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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.

Zhou J.-X.,Beijing Jiaotong University
Journal of Combinatorial Optimization | Year: 2016

A cyclic edge-cut of a connected graph G is an edge set, the removal of which separates two cycles. If G has a cyclic edge-cut, then it is called cyclically separable. For a cyclically separable graph G, the cyclic edge connectivity of a graph G, denoted by λc(G), is the minimum cardinality over all cyclic edge cuts. Let X be a non-empty proper subset of V(G). If [X,X¯]={xy∈E(G)|x∈X,y∈X¯} is a minimum cyclic edge cut of G, then X is called a λc-fragment of G. A λc-fragment with minimum cardinality is called a λc-atom. Let G be a k(k≥3)-regular cyclically separable graph with λc(G)

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.

Bai B.,Beijing Jiaotong University
Yantu Lixue/Rock and Soil Mechanics | Year: 2011

An analytical method is derived for the thermal consolidation of a hollow cylinder saturated porous medium with infinite length. In the coupled governing equations of linear isotropic porous thermoelastic medium, the influences of thermo-osmosis effect and thermal filtration effect are introduced. The solutions in Laplace transform space are first obtained and then numerically inverted by Stehfest method. These solutions consider the variable thermal loading and variable mechanical loading applied on the inner and outer pervious surface of the hollow cylinder with time. Finally, the evolutions of temperature, pore water pressure and displacement along radial direction with time are analyzed by a typical numerical example.

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.

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.

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.

Ke L.-L.,Beijing Jiaotong University | Ke L.-L.,City University of Hong Kong | Yang J.,RMIT University | Kitipornchai S.,University of Queensland
Mechanics of Advanced Materials and Structures | Year: 2013

This article presents a dynamic stability analysis of functionally graded nanocomposite beams reinforced by single-walled carbon nanotubes (SWCNTs) based on Timoshenko beam theory. The material properties of functionally graded carbon nanotube-reinforced composites (FG-CNTRCs) are assumed to vary in the thickness direction and are estimated through the rule of mixture. The differential quadrature method is employed to convert the governing differential equations into a linear system of Mathieu-Hill equations from which the boundary points on the unstable regions are determined by Bolotin's method. Free vibration and elastic buckling are also discussed as subset problems. A parametric study is conducted to investigate the influences of nanotube volume fraction, slenderness ratio, and end supports on the dynamic stability characteristics of FG-CNTRC beams. Numerical results for composite beams reinforced by uniformly distributed carbon nanotube are also provided for comparison. Copyright © Taylor &Francis Group, LLC.

Yan X.,Beijing Jiaotong University | Yan X.,University of Electronic Science and Technology of China | Minnhagen P.,Umea 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.

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.

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.

Li X.,Beijing Jiaotong University | Wong H.-S.,City University of Hong Kong | Wu S.,City University of Hong Kong
Information Sciences | Year: 2012

Fuzzy clustering is an effective clustering approach which associates a data point with multiple clusters. Standard fuzzy clustering models like fuzzy c-means are based on minimizing the total cluster variation, which is defined as the sum of the distances between the data points and their corresponding cluster centers weighted by the membership degrees. In this paper, we propose a fuzzy minimax clustering model by minimizing the maximum value of the set of weighted cluster variations in such a way that they satisfy a prior distribution. We derive a necessary condition for the extremum point of the fuzzy minimax clustering model, and then design an iterative algorithm for solving the extremum point. Several numerical examples on comparing fuzzy c-means and fuzzy minimax clustering models are given, which demonstrate that the prior distribution improves the quality of the clustering results significantly. © 2011 Elsevier Inc. All rights reserved.

Wu M.,Beijing Jiaotong University
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2010

A uniform chain circuit model was built for various electric power feeding systems of AC electrified railways. All electrical elements in the traction network, including the short circuit and the conductor break fault, were described conformably by a serial element or a shunt element. According to the chain circuit structure, the mathematical model of the whole network can be assembled conveniently using the nodal admittance matrices of elements. Considering the relatively large leakage conductance of the return circuit to the ground, the multiphase equivalent π-circuits were adopted for the uniform multi-conductor sections of the traction network. The characteristic admittance matrix, which can be calculated by the phase-modal transformation method, was introduced for the truncation treatment at terminals of the feeding system. The proposed mathematical model provides a base for calculating the power flow, i.e. the voltage and current distribution of the traction network under certain load conditions. This model can also be used in researches such as the steady state short circuit calculation and the harmonic resonance analysis. © 2010 Chin. Soc. for Elec. Eng.

Lu C.,Beijing Jiaotong University
Journal of Convergence Information Technology | Year: 2012

In the decade, the use of agent-based artificial stock market (ASM) which is a bottom-up method for financial complex systems for study various questions of real stock market have been acceptance by more and more social scientists. Firstly, this paper reports the construction of artificial stock market based on the Arthur's artificial stock market. It emerges the similar facts with real data in Chinese stock market, including volatility clustering, the excess kurtosis of the distribution of return, especially fractal structure. From this point, the artificial stock market can not only generate stock price trends and properties rather similar to the real stock market, but also show the fractal structure in deep consistency with the real stock market. Then, this paper applies the artificial stock market in an empirical case--the Pareto principle in the all world stock market, which means that that twenty percent of the people owned eighty percent of the wealth in the stock market. This paper makes use of ASM reappear the 80-20 phenomenon of the wealth in the real stock market, and reveal the producing reason of Pareto rule of the stock market. So, research on the artificial stock market can reveal evolution rule of real stock market, operate mechanism, policy influence and better investment strategy.

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.

Zhou X.,Beijing Jiaotong University | Peng Y.,University of Bradford | Liu B.,Chinese Academy of Sciences
Journal of Biomedical Informatics | Year: 2010

Extracting meaningful information and knowledge from free text is the subject of considerable research interest in the machine learning and data mining fields. Text data mining (or text mining) has become one of the most active research sub-fields in data mining. Significant developments in the area of biomedical text mining during the past years have demonstrated its great promise for supporting scientists in developing novel hypotheses and new knowledge from the biomedical literature. Traditional Chinese medicine (TCM) provides a distinct methodology with which to view human life. It is one of the most complete and distinguished traditional medicines with a history of several thousand years of studying and practicing the diagnosis and treatment of human disease. It has been shown that the TCM knowledge obtained from clinical practice has become a significant complementary source of information for modern biomedical sciences. TCM literature obtained from the historical period and from modern clinical studies has recently been transformed into digital data in the form of relational databases or text documents, which provide an effective platform for information sharing and retrieval. This motivates and facilitates research and development into knowledge discovery approaches and to modernize TCM. In order to contribute to this still growing field, this paper presents (1) a comparative introduction to TCM and modern biomedicine, (2) a survey of the related information sources of TCM, (3) a review and discussion of the state of the art and the development of text mining techniques with applications to TCM, (4) a discussion of the research issues around TCM text mining and its future directions. © 2010 Elsevier Inc.

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.

Gao S.,Fuyang Normal College | Wang J.,Beijing Jiaotong University
RAIRO - Operations Research | Year: 2016

We consider the discrete-time Markovian single-server queue under delayed multiple vacations. Upon arriving, the customers observe the queue length and decide whether to join or balk. We derive equilibrium threshold balking strategies in two cases, according to the information for the server's state. We also illustrate the equilibrium thresholds and the social benefits for systems via numerical experiments. © EDP Sciences, ROADEF, SMAI 2016.

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.

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.

Jiang J.,Beijing Jiaotong University
IATSS Research | Year: 2015

This paper introduces a method of factor decomposition analysis for analyzing the importance of the factors that affect the volume of transportation energy consumption. In choosing the influencing factors from the many possibilities, the paper introduces an indicator analysis to evaluate and select the most important affecting factors. Based on the decomposition results, the paper helps interpret the underlying causes of transportation energy consumption. At the same time, the paper also suggests corresponding policy implications for the improvement of transportation energy efficiency. © 2014.

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.

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.

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.

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.

Shao J.,Beijing Jiaotong University
Beijing Jiaotong Daxue Xuebao/Journal of Beijing Jiaotong University | Year: 2014

Transition probability flow graphs model is an effective method for getting the transition probability of stochastic processes and the generating functions of some random variables. By this method, the paper discusses multinomial distribution, derives the probability generating functions of generalization geometric variables and generalization Pascal variables, and obtains the means, variances and probability distributions of them.

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.

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.

Liu X.,University of Michigan | Liu X.,Beijing Jiaotong University | Kim H.,University of Michigan | Guo L.J.,University of Michigan
Organic Electronics: physics, materials, applications | Year: 2013

In this work, graphene oxide (GO) reduced by thermal annealing was employed as a hole transport layer (HTL) in bulk heterojunction (BHJ) solar cells. Considering the insulating property of nonreduced GO, the annealing temperature plays an important role in recovering the conjugated structure of the graphene sheet, and thereby the conductivity of GO. BHJ solar cells with high-temperature (e.g., 230 °C) reduced GO as the HTL showed much larger fill factor (FF) than devices with low-temperature (e.g., 130 °C) reduced GO as the HTL, indicating the better conductivity of GO annealed at an elevated temperature due to the removal of oxygen functional groups from the graphene sheet to a much-higher level. On the other hand, the work function of GO may be lowered toward that of graphene (4.5 eV) with increasing the reduction temperature, which results in a decreased open-circuit voltage (Voc) for the high-temperature reduced GO devices. By further optimizing the concentration and spin-coating speed of GO dispersion, we achieved a power conversion efficiency (PCE) that is 26% higher than devices without any HTL. This is mainly attributed to the increase in FF as a result of the decreased series resistance (R s). In addition, the PCE of the optimized GO device was ∼85% of the PCE of the conventional device with poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) HTL. We anticipate that further optimization of the reduction conditions (e.g., using chemical reductants) will lead to the better performance of GO solar cells. © 2012 Elsevier B.V. All rights reserved.

Zhao B.,Beijing Jiaotong University
Earthquake Science | Year: 2010

Taking Tianjin as an example, this paper proposed a methodology and process for evaluating near-fault strong ground motions from future earthquakes to mitigate earthquake damage for the metropolitan area and important engineering structures. The result of strong ground motion was predicted for Tianjin main faults by the hybrid method which mainly consists of 3D finite difference method and stochastic Green's function. Simulation is performed for 3D structures of Tianjin region and characterized asperity models. The characterized asperity model describing source heterogeneity is introduced following the fault information from the project of Tianjin Active Faults and Seismic Hazard Assessment. We simulated the worst case that two earthquakes separately occur. The results indicate that the fault position, rupture process and the sedimentary deposits of the basin significantly affect amplification of the simulated ground motion. Our results also demonstrate the possibility of practical simulating wave propagation including basin induced surface waves in broad frequency-band, for seismic hazard analysis near the fault from future earthquakes in urbanized areas. © 2010 The Seismological Society of China and Springer-Verlag Berlin Heidelberg.

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.

Xu X.F.,Beijing Jiaotong University
Frontiers of Structural and Civil Engineering | Year: 2015

The Green-function-based multiscale stochastic finite element method (MSFEM) has been formulated based on the stochastic variational principle. In this study a fast computing procedure based on the MSFEM is developed to solve random field geotechnical problems with a typical coefficient of variance less than 1. A unique fast computing advantage of the procedure enables computation performed only on those locations of interest, therefore saving a lot of computation. The numerical example on soil settlement shows that the procedure achieves significant computing efficiency compared with Monte Carlo method. © 2014, Higher Education Press and Springer-Verlag Berlin Heidelberg.

Liu X.,Beijing Jiaotong University | Liu X.,University of Michigan | Lee J.Y.,University of Michigan | Guo L.J.,University of Michigan
Organic Electronics: physics, materials, applications | Year: 2013

We report on the improved performance and stability of bulk heterojunction (BHJ) polymer solar cells using five stacks of C60/LiF as cathode buffer layer, which was prepared by alternating deposition of C60 and LiF layers. The five-stacked C60/LiF film, even with a large thickness ratio of LiF to C60, exhibits good electrical conductivity. The devices with five stacks of C60/LiF buffer layer show a peak power conversion efficiency (PCE) which is 19% higher than that of the conventional devices with only LiF interlayer, primarily due to the improvement in fill factor (FF) of the device. Moreover, the high efficiency of five-stacked C60/LiF based devices is insensitive to changes in the thickness ratio between C60 and LiF layers. Since much thicker LiF can be used in five-stacked C60/LiF film, these devices also show superior air stability as compared to the devices with only LiF interlayer. Therefore, five-stacked C60/LiF is a promising alternative to pristine LiF as a cathode buffer layer in polymer solar cells. © 2012 Elsevier B.V. All rights reserved.

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.

Ge B.,Beijing Jiaotong University | Ge B.,Michigan State University | Peng F.Z.,Michigan State University | De Almeida A.T.,University of Coimbra | Abu-Rub H.,Texas A&M University at Qatar
IEEE Transactions on Industrial Electronics | Year: 2010

For a cascaded neutral-point-clamped (NPC) inverter applied to the medium-voltage high-power induction-motor (IM) drives, an effective control technique is proposed in this paper. The novel sinusoidal pulsewidth modulation (PWM) pulse-rotation-control approach, for a wide range of output voltage, provides a simple way to implement vector control for IM when the cascaded NPC inverter is employed. The proposed method presents great benefits to the cascaded NPC inverter. The output voltages and power of all inverter modules and the two series-capacitor dc voltages of each inverter module are perfectly balanced. Moreover, a low switch frequency of all inverter modules supports a synthesized high-frequency PWM phase voltage. The internal voltage drop of the inverter, due to the cascade structure of many insulated-gate bipolar transistordiode modules' series connection, is analyzed, which causes the distorted phase voltages and currents at low speeds when the frequency and the output voltage are low. The current closed-loop control compensates the distortion of phase voltages and currents. A rotor-flux-oriented vector control is combined with back-electromotive-force-based model reference adaptive system speed estimation, which results in a speed closed-loop control. The voltage sensors together with the filters of changeable parameters ensure the precision of speed estimation for the whole frequency range. The experimental tests are carried out through an 800-kW 4160-V IM drive fed by the 1-MVA 6000-V 17-level cascaded NPC inverter. The results verify the proposed scheme. © 2006 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.

