoretical and Applied Mechanics | Year: 2013

This paper gives an introduction on the Poisson bracket method in condensed matter physics, Lie group and Lie algebra and their some applications to quasicrystals, liquid crystals and a class of soft matter. It introduces not only derivation on hydrodynamic or elasto-hydrodynamic equations of the materials, but also solutions of relevant equations, some among them explore the mistakes of well-known classic solutions, in addition, the equations and solutions on soft matter quasicrystals are observed for the first time.

Wang Y.,Beijing Institute of Technology | Yin J.,South China Normal University
Mathematical Methods in the Applied Sciences | Year: 2013

In this paper, instead of energy methods, we apply the supersolution and subsolution methods to investigate the critical extinction exponents for a polytropic filtration equation with absorption and source, and improve the results of Mu et al. (J. Math. Anal. Appl. 2012; 391:429-440). Copyright © 2012 John Wiley & Sons, Ltd.

Xiong J.,Beijing Institute of Technology | Liu C.,Tsinghua University | Zhang Y.,Tsinghua University
Atmospheric Environment | Year: 2012

A general analytical model for characterizing emission and sorption of formaldehyde and volatile organic compounds (VOCs) in single-layer building materials is developed. Compared with traditional models, the present model can be applicable for four kinds of typical physical processes, i.e., emission in ventilated and airtight chambers, and sorption in these two types of chambers. Based on the general analytical model, a novel method is proposed to determine the characteristic parameters (the diffusion coefficient, D m, and the material/air partition coefficient, K) of formaldehyde and VOC sorption in ventilated and airtight chambers. It establishes a linear relationship between the logarithm of dimensionless excess concentration and sorption time, and the D m and K can be conveniently obtained from the slope and intercept of the regression line. The results of applying the present model are compared with the experimental data in the literature. The good agreement between them not only validates the model but also demonstrates that the measured characteristic parameters are accurate and reliable. The general analytical model should prove useful for unified characterization and prediction of emission/sorption in building materials as well as for parameter measurement. © 2011 Elsevier Ltd.

Wei W.,Tsinghua University | Zhang Y.,Tsinghua University | Xiong J.,Beijing Institute of Technology | Li M.,Tsinghua University
Atmospheric Environment | Year: 2012

Environmental chambers are widely used to test formaldehyde and other volatile organic compound (VOC) emissions from indoor materials and furniture. However, there is a lack of a proven method to assess the precision of the test results of the chamber system. In this paper, we describe a new standard reference, LIFE (liquid-inner tube diffusion-film-emission), to address this problem. This reference has the following salient features: (1) Constant emission rate, with less than 3.0% change with an ambient airflow speed (>0.014-m/s) at furniture emission range (0.1-1.0-mg/m 3 in a 30-m 3 chamber with air change rate of 1/h) under standard chamber test conditions as specified by ISO 16000-9 (23-°C, 50% RH); (2) Long duration of emissions, on the order of 1000-h; (3) Easy to store, apply and maintain. The design principle and criteria of the LIFE reference are presented. An analytical model and dimensionless analysis were applied to optimize the factors influencing the emission rate, and experiments were conducted to validate the analytical results. In addition, the equivalent emission parameters of the reference, i.e., the initial emittable concentration, the diffusion coefficient and the partition coefficient, were determined through a three-parameter optimizing regression. This can then be used to check the reliability of a chamber method for testing these three parameters. The developed standard reference should prove useful for calibrating chamber systems for indoor material/furniture VOC emissions tests. © 2011 Elsevier Ltd.

Chen X.,Shangqiu Normal University | Zhao G.,Shangqiu Normal University | Mei F.,Beijing Institute of Technology
Nonlinear Dynamics | Year: 2013

A gradient representation and a fractional gradient representation of the Poincaré equations are studied. Firstly, the condition presented here for the Poincaré equation can be considered as a gradient system. Then, a condition under which the Poincaré equation can be considered as a fractional gradient system is obtained. Finally, two examples are given to illustrate applications of the result.

Pu K.-Y.,National University of Singapore | Shi J.,Beijing Institute of Technology | Cai L.,National University of Singapore | Li K.,National University of Singapore | Liu B.,National University of Singapore
Biomacromolecules | Year: 2011

A hyperbranched conjugated polyelectrolyte (HCPE) with a core-shell structure is designed and synthesized via alkyne polycyclotrimerization and click chemistry. The HCPE has an emission maximum at 565 nm with a quantum yield of 12% and a large Stokes shift of 143 nm in water. By virtue of its poly(ethylene glycol) shell, this polymer naturally forms spherical nanoparticles that minimize nonspecific interaction with biomolecules in aqueous solution, consequently allowing for efficient bioconjugation with anti-HER2 affibody via carbodiimide-activated coupling reaction. The resulting affibody-attached HCPE can be utilized as a reliable fluorescent probe for targeted cellular imaging of HER2-overexpressed cancer cells such as SKBR-3. Considering its low cytotoxicity and good photostability, the HCPE nanoprobe holds great promise in practical imaging tasks. This study also provides a molecular engineering strategy to overcome the intrinsic limitations of traditional fluorescent polymers (e.g., chromophore-tethered polymers and linear conjugated polyelectrolytes) for bioconjugation and applications. © 2011 American Chemical Society.

Wang J.,Beijing Institute of Technology
Key Engineering Materials | Year: 2012

Filling-to-packing switchover control during injection molding plays a crucial role in ensuring the quality of the molded parts. In this study, a filling-to-packing switchover mode based on cavity pressure was presented, and it was compared with other two switchover modes by injection time and screw position. The objective of this study was to validate the accuracy of the switchover mode based on cavity pressure, and examine its consistency. Weight of the molded parts served as the main measure to probe the process capabilities. In this study, the change in mold temperature was monitored; variation of mold temperature affecting the process was examined. The results of the verification experiments revealed that the switchover mode based on cavity pressure could yield a better part quality and consistent part weight compared with the other two traditional switchover modes. It was proved that the switchover mode by cavity pressure can be used to improve the precision of the injection molding. However, a suitable switchover pressure must be used for achieving such high process capability, and the position to get the pressure signal and mold temperature should also be considered. © (2012) Trans Tech Publications.

Zhu Y.-L.,Beijing Institute of Technology | Zhu Y.-L.,Keio University | Katayama Y.,Keio University | Miura T.,Keio University
Electrochimica Acta | Year: 2012

The effects of additives, acetone (AC) and thiourea (TU), on electrodeposition of nickel were investigated in a hydrophobic room-temperature ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPTFSA) containing Ni(TFSA)2. The UV-vis spectra showed the coordination environment of Ni(II) species was affected by the presence of AC. The diffusion coefficient of Ni(II) in BMPTFSA was increased slightly and the reduction potential of Ni(II) shifted to the more positive side in the presence of AC. The nucleation/growth process of Ni was not affected by the change in the coordination environment of Ni(II) from the chronoamperometric results. Addition of TU also changed the color of the electrolyte from yellow to yellow-green, while the coordination environment of Ni(II) was not changed with the existence of TU. The overpotential for Ni(II)/Ni with TU was slightly larger than that without the additive. The effects of the additives on the morphology of the Ni deposits were also characterized by SEM, XPS and EDX. © 2012 Elsevier Ltd.

Sun B.,Beijing Institute of Technology
Transactions of the Institute of Measurement and Control | Year: 2013

This paper is concerned with an optimal distributed control problem of a nonlinear viscous dispersive wave equation that approximately describes the unidirectional propagation of long waves. By the Dubovitskii and Milyutin functional analytical approach, we prove the Pontryagin maximum principle of the investigational system. The necessary condition for optimality is established for the controlled object in a fixed final horizon case and, subsequently, a remark on the applicability of the obtained results is made for the illustration. © The Author(s) 2013.

Tu B.,Fudan University | Pang Q.,Fudan University | Wu D.,Fudan University | Song Y.,Beijing Institute of Technology | And 2 more authors.
Journal of the American Chemical Society | Year: 2014

Vacancies are common in solid materials, but it remains a challenge to introduce them at specific locations with controlled distributions. Here we report the creation of ordered metal vacancies and linker vacancies in a cubic metal-organic framework (MOF) based on Zn(II) and pyrazolecarboxylic acid by removing a quarter of the metal ions and half of the linkers. The MOF with ordered vacancies shows increased pore size, thus allowing large dye molecules to fit in the pores. Furthermore, by filling the vacancies with new metals and new linkers, eight new single-crystalline MOFs with multicomponents in absolute order are introduced. The capability of performing stepwise elimination and addition reactions systematically in extended solids without destroying the structural integrity has generated complex MOF structures which otherwise cannot be made. © 2014 American Chemical Society.

Wang Z.,Shanghai JiaoTong University | Wei P.,Shanghai JiaoTong University | Qian Y.,Shanghai JiaoTong University | Liu J.,Beijing Institute of Technology
Composites Part B: Engineering | Year: 2014

In this paper, a novel graphene-based inorganic-organic hybrid flame retardant (GFR) was prepared via sol-gel reaction of FGO and phenyl-bis-(triethoxysilylpropyl) phosphamide (PBTP) and characterized by FT-IR, XPS, XRD, TGA and AFM. The influence of the GFR on the thermal stability and flame retardance of epoxy resin composites were characterized by TGA, LOI as well as micro-cone, which indicated that GFR brought a good effect in enhancing the residual char and flame retardance of epoxy composites. The dynamic mechanical properties and electrical properties of EP composites were also analyzed. © 2013 Elsevier Ltd. All rights reserved.

Tang Q.H.,CAS Institute of Mechanics | Tang Q.H.,Beijing Institute of Technology
Science China: Physics, Mechanics and Astronomy | Year: 2012

The influence of specimen size on the mechanical behavior of Au pillars is studied by means of molecular dynamics (MD) simulations with the EAM potential. Under compression at 300 K, as the deformation of pillars is in the plastic stage, nucleation of partial dislocations is observed. The coupling effect of surface stress and thermal activation is considered when analyzing the size effect on the yield property of the Au pillars. It appears that both the tensile stress component and the temperature in the surface layer impart significant effect on the mechanical behaviors of the nano-sized Au pillars. © 2012 Science China Press and Springer-Verlag Berlin Heidelberg.

Chen Z.,Beijing Institute of Technology | Wang C.-C.,Peregrine Semiconductor | Yao H.-C.,HTC Corp | Heydari P.,University of California at Irvine
IEEE Journal of Solid-State Circuits | Year: 2012

This paper presents a W-band 2$\,\times\,$ 2 focal-plane array (FPA) for passive millimeter-wave imaging in a standard 0.18 $\mu{\hbox{m}}$ SiGe BiCMOS process ($f -{\rm T} /f -{\max} =200/180 ~{\hbox{GHz}}$). The FPA incorporates four Dicke-type receivers representing four imaging pixels. Each receiver employs the direct-conversion architecture consisting of an on-chip slot folded dipole antenna, an SPDT switch, a low noise amplifier, a single-balanced mixer, an injection-locked frequency tripler (ILFT), an IF variable gain amplifier, a power detector, an active bandpass filter and a synchronous demodulator. The LO signal is generated by a shared Ka-band PLL and distributed symmetrically to four local ILFTs. The measured LO phase noise is $-93~{\rm dBc}/{\rm Hz}$ at 1 MHz offset from the 96 GHz carrier. This imaging receiver (without antenna) achieves a measured average responsivity and noise equivalent power of 285 MV/W and 8.1 ${\rm fW}/{\rm Hz} 1/2 respectively, across the 86-106 GHz bandwidth, which results a calculated NETD of 0.48 K with a 30 ms integration time. The system NETD increases to 3 K with on-chip antenna due to its low efficiency at W-band. MMW images have been generated in transmission mode. This work demonstrates the highest integration level of any silicon-based systems in the 94 GHz imaging band. © 1966-2012 IEEE.

Zhang B.,Beijing Institute of Technology | Ng H.D.,Concordia University at Montreal | Lee J.H.S.,McGill University
Shock Waves | Year: 2012

In this paper, the critical energies required for direct initiation of spherical detonations in four gaseous fuels (C 2H 2, C 2H 4, C 3H 8 and H 2)-oxygen mixtures at different initial pressures, equivalence ratios and with different amounts of argon dilution are reported. Using these data, a scaling analysis is performed based on two main parameters of the problem: the explosion length R o that characterizes the blast wave and a characteristic chemical length that characterizes the detonation. For all the undiluted mixtures considered in this study, it is found that the relationship is closely given by R o ≈26λ, where λ is the characteristic detonation cell size of the explosive mixture. While for C 2H 2-2.5O 2 mixtures highly diluted with argon, in which cellular instabilities are shown to play a minor role on the detonation propagation, the proportionality factor increases to 37.3, 47 and 54.8 for 50, 65 and 70% argon dilution, respectively. Using the ZND induction length Δ I as the characteristic chemical length scale for argon diluted or 'stable' mixtures, the explosion length is also found to scale adequately with R o≈2320Δ I. © 2011 Springer-Verlag.

Sun B.,Beijing Institute of Technology
Journal of the Franklin Institute | Year: 2010

In this paper, the optimal boundary control for the Kuramoto-Sivashinsky equation is considered. The Dubovitskii and Milyutin functional analytical approach is adopted in investigation of Pontryagin's maximum principles of the system in both fixed and free final horizon cases. The necessary conditions are, respectively, presented for the optimal boundary control problems in these two cases. © 2009 The Franklin Institute.

Ma X.,Beijing Institute of Technology | Arce G.R.,University of Delaware
Optics Express | Year: 2011

Optical proximity correction (OPC) methods are resolution enhancement techniques (RET) used extensively in the semiconductor industry to improve the resolution and pattern fidelity of optical lithography. In pixel-based OPC (PBOPC), the mask is divided into small pixels, each of which is modified during the optimization process. Two critical issues in PBOPC are the required computational complexity of the optimization process, and the manufacturability of the optimized mask. Most current OPC optimization methods apply the steepest descent (SD) algorithm to improve image fidelity augmented by regularization penalties to reduce the complexity of the mask. Although simple to implement, the SD algorithm converges slowly. The existing regularization penalties, however, fall short in meeting the mask rule check (MRC) requirements often used in semiconductor manufacturing. This paper focuses on developing OPC optimization algorithms based on the conjugate gradient (CG) method which exhibits much faster convergence than the SD algorithm. The imaging formation process is represented by the Fourier series expansion model which approximates the partially coherent system as a sum of coherent systems. In order to obtain more desirable manufacturability properties of the mask pattern, a MRC penalty is proposed to enlarge the linear size of the sub-resolution assistant features (SRAFs), as well as the distances between the SRAFs and the main body of the mask. Finally, a projection method is developed to further reduce the complexity of the optimized mask pattern. © 2011 Optical Society of America.

Huang Y.,University of Electronic Science and Technology of China | Wen G.,University of Electronic Science and Technology of China | Zhu W.,Monash University | Li J.,University of Electronic Science and Technology of China | And 2 more authors.
Optics Express | Year: 2014

We synthesize and systematically characterize a novel type of magnetically tunable metamaterial absorber (MA) by integrating ferrite as a substrate or superstrate into a conventional passive MA. The nearly perfect absorption and tunability of this device is studied both numerically and experimentally within X-band (8-12 GHz) in a rectangular waveguide setup. Our measurements clearly show that the resonant frequency of the MA can be shifted across a wide frequency band by continuous adjustment of a magnetic field acting on the ferrite. Moreover, the effects of substrate/superstrate's thickness on the MA's tunability are discussed. The insight gained from the generic analysis enabled us to design an optimized tunable MA with relative frequency tuning range as larger as 11.5% while keeping the absorptivity higher than 98.5%. Our results pave a path towards applications with tunable devices, such as selective thermal emitters, sensors, and bolometers. © 2014 Optical Society of America.

Peng Z.,Northeast Forestry University | Guo-Qiang N.,Beijing Institute of Technology
Optics and Lasers in Engineering | Year: 2010

A simultaneous measurement scheme for multiple three-dimensional (3D) objects' surface boundary perimeters is proposed. This scheme consists of three steps. First, a binocular stereo vision measurement system with two CCD cameras is devised to obtain the two images of the detected objects' 3D surface boundaries. Second, two geodesic active contours are applied to converge to the objects' contour edges simultaneously in the two CCD images to perform the stereo matching. Finally, the multiple spatial contours are reconstructed using the cubic B-spline curve interpolation. The true contour length of every spatial contour is computed as the true boundary perimeter of every 3D object. An experiment on the bent surface's perimeter measurement for the four 3D objects indicates that this scheme's measurement repetition error decreases to 0.7 mm. © 2009 Elsevier Ltd. All rights reserved.

Liu J.,Beijing Institute of Technology | Pang M.,Substation of China North Engine Research Institute
International Journal of Fatigue | Year: 2012

An analytical method is proposed to calculate the interaction between operation stresses and shot peening caused residual stresses. The obtained variation of residual stress is integrated into Findley model to predict the fatigue life of shot-peened materials. Biaxial stress state is taken into account in conventional Findley model, and critical plane is studied for both in-plane and out-of-plane shear stress. In the end, taking example for AISI 4340 steel, the prediction of fatigue life is made for two different shot peening conditions. A good agreement between measurements and predictions can be observed. © 2012 Elsevier Ltd. All rights reserved.

He Z.,University of Science and Arts of Iran | Yao C.,University of Science and Arts of Iran | Zou J.,Beijing Institute of Technology
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013

Using the weak measurement (WM) and quantum measurement reversal (QMR) approach, robust state transfer and entanglement distribution can be realized in the spin-12 Heisenberg chain. We find that the ultrahigh fidelity and long distance of quantum state transfer with certain success probability can be obtained using proper WM and QMR, i.e., the average fidelity of a general pure state from 80% to almost 100%, which is almost size independent. We also find that the distance and quality of entanglement distribution for the Bell state and the general Werner mixed state can be obviously improved by the WM and QMR approach. © 2013 American Physical Society.

Li Z.,Beijing Institute of Technology | Duan Z.,Peking University | Chen G.,Peking University
IET Control Theory and Applications | Year: 2011

This study concerns the consensus of a network of agents with general linear or linearised dynamics, whose communication topology contains a directed spanning tree. An observer-type consensus protocol based on the relative outputs of the neighbouring agents is adopted. The notion of consensus region is introduced, as a measure for the robustness of the protocol and as a basis for the protocol design. For neutrally stable agents, it is shown that there exists a protocol achieving consensus together with a consensus region that is the entire open right-half plane if and only if each agent is stabilisable and detectable. An algorithm is further presented for constructing such a protocol. For consensus with a prescribed convergence speed, a multi-step protocol design procedure is given, which yields an unbounded consensus region and at the same time maintains a favourable decoupling property. Finally, the consensus algorithms are extended to solve the formation control problems. © 2011 The Institution of Engineering and Technology.

Li Y.,Beijing Institute of Technology | Li Y.,Tsinghua University | Song J.,Tsinghua University | Yang J.,Beihang University
Renewable and Sustainable Energy Reviews | Year: 2014

Structure properties of lithium-ion battery determine the specific energy and specific power of renewable energy vehicle and have attracted extensive concerns. Fundamental innovations in battery system depend on the structure properties, of which graphene and concentration gradient structures become increasingly prospective. As the performance of structure closely relates to the battery performance and the advancement of battery technologies, the paper, based on the research work at our laboratory, discusses about the structure model and energy system design and analyzes the evolution of lithium batteries to provide scientific insights and technical advices for the development of renewable energy vehicle. The review shows that nano and graphene models, with their corresponding energy systems, significantly improve the performance of lithium batteries, thus supporting longer mileage and service life, while providing new ideas for the design of renewable energy vehicles. Compared with other power batteries, lithium-ion batteries are advantageous in addressing the requirements raised by battery electric vehicles, such as, long mileage, high-current charging, and safety. Therefore, lithium batteries are reliable and feasible for the deployment in battery electric vehicles. © 2014 Elsevier Ltd.

Yurur O.,University of South Florida | Liu C.H.,Beijing Institute of Technology | Moreno W.,University of South Florida
IEEE Communications Magazine | Year: 2014

The ever increasing technological advances in embedded systems engineering, together with the proliferation of small-size sensor designs and deployment, have enabled smart devices to recognize daily human-based actions, activities, and interactions. Therefore, inferring a vast variety of user-device-based activities from diverse contexts obtained by a series of sensory observations has drawn much interest to the research area of ubiquitous sensing. The existence and awareness of context provides the capability of being conscious of physical environments or situations around users, and this allows network services to respond proactively and intelligently based on such awareness. Hence, with the evolution of smartphones, software developers have been empowered to create context-aware applications for recognizing human-centric or community based innovative social and cognitive activities in any situation and at any location. However, the middleware services provided in mobile devices have limited resources in terms of power, memory, and bandwidth compared to the capabilities of PCs and servers. Also, power is a major restriction on implementation of context-aware applications. Mobile device batteries do not last a long time while operating sensor(s) constantly. To this end, this article extensively surveys the emerging concepts of context awareness in mobile platforms by providing up-to-date literature and future research directives. We also point out the challenges faced in this regard and enlighten them by offering possible solutions. © 2014 IEEE.

Kong Y.,Northeastern University | Jia Y.,Beijing Institute of Technology | Fu Y.,Northeastern University
IEEE Transactions on Pattern Analysis and Machine Intelligence | Year: 2014

This paper addresses the problem of recognizing human interactions from videos. We propose a novel approach that recognizes human interactions by the learned high-level descriptions, interactive phrases. Interactive phrases describe motion relationships between interacting people. These phrases naturally exploit human knowledge and allow us to construct a more descriptive model for recognizing human interactions. We propose a discriminative model to encode interactive phrases based on the latent SVM formulation. Interactive phrases are treated as latent variables and are used as mid-level features. To complement manually specified interactive phrases, we also discover data-driven phrases from data in order to find potentially useful and discriminative phrases for differentiating human interactions. An information-theoretic approach is employed to learn the data-driven phrases. The interdependencies between interactive phrases are explicitly captured in the model to deal with motion ambiguity and partial occlusion in the interactions. We evaluate our method on the BIT-Interaction data set, UT-Interaction data set, and Collective Activity data set. Experimental results show that our approach achieves superior performance over previous approaches. © 1979-2012 IEEE.

