Beijing, China

Beijing Jiaotong University , formerly Northern Jiaotong University , is one of the oldest universities in mainland China. The main campus is located close to Xizhimen, central Beijing. The university's abbreviated name which locals usually call it by is JiaoDa . JiaoDa is a participant in the Ministry of Education's Project 211. Wikipedia.

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Beijing Jiaotong University | Date: 2016-07-28

Embodiments of the present invention provide a train control method for maximizing utilization of regenerative energy. The method mainly comprises: working out a matching error T of a current matched pair of trains Mx (i, j) of a station in the current running situation; and comparing the matching error T with a preset maximum adjustable error T_(x )of the current matched pair of trains Mx (i, j) of the station and determining a strategy for adjusting train running of the current matched pair of trains Mx (i, j) according to comparison results.

Liu C.,Beijing Jiaotong University | Yao Y.,Beijing Jiaotong University
Journal of Mechanisms and Robotics | Year: 2012

A family of biped spatial four-link mechanisms with two revolute and two cylindric joints is proposed in this paper. Three main categories, including eight configurations are put forward. The primary feature of these mechanisms is that they are made up of four links that are connected end to end through two revolute and cylindric joints, and among the links, two of them are designed as feet. These novel configurations are revealed by different methods and ways: The basic configurations are enumerated by traditional mechanism synthesis method; the conventional configurations are obtained by repetitious trial; the unique configurations are accidentally achieved by inspiration or intuition. Each of them has its own characteristic and can be an alternative option for biped robot design. Compared with most of the existing biped mechanisms, these configurations are simpler in structure and thus easier to control. The singular configuration is cleverly used rather than avoided to perform the walking and turning. Their structure descriptions and walking simulations are accomplished. Afterwards, the kinematic and stability analyses are studied, the design considerations are discussed, and foot-workspace analyses are carried out. Finally, four prototypes are developed to preliminary verify the feasibility of these proposed concepts. © 2012 American Society of Mechanical Engineers.

Zhang D.,Beijing Jiaotong University | Han Z.,Beijing Jiaotong University | Yan G.,Research Division
Proceedings of the ACM Conference on Computer and Communications Security | Year: 2010

Trusted computing technology aims to enhance the security of platform by the TPM. But there are some drawbacks of TCG's Trusted Computing architecture for user-based applications. This paper presents a new concept of portable TPM (PTM) based on USB Key to solve those problems. At first, we use PTM to establish a trusted path between the verifier and the user in remote attestation so as to propagate the trust chain to the end user. Secondly, we design the trust model and platform management mechanism of PTM. In this model the single point failure of TPM and frequent sensitive data migrations between different platforms are avoided based on PTM. At last, we implement the PTM on the USB Key with Java Card Runtime Environment. The test results show that the PTM scheme is feasible for user-based application.

Cheng X.,Peking University | Wang C.-X.,Shandong University | Wang C.-X.,Heriot - Watt University | Ai B.,Beijing Jiaotong University | Aggoune H.,University of Tabuk
IEEE Transactions on Intelligent Transportation Systems | Year: 2014

This paper proposes a generic geometry-based stochastic model for nonisotropic scattering vehicle-to-vehicle (V2V) Ricean fading channels. With the proposed model, the level crossing rate (LCR) and average fade duration (AFD) are derived. The resultant expressions are sufficiently general and subsume many well-known existing LCRs and AFDs as special cases. The derived LCR and AFD are further investigated in terms of some important parameters, e.g., the shape of the scattering region (two-ring or ellipse), mean angle, angle spread, and directions of movement of the Tx and Rx (same or opposite direction). More importantly, in this paper, the impact of the vehicular traffic density on the LCR and AFD for nonisotropic scattering V2V Ricean fading channels is investigated for the first time. Excellent agreement is observed between the theoretical LCRs/AFDs and corresponding measured data, thus demonstrating the validity and utility of the proposed model. © 2013 IEEE.

Meng Q.,National University of Singapore | Weng J.,Beijing Jiaotong University
Traffic Injury Prevention | Year: 2013

Objective: Taking into account the uncertainty caused by exogenous factors, the accident notification time (ANT) and emergency medical service (EMS) response time were modeled as 2 random variables following the lognormal distribution.Method: Their mean values and standard deviations were respectively formulated as the functions of environmental variables including crash time, road type, weekend, holiday, light condition, weather, and work zone type. Work zone traffic accident data from the Fatality Analysis Report System between 2002 and 2009 were utilized to determine the distributions of the ANT and the EMS arrival time in the United States. A mixed logistic regression model, taking into account the uncertainty associated with the ANT and the EMS response time, was developed to estimate the risk of death.Results: The results showed that the uncertainty of the ANT was primarily influenced by crash time and road type, whereas the uncertainty of EMS response time is greatly affected by road type, weather, and light conditions. In addition, work zone accidents occurring during a holiday and in poor light conditions were found to be statistically associated with a longer mean ANT and longer EMS response time. The results also show that shortening the ANT was a more effective approach in reducing the risk of death than the EMS response time in work zones.Conclusions: To shorten the ANT and the EMS response time, work zone activities are suggested to be undertaken during non-holidays, during the daytime, and in good weather and light conditions. © 2013 Copyright Taylor and Francis Group, LLC.

Zou Y.,Nanjing University of Posts and Telecommunications | Wang G.,Beijing Jiaotong University
IEEE Transactions on Industrial Informatics | Year: 2016

This paper studies the intercept behavior of an industrial wireless sensor network (WSN) consisting of a sink node and multiple sensors in the presence of an eavesdropping attacker, where the sensors transmit their sensed information to the sink node through wireless links. Due to the broadcast nature of radio wave propagation, the wireless transmission from the sensors to the sink can be readily overheard by the eavesdropper for interception purposes. In an information-theoretic sense, the secrecy capacity of the wireless transmission is the difference between the channel capacity of the main link (from sensor to sink) and that of the wiretap link (from sensor to eavesdropper). If the secrecy capacity becomes nonpositive due to the wireless fading effect, the sensor's data transmission could be successfully intercepted by the eavesdropper and an intercept event occurs in this case. However, in industrial environments, the presence of machinery obstacles, metallic frictions, and engine vibrations makes the wireless fading fluctuate drastically, resulting in the degradation of the secrecy capacity. As a consequence, an optimal sensor scheduling scheme is proposed in this paper to protect the legitimate wireless transmission against the eavesdropping attack, where a sensor with the highest secrecy capacity is scheduled to transmit its sensed information to the sink. Closed-form expressions of the probability of occurrence of an intercept event (called intercept probability) are derived for the conventional round-robin scheduling and the proposed optimal scheduling schemes. Also, an asymptotic intercept probability analysis is conducted to provide an insight into the impact of the sensor scheduling on the wireless security. Numerical results demonstrate that the proposed sensor scheduling scheme outperforms the conventional round-robin scheduling in terms of the intercept probability. © 2015 IEEE.

Zhu B.,Beijing Jiaotong University | Ren G.,Beijing Jiaotong University | Gao Y.,Beijing Jiaotong University | Yang Y.,Tianjin University of Technology | And 2 more authors.
Optics Express | Year: 2014

We propose in this paper a graphene-coated tapered nanowire probe providing strong field enhancement in the infrared regimes. The analytical field distributions and characteristic equation of the supported surface plasmons mode are derived. Based on the adiabatic approximation, analytic methods are adopted in the investigation of field enhancement along the tapered region and show well consistence with the rigorous numerical simulations. Both the numerical and analytical results have shown that the graphene-coated nanowire probe could achieve an order of magnitude larger field enhancement than the metal-coated probes. The proposed probe may have promising applications for single molecule detection, measurement and nano-manipulation techniques. ©2014 Optical Society of America.

Shu W.,Beijing Jiaotong University | Shen H.,Beijing Jiaotong University | Shen H.,University of Adelaide
International Journal of Approximate Reasoning | Year: 2014

In rough set theory, attribute reduction is a challenging problem in the applications in which data with numbers of attributes available. Moreover, due to dynamic characteristics of data collection in decision systems, attribute reduction will change dynamically as attribute set in decision systems varies over time. How to carry out updating attribute reduction by utilizing previous information is an important task that can help to improve the efficiency of knowledge discovery. In view of that attribute reduction algorithms in incomplete decision systems with the variation of attribute set have not yet been discussed so far. This paper focuses on positive region-based attribute reduction algorithm to solve the attribute reduction problem efficiently in the incomplete decision systems with dynamically varying attribute set. We first introduce an incremental manner to calculate the new positive region and tolerance classes. Consequently, based on the calculated positive region and tolerance classes, the corresponding attribute reduction algorithms on how to compute new attribute reduct are put forward respectively when an attribute set is added into and deleted from the incomplete decision systems. Finally, numerical experiments conducted on different data sets from UCI validate the effectiveness and efficiency of the proposed algorithms in incomplete decision systems with the variation of attribute set. © 2013 Elsevier Inc.

Zhang R.,Beijing Jiaotong University | He R.,Peking University | Zhang X.,Harbin Institute of Technology | Fang D.,Peking University
International Journal of Refractory Metals and Hard Materials | Year: 2014

ZrB2-SiC ceramic composites were prepared through water-based gelcasting and pressureless sintering. Effects of the pressureless sintering temperature (1500-2000 C), heating rate (5-15 C/min) and soaking time (0.5-2 h) on the relative density, microstructure and mechanical properties of the ZrB2-SiC composites were investigated in detail. A sintering temperature of 2000 C, a heating rate of 5 C/min and a soaking time of 2 h were found to be the optimal pressureless sintering procedure. The relative density, flexural strength and fracture toughness of the ZrB2-SiC composite prepared under the optimum condition were 97.8%, 403.1 ± 27.8 MPa and 4.05 ± 0.42 MPa·m1/2, respectively. © 2013 Elsevier Ltd.

He R.,Peking University | Zhang R.,Beijing Jiaotong University | Pei Y.,Peking University | Fang D.,Beijing Jiaotong University
International Journal of Refractory Metals and Hard Materials | Year: 2014

The densification and grain growth behaviors for micron- and nano-sized ZrB2 particles were investigated. The densification on-set temperature (Td-micron) and grain growth on-set temperature (T g-micron) for micron-sized ZrB2 particles were about 1500 °C and 1800 °C, respectively. And the densification on-set temperature (Td-nano) and grain growth on-set temperature (Tg-nano) for nano-sized ZrB2 particles were about 1300 °C and 1500 °C, respectively. A bimodal micron/nano-ZrB2 ceramic was therefore prepared using a novel two-step hot pressing. A high relative density of 99.2%, an improved flexural strength of 580.2 ± 35.8 MPa and an improved fracture toughness of 7.2 ± 0.4 MPa·m1/2 were obtained. The measured critical thermal shock temperature difference (ΔT c) for this bimodal micron/nano-ZrB2 ceramic was as high as 433 °C. © 2014 Elsevier Ltd.

Bianchi E.,Perimeter Institute | Ding Y.,Beijing Jiaotong University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

The two-point correlation function is calculated in the Lorentzian Engle-Pereira-Rovelli-Livine spinfoam model and shown to match with the one in Regge calculus in a proper limit: large boundary spins j→ and small Barbero-Immirzi parameter γ→0, keeping the size of the quantum geometry A∼γj finite and fixed. Compared to the Euclidean case, the definition of a Lorentzian boundary state involves a new feature: the notion of past- and future-pointing intertwiners. The semiclassical correlation function is obtained for a time-oriented semiclassical boundary state. © 2012 American Physical Society.

Wu D.,University of Aalborg | Tang F.,Beijing Jiaotong University | Dragicevic T.,University of Aalborg | Guerrero J.M.,University of Aalborg | Vasquez J.C.,University of Aalborg
IEEE Transactions on Smart Grid | Year: 2015

A low-voltage islanded dc microgrid contains a number of renewable energy sources, local loads, and energy storage systems (ESS). To avoid the over-charging and over-discharging situations of ESS, a coordinated control strategy should be used in islanded dc microgrids. In this paper, a novel bus-signaling method (BSM) is proposed to achieve autonomous coordinated performance of system according to different state of charge conditions. Additionally, a secondary coordinated control is introduced to restore the voltage deviation produced by primary control level without decaying coordinated performance. The proposed control algorithm and controller implementation based on BSM are also presented. Finally, real-time simulation results show the feasibility of the proposed approach by presenting the operation of an islanded dc microgrid in different testing scenarios. © 2010-2012 IEEE.

Zhang C.,Beijing Jiaotong University | Chai Y.,Peking University
Habitat International | Year: 2014

Much like other post-socialist cities, Chinese cities experienced dramatic changes after economic reform. The danwei, or state-owned work unit, was once a fundamental building block of Chinese cities. In addition to being the basic form of economic and social organization, danwei communities defined Chinese urban development before reform, taking the form of gated, walled-off combined factory and residential areas. This paper focuses on spatial changes at the neighborhood scale in danwei, by selecting the Tongrentang pharmaceutical factory in Beijing, China during the time period between 1973 and 2006 as a case study. Through archival material and interviews, this paper describes how the community changed from gated, boring, solidified and strictly constrained work units to un-gated, vibrant, mixed-use and flexible urban neighborhoods. This case study in urban China provides implications for planning professionals and policy makers. By properly redeveloping these brownfield, traditional danwei communities many change to become un-gated, livable, accessible, integrated, and sustainable in the post-socialist era. The implication for current transition theory is that despite the similarity to Central and East European countries, urban China has a local context and unique spatial changes that should be embraced in future transition studies. © 2014 Elsevier Ltd.

Xu W.,Nanjing Southeast University | Xu W.,Beijing Jiaotong University | Dong X.,University of Victoria
IEEE Transactions on Signal Processing | Year: 2012

This correspondence considers a MIMO relay downlink system using precoding and limited feedback. Since the conventional precoding matrices are directly obtained by treating the quantized channel state information (CSI) feedback as real CSI, we propose an optimized relay precoding strategy by taking both effects of channel quantization error and feedback delay into account. Conditioned on the outdated CSI quantization available at the relay station, the relay precoding is optimized via minimizing an expected mean-square error (MSE) criterion over CSI mismatches. By using Karush-Kuhn-Tucker (KKT) conditions, a closed-form solution to the relay design is achieved with comparable computational complexity relative to the conventional approach. Numerical results verify the effectiveness of the proposed scheme. © 1991-2012 IEEE.

Meng Q.,National University of Singapore | Weng J.,Beijing Jiaotong University
Transportation Research Part C: Emerging Technologies | Year: 2013

To mitigate the negative traffic impact caused by work zones, land transport authorities usually impose constraints on queue length and travel delay. In reality, a single or multiple subwork zone strategy can be adopted to mitigate queue length and travel delay. However, contractors conducting work projects are only concerned with the minimization of the total maintenance cost. From the contractor's standpoint, this study proposes a total maintenance cost minimization model to determine the optimal subwork zone length and project start time, subject to queue length and travel delay constraints. Using average hourly traffic (AHT) data, this study shows that total user delay is non-differentiable with respect to the subwork zone length and project start time. This interesting finding demonstrates that previous analytic expressions of the optimal subwork zone length cannot hold for AHT data. To solve the proposed model, an enumeration method is designed. Finally, a numerical example created from the roadside tree trimming in Singapore is used to assess the model and solution method proposed in this study. © 2013 Elsevier Ltd.

Shen C.,Beijing Jiaotong University | Chang T.-H.,University of California at Davis | Wang K.-Y.,National Tsing Hua University | Qiu Z.,Beijing Jiaotong University | Chi C.-Y.,National Tsing Hua University
IEEE Transactions on Signal Processing | Year: 2012

Multicell coordinated beamforming (MCBF), where multiple base stations (BSs) collaborate with each other in the beamforming design for mitigating the intercell interference (ICI), has been a subject drawing great attention recently. Most MCBF designs assume perfect channel state information (CSI) of mobile stations (MSs); however CSI errors are inevitable at the BSs in practice. Assuming elliptically bounded CSI errors, this paper studies the robust MCBF design problem that minimizes the weighted sum power of BSs subject to worst-case signal-to-interference-plus-noise ratio (SINR) constraints on the MSs. Our goal is to devise a distributed optimization method to obtain the worst-case robust beamforming solutions in a decentralized fashion with only local CSI used at each BS and limited backhaul information exchange between BSs. However, the considered problem is difficult to handle even in the centralized form. We first propose an efficient approximation method for solving the nonconvex centralized problem, using semidefinite relaxation (SDR), an approximation technique based on convex optimization. Then a distributed robust MCBF algorithm is further proposed, using a distributed convex optimization technique known as alternating direction method of multipliers (ADMM). We analytically show the convergence of the proposed distributed robust MCBF algorithm to the optimal centralized solution. We also extend the worst-case robust beamforming design as well as its decentralized implementation method to a fully coordinated scenario. Simulation results are presented to examine the effectiveness of the proposed SDR method and the distributed robust MCBF algorithm. © 2012 IEEE.

Lu X.,Beijing Jiaotong University | Li J.,Beijing Normal University | Li J.,Demonstration Center
Nonlinear Dynamics | Year: 2014

With symbolic computation, this paper investigates some integrable properties of a two-dimensional generalization of the Korteweg-de Vries equation, i.e., the Bogoyavlensky-Konoplechenko model, which can govern the interaction of a Riemann wave propagating along the y y -axis and a long wave propagating along the x x -axis. Within the framework of Bell-polynomial manipulations, Bell-polynomial expressions are firstly given, which then are cast into bilinear forms. The N N -soliton solutions in the form of an N N th-order polynomial in the N N exponentials and in terms of the Wronskian determinant are, respectively, constructed with the Hirota bilinear method and Wronskian technique. Bilinear Bäcklund transformation is also derived with the achievement of a family of explicit solutions. © 2014 Springer Science+Business Media Dordrecht.

Chen X.,Beijing Jiaotong University | Phoon K.-K.,National University of Singapore | Toh K.-C.,National University of Singapore
International Journal of Geomechanics | Year: 2012

Biot's symmetric indefinite linear systems of equations are commonly encountered in finite-element computations of geotechnical problems. The development of efficient solution methods for Biot's linear systems of equations is of practical importance to geotechnical software packages. In conjunction with the Krylov-subspace iterative method symmetric quasi-minimal residual (SQMR), some zero-level fillin incomplete factorization preconditioning techniques including a symmetric successive overrelaxation (SSOR) type method and several zerolevel incomplete LU 1/2ILU(0) methods are investigated and compared for Biot's symmetric indefinite linear systems of equations. Numerical experiments are carried out based on three practical geotechnical problems. Numerical results indicate that ILU(0) preconditioners are classical and generally efficient when adequately stabilized. However, the tunnel problem provides a counterexample demonstrating that ILU(0) preconditioners cannot be fully stabilized by preliminary scaling, reordering, making use of perturbed matrices, or dynamically selecting pivots. Compared with the investigated ILU(0) preconditioners, the recently proposed modified SSOR preconditioner is less efficient but is robust over the range of problems studied. © 2012 American Society of Civil Engineers.

Xiong K.,Beijing Jiaotong University | Fan P.,Tsinghua National Laboratory for Information Sciences and Technology | Yang H.-C.,University of Victoria | Letaief K.B.,Hong Kong University of Science and Technology
IEEE Transactions on Wireless Communications | Year: 2014

Space time network coding (STNC) is a recently proposed time-division multiple-access (TDMA)-based cooperative relaying scheme for multi-relay wireless systems, which can achieve full diversity order with low transmission delay by taking advantage of the concepts of network coding and distributed space time coding. However, STNC does not fully exploit the benefit of the broadcast nature of wireless channels, since it only allows relays to receive signals from the sources. To explore the potential capacity of STNC-based systems, in this paper, we propose a new cooperative relaying scheme, termed space-time network coding with overhearing relays (STNC-OR), by allowing each relay to collect the signals transmitted from not only the sources but also its previous relays. Then, we derive some explicit expressions for the outage probability and symbol error rate (SER) for STNC-OR with decode-and-forward relaying over independent non-identically distributed (i.n.i.d) Rayleigh fading channels. For comparison, we also derive the explicit expression of the outage probability for STNC. To further improve the performance of STNC-OR, we investigate the effect of relay ordering on the performance of STNC-OR and then present the optimal relay ordering algorithm. Further, a suboptimal relay ordering is also designed to reduce the complexity. Extensive simulation and numerical results are presented finally to validate our theoretical analysis. It is shown that the proposed STNC-OR achieves much lower outage probability and SER than STNC and traditional pure TDMA relaying schemes. © 2014 IEEE.

Shen H.,Beijing Jiaotong University | Shen H.,University of Adelaide | Chen B.,Cooperation Technology
Computers and Electrical Engineering | Year: 2012

Watermarking as a powerful technique for copyright protection, content verification, covert communication and so on, has been studied for years, and is drawing more and more attention recently. There are many situations in which embedding multiple watermarks in an image is desired. This paper proposes an effective approach to embed dual watermarks by extending the single watermarking algorithms in Xie and Shen (2005) [1] and Xie and Shen (2006) [2] for numerical and logo watermarking, respectively. Experimental results show that the resulting dual watermarking algorithms have a significantly higher PSNR than existing dual watermarking algorithms and also retain the same robustness as and higher sensitivity than the original single watermarking algorithms on which they are based. © 2012 Elsevier Ltd. All rights reserved.

Zhao Z.-H.,Beijing Jiaotong University | Zhao Z.-H.,Shijiazhuang University | Yang S.-P.,Shijiazhuang University
Zhendong yu Chongji/Journal of Vibration and Shock | Year: 2012

The nonlinear dynamic parameter sample entropy was used as a feature for roller bearing fault diagnosis. Vibration signals for normal bearings, those with inner race fault, ball one, and outer race one were used for analysis and diagnosis. The sample entropy of the original vibration signal could be analyzed only in one scale, but information about the characteristics of the vibration signal in different scales could give important information about the fault. A sample entropy method based on ensemble empirical mode decomposition (EEMD) was proposed here. Firstly, the original roller bearing vibration signal was decomposed with EEMD and the intrinsic mode functions containing the most information were chosen to calculate the sample entropy to form a feature vector. Then, SVM method was used as a classifier to identify different faults. Thus, the vibration signal could be analyzed in different scales to give more information about fault. Experimental results with real roller bearing data showed that the proposed method is effective.

Liu Y.C.,Peking University | Xu Z.F.,Tsinghua University | Jin G.R.,Beijing Jiaotong University | You L.,Tsinghua University
Physical Review Letters | Year: 2011

Squeezed spin states possess unique quantum correlation or entanglement and are significantly promising for advancing quantum information processing and quantum metrology. In recent back-to-back publications, reduced spin fluctuations are observed leading to spin squeezing at -8.2 and -2.5dB, respectively, in two-component atomic condensates exhibiting one-axis-twisting interactions. The noise reduction limit for the one-axis twisting scales as 1/N2/3, which for a condensate with N∼103 atoms is about 100 times below the standard quantum limit. We present a scheme using repeated Rabi pulses capable of transforming the one-axis-twisting spin squeezing into the two-axis-twisting type, leading to Heisenberg limited noise reduction 1/N or an extra tenfold improvement for N∼103. © 2011 American Physical Society.

Cheng D.,Beijing Jiaotong University | Guo D.,Guangdong University of Technology
Information Sciences | Year: 2013

The hypercube is one of the best known interconnection networks. Embedding cycles of all possible lengths in faulty hypercubes has received much attention. Let Fv (respectively, Fe) denote the set of faulty vertices (respectively, faulty edges) and fv (respectively, f e) denote the number of faulty vertices (respectively, faulty edge) in an n-dimensional hypercube Qn. Let f(e) denote the number of faulty nodes and/or faulty edges incident with the end-vertices of an edge e â̂̂ E(Qn). In this paper, we assume that each node is incident with at least three fault-free neighbors and at least three fault-free edges. Under this assumption, we show that every fault-free edge lies on a fault-free cycle of every even length from 4 to 2n - 2|Fv| if |Fv| + |Fe| ≤ 2n - 7 and f(e) ≤ n - 2, where n ≥ 5. Under our condition, our result not only improves the previously best known result of Hsieh et al. [S.-Y. Hsieh, T.-H. Shen, Edge-bipancyclicity of a hypercube with faulty vertices and edges, Discrete Applied Mathematics 156 (10) (2008) 1802-1808] where fv + fe ≤ n - 2 was assumed, but also extends the result of Tsai [C.-H. Tsai, Linear array and ring embedding in conditional faulty hypercubes, Theoretical Computer Science 314 (3) (2004) 431-443] where only the faulty edges were considered and Tsai [C.-H. Tsai, Cycle embedding in hypercubes with node failures, Information Processing Letters 102 (6) (2007) 242-246] where only the faulty vertices were considered. © 2013 Elsevier Inc. All rights reserved. © 2013 Elsevier Inc. All rights reserved.

Yin C.,Beijing Jiaotong University | Xu J.-X.,National University of Singapore | Hou Z.,Beijing Jiaotong University
IEEE Transactions on Automatic Control | Year: 2010

In this technical note, we propose a new iterative learning control (ILC) scheme for nonlinear systems with parametric uncertainties that are temporally and iteratively varying. The time-varying characteristics of the parameters are described by a set of unknown basis functions that can be any continuous functions. The iteratively varying characteristics of the parameters are described by a high-order internal model (HOIM) that is essentially an auto-regression model in the iteration domain. The new parametric learning law with HOIM is designed to effectively handle the unknown basis functions. The method of composite energy function is used to derive convergence properties of the HOIM-based ILC, namely the pointwise convergence along the time axis and asymptotic convergence along the iteration axis. Comparing with existing ILC schemes, the HOIM-based ILC can deal with nonlinear systems with more generic parametric uncertainties that may not be repeatable along the iteration axis. The validity of the HOIM-based ILC under identical initialization condition (i.i.c.) and the alignment condition is also explored. © 2006 IEEE.

Shu W.,Beijing Jiaotong University | Shen H.,Sun Yat Sen University | Shen H.,University of Adelaide
Pattern Recognition | Year: 2014

Feature selection plays a vital role in many areas of pattern recognition and data mining. The effective computation of feature selection is important for improving the classification performance. In rough set theory, many feature selection algorithms have been proposed to process static incomplete data. However, feature values in an incomplete data set may vary dynamically in real-world applications. For such dynamic incomplete data, a classic (non-incremental) approach of feature selection is usually computationally time-consuming. To overcome this disadvantage, we propose an incremental approach for feature selection, which can accelerate the feature selection process in dynamic incomplete data. We firstly employ an incremental manner to compute the new positive region when feature values with respect to an object set vary dynamically. Based on the calculated positive region, two efficient incremental feature selection algorithms are developed respectively for single object and multiple objects with varying feature values. Then we conduct a series of experiments with 12 UCI real data sets to evaluate the efficiency and effectiveness of our proposed algorithms. The experimental results show that the proposed algorithms compare favorably with that of applying the existing non-incremental methods. © 2014 Elsevier Ltd.

Weng J.,Beijing Jiaotong University | Meng Q.,National University of Singapore
Transportation Research Part C: Emerging Technologies | Year: 2013

This paper presents a review of the approaches to estimating the work zone operational issues: capacity and traffic delay in work zones. It first explores the factors affecting work zone capacity and then critically reviews three types of approaches including parametric, non-parametric and simulation approaches to estimating work zone capacity. Subsequently, a detailed critical review of the three types of approaches for traffic delay estimation in work zones is presented. Finally, it provides some directions and recommendations for the future research. © 2013 Elsevier Ltd.

Ye H.,Beijing Jiaotong University | Ye H.,Beijing Institute of Biotechnology | Ye H.,Shanghai University
Oncogene | Year: 2014

Although the activation of Ras pathway is frequently observed in human hepatocellular carcinoma (HCC), the in vivo role of Ras activation in HCC initiation and progression is underdetermined. To test the consequence of Kras activation in hepatocyte, we generated a hepatocyte-specific Kras(G12D) transgenic mouse strain and observed spontaneous development of HCC in these mice. Remarkably, HBV X protein (HBx) expression significantly promotes the formation and malignant progression of Kras(G12D)-driven HCC as shown with the accelerated tumor onset, the increased tumor burden and the more poorly differentiated lesions. At the cellular level, concomitant expression of Kras(G12D) and HBx results in a robust increase in hepatocellular proliferation. We reveal that the Akt, MAPK, p53 and TGF-β pathways are deregulated in the Kras(G12D)-driven HCCs. Also, the dysregulation is more pronounced in the HCCs developed in Kras(G12D) and HBx double transgenic mice. In addition, the altered expressions of β-catenin, CD44 and E-cadherin are only observed in the Kras(G12D) and HBx double transgenic mice. These results demonstrate a crucial role of Ras activation in hepatocellular carcinogenesis and the functional synergy between Kras(G12D) and HBx in HCC initiation and progression. The novel genetic mouse models that closely recapitulate the histopathologic progression and molecular alterations of human HCC may potentially facilitate the future therapeutic studies.

Weng J.,Beijing Jiaotong University | Meng Q.,National University of Singapore | Yan X.,Beijing Jiaotong University
Accident Analysis and Prevention | Year: 2014

This study evaluates rear-end crash risk associated with work zone operations for four different vehicle-following patterns: car-car, car-truck, truck-car and truck-truck. The deceleration rate to avoid the crash (DRAC) is adopted to measure work zone rear-end crash risk. Results show that the car-truck following pattern has the largest rear-end crash risk, followed by truck-truck, truck-car and car-car patterns. This implies that it is more likely for a car which is following a truck to be involved in a rear-end crash accident. The statistical test results further confirm that rear-end crash risk is statistically different between any two of the four patterns. We therefore develop a rear-end crash risk model for each vehicle-following pattern in order to examine the relationship between rear-end crash risk and its influencing factors, including lane position, the heavy vehicle percentage, lane traffic flow and work intensity which can be characterized by the number of lane reductions, the number of workers and the amount of equipment at the work zone site. The model results show that, for each pattern, there will be a greater rear-end crash risk in the following situations: (i) heavy work intensity; (ii) the lane adjacent to work zone; (iii) a higher proportion of heavy vehicles and (iv) greater traffic flow. However, the effects of these factors on rear-end crash risk are found to vary according to the vehicle-following patterns. Compared with the car-car pattern, lane position has less effect on rear-end crash risk in the car-truck pattern. The effect of work intensity on rear-end crash risk is also reduced in the truck-car pattern. © 2014 Elsevier Ltd.

Weng J.,Beijing Jiaotong University | Meng Q.,National University of Singapore | Fwa T.F.,National University of Singapore
Transportmetrica A: Transport Science | Year: 2014

This study investigates work zone vehicle headway distribution by disaggregating the vehicle headways into four types: car-car, car-truck, truck-car and truck-truck. It first confirms that the four types of vehicle headways are significantly different by performing the Kruskal-Wallis and Mann-Whitney tests using work zone headway data from Singapore. The statistical test results further show that four factors - traffic flow rate, percentage of trucks, work intensity and lane position - have a significant impact on each type of vehicle headway in work zones. A useful methodology is thus proposed to determine the best-fitted headway distribution model for each type, which includes two procedures: determining the best distribution pattern for each type using the maximum-likelihood estimation and Kolmogorov-Smirnov test techniques and formulating the distribution model parameters as a function of the aforementioned four factors. © 2013 © 2013 Hong Kong Society for Transportation Studies Limited.

Lang C.,Beijing Jiaotong University | Liu G.,National University of Singapore | Yu J.,Beijing Jiaotong University | Yan S.,National University of Singapore
IEEE Transactions on Image Processing | Year: 2012

This paper addresses the problem of detecting salient areas within natural images. We shall mainly study the problem under unsupervised setting, i.e., saliency detection without learning from labeled images. A solution of multitask sparsity pursuit is proposed to integrate multiple types of features for detecting saliency collaboratively. Given an image described by multiple features, its saliency map is inferred by seeking the consistently sparse elements from the joint decompositions of multiple-feature matrices into pairs of low-rank and sparse matrices. The inference process is formulated as a constrained nuclear norm and as an ℓ 2, 1-norm minimization problem, which is convex and can be solved efficiently with an augmented Lagrange multiplier method. Compared with previous methods, which usually make use of multiple features by combining the saliency maps obtained from individual features, the proposed method seamlessly integrates multiple features to produce jointly the saliency map with a single inference step and thus produces more accurate and reliable results. In addition to the unsupervised setting, the proposed method can be also generalized to incorporate the top-down priors obtained from supervised environment. Extensive experiments well validate its superiority over other state-of-the-art methods. © 2011 IEEE.

Li Y.,Beijing Jiaotong University | Shen H.,Sun Yat Sen University | Shen H.,University of Adelaide
IEEE Transactions on Information Forensics and Security | Year: 2013

Data publishing based on hypergraphs is becoming increasingly popular due to its power in representing multirelations among objects. However, security issues have been little studied on this subject, while most recent work only focuses on the protection of relational data or graphs. As a major privacy breach, identity disclosure reveals the identification of entities with certain background knowledge known by an adversary. In this paper, we first introduce a novel background knowledge attack model based on the property of hyperedge ranks, and formalize the rank-based hypergraph anonymization problem. We then propose a complete solution in a two-step framework: rank anonymization and hypergraph reconstruction. We also take hypergraph clustering (known as community detection) as data utility into consideration, and discuss two metrics to quantify information loss incurred in the perturbation. Our approaches are effective in terms of efficacy, privacy, and utility. The algorithms run in near-quadratic time on hypergraph size, and protect data from rank attacks with almost the same utility preserved. The performances of the methods have been validated by extensive experiments on real-world datasets as well. Our rank-based attack model and algorithms for rank anonymization and hypergraph reconstruction are, to our best knowledge, the first systematic study to privacy preserving for hypergraph-based data publishing. © 2005-2012 IEEE.

Lu Q.,University of California at Riverside | Lu Q.,Beijing Jiaotong University | Lu Z.,University of California at Riverside | Lu Y.,Beijing Jiaotong University | And 5 more authors.
Nano Letters | Year: 2013

A photocatalytic strategy has been developed to synthesize colloidal Ag-TiO2 nanorod composites in which each TiO2 nanorod contains a single Ag nanoparticle on its surface. In this rational synthesis, photoexcitation of TiO2 nanorods under UV illumination produces electrons that reduce Ag(I) precursor and deposit multiple small Ag nanoparticles on the surface of TiO2 nanorods. Prolonged UV irradiation induces an interesting ripening process, which dissolves the smaller nanoparticles by photogenerated oxidative species and then redeposits Ag onto one larger and more stable particle attached to each TiO2 nanorod through the reduction of photoexcited electrons. The size of the Ag nanoparticles can be precisely controlled by varying the irradiation time and the amount of alcohol additive. The Ag-TiO2 nanorod composites were used as electron transport layers in the fabrication of organic solar cells and showed notable enhancement in power conversion efficiency (6.92%) than pure TiO2 nanorods (5.81%), as well as higher external quantum efficiency due to improved charge separation and transfer by the presence of Ag nanoparticles. © 2013 American Chemical Society.

Hou Z.,Beijing Jiaotong University | Yan J.,Beijing Jiaotong University | Xu J.-X.,National University of Singapore | Li Z.,CAS Institute of Automation
IEEE Transactions on Intelligent Transportation Systems | Year: 2012

For a freeway traffic system with strict repeatable pattern, iterative learning control (ILC) has been successfully applied to local ramp metering for a macroscopic freeway environment by formulating the original ramp metering problem as an output tracking, disturbance rejection, and error compensation problem. In this paper, we address the freeway traffic ramp-metering system under a nonstrict repeatable pattern. ILC-based ramp metering and ILC add-on to ALINEA strategies are modified to deal with the presence of iteration-dependent parameters, iteration-dependent desired trajectory, and input constraints. Theoretical analysis and extensive simulations are used to verify the effectiveness of the proposed approaches. © 2011 IEEE.

Zhang L.L.,Beijing Jiaotong University | Liu J.X.,Shijiazhuang University | Fang X.Q.,Shijiazhuang University | Nie G.Q.,Shijiazhuang University
European Journal of Mechanics, A/Solids | Year: 2014

In this paper, the dispersion characteristics of elastic waves propagating in a monolayer piezoelectric nanoplate is investigated with consideration of the surface piezoelectricity as well as the nonlocal small-scale effect. Nonlocal electroelasticity theory is used to derive the general governing equations by introducing an intrinsic length, and the surface effects exerting on the boundary conditions of the piezoelectric nanoplate are taken into account through incorporation of the surface piezoelectricity model and the generalized Young-Laplace equations. The dispersion relations of elastic waves based on the current formulation are obtained in an explicit closed form. Numerical results show that both the nonlocal scale parameter and surface piezoelectricity have significant influence on the size-dependent properties of dispersion behaviors. It is also found that there exists an escape frequency above which the waves may not propagate in the piezoelectric plate with nanoscale thickness. © 2014 Elsevier Masson SAS. All rights reserved.

Zhang Y.,Beijing Jiaotong University | Du Y.,Shijiazhuang University | Sun B.,Shijiazhuang University
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2014

Temperature distribution in the roadbed and neighboring soil of high-speed railway (HSR) in seasonally frozen regions has significant influence on the stability of roadbed. The temperature distributions at the toe of slope, a short distance away from the road and at different locations in the roadbed were analyzed based on the results of three years monitoring and the atmospheric temperature data at Shuangcheng district from Harbin-Dalian HSR. Formulae of temperature estimation of different locations and depths were established in terms of the temperature amplitudes and average values. A mathematical model of the unsteady phase transition of geothermal field was presented to analyze the temporal and spatial characteristics of temperatures and to predict the trends of variation of geothermal field. Monitored data and calculated results both indicated that the temperature distributions were related to the soil compositions, the thermal coefficients of diffusion, the climate and the locations, etc. The roadbed of HSR of seasonally frozen regions eventually formed a relatively stable layer of seasonal frozen with a stable temperature and asymmetric geothermal field. The difference of geothermal field of shady and sunny slopes at two sides of embankment exists and may lead to the uneven settlements transversely and longitudinally which may affect the stability of roadbed.

Xiong K.,Beijing Jiaotong University | Xiong K.,Tsinghua University | Fan P.,Tsinghua National Laboratory for Information Sciences and Technology | Xu Z.,China Telecom | And 2 more authors.
IEEE Transactions on Signal Processing | Year: 2014

In this paper, we consider a transmit beamforming design for multiple-input-multiple-output (MIMO) decode-and-forward (DF) half-duplex two-hop relay channels with a direct source-destination link. For the scenario where source and relay nodes are equipped with multiple antennas and the destination node is deployed with single antenna, we formulate and solve the optimal beamforming vectors for source and relay nodes jointly. Specifically, we identify several unique properties of the optimal solutions through mathematical derivation, based on which we develop a systematic approach to arrive at the optimal beamforming vectors for the source and relay nodes for different system configurations. We derive a low-complexity explicit expression for the optimal beamforming vectors for some specific scenarios. Numerical results show that our proposed beamforming design scheme can achieve the ε-optimal solution with low computational complexity for MIMO DF relay networks. © 2014 IEEE.