Zhang X.,Beijing Jiaotong University
Mathematical Problems in Engineering | Year: 2011

A simplified model of magnetic saturation characteristics is proposed in this paper for transient calculation of the electric networks including magnetizing branches. The model represents the magnetic saturation characteristics by the continuous function instead of the piecewise linear approximation. Based on the proposed model, an efficient transient algorithm is developed. The nonlinear differential equations describing the transient behavior of the magnetizing branches are solved by the semiexplicit Runge-Kutta method, in which noniterative computations are involved. The transient calculation for the remaining linear network is performed in terms of the solution to the magnetizing branches. A comparison is made between calculated and experimental results to confirm the validity of the algorithm. © 2011 Xiaoqing Zhang.

Wang D.Z.W.,Nanyang Technological University | Xie D.-F.,Beijing Jiaotong University
International Journal of Sustainable Transportation | Year: 2016

Travel demand is indeed stochastic with day-to-day travel demand variability, because of the underlying characteristic of variability of travel activities. The stochastic travel demand can be described by different probability distribution patterns and has to be considered in transport network design, as it affects travelers' routing choice behavior against stochastic travel time and eventually the traffic flow pattern on the network. However, on the other hand, because of the inaccurate or inconsistent travel demand estimation procedures, the prediction of the travel demand distribution pattern and parameters is susceptible to a certain level of uncertainty. Therefore, both the travel demand day-to-day variability and the uncertainty in terms of estimating travel demand distribution pattern and parameters have to be incorporated in the transportation network design. This study develops an approach to model network design problem with uncertain demand variability. Specifically, it is assumed that the total travel demand comprises two parts, commuters and infrequent travelers, and only the demand of infrequent travelers is stochastic. Then, the travel time reliability is introduced to depict the path choice behavior. A finite-scenario two-stage stochastic programming approach is applied to model the network design problem with uncertain demand variability. Numerical studies are performed to illustrate the model validity and efficiency of solution algorithm. © 2016 Taylor & Francis Group, LLC.

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.

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.

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.

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 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.

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.

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.

Sun H.-J.,MOE Key Laboratory for Urban Transportation Complex Systems Theory | Zhang H.,MOE Key Laboratory for Urban Transportation Complex Systems Theory | Wu J.-J.,Beijing Jiaotong University
Nonlinear Dynamics | Year: 2012

Many transport processes on network depend crucially on the underlying network topology. In this paper, we propose a model to generate correlated scale free transportation networks with community structure by considering the mechanisms of dynamical network evolution and rewiring links. With the introduction of congestion effects, we investigate the performance and carrying capacity of this network. The results show that congestion in the uncorrelated network is more serious than the assortative or disassortative ones. Therefore, the correlated network with communities can bear much more traffic flow. In addition, the networks with lager modularity can enhance the transportation efficiently. © Springer Science+Business Media B.V. 2012.

Yu J.,Qingdao University | Chen B.,Qingdao University | Yu H.,Qingdao University | Yu H.,Beijing Jiaotong University
Nonlinear Dynamics | Year: 2012

This paper focus on the problem of position tracking control for the chaotic permanent magnet synchronous motor drive system with parameter uncertainties. Fuzzy logic systems are used to approximate the nonlinearities and the adaptive backstepping technique is employed to construct controllers. The proposed adaptive fuzzy controllers guarantee that the tracking error converges to a small neighborhood of the origin. Compared with the conventional backstepping, the designed fuzzy controllers' structure is very simple. Simulation results show that the proposed control scheme can suppress chaos of PMSM and guarantee the perfect tracking performance even under the unknown parameters. © Springer Science+Business Media B.V. 2011.

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.

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.

Wei X.,Beijing Jiaotong University | Verhaegen M.,Technical University of Delft
Wind Energy | Year: 2011

In this paper, we consider sensor and actuator fault detection and estimation issues for large scale wind turbine systems where individual pitch control (IPC) is used for load reduction. The faults considered are the blade root bending moment sensor faults and blade pitch actuator faults. In the first part, with the aid of a dynamical model of the wind turbine system, a so-called H∞//H- observer in the finite frequency range, is applied to generate the residual for fault detection. The observer is designed to be sensitive to faults but insensitive to disturbances, such as wind turbulence. When there is a detectable fault, the observer sends an alarm signal if the residual evaluation is larger than a predefined threshold. In addition to the fault detection, we also consider the fault estimation problem, where a dynamic filter is used to estimate the fault magnitude. The effectiveness of the proposed approach is demonstrated by simulation results for several fault scenarios. © 2010 John Wiley & Sons, Ltd.

Sun Z.,Beijing Jiaotong University
Procedia Engineering | Year: 2016

A bi-level programming model was widely used to describe the continuous transportation network design problem. The objective function in upper-level model was to make the sum of total impedance and total investment budget minimal in a traffic network. The lower-level model was a user equilibrium assignment model with fixed demand. In order to make the results more realistic, this paper proposed an improved model with stochastic transportation network design, and presented genetic algorithm and Frank-Wolfe (FW) algorithm to find optimal solution. Then a specific network example was given to prove the effectiveness of the model. The results show that an optimal value of existing links capacities for the formulation can be obtained and it can minimize the sum of total impedance and investment budget, which can provide a reasonable reference for the decision-makers. © 2016 The Authors. Published by Elsevier Ltd.

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).

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.

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.

Wu C.,Beijing Jiaotong University
Guangxue Xuebao/Acta Optica Sinica | Year: 2011

The research achievements of optical buffer based on optical fiber delay line in recent 10 years are introduced. The basic buffer element, dual loop optical buffer (DLOB), is introduced. Based on DLOB, some new structures of buffer for different applications are proposed, such as the buffer with big dynamics of delay from 1 to 9999 T and the eight wavelengths buffer. All of these buffers are operated at the bit rate above 2.5 Gb/s. A polarization-rotation-based optical buffer is proposed. The principle, key technologies and experimental results are introduced for all above buffers. At last, the advantages and development future are discussed.

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.

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.

Chen B.Y.,Hong Kong Polytechnic University | Chen B.Y.,Wuhan University | Lam W.H.K.,Hong Kong Polytechnic University | Lam W.H.K.,Beijing Jiaotong University | And 3 more authors.
Transportation Research Part A: Policy and Practice | Year: 2012

To assess the vulnerability of congested road networks, the commonly used full network scan approach is to evaluate all possible scenarios of link closure using a form of traffic assignment. This approach can be computationally burdensome and may not be viable for identifying the most critical links in large-scale networks. In this study, an " impact area" vulnerability analysis approach is proposed to evaluate the consequences of a link closure within its impact area instead of the whole network. The proposed approach can significantly reduce the search space for determining the most critical links in large-scale networks. In addition, a new vulnerability index is introduced to examine properly the consequences of a link closure. The effects of demand uncertainty and heterogeneous travellers' risk-taking behaviour are explicitly considered. Numerical results for two different road networks show that in practice the proposed approach is more efficient than traditional full scan approach for identifying the same set of critical links. Numerical results also demonstrate that both stochastic demand and travellers' risk-taking behaviour have significant impacts on network vulnerability analysis, especially under high network congestion and large demand variations. Ignoring their impacts can underestimate the consequences of link closures and misidentify the most critical links. © 2011 Elsevier Ltd.

Li X.,Beijing Jiaotong University | Chen X.,Shenzhen Metro Group 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.

Wu Y.,Beijing Jiaotong University | Sheng Q.Z.,University of Adelaide | Shen H.,University of Adelaide | Zeadally S.,University of the District of Columbia
IEEE Transactions on Parallel and Distributed Systems | Year: 2013

In the emerging environment of the Internet of things (IoT), through the connection of billions of radio frequency identification (RFID) tags and sensors to the Internet, applications will generate an unprecedented number of transactions and amount of data that require novel approaches in RFID data stream processing and management. Unfortunately, it is difficult to maintain a distributed model without a shared directory or structured index. In this paper, we propose a fully distributed model for federated RFID data streams. This model combines two techniques, namely, tilted time frame and histogram to represent the patterns of object flows. Our model is efficient in space and can be stored in main memory. The model is built on top of an unstructured P2P overlay. To reduce the overhead of distributed data acquisition, we further propose several algorithms that use a statistically minimum number of network calls to maintain the model. The scalability and efficiency of the proposed model are demonstrated through an extensive set of experiments. © 1990-2012 IEEE.

Xin S.,Beijing Jiaotong University
Proceedings - 2010 1st International Conference on Pervasive Computing, Signal Processing and Applications, PCSPA 2010 | Year: 2010

The architecture of TETRA digital trunking protocol stack is described in this paper. The procedure and development of energy economy mode are stated in details. The protocol conformance tests of energy economy mode are implemented in the simulation environment, and simulation test results show that the devolopmented protocol stacks of energy economy mode are in accordance with "ETS 300 392-2 TETRA V+D Part 2: Air Interface". © 2010 IEEE.

Wang H.,Beijing Jiaotong University | Chu X.,Kings 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 X.,Peking University | Cheng X.,Beijing Jiaotong University | Yang L.,Colorado State University | Shen X.,Peking University
IEEE Transactions on Intelligent Transportation Systems | Year: 2015

Intelligent transportation systems (ITS) are becoming a crucial component of our society, whereas reliable and efficient vehicular communications consist of a key enabler of a well-functioning ITS. To meet a wide variety of ITS application needs, vehicular-to-vehicular and vehicular-to-infrastructure communications have to be jointly considered, configured, and optimized. The effective and efficient coexistence and cooperation of the two give rise to a dynamic spectrum management problem. One recently emerged and rapidly adopted solution of a similar problem in cellular networks is the so-termed device-to-device (D2D) communications. Its potential in the vehicular scenarios with unique challenges, however, has not been thoroughly investigated to date. In this paper, we for the first time carry out a feasibility study of D2D for ITS based on both the features of D2D and the nature of vehicular networks. In addition to demonstrating the promising potential of this technology, we will also propose novel remedies necessary to make D2D technology practical as well as beneficial for ITS. © 2000-2011 IEEE.

Abu-Rub H.,Texas A&M University at Qatar | Holtz J.,University of Wuppertal | Rodriguez J.,Federico Santa Maria 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.

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.

Zheng W.,Beijing Jiaotong University
Jiaotong Yunshu Gongcheng Xuebao/Journal of Traffic and Transportation Engineering | Year: 2012

The general framework of running control system on maglev train was studied according to the running requirements of maglev train running across different control systems. Functional subsystems need to be added was defined. The hierarchical models of system key attributes, maglev operation procedures and the subsystem function were built based on the system theory by using Petri net. The key attributes of whole system were described by the highest model, and the operation procedures of maglev train and the reliabilities of subsystems were presented in the lower level model. The relationship between the failure rates of maglev train running across different control systems and the reliabilities of subsystem components was quantitatively analyzed with the model. It is pointed that the loss ratio of network connecting neibouring control systems should be lower than 10 -6 times per hour when the required failure number of maglev train running across different systems is no more than 1 time per year. The failure rates of maglev train running across different control systems are 1.95×10 -5 and 1.65×10 -5 times per hour when the triggering times equal 0.2 and 2.0 min respectively, and the stepping times equal 4 and 16 min respectively. Simulation result shows that the failure rates of train running across the boundary decrease when the reliabilities of a and b networks are improved, or the triggering time and stepping time of train are prolonged. The reliability requirements of subsystem components based on the required key attributes of system level are quantantatively identified by using the proposed approach.

Xu F.,Beijing Jiaotong University | Xu F.,University of Sydney | Patterson J.C.,University of Sydney | Lei C.,University of Sydney
International Journal of Thermal Sciences | Year: 2013

In this study we investigate the transition from a steady flow to an unsteady flow induced by an adiabatic fin on the sidewall of a differentially heated cavity using numerical simulation. A range of Rayleigh numbers (10 6-109) and various fin lengths with Prandtl number 6.63 are considered. It is found that the flow adjacent to the finned sidewall is unsteady for the cases with Rayleigh numbers higher than a critical value for a given fin length. Such an unsteady flow results from a fluid layer above the fin with an adverse temperature gradient and a through flow, which is a similar mechanism to a Rayleigh-Benard-Poiseuille (RBP) flow, though the configuration is such that it cannot be exactly a RBP flow. The transition from a steady flow to an unsteady flow is sensitive to the fin length, and the critical values of the transition for the different fin lengths are obtained. Moreover, the features of the unsteady flow induced by the fin are characterized and the mechanisms responsible for the unsteadiness are discussed. © 2013 Elsevier Masson SAS. All rights reserved.

Lei L.,Beijing Jiaotong University
2016 23rd International Conference on Telecommunications, ICT 2016 | Year: 2016

Device-to-Device (D2D) communications enable cellular devices in physical proximity to communicate directly over the air instead of through the BSs, which can be applied in Intelligent Transportation Systems (ITS) to efficiently support the communications between vehicles. However, the resource control functions need to adapt to the unique characteristics of vehicular environments and meet the high reliability and low latency requirements of road safety applications. In this paper, we discuss the performance evaluation and dynamic optimization of D2D communications for ITS based on stochastic models, where the complex mobility behavior of vehicles and stochastic nature of traffic arrivals are captured. We focus on two typical scenarios, i.e., safety applications and vehicular cloudlet, and outline the research directions and present the challenges and major issues that need to be addressed. © 2016 IEEE.

Wang X.,Imperial College London | Ishwara T.,Imperial College London | Gong W.,Imperial College London | Gong W.,Beijing Jiaotong University | And 3 more authors.
Advanced Functional Materials | Year: 2012

The use of vapor phase polymerized poly(3,4-ethylenedioxythiophene) (VPP-PEDOT) as a metal-replacement top anode for inverted solar cells is reported. Devices with both i) standard bulk heterojunction blends of poly(3-hexylthiophene) (P3HT) donor and 1-(3-methoxycarbonyl)-propyl-1-phenyl- (6,6)C 60 (PCBM) soluble fullerene acceptor and ii) hybrid inorganic/organic TiO 2/P3HT acceptor/donor active layers are studied. Stamp transfer printing methods are used to deposit both the VPP-PEDOT top anode and a work function enhancing PEDOT:polystyrenesulphonate (PEDOT:PSS) interlayer. The metal-free devices perform comparably to conventional devices with an evaporated metal top anode, yielding power conversion efficiencies of 3% for bulk heterojunction blend and 0.6% for organic/inorganic hybrid structures. These encouraging results suggest that stamp transfer printed VPP-PEDOT provides a useful addition to the electrode materials tool-box available for low temperature and non-vacuum solar cell fabrication. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

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.

