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Analysis of torque transmitting behavior and wheel slip prevention control during regenerative braking for high speed EMU trains

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Acta Mechanica Sinica 2016年第2期32卷 244-251页

作者： Kun xu Guo-Qing xu chun-Hua Zheng Shenzhen Institutes of Advanced Technology Chinese Academy of Sciencesand The Chinese University of Hong Kong Shenzhen College of Advanced Technology University of Chinese Academy of Sciences School of Electronics and Information Tongji University

The wheel-rail adhesion control for regenerative braking systems of high speed electric multiple unit trains is crucial to maintaining the stability,improving the adhesion utilization,and achieving deep energy *** remain technical challenges mainly because of the nonlinear,uncertain,and varying features of wheel-rail contact *** research analyzes the torque transmitting behavior during regenerative braking,and proposes a novel methodology to detect the wheel-rail adhesion ***,applications to the wheel slip prevention during braking are investigated,and the optimal slip ratio control scheme is proposed,which is based on a novel optimal reference generation of the slip ratio and a robust sliding mode *** proposed methodology achieves the optimal braking *** simulation results for uncertain slippery rails verify the effectiveness of the proposed methodology.

关键词： High speed electric multiple unit(EMU) train Regenerative braking Wheel-rail adhesion Optimal slip ratio

Characteristics and control mechanisms of coalbed permeability change in various gas production stages

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Petroleum Science 2015年第4期12卷 684-691页

作者： Da-Zhen Tang chun-miao Deng Yan-Jun Meng Zhi-Ping Li Hao xu Shu Tao Song Li School of Energy Resources China University of Geosciences Coal Reservoir Laboratory of National Engineering Research Center of Coalbed Methane Development & Utilization

According to dimensionless analysis of the coalbed methane （CBM） production data of Fanzhuang block in southern Qinshui basin, the dimensionless gas production rate is calculated to quantitatively divide the CBM well production process into four stages, i.e., drai- nage stage, unstable gas production stage, stable gas pro- duction stage, and gas production decline stage. By the material balance method, the coal reservoir permeability change in different stages is quantitatively characterized. The characteristics and control mechanisms of change in coalbed permeability （CICP） during different production stages are concluded on five aspects, i.e., permeability trend variation, controlling mechanism, system energy, phase state compositions, and production performance. The study reveals that CICP is characterized by first decline, then recovery, and finally by increase and is controlled directly by effective stress and matrix shrinkage effects. Further, the duration and intensity of the matrix shrinkage effect are inherently controlled by adsorption and desorp- tion features.

关键词： Production stage - Coalbed methane Permeability Dynamic change - Control mechanism

Bi-level Optimal Planning of Voltage Regulator in Distribution Systems Considering Maximization of Incentive-based Photovoltaic Energy Integration

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CSEE Journal of Power and Energy Systems 2023年第6期9卷 2008-2017页

作者： xu xu Youwei Jia chun Sing Lai Minghao Wang Zhao xu Department of Electrical and Electronic Engineering Southern University of Science and TechnologyShenzhenChina Department of Electrical Engineering The Hong Kong Polytechnic UniversityHung HomHong Kong SARChina Department of Electrical and Electronic Engineering University Key Laboratory of Advanced Wireless Communications of Guangdong ProvinceSouthern University of Science and TechnologyShenzhen 515100China Department of Electronic and Computer Engineering Brunel Institute of Power SystemsBrunel University LondonLondonUB83PH United Kingdom Department of Electrical Engineering Shenzhen Research InstituteThe Hong Kong Polytechnic UniversityHung HomHong Kong SARChina

This paper focuses on optimal voltage regulator(VR)planning to maximize the photovoltaic(PV)energy integration in distribution *** describe the amount of dynamic PV energy that can be integrated into the power system,the concept of PV accommodation capability(PVAC)is introduced and modeled with *** proposed planning model is formulated as a Benders decomposition based bi-level stochastic optimization *** the upper-level problem,VR planning decisions and PVAC are determined via mixed integer linear programming(MILP)before considering *** in the lower-level problem,the feasibility of first-level results is checked by critical network constraints(*** magnitude constraints and line capacity constraints)under uncertainties considered by time-varying loads and PV *** this paper,these uncertainties are represented in the form of operational scenarios,which are generated by the Gaussian copula theory and reduced by a well-studied backward-reduction *** modified IEEE 33-node distribution grid is utilized to verify the effectiveness of the proposed *** results demonstrate that a PV energy integration can be significantly enhanced after optimal voltage regulator planning.

