Future space missions demand operations on large flexible structures,for example,space webs,the lightweight cable nets deployable in space,which can serve as platforms for very large structures or be used to capture o...Future space missions demand operations on large flexible structures,for example,space webs,the lightweight cable nets deployable in space,which can serve as platforms for very large structures or be used to capture orbital objects.The interest in research on space webs is likely to increase in the future with the development of promising applications such as Furoshiki sat-ellite of JAXA,Robotic Geostationary Orbit Restorer (ROGER) of ESA and Grapple,Retrieve And Secure Payload (GRASP) of NASA.Unlike high-tensioned nets in civil engineering,space webs may be low-tensioned or tensionless,and extremely flexible,owing to the microgravity in the orbit and the lack of support components,which may cause computational difficulties.Mathematical models are necessary in the analysis of space webs,especially in the conceptual design and evaluation for prototypes.A full three-dimensional finite element (FE) model was developed in this work.Trivial truss elements were adopted to reduce the computational complexity.Considering cable is a compression-free material and its tensile stiffness is also variable,we introduced the cable material constitutive relationship to work out an accurate and feasible model for prototype analysis and design.In the static analysis,the stress distribution and global deformation of the webs were discussed to get access to the knowledge of strength of webs with different types of meshes.In the dynamic analysis,special attention was paid to the impact problem.The max stress and global deformation were investigated.The simulation results indicate the interesting phenomenon which may be worth further research.展开更多
城市滨水空间作为城市设计的主要组成部分,对提升居民生活质量、延续城市精神文脉、推动城市经济发展具有重要意义。为探究近年来城市设计过程中国内外滨水空间的研究进展与方向,运用Cite Space文献计量软件,以Web of Science及CNKI核...城市滨水空间作为城市设计的主要组成部分,对提升居民生活质量、延续城市精神文脉、推动城市经济发展具有重要意义。为探究近年来城市设计过程中国内外滨水空间的研究进展与方向,运用Cite Space文献计量软件,以Web of Science及CNKI核心数据库为基础,通过梳理1999年至2023年国内外滨水空间相关文献,对国内外滨水空间研究现状、热点、前沿与主题4个方面进行综合分析,进而从研究内容、视角、方法、机制4个方面对未来国内外滨水空间的相关研究提出建议。研究结果表明,国内外发文量整体呈上升趋势,且均以滨水区的更新改造及生态系统修复为热点议题。此外,国内有关滨水区的相关研究注重对国外滨水区开发经验的总结,而国外则更注重对滨水空间发展效应及管理机制的探讨。展开更多
Deep Web自动分类是建立深网数据集成系统的前提和基础。提出了一种基于领域特征文本的Deep Web分类方法。首先借助本体知识对表达同一语义的不同词汇进行了概念抽象,进而给出了领域相关度的定义,并将其作为特征文本选择的量化标准,避...Deep Web自动分类是建立深网数据集成系统的前提和基础。提出了一种基于领域特征文本的Deep Web分类方法。首先借助本体知识对表达同一语义的不同词汇进行了概念抽象,进而给出了领域相关度的定义,并将其作为特征文本选择的量化标准,避免了人为选取的主观性和不确定性;在接口向量模型构建中,考虑了不同特征文本对于分类作用的差异,提出了一种改进的W-TFIDF权重计算方法;最后采用KNN算法对接口向量进行了分类。对比实验证明,利用所提方法选择的特征文本是准确有效的,新的特征文本权重计算方法能显著地提高分类精度,且在KNN算法中表现出较好的稳定性。展开更多
基于Matlab Web Server和WWW构建了空间虚拟实验室(VLSP),并简单介绍了数据分析系统。通过一个具体的电流片结构分析事例阐述了电流片结构分析模块的具体实现。应用该系统具体分析了2003年8月6日Cluster卫星观测到的重联耗散区附近的电...基于Matlab Web Server和WWW构建了空间虚拟实验室(VLSP),并简单介绍了数据分析系统。通过一个具体的电流片结构分析事例阐述了电流片结构分析模块的具体实现。应用该系统具体分析了2003年8月6日Cluster卫星观测到的重联耗散区附近的电流片结构。该系统具有良好的实用性和可扩展性,极大地方便了科研人员的研究工作。展开更多
文摘Future space missions demand operations on large flexible structures,for example,space webs,the lightweight cable nets deployable in space,which can serve as platforms for very large structures or be used to capture orbital objects.The interest in research on space webs is likely to increase in the future with the development of promising applications such as Furoshiki sat-ellite of JAXA,Robotic Geostationary Orbit Restorer (ROGER) of ESA and Grapple,Retrieve And Secure Payload (GRASP) of NASA.Unlike high-tensioned nets in civil engineering,space webs may be low-tensioned or tensionless,and extremely flexible,owing to the microgravity in the orbit and the lack of support components,which may cause computational difficulties.Mathematical models are necessary in the analysis of space webs,especially in the conceptual design and evaluation for prototypes.A full three-dimensional finite element (FE) model was developed in this work.Trivial truss elements were adopted to reduce the computational complexity.Considering cable is a compression-free material and its tensile stiffness is also variable,we introduced the cable material constitutive relationship to work out an accurate and feasible model for prototype analysis and design.In the static analysis,the stress distribution and global deformation of the webs were discussed to get access to the knowledge of strength of webs with different types of meshes.In the dynamic analysis,special attention was paid to the impact problem.The max stress and global deformation were investigated.The simulation results indicate the interesting phenomenon which may be worth further research.
文摘城市滨水空间作为城市设计的主要组成部分,对提升居民生活质量、延续城市精神文脉、推动城市经济发展具有重要意义。为探究近年来城市设计过程中国内外滨水空间的研究进展与方向,运用Cite Space文献计量软件,以Web of Science及CNKI核心数据库为基础,通过梳理1999年至2023年国内外滨水空间相关文献,对国内外滨水空间研究现状、热点、前沿与主题4个方面进行综合分析,进而从研究内容、视角、方法、机制4个方面对未来国内外滨水空间的相关研究提出建议。研究结果表明,国内外发文量整体呈上升趋势,且均以滨水区的更新改造及生态系统修复为热点议题。此外,国内有关滨水区的相关研究注重对国外滨水区开发经验的总结,而国外则更注重对滨水空间发展效应及管理机制的探讨。
文摘基于Matlab Web Server和WWW构建了空间虚拟实验室(VLSP),并简单介绍了数据分析系统。通过一个具体的电流片结构分析事例阐述了电流片结构分析模块的具体实现。应用该系统具体分析了2003年8月6日Cluster卫星观测到的重联耗散区附近的电流片结构。该系统具有良好的实用性和可扩展性,极大地方便了科研人员的研究工作。