Zhang R.,Beijing Jiaotong University | Cheng X.,Peking University | Fang D.,Peking University | Ke L.,Beijing Jiaotong University | Wang Y.,Beijing Jiaotong University
Materials and Design | Year: 2013

Nearly fully dense ZrB2-SiC-graphite composites were fabricated from commercially available powder at 1900°C by hot pressing. The tensile strength of ZrB2-based ceramics was measured in air up to 1750°C, which is the first reported tensile strength measurement in air above 1500°C. A mechanical testing apparatus capable of testing material in ultra-high temperature under air atmosphere was built, evaluated, and used. Tensile strength was measured as a function of temperature up to 1750°C in air. The respective average values of the tensile strength measured at 1550°C, 1650°C, and 1750°C are 58.4, 44.8, and 21.8MPa, which are 49.4%, 37.9%, and 18.4% of their room-temperature strength (118.2MPa), respectively. Moreover, the tensile fracture behaviors and mechanism of ZrB2-based ceramics at different testing temperatures were discussed based on microstructure characterization. © 2013 Elsevier Ltd.

Liang Y.-S.,National Taiwan University | Chung W.-H.,Academia Sinica, Taiwan | Ni G.-K.,National Taiwan University | Chen I.-Y.,National Taipei University of Technology | And 2 more authors.
IEEE Transactions on Vehicular Technology | Year: 2012

Interference control and quality-of-service (QoS) awareness are the major challenges for resource management in orthogonal frequency-division multiple access femtocell networks. This paper investigates a self-organization strategy for physical resource block (PRB) allocation with QoS constraints to avoid the co-channel and co-tiered interference. Femtocell self-organization including self-configuration and self-optimization is proposed to manage the large femtocell networks. We formulate the optimization problem for PRB assignments where multiple QoS classes for different services can be supported, and interference between femtocells can be completely avoided. The proposed formulation pursues the maximization of PRB efficiency. A greedy algorithm is developed to solve the resource allocation formulation. In the simulations, the proposed approach is observed to increase the system throughput by over 13% without femtocell interference. Simulations also demonstrate that the rejection ratios of all QoS classes are low and mostly below 10%. Moreover, the proposed approach improves the PRB efficiency by over 82% in low-loading scenario and 13% in high-loading scenario. © 2012 IEEE.

Agency: Cordis | Branch: FP7 | Program: CP-IP | Phase: SST.2010.1.1-3. | Award Amount: 4.90M | Year: 2011

As pointed out in the White paper for European transport the aim of the European rail operators is to increase the market share of goods traffic from 8 % in 2001 to 15 % in 2020. The nightly time slots will play an important in this. Railway vibration annoyance and sleep disturbance in residential areas is a potential show stopper for this increase. Therefore the aim of Cargovibes is to develop and assess measures to ensure acceptable levels of vibration for residents living in the vicinity of freight railway lines in order to facilitate the extension of freight traffic on rail. Existing evaluation criteria in use are deemed too strict and not based on relevant surveys. There are no uniform assessment methods available and knowledge about mitigation measures is fractured and hardly common. In this proposal the right criteria will be established, given the characteristics of freight traffic. Existing mitigation measures for conventional railway are not directly applicable to freight trains which generate a different soil vibration pattern than conventional railways in terms of vibration amplitudes and frequency contents. Viable efficient new mitigation measures for freight rail traffic will be designed and validated. In operational terms the project aims at developing a) criteria for the evaluation of the adverse effects. These criteria will be formulated as extensions of current guidelines. b) a protocol for the assessment of the effect of mitigation measures. c) three new mitigation measures: a measure for the rolling stock, one for the track and one in the propagation path. These measures will be pilot tested and validated in service. d) catalogue of mitigation measures, for use of railway community. To ensure that the project will generate products that can readily put to use, a Board of End Users will be put into place which will judge intermediate results and guide the developments in the course of the project.

News Article | November 18, 2015

Almost one year ago, Beijing began to receive water channelled by the South-to-North Water Diversion (SNWD) project. The biggest inter-basin transfer scheme in the world, the SNWD project has the capacity to deliver 25 billion cubic metres of fresh water per year from the Yangtze River in China's south to the drier north by two routes — each of which covers a distance of more than 1,000 kilometres. The project connects four major river basins, three megacities, six provinces and hundreds of millions of water users and polluters. Its success is already in question. Reservoir and canal construction costs have reportedly reached US$80 billion, and more than 300,000 people have been displaced1. Pollution and environmental fallout, as well as high maintenance costs and water prices, make the project unsustainable both ecologically and socially. And the transfer of water does not address the underlying causes of water shortages in the north, namely pollution and inefficient agricultural, industrial and urban use — the effects of which we have been studying over the past decade. North China could be self-sufficient in water without the transfer of water from the south. But the necessary steps — among them, improving local pollution monitoring and building better irrigation infrastructure — are inadequately implemented. Increasing supply is viewed as the main solution to water scarcity because of the conflicting roles of the Chinese government as both entrepreneur and regulator. Incentives for economic growth in China still outweigh incentives for pollution control and limits on water extraction, despite ever stricter environmental laws. Many industries, such as the country's huge hydropower sector, profit from expensive solutions to boosting water supplies. China's water system needs an overhaul. Institutional reforms must divorce profit motives from regulatory functions; data and decisions must be disclosed to the public; and the influence of the hydropower sector on water-resource management needs to be restricted. The volume of water being diverted along existing routes of the SNWD project must be reduced and extensions to the project must be shelved. Better local management of resources is the only way to bring secure and sustainable water to all parts of China. China's history of grand water-engineering projects is almost as old as the nation itself, and is inextricably knit with the country's politics, development and self-image. The first dam was built in around 600 bc at Anfeng Tang in eastern China. It created a still existing reservoir 100 kilometres in circumference that could irrigate an area of 24,000 square kilometres. Ever since, most of China's water-management systems have been created and run by the state. The SNWD project transports water in two ways (see 'South-to-north water transfer'). Its eastern route has the capacity to supply up to 14.8 billion cubic metres of water per year to the provinces of Jiangsu, Anhui, Shandong and Hebei, and to the city of Tianjin. The water travels through a system of pumps, rivers, lakes, reservoirs and canals that includes the Grand Canal, which was built around 500 bc. Its central route will provide up to 9.5 billion cubic metres of water per year, including one-third of Beijing's water, from the Danjiangkou reservoir on the Han River (a tributary of the Yangtze). During the construction of this route, the water level of the reservoir was raised by 13 metres, which resulted in the resettlement of 180,000 people from Shiyan city and 160,000 from Nanyang city. A third, western, route is planned that would divert up to 20 billion cubic metres of water from three tributaries of the upper Yangtze through tunnels to the upper reaches of the Yellow River. Its path is under debate and there has been no commitment to commencing its construction nor any indication of when a decision might be made1. In our view, the scope for improving water management makes this extra route unnecessary. Without question, northern China, which includes the Hai, Huai and Yellow river basins, is short of water. The region's annual per capita water availability is only around half of the international threshold for water stress2. Water scarcity is most acute in the Hai basin, where Beijing is located. Farms and cities have increasingly drawn on groundwater such that 50% of aquifers in the North China Plain are now below sea level. This scarcity is compounded by poor water quality in up to 60% of water in the rivers of the north, which further reduces the supply of clean water for drinking and domestic use2. The problem is more a scarcity of management than of natural water3. Inefficient agricultural production consumes about 75% of the region's water and is growing rapidly. In areas where cereal crops are flood irrigated, losses can exceed 50%. In addition, the lack of storage systems along the Yellow River means that farmers must use water when it is made available — not necessarily when they need it3. The idea of water scarcity in the north is perpetuated by China's government for several reasons. It justifies taking water from the south to achieve President Xi Jinping's ambitions for a mega-economic region that encompasses Beijing, Tianjin and Hebei. And it serves the interests of those in the business of supplying water, including China's huge, state-owned water-engineering firms. But the SNWD project does not ensure a reliable supply to the north. Pollution is a pervasive risk. In response to complaints about quality from provinces receiving water, the National Development and Reform Commission ordered changes in land use across the Danjiangkou reservoir catchment area to reduce urban and agricultural run-off. Development has been prohibited in some areas, and in others communities have been resettled. The use of pesticides and fertilizers has been limited and industry is subjected to stricter pollution controls. In 2015, Danjiangkou reservoir won a national award for water quality — at the cost of the impoverishment of the hundreds of thousands of people who were forced to move. And there are other costs. Wang Mengshu, a civil engineer at Beijing Jiaotong University, has suggested that the expense of maintaining the SNWD conduits was vastly under-estimated. The price of transferred water will be too expensive for farmers, who will therefore continue to exploit groundwater4. The SNWD project also poses risks in source areas. Claims of abundant water in the Yangtze hide the fact that shortages do occur. In the past decade, there have been two severe droughts in the Yangtze basin. And periods of water scarcity are more likely in the future because of an increase in the number of withdrawals and dams, as well as the effects of urbanization and climate change. The timing of water transfers is therefore important: should extractions from the Yangtze occur at times of low flow, saline waters from its estuary could be drawn in. Nearby Shanghai's population of 24 million would then face critical water shortages until discharge levels rose again5. Governance of the SNWD project remains unresolved. Both the state-owned HydroChina Corporation and the central government's SNWD project construction committee seek to control the flow of the project's waters, even though this is a core responsibility of the Chinese Ministry of Water Resources. Corporatization of the state is reaching into the management of water, creating tension between motives and profit, uncertainty about roles and responsibilities and impediments to coordinated management of the nation's water courses. In cities, rainwater harvesting and wastewater recycling can meet much of the demand. According to Qiu Baoxing, a former vice-minister of the Chinese Ministry of Housing and Urban–Rural Development, the SNWD project could have been avoided if one-third of buildings in Beijing collected rainwater. Increased investment in treatment systems, efficient irrigation and the monitoring and enforcement of pollution levels can also improve the supply of usable water2, 6, 7. Lower-quality water could be used for urban landscaping and industry, and some water-intensive activities could be moved to the south. Such solutions require coordination with local governments, which are driven by growth and profit. When bureaucrats behave like businessmen and state-owned enterprises operate like private corporations, even strong environmental laws have little effect6. By contrast, the SNWD project is easy to administrate, politically feasible and drives growth. There are signs of change. Since 2006, environmental targets have been included in performance criteria for local leaders6. And there have been experiments in increasing disclosure to the public of data on the environmental performance of firms7. Both measures have made local governments and businesses more accountable for environmental standards. They have led to lower levels of pollution and encouraged investment in cleaner technologies and the closure of inefficient plants. But the enforcement of standards and laws varies from region to region — the economic imperative still dominates in less-developed regions — and data can be falsified6. The Chinese government's authority rests on maintaining social stability and economic growth. The government must therefore respond to challenges such as corruption, public-health issues and inequality8. Given improved living standards, greater levels of education and the proliferation of social media, high levels of pollution can no longer be ignored. Both the central and local governments in China must be seen to be controlling pollution, which can lead to secrecy and misinformation. In our experience, detailed data on the flow of water and pollution levels in major rivers can be difficult to obtain and must often be paid for. As is already done for air pollution, the central and local Chinese governments should disclose information on water to demonstrate the responsible management of resources to the public. Providing accessible information about the allocation of water rights — as well as the allocation of water itself to provinces, irrigation districts and farmers — would increase public trust in the system and improve the accountability of water managers, local government and firms6. Local environmental-protection bureaus should be given the autonomy and resources to collect and analyse monitoring data independently and to enforce pollution standards. Exporters that rely on foreign investment must increasingly comply with standards and regulations as their parent companies and consumers demand proof of environmental responsibility. Industrial water users should consider cleaner production as a path to savings, new markets and improved competitiveness9. In agriculture, losses can be reduced by lining irrigation canals with concrete. Water should be supplied only at times when irrigation is necessary3. The rotation of wheat with higher-value crops that take less water to grow, such as peanuts, will also improve the efficiency of water use10. Investment in new technologies is needed, including systems to separate urban water according to quality, recycle waste water, encourage water conservation and improve the harvesting of rainwater. This would require performance targets to be set for local managers, as well as investment in and incentives for building smaller-scale water infrastructure. Campaigns to increase public awareness of water issues should also be implemented. Constraining the influence of the hydropower sector on water-resource management will help to shift public investment towards these smaller-scale technologies. The sector is already expanding into overseas markets to compensate for reduced domestic demand in the wake of disquiet about water pollution. As its limitations become clear, the SNWD project might well mark the nadir of big-engineering solutions to China's water problems.

Wang H.,Beijing Jiaotong University | Chu X.,King's College London
Electronics Letters | Year: 2012

A distance-constrained resource-sharing criterion (DRC) is proposed for device-to-device (D2D) communications underlaying cellular systems to mitigate the interference from cellular transmissions to the D2D link. The outage probability analysis and numerical evaluation reveal that there is an optimal minimum distance between the D2D receiver and its paired cellular UE, and the proposed DRC significantly reduces the outage probability of D2D communications. © 2012 The Institution of Engineering and Technology.

Cheng F.,Beijing Jiaotong University | Yu J.,University of Science and Technology Beijing | Xiong H.,Shanghai JiaoTong University
IEEE Transactions on Neural Networks | Year: 2010

The Gaussian process (GP) approaches to classification synthesize Bayesian methods and kernel techniques, which are developed for the purpose of small sample analysis. Here we propose a GP model and investigate it for the facial expression recognition in the Japanese female facial expression dataset. By the strategy of leave-one-out cross validation, the accuracy of the GP classifiers reaches 93.43% without any feature selection/extraction. Even when tested on all expressions of any particular expressor, the GP classifier trained by the other samples outperforms some frequently used classifiers significantly. In order to survey the robustness of this novel method, the random trial of 10-fold cross validations is repeated many times to provide an overview of recognition rates. The experimental results demonstrate a promising performance of this application. © 2010 IEEE.

He R.,Beijing Jiaotong University | Zhong Z.,Beijing Jiaotong University | Ai B.,Beijing Jiaotong University | Ding J.,Beijing Jiaotong University | And 2 more authors.
IEEE Transactions on Antennas and Propagation | Year: 2013

Cuttings are widely used in high-speed railway (HSR) transportation to ensure the flatness of rails. The special structure of cuttings results in rich reflection and scattering, and creates dense multipath components. This paper presents a series of measurements of the propagation channel at 930 MHz conducted along the 'Zhengzhou-Xi'an' HSR of China, to characterize the small-scale fading behavior of rail-cutting scenarios as a function of the geometry of cuttings, including crown width and bottom width. Raw data are collected in six cuttings (five cuttings are used for developing the model, while the other one is used for validation) in rural and suburban environments. We propose a set of effective methods to statistically model the spatial/temporal variations-including fade depth (FD), level crossing rate (LCR), average fade duration (AFD), and Ricean K$-factor-as a function of the structural parameters of cuttings. Akaike's Information Criterion (AIC)-based evaluation indicates that the Ricean distribution is the best to describe small-scale fading. In addition, the rich multipath and directionality of the transmitting antennas lead to a non-monotonous dependence of the K-factor on the distance between transmitter and receiver. The autocovariance function of the deviation of the extracted K-factors from the proposed model is presented and the coherence length is investigated. Our results show that even though a cutting is a scenario with severe fading, a 'wide' cutting (i.e., with both wide crown and bottom widths) is conducive to the reduction of the severity of fading. © 1963-2012 IEEE.

Li W.,George Washington University | Cheng X.,George Washington University | Jing T.,Beijing Jiaotong University | Cui Y.,Tsinghua University | And 2 more authors.
IEEE Journal on Selected Areas in Communications | Year: 2013

This paper investigates the problem of spectrum assignment and sharing to minimize the total delay of multiple concurrent flows in multi-hop cognitive radio networks. We first analyze the expected per-hop delay, which incorporates the sensing delay and transmission delay characterizing the PU activities and spectrum capacities. Then we formulate a minimum delay optimization problem with interference constraints, and propose an approximation algorithm termed MCC to solve the problem. According to our theoretical analysis, MCC has a bounded performance ratio and a low computational complexity. Finally, we exploit the minimum potential delay fairness in spectrum sharing to mitigate the inter-flow contentions. Extensive simulation study has been performed to validate our design and to compare the performance of our algorithms with that of the state-of-the-art. © 2013 IEEE.

Bolin L.,Beijing Jiaotong University | Youqi W.,Sinopce Petroleum Exploration and Production Research Institute
Petroleum Exploration and Development | Year: 2011

The filtration characteristics of low oil saturation reservoirs are obviously different from that of conventional reservoirs. The development performance and the influence factors for low oil saturation reservoirs were studied using laboratory large model physical modeling and reservoir numerical simulation, to match and establish the empirical formula of water cut variation. In the numerical stimulation process, the effect of threshold pressure on filtration for low permeability reservoirs was considered, which made the results more realistic. There wasn't a period of oil recovery without water for low oil saturation reservoirs; the water cut increased rapidly at the beginning, and dropped slightly before the period of oil production with stable water cut. The higher the initial water saturation, the shorter the production time with stable water cut. Recovery changed greatly with the injection/production pressure gradient when the injection/production pressure gradient was close to the pseudo threshold pressure gradient. Recovery changed little, even no change, with the injection/production pressure gradient when the injection/production pressure gradient was far larger than the pseudo threshold pressure gradient. There was a positive correlation between recovery degree and water injection rate when the injection/production pressure gradient was less than the pseudo threshold pressure gradient. © 2011 Research Institute of Petroleum Exploration & Development, PetroChina.

Liu Y.,Beijing Jiaotong University | Guo X.,Beijing Union University | Hu F.,Duquesne University
Energy and Buildings | Year: 2014

In order to initiate economic evaluation of green buildings and foster their development, this article conducts the cost-benefit evaluation of energy efficiency technology application (EETA) on green buildings in China. Based on the economic evaluation theory of construction project (EETCP), the authors first establishes the theoretical framework system of cost-benefit evaluation of the EETA on green buildings and then develops the analysis methods of incremental costs and quantitative calculation formula of incremental benefits of the EETA on green buildings. Using these theories and methods, this article takes the Wanke City project in China as a study case, conducts the cost-benefit empirical analysis of the EETA on green buildings, and draws the following important conclusions: (1) the incremental costs of the EETA account for a large proportion of total incremental costs of green buildings, which are more than 50% in this case; (2) the EETA on green buildings can bring incremental economic benefits, as well as environmental benefits; (3) if only consider the incremental economic benefits of the EETA on green buildings, the financial evaluation indexes show green buildings do not have market investment potential; (4) among all the factors influencing the financial evaluation results of the EETA on green buildings, power price is the most sensitive factor, followed by the unit incremental costs, and the lifetime has the smallest influence. © 2014 Elsevier B.V. All rights reserved.

Zhu L.,Beijing Jiaotong University | Yu F.R.,Carleton University | Ning B.,Beijing Jiaotong University | Tang T.,Beijing Jiaotong University
IEEE Transactions on Intelligent Transportation Systems | Year: 2012

Communication-based train control (CBTC) is an automated control system for railways using data communications. CBTC systems have stringent communication latency requirements. For rail transit systems, wireless local area network (WLAN)-based CBTC is a popular approach due to the wide availability of commercial-off-the-shelf WLAN equipment. However, WLANs were not originally designed for high-speed environments with frequent handoffs, which may result in communication interrupt and long latency. In this paper, we propose a handoff scheme in CBTC systems based on WLANs with multiple-input-multiple-output (MIMO) technologies to improve the handoff latency performance. In particular, we consider channel estimation errors and the tradeoff between MIMO multiplexing gain and diversity gain in making handoff decisions. The handoff problem is formulated as a partially observable Markov decision process (POMDP), and the optimal handoff policy can be derived to minimize the handoff latency. Simulations results based on real field channel measurements are presented to show the effectiveness of the proposed scheme. © 2011 IEEE.

Zhu L.,Beijing Jiaotong University | Yu F.R.,Carleton University | Ning B.,Beijing Jiaotong University | Tang T.,Beijing Jiaotong University
IEEE Journal on Selected Areas in Communications | Year: 2012

Communication-Based Train Control (CBTC) system is an automated train control system using bidirectional train-ground communications to ensure the safe operation of rail vehicles. Handoff design has significant impacts on the train control performance in CBTC systems based on multi-input and multi-output (MIMO)-enabled WLANs. Most of previous works use traditional design criteria, such as network capacity and communication latency, in handoff designs. However, these designs do not necessarily benefit the train control performance. In this paper, we take an integrated design approach to jointly optimize handoff decisions and physical layer parameters to improve the train control performance in CBTC systems. We use linear quadratic cost for the train controller as the performance measure. The handoff decision and physical layer parameters adaptation problem is formulated as a stochastic control process. Simulation result shows that the proposed approach can significantly improve the control performance in CBTC systems. © 2012 IEEE.

Xu C.,Beijing University of Posts and Telecommunications | Zhao F.,Beijing University of Posts and Telecommunications | Guan J.,Beijing University of Posts and Telecommunications | Zhang H.,Beijing University of Posts and Telecommunications | And 2 more authors.
IEEE Transactions on Vehicular Technology | Year: 2013

Recently, many cities around the world have witnessed large-scale deployment of terrestrial broadcasting mobile television (TV) to vehicles. This service is similar to the cable or satellite TV already in the home, and user-centric interactive mobile Video-on-Demand (VoD) over urban vehicular networks is in fact expected. However, providing this new service with focus on user Quality of Experience (QoE) constitutes a significant challenge. This paper introduces a QoE-driven User-centric solution for VoD services in urban vehicular network environments (QUVoD). QUVoD relies on a multihomed hierarchical peer-to-peer (P2P) and vehicular ad-hoc network (VANET) architecture. Vehicles construct a low-layer VANET via Wireless Access in the Vehicular Environment interfaces; they also form an upper layer P2P Chord overlay on top of a cellular network via Fourth-Generation (4G) interfaces. A novel grouping-based storage strategy that uniformly distributes the video segments along the Chord overlay is proposed, reducing segment seeking traffic while also enabling load balancing. A novel segment seeking and multipath delivery scheme that achieves high lookup success rate and very good video data delivery efficiency is also introduced, which achieves high lookup success rate and very good video data delivery efficiency. Furthermore, a new speculation-based prefetching strategy is proposed, which analyses users' interactive viewing behavior and, by estimating video segment playback order, employs prefetching of the expected segments, smoothening the video playback. Simulation results show how QUVoD is a highly efficient user-centric mobile VoD solution in urban vehicular networks in comparison with existing state-of-the-art solutions. © 2012 IEEE.

Lei L.,Beijing Jiaotong University | Zhang Y.,Beijing University of Posts and Telecommunications | Shen X.S.,University of Waterloo | Lin C.,Tsinghua University | Zhong Z.,Beijing Jiaotong University
IEEE Transactions on Wireless Communications | Year: 2013

In this paper, we study the performance of Device-to-Device (D2D) communications with dynamic interference. In specific, we analyze the performance of frequency reuse among D2D links with dynamic data arrival setting. We first consider the arrival and departure processes of packets in a non-saturated buffer, which result in varying interference on a link based on the change of its backlogged state. The packet-level system behavior is then represented by a coupled processor queuing model, where the service rate varies with time due to both the fast fading and the dynamic interference effects. In order to analyze the queuing model, we formulate it as a Discrete Time Markov Chain (DTMC) and compute its steady-state distribution. Since the state space of the DTMC grows exponentially with the number of D2D links, we use the model decomposition and some iteration techniques in Stochastic Petri Nets (SPNs) to derive its approximate steady state solution, which is used to obtain the approximate performance metrics of the D2D communications in terms of average queue length, mean throughput, average packet delay and packet dropping probability of each link. Simulations are performed to verify the analytical results under different traffic loads and interference conditions. © 2013 IEEE.

Zheng K.,Beijing University of Posts and Telecommunications | Liu F.,Beijing University of Posts and Telecommunications | Lei L.,Beijing Jiaotong University | Lin C.,Tsinghua University | Jiang Y.,Norwegian University of Science and Technology
IEEE Transactions on Wireless Communications | Year: 2013

Wireless networks are expected to support a diverse range of quality of service requirements and traffic characteristics. This paper undertakes stochastic performance analysis of a wireless finite-state Markov channel (FSMC) by using em stochastic network calculus. Particularly, delay and backlog upper bounds are derived directly based on the analytical principle behind stochastic network calculus. Both the single user and multi-user cases are considered. For the multi-user case, two channel sharing methods among eligible users are studied, i.e., the em even sharing and em exclusive use methods. In the former, the channel service rate is evenly divided among eligible users, whereas in the latter, it is exclusively used by a user randomly selected from the eligible users. When studying the em exclusive use method, the problem that the state space increases exponentially with the user number is addressed using a novel approach. The essential idea of this approach is to construct a new Markov modulation process from the channel state process. In the new process, the multi-user effect is equivalently manifested by its transition and steady-state probabilities, and the state space size remains unchanged even with the increase of the user number. This significantly reduces the complexity in computing the derived backlog and delay bounds. The presented analysis is validated through comparison between analytical and simulation results. © 2012 IEEE.

Wang J.,Beijing Jiaotong University | Li W.W.,Texas Southern University
IEEE Transactions on Vehicular Technology | Year: 2016

A cognitive radio (CR) system with retrial possibility and an admission cost for secondary users (SUs) to join the retrial group is investigated in this paper. If the SU finds the primary user (PU) band unavailable, it must decide with a probability estimate to either enter a retrial group or give up its service and leave the system. SUs in the retrial group independently retry after an exponentially distributed random time until they successfully access the spectrum. When the PU arrives, the SU's service on the band is interrupted. This interrupted SU is then assumed to occupy the PU band immediately when the PU completes its service. First, the noncooperative joining behavior of SUs that choose to maximize their benefit in a selfish distributed manner is investigated, and an inefficient Nash equilibrium is derived. Second, from the perspective of the social planner, the socially optimal joining strategy when SUs cooperate with each other is studied, and the corresponding Nash equilibrium is exactly derived. Finally, the result that an individually optimal strategy, in general, does not yield the socially optimal strategy is theoretically verified. Furthermore, to bridge the gap between the individually and socially optimal strategies, a novel strategy of imposing an admission fee on SUs to join the retrial group is proposed and investigated with the derivation of an optimal value for the admission fee. The numerical analysis indicates that the proposed admission fee as an equilibrium strategy and the socially optimal strategy of SUs improve efficiency in the utilization of the CR system. © 2015 IEEE.

Bu B.,Beijing Jiaotong University | Yu F.R.,Carleton University | Tang T.,Beijing Jiaotong University
IEEE Transactions on Intelligent Transportation Systems | Year: 2014

Communication-based train control (CBTC) systems use wireless local area networks (WLANs) to transmit train status and control commands. Since WLANs are not originally designed for applications with high mobility, random transmission delays and packet drops are inevitable, which could result in unnecessary traction, brakes or even emergency brakes of trains, loss of line capacity, and passenger satisfaction. In this paper, we study the packet drops introduced by random transmission errors and handovers in CBTC systems, analyze the impact of random packet drops on the stability and performances of CBTC systems, and propose two novel schemes to improve the performances of CBTC systems. Unlike the existing works that only consider a single train and study the communication issues and train control issues separately, we model the system to control a group of trains as a networked control system (NCS) with packet drops in transmissions. Extensive field test and simulation results are presented. We show that our proposed schemes can provide less energy consumption, better riding comfortability, and higher line capacity compared with the existing scheme. © 2000-2011 IEEE.

Zhu L.,Beijing Jiaotong University | Yu F.R.,Carleton University | Ning B.,Beijing Jiaotong University | Tang T.,Beijing Jiaotong University
IEEE Transactions on Vehicular Technology | Year: 2011

In metro passenger information systems (PISs), frequent train handoffs can cause severe video distortion. In this paper, we take an integrated design approach to jointly optimize application-layer parameters and handoff decisions to improve video transmission quality over PISs. We present a train-ground video communication network based on fountain codes and IEEE 802.11p for metro PISs. The metro PIS channel is modeled as a finite-sate Markov chain, and the channel-state transition probability matrix is calculated from the data that were measured in real field tests. The handoff decision and application-layer parameters adaptation problem is formulated as a stochastic semi-Markov decision process (SMDP). Minimizing the end-to-end total video distortion is the objective in our model. Simulation results show that the proposed SMDP-based optimization algorithm can significantly improve the end-to-end video transmission quality in metro PISs. © 2011 IEEE.

Chen S.,Beijing Jiaotong University | Ho T.,University of Wollongong | Mao B.,Beijing Jiaotong University
International Journal of Production Research | Year: 2013

High reliability is the crucial requirement in railway operation and a power supply system is one of the key components of electrified railways. The cost-effectiveness of the maintenance works is also the concern of the railway operators while the time window on trackside maintenance is often limited. Maintenance scheduling is thus essential to uphold reliability and to reduce operation cost. It is however difficult to formulate the optimal schedule to meet both reliability and maintenance cost for a railway power supply system as a whole because of its functional complexity and demanding operation conditions. Maintenance scheduling models to achieve reliability and maintenance cost are proposed in this study. Optimisation algorithms are then developed to attain the solutions of the model. The applicability of the models and efficiency of the solution algorithms are demonstrated in an example. The proposed methods are vitally important for the railway engineers and operators to assure the service quality in the increasing demands of the modern electrified railways. © 2013 Taylor and Francis Group, LLC.

Sun H.,Beijing Jiaotong University | Alleyne A.G.,University of Illinois at Urbana - Champaign
Automatica | Year: 2014

This paper proposes a computationally efficient iterative learning control (ILC) approach termed non-lifted norm optimal ILC (N-NOILC). The objective is to remove the computational complexity issues of previous 2-norm optimal ILC approaches, which are based on lifted system techniques, while retaining the iteration domain convergence properties. The computational complexity needed to implement the proposed method scales linearly with the trial length. Therefore, the approach can be implemented on controlled processes having long trial durations and high sampling rates. Robustness is accomplished by adding a penalty term on the control input in the cost function. Simulations are presented to verify and validate the features of the proposed method. © 2013 The Authors. Published by Elsevier Ltd. All rights reserved.

Tao D.,Beijing Jiaotong University | Tang S.,Temple University | Liu L.,Multimedia University
Proceedings - IEEE 10th International Conference on Mobile Ad-Hoc and Sensor Systems, MASS 2013 | Year: 2013

In this paper, we explore the area coverage optimization problem by directional sensors with tunable sensing orientations. We firstly introduce the concept of 'sensing centroid', which is the geometric center of a sensing sector to simplify the pending problem. Particularly, we regard 'sensing centroid' as artificial fish (AF), and search an optimal solution in the solution space by simulating fish swarm behaviors (such as prey, swarm and follow) with a tendency toward high food consistence. Fully considering that AFs have to satisfy both kinematic constraint and dynamic constraint in the process of motion, we propose a Constrained Artificial Fish-Swarm Algorithm (CAFSA), and discuss the control laws to guide the behaviors of AFs with high convergence speed. Finally, we evaluate the effect of some primary parameters on the performance of our solution through extensive simulations. © 2013 IEEE.

Abu-Rub H.,Texas A&M University at Qatar | Iqbal A.,Texas A&M University at Qatar | Iqbal A.,Aligarh Muslim University | Ahmed S.M.,Texas A&M University at Qatar | And 4 more authors.
IEEE Transactions on Sustainable Energy | Year: 2013

The paper proposes an artificial-intelligence-based solution to interface and deliver maximum power from a photovoltaic (PV) power generating system in standalone operation. The interface between the PV dc source and the load is accomplished by a quasi-Z-source inverter (qZSI). The maximum power delivery to the load is ensured by an adaptive neuro-fuzzy inference system (ANFIS) based on maximum power point tracking (MPPT). The proposed ANFIS-based MPPT offers an extremely fast dynamic response with high accuracy. The closed-loop control of the qZSI regulates the shoot through duty ratio and the modulation index to effectively control the injected power and maintain the stringent voltage, current, and frequency conditions. The proposed technique is tested for isolated load conditions. Simulation and experimental approaches are used to validate the proposed scheme. © 2010-2012 IEEE.

Yang X.,Beijing Jiaotong University | Dong H.,Beijing Jiaotong University | Wang Q.,Beijing Jiaotong University | Chen Y.,Beijing Jiaotong University | Hu X.,KTH Royal Institute of Technology
Physica A: Statistical Mechanics and its Applications | Year: 2014

Pedestrian dynamics is of great theoretical significance for strategy design of emergency evacuation. Modification of pedestrian dynamics based on the social force model is presented to better reflect pedestrians' behavioral characteristics in emergency. Specifically, the modified model can be used for guided crowd dynamics in large-scale public places such as subway stations and stadiums. This guided crowd model is validated by explicitly comparing its density-speed and density-flow diagrams with fundamental diagrams. Some social phenomena such as gathering, balance and conflicts are clearly observed in simulation, which further illustrate the effectiveness of the proposed modeling method. Also, time delay for pedestrians with time-dependent desired velocities is observed and explained using the established model in this paper. Furthermore, this guided crowd model is applied to the simulation system of Beijing South Railway Station for predictive evacuation experiments. © 2014 Elsevier Inc. All rights reserved.

Zhang K.,King's College London | Zhang K.,Beijing Jiaotong University | Dai J.S.,King's College London | Fang Y.,Beijing Jiaotong University
Journal of Mechanical Design, Transactions of the ASME | Year: 2010

This paper presents a metamorphic kinematic pair extracted from origami folds in the context of mechanisms, its evolved metamorphic chain, and the novel metamorphic parallel mechanism. This paper starts from the generic issues of topological representation for metamorphic mechanism, leading to unified elementary matrix operation for presentation of topological variation. Phase matrix and augmented adjacency matrix are developed to present the topological state and geometry of metamorphic mechanism in an evolutionary process. The metamorphic kinematic pair has the ability of changing mobility to generate different motion patterns based on mobility change correlated with the link annex induced topological phase change. This paper then investigates topological variation of the metamorphic chain and the topological subphases are enumerated in accordance with structure evolution. Using the metamorphic chain as chain-legs, a multiloop metamorphic mechanism with ability of performing phase change and orientation switch is constructed. The disposition of constraints and geometric constraints induced bifurcated motion are analyzed based on screw theory. The topological variation of the metamorphic parallel mechanism is addressed and the foldability is verified by physical device. © 2010 American Society of Mechanical Engineers.

Zhang W.,Chinese Academy of science Max Planck Partner Institute for Computational Biology | Liu Y.,Chinese Academy of science Max Planck Partner Institute for Computational Biology | Liu Y.,Beijing Jiaotong University | Sun N.,Chinese Academy of science Max Planck Partner Institute for Computational Biology | And 5 more authors.
Cell Reports | Year: 2013

Ovarian cancer has a poor prognosis, with different outcomes for different patients. The mechanism underlying this poor prognosis and heterogeneity is not well understood. We have developed an unbiased, adaptive clustering approach to integratively analyze ovarian cancer genome-wide gene expression, DNA methylation, microRNA expression, and copy number alteration profiles. We uncovered seven previously uncategorized subtypes of ovarian cancer that differ significantly in median survival time. We then developed an algorithm to uncover molecular signatures that distinguish cancer subtypes. Surprisingly, although the good-prognosis subtypes seem to have not been functionally selected, the poor-prognosis ones clearly have been. One subtype has an epithelial-mesenchymal transition signature and a cancer hallmark network, whereas the other two subtypes are enriched for a network centered on SRC and KRAS. Our results suggest molecular signatures that are highly predictive of clinical outcomes and spotlight "driver" genes that could be targeted by subtype-specific treatments

Lei L.,Beijing Jiaotong University | Zhong Z.,Beijing Jiaotong University | Zheng K.,Beijing University of Posts and Telecommunications | Chen J.,Beijing University of Posts and Telecommunications | And 3 more authors.
IEEE Wireless Communications | Year: 2013

Mobile cloud computing (MCC) is an appealing paradigm enabling users to enjoy the vast computation power and abundant network services ubiquitously with the support of remote cloud. However, the wireless networks and mobile devices have to face many challenges due to the limited radio resources, battery power and communications capabilities, which may significantly impede the improvement of service qualities. Heterogeneous Network (HetNet), which has multiple types of low power radio access nodes in addition to the traditional macrocell nodes in a wireless network, is widely accepted as a promising way to satisfy the unrelenting traffic demand. In this article, we first introduce the framework of HetNet for MCC, identifying the main functional blocks. Then, the current state of the art techniques for each functional block are briefly surveyed, and the challenges for supporting MCC applications in HetNet under our proposed framework are discussed. We also envision the future for MCC in HetNet before drawing the conclusion. © 2013 IEEE.

Yang D.,Sichuan University | Yang Q.,Beijing Jiaotong University | Yang L.,Sichuan University | Luo Q.,Sichuan University | And 3 more authors.
Chemical Communications | Year: 2013

An asymmetrically substituted squaraine ASQC bearing a 9-carbazyl substituent exhibits an extremely deep HOMO energy level of -5.46 eV and a relatively low bandgap of 1.65 eV, hence renders solution-processed organic solar cells with an impressive Voc of up to 1.12 V and a PCE of 2.82%. © 2013 The Royal Society of Chemistry.

Feng Y.,Tongji University | Feng Y.,Beijing Jiaotong University | Chen X.,Beijing Jiaotong University | Xu X.F.,Beijing Jiaotong University | Xu X.F.,Stevens Institute of Technology
Renewable and Sustainable Energy Reviews | Year: 2014

This research focuses on the enhanced geothermal systems (EGS) potential in China and related technology, especially induced microseismicity and carbon storage combination. Hydraulic fracturing mechanisms applied in EGS were compared with similar fracturing mechanisms for shale gas. Besides, geothermal gradient in China was mapped based on the most recent heat flow values with interpolation method. The development history of geothermal plants in China was comprehensively reviewed through case studies. This paper revealed that the geothermal measuring wells in China were too shallow and too few to offer an accurate estimation. A coming work should aim at heat flow survey in deep layer, induced microseismicity mechanisms, and economically feasible scope in China. These problems will strengthen practical understanding and facilitate extensive application of EGS in China. © 2014 Elsevier Ltd.

Ning X.,Beijing Jiaotong University | Tsung F.,Hong Kong University of Science and Technology
IIE Transactions (Institute of Industrial Engineers) | Year: 2012

Statistical Process Control (SPC) techniques are useful tools for detecting changes in process variables. The structure of process variables has become increasingly complex as a result of increasingly complex technologies. The number of variables is usually large and categorical variables may appear alongside continuous variables. Such observations are considered to be high-dimensional and mixed-type observations. Conventional SPC techniques may lose their accuracy and efficiency in detecting changes in a process with high-dimensional and mixed-type observations. This article presents a density-based SPC approach, which is derived from a Local Outlier Factor (LOF) scheme, as a solution to this problem. The parameters in an LOF scheme are investigated and a procedure to design a corresponding control chart is presented. The good performance of the proposed control scheme is demonstrated via numerical simulation. © 2012 Copyright Taylor and Francis Group, LLC.