关键词： Bi-level stochastic optimization problem critical network constraints photovoltaic energy integration uncertainties voltage regulator planning

Multi-scale analysis of subgrid stress and energy dissipation in turbulent channel flow

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Acta Mechanica Sinica 2010年第1期26卷 81-90页

作者： chun-Xiao xu School of Aerospace Tsinghua University 100084 Beijing China

In present study, the subgrid scale （SGS） stress and dissipation for multiscale formulation of large eddy simulation are analyzed using the data of turbulent channel flow at Ret = 180 obtained by direct numerical simulation. It is found that the small scale SGS stress is much smaller than the large scale SGS stress for all the stress components. The dominant contributor to large scale SGS stress is the cross stress between small scale and subgrid scale motions, while the cross stress between large scale and subgrid scale motions make major contributions to small scale SGS stress. The energy transfer from resolved large scales to subgrid scales is mainly caused by SGS Reynolds stress, while that between resolved small scales and subgrid scales are mainly due to the cross stress. The multiscale formulation of SGS models are evaluated a priori, and it is found that the small- small model is superior to other variants in terms of SGS dissipation.

关键词： SGS stress SGS dissipation - Multi-scale energy transfer Multi-scale SGS model - Turbulent channel flow

An overview of the “Three-North” Shelterbelt project in China

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Forestry Studies in China 2012年第1期14卷 70-79页

作者： LI miao-miao LIU An-tian ZOU chun-jing xu Wen-duo Hideyuki SHIMIZU WANG Kai-yun Shanghai Key Laboratory of Urbanization ＆ Ecological Restoration School of Life Science East China Normal University Shang- hai 200062 P. R. China Institute of Applied Ecology Chinese Academy of Sciences Shenyang 110016 P. R. China National Institute for Environmental Studies 16-20nogawa Tsukuba Ibaraki 305-8506 Japan

The ＂Three-North＂ Shelterbelt is the largest and most distinctive artificial ecological engineering project in China. It has been conducted since November 25, 1978 in the ＂Three-North＂（i.e., Northeast China, North China and Northwest China） regions. In this study, the background and the essential benefits of the ＂Three-North＂ Shelterbelt project are summarized. The basic status and future development of the ＂Three-North＂ Shelterbelt project are also studied. As well, we tried to discuss the problems existing in the current shelterbelt system and the strategies to conduct this ecological project rationally.

关键词： "Three-North" Shelterbelt project essential benefits species adaptability

ECC-Based RFID Authentication Protocol

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Journal of Electronic Science and Technology 2020年第4期18卷 320-329页

作者： Xing-chun Yang chun-Xiang xu Chao-Rong Li Department of Computer Science and Technology Sichuan Police CollegeLuzhou 646000 School of Computer Science and Engineering University of Electronic Science and Technology of ChinaChengdu 611731 Department of Computer Science and Information Engineering Yibin UniversityYibin 644000

The radio frequency identification(RFID)technology has been widely used so far in industrial and commercial *** develop the RFID tags that support elliptic curve cryptography(ECC),we propose a scalable and mutual authentication protocol based on *** also suggest a tag privacy model that provides adversaries exhibiting strong abilities to attack a tag’s *** prove that the proposed protocol preserves privacy under the privacy model and that it meets general security *** with other recent ECCbased RFID authentication protocols,our protocol provides tag privacy and performs the best under comprehensive evaluation of tag privacy,tag computation cost,and communications cost.