Li H.,Beijing Institute of Technology | Xu H.,Tsinghua University | Wang J.,Tsinghua University
Journal of Natural Gas Chemistry | Year: 2011

CeO2-promoted Ni/Al2O3-ZrO2 (Ni/Al2O3-ZrO2-CeO2) catalysts were prepared by a direct sol-gel process with citric acid as gelling agent. The catalysts used for the methane reforming with CO2 was studied by infrared spectroscopy (IR), thermal gravimetric analysis (TGA), microscopic analysis, X-ray diffraction (XRD) and temperature-programmed reduction (TPR). The catalytic performance for CO2 reforming of methane to synthesis gas was investigated in a continuous-flow micro-reactor under atmospheric pressure. TGA, IR, XRD and microscopic analysis show that the catalysts prepared by the direct sol-gel process consist of Ni particles with a nanostructure of around 5 nm and an amorphous-phase composite oxide support. There exists a chemical interaction between metallic Ni particles and supports, which makes metallic Ni well dispersed, highly active and stable. The addition of CeO 2 effectively improves the dispersion and the stability of Ni particles of the prepared catalysts, and enhances the adsorption of CO 2 on the surface of catalysts. The catalytic tests for methane reforming with CO2 to synthesis gas show that the Ni/Al 2O3-ZrO2-CeO2 catalysts show excellent activity and stability compared with the Ni/Al2O 3 catalyst. The excellent catalytic activity and stability of the Ni/Al2O3-ZrO2-CeO2 are attributed to the highly, uniformly and stably dispersed small metallic Ni particles, the high reducibility of the Ni oxides and the interaction between metallic Ni particles and the composite oxide supports. © 2011, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. All rights reserved.

Ren B.,Texas Tech University | Wang J.-M.,Beijing Institute of Technology | Krstic M.,University of California at San Diego
Systems and Control Letters | Year: 2013

We consider the problem of stabilization of a linear ODE with input dynamics governed by the linearized Schrödinger equation. The interconnection between the ODE and Schrödinger equation is bi-directional at a single point. We construct an explicit feedback law that compensates the Schrödinger dynamics at the inputs of the ODE and stabilizes the overall system. Our design is based on a two-step backstepping transformation by introducing an intermediate system and an intermediate control. By adopting the Riesz basis approach, the exponential stability of the closed-loop system is built with the pre-designed decay rate and the spectrum-determined growth condition is obtained. A numerical simulation is provided to illustrate the effectiveness of the proposed design. © 2013 Elsevier B.V. All rights reserved.

Zhang X.,China Institute of Policy and Management | De Pablos P.O.,University of Oviedo | Zhang Y.,Beijing Institute of Technology
International Journal of Engineering Education | Year: 2012

Knowledge contribution is a very important issue in online engineering education. This study investigates how to encourage knowledge contribution in a large Asia online engineering education project. Based on long-term empirical research, we found economic incentive is more critical to facilitate explicit knowledge contribution, while social incentive is more important in encouraging tacit knowledge contribution. Moreover, we also found incentives may have different effects due to students' individual difference, e.g., personal value. That is, economic incentive may have positive effect on some students, but none or negative to others. These findings provides some theoretical contributions on e-learning and knowledge management, and also provides some implications for choosing technology in online engineering education system, and designing incentive mechanism. © 2012 TEMPUS Publications.

Pang B.,Beijing Institute of Technology
Fuzzy Sets and Systems | Year: 2014

This paper presents a definition of (L,M)-fuzzy convergence spaces. It is shown that the category (L,M)-FC of (L,M)-fuzzy convergence spaces, which embeds the category (L,M)-FTop of (L,M)-fuzzy topological spaces as a reflective subcategory, is a Cartesian closed topological category. Further, it is proved that the category of (topological) pretopological (L,M)-fuzzy convergence spaces is isomorphic to the category of (topological) (L,M)-fuzzy quasi-coincident neighborhood spaces. Moreover, the relations among (L,M)-fuzzy convergence spaces, pretopological (L,M)-fuzzy convergence spaces and topological (L,M)-fuzzy convergence spaces are investigated in the categorical sense. © 2013 Elsevier B.V.

Sun B.,Beijing Institute of Technology
Nonlinear Analysis: Real World Applications | Year: 2012

In this paper, the optimal distributed control of the viscous DullinGottwaldHolm equation is investigated. Adopting the Dubovitskii and Milyutin functional analytical approach, we obtain the Pontryagin maximum principle of the system. The necessary optimality condition is established for an optimal control problem in fixed final horizon case. Finally, an illustrative example is also given. © 2011 Elsevier Ltd. All rights reserved.

You Y.-Z.,Tsinghua University | Yang F.,Beijing Institute of Technology | Kou S.-P.,Tsinghua University | Weng Z.-Y.,Tsinghua University
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

We study a unified mechanism for spin-density-wave (SDW) and superconductivity in a minimal model in which itinerant electrons and local moments coexist as previously proposed for the iron pnictides. The phase diagram obtained at the mean-field level is in qualitative agreement with the experiment, which shows how the magnetic and superconducting (SC) instabilities are driven by the critical coupling between the itinerant/localized electrons. The spin and charge response functions at the random-phase-approximation level further characterize the dynamical evolution of the system. In particular, the dynamic spin susceptibility displays a Goldstone mode in the SDW phase, which evolves into a gapped resonance-like mode in the SC phase. The latter persists all the way into the normal state above Tc where a strong scattering between the itinerant electrons and local moments is restored, as an essential feature of the model. © 2011 American Physical Society.

Pang B.,Beijing Institute of Technology
Journal of Intelligent and Fuzzy Systems | Year: 2014

In this paper, we introduce L-continuity degree, L-openness degree, L-closedness degree of mappings between L-fuzzifying topological spaces. Moreover, we show that most of elementary results related to continuous mappings, open mappings, and closed mappings in general topology can be extended to L-fuzzifying topological spaces by means of the graded concepts. © 2014-IOS Press and the authors. All rights reserved.

Ma J.,Beijing Institute of Technology | Porter A.L.,Georgia Institute of Technology | Porter A.L.,Search Technology Inc.
Scientometrics | Year: 2015

As a basic knowledge resource, patents play an important role in identifying technology development trends and opportunities, especially for emerging technologies. However patent mining is restricted and even incomplete, because of the obscure descriptions provided in patent text. In this paper, we conduct an empirical study to try out alternative methods with Derwent Innovation Index data. Our case study focuses on nanoenabled drug delivery (NEDD) which is a very active emerging biomedical technology, encompassing several distinct technology spaces. We explore different ways to enhance topical intelligence from patent compilations. We further analyze extracted topical terms to identify potential innovation pathways and technology opportunities in NEDD. © Akadémiai Kiadó, Budapest, Hungary 2014

Huang L.,University of Science and Technology Beijing | Huang L.,Beijing Institute of Technology | Cong D.Y.,University of Science and Technology Beijing | Suo H.L.,Beijing University of Technology | Wang Y.D.,University of Science and Technology Beijing
Applied Physics Letters | Year: 2014

We report a giant effective magnetic refrigeration capacity in a Ni 40Co10Mn40Sn10 multifunctional alloy. With a large magnetization difference between austenite and martensite, this alloy shows a strong magnetic field dependence of transformation temperatures. Complete magnetic-field-induced structural transformation and a considerable magnetic entropy change are observed in a broad operating temperature window of 33K near room temperature. Consequently, an effective magnetic refrigeration capacity of 251J/kg for 5T is achieved, which is the largest value for Ni-Mn-based Heusler alloys and comparable to that of the high-performance Gd-Si-Ge and La-Fe-Si magnetocaloric materials. Incorporating the advantages of low cost and non-toxicity, this alloy shows very promising prospects for room-temperature magnetic refrigeration. © 2014 AIP Publishing LLC.

Yang F.,Beijing Institute of Technology | Wang F.,Peking University | Lee D.-H.,University of California at Berkeley | Lee D.-H.,Lawrence Berkeley National Laboratory
Physical Review B - Condensed Matter and Materials Physics | Year: 2013

We address two important issues that arise in recent studies of iron-based superconductivity. (1) Why are the Tc of AxFe 2-ySe2 (A=K, Rb, Cs) and the single unit cell FeSe on SrTiO3 so high despite both only having electron pockets? (2) What (if any) are the effects of orbital order and orbital fluctuation on the Cooper pairing. Our main conclusions are the following: (1) removing hole pockets releases frustration of Cooper pairing from their band vorticity, therefore can enhance Tc, and (2) orbital fluctuation has negligible effect on Cooper pairing. © 2013 American Physical Society.

Xu H.,Jilin University | Yu B.,Beijing Institute of Technology
Expert Systems with Applications | Year: 2010

Email has become one of the fastest and most economical forms of communication. Email is also one of the most ubiquitous and pervasive applications used on a daily basis by millions of people worldwide. However, the increase in email users has resulted in a dramatic increase in spam emails during the past few years. This paper proposes a new spam filtering system using revised back propagation (RBP) neural network and automatic thesaurus construction. The conventional back propagation (BP) neural network has slow learning speed and is prone to trap into a local minimum, so it will lead to poor performance and efficiency. The authors present in this paper the RBP neural network to overcome the limitations of the conventional BP neural network. A well constructed thesaurus has been recognized as a valuable tool in the effective operation of text classification, it can also overcome the problems in keyword-based spam filters which ignore the relationship between words. The authors conduct the experiments on Ling-Spam corpus. Experimental results show that the proposed spam filtering system is able to achieve higher performance, especially for the combination of RBP neural network and automatic thesaurus construction. © 2009 Elsevier Ltd. All rights reserved.

Huang L.,Beijing Institute of Technology | Zhang Q.T.,City University of Hong Kong | Cheng L.L.,City University of Hong Kong
IEEE Transactions on Signal Processing | Year: 2011

Most existing stopping criteria for turbo decoding have their root in hypothesis test, requiring a subjective threshold for decision making. A consequence is that the turbo decoding receiver so-constructed can converge at high signal-to-noise ratios (SNRs) but fails at low SNRs, thereby calling for a new design philosophy for stopping criteria. In this correspondence, the problem is tackled in the framework of information theoretic criterion, which enables the turbo decoding to properly work in a changing SNR environment. Numerical results are presented for illustrating the good performance of the proposed method. © 2006 IEEE.

Gao Y.,Tsinghua National Laboratory for Information Sciences and Technology | Ji R.,Xiamen University | Zhang L.,Beijing Institute of Technology | Hauptmann A.,Carnegie Mellon University
IEEE Transactions on Circuits and Systems for Video Technology | Year: 2014

Tracking people and objects is a fundamental stage toward many video surveillance systems, for which various trackers have been specifically designed in the past decade. However, it comes to a consensus that there is not any specific tracker that works sufficiently well under all circumstances. Therefore, one potential solution is to deploy multiple trackers, with a tracker output fusion step to boost the overall performance. Subsequently, an intelligent fusion design, yet general and orthogonal to any specific tracker, plays a key role in successful tracking. In this paper, we propose a symbiotic tracker ensemble toward a unified tracking framework, which is based on only the output of each individual tracker, without knowing its specific mechanism. In our approach, all trackers run in parallel, without requiring any details for tracker running, which means that all trackers are treated as black boxes. The proposed symbiotic tracker ensemble framework aims at learning an optimal combination of these tracking results. Our method captures the relation among individual trackers robustly from two aspects. First, the consistency between two successive frames is calculated for each tracker. Then, the pair-wise correlation among different trackers is estimated in the new coming frame by a graph-propagation process. Experimental results on the Caremedia dataset and the Caviar dataset demonstrate the effectiveness of the proposed method, with comparisons to several state-of-the-art methods. © 1991-2012 IEEE.

Zhang X.,University of Western Australia | Hao H.,Curtin University Australia | Wang Z.,Beijing Institute of Technology
Engineering Structures | Year: 2014

A series of field blasting tests of glass windows to blast loadings have been recently conducted. This is the second paper to report the testing data on monolithic tempered glass windows. While the first paper reports the glass panel response and failure modes, the current paper concentrates on the glass fragments induced by the blast loadings. Thermally tempered glass has been often adopted for monolithic windows to reduce ejecting fragment hazards after window fracture. However, previous blast tests conducted on monolithic tempered glass reported that in addition to small cubic fragments the shattered glass panes could break into large and jagged fragments similar to the cases in annealed glass which poses much more debris threats than expected. A thorough study on tempered glass fragments produced by air blast pressure is therefore necessary for better protection of human safety. In this paper, fragment characteristics of monolithic tempered glass windows observed in blasting tests are analyzed and presented. 1.5. m × 1.2. m monolithic panes of two commonly used thicknesses, i.e. 6. mm and 10. mm, fully clamped onto the opening of an enclosed RC frame were tested with 5-10. kg TNT charge detonated at 4.5-12.3. m stand-off distances. Glass fragment mass and splash distributions both in front of and behind the windows were evaluated with respect to reflected pressure and glass specification. Fragment size and shape were also analyzed. High-speed cameras were used to monitor glass window fracture processes. Fragment velocities were determined by post-processing the high-speed camera images. Fragment ejecting velocities were evaluated with respect to the reflected impulse. Negative pressure was found to significantly influence the fragment ejecting velocity and fragment splash distributions. © 2014 Elsevier Ltd.

Huang S.,Tsinghua University | Xiong J.,Beijing Institute of Technology | Zhang Y.,Tsinghua University
Journal of Hazardous Materials | Year: 2013

The indoor pollution caused by formaldehyde and volatile organic compounds (VOCs) emitted from building materials poses an adverse effect on people's health. It is necessary to understand and control the behaviors of the emission sources. Based on detailed mass transfer analysis on the emission process in a ventilated chamber, this paper proposes a novel method of measuring the three emission characteristic parameters, i.e., the initial emittable concentration, the diffusion coefficient and the partition coefficient. A linear correlation between the logarithm of dimensionless concentration and time is derived. The three parameters can then be calculated from the intercept and slope of the correlation. Compared with the closed chamber C-history method, the test is performed under ventilated condition thus some commonly-used measurement instruments (e.g., GC/MS, HPLC) can be applied. While compared with other methods, the present method can rapidly and accurately measure the three parameters, with experimental time less than 12h and R2 ranging from 0.96 to 0.99 for the cases studied. Independent experiment was carried out to validate the developed method, and good agreement was observed between the simulations based on the determined parameters and experiments. The present method should prove useful for quick characterization of formaldehyde/VOC emissions from indoor materials. © 2013 Elsevier B.V.

Tao J.,Nanyang Technological University | Yu X.,Nanyang Technological University | Hu B.,Nanyang Technological University | Hu B.,Beijing Institute of Technology | And 2 more authors.
Optics Letters | Year: 2014

We propose and numerically analyze a plasmonic Bragg reflector formed in a graphene waveguide. The results show that the graphene plasmonic Bragg reflector can produce a broadband stopband that can be tuned over a wide wavelength range by a small change in the Fermi energy level of graphene. By introducing a defect into the Bragg reflector, we can achieve a Fabry-Perot-like microcavity with a quality factor of 50 for the defect resonance mode formed in the stopband. The proposed Bragg reflector could be used as a broadband ultrafast tunable integrated filter and a broadband modulator. In addition, the defect microcavity may find applications in graphene-based resonators. © 2013 Optical Society of America.

Xia Y.,Beijing Institute of Technology
IEEE/CAA Journal of Automatica Sinica | Year: 2015

The concept of cloud control systems is discussed in this paper, which is an extension of networked control systems (NCSs). With the development of internet of things (IOT), the technology of NCSs has played a key role in IOT. At the same time, cloud computing is developed rapidly, which provides a perfect platform for big data processing, controller design and performance assessment. The research on cloud control systems will give new contribution to the control theory and applications in the near future. © 2014 Chinese Association of Automation.

Kim S.,Kyung Hee University | Yoon P.H.,Kyung Hee University | Yoon P.H.,University of Maryland University College | Choe G.S.,Kyung Hee University | Wang L.,Beijing Institute of Technology
Astrophysical Journal | Year: 2015

This paper presents a theory for the asymptotically steady-state solar wind electron velocity distribution function (VDF) in a local equilibrium with plasma wave turbulence. By treating the local solar wind electron VDF as superposition of three populationsthe low-energy Maxwellian core electrons with an energy range of tens of eV, the intermediate ∼103105 eV energy-range halo electrons, and the high ∼103105 eV energy-range superhalo electronsthe present paper puts forth a model in which the halo electrons are in dynamical steady state with the pervasive whistler fluctuations, while the superhalo electrons maintain dynamical steady-state equilibrium with the Langmuir fluctuations, known as the quasi-thermal noise. Customary models of the solar wind electrons include only the Maxwellian core and the halo (plus highly field-aligned strahl). While the present paper does not consider the strahl population in the discussion, the highly energetic superhalo component, which is observed to be present in all solar conditions, is explicitly taken into account as part of the total solar wind electron model. Comparisons with STEREO and WIND spacecraft observations are also made. © 2015. The American Astronomical Society. All rights.

Zhang X.,University of Western Australia | Hao H.,Curtin University Australia | Wang Z.,Beijing Institute of Technology
International Journal of Impact Engineering | Year: 2015

Laminated glass panes are widely adopted as blast-resistant glass windows to mitigate the hazard from ejecting fractured glass fragments. The response of laminated glass windows under blast loads is often predicted by equivalent static analysis or simplified equivalent single degree of freedom (SDOF) analysis. The equivalent SDOF and equivalent static analyses are also respectively adopted in UFC and ASTM design guide for glass window designs. Owing to the inherent problems, the SDOF analysis can only predict the global responses of glass windows and the predictions are not necessarily always satisfactory. Therefore the accuracy and applicability of the SDOF analysis is sometimes questioned. Often numerical simulations and/or experimental tests have to be carried out for reliable predictions of laminated glass window responses to blast loads. In this study, experimental tests on laminated glass windows subjected to impact and blast loads were carried out to evaluate the accuracy of available analyses and design methods. Pendulum impact tests were conducted first on laminated panes of various thicknesses. Full-scale field blast tests were performed on laminated glass windows of dimension 1.5 m × 1.2 m. Glass pane deflections were monitored by mechanical linear voltage displacement transducer (LVDT) and high-speed cameras. The responses of the tested windows are compared with the estimations of SDOF models and design standards in this paper. Available blast testing data by other researchers are also included together with the current testing data to evaluate the accuracy of the SDOF and equivalent static analyses defined in the design guides. The adequacy of these simplified approaches in predicting laminated glass window responses to blast loads is discussed. © 2014 Elsevier Ltd. All rights reserved.

Jiang C.,Key Laboratory of Cluster Science | Jiang C.,Ohio State University | Hu C.,Key Laboratory of Cluster Science | Dong Z.,Key Laboratory of Cluster Science | And 4 more authors.
ACS Nano | Year: 2013

Large-scale assembly of graphenes in a well-controlled macroscopic fashion is important for practical applications. We have developed a facile and straightforward approach for continuous fabrication of neat, morphology-defined, graphene-based hollow fibers (HFs) via a coaxial two-capillary spinning strategy. With a high throughput, HFs and necklace-like HFs of graphene oxide have been well-controlled produced with the ease of functionalization and conversion to graphene HFs via simply thermal or chemical reduction. This work paves the way toward the mass production of graphene-based HFs with desirable functionalities and morphologies for many of important applications in fluidics, catalysis, purification, separation, and sensing. © 2013 American Chemical Society.

Chang H.-R.,Sichuan Normal University | Zhou J.,Carnegie Mellon University | Zhang H.,Ohio University | Yao Y.,Beijing Institute of Technology
Physical Review B - Condensed Matter and Materials Physics | Year: 2014

We theoretically investigated two kinds of density oscillations, the Friedel oscillation and collective excitation in the silicene and germanene within the random phase approximation, and found that the tunable spin-valley coupled band structure could lead to some exotic properties in these two phenomena. Based on an exact analytical and numerical analysis, we demonstrated that the beating of the screened potential as well as the undamped plasmon mode can be taken as fingerprints of a topological phase transition in doped silicene and doped germanene. Thus our proposal here establishes the connection between the topological phase transition and the density oscillations that can be accessed by a variety of experimental techniques. © 2014 American Physical Society.

Liu H.,CAS Beijing National Laboratory for Molecular | Du D.-M.,Beijing Institute of Technology | Du D.-M.,CAS Beijing National Laboratory for Molecular
Advanced Synthesis and Catalysis | Year: 2010

The new diphenylamine-linked bis(imidazoline) ligands were prepared through Kelly-You's imidazoline formation procedure mediated by Hendrickson 's reagent in good yields. The novel ligands were tested in the asymmetric Friedel-Crafts alkylation of indole derivatives with nitroalkenes. In most cases, good yields (up to 97%) and excellent enantioselectivities (up to 98%) can be achieved. The optimized bis(imidazoline) ligand with trans-diphenyl substitution on the imidazoline ring gave better enantioselectivity than the corresponding bis(oxazoline) ligand. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA,.

Liang M.,Beijing Institute of Technology
Quantum Information Processing | Year: 2013

Suppose some data have been encrypted, can you compute with the data without decrypting them? This problem has been studied as homomorphic encryption and blind computing. We consider this problem in the context of quantum information processing, and present the definitions of quantum homomorphic encryption (QHE) and quantum fully homomorphic encryption (QFHE). Then, based on quantum one-time pad (QOTP), we construct a symmetric QFHE scheme, where the evaluate algorithm depends on the secret key. This scheme permits any unitary transformation on any $$n$$ n -qubit state that has been encrypted. Compared with classical homomorphic encryption, the QFHE scheme has perfect security. Finally, we also construct a QOTP-based symmetric QHE scheme, where the evaluate algorithm is independent of the secret key. © 2013 Springer Science+Business Media New York.

Wang Y.,Beijing Institute of Technology | Yin J.,South China Normal University
Nonlinear Analysis: Real World Applications | Year: 2011

In this paper, we investigate a class of degenerate parabolic periodic equations with nonlocal terms under Neumann boundary conditions. By using the theory of the Leray-Schauder degree, we obtain the existence of non-trivial nonnegative periodic solutions. © 2011 Elsevier Ltd. All rights reserved.

Bi L.,Beijing Institute of Technology | Tsimhoni O.,General Motors | Liu Y.,University of Michigan
IEEE Transactions on Systems, Man, and Cybernetics Part A:Systems and Humans | Year: 2011

Empirical data modeling can be used to model human performance and explore the relationships between diverse sets of variables. A major challenge of empirical data modeling is how to generalize or extrapolate the findings with a limited amount of observed data to a broader context. In this paper, we introduce an approach from machine learning, known as support vector regression (SVR), which can help address this challenge. To demonstrate the method and the value of modeling human performance with SVR, we apply SVR to a real-world human factors problem of night vision system design for passenger vehicles by modeling the probability of pedestrian detection as a function of image metrics. The results indicate that the SVR-based model of pedestrian detection shows good performance. Some suggestions on modeling human performance by using SVR are discussed. © 2006 IEEE.

