Beijing, China

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

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Beijing Jiaotong University | Date: 2016-07-28

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

Zhao H.,Beijing Jiaotong University | Hailin J.,Beijing Jiaotong University
Proceedings of 2016 IEEE Advanced Information Management, Communicates, Electronic and Automation Control Conference, IMCEC 2016 | Year: 2016

Different services are transmitted separately by independent communication networks in existing urban rail transit system, and most of them are adopting WLAN (Wireless Local Area Network) technologies. To transmit the service in single radio access network, An integrated TD-LTE based train ground radio communication system for the metro system (LTE-M) is designed and built on the ring rail line in Beijing to perform the field test of the performance. The transmission media between the train and ground are the dual leaky coaxial cables (LCX) to implement the MIMO transmission. Extensive test cases are designed and implemented in the field test to get the transmission performance of the different applications. The results show that the LTE-M can reliably transmit the integrated services in real time. © 2016 IEEE.

Yu H.,Beijing Jiaotong University | Wang J.,Beijing Jiaotong University
Proceedings of 2016 IEEE Advanced Information Management, Communicates, Electronic and Automation Control Conference, IMCEC 2016 | Year: 2016

This paper presents a method to compute the Horizontal Protection Level (HPL) using the vertical projection, which will exploit advances in computational power to meet the requirement of Time to Alert (TTA) and simplify the process. And a traditional method to calculated HPL and vertical projection method is discussed. It is validated with results that the new method is achieved with the requirements of safety threshold. © 2016 IEEE.

Ye H.,Beijing Jiaotong University | Zheng W.,Beijing Jiaotong University
Proceedings of 2016 IEEE Advanced Information Management, Communicates, Electronic and Automation Control Conference, IMCEC 2016 | Year: 2016

This paper presents an improved conditional probability tables (CPT) building method for Bayesian networks (BN), which is suitable for human reliability analysis (HRA). This method is based on an existing CPT assignment method in the field of HRA and the improvement is realized by using the fuzzy inference theory. Mamdani method is applied to replace parameter R assignment process in the original method. The experts only need to estimate the weight value of all the parent nodes of a child node in the BN, and then the CPT can be obtained through fuzzy reasoning. Compared with the original method, the workload of experts can be significantly reduced. The improved method also has better stability because it can greatly reduce experts' bias. In this paper, the improved CPT assignment method is applied to automatically assign the CPT of the BN in the HRA model of the train driver of high-speed railway. After quantitative analysis, the human reliability of the train driver can be calculated accurately. © 2016 IEEE.

Yan L.,Beijing Jiaotong University | He B.,Beijing Jiaotong University
Bioresource Technology | Year: 2017

A clean power generation system was built based on the steam co-gasification of biomass and coal in a quadruple fluidized bed gasifier. The chemical looping with oxygen uncoupling technology was used to supply oxygen for the calciner. The solid oxide fuel cell and the steam turbine were combined to generate power. The calcium looping and mineral carbonation were used for CO2 capture and sequestration. The aim of this work was to study the characteristics of this system. The effects of key operation parameters on the system total energy efficiency (ŋten), total exergy efficiency (ŋtex) and carbon sequestration rate (Rcs) were detected. The energy and exergy balance calculations were implemented and the corresponding Sankey and Grassmann diagrams were drawn. It was found that the maximum energy and exergy losses occurred in the steam turbine. The system ŋten and ŋtex could be ∼50% and ∼47%, and Rcs could be over unit. © 2017 Elsevier Ltd

Zhan Q.,Beijing Jiaotong University | Zheng W.,Beijing Jiaotong University | Zhao B.,Beijing Jiaotong University
Safety Science | Year: 2017

Accidents continue to be the major concern in the railway industry, and human factors have been proved to be the prime causes to railway accidents. In this paper, the Human Factors Analysis and Classification System-Railway Accidents (HFACS-RAs) framework is proposed to identify and classify human and organizational factors involved in railway accidents. To establish an applicable HFACS-RAs framework, large amount of incident and accident data are collected and the existing safety flaws are identified by safety experts, manufactures and railway managers who have attended the HFACS workshop. To find out the leading accident casual factors, the Analytical Network Process (ANP) method combined with Fuzzy Decision Making Trail and Evaluation (DEMATEL) method is adopted to analyze the influence relationships of human and organization factors classified by HFACS-RAs framework after its reliability is demonstrated. The expert judgement is required in most phases in this study for the uncertainty and complexity of the human and organizational factors and the proposed method to identify the main casual factors is elaborated in the case study. The relevant preventative measures can be raised to avoid the recurrence of similar accidents after the investigation. Finally some considerations on further work are discussed. © 2016 Elsevier Ltd

Cheng Y.,Beijing Jiaotong University
Neural Processing Letters | Year: 2017

The fully connected cascade (FCC) networks are a recently proposed class of neural networks where each layer has only one neuron and each neuron is connected with all the neurons in its previous layers. In this paper we derive and describe in detail an efficient backpropagation algorithm (named BPFCC) for computing the gradient for FCC networks. Actually, the backpropagation in BPFCC is an elaborately designed process for computing the derivative amplification coefficients, which are essential for gradient computation. The average time complexity for computing an entry of the gradient is O(1). BPFCC needs to be called by training algorithms to do any useful work, and we wrote a program FCCNET for that purpose. Currently, FCCNET uses the Levenberg–Marquardt algorithm to train FCC networks, and the loss function for classification is designed based on a nonlinear extension of logistic regression. For two-class classification, we derive a Gauss–Newton-like approximation for the Hessian of the loss function, and when the number of classes is more than two, numerical approximation of the Hessian is used. Experimental results confirm the efficiency of BPFCC, and the validity of the companion techniques. © 2017 Springer Science+Business Media New York

Wang C.,Beijing Jiaotong University | Si X.,Beijing Jiaotong University | Xin H.,Beijing Jiaotong University
ECCE 2016 - IEEE Energy Conversion Congress and Exposition, Proceedings | Year: 2016

The neutral-point voltage balancing problem is a key issue for three-level three-leg neutral-point clamped (NPC) inverter used in three-phase four-wire system. In this paper, a detailed discussion on this issue and a mathematical model for the neutral-point voltage fluctuation are given. Then a novel neutral-point voltage control strategy based on the disassembly of zero level is proposed. To balance the neutral-point voltage, a variable which can depict the disassembly margin of each phase, named neutral point control margin (NPCM) is defined. The duty ratio of zero level in the phase selected on the basis of NPCM is decomposed to positive and negative level equivalently in order to balance the neutral-point voltage while the average value of the output voltage is preserved unchanged. Furthermore, the relationship between the proposed control strategy and the existing method based on 3-D space vector modulation (3DSVM) in a-b-c coordinates is analyzed. It is showed that the proposed control strategy is superior in simplifying the algorithm and improving the control performance compared with the 3DSVM method. The proposed control strategy is verified by simulation and experiment. © 2016 IEEE.

Zheng L.,Central South University | He Z.,Beijing Jiaotong University | He T.,Hunan Normal University
Transportmetrica A: Transport Science | Year: 2017

This study proposes an anisotropic continuum model derived from a simplified Helly's model. Its admissibility of a wide cluster solution is then analyzed by the nonlinear weak solution theory. After that, it is calibrated by a monkey algorithm with dynamic adaptation (DAMA) under two cases, and it is concluded that (1) DAMA makes the performance index and model parameters converge to their optimal values in limited iterations; (2) this calibrated model well reproduces the traffic congestions originating from a rubberneck effect within US101 site, besides of those propagated from the downstream boundary; (3) this proposed model with relations of Del Castillo and Benitez, or Greedshields gets better calibration and validation results; (4) the performance index is more sensitive to density-related parameters than to speed-related parameters. In summary, this anisotropic model calibrated by DAMA can well reproduce real traffic waves, and DAMA is a promising algorithm for the higher-order model calibration. © 2017 Hong Kong Society for Transportation Studies Limited

Yang J.,Beijing Jiaotong University | Peng G.,Beijing Jiaotong University
Fuhe Cailiao Xuebao/Acta Materiae Compositae Sinica | Year: 2016

Plain concrete, steel fiber and hybrid fiber reinforced ultra-high-performance concretes, with 140-160 MPa compressive strength at 56 d, were prepared using common raw materials. The residual compressive strength and tensile splitting strength of these concretes after exposure to high temperature were determined experimentally. Explosive spalling test was carried out on the specimens with 100% moisture content and two heating rates were employed to study the effect of heating rate on spalling behavior of ultra-high-performance concrete. The results indicate that residual compressive strength of each type of concrete increases firstly, and then decreases with increasing temperature. After exposure to 800℃, residual compressive strength is approximately 30% of that at normal temperature. Residual tensile splitting strength of both steel fiber reinforced concrete and hybrid fiber reinforced concrete also increase firstly and then decrease, which are 15.1% and 35.4% of the original strength, respectively. Residual tensile splitting strength of plain concrete decreases with increasing temperature, which is 20.3% of its original strength after exposure to 800℃. At 7.5℃/min heating rate, explosive spalling of each type of concrete specimens with 100% moisture content is quite severe. Nevertheless, steel fiber can alleviate explosive spalling but does not avoid the occurrence of explosive spalling, and the effect of hybrid fiber on improving spalling resistance behavior of ultra-high-performance concrete is not significantly superior to that of steel fiber. At 2.5℃/min heating rate, incorporating hybrid fiber inhibits the occurrence of explosive spalling in some specimens. © 2016, BUAA Culture Media Group Ltd. All right reserved.

