检索结果-南通市图书馆

Preconditioned pseudo-compressibility methods for incompressible Navier-Stokes equations

中国科学：物理学、力学、天文学英文版 2010年第11期53卷 2090-2102页

作者： QIAN ZhanSen ,zhang JingBai & LI ChunXuan school of Aeronautics Science and Engineering,Beihang{{2.,Beijing 100191,china school of Aeronautics Science and Engineering Beihang University Beijing China

This paper investigates the pseudo-compressibility method for the incompressible Navier-Stokes equations and the preconditioning technique for accelerating the time marching for stiff hyperbolic equations,and derives and presents the eigenvalues and eigenvectors of the Jacobian matrix of the preconditioned pseudo-compressible Navier-Stokes equations in generally cur-vilinear *** on the finite difference discretization the cored for efficiently solving incompressible flows numerically is *** reliability of the procedures is demonstrated by the application to the inviscid flow past a circular cylinder,the laminar flow over a flat plate,and steady low Reynolds number viscous incompressible flows past a circular *** is found that the solutions to the present algorithm are in good agreement with the exact solutions or experimental *** effects of the pseudo-compressibility factor and the parameter brought by preconditioning in convergence characteristics of the solution are investigated *** results show that the upwind Roe’s scheme is superior to the second order central scheme,that the convergence rate of the pseudo-compressibility method can be effectively improved by preconditioning and that the self-adaptive pseudo-compressibility factor can modify the numerical convergence rate significantly compared to the constant form,without doing artificial tuning depending on the specific flow *** validation is also performed by numerical simulations of unsteady low Reynolds number viscous incompressible flows past a circular *** results are also found in good agreement with the existing numerical results or experimental data.

关键词： pseudo-compressibility method preconditioning upwind scheme incompressible flow Navier-Stokes equations

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Magnetism of NaYbS_(2.:From finite temperatures to ground state

引用

Science china(Physics,Mechanics & Astronomy) 2024年第10期67卷 92-104页

作者： Weizhen Zhuo Zheng zhang Mingtai Xie Anmin zhang Jianting Ji Feng Jin Qingming zhang school of Physical Science and Technology Lanzhou UniversityLanzhou 730000China Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China

Rare-earth chalcogenide compounds ARECh_(2.(A=alkali or monovalent metal,RE=rare earth,Ch=O,S,Se,Te)are a large family of quantum spin liquid(QSL)candidate ***2.s a representative member of the *** key issues on NaYbS_(2.,particularly how to determine the highly anisotropic spin Hamiltonian and describe the magnetism at finite temperatures and the ground state,remain to be *** this paper,we conducted an in-depth and comprehensive study on the magnetism of NaYbS_(2. from finite temperatures to the ground ***,we successfully detected three crystalline electric field(CEF)excitation energy levels using low-temperature Raman scattering *** them with the CEF theory and magnetization data,we worked out the CEF parameters,CEF energy levels,and CEF *** further determined a characteristic temperature of~40 K,above which the magnetism is dominated by CEF excitations while below which the spinexchange interactions play a main *** characteristic temperature has been confirmed by the temperature-dependent electron spin resonance(ESR)***-temperature ESR experiments on the dilute magnetic doped crystal of NaYb_(0.1)Lu_(0.9)S_(2. further helped us to determine the accurate ***,we quantitatively obtained the spin-exchange interactions in the spin Hamiltonian by consistently simulating the magnetization and specific heat ***,the above studies allow us to explore the ground state magnetism of NaYbS_(2. by using the density matrix renormalization *** combined numerical calculations and experimental results to demonstrate that the ground state of NaYbS_(2. is a Dirac-like QSL.

关键词： rare-earth chalcogenide anisotropic spin Hamiltonian quantum spin liquid

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

A Survey on Blockchain-Based Federated Learning:Categorization,Application and Analysis

引用

computer Modeling in Engineering & Sciences 2024年第6期139卷 2451-2477页

作者： Yuming Tang Yitian zhang Tao Niu Zhen Li Zijian zhang Huaping Chen Long zhang school of Cyberspace Science&Technology Beijing Institute of TechnologyBeijing100081China school of computer Science&Technology Beijing Institute of TechnologyBeijing100081China Southeast Institute of Information Technology Beijing Institute of TechnologyPutian351100China Qianxin Technology Group Co. Ltd.Beijing100044China

