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Comparison and analysis of two Coulomb friction models on the dynamic behavior of slider-crank mechanism with a revolute clearance joint

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Applied Mathematics and Mechanics(English Edition) 2018年第9期39卷 1239-1258页

作者： Xudong ZHENG runsen zhang Qi WANG School of Aeronautic Science and Engineering Beihang University

The objective of this study is to investigate the effects of the Coulomb dry friction model versus the modified Coulomb friction model on the dynamic behavior of the slider-crank mechanism with a revolute clearance joint. The normal and tangential forces acting on the contact points between the journal and the bearing are described by using a Hertzian-based contact force model and the Coulomb friction models, respectively.The dynamic equations of the mechanism are derived based on the Lagrange equations of the first kind and the Baumgarte stabilization method. The frictional force is solved via the linear complementarity problem(LCP) algorithm and the trial-and-error algorithm.Finally, three numerical examples are given to show the influence of the two Coulomb friction models on the dynamic behavior of the mechanism. Numerical results show that due to the stick friction, the slider-crank mechanism may exhibit stick-slip motion and can balance at some special positions, while the mechanism with ideal joints cannot.

关键词： revolute clearance joint slider-crank mechanism stick friction stick-slip linear complementarity problem(LCP)

A generalized approach for implicit time integration of piecewise linear/nonlinear systems

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International Journal of Mechanical System Dynamics 2021年第1期1卷 108-120页

作者： Huimin zhang runsen zhang Andrea Zanoni Pierangelo Masarati School of Aeronautic Science and Engineering Beihang UniversityBeijingChina Dipartimento di Scienze e Tecnologie Aerospaziali Politecnico di MilanoMilanoItaly

A generalized solution scheme using implicit time integrators for piecewise linear and nonlinear systems is developed.The piecewise linear characteristic has been well‐discussed in previous studies,in which the original problem has been transformed into linear complementarity problems(LCPs)and then solved via the Lemke algorithm for each time step.The proposed scheme,instead,uses the projection function to describe the discontinuity in the dynamics equations,and solves for each step the nonlinear equations obtained from the implicit integrator by the semismooth Newton iteration.Compared with the LCP‐based scheme,the new scheme offers a more general choice by allowing other nonlinearities in the governing equations.To assess its performances,several illustrative examples are solved.The numerical solutions demonstrate that the new scheme can not only predict satisfactory results for piecewise nonlinear systems,but also exhibits substantial efficiency advantages over the LCP‐based scheme when applied to piecewise linear systems.

关键词： implicit time integrator piecewise linear and nonlinear systems projection function

Impacts of Transportation Arteries on Land Use Patterns in Urbanrural Fringe: A Comparative Gradient Analysis of Qixia District, Nanjing City, China

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Chinese Geographical Science 2013年第3期23卷 378-388页

作者： zhang runsen PU Lijie ZHU Ming School of Geographic and Oceanographic Sciences Nanjing University Key Laboratory of Land Use Ministry of Land and Resources

Integrated transportation and land use studies are of major interest to planners because they consider the interaction between transportation development and land use change. Quantifying the impact of transport infrastructure on land use change is necessary for evaluating the role of transportation development in the process of land use and land cover change in the urban-rural fringe. Taking Qixia District of Nanjing City, Jiangsu Province, China as a typical urban-rural fringe area, this paper analyzes the patterns and characteristics of land use change along three major transportation arteries using land use data from 2000 and 2008. We examine the spatial differentiation and gradient of land use pattern around railway, expressway, and highway corridors to investigate whether land use change in the urban-rural fringe is related to distance from transportation arteries and to clarify the varying impacts of different forms of transport infrastructure on land use patterns. We find that construction land generally tends to be located close to major transportation arteries, and that railways have the most obvious influence on land use change in the urban-rural fringe, while the impact of expressways was not significant. We conclude that there exists a causal relationship between the presence of transportation arteries and land use change in the urban-rural fringe, but this relationship varies across different types of linear transport infrastructure.

