Dynamic Modeling and Analysis of 4UPS-UPU Spatial Parallel Mechanism with Spherical Clearance Joint

Clearance between the moving joints is unavoidable in real working process. At present, many researches are mainly focused on dynamics of plane revolute joint in plane mechanism, but few on dynamics of spatial spherical joint clearance in spatial parallel mechanism. In this paper, a general method is proposed for establishing dynamic equations of spatial parallel mechanism with spatial spherical clearance by Lagrange multiplier method. The kinematic model and contact force model of the spherical joint clearance were established successively. Lagrange multiplier method was used to deduce the dynamics equation of 4 UPS-UPU mechanism with spherical clearance joint systematically. The influence of friction coefficient on dynamics response of 4 UPS-UPU mechanism with spherical clearance joint was analyzed. Non-linear characteristics of clearance joint and moving platform were analyzed by Poincare map, phase diagram, and bifurcation diagram. The results show that variation of friction coefficient and clearance value had little effect on stability of the mechanism, but the chaotic phenomenon was found at spherical clearance joint. The research has theoretical guiding significance for improving the dynamic performance and avoiding of chaos of parallel mechanisms including spherical joint clearance.

Dynamic Modeling of Heterogeneous Spatial Analysis for Energy and Natural Resources in Grid Integration Environment

With the high-tech industrialization of earth observation satellite remote sensing and the implementation of digital earth strategy,the energy and natural resources have been decided to be the key research fields in China.In these fields,from the model based on topology data,through simple feature data model to rule-based data model,the basic spatial analysis algorithms have been developed

Shift-share Analysis on International Tourism Competitiveness——A Case of Jiangsu Province

Shift-share analysis has been confirmed a useful approach in the study of regional economics and many kinds of extended shift-share models have been advanced and put into practice in economic studies, but few have hitherto been introduced and applied to the tourism research in China. Moreover understanding the spatially competitive relationship is of paramount importance for marketers, developers, and planners involved in tourism strategy development. Based on international tourism receipts from 1995 to 2004, this study aims at probing into the spatial competitiveness of interna- tional tourism in Jiangsu Province in comparison with its neighbors by applying a spatially extended shift-share model and a modified dynamic shift-share model. The empirical results illustrate that exceptional years may exist in the ap- plication of dynamic shift-share models. To solve this issue, modifications to dynamic shift-share model are put forward. The analytical results are not only presented but also explained by the comparison of background conditions of tourism development between Jiangsu and its key competitors. The conclusions can be drawn that the growth of international tourism receipts in Jiangsu mainly attributes to the national component and the competitive component and Zhejiang is the most important rival to Jiangsu during the period of 1995-2004. In order to upgrade the tourism competitiveness, it is indispensable for Jiangsu to take proper positioning, promoting and marketing strategies and to cooperate and integrate with its main rivals.

Research on spatial calculating analysis model of landuse change

The spatial calculating analysis model is based on GIS overlay. It will compartmentalize the land in research district into three spatial types: unchanged parts, converted parts and increased parts. By this method we can evaluate the numerical model and dynamic degree model for calculating land-use change rates. Furthermore, the paper raises the possibility of revising the calculating analysis model of spatial information in order to predicate more precisely the dynamic changing level of all types of land uses. In the most concrete terms, the model is used mainly to understand changed area and changed rates (increasing or decreasing) of different land types from microcosmic angle and establish spatial distribution and spatio-temporal principles of the changing urban lands. And we will try to find out why the situation can take place by combining social and economic situations. The result indicates the calculating analysis model of spatial information can derive more accurate procedure of spatial transference and increase of all kinds of land from microcosmic angle. By this model and technology we can conduct the research of land-use spatio-temporal structure evolution more systematically and more deeply, and can obtain a satisfactory result. The result will benefit the rational planning and management of urban land use of developed coastal areas in China in the future.