关键词： Elliptic curve cryptography radio frequency identification(RFID) authentication protocol privacy

In-situ evaluation for corrosion process at fusion boundary of stainless steel strip overlay joints in H2S containing solution

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中国有色金属学会会刊：英文版 2004年第z1期14卷 413-419页

作者： ZOU Yang PAN chun-xu FU Qiang Department of Physics & Center for Electron Microscopy Wuhan University Wuhan 430063 China Department of Physics & Center for Electron Microscopy Wuhan University Wuhan 430063 China Department of Physics & Center for Nano-Science and Technology Wuhan University Wuhan 430063 China

The present work studied the corrosion properties around the fusion boundaries of 2.25Cr-1Mo steel with stainless steel strip overlay joints under as welded condition and after post-weld heat treatment (PWHT) in H2 S containing solution (NACE TM-01-77 standard) with different time. An in-situ observation method was introduced for evaluating corrosive progress in the fusion boundary in H2 S containing solution, that is, the samples were marked firstly at the boundary and then treated in the solution for variant time. Each time after the corrosion treatment, the observations were kept to focus at the same marked area by using scanning electron microscopy (SEM) to observe the corrosion progress. The results reveal that the fusion boundary is the worst region for corrosion resistance when comparing with other boundaries, and a broad fusion boundary has a stronger resistance for "hydrogen induced disbonding" than a narrow one.

关键词： dissimilar steel welding fusion boundary H2S corrosion post-weld heat treatment

Crystal structure determination of a chimeric FabF by XRD

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Nuclear Science and Techniques 2017年第9期28卷 63-68页

作者： Ke Li Li Li Ye-chun xu College of Science Shanghai University CAS Key Laboratory of Receptor Research Drug Discovery and Design Center Shanghai Institute of Materia MedicaChinese Academy of Sciences (CAS)

Beta-ketoacyl-acyl-carrier-protein synthase Ⅱ,an important enzyme in biosynthesis of bacterial fatty acid,is an attractive target in antibacterial drug design. Platensimycin(PTM), produced by Streptomyces platensis, has a strong, broad-spectrum Gram-positive antibacterial activity by selectively targeting to Fab F but exhibits no inhibition to the Fab F from Streptomyces platensis(spFabF). To study the self-resistance mechanism within the PTM-producing strain and provide hint for development of novel antibiotics, it is imperative to solve the structure of spFabF and elucidate the difference between spFabF and other Fab Fs which are not resistant to PTM. To this end, we constructed four chimeric Fab Fs based on the sequence of spFabF and its homologous protein after the expression of wide-type spFabF was failed. The crystal structure of one chimera, js_(200)FabF, of 91.2% sequence identity to spFabF,was solved. A structure comparison of js_(200)FabF with a PTM-bound Fab F suggested that three loops nearby the catalytic site might play key roles in preventing the binding of PTM to spFabF. The results provide an encouraging basis for further studies on the self-resistance mechanismand structure-based design of novel antibiotics targeting FabFs.

关键词：晶体结构嵌合体 XRD 广谱抗菌活性测定药物设计生产菌株 PTM

Microstructure and tensile properties of A356 alloy with different Sc/Zr additions

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Rare Metals 2021年第9期40卷 2514-2522页

作者： Shou-Peng xu chun-Sheng Shi Nai-Qin Zhao chun-Nian He School of Materials Science and Engineering and Tianjin Key Laboratory of Composites and Functional Materials Tianjin UniversityTianjin 300350China Collaborative Innovation Center of Chemical Science and Engineering Tianjin 300072China

Addition of rare earth elements for improving the tensile properties of aluminum alloys has attracted great attention. In this study, a systematic analysis on the microstructure and tensile properties of A356–0.13 Ti alloys with different contents of scandium(Sc) and scandium/zirconium(Sc/Zr) after solution and aging treatment process was carried out. The addition of Sc/Zr into A356–0.13 Ti alloys can greatly refine the grain size and modify the deleterious coarse eutectic Si structure and harmful acicular iron-containing phase morphology. As a result, the maximum value of strength(298 MPa) and ductility(elongation of 8.4%) are acquired by co-addition of Sc/Zr after solution and aging treatment process, which indicates that the tensile properties of A356 alloy are greatly enhanced by the synergistic effect of co-addition of Sc/Zr.

关键词： Aluminum alloys Sc/Zr Tensile properties Solution and aging treatment