Lin J.,Beijing Jiaotong University | Miao Z.,Beijing Jiaotong University
International Conference on Signal Processing Proceedings, ICSP | Year: 2017

Image enhancement is widely used and approved in the field of business, education and academia. As one classic model of enhancement, Retinex theory based model can obtain high-quality results in most cases. However, it is difficult for Retinex theory based model to deal with the problem of color distortion and halo artifacts. Aiming at the problem above, we proposed one multi-scale MSRCP algorithm based on guided image filtering. Firstly, we extract the data of image intensity and then estimate the illumination component of the scene base on the guided filter. Next, the combination of different box filter and simplest color balance algorithm contribute to achieve multi-scale MSRCP algorithm. Experimental results indicate that our model can eliminate noise, conserve color fidelity and recognize target effectively compared to other traditional methods. More importantly, experimental results using a large database show the superiority and robustness of the proposed method. © 2016 IEEE.

Liu Z.,Beijing Jiaotong University
International Journal of Simulation: Systems, Science and Technology | Year: 2016

Based on the interlanguage corpus, this paper determines 78 groups of cross-class confusable words by the learners with different backgrounds of native language, distinguishes the common word confusion and specific word confusion of the learners with English, Japanese, Korean, Indonesia and Mongol background. It reveals the main influence factors of cross-class confusion by learners with different backgrounds on the basis of analyzing its part of speech, structural relationship and semantic relation. These includoe: i) the cross-class confusion of common words by the learners with multiple backgrounds of native language being mainly due to the interference of same morphemes and the influence of semantic correlation, ii) while the cross-class confusion of specific words by the learners with different backgrounds of native language is mainly due to the wrong inference to the meaning of native language and the interference by cognate of native language. © 2017, UK Simulation Society. All rights reserved.

Liang W.,Princeton University | Liu J.,Princeton University | Liu J.,Beijing Jiaotong University | Law C.K.,Princeton University
Combustion and Flame | Year: 2017

The pressure–temperature explosion limits of H2/CO/O2 mixtures were analyzed computationally and theoretically. It is shown that, with the addition of even a minute quantity of H2, the mixture explosion limits evolve from being monotonic to the non-monotonic Z-shaped response characteristic of H2/O2 mixtures. It is further shown that the explosion limit at various conditions can be reproduced well with a reduced mechanism of 12 elementary steps and 10 species. Eigenvalue analysis of this mechanism leads to an analytic solution for the explosion limits, yielding explicit expressions for the degenerate high- and low-pressure explosion peninsulas as well as the individual first, second and third limits. The separate and coupled roles of H2 and CO oxidation are identified, leading to enhanced insight of this foundational component in the mechanisms of hydrocarbon oxidation, as well as useful information in the utilization of syngas. © 2017 The Combustion Institute

Dian L.,Beijing Jiaotong University | Sun D.,Beijing Jiaotong University
International Conference on Signal Processing Proceedings, ICSP | Year: 2017

Palmprint recognition has become the novel and effective technology in biological recognition fields. The contactless palmprint recognition is the mainstream way with its unique advantages. However, hand pose variations, rotations, translations, complicated backgrounds are the common problems in contactless palmprint recognition. To solve these problems, this paper proposes a palmprint recognition approach based the convolutional neural network (CNN), which consists of three main parts, namely, image preprocessing, CNN feature extraction and matching. First palmprint images are preprocessed using the improved fuzzy enhancement algorithm, then using the AlexNet with eight layers network structure for palmprint feature extraction. Finally match the feature with the hausdorff distance. The results of the experiments on three public available databases in different circumstances indicate that the proposed method achieves the best equal error rate (EER) 0.044% with respect to some typical methods of the state of the art. © 2016 IEEE.

Yang X.,Beijing Jiaotong University | Sun D.,Beijing Jiaotong University
International Conference on Signal Processing Proceedings, ICSP | Year: 2017

Canonical Correlation Analysis (CCA) is a standard tool in statistical analysis that measures the linear relationship between two data sets. In this paper, a multi-biometric approach which combines palm print feature and palm vein feature based on Canonical Correlation Analysis is proposed. First, using a series of pre-processing and extracted the ROI (Region of interest) which has enhanced of the palmprint and palm vein images. Then, using local binary pattern (LBP) to extract the palm print and palm vein feature. Next, these two features are fused by CCA to form a combined feature which is applied to denote the identity of a person. This method makes it possible to fuse these features mentioned above together and decrease the dimension of the fusion feature. The results of experiments conducted on a database of 100 hands show that the CCA-based feature level fusion method has good performance. © 2016 IEEE.

Wang P.,Beijing Jiaotong University | Sun D.,Beijing Jiaotong University
International Conference on Signal Processing Proceedings, ICSP | Year: 2017

Palm vein recognition is a promising biometric technology, it uses vascular pattern as personal identification data. In this paper, we propose a new algorithm of palm vein recognition and use local binary pattern (LBP) matching strategy to conduct experiments. First, we discuss two methods to obtain ROI of palm vein. Then the maximal principal curvature (MPC) algorithm and k-means method are utilized to extract the features of palm vein. Finally, template matching and LBP are used to recognize the feature. A series of experiments on CASIA multispectral palm image database were conducted. The lowest equal error rate (EER) is 0.01965. And relative side length could extract more useful information than fixed side length. © 2016 IEEE.

Ma Y.,Beijing Jiaotong University | Wang D.,Beijing Jiaotong University
International Conference on Signal Processing Proceedings, ICSP | Year: 2017

This paper presents a fast and generic hardware architecture for channel matrix singular value decomposition (SVD) in massive multiple-input multiple-output (MIMO) system. A fixed-pointed pipelined hardware architecture which implemented Hestenes-Jacobi method was developed to reduce the computing time in order to adapt real time processing requirements. Our proposed design was implemented on a Xilinx Kinect-7 series FPGA, which achieved an 8.5x to 15.3x improvement in speed when compared to software implementation by using MATALB and a 2.1x to 6.3x speed-up when compared to using general-purpose GPU programming scheme in processing 8×8 to 128×128 matrices. © 2016 IEEE.

Jia J.,Beijing Jiaotong University | Ruan Q.,Beijing Key Laboratory of Advanced Information Science and Network Technology
International Conference on Signal Processing Proceedings, ICSP | Year: 2017

Person re-identification aims to match people across non-overlapping camera views. One of the challenges in re-identification is cross view matching, where the gallery and query data belong to different views. This problem is difficult because the person's appearance varies greatly due to significant viewpoint and poses changes. In this paper, we perform Kernel Canonical Correlation Analysis (KCCA) for each feature type to project data from different views into a coherent subspace in which the correlations from different views are maximized with this specific feature representation. A similarity score between query and gallery images is derived from each subspace. Then the scores of different features are fused with query adaptive weights to reach a final decision. This scheme is different from current KCCA approaches which only learn one single subspace for all the features and ignore the diversity of multiple features. The effectiveness of the method is evaluated on two publicly available datasets (VIPeR and PRID), yielding state-of-the-art performance with respect to recent techniques. © 2016 IEEE.

Zhang X.,Beijing Jiaotong University | Wang D.,Beijing Jiaotong University
International Conference on Signal Processing Proceedings, ICSP | Year: 2017

In this paper we present an efficient motion adaptive de-interlacing algorithm. The motion detection method and the intra-field interpolation are two main factors that affect the efficiency of motion adaptive de-interlacing. To improve the accuracy of motion detection, five consecutive interlaced fields are used and we also introduce a Gaussian filter to eliminate the affection of noise. The adaptive threshold adjusting is also helpful for the determination about which region is moving. For the moving area, we also introduce a texture detector to distinguish texture area and smooth area. Our algorithm adopts conventional edge-based line averaging (ELA) interpolation in the texture area and modified ELA interpolation is adopted in the smooth area. As a result, our algorithm outperforms other conventional non-motion compensated methods both objectively and subjectively. © 2016 IEEE.