Xu X.F.,Beijing Jiaotong University
Safety, Reliability, Risk and Life-Cycle Performance of Structures and Infrastructures - Proceedings of the 11th International Conference on Structural Safety and Reliability, ICOSSAR 2013 | Year: 2013

There is a strong demand for theoretical breakthroughs in scale-coupling mechanics to accelerate the development of nonlinear multiscale methods. The author's recent studies on linear theory of scale-coupling mechanics and the Green-function-based multiscale method motivate a further extension into the nonlinear regime. In this paper nonlinear variational principles are formulated for scale-coupling and scale separation problems. As an example of application, a new nonlinear bound is further derived. © 2013 Taylor & Francis Group, London.

Lu X.,Beijing Jiaotong University | Lu X.,University of South Florida
Nonlinear Dynamics | Year: 2015

Within the framework of the Madelung fluid description, in the present paper, we will derive bright and dark (including gray- and black-soliton) envelope solutions for a generalized mixed nonlinear Schrödinger model (formula presented) by virtue of the corresponding solitary wave solutions for the generalized stationary Gardner equations. Via corresponding parametric constraints, our results are achieved under suitable assumptions for the current velocity associated with different boundary conditions of the fluid density $$\rho $$ρ, while we have only considered the motion with stationary-profile current velocity case and excluded the motion with constant current velocity case. Note that our model is a generalized one with the inclusion of multiple coefficients (a, b, c and d). © 2015, Springer Science+Business Media Dordrecht.

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.

Wang Z.,Beijing Jiaotong University
Tumu Gongcheng Xuebao/China Civil Engineering Journal | Year: 2012

Experiments were conducted on concrete cube specimens of 100 mm side length in plane strain state. The loading procedure involves two steps: apply the designated hydrostatic pressure, then monotonically increase the Y-axial strain, in the direction of the maximum compressive stress, while keep the Z-axial strain constant and different constant ratios of stress rates between X and Y axes. A total of 25 experimental groups were defined according to loading paths determined by a combination of the designated hydrostatic stresses in 9 levels and the ratios of stress rates, and each group contained 2 or 3 concrete specimens. All specimens failed in wedge-shapes, resulted from shear and companion compression. The experiments showed that the hydrostatic pressure did not affect the initial shear modulus when the concrete specimen experienced only monotonic increase of hydrostatic pressure, and a coinciding part was found in the curves of shear stress vs. shear strain for different experimental groups. In most experimental groups, it was found that shear contraction was followed by shear dilation during increase in shear strain. But in some experimental groups, only shear contraction occurred without shear dilation until the loading finished during or after softening. The experimental result loading in quasi-plane strain state was compared with those from proportioned triaxial compressive experiment with two equal principal stresses for the parallel concrete specimens, and it was found that the shear strengths from both of the experiments met the Mohr-Coulomb failure criterion, but the shear strength of the latter was lower than that of the former. Further analysis showed that the intermediate principal stress only influences the cohesion, but has little effect on the angle of internal friction.

Guo Y.,Beijing Jiaotong University
Tumu Gongcheng Xuebao/China Civil Engineering Journal | Year: 2013

Due to the limitations of underground space and subway routing, a double-track tunnel designing scheme was adopted for the tunnel section between Dongfengbeiqiao station and Jingshun station of Beijing subway Line 14, and for this section the tunnel was excavated by using a 10m-diameter earth pressure balance shield. To understand the ground surface movements induced by the shield tunneling process, the ground surface movements were measured by a series of monitoring points along the line. Based on the statistical analyses of measured data and tunneling parameters such as regression and fitting analysis, the key characteristic parameters, including the maximum ground surface settlement, the width of settlement trough and the ground loss ratio, and the general characteristics of ground surface movements were attained. Furthermore, based on the selected monitoring cross sections, the impacts of the tunnel depth, overlying soil types (clay or sandy soil), synchronous grouting amount and chamber earth pressure on ground surface movement were evaluated. The findings in this study may provide a good reference to other identical projects involving large-diameter earth pressure balance shield tunneling.

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.

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.

Liu J.,Beijing Jiaotong University
Beijing Gongye Daxue Xuebao/Journal of Beijing University of Technology | Year: 2013

By high-accuracy GPS dynamic data acquisition instrument, the author designed the experimental plan of drivers' overtaking on the two-lane highways with the drivers' perceive to measure the overtakable gap and the returnable gap. The experimental results could be used as the basis for the study of two-lane highways' capacity, drivers' overtaking behavior, the design of overtaking sight distance and intelligent transportation system.

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.

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.

Zhang S.-J.,Beijing Jiaotong University
Guangdianzi Jiguang/Journal of Optoelectronics Laser | Year: 2013

Detection of architectural distortion (AD) in mammograms is one of important approaches in breast cancer diagnosis. Using support vector machine (SVM) to detect AD can achieve high accuracy rate, but it is also with slow speed, making it not suitable for clinical application. To solve the above problems, a method to detect AD in mammograms based on relevance vector machine (RVM) is proposed. Firstly, the discrete wavelet transform is applied to extract features in region of interest (ROI). Then the cross validation (CV) method is used to determine the optimum type and parameters of RVM kernel function. Lastly, RVM is applied to classify the test samples to obtain the detection results of AD. The proposed method is evaluated on mammograms from the mammographic image analysis society (Mini-MIAS) and those from the breast cancer of Peking University People's Hospital. The results show that compared with SVM method, the proposed method achieves essentially the same sensitivity with much higher speed of detection, which can shorten the detection time of AD more than 90%. The proposed method is more applicable for mammograms with different characteristics of both oriental and occidental women.

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.

Li Z.-X.,Tianjin University | Lv Y.,Tianjin University | Xu L.-H.,Beijing Jiaotong University | Ding Y.,Tianjin University | Zhao Q.,Tianjin University
Engineering Structures | Year: 2013

This article presents experimental studies on the feasibility of nonlinear seismic control of a 3-story steel-concrete hybrid structure using magnetorheological (MR) dampers. The control strategies included passive-on control, passive-off control and semi-active control, and strains gathered at the bottom of the steel columns were used as feedbacks to build the semi-active controller. For each control type, the control efficacy on structural response and damage was verified for the El Centro, Taft and Tianjin earthquake with specified peak ground acceleration (PGA) of 0.2. g, 0.4. g, 0.9. g and 1.2. g respectively. The test results show that (1) it is feasible to control the seismic response of the steel-concrete hybrid structure using MR dampers; (2) structure with semi-active control and passive-on control perform better in the shaking table test considering the maximum inter-story drift, displacement time history and energy dissipation capacity, compared to uncontrolled structure and structure with passive-off control; (3) there is also more structural damage in the passive-off and uncontrolled cases, proving the effectiveness of MR dampers in damage control. In addition, an inverse calculation method for strain is proposed to effectively utilize the strains measured during the shaking table test to obtain the stress and material damage process at measured positions, using damage model of the steel and concrete material. © 2012 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.

Yang X.,Beijing Jiaotong University
Advanced Materials Research | Year: 2011

Based on the FLAC2D finite difference software, We can use strength reduction theory to gained the stability factor of the 48 soil slopes under the different conditions, Grey Correlation Analysis Method of the Grey System Theory is employed to analyze the sensitivities of factor influencing slope stability. The matrix of correlation data is setup, the elements of which are transformed to dimensionless parameters. The grey correlative factors and grey correlative degrees which respect to the influencing factor and the slope stability factor are computed, and the sensible factors influence slope stability are decided. The results show that the cohesion of the soil. The density and the internal friction angle are the most sensitive factors to the slope stability, and the dilatancy angle, slope angle and the slope height are taken second place, which provide a reference to the reasonably and effectively design of the actual slope works. © (2011) Trans Tech Publications, Switzerland.

Wang Y.,Xidian University | Wang L.-H.,Xidian University | Ge J.-H.,Xidian University | Ai B.,Beijing Jiaotong University
IEEE Transactions on Broadcasting | Year: 2012

In this paper, an efficient nonlinear companding scheme is proposed to reduce the peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals. By transforming the statistics of original signals into a specified distribution form along with remaining an unchanged average output power level, this scheme can achieve significant reduction in PAPR as well as an improved BER performance simultaneously. Moreover, by properly adjusting the transform parameters, more design flexibility in companding form can also be given by this scheme to satisfy various system requirements. The theoretical analysis results regarding the transform gain, companding distortion and the selection criteria of parameters are derived. It is proved that this scheme may lead to less signal distortion compared to existing companding schemes. Simulation results demonstrate that the proposed scheme can substantially offer better overall performance of OFDM system in terms of PAPR reduction, BER performance and bandwidth efficiency. © 2012 IEEE.

Chen F.-M.,Beijing Jiaotong University
Nuclear Physics B | Year: 2013

We demonstrate that the general D=. 3, N=5 Chern-Simons matter theory possesses a full OSp(5|4) superconformal symmetry, and construct the corresponding superconformal currents. The closure of the superconformal algebra is verified in detail. We also show that the conserved OSp(6|4) superconformal currents in the general N=6 theory can be obtained as special cases of the OSp(5|4) currents by enhancing the R-symmetry of the N=5 theory from USp(4) to SU(4). © 2013 Elsevier B.V.

Jin S.,Beijing Jiaotong University
Journal of Vibroengineering | Year: 2016

The paper investigates the dynamic response of the slab track under the action of vehicles. Based on finite element method and multibody dynamics, the vehicle-slab track coupling model and moving sprung mass model on slab are developed to simulate the vehicle and slab track interaction at any speed. The resonance mechanism and conditions of slab track system are investigated through theoretical derivations and numerical simulations. In a numerical case study, the effect of rail pad stiffness and slab bearing stiffness on resonance phenomena of track system are analyzed. © JVE INTERNATIONAL LTD.

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.

Li Q.,Beijing Jiaotong University | Lu W.,Chinese Academy of Meteorological Sciences | Yang J.,Chinese Academy of Meteorological Sciences
Journal of Atmospheric and Oceanic Technology | Year: 2011

Cloud detection is the precondition for deriving other information (e.g., cloud cover) in ground-based sky imager applications. This paper puts forward an effective cloud detection approach, the Hybrid Thresholding Algorithm (HYTA) that fully exploits the benefits of the combination of fixed and adaptive thresholding methods. First, HYTA transforms an input color cloud image into a normalized blue/red channel ratio image that can keep a distinct contrast, even with noise and outliers. Then, HYTAidentifies the ratio image as either unimodal or bimodal according to its standard deviation, and the unimodal and bimodal images are handled by fixed and minimum cross entropy (MCE) thresholding algorithms, respectively. The experimental results demonstrate that HYTA shows an accuracy of 88.53%, which is far higher than those of either fixed or MCE thresholding alone. Moreover, HYTA is also verified to outperform other state-of-the-art cloud detection approaches. © 2011 American Meteorological Society.

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.

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.

Liu Y.,Beijing Jiaotong University | Kokko A.,Copenhagen Business School
Energy Policy | Year: 2013

This paper provides an overview of the Chinese new energy vehicle industry and discusses the role of state in the industry's development. Chinese policies have aimed to promote the development of new energy technologies and to reduce the consumer price of new energy vehicles. Chinese authorities have also been concerned about the balance between collaboration and competition in the sector, since most key actors are owned by the state. One solution has been the establishment of a number of industry alliances linking auto enterprises, universities and research institutes, to promote both collaboration (within each alliance) and competition (between alliances). © 2012 Elsevier Ltd.

Jing L.,Beijing Jiaotong University | Ng M.K.,Hong Kong Baptist University
BMC Bioinformatics | Year: 2010

Background: In the literature, there are fruitful algorithmic approaches for identification functional modules in protein-protein interactions (PPI) networks. Because of accumulation of large-scale interaction data on multiple organisms and non-recording interaction data in the existing PPI database, it is still emergent to design novel computational techniques that can be able to correctly and scalably analyze interaction data sets. Indeed there are a number of large scale biological data sets providing indirect evidence for protein-protein interaction relationships.Results: The main aim of this paper is to present a prior knowledge based mining strategy to identify functional modules from PPI networks with the aid of Gene Ontology. Higher similarity value in Gene Ontology means that two gene products are more functionally related to each other, so it is better to group such gene products into one functional module. We study (i) to encode the functional pairs into the existing PPI networks; and (ii) to use these functional pairs as pairwise constraints to supervise the existing functional module identification algorithms. Topology-based modularity metric and complex annotation in MIPs will be used to evaluate the identified functional modules by these two approaches.Conclusions: The experimental results on Yeast PPI networks and GO have shown that the prior knowledge based learning methods perform better than the existing algorithms. © 2010 Ng and Jing; licensee BioMed Central Ltd.

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.

Chen W.,Beijing Jiaotong University | Rodrigues M.R.D.,University College London | Wassell I.J.,University of Cambridge
IEEE Transactions on Signal Processing | Year: 2013

In this paper, we develop a framework to design sensing matrices for compressive sensing applications that lead to good mean squared error (MSE) performance subject to sensing cost constraints. By capitalizing on the MSE of the oracle estimator, whose performance has been shown to act as a benchmark to the performance of standard sparse recovery algorithms, we use the fact that a Parseval tight frame is the closest design - in the Frobenius norm sense - to the solution of a convex relaxation of the optimization problem that relates to the minimization of the MSE of the oracleestimator with respect to the equivalent sensing matrix, subject to sensing energy constraints. Based on this result, we then propose two sensing matrix designs that exhibit two key properties: i) the designs are closed form rather than iterative; ii) the designs exhibit superior performance in relation to other designs in the literature, which is revealed by our numerical investigation in various scenarios with different sparse recovery algorithms including basis pursuit de-noise (BPDN), the Dantzig selector and orthogonal matching pursuit (OMP). © 1991-2012 IEEE.

