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Significant coastline changes in China during 1991–2015 tracked by Landsat data

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Science Bulletin 2018年第14期63卷 883-886页

作者： nan xu Peng Gong Ministry of Education Key Laboratory for Earth System Modelling Department of Earth System Science Tsinghua University Beijing 100084 China Joint Center for Global Change Studies Beijing 1008F5 China

In China,following national economic reform and the opendoor policy in 1978,there has been a rapid industrialization and urbanization of coastal regions which has dramatically changed the environment and ecosystems in these areas[1].Regions with rapidly growing economies,such as Shanghai and Shenzhen,face the double pressure of limited land area and population growth,

关键词： Landsat 海岸线中国追踪经济改革生态系统都市化工业化

Effects of solution and aging treatments on microstructures and mechanical properties of AZ61 magnesium alloy welded joints

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Rare Metals 2012年第1期31卷 12-16页

作者： Shen, Jun xu, nan College of Materials Science & Engineering Chongqing University Chongqing 400044 China

The effects of solution and aging treatments on the microstructures and mechanical properties of tungsten inert gas arc welded AZ61 magne-sium alloy joints were investigated by microstructural observations,microhardness tests and tensile *** results showed that the solution treatment led to the β-Mg17Al12 particles dissolved into the α-Mg ***,the microhardness of the fusion zone and the ultimate tensile strength of the welded joints were the *** the increase of the aging temperature,the volume fraction of the β-Mg17Al12 particles in the fusion zone increased and this enhanced the microhardness of the fusion zone ***,the elongation of the welded joints was in-creased slightly with the increase of the volume fraction of the β-Mg17Al12 ***,the ultimate tensile strength of the welded joints increased at first and dropped at 190 ?C due to cracks formed at the boundaries of the β-Mg17Al12 particles.

关键词： magnesium alloy heat treatment microstructure mechanical properties

A Discrete Tire Model for Cornering Properties Considering Rubber Friction

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Automotive Innovation 2020年第2期3卷 133-146页

作者： nan xu Yiyang Yang KonghuiGuo State Key Laboratory of Automotive Simulation and Control Jilin UniversityChangchun 130025Jilin ProvinceChina Pan Asia Technical Automotive Center Co. LtdPudong 201208ShanghaiChina

In this paper,a discrete tire model of comering properties for road vehicles relating to tire grip performance,which is important for driving stability and safety,is *** proposed tire model combines realistic rubber friction related to velocity and tire grip performance with deformation of the *** model can describe the stress and strain of the carcass and tread,and the rubber friction coefficient at each point of the contact patch,which is affected by the di stribution of the slip ***,the model incorporates the effects of the viscoelastic rubber material and power spectrum of the road,which are explicitly reflected in the rubber friction ***,an improved rubber friction model based on the Persson theory of rubber friction is introduced in this paper.A discrete analytical tire model,which considers carcass compliance and the discretization of the tread,is then *** addition,important phenomena of tire properties arising from the carcass compl iance and rubber friction are analyzed and the effectiveness of the discrete analytical tire model is validated *** proposed model provides a new way to optimize the grip performance of a tire by adjusting the tire or rubber physical parameters even before the tire is made.

关键词： Road vehicle Tire model Grip performance Rubber friction Running velocity

Effect of Zener-Hollomon Parameter on Microstructure and Mechanical Properties of Copper Subjected to Friction Stir Welding

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Acta Metallurgica Sinica(English Letters) 2020年第2期33卷 319-326页

作者： nan xu Ruo-nan Feng Wen-Feng Guo Qi-Ning Song Ye-Feng Bao College of Mechanical and Electrical Engineering Hohai UniversityChangzhou 213022China

In this work,the influence of the Zener-Hollomon(Z)parameter on the microstructure and mechanical properties of copper subjected to friction stir welding(FSW)was *** N2 cooling was conducted to control the cooling rate after the *** obtained results demonstrate that the Z parameter was dependent on the tool rotation rate during the FSW,i.e.,a higher tool rotating rate resulted in a lower Z *** grain size in the stir zone decreased with the increase in the Z *** relationship between the yield strength and the Z parameter is established asσ0.2=σ0+*** relationship exhibited two different plots under the conditions of air cooling and liquid N2 *** at a similar Z parameter,a significant yield strength difference occurred because massive dislocations,which were caused by the prevention of the post-annealing effect,were maintained in the stir *** study suggests that the influence of the post-annealing effect should not be neglected when analyzing the relationship between the Z parameter,micro structure,and mechanical properties.