Dynamic Modeling of Variable Stiffness and Damping for Spatial Linkage Weft Insertion Mechanism with Clearance

In order to further analyze the influence of clearance on the kinematic performance of spatial linkage weft insertion mechanism,it is necessary to study the dynamic characteristics of contact impact force model with the variable stiffness and damping coefficient.Firstly,the parameters in the output process of the system are solved by describing of the flexible joint clearance.Then,based on Lankarani-Nikravesh contact force model,the contact impact stiffness and damping coefficient is modified from fixed values to time-varying coefficients.The dynamic model of spatial linkage weft insertion mechanism with modified clearance is established by Lagrange method,and the dynamic characteristics of the system are calculated.The results show that the joint clearance can directly affect the output performance of the mechanism.With the increase of the clearance value,the curve fluctuations of acceleration,driving torque and collision force are obvious,and it will be further intensified with the increase of spindle speed,which greatly affects the stability of mechanism and fabric quality.Finally,the virtual prototype is established by the SolidWorks software and simulated by the ADAMS software.The simulation results are compared with the numerical results,which verifies the accuracy of the modeling method in this paper.

数字经济对区域经济增长收敛的影响研究

共享型经济的发展对落后地区经济增长和推动共同富裕具有重大意义。本文以2013~2022年长江经济带的110个城市为研究样本,将数字经济纳入空间杜宾模型分析框架,实证考察数字经济对区域经济增长收敛的影响。研究发现:(1)长江经济带城市的经济增长总体上呈明显的收敛态势,数字经济的发展能够显著促进经济增长收敛,且这一结论在替换空间权重矩阵及解释变量后依然成立;(2)长江经济带城市经济增长的收敛性存在一定的空间溢出效应,且数字经济对经济增长收敛的促进作用也存在明显的空间溢出效应;(3)从空间维度来看,数字经济对经济增长收敛的促进作用在长江经济带上游城市影响最大,中游城市次之,下游城市最小;(4)从时间维度来看,2013~2022年期间长江经济带的收敛速度呈现逐步增长的趋势,且数字经济对经济增长收敛的影响具有明显的缓冲期,2016年以后其促进作用才显现出来。

中国开放型经济时空格局演化与影响因素

开放型经济时空格局的研究有利于制定不同类型省份开放型经济发展路径,促进区域间的协调发展.从贸易开放、投资开放和战略耦合3个维度构建开放型经济评价体系,分别采用熵权TOPSIS法、探索性时空数据分析、动态空间面板模型对2001—2021年中国省域开放型经济发展水平、时空格局演化以及影响因素进行分析.结果表明:中国开放型经济发展整体水平提升,但不同地区省份的变化迥异.“东高中西低”的梯度格局被打破,东西协同的“T字型”架构初步建立并稳步提升.开放型经济空间异质性逐渐弱化,空间自相关性更加显著.LISA时间路径相对长度在空间上呈现由沿海沿边向内陆地区递减趋势,LISA时间路径弯曲度呈现从沿边地区到其邻接省份再到沿海和内陆地区依次递减趋势.制度环境、自然资源禀赋、国家优惠政策、基础设施水平、邻接省份效应等因素驱动了开放型经济发展.