Zhang J.,Beijing Jiaotong University | Xu W.,Zhejiang Sci-Tech University | Wang X.,Columbia University
Journal of Lightwave Technology | Year: 2012

Recently, the hybrid wireless-optical broadband network integrating optical backbone networks, passive optical networks (PON), and wireless access networks have been proposed to provide the high-bandwidth, low-cost, and ubiquitous communication connections. In this paper, we consider the design of network coding-based multicast applications in such networks with the objective of maximizing the total network utility and minimizing the deployment cost, subject to QoS constraints. The problem is formulated as a mixed integer nonlinear programming problem and the exact solution is prohibitively complex. In order to make the problem more tractable, we develop a two-step optimization procedure that iteratively selects the optical network unit and gateways for the multicast sessions. During each iteration, two subproblems are solved, i.e., a network coding design problem for the optical network, and a user assignment and bandwidth allocation problem for the wireless network. The former is solved in a distributed way based on the Lagrangian-dual decomposition; the latter is solved based on the generalized bender decomposition. Simulation results are provided to illustrate the effectiveness of the proposed solutions. © 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.

Cheng X.-Y.,Beijing Jiaotong University | Zhong C.,Tianjin University of Science and Technology
Energy and Fuels | Year: 2014

Biogas yield from anaerobic digestion of cotton stalk (CS) at feed to inoculum (F/I) ratios of 2-4 reached 175-180 mL/(g of VSadded) against 113 mL/(g of VSadded) observed at the F/I ratio of 6. CS was proven to be a promising co-substrate in the digestion of swine manure (SM), and a CS/SM ratio of 50:50 with a C/N ratio of 25 was found to be the best in terms of the biogas production rate and yield with increases up to 1.8- and 1.9-fold, respectively, as compared to the control. The highest biogas yield (449 mL/(g of VSadded)) and production rate (0.65 L/(L·day)) with comparable technical digestion time were obtained in co-digestion of SM with CS pretreated by NaOH, which was 241-255% of those achieved in the control. This study indicates that co-digestion of SM with alkali-pretreated CS is a potential option for alleviating the insufficient substrate resource problems and improving the energy output. © 2014 American Chemical Society.

Yuan X.,Beijing Jiaotong University
International Journal of Simulation: Systems, Science and Technology | Year: 2015

With the development and application of computer information system, the related problems of reliability are increasing, which directly promote the reliability research and quantitative analysis of information system. But there is still a long distance between the theory and the application of the establishment of reliability analysis model, the application situation is not satisfactory. Therefore, this paper mainly focuses on the research on the establishment of economic reliability analysis model based on computer Bayesian network. Based on a brief introduction of the related theories and technologies, the Bayesian network and its qualitative and quantitative analysis are elaborated in detail, according to Modern Bayesian network method with the characteristics of precise reasoning, intuitive understanding and good operating, the analysis results of system reliability calculation probability and system diagnosis can be obtained through the example analysis of economic information system. Experimental results show that the model can be easily used in reliability calculation and system reliability diagnosis of economic information system, and can be used in the reliability analysis of third party components and heterogeneous environment. © 2015, UK Simulation Society. All right reserved.

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.

Ke L.-L.,City University of Hong Kong | Ke L.-L.,Beijing Jiaotong University | Yang J.,RMIT University | Kitipornchai S.,City University of Hong Kong
Composite Structures | Year: 2010

This paper investigates the nonlinear free vibration of functionally graded nanocomposite beams reinforced by single-walled carbon nanotubes (SWCNTs) based on Timoshenko beam theory and von Kármán geometric nonlinearity. The material properties of functionally graded carbon nanotube-reinforced composites (FG-CNTRCs) are assumed to be graded in the thickness direction and estimated though the rule of mixture. The Ritz method is employed to derive the governing eigenvalue equation which is then solved by a direct iterative method to obtain the nonlinear vibration frequencies of FG-CNTRC beams with different end supports. A detailed parametric study is conducted to study the influences of nanotube volume fraction, vibration amplitude, slenderness ratio and end supports on the nonlinear free vibration characteristics of FG-CNTRC beams. The results for uniformly distributed carbon nanotube-reinforced composite (UD-CNTRC) beams are also provided for comparison. Numerical results are presented in both tabular and graphical forms to investigate the effects of nanotube volume fraction, vibration amplitude, slenderness ratio, end supports and CNT distribution on the nonlinear free vibration characteristics of FG-CNTRC beams. © 2009 Elsevier Ltd. All rights reserved.

Yuan Y.,Heriot - Watt University | Wang C.-X.,Heriot - Watt University | Wang C.-X.,Shandong University | Cheng X.,Peking University | And 2 more authors.
IEEE Transactions on Wireless Communications | Year: 2014

This paper proposes a novel three-dimensional (3D) theoretical regular-shaped geometry-based stochastic model (RSGBSM) and the corresponding sum-of-sinusoids (SoS) simulation model for non-isotropic multiple-input multiple-output (MIMO) vehicle-to-vehicle (V2V) Ricean fading channels. The proposed RS-GBSM, combining line-of-sight (LoS) components, a two-sphere model, and an elliptic-cylinder model, has the ability to study the impact of the vehicular traffic density (VTD) on channel statistics, and jointly considers the azimuth and elevation angles by using the von Mises Fisher distribution. Moreover, a novel parameter computation method is proposed for jointly calculating the azimuth and elevation angles in the SoS channel simulator. Based on the proposed 3D theoretical RS-GBSM and its SoS simulation model, statistical properties are derived and thoroughly investigated. The impact of the elevation angle in the 3D model on key statistical properties is investigated by comparing with those of the corresponding two-dimensional (2D) model. It is demonstrated that the 3D model is more accurate to characterize real V2V channels, in particular for pico cell scenarios. Finally, close agreement is achieved between the theoretical model, SoS simulation model, and simulation results, demonstrating the utility of the proposed models. © 2014 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.

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.

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

The large data involves a large amount of information, and the large data technology changes the thought and method for human to understand the world. The intelligent logistics is to make the logistics system has the ability such as thinking, perception, learning, reasoning and judging, and to solve some problems in logistics, using integrated, intelligent and mobility technology. The intelligent logistics contains many items basic activities such as intelligent transportation, automated storage, dynamic distribution, and acquisition, processing and treatment of intelligent information. It provides the maximum profit for the supplier, provides the best service for the consumer, and consumes the least natural resources and social resources, thereby forming the integration of management and control for intelligent logistics. The 37th conference of "Traffic and Transportation 7 + 1 Forum" sets its theme as "Large Data and Intelligent Logistics". To the application problem for large data technology in intelligent logistics field, it puts emphasis on the system, theory and method of intelligent logistics under the background of large data. It promotes the healthy development of modern logistics industry in China. Copyright © 2015 by Science Press.

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.

Gao Y.,Queens University | Ke J.H.,Queens University | Zhong K.P.,Queens University | Zhong K.P.,Beijing Jiaotong University | And 2 more authors.
Journal of Lightwave Technology | Year: 2012

For 112 Gb/s dual-polarization 16-ary quadrature amplitude modulation systems, the performance and complexity of the low-pass filter (LPF)-assisted digital back-propagation (DBP) algorithm for mitigating intrachannel fiber nonlinearity are investigated. Comparison is made with both linear equalization and the standard DBP algorithm for single-channel transmission (simulation and experiment) and for wavelength division multiplexed (WDM) transmission with channel spacings of 50 and 35 GHz (simulation). With optimized values for the algorithm parameters, the simulation results show that, compared to linear equalization, the 0.2 steps/span LPF-assisted DBP algorithm can increase the transmission distance by 84%, 40%, and 17% for a single-channel, 50 GHz channel-spaced WDM, and 35 GHz channel-spaced WDM transmission, respectively. These improvements in the transmission distance are 54%, 75%, and 77% of those achieved with the 4 steps/span standard DBP algorithm but at considerably lower complexity. Single-channel experimental results show that the 0.25 steps/span LPF-assisted DBP algorithm can increase the transmission distance by 43%, which is 68% of the improvement achieved with the 4 steps/span standard DBP algorithm. Compared to the standard DBP algorithm, the LPF-assisted DBP algorithm can allow a reduction in the number of steps/span, but with an increased computational complexity for each step. The two DBP algorithms are compared in terms of the number of real multiplications per bit, thus allowing the algorithm with lower complexity to be determined at a given level of performance. © 2012 IEEE.

Ke J.H.,Queens University | Zhong K.P.,Queens University | Zhong K.P.,Beijing Jiaotong University | Gao Y.,Queens University | And 3 more authors.
Journal of Lightwave Technology | Year: 2012

Two novel linewidth-tolerant, low-complexity feedforward carrier phase estimation algorithms are described for dual-polarization 16-ary quadrature-amplitude-modulation with coherent detection. For both algorithms, the carrier phase is estimated in two stages. The first stage employs either a simplified quadrature-phase-shift-keying (QPSK) partitioning algorithm or the blind phase search (BPS) algorithm. The second stage employs a novel QPSK constellation transformation algorithm. The performance and linewidth tolerance of both algorithms are evaluated using experimental and simulation data, and the hardware complexity is assessed. For both proposed two-stage algorithms, the linewidth symbol duration product is $1.3\times 10-4 for a 1 dB penalty in optical signal-to-noise ratio at a bit error ratio of $10-3. This performance is comparable to a single-stage BPS algorithm with a large number of test phases, but with a reduction of the hardware complexity by factors of about 2.5-11. © 2012 IEEE.

Tungsten- and titanium-doped indium oxide (IWO and ITiO) films were deposited at room temperature by radio frequency (RF) magnetron sputtering, and vacuum post-annealing was used to improve the electron mobility. With increasing deposition power, the as deposited films showed an increasingly crystalline nature. Compared with ITiO films, IWO films showed crystallinity at lower RF power. IWO films are partially crystallized at 10 W deposition power and become nearly fully crystalline at 20 W. ITiO films are fully crystalline only at 75 W. For this reason, film thickness has a greater impact on the electrical properties of IWO films than ITiO films. Vacuum post-annealing is more effective in improving electron mobility for amorphous than for (partially) crystalline IWO and ITiO films. Changes in the electrical properties of ITiO films can be better controlled as a function of annealing temperature than those of IWO films. Finally, post annealed 308 nm-thick IWO and 325 nm-thick ITiO films have approximately 80% transmittance in visible and near infrared wavelengths (up to 1100 nm), while their sheet resistances decrease to 9.3 and 10 Ω/□, and their electron mobilities are 51 cm 2V - 1 s - 1 and 50 cm 2V - 1 s - 1, respectively, making them suitable for use as Transparent Conductive Oxide layers of low bandgap solar cells. © 2011 Elsevier B.V. All rights reserved.

Xu F.,Beijing Jiaotong University
International Communications in Heat and Mass Transfer | Year: 2014

The convective instability of a vertical thermal boundary layer adjacent to the sidewall of a water-filled differentially heated cavity over a range of Rayleigh numbers (5×107-3.44×109) is investigated using direct stability analysis. The results show that the dominant frequency of the convective instability changes as perturbations travel downstream due to the presence of the horizontal boundaries, which is different from that of the vertical thermal boundary layer adjacent to an infinite or semi-infinite thermal wall. The features of the convective instability of the vertical thermal boundary layer adjacent to the sidewall are described, and the dependence of the dominant frequency on the Rayleigh number is obtained. Furthermore, the dependence of the flow rate and heat transfer through the cavity on the Rayleigh number is quantified by numerical results. © 2014 Elsevier Ltd.

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.

Tian L.-J.,Beihang University | Tian L.-J.,Fuzhou University | Huang H.-J.,Beihang University | Gao Z.-Y.,Beijing Jiaotong University
Networks and Spatial Economics | Year: 2012

This paper presents a cumulative perceived value-based dynamic user equilibrium model by applying the prospect theory to formulate the travelers' risk evaluation on arrival time. The network uncertainty caused by link exit capacity degradation is incorporated into the analysis. The model which considers departure time and route choices simultaneously is expressed by a variational inequality in a discrete time space. Numerical results show that the travelers' risk preference indeed has big influence on flow distribution. Our study constitutes a deepening of cognition in developing more realistic dynamic traffic assignment technologies. © 2011 Springer Science+Business Media, LLC.

Xue X.,Beijing Jiaotong University
Physica A: Statistical Mechanics and its Applications | Year: 2016

In this paper we are concerned with contact processes with random recovery rates and edge weights on rooted regular trees TN. Let ρ and ξ be two nonnegative random variables such that P(ϵ≤ξ<+∞,ρ≤M)=1 for some ϵ,M>0. For each vertex x on TN, ξ(x) is an independent copy of ξ while for each edge e on TN, ρ(e) is an independent copy of ρ. An infected vertex x becomes healthy at rate ξ(x) while an infected vertex y infects an healthy neighbor z at rate proportional to ρ(y,z). For this model, we prove that the critical value under the annealed measure approximately equals (NEρE1/ξ)−1 as N grows to infinity. Furthermore, we show that the critical value under the quenched measure equals that under the annealed measure when the cluster containing the root formed with edges with positive weights is infinite. © 2016

Yang T.W.,Beijing Jiaotong University | Xu W.L.,Massey University | Da Han J.,CAS Shenyang Institute of Automation
IEEE Transactions on Control Systems Technology | Year: 2010

Macro-micro architecture, which consists of macro and micro manipulators, is used here to eliminate errors at the tip of a flexible manipulator. The macro uses long arms and has such advantages as larger work volume and lower energy consumption but suffers from large deformations and vibrations. The micro is a smaller rigid manipulator and is attached on the end of the macro to isolate the system endpoint from the undesirable flexibility of the macro. Using perturbation theories, a new kinematical method is introduced, first, by redefining the micro's motion as a means of compensating for the errors at the endpoint of the macro. Then, an excellent practical control scheme is proposed to realize the endpoint control with the feedback of joint angles and vibrations. A PD controller is applied to the micro, which augmented the compensation quantities. To damp out vibrations, a nonlinear control law is proposed for the macro, taking the interacting dynamics of the micro to the macro into account. The compensation and control algorithms work very well on a macro-micro setup, and numerous experimental results prove the applicability of the proposed schemes. © 2009 IEEE.