Li Q.,Beijing Jiaotong University | Ren S.,China Academy of Railway Sciences
IEEE Transactions on Systems, Man and Cybernetics Part C: Applications and Reviews | Year: 2012

Discrete surface defects are the most common anomalies of rails and they should be carefully inspected. However, it is a challenge to detect such defects in a vision system because of illumination inequality and the variation of reflection property of rail surfaces. This paper presents an intelligent vision detection system (VDS) for discrete surface defects and focuses on two key issues of VDS: image enhancement and automatic thresholding. We propose the local Michelson-like contrast (MLC) measure to enhance rail images. MLC-based method is nonlinear and illumination independent; therefore, it notably improves the distinction between defects and background. In addition, we put forward the new automatic thresholding method-proportion emphasized maximum entropy (PEME) thresholding algorithm. PEME selects a threshold that maximizes the object entropy and meanwhile keeps the defect proportion in a low level. Our experimental results demonstrate that VDS detects the Type-II defects with a recall of 91.61% and Type-I defects with a recall of 88.53%, and the proposed MLC-based image enhancement method and PEME thresholding algorithm outperform the related well-established approaches. © 1998-2012 IEEE.

Zhang T.,Beihang University | Shi Z.,Beijing Jiaotong University
Smart Materials and Structures | Year: 2011

An analytical model of the dynamic properties of the 2-2 cement based piezoelectric transducer is proposed using the piezoelectric effect, based on Li's experiments. Then, the exact solutions are obtained by using the displacement method; comparison and discussion with Li's experimental results in related literature are also given and good agreement is found, which could be used for better understanding of Li's experiment. A theoretical method for applying the cement based piezoelectric composite in civil engineering is provided. © 2011 IOP Publishing Ltd.

Zhang Y.M.,Beijing Jiaotong University | Li X.W.,Beijing Jiaotong University | Yang W.,Beijing Computational Science Research Center | Jin G.R.,Beijing Jiaotong University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013

We investigate the performance of entangled coherent states for quantum-enhanced phase estimation. An exact analytical expression of quantum Fisher information is derived to show the role of photon losses on the ultimate phase sensitivity. We find a transition of the sensitivity from the Heisenberg scaling to the classical scaling due to quantum decoherence of the photon state. This quantum-classical transition is uniquely determined by the number of photons being lost, instead of the number of incident photons or the photon loss rate alone. Our results also reveal that a crossover of the sensitivity between the entangled coherent state and the NOON state can occur even for very small photon loss rate. © 2013 American Physical Society.

Xiong K.,Beijing Jiaotong University | Xiong K.,Tsinghua University | Fan P.,Tsinghua University | Li T.,Tsinghua University | Letaief K.B.,Hong Kong University of Science and Technology
IEEE Transactions on Vehicular Technology | Year: 2014

In this paper, we analyze the outage probability of space-time network coding (STNC) in a distributed cooperative relaying system, where multiple sources transmit their information to a common destination with the help of multiple decode-and-forward (DF) relays in timedivision multiple-access (TDMA) mode. We first derive an exact closed-form expression of the outage probability for STNC with an arbitrary number of relays for independent but not necessarily identically distributed (i.n.i.d.) Rayleigh fading channels. With the developed result, we discuss the impact of the transmit SNR, the outage threshold, the number of relays, the nonorthogonal codes, and the relay position on the system performance. © 2013 IEEE.

Tao D.,Beijing Jiaotong University | Wu T.-Y.,National Ilan University
IEEE Sensors Journal | Year: 2015

Barrier coverage guarantees to detect any intruder attempting to cross the barrier of sensor networks. In the majority of studies on barrier coverage using wireless sensor networks, sensors are assumed to have an isotropic sensing model. However, in certain applications like monitoring a region using video cameras, the sensors have directional sensing model. The nature of directional sensor networks demands novel algorithms and solutions. In directional sensor networks, this paper starts from the concept and characteristics of a directional sensing model, and then summarizes the sensing properties and behaviors of directional sensors. In particular, we classify the existing research results into different categories, such as strong barrier and weak barrier, 1-barrier and k -barrier, worst and best-case coverage and exposure path coverage, any-view coverage and full-view coverage, and overview each category in terms of problem definition, assumption, usage, solution, and performance. Finally, the open research problems to be solved and future work are also discussed. © 2001-2012 IEEE.

Tian Q.,Beihang University | Huang H.-J.,Beihang University | Yang H.,Hong Kong University of Science and Technology | Gao Z.,Beijing Jiaotong University
Transportation Research Part C: Emerging Technologies | Year: 2012

This paper investigates the efficiency and equity of morning peak ramp control schemes in a freeway corridor with limited capacity. In terms of efficiency, both short-run and long-run optimal ramp control schemes are obtained by minimizing the total travel cost and maximizing the total social benefit along the corridor. It is found that for a short-run optimum with inelastic demand, the morning peak period is of the same duration for different on-ramp locations. But for a long-run optimum with elastic demand, the peak duration for various on-ramps increases with the local capacity elasticity of demand. In terms of equity, two measures are defined from a demand-based viewpoint and a space-based viewpoint. It is shown that the short-run optimal ramp control scheme is perfectly fair from a demand-based equity viewpoint. Consequently, two typical ramp control schemes-a perfect demand-based equity scheme and a perfect space-based equity scheme-are introduced and compared with the long-run optimal ramp control scheme in terms of efficiency and equity. Numerical simulations using survey data from China suggest that the perfect demand-based equity scheme attains an economic welfare level that is very close to the optimal one and the conflict between efficiency and equity diminishes as demand becomes less elastic. © 2011 Elsevier Ltd.

Zhang L.M.,Hong Kong University of Science and Technology | Li X.,Beijing Jiaotong University
Journal of Geotechnical and Geoenvironmental Engineering | Year: 2010

To date the microporosity structures of coarse soils with various coarse/fines contents are still not fully understood. In this study, the pore-size distributions (PSDs) of five types of soil varying from gravel to clay were characterized using mercury intrusion porosimetry. The soil with a coarse content below 70% (i.e., fines content above 30%) is found to have a fines-controlled microstructure, which is sensitive to water content changes. Such soil forms a dual-porosity structure due to compaction, in which both intraaggregate pores and interaggregate pores are dominant. After saturation, the dual-porosity structure evolves into a unimodal porosity structure dominated by the intraaggregate pores. During drying, such soil exhibits a significant reduction of total volume. The soil with a coarse content above 70% instead has a coarse-controlled microstructure, which is stable upon water content changes. Such soil maintains dual-porosity structures no matter if the soil is compacted, saturated, or dried. As an example of application, the measured PSDs are used to predict the soil water characteristic curves (SWCCs) for the test soils and the predictions are consistent with the SWCCs measured in the laboratory. © 2010 ASCE.

Liu X.,Beijing Jiaotong University | Liu X.,Zhejiang University | Ortega R.,Laboratoire des Signaux et Systemes | Su H.,Zhejiang University | Chu J.,Zhejiang University
Systems and Control Letters | Year: 2011

A new framework to design immersion and invariance adaptive controllers for nonlinearly parameterized, nonlinear systems was recently proposed by the authors. The key step is the construction of a monotone mapping, via a suitable selection of a controller tuning function, which has to satisfy some integrability conditionsthis translates into the need to solve a partial differential equation (PDE). In this paper this result is extended providing some answers to the questions of characterization of "monotonizable" systems and solvability of the PDE. First, adding to the design a nonlinear dynamic scaling, we obviate the need to solve the PDE. Second, for the case of factorizable nonlinearities, the following results are established. (i) It is shown that the monotonicity condition is satisfied if a linear matrix inequality is feasible. (ii) Directly verifiable involutivity conditions that ensure the solution of the PDE are presented. (iii) An explicit formula for the required tuning function is given, provided the regressor matrix satisfies some rank conditions. Hence, adding a dynamic scaling, this yields a constructive solution to the problem. © 2010 Elsevier B.V. All rights reserved.

Ning X.,Beijing Jiaotong University | Tsung F.,Hong Kong University of Science and Technology
IIE Transactions (Institute of Industrial Engineers) | Year: 2013

Statistical Process Control (SPC) techniques that originated in manufacturing have also been used to monitoring the quality of various service processes, which can be characterized by one or several variables. In the literature, these variables are usually assumed to be either continuous or categorical. However, in reality, the quality characteristics of a service process may include both continuous and categorical variables (i.e., mixed-type variables). Direct application of conventional SPC techniques to monitor such mixed-type variables may cause increased false alarm rates and misleading conclusions. One promising solution is the kernel distance-based chart (K-chart), which makes use of Support Vector Machine (SVM) methods and requires no assumption on the variable distribution. This article provides an improved design of the SVM-based K-chart. A systematic approach to parameter selection for the considered charts is provided. An illustration and comparison are presented based on a real example from a logistics firm. The results confirm the improved performance obtained by using the proposed design scheme. © 2013 Copyright Taylor and Francis Group, LLC.

Liu X.,Nanjing Southeast University | Liu X.,Beijing Jiaotong University
Information Sciences | Year: 2012

This paper proposes a general optimization model for determining ordered weighted averaging (OWA) operators and three specific models for generating monotonic and symmetric OWA operators, as well as those with any function shape. In these models, entropy and variance concepts are generalized as general dispersion indices for use in the objective functions, while the ordinary orness level constraints are used in the constraint equations as a special case. We define an orness function for monotonic OWA operators, which measures the closeness of the aggregation value to the maximum value, and a medianness function for symmetric OWA operators, which measures the closeness of the aggregation value to the median value. We also extend the commonly used models for determining OWA operators under given orness values to determine monotonic OWA operators with given orness function values and symmetric OWA operators with given medianness function values. Analytical solutions and properties of these models are discussed. We also provide analytical solutions of the maximum entropy and minimum variance problems with given linear medianness values. By setting different forms of the objective function and constraints, the parameterized OWA operator family elements can achieve various distributions in any desired shape. Two examples are given to show the OWA operator elements distributed in quadratic and Gaussian distribution function shapes. © 2011 Elsevier Inc. All rights reserved.

Cong L.,Nanyang Technological University | Tan S.,Oklahoma State University | Tan S.,Beijing Jiaotong University | Yahiaoui R.,CNRS XLIM Research Institute, Limoges | And 3 more authors.
Applied Physics Letters | Year: 2015

Planar metasurfaces and plasmonic resonators have shown great promise for sensing applications across the electromagnetic domain ranging from the microwaves to the optical frequencies. However, these sensors suffer from lower figure of merit and sensitivity due to the radiative and the non-radiative loss channels in the plasmonic metamaterial systems. We demonstrate a metamaterial absorber based ultrasensitive sensing scheme at the terahertz frequencies with significantly enhanced sensitivity and an order of magnitude higher figure of merit compared to planar metasurfaces. Magnetic and electric resonant field enhancement in the impedance matched absorber cavity enables stronger interaction with the dielectric analyte. This finding opens up opportunities for perfect metamaterial absorbers to be applied as efficient sensors in the finger print region of the electromagnetic spectrum with several organic, explosive, and bio-molecules that have unique spectral signature at the terahertz frequencies. © 2015 AIP Publishing LLC.

Gao Y.,Beijing Jiaotong University | Qin Z.,Beihang University
IEEE Transactions on Fuzzy Systems | Year: 2016

Uncertain graphs are employed to describe graph models with imprecise expert data. In uncertain graphs, due to the existence of uncertain edges, edge-connectivity is essentially an uncertain variable. Different from that in a deterministic graph, it is more suitable to investigate the possibility (uncertain measure) that an uncertain graph is $k$-edge-connected, which is the main aim of this paper. We first deduce a theoretical formula to calculate the uncertain measure, and on this basis, we then propose an algorithm, which is derived from maximum flow algorithms, to numerically calculate the uncertain measure. The proposed algorithm is also proved to be a polynomial time algorithm, and its effectiveness and efficiency are illustrated by numerical examples. © 2015 IEEE.

Jin H.,Beijing Jiaotong University | Liu W.-N.,Beijing Jiaotong University | Wang W.-B.,China Academy of Railway Sciences
Gongcheng Lixue/Engineering Mechanics | Year: 2013

The ladder track was one of the best methods to control train-track vibrations. But the laying type of damping pads under sleepers had not been researched systematically. According to the MIMO (multiple input multiple output) method, three laying types of damping pads under a sleeper were analyzed how to affect the dynamic characteristics of the ladder track. Results show that the former laying type of damping pads has the smallest natural frequency (33 Hz). The ladder track with 10 damping pads (side) has the biggest damping ratio (4.2%). First six damping ratios of the ladder track of three laying types have a down-up manner and the first modal shape is symmetric along the centerline of the ladder track. The second modal shape of the ladder track with 5 and 7 damping pads (side) is antisymmetric along the centerline of the ladder track, contrary with the ladder track with 10 damping pads (side). The analysis provides an engineering reference for the ladder track application.

Maire E.,INSA Lyon | Zhou S.,Beijing Jiaotong University | Adrien J.,Beijing Jiaotong University | Dimichiel M.,European Synchrotron Radiation Facility
Engineering Fracture Mechanics | Year: 2011

This paper presents results obtained using in situ tensile experiments allowing the observation of damage nucleation, growth and coalescence. Three different aluminium alloys (2024, 7449 and 5754) exhibiting various mechanical properties were chosen to produce a wide data base. Smooth and notched axisymetric samples were cut out of the raw materials to introduce different levels of initial stress triaxiality using the geometry of the samples. In the different cases, the damage steps (initiation, growth and coalescence) were clearly visualised during interrupted and continuous in situ tensile tests in synchrotron X-ray tomography. The imaging was performed with a voxel size of 1.6. μm. The X-ray tomography method also gives a precise image of the outer shape of the sample and its change during deformation can then be analysed. This allows to calculate precisely the true strain vs true stress curve and also an approximation of the stress triaxiality using the Bridgman formula. The results show that damage can be visualised but also quantified precisely in the different cases in terms of nucleation and growth, coalescence being also evident in the results but still hard to quantify so far. Finally, a previously developed model for damage growth during ductile straining based on the Rice and Tracey approach can be fitted to the results. © 2011 Elsevier Ltd.

Zhang L.,Beijing Jiaotong University | Gao D.,Beijing Jiaotong University | Zhao W.,Beijing Jiaotong University | Chao H.-C.,National Ilan University
Mathematical and Computer Modelling | Year: 2013

As city road congestion problems become more serious, many researchers have started to use the technique of vehicle ad hoc networks (VANETs) for road congestion detection. However, various on-board sensors equipped in vehicles may generate lots of atomic messages, which usually cause serious channel competition problems. In this paper, we propose a multilevel information fusion approach by combining the fuzzy clustering-based feature level information fusion (FCMA) and the modified Dempster-Shafer evidence reasoning-based decision level information fusion (D-SEMA). The FCMA can extract the key features from atomic messages, thereby greatly reducing the network traffic load. Furthermore, the D-SEMA mechanism is used to judge whether the road congestion event occurs. Performance analysis and simulation results under ONE simulator show that the proposed multilevel information fusion approach can detect road congestion efficiently with low bandwidth consumption. © 2013 Elsevier Ltd.

Wang W.,Nanjing Southeast University | Liu X.,Beijing Jiaotong University
IEEE Transactions on Fuzzy Systems | Year: 2012

Aggregation of fuzzy information is a new branch of Atanassovs intuitionistic fuzzy set (AIFS) theory, which has attracted significant interest from researchers in recent years. In this paper, we treat the intuitionistic fuzzy aggregation operators with the help of Einstein operations. We first introduce some new operations of AIFSs, such as Einstein sum, Einstein product, and Einstein scalar multiplication. Then, we develop some intuitionistic fuzzy aggregation operators, such as the intuitionistic fuzzy Einstein weighted averaging operator and the intuitionistic fuzzy Einstein ordered weighted averaging operator, which extend the weighted averaging operator and the ordered weighted averaging operator to aggregate Atanassovs intuitionistic fuzzy values, respectively. We further establish various properties of these operators and analyze the relations between these operators and the existing intuitionistic fuzzy aggregation operators. Moreover, we give some numerical examples to illustrate the developed aggregation operators. Finally, we apply the intuitionistic fuzzy Einstein weighted averaging operator to multiple attribute decision making with intuitionistic fuzzy information. © 2012 IEEE.

Zhao P.,Beijing Jiaotong University | Zhao C.,Tianjin Normal University
Circuits, Systems, and Signal Processing | Year: 2012

The paper provides a novel technique for designing tight frame wavelet filters through the use of Bernstein polynomials. The perfect-reconstruction conditions of tight wavelet frame filters are established by using parameters of the Bernstein polynomials. The desired number of vanishing moments can be easily achieved by setting the appropriate parameters of the Bernstein polynomial to zero. The filters are obtained by the spectral factorization method and constructed by the appropriate parameters. The design technique is flexible in that it allows low-pass filters and high-pass filters with different characteristics to be designed easily. © Springer Science+Business Media, LLC 2012.

Tang T.,Beihang University | Wang Y.,Beihang University | Yang X.,Beijing Jiaotong University | Wu Y.,Curtin University Australia
Nonlinear Dynamics | Year: 2012

In this paper, we develop a new car-following model with consideration of varying road condition based on the empirical data. Firstly, we explore the effects of road condition on uniform flow from analytical and numerical perspectives. The results indicate that road condition has great influences on uniform flow, i.e., good road condition can enhance the velocity and flow and their increments will increase when road condition becomes better; bad road conditions will reduce the velocity and flow and their reductions will increase when road condition turns worse. Secondly, we study the effects of road conditions on the starting and braking processes. The numerical results show that good road condition will speed up the two processes and that bad road condition will slow down the two processes. Finally, we study the effects of road condition on small perturbation. The numerical results indicate that the stop-and-go phenomena resulted by small perturbation will become more serious when the road condition becomes better. © Springer Science+Business Media B.V. 2012.

Tang T.Q.,Beihang University | Li J.G.,Beihang University | Huang H.J.,Beihang University | Yang X.B.,Beijing Jiaotong University
Measurement: Journal of the International Measurement Confederation | Year: 2014

In this paper, we use empirical data to calibrate the speed-headway function and propose a car-following model to investigate the effects of real-time road condition on each vehicle's speed, acceleration, headway, fuel consumption, CO, HC and NOX under uniform flow. Numerical results illustrate that real-time road condition produces oscillating phenomena and enhance each vehicle's fuel consumption and exhaust emissions. These results can help researchers understand the effects of real-time road condition on the driving behavior and help traffic engineers construct the theory of homogeneous roads in order to reduce the vehicle's fuel consumption and exhaust emissions. © 2013 Elsevier Ltd. All rights reserved.

Li Q.,Beijing Jiaotong University | Ren S.,China Academy of Railway Sciences
IEEE Transactions on Instrumentation and Measurement | Year: 2012

Discrete surface defects impact the riding quality and safety of a railway system. However, it is a challenge to inspect such defects in a vision system because of illumination inequality and the variation of reflection property of rail surfaces. This paper puts forward a real-time visual inspection system (VIS) for discrete surface defects. VIS first acquires a rail image by the image acquisition system, and then, it cuts the subimage of rail track by the track extraction algorithm. Subsequently, VIS enhances the contrast of the rail image using the local normalization (LN) method, which is nonlinear and illumination independent. At last, VIS detects defects using the defect localization based on projection profile (DLBP), which is robust to noise and very fast. Our experimental results demonstrate that VIS detects the Type-II defects with a recall of 93.10% and Type-I defects with a recall of 80.41%, and the proposed LN method and DLBP algorithm are better than the related well-established approaches. Furthermore, VIS is very fast with a linear computational time complexity, and it can be in real time to run on a 216-km/h test train under our experimental setup. © 1963-2012 IEEE.

Li X.,Beijing Jiaotong University | Li J.H.,Harbin Institute of Technology | Zhang L.M.,Hong Kong University of Science and Technology
Computers and Geotechnics | Year: 2014

Experimental evidence shows that a gap-graded soil or a widely-graded granular material may have a bimodal soil-water characteristic curve (SWCC) and a bimodal permeability function. A bimodal SWCC or a bimodal permeability function originates from a dual-porosity structure. To date, the prediction of bimodal SWCCs for gap-graded soils is still a difficult task. In this paper, a bimodal SWCC model is proposed to describe the drying process of granular soils considering a dual-porosity structure. The new SWCC model shows powerful capability in fitting the SWCCs for soils varying from gravel to silt. Regression analysis is conducted to establish empirical relations between the model parameters and the indexes of soil grain-size distribution (GSD). Based on these relations, the new model predicts well both the bimodal SWCCs for gap-graded soils and the unimodal SWCCs for well-graded soils and uniform soils. A bimodal permeability function is also proposed and linked to the new SWCC model. In the absence of experimental SWCCs and permeability functions, the new model can be used to obtain preliminary SWCCs and permeability functions for granular soils. It should be mentioned that the prediction of the SWCC from the GSD is still empirical and does not address the cyclic wetting/drying process. Measurement of the SWCC should be performed wherever an accurate SWCC is required. © 2014 Elsevier Ltd.

Wang W.,Nanjing Southeast University | Liu X.,Nanjing Southeast University | Qin Y.,Beijing Jiaotong University
Knowledge-Based Systems | Year: 2012

Interval type-2 fuzzy sets (IT2 FSs) are a very useful means to depict the decision information in the process of decision making. In this article, we investigate the group decision making problems in which all the information provided by the decision makers (DMs) is expressed as IT2 fuzzy decision matrices, and the information about attribute weights is partially known, which may be constructed by various forms. We first use the IT2 fuzzy weighted arithmetic averaging operator to aggregate all individual IT2 fuzzy decision matrices provided by the DMs into the collective IT2 fuzzy decision matrix, then we utilize the ranking-value measure to calculate the ranking value of each attribute value and construct the ranking-value matrix of the collective IT2 fuzzy decision matrix. Based on the ranking-value matrix and the given attribute weight information, we establish some optimization models to determine the weights of attributes. Furthermore, we utilize the obtained attribute weights and the IT2 fuzzy weighted arithmetic average operator to fuse the IT2 fuzzy information in the collective IT2 fuzzy decision matrix to get the overall IT2 fuzzy values of alternatives by which the ranking of all the given alternatives can be found. Finally, we give an illustrative example. © 2012 Elsevier B.V. All rights reserved.

Long J.,Beihang University | Gao Z.,Beijing Jiaotong University | Orenstein P.,Seton Hall University | Ren H.,Beijing Jiaotong University
IEEE Transactions on Intelligent Transportation Systems | Year: 2012

Effective control strategies are required to disperse incident-based traffic jams in urban networks when dispersal cannot be achieved simply by removing the obstruction. This paper develops a selection of such control strategies and demonstrates their effectiveness in dispersing incident-based traffic jams in two-way rectangular grid networks. Using the spatial topology of traffic jam propagation, we apply the concept of vehicle movement ban, which is frequently adopted in real urban networks as a temporary traffic management measure. Four control strategies were developed, which are referred to as single-line control, multiline control, area control, and diamond control. We also explore a combination of these control strategies and evaluate the impact of these control strategies on the changes in traffic jam size and congestion delay. Finally, we simulate the processes of traffic jam formation and dissipation using the cell transmission model and demonstrate the performance of the proposed strategies. Simulation results show that the proposed strategies can indeed disperse incident-based traffic jams efficiently. © 2011 IEEE.

Tang T.Q.,Beijing Jiaotong University | Tang T.Q.,Beihang University | Li P.,Beihang University | Yang X.B.,Beijing Jiaotong University
Physica A: Statistical Mechanics and its Applications | Year: 2013

In this paper, we propose a macro model with consideration of multi static bottlenecks to study the impacts of multi static bottlenecks on traffic flow. The numerical results show that the influences are related to the number of static bottlenecks, the distance between two adjacent static bottlenecks and the initial density. © 2013 Elsevier B.V. All rights reserved.

Bianconi G.,Queen Mary, University of London | Rahmede C.,Karlsruhe Institute of Technology | Wu Z.,Beijing Jiaotong University
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2015

Networks are topological and geometric structures used to describe systems as different as the Internet, the brain, or the quantum structure of space-time. Here we define complex quantum network geometries, describing the underlying structure of growing simplicial 2-complexes, i.e., simplicial complexes formed by triangles. These networks are geometric networks with energies of the links that grow according to a nonequilibrium dynamics. The evolution in time of the geometric networks is a classical evolution describing a given path of a path integral defining the evolution of quantum network states. The quantum network states are characterized by quantum occupation numbers that can be mapped, respectively, to the nodes, links, and triangles incident to each link of the network. We call the geometric networks describing the evolution of quantum network states the quantum geometric networks. The quantum geometric networks have many properties common to complex networks, including small-world property, high clustering coefficient, high modularity, and scale-free degree distribution. Moreover, they can be distinguished between the Fermi-Dirac network and the Bose-Einstein network obeying, respectively, the Fermi-Dirac and Bose-Einstein statistics. We show that these networks can undergo structural phase transitions where the geometrical properties of the networks change drastically. Finally, we comment on the relation between quantum complex network geometries, spin networks, and triangulations.

Zhang Z.-J.,Beijing Jiaotong University | Lai C.-F.,National Chung Cheng University | Chao H.-C.,National Ilan University
IEEE Wireless Communications | Year: 2014

In recent years, the workmanship of manufacturing sensors has achieved great success. The wide application of inexpensive hardware, such as complementary metal oxide semiconductor cameras and tiny microphones, has contributed to the development of WMSNs. WMSNs are composed of wirelessly connected devices that are able to collect information from the environment at any time. Most often, the types of information collected by WMSNs are video and audio streams, still images, and scalar sensor data. As with wireless sensor networks, the sensor devices in WMSNs are also strictly constrained in terms of memory, processing capability, storage capability, and especially energy. Although batteries can provide wireless sensors with energy, the energy is extremely limited. In practical applications, it is impossible for WMSNs to upload all of the multimedia data to users in remote regions. Hence, it is significant to develop energy-efficient techniques for data communication in WMSNs by in-network processing. In this article, a mechanism based on information fusion is proposed for reducing the volume of data being transferred. The mechanism is a trade-off between uploading the results of in-network data processing and uploading all of the raw data. Based on users' requirements, proper data will be uploaded, and the accuracy of querying will be as good as, or better than, uploading all of the raw data. Finally, the shortcomings and challenges of the mechanism are also described. © 2002-2012 IEEE.

Feng X.M.,Beijing Jiaotong University | Jin G.R.,Beijing Jiaotong University | Yang W.,Beijing Computational Science Research Center
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2014

Optimal measurement scheme with an efficient data processing is important in quantum-enhanced interferometry. Here we prove that for a general binary-outcome measurement, the simplest data processing based on inverting the average signal can saturate the Cramér-Rao bound. This idea is illustrated by binary-outcome homodyne detection, even-odd photon counting (i.e., parity detection), and zero-nonzero photon counting that have achieved super-resolved interferometric fringe and shot-noise limited sensitivity in coherent-light Mach-Zehnder interferometer. The roles of phase diffusion are investigated in these binary-outcome measurements. We find that the diffusion degrades the fringe resolution and the achievable phase sensitivity. Our analytical results confirm that the zero-nonzero counting can produce a slightly better sensitivity than that of the parity detection, as demonstrated in a recent experiment. © 2014 American Physical Society.

Kendoul F.,Chiba University | Yu Z.,Beijing Jiaotong University | Nonami K.,Chiba University
Journal of Field Robotics | Year: 2010

Small unmanned aerial vehicles (UAVs) are becoming popular among researchers and vital platforms for several autonomous mission systems. In this paper, we present the design and development of a miniature autonomous rotorcraft weighing less than 700 g and capable of waypoint navigation, trajectory tracking, visual navigation, precise hovering, and automatic takeoff and landing. In an effort to make advanced autonomous behaviors available to mini- and microrotorcraft, an embedded and inexpensive autopilot was developed. To compensate for the weaknesses of the low-cost equipment, we put our efforts into designing a reliable modelbased nonlinear controller that uses an inner-loop outer-loop control scheme. The developed flight controller considers the system's nonlinearities, guarantees the stability of the closed-loop system, and results in a practical controller that is easy to implement and to tune. In addition to controller design and stability analysis, the paper provides information about the overall control architecture and the UAV system integration, including guidance laws, navigation algorithms, control system implementation, and autopilot hardware. The guidance, navigation, and control (GN&C) algorithms were implemented on a miniature quadrotor UAV that has undergone an extensive program of flight tests, resulting in various flight behaviors under autonomous control from takeoff to landing. Experimental results that demonstrate the operation of the GN&C algorithms and the capabilities of our autonomous micro air vehicle are presented. © 2009 Wiley Periodicals, Inc.

Zhou C.,Beijing Jiaotong University | Zhou C.,University of Jinan
Optics and Lasers in Engineering | Year: 2012

Photonic crystal fiber (PCF) refractive index sensor was analyzed utilizing silver nanocubes, which were embedded in the large air hole of the PCF. According to quasi-state theoretical functions, we have simulated the dependence of extinction ratio for the silver nanocube, one is on the refractive index of the surrounding medium, another is on the operational wavelength at a given length of the nanocube. It is founded that the resonance wavelength (i.e. optimal wavelength) evidently exists for a given refractive index n and linearly increases when the refractive index of the medium surrounding the silver nanocube linearly increases. The sensitivity of the sensor versus the refractive index of the medium surrounding the nanocube and via the edge length of the nanocube is discussed in detail. The sensitivity R is 10 3 larger and linearly increases when the medium refractive index surrounding the nanocube increases for a given edge length L (e.g. L=30 nm). The sensitivity R and the spectrum width exponentially decrease when the edge length L of the nanocube increases, for a given refractive index of the medium, n (e.g. n=2.0). Based on the results, the silver nanocube with 30 nm edge length at the refractive index 2.0 is chosen as our objective. The sensitivity of the sensor is 3774.2 nm/RIU. The confinement of light in the PCF also is shown at resonance wavelength 551 nm. This study provides a basis for investigating the PCF refractive index sensor based on the LSPR of the metal nanoparticles. © 2012 Elsevier Ltd.

Zhou Y.,Beijing Jiaotong University | Chen Y.,Tsinghua University
IEEE Transactions on Systems, Man, and Cybernetics Part A:Systems and Humans | Year: 2010

Based on the life cycle of business process reengineering (BPR), BPR is decomposed into business reengineering (BR) at the strategic and tactical levels and process reengineering at the operational level, including process structural and parametric optimization, respectively. Quality-function- deployment-centered integrated tools are proposed to support the rational analysis and decision making in BR. The analytic hierarchy process is utilized to evaluate the intangible attributes. Questionnaire and stochastic simulation are used to determine the strategic goals. Correlation analysis is employed to appraise the effects of each reengineering objective on customer requirements and other reengineering objectives. The slack-adjusted assurance region data envelopment analysis model is developed to estimate the performance levels of benchmarked organizations and to predict the possible investment and incurred performances. Finally, the decision of reengineering objectives and their performance levels in a specified phase is made through the 01 integer programming model considering cost-effective predictive results, which brings about the formation of tactical goals. The proposed tools provide structured approaches to set strategic and tactical goals, and organically link them. Thus, they can provide a powerful support for aligning business strategies, information technology tactics, and business processes of reengineering organization with customer requirements. An illustrative example demonstrates the application of the systematic analysis and decision-making methodology supported by the proposed analytic tools. © 2009 IEEE.

Lei L.,Beijing Jiaotong University | Zhong Z.,Beijing Jiaotong University | Lin C.,Tsinghua University | Shen X.,University of Waterloo
IEEE Wireless Communications | Year: 2012

This article studies direct communications between user equipments in the LTE-advanced cellular networks. Different from traditional device-to-device communication technologies such as Bluetooth and WiFi-direct, the operator controls the communication process to provide better user experience and make profit accordingly. The related usage cases and business models are analyzed. Some technical considerations are discussed, and a resource allocation and data transmission procedure is provided. © 2012 IEEE.

Gijsenij A.,Alten PTS | Lu R.,Beijing Jiaotong University | Gevers T.,University of Amsterdam | Gevers T.,Autonomous University of Barcelona
IEEE Transactions on Image Processing | Year: 2012

Color constancy algorithms are generally based on the simplifying assumption that the spectral distribution of a light source is uniform across scenes. However, in reality, this assumption is often violated due to the presence of multiple light sources. In this paper, we will address more realistic scenarios where the uniform light-source assumption is too restrictive. First, a methodology is proposed to extend existing algorithms by applying color constancy locally to image patches, rather than globally to the entire image. After local (patch-based) illuminant estimation, these estimates are combined into more robust estimations, and a local correction is applied based on a modified diagonal model. Quantitative and qualitative experiments on spectral and real images show that the proposed methodology reduces the influence of two light sources simultaneously present in one scene. If the chromatic difference between these two illuminants is more than 1°, the proposed framework outperforms algorithms based on the uniform light-source assumption (with error-reduction up to approximately 30%). Otherwise, when the chromatic difference is less than 1° and the scene can be considered to contain one (approximately) uniform light source, the performance of the proposed method framework is similar to global color constancy methods. © 2011 IEEE.

Chen Y.,Beijing Jiaotong University | Lu J.,CAS Academy of Mathematics and Systems Science | Lin Z.,University of Virginia
Automatica | Year: 2013

A multi-agent system (MAS) consists of multiple agents, each under the influence of a local rule that represents its interaction with other agents. Most recent research on discrete-time MASs concentrates on local rules that are linear and does not deal with communication constraints on the information exchange among agents. However, local interactions between agents in the real world are more likely governed by nonlinear rules and are in the presence of time-varying delays. This paper aims to investigate the consensus of a discrete-time MAS with transmission nonlinearity and time-varying delays. In particular, based on a representative general nonlinear model, we obtain several basic criteria for the consensus of the MAS. These results cover several existing results as their special cases. Moreover, the model we consider does not satisfy the convexity assumption which was commonly taken as an important condition for the consensus of discrete-time MASs. The assumptions we make on the nonlinear transmission function are necessary in the sense that, if they are not satisfied, a connected topology can be constructed that does not guarantee consensus. © 2013 Elsevier Ltd. All rights reserved.

Ma Z.,Chang'an University | Shao C.,Beijing Jiaotong University | Ma S.,Chinese People's Public Security University | Ye Z.,Beijing Transportation Research Center
Expert Systems with Applications | Year: 2011

The main goal of this paper is to construct three sets of road safety performance indicators, which are regional road safety performance indicators, urban road safety performance indicators and highway safety performance indicators, respectively. Fuzzy Delphi Method and Grey Delphi Method are applied to quantify experts' attitudes to regional road safety, urban road safety and highway safety. Comparing the results of two methods, the different results of two methods are analyzed, and then the final safety performance indicators are obtained by taking the intersection of results of two methods. Finally, three sets of performance indicators are constructed, which can be described and evaluated the safety level of region, urban road and highway, respectively. The research findings show that the method used in this paper is feasible and practical and can be provided as a reference for the administrative authority of road safety. © 2010 Elsevier Ltd. All rights reserved.

Sun H.,Beijing Jiaotong University | Hou Z.,Beijing Jiaotong University | Li D.,University of Bedfordshire
IEEE Transactions on Automation Science and Engineering | Year: 2013

This work embodies the overspeed protection and safe headway control into an iterative learning control (ILC) based train trajectory tracking algorithm to satisfy the high safety requirement of high-speed railways. First, a D-type ILC scheme with overspeed protection is proposed. Then, a corresponding coordinated ILC scheme with multiple trains is studied to keep the safe headway. Finally, the control scheme under traction/braking force constraint is also considered for this proposed ILC-based train trajectory tracking strategy. Rigorous theoretical analysis has shown that the proposed control schemes can guarantee the asymptotic convergence of train speed and position to its desired profiles without requirement of the physical model aside from some mild assumptions on the system. Effectiveness is further evaluated through simulations. © 2004-2012 IEEE.

Xu F.,Beijing Jiaotong University | Saha S.C.,Queensland University of Technology
International Journal of Heat and Mass Transfer | Year: 2014

The transition from a steady to an unsteady flow induced by an adiabatic fin on the sidewall of a differentially heated air-filled cavity is numerically investigated. Numerical simulations have been performed over the range of Rayleigh numbers from Ra = 105-109. The temporal development and spatial structures of natural convection flows in the cavity with a fin are described. It has been demonstrated that the fin may induce the transition to an unsteady flow and the critical Rayleigh number for the occurrence of the transition is between 3.72 × 106 and 3.73 × 106. Furthermore, the peak frequencies of the oscillations triggered by different mechanisms are obtained through spectral analysis. It has been found that the flow rate through the cavity with a fin is larger than that without a fin under the unsteady flow, indicating that the fin may improve the unsteady flow in the cavity. © 2013 Elsevier Ltd. All rights reserved.

Xu M.,Tsinghua University | Wen X.,Tsinghua University | Yu Z.,Tsinghua University | Li Y.,Beijing Jiaotong University | Huang X.,Tsinghua University
Bioresource Technology | Year: 2011

Anaerobic membrane bioreactor and online ultrasonic equipment used to enhance membrane filtration were coupled to form a hybrid system (US-AnMBR) designed for long-term digestion of waste activated sludge. The US-AnMBR was operated under volatile solids loading rates of 1.1-3.7. gVS/L·d. After comprehensive studies on digestion performance and membrane fouling control in the US-AnMBR, the final loading rate was determined to be 2.7. gVS/L·d with 51.3% volatile solids destruction. In the US-AnMBR, the improved digestion was due to enhanced sludge disintegration, as indicated by soluble matter comparison in the supernatant and particle size distribution in the digested sludge. Maximum specific methanogenic activity revealed that ultrasound application had no negative effect on anaerobic microorganisms. Furthermore, implementing ultrasound effectively controlled membrane fouling and successfully facilitated membrane bioreactor operation. This lab-scale study demonstrates the potential feasibility and effectiveness of setting up a US-AnMBR system for sludge digestion. © 2011 Elsevier Ltd.