Wu T.,Beijing Jiaotong University | Miao Z.,Beijing Jiaotong University
International Conference on Signal Processing Proceedings, ICSP | Year: 2017

Image matching is a classic technique in computer vision. However, the traditional local invariant features image matching algorithm has two problems, narrow scale range and long time consuming. Aiming at these problems, we proposed a fast image matching algorithm with the aid of improved local invariant features based on Locality-Sensitive Hashing. Firstly, by building simple Gaussian pyramid and achieving FAST keypoint detection, keypoints are extracted from the reference image and the candidate matching image. Then Fast Retina Keypoint feature descriptor is calculated and weighted. Furthermore, the high-dimensional data is mapped to a low dimensional space and hash indexes are built through the local sensitive hashing algorithm in aiming of finding the approximate nearest neighbor. The experimental results in different datasets indicate that the improved algorithm achieves real-time processing in image matching, and has better robustness and shorter processing time than most classical methods. © 2016 IEEE.

An J.,Beijing Jiaotong University | Wang D.,Beijing Jiaotong University
International Conference on Signal Processing Proceedings, ICSP | Year: 2017

Singular value decomposition (SVD) an important part of numerical calculation, widely used in many areas such as biological medicine, meteorology and quantum mechanics. Improving the speed and accuracy of SVD algorithm becomes an important issue, so we study efficient parallel SVD algorithm on AMD GPU using OpenCL language. In recent years, there are many approaches for SVD hardware computation have been proposed, however, which are limited by speed and we propose an One-sided Jacobi parallel algorithm on AMD Graphics Processing Unit by using OpenCL. In the front part of this paper, SVD algorithm and One-sided Jacobi algorithm are introduced and by using the Ring Jacobi Ordering we achieve our parallelism computation. The next we give SVD workflow and implement 8×8, 16×16, 32×32, 64×64,128×128 and 256×256 matrices on GPU. By comparing with MATLAB and other paper, our speedups are respective approximately 3.25× and 1.24×. © 2016 IEEE.

Ma H.,Beijing Jiaotong University | Zhang L.,Beijing Jiaotong University
International Conference on Signal Processing Proceedings, ICSP | Year: 2017

A hybrid construction for LDPC codes based on (14, 8) extended Hamming code and (7, 7, 3, 3, 1) BIBD is proposed. The two short codes are used as components in the parity-check matrix of LDPC codes due to elegant decoding performance and structure properties. The new construction algorithm results in LDPC codes with high code rate, and graceful performance using sum-product algorithm (SPA). Experimental results show that hybrid codes constructed with progressive edge-growth (PEG) algorithm and (14, 8) extended Hamming code or (7, 7, 3, 3, 1) BIBD perform well. Code with PEG algorithm and (7, 7, 3, 3, 1) BIBD is 2 dB away from Shannon limit in AWGN channel. © 2016 IEEE.

An S.,Beijing Jiaotong University | Ruan Q.,Beijing Jiaotong University
International Conference on Signal Processing Proceedings, ICSP | Year: 2017

Facial expression which carries rich information of body behavior is the leading carrier of human affective and the symbol of intelligence. The main purpose of this paper is to recognize 3D human facial expression. The research in this paper includes the expression feature extraction algorithm and fusion with different kinds of feature. To contain more local texture feature information, we proposed a new feature of 3D facial expression named Local Threshold Binary Pattern (LTBP) which based on Local Binary Pattern (LBP). We calculate the difference of gray value standard between neighboring pixels and the center pixel as a threshold to binary instead of the traditional LBP operation which only comparison of size between neighboring pixels and the center pixel. After we get the LTBP feature, we fuse the LTBP and HOG (Histogram of Oriented Gradient) features to get multi-feature fusion for 3D facial expression recognition. Our algorithm of 3D facial expression recognition comprises three steps: (1) extracting two sets of feature vectors and establishing the correlation criterion function between the two sets of feature vectors; (2) solving the two sets canonical projective vectors and extracting their canonical correlation features by the framework of canonical correlation analysis algorithm; (3) doing feature fusion for classification by using proposed strategy. We have performed comprehensive experiments on the BU-3DFE database which is presently the largest available 3D face database. We have achieved verification rates of more than 90% for the 3D facial expression recognition. © 2016 IEEE.

Wang Z.,Beijing Jiaotong University | Zhao B.,Beijing Jiaotong University
Soil Dynamics and Earthquake Engineering | Year: 2017

We proposed a set of high-precision combination algorithms to detect and pick seismic phases for the earthquake early warning (EEW). First by the polarisation analysis of the three-component seismograms, we developed two filters to separate P and S waves for each record through a sliding time window. Then based on the short term average/long term average characteristic function on the polarised traces, an amplification coefficient, in terms of δ, was introduced to be multiplied by the original ratio to sensitively reflect the changes of signals’ amplitude and frequency, where a better detection of the phase arrival was achieved. Next according to the preliminary detections, we used the Akaike information criteria function combined with the higher order statistics to refine the signal and lock on the arrival time with a higher degree of accuracy. We tested our techniques to the main-shock and aftershocks of the Ms 8.0 Wenchuan earthquake, where hundreds of three-component acceleration records over magnitudes of Ms 5.0 were treated. In comparison to the analyst picks, the results of the proposed detection algorithms were shown to perform well and can be applied for the early warning of impending earthquakes occurred with diverse focal mechanisms, complicated propagation process and site effects. © 2017 Elsevier Ltd

Li W.,Beijing Jiaotong University | Huang H.,Beijing Jiaotong University | Xu X.,China Aerospace Science and Technology Corporation
International Journal of Heat and Mass Transfer | Year: 2017

The surface ablation of charring composites is critical for estimating the performance of the thermal protection system of a hypersonic vehicle during reentry. A coupled thermal/fluid/chemical/ablation method is proposed to solve the surface ablation of charring composites with the pyrolysis. Comparing to the previous method, it considers that the chemical reactions between the pyrolysis gases and the oxidative gases in the boundary layer have further influences on the oxidation of surface char in the Park's model. The new mathematical models are discretized by using the center and up-wind formats, and solved by the FORTRAN and MATLAB codes written. The numerical results indicate that the coupled method shows a validation in solving the surface ablation by comparing to the experimental data, and it can more accurately determine the surface recession rate of charring materials. This study will be helpful for the design of the thermal protection systems in hypersonic reentry vehicles. © 2017 Elsevier Ltd

Li R.,Beijing Jiaotong University | Yao Y.,Beijing Jiaotong University
Jixie Gongcheng Xuebao/Journal of Mechanical Engineering | Year: 2016

To explore new types of mobile mechanisms and their movement modes, a mobile serial-parallel mechanism with scalable platforms is proposed. The mechanism is comprised of two hybrid 3-RPR parallel mechanisms connected in series. Three mobile platforms of the serial-parallel mechanism are scalable. By combining the movements of platforms and limbs, the mechanism can achieve inchworm locomotion. The proposed mechanism possesses advantages of both series mechanisms and parallel mechanisms. The screw theory is used to calculate the degree-of-freedom (DOF) of the mechanism and the vector method is used to analyze the kinematics of the mechanism. The detailed gaits of inchworm locomotion are introduced by applying the mechanism to climbing the pipeline. The detailed mechanism structure is designed by Solidworks. Dynamic simulation of climbing pipeline is carried out by Adams to obtain the displacement curves of three platforms and length curves of limbs. A prototype is fabricated to verify the DOF characteristic and the inchworm locomotion gaits. © 2016 Journal of Mechanical Engineering.

Zhang Y.,Beijing Jiaotong University | Wang J.,Beijing Jiaotong University | Hu F.,Beijing Jiaotong University | Wang Y.,Beijing Jiaotong University
Renewable and Sustainable Energy Reviews | Year: 2017

Buildings consume large amounts of energy and resources and have a significant impact on environment. In 2010 buildings accounted for 32% of total global final energy use and 19% of energy-related GHG emissions. This energy use and related emissions may double or potentially even triple by mid-century. China is the world's largest energy consumer and CO2 emitter. With the process of urbanization, China has been entering into a period of great prosperity for construction, about 1.6–2.0 billion m2 buildings are constructed each year, which accounts for about 40% of the world's total new buildings. It is predicted that China's building energy use and related emissions will continue to increase over the next 15 years. Therefore, promoting green building development has become an urgent issue in China. However, green building is a highly complicated system engineering, its promotion needs evaluation standards as technical support. Many countries had issued a series of green building evaluation standards since 1990. Currently, there are some representative green building assessment schemes. Code for Sustainable Homes (CSH) has been fully implemented as the national authoritative standard of the UK since 2010. Leadership in Energy and Environmental Design (LEED) developed by the USA, was revised and updated regularly with the latest version issued in 2013. China enacted its national evaluation standard for green building in 2006, and revised the standard in 2014. Based on introducing the latest evaluation standards for green buildings in China, Britain and United States, the paper compared these standards from 5 aspects including energy-saving, water-saving, material-saving, site selection and the outdoor and indoor environmental quality. The comparison mainly focuses on evaluation methods and evaluation indicators in the three standard systems. Besides, the characteristics of each standard system were summarized and some suggestions for improving China's evaluation standard for green building were proposed. © 2016 Elsevier Ltd

