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Electrical bearing failures in electric vehicles

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Friction 2020年第1期8卷 4-28页

作者： Feng HE guoxin XIE Jianbin LUO State Key Laboratory of Tribology Department of Mechanical EngineeringTsinghua UniversityBeijing 100084China

In modern electric equipment,especially electric vehicles,inverter control systems can lead to complex shaft voltages and bearing *** an electric motor,many parts have electrical failure problems,and among which bearings are the most sensitive and vulnerable *** recent years,electrical failures in bearing have been frequently reported in electric vehicles,and the electrical failure of bearings has become a key issue that restricts the lifetime of all‐electric motor‐based power systems in a broader *** purpose of this review is to provide a comprehensive overview of the bearing premature failure in the mechanical systems exposed in an electrical environment represented by electric *** electrical environments in which bearing works including the different components and the origins of the shaft voltages and bearing currents,as well as the typical modes of electrical bearing failure including various topographical damages and lubrication failures,have been *** fundamental influence mechanisms of voltage/current on the friction/lubrication properties have been summarized and analyzed,and corresponding countermeasures have been ***,a brief introduction to the key technical flaws in the current researches will be made and the future outlook of frontier directions will be discussed.

关键词： electric vehicles bearing premature failure electrical environment shaft voltage

Simulation of hydraulic fracture utilizing numerical manifold method

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Science China(Technological Sciences) 2015年第9期58卷 1542-1557页

作者： ZHANG guoxin LI Xu LI HaiFeng State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin China Institute of Water Resources and Hydropower Research School of Civil Engineering Beijing Jiaotong University

A 2nd order numerical manifold method(NMM) based method is developed to simulate the hydraulic fractures propagating process in rock or concrete. The proposed method uses a weak coupling technique to analyze the fluid phase and solid phase. To study the seepage behavior of the fluid phase, all the fractures in solid are identified by a block cutting algorithm and form a flow network. Then the hydraulic heads at crack ends are solved. To study the deformation and destruction of solid phase, the 2-order NMM and sub-region boundary element method are combined to solve the stress-strain field. Crack growth is controlled by the well-accepted criterion, including the tension criterion or Mohr-Coulomb criterion for the initialization of cracks and the maximum circumferential stress theory for crack propagation. Once the crack growth occurs, the seepage and deformation analysis will be resolved in the next simulation step. Such weak coupling analysis will continue until the structure becomes stable or is destructed. Five examples are used to verify the new method. The results demonstrate that the method can solve the SIFs at crack tip and fluid flow in crack network precisely, and the method is effective in simulating the hydraulic facture problem. Besides, the NMM shows great convenience and is of high accuracy in simulating the crack growth problem.

关键词： hydraulic fracture numerical manifold method crack growth crack network flow sub-region boundary element method

Guest editorial:Special Issue on Biomedical Tribology

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Friction 2022年第1期10卷 2-3页

作者： guoxin XIE Jianbin LUO State Key Laboratory of Tribology Tsinghua UniversityBeijing 100084China

Biomedical tribology has developed rapidly with the joint efforts of medical and tribological researchers,and it concerns various kinds of friction that existed inside and out side the body,such as the friction of joints,the friction between skin and clothing,and the friction in the lumen(blood vessels,trachea,digestive tube,and excretory tube),which causes maiiy physiological changes and diseases in the human ***,many medical devices have been used to treat or alleviate various *** tribology plays a vital role in solving the widespread tribological issues in the medical devices field,aiming to improve the performance of medical devices and prolong the service life.

关键词： friction tribological service

Guidance law with impact time and impact angle constraints

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Chinese Journal of Aeronautics 2013年第4期26卷 960-966页

作者： Zhang Youan Ma guoxin Liu Aili Department of Control Engineering Naval Aeronautical and Astronautical University

A novel closed-form guidance law with impact time and impact angle constraints is pro- posed for salvo attack of anti-ship missiles, which employs missile＇s normal acceleration （not jerk） as the control command directly. Firstly, the impact time control problem is formulated as tracking the designated time-to-go （the difference between the designated impact time and the current flight time） for the actual time-to-go of missile, and the impact angle control problem is formulated as tracking the designated heading angle for the actual heading angle of missile. Secondly, a biased proportional navigation guidance （BPNG） law with designated heading angle constraint is constructed, and the actual time-to-go estimation for this BPNG is derived analytically by solving the system differential equations. Thirdly, by adding a feedback control to this constructed BPNG to eliminate the time-to-go errorthe difference between the standard time-to-go and the actual time-to-go, a guidance law with adjustable coefficients to control the impact time and impact angle simultaneously is developed. Finally, simulation results demonstrate the performance and feasibility of the proposed approach.

关键词： Feedback control Guidance law Impact angle Impact time Missiles Proportional navigation guidance

A NONPARAMETRIC TEST AGAINST AN UMBRELLA ALTERNATIVE FOR STRATIFIED DATA

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Journal of Systems Science & Complexity 2011年第4期24卷 738-752页

作者： Yanqin FENG Jinde WANG guoxin ZUO School of Mathematics and Statistics Wuhan University Wuhan 430072 China. School of Mathematics and Statistics HuaZhong Normal University Wuhan 430079 China. Department of Mathematics Nanjing University Nanjing 210093 China.

