检索结果-南通市图书馆

Bootstrap Algebraic Multigrid: Status Report, Open Problems, and Outlook

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

Numerical Mathematics(Theory,Methods and Applications) 2015年第1期8卷 112-135页

作者： Achi Brandt James Brannick Karsten Kahl ira livshits Department of Applied Mathematics&Computer Science The Weizmann Institute of Science76100 RehovotIsrael Department of Mathematics The Pennsylvania State UniversityUniversity ParkPA 16802USA Department of Mathematics University of WuppertalWuppertalGermany Department of Mathematical Sciences Ball State UniversityMuncieIN 47306USA

This paper provides an overview of the main ideas driving the bootstrap algebraic multigrid methodology,including compatible relaxation and algebraic dis-tances for defining effective coarsening strategies,the least squares method for com-puting accurate prolongation operators and the bootstrap cycles for computing the test vectors that are used in the least squares process.We review some recent re-search in the development,analysis and application of bootstrap algebraic multigrid and point to open problems in these areas.Results from our previous research as well as some new results for some model diffusion problems with highly oscillatory diffusion coefficient are presented to illustrate the basic components of the BAMG algorithm.

关键词： Bootstrap algebraic multigrid compatible relaxation algebraic distance least squares interpolation

Thermoviscoelastic Analysis of Stress in Composite Structures Micro-to-Structural Approach

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

Transactions of Nanjing University of Aeronautics and Astronautics 2014年第2期31卷 191-194页

作者： Liri Shemesh Jacob Aboudi Rami Eliasi David livshits Department of Mechanical Engineering Tel Aviv University Israel Israel Military Industries Ltd. Israel

Manufacturing of composite materials is usually accompanied with residual stresses.These stresses should be evaluated and assessed.To this end,a micromechanical model for periodic material whose temperature dependent constituents behave as thermorheologically complex materials(TCM)has been developed.This model,referred as the high fidelity generalized method of cells(HFGMC),takes into account the detailed interaction between the fiber and resin,their volume ratios,the fibers distribution and their waviness.This model is linked,in conjunction with a special UMAT subroutine,to the ABAQUS finite element code for prediction of the response of thermoviscoelastic composite structures during cool down process.The present investigation shows the effect of the cool down rate on the residual stress developed in the composite cylindrical structures.

关键词： cool down thermorheologically complex materials(TCM) epoxy high fidelity generalized method of cells(HFGMC) finite element method(FEM)

Advanced Polymer Electrolytes for High-energy-density Power Sources

在线全文

学校读者我要写书评

暂无评论

复旦学报（自然科学版） 2005年第5期44卷 670-671页

作者： D. Golodnitsky E. livshits R. Kovarsky E. Peled School of Chemistry Tel Aviv UniversityTel Aviv 69978Israel

The preparation of highly controlled thin films of lithium ion conducting organic materials is becoming a challenging but rewarding goal in view of obtaining high-performance technological devices like solid-state polymer batteries and capacitors. The classical polymer electrolyte consists of organic macromolecules (usually polyether polymer) that are doped with inorganic (typically lithium) salts. Poly(ethylene oxide) (PEO) is the most commonly employed polymer in PEs because of the peculiar array in the (-CH2-CH2-O-)n chain providing the ability to solvate low-lattice-energy lithium salts. For three decades the major research attention was focused on amorphous polymer electrolytes in the belief that ionic conductivity occurs in a manner somewhat analogous to gas diffusion through polymer membranes. Segmental motion of the polymer chains continuously creates free volume, into which the ions migrate, and this process allows ions to progress across the electrolyte. Such a view was established by a number of experiments, and denied the possibility of ionic conductivity in crystalline polymer phases. This concept has been recently overturned by our group, demonstrating that conductivity comes about as a result of permanent conducting pathways for the movement of ions.

关键词：锂电池聚合体电解液电化学高能密度

研究程度低的含油气盆地中油气田数量或然性特征的评价

在线全文

学校读者我要写书评

暂无评论

新疆石油地质 2006年第5期27卷 633-642页

作者： В.Р.里伏什茨俄罗斯科学院西伯利亚分院石油与天然气研究所俄罗斯新西伯利亚630090

用维布尔分布法逼近含油气盆地中油气田的总数量。采用了反映油田数量的统计学特征与帕列托截断分布参数有关的公式。介绍了在已查明的几个大型油气田储量的基础上,计算油气田数量的方法,并确定了它们的统计学特征。

关键词：含油气盆地原始地质资源帕列托分布油气田数量概率蒙特卡洛法

在线全文

学校读者我要写书评

暂无评论

微积分的再思考

数学的实践与认识 2009年第11期39卷 211-216页

作者：米哈伊·列夫舍茨麻省剑桥02138 美国

基于代数和显式一致估计的微积分思想可以追溯到前牛顿时代,或者欧拉和拉格朗日.由于所涉及的数学非常简单,新的方法可以从一些简单的例子出发,直接、自然却严格地建立微分和积分的流线型理论,并不需要连续性、极限和紧性的概念.