Huang J.,Beijing Forestry University | Liu W.,Beijing Forestry University | Shi Z.,Beijing Jiaotong University
Construction and Building Materials | Year: 2017

A layered periodic structure is proposed to construct a periodic wave barrier, which is defined by extended typical cells consisting of two different components. The periodic structure with reasonable design has attenuation zones (AZs) which can block wave propagation. The surface-wave dispersion curves and material/geometric parameters of layered periodic structures were investigated using finite element method. A typical three-dimensional simulation model was applied to verify the efficiency of the proposed periodic wave barrier in terms of ground vibration isolation. The results showed that simulated frequency zones of vibration reduction are consistent with the theoretical surface-wave AZs, and that periodic wave barriers can greatly reduce train-induced vibrations. © 2017 Elsevier Ltd

Huang C.,Beijing Jiaotong University | Lv Y.,Beijing Jiaotong University
Revista de la Facultad de Ingenieria | Year: 2017

Traditional SON uses fixed step in parameter adjustment, which causes too long deployment stage. In this paper, we improve the parameter adjustment and propose a fast-starting SON parameter adjustment method, which is similar to TCP Fast Open. In this method, the parameter adjustment step is adjusted automatically. The simulation result shows that the new algorithm considerably improves the overall performance of SON during the deployment.

Zhang D.,Beijing Jiaotong University | Tai Q.,Beijing Jiaotong University | Fang Q.,Beijing Jiaotong University
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2017

The prominent issues in tunnel design and safety control, especially the design of tunnel in complex surrounding rock are highlighted based on the analysis of existing classification methods of rock. The existing methods of rock classification are unsuitable for the complex rock conditions and strict requirements of environmental control. Moreover, they provide little guidance for tunneling in complex conditions. In this paper, the concept of safety of surrounding rock and support system of tunnel is proposed based on the surrounding rock control. The safety of tunnelling in complex surrounding rock with limited self-stability is studied. The safety evaluation model of surrounding rock is proposed. The importance of ground pre-reinforcement in weak ground tunneling is illustrated and the analysis method considering the effects of ground pre-reinforcement is proposed. The relationship between the scale of surrounding rock and its response is established based on the analysis of the scale effect and the structure effect(time effect) of surrounding rock. Meanwhile, the factors that affect the tunnelling stability are analyzed in the mesoscopic level. The safety evaluation system of surrounding rock under complex geological conditions is established based on the analysis of the relationship between surrounding rock and tunnel support. The deformation ahead of tunnel face, the failure zone ahead of tunnel face and the effectiveness of ground reinforcement are taken as the key parameters to classify the tunnel safety in complex conditions. An evaluation system of tunnel safety composed of nine indices is therefore put forward. A project is also given to introduce the use of the proposed classification method of tunnel safety. © 2017, Science Press. All right reserved.

Zhang Y.,Beijing Jiaotong University | Li Q.,Beijing Jiaotong University
Beijing Jiaotong Daxue Xuebao/Journal of Beijing Jiaotong University | Year: 2017

In order to estimate the special conditions of EMU (electric multiple units) bolster damage, stress data of some critical points during the train passing through typical operating conditions, such as small-radius curved tracks and turnouts are adopted, and the damage is calculated accordingly. The results are then validated and the fatigue life ranges of critical points are estimated by the bootstrap method. Finally, the influence of typical operating conditions on critical points of bolsters is revealed by comparative analysis. © 2017, Editorial Department of Journal of Beijing Jiaotong University. All right reserved.

Li H.-L.,Nanjing Southeast University | Xia H.,Beijing Jiaotong University
Gongcheng Lixue/Engineering Mechanics | Year: 2017

Based on the random vibration analysis of a coupled train-bridge system, an approach for fatigue reliability assessment of railway steel bridges is presented. A coupled train-bridge system model is established. Train speed and track irregularities are selected as the basic random variables to perform the random vibration analysis and to identify probabilistic models of the equivalent fatigue stress range and its cyclic number of bridge components. On this basis, a fatigue limit state function is constructed to conduct fatigue reliability analysis by using the S-N curve approach. As an illustrative example, the fatigue reliability assessment is performed for a through steel truss bridge on railroad. The effects of train speed and track irregularities on the fatigue reliability of components are discussed. The results show that the presented approach can be utilized to effectively assess the fatigue reliability of railway steel bridges. Because of the randomness in train speed and track irregularities, both the train-induced equivalent fatigue stress range and its number of cycles of bridge components are indeterminate, which should be considered as random variables and can be represented by a lognormal distribution. Train speed and track irregularities can significantly affect the fatigue reliability of bridge members. The reliability indexes of fatigue-critical members increase with the enhancement in track smoothness. © 2017, Engineering Mechanics Press. All right reserved.

Li L.,Beijing Jiaotong University | Tan Z.,Beijing Jiaotong University
Tiedao Xuebao/Journal of the China Railway Society | Year: 2017

Railway tunnels are subject to various actions with disparity in probability and distribution. In the past, the designers of railway tunnel combined the effects of actions with total effect being multiplied by an adjustment factor to reflect the standard value of the internal force of the tunnel structure, when they considered the impacts of different actions on the railway tunnel structure. This design idea was conservative and can hardly reflect the occurrence probability of different actions and their impacts on the tunnel structure. In this paper, corresponding relationship between the combination coefficients and the variable actions was established to form corresponding expression for combination of actions. Corresponding coefficients for combination of actions were obtained by experience analogy and calibration. The combined actions were applied on the tunnel structure using load-structure model to calculate the design value of the structural internal force. The proposed method could reflect the proportion of the effects of different actions in the internal force of the tunnel structure and by this method, the limit state would be effectively found under the most unfavorable combination of actions, which will help increase the safety, economy and applicability of the tunnel structure. © 2017, Editorial Office of Journal of the China Railway Society. All right reserved.

Li X.,Beijing Jiaotong University | Liu Z.,Beijing Jiaotong University
Tiedao Xuebao/Journal of the China Railway Society | Year: 2017

As angular deflection during balise installation affects the reception of tele-powering signals and the transmission of up-link signals, it is necessary to study the influence of balise angular deflection on the transmission performance. In this paper, the transmission process of Interface A of the balise was analyzed. The up-link transmitting model and the tele-powering receiving model were established to target cases when the balise tilted, pitched and yawed. After the determination of the conformity assessment methods of tele-powering field and up-link field, the conformity of balise angular deflection was evaluated using these models. Based on the establishment of the transmission process for Interface A of the balise as well as the calculation of the effective range of balise, the location accuracy of the balise was evaluated. The results indicated that the conformity requirements of Interface A of standard size balise were met when the tilt angle, pitch angle and yaw angle were within the range of (-2°28', +2°28'), (-4°40', +4°40') and (-7°25', +7°25') respectively. The larger the tilt angle or pitch angle, the smaller the effective range of balise. The larger the yaw angle, the greater the effective range of balise. © 2017, Editorial Office of Journal of the China Railway Society. All right reserved.

Li G.,Beijing Jiaotong University | Zhou H.,Beijing Jiaotong University
Tiedao Xuebao/Journal of the China Railway Society | Year: 2017

Based on the Delay Tolerant Network (DTN) architecture, a novel transmission schema of streaming media in integrated space-air-ground network was purposed to improve the performance of Bundle Streaming Service Protocol (BSSP) through stream data shaping and protocol conversion. The results of performance experiments showed that the proposed schema can significantly improve the performance of original BSSP under large time delay and high BER (bit error rate). Further, the results of application test showed that the proposed schema can support long-term streaming media service with variable topology. © 2017, Editorial Office of Journal of the China Railway Society. All right reserved.

Han G.,China Railway Siyuan Survey and Design Group Co. | Wang X.,Beijing Jiaotong University | Wang B.,Beijing Jiaotong University
Modern Tunnelling Technology | Year: 2017

Using the concept of protection by shield shell and flexibility of NATM for complex geology, large-section excavation is possible under the protection of a pre-built arch using the mechanical pre-cutting method, which has obvious advantages in low-strength sand and soil strata approaching construction. Regarding the problem of difficult spraying and pouring of concrete in the slot, such special requirements as concrete strength and other properties are discussed based on an investigation and calculation analysis. It is concluded that the compressive strength of concrete in the slot after 8 hours should reach 12 MPa for a double-track loess tunnel with a large section; the traditional concrete spraying equipment needs to be improved, and the mixing ratio of concrete should be optimized and an indoor experiment for concrete in the slot should be compared with the coring test at the site. © 2017, Editorial Office of "Modern Tunnelling Technology". All right reserved.