Federated Learning(FL),as an emergent paradigm in privacy-preserving machine learning,has garnered significant interest from scholars and engineers across both academic and industrial *** its innovative approach to model training across distributed networks,FL has its vulnerabilities;the centralized server-client architecture introduces risks of single-point ***,the integrity of the global model—a cornerstone of FL—is susceptible to compromise through poisoning attacks by malicious *** attacks and the potential for privacy leakage via inference starkly undermine FL’s foundational privacy and security *** these reasons,some participants unwilling use their private data to train a model,which is a bottleneck in the development and industrialization of federated *** technology,characterized by its decentralized ledger system,offers a compelling solution to these *** inherently prevents single-point failures and,through its incentive mechanisms,motivates participants to contribute computing ***,blockchain-based FL(BCFL)emerges as a natural progression to address FL’s *** study begins with concise introductions to federated learning and blockchain technologies,followed by a formal analysis of the specific problems that FL *** discusses the challenges of combining the two technologies and presents an overview of the latest cryptographic solutions that prevent privacy leakage during communication and incentives in *** addition,this research examines the use of BCFL in various fields,such as the Internet of Things and the Internet of ***,it assesses the effectiveness of these solutions.

关键词： Federated learning blockchain privacy-preserving

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

OPTIMAL CONTROL APPLIED IN AUTOMATIC CLUTCH ENGAGEMENTS OF VEHICLES

引用

Chinese Journal of Mechanical Engineering 2004年第2期17卷 280-283页

作者： Sun Chengshun zhang Jianwu school of Mechanical and Power Engineering,Shanghai Jiaotong{{2.,Shanghai {2.0030, china school of Mechanical and Power Engineering Shanghai Jiaotong University 上海 200030

Start-up working condition is the key to the research of optimal engagementof automatic clutch for AMT. In order to guarantee an ideal dynamic performance of the clutchengagement, an optimal controller is designed by considering throttle angle, engine speed, gearratio, vehicle acceleration and road condition. The minimum value principle is also introduced toachieve an optimal dynamic performance of the nonlinear system compromised in friction plate wearand vehicle drive quality. The optimal trajectory of the clutch engagement can be described in theform of explicit and analytical expressions and characterized by the deterministic and accuratecontrol strategy in stead of indeterministic and soft control techniques which need thousands ofexperiments. For validation of the controller, test work is carried out for the automated clutchengagements in a commercial car with an traditional mechanical transmission, a hydraulic actuator, agroup of sensors and a portable computer system. It is shown through experiments that dynamicbehaviors of the clutch engagement operated by the optimal control are more effective and efficientthan those by fuzzy control.

关键词： Automatic clutch Optimal control Nonlinear system dynamics

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

缆索涂装机器人模糊故障树分析

引用

上海交通大学学报 2003年第Z1期37卷 62-65页

作者：张家梁吕恬生东华大学机械工程学院上海200051 上海交通大学机械与动力工程学院上海200030

根据研制的缆索涂装机器人高可靠性要求,建立了以机器人不能完成高空爬升和涂装作业任务为顶事件的故障树,基于各底事件故障发生概率为三角形模糊数情况对故障树进行了模糊分析,并采用模糊数中值法计算各基本事件模糊重要度.故障树分析... 详细信息

根据研制的缆索涂装机器人高可靠性要求,建立了以机器人不能完成高空爬升和涂装作业任务为顶事件的故障树,基于各底事件故障发生概率为三角形模糊数情况对故障树进行了模糊分析,并采用模糊数中值法计算各基本事件模糊重要度.故障树分析对该机器人成功进行现场试验提供了指导作用.

关键词：模糊可靠性故障树分析重要度分析机器人缆索涂装机器人

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

五杆式人机合作机器人控制策略仿真研究

引用

系统仿真学报 2008年第20期20卷 5596-5599页

作者：路敦民张立勋杨向东陈恳北京林业大学工学院北京100083 哈尔滨工程大学机电工程学院黑龙江哈尔滨150001 清华大学精仪系北京100084

轨迹控制策略是人机合作机器人实现人机合作的重要条件。介绍了五杆Cobot的机构及其控制系统,提出了基于速度约束和位置约束的人机合作机器人轨迹控制策略,建立了相应的控制模型。两种控制策略均具有被动和约束的特征,主要区别是产生控... 详细信息

轨迹控制策略是人机合作机器人实现人机合作的重要条件。介绍了五杆Cobot的机构及其控制系统,提出了基于速度约束和位置约束的人机合作机器人轨迹控制策略,建立了相应的控制模型。两种控制策略均具有被动和约束的特征,主要区别是产生控制量的方法不同。利用MATLAB对两种控制策略跟踪直线和圆弧轨迹进行了仿真,结果表明,两种控制策略均可实现人机合作的要求,但位置约束控制策略轨迹约束精度更高一些。

关键词：人机合作机器人虚拟轨迹控制控制策略速度约束位置约束

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Decentralized Control for Similar Composite Systems with Interconnections Satisfying Interconnected Condition

引用

Systems Science and Systems Engineering 2000年第3期10卷 272-279页

作者： WANG zheng 1,\ LI Zhong\|hai 1,\ zhang Si\|ying 1,\ HOU Xue\|zhang {{2..{2. of Information Science and Information Engineering, Northeastern university, Shenyang 110006, china {2.Mathematics Department,Towson university,Baltimore, Maryland {2.