基于服务簇的沱江流域生态系统服务权衡/协同关系演变

明确流域生态系统服务簇的时空格局以及簇内生态系统服务动态权衡/协同关系对管理和维持流域生态系统结构与功能的稳定性和可持续性有重要意义。基于InVEST模型、土壤流失方程等方法估算2010、2015、2020年3期沱江流域生态系统服务,并使用K-means聚类识别生态系统服务簇,以服务簇视角衡量服务簇内部主要生态系统服务间动态权衡/协同关系,讨论权衡/协同关系及服务簇的时空变化规律,针对不同簇模式提出相应的分区管控建议。结果表明:(1)2010—2020年沱江流域各生态系统服务空间格局稳定,生态系统服务变化各异。生境质量、产水、固碳服务总量上升,粮食生产、水土保持服务总量下降。固碳、水土保持以及生境质量服务高值区表现为在北部及中北部集中分布,产水服务量由南向北减小,粮食生产服务高值区主要集中于流域中北部和南部耕地区,文化娱乐服务高值区呈现出显著的城市及城市间网络状连接趋势。(2)根据聚类结果将流域划分为5种生态系统服务簇,各簇存在时空异质性。粮食生产簇占比为72.9%,以粮食生产、产水服务为主;生态保育簇占比为15.2%,以生境质量、固碳服务为主;文化娱乐簇占比为6.9%,以文化娱乐服务为主;多功能耦合簇占比为4.4%,以生境质量、固碳、水土保持服务为主;水土保持簇占比为0.5%,以水土保持服务为主。(3)宏观而言,沱江流域整体权衡关系多于协同关系,服务簇内部各服务协同关系多于权衡关系,应因地制宜采取管控措施。不同生态系统服务簇内部各服务权衡/协同关系存在相似与差异性,不同服务簇内各相同服务组合的权衡/协同关系强弱不同,服务簇内部各服务协同关系多于权衡关系,流域整体权衡关系多于协同关系。研究成果可为沱江流域区域未来生态系统管理与优化、生态文明建设及可持续性发展提供科学依据。

空间并联指向机构实验平台动力学建模与仿真分析

为了提高学生的动力学建模和分析能力,基于3自由度3-转动副-转动副-转动副-转动副-转动副(3-RRRRR)空间并联指向机构实验平台,开展动力学建模与仿真分析研究。首先,分析3-RRRRR空间并联指向机构实验平台的结构特征,建立并联指向机构平台的运动学模型;然后,利用拉格朗日乘子法推导并联指向机构平台的刚体动力学模型,基于四阶龙格库塔(Runge-Kutta)算法求解机构平台动力学模型,通过数值仿真分析不同驱动速度对并联指向机构平台动力学响应的影响;最后,采用ADAMS虚拟样机仿真验证动力学模型及模型求解的正确性。该研究为空间并联机构实验平台刚体动力学建模和仿真分析提供了有效方法,为机构动力学分析与控制奠定了理论基础。

消费者考虑集视角下在线品牌动态竞争关系研究

如何根据在线市场消费者客观地考虑集信息研究品牌间动态竞争关系已成为运作管理领域急需解决的关键问题之一.针对该问题,该文首先根据京东网站消费者考虑集信息构建在不同时间窗下品牌间动态竞争关系网络;其次,分别计算在各时间窗竞争关系网络中结构洞及中心性指标;最后,考虑不同时间窗同一品牌竞争强度的相互依赖性,采用空间杜宾模型研究社交网络属性因素对品牌动态竞争强度的影响.研究发现:结构洞和度中心性指标对品牌动态竞争强度具有正向影响,而介数中心性指标对品牌动态竞争强度具有负向影响.基于该研究结果,在进行产品设计时各品牌应注重细分市场产品属性的创新,以增加品牌的动态竞争强度.

智慧城市建设与区域创新——时空效应与机制检验

本文基于中国223个地级市面板数据,采用多期双重差分模型、空间计量模型、中介效应模型以及调节效应模型实证分析智慧城市建设与区域创新的时空效应、作用机制以及异质性约束。研究发现,智慧城市建设可对区域创新产生长期而深远的积极影响,并且试点政策对经济特征相近地区的溢出效应显著为正,但对地理区位相邻城市的空间影响却不明显。机制分析表明,人力资本、科技投入与互联网发展均正向中介试点政策与区域创新的内在联系,并且在三大机制变量的调节作用下,智慧城市建设对区域创新的促进作用还可呈现边际递增的非线性变化趋势。进一步分析显示,智慧城市建设的创新驱动效果在不同城市区位、等级、性质以及规模条件下存在异质性特征,东、中部地区、一二三线城市、非资源型地区、非老工业基地以及大中规模城市的智慧化转型,对区域创新的积极影响更为明显。

A computational fluid dynamics model for wind simulation:model implementation and experimental validation