Xue J.,Jinan University | Yuan D.,Jinan University | Han F.,Beijing Institute of Technology | Liu R.,Jinan University
European Journal of Mechanics, A/Solids | Year: 2013

Conventionally cylindrical shells are often treated as shallow shells whose governing equation, according to Karman-Donnell's theory, can be approximated by those of thin plates. In this paper Karman-Donnell's theory for shallow shells is extended for long cylindrical shells undergoing large, nonlinear flexural deflection. The kinematic relations between the changes of curvature and the displacement are derived and the governing equations are established by considering the influence of the initial curvature of the cylindrical shells. In particular, the extended Karman-Donnell's theory is applied for the failure analysis of infinitely cylindrical shell under lateral pressure. A regional collapse mode is identified to occur in the shell with a longitudinal span proportional to (radius 3/thickness) (1/2) and a transverse profile of dog bone shape. It is found that the buckling pressure of the shell is in proportion to (thickness/radius) 3 and converges to the classic solution given by Timoshenko and Gere (1961). A comparison to the previous works indicates that ignoring the effect of the initial curvature will result in an overestimate of the buckling pressure for 33%. It shows that the initial curvature of long cylindrical shells has significant influence on the load carrying capacity and the extended Karman-Donnell's equations give very accurate predictions. © 2012 Elsevier Masson SAS. All rights reserved.

Yu L.-W.,Nankai University | Zhao Q.,Beijing Institute of Technology | Ge M.-L.,Nankai University
Annals of Physics | Year: 2014

This paper investigates the physical effects of the Yang-Baxter equation (YBE) to quantum entanglements through the 3-body S-matrix in entangling parameter space. The explicit form of 3-body S-matrix Ř123(θ,φ) based on the 2-body S-matrices is given due to the factorization condition of YBE. The corresponding chain Hamiltonian has been obtained and diagonalized, also the Berry phase for 3-body system is given. It turns out that by choosing different spectral parameters the Ř(θ,φ)-matrix gives GHZ and W states respectively. The extended 1-D Kitaev toy model has been derived. Examples of the role of the model in entanglement transfer are discussed. © 2014 Elsevier Inc.

Xiao F.,Beijing Institute of Technology | Xiao F.,University of Alberta | Chen T.,University of Alberta
IEEE Transactions on Automatic Control | Year: 2012

This technical note studies the state consensus of multiple double integrators in a sampled-data setting with the assumption that the position-like states are the only detectable information transmitted over the network. Based on local information, it proposes a novel consensus protocol, under which each agent follows a closed-loop continuous-time dynamics between sampling instants. A necessary and sufficient condition and a sufficient condition are developed for the uniform and nonuniform data-sampling cases, respectively. Unlike the existing sampled-data consensus results, the presented protocol has the advantage of being applicable to the case with large sampling periods. Furthermore, the protocol parameters can be chosen independently of the network structures. © 1963-2012 IEEE.

Pang B.,Beijing Institute of Technology
Journal of Intelligent and Fuzzy Systems | Year: 2014

This paper presents a definition of enriched (L,M)-fuzzy convergence spaces. It is shown that the resulting category E(L,M)-FC is a Cartesian closed topological category, which can embed the category E(L,M)-FTop of enriched (L,M)-fuzzy topological spaces as a reflective subcategory. Also, it is proved that the category of topological enriched (L,M)-fuzzy convergence spaces is isomorphic to E(L,M)-FTop and the category of pretopological enriched (L,M)-fuzzy convergence spaces is isomorphic to the category of enriched (L,M)-fuzzy quasi-coincident neighborhood spaces. © 2014 - IOS Press and the authors. All rights reserved.

Hou F.,Beijing Institute of Technology
Fundamenta Informaticae | Year: 2016

Pairwise comparisons (PC) method is an efficient technique and hierarchical analysis is a popular means coping with complex decision problems. Based on two proposed theorems, this paper shows that the PC-based hierarchical decision models stem from the weighted average methods (including the arithmetic form and the geometric form). Some issues (including the rank reversal, the criterion for acceptable consistency and the method for deriving priorities, etc) associated with the current PC-based hierarchical models (including the AHP, the multiplicative AHP and the FPR-AHP) are investigated. Another PC-based hierarchical decision model, which is different from the Saaty's AHP, is introduced for applications by virtue of its desirable traits (such as the rank preservation, the isomorphic correspondence, etc).

Xu M.,Shandong University of Science and Technology | Hu H.,Beijing Institute of Technology
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences | Year: 2011

A ballistic-diffusive heat conduction model is derived from the Boltzmann transport equation by a coarse-graining approach developed in the present study. By taking into account of the lagging effect, this model avoids the infinite heat propagation speed implied by the classical Fourier law. By expressing the heat conductivity as a function of the Knudsen number, it accounts for the size effect of the nanoscale heat conduction. The variation of the obtained effective heat conductivity with respect to the characteristic length shows an agreement with the experimental results for thin silicon films and nanowires in the nanoscale regime.© 2011 The Royal Society.

Zhang Y.,Beijing Normal University | Wan W.-H.,Beijing Institute of Technology
Frontiers of Physics | Year: 2014

A network is named as mixed network if it is composed of N nodes, the dynamics of some nodes are periodic, while the others are chaotic. The mixed network with all-to-all coupling and its corresponding networks after the nonlinearity gap-condition pruning are investigated. Several synchronization states are demonstrated in both systems, and a first-order phase transition is proposed. The mixture of dynamics implies any kind of synchronous dynamics for the whole network, and the mixed networks may be controlled by the nonlinearity gap-condition pruning. © 2014, Higher Education Press and Springer-Verlag Berlin Heidelberg.

Xing Y.,Beijing Institute of Technology | Xing Y.,University of Hong Kong | Zhang L.,University of Hong Kong | Wang J.,University of Hong Kong
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

We study the nature of the disorder-induced quantized conductance, i.e., the phenomena of topological Anderson insulator (TAI). The disorder effect in several different systems where the anomalous Hall effect exists is numerically studied using the tight-binding Hamiltonian. It is found that the TAI phenomena can also exist in the modified Dirac model where the quadratic corrections k2σz are included and the electron-hole symmetry is kept. These phenomena also occur in the graphene system with the next-nearest-neighbor coupling and the staggered sublattice potential. For the graphene sheet with Rashba spin-orbit interaction as well as an exchange field, a precursor of TAI is observed. A comparison between the localization length of the two-dimensional ribbon and two-dimensional cylinder structures clearly reveals the topological nature of these phenomena. Furthermore, analysis on the local current density in anomalous quantum Hall systems where the TAI phenomena may or may not arise reveals the nature of TAI phenomena. In the presence of small disorders, the conductance is not quantized and the bulk and edge states coexist in the system. As disorder strength increases, the bulk state is quickly destroyed, while the robust edge state may survive. When the edge state is robust enough to sustain the strong disorder that completely kills the bulk state, TAI phenomena arise. © 2011 American Physical Society.

Shen J.,Swinburne University of Technology | Lu G.,Nanyang Technological University | Zhao L.,Taiyuan University of Technology | Zhang Q.,Beijing Institute of Technology
Engineering Structures | Year: 2013

The response of sandwich tubes under internal explosive loading was investigated experimentally, numerically and analytically in this paper. Experiments were conducted first to capture the fundamental deformation and failure patterns and they served as a basis of validation for both the FE and analytical models. Further detailed deformation and blast loading history were revealed by the FE model. An explicit analytical solution for the deformation of sandwich tubes under blast loading has been worked out and used to obtain the optimum sandwich configurations, which would outperform their corresponding monolithic tubes. © 2011 Elsevier Ltd.

Lu Y.J.,University of Duisburg - Essen | Lu Y.J.,Beijing Institute of Technology | Entel P.,University of Duisburg - Essen
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

We study the thermophysical properties and structure of liquid Ni-Si alloys using molecular dynamics simulations. The liquid Ni-5% and 10%Si alloys crystallize to form the face-centered cubic (Ni) at 900 and 850 K, respectively, and the glass transitions take place in Ni-20% and 25%Si alloys at about 700 K. The temperature-dependent self-diffusion coefficients and viscosities exhibit more pronounced non-Arrhenius behavior with the increase of Si content before phase transitions, indicating the enhanced glass-forming ability. These appearances of thermodynamic properties and phase transitions are found to closely relate to the medium-range order clusters with the defective face-centered cubic structure characterized by both local translational and orientational order. This locally ordered structure tends to be destroyed by the addition of more Si atoms, resulting in a delay of nucleation and even glass transition instead. © 2011 American Physical Society.

Zhang L.,University of Hong Kong | Xing Y.,University of Hong Kong | Xing Y.,Beijing Institute of Technology | Wang J.,University of Hong Kong
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

Based on the nonequilibrium Green's function (NEGF) and time-dependent density-functional theory (TDDFT), we propose a formalism to study the time-dependent transport behavior of molecular devices from first principles. While this approach is equivalent to the time-dependent wave-function approach within TDDFT, it has the advantage that the scattering states and bound states are treated on equal footing. Furthermore, it is much easier to implement our approach numerically. Different from the time-dependent wave-function [ψ(t,E)] approach, our formalism is in the time space [Gr(t,t ′)], making this method superior in the time-dependent transport problem with many subbands in the transverse direction. For the purpose of numerical implementation on molecular devices, a computational tractable numerical scheme is discussed in detail. We have applied our formalism to calculate the transient current of two molecular devices Al-1,4-dimethylbenzene-Al and Al-benzene-Al from first principles. In the calculation, we have gone beyond the wideband limit and used the adiabatic local density approximation that was used within TDDFT. It is known that when the wideband limit is abandoned, the boundary condition of the transport problem is non-Markovian, resulting in a memory term in the effective Hamiltonian of the scattering region. To overcome the computational complexity due to the memory term, we have employed a fast algorithm to speed up the calculation and reduced the CPU time from the scaling N3 to N2log22(N) for the steplike pulse, where N is the number of time steps in the time evolution of the Green's function. To ensure the accuracy of our method, we have done a benchmark transient calculation on an atomic junction using a time-dependent wave-function approach within TDDFT in momentum space, which agrees very well with the result from our method. © 2012 American Physical Society.

Cai L.,Beijing Institute of Technology | Hansen F.,Copenhagen University
Letters in Mathematical Physics | Year: 2010

We give a truly elementary proof of the convexity of metric-adjusted skew information following an idea of Effros. We extend earlier results of weak forms of superadditivity to general metric-adjusted skew information. Recently, Luo and Zhang introduced the notion of semi-quantum states on a bipartite system and proved superadditivity of the Wigner-Yanase-Dyson skew informations for such states. We extend this result to the general metric-adjusted skew information. We finally show that a recently introduced extension to parameter values 1 < p ≤ 2 of the WYD-information is a special case of (unbounded) metric-adjusted skew information. © 2010 Springer.

Liu J.,Beijing Institute of Technology
International Journal of Fatigue | Year: 2013

In the present work numerical analysis for effects of shot peening on fatigue crack growth are reported and discussed. Simulations reported in the present work use irreversible cohesive zone model and are based on experimental data for a Nickel-based superalloy. The capability of the cohesive zone model to catch the effects of short crack is investigated. The two-dimensional computations fit known experimental records in the CT specimen which confirms that the cohesive zone model has the potential for engineering application. The fatigue crack growth of shot-peened specimens are studied for different loading amplitudes and different shot peening intensities. The numerical results reveal that the crack initiation position and time depend not only on the shot peening intensity but also on the cyclic loading amplitude. Retardation of fatigue crack growth is more effective at lower loading amplitude for shot-peened specimens, and higher applied loading will eliminate the beneficial effects of shot peening. © 2012 Elsevier Ltd. All rights reserved.

Feng Y.,Beijing Institute of Technology | Lapata M.,University of Edinburgh
IEEE Transactions on Pattern Analysis and Machine Intelligence | Year: 2013

This paper is concerned with the task of automatically generating captions for images, which is important for many image-related applications. Examples include video and image retrieval as well as the development of tools that aid visually impaired individuals to access pictorial information. Our approach leverages the vast resource of pictures available on the web and the fact that many of them are captioned and colocated with thematically related documents. Our model learns to create captions from a database of news articles, the pictures embedded in them, and their captions, and consists of two stages. Content selection identifies what the image and accompanying article are about, whereas surface realization determines how to verbalize the chosen content. We approximate content selection with a probabilistic image annotation model that suggests keywords for an image. The model postulates that images and their textual descriptions are generated by a shared set of latent variables (topics) and is trained on a weakly labeled dataset (which treats the captions and associated news articles as image labels). Inspired by recent work in summarization, we propose extractive and abstractive surface realization models. Experimental results show that it is viable to generate captions that are pertinent to the specific content of an image and its associated article, while permitting creativity in the description. Indeed, the output of our abstractive model compares favorably to handwritten captions and is often superior to extractive methods. © 1979-2012 IEEE.

Li J.,Beijing Institute of Technology | Chu F.,University of Evry Val dEssonne | Chen H.,University of Technology of Troyes
Computers and Industrial Engineering | Year: 2011

In this paper, we consider a distribution system where a warehouse is responsible for replenishing the inventories at multiple retailers by a fleet of vehicles of limited capacity. If a distribution policy of the system involves split deliveries, that is, the inventory of at least one retailer is replenished by using multiple vehicle routes, the coordination of the deliveries can further reduce the inventory cost of the retailer. We consider the coordination where two split deliveries are realized by direct shipping and multiple-stop shipping, respectively. To the best of our knowledge, this kind of coordination was never studied in the literature but can find its application in inventory routing problems. This paper proposes and analyses a class of coordination policies for the split deliveries which can reduce the inventory costs of the retailers without increasing transportation costs. A non-linear programming model is established for formulating the class of polices. Because the optimal coordination policy corresponding to an optimal solution of the model may be hard to find and/or implement, two simple but effective coordination policies are proposed. The inventory cost savings realized by the two policies are evaluated analytically and algorithmically. Our theoretical analysis and computational experiments show that both policies are effective. Under certain conditions, they can save 50% of the inventory costs at the retailers without increasing transportation costs. © 2010 Elsevier Ltd. All rights reserved.

Wen G.,Peking University | Duan Z.,Peking University | Li Z.,Beijing Institute of Technology | Chen G.,City University of Hong Kong
IET Control Theory and Applications | Year: 2012

In this study, the problem of stochastic consensus in multi-agent systems of non-linear dynamical agents with state-dependent noise perturbations and repairable actuator failures is investigated. By appropriately constructing a Lyapunov function and using tools from the stochastic differential equations theory, it is proved that mean-square consensus in the closed-loop multi-agent systems with a fixed strongly connected topology can be achieved exponentially if the coupling strength of relative states among neighbouring agents is larger than a threshold value depending on the actuator failure rate. The convergence rate is also analytically given. The results are then extended to the more general case where the communication topology only contains a directed spanning tree. Numerical simulations are finally provided to illustrate the effectiveness of the theoretical analysis. © 2012 The Institution of Engineering and Technology.

Xing C.,Beijing Institute of Technology | Xia M.,King Abdullah University of Science and Technology | Gao F.,Tsinghua National Laboratory for Information Sciences and Technology | Wu Y.-C.,University of Hong Kong
IEEE Journal on Selected Areas in Communications | Year: 2012

In this paper, robust transceiver design with Tomlinson-Harashima precoding (THP) for multi-hop amplify-and-forward (AF) multiple-input multiple-output (MIMO) relaying systems is investigated. At source node, THP is adopted to mitigate the spatial intersymbol interference. However, due to its nonlinear nature, THP is very sensitive to channel estimation errors. In order to reduce the effects of channel estimation errors, a joint Bayesian robust design of THP at source, linear forwarding matrices at relays and linear equalizer at destination is proposed. With novel applications of elegant characteristics of multiplicative convexity and matrix-monotone functions, the optimal structure of the nonlinear transceiver is first derived. Based on the derived structure, the transceiver design problem reduces to a much simpler one with only scalar variables which can be efficiently solved. Finally, the performance advantage of the proposed robust design over non-robust design is demonstrated by simulation results. © 2012 IEEE.

He Y.,Beijing Institute of Technology
Logical Methods in Computer Science | Year: 2014

We study a natural hierarchy in first-order logic, namely the quantifier structure hierarchy, which gives a systematic classification of first-order formulas based on structural quantifier resource. We define a variant of Ehrenfeucht-Fraïssé games that characterizes quantifier classes and use it to prove that this hierarchy is strict over finite structures, using strategy compositions. Moreover, we prove that this hierarchy is strict even over ordered finite structures, which is interesting in the context of descriptive complexity. © Yuguo He.

Dai L.,Case Western Reserve University | Xue Y.,Case Western Reserve University | Qu L.,Beijing Institute of Technology | Choi H.-J.,Ulsan National Institute of Science and Technology | Baek J.-B.,Ulsan National Institute of Science and Technology
Chemical Reviews | Year: 2015

The rising global energy demand and environmental impact of traditional energy resources pose serious challenges to human health, energy security, and environmental protection. One promising solution is fuel cell technology, which provides clean and sustainable power. Besides, the catalytic performance of many non-precious metal catalysts still needs to be further improved to meet the requirement for practical applications. These special physicochemical properties, in turn, allow for controlled structural modifications of fullerenes, leading to the formation of various advanced fullerene derivatives with appropriate properties for many potential applications.

Pang B.,Beijing Institute of Technology
Fuzzy Sets and Systems | Year: 2014

In this paper, the concepts of stratified L-filter space, complete stratified L-filter space and symmetric stratified L-Kent convergence space are introduced. It is shown that (1) the category of stratified L-filter spaces with Cauchy continuous maps is a strong topological universe; (2) the category of complete stratified L-filter spaces, as a bicoreflective subcategory of the category of stratified L-filter spaces, is isomorphic to the category of symmetric stratified L-Kent convergence spaces; (3) the category of complete stratified L-filter spaces, as an isomorphism-closed full subcategory of the category of stratified L-filter spaces, is strongly Cartesian closed. © 2013 Elsevier B.V. All rights reserved.

Zhu W.,Nanjing University of Science and Technology | Zhu W.,Beijing Institute of Technology | Xiao H.,Nanjing University of Science and Technology
Journal of Physical Chemistry C | Year: 2011

Ab initio molecular dynamics simulations have been performed to study the effects of different temperatures on the structure and stability of energetic solid silver azide. The results indicate that the N-N bond fission takes place at 523 K. The azide sublattice structure broke down prior to the silver sublattice. The initiation decomposition of silver azide is triggered by the N-N bond breaking. This will initiate many decomposition reactions and produce many nitrogen radicals, N2, and silver clusters. Silver azide has metallic properties at 573 K. As the temperature increases, its sensitivity becomes more and more sensitive. The calculated power spectra of the velocity autocorrelation function show that the low-frequency vibrational modes become more prominent than the high-frequency ones with increasing temperature. This would allow low-frequency vibrations and rotations to occur more freely than in the solid. © 2011 American Chemical Society.

Zhang R.,Taiyuan University of Technology | Song L.,Taiyuan University of Technology | Wang Y.,Beijing Institute of Technology
Applied Surface Science | Year: 2012

A density functional theory slab calculations of CH 4 dissociation on Pt(h k l) surfaces have been systematically presented. On the basis of the energetic analysis, the favorable adsorption sites and stable configurations of CH x(x = 0-4) and H species on Pt(1 1 1), Pt(1 1 0) and Pt(1 0 0) surfaces are first obtained, respectively. Afterwards, the most stable configurations of coadsorbed CH x/H(x = 0-3) are located. Further, the kinetic and thermodynamical results of CH 4 dissociation on Pt(h k l) surface suggest that CH is the most abundant CH x species. Our results mean that Pt catalyst can resist the carbon deposition in the CH 4 dissociation, which can give a microscopic reason that why Pt catalyst can lead to lower carbon deposition and show a high activity in the reaction related to CH 4. © 2012 Elsevier B.V.

Luo Q.,South China Normal University | Luo Q.,Beijing Institute of Technology
Physical Chemistry Chemical Physics | Year: 2012

The neutral carbon aluminium cluster Al 3C and its anion Al 3C - have been investigated at the B3LYP/6-311+G(d) and BP86/6-311+G(d) levels of theory. It is suggested that the C 2v neutral cluster Al 3C could be considered as a pseudohalogen superatom with a smaller electron affinity than the iodine atom. The DFT calculation results confirm that, similar to the halogen atoms, the pseudohalogen superatom Al 3C cluster could form the compounds corresponding to the dimer, salts, interhalogen compounds, oxides, acid radicals, and coordination complexes as well as superatom compounds of halogen, showing that Al 3C has similar chemical properties to halogens and maintains its integrity in the related reactions. Based on the maintenance of integrity in the chemical assemblies [(Al 3C)(KCAl 3) n] - (n = 1-5), it could be anticipated that the neutral cluster Al 3C holds great potential as a building block for the development of future nanostructured materials. Further, corresponding experimental verifications are invited. This journal is © 2012 the Owner Societies.

Li C.,Tsinghua University | Liu Z.,Beijing Institute of Technology | Xie H.,Tsinghua University | Wu D.,Tsinghua University
Optics Express | Year: 2013

A 3D SEM Moiré Method (SMM) is proposed in this investigation for the first time for 3D shape measurement with nano-scale sensitivity. The geometric model of the 3D SMM has been theoretically established, combining the stereovision technology in an SEM with the existing principles of in-plane SMM. The Virtual Projection Fringe (VPF) generated under different conditions has been analyzed for 3D reconstructions. Two typical applications have been used to experimentally validate the theoretical model. Experimental results, with the height measurement sensitivity less than 10nm, agree well with the theoretical model we proposed. The uncertainty analysis for the method has also been performed by other auxiliary measurements. © 2013 Optical Society of America.