Luo J.,Beijing Jiaotong University | Lei G.,Beijing Urban Engineering Design and Research Institute Co. | Hua F.,Beijing Urban Engineering Design and Research Institute Co.
Modern Tunnelling Technology | Year: 2017

Proper evaluation and correct selection of the waterproofing and drainage types for metro tunnels is an effective way to reduce water leakage during tunnel operation. Regarding selection of waterproofing and drainage patterns, normally a single evaluation factor of water inflow is used for evaluation and analasis instead of comprehensive evaluation system. Based on previous studies of waterproofng and drainage of metro tunnels, an AHP-based judgement system for types of waterproofing and drainage is put forward, a mathematical evaluation model of the analytic hierarchy process is established, weights of the hierachy index affecting influential factors of waterproofing and drainage in metro tunnels are determined, and quantification of the types of waterproofing and drainage is achieved with established criteria and standards. Practical cases show that the fuzzy synthetic evaluation method is consistant with the actual situation. Further study and verification are required for this application using a concrete project. © 2017, Editorial Office of "Modern Tunnelling Technology". All right reserved.

Li J.,Beijing Jiaotong University | Bai C.,Capital Normal University
Journal of Computational and Theoretical Nanoscience | Year: 2017

We propose a new aperiodic pixel layout based on the Ammann-Beenker tiling. It is uniformly three-colorable and uses only two simple pixel shapes, making it advantageous over other irregular layouts for color imaging. The existing Penrose pixel layout, which is another aperiodic pixel layout in rhombus Penrose tiling, also has the same properties. However, the Penrose pixel layout uses 36-degree and 72-degree rhombus pixel shapes, while the Ammann-Beenker pixel layout uses square and 45-degree rhombus pixel shapes. Hence the manufacture of Ammann-Beenker pixels is much more feasible than that of Penrose. We evaluate the performance of Ammann-Beenker pixel layout with two problems: super-resolution and demosaicking. Experimental results show that Ammann-Beenker pixel layout outperforms square one and is highly competitive with Penrose one. © 2017 American Scientific Publishers.

Peng B.,Beijing Jiaotong University | Zhang N.,Beijing Jiaotong University
Journal of Railway Engineering Society | Year: 2017

Research purposes: Exploitation of underground large space structures became hotspot in the development process of urbanization in recent years, some seismic codes went into effect in these years, but the level of seismic theory and application still have room for improvement compared with ground structures, it's not adaptable with the fast development of underground construction. Based on time history analysis method, this paper simulates and analyzes the subway station which has a overpass bridge on top, result data of 2 conditions which describe the different position of subway station and overpass bridge is analyzed and concluded, hoping it is helpful to the recognition and method perfection of seismic design of underground structures. Research conclusions: (1) Displacement difference between top plate and bottom plate of the station under all conditions can meet the requirement of the limit of elastic inter-story displacement angle in the relevant codes. (2) Under the condition that deformation and bearing capacity of structure meet the requirements of code, the bridge-station separated plan saves more expenditure and labor cost. (3) Results of time history analysis of underground constructions should be compared with the corresponding results of other seismic analysis methods and be corrected, the analysis of seismic performance of underground structure should be analyzed qualitatively and taken as reference of structure design. (4) The research results have reference value for the seismic analysis and structural design of underground engineering. © 2017, Editorial Department of Journal of Railway Engineering Society. All right reserved.

Wang Y.,Beijing Jiaotong University | Yang W.,Beijing Jiaotong University | Liu T.,Beijing Jiaotong University
IET Generation, Transmission and Distribution | Year: 2017

Demand side management can bring a lot of benefits to smart grid, including reducing peak load demand, reshaping demand file and increasing grid sustainability. To obtain a more practical and rational demand side response optimisation, the authors first build a power network model with suppliers, utility companies, consumers with appliances and energy storage systems. Unlike other power network models previously proposed, power consumptions and work patterns of appliances have been considered in the authors' work. They classify appliances into elastic and inelastic ones according to their distinct constraints on power consumptions, while all appliances' work patterns are modelled based on their functions and common users' habits in reality. With the help of convex optimisation, a distributed load scheduling algorithm is proposed subject to social welfare maximisation. Simulation results confirm that the proposed load scheduling algorithm can lead to a suitable power consumption schedule to improve the social welfare than other load scheduling algorithm does. The effect of energy storage system on reducing the fluctuation of power network is also tested and proved to be effective. At last, a strategy of charge rate is also given to satisfy power consumption and avoid energy waste, which is further verified to be competent. © The Institution of Engineering and Technology 2016.

Jia T.-M.,Beijing Jiaotong University | Yu Y.-S.,Beijing Jiaotong University | Li G.-X.,Beijing Jiaotong University
Experimental Thermal and Fluid Science | Year: 2017

Modern diesel engines employ higher injection pressure in the common-rail injection system that utilizes high-speed fuel jet to achieve rapid fuel-air mixing for spray atomization improvement. However, the spray characteristics under super high pressure are not well understood. To provide more information on spray characteristics, both the macro- and micro-characteristics of spray have been investigated under super high pressures (up to 300 MPa) via an experimental method. The spray penetration and spray cone angle were measured using a high speed camera and the microscopic characteristic of Sauter mean diameter (SMD) was obtained via Malvern Spray Tec to analyze the influence of super high injection pressure on diesel spray atomization. Induced shock waves were captured using a Schlieren system when the spray tip velocity was greater than the local sound velocity accompanied by diesel spray. The results obtained show that higher injection pressures lead to larger spray velocities and a smaller shock wave angle if it exists, with connection between spray and shock waves, and generates a smaller SMD with less decreasing amplitude. Additionally, two different types of leading shock waves—bow and oblique shock wave appeared sequentially with increasing injection pressure. © 2017 Elsevier Inc.

Zu Q.,Beijing Jiaotong University | Tang X.-Z.,Beijing Jiaotong University | Xu S.,Wuhan University of Technology | Guo Y.-F.,Beijing Jiaotong University
Acta Materialia | Year: 2017

The formation of the basal/prismatic (BP) interfaces during nucleation and growth of a reoriented crystal in Mg single crystals under c-axis tension is investigated by molecular dynamics simulations. The BP interfaces nucleate by a shuffling mechanism via local atomic rearrangement. Both two-layer disconnection and one-layer disconnection contribute to the migration of the BP interfaces. The three-dimensional analysis reveals that the two-layer disconnection forms at the junction between the partial pyramidal dislocation and BP interface. The BP interfacial disconnections prefer to move towards the [12¯10] direction rather than the [1¯010]/[0001] direction due to the accumulation of mismatches along the [1¯010]/[0001] direction. Moreover, the BP interface can transform to the {101¯2} twin boundary and vice versa. The transformation from a BP interface to a twin boundary occurs through the diagonal pile-up of BP interface disconnections, and the reverse transformation involves an upright pile-up process. Both BP transformation and {101¯2} twinning can effectively accommodate the applied tensile strain along the c-axis. The co-existing BP interfaces and {101¯2} twin boundaries allow for large deviations of a twin interface from the {101¯2} twin plane. © 2017 Acta Materialia Inc.

Bao P.,Beijing Jiaotong University | Bao P.,University of Illinois at Urbana - Champaign | Zhai C.,University of Illinois at Urbana - Champaign
Scientometrics | Year: 2017

Collaboration among researchers is an essential component of the scientific process, playing a particularly important role in findings with significant impact. While extensive efforts have been devoted to quantifying and predicting scientific impact, the question of how credit is allocated to coauthors of publications with multiple authors within a complex evolving system remains a long-standing problem in scientometrics. In this paper, we propose a dynamic credit allocation algorithm that captures the coauthors’ contribution to a publication as perceived by the scientific community, incorporating a reinforcement mechanism and a power-law temporal relaxation function. The citation data from American Physical Society are used to validate our method. We find that the proposed method can significantly outperform the state-of-the-art method in identifying the authors of Nobel-winning papers that are credited for the discovery, independent of their positions in the author list. Furthermore, the proposed methodology also allows us to determine the temporal evolution of credit between coauthors. Finally, the predictive power of our method can be further improved by incorporating the author list prior appropriately. © 2017 Akadémiai Kiadó, Budapest, Hungary

Zhao D.,Beijing Jiaotong University | Liu Y.,Beijing Jiaotong University | Liu C.,Beijing Jiaotong University
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2017

Being a rubber-like liquid crystalline elastomer, a nematic elastomer (NE) is anisotropic viscoelastic, and displays dynamic soft elasticity. In this paper, the transverse vibration of a NE Timoshenko beam is studied based on the linear viscoelasticity theory of nematic elastomers. The governing equation of motion for the transverse vibration of a NE Timoshenko beam is derived. A complex modal analysis method is used to obtain the natural frequencies and decrement coefficients of NE beams. The influences of the nematic director rotation, the rubber relaxation time, and the director rotation time on the vibration characteristic of NE Timoshenko beams are discussed in detail. The sensitivity of the dynamic performance of NE beams to director initial angle and relaxation times provides a possibility of intelligent controlling of their dynamic performance. © 2017 American Physical Society.