To provide physically based wind modelling for wind erosion research at regional scale, a 3D computational fluid dynamics (CFD) wind model was developed. The model was programmed in C language based on the Navier-Stokes equations, and it is freely available as open source. Integrated with the spatial analysis and modelling tool (SAMT), the wind model has convenient input preparation and powerful output visualization. To validate the wind model, a series of experiments was con- ducted in a wind tunnel. A blocking inflow experiment was designed to test the performance of the model on simulation of basic fluid processes. A round obstacle experiment was designed to check if the model could simulate the influences of the obstacle on wind field. Results show that measured and simulated wind fields have high correlations, and the wind model can simulate both the basic processes of the wind and the influences of the obstacle on the wind field. These results show the high reliability of the wind model. A digital elevation model (DEM) of an area (3800 m long and 1700 m wide) in the Xilingele grassland in Inner Mongolia (autonomous region, China) was applied to the model, and a 3D wind field has been successfully generated. The clear imple- mentation of the model and the adequate validation by wind tunnel experiments laid a solid foundation for the prediction and assessment of wind erosion at regional scale.

中国水稻生产的时空动态分析

【目的】绘制中国南北稻区不同稻作制度下的水稻播种面积和产量重心变动图,分析成因,找出影响现阶段中国水稻总产稳定的关键因素。【方法】利用重心拟合模型对水稻生产的时空动态进行分析,敏感性分析方法找出该变动背景下影响中国水稻总产稳定的关键因素。【结果】新中国成立以来除20世纪60、70年代中国水稻播种面积重心和产量重心向东南和东部发生偏移以外,总体上向东北方向移动。1979—2009年北方稻重心由华北快速移动到了东北松辽盆地。中稻和一季晚稻重心移动方向为先东北后东南与南方稻作制度"双改单"变化顺序由北向南相吻合。早稻和双季晚稻重心移动方向都为西南。南方稻区单季稻比例明显上升,"双改单"现象明显,这是导致中国水稻种植面积下降的主要原因。结合敏感性分析得出播种面积已成为目前最有可能造成中国水稻总产量大幅下滑的关键因素。【结论】市场机制的调控和技术进步是目前影响中国水稻时空变动的两个主要因素。在继续坚持以市场为指导的前提下,依据国情从粮食安全的角度出发,重点对面积呈下滑趋势的早稻和双季晚稻进行调控,同时兼顾水稻总面积,防止其出现较大波动,努力提高水稻单产,是确保现阶段中国水稻总产稳中有升的关键。

土地利用动态变化的空间分析测算模型

论文首先从土地利用变化的空间涵义出发,细分出未变化部分、转移部分和新增部分等3种空间类型,并据此对现有测算土地利用变化速率的数量分析和动态度模型进行了评析,提出了修正后的空间分析测算模型,旨在更为精细和准确地测算各土地利用类型的动态变化程度;并以北京城市边缘区的土地利用变化作为案例,对3种模型的测算结果进行了比较分析。结果表明:空间分析测算模型由于细分并同时考虑了各土地利用类型的空间转移及新增过程,能更为准确地测算出各种土地利用类型的动态变化程度与速率。

中国西部兰白西城市群经济增长结构分解及空间特征

采用偏离—份额四分量模型,分解2010—2015年兰白西城市群41个县(区)经济增长结构;采用空间数据分析方法,分析41个县(区)经济增长总量及各分量空间特征。结果表明:(1)兰白西城市群呈现以兰州市和西宁市为双核心的"中心—外围"经济结构,兰州市的经济中心地位更为显著。(2)根据经济增长总量及各分量,将兰白西城市群41个县(区)分为经济快速增长型、经济滞后增长型、竞争力优势推动型和资源配置优势推动型等4种类型。(3)经济增长总量、份额偏离分量、产业结构分量在空间上存在集聚性特征,竞争力分量在空间上存在随机分布性特征,资源配置分量在空间上存在负相关性特征。(4)份额偏离分量、产业结构分量与经济增长总量的空间重合度较高,竞争力分量、资源配置分量与经济增长总量的空间重合度有待优化。