Zhou G.,University of Chinese Academy of Sciences | Chung W.,University of Hong Kong | Zhang Y.,Beijing Institute of Technology
Expert Systems with Applications | Year: 2014

This study presents an application of data envelopment analysis (DEA) approach with considering undesirable outputs, and not only examines the energy efficiency performance of China's transport sector from 2003 to 2009, but also maximizes energy-saving potential of transport sector of China's 30 administrative regions. Environmental DEA technology is adopted, which treats undesirable measures by distinguishing between weak and strong disposability. The output directional distance function is used, which explicitly expands desirable outputs and simultaneously reduces undesirable outputs. From the empirical results, the lowest number of efficient regions was recorded in 2007 or 2008, which eventually slightly recovered. Similarly, the overall average energy efficiency reached the lowest record in 2007 or 2008. These results are consistent with the policy guidance in the 11th Five-Year Plan (2006-2010) period that a series of new policies in the transport sector are implemented to reverse the trend of energy intensity increase. The Eastern area generally performed better than the Central area and Western area. The Central area was better than the Western area, except in some critical years such as in 2008, the financial crisis significantly affected port turnover. The total potential energy saving from 2003 to 2009 was 35.72 Mtce, the total potential energy saving was approximately 2.75% of the total transport energy use. © 2013 Elsevier Ltd. All rights reserved.

Qu S.-W.,University of Electronic Science and Technology of China | Chen Q.-Y.,Beijing Institute of Technology | Xia M.-Y.,Peking University | Zhang X.Y.,South China University of Technology
IEEE Transactions on Antennas and Propagation | Year: 2014

This paper presents two kinds of novel elements to design single-layer dual-band reflectarray, with identical polarization in two closely separated bands. Several degrees of freedom of the proposed elements are tuned to match the desired phase compensations at two center frequencies simultaneously. It is noted that the dual-band characteristics are realized by a single integrated element rather than conventional dual-band elements with independent tunable components corresponding to two center frequencies. A 10× 10-element offset-fed reflectarray operating at 9 and 13.5 GHz, with a ratio of the center frequencies 1.5, is designed and fabricated to validate the performance of the element, and the measured results show reasonable agreements with simulations. Due to the incompleteness of reflection phase distribution at the two center frequencies of the presented element, a complementary element with four resonances is introduced. Then, a 20× 20-element reflectarray composed of both kinds of elements is also designed, and the measured results demonstrate a good availability of the proposed elements. © 2013 IEEE.

Su Y.,Beijing Institute of Technology
Acta Mechanica | Year: 2013

The dynamics of vortex structure for polarizations in free-standing ferroelectric nanoparticles has been numerically investigated based on a thermodynamics-based continuum phase field approach under open-circuit boundary conditions. Both size effect and surface effect have been considered in this work: different assumptions for the extrapolation length have been made for the electric boundary condition and therefore accounting for the intrinsic size effect; the surface effect is studied by introducing the intrinsic surface stress, which causes volume mechanical balancing stress in the nanoparticles below free surfaces. The computed results are summarized in this article for square-shaped nanodots. It has been noticed that the particle size and intrinsic surface stress together play significant roles in the dynamics of vortex structure for polarizations. They affect both polarization configuration and existence conditions in ferroelectric nanoparticles. © 2013 Springer-Verlag Wien.

Zhang X.,Beijing Institute of Technology | Chen R.,Huazhong University of Science and Technology
International Journal of Production Economics | Year: 2013

Asymmetric effects and regulatory focus are two fundamental rules behind an individual's judgment and motivation. While recent research on loss aversion presents mixed evidence, the literature on satisfaction studies provides little insight into the influence of regulatory systems on satisfaction. Moreover, literature regarding the potential interactions between asymmetric effects and regulatory focus is missing. In this paper, we examined the inconsistent evidence regarding loss aversion and various asymmetric effects in different types of regulatory focus at the attribute level. We conducted an experimental study in a setting of airline overbooking recovery in the Chinese airline industry. Our evidence shows that regulatory focus influences asymmetric effects. Participants with different types of regulatory focus have different priorities in recovery attributes and exhibit quite different patterns of asymmetric effects. We identify four different asymmetric effects and find one failure to present - an effect in our study. In addition, we present a regulatory focus-based dummy regression model, which is a more general method that nests previous research on attribute-satisfaction as a special case. The results, together with the newly proposed passenger classification (time fixed versus time flexible), underpin a more realistic assumption for future theory building and can thus help airline companies design a better recovery strategy for revenue management. © 2012 Elsevier B.V. All rights reserved.

Dong Z.,Key Laboratory of Cluster Science | Jiang C.,Key Laboratory of Cluster Science | Cheng H.,Key Laboratory of Cluster Science | Zhao Y.,Key Laboratory of Cluster Science | And 3 more authors.
Advanced Materials | Year: 2012

Macroscopic graphene fibers with strength comparable to carbon nanotube yarns have been fabricated with a facile dimensionally-confined hydrothermal strategy from low-cost, aqueous graphite oxide suspensions, which is shapable, weavable, and has a density of less than 1/7 conventional carbon fibers. In combination with the easy in situ and post-synthesis functionalization, the highly flexible graphene fibers can be woven into smart textiles. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tan E.-Z.,Beihang University | Tan E.-Z.,Beijing Institute of Technology | Yin P.-G.,Beihang University | You T.-T.,Beihang University | And 2 more authors.
ACS Applied Materials and Interfaces | Year: 2012

We have designed a large-scale three-dimensional (3D) hybrid nanostructure as surface-enhanced Raman scattering (SERS) sensor by decorating silver nanoparticles on TiO 2 nanorods scaffold (Ag/TiO 2). Taking p-mercaptobenzoic acid (PMBA) as the probe molecule, the SERS signals collected by point-to-point and time mapping modes show that the relative standard deviation (RSD) in the intensity of the main Raman vibration modes (1079, 1586 cm -1) is less than 10%, demonstrating good spatial uniformity and time stability. This hybrid substrate also exhibits excellent SERS enhancement effect due to the formation of high-density hot spots among the AgNPs, which was proved by finite-difference time-domain (FDTD) simulations. The application of the new nanostructures as SERS sensors was demonstrated with the detection of malachite green (MG). The quantification of MG can be accomplished with the detection limit of 1 × 10 -12 M based on the Raman intensity. The results show that the Ag/TiO 2 nanostructure can be a promising candidate for SERS sensor. © 2012 American Chemical Society.

Zhao X.,Beijing University of Technology | Xia Z.,Beijing Institute of Technology | Xia D.,Peking University
Electrochimica Acta | Year: 2010

Sn/Cu nanowire composite film was electrodeposited on copper foil substrates and used as an anode material for lithium-ion batteries. The structure of the obtained composite film anode was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical performance was evaluated by cyclic voltammetry, galvanostatic cycling and impedance spectroscopy. It was found that the Sn/Cu nanowire composite film anode showed a better cycle stability than Sn film anode, whereas the Sn/CNT composite film anode indicated poor capacity retention. It could be deduced that copper nanowire reinforced the Sn film anode due to the better wetting property of Sn on the surface of copper and reduced the loss of electric contact among tin particles in the Sn/Cu nanowire composite film anode. © 2010 Elsevier Ltd. All rights reserved.

Meng F.,Qingdao Technological University | Tan C.,Central South University | Zhang Q.,Beijing Institute of Technology
Knowledge-Based Systems | Year: 2013

The Shapley function is a very effective tool to measure the importance of elements, which can reflect the interactive characteristics among them. In this study we use the Shapley function to propose an induced generalized interval-valued intuitionistic fuzzy hybrid Shapley averaging (IG-IVIFHSA) operator. This operator does not only globally consider the importance of elements and their ordered positions, but also overall reflect the interaction among them and among their ordered positions. It is worth pointing out that most of the existing hybrid aggregation operators are special cases of our operator. Meantime, some important cases are considered, and some desirable properties are studied. Furthermore, the models for the optimal fuzzy measures on attribute set and ordered set are established, respectively. Moreover, an approach to multi-attribute decision making under interval-valued intuitionistic fuzzy environment is developed. Finally, two numerical examples are given to verify the developed method and demonstrate its practicality and feasibility. © 2013 Elsevier B.V. All rights reserved.

Meng F.,Qingdao Technological University | Zhang Q.,Beijing Institute of Technology | Cheng H.,Qingdao Technological University
Knowledge-Based Systems | Year: 2013

In this paper, two new aggregation operators called the arithmetical interval-valued intuitionistic fuzzy generalized λ-Shapley Choquet (AIVIFGSCgλ) operator and the geometric interval-valued intuitionistic fuzzy generalized λ-Shapley Choquet (GIVIFGSC gλ) operator are proposed. These operators not only globally consider the importance of combinations or their ordered positions, but also overall reflect the correlations among combinations or their ordered positions. Based on the operational laws on interval-valued intuitionistic fuzzy values, the specific expressions of the AIVIFGSCgλ and GIVIFGSC gλ operators are given, which are also interval-valued intuitionistic fuzzy values. Meantime, some desirable properties are studied. Furthermore, two new approaches to multi-criteria group decision making under interval-valued intuitionistic fuzzy environment are proposed. Finally, a numerical example is provided to illustrate the developed procedures. © 2012 Elsevier B.V. All rights reserved.

Mukhtar A.,Petronas University of Technology | Xia L.,Beijing Institute of Technology | Tang T.B.,Petronas University of Technology
IEEE Transactions on Intelligent Transportation Systems | Year: 2015

Over the past decade, vision-based vehicle detection techniques for road safety improvement have gained an increasing amount of attention. Unfortunately, the techniques suffer from robustness due to huge variability in vehicle shape (particularly for motorcycles), cluttered environment, various illumination conditions, and driving behavior. In this paper, we provide a comprehensive survey in a systematic approach about the state-of-the-art on-road vision-based vehicle detection and tracking systems for collision avoidance systems (CASs). This paper is structured based on a vehicle detection processes starting from sensor selection to vehicle detection and tracking. Techniques in each process/step are reviewed and analyzed individually. Two main contributions in this paper are the following: survey on motorcycle detection techniques and the sensor comparison in terms of cost and range parameters. Finally, the survey provides an optimal choice with a low cost and reliable CAS design in vehicle industries. © 2000-2011 IEEE.

Chen Y.,Beijing Institute of Technology | He L.,Tsinghua University
Archive for Rational Mechanics and Analysis | Year: 2011

In this work, we are concerned with the regularities of the solutions to the Boltzmann equation with physical collision kernels for the full range of intermolecular repulsive potentials, r-(p-1) with p < 2. We give new and constructive upper and lower bounds for the collision operator in terms of standard weighted fractional Sobolev norms. As an application, we get the global entropy dissipation estimate which is a little stronger than that described by Alexandre et al. (Arch Rational Mech Anal 152(4):327-355, 2000). As another application, we prove the smoothing effects for the strong solutions constructed by Desvillettes and Mouhot (Arch Rational Mech Anal 193(2):227-253, 2009) of the spatially homogeneous Boltzmann equation with "true" hard potential and "true" moderately soft potential. © 2010 Springer-Verlag.

Xue K.,Beijing Institute of Technology | Xu Z.,Massachusetts Institute of Technology
Applied Physics Letters | Year: 2010

In this letter we discuss basal-plane hydrogenation of graphene, in the extent of intercoupling between strain and electronic structure. Our first-principles calculations reveal that the atomic structures, binding energies, mechanical and electronic properties of graphene are significantly modified by applying strain. At a biaxial strain of 10%, binding energies of hydrogen on graphene can be improved by 53.89% and 23.56% in the symmetric and antisymmetric phase. In symmetric phase, carbon-hydrogen binding is unstable in compression. In antisymmetric phase, binding of hydrogen atoms reduces the sp2 characteristic of graphene, which is partially recovered at finite tensile strain. © 2010 American Institute of Physics.

Xia M.,King Abdullah University of Science and Technology | Xing C.,Beijing Institute of Technology | Wu Y.-C.,University of Hong Kong | Aissa S.,University of Quebec at Montreal
IEEE Transactions on Wireless Communications | Year: 2011

Relay transmission is promising for future wireless systems due to its significant cooperative diversity gain. The performance of dual-hop semi-blind amplify-and-forward (AF) relaying systems was extensively investigated, for transmissions over Rayleigh fading channels or Nakagami-m fading channels with integer fading parameter. For the general Nakagami-m fading with arbitrary m values, the exact closed-form system performance analysis is more challenging. In this paper, we explicitly derive the moment generation function (MGF), probability density function (PDF) and moments of the end-to-end signal-to-noise ratio (SNR) over arbitrary Nakagami-m fading channels with semi-blind AF relay. With these results, the system performance evaluation in terms of outage probability, average symbol error probability, ergodic capacity and diversity order, is conducted. The analysis developed in this paper applies to any semi-blind AF relaying systems with fixed relay gain, and two major strategies for computing the relay gain are compared in terms of system performance. All analytical results are corroborated by simulation results and they are shown to be efficient tools to evaluate system performance. © 2011 IEEE.

Mahmoud M.S.,King Fahd University of Petroleum and Minerals | Xia Y.,Beijing Institute of Technology
International Journal of Robust and Nonlinear Control | Year: 2011

The objective of this paper is to design a switched robust control for a class of continuous-time systems subject to linear fractional uncertainty and interval time delays. The controller is based on state feedback and the LMI-based stability conditions are derived using an improved Lyapunov-Krasovskii functional. Moreover, the switching rule as well as the state feedback gains are determined from the minimization of a guaranteed cost function. The theoretical results are illustrated with a numerical example. Copyright © 2010 John Wiley & Sons, Ltd.

Jin Y.-F.,Beijing Institute of Technology
Chinese Physics B | Year: 2015

In this paper, we investigate the solution moment stability for a Harrison-type predator-prey model with parametric dichotomous noises. Using the Shapiro-Loginov formula, the equations for the first-order and second-order moments are obtained and the corresponding stable conditions are given. It is found that the solution moment stability depends on the noise intensity and correlation time of noise. The first-order and second-order moments become unstable with the decrease of correlation time. That is, the dichotomous noise can improve the solution moment stability with respect to Gaussian white noise. Finally, some numerical results are presented to verify the theoretical analyses. © 2015 Chinese Physical Society and IOP Publishing Ltd.

Li X.,Lanzhou University | Yang L.,Lanzhou University | Li Y.,Lanzhou University | Ye Z.,Beijing Institute of Technology | He A.,Lanzhou University
Journal of Environmental Engineering (United States) | Year: 2012

Batch adsorption experiments were conducted using environment-friendly prepared chelating ethylenediaminetetraacetic sodium modified polystyrene-based (PS-EDTA) resins as an adsorbent to adsorb Cd2+ from aqueous system in which experimental parameters were studied including solution pH, adsorbent dose, contact time, initial metal concentration and temperature. The Langmuir, Freundlich, and Dubinin-Radushkevich (DR) isotherm models were employed to analyze the experimental data among which Freundlich isotherm model was found to be suitable for Cd2+ adsorption. In addition, Cd2+ adsorption on PS-EDTA resins fitted well to the pseudo-second-order kinetic model. Intraparticle diffusion studies revealed that surface adsorption and intraparticle diffusion were both involved in the adsorption of Cd2+ ions. Thermodynamic parameters such as Gibbs free energy (ΔG), enthalpy change (ΔH), and entropy change (ΔS) were calculated and indicated that adsorption of Cd2+ ions onto PS-EDTA resins was a spontaneous and endothermic process. The effects of various salts and coexisting heavy metal ions on Cd2+ ions adsorption were also investigated. Moreover, the results from the sequential adsorption-desorption cycles showed that PS-EDTA resins held good reusability and this could be a potential application in the fixed-bed continuous-flow column for the removal of heavy metals. © 2012 American Society of Civil Engineers.

Shi L.-J.,Beijing Institute of Technology | Shi L.-J.,CAS Institute of Semiconductors
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2010

Using first-principles band structure methods, we have systematically studied the electronic structures, magnetic stabilities, and half-metal properties of 3d transition-metal (TM) doped Rocksalt MgO compounds TMMg3O4 (TM = V, Cr, Mn, Fe, Co, and Ni). The calculations reveal that only CrMg3O4 has a ferromagnetic stability among the six compounds, which is explained by double-exchange mechanism. The magnetic stability is affected by the doping concentration of TM if the top valance band is composed of partially occupied t2 g states. In addition, CrMg3O4 is a half-metallic ferromagnet. The origins of half-metallic and ferromagnetic properties are explored. The Curie temperature (Tc) of CrMg3O4 is 182 K. And it is hard for CrMg3O4 to deform due to the large bulk modulus and shear modulus, so it is a promising spintronic material. Our calculations provide the first available information on the magnetic properties of 3d TM-doped MgO. © 2010.

Liu Z.,Beijing Institute of Technology | Chen W.,CAS Academy of Mathematics and Systems Science
Designs, Codes, and Cryptography | Year: 2010

The properties satisfied by the value function are given. These properties can be used to study the generalized Hamming weight and the relative generalized Hamming weight of certain linear codes. © 2009 Springer Science+Business Media, LLC.

Ji B.-H.,Beijing Institute of Technology
Yiyong Shengwu Lixue/Journal of Medical Biomechanics | Year: 2011

As the frontier of biomechanics research, cellular and molecular biomechanics is an interdisciplinary research field at the cutting edge of applied mechanics and life science and biology, which brings us many challenging problems to the current theories and techniques in biomechanics due to its importance and complexity. This paper will give a brief review on several of these challenging problems and make some comments on the papers included in this special issue, such as the mechanical properties and modeling methods of cell, the modeling of mechanochemical couplig and multiscale modeling methods in cell mechanics, so as to stimulate the common interest within not only the biomechanics but also the applied mechanics community.

Zhu C.,National University of Defense Technology | Zhou H.,Beijing Institute of Technology | Wang R.,National University of Defense Technology | Guo J.,National University of Defense Technology
IEEE Transactions on Geoscience and Remote Sensing | Year: 2010

Ship detection from remote sensing imagery is very important, with a wide array of applications in areas such as fishery management, vessel traffic services, and naval warfare. This paper focuses on the issue of ship detection from spaceborne optical images (SDSOI). Although advantages of synthetic-aperture radar (SAR) result in that most of current ship detection approaches are based on SAR images, disadvantages of SAR still exist, such as the limited number of SAR sensors, the relatively long revisit cycle, and the relatively lower resolution. With the increasing number of and the resulting improvement in continuous coverage of the optical sensors, SDSOI can partly overcome the shortcomings of SAR-based approaches and should be investigated to help satisfy the requirements of real-time ship monitoring. In SDSOI, several factors such as clouds, ocean waves, and small islands affect the performance of ship detection. This paper proposes a novel hierarchical complete and operational SDSOI approach based on shape and texture features, which is considered a sequential coarse-to-fine elimination process of false alarms. First, simple shape analysis is adopted to eliminate evident false candidates generated by image segmentation with global and local information and to extract ship candidates with missing alarms as low as possible. Second, a novel semisupervised hierarchical classification approach based on various features is presented to distinguish between ships and nonships to remove most false alarms. Besides a complete and operational SDSOI approach, the other contributions of our approach include the following three aspects: 1) it classifies ship candidates by using their class probability distributions rather than the direct extracted features; 2) the relevant classes are automatically built by the samples appearances and their feature attribute in a semisupervised mode; and 3) besides commonly used shape and texture features, a new texture operator, i.e., local multiple patterns, is introduced to enhance the representation ability of the feature set in feature extraction. Experimental results of SDSOI on a large image set captured by optical sensors from multiple satellites show that our approach is effective in distinguishing between ships and nonships, and obtains a satisfactory ship detection performance. © 2006 IEEE.

Mahmoud M.S.,King Fahd University of Petroleum and Minerals | Xia Y.,Beijing Institute of Technology
Neurocomputing | Year: 2010

In this paper, we investigate the problem of global exponential stability analysis for a class of bidirectional associative memory (BAM) neural networks with interval time-delays. Improved exponential stability condition is derived by employing new Lyapunov-Krasovskii functional and the integral inequality. Several special cases of interest are derived. The developed stability criteria are delay dependent and characterized by linear matrix inequalities (LMIs). The developed results are shown to be less conservative than previous published ones in the literature. Finally, simulations of two numerical examples are provided to demonstrate the efficacy of our approach. © 2010 Elsevier B.V.

In this paper, we study the optimal solution of minimizing a linear objective function subject to the fuzzy relation inequalities with addition-min composition. We first discuss some properties about the minimal solutions of fuzzy relation inequalities with addition-min composition, and define the pseudo-minimal indexes of this system. Next we give an algorithm to get the set of the pseudo-minimal indexes, which is called PMI algorithm. Finally, we obtain an algorithm for this optimization system by utilizing these concepts and results. The example is provided to show that our algorithm is simple and convenient. © 2014 Elsevier B.V.

Wang J.-C.,Beijing Institute of Technology | Lau A.H.-L.,University of Hong Kong | Lau H.-S.,University of Hong Kong
International Journal of Production Economics | Year: 2012

A manufacturer supplies a newsvendor product to a dominant retailer, who does not know the manufacturers unit production cost k. The expected retail demand is a function of the unit retail price p. For this increasingly prevalent but rarely analyzed scenario, we compare the performance of several promising contract formats, including two new contract formats designed explicitly for a dominant retailer to implement, namely: (i) a retailer-implemented two-part tariffs where the retailer charges an upfront lump sum fee besides a fixed percentage markup over any given unit wholesale price, and (ii) a retailer-implemented volume discount scheme. We show that these two new formats perform substantially better than the currently-used practical formats. Thus, they form a basis for a dominant retailer to design a practical and effective purchase contract that approaches the power of the theoretically-optimal but impractical menu of contracts. © 2012 Elsevier B.V. All rights reserved.

Wang H.,Beijing Institute of Technology
Journal of Intelligent and Fuzzy Systems | Year: 2016

This paper provides some existence results about first-order fuzzy differential equation with two-point boundary value condition. Firstly, we study a class of linear fuzzy differential equation and some necessary conditions for the existence of solutions are provided. Based on these conditions and the upper and lower solutions method, we obtain some existence results about first-order nonlinear differential equations with the same boundary value condition. © 2016 - IOS Press and the authors. All rights reserved.

Dong C.Y.,Beijing Institute of Technology
International Journal of Heat and Mass Transfer | Year: 2015

This paper presents a new boundary integral formulation of the heat energy calculation of steady state heat conduction in heterogeneous media using two methods, i.e. one which is based on some formulations from Hatta and Taya (1986) who investigated equivalent inclusion method, and another one which is closely similar to the method from Christensen (1979) who studied elastic inclusion problem. For the generalized self-consistent scheme (GSCS) model, the corresponding heat energy formulation is also given. Based on the obtained interface heat energy formulation, the boundary element method together with the Maxwell homogeneous scheme are used to calculate the effective heat conduction of 2D and 3D heterogeneous steady state heat conduction media. © 2015 Elsevier Ltd. All rights reserved.