Li Z.,Beijing Jiaotong University | Yao J.,Beijing Jiaotong University | Li D.,Beijing Jiaotong University
Journal of Magnetism and Magnetic Materials | Year: 2017

A perfluoropolyether based ferrofluid was prepared using co-precipitation method and the rheological properties of the ferrofluid were studied by a rotational rheometer. A series of experiments were designed to study the influence of magnetic field, shear rate and temperature on the magnetoviscous effect of the perfluoropolyether based ferrofluid. Consecutive measurements of the megnetoviscous parameter with the temperature-increasing process were made and totally different tendency of the curves was observed under a range of shear rates. The magnetic field strength influence on the observed temperature dependencies was also studied experimentally. A discussion on the different mechanisms of the influence of temperature on magnetoviscous effect is presented based on the chain model of magnetic particles and the viscosity-temperature characteristics of the base carrier liquid. © 2016

Xing J.,Beijing Jiaotong University | Chen A.,Beijing Jiaotong University | Yang Q.,Beijing Jiaotong University
Journal of Constructional Steel Research | Year: 2017

Cruciform diaphragm welded joints (CDWJ) has been adopted in large-span single-layer latticed shell as a new type of joint. The behavior of such kind of joint has not been well studied and understood. In this paper, the in-plane bending hysteretic behavior with axial force of CDWJ was investigated by performing both experimental tests in full scale prototypes and nonlinear numerical analyses. The results in terms of behavior, ultimate load and collapse mode were analyzed and compared. Experimental and numerical analysis results had good agreement for the CDWJ. Parametric analysis was performed on 14 CDWJ considering the influence of geometric size of components, angle between tubes and the axial compressive ratio. Moreover, Menegotto-Pinto mathematical model was established to describe the nonlinear rotation stiffness of CDWJ. © 2016 Elsevier Ltd

Peng H.-Q.,Beijing Jiaotong University | Zhang G.-W.,Beijing Jiaotong University
Jiaotong Yunshu Xitong Gongcheng Yu Xinxi/Journal of Transportation Systems Engineering and Information Technology | Year: 2017

It is of great significance to improve the planning and management of urban parking resources for smart city construction, promotion of urban comprehensive competitiveness and sustainable development of cities. It plays an important guiding role that The National Development and Reform Commission, Ministry of Housing and Urban- rural Development of the People's Republic of China, and Ministry of Transport of the People' Republic of China etc. have issued the parking planning specification, information integration policy and construction requirements for using parking resources. The 45th conference of "Traffic and Transportation 7 + 1" sets its theme as "Parking Specification and Intelligent Parking". Through the information integration management of 'one berth one code', mobile communication technology and Internet technology are used in parking demand management. Static resources in urban parking realize dynamic management and real time utilization. These become one of the basic conditions for the construction of urban intelligent platform. Demonstration and promotion of multifunctional parking service in online and offline based on Internet+, proof that intelligent parking can play an important role in solving city parking problem and promoting the efficient use of parking resources. Intelligent parking is an effective way to utilize road resources and optimize urban traffic structure. Copyright © 2017 by Science Press.

Zhang H.,Beijing Jiaotong University | Dong P.,Beijing Jiaotong University | Yu S.,Deakin University | Song J.,Beijing Jiaotong University
IEEE Wireless Communications | Year: 2017

Due to the dramatic development of mobile devices and technologies, wireless networks have become a convenient and popular means of accessing the Internet for the public. However, the existing wireless networking techniques still face several fundamental inherent problems, such as network scalability, flexibility, and interoperability. As a result, future wireless communication networking, such as 5G, is expected to address these problems. In this article, we present a hierarchical identifier network, a novel and practical hierarchical network architecture based on the idea of network/user separation and mapping. We performed extensive experiments in a realworld high-mobility scenario to evaluate the proposed wireless network architecture. The results demonstrate that the hierarchical identifier network achieves better performance on scalability, flexibility, and interoperability compared to its existing counterparts. © 2002-2012 IEEE.

Shi J.,Lancaster University | Song Z.,Beijing Jiaotong University | Ni Q.,Lancaster University
IEEE Transactions on Wireless Communications | Year: 2017

This paper investigates the allocation of resources, including subcarriers and spreading codes, as well as intercell interference (ICI) mitigation for multicell downlink multicarrier direct-sequence code division multiple-access systems, which aim to maximize the system's spectral efficiency (SE). The analytical benchmark scheme for resource allocation and ICI mitigation is derived by solving or closely solving a series of mixed integer non-convex optimization problems. Based on the optimization objectives the same as the benchmark scheme, we propose a novel distributed resource allocation assisted by ICI mitigation scheme referred to as resource allocation assisted by ICI mitigation (RAIM), which requires very low implementation complexity and demands little backhaul resource. Our RAIM algorithm is a fully distributed algorithm, which consists of the subcarrier allocation (SA) algorithm named RAIM-SA, spreading code allocation (CA) algorithm called RAIM-CA and the ICI mitigation algorithm termed RAIM-IM. The advantages of the RAIM are that its CA only requires limited binary ICI information of intracell channels, and it is able to make mitigation decisions without any knowledge of ICI information. Our simulation results show that the proposed RAIM scheme, with very low complexity required, achieves significantly better SE performance than other existing schemes, and its performance is very close to that obtained by the benchmark scheme. © 2016 IEEE.

Fu J.,Beijing Jiaotong University | Liu Y.,Beijing Jiaotong University
Qinghua Daxue Xuebao/Journal of Tsinghua University | Year: 2017

The increased number of wireless sensor networks requires security for the sensor nodes. Since traditional information security systems based on cryptography cannot serve the complex safety issues threatening sensor nodes, the reputation system has been introduced into wireless sensor networks to periodically evaluate security nodes and assign reputation values. However, the reputation system cannot always distinguish some abnormal behavior in the sensor nodes, such as the monitoring data accuracy. As a result, some nodes can avoid monitoring by the reputation system which will affect user decisions. This paper presents a wireless sensor network node security model combining the reputation system with data noise detection. The reputation system provides the node reputations to the data noise detection model to more effectively detect data noise. The data noise detection model then feeds information back to the reputation system which accelerates the convergence rate of the reputation system. Simulations show that this node security model can simultaneously detect network and data attacks better than the traditional credit system model with a higher convergence rate. © 2017, Tsinghua University Press. All right reserved.

Yang K.,Beijing Jiaotong University | Yang L.,Beijing Jiaotong University | Gao Z.,Beijing Jiaotong University
Information Sciences | Year: 2017

This paper proposes a bi-objective hub-and-spoke (H&S) network design problem with type-2 (T2) fuzzy transportation cost and travel time described by parametric secondary possibility distributions, which are obtained using three types of mean value (MV) reduction methods. The considered objectives jointly minimize the generalized expectation of the total transportation costs and the maximum travel time requirement in terms of generalized value-at-risk (VaR). To solve the fuzzy bi-objective H&S network design problem, we develop a two-phase approach, where in the first phase we convert the proposed model into its equivalent parametric mixed-integer programming problems by applying an equivalent transformation method. This is followed by the second phase using a fuzzy linear programming approach implemented with an augmented max-min operator to obtain a non-dominated solution that has an equal satisfactory degree on both objectives. Finally, a case study based on the Civil Aeronautics Board (CAB) data set is conducted to demonstrate the effectiveness of the proposed model and solution approach. © 2017 Elsevier Inc.

Li Y.,Zhejiang University of Technology | Hou Z.,Beijing Jiaotong University | Feng Y.,Zhejiang University of Technology | Chi R.,Qingdao University of Science and Technology
Automatica | Year: 2017

Features of the data-driven approximate value iteration (AVI) algorithm, proposed in Li et al. (2014) for dealing with the optimal stabilization problem, include that only process data is required and that the estimate of the domain of attraction for the closed-loop is enlarged. However, the controller generated by the data-driven AVI algorithm is an approximate solution for the optimal control problem. In this work, a quantitative analysis result on the error bound between the optimal cost and the cost under the designed controller is given. This error bound is determined by the approximation error of the estimation for the optimal cost and the approximation error of the controller function estimator. The first one is concretely determined by the approximation error of the data-driven dynamic programming (DP) operator to the DP operator and the approximation error of the value function estimator. These three approximation errors are zeros when the data set of the plant is sufficient and infinitely complete, and the number of samples in the interested state space is infinite. This means that the cost under the designed controller equals to the optimal cost when the number of iterations is infinite. © 2016 Elsevier Ltd

Zhao B.,Beijing Jiaotong University | Tang T.,Beijing Jiaotong University | Ning B.,Beijing Jiaotong University
Safety Science | Year: 2017