植物群落动态的模型分析

植物群落的动态是植物群落学的中心问题之一,包括更新、波动、演替、进化等主要内容。空间格局对种群和群落的动态起着至关重要的作用,种群空间格局和群落空间结构是群落中各种过程相互作用的产物。模型是描述群落动态、认识植物群落组建和维持机理的有效工具。本文阐述和比较了描述群落动态的四种具有代表性的经验模型,即镶嵌循环模型、随意游走模型、同资源种团比例模型、空间抢先占有模型及其机理。四种经验模型的空间性及缺陷分别是:(1)“镶嵌循环模型”考虑到了相邻斑块之间的植被空间结合在群落动态中的作用,而另外三种模型没有考虑到这一点;(2)在一定程度上,四种植物群落动态模型对各自针对的植物群落可能是适合的,但要作为描述群落动态发展的一般性模型还需要不断完善和发展;因为四种模型均没有考虑到自然干扰和人类干扰对植物群落动态的影响。作者对将来植物群落动态的研究及实践意义做出以下展望:(1)在不同空间尺度上,更加有效地评价控制群落动态变化的各种过程的相对重要性,并进一步将它们之间的复杂相互作用整合到群落动态模型中;(2)充分认识植物群落中存在的各种自然环境条件和生物群体的结构配置对植物群落动态发展的重要性;(3)

省级区域旅游产业-社会经济-生态环境耦合协调度空间相关性研究——以广西为例

构建了广西旅游产业-社会经济-生态环境耦合协调度评价指标体系,计算广西各地级市的耦合协调度,引入ESDA方法及灰色预测模型进行空间相关性研究与模拟预测.结果表明,全局空间自相关为负自相关关系,空间单元为离散状态并逐步向随机状态转化;Moran散点图与LISA聚集图显示的局部空间自相关关系中,空间关联特征主要表现为"高低(HL)"和"低高(LH)"两种模式,南宁、来宾通过显著性检验.近期耦合协调发展水平趋势稳定,但整体水平不高,导致整体空间关联格局不会产生根本性变化.

动态偏离-份额分析空间模型及湖北产业竞争力分析

传统动态偏离-份额分析只简单分析国家对研究区域发展的影响，认为研究区域和该国内的其他区域是孤立的。动态偏离-份额分析空间模型在传统动态偏离-份额分析模型的基础上，引入了区域与邻近区域之间存在空间相互作用的思想，同时考虑国家、邻近区域对研究区域的综合作用。对动态偏离-份额分析空间模型进行介绍，将其应用到湖北2001～2008年各产业经济增长分析中，对比偏离-份额分析传统模型和空间模型结果中的竞争偏离分量，进而提出提高湖北产业竞争力的建议。

散乱数据点云型面特征分析算法的研究与应用

提出一种产品散乱数据点云型面特征快速分析算法。该算法基于R*-tree动态空间存取模型,能快速、准确地获取点云局部型面参考数据,并采用最小面积包围矩形法对其进行参数化;以自由曲面逼近产品局部型面,估算数据点云型面曲率值;将点云型面曲率映射为RGB颜色值,以曲率云图反映产品型面特征分布。该算法运行效率高,产品数据适应性强,型面特征分析结果准确。

磁流变阻尼器受控框架结构的空间杆系计算模型

为了分析加入磁流变阻尼器(MRD)框架结构的多维减震性能和扭转振动特性,基于杆系模型建立了MRD受控框架结构的空间杆系计算模型。以十层钢筋混凝土(RC)框架结构为例,采用Matlab软件开发了无控和MRD受控RC框架结构的空间杆系计算模型程序,在地震荷载作用下分别进行了动力时程分析,对未控和有控下框架典型节点X、Y、Z向的位移、加速度时程响应和结构的空间扭转振动响应进行了对比。结果表明,MRD可有效减小RC框架结构的多维位移和加速度时程响应,若阻尼器位置设置不当,将会增大结构的扭转振动响应。结果验证了MRD受控框架结构的空间杆系计算模型及其Matlab程序的正确性和有效性。