Wang X.,Beijing Jiaotong University
2010 International Conference on E-Product E-Service and E-Entertainment, ICEEE2010 | Year: 2010

The mitigation of single event upsets (SEUs) in field programmable gate arrays (FPGAs) is an increasingly important subject as both the static random access memory (SRAM) cells and the logic circuits in FPGAs are susceptible to SEUs. Among all SEU mitigation techniques, the triple modular redundancy (TMR) has become the most common practice because of its straightforward implementation and reliable results. The methodologies to perform partitioning TMR insertion to reduce SEUs in the FPGA logic paths are presented in this paper. It is proved that the maximal probability of two simultaneous errors decreases dramatically with the number of logic partitions in the TMR designs. It is reduced from 66.67% for minimum logic partition to 4.44% for maximum logic partition for the test circuit. The results presented in this paper suggest that there is a tradeoff between the number of logic partitions and combination property of TMR designs. For ground-based systems such as nuclear power plant (NPPs), where the overhead is insignificant, especially compared to reliability requirements, the maximum partition can be the best. While in space applications where area is at a premium, the optimal logic partition should be the medium partition. ©2010 IEEE.

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.

Liu P.,Shandong University of Finance and Economics | Jin F.,Shandong University of Finance and Economics | Zhang X.,Shandong University of Finance and Economics | Su Y.,Shandong University of Finance and Economics | Wang M.,Beijing Jiaotong University
Knowledge-Based Systems | Year: 2011

With respect to risk decision making problems with interval probability in which the attribute values take the form of the uncertain linguistic variables, a multi-attribute decision making method based on prospect theory is proposed. To begin with, the uncertain linguistic variables can be transformed into the trapezoidal fuzzy number, and the prospect value function of the trapezoidal fuzzy number based on the decision-making reference point of each attribute and the weight function of interval probability can be constructed; then the prospect value of attribute for every alternative is calculated through prospect value function of the trapezoidal fuzzy number and the weight function of interval probability, and the weighted prospect value of alternative is acquired by using weighted average method according to attribute weights, and all the alternatives are sorted according to the expected values of the weighted prospect values; Finally, an illustrate example is given to show the decision-making steps, the influence on decision making for different parameters of value function and different decision-making reference point, and the feasibility of the method. © 2011 Elsevier B.V. All rights reserved.

Wang J.,Beijing Jiaotong University
Journal of Systems Science and Complexity | Year: 2012

This paper considers a discrete-time Geo/G/1 retrial queue where the retrial time has a general distribution and the server is subject to Bernoulli vacation policy. It is assumed that the server, after each service completion, begins a process of search in order to find the following customer to be served with a certain probability, or begins a single vacation process with complementary probability. This paper analyzes the Markov chain underlying the queueing system and obtain its ergodicity condition. The generating functions of the number of customers in the orbit and in the system are also obtained along with the marginal distributions of the orbit size when the server is idle, busy or on vacation. Finally, the author gives two stochastic decomposition laws, and as an application the author gives bounds for the proximity between the system size distributions of the model and the corresponding model without retrials. © 2012 Institute of Systems Science, Academy of Mathematics and Systems Science, CAS and Springer-Verlag Berlin Heidelberg.

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

It has been one of the hot issues in the field of transportation that the interaction and coordination between high- speed railway and civil aviation transportation since the opening of the highspeed railway. The 41st conference of "Traffic and Transportation 7+1 Forum"sets its theme as "Status and Development of High-speed Railway and Civil Aviation Transportation". It focuses on the competition and coordination between the high-speed railway and civil aviation transportation in the background of the integrated transportation. It thinks that in a certain range, high-speed railway and civil aviation transportation can replace each other, and they are mutual competition of transportation mode. On the other hand, the development of high-speed railway is also conducive to the accumulation of air passengers through the railway to the large hub airport. It makes travel more active which through constructing a large comprehensive transportation hub to form a coexisted and complementary market relation Copyright © 2016 by Science Press.

Zhong K.P.,Queens University | Zhong K.P.,Beijing Jiaotong University | Ke J.H.,Queens University | Gao Y.,Queens University | Cartledge J.C.,Queens University
Journal of Lightwave Technology | Year: 2013

Three novel linewidth-tolerant, low-complexity, two-stage feed-forward carrier phase estimation algorithms are introduced for dual-polarization 16-ary quadrature amplitude modulation (DP 16-QAM) with coherent detection. The first stage employs either the quadrature phase-shift keying (QPSK) partitioning algorithm, simplified QPSK partitioning algorithm, or blind phase search (BPS) algorithm. The second stage employs a novel modified QPSK partitioning algorithm. Based on experimental data, all three algorithms achieve comparable performance for DP 16-QAM back to back and transmission systems. The linewidth tolerance for the three algorithms is numerically studied. A linewidth symbol duration product of 1.3,×, 10-4 is demonstrated for a 1 dB optical signal-to-noise-ratio penalty at a bit error ratio of 10-3 for all the proposed algorithms, which is comparable to the single-stage BPS algorithm with a large number of test phases. Reductions in the hardware complexity by factors of about 1.7-5.3 are achieved in comparison to the single-stage BPS algorithm. © 2012 IEEE.

Wang M.,Beijing Jiaotong University | Wang M.,University of Ottawa | Yao J.,University of Ottawa
Journal of Lightwave Technology | Year: 2013

A continuously tunable photonic radio-frequency (RF) phase shifter based on polarization modulation and all-optical differentiation using a polarization modulator (PolM) and an optical frequency discriminator is proposed, theoretically analyzed and experimentally demonstrated. In the proposed phase shifter, two light waves at different wavelengths are injected into a PolM which is driven by an RF signal to be phase shifted. For one wavelength, the state of polarization (SOP) of the light wave is aligned with one principal axis of the PolM, thus the PolM operates jointly with an optical frequency discriminator as an optical differentiator to produce a quadrature (Q) signal. For the other wavelength, the SOP of the light wave is oriented with 45° or 135° with the principal axis of the PolM, thus the PolM operates jointly with a polarizer as an intensity modulator to produce an in-phase (I) signal. By detecting the I-Q optical signals at a photodetector (PD), a phase-shifted RF signal is generated. The value of the phase shift is determined by the amplitudes of the I-Q signals, which can be continuously tuned by controlling the powers of the light waves. An experiment is performed. A phase shifter with a full tunable range of 360° at an RF frequency tunable from 3 to 10 GHz is demonstrated. © 1983-2012 IEEE.

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

A novel substrate integrated waveguide (SIW)-fed end-fire magnetoelectric (ME) dipole antenna is proposed. The antenna consisting of an open-ended SIW and a pair of electric dipoles has a simple structure that can be integrated into substrates conveniently. Both the open-ended SIW and the electric dipoles are effectively radiated together. Excellent performance, including a bandwidth of 44%, symmetrical radiation patterns that are almost identical in two orthogonal planes, low backward radiation, low cross polarizations, stable gain of around 5 dBi, and wide beamwidth of around 110°, are also obtained. An 8 × 8 SIW Butler matrix is then designed. Modifications to the geometry of the matrix provide more spacing to locate SIW phase shifters and phase compensation structures with wide bandwidth. By employing the proposed end-fire ME-dipole antenna array and the 8 × 8 Butler matrix, an eight-beam antenna array is realized. The fabricated prototype demonstrates that wide bandwidth, stable radiation patterns with cross polarizations of less than -28 dB and gain varying from 9 to 12 dBi can be obtained. The proposed multibeam end-fire ME-dipole antenna array would be an attractive candidate for millimeter-wave wireless applications due to its good performance, ease of integration, and low fabrication cost. © 2016 IEEE.

Liu W.,University of Ottawa | Wang M.,University of Ottawa | Wang M.,Beijing Jiaotong University | Yao J.,University of Ottawa
Journal of Lightwave Technology | Year: 2013

Frequency quadrupling for tunable microwave and sub-terahertz generation using a single polarization modulator (PolM) in a Sagnac loop without using an optical filter or a wideband microwave phase shifter is proposed and experimentally demonstrated. In the proposed system, a linearly polarized continuous wave from a tunable laser source (TLS) is split into two orthogonally polarized optical waves by a polarization beam splitter (PBS) and sent to the Sagnac loop traveling along the clockwise and counter-clockwise directions. A PolM to which a reference microwave signal is applied is incorporated in the loop. The PolM is a traveling-wave modulator, due to the velocity mismatch only the clockwise light wave is effectively modulated by the reference microwave signal, and the counter-clockwise light wave is not modulated. This is the key point that ensures the cancelation of the optical carrier without the need of an optical filter. Along the clockwise direction, the joint operation of the PolM, a polarization controller (PC), and a polarizer corresponds to a Mach-Zehnder modulator (MZM) with the bias point controlled to suppress the odd-order sidebands. The optical carrier is then suppressed by the counter-clockwise light wave at the polarizer. As a result, only two ${\pm}2$nd-order sidebands are generated, which are applied to a photodetector (PD) to generate a microwave signal with a frequency that is four times that of the reference microwave signal. A theoretical analysis is developed, which is validated by an experiment. A frequency-quadrupled electrical signal with a large tunable range from 2.04 to 100 GHz is generated. The performance of the proposed system in terms of stability and phase noise is also evaluated. © 1983-2012 IEEE.

Xu F.,Beijing Jiaotong University
International Communications in Heat and Mass Transfer | Year: 2015

The transition from steady to unsteady coupled thermal boundary layers induced by a fin on the partition of a differentially heated cavity was numerically investigated. Numerical simulations were performed over the range of Rayleigh numbers from Ra=107 to 2 × 1010 (Pr=6.63). The temporal development and spatial structure of natural convection flows in the partitioned cavity with a fin are described. It has been demonstrated that the fin may induce a transition to unsteady coupled thermal boundary layers and the critical Rayleigh number for the occurrence of the transition is between 3.5 and 3.6 × 108. Furthermore, the peak frequency of the oscillations induced by the fin has been 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 unsteady flow, indicating that the fin may improve unsteady flow in the partition cavity. © 2015 Elsevier Ltd.

Wang Y.-F.,Beijing Jiaotong University | Wu H.-L.,Chinese Research Institute of Highway
Journal of Composites for Construction | Year: 2011

Most previous studies on concrete short columns confined with fiber-reinforced polymer (FRP) composites were based on small-scale testing, and size effect of the columns still has not been studied thoroughly. In this study, 99 confined concrete short columns wrapped with aramid FRP (AFRP) jackets and 36 unconfined concrete short columns with circular and square cross sections were tested under axial compressive loading. The circular specimens were divided into six groups, and the square specimens were divided into five groups, with each group containing different levels of the AFRP's confinement. In each group, the specimens were geometrically similar to one another and had three different scaling dimensions. Statistical analyses were used to evaluate the size and interaction effects between the specimen size and the AFRP's confinement, and a size-dependent model for predicting the strength of the columns was developed by modifying Baznt's size-effect law. The experimental results showed that the size of a specimen had a significant effect on the strength of AFRP-confined concrete short columns, lesser effect on the axial stress-strain curves, and slight effect on the failure modes. The modified Baznt model was in good agreement with the experimental data. © 2011 American Society of Civil Engineers.

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.

Ding S.,Beijing Jiaotong University
Applied Mechanics and Materials | Year: 2012

This paper introduces two technical innovations in the signal demonstration project of Beijing Subway Yizhuang Line: the "free wave antenna + waveguide" combined transmission and the "minimum system" simulation. It also summaries the demonstration project management concepts and innovative practice experiences. Analyzing the technology and management innovation, we expect to provide a reference for the progress of the autonomy of the other rail transport high-end and core technology. © (2012) Trans Tech Publications, Switzerland.

Faist M.A.,Imperial College London | Shoaee S.,Imperial College London | Tuladhar S.,Imperial College London | Dibb G.F.A.,Imperial College London | And 7 more authors.
Advanced Energy Materials | Year: 2013

The use of fullerenes with two or more adducts as acceptors has been recently shown to enhance the performance of bulk-heterojunction solar cells using poly(3-hexylthiophene) (P3HT) as the donor. The enhancement is caused by a substantial increase in the open-circuit voltage due to a rise in the fullerene lowest unoccupied molecular orbital (LUMO) level when going from monoadducts to multiadducts. While the increase in the open-circuit voltage is obtained with many different polymers, most polymers other than P3HT show a substantially reduced photocurrent when blended with fullerene multiadducts like bis-PCBM (bis adduct of Phenyl-C61-butyric acid methyl ester) or the indene C 60 bis-adduct ICBA. Here we investigate the reasons for this decrease in photocurrent. We find that it can be attributed partly to a loss in charge generation efficiency that may be related to the LUMO-LUMO and HOMO-HOMO (highest occupied molecular orbital) offsets at the donor-acceptor heterojunction, and partly to reduced charge carrier collection efficiencies. We show that the P3HT exhibits efficient collection due to high hole and electron mobilities with mono- and multiadduct fullerenes. In contrast the less crystalline polymer Poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5- thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl (PCDTBT) shows inefficient charge carrier collection, assigned to low hole mobility in the polymer and low electron mobility when blended with multiadduct fullerenes. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Shen D.,Intelligent Systems Technology, Inc. | Hou Z.,Beijing Jiaotong University
IEEE Transactions on Neural Networks | Year: 2011

Iterative learning control (ILC) is considered for both deterministic and stochastic systems with unknown control direction. To deal with the unknown control direction, a novel switching mechanism, based only on available system tracking error data, is first proposed. Then two ILC algorithms combined with the novel switching mechanism are designed for both deterministic and stochastic systems. It is proved that the ILC algorithms would switch to the right control direction and stick to it after a finite number of cycles. Moreover, the input sequence converges to the desired one under the deterministic case. The input sequence converges to the optimal one with probability 1 under stochastic case and the resulting tracking error tends to its minimal value. © 2006 IEEE.