The automatic metro inspires a new way of thinking about the development of urban transportation systems, specifically how the overall system completes the automatic functions. The insights into the potential correlation between safety and system variation are crucial for safe and effective operation management in the automatic metro. Thus, this paper propose a system dynamics (SD)-based model to construct the operational feedback mechanisms of the automatic metro through investigation, interview, and empirical analysis of the Beijing and Shanghai metro systems, covering the aspects of organization resource assignment, organizational experience and avoidance of driver error. From the model, the variation trend of the dynamic processes can be used to analyse the key elements or variables over time. Three key factors (the safety policy, delay time for organizational experience, and resource assignment coefficient), are identified to evaluate the crucial linkage between safety and variation over time. The changing trend of system risk influenced by the combination of these three factors is further analysed to demonstrate how the functionalities of organization should be synchronized with the transformation of different grades of automation. The paper specifies an explicit framework that recognizes the relationships among the automation degree, organization policy and system risk at the macro level and comprehensively reveals the adaptation process of organization corresponding to the revolution process of the automation degree of the metro. © 2017

Sun J.,Beijing Jiaotong University | Wang K.,Beijing Jiaotong University | Xia L.,Beijing Municipal Engineering Consulting Corporation
Journal of Engineering Mechanics | Year: 2017

Multiribbed composite wall structures with an open frame at the bottom (MRCWSFB) have been developed in recent years and increasingly used in China. This paper develops an analytical model to analyze vertical stress distribution of a wall beam in the MRCWSFB. The multiribbed composite wall can be equivalent to the elastic foundation and the trimmer beam can be treated as inverted elastic foundation beam. Therefore, the vertical stress distribution of the wall beam can be obtained using the Pasternak double-parameter elastic foundation beam theory. The accuracy of this model is verified against the results from finite-element analysis. A parametric study is then carried out using the analytical model to study the effects of the section of the frame column, section height of the concealed beam, wall depth, division of the ribbed frame, and the Young's modulus of filling blocks on the internal forces of the bottom trimmer beams, where the influencing factors are identified. © 2016 American Society of Civil Engineers.

Li X.,Purdue University | Li X.,Beijing Jiaotong University | Hibiki T.,Purdue University
Applied Thermal Engineering | Year: 2017

1029 frictional pressure drop data of two-phase flow in mini/micro multi-channels were collected from 11 literatures. This database included 8 working fluids: R134a, R22, R404a, FC-72, water, CO2, R236fa and R245fa. The channel dimension ranged from 0.109 to 2.13 mm. Frictional pressure drop range of the database was from 5 to 150 kPa. The applicability of 11 existing correlations developed for mini/micro single channels to mini/micro multi-channels were evaluated with the multi-channel database. Among the existing correlations, the correlation of Lee-Mudawar predicted the database with the mean absolute percentage error (MAPE) of 35.3%, the correlations of Lee-Garimella and Sun-Mishima had MAPEs within 45.0%. In the process of new correlation development, the database was divided into three categories (namely, 1: gas laminar-liquid laminar, 2: gas turbulent-liquid laminar, 3: gas turbulent-liquid turbulent) in terms of liquid Reynolds number and gas Reynolds number, since gas laminar-liquid turbulent data did not exist in the literature. The newly developed correlation was formulated by a function of the two-phase Reynolds number, Retp, the two-phase viscosity number, Nμtp, and the vapor quality, x. The correlation could predict the measured frictional pressure drop with the MAPE of 18.9%. The correlation demonstrated an excellent performance of the two-phase flow frictional pressure drop prediction in mini/micro multi-channels. © 2017 Elsevier Ltd

Hu D.,Beijing Jiaotong University | Cao H.,Beijing Jiaotong University
Nonlinear Analysis: Real World Applications | Year: 2017

The stability and bifurcation analysis for a predator–prey system with the nonlinear Michaelis–Menten type predator harvesting are taken into account. The existence and stability of possible equilibria are investigated. Specially, the stability of some positive equilibria is determined by using numerical simulation method due to the fact that the expressions of determinant and trace of the Jacobian matrix at these equilibria are very complex. The rigorous mathematical proofs of the existence of saddle–node bifurcation and transcritical bifurcation are derived with the help of Sotomayor's theorem. Furthermore, in order to determine the stability of limit cycle of Hopf bifurcation, the first Lyapunov number is calculated and a numerical example is given to illustrate graphically. Choosing two parameters of the system as bifurcation parameters, we prove that the system exhibits Bogdanov–Takens bifurcation of codimension 2 by calculating a universal unfolding near the cusp. Numerical simulations are carried out to demonstrate the validity of theoretical results. Our research will be useful for understanding the dynamic complexity of ecosystems or physical systems when there is the nonlinear Michaelis–Menten type harvesting effect on predator population. This kind of nonlinear harvesting is more realistic and reasonable than the model with constant-yield harvesting and constant-effort harvesting. It can be thought as a supplement to existing literature on the dynamics of this system, since there is little literature involved in nonlinear type harvesting for the system up to now. © 2016 Elsevier Ltd

Qi L.,Beijing Jiaotong University
Soft Computing | Year: 2017

A suitable and attractive contract may bring large profits and lower the risk caused by uncertain information in project management; thus, how to design incentive contracts under uncertainty has been the most pressing demand for the owner. This paper investigates the project incentive contract design problem with random asymmetric information, in which a risk-neutral owner (he) engages a risk-averse contractor (she) to complete a project. The contractor’s construction capacity is private information and characterized as a random variable. Furthermore, two incentive contracts, duration-based contract and deadline-based contract, are designed, where the owner offers a fixed payment and a penalty or bonus factor based on the real project duration and a predetermined deadline for the contractor in these two different contracts. Then, a project duration contract and a deadline-based contract model are developed with the purpose of maximizing the owner’s expected payoff, respectively. The optimal contracts are investigated, and the values of the contractor’s construction capacity information for the owner under these two contracts are quantified. The results show that the owner benefits better from getting more construction capacity information and should commit an information rent to the contractor due to asymmetric information, which distorts the penalty factor under both contracts. Moreover, regardless of contract type, the deadline has no effects on the owner’s incentive term and only affects the fixed payments. Further, the contractor is more likely to keep information private, while the owner benefits more from knowing the contractor’s construction capacity when the deadline-based contract is used. © 2017 Springer-Verlag Berlin Heidelberg

Mo H.,Beijing Jiaotong University | Wang J.,Beijing Jiaotong University
Soft Computing | Year: 2017

A return scaling cross-correlation function of exponential parameter is introduced in the present work, and a stochastic time strength neural network model is developed to predict the return scaling cross-correlations between two real stock market indexes, Shanghai Composite Index and Shenzhen Component Index. In the proposed model, the stochastic time strength function gives a weight for each historical data and makes the model have the effect of random movement. The empirical research is performed in testing the model forecasting effect of long-term cross-correlation relationships by training short-term cross-correlations, and a corresponding comparison analysis is made to the backpropagation neural network model. The empirical results show that the proposed neural network is advantageous in increasing the forecasting precision. © 2017 Springer-Verlag Berlin Heidelberg

Sun L.-F.,Beijing Jiaotong University | Wen T.-X.,LIAONING Technical University
2016 3rd International Conference on Systems and Informatics, ICSAI 2016 | Year: 2016

In order to predict risk of water inrush from coal floor accurately and effectively, on the basis of entropy and normal cloud theory, the model was established for prediction of water inrush from coal floor. Firstly, based on the analysis of main causes of water inrush from coal floor, thirteen parameters were chosen as the criterion indexes for identification and classification of risk assessment of water inrush from coal floor. Secondly, the entropy is adopted to determine the weighting coefficient for each evaluation index, the normal cloud model is used to calculate the cloud characteristics for each evaluation index in water inrush prediction, which generates the normal cloud droplets, and the comprehensive degree of membership are obtained by considering the measured evaluation index values and the corresponding index weights. The risk level of waterinrush is specified by the Maximum Membership Degree Principle. Finally, the proposed model is validated with a series of typical projects, the results show that the accuracy of cloud model is higher than other methods, the fuzziness and randomness in predicting the risk water inrush from coal floor can be well solved, the normal cloud theory is applicable and effective. © 2016 IEEE.

Kang Y.,Beijing Jiaotong University | Liu R.,Beijing Jiaotong University
2016 3rd International Conference on Systems and Informatics, ICSAI 2016 | Year: 2016

Because of the increase in the speed of passenger trains and the gross weight of freight trains, and the evolution of China's railway system, the maintenance of way department is facing significantly higher safety challenges. Risk management is essential to achieve safe operation of the railway system. This article presents a study on the development of rail breaking risk management information system using related risk management theories. This study has a real life application in Lanzhou Railway Bureau. © 2016 IEEE.