Wang Y.,Beijing Jiaotong University | Hazen B.T.,University of Tennessee at Knoxville
International Journal of Production Economics | Year: 2016

Throughout both the developing and the developed world, lack of consumer acceptance of remanufactured products prevents closed-loop supply chains of the circular economy from realizing the full potential value from remanufacturing. In this study, we examine how knowledge of remanufactured products in terms of cost, quality, and green attributes affects consumers׳ perception of both risk and value associated with purchasing remanufactured products, and how these perceptions subsequently affect consumers׳ purchase intentions in China. Based on prospect theory and literature on consumer perceived value and perceived risk, we use a 2×2×2 inter-group experiment to assess consumers׳ intention to purchase remanufactured products. The results of our structural equation modeling indicate that purchase intention is positively influenced by perceived value and negatively influenced by perceived risk. Perceived value is most influenced by quality knowledge, followed by cost knowledge and green knowledge. Perceived risk is most influenced by quality knowledge, followed by cost knowledge. The findings can help remanufacturers and closed-loop supply chain managers to develop management policies and marketing strategies. Our theory-based model can be used as the basis for future research regarding the consumer׳s role in the close-loop supply chain. © 2015 Elsevier B.V.

Sun D.,Beijing Jiaotong University | Ge B.,Beijing Jiaotong University | Ge B.,Michigan State University | Bi D.,Tsinghua University | Peng F.Z.,Michigan State University
International Journal of Electrical Power and Energy Systems | Year: 2013

The quasi-Z-source inverter (qZSI) has some unique advantages and is suitable for photovoltaic (PV) system. This paper proposes a new topology - a qZSI with battery for PV power generation system. Battery is paralleled with one of the capacitors in quasi-Z-source (qZS) network, instead of an additional DC/DC converter. This system inherits all the advantages of qZSI. Besides, with a battery, the system can smooth the grid-injected power when PV power fluctuates. The operating principle of the new topology is analyzed and the design scheme of the qZS network is presented. And then, closed-loop control strategy for the proposed system is designed to manage the three power flows of PV panel, grid, and battery in the system. Maximum Power Point Tracking (MPPT) has been implemented in the qZSI with battery-based PV system by using the proposed control scheme. Different operating modes are simulated. A small-scale power prototype with a real PV panel is built to test the proposed system. The simulation results and experimental results verify the proposed circuit, theoretical analysis, and the control scheme. © 2012 Elsevier Ltd. All rights reserved.

Qiu P.-C.,Beijing Jiaotong University | Ge B.-M.,Beijing Jiaotong University | Bi D.-Q.,Tsinghua University
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2011

An energy storage-based grid-connected photovoltaic (PV) power generation system is proposed to overcome the fluctuation of grid-injected power caused by the change of illumination intensity and temperature. On the basis of Maximum Power Point Tracking (MPPT) and grid-connected DC/AC conversion, a battery-based energy storage control system is employed to smooth the grid-injected power. Two-stage power conversion structure is adopted to minimize the capacity of switching devices and make the MPPT and DC/AC control decoupling. A bi-directional DC/DC converter couples the DC link bus to control the charging and discharging of battery bank, and double closed-loops improve the performance of energy storage system, where the inner loop controls the battery current and the outer loop controls the grid-injected power normally or DC link voltage when the grid disconnects. The proposed system not only has the function of MPPT and grid-connected generation, but also possesses the ability of power stabilization. It can keep the DC-link voltage constant through storing solar energy in the battery during the grid fault, which will improve the power generation efficiency greatly. The simulated model and experimental model of the whole system are estabilished and the simulated and experimental results verify the feasibility and effectiveness of the proposed control system.

Liu Y.C.,Beijing Jiaotong University | Jin G.R.,Beijing Jiaotong University | You L.,Tsinghua University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2010

Including collisional decoherence explicitly, phase sensitivity for estimating effective scattering strength χ of a two-component Bose-Einstein condensate is derived analytically. With a measurement of spin operator J̌x, we find that the optimal sensitivity depends on initial coherent spin state. It degrades by a factor of (2γ)1/3 below super-Heisenberg limit 1/N3/2 for particle number N and the dephasing rate 1γ

Zhou C.,Beijing Jiaotong University | Zhou C.,University of Jinan
Optics Communications | Year: 2013

Double-large-microfluidic-channels photonic crystal fiber (PCF) sensors filled with silver nanowires are presented to achieve localized surface plasmon resonance sensors and to overcome the manipulating difficulty in implementing the experimentation. Optical field distribution of the fiber at a certain wavelength is calculated and simulated using the finite element method (FEM), and the sensing properties are discussed in both areas of resonant wavelength and intensity detection. Numerical results show excellent sensing characteristics when diameter and amount of silver nanowires are selected at d=300 nm and m=5, respectively. Besides, spectral and amplitude sensitivities are 4400 nm/RIU and 1407 dB/RIU, respectively. Furthermore, the sensor resolutions are 2.3×10 -6 RIU and 3.1×10 -5 RIU, respectively. © 2012 Elsevier B.V.

Dong C.,University of Tennessee at Knoxville | Shao C.,Beijing Jiaotong University | Richards S.H.,University of Tennessee at Knoxville | Han L.D.,University of Tennessee at Knoxville
Transportation Research Part C: Emerging Technologies | Year: 2014

Short-term predictions of traffic parameters such as flow rate and time mean speed is a crucial element of current ITS structures, yet complicated to formulate mathematically. Classifying states of traffic condition as congestion and non-congestion, the present paper is focused on developing flexible and explicitly multivariate state space models for network flow rate and time mean speed predictions. Based on the spatial-temporal patterns of the congested and non-congested traffic, the NSS model and CSS model are developed by solving the macroscopic traffic flow models, conservation equation and Payne-Whitham model for flow rate and time mean speed prediction, respectively. The feeding data of the proposed models are from historical time series and neighboring detector measurements to improve the prediction accuracy and robustness. Using 2-min measurements from urban freeway network in Beijing, we provide some practical guidance on selecting the most appropriate models for congested and non-congested conditions. The result demonstrates that the proposed models are superior to ARIMA models, which ignores the spatial component of the spatial-temporal patterns. Compared to the ARIMA models, the benefit from spatial contribution is much more evident in the proposed models for all cases, and the accuracy can be improved by 5.62% on average. Apart from accuracy improvement, the proposed models are more robust and the predictions can retain a smoother pattern. Our findings suggest that the NSS model is a better alternative for flow rate prediction under non-congestion conditions, and the CSS model is a better alternative for time mean speed prediction under congestion conditions. © 2014 Elsevier Ltd.

Lei S.-F.,Hunan Normal University | Lei S.-F.,University of Missouri - Kansas City | Papasian C.J.,University of Missouri - Kansas City | Deng H.-W.,Hunan Normal University | And 3 more authors.
Journal of Bone and Mineral Research | Year: 2011

MicroRNAs (miRNAs) regulate posttranscriptional gene expression usually by binding to 3'-untranslated regions (3'-UTRs) of target message RNAs (mRNAs). Hence genetic polymorphisms on 3'-UTRs of mRNAs may alter binding affinity between miRNAs target 3'-UTRs, thereby altering translational regulation of target mRNAs and/or degradation of mRNAs, leading to differential protein expression of target genes. Based on a database that catalogues predicted polymorphisms in miRNA target sites (poly-miRTSs), we selected 568 polymorphisms within 3'-UTRs of target mRNAs and performed association analyses between these selected poly-miRTSs and osteoporosis in 997 white subjects who were genotyped by Affymetrix Human Mapping 500K arrays. Initial discovery (in the 997 subjects) and replication (in 1728 white subjects) association analyses identified three poly-miRTSs (rs6854081, rs1048201, and rs7683093) in the fibroblast growth factor 2 (FGF2) gene that were significantly associated with femoral neck bone mineral density (BMD). These three poly-miRTSs serve as potential binding sites for 9 miRNAs (eg, miR-146a and miR-146b). Further gene expression analyses demonstrated that the FGF2 gene was differentially expressed between subjects with high versus low BMD in three independent sample sets. Our initial and replicate association studies and subsequent gene expression analyses support the conclusion that these three polymorphisms of the FGF2 gene may contribute to susceptibility to osteoporosis, most likely through their effects on altered binding affinity for specific miRNAs. © 2011 American Society for Bone and Mineral Research.

Yang F.,Beijing Jiaotong University | Li C.,Beijing Jiaotong University | Lin Y.,Beijing Jiaotong University | Wang C.-A.,Tsinghua University
Materials Letters | Year: 2012

In this paper, porous mullite/corundum ceramics with high porosity, high strength and low thermal conductivity were fabricated by foam-gelcasting method using fused mullite powder as raw material. Effects of sintering temperature on linear shrinkage, bulk density, apparent porosity, compressive strength and thermal conductivity of the porous mullite/corundum ceramics were researched. As sintering temperature increased from 1350 to 1550°C, linear shrinkage increased from 2.6 to 9.5%, porosity decreased from 81 to 78%, bulk density increased from 0.59 to 0.69 g/cm 3, compressive strength increased from 3.1 to 11.7 MPa and thermal conductivity increased from 0.14 to 0.35 W/m•K. Porous microstructure was complex, where large spherical pores contained small cellular pores on their internal walls. © 2011 Elsevier B.V. All rights reserved.

Yao K.,Tsinghua University | Li X.,Beijing Jiaotong University
IEEE Transactions on Fuzzy Systems | Year: 2012

Uncertain process is a sequence of uncertain variables indexed by time and space. First, this paper presents a kind of uncertain process, known as the uncertain alternating renewal process, whose alternating interarrival times are uncertain variables. Then, it proves an uncertain alternating renewal theorem on the limit value of average working rate. Finally, an application of the alternating renewal theorem is discussed. © 2012 IEEE.

Zhang J.-L.,Beijing Jiaotong University | Chen J.,Tsinghua University
Computers and Operations Research | Year: 2013

In this paper, we study the supplier selection and procurement decision problem with uncertain demand, quantity discounts and fixed selection costs. In addition, a holding cost is incurred for the excess inventory if the buyer orders more than the realized demand and the shortage must be satisfied by an emergent purchase at a higher price otherwise. The objective is to select the suppliers and to allocate the ordering quantity among them to minimize the total cost (including selecting, procurement, holding and shortage costs, etc.). The problem is modeled as a Mixed Integer Programming (MIP) and is shown to be NP-hard. Some properties of the optimal policy are provided and an optimal algorithm is proposed based on the generalized Bender's decomposition. Numerical experiments are conducted to show the efficiency of the algorithm and to obtain some managerial insights. © 2013 Elsevier Ltd.

Xia M.,Beijing Jiaotong University | Chen J.,Tsinghua University
Fuzzy Sets and Systems | Year: 2015

The aim of a valued pairwise comparison matrix is to derive the priority structure over a set of criteria (or alternatives) in decision making. The consistency and consensus of a pairwise comparison matrix should be measured and improved to avoid a misleading priority structure. The basic entries of a pairwise comparison matrix can be described in different forms; hence, different consistency and consensus methods should be developed for different types of matrices. To provide a general framework, the pairwise comparison matrix based on Abelian linearly ordered group is first introduced. A consistency index is defined by constructing the nearest consistent pairwise comparison matrix from an inconsistent one, and two consistency improving methods are introduced. A group pairwise comparison matrix is derived, a consensus index of individual pairwise comparison matrices is defined and two consensus improving methods are developed by introducing a general aggregation operator based on Abelian linearly ordered group. The proposed consistency and consensus methods are convergent and can provide a general framework for existing methods. © 2014 Elsevier B.V. All rights reserved.

Zhang J.,Beijing Jiaotong University | Chen J.,Tsinghua University
International Journal of Production Economics | Year: 2013

In this paper, we study information sharing in a supply chain consisting of one supplier and one retailer, in which both the supplier and the retailer possess partial information on the demand. Under the single price contract, we show that whether a firm reveals its private information depends on the quality (variance) and the correlation of the two firms' information and the other firm's information revelation behavior. For the case that one firm (the retailer or the supplier) has complete information on the demand, the equilibrium is that the firm with complete information conceals its information and another reveals its information. Finally, we show that revenue sharing contract is coordinative, which ensures that both firms share their information completely and the retailer chooses the sale quantity which maximizes the total profit of the supply chain. This study shows that the members in a supply chain must sign coordinative contract in order to ensure that they share their information. © 2013 Elsevier B.V. All rights reserved.

Zhang J.,Beijing Jiaotong University | Shou B.,City University of Hong Kong | Chen J.,Tsinghua University
International Journal of Production Economics | Year: 2013

This paper studies the problem of how to coordinate postponed product differentiation and forecast update to improve manufacturing efficiency. We consider a two-stage model of multiple products with a common component. In stage 1, the manager obtains a prior demand distribution of each product and decides the production quantity of the common component. In stage 2, the demand forecast is updated and the common component is differentiated into various final products. Then the final demand of each product is realized and inventory leftover (shortage) is assessed. We use stochastic programming to model this problem, and propose an optimal bundle-type algorithm to solve it. Furthermore, we develop some simple and effective approximation algorithms for several special cases. Extensive numerical experiments are conducted to show the effectiveness of the approximation algorithms, to compare the performance between the traditional production model and the postponement production model, and to examine the impact of parameters on the performances of the two systems. © 2012 Elsevier B.V.

Wang C.,Beijing Jiaotong University | Li Y.,Tsinghua University
IEEE Transactions on Industrial Electronics | Year: 2010

The neutral-point (NP) potential of the three-level neutral-point-clamped converters is needed to maintain balancing. Zero-sequence voltage is the only freedom degree when carrier-based pulsewidth modulation is utilized. Appropriate zero-sequence voltage should be identified to control the NP potential. The relationship between the neutral current and injected zero-sequence voltage is studied comprehensively, and two balancing algorithms of NP potential, respectively adopting searching-optimization and interpolation methods, are presented. The theoretical optimum zero-sequence voltage for controlling NP potential can be obtained by the latter proposed algorithm. Simulation and experimental results are shown to verify the validity and practicability of the proposed algorithms. © 2010 IEEE.

Li Y.,Beijing Institute of Technology | Hu Y.,Beijing Institute of Technology | Zhao Y.,Beijing Institute of Technology | Shi G.,Tsinghua University | And 3 more authors.
Advanced Materials | Year: 2011

Green-luminescent functional graphene quantum dots (GQDs) are prepared by a facile electrochemical approach. The GQDs are rich in oxygen-containing functional groups and soluble in aqueous or organic media, facilitating further functionalization and various applications. Polymer photovoltaic devices using GQDs as a new type of electron-acceptor material are also demonstrated. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gao Y.,Beijing Jiaotong University | Ren G.,Beijing Jiaotong University | Zhu B.,Beijing Jiaotong University | Wang J.,Science and Technology on Optical Radiation Laboratory | Jian S.,Beijing Jiaotong University
Optics Letters | Year: 2014

We propose in this Letter a single-mode graphene-coated nanowire surface plasmon waveguide. The single-mode condition and modal cutoff wavelength of high order modes are derived from an analytic model and confirmed by numerical simulation. The mode number diagram of the proposed waveguide in the wavelength-radius space is also demonstrated. By changing the Fermi level of graphene, the performance of the proposed waveguide could be tuned flexibly, offering potential application in tunable nanophotonic devices. © 2014 Optical Society of America

Dong Q.,CAS Institute of Automation | Li L.,Beijing Jiaotong University
Neurocomputing | Year: 2013

Low-rank matrix factorization with missing elements has many applications in computer vision. However, the original model without taking any prior information, which is to minimize the total reconstruction error of all the observed matrix elements, sometimes provides a physically meaningless solution in some applications. In this paper, we propose a regularized low-rank factorization model for a matrix with missing elements, called Smooth Incomplete Matrix Factorization (SIMF), and exploit a novel image/video denoising algorithm with the SIMF. Since data in many applications are usually of intrinsic spatial smoothness, the SIMF uses a 2D discretized Laplacian operator as a regularizer to constrain the matrix elements to be locally smoothly distributed. It is formulated as two optimization problems under the l1 norm and the Frobenius norm, and two iterative algorithms are designed for solving them respectively. Then, the SIMF is extended to the tensor case (called Smooth Incomplete Tensor Factorization, SITF) by replacing the 2D Laplacian by a high-dimensional Laplacian. Finally, an image/video denoising algorithm is presented based on the proposed SIMF/SITF. Extensive experimental results show the effectiveness of our algorithm in comparison to other six algorithms. © 2013 Elsevier B.V.

Li W.,Beijing Jiaotong University | Zhang X.,Harbin Institute of Technology | Cheng S.,Harbin Institute of Technology | Cao J.,Beijing Jiaotong University
IEEE Transactions on Industrial Electronics | Year: 2013

High-speed permanent-magnet generators (HSPMGs) are common and important power generation equipment used in distributed generation systems. A 100-kW-level HSPMG is investigated in this paper, and its cooling system is optimized through electromagnetic-fluid-thermal analysis. First, the 2-D electromagnetic field of the machine is calculated by using the time-stepping finite element method, and the electromagnetic performance and loss distributions (heat sources) are determined, particularly the eddy loss of the rotor sleeve. Then, a thermal analysis model of the fluid for the HSPMG is established. Through numerical calculating, the whole region 3-D temperature distribution in the HSPMG is obtained, in which the influence of temperature on material properties is considered. Considering the variations of heat transfer abilities of the cooling medium, the temperatures in machines with different cooling structures are comparatively analyzed, and new cooling grooves with variable cross sections are proposed, which make the temperatures in the machine lower and more evenly distributed. The obtained conclusions may provide useful reference for the optimal design and research of HSPMGs. © 2012 IEEE.

Shu W.,Beijing Jiaotong University | Qian W.,Nanchang University | Qian W.,Beijing Key Laboratory of Knowledge Engineering for Materials Science
Knowledge-Based Systems | Year: 2014

Attribute measures, used to evaluate the quality of candidate attributes, play an important role in the process of attribute reduction. They largely affect the computational efficiency of attribute reduction. Existing attribute measures are acted on the whole universe in complete decision systems. There are few studies on improving attribute reduction algorithms from the perspective of attribute measures in incomplete decision systems, which motivates the study in this paper. This paper proposes new attribute measures that act on a dwindling universe to quicken the attribute reduction process. In particular, the monotonicity guarantees the rationality of the proposed attribute measures to evaluate the significance of candidate attributes. On this basis, the corresponding attribute reduction algorithms are developed in incomplete decision systems based on indiscernibility relation and discernibility relation, respectively. Finally, a series of comparative experiments are conducted with different UCI data sets to evaluate the performance of our proposed algorithms. The experimental results indicate that the proposed algorithms are efficient and feasible. © 2014 Elsevier B.V. All rights reserved.

Weng Q.,Japan International Center for Materials Nanoarchitectonics | Wang X.,Japan International Center for Materials Nanoarchitectonics | Wang X.,Beijing Jiaotong University | Bando Y.,Japan International Center for Materials Nanoarchitectonics | Golberg D.,Japan International Center for Materials Nanoarchitectonics
Chemical Society Reviews | Year: 2016

Functionalization is an important way to breed new properties and applications for a material. This review presents an overview of the progresses in functionalized hexagonal boron nitride (h-BN) nanomaterials. It begins with an introduction of h-BN structural features, physical and chemical properties, followed by an emphasis on the developments of BN functionalization strategies and its emerging properties/applications, and ends with the research perspectives. Different functionalization methods, including physical and chemical routes, are comprehensively described toward fabrication of various BN derivatives, hetero- and porous structures, etc. Novel properties of functionalized BN materials, such as high water solubility, excellent biocompatibility, tunable surface affinities, good processibility, adjustable band gaps, etc., have guaranteed wide applications in biomedical, electronic, composite, environmental and "green" energy-related fields. © 2016The Royal Society of Chemistry.

Ma L.,Beijing Jiaotong University | Srinivasan S.,University of Florida
Transportation Research Part A: Policy and Practice | Year: 2016

This study contributes by presenting an empirical assessment of the accuracy of the target-year populations synthesized with different base-year populations, data-fusion methods, and control tables. Forty-five synthetic populations were generated for 12 census tracts in Florida for this purpose. The empirical results indicate the value of synthesizing base-year populations more accurately by accommodating multi-level controls. Although fewer controls are typically available for target years, the use of multi-level controls in the target year with appropriate synthesis methods does benefit the accuracy of the synthetic population. This study also establishes that the magnitude of the overall error in the synthesized population appears to be linearly related to the magnitude of the input errors introduced via the control tables. The improvements in accuracy are statistically significant and hold after controlling for differences in population sizes and growth rates for the different census tracts. Overall, efforts to accurately synthesize base-year populations and to good forecasts of target-year controls can help synthesize accurate target-year populations. © 2016 Elsevier Ltd.

Weili L.,Beijing Jiaotong University | Chunwei G.,Harbin Institute of Technology | Yuhong C.,Harbin University of Science and Technology
IEEE Transactions on Energy Conversion | Year: 2013

In the premise of the measured circulation flow rate, the conjugate heat transfer in turbulent flow within one coupled rotor model of a 250-MW hydrogenerator was calculated. The flow rate changes of the fluid in the support, yoke ducts, pole gap, and the air gap between stator and rotor were researched using the finite volume method, also their effects on the operating rotor temperature. The analysis shows that it can accurately simulate the fluid field of the rotor ventilation system, which will provide theory basis for the design and improvement of the generator ventilation system. The calculated average temperature of the excitation winding is compared with its measured value, and the error is less than 1%. Thus, the results can be used to simulate temperatures of the rotor which cannot be easily measured. © 1986-2012 IEEE.

Song Y.,Beijing Jiaotong University | Li Q.,CAS Institute of Automation
2011 IEEE International Conference on Mechatronics and Automation, ICMA 2011 | Year: 2011

The tracking by detection algorithms treat visual tracking as the on-line object and its local surround background classification problem. The main shortcoming of the algorithms is the template drift due to the online self-learning mechanism of the visual tracker. To overcome the problem, a novel online Multiple Instance Learning (MIL) particle filter visual tracking algorithm is proposed. Main contributions of our work are: Firstly, we introduce online MIL Boosting algorithm in particle filter visual tracking framework to deal with the problem of target appearance model online learning by noisy labeled samples and to evaluate the importance weight for each particle; Secondly, the particle set, which represents the probability distribution density of the tracked target state, is utilized to construct the online training positive bag for the MIL Boosting classifier; At last, some experimental results show the proposed algorithm is a robust and accuracy tracking algorithm. © 2011 IEEE.

Hu Y.,Beijing Jiaotong University | Li D.,Beijing Jiaotong University | Shu S.,Xiangtan University | Niu X.,Shantou University
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2015

In this paper a full Eulerian lattice Boltzmann model is proposed for conjugate heat transfer. A unified governing equation with a source term for the temperature field is derived. By introducing the source term, we prove that the continuity of temperature and its normal flux at the interface is satisfied automatically. The curved interface is assumed to be zigzag lines. All physical quantities are recorded and updated on a Cartesian grid. As a result, any complicated treatment near the interface is avoided, which makes the proposed model suitable to simulate the conjugate heat transfer with complex interfaces efficiently. The present conjugate interface treatment is validated by several steady and unsteady numerical tests, including pure heat conduction, forced convection, and natural convection problems. Both flat and curved interfaces are also involved. The obtained results show good agreement with the analytical and/or finite volume results. © 2015 American Physical Society.

Hu Y.,Beijing Jiaotong University | Li D.,Beijing Jiaotong University | Shu S.,Xiangtan University | Niu X.,Shantou University
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2015

In this paper, a modified momentum exchange method for fluid-particle interactions is proposed based on the finite-volume lattice Boltzmann method. The idea of the improvement is to remove the restriction that the boundary points must be set as the midpoints of the grid lines or the intersection of the grid lines with the solid boundaries. The particle surface is represented by a set of arc (area) elements, and the interior fluid is used which the geometric conservation law is naturally satisfied. The interactions between fluid and arc (area) elements of particle boundary are considered using the momentum exchange method, and the mass of the fluid particles which collide with an arc (area) element is obtained by means of numerical integration in the control volume. The fluid field is corrected with the help of the smooth kernel function. Moreover, a generalized explicit time marching scheme is introduced to resolve the motion of particle in the problems with the ratio of particle density to fluid density is close to or less than 1. Finally, some numerical case studies of particle sedimentation are carried out to validate the present method. The corresponding results have a good agreement with the previous literature, which strongly demonstrates the capability of the improved method. © 2015 American Physical Society.

Liu J.,Beijing Jiaotong University | Liu J.,University of Toronto | Li J.,Xidian University | Feng L.,CAS Institute of Automation | And 4 more authors.
Cortex | Year: 2014

Face pareidolia is the illusory perception of non-existent faces. The present study, for the first time, contrasted behavioral and neural responses of face pareidolia with those of letter pareidolia to explore face-specific behavioral and neural responses during illusory face processing. Participants were shown pure-noise images but were led to believe that 50% of them contained either faces or letters; they reported seeing faces or letters illusorily 34% and 38% of the time, respectively. The right fusiform face area (rFFA) showed a specific response when participants "saw" faces as opposed to letters in the pure-noise images. Behavioral responses during face pareidolia produced a classification image (CI) that resembled a face, whereas those during letter pareidolia produced a CI that was letter-like. Further, the extent to which such behavioral CIs resembled faces was directly related to the level of face-specific activations in the rFFA. This finding suggests that the rFFA plays a specific role not only in processing of real faces but also in illusory face perception, perhaps serving to facilitate the interaction between bottom-up information from the primary visual cortex and top-down signals from the prefrontal cortex (PFC). Whole brain analyses revealed a network specialized in face pareidolia, including both the frontal and occipitotemporal regions. Our findings suggest that human face processing has a strong top-down component whereby sensory input with even the slightest suggestion of a face can result in the interpretation of a face. © 2014 Elsevier Ltd.

Wang X.,University of East Anglia | Li D.,University of Liverpool | Shi X.,Beijing Jiaotong University
Production Planning and Control | Year: 2012

The food industry is under pressure to improve food product safety, implement efficient risk management and rapid response capability, and manage quality from farm to fork. In this article, a new risk assessment approach is proposed to perform structured analysis of aggregative food safety risk in the food supply chain by using the concepts of fuzzy set theory and analytical hierarchy process. The novelty of this research lies in performing structured risk assessment and establishing an aggregative food safety risk indicator. It provides a single value representing the risk rating which can be effectively employed in incorporating the safety objectives into operations planning. It can function as a part of practical food safety management tool and help managers to understand how the risk changes and transfers in a supply chain. It will therefore improve food safety and quality through integrating the risk control with supply chain management. © 2012 Taylor & Francis.

Jun M.,Beijing Jiaotong University | Yanhong X.,Beijing Jiaotong University | Liguo Y.,China Academy of Building Research
Engineering Failure Analysis | Year: 2011

It is very important to study fluid-solid coupling problems of turbomachines which occur in the large revolving fluid machinery. Especially, the coupling between the fluid and the elastic solid is the most difficult problem in fluid-solid coupling of turbomachines. In order to solve this, the effect of the deformation and vibration of the elastic solid on the flow field and the reaction from the vibrating flow field on the solid need to be considered. The No. 18 axial-flow fan in Beijing's subway is selected as illustration to discuss the computational method for solving the fluid-solid coupling problem by considering the interaction of the blade deformation and the flow field using a numeric simulation analysis of the blade's pneumatic elasticity. The kind of coupling used is partitioned but loosely coupled with the software CFX to describe the flow field and the software ANSYS to describe the reaction of the structure. Both computational results will be shared on the exchanging platform MFX-ANSYS/CFX and compared with the situation where no elastic deformation is considered. It is indicated that the maximum stress including the pneumatic elasticity is twice the maximum stress without the pneumatic elasticity considered. The minimum safety coefficients approximate the permitted safety coefficients with the pneumatic elasticity considered. Contrarily, the actual minimum safety coefficients are far over the permitted safety coefficient, this is not consistent with the real situation and will magnify the safety of the blade structure, which demand the necessity of the pneumatic elastic analysis. © 2011 Elsevier Ltd.

Li J.,Beijing Jiaotong University | Li J.,University of East Anglia | He Z.,Beijing Jiaotong University | Gopee H.,University of East Anglia | Cammidge A.N.,University of East Anglia
Organic Letters | Year: 2010

[Chemical equaction presented] Novel triphenylene dimers linked by a central crown ether core have been synthesized and characterized. The crown ether is most conveniently formed as a final step to permit purification and isolation of ion-free material, and extension of the protocol permits synthesis of triad structures linked though a 27-crown-9 macrocycle. The latter compounds present a new discotic motif that supports mesophase formation. © 2010 American Chemical Society.

Qi H.-D.,University of Southampton | Xiu N.,Beijing Jiaotong University | Yuan X.,Hong Kong Baptist University
IEEE Transactions on Signal Processing | Year: 2013

The single-source localization problem (SSLP), which is nonconvex by its nature, appears in several important multidisciplinary fields such as signal processing and the global positioning system. In this paper, we cast SSLP as a Euclidean distance embedding problem and study a Lagrangian dual approach. It is proved that the Lagrangian dual problem must have an optimal solution under the generalized Slater condition. We provide a sufficient condition for the zero-duality gap and establish the equivalence between the Lagrangian dual approach and the existing Generalized Trust-Region Subproblem (GTRS) approach studied by Beck ['Exact and Approximate Solutions of Source Localization Problems,' IEEE Trans. Signal Process., vol. 56, pp. 1770-1778, 2008]. We also reveal new implications of the assumptions made by the GTRS approach. Moreover, the Lagrangian dual approach has a straightforward extension to the multiple-source localization problem. Numerical simulations demonstrate that the Lagrangian dual approach can produce localization of similar quality as the GTRS and can significantly outperform the well-known semidefinite programming solver SNLSDP for the multiple source localization problem on the tested cases. © 1991-2012 IEEE.

Xiao Y.,Beijing Jiaotong University | Zeng T.,Hong Kong Baptist University | Yu J.,Beijing Jiaotong University | Ng M.K.,Hong Kong Baptist University
Pattern Recognition | Year: 2011

In this paper, we study the restoration of images corrupted by Gaussian plus impulse noise, and propose a l1l0 minimization approach where the l1 term is used for impulse denoising and the l0 term is used for a sparse representation over certain unknown dictionary of images patches. The main algorithm contains three phases. The first phase is to identify the outlier candidates which are likely to be corrupted by impulse noise. The second phase is to recover the image via dictionary learning on the free-outlier pixels. Finally, an alternating minimization algorithm is employed to solve the proposed minimization energy function, leading to an enhanced restoration based on the recovered image in the second phase. Experimental results are reported to compare the existing methods and demonstrate that the proposed method is better than the other methods. © 2011 Elsevier Ltd. All rights reserved.

Deng X.,Beijing Jiaotong University | Yang W.,University of Manchester
Measurement Science Review | Year: 2012

The two-phase flow widely exists in the nature and industrial processes. The measurement of two-phase flows, including gas/solids, gas/liquid and liquid/liquid flows, is still challenging. Fusions of electrical tomography with conventional sensors provide possibilities to improve two-phase flow accurate measurement. In this paper, fusions of (1) electrical resistance tomography (ERT) with electromagnetic (EM) flowmeter, (2) electrical capacitance tomography (ECT) with ERT and (3) ECT with electrostatic sensor are introduced. Some research results of fusion methods are presented and discussed. This paper can provide the theoretical support for the multi-sensor fusion for two-phase flow measurement.

Zhang H.D.,Tianjin Institute of Urban Construction | Wang Y.F.,Beijing Jiaotong University
Steel and Composite Structures | Year: 2012

As an alternative to current conventional force-based assessment methods, the energy-based seismic performance of a code-designed 20-storey high-rise steel building is evaluated in this paper. Using 3D nonlinear dynamic time-history method with consideration of additional material damping effect, the influences of different restoring force models and P-Δ /δ effects on energy components are investigated. By combining equivalent viscous damping and hysteretic damping ratios of the structure subjected to strong ground motions, a new damping model, which is amplitude-dependent, is discussed in detail. According to the analytical results, all energy components are affected to various extents by P-Δ /δ effects and a difference of less than 10% is observed; the energy values of the structure without consideration of P-Δ /δ effects are larger, while the restoring force models have a minor effect on seismic input energy with a difference of less than 5%, but they have a certain effect on both viscous damping energy and hysteretic energy with a difference of about 5~15%. The paper shows that the use of the hysteretic energy at its ultimate state as a seismic design parameter has more advantages than seismic input energy since it presents a more stable value. The total damping ratio of a structure consists of viscous damping ratio and hysteretic damping ratio and it is found that the equivalent viscous damping ratio is a constant for the structure, while the equivalent hysteretic damping ratio approximately increases linearly with structural response in elasto-plastic stage.

Wang L.,Beijing Jiaotong University | Singh R.S.,University of Waterloo
Computational Statistics and Data Analysis | Year: 2014

For the two-parameter exponential family, a linear Bayes method is proposed to simultaneously estimate the parameter vector consisting of location and scale parameters. The superiority of the proposed linear Bayes estimator (LBE) over the classical UMVUE is established in terms of the mean square error matrix (MSEM) criterion. The proposed LBE is simple and easy to use compared with the usual Bayes estimator, which is obtained by the MCMC method. Numerical results are presented to verify that the LBE works well. In the empirical Bayes framework, the paper invokes a linear empirical Bayes estimator (LEBE) by using a linear combination of historical samples. It is shown under some mild regularity conditions that the LEBE is superior to the classical UMVUE and the maximum likelihood estimator in terms of MSEM. It is further shown with numerical results that the performance of LEBE gets better with the increase in the number of historical samples. © 2013 Elsevier B.V. All rights reserved.

Wang Z.,Beijing Jiaotong University | Wang Z.,Hebei University | Lou S.,Beijing Jiaotong University | Li P.,Hebei University
Journal of Alloys and Compounds | Year: 2014

A series of Sm3+, Eu3+, and Sm3 +-Eu3+ doped Sr3La(PO4)3 (SLP) are synthesized by using a high temperature solid-state method. SLP:Eu3+ emits red light, and the strongest peak locates at 613 nm under the 392 nm radiation excitation, which is attributed to the 5D0 → 7F2 transition of Eu 3+. SLP:Sm3+ produces red-orange light, and the peak locates at 598 nm under the 400 nm radiation excitation, which is assigned to the 4G5/2 → 6H7/2 transition of Sm3+. The energy transfer from Sm3+ to Eu3+ in SLP has been validated and the critical distance (Rc) of Sm 3+ to Eu3+ in SLP is calculated to be 1.50 nm. With increasing the Eu3+ doped concentration, the energy transfer efficiency (Sm3+ → Eu3+) gradually increases to 59.6%. Moreover, the emission color and emission intensity of SLP:Sm 3+, Eu3+ can be tuned by properly tuning the relative doped composition of Sm3+-Eu3+. © 2013 Elsevier B.V. All rights reserved.

Jing L.,Beijing Jiaotong University | Zhang C.,Beijing Jiaotong University | Ng M.K.,Hong Kong Baptist University
IEEE Transactions on Image Processing | Year: 2012

In this paper, we propose a novel supervised nonnegative matrix factorization-based framework for both image classification and annotation. The framework consists of two phases: training and prediction. In the training phase, two supervised nonnegative matrix factorizations for image descriptors and annotation terms are combined to identify the latent image bases, and to represent the training images in the bases space. These latent bases can capture the representation of the images in terms of both descriptors and annotation terms. Based on the new representation of training images, classifiers can be learnt and built. In the prediction phase, a test image is first represented by the latent bases via solving a linear least squares problem, and then its class label and annotation can be predicted via the trained classifiers and the proposed annotation mapping model. In the algorithm, we develop a three-block proximal alternating nonnegative least squares algorithm to determine the latent image bases, and show its convergent property. Extensive experiments on real-world image data sets suggest that the proposed framework is able to predict the label and annotation for testing images successfully. Experimental results have also shown that our algorithm is computationally efficient and effective for image classification and annotation. © 2012 IEEE.

Jing L.,Beijing Jiaotong University | Ng M.K.,Hong Kong Baptist University | Huang J.Z.,University of Hong Kong
Knowledge and Information Systems | Year: 2010

This paper presents a new knowledge-based vector space model (VSM) for text clustering. In the new model, semantic relationships between terms (e.g., words or concepts) are included in representing text documents as a set of vectors. The idea is to calculate the dissimilarity between two documents more effectively so that text clustering results can be enhanced. In this paper, the semantic relationship between two terms is defined by the similarity of the two terms. Such similarity is used to re-weight term frequency in the VSM. We consider and study two different similarity measures for computing the semantic relationship between two terms based on two different approaches. The first approach is based on the existing ontologies like WordNet and MeSH. We define a new similarity measure that combines the edge-counting technique, the average distance and the position weighting method to compute the similarity of two terms from an ontology hierarchy. The second approach is to make use of text corpora to construct the relationships between terms and then calculate their semantic similarities. Three clustering algorithms, bisecting k-means, feature weighting k-means and a hierarchical clustering algorithm, have been used to cluster real-world text data represented in the new knowledge-based VSM. The experimental results show that the clustering performance based on the new model was much better than that based on the traditional term-based VSM. © 2009 Springer-Verlag London Limited.

Peng H.-S.,University of Regensburg | Peng H.-S.,Beijing Jiaotong University | Stolwijk J.A.,University of Regensburg | Sun L.-N.,University of Regensburg | And 2 more authors.
Angewandte Chemie - International Edition | Year: 2010

Figure Presented A ratiometric fluorescent nanogel can sense pH over a range that is applicable to physiological studies. It can be easily prepared and made pH-responsive by addition of a pH probe and a FRET system that utilizes the gel to hold dyes in close proximity (see picture; overlay of coumarin dye and Nile Red fluorescence in kidney cells). © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zhao J.,Beijing Jiaotong University | Zheng J.-J.,Zhejiang University of Technology | Peng G.-F.,Beijing Jiaotong University | Van Breugel K.,Technical University of Delft
Cement and Concrete Research | Year: 2014

High-performance concrete (HPC) is prone to spalling under fire conditions. However, few quantitative theoretical studies on the spalling mechanism are available in the literature and the spalling mechanism has not been well interpreted. In this paper, the spalling behavior of cubic specimens is numerically modeled and the spalling mechanism is investigated at a meso-level. In modeling, the temperature field, the thermal decomposition of cement paste, the build-up vapor pressure, the moisture transport, and the distribution and evolution of thermal stresses in concrete are analyzed in a quantitative manner. Based on the numerical results, the spalling mechanism is interpreted from different angles. It is concluded that the explosive spalling of HPC specimens under fire exposure is mainly attributed to the temperature gradient-induced thermal stress. © 2014 Elsevier Ltd.

Chang M.K.,Hong Kong Baptist University | Cheung W.,Chinese University of Hong Kong | Tang M.,Beijing Jiaotong University
Information and Management | Year: 2013

Lack of trust has been shown to be a major obstacle to the adoption of online shopping. However, there has been little investigation of the effectiveness of various trust building mechanisms and their interactions. In our study, three trust building mechanisms (third-party certification, reputation, and return policy), were examined. A scenario survey method was used for data collection. 463 usable questionnaires were collected from respondents with diverse backgrounds. Regression results showed that all three trust building mechanisms had significant positive effect on trust of the online vendor. However, their effects were not simple; they interacted to produce a different overall effect on the level of trust. These results have both theoretical and practical implications. © 2013 Elsevier B.V.

