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21.
输电线路覆冰对电力系统安全运行具有严重威胁,目前已经发展了多种防冰除冰方法,但每种方法都有其局限性,对于一些具有微气象、微地形特征的重覆冰地区尚未有较好的解决方法。文中考虑到扩径导线的特点和分裂导线输电线路的局限性,根据波阻抗和自然功率将分裂导线等效为单导线,并考虑电流的集肤效应,得到了等效的单根扩径导线,进而分析比较覆冰地区的分裂导线及其等效的单根扩径导线的表面电场特性。研究表明:等效前后导线截面面积相同且波阻抗一致时,扩径导线与分裂导线相比,不仅显著降低了子导线根数和输电线路的覆冰荷载,而且在扩径导线的半径等于分裂导线的等效单导线半径时,扩径导线的表面最大电场强度小于分裂导线。因此,在严重覆冰地区,采用分裂导线等效半径的扩径导线具有非常好的表面电场特性,且可显著降低冰风荷载,提高抗冰强度。 相似文献
22.
洪勇 《四川师范大学学报(自然科学版)》1998,21(6):620-623
利用向量形式的微分中值定理,把一阶微分中值定理推广到全新的高阶微分中值定理,并研究了它的应用. 相似文献
23.
Xiaohuan Mo 《科学通报(英文版)》1998,43(6):447-447
The history of Finsler geometry is reviewed and briefly recent development in Finsler geometry and its application is completed
systematically. Furthermore, an interesting open problem has been proposed in this field. 相似文献
24.
James Belak 《Theoretical chemistry accounts》1993,84(4-5):315-323
Recent developments in microprocessor technology have led to performance on scalar applications exceeding traditional supercomputers. This suggests that coupling hundreds or even thousands of these killer-micros (all working on a single physical problem) may lead to performance on vector applications in excess of vector supercomputers. Also, future generation killer-micros are expected to have vector floating point units as well. The purpose of this paper is to present an overview of the parallel computing environment at Lawrence Livermore National Laboratory. However, the perspective is necessarily quite narrow and most of the examples are taken from the author's implementation of a large-scale molecular dynamics code on the BBN-TC2000 at LLNL. Parallelism is achieved through a geometric domain decomposition — each processor is assigned a distinct region of space and all atoms contained therein. As the atomic positions evolve, the processors must exchange ownership of specific atoms. This geometric domain decomposition proves to be quite general and we highlight its application to image processing and hydrodynamics simulations as well.Work performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under contract No. W-7405-ENG-48 相似文献
25.
In this paper, we present a general scheme for bundle-type algorithms which includes a nonmonotone line search procedure and for which global convergence can be proved. Some numerical examples are reported, showing that the nonmonotonicity can be beneficial from a computational point of view.This work was partially supported by the National Research Program on Metodi di ottimizzazione per le decisioni, Ministero dell' Universitá e della Ricerca Scientifica e Tecnologica and by ASI: Agenzia Spaziale Italiana. 相似文献
26.
27.
28.
Ludovic Jullien Jean-Marie Lehn 《Journal of inclusion phenomena and macrocyclic chemistry》1992,12(1-4):55-74
An approach to a transmembrane cation channel is described. It is based on the grafting of oxygen bearing side-chains on a macrocyclic polyether unit that constitutes the organizing core. The resulting species has a structure of overall bouquet shape. The synthesis of such a molecule .
M
0
,14a is described, together with that of its analogue bearing polymethylene side-chains
M
C
,14b. The physicochemical properties of these molecules indicate that they possess the features expected on the basis of their structure.This paper is dedicated to the memory of the late Dr C. J. Pedersen. 相似文献
29.
Yoshisuke Ueda 《Journal of statistical physics》1979,20(2):181-196
This paper deals with turbulent or chaotic phenomena which occur in the system governed by Duffing's equation, a special type of two-dimensional periodic system. By using analog and digital computers, experiments are carried out with special reference to the change of attractors and of average power spectra of the random processes under the variation of the system parameters. On the basis of the experimental results, an outline of the random process is made clear. The results obtained in this paper will be applied to various physical problems and will also serve as material for the development of a proper mathematics of this phenomenon. 相似文献
30.
水稻穗颈大小维管束数株内茎间差异明显,株内茎的次数分布呈正态分布,研究群体穗颈维管束时,可取中等株内中等茎为样本,株内各茎的穗颈大小维管束数之比和第2节间与穗颈大维管束数比值都表现亚种特性,中等茎具有代表性。 相似文献