Zhang Z.,Beijing Jiaotong University | Jia L.,Beijing Jiaotong University | Qin Y.,Beijing Jiaotong University
Safety Science | Year: 2017

The smooth and fast evacuation of a pedestrian group is dependent on guidance services provided by signage systems. This paper investigates the location method of an evacuation signage system in a public space. We proposed a calculation method to determine the guidance efficiency of signage and further present a piece-wise probability function to explain interactions between pedestrians and signage. The interaction between one pedestrian and one signage was extended to the interaction between a pedestrian crowd and a signage system. A location model of the signage system was proposed to determine the minimum number of signs necessary to meet guidance demands. The location model was based on the Cooperative Location Set Cover Problem (CLSCP) and was correspondingly solved by a proposed exponential binary heuristic search algorithm (EBHS), i.e., a combined exponential binary search method and a heuristic search algorithm for solving the Cooperative Maximum Cover Location Problem (CMCLP). Finally, the proposed model was applied to determine the location of an evacuation signage system in a hall. The parameters used in the location model were calibrated based on experimental data. The model results showed that the proposed model can suggest the optimal number and best locations of signs. A sensitivity analysis showed that the guidance capacity of the signage system can be increased by improving the attractiveness of signage and pedestrian trust and familiarity with environment. The same number of signs is suggested for evacuation scenarios wherein crowd following behavior is present. © 2016

Huang L.,Beijing Jiaotong University | Liao Y.,University of Kentucky
Chinese Journal of Electronics | Year: 2017

The frequency of the input signal is selected specially to ensure that the input frequency just exceeds the cut-off frequency of analog filters. Because input signal is restrained partly by the attenuation of analog filters, output signal is sensitive to the variation of fault components. The peak voltage of key points is measured to construct fault samples of analog filters. The relationship between fault components and fault samples is analyzed to verify that fault samples have strong fault information of analog filters. The experimental results show that high-quality fault samples can be acquired efficiently, and fault feature of samples can be verified objectively by the present method. © 2017 Chinese Institute of Electronics.

Tan Q.,Beijing Jiaotong University | Li Q.,Beijing Jiaotong University
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2017

The method of building the FEA model of traction converter box in high-speed EMU and analyzing the static strength and fatigue strength of traction converter box based on IEC 61373-2010 and EN 12663 standards is presented in this paper. The load-stress correlation coefficients of weak points is obtained by FEA model, applied to transfer the load history of traction converter box to stress history of each point. The fatigue damage is calculated based on Miner's rule and the fatigue life of traction converter box is predicted. According to study, the structural strength of traction converter box meets design requirements. © 2017 SPIE.

Hou H.,Beijing Jiaotong University | Wang J.,Beijing Jiaotong University
ISAPE 2016 - Proceedings of the 11th International Symposium on Antennas, Propagation and EM Theory | Year: 2016

H-shaped patches with different sizes are used to design the gradient index surfaces for changing the phase of reflected wave along the surface, so the reflected wave from the surface can be distributed in a wide angular range, as a result, the backward radar cross section (RCS) can be reduced significantly. The whole surfaces are divided into several sections, and wave numbers in different sections are different, so that the incident wave can be reflected into different directions in the far region. The gradient index surfaces are simulated by HFSS. Comparing with the perfect electronic conducting plate (PEC) with the same size, the backward RCS of the gradient index surfaces can be reduced as large as 12 dB. © 2016 IEEE.

Geng Y.,Beijing Jiaotong University | Wang J.,Beijing Jiaotong University
ISAPE 2016 - Proceedings of the 11th International Symposium on Antennas, Propagation and EM Theory | Year: 2016

A novel broad beamwidth leaky-wave antenna (LWA) array with non-uniform transverse slots etched on substrate integrated waveguide (SIW) is proposed. A four-way SIW power divider with equal outputs of phase and amplitude is designed to feed four SIW LWAs with different periodic tapered slots. All these LWAs are working on the 1th spatial harmonic radiation mode, and by choosing periods of slots properly, the radiation beams of them can point to different directions, and therefore, results in a broad beamwidth. Meanwhile, for each SIW LWA, by tuning the length of the radiating slots etched on the top wall of SIW according to the Binomial aperture distribution, the beamwidth can be significantly broadened and the sidelobe level can be effectively reduced. The proposed LWA array shows a 3dB beam width up to 56.8° in the backward side. © 2016 IEEE.

Hou H.,Beijing Jiaotong University | Wang J.,Beijing Jiaotong University
APCAP 2016 - 2016 IEEE 5th Asia-Pacific Conference on Antennas and Propagation, Conference Proceedings | Year: 2016

Square patches with different sizes are used to construct gradient-index meta-surfaces in this paper, and the scattering properties of the surfaces are studied. Two types of the gradient-index surface are discussed, one is designed for transforming incident wave to surface wave, and the other is designed for reflecting incident wave to scattering wave to a fix direction in far field. The backward RCSs of these two kinds of surfaces are reduced 16 dB and 8 dB respectively. The scattering properties are further analyzed by transforming the E-fields above the surfaces into K-space, and the propagation constants of the waves bounded on the surfaces are discussed. © 2016 IEEE.

Xia M.,Beijing Jiaotong University | Xu Z.,University of Sichuan
International Journal of Machine Learning and Cybernetics | Year: 2017

Due to the advantages in dealing with fuzziness and uncertainty, hesitant fuzzy sets have attracted many attentions of researchers. To enlarge the range of their application, it is necessary to give an intensive study about the basic operations and properties of hesitant fuzzy sets. Based on Archimedean t-norm and t-conorm, some operations about hesitant fuzzy sets are introduced, and the properties and correlations of them are also investigated. The developed operations can be considered as the extension of the existing ones and can lay a foundation for further research and application of hesitant fuzzy theory. © 2015, Springer-Verlag Berlin Heidelberg.

Wang J.,Beijing Jiaotong University
Neural Networks | Year: 2017

In an attempt to improve the forecasting accuracy of stock price fluctuations, a new one-step-ahead model is developed in this paper which combines empirical mode decomposition (EMD) with stochastic time strength neural network (STNN). The EMD is a processing technique introduced to extract all the oscillatory modes embedded in a series, and the STNN model is established for considering the weight of occurrence time of the historical data. The linear regression performs the predictive availability of the proposed model, and the effectiveness of EMD–STNN is revealed clearly through comparing the predicted results with the traditional models. Moreover, a new evaluated method (q-order multiscale complexity invariant distance) is applied to measure the predicted results of real stock index series, and the empirical results show that the proposed model indeed displays a good performance in forecasting stock market fluctuations. © 2017 Elsevier Ltd

Su X.-X.,Beijing Jiaotong University | Wang Y.-S.,Beijing Jiaotong University | Zhang C.,University of Siegen
Journal of Computational Physics | Year: 2017

A time-domain method for calculating the defect states of scalar waves in two-dimensional (2D) periodic structures is proposed. In the time-stepping process of the proposed method, the column vector containing the spatially sampled field values is updated by multiplying it with an iteration matrix, which is written in a matrix-exponential form. The matrix-exponential is first computed by using the Suzuki's decomposition based technique of the fourth order, in which the Floquet–Bloch boundary conditions are incorporated. The obtained iteration matrix is then squared to enlarge the time-step that can be used in the time-stepping process (namely, the squaring technique), and the small nonzero elements in the iteration matrix is finally pruned to improve the sparse structure of the matrix (namely, the pruning technique). The numerical examples of the super-cell calculations for 2D defect-containing phononic crystal structures show that, the fourth order decomposition based technique for the matrix-exponential computation is much more efficient than the frequently used precise integration technique (PIT) if the PIT is of an order greater than 2. Although it is not unconditionally stable, the proposed time-domain method is particularly efficient for the super-cell calculations of the defect states in a 2D periodic structure containing a defect with a wave speed much higher than those of the background materials. For this kind of defect-containing structures, the time-stepping process can run stably for a sufficiently large number of the time-steps with a time-step much larger than the Courant–Friedrichs–Lewy (CFL) upper limit, and consequently the overall efficiency of the proposed time-domain method can be significantly higher than that of the conventional finite-difference time-domain (FDTD) method. Some physical interpretations on the properties of the band structures and the defect states of the calculated periodic structures are also presented. © 2017 Elsevier Inc.

Xiong Z.,Beijing Jiaotong University | Yao Z.,Beijing Municipal Institute of City Planning and Design
Proceedings - 2016 9th International Congress on Image and Signal Processing, BioMedical Engineering and Informatics, CISP-BMEI 2016 | Year: 2016

Short-term predicting of traffic flow is the key to intelligent transportation system which is the most important suggestion to relieve traffic jam, reduce the emission of traffic as well as decrease the traffic accident. This paper begins with the review of previous attempts to forecast the short-term traffic flow. In addition, the comparison among the linear system theory, artificial intelligence method and nonlinear system theory is proposed on the basis of the summarization of the short-time forecasting method of road network. Additionally, the empirical results show that these three methods under multi-cross-sections condition were superior to single-cross-section. Meanwhile, these three methods have their own advantages and disadvantages and applicable scope in the aspect of calculation efficiency, parameter selection and data demand. © 2016 IEEE.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

News Article | November 18, 2015

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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