Yu J.,University of Regensburg | Sun L.,University of Regensburg | Sun L.,University of Shanghai for Science and Technology | Peng H.,University of Regensburg | And 2 more authors.
Journal of Materials Chemistry | Year: 2010

Organic europium (III) and terbium (III) complexes (refered to as Eu1, Eu2, and Tb-L1, Tb-L2, respectively) have been synthesized that display bright emission and small bandwidth. Tb-L1 and Tb-L2 show lifetimes in the order of almost 1 ms at room temperature, good color purity, and high relative photoluminescence quantum yields. This makes them excellent probes for sensing temperature via measurement of luminescence lifetime. Probes Eu1, Eu2, Tb-L1 and Tb-L2 were incorporated into various polymer matrices to give sensor films for use as temperature-sensitive paints (TSPs). Eu (III) complexes have the advantage of being effectively excited by purple light-emitting diodes with their peak wavelengths of 405 nm. All TSPs based on these europium and terbium probes display good sensitivities to temperature, in particular, TSP based on Tb-L1 and Tb-L2 can show temperature-lifetime sensitivities of -13.8 μs per °C and - 9.2 μs per °C, respectively. Assuming a precision of ± 1 μs in the determination of lifetime, this will enable temperature to be determined with a precision of around ± 0.1 °C. This temperature dependence is the highest one reported so far for lanthanide complexes. © 2010 The Royal Society of Chemistry.

Song D.,University of Waterloo | Zhao S.,Beijing Jiaotong University | Aziz H.,University of Waterloo
Advanced Functional Materials | Year: 2011

Time resolved photoluminescence and electroluminescence measurements are used to study changes in the emission characteristics of materials typically used in phosphorescent organic light emitting devices (PhOLEDs). Studies on archetypical PhOLEDs with phosphorescent material, fac-tris(2-phenylpyridine) iridium (Ir(ppy) 3), show that the lifetime of triplet exciton is modified when in close proximity to a metal layer. Interactions with a metal layer ∼30-100 nm away, as is typically the case in PhOLEDs, result in an increase in the spontaneous emission decay rate of triplet excitons, and causes the exciton lifetime to become shorter as the distance between the phosphorescent material and the metal becomes smaller. The phenomenon, possibly the result of the confined radiation field by the metal, affects device efficiency and efficiency roll-off behavior. The results shed the light on phenomena affecting the efficiency behavior of PhOLEDs, and provide new insights for device design that can help enhance efficiency performance. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Song D.,University of Waterloo | Song D.,Beijing Jiaotong University | Zhao S.,Beijing Jiaotong University | Luo Y.,University of Waterloo | Aziz H.,University of Waterloo
Applied Physics Letters | Year: 2010

Delayed electroluminescence measurements are used to probe and differentiate between triplet-triplet-annihilation (TTA) and triplet-polaron-quenching (TPQ) processes and their correlation with efficiency roll-off in fac-tris(2-phenylpyridine) iridium-based phosphorescent organic light emitting devices. Investigations on devices employing 4, 4′ -bis(9-carbazolyl)- 1, 1′ -biphenyl (CBP) and 4, 4′, 4″ -tris(N -carbazolyl) triphenylamine, two widely used host materials, show that the efficiency roll-off is primarily due to TPQ processes. Guest-guest TTA, on the other hand, is found to play no major role, contrary to speculations, especially at low guest concentrations. Evidence of host-host TTA in certain cases, and its possible contribution to exciton quenching in the case of devices with CBP host, is also reported. © 2010 American Institute of Physics.

Chen X.,Hong Kong Polytechnic University | Ng M.K.,Hong Kong Baptist University | Zhang C.,Beijing Jiaotong University
IEEE Transactions on Image Processing | Year: 2012

Nonsmooth nonconvex regularization has remarkable advantages for the restoration of piecewise constant images. Constrained optimization can improve the image restoration using a priori information. In this paper, we study regularized nonsmooth nonconvex minimization with box constraints for image restoration. We present a computable positive constant θ for using nonconvex nonsmooth regularization, and show that the difference between each pixel and its four adjacent neighbors is either 0 or larger than θ in the recovered image. Moreover, we give an explicit form of θ for the box-constrained image restoration model with the non-Lipschitz nonconvex l p-norm (0

Jing L.,Beijing Jiaotong University | Ng M.K.,Hong Kong Baptist University
IEEE Transactions on Image Processing | Year: 2014

Image label prediction is a critical issue in computer vision and machine learning. In this paper, we propose and develop sparse label-indicator optimization methods for image classification problems. Sparsity is introduced in the label-indicator such that relevant and irrelevant images with respect to a given class can be distinguished. Also, when we deal with multi-class image classification problems, the number of possible classes of a given image can also be constrained to be small in which it is valid for natural images. The resulting sparsity model can be formulated as a convex optimization problem, and it can be solved very efficiently. Experimental results are reported to illustrate the effectiveness of the proposed model, and demonstrate that the classification performance of the proposed method is better than the other testing methods in this paper. © 2014 IEEE.

Jiang X.,Beijing Jiaotong University | Zhang L.,University of Maryland University College | Chen M.X.,University of Maryland University College
Transportation Research Part C: Emerging Technologies | Year: 2014

Short-term forecasting of high-speed rail (HSR) passenger flow provides daily ridership estimates that account for day-to-day demand variations in the near future (e.g., next week, next month). It is one of the most critical tasks in high-speed passenger rail planning, operational decision-making and dynamic operation adjustment. An accurate short-term HSR demand prediction provides a basis for effective rail revenue management. In this paper, a hybrid short-term demand forecasting approach is developed by combining the ensemble empirical mode decomposition (EEMD) and grey support vector machine (GSVM) models. There are three steps in this hybrid forecasting approach: (i) decompose short-term passenger flow data with noises into a number of intrinsic mode functions (IMFs) and a trend term; (ii) predict each IMF using GSVM calibrated by the particle swarm optimization (PSO); (iii) reconstruct the refined IMF components to produce the final predicted daily HSR passenger flow, where the PSO is also applied to achieve the optimal refactoring combination. This innovative hybrid approach is demonstrated with three typical origin-destination pairs along the Wuhan-Guangzhou HSR in China. Mean absolute percentage errors of the EEMD-GSVM predictions using testing sets are 6.7%, 5.1% and 6.5%, respectively, which are much lower than those of two existing forecasting approaches (support vector machine and autoregressive integrated moving average). Application results indicate that the proposed hybrid forecasting approach performs well in terms of prediction accuracy and is especially suitable for short-term HSR passenger flow forecasting. © 2014 Elsevier Ltd.

Jing L.,Beijing Jiaotong University | Ng M.K.,Hong Kong Baptist University | Zeng T.,Hong Kong Baptist University
IEEE Transactions on Neural Networks and Learning Systems | Year: 2013

In this paper, we study dictionary learning (DL) approach to identify the representation of low-dimensional subspaces from high-dimensional and nonnegative data. Such representation can be used to provide an affinity matrix among different subspaces for data clustering. The main contribution of this paper is to consider both nonnegativity and sparsity constraints together in DL such that data can be represented effectively by nonnegative and sparse coding coefficients and nonnegative dictionary bases. In the algorithm, we employ the proximal point technique for the resulting DL and sparsity optimization problem. We make use of coding coefficients to perform spectral clustering (SC) for data partitioning. Extensive experiments on real-world high-dimensional and nonnegative data sets, including text, microarray, and image data demonstrate that the proposed method can discover their subspace structures. Experimental results also show that our algorithm is computationally efficient and effective for obtaining high SC performance and interpreting the clustering results compared with the other testing methods. © 2012 IEEE.

Peng H.-S.,Beijing Jiaotong University | Huang S.-H.,Beijing Jiaotong University | Wolfbeis O.S.,University of Regensburg
Journal of Nanoparticle Research | Year: 2010

A ratiometric type of fluorescent nanoparticle was prepared via an encapsulation-reprecipitation method. By introducing an alkoxysilanized dye as a reference, the nanoparticles (NPs) give both a green and a red fluorescence under one single-wavelength excitation. The resulted ratiometric fluorescence is found to be highly temperature-dependent in the physiological range (25-45 °C), with an intensity temperature sensitivity of -4.0%/°C. Given the small size (20-30 nm in diameter) and biocompatible nature (silica out layer), such kind of NPs were very promising as temperature nanosensors for cellular sensing and imaging. © 2010 Springer Science+Business Media B.V.

Wang X.-H.,Beijing Jiaotong University | Peng H.-S.,Beijing Jiaotong University | Yang L.,Beijing Jiaotong University | You F.-T.,Beijing Jiaotong University | And 3 more authors.
Angewandte Chemie - International Edition | Year: 2014

Cellular respiration is a worthwhile criterion to evaluate mitochondrial dysfunction by measuring the dissolved oxygen. However, most of the existing sensing strategies merely report extracellular (ec-) or intracellular (ic-) O2 rather than intramitochondrial (im-) O2. Herein we present a method to assess tumor mitochondrial dysfunction with three phosphorescent nanosensors, which respond to ec-, ic-, and im-O2. Time-resolved luminescence is applied to determine the respective oxygen consumption rates (OCRs) under varying respiratory conditions. Data obtained for the OCRs and on (intra)cellular O2 gradients demonstrate that mitochondria in tumor cells are distinctly less active than those of healthy cells, resulting from restrained glucose utilization of and physical injury to the mitochondria. We believe that such a site-resolved sensing strategy can be applied to numerous other situations, for example to evaluate the adverse effects of drug candidates. © 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Peng H.,Beijing Jiaotong University | Stich M.I.J.,University of Regensburg | Yu J.,University of Regensburg | Sun L.-N.,University of Regensburg | And 2 more authors.
Advanced Materials | Year: 2010

Europium(III) Nanoparticles are fabricated for sensing and imaging of physiological temperatures (see image). The material shows visible-light excitation, line-like emission, inertness to external perturbers (such as oxygen in air), and a dynamic range that covers temperatures encountered in medicine and (cellular) biology. The resolution is ±0.3 °C. The nanoparticles may also be incorporated into a (conceivably sprayable) sensor film. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zhang C.D.,Beijing Jiaotong University | Ji S.W.,Beijing Jiaotong University | Dang S.P.,University of Manchester
Applied Mechanics and Materials | Year: 2014

With the development and proliferation of smart grid and the relevant techniques, smart the electricity monitor is increasingly important for improving the overall performance of power network. With a number of new attributes, the smart electricity monitor is significantly different from these conventional electricity meters. For example, it actively provides the information for the management, reliability and maintainability purposes and acts as an irreplaceable component in the power network. In this paper, we mainly focus on the design and implementation of the smart grid which integrates a series of innovative functions, for example demand forecasting and status estimation. Specifically, the research backgrounds pertaining to this field will be briefly introduced and the state-or-the-art mathematical models related to both demand forecasting and status estimation will be constructed accordingly. Also, to investigate their feasibility and efficiency, a set of simulations based on MATLAB will be conducted and the simulated results will be presented. Finally, a complete and innovative prototype of smart electricity use monitor integrating forecasting and status estimation functions can be constructed, verified and analysed in depth by both of mathematical expressions and simulated results. © (2014) Trans Tech Publications, Switzerland.

Chen D.X.,National University of Defense Technology | Deng X.,Beijing Jiaotong University | Yang W.Q.,University of Manchester
Review of Scientific Instruments | Year: 2010

The capacitance of a single electrode is usually measured by injecting a current to the electrode and measuring the resultant voltage on the electrode. In this case, a voltage-controlled current source with a high bandwidth is needed because the impedance is inversely proportional to the excitation frequency. In this design note, three different current sources are discussed: (1) the Howland current source, (2) a modified Howland current source, and (3) a dual op-amp current source. The principle and dynamic performances are presented and compared. Simulation and experimental results show that although the Howland current source has the lowest (i.e., worst) output impedance, its output is the most stable among the three current sources when the frequency changes. Therefore, it is suitable for single-electrode capacitance measurement. Initial tests have proven the feasibility of single-electrode capacitance sensor with the Howland current source. © 2010 American Institute of Physics.

Deng X.,Beijing Jiaotong University | Chen D.,National School of Technology | Yang W.,University of Manchester
Review of Scientific Instruments | Year: 2011

Accurate measurement of multiphase flows, including gassolids, gasliquid, and liquidliquid flows, is still challenging. In principle, electrical capacitance tomography (ECT) can be used to measure the concentration of solids in a gassolids flow and the liquid (e.g., oil) fraction in a gasliquid flow, if the liquid is non-conductive. Electrical resistance tomography (ERT) can be used to measure a gasliquid flow, if the liquid is conductive. It has been attempted to use a dual-modality ECTERT system to measure both the concentration profile and the velocity profile by pixel-based cross correlation. However, this approach is not realistic because of the dynamic characteristics and the complexity of multiphase flows and the difficulties in determining the velocities by cross correlation. In this paper, the issues with dual modality ECTERT and the difficulties with pixel-based cross correlation will be discussed. A new adaptive multi-modality (ECT, ERT and electro-dynamic) sensor, which can be used to measure a gassolids or gasliquid flow, will be described. Especially, some details of the electrodynamic sensor of multi-modality system such as sensing electrodes optimum design, electrostatic charge amplifier, and signal processing will be discussed. Initial experimental results will be given. © 2011 American Institute of Physics.

Lin C.,Beijing Jiaotong University | Tillo T.,Xi'an Jiaotong - Liverpool University | Zhao Y.,Beijing Jiaotong University | Jeon B.,Sungkyunkwan University
IEEE Transactions on Circuits and Systems for Video Technology | Year: 2011

In this paper, a novel multiple description video coding scheme is proposed to insert and control the redundancy at macro block (MB) level. By analyzing the error propagation paths, the relative importance of each MB is determined. The paths, in practice, depend on both the video content and the adopted video coder. Considering the relative importance of the MB and the network status, an unequal protection for the video data can be realized to exploit the redundancy effectively. In addition, a simple and effective approach is introduced to tune the quantization parameter for the variable rate coding case. The whole scheme is implemented in H.264/AVC by employing its coding options, thus generating descriptions that are compatible with the baseline profile and extended profile of H.264/AVC. Due to its general property, the proposed approach can be employed for other hybrid video codecs. The results demonstrate the advantage of the proposed approach over other H.264/AVC multiple description schemes. © 2011 IEEE.

Ma L.,Beijing Jiaotong University | Moisan L.,University of Paris Descartes | Yu J.,Beijing Jiaotong University | Zeng T.,Hong Kong Baptist University
IEEE Transactions on Medical Imaging | Year: 2013

The restoration of images corrupted by blur and Poisson noise is a key issue in medical and biological image processing. While most existing methods are based on variational models, generally derived from a maximum a posteriori (MAP) formulation, recently sparse representations of images have shown to be efficient approaches for image recovery. Following this idea, we propose in this paper a model containing three terms: a patch-based sparse representation prior over a learned dictionary, the pixel-based total variation regularization term and a data-fidelity term capturing the statistics of Poisson noise. The resulting optimization problem can be solved by an alternating minimization technique combined with variable splitting. Extensive experimental results suggest that in terms of visual quality, peak signal-to-noise ratio value and the method noise, the proposed algorithm outperforms state-of-the-art methods. © 1982-2012 IEEE.

Bu X.,Henan Polytechnic University | Yu F.,Henan Polytechnic University | Hou Z.,Beijing Jiaotong University | Wang F.,Henan Polytechnic University
Nonlinear Analysis: Real World Applications | Year: 2013

This paper considers the problem of iterative learning control (ILC) for a class of nonlinear systems with random packet dropouts. It is assumed that an ILC scheme is implemented via a networked control system (NCS), and that during the packet transfer between the remote nonlinear plant and the ILC controller packet dropout occurs. A new formulation is employed to model the packet dropout case, where the random dropout rate is transformed into a stochastic parameter in the system's representation. Through rigorous analysis, it is shown that under some given conditions, the iterative learning control can guarantee the convergence of the tracking error although some packets are missing. The analysis is also supported by a numerical example. © 2012 Published by Elsevier Ltd.

Bu X.,Henan Polytechnic University | Hou Z.,Beijing Jiaotong University | Yu F.,Henan Polytechnic University
International Journal of Control, Automation and Systems | Year: 2011

This paper presents a stability analysis of the iterative learning control (ILC) problem for discrete-time systems when the plants are subject to output measurement data dropouts. It is assumed that data dropout occurs during the data transfers from the plant to the ILC controller, resulting in what is called intermittent ILC. Using the super-vector approach for ILC, the expectation of output error is used to develop conditions for stability of the first order ILC and high order ILC processes. Through the theoretical analysis, it is shown that the convergence of the intermittent ILC is guaranteed although some measurements are missing. The analysis is also supported by numerical examples. © ICROS, KIEE and Springer 2011.

Xing X.,Beijing Jiaotong University | Jing T.,CAS Changchun Institute of Optics and Fine Mechanics and Physics | Cheng W.,George Washington University | Huo Y.,Beijing Jiaotong University | Cheng X.,University of Minnesota
IEEE Wireless Communications | Year: 2013

Spectrum sensing, spectrum decision, spectrum sharing, and spectrum mobility are four major functions of cognitive radio systems. Spectrum sensing is utilized to observe the spectrum occupancy status and recognize the channel availability, while CR users dynamically access the available channels through the regulation processes of spectrum decision, spectrum sharing, and spectrum mobility. To alleviate the processing delays involved in these four functions and to improve the efficiency of spectrum utilization, spectrum prediction for cognitive radio networks has been extensively studied in the literature. This article surveys the state of the art of spectrum prediction in cognitive radio networks. We summarize the major spectrum prediction techniques, illustrate their applications, and present the relevant open research challenges. © 2002-2012 IEEE.

Xu X.,National University of Defense Technology | Hou Z.,Beijing Jiaotong University | Lian C.,National University of Defense Technology | He H.,University of Rhode Island
IEEE Transactions on Neural Networks and Learning Systems | Year: 2013

In the past decade, adaptive critic designs (ACDs), including heuristic dynamic programming (HDP), dual heuristic programming (DHP), and their action-dependent ones, have been widely studied to realize online learning control of dynamical systems. However, because neural networks with manually designed features are commonly used to deal with continuous state and action spaces, the generalization capability and learning efficiency of previous ACDs still need to be improved. In this paper, a novel framework of ACDs with sparse kernel machines is presented by integrating kernel methods into the critic of ACDs. To improve the generalization capability as well as the computational efficiency of kernel machines, a sparsification method based on the approximately linear dependence analysis is used. Using the sparse kernel machines, two kernel-based ACD algorithms, that is, kernel HDP (KHDP) and kernel DHP (KDHP), are proposed and their performance is analyzed both theoretically and empirically. Because of the representation learning and generalization capability of sparse kernel machines, KHDP and KDHP can obtain much better performance than previous HDP and DHP with manually designed neural networks. Simulation and experimental results of two nonlinear control problems, that is, a continuous-action inverted pendulum problem and a ball and plate control problem, demonstrate the effectiveness of the proposed kernel ACD methods. © 2013 IEEE.

Hu H.,East China Jiaotong University | Hu H.,Beijing Jiaotong University
Applied Mechanics and Materials | Year: 2012

According to an energy-efficient mathematical model which usually uses GA algorithm to solve, a new algorithm based on firefly optimization algorithm is applied to solve it. Through calculation for a cited example, simulation results such as speed-position curve are got. Compared with other methods, it demonstrates this new FA-based algorithm has a better performance and can be considered to be put into practical use. © (2012) Trans Tech Publications, Switzerland.

Jeevarathinam C.,Bharathidasan University | Rajasekar S.,Bharathidasan University | Sanjuan M.A.F.,Rey Juan Carlos University | Sanjuan M.A.F.,Beijing Jiaotong University
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2011

The influence of linear time-delayed feedback on vibrational resonance is investigated in underdamped and overdamped Duffing oscillators with double-well and single-well potentials driven by both low frequency and high frequency periodic forces. This task is performed through both theoretical approach and numerical simulation. Theoretically determined values of the amplitude of the high frequency force and the delay time at which resonance occurs are in very good agreement with the numerical simulation. A major consequence of time-delayed feedback is that it gives rise to a periodic or quasiperiodic pattern of vibrational resonance profile with respect to the time-delayed parameter. An appropriate time delay is shown to induce a resonance in an overdamped single-well system which is otherwise not possible. For a range of values of the time-delayed parameters, the response amplitude is found to be larger than in delay-time feedback-free systems. © 2011 American Physical Society.

Luo H.,Beijing Jiaotong University | Zhang H.,Beijing Jiaotong University | Qiao C.,State University of New York at Buffalo
IEEE Transactions on Vehicular Technology | Year: 2011

In networks with locator/identifier separation, it is of critical importance to design an elegant mapping service to map identifiers onto locators. While there are many mapping services in the literature, how to support efficient host mobility is still an open issue. In this paper, we first borrow the idea of indirection from proxy mobile IPv6 and incorporate it into the design of a mapping service. In particular, we divide the network into many rendezvous domains (RDs) and assign a rendezvous point (RP) to a mobile node (MN) when it moves into an RD. In addition, the mapping registered into a mapping system for the MN is the mapping from the MN's identifier onto the RP's locator. When other nodes send packets to the MN, these packets are first sent to the MN's RP, which then sends packets to the attaching egress tunnel router. This way, the identifier-to-locator mapping for the MN remains unchanged as long as it roams within the same RD, thus supporting efficient host mobility. We then propose a method to build large RDs and handover processes to deal with host mobility. We also present numerical results to demonstrate the performance of the proposed approaches. © 2011 IEEE.

Du J.-S.,Beijing Jiaotong University | Au F.T.K.,University of Hong Kong
Gongcheng Lixue/Engineering Mechanics | Year: 2014

In the design of unbonded partially prestressed concrete (UPPC) beams, it is necessary to estimate the deflection of the member under service loads so as to satisfy the requirements of a serviceability limit state. Because of the unbonding between the prestressing tendons with their surrounding concrete and the variation of the neutral axis with the applied moment, the centroid location of the cracked section varies and therefore the corresponding cracked moment of inertia varies too. It is not easy to determine the deflection of a UPPC beam. The moment of inertia of cracked sections is first determined for UPPC beams. Then, based on the Branson's method, the effective moment of inertias as well as deflections for UPPC members can be easily calculated. The computed effective moment of inertia is close to that from Chinese Code for Design of Concrete Structures (GB50010-2010), and the ratio of the former to the latter is between 0.89~1.10. The computed deflections are compared with three researcher's test results, it is indicated that the developed method is correct and also applicable to UPPC beams with unbonded FRP tendons. While the current Chinese Code is not applicable to the deflections for UPPC beams with unbonded FRP tendons.

Xu S.,Beijing Jiaotong University | Xu S.,University of Hong Kong | Guo Y.F.,Beijing Jiaotong University | Ngan A.H.W.,University of Hong Kong
International Journal of Plasticity | Year: 2013

Molecular dynamics are employed to simulate the compression process of Al nanopillars with different orientations. The simulations show that the initial dislocations always nucleate at free surfaces but the compression orientation plays a decisive role in the subsequent microstructural evolution and stress-strain response of the pillars. For higher symmetry orientations of [0 0 1] and [1 1 1], frequent dislocation interactions make the dislocation- starvation state not easily achievable, and the more mean-field interaction condition leads to less serrated stress-strain response. Lower symmetry orientations behave in the opposite way. Simulation of the presence of a rigid coating on the pillar's surface also shows that dislocations are trapped by the coating with smooth strain-hardening after the initial dislocations are generated. The results show that whether the dislocation-starvation state can be achieved is a crucial factor governing the stress-strain response of small crystals. © 2012 Elsevier Ltd. All rights reserved.

Shang Z.-J.,Beijing Jiaotong University | Zhou H.,Beijing Jiaotong University | Wang T.-H.,Beijing Institute of Technology
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2012

Based on the analysis of complementary characteristics between wind power and hydropower, we construct a complementary system containing energy storage devices (such as batteries) of wind power and hydropower to improve synthetic power output characteristic, ensuring safe operation for the integrated main grid. Firstly, a mathematical model of optimal operation for hybrid wind with battery storage and hydropower system is constructed and maximum daily profit is therefore used as objective function. Then, based on wind speed data which is measured on spot as well as historical run-off data, and considering complicated constraints including acceptable power injection/supply and power balance equation and so on, we apply PSO algorithm to solve the given problem. The simulation demonstrats that the operation scheme that wind power is required to carry the base-load and hydropower to carry peak-load is feasible as long as the capacity of battery storage is appropriate during dry season. In this case, the output of hybrid wind-hydro power system is ensured to be within the permitted limit, and renewable energy will be fully utilized with satisfactory benefits.

Yu J.,Beijing Jiaotong University | Donohue K.D.,University of Kentucky
Journal of the Acoustical Society of America | Year: 2013

Complex relationships between array gain patterns and microphone distributions limit the application of optimization algorithms on irregular arrays. This paper proposes a Genetic Algorithm (GA) for microphone array optimization in immersive (near-field) environments. Geometric descriptors for irregular arrays are proposed for use as objective functions to reduce optimization time by circumventing the need for direct array gain computations. In addition, probabilistic descriptions of acoustic scenes are introduced for incorporating prior knowledge of the source distribution. To verify the effectiveness of the proposed optimization, signal-to-noise ratios are compared for GA-optimized arrays, regular arrays, and arrays optimized through direct exhaustive simulations. Results show enhancements for GA-optimized arrays over arbitrary randomly generated arrays and regular arrays, especially at low microphone densities where placement becomes critical. Design parameters for the GA are identified for improving optimization robustness for different applications. The rapid convergence and acceptable processing times observed during the experiments establish the feasibility of this approach for optimizing array geometries in immersive environments where rapid deployment is required with limited knowledge of the acoustic scene, such as in mobile platforms and audio surveillance applications. © 2013 Acoustical Society of America.

Yang L.,Renmin University of China | Zheng G.,Renmin University of China | Zhu X.,Beijing Jiaotong University
Habitat International | Year: 2013

This paper aims to describe the joint choice of residential location, travel mode, and departure time. First, based on random utility maximization theory, the Cross-Nested Logit model and traditional NL models are formulated respectively. House price, travel time, travel cost, and factors depicting the individual socio-economic characteristics are defined as exogenous variables, and the model choice sets are the combination of residential location subset, departure time subset, and travel mode choice subset. Second, using Beijing traffic survey data of 2005, the model parameters are estimated, and the direct and cross elasticity are calculated to analyze the change of alternatives probability brought by factors variation. Estimation results show the Cross-Nested Logit model outperforms the three kinds of NL model. It is also found by estimation results that decision makers will change first their departure times, then their travel modes, and finally their residential locations, when exogenous variables alter. Moreover, elasticity analysis results suggest that, for long-distance commuting, it is difficult to decrease car travels even if additional charges are imposed on car users. The effect on choice probability by variations in travel time of other travel mode can be considered as negligible for alternatives within 5. km commuting distance, and this effect are greatest for alternatives between 10 and 20. km commuting distance. These findings have important implications for transport demand management and residence planning. © 2012 Elsevier Ltd.

Jin Y.,Beijing Institute of Technology | Xu M.,Beijing Jiaotong University | Gao Z.,Beijing Jiaotong University
Journal of Computational and Nonlinear Dynamics | Year: 2011

An extended car-following model is proposed in this paper by using the generalized optimal velocity function and considering the multivelocity differences. The stability condition of the model is derived by using the linear stability theory. From the reductive perturbation method and nonlinear analysis, the Korteweg-de Vries (KdV) and modified Korteweg-de Vries (mKdV) equations are derived to describe the traffic behaviors near the neutral stability line and around the critical point, respectively. The corresponding soliton wave and kink-antikink soliton solution are used to describe the different traffic jams. It is found that the generalized optimal velocity function and multivelocity differences consideration can further stabilize traffic flow and suppress traffic jams. The theoretical results are well verified through numerical simulations. © 2011 American Society of Mechanical Engineers.

Chen Y.,Beijing Jiaotong University | Lu J.,CAS Academy of Mathematics and Systems Science | Yu X.,RMIT University | Hill D.J.,University of Hong Kong | Hill D.J.,University of Sydney
IEEE Circuits and Systems Magazine | Year: 2013

It is well known that a multi-agent system (MAS) is a specific system consisting of multiple interacting autonomous agents. Consensus or synchronization, as one of the typical collective behaviors, is ubiquitous in nature. Over the last decades, consensus has been widely investigated in various disciplines, including mathematics, physics, biology, engineering, and social sciences. In particular, consensus of MAS with dynamical topology is an emerging new topic motivated by many real-world applications, such as wireless communication and sensor networks. However, the collective behavior of MAS with dynamical topology is very complex and cannot be easily analyzed by the traditional approaches. To resolve the issue of dynamical topology, various techniques and methods have been developed in the last decade. This paper aims to review the main advances in the consensus of MAS with dynamical topology, including several fundamental models and the corresponding methods. The main purpose is to promote this emerging topic on multi-agent systems, with emphasis on the interdisciplinary interest from the circuits and systems engineering communities. © 2001-2012 IEEE.

Su L.-W.,Beijing Institute of Technology | Li X.-R.,Beijing Institute of Technology | Sun Z.-Y.,Beijing Institute of Technology | Sun Z.-Y.,Beijing Jiaotong University
Renewable and Sustainable Energy Reviews | Year: 2013

Methanol is considered as one of the potential materials for fossil-based fuel since its available applications in the fields of fuel and chemical materials. China has become the biggest methanol production country since 2006, so analyzing the consumption, production and transportation of methanol in China has great importance. In the present paper, the flow chart of methanol from production to consumption in China has been systematically described. Chinese industry and statistics data are introduced to analyze and discuss the total and segmental methanol amount in both production and consumption. In China, most of the methanol is primarily consumed in the synthesis of formaldehyde, alternative fuels, and acetic acid synthesis with the corresponding percentage of 35%, 33%, and 8%. Synthesis approaches from methanol to these downstream products are analyzed and the variation tendencies of the demand on these downstream products are predicted. In 2011, about 22.27 million t methanol was generated on-site, in which, 63.7%, 23.0% and 11.3% are produced by coal, natural gas and coke-oven gas respectively. Energy flows of each synthesis process based on these feedstocks are given and the energy efficiency are calculated and compared. As for the transportation, approximately 82.6% of methanol is relied on overland freight, 9% by marine and the rest 8.4% by train. Crown Copyright © 2013 Published by Elsevier Ltd. All rights reserved.

Ke L.-L.,Beijing Jiaotong University | Ke L.-L.,City University of Hong Kong | Yang J.,RMIT University | Kitipornchai S.,University of Queensland | Bradford M.A.,University of New South Wales
Composite Structures | Year: 2012

The bending, buckling and free vibration of annular microplates made of functionally graded materials (FGMs) are investigated in this paper based on the modified couple stress theory and Mindlin plate theory. This microplate model incorporates the material length scale parameter that can capture the size effect in FGMs. The material properties of the FGM microplates are assumed to vary in the thickness direction and are estimated through the Mori-Tanaka homogenization technique. The higher-order governing equations and boundary conditions are derived by using Hamilton's principle. The differential quadrature (DQ) method is employed to discretize the governing equations and to determine the deflection, critical buckling load and natural frequencies of FGM microplates. A parametric study is then conducted to investigate the influences of the length scale parameter, gradient index and inner-to-outer radius ratio on the bending, buckling and vibration characteristics of FGM microplates with hinged-hinged and clamped-clamped supports. The results show that the size effect on the bending, buckling and vibration characteristics is significant when the ratio of the microplate thickness to the material length scale parameter is smaller than 10. © 2012 Elsevier Ltd.

Jin Y.-F.,Beijing Institute of Technology | Xu M.,Beijing Jiaotong University
Chinese Physics Letters | Year: 2010

Bifurcation is investigated with the full velocity difference traffic model. Applying the Hopf theorem, an analytical Hopf bifurcation calculation is performed and the critical road length is determined for arbitrary numbers of vehicles. It is found that the Hopf bifurcation critical points locate on the boundary of the linear instability region. Crossing the boundary, the uniform traffic flow loses linear stability via Hopf bifurcation and the oscillations appear. © 2010 Chinese Physical Society and IOP Publishing Ltd.

Chen M.,Hunan University | He J.,Hunan University | Tang J.,Hunan University | Wu X.,Beijing Jiaotong University | Chen L.,Hunan University
Optics Express | Year: 2014

In this paper, a FPGAs-based real-time adaptively modulated 256/64/16QAM-encoded base-band OFDM transceiver with a high spectral efficiency up to 5.76bit/s/Hz is successfully developed, and experimentally demonstrated in a simple intensity-modulated direct-detection optical communication system. Experimental results show that it is feasible to transmit a raw signal bit rate of 7.19Gbps adaptively modulated real-time optical OFDM signal over 20km and 50km single mode fibers (SMFs). The performance comparison between real-time and off-line digital signal processing is performed, and the results show that there is a negligible power penalty. In addition, to obtain the best transmission performance, direct-current (DC) bias voltage for MZM and launch power into optical fiber links are explored in the real-time optical OFDM systems. © 2014 Optical Society of America.

Li W.,George Washington University | Cheng X.,George Washington University | Jing T.,Beijing Jiaotong University | Xing X.,Beijing Jiaotong University
Proceedings - IEEE INFOCOM | Year: 2013

The cooperation between the primary and the secondary users has attracted a lot of attention in cognitive radio networks. However, most existing research mainly focuses on the single-hop relay selection for a primary transmitter-receiver pair, which might not be able to fully explore the benefit brought by cooperative transmissions. In this paper, we study the problem of multi-hop relay selection by applying the network formation game. In order to mitigate interference and reduce delay, we propose a cooperation framework FTCO by considering the spectrum sharing in both the time and the frequency domain. Then we formulate the multi-hop relay selection problem as a network formation game, in which the multi-hop relay path is computed via performing the primary player's strategies in the form of link operations. We also devise a distributed dynamic algorithm PRADA to obtain a global-path stable network. Finally, we conduct extensive numerical experiments and our results indicate that cooperative multi-hop relaying can significantly benefit both the primary and the secondary network, and that the network graph resulted from our PRADA algorithm can achieve the global-path stability. © 2013 IEEE.

Li X.,Beijing University of Chemical Technology | Yang X.,Beijing Jiaotong University
International Journal of Uncertainty, Fuzziness and Knowlege-Based Systems | Year: 2013

With fixed running times at sections, cooperative scheduling (CS) approach optimizes the dwell times and the headway time to coordinate the accelerating and braking processes for trains, such that the recovery energy generated from the braking trains can be used by the accelerating trains. In practice, trains always have stochastic departure delays at busy stations. For reducing the divergence from the given timetable, the operation company generally adjusts the running times at the following sections. Focusing on the randomness on delay times and running times, this paper proposes a stochastic cooperative scheduling (SCS) approach. Firstly, we estimate the conversion and transmission losses of recovery energy, and then formulate a stochastic expected value model to maximize the utilization of the recovery energy. Furthermore, we design a binary-coded genetic algorithm to solve the optimal timetable. Finally, we conduct experimental studies based on the operation data from Beijing Yizhuang subway line. The results show that the SCS approach can save energy by 15.13% compared with the current timetable, and 8.81% compared with the CS approach. © 2013 World Scientific Publishing Company.

Yan X.,Beijing Jiaotong University | Yan X.,University of Electronic Science and Technology of China | Minnhagen P.,Umeå University
PLoS ONE | Year: 2015

The word-frequency distribution of a text written by an author is well accounted for by a maximum entropy distribution, the RGF (random group formation)-prediction. The RGF-distribution is completely determined by the a priori values of the total number of words in the text (M), the number of distinct words (N) and the number of repetitions of the most common word (kmax). It is here shown that this maximum entropy prediction also describes a text written in Chinese characters. In particular it is shown that although the same Chinese text written in words and Chinese characters have quite differently shaped distributions, they are nevertheless both well predicted by their respective three a priori characteristic values. It is pointed out that this is analogous to the change in the shape of the distribution when translating a given text to another language. Another consequence of the RGF-prediction is that taking a part of a long text will change the input parameters (M, N, kmax) and consequently also the shape of the frequency distribution. This is explicitly confirmed for texts written in Chinese characters. Since the RGF-prediction has no system-specific information beyond the three a priori values (M, N, kmax), any specific language characteristic has to be sought in systematic deviations from the RGF-prediction and the measured frequencies. One such systematic deviation is identified and, through a statistical information theoretical argument and an extended RGF-model, it is proposed that this deviation is caused by multiple meanings of Chinese characters. The effect is stronger for Chinese characters than for Chinese words. The relation between Zipf's law, the Simon-model for texts and the present results are discussed. © 2015 Yan, Minnhagen.

Su S.,Beijing Jiaotong University | Li X.,Beijing Jiaotong University | Tang T.,Beijing Jiaotong University | Gao Z.,Beijing University of Chemical Technology
IEEE Transactions on Intelligent Transportation Systems | Year: 2013

Given rising energy prices and environmental concerns, train energy-efficient operation techniques are paid more attention as one of the effective methods to reduce operation costs and energy consumption. Generally speaking, the energy-efficient operation technique includes two levels, which optimize the timetable and the speed profiles among successive stations, respectively. To achieve better performance, this paper proposes to optimize the integrated timetable, which includes both the timetable and the speed profiles. First, we provide an analytical formulation to calculate the optimal speed profile with fixed trip time for each section. Second, we design a numerical algorithm to distribute the total trip time among different sections and prove the optimality of the distribution algorithm. Furthermore, we extend the algorithm to generate the integrated timetable. Finally, we present some numerical examples based on the operation data from the Beijing Yizhuang subway line. The simulation results show that energy reduction for the entire route is 14.5%. The computation time for finding the optimal solution is 0.15 s, which implies that the algorithm is fast enough to be used in the automatic train operation (ATO) system for real-time control. © 2011 IEEE.

Jing T.,Beijing Jiaotong University | Zhu S.,Beijing Jiaotong University | Li H.,George Washington University | Cheng X.,George Washington University | Huo Y.,Beijing Jiaotong University
Proceedings - IEEE INFOCOM | Year: 2013

The benefits of cognitive radio networks have been well recognized with the dramatic development of the wireless applications in recent years. While many existing works assume that the secondary transmissions are negative interference to the primary users (PUs), in this paper, we take secondary users (SUs) as positive potential cooperators for the primary users. In particular, we consider the problem of cooperative relay selection, in which the PUs actively select appropriate SUs as relay nodes to enhance their transmission performance. The most critical challenge for such a problem of cooperative relay selection is how to select a relay efficiently. But due to the potentially large number of secondary users, it is infeasible for a PU transmitter to first scan all the SUs and then pick the best one. Basically, the PU transmitter intends to observe the SUs sequentially. After observing a SU, the PU needs to make a decision on whether to terminate its observation and use the current SU as its relay or to skip it and observe the next SU. We address this problem by using the optimal stopping theory, and derive the optimal stopping rule. To evaluate the performance of our proposed scheme, we conduct an extensive simulation study. The results reveal the impact of different parameters on the system performance, which can be adjusted to satisfy specific system requirements. © 2013 IEEE.