In this paper, a class of similar composite systems is discussed, and the interconnections in such systems may be asymmetrical and mismatched. To make full use of the interconnections, the two steps method is proposed to design the decentralized controllers. First step: design unreal interconnections to change the system into new form with matched condition; second step: design the decentralized controllers by the regular method for the new system. The controllers we have guarantee the system quadratic stability.

关键词： similar composite system interconnection condition robust decentralized control

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

一种简化的巴斯德毕赤酵母基本培养基

引用

微生物学通报 2009年第12期36卷 1935-1937页

作者：孔艺萌孔庆忠山东大学生命科学学院山东济南250100 山东蓝金生物工程有限公司山东济南250100

通过逐步减少巴斯德毕赤酵母基本培养基中生长因子和微量元素的组成种类,最终确认维持巴斯德毕赤酵母在平板上的生长,除生物素外其它生长因子和微量元素不必额外添加。据此提出了一种简化的巴斯德毕赤酵母基本培养基SPMD,其成分为6种无... 详细信息

通过逐步减少巴斯德毕赤酵母基本培养基中生长因子和微量元素的组成种类,最终确认维持巴斯德毕赤酵母在平板上的生长,除生物素外其它生长因子和微量元素不必额外添加。据此提出了一种简化的巴斯德毕赤酵母基本培养基SPMD,其成分为6种无机盐、生物素和葡萄糖。除葡萄糖单独灭菌外,配制时可以高温高压灭菌。使用该培养基用于转化子的筛选实验中,获得了与使用常规MD培养基基本相当的转化效率。

关键词：巴斯德毕赤酵母基本培养基转化

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Spatial evolution and spatial production of traditional villages from "backward poverty villages" to "ecologically well-off villages": Experiences from the hinterland of national nature reserves in china

引用

Journal of Mountain Science 2024年第4期21卷 1100-1118页

作者： zhang Yiyi LI Yangbing College of Geography and Environmental Sciences Guizhou Normal UniversityGuiyang 550001China

With the rapid urbanization process,the space of traditional villages in china is undergoing significant *** the spatial evolution of traditional villages is significant in promoting rural spatial transformation and realizing rural revitalization and sustainable rural *** on the traceability analysis of spatial production theory,this paper constructed an analytical framework for the spatial production evolution of traditional villages,analyzed the spatial evolution process and characteristics of traditional villages by using buffer analysis,spatial syntax,and other research methods,and revealed the characteristics of the spatial production evolution of traditional villages and the driving *** results show that:(1)The village spatial formation and development follow the village life cycle theory and usually develop from embryonic villages to diversified and integrated villages;(2.The evolution of village spatial production is characterized by the diversity of material space,the sublimation of daily life space,and the integration of social system space and generalization of emotional space;(3)The evolution of village spatial production from backward and poor village to ecologically well-off village is influenced by a combination of factors;(4)The village has formed a spatial structure of"people-land-scape-culture-industry",realized comprehensive reconstruction and spatial *** study results reflect the spatial evolution characteristics of traditional villages in mountainous areas in a more comprehensive way,which helps to promote the protection and development of traditional villages in mountainous areas and,to a certain extent,provides a reference for the development of rural revitalization.

关键词： Traditional villages Spatial production Spatial evolution Spatial reconstruction

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Impact of Long-term Exposure to Air Particulate Matter on Life Expectancy and Survival Rate of Shanghai Residents

引用

Biomedical and Environmental Sciences 2002年第3期15卷 209-214页

作者： KAN HAI-DONG1 AND CHEN BING-HENG Department of Environmental Health, school of Public Health, Fudan university, Shanghai {2.003{2.{{2. Department of Environmental Health School of Public Health Fudan University 上海 200032

Objective To evaluate the impact of long-term air particulate matter exposure on the life expectancy and survival rate of Shanghai residents. Methods Epidemiology - based exposure-response function was used for the calculation of attributable deaths to air particulate matter in Shanghai, and the effect of long-term exposure to particulate matter on life expectancy and survival rate was estimated using the life table of Shanghai residents in 1999. Results It was shown that in 1999, the long-term air particulate matter exposure caused 1.34-1.69 years reduction of life expectancy and a decrease of survival rate for each age group of Shanghai residents. Conclusion The effect of long-term exposure to air particulate matter on life expectancy is substantial in Shanghai.

关键词： Particulate matter Life expectancy Survival rate Shanghai

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：