Sheng X.,Inner Mongolia Agricultural University | Zhang J.,Beijing Institute of Technology
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2011

Sustaining an air layer on superhydrophobic surface is known necessary for the applications of the "air layer effect" underwater on basis of previous literatures. However, the air layer becomes unstable when put underwater and even disappears when the hydraulic pressure increases. Thus much attention has been focused on the sustainability of an air layer on a superhydrophobic surface. This article studies the sustainability of the air layer on the surface of a lotus leaf by applying external pressure on the surface, which is a direct method to measure the sustainability of the air layer. It is displayed that the hydraulic pressure is a key factor to sustain an air layer on a superhydrophobic surface. Maintaining a certain amount of hydraulic pressure is necessary to sustain an air layer on a superhydrophobic surface, which may be important for the low drag or friction reduction of a superhydrophobic surface underwater. Therefore, we believe that the micro-designs of superhydrophobic surface which is capable of the "air layer effect" underwater should be connected with hydraulic pressure applied on it. © 2011 Elsevier B.V.

Liu W.,Beijing Institute of Technology
Journal of Renewable and Sustainable Energy | Year: 2016

Study on how renewable energy use and economic growth interact with each other has been an active area of research. This study examines the impacts of renewable energy production (and consumption) on local economic development and income, for a panel data of the 31 provinces of China over the period 2000-2010 within a multivariable framework. Using regression with panels corrected standard errors, this study investigates the effects of renewable energy use on provincial real gross domestic production and local rural income. It is found that deployment of renewable energy use in rural areas has shown significant positive effects on income increase of rural households. But in general, most renewable energy use has negative impacts on economic growth except hydro power generation, improving the economic efficiency of renewable energy production and adjusting renewable energy related subsidy policies are of prime importance. © 2016 AIP Publishing LLC.

Xing C.,Beijing Institute of Technology | Ma S.,University of Macau | Zhou Y.,CAS Institute of Computing Technology
IEEE Transactions on Signal Processing | Year: 2015

For MIMO systems, due to the deployment of multiple antennas at both the transmitter and the receiver, the design variables, e.g., precoders, equalizers, and training sequences, are usually matrices. It is well known that matrix operations are usually more complicated compared with their vector counterparts. In order to overcome the high complexity resulting from matrix variables, in this paper, we investigate a class of elegant multi-objective optimization problems, namely matrix-monotonic optimization problems (MMOPs). In our work, various representative MIMO optimization problems are unified into a framework of matrix-monotonic optimization, which includes linear transceiver design, nonlinear transceiver design, training sequence design, radar waveform optimization, the corresponding robust design and so on as its special cases. Then, exploiting the framework of matrix-monotonic optimization the optimal structures of the considered matrix variables can be derived first. Based on the optimal structure, the matrix-variate optimization problems can be greatly simplified into the ones with only vector variables. In particular, the dimension of the new vector variable is equal to the minimum number of columns and rows of the original matrix variable. Finally, we also extend our work to some more general cases with multiple matrix variables. © 2014 IEEE.

Li Z.,South China University of Technology | Xia Y.,Beijing Institute of Technology | Sun F.,Tsinghua University
IEEE Transactions on Fuzzy Systems | Year: 2014

In this paper, an adaptive fuzzy control is investigated for multilateral teleoperation of two cooperating robotic manipulators that manipulate an object with constrained trajectory/force in the presence of dynamics uncertainties and random network-induced delays. First, the interconnected dynamics that consist of two master robots and cooperating slave robots are formulated. To consider multiple stochastic delays in communication channels, Markov processes are used to model these random network-induced delays. The interconnected dynamics of the teleoperation are divided into a local master/slave position/force subsystem and a stochastic-delayed motion synchronization subsystem. Then, an adaptive fuzzy control strategy, which is based on linear matrix inequalities (LMIs) that combine adaptive update techniques, is proposed to suppress the dynamics uncertainties, the external disturbances, and the multiple stochastic delays in communication channels. The control approach ensures that the defined synchronization errors converge to zero. The stochastic stability in mean square of the closed-loop system is proved using LMIs based on Lyapunov-Krasovskii functional synthesis. The proposed controls are validated using extensive simulation studies. © 1993-2012 IEEE.

Shen Y.,Beijing Institute of Technology | Shen Y.,Tianshui Normal University
Information Sciences | Year: 2014

In this paper, some useful properties associated with the probabilistic Hausdorff distance are further derived. Especially, we provide a direct proof for an existing important result. Afterwards, the t-norm-based probabilistic decomposable measure is presented, in which the value of measure is characterized by a probability distribution function. Meantime, several examples are constructed to illustrate different notions, and then further properties are examined. Moreover, for a given Menger PM-space, a probabilistic decomposable measure can be induced by means of the resulting probabilistic Hausdorff distance. We prove that this type of measure is (σ)- probabilistic subdecomposable measure for the strongest t-norm. Furthermore, we also prove that the class of all measurable sets forms an algebra. Finally, an outer probabilistic measure is induced by a class of probabilistic decomposable measures and the t-norm. Based on this kind of measure, a Menger probabilistic pseudometric space can be obtained for a non-strict continuous Archimedean t-norm. © 2014 Published by Elsevier Inc.

Alpha-synuclein is one of the important components of Lewy body which involved in neuropathology of Parkinson's disease (PD). The relationship between α-synuclein and cell death is still unclear. In the study, PC12 cell, stably over expressing α-synuclein model was used, and we investigated the level of intracellular oxidative stress, dopamine and endogenous neurotoxin. The results showed that the level of oxidative stress and intracytoplasmic dopamine (DA) was increased in cells over expressing α-synuclein compared with normal PC12 cells. Simultaneously, additional generation of endogenous neurotoxins 1-methyl-4-phenyl-1,2,3,4-tetrahydroisoquinoline (salsolinol) and 1(R),2(N)-dimethyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinolin (NM-salsolinol) was detected and this phenomenon was exacerbated after exposed to H2O2 for 24 h, but mitigated when treated with dopamine synthesis inhibitors. The presence of endogenous neurotoxins exacerbated α-synuclein induced mitochondrial damage. These results suggest that the endogenous neurotoxins may become a bridge between α-synuclein and cell death. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Meng F.,Central South University | Meng F.,Qingdao Technological University | Chen X.,Central South University | Zhang Q.,Beijing Institute of Technology
Information Sciences | Year: 2014

In this paper, a new class of fuzzy sets called linguistic hesitant fuzzy sets (LHFSs) is defined, which can address the qualitative preferences of experts as well as reflect their hesitancy, uncertainty and inconsistency. Based on the defined operational laws of LHFSs and the order relationship, two linguistic hesitant fuzzy hybrid aggregation operators are defined: the generalized linguistic hesitant fuzzy hybrid weighted averaging (GLHFHWA) operator and the generalized linguistic hesitant fuzzy hybrid geometric mean (GLHFHGM) operator. Furthermore, to address the situation in which the elements in a set are interdependent, the generalized linguistic hesitant fuzzy hybrid Shapley weighted averaging (GLHFHSWA) operator and the generalized linguistic hesitant fuzzy hybrid Shapley geometric mean (GLHFHSGM) operator are presented, which are extensions of the GLHFHWA and GLHFHGM operators. Models designed to obtain the optimal fuzzy measures and additive measures on an attribute set and on an ordered set are, respectively, constructed. Then, an approach to linguistic hesitant fuzzy multi-attribute decision analysis is developed. Finally, two numerical examples are provided to demonstrate the practicality and efficiency of the proposed procedure. © 2014 Elsevier Inc. All rights reserved.

Yue F.,Beijing Institute of Technology | Zuo W.,Harbin Institute of Technology
Information Sciences | Year: 2014

A typical palmprint identification system identifies a query palmprint by matching it with the templates in the database and comparing the similarity score with a pre-defined threshold. However, continual database expansion would make conventional brute force search method inefficient for large-scale palmprint identification. In this paper, we propose a consistent orientation pattern (COP) hashing method to enforce fast search. Using the orientation and response features extracted by steerable filter, we first give an analysis on the consistency of orientation features, and then introduce a method to construct COP using the consistent features. Because the COP is very stable across the samples of the same subject, the COP hashing method can find the target template quickly and thus can lead to early termination of the searching process. Experiments have been carried out on several real and synthetic databases, and the results show that the COP hashing method can accelerate the identification process by more than an order of magnitude, and can achieve comparable identification accuracy while compared with the state-of-the-art approaches. © 2013 Elsevier Inc. All rights reserved.

Xu W.,Pohang University of Science and Technology | Wang F.,Beijing Institute of Technology | Rhee S.-W.,Pohang University of Science and Technology
Journal of Materials Chemistry | Year: 2012

In this study, we report the observation of quasi-ordering in spontaneously associated highly polar surface functional groups (CN) in the high-k polymer dielectric, cyanoethyl pullulan, and its impact on the organic field-effect transistor (OFET) characteristics. We find that the association originates from CN⋯H-C-CN hydrogen bonding as confirmed by XPS, NEXAFS experiments and molecular simulations. The quasi-ordered surface dipoles preferentially induce vertically well-stacked local semiconductor molecular clusters during the initial deposition process, which then promote large-area layer-by-layer growth. By maintaining sufficient quasi-ordering, high transistor performance (μ ≈ 6.5 cm 2 V -1 s -1, SS ≈ 0.062 V dec -1) is obtained under low driving voltages (-3 to -5 V), while breakup of the association at higher baking temperatures leads to a dramatic drop in μ by a factor of ∼10. Our results demonstrate that local quasi-ordering of polymeric surface dipoles, which has a significant effect on the initial semiconductor molecular growth, represents a novel and sensitive factor affecting OFET characteristics. © The Royal Society of Chemistry 2012.

Tam H.-y.,City University of Hong Kong | Cheng H.,Beijing Institute of Technology
Journal of Materials Processing Technology | Year: 2010

Uniformity of removal affects the finishing, and in some cases, the form accuracy of the polished surface. Tool paths are required for the automation of surface polishing. How the tool path may affect the removal of material in polishing is investigated in this paper. An analysis of how removal at a location due to polishing along adjacent path lines is presented. Four tool paths reportedly used in polishing are covered: scanning, bi-scanning, Hilbert and Peano paths. Removal in the inner surface as well as near the edges of surfaces is examined through simulations and analysis. The results show that, for the same path pitch, the peak-to-valley height (hpv) in the inner part of the removal map is the same for scanning, bi-scanning and Peano, while the texture of the removal maps can be quite different. The hpv values of Hilbert are more than double those of Peano, although both are fractal paths. Removal near the edges is particularly severe for scanning-type tool paths. The ratio of the edge peak height to the inner peak height is about 1.6 on average for scanning. The uniformity of removal further deteriorates as the ellipticity of the tool contact increases. When the contact direction is closely aligned with the path line direction, that ratio goes up to about 2.9 for contact ellipticity of 2. Polishing experiments have also been conducted. Both experiments and simulations point to the presence of edge effects in scanning paths and its absence in Peano paths. It is further proposed that, for more uniform removal of material: (1) changes in the tool path direction should be well distributed and (2) the direction of the path lines should be well balanced over the entire surface. Crown Copyright © 2010.

Lu Y.J.,Beijing Institute of Technology | Lu Y.J.,Zhejiang University
Philosophical Magazine | Year: 2015

The difficulty in synthesizing guest-free semiconductor clathrates complicates the process of determining how these cage-like structures form. This work studies the microscopic mechanism of the nucleation of guest-free Si136 clathrate using molecular dynamics simulations with the Stillinger-Weber potential. The homogeneous nucleation of Si136, which is realized in a narrow negative pressure range before liquid cavitation, exhibits the characteristic feature of the two-dimensional (2D) mode. The critical nucleus is composed of one to two five-membered rings, and the nucleation barrier is close to 1 kBT. According to a thermodynamic model based on atomistic nucleation theory, the effective binding energy associated with the formation of 2D critical nuclei is significantly low, which is responsible for the low nucleation barrier of Si136 clathrate. In the post-nucleation period, the critical nucleus preferentially grows into a dodecahedron, and the latter continuously grows with sharing face along 〈1 1 0〉. © 2015 Taylor & Francis.

Zhang W.,Hefei University of Technology | Hu X.,Hefei University of Technology | Li X.,Beijing Institute of Technology | Yu N.,Hefei University of Technology
IEEE Transactions on Image Processing | Year: 2013

State-of-the-art schemes for reversible data hiding (RDH) usually consist of two steps: first construct a host sequence with a sharp histogram via prediction errors, and then embed messages by modifying the histogram with methods, such as difference expansion and histogram shift. In this paper, we focus on the second stage, and propose a histogram modification method for RDH, which embeds the message by recursively utilizing the decompression and compression processes of an entropy coder. We prove that, for independent identically distributed (i.i.d.) gray-scale host signals, the proposed method asymptotically approaches the rate-distortion bound of RDH as long as perfect compression can be realized, i.e., the entropy coder can approach entropy. Therefore, this method establishes the equivalency between reversible data hiding and lossless data compression. Experiments show that this coding method can be used to improve the performance of previous RDH schemes and the improvements are more significant for larger images. © 1992-2012 IEEE.

Niemi A.J.,Uppsala University | Niemi A.J.,University of Tours | Niemi A.J.,Beijing Institute of Technology | Sutcliffe P.,Durham University
Nonlinearity | Year: 2014

Vortex rings are ubiquitous in fluids, with smoke rings being a familiar example. The interaction of multiple vortex rings produces complex dynamical behaviour, such as the leapfrogging motion first analysed by Helmholtz more than a century and a half ago. Here we report on numerical investigations of vortex ring dynamics in a different setting from fluids, namely, as solutions of the Landau-Lifshitz equation that models the evolution of the local magnetization in a ferromagnetic medium. We present the results of the first study on the dynamics of interacting magnetic vortex rings and provide a novel link between fluids and magnetism, by showing that a range of phenomena familiar in fluids are reproduced in ferromagnets. This includes the leapfrogging motion of a pair of vortex rings and evidence for the chaotic dynamics of a trio of rings. © 2014 IOP Publishing Ltd & London Mathematical Society.

Gong Z.,University of Hong Kong | Liu G.-B.,University of Hong Kong | Liu G.-B.,Beijing Institute of Technology | Yu H.,University of Hong Kong | And 4 more authors.
Nature Communications | Year: 2013

In monolayer group-VI transition metal dichalcogenides, charge carriers have spin and valley degrees of freedom, both associated with magnetic moments. On the other hand, the layer degree of freedom in multilayers is associated with electrical polarization. Here we show that transition metal dichalcogenide bilayers offer an unprecedented platform to realize a strong coupling between the spin, valley and layer pseudospin of holes. Such coupling gives rise to the spin Hall effect and spin-dependent selection rule for optical transitions in inversion symmetric bilayer and leads to a variety of magnetoelectric effects permitting quantum manipulation of these electronic degrees of freedom. Oscillating electric and magnetic fields can both drive the hole spin resonance where the two fields have valley-dependent interference, making an interplay between the spin and valley as information carriers possible for potential valley-spintronic applications. We show how to realize quantum gates on the spin qubit controlled by the valley bit. © 2013 Macmillan Publishers Limited. All rights reserved.

Mu C.,Beijing Institute of Technology | Li Y.,Singapore Management University
Expert Systems with Applications | Year: 2010

An intrusion response decision-making model based on hierarchical task network (HTN) planning is presented in the paper. Compared with other response decision-making models, the response decision-making model consists of not only the response measure decision-making process but also response time decision-making process that is firstly proposed in the paper. The response time decision-making model is able to determine response time for different response HTN subtasks. Owing to the introduction of the response time decision-making, the intrusion response system can apply different response strategies to achieve different response goals set by administrators. The proposed response measure decision-making model can optimize a response plan by balancing the response effectiveness and the response negative impact in both a single response measure and a set of response measures. The response decision-making model is self-adaptive and has the ability of tolerating to false positive IDS alerts. The proposed model has been used in the intrusion detection alert management and intrusion response system (IDAM&IRS) developed by us. The functions and architecture of IDAM&IRS are introduced in this paper. In addition, the intrusion response experiments of IDAM&IRS are presented, and the features of the response decision-making model are summarized. © 2009 Elsevier Ltd. All rights reserved.

Wang W.,China Aerospace Science and Technology Corporation | Liu X.,Beijing Institute of Technology
Mechatronics | Year: 2010

A new fuzzy sliding mode hysteresis compensating control strategy for a kind of typical piezoelectric system (PES) is proposed in this paper. Firstly, a typical nonlinear dynamic model of the PES is introduced. In order to compensate the hysteresis of the PES, an ideal linear hysteretic model is introduced by analyzing the characteristic of dynamic hysteretic model. Then, the ideal hysteretic model is transformed into an expected linear model by multiplying a slope conversion factor which can be obtained by experiment. Further, the sliding mode control principle is constructed to calculate the hysteretic compensating control law, which can guarantee the practical hysteretic characteristic to reach the expected linear output feature. Consider the unmeasured hysteresis output of the PES, we further design a sliding mode estimator to estimate the hysteretic part's output. Finally, we derive the adaptive law of the fuzzy sliding mode controller, and demonstrate its stability through Lyapunov stability theory. The simulation results show the validity of the sliding mode compensator for this kind of nonlinear dynamic model of PES. © 2010 Elsevier B.V. All rights reserved.

Zhang Q.,Beijing Institute of Technology
Zeitschrift fur Angewandte Mathematik und Physik | Year: 2014

This paper is devoted to the stability analysis of an interaction system comprised of a wave equation and a heat equation with memory, where the hereditary heat conduction is due to Gurtin–Pipkin law or Coleman–Gurtin law. First, we show the strong asymptotic stability of solutions to this system. Then, the exponential stability of the interaction system is obtained when the hereditary heat conduction is of Gurtin–Pipkin type. Further, we show the lack of uniform decay of the interaction system when the heat conduction law is of Coleman–Gurtin type. © 2013, Springer Basel.

Wei H.,Beijing Institute of Technology
Classical and Quantum Gravity | Year: 2012

In the present work, we reconsider the idea of holographic dark energy. One of its key points is the formation of the black hole. We then propose the so-called pilgrim dark energy based on the speculation that the repulsive force contributed by the phantom-like dark energy (w < -1) is strong enough to prevent the formation of the black hole. We also consider the cosmological constraints on pilgrim dark energy by using the latest observational data. Of course, one can instead regard pilgrim dark energy as a purely phenomenological model without any physical motivation. We also briefly discuss this issue. © 2012 IOP Publishing Ltd.

Lu Y.J.,Beijing Institute of Technology
Philosophical Magazine Letters | Year: 2012

The crystal growth velocity of Ni 95Si 5 and Ni 90Si 10 alloys as a function of undercooling is investigated using molecular dynamics simulations. The modified imbedded atom method potential yields the equilibrium liquidus temperatures T L≈1505 and 1387K for Ni 95Si 5 and Ni 90Si 10 alloys, respectively. From the liquidus temperatures down to the deeply undercooled region, the crystal growth velocities of both the alloys rise to the maximum with increasing undercooling and then drop slowly, whereas the athermal growth process presented in elemental Ni is not observed in Ni-Si alloys. Instead, the undercooling dependence of the growth velocity can be well-described by the diffusion-limited model, furthermore, the activation energy associated with the diffusion from melt to interface increases as the concentration increases from 5 to 10at.% Si, resulting in the remarkable decrease of growth velocity. © 2012 Copyright Taylor and Francis Group, LLC.

Wei H.,Beijing Institute of Technology
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2012

Recently, Geng et al. proposed to allow a non-minimal coupling between quintessence and gravity in the framework of teleparallel gravity, motivated by the similar one in the framework of General Relativity (GR). They found that this non-minimally coupled quintessence in the framework of teleparallel gravity has a richer structure, and named it "teleparallel dark energy". In the present work, we note that there might be a deep and unknown connection between teleparallel dark energy and Elko spinor dark energy. Motivated by this observation and the previous results of Elko spinor dark energy, we try to study the dynamics of teleparallel dark energy. We find that there exist only some dark-energy-dominated de Sitter attractors. Unfortunately, no scaling attractor has been found, even when we allow the possible interaction between teleparallel dark energy and matter. However, we note that w at the critical points is in agreement with observations (in particular, the fact that w=-1 independently of ξ is a great advantage). © 2012 Elsevier B.V.

Wen G.,Peking University | Duan Z.,Peking University | Li Z.,Beijing Institute of Technology | Chen G.,City University of Hong Kong
International Journal of Robust and Nonlinear Control | Year: 2012

In this paper, the problem of flocking control in networks of multiple dynamical agents with intermittent nonlinear velocity measurements is studied. A new flocking algorithm is proposed to guarantee the states of the velocity variables of all the dynamical agents to converge to consensus while ensuring collision avoidance of the whole group, where each agent is assumed to obtain some nonlinear measurements of the relative velocity between itself and its neighbors only on a sequence of non-overlapping time intervals. The results are then extended to the scenario of flocking with a nonlinearly dynamical virtual leader, where only a small fraction of agents are informed and each informed agent can obtain intermittent nonlinear measurements of the relative velocity between itself and the virtual leader. Theoretical analysis shows that the achieved flocking in systems with or without a virtual leader is robust against the time spans of the agent speed-sensors. Finally, some numerical simulations are provided to illustrate the effectiveness of the new design. Copyright © 2011 John Wiley & Sons, Ltd. Copyright © 2011 John Wiley & Sons, Ltd.

Jiang T.,Huazhong University of Science and Technology | Li X.,Beijing Institute of Technology
IEEE Transactions on Vehicular Technology | Year: 2010

In this paper, we apply fountain codes to control the peak-to-average power ratio (PAPR) of orthogonal frequency-division multiplexing (OFDM) signals. The main key idea of the proposed scheme is based on the fact that the best fountain-coded OFDM packets can be generated with a low PAPR. Both theoretical analysis and simulation results prove that the proposed scheme can effectively obtain the desirable PAPR and good throughput with rateless codes. Moreover, the flexibility of controlling PAPR makes the proposed scheme more suitable for implementing random frame sizes and providing effective error detection. © 2006 IEEE.