关键词： Copper Friction stir welding Microstructure Mechanical properties

Torque allocation of four-wheel drive EVs considering tire slip energy

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Science China(Information Sciences) 2022年第2期65卷 61-74页

作者： Bingzhao GAO Yongjun YAN Hong CHU Hong CHEN nan xu State Key Laboratory of Automotive Simulation and Control Jilin University Clear Energy Automotive Engineering Center Tongji University

With the increasing peak torque of the in-wheel motor, the tire slip energy dissipation becomes as considerable as the motor energy loss. The actuation redundancy in four-wheel drive electric vehicles has the innate advantage of reducing the energy dissipation of the tire slip according to different criteria. This study innovatively optimizes the energy loss of the motor and the slip energy consumption of the tire under a unified framework. A more accurate calculation model of the tire slip force and slip energy is adopted in the cost function. Its feasibility and potential are shown through simulation case studies based on different road adhesion coefficients among three allocation methods: considering both motor energy loss and tire slip loss, only considering the motor energy loss, and only considering the axis load distribution. The simulation results demonstrate that the torque allocation method considering both motor energy loss and tire slip loss can dramatically reduce the tire slip energy and tire wear with an acceptable motor energy efficiency sacrifice compared to the present allocation algorithms.

关键词： control allocation four-wheel drive electric vehicles tire slip energy model multi-objective optimization

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Investigation and Application on the Vertical Vibration Models of the Seated Human Body

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Automotive Innovation 2018年第3期1卷 263-271页

作者： Xiong Shao nan xu Xiang Liu Advanced Product Development Department Dongfeng Commercial Vehicle Technical CenterNo.10 Dongfeng RoadWuhan 430056China College of Automotive Engineering Jilin UniversityChangchun 130000China

Investigation of the vertical vibration characteristics of the seated human body is beneficial for the design and development of vehicle ride *** this study,we first established models of the seated human body with two,three and four degrees of freedom(DOF).Then,the vibration characteristics of 30 volunteers were tested under standard conditions with a vibration test rig to obtain data for the apparent mass,driving point mechanical impedance,and seat-to-head transfer *** on the experimental data,the parameters of these models are identified and the results show that the four-DOF model can simulate the vertical vibration characteristics of the seated human body more ***,different seated human body models were applied to optimize the damping of shock *** results show that the optimized damping with the four-DOF Chinese seated human body model is 27%more than that with rigid mass and 7%less than that with ISO 5982:2001 seated human body model.

关键词： Seated human body model Apparent mass Driving point mechanical impedance Seat-to-head transfer function Optimization design of damping

Medium optimization for enhanced production of cytosine-substituted mildiomycin analogue (MIL-C) by Streptoverticillium rimofaciens ZJU 5119

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Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2008年第1期9卷 77-84页

作者： Dan YE Zhi-nan xu Pei-lin CEN Department of Chemical and Biochemical Engineering Zhejiang University Hangzhou 310027 China

Cytosine-substituted mildiomycin analogue （MIL-C） was produced effectively by supplementing cytosine into the culture of Streptoverticillium rimofaciens. In order to improve the yield of MIL-C, statistically-based experimental designs were applied to optimize the fermentation medium for S. rimofaciens ZJU 5119. Fifteen culture conditions were examined for their significances on MIL-C production using Plackett-Burman design. The Plackett-Burrnan design and one-variable-at-a-time design indicated that glucose and rice meal as the complex carbon sources, and peanut cake meal and NH4NO3 as the complex nitrogen sources were beneficial for MIL-C production in S. rimofaciens ZJU 5119. The results of further central composition design （CCD） showed that the optimal concentration of glucose, rice meal and peanut cake meal were 18.7 g/L, 64.8 g/L and 65.1 g/L, respectively. By using this optimal fermentation medium, the MIL-C concentration was increased up to 1336.5 mg/L, an approximate 3.8-fold improvement over the previous concentration （350.0 mg/L） with un-optimized medium. This work will be very helpful to the large-scale production of MIL-C in the future.