Zhang X.,Beijing Jiaotong University
Journal of Circuits, Systems and Computers | Year: 2016

This paper proposes a realistic model of magnetizing branches for transient calculation of electric power circuits. The model represents the nonlinear relationship between flux linkage and exciting current of magnetizing branches with a major loop and a family of minor loop trajectories, which has the capability of simulating the multi-valued hysteresis behavior. By applying the proposed model to transient calculation, an efficient algorithm is developed for obtaining the transient responses in electric power circuits. In the algorithm, the electric power circuit is divided into the magnetizing branches and the remaining linear part. The nonlinear differential equations are set up for the magnetizing branches and solved by the semi-explicit Runge–Kutta method. The transient calculation for the remaining linear part is performed on the basis of the solution to the magnetizing branches. Then, a laboratory measurement is made with a reduced-scale experimental arrangement. The measured results are compared with the calculated ones and a reasonable agreement is shown between them. © 2016 World Scientific Publishing Company

Tan K.,Microsoft | Liu H.,University of California at San Diego | Zhang J.,Microsoft | Zhang Y.,Microsoft | And 2 more authors.
Communications of the ACM | Year: 2011

This paper presents Sora, a fully programmable software radio platform on commodity PC architectures. Sora combines the performance and fidelity of hardware software-defined radio (SDR) platforms with the programmability and flexibility of general-purpose processor (GPP) SDR platforms. Sora uses both hardware and software techniques to address the challenges of using PC architectures for high-speed SDR. The Sora hardware components consist of a radio front-end for reception and transmission, and a radio control board for highthroughput, low-latency data transfer between radio and host memories. Sora makes extensive use of features of contemporary processor architectures to accelerate wireless protocol processing and satisfy protocol timing requirements, including using dedicated CPU cores, large low-latency caches to store lookup tables, and SIMD processor extensions for highly efficient physical layer processing on GPPs. Using the Sora platform, we have developed a few demonstration wireless systems, including SoftWiFi, an 802.11a/b/g implementation that seamlessly interoperates with commercial 802.11 NICs at all modulation rates, and SoftLTE, a 3GPP LTE uplink PHY implementation that supports up to 43.8Mbps data rate. © 2011 ACM.

Yang Y.,Tianjin University | Liu Y.,Beijing Jiaotong University
Electronic Journal of Combinatorics | Year: 2010

A type of rooted map called (p, q, n)-dipole, whose numbers on surfaces have some applications in string theory, are defined and the numbers of (p, q, n)-dipoles on orientable surfaces of genus 1 and 2 are given by Visentin and Wieler (The Electronic Journal of Combinatorics 14 (2007),#R12). In this paper, we study the classification of (p, q, n)-dipoles on nonorientable surfaces and obtain the numbers of (p, q, n)-dipoles on the projective plane and Klein bottle.

Xia M.,Beijing Jiaotong University
Journal of Intelligent and Fuzzy Systems | Year: 2015

Intuitionistic multiplicative set uses the unbalanced distributed scale instead of the balanced one to describe the membership and non-membership information. It can avoid some disadvantages in calculating process. We develop a series of point operators to reduce the uncertain information in intuitionistic multiplicative set. The proposed operator can redistribute the uncertain information according to the difference preference of decision makers. © 2015-IOS Press and the authors.

Yang L.,Anhui University of Science and Technology | Xue L.-L.,Anhui University of Science and Technology | Lu Y.-C.,Beijing Jiaotong University | Huang W.-P.,McMaster University
Optics Express | Year: 2010

To facilitate the analysis of radiation mode couplings, quasi leaky mode approximations were utilized in coupled-mode analysis. The key to effectively and accurately apply this approach is how to well approximate radiation modes by the quasi leaky modes in an equivalent closed waveguide model. In this paper, the principle, applicability and accuracy of the approximations are demonstrated, and the detailed implementation is also suggested by applying a unified coupled-mode analysis to fiber gratings. First of all, based on a thorough study on the characteristics of the complex modes, for the first time, quasi leaky modes are classified into guided-mode-like inner-cladding and radiation-mode-like outer-cladding leaky modes so as to explicitly establish equivalence relationships between the discrete leaky modes and the continuous radiation modes. With this new insight, the whole analysis process especially for some of the practically tricky issues such as the criteria for developing the proper equivalent waveguide model and the subsequent mode expansion basis are better understood and easier to be dealt with for different problems where radiation modes come into play. Moreover, as essential preconditions to extend the conventional coupled mode analysis to the present unified one, the couplings between the guided core mode and a leaky mode are studied in a systematic and consistent manner. An intuitive and then a deep understanding on the roles of complex modes on mode coupling and power exchanging are thus gained for further simulations. Lastly, the transmission spectra of fiber gratings with different surrounding indices are simulated. The simulated results agree well with those obtained theoretically and experimentally in the literatures, which strongly validate the principle of quasi leaky mode approximations and its implementation on the unified coupled-mode analysis expounded in this paper. © 2010 Optical Society of America.

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.

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.

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.

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.

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.

Hou Z.-S.,Beijing Jiaotong University | Wang Z.,University of Illinois at Chicago
Information Sciences | Year: 2013

This paper is a brief survey on the existing problems and challenges inherent in model-based control (MBC) theory, and some important issues in the analysis and design of data-driven control (DDC) methods are here reviewed and addressed. The necessity of data-driven control is discussed from the aspects of the history, the present, and the future of control theories and applications. The state of the art of the existing DDC methods and applications are presented with appropriate classifications and insights. The relationship between the MBC method and the DDC method, the differences among different DDC methods, and relevant topics in data-driven optimization and modeling are also highlighted. Finally, the perspective of DDC and associated research topics are briefly explored and discussed. © 2012 Elsevier Inc. All rights reserved.

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.

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.

Fang W.,Beijing Jiaotong University
IEEE Transactions on Wireless Communications | Year: 2013

In , the authors proposed a distributed robust routing protocol RRP for mobile sensor networks based on node cooperation, and compared the energy efficiency of cooperative and non-cooperative routing through analysis and simulation. However, the model for energy consumption of sensor nodes is not correct. Therefore, we present a new energy analysis in this note. © 2002-2012 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.

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 J.,Beijing Jiaotong University | Wang J.,Duke University | Zhu Y.,Duke University | Zhang R.,Duke University | Gauthier D.J.,Duke University
Optics Express | Year: 2011

Forward stimulated Brillouin scattering (FSBS) is observed in a standard 2-km-long highly nonlinear fiber. The frequency of FSBS arising from multiple radially guided acoustic resonances is observed up to gigahertz frequencies. The tight confinement of the light and acoustic field enhances the interaction and results in a large gain coefficient of 34.7 W-1 at a frequency of 933.8 MHz. We also find that the profile on the anti-Stokes side of the pump beam have lineshapes that are asymmetric, which we show is due to the interference between FSBS and the optical Kerr effect. The measured FSBS resonance linewidths are found to increase linearly with the acoustic frequency. Based on this scaling, we conclude that dominant contribution to the linewidth is from surface damping due to the fiber jacket and structural nonuniformities along the fiber. © 2011 Optical Society of America.

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.

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.

Yin G.,University of Ottawa | Yin G.,Beijing Jiaotong University | Wang X.,University of Ottawa | Bao X.,University of Ottawa
Applied Optics | Year: 2011

A tunable fiber ring laser based on an in-line two-taper Mach-Zehnder interferometer (MZI) filter was realized, and the effect of beam waists of the tapers on performance of the laser was investigated with different beam waists of 70 μm, 49 μm, and 33 μm. Experimental results show that the tunable laser with MZI length of 1m and beam waist of 49 μm can cover 16:1nm with tuning steps of 0:07-0:5nm, a bandwidth of 10pm, and a side mode suppression ratio (SMSR) of 40-50 dB. Tuning range is not only determined by the number of the cladding modes but is also affected by the filter loss. Tuning step is determined by the differences of the effective refractive indexes between the cladding modes and the core mode. SMSR is determined by the balance between the extinction ratio of the filter and the cavity loss of the laser due to MZI filter. © 2011 Optical Society of America.

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.

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.

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.

Ledezma Estrada A.,Tohoku University | Ledezma Estrada A.,Polytechnic School of Algiers | Li Y.-Y.,Tohoku University | Li Y.-Y.,Xian University of Architecture and Technology | And 2 more authors.
Journal of Hazardous Materials | Year: 2012

The comparative degradation behavior of cefalexin (CLX) using advanced oxidation processes (AOPs) with the aim of improving CLX biodegradability was studied. Among the AOPs used, RuO 2/Ti anodic oxidation (AO), AO in the presence of electro-generated H 2O 2 (AO-H 2O 2), and the electro-Fenton (EF) process, the EF process was the most effective. In the EF process an activated carbon fiber (ACF) was used as a cathode. Different input variables, including catalyst concentration, pH, and current density were evaluated to find the optimum conditions for the EF. The most suitable operational conditions were as follows: a current density of 6.66mA/cm 2, a pH of 3, and a concentration of 1mM of Fe 2+ as the catalyst. Different CLX concentrations were analyzed as well of different reaction times to assess the degree of mineralization. The change in biodegradability was evaluated by the BOD 5/COD and the BOD 14/COD ratios. The EF did not effectively remove the COD, but removed enough to achieve suitable biodegradability for a further biological process. © 2012 Elsevier B.V..

Wang X.,Beijing Jiaotong University
ICTE 2015 - Proceedings of the 5th International Conference on Transportation Engineering | Year: 2015

The vigorous development of cloud computing and mobile internet provides a new opportunity for the collection, storage, development and utilization of traffic data. By literature investigation, considering the transformation trend of the functions of government agencies in China, this paper reviewed to effectively identify the traffic state of urban road based on the cloud due to Internet of Things (IoT), put forward employing the cloud cooperation applications to dynamic optimization urban freight activities such as consolidation and parking, finally summarized that the cloud logistics mode has promoted as a new logistics service mode. This study improves understanding of how this technology may diffuse within the supply chain. © ASCE.

Wang R.-F.,Beijing Jiaotong University
Frontiers of Physics | Year: 2015

Most studies on the magnetic Aharonov-Bohm (A-B) effect focus on the action exerted by the magnetic flux on the electron beam, but neglect the back-action exerted by the electron beam on the magnetic flux. This paper focuses on the latter, which is the electromotive force ΔU across the solenoid induced by the time-dependent magnetic field of the electron beam. Based on the back-action analysis, we observe that the magnetic A-B effect arises owing to the interaction energy between the magnetic field of the electron beam and the magnetic field of the solenoid. We also demonstrate that the interpretation attributing the magnetic A-B effect to the vector potential violates the uncertainty principle. © 2015, Higher Education Press and Springer-Verlag Berlin Heidelberg.

Bo Y.,Beijing Jiaotong University | Fowlkes C.C.,University of California at Irvine
Proceedings of the IEEE Computer Society Conference on Computer Vision and Pattern Recognition | Year: 2011

We describe a simple model for parsing pedestrians based on shape. Our model assembles candidate parts from an oversegmentation of the image and matches them to a library of exemplars. Our matching uses a hierarchical decomposition into a variable number of parts and computes scores on partial matchings in order to prune the search space of candidate segment. Simple constraints enforce consistent layout of parts. Because our model is shape-based, it generalizes well. We use exemplars from a controlled dataset of poses but achieve good test performance on unconstrained images of pedestrians in street scenes. We demonstrate results of parsing detections returned from a standard scanning-window pedestrian detector and use the resulting parse to perform viewpoint prediction and detection re-scoring. © 2011 IEEE.

Wang R.-F.,Beijing Jiaotong University
Indian Journal of Pure and Applied Physics | Year: 2015

The penetration depth is an important parameter of superconductors, but its absolute value is difficult to measure without a special device. By introducing the modern microfabrication technology, this paper proposes a new experimental scheme to measure the susceptibility of a superconducting film. By this new method, the absolute value of the penetration depth can be determined with satisfactory accuracy. The accuracy was estimated from the measurement error of the experimental scheme. This method should be useful for investigating the pairing mechanisms of superconductors by measuring the temperature dependence of the penetration depth.

Yan Q.,Beijing Jiaotong University | Wu J.Y.,Hong Kong Polytechnic University | Liu R.,CAS Institute of Process Engineering
Biotechnology Letters | Year: 2011

Modeling of tanshinone synthesis and phase distribution under the combined effect of elicitation and adsorption was studied. The simulated results showed that enhancement of tanshinone production was mainly due to the effect of the elicitor and that resin addition resulted in adsorbance of the tanshinones from the root and alteration of tanshinone distribution. Furthermore, parameter sensitivities analysis showed that the rate of transport of tanshinones from the root to the medium was the important factor that influenced tanshinone accumulation in the resin. In conclusion, the modeling of tanshinone synthesis and phase distribution identified the process mechanism under the combined effect of elicitation and adsorption and this modeling can be used in similar plant tissue culture systems. © 2010 Springer Science+Business Media B.V.

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

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.

Xiao J.,Taishan University | Deng Z.,Beijing Jiaotong University
Synthetic Metals | Year: 2012

A novel white organic electroluminescent device was fabricated by inserting a thin lithium fluoride (LiF) layer in the emitting layer (tris-(8- hydroxyquinoline) aluminum (Alq3)). The electroluminescence device with the configuration indium tin oxide (ITO)/N,N′-diphenyl-N,N′- bis(l-napthyl)-1,1′-biphenyl-4,4′-diamine (NPB; 45 nm)/tris-(8-hydroxyquinoline) aluminum (Alq3; x nm)/LiF (0.3 nm)/Alq3 ((45 - x) nm)/Al (150 nm) showed expanded electroluminescence (EL) spectra. The spectra contain tricolor, so this should be a simple method to realize white light emitting. We also elucidated the mechanism of expanded EL spectra formation and investigated the properties of these devices. © 2012 Elsevier B.V. All rights reserved.

Wu L.-N.,Tsinghua University | Jin G.-R.,Beijing Jiaotong University | You L.,Tsinghua University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2015

In the absence of decay, the conditional dynamics for an open system is often describable by a non-Hermitian Hamiltonian. This study investigates spin squeezing (SS) in a non-Hermitian one-axis twisting (OAT) model. Somewhat surprisingly, SS close to the limit of Hermitian two-axis counter twisting (TACT) Hamiltonian is achievable for some parameters, which significantly improves upon the optimal value realizable by the Hermitian OAT model. The drawback is like with all conditional schemes, it takes on average longer time to evolve into a steady state, and the probability of no decay or success decreases as the number of atoms (spins) increases. The result above for the steady-state SS in a non-Hermitian OAT Hamiltonian is thus limited to small systems. For other parameter regimes, however, desirable SS arrives dynamically before a steady state is achieved, with a greatly shortened evolution time and enhanced probability of success, while still remains significantly improved over the limit of Hermitian OAT. © 2015 American Physical Society. ©2015 American Physical Society.