Qin L.,Beijing Jiaotong University | Zhu C.,University of Electronic Science and Technology of China | Zhao Y.,Beijing Jiaotong University | Bai H.,Beijing Jiaotong University | Tian H.,Beijing Jiaotong University
IEEE Transactions on Circuits and Systems for Video Technology | Year: 2013

Snakes, or active contours, have been widely used in image processing applications. An external force for snakes called gradient vector flow (GVF) attempts to address traditional snake problems of initialization sensitivity and poor convergence to concavities, while generalized GVF (GGVF) aims to improve GVF snake convergence to long and thin indentations (LTIs). In this paper, we find and show that both GVF and GGVF snakes essentially yield the same performance in capturing LTIs of odd widths, and generally neither can converge to even-width LTIs. Based on a thorough investigation of the GVF and GGVF fields within the LTI during their iterative processes, we identify the crux of the convergence problem, and accordingly propose a novel external force termed as component-normalized GGVF (CN-GGVF) to eliminate the problem. CN-GGVF is obtained by normalizing each component of initial GGVF vectors with respect to its own magnitude. Experimental results and comparisons against GGVF snakes show that the proposed CN-GGVF snakes can capture LTIs regardless of odd or even widths with a remarkably faster convergence speed, while preserving other desirable properties of GGVF snakes with lower computational complexity in vector normalization. © 1991-2012 IEEE.

Xu L.-H.,Beijing Jiaotong University | Shan X.,Beijing Jiaotong University | Li Z.-X.,Tianjin University
Gongcheng Lixue/Engineering Mechanics | Year: 2013

An improved two-parameter damage model is established by considering the effect of hysteretic deformation amplitude to accumulative damage energy dissipation. A new method of seismic damage assessment based on vulnerability analysis is proposed and the maximum inter-story drift angle is taken as the variable index to evaluate the global performance of structures. According to the response characteristics of a 9-story benchmark steel model structure under strong earthquakes, the optimization design is made to the weak stories and the theoretical vulnerability curves of the original steel frame structure and the one after optimization are obtained respectively, the damage status of the structures under different intensity earthquakes are evaluated. The analysis of structural anti-collapse capability on both structures is conducted based on Collapse Margin Ratio and results indicate that the proposed method can accurately evaluate the damage of a steel structure under strong earthquakes, and the anti-collapse capability of the optimized structure is improved largely.

Zhang X.,Beijing Jiaotong University | Zhu H.,Beijing University of Chemical Technology | Guo Z.,Beijing Jiaotong University | Wei Y.,Beijing Jiaotong University | Wang F.,Beijing University of Chemical Technology
Journal of Power Sources | Year: 2011

We report on the synthesis of sulfated SnO2 modified multi-walled carbon nanotubes (MWCNTs) composites as new supports of Pt catalyst (Pt-S-SnO2/MWCNTs) with the aims to enhance electron and proton conductivity and also catalytic activity for ethanol oxidation. The Pt-S-SnO2/MWCNTs catalyst is synthesized by a combination of improved sol-gel and pulse-microwave assisted polyol methods. The surface presence, morphology and structure of the Pt-S-SnO2/MWCNTs catalyst are characterized by Fourier transform infrared spectroscopy (FT-IR), high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD), respectively. The electrocatalytic properties of the Pt-S-SnO 2/MWCNTs catalyst for ethanol oxidation reactions are investigated by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. The results show that Pt-S-SnO2/MWCNTs catalyst exhibits higher catalytic activity for ethanol oxidation than Pt supported on non-sulfated SnO2/MWCNTs composites. © 2010 Published by Elsevier B.V. All rights reserved.

Cai W.-H.,Beijing Jiaotong University | Sun T.-T.,China Nuclear Power Technology Research Institute
Proceedings - 2011 2nd International Conference on Innovations in Bio-Inspired Computing and Applications, IBICA 2011 | Year: 2011

This article provides a new generation intelligent transportation system on the basis of cloud computing, aiming at existing problems and challenges of present intelligent transportation system. It describes architecture of a cloud transportation system from viewpoints of technology and presents how to build the cloud transportation system from perspectives of management. Because our intelligent transportation industry is in the primary phase, and cloud-computing application as the resource deliver mode is just in the research phase in transportation field, this article also takes some measures to promote the application of cloud computing in the transportation field. © 2011 IEEE.

Su S.,Beijing Jiaotong University | Tang T.,Beijing Jiaotong University | Li X.,Beijing University of Chemical Technology | Gao Z.,Beijing Jiaotong University
IEEE Transactions on Intelligent Transportation Systems | Year: 2014

Energy efficiency is paid more and more attention in railway systems for reducing the cost of operation companies and emissions to the environment. In subway systems, the optimizations on timetable and driving strategy are two important and closely dependent parts of energy-efficient operations. The former regulates the fleet size and the trip time at interstations, and the latter determines the control sequences of traction and braking force during the trip. Most conventional research optimized the timetable and the driving strategy separately such that global optimality cannot be achieved. In this paper, we analyze the hierarchy of energy-efficient train operation and then propose an integrated algorithm to generate the globally optimal operation schedule, which can get better energy-saving performance. Within the criteria of meeting the passenger demand, the integrated energy-efficient algorithm can simultaneously obtain the optimal timetable and driving strategy for trains, which realizes the combination of the high-level transportation management and the low-level train operation control. The simulation results based on the Beijing Yizhuang Subway Line illustrate that the integrated algorithm can achieve a 24.0% energy reduction for one day, on average. In addition, the computation time is within 2 s, which is short enough to be applied for real-time control system. © 2000-2011 IEEE.

Jing T.,Beijing Jiaotong University | Chen X.,Beijing Jiaotong University | Huo Y.,Beijing Jiaotong University | Cheng X.,George Washington University
Proceedings - IEEE INFOCOM | Year: 2012

Spectrum sharing is an emerging mechanism to resolve the conflict between the spectrum scarcity and the growing demands for the wireless broadband access. In this paper we investigate the achievable transmission capacity of a wireless backhaul mesh network that shares the spectrums of the underutilized cellular uplink over the underlay spectrum sharing model with several commonly adopted medium access control protocols: slotted-ALOHA, CSMA/CA, and TDMA. By employing stochastic geometry, we derive the probabilities for a packet to be successfully transmitted in the primary cellular uplink and the secondary mesh networks. The achievable transmission capacity of the secondary network with outage probability constraints from both the primary and the secondary systems is obtained according to Shannon's Theory. The capacity region and the achievable capacity when the outage probabilities equal their corresponding threshold values are analyzed numerically and the results illustrate the effect of adjusting the mesh network parameters on the achievable transmission capacity under different MAC protocols. © 2012 IEEE.

Wang X.,Ningbo University | Chang Y.,Beijing Jiaotong University | Feng T.,Beijing Jiaotong University
IEEE Transactions on Information Theory | Year: 2013

Optical orthogonal codes are commonly used as signature codes for optical code-division multiple access systems. So far, research on 2-D optical orthogonal codes has mainly concentrated on the same autocorrelation and cross-correlation constraints. In this paper, we are concerned about optimal 2-D optical orthogonal codes with the autocorrelation λa and the cross-correlation 1. Some combinatorial constructions for 2-D (n× m,k,λa,1)-optical orthogonal codes are presented. When k=3 and λa=2, the exact number of codewords of an optimal 2-D (n× m,3,2,1)-optical orthogonal code is determined for any positive integers n≡ 0,1,3,6,9,10;(mod 12) and m≡ 2;(mod 4). © 2012 IEEE.

Liu Y.,Beijing Jiaotong University | Kokko A.,Copenhagen Business School | Kokko A.,Stockholm School of Economics
Energy Policy | Year: 2010

The capacity of the Chinese wind power sector has increased rapidly over the past half-decade, essentially doubling every year since 2005. The purpose of this paper is to describe the industry's recent development and to discuss some of the policies and policy challenges related to the particular business environment in China. Three issues are highlighted: pricing policies, transmission capacity, and the structure of the equipment manufacturing industry, where substantial overcapacity is emerging as a serious problem. © 2010 Elsevier Ltd. All rights reserved.

Yang X.,Beijing Jiaotong University | Ning B.,Beijing Jiaotong University | Li X.,Beijing University of Chemical Technology | Tang T.,Beijing Jiaotong University
IEEE Transactions on Intelligent Transportation Systems | Year: 2014

The train timetable optimization problem in subway systems is to determine arrival and departure times for trains at stations so that the resources can be effectively utilized and the trains can be efficiently operated. Because the energy saving and the service quality are paid more attention, this paper proposes a timetable optimization model to increase the utilization of regenerative energy and, simultaneously, to shorten the passenger waiting time. First, we formulate a two-objective integer programming model with headway time and dwell time control. Second, we design a genetic algorithm with binary encoding to find the optimal solution. Finally, we conduct numerical examples based on the operation data from the Beijing Yizhuang subway line of China. The results illustrate that the proposed model can save energy by 8.86% and reduce passenger waiting time by 3.22% in comparison with the current timetable. © 2000-2011 IEEE.

Liu X.,Beijing Jiaotong University | Ortega R.,Supelec | Su H.,Zhejiang University | Chu J.,Zhejiang University
IEEE Transactions on Automatic Control | Year: 2010

A new framework to design adaptive controllers for nonlin-early parameterized systems is proposed in this technical note. The key step is the construction of a monotone mapping, which explicitly depends on some of the estimator tuning parameters. Convexity-that is related to monotonicity-has been explored by several authors. The property is assumed a priori and is useful for the design only in some region of state space, which is completed switching the controller. In our approach monotonicity can be used in the whole state space and, moreover, is enforced by the designer, effectively becoming a synthesis tool. One consequence of these features is that the controller does not rely on state-dependent switching. In order to dispose of degrees of freedom to render the function monotone we depart from standard adaptive control and adopt instead the recently introduced Immersion and Invariance approach. © 2010 IEEE.

Ke L.L.,Beijing Jiaotong University | Wang Y.S.,Beijing Jiaotong University | Reddy J.N.,Texas A&M University
Composite Structures | Year: 2014

Thermo-electro-mechanical vibration of piezoelectric cylindrical nanoshells is studied using the nonlocal theory and Love's thin shell theory. The governing equations and boundary conditions are derived using Hamilton's principle. An analytical solution is first given for the simply supported piezoelectric nanoshell by representing displacement components in the double Fourier series. Then, the differential quadrature (DQ) method is employed to obtain numerical solutions of piezoelectric nanoshells under various boundary conditions. The influence of the nonlocal parameter, temperature rise, external electric voltage, radius-to-thickness ratio and length-to-radius ratio on natural frequencies of piezoelectric nanoshells are discussed in detail. It is found that the nonlocal effect and thermoelectric loading have a significant effect on natural frequencies of piezoelectric nanoshells. © 2014 Elsevier Ltd.

Ke B.-R.,National Penghu University of Science and Technology | Ke B.-R.,Beijing Jiaotong University | Lin C.-L.,National Chung Hsing University | Lai C.-W.,National Chung Hsing University
Control Engineering Practice | Year: 2011

This paper presents a method to optimize the train-speed trajectory and control between successive stations for mass rapid transit systems with the cable signaling system. The MAX-MIN ant system is utilized to search for the optimal speed codes of each section while taking track gradient, average speed, restriction of train speed, acceleration and jerk into consideration. The train acceleration is further regulated by a fuzzy-PID gain scheduler to meet the speed commands determined. Satisfactory simulation results show applicability and effectiveness of the proposed approach as a tool for designing an energy-saving mass rapid transit system. © 2011 Elsevier Ltd.

Li X.,Beijing Jiaotong University | Chen X.,Shenzhen Metro Group Ltd. Co.
Journal of Construction Engineering and Management | Year: 2012

Grouting control of shield tunneling is of paramount importance to reduce settlements of existing tunnels below-passed by shield tunneling along a curved alignment and in crowded urban areas. The methodology and scheme of the grouting control of shield tunneling is illustrated taking the first Earth Pressure Balanced (EPB) shield below-crossing existing interval tunnels from Kexueguan station to Dajuyuan station of the Shenzhen metro line No. 1, for example. A combination methodology of the observational method and the predefined design method was set up to deal with parameters concerning the grouting control of shield tunneling. Some parameters of the grouting control were predefined or suggested before the below-crossing, and other parameters might be adjusted during construction on the basis of the observational method. The scheme primarily consists of preparation work before the below-crossing, automatic motoring system used in operation tunnels, simultaneous backfilling grouting and grouting directly through segment holes. For the simultaneous backfilling grouting, enough grouting was filled in the tail void with shield advance. With the help of automatic motoring system, the grouting directly through segment holes was employed in light of the measured settlements of existing tunnels. The maximum of the final measured settlements of existing tunnels is about 70% of the predefined allowable settlement of 20mm, which shows that the grouting control of shield tunneling is effective in reducing settlements of existing tunnels. The grouting practice can be used as references in similar conditions. © 2012 American Society of Civil Engineers.

Wang D.,Jinzhong University | Zheng Y.,Beijing Jiaotong University
Guangxue Xuebao/Acta Optica Sinica | Year: 2011

Dispersion of fiber may broaden the pulse width and lead to error, which must be avoided in optical communications. Using the finite element method (FEM) and considering the material dispersion of SiO2, the mode field, the effective index of fundamental mode and the dispersion property of double-cladding photonic crystal fiber (PCF) with circular arrangement are numerically simulated. Results show that the distance between large air holes and small air holes of the first layer and the diameter of large air holes determine the shape of dispersion curve when the distance and diameter of small air holes are unchanged. As some dispersion-compensating fiber, the effective mode refractive index has a transition at a wavelength, thus flattened dispersion can be realized. For example, when diameter d1=3.1 μm, d2=1 μm, distance Λ1=5 μm and Λ2=4 μm, within the wavelength range of 1.22~1.6 μm, the difference between the maximun and minimum of dispersion is less than 4 ps/(nm·km).

Wang F.,Beijing Jiaotong University | Liew S.C.,Chinese University of Hong Kong | Guo D.,Northwestern University
IEEE Journal on Selected Areas in Communications | Year: 2012

A wireless relay with multiple antennas is called a multiple-input- multiple-output (MIMO) switch if it maps its input links to its output links using precode-and-forward. Namely, the MIMO switch precodes the received signal vector in the uplink using some matrix for transmission in the downlink. This paper studies the scenario of K stations and a MIMO switch, which has full channel state information. The precoder at the MIMO switch is either a zero-forcing matrix or a network-coding matrix. With the zero-forcing precoder, each destination station receives only its desired signal with enhanced noise but no interference. With the network-coding precoder, each station receives not only its desired signal and noise, but possibly also self-interference, which can be canceled. Precoder design for optimizing the received signal-to-noise ratios at the destinations is investigated. For zero-forcing relaying, the problem is solved in closed form in the two-user case, whereas in the case of more users, efficient algorithms are proposed and shown to be close to what can be achieved by extensive random search. For network-coded relaying, we present efficient iterative algorithms that can boost the throughput further. © 2012 IEEE.

Ke J.,Beijing Jiaotong University | Li S.,Bank of Communications Beijing Branch
Advances in Information Sciences and Service Sciences | Year: 2012

Based on the cognitive, psychological and behavioral level, as well as the information disclosure of listed companies, this paper presents a study of noise trading on China's stock market. From the perspective of market efficiency and market risk, the impact of noise on the stock market is analyzed. Firstly, the statistical characteristics of the time series and the variance ratio is tested, the results show that the stock return series does not follow a standard random walk which reflects the existence of noise trading. Secondly, based on the theory of behavioral finance and the shares of listed companies selected as the sample data, the traditional capital asset pricing model and the behavior of capital asset pricing model are validated, the results show that the traditional Beta of capital asset pricing model is generally higher than behavior Beta, which implies the noise trader risk.

Wang D.,Jinzhong University | Zheng Y.,Beijing Jiaotong University
Guangxue Xuebao/Acta Optica Sinica | Year: 2013

Using the finite element method, the dispersion property, mode area and nonlinear coefficient are numerically simulated by artificially choosing the parameters of the proposed novel holey fiber. The results show that the novel fiber not only has a relatively simple structure, but also has better dispersion property. By optimizing the structure parameters, a flattened dispersion holey fiber with three zero-dispersion wavelengths (λ=1.0 μm, λ=1.53 μm, λ=1.81 μm) in the 900 nm wavelength range has been designed. These results can be used to guide the design of novel holey fiber.

Liu Y.,Beijing Jiaotong University | Wu H.-X.,Beijing Jiaotong University | Wang B.,Brunel University
Composites Part B: Engineering | Year: 2012

Metal hollow sphere (MHS) structures with a density gradient have attracted increasing attention in the effort to pursue improved energy absorption properties. In this paper, dynamic crushing of MHS structures of different gradients are discussed, with the gradients being received by stacks of hollow spheres of the same external diameter but different wall thicknesses in the crushing direction. Based on the dynamic performance of MHS structures with uniform density, a crude semi-empirical model is developed for the design of MHS structures in terms of gradient selections for energy absorption and protection against impact. Following this, dynamic responses of density graded MHS foams are comparatively analyzed using explicit finite element simulation and the proposed formula. Results show that the simple semi-empirical model can predict the response of density gradient MHS foams and is ready-to-use in the gradient design of MHS structures. © 2011 Elsevier Ltd. All rights reserved.

Yang L.,Beijing Jiaotong University | Zhou X.,University of Utah | Gao Z.,Beijing Jiaotong University
Soft Computing | Year: 2013

Severe weather conditions and inherent uncertainties in various components of railway traffic systems can lead to equipment breakdown and reduced capacity on tracks and stations. This paper formulates a two-stage fuzzy optimization model to obtain a robust rescheduling plan under irregular traffic conditions, and a scenario-based representation is adapted to characterize fuzzy recovery time durations on a double-track railway line. The model aims to minimize the expected total delay time in the rescheduled train schedule with respect to the original timetable. Two decomposed sub-models are further developed corresponding to the trains in different directions, and then GAMS optimization software is used to obtain the robust rescheduling plan. The numerical experiments demonstrate the effectiveness of the proposed approaches. © 2012 Springer-Verlag.

Wang F.,Beijing Jiaotong University | Yuan X.,Chinese University of Hong Kong | Liew S.C.,Chinese University of Hong Kong | Li Y.,University of Sydney
IEEE Journal on Selected Areas in Communications | Year: 2013

In this paper, we consider a bidirectional cellular relay network with distributed relays where a single base station exchanges information with multiple independent users through multiple single-antenna relays. We design the transceivers at the base station, the relays, and the users. The related optimization problems are generally non-convex and difficult to solve. In this paper, we propose a unified framework to design the transceiver algorithms based on two criteria, i.e. weighted sum MSE minimization and sum rate maximization. Specifically, we show that the sum rate maximization problem can be converted into an iterative weighted sum MSE minimization problem. Low-complexity iterative algorithms are developed for both weighted sum MSE minimization and sum rate maximization optimization problems. However, the convergence points of the proposed iterative algorithms are sensitive to the initial conditions, especially in the high signal-to-noise ratio (SNR) regime. For this reason, we further derive the high-SNR asymptotically optimal solutions and use them as the initials for the proposed iterative algorithms. Simulation results show that the proposed scheme can approximately double the system throughput, compared to the conventional four-stage transmission schemes. © 2013 IEEE.

Li W.,Beijing Jiaotong University | Qiu H.,Harbin University of Science and Technology | Zhang X.,Beijing Jiaotong University | Cao J.,Beijing Jiaotong University | Yi R.,Beijing Jingyi Jingye Electrical Technology Company
IEEE Transactions on Industrial Electronics | Year: 2014

In this paper, a superhigh-speed permanent-magnet generator (SHSPMG) which has an alloy sleeve on the rotor outer surface is investigated. The purpose of the sleeve is to fix the permanent magnets and protect them from being destroyed by the large centrifugal force. However, the sleeve material characteristics have much influence on the superhigh-speed machine, and therewith, most of rotor eddy-current losses are generated in the alloy rotor sleeve, which could increase the device temperature. Taking a 117-kW 60 000-r/min SHSPMG as an example, the influence of the sleeve on the generator output performance is analyzed when the generator sleeve is made of stainless steel, carbon fiber, copper-iron alloy, and copper. In addition, the eddy-current loss distributions could be gotten, and therewith, the variations of the eddy-current losses in different kinds of sleeves are analyzed. Based on the 3-D coupling field between the fluid and temperature, the temperature distributions were obtained when the sleeve adopts different materials. Moreover, the temperature variations of the permanent magnets are further analyzed. The obtained conclusions may provide some references for the design and analyses of the SHSPMG. © 1982-2012 IEEE.

Wang F.,Beijing Jiaotong University | Liew S.C.,Chinese University of Hong Kong | Guo D.,Northwestern University
IEEE Transactions on Information Theory | Year: 2013

This paper addresses joint transceiver and relay design for a wireless multiple-input multiple-output (MIMO) switching scheme that enables data exchange among multiple users. Here, a multiantenna relay linearly precodes the received (uplink) signals from multiple users and forwards the signal in the downlink, where the purpose of precoding is to let each user receive its desired signal with interference from other users suppressed. The problem of optimizing the precoder based on various design criteria is typically nonconvex and difficult to solve. The main contribution of this paper is a unified approach to solve the weighted sum mean square error (MSE) minimization and weighted sum rate maximization problems in MIMO switching. Specifically, an iterative algorithm is proposed for jointly optimizing the relay's precoder and the users' receive filters to minimize the weighted sum MSE. It is also shown that the weighted sum rate maximization problem can be reformulated as an iterated weighted sum MSE minimization problem and can, therefore, be solved similarly to the case of weighted sum MSE minimization. With properly chosen initial values, the proposed iterative algorithms are asymptotically optimal in both high- and low-signal-to-noise-ratio regimes for MIMO switching, either with or without self-interference cancellation (a.k.a., physical-layer network coding). Numerical results show that the optimized MIMO switching scheme based on the proposed algorithms significantly outperforms existing approaches in the literature. © 1963-2012 IEEE.

Cao H.,Beijing Jiaotong University | Wu Y.,Nanyang Normal University
International Journal of Bifurcation and Chaos | Year: 2013

Based on the detailed bifurcation analysis and the master stability function, bursting types and stable domains of the parameter space of the Rulkov map-based neuron network coupled by the mean field are taken into account. One of our main findings is that besides the square-wave bursting, there at least exist two kinds of triangle burstings after the mean field coupling, which can be determined by the crisis bifurcation, the flip bifurcation, and the saddle-node bifurcation. Under certain coupling conditions, there exists two kinds of striking transitions from the square-wave bursting (the spiking) to the triangle bursting (the square-wave bursting). Stable domains of fixed points, periodic solutions, quasiperiodic solutions and their corresponding firing regimes in the parameter space are presented in a rigorous mathematical way. In particular, as a function of the intrinsic control parameters of each single neuron and the external coupling strength, a stable coefficient of the Neimark-Sacker bifurcation is derived in a parameter plane. These results show that there exist complex dynamics and rich firing regimes in such a simple but thought-provoking neuron network. © 2013 World Scientific Publishing Company.

Fan L.-L.,Beijing Jiaotong University | Song Y.-D.,Beijing Jiaotong University | Song Y.-D.,Chonqing University
IET Control Theory and Applications | Year: 2012

This work investigates the model-following control problem associated with a class of non-linear systems in the presence of modelling uncertainties and actuator failures. The particular interest lies in the development of designer-friendly and cost-effective control scheme. By combining model-reference mechanism with robust adaptive radial basis function (RBF) neural network (NN), several control algorithms are derived without the need for precise system parameters or analytical-bound estimation on actuator failure variables. It is shown that the developed control algorithms are structurally simple and computationally inexpensive. Application of the proposed strategies to individual pitch control of wind turbines is also addressed. Formative stability analysis and numerical simulation on severe failure scenarios confirm the effectiveness of the proposed methods. © 2012 The Institution of Engineering and Technology.

Tian F.,Beijing Jiaotong University | Ohki Y.,Waseda University
IEEE Transactions on Dielectrics and Electrical Insulation | Year: 2014

Complex electric modulus, defined as the inverse of complex relative permittivity, can be a significantly powerful tool for analyzing dielectric behavior of a polymeric insulating material, especially at relatively high temperatures, where complex permittivity usually becomes very high due to electrode polarization and carrier transport. In this paper, a typical example of the above is clearly shown by referring to an experimental result obtained for epoxy resin. © 2014 IEEE.

Feng C.,University of Toronto | Feng C.,Beijing Jiaotong University | Au W.S.A.,University of Toronto | Valaee S.,King's College | Tan Z.,Beijing Jiaotong University
IEEE Transactions on Mobile Computing | Year: 2012

The recent growing interest for indoor Location-Based Services (LBSs) has created a need for more accurate and real-time indoor positioning solutions. The sparse nature of location finding makes the theory of Compressive Sensing (CS) desirable for accurate indoor positioning using Received Signal Strength (RSS) from Wireless Local Area Network (WLAN) Access Points (APs). We propose an accurate RSS-based indoor positioning system using the theory of compressive sensing, which is a method to recover sparse signals from a small number of noisy measurements by solving an ℓ1-minimization problem. Our location estimator consists of a coarse localizer, where the RSS is compared to a number of clusters to detect in which cluster the node is located, followed by a fine localization step, using the theory of compressive sensing, to further refine the location estimation. We have investigated different coarse localization schemes and AP selection approaches to increase the accuracy. We also show that the CS theory can be used to reconstruct the RSS radio map from measurements at only a small number of fingerprints, reducing the number of measurements significantly. We have implemented the proposed system on a WiFi-integrated mobile device and have evaluated the performance. Experimental results indicate that the proposed system leads to substantial improvement on localization accuracy and complexity over the widely used traditional fingerprinting methods. © 2012 IEEE.

Liu H.,Beijing Jiaotong University | Xu L.,Ohio State University
2nd International Symposium on Power Electronics for Distributed Generation Systems, PEDG 2010 | Year: 2010

In this paper, a novel doubly excited brushless machine (DEBM) with the radially laminated magnetic barrier rotor (RLMB-rotor) for wind power generator application is designed and built. The performance studies of the prototype RLMB-rotor DEBM with 10 rotor pole numbers by using the 2D transient finite element analysis model and the experimental method are presented. The magnetic fields, the no-load and loaded characteristics, the electromagnetic torque characteristics of the prototype machine are investigated. The experiment results validate the theoretical analysis results and all studies in this paper show that the prototype RLMB-rotor DEBM is a high efficiency wind power generator. © 2010 IEEE.

Wan J.,Beijing Jiaotong University | Ruan Q.,Beijing Jiaotong University | Li W.,Beijing Jiaotong University | Deng S.,China Machinery TDI International Engineering Co.
Journal of Machine Learning Research | Year: 2013

For one-shot learning gesture recognition, two important challenges are: how to extract distinctive features and how to learn a discriminative model from only one training sample per gesture class. For feature extraction, a new spatio-temporal feature representation called 3D enhanced motion scale-invariant feature transform (3D EMoSIFT) is proposed, which fuses RGB-D data. Compared with other features, the new feature set is invariant to scale and rotation, and has more compact and richer visual representations. For learning a discriminative model, all features extracted from training samples are clustered with the k-means algorithm to learn a visual codebook. Then, unlike the traditional bag of feature (BoF) models using vector quantization (VQ) to map each feature into a certain visual codeword, a sparse coding method named simulation orthogonal matching pursuit (SOMP) is applied and thus each feature can be represented by some linear combination of a small number of codewords. Compared with VQ, SOMP leads to a much lower reconstruction error and achieves better performance. The proposed approach has been evaluated on ChaLearn gesture database and the result has been ranked amongst the top best performing techniques on ChaLearn gesture challenge (round 2). © 2013 Jun Wan, Qiuqi Ruan, Shuang Deng and Wei Li.

Xu Y.-H.,Beijing Jiaotong University | Long S.,Ohio State University
Acta Crystallographica Section E: Structure Reports Online | Year: 2012

The title compound, C13H11BrN2O 2, consists of two six-membered rings linked by an amide group and adopts a near planar conformation. The dihedral angle between the two rings is 8.38 (11)°. In the crystal structure, there are intra-and inter-molecular N-H⋯O hydrogen bonds, the latter forming inversion dimers.

Tian F.,Waseda University | Tian F.,Beijing Jiaotong University | Ohki Y.,Waseda University
Journal of Physics D: Applied Physics | Year: 2014

Complex permittivity spectra were measured for epoxy resin at various temperatures and numerically fitted to theories of electrode polarization (EP) and ac conduction. Complex permittivity at high temperatures fits the Cole-Cole relation for EP well, with the shape parameter relating to the electrode blockage coefficient for ions. The Debye length, ion density and mobility, hopping rate and distance, and other parameters controlling the charge transport can be obtained. Both the density and mobility of ions are thermally activated, and the sum of their activation energies is nearly the same as the activation energy of ac conductivity. It is indicated that the theory of power-law frequency response as a result of short-range hopping of ions is an extension of the EP theory above its peak frequency. On the other hand, the relaxation of ac conduction revealed by electric modulus and that of EP appearing at low frequencies are due to long-range hopping of ions. It is demonstrated that data fitting of complex permittivity to the theories of EP and ac conduction in combination with the electric modulus analysis is effective to estimate various characteristic parameters of charge transport. © 2014 IOP Publishing Ltd.

Ding S.,Henan University of Technology | Gao Y.,Beijing Jiaotong University
Expert Systems with Applications | Year: 2014

This paper derives an optimal (σ,S) policy for uncertain multi-product newsboy problem. Demands for the products are estimated by experts and assumed to be independent uncertain variables. Uncertainty theory, which is a new mathematical tool to deal with human uncertainty, is employed to model demand distributions. A fixed setup cost and a linear ordering cost are incurred if products are ordered. Setup cost is variant and depends on whether a joint order or an individual order is placed. A methodology is proposed for determining the optimal (σ,S) policy. Finally, a two-product example is provided to show how to design an optimal (σ,S) policy in realistic situation. © 2013 Elsevier Ltd. All rights reserved.

Yin J.,Beijing Jiaotong University | Chen D.,Beijing Jiaotong University | Li L.,Indiana University – Purdue University Indianapolis
IEEE Transactions on Intelligent Transportation Systems | Year: 2014

Current research in automatic train operation concentrates on optimizing an energy-efficient speed profile and designing control algorithms to track the speed profile, which may reduce the comfort of passengers and impair the intelligence of train operation. Different from previous studies, this paper presents two intelligent train operation (ITO) algorithms without using precise train model information and offline optimized speed profiles. The first algorithm, i.e., ITOe, is based on an expert system that contains expert rules and a heuristic expert inference method. Then, in order to minimize the energy consumption of train operation online, an ITOr algorithm based on reinforcement learning (RL) is developed via designing an RL policy, reward, and value function. In addition, from the field data in the Yizhuang Line of the Beijing Subway, we choose the manual driving data with the best performance as ITOm. Finally, we present some numerical examples to test the ITO algorithms on the simulation platform established with actual data. The results indicate that, compared with ITOm, both ITOe and ITOr can improve punctuality and reduce energy consumption on the basis of ensuring passenger comfort. Moreover, ITOr can save about 10% energy consumption more than ITOe. In addition, ITOr is capable of adjusting the trip time dynamically, even in the case of accidents. © 2000-2011 IEEE.

An Q.,Beijing Jiaotong University | Zhang F.,Beijing Jiaotong University | Li L.,Beijing Jiaotong University | Wang J.,Beijing Jiaotong University | And 3 more authors.
ACS Applied Materials and Interfaces | Year: 2014

We present performance improved ternary bulk heterojunction polymer solar cells by doping a small molecule, 2,4-bis[4-(N,N-diisobutylamino)-2,6- dihydroxyphenyl] squaraine (DIB-SQ), into the common binary blend of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM). The optimized power conversion efficiency (PCE) of P3HT:PC71BM-based cells was improved from 3.05% to 3.72% by doping 1.2 wt % DIB-SQ as the second electron donor, which corresponds to ∼22% PCE enhancement. The main contributions of doping DIB-SQ material on the improved performance of PSCs can be summarized as (i) harvesting more photons in the low-energy range, (ii) increased exciton dissociation, energy transfer, and charge carrier transport in the ternary blend films. The energy transfer process from P3HT to DIB-SQ is demonstrated by time-resolved transient photoluminescence spectra through monitoring the lifetime of 700 nm emission from neat P3HT, DIB-SQ and blended P3HT:DIB-SQ solutions. The lifetime of 700 nm emission is increased from 0.9 ns for neat P3HT solution, to 4.9 ns for neat DIB-SQ solution, to 6.2 ns for P3HT:DIB-SQ blend solution. © 2014 American Chemical Society.

Jiang Z.-Y.,Northwest University, China | Liang M.-G.,Beijing Jiaotong University | An W.-J.,Beijing Jiaotong University
Physica A: Statistical Mechanics and its Applications | Year: 2014

The transport efficiency of a network strongly depends on the underlying structure. The traffic capacity of one real network may be actually very small due to the heterogeneous degree distribution of the network under the global shortest path routing strategy. For the purpose of improving the traffic capacity of the network, in this paper, we propose three edge rewiring strategies. Extensive simulations under the efficient routing (ER) and the shortest path (SP) routing are applied to verify the effectiveness of the proposed edge rewiring mechanisms. It is found that the traffic capacity of the network can be substantially enhanced and the edge rewiring strategies are beneficial to the improvement of overall traffic handling and delivering ability of the network, especially under the SP routing strategy. The edge rewiring methods can be used incrementally to ameliorate the network transportation performance by network service providers. © 2013 Elsevier B.V. All rights reserved.

Liu L.,Beijing Jiaotong University | Tao C.,Beijing Jiaotong University | Tao C.,China Mobile | Qiu J.,Beijing Jiaotong University | And 4 more authors.
IEEE Journal on Selected Areas in Communications | Year: 2012

This paper presents a novel and practical study on the position-based radio propagation channel for High-Speed Railway by performing extensive measurements at 2.35 GHz in China. The specification on the path loss model is developed. In particular, small scale fading properties such as K-factor, Doppler frequency feature and time delay spread are parameterized, which show dynamic variances depending on the train location and the transceiver separation. Finally, the statistical position-based channel models are firstly established to characterize the High-Speed Railway channel, which significantly promotes the evaluation and verification of wireless communications in relative scenarios. © 2012 IEEE.

Zheng C.,Fudan University | Chen J.J.,Fudan University | Chen J.J.,Beijing Jiaotong University | Fan R.,Fudan University
Organic Letters | Year: 2014

A facile approach to construct 3,4-fused tricyclic azepino[5,4,3-cd]indoles from 2-alkynyl anilines, isocyanides, and α,β-unsaturated acids is reported. This synthetic process involves a regioselective meta- functionalization of 2-alkynylanilines using a dearomatization strategy and a palladium(II)-catalyzed domino heterocyclization/Heck reaction. © 2014 American Chemical Society.

Gao S.,Beijing Jiaotong University | Zhang H.,Beijing Jiaotong University | Das S.K.,University of Texas at Arlington
IEEE Transactions on Mobile Computing | Year: 2011

Recent work has shown that sink mobility along a constrained path can improve the energy efficiency in wireless sensor networks. However, due to the path constraint, a mobile sink with constant speed has limited communication time to collect data from the sensor nodes deployed randomly. This poses significant challenges in jointly improving the amount of data collected and reducing the energy consumption. To address this issue, we propose a novel data collection scheme, called the Maximum Amount Shortest Path (MASP), that increases network throughput as well as conserves energy by optimizing the assignment of sensor nodes. MASP is formulated as an integer linear programming problem and then solved with the help of a genetic algorithm. A two-phase communication protocol based on zone partition is designed to implement the MASP scheme. We also develop a practical distributed approximate algorithm to solve the MASP problem. In addition, the impact of different overlapping time partition methods is studied. The proposed algorithms and protocols are validated through simulation experiments using OMNET++. © 2011 IEEE.

Peng H.-S.,University of Washington | Peng H.-S.,Beijing Jiaotong University | Chiu D.T.,University of Washington
Chemical Society Reviews | Year: 2015

Soft fluorescent nanomaterials have attracted recent attention as imaging agents for biological applications, because they provide the advantages of good biocompatibility, high brightness, and easy biofunctionalization. Here, we provide a survey of recent developments in fluorescent soft nano-sized biological imaging agents. Various soft fluorescent nanoparticles (NPs) (including dye-doped polymer NPs, semiconducting polymer NPs, small-molecule organic NPs, nanogels, micelles, vesicles, and biomaterial-based NPs) are summarized from the perspectives of preparation methods, structure, optical properties, and surface functionalization. Based on both optical and functional properties of the nano-sized imaging agents, their applications are then reviewed in terms of in vitro imaging, in vivo imaging, and cellular-process imaging, by means of specific or nonspecific targeting. This journal is © The Royal Society of Chemistry 2015.

Li F.-L.,Beijing Jiaotong University | Wang Y.-S.,Beijing Jiaotong University | Zhang C.,University of Siegen | Yu G.-L.,Beijing Jiaotong University
Wave Motion | Year: 2013

A boundary element method (BEM) is presented to compute the bandgaps of two-dimensional (2D) solid-fluid phononic crystals which are composed of square or triangular lattices with arbitrarily shaped scatterers. The system may be either an array of solid scatterers embedded in the fluid matrix or an array of fluid scatterers embedded in a solid matrix. The boundary integral equations of both matrix and scatterer are established for a periodic unit cell. Substituting the quasi-periodic boundary condition (i.e. Bloch-Floquet condition) and the interface conditions, an eigenvalue equation dependent on the Bloch wave vector is derived. The present method takes into account the solid-fluid interface conditions and the transverse wave mode in the solid component which has been proved to be significant. Some typical examples are illustrated to discuss the accuracy of the presented method and analyze the localization mode of the fluid scatterers. © 2012 Elsevier B.V.