关键词： Cytosine-substituted mildiomycin analogue (MIL-C) Plackett-Burman design Response surface methodology Streptoverticillium rimofaciens Nucleoside antibiotic

Cellular signaling pathways of T cells in giant cell arteritis

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Journal of Geriatric Cardiology 2021年第9期18卷 768-778页

作者： Hai-Yan LI Jun-nan xu Zong-Wen SHUAI Department of Rheumatology and Immunology the First Affiliated Hospital of Anhui Medical UniversityHefeiChina

Giant cell arteritis(GCA)is a commonly occurring large vacuities characterized by angiopathy of medium and large-sized *** granulomatous formation plays an important role in the pathogenesis of *** of T cell lineages and signaling pathways in GCA have revealed the essential role of T cells in the pathology of GCA.T cells are the dominant population present in GCA ***4+T cell subtypes that are present include Th1,Th2,Th9,Th17,follicular helper T(Tfh)cells,and regulatory T(Treg)***8 T cells can primarily differentiate into cytotoxic CD8+T lymphocytes and Treg *** instrumental part of GCA is the interplay between dendritic cells,macrophages and endothelial cells,which can result in the vascular injury and the characteristics granulomatous infiltrates *** the inflammatory loop of GCA,several signaling pathways have been reported to play an essential role in recruiting,activating and differentiating T cells,including T-cell receptor(TCR)signaling,vascular endothelial growth factor(VEGF)-Jagged-Notch signaling and the Janus kinase and signal transducer and activator of transcription(STAT)pathway(JAK-STAT)*** this review,we have focused on the role of T cells and their potential signaling mechanism(s)that are involved in the pathogenesis of GCA.A better understanding of the role of T cells mediated complicated orchestration during the homeostasis and the changes could possibly favor developments of novel treatment strategies against immunological disorders associated with GCA.

关键词： GCA Cellular signaling pathways of T cells in giant cell arteritis

A new saikogenin from the roots of Bupleurum bicaule

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Chinese Journal of Natural Medicines 2014年第4期12卷 305-308页

作者： xu nan SHI Ya-nan ZHONG xu CAO Yue WANG Li JIA Tian-Zhu College of Pharmacy Liaoning University of Traditional Chinese Medicine Dalian Statute of Drug and Food examination

AIM: To study the chemical constituents from the roots of Bupleurum bicaule Helm(Apiaceae). METHOD: Silica gel, Sephadex LH-20, MPLC Rp-C18 column chromatography, and HPLC were used for isolation of compounds. The structures were elucidated on the basis of 1D- and 2D-NMR technology and HRESI-MS. Compounds were evaluated in vitro for their inhibitory ability against the proliferation of rat mesangial cells by the MTT method. RESULTS: Twelve compounds were isolated, and their structures were identified on the basis of their spectroscopic and ico-chemical properties as 13, 28-epoxy-olean-11-en-3-one(1), saikogenin E(2), saikogenin G(3), 11α-methoxy-3β, 16β, 23, 28-tetrahydroxyolean-12-ene(4), saikogenin D(5), prosaikogenin F(6), prosaikogenin A(7), prosaikogenin G(8), prosaikogenin D(9), laccaic acid(10), methyl gallate(11), and ethyl gallate(12). Compounds 1, 2, 7, 8, and 10 were observed to have inhibitory activity against mesangial cell proliferationin to different degrees. CONCLUSION: Compound 1, 8, and 10 exhibit significant inhibitory effects on rat mesangial cell proliferation induced by Ang II.

关键词： Bupleurum bicaule Saikogenins Triterpenoid saponins Anti-proliferation