关键词：微积分简化代数流线型理论

1.3 μm InGaAsN/ GaAs Lasers Grown by MOCVD Using TBAs and DMHy Sources

在线全文

学校读者我要写书评

暂无评论

光学学报 2003年第S1期23卷 325-326页

作者： Gray Lin C. M. Lu C. H. Chiou I. F. Chen T. D. Lee J. Y. Chi D.A. livshits Industrial Technology Research Institute Hsinchu 310 TaiwanIndustrial Technology Research Institute Hsinchu 310 TaiwanIndustrial Technology Research Institute Hsinchu 310 TaiwanIndustrial Technology Research Institute Hsinchu 310 TaiwanIndustrial Technology Research Institute Hsinchu 310 TaiwanIndustrial Technology Research Institute Hsinchu 310 TaiwanA. F. loffe Physico Technical Institute St. Petersburg 194021 Russia

We have demonstrated InGaAsN/ GaAs single quantum well (SQW) lasers grown by MOCVD using TBAs and DMHy sources. For un-buffer-strained InGaAsN/GaAs system, our SQW lasers of 1.3μm range is among the best in terms of ... 详细信息

关键词： GaAs Lasers Grown by MOCVD Using TBAs and DMHy Sources in as have MOCVD m InGaAsN by

在线全文

学校读者我要写书评

暂无评论

汽轮发电机定子现场更新改造技术创新

国外大电机 2015年第1期 64-67页

作者： A.L. livshits 赵海军

近年来统计数据表明：定子铁心对大型汽轮发电机使用寿命和可靠性起决定性作用。其主要的问题如下：-压圈的紧固螺母松动；-拉紧螺杆尾部螺纹部分断裂；-定子铁心顶部拉紧螺杆径向连接处松动，齿部有效硅钢片悬臂部分断裂；-因压指绝缘... 详细信息

近年来统计数据表明：定子铁心对大型汽轮发电机使用寿命和可靠性起决定性作用。其主要的问题如下：-压圈的紧固螺母松动；-拉紧螺杆尾部螺纹部分断裂；-定子铁心顶部拉紧螺杆径向连接处松动，齿部有效硅钢片悬臂部分断裂；-因压指绝缘套磨损和铁心边段胶粘破坏而产生局部过热。这些问题会造成定子绕组的重大事故。由于降低定子运行可靠性而需在工厂进行昂贵维修或者定子因超出其所预算的寿命期限（获者定子铁心的服务能力）而需在现场重新更换。对于定子铁心的动力恢复过程有一种误解。尽管在一些领军公司在定子铁心与绕组的装配中应用“短期更换法”，争议的原因仍不明了。我们已经进行了大量的统计资料分析，认为最重要的发现是定子轴向振动的最新测量和在大型汽轮发电机在安装现场定子铁心的各种机械应力。最新的研究发现存在争议的主要原因在于定子铁心受力过程的误解。研究发现，在定子铁心中存在与气隙磁拉力同样大小的复杂内力。因此设计大型汽轮发电机时应考虑这些力的存在。这些电磁（＂ponderomotoric＂）力是电流相互作用的结果。根据传统理论，在空心线圈的电流具有轴向推力和径向拉力的特性。同样的现象存在于由安培流作用于铁磁性材料所产生的磁通量。结果在铁磁性材料内部产生了相同方向的内部压力。其大小与磁感的平方成正比。这些压力的交替变换频率是交变感应电流变换频率的三倍多。由于共振，这些轴向电．机械力对汽轮发电机带来不良的影响，在运行过程中导致铁心叠装压力下降。这些有害的机械振动是上述所列缺陷产生的原因。对于大多数运行中的发电机，在电厂的更新改造过程中都可以实施必要的技术改进。本文提出了状态评估和现代化升级改造的新方法，并将此方法实施在大型汽轮发电机的进一步技术维护上。这些创新实践大大提高了目前正在运行的发电机运行的可靠性指标和使用寿命。

关键词：汽轮发电机定子更新改造创新方法