Trend test in dose-response has been a central problem in medicine. This paper treats the problem of comparing umbrella pattern treatment effects. Under an ordered m × r × k table, this article considers testing the hypothesis that all multinomial populations are conditional independence against the alternative that they are in an umbrella trend. For this hypothesis test problem, this article introduces a model-free test method by using likelihood ratio test statistic and gives the asymptotic distribution of the test statistic. Simulation study is conducted to compare the empirical power per- formed via the proposed method and others. Finally, two real data are studied to illustrate the validity of the proposed method.

关键词： Asymptotic distribution chi-bar-squared distribution likelihood ratio test stratifieddata umbrella order.

Effects of Anions and Cations on π-Complexation Between Olefin and Metal Halide

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Chemical Research in Chinese Universities 2005年第2期21卷 217-219页

作者： ZHOUJin-xia ZHANGYong-chun guoxin-wen StateKeyLaboratoryofFineChemical DalianUniversityofTechnologyDalian116012P.R.China

An ab initio molecular orbital study was performed to determine the effects of anions and cations on the π-complexation of C_2H_4 on MX(M=Ag, Cu; X=F, Cl). The calculated results show the following order of adsorption strength: F ->Cl - for anions; Cu +>Ag + for cations. The results can be explained by the detailed analysis of atomic charge, orbital energy and orbital population by using the natural bond orbital(NBO) theory: (1) anions with stronger electronegativity can attract more electrons from the s orbital of M, while at the same time it does not obviously weaken the d orbital occupation of M, thus the nearly vacant s orbital and the sufficiently filled d orbitals of M help with forming σ-donation and d-π * backdonation with the π orbital and the π * orbital of olefin, respectively; (2) a smaller energy gap of symmetry-adapted orbitals between olefin and a cation can favor the electron transfer, that is why Cu + forms stronger adsorption with olefin than Ag + does.

关键词： Complexation ab initio Calculation Olefin Anion Cation

A Note on Dn-Testability for Varieties of Bands

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Algebra Colloquium 2014年第3期21卷 511-516页

作者： guoxin Liu Hongqin Yan ZhengpanWang School of Mathematics and Statistics Southwest University Chongaing 400715. China

Assume that B is the variety of bands, and the identities of V∈l（B） involve n variables （n≥ 2）. In this paper, we show that V is Dn-1-testable and is not ：Dn-2- testable.

关键词： band variety identity :Dn-1-testability

Styrene polymerization catalyzed by nickel complexes bearing hydroxyindanone-iminate ligands

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Chinese Science Bulletin 2008年第18期53卷 2764-2769页

作者： TANG GuangRong JIN guoxin Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials Department of Chemistry Fudan University Shanghai200433 China

Activated by methylaluminoxane, mononuclear bis(hydroxyindanone-iminate)nickel complexes Ni[ArN == CC_2H_3(CH3)C_6H_2(R)O]_2 (Ar = 2,6-i-Pr2C6H3, R = Me (1), R = Cl (2), and R = H (3)) showed good activity for the styrene polymerization. The effect of many reaction parameters including the Al/Ni ratio, tempera- ture, and reaction time on catalytic activities of catalytic systems and the molecular weights of the ob- tained polystyrene was ascertained. The highest activity of 1.34×105 g(PS)·mol^(-1)(Ni)·h^(-1) was obtained under the optimum reaction condition. The 13C NMR spectra of the polymers revealed that the polymer was isotactic-rich atactic polystyrene. And the coordination mechanism was confirmed by the analyses of the polymer chain end-groups.

关键词：苯乙烯聚合反应镍混合物甲缩醛

A"One Engine with Six Gears"System Engineering Methodology for the Economic Development of Unconventional Oil and Gas in China

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Engineering 2022年第11期18卷 105-115页

作者： guoxin Li Chenggang Xian He Liu State Key Laboratory of Petroleum Resources and Prospecting China University of Petroleum(Beijing)Beijing 102249China PetroChina Qinghai Oil Co. Ltd.Mangya 817500China PetroChina Research Institute of Petroleum Exploration&Development Beijing 100083China

Unconventional oil and gas resources have become the most important and realistic field for increasing China’s domestic oil and gas reserves and *** present,the production scale does not match the massive amount of resources and the rapid growth of proven geological *** challenges of technology,cost,management,and methodology restrict large-scale and economic *** on successful practices,a"one engine with six gears"system engineering methodology is put forward,which includes life-cycle management,overall synergy,interdisciplinary cross-service integration,marketoriented operation,socialized support,digitalized management,and low-carbon and green *** methodology has been proved to be effective in multiple unconventional oil and gas national demonstration areas,including the Jimusar continental shale oil demonstration *** views are introduced-namely,that unconventional oil and gas do not necessarily yield a low return,nor do they necessarily have a low recovery factor.A determination to achieve economic benefit must be a pervasive underlying goal for managers and *** and recovery factors,as primary focuses,must be adhered to during China’s development of unconventional oil and *** required methodology transformation includes a revolution in management systems to significantly decrease cost and increase production,resulting in technological innovation.

关键词： Unconventional oil and gas resources System engineering Methodology transformation Life-cycle management Geoscience-to-engineering integration