Yu H.,University of Hong Kong | Wu Y.,University of Hong Kong | Liu G.-B.,University of Hong Kong | Liu G.-B.,Beijing Institute of Technology | And 2 more authors.
Physical Review Letters | Year: 2014

The controlled flow of spin and valley pseudospin is key to future electronics exploiting these internal degrees of freedom of carriers. Here, we discover a universal possibility for generating spin and valley currents by electric bias or temperature gradient only, which arises from the anisotropy of Fermi pockets in crystalline solids. We find spin and valley currents to the second order in the electric field as well as their thermoelectric counterparts, i.e., the nonlinear spin and valley Seebeck effects. These second-order nonlinear responses allow two unprecedented possibilities to generate pure spin and valley flows without net charge current: (i) by an ac bias or (ii) by an arbitrary inhomogeneous temperature distribution. As examples, we predict appreciable nonlinear spin and valley currents in two-dimensional (2D) crystals including graphene, monolayer and trilayer transition-metal dichalcogenides, and monolayer gallium selenide. Our finding points to a new route towards electrical and thermal generations of spin and valley currents for spintronic and valleytronic applications based on 2D quantum materials. © 2014 American Physical Society.

Zhang X.-J.,Beihang University | Wang G.-S.,Beihang University | Wei Y.-Z.,Beihang University | Guo L.,Beihang University | Cao M.-S.,Beijing Institute of Technology
Journal of Materials Chemistry A | Year: 2013

Novel reduced graphene oxide (RGO)/CuS nanocomposites, featuring CuS microspheres embedded in reduced graphene oxide (RGO) layers, are successfully fabricated by using an in situ growth approach in the presence of cexadecyl trimethyl ammonium bromide (CTAB) under mild wet-chemical conditions (140 °C). Characterization of the nanocomposites indicates that the CuS complex microspheres with relatively uniform size are embedded in the RGO layers to form unique core-shell nanostructures. A simple hot-press process is employed to synthesize the RGO/CuS/PVDF composites. With a filler loading of 15 wt%, the dielectric constant of the composites can reach 36 at 2 GHz, which is 10 times higher than that of pure PVDF. The composites with a filler loading of 5 wt% exhibit high values of reflection loss and the maximum loss is 32.7 dB at 10.7 GHz when the thickness is just 2.5 mm, and it can be adjusted by the thickness. The enhanced mechanism is also explained based on the Debye dipolar relaxation of the composites. The composite with a high dielectric constant is a promising material in high capacitance, while the composite with enhanced absorption can decrease the environmental pollution caused by microwave irradiation. © 2013 The Royal Society of Chemistry.

This paper provides a description of how market competitiveness evaluations concerning mechanical equipment can be made in the context of multi-criteria decision environments. It is assumed that, when we are evaluating the market competitiveness, there are limited number of candidates with some required qualifications, and the alternatives will be pairwise compared on a ratio scale. The qualifications are depicted as criteria in hierarchical structure. A hierarchical decision model called PCbHDM was used in this study based on an analysis of its desirable traits. Illustration and comparison shows that the PCbHDM provides a convenient and effective tool for evaluating the market competitiveness of mechanical equipment. The researchers and practitioners might use findings of this paper in application of PCbHDM. © 2016 Fujun Hou. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Wang G.-S.,Beihang University | Zhang X.-J.,Beihang University | Wei Y.-Z.,Beihang University | He S.,Beihang University | And 2 more authors.
Journal of Materials Chemistry A | Year: 2013

Graphite was modified by a simple method, and the structure of the graphite intercalated composite (GIC) was investigated by SEM, XRD and XPS. The increased absorption properties at frequencies from 2 to 18 GHz were studied in detail. The results show that the PVDF-GIC composites exhibit strong microwave absorbing intensities (-64.4 dB at 10.59 GHz) with a low filler loading (9.0 wt%), while the composites are still as flexible as pure PVDF. This journal is © The Royal Society of Chemistry 2013.

Li J.,Beijing Institute of Technology
Gaodianya Jishu/High Voltage Engineering | Year: 2014

In order to find a universal parameter that can relate the researches of electromagnetic (EM) railguns with different calibers, taking the tradition interior ballistic theory into consideration, we investigated the interior ballistic of railgun from aspects of both microcosmic and macrocosmic, by demonstrating the differential equations of railgun launch process and analytically analyzing the EM forces in railgun. Analysis shows that the magnetic flux density, stress, rail stress, and temperature fields depend on not current or caliber separately, but the ration of current to caliber, namely, the linear current density. Meanwhile, the square of linear current density is linearly proportional to rail stress and projectile pressure, and it represents the electromagnetic pressure in railgun. It is proposed that linear current density is a key parameter of railgun, which can be considered as the bore pressure of railgun, referencing the similar idea in interior ballistic theory. Comparison between launch simulation of railguns with different calibers indicates that, using linear current density as the character parameter, the patterns of parameters in railgun with different calibers can be effectively connected.

Wen W.,Zhejiang University | Wu J.-M.,Zhejiang University | Cao M.-H.,Beijing Institute of Technology
Nano Energy | Year: 2013

Rapid and economical fabrications of macroporous materials are of general interest in various fields of energy storage, energy conversion, catalysis and gas sensors. In this paper, macroporous NiO/Ni powders were achieved in a flash by the direct decomposition of a metal complex, which is template-free, surfactant-free and highly effective. The metal complex was achieved by simply mixing nickel acetate, nickel nitrate, hydrazine hydrate and glycine in water. The pore size, porosity and even morphology of the porous network (three- or two-dimensional architectures) can be conveniently tuned by adjusting the composition of the complex. It is found that, the amounts of hydrazine hydrate and glycine in the reactants affected the morphology of the porous network; whilst that of nickel acetate determined the macropores. The electrochemical performance of the achieved macroporous NiO/Ni as anodes in Li-ion batteries was comparatively investigated. The 3D macroporous NiO/Ni powders exhibited better electrochemical performances than that of 2D macroporous NiO/Ni and 3D compact NiO/Ni because of its better electrical conductivity and unique porous architecture. The presence of Ni and the continuous network of 3D structures improved the electrical conductivity of electrode materials. In addition, the macroporous architectures not only favored the ingress of electrolytes but also compensated the large volume change of the active materials during the cycling. © 2013 Elsevier Ltd.

Miao L.-X.,Beijing Institute of Technology | Miao L.-X.,Beijing Research Institute of Chemical Defense | Wang W.-K.,Beijing Research Institute of Chemical Defense | Wang A.-B.,Beijing Research Institute of Chemical Defense | And 2 more authors.
Journal of Materials Chemistry A | Year: 2013

Lithium-sulfur (Li-S) batteries have received significant attention in recent years because of their high theoretical specific capacity (1675 mA h g-1) and energy density (2600 W h kg-1). Many papers focus on cells that exhibit very high capacity per gram of sulfur, which contain sulfur contents well below 50% which greatly reduces their overall energy density per gram of cathode. Moreover, they do not address the issues of practical sulfur loading and large-scale technology for commercial applications. In general, the lower the sulfur content, the higher the sulfur capacity. In this paper, a high sulfur content (80% S) carbon-sulfur (P-AB@S) material with core-shell structure has been successfully synthesized by grafting of polymer electrolyte (polyethylene glycol, PEG) chains and depositing sulfur onto the surface of electronically conductive acetylene black (AB). The PEG chains are inserted into the sulfur layer to reinforce the material's structural stability. More importantly, with a cathode containing 66% sulfur and approximately 3 mg cm-2 sulfur loading on the electrode, P-AB@S as a cathode material for lithium sulfur batteries shows a specific capacity of 577 mA h g -1 after 500 cycles at 100 mA g-1 between 1.5 V and 2.8 V. Moreover, the preparation method of the P-AB@S composite is a facile, cost-effective and template-free method and easy to implement large-scale technology for commercial applications. © 2013 The Royal Society of Chemistry.

Wen W.,Zhejiang University | Wu J.-M.,Zhejiang University | Cao M.-H.,Beijing Institute of Technology
Journal of Materials Chemistry A | Year: 2013

A novel approach was developed to achieve three-dimensional macroporous NiO/Ni powders. The unique architecture, together with the highly distributed Ni additive ensures the remarkably enhanced discharge capacity, initial coulombic efficiency, cycling stability, and rate capability when utilized as anodes in lithium-ion batteries. © 2013 The Royal Society of Chemistry.

Zhang X.,Argonne National Laboratory | Belharouak I.,Argonne National Laboratory | Li L.,Beijing Institute of Technology | Lei Y.,Argonne National Laboratory | And 5 more authors.
Advanced Energy Materials | Year: 2013

Nanolayers of Al2O3 and TiO2 coatings were applied to lithium- and manganese-rich cathode powder Li1.2Ni 0.13Mn0.54Co0.13O2 using an atomic layer deposition (ALD) method. The ALD coatings exhibited different surface morphologies; the Al2O3 surface film appeared to be uniform and conformal, while the TiO2 layers appeared as particulates across the material surface. In a Li-cell, the Al2O3 surface film was stable during repeated charge and discharge, and this improved the cell cycling stability, despite a high surface impedance. The TiO 2 layer was found to be more reactive with Li and formed a Li xTiO2 interface, which led to a slight increase in cell capacity. However, the repetitive insertion/extraction process for the Li + ions caused erosion of the surface protective TiO2 film, which led to degradation in cell performance, particularly at high temperature. For cells comprised of the coated Li1.2Ni0.13Mn 0.54Co0.13O2 and an anode of meso-carbon-micro-beads (MCMB), the cycling stability introduced by ALD was not enough to overcome the electrochemical instability of MCMB graphite. Therefore, protection of the cathode materials by ALD Al2O3 or TiO2 can address some of the capacity fading issues related to the Li-rich cathode at room temperature. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zhao Y.,University of Oxford | Zhao Y.,Beijing Institute of Technology | Eley C.,University of Oxford | Hu J.,University of Oxford | And 4 more authors.
Angewandte Chemie - International Edition | Year: 2012

Nb 2O 5 nanorods and nanospheres were synthesized, and their photocatalytic activity for methylene blue decomposition in water compared. Nb 2O 5 nanorods clearly displayed higher activity, despite their comparable surface area. With a shape-dependent surface acidity, hydrothermal stability, and high photoactivity, these Nb 2O 5 nanorods are a unique and exciting nanomaterial for non-classical photocatalytic mineralization of organic compounds in water. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chen C.,Beijing Institute of Technology
European Physical Journal D | Year: 2015

The 1s 22s 22p 2P ground state and the 1s 22s 2 np (n = 3, 4) 2P, 1s 22s 23s 2S, 1s 22s2p 2 4P, 2L (L = S, P, D), 1s 22s2p3s 4Po, 1s 22s2p3p 4S, and 1s 22p 3 4S o, 2Lo (L = P, D) excited states of boron are calculated using the Rayleigh-Ritz variational method with multiconfiguration interaction wave functions. Energies, expectation values such as the electron density at the nucleus ρ(0) and radial moments 〈r n 〉, and fine-structure splittings are calculated. Hyperfine structure parameters and magnetic coupling constants of these states are also calculated. The present results are in good agreement with theoretical and experimental data available in the literature and should provide valuable reference data for future theoretical calculations and experimental measurements. Graphical abstract: [Figure not available: see fulltext.]. © 2015 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg.

Liu C.H.,Beijing Institute of Technology | Kind A.,IBM | Vasilakos A.,National Technical University of Athens
IEEE Network | Year: 2013

Data center networks are expected to support emerging types of bandwidth-hungry applications to perform real-time search and data analysis. They impose significant challenges to identify the cause of congestion down to the flow level on a physical port of a switch/router in real time with high accuracy, low computational complexity and good scalability with the exploding data. In this article, we propose two sketch-based algorithms, called α-CU and P(d)-CU, based on the existing Conservative Update (CU) approach. α-CU adds no extra implementation cost to traditional CU, but successfully trades off the achieved error with time complexity. P(d)-CU fully considers the amount of skew for different network services to aggregate traffic statistics of each service type at individual horizontally partitioned sketches. We also introduce a way to produce the real-time moving average of the reported results. The effectiveness of the proposed algorithms is verified by sufficient experiments by a real DCN trace. © 1986-2012 IEEE.

Zhong Y.,University of Tokyo | Ma J.,University of Tokyo | Ma J.,Beijing Institute of Technology | Hashimoto K.,University of Tokyo | And 2 more authors.
Advanced Materials | Year: 2013

Order of dipole moment layers at donor and acceptor interfaces in bilayer organic solar cells is manipulated reversibly by applying bias voltages. The energy level shifts at the interfaces induce reversible changes in the open circuit voltage and the diode properties. This finding could lead to a better understanding of the structure-property relationship at the materials interfaces in organic optoelectronic devices. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chen K.,University of Siegen | Shu Q.,Beijing Institute of Technology | Schmittel M.,University of Siegen
Chemical Society Reviews | Year: 2015

This review highlights the currently exploited working concepts of lab-on-a-molecule probes, with a particular focus on what is required for multianalyte detection and quantification in competitive assays. Both, chemosensor and chemodosimeter approaches are considered. The multifaceted design strategies and the orthogonal protocols are evaluated in order to identify and categorise the successful conceptions and to single out unknown territory and challenges for future work. © The Royal Society of Chemistry 2015.

Zhang X.,Beijing Institute of Technology
Energy Policy | Year: 2014

In this paper, we extend previous reference-dependence newsvendor research by incorporating both consumer trade-offs and government subsidies to evaluate the relevant influences on the optimal electric vehicle (EV) production decisions. We present the properties of the model, derive the closed-form solutions for the model given the relevant constraints, and use numerical experiments to illustrate the results. We find that subsidies, loss aversion, the performance of both EVs and internal combustion engine-powered vehicles (ICEVs), and the coefficient of variation of demand are significant factors influencing the optimal production quantity and the expected utilities of EV production. The high selling price and other high costs of ICEVs help offset the influence of loss aversion, whereas the high costs of EV enhance loss aversion. Our study enriches the literature on subsidies for EVs by establishing a behavioral model to incorporate the decision bias in terms of loss aversion at the firm level. These findings provide guiding principles for both policymakers and EV managers for making better strategies to promote EVs in the early immature market. © 2013 Elsevier Ltd.

Tada A.,University of Tokyo | Geng Y.,University of Tokyo | Geng Y.,Beijing Institute of Technology | Wei Q.,Japan Science and Technology Agency | And 4 more authors.
Nature Materials | Year: 2011

In an ideal model, a p-n junction is formed by two stacked slabs of semiconductors. Although the construction of actual devices is generally more complex, we show that such a simple method can in fact be applied to the formation of organic heterojunctions. Two films of the organic semiconductors poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) can be connected by a simple film-transfer method without disturbing their flat surfaces. Each film can further be modified with a surface-segregated monolayer to tune the strength and direction of the surface dipole moment. Using this method, we fabricated bilayer organic photovoltaic devices with interfacial dipole moments that were selected to align the energy levels at the heterojunction. The open-circuit voltages of the P3HT/PCBM devices could be tuned over a wide range between 0.3 and 0.95 V, indicating that, even if the same combination of bulk materials is used, the interfacial properties drastically alter the performance of organic photovoltaic devices. © 2011 Macmillan Publishers Limited. All rights reserved.

Zheng J.,Beijing Institute of Technology
Optimal Control Applications and Methods | Year: 2015

SummaryThis paper is concerned with the time optimal control problem governed by the internal controlled Cahn-Hilliard equation. We prove the existence of optimal controls. Moreover, we give necessary optimality conditions for an optimal control of our original problem by using the one of the approximate problems. Copyright © 2014 John Wiley & Sons, Ltd. Copyright © 2014 John Wiley & Sons, Ltd.

Cheng H.,Key Laboratory of Cluster Science | Liu J.,Key Laboratory of Cluster Science | Zhao Y.,Key Laboratory of Cluster Science | Hu C.,Key Laboratory of Cluster Science | And 4 more authors.
Angewandte Chemie - International Edition | Year: 2013

Enough to make your hair curl! Moisture-responsive graphene (G) fibers can be prepared by the positioned laser reduction of graphene oxide (GO) counterparts. When exposed to moisture, the asymmetric G/GO fibers display complex, well-controlled motion/deformation in a predetermined manner. These fibers can function not only as a single-fiber walking robot under humidity alternation but also as a new platform for woven devices and smart textiles. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Feng X.,Japan Institute for Molecular Science | Feng X.,Beijing Institute of Technology | Ding X.,Japan Institute for Molecular Science | Jiang D.,Japan Institute for Molecular Science | Jiang D.,Japan Science and Technology Agency
Chemical Society Reviews | Year: 2012

Covalent organic frameworks (COFs) are a class of crystalline porous polymers that allow the atomically precise integration of organic units to create predesigned skeletons and nanopores. They have recently emerged as a new molecular platform for designing promising organic materials for gas storage, catalysis, and optoelectronic applications. The reversibility of dynamic covalent reactions, diversity of building blocks, and geometry retention are three key factors involved in the reticular design and synthesis of COFs. This tutorial review describes the basic design concepts, the recent synthetic advancements and structural studies, and the frontiers of functional exploration. This journal is © The Royal Society of Chemistry 2012.

Yang D.,Beijing Institute of Technology
Sensors and Transducers | Year: 2013

Wireless Sensor Networks (WSNs) have been attracting the attention of both academic and industrial research communities for the past few years. To find an optimal topology control strategy in 3-dimensional (3D) WSNs is a new challenge. In this paper, we discuss issues related to the topology control in 3D WSNs, review a 2D model for WSNs, and introduce a 3D model for WSNs. An Immunity-Based Ant Colony Optimization Topology Control Algorithm for 3D WSNs is introduced, which has better performance with the nature of feedback and paradigm of ant colony and immunity algorithm reducing the redundancy iteration. The advantage of both the Ant Colony Optimization algorithm (ACO) and Connected Dominating Set (CDS) are fully taken in this algorithm. Simulation results show that the CDS-ACO has the better performance in WSNs. © 2013 IFSA.

Wang J.,Zhejiang University | Su Y.,Beijing Institute of Technology
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2011

The state of polarization vortices within a ferroelectric nanoparticle could be affected by the long-range electrostatic and elastic interactions from the neighboring particles. Phase field simulations were conducted to investigate the stability of polarization vortices within two interacting ferroelectric nanodots embedded in a non-ferroelectric medium. The interaction between these two nanodots can be neglected if the intermediate distance is larger than a critical distance, whereas the interaction becomes visible once the distance is smaller than that. Two separate vortices were observed to merge into one single vortex once an extreme state of perfect contact condition has been virtually achieved. © 2011 Elsevier B.V.

Liang J.-H.,Beijing Institute of Technology
Expert Opinion on Therapeutic Patents | Year: 2014

Infections caused by antibiotic-resistant bacteria pose an increasing risk for clinical treatment. Macrolide-lincosamide-streptogramin B is becoming increasingly ineffective due to the methylation at the binding site of bacteria. Despite great efforts on the natural product, erythromycin, only one derivative, that is, telithromycin, capable of fighting against resistant bacteria has so far been marketed. However, the 3'-dimethylamino group is readily metabolized to a nitroso group, which would inhibit CYP3A4, a very important metabolic enzyme responsible for nearly half of all marketed drugs. Areas covered: Modifications at C-10 of erythromycin were seldom reported. This invention disclosed novel ketolides that had a side chain comprising additional nitrogen atoms in place of the original 10-methyl group. Surprisingly, introduction of the side chain at C-10 led to reduced cytochrome inhibition and increased metabolic stability. As a result, the limited ability to inhibit CYP3A4 would relieve the drug-drug interaction and improve the safety of drug co-administration. Expert opinion: This invention opens a new avenue for future modifications to the erythromycin family. It remains unclear how the side chain effected on reduction of CYP inhibition. To fully identify structure-activity relationships, the MIC data of the derivatives on gram-negative bacteria is desirable. © Informa UK, Ltd.

Zhu W.,Monash University | Rukhlenko I.D.,Monash University | Si L.-M.,Beijing Institute of Technology | Premaratne M.,Monash University
Applied Physics Letters | Year: 2013

We present an effective method for actively controlling intrinsic resonances of optical metamaterials using graphene. Exploiting the Fermi level shift and associated variations in optical transitions of graphene due to voltage biasing, we attain the ability to significantly modulate the intrinsic resonance of the fishnet structure. Despite being atomically thin and having a weak optical response, graphene can be strongly coupled with the left-handed resonance of the fishnet metamaterial. We unambiguously demonstrate that the resonant transmission, absorption, and effective constitutive parameters of the graphene-coupled fishnet metamaterial can be precisely controlled by varying the bias voltage. © 2013 American Institute of Physics.

Yang J.,Hebei Medical University | Liang S.,Beijing Institute of Technology | Zhang Y.,Hebei Medical University
PLoS ONE | Year: 2011

This paper is concerned with the existence of travlelling waves to a SIR epidemic model with nonlinear incidence rate, spatial diffusion and time delay. By analyzing the corresponding characteristic equations, the local stability of a disease-free steady state and an endemic steady state to this system under homogeneous Neumann boundary conditions is discussed. By using the cross iteration method and the Schauder's fixed point theorem, we reduce the existence of travelling waves to the existence of a pair of upper-lower solutions. By constructing a pair of upper-lower solutions, we derive the existence of a travelling wave connecting the disease-free steady state and the endemic steady state. Numerical simulations are carried out to illustrate the main results. © 2011 Yang et al.

Liu Z.,Beijing Institute of Technology | Liu Z.,Twi Ltd. | Gao J.,Twi Ltd.
Optics Express | Year: 2011

In this paper, a digital speckle correlation method for coefficient of thermal expansion (CTE) measurement of film is developed, in which CTE is the intrinsic parameter and direct variable. Deformation pattern governed by the CTE and temperature is used to affine transform the image captured after the film is heated. If the values of CTE are properly chosen, the image after affine transformation will have a highest similarity to the original image. This turns CTE measurement into a purely numerical search of an optimal trial CTE. Results of CTEs from this method and conventional DIC methods are compared with the actual CTE, showing an improved accuracy. © 2011 Optical Society of America.

Yan Z.-Z.,Beijing Institute of Technology | Zhang C.,University of Siegen
Physica B: Condensed Matter | Year: 2012

The band structures and localization properties of in-plane elastic waves with coupling of longitudinal and transverse modes oblique propagating in aperiodic phononic crystals based on ThueMorse and RudinShapiro sequences are studied. Using transfer matrix method, the concept of the localization factor is introduced and the correctness is testified through the Rytov dispersion relation. For comparison, the perfect periodic structure and the quasi-periodic Fibonacci system are also considered. In addition, the influences of the random disorder, local resonance, translational and/or mirror symmetries on the band structures of the aperiodic phononic crystals are analyzed in this paper. © 2012 Elsevier B.V. All rights reserved.