Li F.-L.,Beijing Jiaotong University | Wang Y.-S.,Beijing Jiaotong University | Zhang C.,University of Siegen
Physica Scripta | Year: 2011

A numerical method based on the Dirichlet-to-Neumann (DtN) map is presented to compute the bandgaps of two-dimensional phononic crystals, which are composed of square or triangular lattices of circular solid cylinders in a fluid matrix. The DtN map is constructed using the cylindrical wave expansion in a unit cell. A linear eigenvalue problem, which depends on the Bloch wave vector and involves relatively small matrices, is formulated. Numerical calculations are performed for typical systems with various acoustic impedance ratios of the solid inclusions and the fluid matrix. The results indicate that the DtN-map based method can provide accurate results for various systems efficiently. In particular it takes into account the fluid-solid interface conditions and the transverse wave mode in the solid component, which has been proven to be significant when the acoustic impedance of the solid inclusions is close to or smaller than that of the fluid matrix. For systems with an acoustic impedance of the inclusion much less than that of the matrix, physical flat bands appear in the band structures, which will be missed if the transverse wave mode in the solid inclusions is neglected. © 2011 The Royal Swedish Academy of Sciences.

Li F.-L.,Beijing Jiaotong University | Wang Y.-S.,Beijing Jiaotong University | Zhang C.,University of Siegen | Yu G.-L.,Beijing Jiaotong University
Engineering Analysis with Boundary Elements | Year: 2013

A boundary element method (BEM) is developed to calculate the elastic band gaps of two-dimensional (2D) phononic crystals which are composed of square or triangular lattices of solid cylinders in a solid matrix. In a unit cell, the boundary integral equations of the matrix and the scatterer are derived, the former of which involves integrals over the boundary of the scatterer and the periodic boundary of the matrix, while the latter only involves the boundary of the scatterer. Constant boundary elements are adopted to discretize the boundary integral equations. Substituting the periodic boundary conditions and the interface conditions, a linear eigenvalue equation dependent on the Bloch wave vector is derived. Some numerical examples are illustrated to discuss the accuracy, efficiency, convergence and the computing speed of the presented method. © 2012 Elsevier Ltd.

Golub M.V.,Kuban State University | Zhang C.,University of Siegen | Wang Y.-S.,Beijing Jiaotong University
Journal of Sound and Vibration | Year: 2012

Plane SH-wave propagation in periodically layered elastic composites with a damaged layer is investigated. Two different models are developed to approximate the damaged layer, namely, a periodic array of cracks and continuously distributed springs in the layer. In the first model, the total wave field in the elastic stack of layers with cracks is described as a sum of incident wave field modeled by the transfer matrix method and the scattered wave field governed by an integral representation in terms of the crack-opening-displacements on the crack-faces. The integral equation derived from the boundary conditions on the crack-faces is solved numerically by a Galerkin method. By using BlochFloquet theorem the crack-opening-displacements for a periodic array of cracks are expressed by the crack-opening-displacement on a reference crack. In the spring model, the spring constant is estimated by the material properties and the crack density and the modified transfer matrix method is used to compute the wave reflection and transmission coefficients. Numerical results obtained by both models are presented and discussed. Special attention of the analysis is devoted to wave transmissions and reflections, band gaps, wave localization and resonance phenomena due to damages. The influences of the damage types (periodic cracks and stochastic cracks approximated by distributed springs) on the wave field pattern and the band gaps are analyzed. © 2011 Elsevier Ltd.

Abu-Rub H.,Texas A&M University at Qatar | Holtz J.,University of Wuppertal | Rodriguez J.,Federico Santa María Technical University | Baoming G.,Beijing Jiaotong University
IEEE Transactions on Industrial Electronics | Year: 2010

This paper gives an overview of medium-voltage (MV) multilevel converters with a focus on achieving minimum harmonic distortion and high efficiency at low switching frequency operation. Increasing the power rating by minimizing switching frequency while still maintaining reasonable power quality is an important requirement and a persistent challenge for the industry. Existing solutions are discussed and analyzed based on their topologies, limitations, and control techniques. As a preferred option for future research and application, an inverter configuration based on three-level building blocks to generate five-level voltage waveforms is suggested. This paper shows that such an inverter may be operated at a very low switching frequency to achieve minimum on-state and dynamic device losses for highly efficient MV drive applications while maintaining low harmonic distortion. © 2006 IEEE.

Wang J.,Beijing Information Science and Technology University | Mu X.,Beijing Jiaotong University
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2012

In view of the nonlinear mathematical model of the photovoltaic(PV) grid-connected inverter, the passivity-based control(PBC) is adapted for the inverter, and it can make the inverter possess excellent dynamic and static characteristics. In this paper the control law that can decouple dq axis currents at AC side of the grid based on the Euler-Lagrange(EL) model, and the passivity of inverter is proved. In order to improve the dynamic performance of the inverter, we can adopt the approach called injecting damping to optimize the controllerps adopted, and it can also make the current to fast track the desired one and track the PV array maximum power point. Simulation and 4 kW prototype results show that the current control strategy of Photovoltaic grid-connected inverter based on passivity is practicable.

Golub M.V.,University of Siegen | Fomenko S.I.,Kuban State University | Bui T.Q.,University of Siegen | Zhang C.,University of Siegen | Wang Y.-S.,Beijing Jiaotong University
International Journal of Solids and Structures | Year: 2012

Time-harmonic plane elastic SH-waves propagating in periodically laminated composites with functionally graded (FG) interlayers are investigated in this paper. A finite stack of periodic layers between two identical elastic half-planes is considered. Two different power laws are used to describe the property variation of the FG interlayers within the unit-cell. Two different models are developed to deal with the FG interlayers, namely, the explicit FG model and the multilayer model. In conjunction with the transfer matrix method, the wave reflection and transmission coefficients, and band gaps of the FG periodic laminates are computed. Numerical results are presented and discussed to reveal the influences of the FG and homogeneous interlayers, the incidence angle of time-harmonic plane SH wave on the location and width of band gaps. The explicit FG model developed in this study is accurate and capable to simulate the full wave pattern within the periodic laminates, and it can be easily extended to periodic laminates with defects. The corresponding results presented in this paper may have important applications in optimizing and developing novel acoustic devices such as wave filters and noise insulators. © 2011 Elsevier Ltd. All rights reserved.

Guan K.,Beijing Jiaotong University | Guan K.,TU Braunschweig | Zhong Z.,Beijing Jiaotong University | Ai B.,Beijing Jiaotong University | Kurner T.,TU Braunschweig
IEEE Transactions on Vehicular Technology | Year: 2014

Bridges that cross a railway's right-of-way are one of the most common obstacles for wave propagation along a highspeed railway. They can lead to poor coverage or handover failure but have been rarely investigated before. To describe the influence of this nonnegligible structure on propagation, measurements have been taken at 930 MHz along a real high-speed railway in China. Based on different mechanisms, the entire propagation process is presented by four zones in the case of an independent crossing bridge (ICB) and two zones in the case of groups of crossing bridges. First, all the propagation characteristics, including extra propagation loss, shadow fading, small-scale fading, and fading depth, have been measured and extracted. The results are shown in a complete table for accurate statistical modeling. Then, two empirical models, i.e., ICB and crossing bridges group (CBG), are first established to describe the extra loss owing to the crossing bridges. The proposed models improve on the state-of-the-art models for this problem, achieving a root mean square error (RMSE) of 3.0 and 3.7 dB, respectively. © 2013 IEEE.

Guan K.,Beijing Jiaotong University | Zhong Z.,Beijing Jiaotong University | Ai B.,Beijing Jiaotong University | Kurner T.,TU Braunschweig
IEEE Transactions on Vehicular Technology | Year: 2014

Train stations are one of the most common structures along a high-speed railway. They can block the line of sight (LOS), generate multiple reflected and scattered waves, and aggravate the fading behavior; however, these effects have been rarely investigated. This paper presents a group of 930-MHz measurements conducted on train stations of high-speed railways in China. The whole process of a train passing stations has been measured with two typical types of stations. The results indicate that, when the station is far from the transmitter (Tx), the semi-closed station (in which the awnings cover both the platforms and the rails) influences the propagation much more seriously than the open station (in which the awnings only cover the platforms supporting a clear free space over the tracks). When the station is near the Tx, the fact of whether the train keeps the LOS and stays inside the station determines the propagation for both types of stations. All the propagation characteristics, including extra propagation loss, shadow fading, small-scale fading, level crossing rate (LCR), average fade duration (AFD), and fading depth (FD), have been measured and computed for the first time. Specific findings of propagation characteristics in the train station scenario are provided. Afterward, by filling the gap of the train station scenario, a table is made to establish the comprehensive understanding of main scenarios in the high-speed railway. Furthermore, comparisons of the propagation characteristics between the train station scenario and ten standard scenarios are made to emphasize the significance of the modeling exclusively for the train station scenario. Finally, rules of the influence of four conditions are quantitatively revealed. The measured results and quantitative analysis are significant for leading the simulation and design of signaling and train control communications systems toward the reality. © 2014 IEEE.

He R.,Beijing Jiaotong University | Zhong Z.,Beijing Jiaotong University | Ai B.,Beijing Jiaotong University | Wang G.,Beijing Jiaotong University | And 2 more authors.
IEEE Transactions on Wireless Communications | Year: 2013

This paper reports (i) a set of measurements of the wireless propagation channel at 930 MHz, conducted along the «Zhengzhou-Xian» high-speed railway of China in various railway viaduct scenarios, and (ii) an analysis and modeling of the small-scale and large-scale channel parameters based on those measurements. The environment can be categorized into four cases, covering viaducts with different heights and in different suburban environments. Small values of fade depth, level crossing rates, and average fade duration are observed. Akaike's Information Criterion (AIC)-based evaluation indicates that the Ricean distribution is the best to describe small-scale amplitude fading. An analysis of the envelope autocovariance function shows that the coherence distance is less than 10 cm. The Ricean K-factor is modeled as a piecewise-linear function of distance. Moreover, a breakpoint path loss model is developed and shadow fading is investigated using the same break point as for the distance-dependent K-factor model. The Suzuki distribution is found to offer a good fit for the composite multipath/shadowing channels. We find that the viaduct height H, together with the number of surrounding scatterers, significantly affects the small- and large-scale channel parameters. These results are applicable to both normal-speed and high-speed railways, and will be useful in the modeling of railway viaduct channels and the design of railway wireless communication systems. © 2013 IEEE.

Xiao Y.,Beijing Jiaotong University | Kim K.,Gwangju Institute of Science and Technology
Chinese Journal of Electronics | Year: 2010

The real application of Differentiated services (DiffServ) network requires the DiffServ routers to support different data rates and time delays for the subscribers with different priorities. However, classical routers and AQM algorithms for the routers can not meet the requirements. To solve the problems, this paper develops the schemes of DiffServ edge router (DER) and DiffServ core router (DCR) with multiqueues, classifier and scheduler and a DiffServ AQM algorithm. The proposed DiffServ AQM algorithm based on DER can process the heterogeneous and classified traffic flows. The Diff-Serv AQM algorithm is derived from two theorems about the congestion conditions of DiffServ network in different links, it can prevent the possible congestion and ensure the data rates and time delays for the subscribers with higher priorities. The system simulations validate the proposed DiffServ routers and DiffServ AQM algorithm.

Ma T.-X.,Beijing Jiaotong University | Wang Y.-S.,Beijing Jiaotong University | Zhang C.,University of Siegen
Optics Communications | Year: 2014

Phoxonic crystal is a promising artificial periodic material for optomechanical systems and acousto-optical devices. In this paper, two-dimensional phoxonic crystals with veins in square, triangle and honeycomb lattices are investigated. Detailed discussion is presented on the variation of the photonic and phononic bandgaps with the geometry and lattice form of the structure. The results show that simultaneous large complete photonic and phononic bandgaps can exist over a wide range of geometry parameters for the square and honeycomb lattices. These large regions offer good tolerance for the technological realization and flexibility in designing this phoxonic crystal structure. © 2013 Elsevier B.V. All rights reserved.

Zhen N.,Beijing Jiaotong University | Wang Y.-S.,Beijing Jiaotong University | Zhang C.,University of Siegen
Mechanics Research Communications | Year: 2012

The band structures of transverse waves propagating in a two-dimensional phononic crystal composed of nanosized holes or elastic inclusions embedded in an elastic solid is calculated using the method based on the Dirichlet-to-Neumann map. The surface/interface effect of the nanosized holes/inclusions are taken into account by assuming the Young-Laplace equation at the surface/interface. Both square and triangular lattices are considered. Detailed calculations are presented for two cases: a square or triangular lattice of nanosized holes in an aluminum host and a square or triangular lattice of aluminum inclusions in a tungsten host. The results show that the consideration of the surface/interface effect is significant for nanosized phononic crystals. © 2012 Elsevier Ltd.

Li F.-L.,Beijing Jiaotong University | Wang Y.-S.,Beijing Jiaotong University | Zhang C.,University of Siegen
Optics Communications | Year: 2012

A boundary element method for computing bandgap structures of two-dimensional photonic crystals is developed. For photonic crystals composed of a square or triangular lattice of parallel cylinders with arbitrarily shaped cross-sections, the boundary integral equations are formulated for a unit cell. Constant boundary elements are adopted to discretize the boundaries. Applying the periodic boundary conditions and the interface conditions, we obtain a linear eigenvalue equation with relatively small matrices. The solution of the eigenvalue equation yields the Bloch wave vectors for given frequencies. The convergence of the method for the desired accuracy and efficiency is examined by some typical numerical examples. It is shown that the present method is efficient and accurate and thus provides a flexible treatment of electromagnetic waves in periodic structures with inclusions of arbitrary shape. © 2011 Elsevier B.V. All rights reserved.

Zhen N.,Beijing Jiaotong University | Wang Y.-S.,Beijing Jiaotong University | Zhang C.,University of Siegen
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2013

In the present paper, the band structures of in-plane waves propagating in two-dimensional nanoscale phononic crystals composed of voids/inclusions in an elastic solid in square and triangular lattices are calculated by the method based on the Dirichlet-to-Neumann map. The surface/interface effects are taken into account due to the high surface-to-volume ratio by applying the Young-Laplace equilibrium equation at the surface/interface. Three systems at nanoscale are calculated in details: vacuum holes in an aluminum matrix in square and triangular lattices, aluminum cylinders in tungsten matrix in a square lattice, and tungsten cylinders in aluminum in a square lattice. The results show that the surface/interface effects are significant when the dimensions of the phononic crystals approach the nanometer scale. © 2013 Elsevier B.V.

Dong H.-W.,Beijing Jiaotong University | Su X.-X.,Beijing Jiaotong University | Wang Y.-S.,Beijing Jiaotong University | Zhang C.,University of Siegen
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2014

The multiple elitist genetic algorithm with the adaptive fuzzy fitness granulation (AFFG) is used to design the phononic crystals with large relative bandgap width (BGW) for combined out-of-plane and in-plane wave modes. Without assumption on the symmetry of the unit-cell, we obtain an asymmetrical phononic crystal with the relative BGW which is quite larger than that of the optimized symmetrical structure. With the help of AFFG, the number of the fitness function evaluations is reduced by over 50% and the procedure converges 5 times faster than the conventional evolutionary algorithm to reach the same final fitness values. © 2013 Elsevier B.V.

Huang J.,Beijing Jiaotong University | Huang J.,Beijing Information Science and Technology University | Shang P.,Beijing Jiaotong University
Physica A: Statistical Mechanics and its Applications | Year: 2015

This paper introduces a multiscale multifractal diffusion entropy analysis (MMDEA) method to analyze long-range correlation then applies this method to stock index series. The method combines the techniques of diffusion process and Rényi entropy to focus on the scaling behaviors of stock index series using a multiscale, which allows us to extend the description of stock index variability to include the dependence on the magnitude of the variability and time scale. Compared to multifractal diffusion entropy analysis, the MMDEA can show more details of scale properties and provide a reliable analysis. In this paper, we concentrate not only on the fact that the stock index series has multifractal properties but also that these properties depend on the time scale in which the multifractality is measured. This time scale is related to the frequency band of the signal. We find that stock index variability appears to be far more complex than reported in the studies using a fixed time scale. © 2014 Elsevier B.V. All rights reserved.

Iacovacci J.,Queen Mary, University of London | Wu Z.,Beijing Jiaotong University | Bianconi G.,Queen Mary, University of London
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2015

Multiplex networks describe a large variety of complex systems, whose elements (nodes) can be connected by different types of interactions forming different layers (networks) of the multiplex. Multiplex networks include social networks, transportation networks, or biological networks in the cell or in the brain. Extracting relevant information from these networks is of crucial importance for solving challenging inference problems and for characterizing the multiplex networks microscopic and mesoscopic structure. Here we propose an information theory method to extract the network between the layers of multiplex data sets, forming a "network of networks." We build an indicator function, based on the entropy of network ensembles, to characterize the mesoscopic similarities between the layers of a multiplex network, and we use clustering techniques to characterize the communities present in this network of networks. We apply the proposed method to study the Multiplex Collaboration Network formed by scientists collaborating on different subjects and publishing in the American Physical Society journals. The analysis of this data set reveals the interplay between the collaboration networks and the organization of knowledge in physics. ©2015 American Physical Society.

Xiang H.J.,Beijing Jiaotong University | Shi Z.F.,Beijing Jiaotong University | Wang S.J.,National Center for Research on Earthquake Engineering | Mo Y.L.,University of Houston
Smart Materials and Structures | Year: 2012

Guided by the recent advances in solid-state research in periodic materials, a new type of layered periodic foundation consisting of concrete and rubber layers is experimentally investigated in this paper. The distinct feature of this new foundation is its frequency band gaps. When the frequency contents of a wave fall within the range of the frequency band gaps, the wave, and hence its energy, will be weakened or cannot propagate through the foundation, so the foundation itself can serve as a vibration isolator. Using the theory of elastodynamics and the Bloch-Floquet theorem, the mechanism of band gaps in periodic composites is presented, and a finite element model is built to show the isolation characteristic of a finite dimensional periodic foundation. Based on these analytical results, moreover, a scaled model frame and a periodic foundation were fabricated and shake table tests of the frame on the periodic foundation were performed. Ambient, strong and harmonic vibration attenuations are found when the exciting frequencies fall into the band gaps. © 2012 IOP Publishing Ltd.

Wen Y.-K.,Beijing Jiaotong University | Sun L.-M.,Tongji University
Gongcheng Lixue/Engineering Mechanics | Year: 2011

This research is on the design optimization and performance control of tuned mass dampers (TMDs) and active tuned mass dampers (ATMDs). H ∞ control synthesis algorithm is used to design the multi-distributed TMDs and ATMDs, and through the estimation of control efficiency, an optimal control scheme is obtained. Taking the 3rd Nanjing Bridge over Yangtze River as an example, the analytical model is established here. Considering the contribution of self-excited force to aerodynamic damping and stiffness, the parameters of the multi-distributed TMDs and ATMDs are optimized at the same time and the controller is designed. Controlled performance for buffeting response of the bridge is numerically analyzed. Results show that both the multi-distributed TMDs and ATMDs have limitation in practice and can not achieve good performance for the control of displacement response and acceleration response of the cable-stayed bridge under construction at the same time. An effective scheme of hybrid system combining TMDs with ATMDs that are tuned to different modes shows good efficiency for the wind-induced vibration control of the cable-stayed bridge.

Golub M.V.,Kuban State University | Zhang C.,University of Siegen | Wang Y.-S.,Beijing Jiaotong University
Journal of Sound and Vibration | Year: 2011

This paper presents a dynamic analysis of time-harmonic plane SH-waves propagating in periodically multilayered elastic composites with a strip-like crack. The total wave field in the multilayered elastic structure is described as a sum of incident wave field modeled by the transfer matrix method and the scattered wave field governed by an integral representation containing the crack-opening-displacement. The integral equation derived from the boundary conditions on the crack-faces is solved numerically by a Galerkin method. The paper focuses on resonant and non-resonant regimes of anti-plane wave motion in a stack of elastic layers weakened by a single strip-like crack and wave localization in the vicinity of the crack. The scattered extra displacement induced by the presence of the crack is investigated in detail for both situations of high and low contrast in material properties. Numerical results for the average crack-opening-displacement, the transmission coefficient, the stress intensity factor and the average energy flow are presented and discussed to reveal wave resonance and localization phenomena within the band-gaps and the pass-bands. © 2011 Elsevier Ltd.

Zhang G.-W.,Beijing Jiaotong University
Jiaotong Yunshu Xitong Gongcheng Yu Xinxi/Journal of Transportation Systems Engineering and Information Technology | Year: 2016

High-speed railway as a new kind of transportation model, its rapid development has brought a great leap forward in the history of transportation. Though its development and construction is short, China's high-speed railway has become the fastest growing, the longest operating mileage and the largest construction scale country in the world. The safety and technology of high- speed railway is required very high. The 42nd conference of"Traffic and Transportation 7+1" sets its theme as "Safety and Technology of High-speed Railway in China". It pays attention to the safety of operation control, infrastructure, mobile equipment, etc. It also discusses that the theory and practice of the operation safety, fatigue design of welded structure, the theory, method and application of health monitoring, design and manufacture of brake pads for high speed trains, in China's high-speed railway. Copyright © 2016 by Science Press.

Zhu H.,University of Kent | Xia B.,Huawei | Tan Z.,Beijing Jiaotong University
IEEE Journal on Selected Areas in Communications | Year: 2011

In this paper, the performance of multi-level quadrature amplitude modulation (M-QAM) systems is studied analytically when Alamouti space-time transmit diversity (STTD) coding is used for transmission over Rayleigh fading channels. The effect of self-interference (interference from another simultaneously transmitted symbol in the STTD scheme for the same user) due to imperfect channel estimation is investigated. Based on the characteristic function method, a closed-form expression of the bit error rate (BER) is derived. Numerical results for 16/64- QAM show that, with the Alamouti STTD technique, the BER performance of the QAM system can be improved significantly. The effect of receive antenna diversity is also investigated. It is shown that high-order QAM constellations can be employed even in low signal to noise ratio (SNR) with the transmit diversity technique in conjunction with receive antenna diversity. © 2011 IEEE.

Zhang G.-W.,Beijing Jiaotong University
Jiaotong Yunshu Xitong Gongcheng Yu Xinxi/Journal of Transportation Systems Engineering and Information Technology | Year: 2015

Traffic accident brings immeasurable loss to the people's life and property, social stability and harmony. Most of the heavy road traffic accidents occur in the road transport vehicles with the large passenger capacity and the large tonnage. Dangerous goods transportation accidents are also different from general transportation accidents, it also derives from the combustion, explosion, leakage and other more serious consequences, resulting in economic and property loss, environmental pollution, ecological destruction, casualties and a series of problems. The 40 th conference of "Traffic and Transportation 7 + 1 Forum" sets its theme as "Safety and Management of Road Transportation". As an important part of the public safety, transportation safety concerns the safety of people's life and property, the coordinated development of economic society, the harmony and stability of society, and it is a major people's livelihood issues. It discusses the mechanism and measures to prevent, contain and reduce the occurrence of heavy traffic accident, guarantee road transportation safety, comprehensively improve the management level of road transportation safety, such as enhance safety consciousness, improve the safety management mechanism, innovative security management means model, reinforce the safety management foundation and so on. ©, 2015, Science Press. All right reserved.

Zhang G.-W.,Beijing Jiaotong University
Jiaotong Yunshu Xitong Gongcheng Yu Xinxi/Journal of Transportation Systems Engineering and Information Technology | Year: 2015

As the basic and strategic industry, traffic plays an important role in the national development strategy. With mobile internet, cloud computing, large data, internet of thing and other advanced technology, the internet and transportation to carry out effective permeation and fusion, form the new formats and new models: on-line resources can be reasonably allocated, and off-line can be high efficiently and high quality operated. Meet the needs of public that more convenient travel, more human nature services, and the industry more scientific decision. The 39th conference of "Traffic and Transportation 7+1 Forum "sets its theme as "Towards New Heights of Traffic-to Commemorate the 60th Anniversary of Tsien Hsueshen Homecoming". It aims at applying the systematic thinking and overall thought which are advocated by Tsien Hsueshen to provide new thinking and theoretical guidance for the development of internet and traffic. It promotes transportation industry from the traditional to the modern service industry transformation and upgrading, the traffic development towards new heights. Copyright © 2015 by Science Press.

Ke L.-L.,Beijing Jiaotong University | Wang Y.-S.,Beijing Jiaotong University
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2011

Vibration and instability of fluid-conveying double-walled carbon nanotubes (DWNTs) are investigated in this paper based on the modified couple stress theory and the Timoshenko beam theory. The microstructure-dependent Timoshenko beam model, which contains a material length scale parameter and can take the size effect into account, is employed. The Poissons ratio effect is also included in this model. The surrounding elastic medium is described as the Winkler model characterized by the spring. The higher-order governing equations and boundary conditions are derived by using Hamiltons principle. The differential quadrature (DQ) method is employed to discretize the governing equations, which are then solved to obtain the resonant frequencies of fluid-conveying DWNTs with different boundary conditions. A detailed parametric study is conducted to study the influences of length scale parameter, Poissons ratio, spring constant, aspect ratio of the DWNTs, velocity of the fluid and end supports on the vibration and flow-induced instability of DWNTs. Results show that the imaginary component of the frequency and the critical flow velocity of the fluid-conveying DWNTs increase with increase in the length scale parameter. © 2010 Elsevier B.V. All rights reserved.

Liu J.,Beijing Jiaotong University | Ke L.-L.,Beijing Jiaotong University | Wang Y.-S.,Beijing Jiaotong University
International Journal of Solids and Structures | Year: 2011

The two-dimensional thermoelastic sliding frictional contact of functionally graded material (FGM) coated half-plane under the plane strain deformation is investigated in this paper. A rigid punch is sliding over the surface of the FGM coating with a constant velocity. Frictional heating, with its value proportional to contact pressure, friction coefficient and sliding velocity, is generated at the interface between the punch and the FGM coating. The material properties of the coating vary exponentially along the thickness direction. In order to solve the heat conduction equation analytically, the homogeneous multi-layered model is adopted for treating the graded thermal diffusivity coefficient with other thermomechanical properties being kept as the given exponential forms. The transfer matrix method and Fourier integral transform technique are employed to convert the problem into a Cauchy singular integral equation which is then solved numerically to obtain the unknown contact pressure and the in-plane component of the surface stresses. The effects of the gradient index, Peclet number and friction coefficient on the thermoelastic contact characteristics are discussed in detail. Numerical results show that the distribution of the contact stress can be altered and therefore the thermoelastic contact damage can be modified by adjusting the gradient index, Peclet number and friction coefficient. © 2011 Elsevier Ltd. All rights reserved.

Ke L.-L.,Beijing Jiaotong University | Wang Y.-S.,Beijing Jiaotong University | Wang Z.-D.,Beijing Jiaotong University
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2011

Based on the modified couple stress theory, free vibration and buckling of the microbeams with the effect of the temperature change are investigated. The non-classical Timoshenko beam model, which contains a material length scale parameter, is developed to interpret the size effect in microscale structures. The higher-order governing equations and boundary conditions are derived by using the Hamilton principle. The differential quadrature method is employed to determine the natural frequency and the critical buckling load of the microbeams with different boundary conditions. The effects of the temperature change, length scale parameter, slenderness ratio and end supported conditions on the free vibration and buckling of the microbeams are discussed in detail. Results show that the thermal effect on the fundamental frequency and critical buckling load is slight when the thickness of the microbeam has a similar value to the material length scale parameter, but it becomes significant when the thickness of the microbeams becomes larger. © 2011 Elsevier B.V. All rights reserved.

Chen A.-L.,Beijing Jiaotong University | Wang Y.-S.,Beijing Jiaotong University
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2011

The scaling law does not hold when the sizes of the phononic crystals reach the nanoscale dimension [Ramprasad et al., Applied Physics Letters 87 (2005) [9]]111101. This paper discusses the size-effect on the band structures of nanoscale phononic crystals. The transfer matrix method based on the nonlocal elastic continuum theory is developed to compute the band structures of a nanoscale layered phononic crystal. Detailed calculations are performed for a nanoscale HfO 2ZrO 2 multilayer stack. It is shown that the nonlocal elastic continuum solution deviates from the classical elastic continuum one and finally approaches the first-principle result as the thickness of each individual layer decreases. When the thickness of each layer is much larger than several nanometers, the correspondence between the nonlocal and classical elastic methods is shown, and the size effects can be neglected. The developed nonlocal elastic continuum method is expected to overcome the limits of the classical continuum description for wave propagation in phononic crystals when dimensions are in nanometer-length scales. © 2011 Elsevier B.V. All rights reserved.

Kumar N.,University of Kansas | Cui Q.,University of Kansas | Ceballos F.,University of Kansas | He D.,Beijing Jiaotong University | And 2 more authors.
Nanoscale | Year: 2014

The exciton dynamics in monolayer and bulk MoSe2 samples are studied by transient absorption microscopy with a high spatiotemporal resolution. Excitons are injected with a point-like spatial distribution using a tightly focused femtosecond pulse. The spatiotemporal dynamics of these excitons are monitored by measuring transient absorption of a time-delayed and spatially scanned probe pulse. We obtain the exciton diffusion coefficients of 12 ± 3 and 19 ± 2 cm2 s-1 and exciton lifetimes of 130 ± 20 and 210 ± 10 ps in the monolayer and bulk samples, respectively. These values are useful for understanding excitons and their interactions with the environment in these structures and potential applications of MoSe2 in optoelectronics and electronics. © 2014 the Partner Organisations.

Kumar N.,University of Kansas | Cui Q.,University of Kansas | Ceballos F.,University of Kansas | He D.,Beijing Jiaotong University | And 2 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2014

We investigate the excitonic dynamics in MoSe2 monolayer and bulk samples by femtosecond transient absorption. Excitons are resonantly injected by a 750-nm and 100-fs laser pulse, and are detected by measuring a differential reflection of a probe pulse tuned in the range 790-820 nm. We observe a strong density-dependent initial decay of the exciton population in monolayers, which can be well described by the exciton-exciton annihilation. Such a feature is not observed in a bulk sample under comparable conditions. We also observe the saturated absorption induced by excitons in both monolayers and the bulk in the differential reflection measurements, which indicates their potential applications as saturable absorbers. © 2014 American Physical Society.

Ren G.,Beijing Jiaotong University | Lin Z.,Beijing Jiaotong University | Zheng S.,Beijing Jiaotong University | Jian S.,Beijing Jiaotong University
Optics Letters | Year: 2013

We report in this Letter the resonant coupling mechanism in bending trenched bend-insensitive fiber (BIF). It is found that among the trench parameters, the core-trench distance is predominant for optimized BIF design. We reveal that resonant coupling is an intrinsic characteristic of bending trenched BIF, and resonant coupling between the fiber core and the innermost cladding would limit the ultimate bending loss of BIF under tight bend. Resonant coupling is also present in double-trenched BIF, and would impair its bending performance. © 2013 Optical Society of America.

Chen F.-M.,Beijing Jiaotong University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We prove explicitly that the general D=3, N=4 Chern-Simons-matter theory has a complete OSp(4|4) superconformal symmetry and construct the corresponding conserved currents. We rederive the OSp(5|4) superconformal currents in the general N=5 theory as special cases of the OSp(4|4) currents by enhancing the supersymmetry from N=4 to N=5. The closure of the full OSp(4|4) superconformal algebra is verified explicitly. © 2013 American Physical Society.

This paper firstly demonstrated the refractive index (RI) characteristics of a singlemode-claddingless-singlemode fiber structure filter based fiber ring cavity laser sensing system. The experiment shows that the lasing wavelength shifts to red side with the ambient RI increase. Linear and parabolic fitting are both done to the measurements. The linear fitting result shows a good linearity for applications in some areas with the determination coefficient of 0.993. And a sensitivity of ∼131.64nm/RIU is experimentally achieved with the aqueous solution RI ranging from 1.333 to 1.3707, which is competitively compared to other existing fiber-optic sensors. While the 2 order polynomial fitting function, which determination relationship is higher than 0.999, can be used to some more rigorous monitoring. The proposed fiber laser has a SNR of ∼50dB, and 3dB bandwidth ∼0.03nm. © 2014 Optical Society of America.

Yin G.,University of Ottawa | Yin G.,Beijing Jiaotong University | Saxena B.,University of Ottawa | Bao X.,University of Ottawa
Optics Express | Year: 2011

A tunable and single longitudinal mode Er-doped fiber ring laser (SLM-EDFRL) is proposed and demonstrated based on Rayleigh backscattering (RBS) in single mode fiber-28e (SMF-28e). Theory and experimental study on formation of SLM from normal multi-mode ring laser is demonstrated. The RBS feedback in 660 m SMF-28e is the key to ensure SLM laser oscillation. This tunable SLM laser can be tuned over 1549.7-1550.18 nm with a linewidth of 2.5-3.0 kHz and a side mode suppression ratio (SMSR) of ∼72 dB for electrical signal power. The tuning range is determined by the bandpass filter and gain medium used in the experiment. The laser is able to operate at S+C+L band. © 2011 Optical Society of America.

Yu J.,Beijing Jiaotong University
Zidonghua Xuebao/Acta Automatica Sinica | Year: 2016

This paper discusses relation between three language functions (denotation, connotation, annotation) and Turing test, and points out that it is usually assumed that three language functions (denotation, connotation, annotation) are equivalent in early stage of AI research. Under such assumption, many efforts are devoted to implementing one of three language functions and suppose that one becoming true results in two others. For example, intelligence can be fully implemented through annotation function of language in Turing test. However, it has been proved that three language functions (denotation, connotation, annotation) are not equivalent, which bring great challenges to AI research. In this paper, we list some open problems in AI research, such as computational theory of dialogue. Copyright © 2016 Acta Automatica Sinica. All rights reserved.

Xu S.,Beijing Jiaotong University | Guo Y.-F.,Beijing Jiaotong University | Wang Z.-D.,Beijing Jiaotong University
Computational Materials Science | Year: 2013

Molecular dynamics simulations are employed to analyze the tension mechanical properties of single-crystalline nano-Cu films. Attention is directed to elucidate the microstructure evolution and deformation mechanisms. Computational results show that the plastic deformation mechanism of the {100} oriented nano-Cu films is more likely due to short-distance sliding of the atoms, which results in the formation of stacking faults, microtwins, dislocation locks and vacancies. In particular, vacancy generation and migration in the film are carefully examined at the atomistic scale, which is closely related with the intersection of stacking faults and the gliding of jogged dislocations. © 2011 Elsevier B.V. All rights reserved.

Li Z.Y.,Beijing Jiaotong University
Advanced Materials Research | Year: 2014

The road traffic safety measures decisions plays an increasingly prominent role not only in the road traffic management but also in the development of social economy. Combining the Changhong Road, Xiangyang, Hubei Province road traffic situation, the paper makes the road traffic safety measures decisions by using relational matrix analysis(RMA) and through the expected effect of the application of the RMA, this paper pointes out the practice significance of the application of RMA to the road traffic safety measures decisions. © (2014) Trans Tech Publications, Switzerland.

Zhang X.,Beijing Jiaotong University | Nie L.,Beijing Jiaotong University
Transportation Research Part C: Emerging Technologies | Year: 2016

Compared with most optimization methods for capacity evaluation, integrating capacity analysis with timetabling can reveal the types of train line plans and operating rules that have a positive influence on improving capacity utilization as well as yielding more accurate analyses. For most capacity analyses and cyclic timetabling methods, the cycle time is a constant (e.g., one or two hours). In this paper, we propose a minimum cycle time calculation (MCTC) model based on the periodic event scheduling problem (PESP) for a given train line plan, which is promising for macroscopic train timetabling and capacity analysis. In accordance with train operating rules, a non-collision constraint and a series of flexible overtaking constraints (FOCs) are constructed based on variations of the original binary variables in the PESP. Because of the complexity of the PESP, an iterative approximation (IA) method for integration with the CPLEX solver is proposed. Finally, two hypothetical cases are considered to analyze railway capacity, and several influencing factors are studied, including train regularity, train speed, line plan specifications (train stops), overtaking and train heterogeneity. The MCTC model and IA method are used to test a real-world case involving the timetable of the Beijing-Shanghai high-speed railway in China. © 2016 Elsevier Ltd.

Gu Y.,Beijing Jiaotong University | Li Q.,Beijing Jiaotong University
Chinese Physics B | Year: 2014

We present a new pattern recognition system based on moving average and linear discriminant analysis (LDA), which can be used to process the original signal of the new polymer quartz piezoelectric crystal air-sensitive sensor system we designed, called the new e-nose. Using the new e-nose, we obtain the template datum of Chinese spirits via a new pattern recognition system. To verify the effectiveness of the new pattern recognition system, we select three kinds of Chinese spirits to test, our results confirm that the new pattern recognition system can perfectly identify and distinguish between the Chinese spirits. © 2014 Chinese Physical Society and IOP Publishing Ltd.

Li N.,Beijing Jiaotong University | Huang M.,Beijing Jiaotong University
Dianwang Jishu/Power System Technology | Year: 2011

The harmonics caused by connecting different types of battery chargers for electric vehicles (EVs) to power network are mainly from the rectifiers of the chargers, so it is necessary to perform comparative analysis on harmonics produced by connecting the EV chargers, which are composed of different rectifying devices, to power network for reference in harmonic suppression and selection of EV battery charger. Utilizing PSCAD software, a model to measure harmonics caused by EV charger is designed and simulation models for EV battery chargers adopting three-phase uncontrolled rectifier, 12-pulse rectifier and pulse width modulation rectifier are built respectively, and the measured data are compared and analyzed. The proposed models are available for reference in the selection of EV battery charger. The proposed method can be applied to analyze power network harmonics produced by large-scale centralized charging stations adopting traditional charging mode.

Wang M.,Beijing Jiaotong University | Yao J.,University of Ottawa
IEEE Photonics Technology Letters | Year: 2013

An optical vector network analyzer (OVNA) based on unbalanced double-sideband (UB-DSB) modulation with improved measurement accuracy is proposed and experimentally demonstrated. It is different from an OVNA based on optical single-sideband (OSSB) modulation in which one-to-one mapping between the optical and radio frequency responses is employed to measure the magnitude and phase responses of an optical component, the proposed technique measures the magnitude and phase responses by taking into consideration of the power of the other sideband through solving two equations that are associated with the UB-DSB modulation, thus the errors due to the residual power of the other sideband in an OSSB modulation based approach are completely eliminated. A mathematical model providing the transfer function of an optical component is derived. The measurement of a phase-shifted fiber Bragg grating and a linearly chirped fiber Bragg grating is performed. Comparing with the measured results based on OSSB modulation, obvious improvement in measurement accuracy is demonstrated. © 1989-2012 IEEE.