Zhang G.-W.,Beijing Jiaotong University
Jiaotong Yunshu Xitong Gongcheng Yu Xinxi/ Journal of Transportation Systems Engineering and Information Technology | Year: 2010

The 18th Conference of "Traffic and Transportation Forum 7+1" sets its theme as "energy conservation and emission reduction of integrated transportation system". With the rapid development of economy, the contradiction between increasing transport capacity and limited energy resource appears to be more serious than ever. The energy consumption and emission is directly identified in the process of service production. While, its amount have strong relationship with the overall planning, layout, equipment, and structure of the integrated transportation system, instead of merely determined by the production process. The differences of the domestic and international statistical caliber are analyzed, and the energy consumption level in China is estimated with the international caliber. The results indicate that the transportation consumption level is underestimated in Chinese transport industry, especially the level of petroleum. The consumption factors of different transport mode are presented then. Moreover, the coming challenge, future direction, and relevant count measures are discussed for energy conservation and emission reduction of integrated transportation system. ©2010 by Science Press.

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.

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.

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.

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.

Wei X.,Beijing Jiaotong University | Verhaegen M.,Technical University of Delft
European Journal of Control | Year: 2010

This paper addresses the robust fault detection observer and fault estimation filter design issues for linear time invariant (LTI) systems with parameter uncertainties in a polytope and the systems are subject to unknown inputs as well. The observer and filter design are investigated in the H ∞/H - index framework in the finite frequency interval by using the generalized KYP lemma. The threshold design and the worst undetectable fault size estimation are discussed. A numerical example is given to illustrate the effectiveness of the derived algorithms. © 2010 EUCA.

Yang J.,RMIT University | Ke L.L.,City University of Hong Kong | Ke L.L.,Beijing Jiaotong University | Kitipornchai S.,City University of Hong Kong
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2010

Nonlinear free vibration of single-walled carbon nanotubes (SWCNTs) is studied in this paper based on von Kármán geometric nonlinearity and Eringen's nonlocal elasticity theory. The SWCNTs are modeled as nanobeams where the effects of transverse shear deformation and rotary inertia are considered within the framework of Timoshenko beam theory. The governing equations and boundary conditions are derived by using the Hamilton's principle. The differential quadrature (DQ) method is employed to discretize the nonlinear governing equations which are then solved by a direct iterative method to obtain the nonlinear vibration frequencies of SWCNTs with different boundary conditions. Zigzag (5, 0), (8, 0), (9, 0) and (11, 0) SWCNTs are considered in numerical calculations and the elastic modulus is obtained through molecular mechanics (MM) simulation. A detailed parametric study is conducted to study the influences of nonlocal parameter, length and radius of the SWCNTs and end supports on the nonlinear free vibration characteristics of SWCNTs. © 2010 Elsevier B.V. All rights reserved.

Zhao W.,Beijing Jiaotong University
International Conference on Signal Processing Proceedings, ICSP | Year: 2015

A method for implementing Gaussian low-pass filter by using switched-current technique has been presented in this paper. The stable rational transfer function for Gaussian-shaped low-pass filter is approximated by the multiplication of the follower-integrator functions based on central limit theorem. An SI filter structure constructed from the inverse follow-the-leader feedback configuration has been proposed to synthesize the obtained transfer function, in which the switched-current bilinear integrator is employed as the building cell. Explicit design formulas are also derived. The 8th-order Gaussian low-pass filter is selected as the example to elaborate the design details. Simulation result shows that the proposed design method has high approximation precision and low magnitude sensitivity. © 2014 IEEE.

Lu W.,University of Sydney | Lu W.,Beijing Jiaotong University | Argyros A.,University of Sydney
Journal of Lightwave Technology | Year: 2014

A flexible tube-lattice fiber is introduced into a terahertz time-domain spectroscopy system as a probe in an endoscope geometry and used to guide radiation to and from a sample. This allows hyperspectral imaging to be performed by scanning the endface of the probe, rather than the sample or components of the terahertz system itself. Hyperspectral imaging is demonstrated through the identification of various substances in the image and visualized through the implementation of a false-color system. The resolution of such an imaging system is discussed and quantified, finding excellent agreement with the experimental measurements. © 1983-2012 IEEE.

Chen F.-M.,Beijing Jiaotong University
Journal of High Energy Physics | Year: 2014

We construct a general nonabelian (1, 0) tensor multiplet theory in six dimensions. The gauge field of this (1, 0) theory is non-dynamical, and the theory contains a continuous parameter b. When b = 1/2, the (1, 0) theory possesses an extra discrete symmetry enhancing the supersymmetry to (2, 0), and the theory turns out to be identical to the (2, 0) theory of Lambert and Papageorgakis (LP). Upon dimension reduction, we obtain a general N = 1 supersymmetric Yang-Mills theory in five dimensions. The applications of the theories to D4 and M5-branes are briefly discussed.

Krikke H.,Open Box | Hofenk D.,Wageningen University | Wang Y.,Beijing Jiaotong University
Resources, Conservation and Recycling | Year: 2013

Forward supply chain actors are increasingly involved in the full life cycle of their products and the packaging used. Where in the past these were disposed of via (public) waste management systems or sold in cascade markets, now returns management becomes key to focal companies. Moreover, recent literature emphasizes that returns can be a value creator rather than a cost of business as it can save the environment, provide critical resources and customer value. But relevant, up-to-date data on returns and return practices is scarce, whereas such data is essential to show the potential value of returns and make a business case for returns management to practitioners. Based on a global survey among manufacturers/wholesalers/retailers and third party service providers, this paper presents comprehensive descriptive statistics on and analysis of current return practices. We develop and test propositions on the drivers, volumes and value of different returns along the life cycle; show the inefficiencies in current return practices leading to value destruction instead of the advocated value creation; and compare return practices in different regions and industries. We also provide recommendations for converting value destruction into value creation. Although progress is slow, there are hopeful signals that the potential of returns managements will be unlocked in the near future. © 2013 Elsevier B.V.

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.

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.

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.

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.

Duan K.,Beijing Jiaotong University | Li D.,Beijing Information Science and Technology University
Yi Qi Yi Biao Xue Bao/Chinese Journal of Scientific Instrument | Year: 2013

To reduce the impact of noises on fiber optic gyroscope north seeking and improve the north seeking accuracy, a processing scheme was proposed, which uses a nonlinear filtering method, i.e. particle filtering methoed in FOG four position north seeking. A FOG north seeking system model based on the four-position scheme was investigated and the nonlinear state space model was established. The particle filters based on systematic resampling and based on MCMC moving algorithm were applied to the nonlinear filtering of the FOG north-seeking system, respectively. A closed loop FOG with the bias stability of 0.05°/h was used to perform experiment operation. The experiment results show that both the particle filters can improve the north seeking accuracy and north seeking speed effectively. The systematic resampling based particle filter has a divergence trend, which is caused by the loss of particle diversity under small number of particles; while the MCMC based particle filter has good convergence performance. The repeat experiment results prove that better north-seeking accuracy can be obtained using the MCMC based particle filter.

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.

Chen W.,Beijing Jiaotong University | Wassell I.J.,University of Cambridge
IEEE Transactions on Vehicular Technology | Year: 2016

In this paper, we propose an active node selection framework for compressive sleeping wireless sensor networks (WSNs) to improve signal acquisition performance, network lifetime, and the use of spectrum resources. While conventional compressive sleeping WSNs only exploit the spatial correlation of sensor nodes, the proposed approach further exploits the temporal correlation by selecting active nodes using the support of the data reconstructed in the previous time instant. The node selection problem is framed as the design of a specialized sensing matrix, where the sensing matrix consists of selected rows of an identity matrix. By capitalizing on a genie-aided reconstruction procedure, we formulate the active node selection problem into an optimization problem, which is then approximated by a constrained convex relaxation plus a rounding scheme. Simulation results show that our proposed active node selection approach leads to an improved reconstruction performance, network lifetime, and spectrum usage, in comparison to various node selection schemes for compressive sleeping WSNs. © 1967-2012 IEEE.

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.

Liu P.,Beijing Jiaotong University | Au S.-K.,City University of Hong Kong
Probabilistic Engineering Mechanics | Year: 2013

A Bayesian probabilistic approach is applied for parameter identification of a hysteretic model using laboratory test data in this paper. A hysteretic model for multi-grid composite walls is proposed to model the behavior of multi-grid composite wall specimens under lateral cyclic loading. Effects of stiffness degradation, strength degradation and pinching are considered. The test data consists of observed hysteretic curves of precast composite wall specimen, composite wall specimen reinforced by light steel, retrofitted composite wall specimen and cast-in-place composite wall specimen. Using the Bayesian approach, the identification results are presented in terms of the most probable value and posterior covariance matrix of model parameters. The implied hysteretic and backbone curves with their uncertainties identified based on the test data are compared with their observed counterparts. © 2013 Elsevier Ltd.

Zhang G.-W.,Beijing Jiaotong University
Jiaotong Yunshu Xitong Gongcheng Yu Xinxi/Journal of Transportation Systems Engineering and Information Technology | Year: 2013

In view of the increasing need of developing urban transport systems, the 30th conference of "Traffic and Transportation Forum 7+1" addresses the issue of "IOT-Based Intelligent Transportation Systems and the Integrated Transport Information Service". It discusses the definition of the IOT-based intelligent transportation systems. The practical and new technologies of internet of things (IOT) are introduced into the intelligent transportation systems (ITS), and the diversified and advanced technologies of intelligent transportation and artificial intelligent (AI) are also applied in the field of traffic management, information service and vehicle control. The harmony of human, vehicle, road and environment can thus be achieved and urban integrated transport system can be formed with high efficiency, punctuality, comfort and low carbon emission. As per the integrated transport information service, it is suggested to be with the deep and personalized contents and the user-friendly and intelligent patterns.

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.

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.

Yue J.,Beijing Jiaotong University
International Journal of Hydrogen Energy | Year: 2016

Experiment of low heat value gas blended with hydrogen in a modified single-cylinder CNG engine is studied. The components of low heat value gas contain natural gas and N2, the natural gas contents from 60% to 80% by volume, N2 content is from 20% to 40% by volume. The hydrogen blending ratio is from 10% to 30% by volume. Results show that with the increase of N2 proportion, the engine power, CO and NOx emissions are decreased, but HC emissions is increased. When hydrogen blending ratio is increased, CO emission is increased while HC emission is decreased. When properly increases hydrogen blending ratio, the maximum cylinder pressure and engine torque are increased. However, large hydrogen blending ratio will decrease engine power. NOx emission is related to N2 proportion of low heat value gas. © 2016 Hydrogen Energy Publications, LLC.

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.

Chi R.-H.,Qingdao University of Science and Technology | Hou Z.-S.,Beijing Jiaotong University
Zidonghua Xuebao/Acta Automatica Sinica | Year: 2010

In this paper, a novel model-free periodic adaptive ramp metering scheme is presented for a freeway traffic system, which can be formulated as a general MIMO nonlinear system. The proposed method is model-free in nature, and the control inputs and the pseudo Jacobi parameters are updated periodically in a pointwise manner over the entire period, by directly using the I/O data obtained in the preceding periods. The geometrical tracking performance is shown with rigorous analysis. The simulation results illustrate the validity of the proposed method. Copyright © 2010 Acta Automatica Sinica. All rights reserved.

Xie Z.,CAS Institute of Atmospheric Physics | Di Z.,Beijing Jiaotong University | Luo Z.,North China Electrical Power University | Ma Q.,CAS Institute of Atmospheric Physics
Journal of Hydrometeorology | Year: 2012

In this study, a quasi-three-dimensional, variably saturated groundwater flow model was developed by approximately dividing the three-dimensional soil water and groundwater flow into an unsaturated vertical soil water flow and a horizontal groundwater flow to simulate the interactions among soil water, groundwater, and vegetation. The developed model consists of a one-dimensional unsaturated soil water flow model with the water table as the moving boundary using an adaptive grid structure for a vertical soil column formed based on discrete grid cells in a horizontal domain, a two-dimensional groundwater flow model for the horizontal domain, and an interface model connecting the two components for the horizontal grid cells in the domain. Synthetic experiments by the model were conducted to test the sensitivities of the model parameters of river elevation, ground surface hydraulic conductivity, and surface flux, and the results from the experiments showed the robustness of the proposed model under different conditions. Comparison of the simulation by the model and that by a full three-dimensional scheme showed its feasibility and efficiency. A case of stream water conveyance in the lower reaches of the Tarim River was then applied to validate the developed model for simulation of the water table elevations at the Yingsu section. Finally, a numerical experiment by the model for the Tarim River basin was conducted to discuss the groundwater latent flow for large-scale highrelief topography with stream water conveyance. The results show that the model can simulate the water table reasonably well. © 2012 American Meteorological Society.

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.

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.

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.

Tang T.-Q.,Beihang University | Caccetta L.,Curtin University Australia | Wu Y.-H.,Curtin University Australia | Huang H.-J.,Beihang University | Yang X.-B.,Beijing Jiaotong University
Journal of Advanced Transportation | Year: 2014

In this paper, we develop a macro traffic flow model with consideration of varying road conditions. Our analytical and numerical results illustrate that good road condition can enhance the speed and flow of uniform traffic flow whereas bad road condition will reduce the speed and flow. The numerical results also show that good road condition can smooth shock wave and improve the stability of traffic flow whereas bad road condition will lead to steeper shock wave and reduce the stability of traffic flow. Our results are also qualitatively accordant with empirical results, which implies that the proposed model can qualitatively describe the effects of road conditions on traffic flow. These results can guide traffic engineers to improve the road quality in traffic engineering. © 2012 John Wiley & Sons, Ltd.