Pang C.-S.,Beijing Institute of Technology | Pang C.-S.,North University of China
Tien Tzu Hsueh Pao/Acta Electronica Sinica | Year: 2012

The echo of accelerating targets can be approximated as a linear frequency modulated signal which may degrades the MTD's coherent integration performance. This paper presents an LFM detection method based on both discrete polynomial phase transform (DPT) and the fractional Fourier transform (FRFT). First, the interrelation between frequency resolution, cross-correlation delay, pulse length and integration performance of the classic DPT algorithm are analyzed. The result shows that detection performance of the DPT algorithm with a small time delay can be improved 3dB than classical algorithm. This is helpful to detect accelerating target under low SNR, but causes large parameter estimation error. Second, based on DPT algorithm, the FRFT is applied to further improve the accuracy of chirp rate estimation. When the input signal-to-noise ratio (SNR) is greater than-11 dB, one-dimensional Newton's iteration method can help to improve the operation speed in the fractional domain. Finally, the algorithm complexity and the theory of estimation error are presented, and the validity of proposed algorithm is verified by simulation results which make the theory perfect.

Yu Y.,Beijing Institute of Technology
Journal of Beijing Institute of Technology (English Edition) | Year: 2010

For high Re number flows, a new computational fluid dynamics (CFD) validation method, namely, wall-surface compatibility criteria method and also called Gao's criteria, is proposed to verify near wall flows. As examples, Gao's criteria method and other two CFD verification methods (analytic solutions method and grid convergence analysis) are used to verify FLUENT's near wall flows solutions for two-dimensional incompressible laminar stagnation-point flows. The exact solution of the Navier-Stokes equations for laminar stagnation-point flows satisfy accurately all Gao's criteria, numerical simulations of laminar stagnation-point flows show that when physical parameters (the pressure coefficient and the Stanton number at wall surface) achieve convergence with more and more fine-screen grid, a part of Gao's criteria are not satisfied.

Wen W.,Zhejiang University | Wu J.-M.,Zhejiang University | Cao M.-H.,Beijing Institute of Technology
Nanoscale | Year: 2014

A facile strategy is developed for mass fabrication of porous Co3O4 networks via the thermal decomposition of an amorphous cobalt-based complex. At a low mass loading, the achieved porous Co3O4 network exhibits excellent performance for lithium storage, which has a high capacity of 587 mA h g-1 after 500 cycles at a current density of 1000 mA g-1. © 2014 the Partner Organisations.

Zhao Y.,Beijing Institute of Technology
2012 7th IEEE International Conference on Nano/Micro Engineered and Molecular Systems, NEMS 2012 | Year: 2012

This paper presents a novel bi-stable and integrated single use MEMS blowout switch based on electro-thermal theory. The switch mechanically breaks a metallic line. Switching between the two stable states is accomplished by a DC signal through an integrated heating resistance underneath the electrical lines to be melted. Some key features are that switches are bi-stable, integratable and IC compatible. They are compatible with various voltages operation for different applications, operation in ambient environment may be possible; predicted lifetime is very long and therefore both switches can be used for long life systems. Batch fabrication using planar processing methods is used. The ETBS could be manufacture easily in great amount. The switch can also be applied in some areas of high-energy control such as initiation security and self-control in failure. © 2012 IEEE.

Xing X.,Beijing Institute of Technology
Science China: Physics, Mechanics and Astronomy | Year: 2010

In this paper the author presents an overview on his own research works. More than ten years ago, we proposed a new fundamental equation of nonequilibrium statistical physics in place of the present Liouville equation. That is the stochastic velocity type's Langevin equation in 6N dimensional phase space or its equivalent Liouville diffusion equation. This equation is time-reversed asymmetrical. It shows that the form of motion of particles in statistical thermodynamic systems has the drift-diffusion duality, and the law of motion of statistical thermodynamics is expressed by a superposition of both the law of dynamics and the stochastic velocity and possesses both determinism and probability. Hence it is different from the law of motion of particles in dynamical systems. The stochastic diffusion motion of the particles is the microscopic origin of macroscopic irreversibility. Starting from this fundamental equation the BBGKY diffusion equation hierarchy, the Boltzmann collision diffusion equation, the hydrodynamic equations such as the mass drift-diffusion equation, the Navier-Stokes equation and the thermal conductivity equation have been derived and presented here. What is more important, we first constructed a nonlinear evolution equation of nonequilibrium entropy density in 6N, 6 and 3 dimensional phase space, predicted the existence of entropy diffusion. This entropy evolution equation plays a leading role in nonequilibrium entropy theory, it reveals that the time rate of change of nonequilibrium entropy density originates together from its drift, diffusion and production in space. From this evolution equation, we presented a formula for entropy production rate (i.e. the law of entropy increase) in 6N and 6 dimensional phase space, proved that internal attractive force in nonequilibrium system can result in entropy decrease while internal repulsive force leads to another entropy increase, and derived a common expression for this entropy decrease rate or another entropy increase rate, obtained a theoretical expression for unifying thermodynamic degradation and self-organizing evolution, and revealed that the entropy diffusion mechanism caused the system to approach to equilibrium. As application, we used these entropy formulas in calculating and discussing some actual physical topics in the nonequilibrium and stationary states. All these derivations and results are unified and rigorous from the new fundamental equation without adding any extra new assumption. © 2010 Science China Press and Springer-Verlag Berlin Heidelberg.

Xiong J.,Beijing Institute of Technology | Cao J.,Tsinghua University | Zhang Y.,Tsinghua University
Building and Environment | Year: 2016

The accurate and rapid determination of the emission parameters of semi-volatile organic compounds (SVOCs) from indoor materials is of great importance for estimating and controlling indoor exposure. By virtue of a simplified mass transfer model we derived, a new method called the early stage C-history method, has been developed to measure the key emission parameters: the gas phase SVOC concentration adjacent to the material surface (y0) and the convective mass transfer coefficient (hm). We validate this model using experimental data found in the literature. When compared with established methods, the new method has the following salient features: (1) rapid (the experimental time is reduced from several months to several days); (2) accurate (R2 in the range of 0.92-0.97). Further analysis shows that both features can be further improved if the test system has a smaller chamber wall/air partition coefficient. The new method is also extended to measure the key parameters of SVOCs from sorption materials. This method should prove useful for screening SVOC emission characteristics and for assessing exposure, as well as for chamber and test design. © 2015 Elsevier Ltd.

Xiusan X.,Beijing Institute of Technology
Science China: Physics, Mechanics and Astronomy | Year: 2010

In this paper, we develop dynamic statistical information theory established by the author. Starting from the ideas that the state variable evolution equations of stochastic dynamic systems, classical and quantum nonequilibrium statistical physical systems and special electromagnetic field systems can be regarded as their information symbol evolution equations and the definitions of dynamic information and dynamic entropy, we derive the evolution equations of dynamic information and dynamic entropy that describe the evolution laws of dynamic information. These four kinds of evolution equations are of the same mathematical type. They show in unison when information transmits in coordinate space outside the systems that the time rate of change of dynamic information densities originates from their drift, diffusion and dissipation in state variable space inside the systems and coordinate space in the transmission processes, and that the time rate of change of dynamic entropy densities is caused by their drift, diffusion and production in state variable space inside the systems and coordinate space in the transmission processes. When space noise can be neglected, an information wave will appear. If we only consider the information change inside the systems, dynamic information evolution equations reduce to information equations corresponding to the dynamic equations which describe evolution laws of the above dynamic systems. This reveals that the evolution laws of respective dynamic systems can be described by information equations in a unified fashion. Hence, the evolution processes of these dynamic systems can be abstracted as the evolution processes of information. Furthermore, we present the formulas for information flow, information dissipation rate, and entropy production rate. We prove that the information production probably emerges in a dynamic system with internal attractive interaction between the elements, and derive a formula for this information production rate. Thereby, we obtain an expression for the time rate of total information change of a dynamic system, which is equal to the algebraic sum of the formulas for information dissipation rate, information production rate and information inflow rate, and which exhibits a unified information description for the evolution including degradation and self-organizing evolution of dynamic systems. © Science China Press and Springer-Verlag Berlin Heidelberg 2010.

Chen L.,CAS Institute of Physics | Liu C.-C.,CAS Institute of Physics | Feng B.,CAS Institute of Physics | He X.,CAS Institute of Physics | And 6 more authors.
Physical Review Letters | Year: 2012

Silicene, a sheet of silicon atoms in a honeycomb lattice, was proposed to be a new Dirac-type electron system similar to graphene. We performed scanning tunneling microscopy and spectroscopy studies on the atomic and electronic properties of silicene on Ag(111). An unexpected √3×√3 reconstruction was found, which is explained by an extra-buckling model. Pronounced quasiparticle interferences (QPI) patterns, originating from both the intervalley and intravalley scatter, were observed. From the QPI patterns we derived a linear energy-momentum dispersion and a large Fermi velocity, which prove the existence of Dirac fermions in silicene. © 2012 American Physical Society.

Yang F.,Beijing Institute of Technology | Yao H.,Tsinghua University | Yao H.,Stanford University
Physical Review Letters | Year: 2012

Resonating valence bond (RVB) states are of crucial importance in our intuitive understanding of quantum spin liquids in 2D. We systematically classify short-range bosonic RVB states into symmetric or nematic spin liquids by examining their flux patterns. We further map short-range bosonic RVB states into projected BCS wave functions, on which we perform large-scale MonteCarlo simulations without the minus sign problem. Our results clearly show that both spin and dimer correlations decay exponentially in all the short-range frustrated (nonbipartite or Z 2) bosonic RVB states we studied, indicating that they are gapped Z 2 quantum spin liquids. Generically, we conjecture that all short-range frustrated bosonic RVB states in 2D have only short-range correlations. © 2012 American Physical Society.

Faist M.A.,Imperial College London | Kirchartz T.,Imperial College London | Gong W.,Imperial College London | Gong W.,Beijing Institute of Technology | And 6 more authors.
Journal of the American Chemical Society | Year: 2012

We study the appearance and energy of the charge transfer (CT) state using measurements of electroluminescence (EL) and photoluminescence (PL) in blend films of high-performance polymers with fullerene acceptors. EL spectroscopy provides a direct probe of the energy of the interfacial states without the need to rely on the LUMO and HOMO energies as estimated in pristine materials. For each polymer, we use different fullerenes with varying LUMO levels as electron acceptors, in order to vary the energy of the CT state relative to the blend with [6,6]-phenyl C61-butyric acid methyl ester (PCBM). As the energy of the CT state emission approaches the absorption onset of the blend component with the smaller optical bandgap, E opt,min min{E opt,donor; E opt,acceptor}, we observe a transition in the EL spectrum from CT emission to singlet emission from the component with the smaller bandgap. The appearance of component singlet emission coincides with reduced photocurrent and fill factor. We conclude that the open circuit voltage V OC is limited by the smaller bandgap of the two blend components. From the losses of the studied materials, we derive an empirical limit for the open circuit voltage: V OC ≲ E opt,min/e - (0.66 ± 0.08)eV. © 2011 American Chemical Society.

Liang X.,Beijing Institute of Technology | Liang X.,Stanford University
IEEE Transactions on Neural Networks | Year: 2010

Support vector machine (SVM) classifiers often contain many SVs, which lead to high computational cost at runtime and potential overfitting. In this paper, a practical and effective method of pruning SVM classifiers is systematically developed. The kernel row vectors, with one-to-one correspondence to the SVs, are first organized into clusters. The pruning work is divided into two phases. In the first phase, orthogonal projections (OPs) are performed to find kernel row vectors that can be approximated by the others. In the second phase, the previously found vectors are removed, and crosswise propagations, which simply utilize the coefficients of OPs, are implemented within each cluster. The method circumvents the problem of explicitly discerning SVs in the high-dimensional feature space as the SVM formulation does, and does not involve local minima. With different parameters, 3000 experiments were run on the LibSVM software platform. After pruning 42% of the SVs, the average change in classification accuracy was only -0.7%, and the average computation time for removing one SV was 0.006 of the training time. In some scenarios, over 90% of the SVs were pruned with less than 0.1% reduction in classification accuracy. The experiments demonstrate the existence of large numbers of superabundant SVs in trained SVMs, and suggest a synergistic use of training and pruning in practice. Many SVMs already used in applications could be upgraded by pruning nearly half of their SVs. © 2009 IEEE.

Zou L.,Beijing Institute of Technology | Chen L.,Hong Kong University of Science and Technology
IEEE Transactions on Knowledge and Data Engineering | Year: 2011

Given a record set D and a query score function F, a top-k query returns k records from D, whose values of function F on their attributes are the highest. In this paper, we investigate the intrinsic connection between top-k queries and dominant relationships between records, and based on which, we propose an efficient layer-based indexing structure, Pareto-Based Dominant Graph (DG), to improve the query efficiency. Specifically, DG is built offline to express the dominant relationship between records and top-k query is implemented as a graph traversal problem, i.e., Traveler algorithm. We prove theoretically that the size of search space (that is the number of retrieved records from the record set to answer top-k query) in our algorithm is directly related to the cardinality of skyline points in the record set (see Theorem 3). Considering I/O cost, we propose cluster-based storage schema to reduce I/O cost in Traveler algorithm. We also propose the cost estimation methods in this paper. Based on cost analysis, we propose an optimization technique, pseudorecord, to further improve the search efficiency. In order to handle the top-k query in the high-dimension record set, we also propose N-Way Traveler algorithm. In order to handle DG maintenance efficiently, we propose Insertion and Deletion algorithms for DG. Finally, extensive experiments demonstrate that our proposed methods have significant improvement over its counterparts, including both classical and state art of top-k algorithms. © 2006 IEEE.

Xia Y.,Beijing Institute of Technology | Xie W.,Key Laboratory of Intelligent Control | Liu B.,Key Laboratory of Intelligent Control | Wang X.,Key Laboratory of Intelligent Control
Information Sciences | Year: 2013

This paper is concerned with the problem of data-driven predictive control for networked control systems (NCSs), which is designed by applying the subspace matrices technique, obtained directly from the input/output data transferred from networks. The networked predictive control consists of the control prediction generator and network delay compensator. The control prediction generator provides a set of future control predictions to make the closed-loop system achieve the desired control performance and the network delay compensator eliminates the effects of the network transmission delay. The effectiveness and superiority of the proposed method is demonstrated in simulation as well as experiment study. © 2012 Elsevier Inc. All rights reserved.

Shao J.R.,CAS Institute of Mechanics | Li H.Q.,Beijing Institute of Technology | Liu G.R.,University of Cincinnati | Liu M.B.,CAS Institute of Mechanics
Computers and Structures | Year: 2012

Smoothed particle hydrodynamics (SPH) is a popular meshfree, Lagrangian particle method with attractive features in modeling liquid sloshing dynamics, which is usually associated with changing and breakup of free surfaces, strong turbulence and vortex, and "violent" fluid-solid interaction. This paper presents an improved SPH method for modeling liquid sloshing dynamics. Firstly, modified schemes for approximating density (density correction) and kernel gradient (kernel gradient correction, or KGC) have been used to achieve better accuracy with smoother pressure field. Secondly, the Reynolds Averaged turbulence model is incorporated into the SPH method to describe the turbulence effects. Thirdly, a coupled dynamic solid boundary treatment (SBT) algorithm has been proposed to improve the accuracy near the solid boundary areas. The new SBT algorithm consists of a kernel-like, soft repulsive force between approaching fluid and solid particles, and a reliable numerical approximation scheme for estimating field functions of virtual solid particles. Three numerical examples are modeled using this improved SPH method, and the obtained numerical results agree well with experimental observations and results from other sources. © 2012 Elsevier Ltd. All rights reserved.

Wu J.,Shijiazhuang University of Economics | Chen F.,Shijiazhuang University of Economics | Nie C.,Shijiazhuang Mechanical Engineering College | Zhang Q.,Beijing Institute of Technology
Information Sciences | Year: 2013

Our purpose in this paper is to show the integration properties of the intuitionistic fuzzy-valued Choquet integrals, by which improper applications of this type of Choquet integral in the multicriteria decision making can be avoided. We first propose some important operational properties of intuitionistic fuzzy values (IFVs) and give a short review of the methods of comparing IFVs in the framework of the multicriteria decision making. Then we give a detailed discussion on the aggregation properties of the intuitionistic fuzzy-valued Choquet integral (IFCI) and the intuitionistic fuzzy-valued conjugate Choquet integral (IFCCI). The difference in aggregation characteristics between the IFCI and the IFCCI in multicriteria decision making are also be investigated. Finally, we present an application of the IFCI and IFCCI-based multicriteria decision making method to assess the software development risks. © 2012 Elsevier Inc. All rights reserved.

Qiao Z.,University of Texas at Austin | Tse W.-K.,University of Texas at Austin | Jiang H.,University of Texas at Austin | Jiang H.,Peking University | And 4 more authors.
Physical Review Letters | Year: 2011

We show that gated bilayer graphene hosts a strong topological insulator (TI) phase in the presence of Rashba spin-orbit (SO) coupling. We find that gated bilayer graphene under preserved time-reversal symmetry is a quantum valley Hall insulator for small Rashba SO coupling λ R, and transitions to a strong TI when λ R>√U2+t2, where U and t are, respectively, the interlayer potential and tunneling energy. Different from a conventional quantum spin Hall state, the edge modes of our strong TI phase exhibit both spin and valley filtering, and thus share the properties of both quantum spin Hall and quantum valley Hall insulators. The strong TI phase remains robust in the presence of weak graphene intrinsic SO coupling. © 2011 American Physical Society.

You Y.-Z.,Tsinghua University | Yang F.,Beijing Institute of Technology | Kou S.-P.,Beijing Normal University | Weng Z.-Y.,Tsinghua University
Physical Review Letters | Year: 2011

We propose a theoretical description of the phase diagram and physical properties in A2Fe4Se5-type (A=K, Tl) compounds based on a coexistent local moment and itinerant electron picture. Using neutron scattering and angle-resolved photoemission spectroscopy measurements to fix the general structure of the local moment and itinerant Fermi pockets, we find a superconducting phase with s-wave pairing at the M pockets and an incipient sign-change s wave near the Γ point, which is adjacent to the insulating phases. The uniform susceptibility and resistivity are found to be consistent with the experiment. The main distinction with iron pnictide superconductors is also discussed. © 2011 American Physical Society.

Feng B.,CAS Institute of Physics | Ding Z.,CAS Institute of Physics | Meng S.,CAS Institute of Physics | Yao Y.,CAS Institute of Physics | And 5 more authors.
Nano Letters | Year: 2012

In the search for evidence of silicene, a two-dimensional honeycomb lattice of silicon, it is important to obtain a complete picture for the evolution of Si structures on Ag(111), which is believed to be the most suitable substrate for growth of silicene so far. In this work we report the finding and evolution of several monolayer superstructures of silicon on Ag(111), depending on the coverage and temperature. Combined with first-principles calculations, the detailed structures of these phases have been illuminated. These structures were found to share common building blocks of silicon rings, and they evolve from a fragment of silicene to a complete monolayer silicene and multilayer silicene. Our results elucidate how silicene forms on Ag(111) surface and provides methods to synthesize high-quality and large-scale silicene. © 2012 American Chemical Society.

Peng X.-W.,South China University of Technology | Ren J.-L.,South China University of Technology | Sun R.-C.,South China University of Technology | Sun R.-C.,Beijing Institute of Technology
Biomacromolecules | Year: 2010

Generation of bioenergy, new functional polymers, or chemicals and biomaterials from hemicelluloses are important uses for biomass. In this paper, a novel functional biopolymer with carbon-carbon double bond and carboxyl groups was prepared by a homogeneous esterification of xylan-rich hemicelluloses (XH) with maleic anhydride in 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) ionic liquid using LiOH as catalyst. The biopolymers with degrees of substitution (DS) between 0.095 and 0.75 were accessible in a completely homogeneous system by changing reaction temperature, reaction time, the dosage of catalyst, and the molar ratio of maleic anhydride to anhydroxylose unit in XH. Results obtained from FT-IR and 13C NMR spectroscopies confirmed the structure of hemicellulosic derivatives with carbon-carbon double bond and carboxyl groups, implying an efficient method to prepare a novel and important functional biopolymer for biomaterials. © 2010 American Chemical Society.

Wei Hao H.,Beijing Institute of Technology
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011

Recently, the so-called Elko spinor field has been proposed to be a candidate of dark energy. It is a non-standard spinor and has unusual properties. When the Elko spinor field is used in cosmology, its unusual properties could bring some interesting consequences. In the present work, we discuss the cosmological coincidence problem in the spinor dark energy models by using the dynamical system method. Our results show that the cosmological coincidence problem should be taken to heart in the investigations of spinor dark energy models. © 2010 Elsevier B.V.

Hu X.,University of Michigan | Hu X.,Beijing Institute of Technology | Li S.,University of Michigan | Peng H.,University of Michigan
Journal of Power Sources | Year: 2012

This paper presents a comparative study of twelve equivalent circuit models for Li-ion batteries. These twelve models were selected from state-of-the-art lumped models reported in the literature. The test data used is obtained from a battery test system with a climate chamber. The test schedule is designed to measure key cell attributes under highly dynamical excitations. The datasets were collected from two types of Li-ion cells under three different temperatures. The multi-swarm particle swarm optimization algorithm is used to identify the optimal model parameters for the two types of Li-ion cells. The usefulness of these models is then studied through a comprehensive evaluation by examining model complexity, model accuracy, and robustness of the model by applying the model to datasets obtained from other cells of the same chemistry type. © 2011 Elsevier B.V. All rights reserved.

Zhang Y.,Beijing Institute of Technology
Optik | Year: 2013

An in-motion alignment algorithm of strapdown inertial navigation system (SDINS) aided by Dopplervelocity log (DVL) is described. As the bias and scale factor errors of DVL cannot be estimated by usingconventional algorithm, error model of DVL along axes on local level navigation frame is developed whilethe ship is sailing at a constant speed. Analysis shows that by using this error model in Kalman filter, theobservability of state variable can be improved by the angular motion of the ship. Simulation results showthat the DVL measurement error can be estimated precisely and the accuracy of the DVL-aided in-sailalignment can be enhanced greatly by using the proposed approach. © 2013 Elsevier GmbH. All rights reserved.