关键词：土地利用方式城乡结合部综合交通梯度分析栖霞区南京市中国土地利用变化

Soil salinization research in China： Advances and prospects

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Journal of Geographical Sciences 2014年第5期24卷 943-960页

作者： LI Jianguo PU Lijie HAN Mingfang ZHU Ming zhang runsen XIANG Yangzhou School of Geographic and Oceanographic Sciences Nanjing University Nanjing 210023 China Key Laboratory of Coastal Zone Exploitation and Protection Ministry of Land and Resources Nanjing210023 China Guizhou Institute of Forest Inventory and Planning Guiyang 550003 China

With the environmental deterioration caused by the advance of climate change, soil salinization is a serious and growing global problem. Currently about 7% of the world＇s land surface is threatened by salinization. China is a country whose soils are severely affected by this problem, which, due to its extensive area, and wide distribution poses a serious threat to regional agricultural development. In this review, we summarize the framework for soil salinization research in China over the past 70 years, assess the weaknesses of existing research in both a domestic and international context, highlight the trends and key findings of global research about saline soils over the past 30 years, and propose six major fields and directions for future research on saline soil.

关键词： saline soil research framework advances prospects

Monitoring Soil Salt Content Using HJ-1A Hyperspectral Data: A Case Study of Coastal Areas in Rudong County, Eastern China

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Chinese Geographical Science 2015年第2期25卷 213-223页

作者： LI Jianguo PU Lijie ZHU Ming DAI Xiaoqing XU Yan CHEN Xinjian zhang Lifang zhang runsen School of Geographic and Oceanographic Sciences Nanjing University Key Laboratory of the Coastal Zone Exploitation and Protection Ministry of Land and Resources School of Public Administration Nanjing University of Finance & Economics

Hyperspectral data are an important source for monitoring soil salt content on a large scale. However, in previous studies, barriers such as interference due to the presence of vegetation restricted the precision of mapping soil salt content. This study tested a new method for predicting soil salt content with improved precision by using Chinese hyperspectral data, Huan Jing-Hyper Spectral Imager(HJ-HSI), in the coastal area of Rudong County, Eastern China. The vegetation-covered area and coastal bare flat area were distinguished by using the normalized differential vegetation index at the band length of 705 nm(NDVI705). The soil salt content of each area was predicted by various algorithms. A Normal Soil Salt Content Response Index(NSSRI) was constructed from continuum-removed reflectance(CR-reflectance) at wavelengths of 908.95 nm and 687.41 nm to predict the soil salt content in the coastal bare flat area(NDVI705 < 0.2). The soil adjusted salinity index(SAVI) was applied to predict the soil salt content in the vegetation-covered area(NDVI705 ≥ 0.2). The results demonstrate that 1) the new method significantly improves the accuracy of soil salt content mapping(R2 = 0.6396, RMSE = 0.3591), and 2) HJ-HSI data can be used to map soil salt content precisely and are suitable for monitoring soil salt content on a large scale.

关键词：东部沿海地区土壤含盐量中国东部地区高光谱数据盐分含量如东县监测数据预测

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浮放物体平面多刚体动力学建模与算法研究

力学学报 2017年第6期49卷 1370-1379页

作者：张润森王琪北京航空航天大学航空科学与工程学院北京100191

采用非光滑多体系统动力学的方法研究浮放物体与基础平台组成的多体系统,建立其非光滑接触的动力学方程与数值算法.浮放物体由主体部分和支撑腿组成,其间通过含黏弹性阻力偶的转动铰连接.支撑腿与基础平台间的接触力简化为接触点的法向... 详细信息

采用非光滑多体系统动力学的方法研究浮放物体与基础平台组成的多体系统,建立其非光滑接触的动力学方程与数值算法.浮放物体由主体部分和支撑腿组成,其间通过含黏弹性阻力偶的转动铰连接.支撑腿与基础平台间的接触力简化为接触点的法向接触力和摩擦力,采用扩展的赫兹接触力模型描述接触点的法向接触力,采用库伦干摩擦模型描述其摩擦力.采用笛卡尔坐标系下的位形坐标作为系统的广义坐标.首先,将基础平台运动看作非定常约束,用第一类拉格朗日方程建立系统的动力学方程,并采用鲍姆加藤约束稳定化的方法解决违约问题.随后给出基于事件驱动法和线性互补方法的数值算法.当相对切向速度为零时,构造静滑动摩擦力的正负余量和正、负向加速度的互补关系,从而将接触点黏滞-滑移切换的判断以及静滑动摩擦力的计算转化为线性互补问题进行求解,并采用Lemke算法求解线性互补问题.最后,通过数值仿真选择合适的步长;通过仿真结果说明浮放物体运动中存在的黏滞-滑移切换现象以及基础平台运动、质心位置对浮放物体运动的影响.