Feng X.,Beijing Jiaotong University | Mao B.,Beijing Jiaotong University | Feng J.,Beijing Jiaotong University
Energy | Year: 2011

By following a computer-aided simulation procedure, this research analyzes the traction energy cost and transport operation time per 10,000 passenger-kilometers of two representative types of metro trains in China under various top speeds between different stations along a hypothetically straight and smooth metro line, from the perspective of both energy saving and transport efficiency improvement in consideration of multi-factors. It is empirically confirmed that if the transport distance between stops is shorter than 1,800 m, the metro trains should set their maximum speeds lower than 70 km/h but higher than 30 km/h. And a shorter stop-spacing requires a lower maximum speed in this speed range to get the least costs of energy and time. The exact value of the maximum speed in this speed range ought to be further determined based on the integrated performances of the train's passenger capacity, engines, streamline body design, etc. If the transport distance is longer than 1,800 m, the generalized expense of energy and time per 10,000 passenger-kilometers decreases with the increase of the maximum speed of a train. Nevertheless, such decreases become very slow when the maximum speeds of the trains exceed 70 km/h. © 2011 Elsevier Ltd.

Wang T.,University of Sydney | Wang T.,Beijing Jiaotong University | Shao L.-Y.,University of Sydney | Shao L.-Y.,Hong Kong Polytechnic University | And 2 more authors.
Optics Letters | Year: 2013

Both temperature and strain characterization of seed and regenerated gratings with and without post annealing is reported. The high temperature regeneration has significant impact on thermal characterization and mechanical strength of gratings while the post annealing has little effect. The observed difference is evidence of viscoelastic changes in glass structure. © 2013 Optical Society of America.

Li Y.,Beijing Jiaotong University | Luk K.-M.,City University of Hong Kong
IEEE Transactions on Antennas and Propagation | Year: 2016

A novel circularly polarized (CP) aperture-coupled magneto-electric (ME) dipole antenna is proposed. The CP ME-dipole antenna fed by a transverse slot etched on the broad wall of a section of shorted-end substrate integrated waveguide (SIW) is convenient to integrate into substrates. An impedance bandwidth of wider than 28.8%, a wide 3-dB axial ratio (AR) bandwidth of 25.9%, and gain of 7.7 ± 1.4 dBic over the operating band are achieved. Additionally, since the CP radiation is generated by the combination of two orthogonal ME-dipole modes, the antenna element has stable unidirectional radiation patterns that are almost identical in two principle planes throughout the operating band, which is desirable to array applications. By employing the proposed CP ME-dipole as radiating elements, an 8 × 8 high-gain wideband planar antenna array is proposed for 60-GHz millimeter-wave applications. A fabrication procedure of using conductive adhesive films to bond all print circuit board (PCB) layers together is successfully implemented to realize the array design with a three-layered geometry, which has advantages of low costs and possibility of large-scale manufacture. The measured impedance bandwidth of the fabricated prototype is 18.2% for |S11| < -10 dB. Because of the wide AR bandwidth of the new antenna element, a wide AR bandwidth of 16.5% can be achieved by this array without the use of sequential feed. Gain up to 26.1 dBic and good radiation efficiency of around 70% are also obtained due to the use of a full-corporate SIW feed network with low insertion loss at millimeter-wave frequencies. © 2016 IEEE.

In the pursuit of higher operation speed at the passenger train services in China, the impacts of high-speed operation on energy consumption and transport efficiency are however not clearly identified. This research attempts to analyze the traction energy cost and transport operation time per 10,000 passenger-kilometers of high-speed railway (HSR) trains with a range of target speeds on certain HSR lines in China through a simulation approach. Having considered the effect of inter-stop transport distances, traction characteristics of HSR trains and gradients, curvatures, etc. of the rail lines, this study has deduced that the target speed of a HSR train for an inter-stop transport distance shorter than 100. km should be below 190. km/h from the perspectives of traction energy saving and transport efficiency improvement. Moreover, the study results also indicate that, unlike the actual HSR operation, the target speed should be dynamically adjusted according to the transport distances between stops if the transport capacity of the rail line is not extensively used. The exact target speed for each inter-stop transport distance shorter than 100. km should be further determined according to the traction characteristics of the train and the track geometry of the rail line. © 2011 Elsevier Ltd.

Zou H.,Beijing Jiaotong University | Lou S.,Beijing Jiaotong University | Yin G.,Beijing Jiaotong University | Su W.,Beijing Jiaotong University
IEEE Photonics Technology Letters | Year: 2013

A stable and switchable dual-wavelength polarization-maintaining erbium-doped fiber ring laser is proposed and demonstrated experimentally by using a novel filter, which is formed from dual-pass Mach-Zehnder interferometer incorporating a sagnac loop. By adjusting the polarization controllers, the output laser can be switched between single-and dual-wavelength. The wavelength spacing of the dual-wavelength can be tuned from 0.084 to 4.26 nm. Its 3-dB bandwidth and side mode suppression ratio are less than 0.015 nm and higher than 64 dB, respectively. In addition, the peak power fluctuation and wavelength shift are monitored to be less than 0.5 dB and 0.01 nm during an hour, respectively. The characteristics of the novel filter in experimental measurement accord with the result of theoretical analysis. © 1989-2012 IEEE.

Wang M.,Beijing Jiaotong University | Wang M.,University of Ottawa | Yao J.,University of Ottawa
IEEE Photonics Technology Letters | Year: 2013

A novel approach to the generation of an optical frequency comb with a widely tunable center wavelength and comb spacing based on an optoelectronic oscillator (OEO) is proposed and experimentally demonstrated. The OEO is implemented using a polarization modulator (PolM), a phase-shifted fiber Bragg grating (PS-FBG), and a photodetector (PD). The PolM is a special phase modulator that supports phase modulation along the two principal axes with opposite modulation indexes. The joint operation of the PolM, the PS-FBG, and the PD corresponds to a frequency-tunable microwave photonic bandpass filter. When the output from the PD is fed back to the PolM, the OEO starts to oscillate and the oscillation frequency can be tuned by tuning the center frequency of the microwave photonic bandpass filter through tuning the optical wavelength. The optical comb is then generated by tapping part of the optical signal from the PolM and sending it to a second PolM. The joint operation of the two PolMs generates an optical comb with the comb spacing tunable by tuning the center frequency of the microwave photonic filter. Through introducing a second wavelength into the OEO, a duplicated optical comb at the second wavelength is generated. An experiment is performed. An optical frequency comb with tunable frequency spacing from 6.6 to 15.3 GHz and a tunable center wavelength from 1500 to 1580 nm is generated. © 1989-2012 IEEE.

Bai S.,Beijing Jiaotong University
Sensing and Imaging | Year: 2015

In daily life, one kind of images are common, in which many people are present and performing certain activities. We call these images human-centric images. As the number of such images gets increasingly larger, to organize and access them efficiently becomes urgent. Since the categories of human-centric images are determined by human activities in the images, in this paper, we propose to classify human-centric images by analyzing poses of all humans in them. Specifically, first, we introduce the notion of poselets, which represent parts of poses of humans and a method to detect human based on the poselets. Given a human-centric image, to determine its category, we use the poselets and the human detection method to detect all possible poselet activations in it and create a statistical representation of the poses of humans in the image. Additionally, we also investigated the influence of contextual information on the categorization of human-centric images. Finally, for evaluating the human-centric image categorization method, five categories of human-centric images are collected from the internet and used for experiments. Experiment results show that the poselet distribution representations are more suitable for representing human-centric images than the popular bag of visual words method. © 2014, Springer Science+Business Media New York.

Huang C.,Beijing Jiaotong University | Cai Y.,Beijing Jiaotong University
Advanced Materials Research | Year: 2013

In this paper, the cutting acreage model of every cutting edge point in turn-milling is established firstly. Then according to the calculation of the above model, the cutter wears with different cutting parameters are analyzed. Aiming at balancing the wears of different areas along the cutting edge, the cutting parameters are changed to optimize the cutter wears. Finally the model and the optimization are proved correct by machining experiments with different cutting parameters. © (2013) Trans Tech Publications, Switzerland.

Gao T.,Beijing Jiaotong University | Sun B.,BeiJing LiuJie Technology Co
ICEIE 2010 - 2010 International Conference on Electronics and Information Engineering, Proceedings | Year: 2010

Along with the developments of the high-speed railway, higher and higher technical requirements for the high-speed railway mobile communication system are raised. Since the "Global System for Mobile Communications Railways" (GSM-R) implemented today is based on GSM, the new technology in GSM evolution can be used in the high-speed railway mobile communication system to adapt to the new requirements. This paper introduces a high-speed railway mobile communication system based on "Long Term Evolution" (LTE), describes its network architecture, and especially analyzes the technical advantages and application value of the system in the high-speed railway wireless communication comparing with the existing GSM-R system. It also discusses feasibility of the GSM-R system's evolution to this high-speed railway mobile communication system and proposes the possible evolution model. © 2010 IEEE.

Sun Y.,Beijing Jiaotong University
2016 International Conference on Industrial Economics System and Industrial Security Engineering, IEIS 2016 - Proceeding | Year: 2016

With the opening development of China's publishing and media market, foreign direct investment has been widely infiltrated into almost all the fields of the publishing and media industry. Foreign direct investment will give positive impacts on optimizing the allocation of the publishing and media resources, improving the publishing efficiency, and adjusting the industrial structure. While to some extent, it brings negative impacts on human resources, markets, industrial capital, and cases of looting excellent cultural resources have been found. To effectively protect the safety of China's publishing and media market, we should regulate the access rules of foreign direct investment, improve the investment and financing system, establish and improve the risk prevention mechanism of foreign direct investment. © 2016 IEEE.

Cuiyi A.,Beijing Jiaotong University
2016 International Conference on Industrial Economics System and Industrial Security Engineering, IEIS 2016 - Proceeding | Year: 2016

The evaluation and selection of funds are a classification problem essentially. The paper builds evaluation index sets including fund companies, fund managers, risk level and the level of risk-adjusted earnings, and uses independent samples t-test, linear regression and KPCA and SVM model to evaluate and classify securities investment funds. According to the empirical analysis, the model is practicable, and using this way to choose funds is simple, straight, and practical. © 2016 IEEE.

Chen L.,Beijing Jiaotong University
2016 International Conference on Industrial Economics System and Industrial Security Engineering, IEIS 2016 - Proceeding | Year: 2016

Public Private Partnership is a new financing model and has been used in constructing public facilities. In this way, government attracts social capital to reduce the financial burden, enterprises earn revenue through private investment, and both of them ultimately achieve a win-win outcome. However, successful implementation of the PPP model requires us to balance many factors. This paper analyzes the failure of the London Underground PPP project and the success of Beijing Metro Line 4 and makes some suggestions, hoping that it can be served as a reference for the implementation of PPP projects in the future, better promoting the construction of public facilities. © 2016 IEEE.

Guo B.,Beijing Jiaotong University
2016 International Conference on Industrial Economics System and Industrial Security Engineering, IEIS 2016 - Proceeding | Year: 2016

The problem of financing of minor enterprises has been a difficult problem all over the world, but the emergence of Internet finance gives them a new chance. However, the success rate of P2P network lending has been maintained at a low level. This paper takes the case of Renrendai Online Lending as an example, firstly illustrates the selection of model and uses binary Logit model to do regression test. Further, the Crystal ball software is used to do Monte Carlo simulation. Finally, it gives suggestions and possible solutions from the perspective of lenders and borrowers. © 2016 IEEE.

Cuiyi A.,Beijing Jiaotong University
2016 International Conference on Industrial Economics System and Industrial Security Engineering, IEIS 2016 - Proceeding | Year: 2016

In the macro-finance perspective, the financial industry and financial security is viewed as an integrated system, and should be studied based on the idea of system theory. In this paper, we discuss the composition of China's financial industry system security, and the fuzzy uncertainty of the security of the financial system, random uncertainty and complex coupling uncertainty analysis. We also establish the basic framework of the security of the financial system modeling and optimization, and introduce the idea of financial system dynamics. At last, we discuss on the financial system security and reliability of the SD flow chart analysis. The result of the paper contributes to China's financial system security and optimization. © 2016 IEEE.

Yu L.,Beijing Jiaotong University
2016 International Conference on Industrial Economics System and Industrial Security Engineering, IEIS 2016 - Proceeding | Year: 2016

In this paper, the main content is to analyze the amount of Chinese medicine industry policies and regulations. And by analyzing the total annual quantity of policies to point out the macro-control from Chinese Government. And continue analyzing the paper (I) in this meeting last year. © 2016 IEEE.

Sun H.,Beijing Jiaotong University
2016 International Conference on Industrial Economics System and Industrial Security Engineering, IEIS 2016 - Proceeding | Year: 2016

In the face of all sorts of environmental problems, it is necessary to promote the optimization and adjust the industrial structure in order to realize the strong growth in industry and the better environment. The industrial structure of Hebei Province in 2014 is analyzed by using the factor analysis method in the paper. And all the indicators were summarized out four factors. They are the scale, efficiency, management, and market factors. And the indexes of energy consumption and water withdrawals will be considered to analyze the characteristics of industrial structure completely. © 2016 IEEE.

Liu L.,Beijing Jiaotong University
2016 International Conference on Industrial Economics System and Industrial Security Engineering, IEIS 2016 - Proceeding | Year: 2016

The main objective of the paper is to study how the rail transit system promotes the development of Beijing metropolitan area. The paper finds Beijing is in a critical period to develop metropolitan area and commuter railway by analyzing the evolution of Beijing city spatial structure and rail transit. Then, it analyses how rail transit promote the Beijing metropolitan area from the perspective of stations, lines and network using the 'Points-axis' theory by comparing with the Tokyo metropolitan area. Results shows that in the guide of the multi-level rail transit system which includes urban subway as the principal axis within the radius of 0-15km, light railway as the secondary axis within the radius of 15-30km, commuter railway as the tertiary axis within the radius of 30-70km, Beijing metropolitan area in the future, therefore, will form the reasonable spatial structure in which core area within the radius of 0-15km is the center, new cities such as Shunyi, Tongzhou and Daxing within the radius of 15-30km will be sub-centers and satellite towns includes Pinggu, Yanjiao and Guan within the radius of 30-70km. © 2016 IEEE.

Chu Y.,Beijing Jiaotong University
2016 International Conference on Industrial Economics System and Industrial Security Engineering, IEIS 2016 - Proceeding | Year: 2016

Financial openness is one part of economic globalization, which has been a defining trend in the world. In this study, the aim of our research is to investigate the impact of financial openness on the performance of Chinese commercial banks. The data of the first 5 big Chinese commercial banks have been analyzed for the period of 1997-2013. Two approaches have been taken: one is PCA, which helps to build the Financial Openness Index; the other is PLS to estimate the impact of financial openness on Chinese banks performance. Result shows that a slightly positive relationship between financial openness and commercial bank performance. Furthermore, increasing the lever of bank deposits and controlling the scale of commercial banks can also play an important role in increasing commercial bank performance. © 2016 IEEE.

Guo J.,Beijing Jiaotong University
2016 International Conference on Industrial Economics System and Industrial Security Engineering, IEIS 2016 - Proceeding | Year: 2016

Nowadays, the competence and controlling power of banking industry in our country are at a rather high level and relies little on the outside world and it runs in a fine state generally. However, banking industry begins to face to severe challenges with the Economy's entering the new normal, interest rates liberalization reform, the crash of internet finance and the internalization of RMB, we have to accelerate transformation development, perfect supporting policies, recreate the traditional banks and fasten the service globalization, only in this way can the banking industry develop in a safe, stable, healthy and rapid way. © 2016 IEEE.

Song H.,Beijing Jiaotong University | Wu J.,Beijing Jiaotong University
Dianwang Jishu/Power System Technology | Year: 2013

Controlled islanding is an effective protection measure to prevent blackout spread and power system collapse. To promote the application of wide area measurement system (WAMS) in the research on power system controlled islanding, firstly the defects in traditional out-of-step islanding control is analyzed and in three aspects, namely the identification of instability modes, searching of separating tie lines and stable and balance control of islands, the key technical problems to be solved for a complete controlled islanding and the progress of related research are summarized, and the thinking of constructing controlled islanding strategy by use of real-time dynamic information provided by WAMS is proposed to lay the foundation for the implementation of centralized control and on-line decision-making. Finally, new development direction of controlled islanding, along which the breakthrough could be attained, is put forward.

Huan M.,Beijing Jiaotong University | Yang X.-B.,Beijing Jiaotong University
Scientific World Journal | Year: 2014

The paper proposed a model for estimating waiting endurance times of electric two-wheelers at signalized intersections using survival analysis method. Waiting duration times were collected by video cameras and they were assigned as censored and uncensored data to distinguish between normal crossing and red-light running behavior. A Cox proportional hazard model was introduced, and variables revealing personal characteristics and traffic conditions were defined as covariates to describe the effects of internal and external factors. Empirical results show that riders do not want to wait too long to cross intersections. As signal waiting time increases, electric two-wheelers get impatient and violate the traffic signal. There are 12.8% of electric two-wheelers with negligible wait time. 25.0% of electric two-wheelers are generally nonrisk takers who can obey the traffic rules after waiting for 100 seconds. Half of electric two-wheelers cannot endure 49.0 seconds or longer at red-light phase. Red phase time, motor vehicle volume, and conformity behavior have important effects on riders' waiting times. Waiting endurance times would decrease with the longer red-phase time, the lower traffic volume, or the bigger number of other riders who run against the red light. The proposed model may be applicable in the design, management and control of signalized intersections in other developing cities. © 2014 Mei Huan and Xiao-bao Yang.

Ni M.,Beijing Jiaotong University | Zhong Z.,Beijing Jiaotong University | Zhao D.,McMaster University
IEEE Transactions on Vehicular Technology | Year: 2011

Creating a hierarchical structure by clustering has been considered an effective method to improve the performance of ad hoc networks, such as scalability and stability. This is particularly important for networks with mobile nodes, where the mobility can cause randomly and dynamically changed network topology. In this paper, we propose a mobility prediction-based clustering (MPBC) scheme for ad hoc networks with high mobility nodes, where a node may change the associated cluster head (CH) several times during the lifetime of its connection. The proposed clustering scheme includes an initial clustering stage and a cluster maintaining stage. The Doppler shifts associated with periodically exchanged Hello packets between neighboring nodes are used to estimate their relative speeds, and the estimation results are utilized as the basic information in MPBC. In the initial clustering stage, the nodes having the smallest relative mobility in their neighborhoods are selected as the CHs. In the cluster maintaining stage, mobility prediction strategies are introduced to handle the various problems caused by node movements, such as possible association losses to current CHs and CH role changes, for extending the connection lifetime and providing more stable clusters. An analytical model is developed to find the upper and lower bounds of the average connection lifetime and to find the average association change rate of MPBC. Numerical results verify the analysis and further show that the proposed clustering scheme outperforms the existing clustering schemes in ad hoc networks with high mobility nodes. © 2011 IEEE.

Shang J.-Q.,Beijing Jiaotong University
Conference Proceedings of the 4th International Symposium on Project Management, ISPM 2016 | Year: 2016

The influence on road segment caused by working vehicle is the foundation of making energy-saving, safe, green work scheme. The influence contains two aspects: vehicles' delays and driving security on road segment. The effect varies with the factors of working speed, working lane, road segment's traffic volume and the number of lanes. Based on Paramics simulation software, the research introduces a delay and security analysis model on microscopic level according to its API interface. By simulating different working scenarios result from different choice of working parameter, the effect was obtained about vehicles' delays and security on road segment. The results show that operating speed is crucial factors which have impact on safety and delay of vehicles on road segment. The lower the speed of operation, the greater the influence. The influence is also different between two lanes and three lanes road of single direction when working vehicle operates on different lane. Besides, vehicles' delay on road segment increase and vehicles' driving safety reduce with the increase of traffic flow. When traffic flow reaches a certain level, vehicles' driving safety will be increased slightly. The effects of vehicles' delays and security on road segment from the factors are deeply studied, which contributing to optimize the operation scheme better.

Ding Z.-X.,Beijing Jiaotong University
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2013

Although the variation of shear modulus with depth can be considered in Gibson's soil model, it has always been a problem for engineering practice to determine the parameters in the model. Based on both oedometer test results of soils and a hyperbolic model using the secant modulus method by Wei Rulong (1980), a method for determining the parameters in Gibson soils is proposed for both the single-layered and the multi-layered cases. The method can be applied to soils whose stress-strain behaviors of compression obey the hyperbolic model using the secant modulus method. The results of analyzing several representative project sites in coastal regions of Zhejiang Province, China show that the special Gibson soils with a value of zero for shear modulus at ground surface keep nearly non-existent. Through the case study of a foundation treatment project using surcharge combined with the vacuum preloading technology, the multi-layered Gibson soil model with parameters calculated by means of the proposed method is thoroughly compared with other models with respect to the settlement prediction. The multi-layered Gibson soil model can give a settlement prediction with remarkably higher precision, and is also convenient in engineering applications. In the case that the effective reinforcement depth of ground is in the normal range, the Gibson soil model is recommended instead of the traditional models which ignore the variation of shear modulus of soils with depth.

Wang F.,Beijing Jiaotong University | Wang J.,Beijing Jiaotong University
Computers and Industrial Engineering | Year: 2012

We investigate and compare the scaling behaviors of the return intervals for Shanghai composite index and a financial model, where the financial price model is developed by the stochastic lattice percolation theory (a random network). For the different values of threshold, the probability density functions of the return intervals for both Shanghai composite index and the simulation data are analyzed and described by the computer computations and simulations, and the trends of the corresponding distributions are also studied by the empirical research. Further, according to the randomness and the nonlinear nature of return interval, the artificial neural network which has the strong non-linear approximation capability is introduced to train and forecast the fluctuations of the return intervals for the real and the simulative data.

Wei X.,Beijing Jiaotong University | Verhaegen M.,Technical University of Delft
International Journal of Adaptive Control and Signal Processing | Year: 2011

This paper addresses the mixed H-/H∞ fault detection observer design issue for a class of linear parameter-varying (LPV) systems. Analogous to the definition of the quadratic H∞ performance for LPV systems and the H- index for linear time invariant (LTI) systems, the quadratic H- index and the affine quadratic H- index for LPV systems are defined in terms of linear matrix inequalities (LMIs). The first algorithm for designing the mixed H -/H∞ observer is proposed, which aims at minimizing the quadratic H∞ performance and maximizing the quadratic H- index of the observer error dynamic systems. To reduce the conservativeness of this algorithm, the affine quadratic H∞ performance and the affine H- index for LPV systems are utilized. The robustness conditions and affine H- index conditions for the underlying observer optimization issue are formulated as parameter-dependent LMIs. The Gridding technique and multi-convexity concept are applied, respectively, for reducing the parameter-dependent LMIs to finite LMI constraints. Correspondingly, two iterative algorithms are proposed. Furthermore, the threshold design and the estimation of the worst undetectable fault size are investigated. An example is studied to demonstrate the effectiveness of the proposed algorithms. © 2010 John Wiley & Sons, Ltd.

Financial market dynamics forecasting has long been a focus of economic research. A stochastic time effective function neural network (STNN) with principal component analysis (PCA) developed for financial time series prediction is presented in the present work. In the training modeling, we first use the approach of PCA to extract the principal components from the input data, then integrate the STNN model to perform the financial price series prediction. By taking the proposed model compared with the traditional backpropagation neural network (BPNN), PCA-BPNN and STNN, the empirical analysis shows that the forecasting results of the proposed neural network display a better performance in financial time series forecasting. Further, the empirical research is performed in testing the predictive effects of SSE, HS300, S&P500 and DJIA in the established model, and the corresponding statistical comparisons of the above market indices are also exhibited. © 2015 Elsevier B.V.

Tang C.,Beijing Jiaotong University | Liu J.,Beijing Jiaotong University
Computers and Security | Year: 2015

Software as a Service (SaaS) offers major business and IT benefits that organizations are looking to take advantage of. SaaS adoption presents serious and unique security risks. Moving a company's sensitive data into the hands of cloud providers expands and complicates the risk landscape in which the organization operates. This paper highlights the significance and ramifications of a structured selection of a Cloud Service Provider (CSP) in achieving the required assurance level based on an organization's specific security posture. This paper proposes a holistic model, known as the Function, Auditability, Governability and Interoperability or FAGI, as an approach to help a Cloud Service Consumer (CSC) to engage and select a trusted CSP through four major decisions: Selecting a safe cloud that has adequate security functions; Choosing an auditable cloud via third-party certifications/assessments or self tests; Picking out a governable cloud that provides the required transparency; Opting for a portable cloud that ensures the desired portability. A case study reveals the FAGI approach offers an objective and efficient way to choose a qualified and trusted cloud service and in turn saves CSCs' time, effort, and grief. © 2015 Elsevier Ltd. All rights reserved.

Du Z.,Northwestern University | Zhang Y.,Beijing Jiaotong University | Li L.,Northwestern University
Cell Reports | Year: 2016

Although transcription factors are prevalent among yeast prion proteins, the role of prion-mediated transcriptional regulation remains elusive. Here, we show that the yeast prion [SWI +] abolishes flocculin (FLO) gene expression and results in a complete loss of multicellularity. Further investigation demonstrates that besides Swi1, multiple other proteins essential for FLO expression, including Mss11, Sap30, and Msn1 also undergo conformational changes and become inactivated in [SWI +] cells. Moreover, the asparagine-rich region of Mss11 can exist as prion-like aggregates specifically in [SWI +] cells, which are SDS resistant, heritable, and curable, but become metastable after separation from [SWI +]. Our findings thus reveal a prion-mediated mechanism through which multiple regulators in a biological pathway can be inactivated. In combination with the partial loss-of-function phenotypes of [SWI +] cells on non-glucose sugar utilization, our data therefore demonstrate that a prion can influence distinct traits differently through multi-level regulations, providing insights into the biological roles of prions. Du et al. report that the yeast prion [SWI +] eliminates FLO gene expression and multicellularity. They demonstrate that multiple FLO gene upregulators undergo conformational changes in the presence of [SWI +], changes that are responsible for the observed defects in multicellularity. © 2015 The Authors.

Pan R.,Beijing Jiaotong University | Chang Y.,The Interdisciplinary Center
IEEE Transactions on Information Theory | Year: 2015

Kitayama proposed a novel code-division multipleaccess (CDMA) network for image transmission called spatial CDMA. Optical orthogonal signature pattern codes (OOSPCs) have attracted wide attention as signature patterns of spatial CDMA. An (m, n, k,λ)-OOSPC is a set of m × n (0, 1)-matrices with Hamming weight k and maximum correlation value λ. Let θ(m, n, k,λ) be the largest possible number of codewords among all (m, n, k,λ)-OOSPCs. In this paper, we concentrate on the calculation of the exact value of θ (m, n, 3, 1) and the construction of an (m, n, 3, 1)-OOSPC with θ (m, n, 3, 1) codewords. As a consequence, we show that θ(m, n, 3, 1) = ⌊mn-1 ⌋-1 when mn ≡ 14, 20 (mod 24), or mn ≡ 8, 16 (mod 24) and gcd(m, n, 4) = 2, or mn ≡ 2 (mod 6) and gcd(m, n, 4) = 4, and θ(m, n, 3, 1) = ⌊mn-1⌋ otherwise. © 1963-2012 IEEE.

Song Q.,Beijing Jiaotong University | Song Y.-D.,Beijing Jiaotong University | Tang T.,Beijing Jiaotong University | Ning B.,Beijing Jiaotong University
IEEE Transactions on Intelligent Transportation Systems | Year: 2011

The problem of the position and velocity tracking control of high-speed trains becomes interesting yet challenging when simultaneously considering inevitable factors such as the resistive friction and aerodynamic drag forces, the interactive impacts among the vehicles, and the nonlinear traction/braking notches inherent in train systems. In this paper, a multiple point mass with a single-coordinate dynamic model that reflects resistive and transient impacts is derived, and based on this, computationally inexpensive robust adaptive control designs with optimal task distribution for speed and position tracking are proposed under traction/braking nonlinearities and saturation limitations. It is shown that the proposed method is not only robust to external disturbances, aerodynamic resistance, mechanical resistance, and transient impacts but adaptive to unknown system parameters as well. The effectiveness of the proposed approach is also confirmed through numerical simulations. © 2011 IEEE.

Liu X.-Y.,Beijing Jiaotong University | Yuan D.-J.,Beijing Jiaotong University
Journal of Zhejiang University: Science A | Year: 2014

When performing a slurry shield excavation in the shallow earth cover under a waterway, the support pressure is difficult to calibrate. If not carefully monitored, slurry fracturing or even slurry breakout can occur; water from the river can rush into the slurry circulating system, threatening the security of the project. In this study, an in-situ slurry fracturing apparatus was created to analyze the phenomena of slurry fracturing and fracture propagation. First, the fracturing test procedures and the method of identifying slurry fracturing are introduced. Then, mechanical models of the slurry fracturing and fracture propagation are described and validated with in-situ tests. The models provide fairly good predictions: the driving pressure is related to the properties of both the soil and slurry. Slurry with large parameters for bulk density and viscosity is beneficial for preventing slurry fracturing propagation. However, such parameters have little influence and can be neglected when determining the initial fracturing pressure. Preventing slurry fracturing and breakout is important for not only shield tunnel preparation, but also shield tunneling under dangerous conditions. A crucial factor is setting and limiting the maximum support pressure values. These pressures can be obtained through the in-situ tests and mechanical models described here. These results provide useful references for the Weisan Road Tunnel to be built under the Yangtze River in Nanjing, China. © Zhejiang University and Springer-Verlag Berlin Heidelberg 2014.

Hanif M.,National University of Sciences and Technology | Salik M.,Beijing Jiaotong University
Journal of Russian Laser Research | Year: 2014

We study the optical emission characteristics of a molybdenum (Mo) plasma produced at the surface of a target material in air at atmospheric pressure using the fundamental (1,064 nm) wavelength of an Nd: YAG laser. We estimate the temperature using the Boltzmann plot method, whereas the number density is calculated using the Stark broadening profile of the neutral iron (Fe I) transition line at 538.34 nm. We investigate variations in the temperature and number density at different laser irradiance as well as the distance from the target surface along the axial direction of plasma propagation using the spectroscopic technique. We observe that the temperature and number density increase with increase in the laser irradiance. © 2014 Springer Science+Business Media New York.

Wang S.,Beijing Jiaotong University | Yu Y.,Beijing Jiaotong University | Diao M.,Beijing Jiaotong University
Physica A: Statistical Mechanics and its Applications | Year: 2010

The hybrid projective synchronization of different dimensional fractional order chaotic systems is investigated in this paper. It is shown that the slave system can be synchronized with the projection of the master system generated through state transformation. Based on the stability theorem of linear fractional order systems, a suitable controller for achieving the synchronization is given. The hybrid projective synchronization between the fractional order chaotic system and hyperchaotic system is successfully achieved in both reduced order and increased order. The corresponding numerical results verify the effectiveness of the proposed method. © 2010 Elsevier B.V. All rights reserved.

Wang Z.D.,Beijing Jiaotong University | Gu Y.,Beijing Jiaotong University | Wang Y.S.,Beijing Jiaotong University
Journal of Magnetism and Magnetic Materials | Year: 2012

Magnetic techniques are most important NDT technologies to characterize the mechanical features of ferromagnetic materials based on the physical principle of magnetic-stress coupling. A review is presented in this paper about the development of the magnetic NDT technologies. After a brief outline of the theoretical studies of the magnetic-stress coupling effect, the three popular magnetic NDT technologies are reviewed, which are magnetic flux leakage (MFL), magnetic Barkhausen noise (MBN) and recently developed metal magnetic memory (MMM). The first two are ascribed to the active magnetic method, and the last one is the passive method. Based on an extensive literature survey in this field, this paper focuses on the discussion of the physical mechanism and some important experimental results relevant to the three NDT technologies. The challenges for each technique in this field are also summarized. © 2011 Elsevier B.V.

Chen W.,Beijing Jiaotong University | Rodrigues M.R.D.,University College London
IEEE Signal Processing Letters | Year: 2013

In this letter, we propose a new method for the joint design of both the projections and the sparsifying dictionary in order to improve signal reconstruction performance in compressive sensing (CS) applications. By capitalizing on the optimized projection matrix design in [1], which admits a closed-form expression as a function of any overcomplete dictionary, the proposed method does not need to involve directly the projection matrix. The projection matrix of our joint design can be directly derived based on the learned dictionary. Simulation results show that our joint design framework, which is constituted based on a set of training image patches, leads to an improved reconstruction performance in comparison to other recent approaches. © 1994-2012 IEEE.

Peng M.,Beijing Jiaotong University | Yang X.,North China Electrical Power University
Chaos | Year: 2010

A detailed analysis of zero distributions in a special polynomial of the form λτ(λ-a1)(λ-a2)⋯(λ-an)-(c+id) is proposed, where all ai(i=1,2,...,) have the same sign. As its applications, new criteria for asymptotic behavior of nonlinear delayed coupled systems with different topological structures are established. All possible bifurcations, including codimension-two bifurcations with 1:4/1:3 strong resonance in such a delayed difference system, are discussed. Numerical simulation gives a solid verification of the theoretical analysis. © 2010 American Institute of Physics.

Zhao H.,Beijing Jiaotong University | Gao Z.,Beijing Jiaotong University
Journal of Physics A: Mathematical and Theoretical | Year: 2010

A modified cellular automata model is proposed to simulate the pedestrian evacuation behavior in a room with multiple exits by considering the reserve capacity of the exit. The main idea is motivated by the original concept of minority game, which means less congested exits may be preferentially chosen together with the floor fields. The model outperforms previous ones under the condition in which pedestrians are distributed heterogeneously. Simulation results show that wise exit choosing with the consideration of reserve capacity may reduce the evacuation time apparently, which is more realistic. Furthermore, the impacts of the room geometry and parameter settings are investigated extensively. © 2010 IOP Publishing Ltd.

Tang Y.,Beijing Jiaotong University | Liu R.,Beijing Jiaotong University | Sun Q.,Beijing Jiaotong University
Automation in Construction | Year: 2014

China Railway is undertaking massive construction and development projects. A reasonable and resource-leveled schedule that allows for adjustments for unforeseen circumstances during construction is critical for managing railway construction projects. Currently, most construction projects use traditional network planning methods or the Gantt schedule for project management. However, these methods have limited applicability to railway construction projects, which are typically linear. This study uses the linear scheduling method and constraint programming techniques for solving schedule control problems faced during railroad construction. The proposal comprises a schedule control model, scheduling model, and schedule control system; the scheduling model is central to the schedule control model. Characteristics such as high flexibility and practicality facilitate multi-objective optimization during scheduling and modification of the linear schedule. The proposed model and algorithm were validated by comparing results with actual data from a highway construction project and the Urumqi-Dzungaria railway construction project. © 2013 Elsevier B.V.

Xiaoqing Z.,Beijing Jiaotong University
Scientific World Journal | Year: 2014

A circuit model is proposed in this paper for calculating the transient potential rise on the wind turbine struck by lightning. The model integrates the blade, sliding contact site, and tower and grounding system of the wind turbine into an equivalent circuit. The lightning current path from the attachment point to the ground can be fully described by the equivalent circuit. The transient potential responses are obtained in the different positions on the wind turbine by solving the circuit equations. In order to check the validity of the model, the laboratory measurement is made with a reduced-scale wind turbine. The measured potential waveform is compared with the calculated one and a better agreement is shown between them. The practical applicability of the model is also examined by a numerical example of a 2 MW Chinese-built wind turbine. © 2014 Zhang Xiaoqing.

Liu X.,Beijing Jiaotong University | Chen M.,Beijing Jiaotong University | Wei Y.,Beijing Jiaotong University
Renewable Energy | Year: 2015

The combustion performance of two typical herbaceous and woody samples (corncob and hardwood) and bituminous coal is evaluated using a thermal analysis technique. The biomasses show better ignition performance, volatile matter release performance and comprehensive combustion performance than those of the bituminous coal. With increasing the heating rates, the performances of corncob, hardwood and biomass/coal blends get obviously improved. The dominant mechanisms associated with combustion kinetics for corncob and most corncob/coal blends at pre-peak and post-peak are described by the Avrami-Erofeev equations (n=3 or n=4). The dominant mechanisms associated with combustion kinetics for hardwood and hardwood/coal blends at pre-peak are described by the Avrami-Erofeev equations (n=3 or n=4) or Z-L-T equation (n=2). The dominant mechanisms associated with combustion kinetics for hardwood and hardwood/coal blends at post-peak are described by the Avrami-Erofeev equations (n=3 or n=4). The dominant mechanisms of combustion for bituminous coal during the pre-peak and post-peak period are determined to be the reaction order equations. Some significant synergistic interactions are detected between Chinese bituminous coal and corncob or hardwood, especially for all corncob/coal blends at heating rate of 90°C/min and 80Cc20C blend at heating rate of 70°C/min during the co-combustion. © 2015 Elsevier Ltd.

Gong Y.-F.,Beijing Jiaotong University
Journal of Railway Engineering Society | Year: 2014

Research purposes: Prevention and Rescue of disasters happening in extra-long tunnels or tunnel groups is related to the operation safety of the train. According to Code for Design on Evacuation Engineering for Disaster Prevention and Rescue of Railway Tunnels, extra-long tunnels or tunnel groups longer than 20 km should set up an emergency rescue station. But how to combine the design of the concrete project with the emergency station is worthy of research. The paper is valuable for similar engineering design and revision of the norms. Research conclusions: The paper introduces the main principles and contents of the design of the emergency rescue station of Qingyunshan tunnel, It is concluded that: (1) It should consider circumstances of each tunnel, including its structural type, construction methods and auxiliary tunnel arrangements, etc to design individual emergency station; (2) The emergency rescue station design should be rational allocation of personnel safety evacuation and temporary shelter construction facilities, reasonable tunnel ventilation and smoke exhaust scheme, scientific layout of disaster prevention and rescue system, related to disaster prevention and rescue measures are reasonable and effective; (3) It should regard prevention and rescue of disasters in railway tunnels as a systematic engineering, which implies systematic maintenance, management and commanding is the key of the system; (4) The research results has a certain reference value for similar engineering design and revision of the "norm".

Zhao H.,Beijing Jiaotong University | Zhao H.,Virginia Commonwealth University | Zhou J.,Virginia Commonwealth University | Jena P.,Virginia Commonwealth University
Angewandte Chemie - International Edition | Year: 2016

Multiply charged negative ions are seldom stable in the gas phase. Electrostatic repulsion leads either to autodetachment of electrons or fragmentation of the parent ion. With a binding energy of the second electron at 0.9 eV, B12H12 2- is a classic example of a stable dianion. It is shown here that ligand substitution can lead to unusually stable multiply charged anions. For example, dodecacyanododecaborate, B12(CN)12 2-, created by substituting H by CN is found to be highly stable with the second electron bound by 5.3 eV, which is six times larger than that in the B12H12 2-. Equally important is the observation that CB11(CN)12 2-, which contains one electron more than needed to satisfy the Wade-Mingos rule, is also stable with its second electron bound by 1.1 eV, while CB11H12 2- is unstable. The ability to stabilize multiply charged anions in the gas phase by ligand manipulation opens a new door for multiply charged species with potential applications as halogen-free electrolytes in ion batteries. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.