Xin B.-P.,Beijing Institute of Technology | Wu C.-H.,National Yunlin University of Science and Technology | Lin C.-W.,National Yunlin University of Science and Technology
Journal of Hazardous Materials | Year: 2013

Ineffective biostimulation requires immediate development of new technologies for remediation of high concentration BTEX-contaminated (benzene, toluene, ethylbenzene and xylene) groundwater. In this study, bioaugmentation with Mycobacterium sp. CHXY119 and Pseudomonas sp. YATO411 immobilized bead was used to remediate BTEX-contaminated groundwater with about 100mgl-1 in total concentration. The batch test results showed that the CHXY119 and YATO411 immobilized bead completely biodegraded each BTEX compound, and the maximum biodegradation rates were 0.790mgl-1h-1 for benzene, 1.113mgl-1h-1 for toluene, 0.992mgl-1h-1 for ethylbenzene and 0.231mgl-1h-1 for p-xylene. The actual mineralization rates were 10.8% for benzene, 10.5% for toluene, 5.8% for ethylbenzene and 11.4% for p-xylene, which indicated that the bioremediation of BTEX by the immobilized bead requires a rather small oxygen supply. Degradation rates achieved by the bioaugmented permeable reactive barrier (Bio-PRB) system of the immobilized bead were 97.8% for benzene, 94.2% for toluene, 84.7% for ethylbenzene and 87.4% for p-xylene; and the toxicity of the groundwater fell by 91.2% after bioremediation by the bioaugmented PRB, which confirmed its great potential for remediating groundwater with high concentrations of contaminants. © 2012 Elsevier B.V.

Kuang W.,Shandong Polytechnic University | Kuang W.,Shandong University | Zhao X.,Beijing Institute of Technology
Reactive and Functional Polymers | Year: 2013

Novel fluorinated associative copolymers poly(ethylene glycol)-b-poly(2- (perfluorohexyl)ethyl methacrylate (PFHEMA)-co-3-[N -(2-methacroyloylethyl)-N,N -dimethylammonio]-propane sulfonate (DMAPS)) (PEG-b-PPFHEMA/PDMAPS) were prepared as a type of non-viral gene vector. The series of PEG-b-PFHEMA/ DMAPS with different molecular weights and compositions were characterized by gel permeation chromatographymulti-angle light scattering, 1H NMR, 19F NMR, and elemental analysis. The interactions of the copolymers with calf thymus DNA and the morphologies of the resulting complexes were studied by fluorescence spectroscopy, dynamic light scattering, and transmission electron microscopy. In addition, the DNApolymer interaction, as determined by the gel retardation assay, and the low cytotoxicity of PEG-b-PPFHEMA/PDMAPS demonstrated that these copolymers have good DNA binding capacity and potential for high performance in the practical application of DNA delivery. © 2013 Elsevier Ltd. All rights reserved.

Fan T.Y.,Beijing Institute of Technology
Philosophical Magazine Letters | Year: 2012

A plastic crack model for smectic A liquid crystals is suggested in this article. The solution for the crack problem is based on the dislocation pile-up principle and the singular integral equation method. From the solution we can determine the size of the plastic zone at the crack tip and the crack tip opening (sliding) displacement, which are parameters relevant to the stability/instability of materials. The results may be useful in developing soft-matter mechanics. © 2012 Taylor & Francis.

Zhu Z.-S.,Beijing Institute of Technology
Hangkong Cailiao Xuebao/Journal of Aeronautical Materials | Year: 2014

The output capacity of titanium sponge and mill products in China has ranked the first in the world. Compared with the developed countries, the aviation application level and amount of high performance titanium alloys in China still far lags behind that of developed countries. Based on the summary of research situation in titanium alloys technology, the technology maturity promotion approaches of new type and key titanium alloys is given by means of the optimization of synthetical properties, the variety and complete specifications, the expansion of the application scales, the sophistication of standard and specifications, the sufficiency of testing and verification, etc. And it is also very necessary to establish an aviation-oriented titanium alloys system with Chinese characteristics, to meet the design requirements of high performance, low cost, and a raised amount of consumption and application level of titanium alloys.

Zhang B.,Beijing Institute of Technology | Kamenskihs V.,McGill University | Ng H.D.,Concordia University at Montreal | Lee J.H.S.,McGill University
Proceedings of the Combustion Institute | Year: 2011

In this study, direct initiation of spherical detonations in highly argon diluted mixtures is investigated. Direct initiation is achieved via a high voltage capacitor spark discharge and the critical energy is estimated from the analysis of the current output. Stoichiometric acetylene-oxygen mixtures highly diluted with 70% argon is used in the experiment. Previous investigations have suggested that detonations in mixtures that are highly diluted with argon have been shown to be "stable" in that the reaction zone is at least piecewise laminar described by the ZND model and cellular instabilities play a minor role on the detonation propagation. For the acetylene-oxygen mixture that is highly diluted with argon, the experimental results show that the critical energy where the detonation is "stable" is in good agreement with the Zel'dovich criterion of the cubic dependence on the ZND reaction length, which can be readily determined using the chemical kinetic data of the reaction. The experimental results are also compared with those estimated using Lee's surface energy model where empirical data on detonation cell sizes are required. Good agreement is found between the experimental measurement and theoretical model prediction, where the breakdown of the 13λ relationship for critical tube diameter - and hence a different propagation and initiation mechanism - is elucidated in highly argon diluted mixtures and this appears to indicate that cellular instabilities do not have a prominent effect on the initiation process of a stable detonation. © 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Jiang H.,Beijing Institute of Technology | Lu T.,Peking University | Cai W.,University of North Carolina at Charlotte
Journal of Computational Physics | Year: 2014

In this paper, an improved inflow boundary condition is proposed for Wigner equations in simulating a resonant tunneling diode (RTD), which takes into consideration the band structure of the device. The original Frensley inflow boundary condition prescribes the Wigner distribution function at the device boundary to be the semi-classical Fermi-Dirac distribution for free electrons in the device contacts without considering the effect of the quantum interaction inside the quantum device. The proposed device adaptive inflow boundary condition includes this effect by assigning the Wigner distribution to the value obtained from the Wigner transform of wave functions inside the device at zero external bias voltage, thus including the dominant effect on the electron distribution in the contacts due to the device internal band energy profile. Numerical results on computing the electron density inside the RTD under various incident waves and non-zero bias conditions show much improvement by the new boundary condition over the traditional Frensley inflow boundary condition. © 2013 Elsevier Inc.

Mahmoud M.S.,King Fahd University of Petroleum and Minerals | Xia Y.,Beijing Institute of Technology
International Journal of Robust and Nonlinear Control | Year: 2010

A novel delay-dependent filtering design approach is developed for a class of linear piecewise discrete-time systems with convex-bounded parametric uncertainties and time-varying delays. The time-delays appear in the state as well as the output and measurement channels. The filter has a linear full-order structure and guarantees the desired estimation accuracy over the entire uncertainty polytope. The desired accuracy is assessed in terms of either ℋ∞-performance or ℒ2- ℒ∞ criteria. A new parametrization procedure based on a combined Finsler's Lemma and piecewise Lyapunov-Krasovskii functional is established to yield sufficient conditions for delay-dependent filter feasibility. The filter gains are determined by solving a convex optimization problem over linear matrix inequalities. In comparison to the existing design methods, the developed methodology yields the least conservative measures since all previous overdesign limitations are almost eliminated. By means of simulation examples, the advantages of the developed technique are readily demonstrated. © 2009 John Wiley & Sons, Ltd.

Qu L.,Beijing Institute of Technology | Liu Y.,Wenzhou Medical College | Baek J.-B.,Ulsan National Institute of Science and Technology | Dai L.,Case Western Reserve University
ACS Nano | Year: 2010

Nitrogen-doped graphene (N-graphene) was synthesized by chemical vapor deposition of methane in the presence of ammonia. The resultant N-graphene was demonstrated to act as a metal-free electrode with a much better electrocatalytic activity, long-term operation stability, and tolerance to crossover effect than platinum for oxygen reduction via a four-electron pathway in alkaline fuel cells. To the best of our knowledge, this is the first report on the use of graphene and its derivatives as metal-free catalysts for oxygen reduction. The important role of N-doping to oxygen reduction reaction (ORR) can be applied to various carbon materials for the development of other metal-free efficient ORR catalysts for fuel cell applications, even new catalytic materials for applications beyond fuel cells. © 2010 American Chemical Society.

Yan Z.-Z.,Beijing Institute of Technology | Zhang C.,University of Siegen
Ultrasonics | Year: 2012

The localization properties of in-plane elastic waves propagating in two-dimensional porous phononic crystals with one-dimensional aperiodicity are initially analyzed by introducing the concept of the localization factor that is calculated by the plane-wave-based transfer-matrix method in this paper. The band structures characterized by using localization factors are calculated for different phononic crystals by altering matrix material properties and geometric structure parameters. Numerical results show that the effect of matrix material properties on wave localization can be ignored, while the effect of geometric structure parameters is obvious. For comparison, the periodic porous system and Fibonacci system with rigid inclusion are also analyzed. It is found that the band gaps are easily formed in aperiodic porous system, but hard for periodic porous system. Moreover, compared with aperiodic system with rigid inclusion, the wider low-frequency band gaps appear in the aperiodic porous system. © 2011 Elsevier B.V. All rights reserved.

Liu H.,CAS Beijing National Laboratory for Molecular | Du D.-M.,CAS Beijing National Laboratory for Molecular | Du D.-M.,Beijing Institute of Technology
European Journal of Organic Chemistry | Year: 2010

A diphenylamine-linked bis(oxazoline) ligand with trans-diphenyl substitution on the oxazoline rings has been immobilized onto one- to three-generation Fréchet-type dendrimers and a C3-symmetric core structure. The catalytic activities and enantioselectivities of these new ligands were tested in the asymmetric Friedel-Crafts alkylation reactions of indole derivatives with, nitroalkenes. The two types of immobilized ligands exhibited similar enantioselectivities and substrate compatibilities to the free ligand trans-DPBO we reported previously. No dendrimer effect was observed in the kinetic investigation of the Fréchet-type dendrimer-immobilized ligands. The in situ recycling of the catalysts was also tested to illustrate the effect of reducing catalyst loading and the efficiency of our system. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.

Lu Y.,Beijing Institute of Technology | Chen M.,Tsinghua University
Acta Materialia | Year: 2012

The crystallization of Ni 90Si 10 drops has been studied using molecular dynamics simulations. The atoms in the surface monolayer of the drop prematurely pack into a long-range ordered structure prior to volume crystallization, whereas diffusion dynamics maintains characteristic liquid-like features until the onset of volume crystallization. This surface crystallization process arises from strong density layering in the direction perpendicular to the drop surface. Due to density oscillations induced by the surface layering a high density state is produced in the drop surface, which is analogous to the effect of high pressure and locally increases the crystallization temperature of the surface layer, ultimately initiating crystallization from the surface. Such a layered structure causes pressure oscillation near the surface that produce a decrease in surface tension with decreasing temperature. The high density crystalline nature of the surface does not thermodynamically favor volume crystallization, which occurs separately via homogeneous nucleation in the interior with further decreasing temperature. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Sun L.,Shenzhen University | Hu C.,Beijing Institute of Technology
Materials Research Bulletin | Year: 2011

Different Mg-Al layered double hydroxide (LDH) 3D micro-nano structures had been synthesized via a facile solvothermal method. By carefully controlling the fundamental experimental parameters, the morphologies of hexagonal nanoplates, rose-like micro-nano structures, chrysanthemum-like micro-nano structures, and spherical micro-nano structures have been efficiently obtained, respectively. And these micro-nano structures are formed from self-assembly of nanoplates in a spontaneous process in solvothermal system. It is also found that the concentration of the reactant and the dosage of CTAB have significant effects on the morphology of the products. The FT-IR spectra and thermal stability of the micro-nano structures were explored. © 2011 Elsevier Ltd. All rights reserved.

Li T.,Renmin University of China | Yang F.,Beijing Institute of Technology
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

A Gutzwiller-type variational wave function is proposed for the neutron resonance mode in the cuprate superconductors. An efficient reweighting technique is devised to perform variational Monte Carlo simulation on the proposed wave function which is composed of linearly superposed Gutzwiller projected Slater determinants. The calculation, which involves no free parameter, predicts qualitatively correct behavior for both the energy and the spectral weight of the resonance mode as functions of doping. © 2010 The American Physical Society.

Shi H.,Beijing Institute of Technology | Jia R.,University of Wuppertal | Eglitis R.I.,University of Latvia
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

H center, a hole trapped at an interstitial anion site, placed on the (111) surface of Barium fluoride BaF2 has been studied by using density functional theory (DFT) with hybrid exchange potentials, namely, DFT-B3PW. Two different configurations of surface H center are investigated carefully. Both surface H -center systems have strong relaxations because of the surface effect. In the configuration that the interstitial fluorine atom is within the surface, named case 1 in this paper, the unpaired electron is almost equally distributed onto the two atoms of the H center, which is quite different from the bulk H -center case. The other configuration with one of the F atoms of the H center located above the BaF2 (111) surface (case 0) has a more polarized charge distribution as compared to that obtained in the bulk case and case 1. The calculation on total energies of different surface H -center configurations implies that H centers have a trend to locate near the surface. The creation of a surface H center in BaF2 results in a new β -hole band located at the Γ point 3.99 and 2.70 eV, for the cases 0 and 1, respectively, above the top of valence bands. According to our calculations on density of states, the constituents of the defect bands are cleared and the β -hole band is primarily composed of pz orbitals localized on the H center. © 2010 The American Physical Society.

Yang F.,Beijing Institute of Technology | Kou S.-P.,Beijing Normal University | Weng Z.-Y.,Tsinghua University
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

We study collective spin excitations of a magnetically ordered state in a multicomponent system composed of both itinerant electrons and local moments. Here the induced spin-density-wave (SDW) ordering of itinerant electrons and the collinear antiferromagnetic ordering of local moments are locked together via a Hund's rule coupling. We show that the Goldstone theorem still holds at the random-phase approximation level with the gapless spin wave protected inside the small SDW gap of itinerant electrons, which, however, is fragile in the presence of ion anisotropy. A gapped "out-of-phase" spin mode extending over a much wider energy scale above the SDW gap is found to be more robust against the ion anisotropy, which is mainly contributed by the local moment fluctuations. While the scattering between the Goldstone mode and itinerant electrons diminishes within the SDW gap, the out-of-phase mode will strongly interact with itinerant electrons and thus dominate the spin and charge dynamics in such an ordered phase. Possible relevance of such a model to the iron pnictides will be also discussed. © 2010 The American Physical Society.

Liu N.,Beijing Institute of Technology
Sensors (Basel, Switzerland) | Year: 2013

The bell-shaped vibratory angular rate gyro (abbreviated as BVG) is a novel shell vibratory gyroscope, which is inspired by the Chinese traditional bell. It sensitizes angular velocity through the standing wave precession effect. The bell-shaped resonator is a core component of the BVG and looks like the millimeter-grade Chinese traditional bell, such as QianLong Bell and Yongle Bell. It is made of Ni43CrTi, which is a constant modulus alloy. The exciting element, control element and detection element are uniformly distributed and attached to the resonator, respectively. This work presents the design, analysis and experimentation on the BVG. It is most important to analyze the vibratory character of the bell-shaped resonator. The strain equation, internal force and the resonator's equilibrium differential equation are derived in the orthogonal curvilinear coordinate system. When the input angular velocity is existent on the sensitive axis, an analysis of the vibratory character is performed using the theory of thin shells. On this basis, the mode shape function and the simplified second order normal vibration mode dynamical equation are obtained. The coriolis coupling relationship about the primary mode and secondary mode is established. The methods of the signal processing and control loop are presented. Analyzing the impact resistance property of the bell-shaped resonator, which is compared with other shell resonators using the Finite Element Method, demonstrates that BVG has the advantage of a better impact resistance property. A reasonable means of installation and a prototypal gyro are designed. The gyroscopic effect of the BVG is characterized through experiments. Experimental results show that the BVG has not only the advantages of low cost, low power, long work life, high sensitivity, and so on, but, also, of a simple structure and a better impact resistance property for low and medium angular velocity measurements.

Wang K.,Beijing Institute of Technology | Wang K.,Energy and Environmental Research Center | Yu S.,Energy and Environmental Research Center | Yu S.,University of Management and Economics | Zhang W.,University of Jinan
Mathematical and Computer Modelling | Year: 2013

Data envelopment analysis (DEA) has recently become a popular approach in measuring the energy and environmental performance at the macro-economy level. A common limitation of several previous studies is that they ignored the undesirable outputs and did not consider the separation of inputs into energy resources and non-energy resources under the DEA framework. Thus, within a joint production framework of considering both desirable and undesirable outputs, as well as energy and non-energy inputs, this study analyzes China's regional total-factor energy and environmental efficiency. This paper utilizes improved DEA models to measure the energy and environmental efficiency of 29 administrative regions of China during the period of 2000-2008. In addition, the DEA window analysis technique is applied to measure the efficiency in cross-sectional and time-varying data. The empirical results show that the east area of China has the highest energy and environmental efficiency, while the efficiency of the west area is worst. All three areas of China have similar trends in the variation of efficiency and in general the energy and environmental efficiency of China slightly increased from 2000 to 2008. The regions of the east area have a more balanced development than the regions of the central area and west area according to energy and environmental efficiency. © 2011 Elsevier Ltd.

Shen Y.,Tianshui Normal University | Shen Y.,Beijing Institute of Technology
Fuzzy Sets and Systems | Year: 2015

In this paper we investigate, under some suitable conditions and generalized differentiability, the Ulam stability problems of three variants of first order linear fuzzy differential equations, respectively. © 2015 Elsevier B.V.

Xing Y.,University of Hong Kong | Xing Y.,Beijing Institute of Technology | Wang B.,University of Hong Kong | Wang J.,University of Hong Kong
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

We report a computationally tractable approach to first-principles investigation of time-dependent current of molecular devices under a steplike pulse. For molecular devices, all the resonant states below Fermi level contribute to the time-dependent current. Hence calculation beyond wideband limit must be carried out for a quantitative analysis of transient dynamics of molecules devices. Based on the exact nonequilibrium Green's-function (NEGF) formalism of calculating the transient current, we develop two approximate schemes going beyond the wideband limit, they are all suitable for first-principles calculation using the NEGF combined with density-functional theory. Benchmark test has been done by comparing with the exact solution of a single level quantum dot system. Good agreement has been reached for two approximate schemes. As an application, we calculate the transient current using the first approximated formula with opposite voltage VL (t) =- VR (t) in two molecular structures: Al-C5 -Al and Al-C60 -Al. As illustrated in these examples, our formalism can be easily implemented for real molecular devices. Importantly, our new formula has captured the essential physics of dynamical properties of molecular devices and gives the correct steady state current at t=0 and t→∞. © 2010 The American Physical Society.

Xiong J.,Beijing Institute of Technology | Huang S.,Tsinghua University | Zhang Y.,Tsinghua University
PLoS ONE | Year: 2012

The diffusion coefficient (Dm) and material/air partition coefficient (K) are two key parameters characterizing the formaldehyde and volatile organic compounds (VOC) sorption behavior in building materials. By virtue of the sorption process in airtight chamber, this paper proposes a novel method to measure the two key parameters, as well as the convective mass transfer coefficient (hm). Compared to traditional methods, it has the following merits: (1) the K, Dm and hm can be simultaneously obtained, thus is convenient to use; (2) it is time-saving, just one sorption process in airtight chamber is required; (3) the determination of hm is based on the formaldehyde and VOC concentration data in the test chamber rather than the generally used empirical correlations obtained from the heat and mass transfer analogy, thus is more accurate and can be regarded as a significant improvement. The present method is applied to measure the three parameters by treating the experimental data in the literature, and good results are obtained, which validates the effectiveness of the method. Our new method also provides a potential pathway for measuring hm of semi-volatile organic compounds (SVOC) by using that of VOC. © 2012 Xiong et al.

Sutton J.E.,University of Delaware | Guo W.,University of Delaware | Guo W.,Beijing Institute of Technology | Katsoulakis M.A.,University of Massachusetts Amherst | Vlachos D.G.,University of Delaware
Nature Chemistry | Year: 2016

Kinetic models based on first principles are becoming common place in heterogeneous catalysis because of their ability to interpret experimental data, identify the rate-controlling step, guide experiments and predict novel materials. To overcome the tremendous computational cost of estimating parameters of complex networks on metal catalysts, approximate quantum mechanical calculations are employed that render models potentially inaccurate. Here, by introducing correlative global sensitivity analysis and uncertainty quantification, we show that neglecting correlations in the energies of species and reactions can lead to an incorrect identification of influential parameters and key reaction intermediates and reactions. We rationalize why models often underpredict reaction rates and show that, despite the uncertainty being large, the method can, in conjunction with experimental data, identify influential missing reaction pathways and provide insights into the catalyst active site and the kinetic reliability of a model. The method is demonstrated in ethanol steam reforming for hydrogen production for fuel cells. © 2016 Macmillan Publishers Limited. All rights reserved.

Li Z.,South China University of Technology | Xia Y.,Beijing Institute of Technology
International Journal of Robust and Nonlinear Control | Year: 2014

In this paper, adaptive NN control is proposed for bilateral teleoperation system with dynamic uncertainties, unknown external disturbances, and unsymmetrical stochastic delays in communication channel to achieve transparency and robust stability. Compared with previous passivity-based teleoperation framework, the communication delays are unsymmetrical and stochastic. By partial feedback linearization using nominal dynamics, the nonlinear dynamics of the teleoperation system are transformed into two subsystems: local master/slave dynamics control and time-delay motion tracking. By integrating Markov jump systems and adaptive parameters updating, adaptive NN control strategy is developed. The stability of the closed-loop system and the boundedness of tracking errors are proved using Lyapunov-Krasovskii functional synthesis under specific linear matrix inequalities conditions. The proposed adaptive NN control is robust against motion disturbances, parametric uncertainties, and unsymmetrical stochastic delay, which effectiveness is validated by extensive simulation studies. Copyright © 2013 John Wiley & Sons, Ltd.

Ma J.,Beijing Institute of Technology | Ma J.,University of Tokyo | Hashimoto K.,University of Tokyo | Koganezawa T.,Japan Synchrotro