关键词：浮放物体非光滑库伦干摩擦线性互补接触力

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土地利用/覆被变化的大气环境效应研究进展

地域研究与开发 2013年第4期32卷 123-128页

作者：张润森濮励杰刘振南京大学地理与海洋科学学院南京210093 国土资源部土地利用重点实验室北京100029 南京大学大气科学学院南京210093

土地利用/覆被变化是全球环境变化的重要原因,随着气候变化问题的日益突出,土地利用/覆被变化的大气环境效应已成为国内外全球变化的前沿和热点课题。通过对土地利用/覆被变化对大气环境系统的作用机制分析,认为目前土地利用/覆被变化... 详细信息

土地利用/覆被变化是全球环境变化的重要原因,随着气候变化问题的日益突出,土地利用/覆被变化的大气环境效应已成为国内外全球变化的前沿和热点课题。通过对土地利用/覆被变化对大气环境系统的作用机制分析,认为目前土地利用/覆被变化对大气质量、大气污染以及气候变化产生了重要的影响,尤其随着快速城市化进程的推进,带来了显著的城市空气污染和热岛效应,而土地利用/覆被变化在全球尺度上的气候效应则存在较多的争论。今后应加强土地变化科学和大气科学的融合,从多尺度探讨土地利用/覆被变化的大气环境效应,并注重大气环境改善视角下的土地利用策略和空间规划研究。

关键词：土地利用覆被变化大气环境气候效应进展

含摩擦阻尼器非光滑振动系统的建模与数值仿真

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动力学与控制学报 2017年第2期15卷 172-177页

作者：朱琳王琪张润森北京航空航天大学航空科学与工程学院北京100083

研究了含干摩擦粘/弹性构件的两类非光滑减振器的动力学问题.首先,建立了含摩擦粘性构件和含摩擦弹性构件的力学模型,其中摩擦模型采用Coulomb干摩擦模型,不计弹性构件和粘性构件的质量,给出了该构件粘性力和弹性力的计算方法,通过控制... 详细信息

研究了含干摩擦粘/弹性构件的两类非光滑减振器的动力学问题.首先,建立了含摩擦粘性构件和含摩擦弹性构件的力学模型,其中摩擦模型采用Coulomb干摩擦模型,不计弹性构件和粘性构件的质量,给出了该构件粘性力和弹性力的计算方法,通过控制摩擦阻尼器的正压力调整混合阻尼器的粘性力的最大值和弹簧力的最大值.分别建立了含摩擦粘/弹性阻尼器的单自由度和二自由度振动系统的动力学方程,通过数值仿真,首先分析了动、静摩擦系数对含摩擦粘/弹性构件单自由度振动系统动力学特性的影响,然后分析了含摩擦粘/弹性构件二自由度振动系统的动力学特性,仿真结果表明,通过控制摩擦阻尼器受到的的正压力获得更好的减振效果.

关键词：非光滑动力学摩擦阻尼器 Coulomb干摩擦数值仿真

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土壤盐渍化研究现状及未来研究热点

地理学报 2012年第9期67卷 1233-1245页

作者：李建国濮励杰朱明张润森南京大学国土资源与旅游学系南京210093 国土资源部土地利用重点实验室北京100029

随着全球气候暖化问题的日益加剧,土壤盐渍化问题已经成为各国关心的全球性问题,全球约有7%的土地受到盐渍化的威胁,而且这个数字还在上升。我国是土壤盐渍化比较严重的国家,盐渍化土壤面积大,分布广,对区域农业发展构成了严重的威胁。... 详细信息

随着全球气候暖化问题的日益加剧,土壤盐渍化问题已经成为各国关心的全球性问题,全球约有7%的土地受到盐渍化的威胁,而且这个数字还在上升。我国是土壤盐渍化比较严重的国家,盐渍化土壤面积大,分布广,对区域农业发展构成了严重的威胁。本文对70年来我国土壤盐渍化研究的内容框架进行了梳理和概括,并结合国内外的相关研究成果对已有研究中存在的不足进行了评述;借助文献数据库和相关数据共享网络对近30年来国内外盐渍土研究的趋势和总体概况进行了总结,提出了新形势下土壤盐渍化研究的5个重点领域和方向,旨在为今后开展盐渍土研究提供新的思路。

关键词：盐渍土研究进展现状热点