Zhang C.,Beijing Jiaotong University
2015 International Conference on Logistics, Informatics and Service Science, LISS 2015 | Year: 2015

During investigation process of organization informatization management, prone to produce shortage problem of the wireless spectrum resource, the traditional organization informatization management method based on service information causes congestion and waste of resources, due to the low utilization of information, cannot effectively achieve organizational information management, an organization informatization management method based on information resources sharing mechanism is proposed, two conditions need to meet shared agreement between organizations. Two quasi matrix for tagging channel characteristics in information resource sharing mechanism are analyzed. With the information resource sharing mechanism to complete the two scene of organization informatization management. When a plurality of non-authorized users compete at the same time, priority of all the node is found, under the condition of no effect on the authorized user normal communication, the non-authorized users of largest priority accessed in the organization. In order to reduce the interference authorized users have, need to reject non authorized user, and solve priority of rejection of any node, higher priority is easier to be refused. Simulation results show that, the proposed method has high effectiveness and practicability in the organization informatization management. © 2015 IEEE.

Hu S.,Beijing Jiaotong University
2015 International Conference on Logistics, Informatics and Service Science, LISS 2015 | Year: 2015

The Internet of Things is very important to monitor aquaculture environment. Pre-warning on aquaculture safety is an important measure to ensure quality safety of aquatic products. At present, most pre-warning methods on aquaculture safety are restrained by single factor, e.g., water quality, bacteria, viruses and other single factor. And meanwhile, those pre-warning methods are confronted with the difficulties such as real-time constraint, heterogeneity problem and so on. To deal with the above problems, services in the Internet of Things are to be introduced into the project. The project is also useful to related domains. © 2015 IEEE.

Wang W.,Beijing Jiaotong University
2015 International Conference on Logistics, Informatics and Service Science, LISS 2015 | Year: 2015

This paper considers the way how supermarket, logistics companies and supplier interact with each other to optimize their benefits during the benefits distribution in cold chain distribution process. The quality of cold chain distribution depends on distribution methods, quality level and the accurate controls during distribution process; this requires qualified specialized logistics companies to fulfill. Due to the strict requirement and high cost of cold chain distribution, its participants are willing to form a cooperative entirety to make more benefit. The benefits distribution in turn affects the overall benefit in the cold chain food logistics. Therefore, we need research benefits distribution in the cold chain food logistics under different conditions. The problem is formulated as a Stackelberg game with two sub-games. One is the alliance of logistics companies and supermarket and the other is the alliance of logistics companies and supplier. We analysis in-depth benefits distribution of different parts as well as the entire supply chain under different circumstances by discussing the distribution of benefits among supermarket, supplier and logistics companies. A numerical example is conducted to test the proposed model and algorithm, and gain managerial implications. © 2015 IEEE.

Liu P.,Beijing Jiaotong University
2015 International Conference on Logistics, Informatics and Service Science, LISS 2015 | Year: 2015

Now the waterway passenger transport of Shenzhen is the national development of the best waterway passenger transport market. With the better understanding of the future of Shenzhen waterway passenger demand trend, we can grasp the development direction of Shenzhen waterway passenger transport more clearly. Based on the gray theory forecasting method, the prediction of the Shenzhen waterway passenger volume is more accurate. It is also proved that the result of prediction in using this model is very credible. The prediction has good feasibility and operability. It will also provide better reference for the development of both waterway passenger transport and other related industries. And then it will provide a scientific basis for Shenzhen waterway passenger to define related development policy. © 2015 IEEE.

Han X.,Beijing Jiaotong University
2015 International Conference on Logistics, Informatics and Service Science, LISS 2015 | Year: 2015

This paper, utilizing correlation analysis and path analysis methods, researches the impact path of negative Internet word related to the mouth on brand equity and quality through cognitive trust concept by regarding universal consumers as study principal body. This research aims to further promote the IWOM research system in China. The empirical conclusions unveil some relationship: (1) the cognitive trust of negative IWOM has negative correlation with cognitive qualified and positively correlated with the brand association at the 0.05 level of significance, however, no prominent correlation was figured out between cognitive trust and brand loyalty; (2) the cognitive trust of negative IWOM influences the brand association directly, meanwhile indirectly, the risk perception influences brand association indirectly, which can conclude and abstract the effect mechanism of the cognitive trust of negative IWOM on brand equity and quality. © 2015 IEEE.

Huan L.,Beijing Jiaotong University
2015 International Conference on Logistics, Informatics and Service Science, LISS 2015 | Year: 2015

Board governance is at the core of the corporate governance, to establish a standard and reasonable structure is the important content of perfecting corporate governance mechanism. Board governance in China is in its infancy, the listed company's board of directors' governance situation is worrying, problems like the unreasonable structure, lack of effective incentive, insufficient supervision and constraint still exist. In this context, this paper selected the China's A-share listed companies as samples, based on the result of the empirical research of 2011-2013 data, we found board size, the chairman and general manager conditions, the number of board meetings were negatively correlated with corporate performance; the number of committees and the proportion of board shareholding were positively correlated with corporate performance. © 2015 IEEE.

Zhang X.,Beijing Jiaotong University
International Journal of Electrical Engineering Education | Year: 2010

An efficient algorithm is proposed for calculating lightning transients in cage-like multiconductor systems. Capacitance and impedance parameters of the conducting branches are evaluated by the mean potential method and Neumann's formula, respectively. The equivalent network is formed for the multiconductor systems by a series of coupled p-type circuits. The lightning transient responses in the multiconductor systems are then obtained using Fourier transform. When the algorithm was tested using an experimental set-up, good agreement was found between the calculated and measured results.

Tan Q.,Beijing Jiaotong University
Acta Geodaetica et Cartographica Sinica | Year: 2010

Building extraction in urban environment requires high spatial resolution remotely sensed data. However, traditional pixel-based classifiers based on spectral features are ineffective for high-resolution multi-spectral images due to large within-class spectral variations and between-class spectral confusions. In this study, a rule-based object-oriented classification method for building extraction was developed from an IKONOS urban scene. The method included the following steps, 1 fusion of 1 m panchromatic and 4 m multispectral bands to produce a pan-sharpened 1 m multispectral image; 2 segmentation of the 1 m dataset; 3 supervised object-based classification into broad spectral classes; 4 spectral, spatial, textural and contextual parameters developed from sample building objects were implemented in a fuzzy logic rule base to separate building rooftops from other impervious surface classes. The rule-based method identifies building rooftops with 93% accuracy in the experiment.

Mao B.-H.,Beijing Jiaotong University
Jiaotong Yunshu Xitong Gongcheng Yu Xinxi/Journal of Transportation Systems Engineering and Information Technology | Year: 2014

Planning is of great significance to the facility development in developing areas. Based on the concept of integrated transport, the paper explores some issues of the ideal and the strategic design involved in integrated transport planning. Upon the analysis on the principles in transport operations, it points out the problems, mistakes and key relationships among factors in practical transport planning of China. With author's experiences in regional planning and researches, it also advances the techniques and methods that may be applied in avoiding problems in integrated transport planning. The author concludes that a good strategic design relates to the understanding of the social and economic development goals in the planning region. It is important to emphasize the constraints of strategic planning targets on the context of short-term and middleterm planning schemes. The level of service, instead of network scale, is a more important indicator to evaluate a regional transport planning, and the operational planning is also a key to transport planning schemes even during preliminary planning stages.

Sun H.,MOE Key Laboratory for Urban Transportation Complex Systems Theory | Wu J.,Beijing Jiaotong University | Wang W.,MOE Key Laboratory for Urban Transportation Complex Systems Theory | Gao Z.,MOE Key Laboratory for Urban Transportation Complex Systems Theory
Information Sciences | Year: 2014

As the demands on urban transportation networks grow rapidly, problems of network design have attracted a great deal of interest because of the need to effectively handle urban transport planning using information technology. A bi-level continuous network design model is proposed in this paper to address the optimal road capacity expansion of existing links. Based on the fact that every origin-destination demand is random and affected by traffic travel information, the network is subject to relatively minimal day-to-day events of stochastic link capacity variations. Therefore, the primary objective is to maximize the reliability of the total travel time, while the lower level model, utilizing the behaviors of stochastic route choice, is aimed at reducing drivers' travel time uncertainty through traffic information provided by advanced traveler information systems. The Particle Swarm Optimization algorithm is used to solve the suggested model, and a numerical example using the Sioux Falls network is provided. The computation results show that travel time reliability is improved by system optimization using traffic information. © 2014 Published by Elsevier Inc.

Shen C.,Beijing Jiaotong University | Shen C.,Xidian University | Li W.-C.,National Tsing Hua University | Chang T.-H.,National Taiwan University of Science and Technology
IEEE Transactions on Signal Processing | Year: 2014

This paper considers the transmitter design for wireless information and energy transfer (WIET) in a multiple-input single-output (MISO) interference channel (IFC). The design problem is to maximize the system throughput subject to individual energy harvesting constraints and power constraints. It is observed that the ideal scheme, where the receivers simultaneously perform information detection (ID) and energy harvesting (EH) from the received signal, may not always achieve the best tradeoff between information transfer and energy harvesting, but simple practical schemes based on time splitting may perform better. We therefore propose two practical time splitting schemes, namely the time-division mode switching (TDMS) and time-division multiple access (TDMA), in addition to the existing power splitting (PS) scheme. In the two-user scenario, we show that beamforming is optimal to all the schemes. Moreover, the design problems associated with the TDMS and TDMA schemes admit semi-analytical solutions. In the general K -user scenario, a successive convex approximation method is proposed to handle the WIET problems associated with the ideal scheme, the PS scheme and the TDMA scheme, which are known NP-hard in general. Simulation results show that none of the schemes under consideration can always dominate another in terms of the sum rate performance. Specifically, it is observed that stronger cross-link channel power improves the achievable sum rate of time splitting schemes but degrades the sum rate performance of the ideal scheme and PS scheme. As a result, time splitting schemes can outperform the ideal scheme and the PS scheme in interference dominated scenarios. © 1991-2012 IEEE.

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.

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.

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.

Yujiao W.,Beijing Jiaotong University
2015 International Conference on Logistics, Informatics and Service Science, LISS 2015 | Year: 2015

Opinion shopping has attracted extensive researches in accounting. There have been the changes of auditors to achieve the improvement of audit opinion or opinion shopping in practice. Regulators are also highly concerned about audit opinion shopping. However, the results of empirical researches have not yielded a consistent conclusion. The conventional wisdom in the literature focused on the single public company to study audit switching and opinion shopping. In emerging markets, the business group is the main form of organizations. This paper regards business group as a whole entity to analyze the impact of audit switching on audit opinion. We find that auditors will lose more than one client within a business group if they issue modified opinion to a listed company in the business group. Accounting firm that takes over group business for the first time is easier to cater to the group firm to achieve opinion shopping. And the audit opinion can be improved if the business group switches the auditor. These findings imply that the business group successfully engages in opinion shopping. © 2015 IEEE.

Ren J.,Beijing Jiaotong University
2015 International Conference on Logistics, Informatics and Service Science, LISS 2015 | Year: 2015

In the early days of bar coding, an Efficient Foodservice Response (EFR) study identified $847 million in savings. Today, technologies, techniques, and standards exist to help organizations throughout the food supply chain gain complete traceability for safety, compliance, and business process improvement. RF identification systems use RF tag to transmit information between RF tags and reading devices through sensors, radio wave or microwave for non-contact bidirectional communications, in order to identify objects automatically. This write paper examines how the food industry can take advantage of RFID technology to improve safety, reduce operating expenses, meet compliance requirements, and improve efficiency. © 2015 IEEE.

Liu Q.,Beijing Jiaotong University
2015 International Conference on Logistics, Informatics and Service Science, LISS 2015 | Year: 2015

This paper gives a brief analysis of the current China's Internet financial ecosystem, analyzes the Internet financial important ten types of products on the market, briefly analyzes the relationship between them, and its importance in the future development. © 2015 IEEE.

Cheng H.,Beijing Jiaotong University
2015 International Conference on Logistics, Informatics and Service Science, LISS 2015 | Year: 2015

This paper tries to shed light on whether emotional intelligence (EI) predicts leadership effectiveness (LE) in the Chinese context. To do this, we apply Bar-On's EI dimensions and LE dimensions in Leadership Effectiveness Analysis as the instrument in this study. The finding, contrast to the hypothesis, is that EI can not predict LE in the Chinese context. As one of the pioneer research in such domain, this study has important literature contribution in cross-cultural leadership effectiveness, and helps companies in talent assessment. © 2015 IEEE.

Wu P.,China Tourism Academy | Shi P.,China Tourism Academy | Shi P.,Beijing Jiaotong University
Journal of Geographical Sciences | Year: 2011

In 2009, nearly 900 million international tourist arrivals were counted worldwide. A global activity of this scale can be assumed to have a substantial impact on the environment. In this contribution, five major aspects such as the change of LUCC and the use of energy and its associated impacts had been recognized. Recently, the impact of tourism on environment and climate attracts the attention of international organizations and societies in pace with rapid development of tourism industry. Energy consumption and CO2 emissions in tourism sector are becoming a hot spot of international tourism research in recent five years. The use of energy for tourism can be divided according to transport-related purposes (travel to, from and at the destination) and destination-related purposes excluding transports (accommodation, food, tourist activities, etc.). In addition, the transports, accommodation and foods are related to many other industries which are dependent on energy. Thus, the estimations of energy consumption and CO2 emissions in tourism sector have become a worldwide concern. Tourism in China grows rapidly, and the number of domestic tourists was 1902 million in 2009. Energy use and its impact on the environment increase synchronously with China's tourism. It is necessary to examine the relationship between energy use and CO2 emissions. In this article, a preliminary attempt was applied to estimate the energy consumption and CO2 emissions from China's tourism sector in 2008. Bottom-up approach, literature research and mathematical statistics technology were also adopted. According to the calculations, Chinese tourism-related may have consumed approximately 428.30 PJ of energy in 2008, or about 0.51% of the total energy consumptions in China. It is estimated that CO2 emissions from tourism sector amounted to 51.34 Mt, accounting for 0.86% of the total in China. The results show that tourism is a low-carbon industry and also a pillar industry coping with global climate change, energy-saving and CO2 emission reduction. Based on this, the authors suggested that tourism should become an important field in low-carbon economic development. © 2011 Science China Press and Springer-Verlag Berlin Heidelberg.

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