电力系统电流互感器饱和特性的柔性神经网络补偿法

电流互感器(CT)由于饱和使得副边电流变形,进而导致保护与测量应用中的许多问题。为此,提出一种补偿CT饱和特性的方法,以改善其测量性能。所提算法基于具有2个可变参数的sigmoid函数,构建了新型柔性神经网络,以估算CT励磁电流。实时地将估算所得励磁电流与扭曲的副边测量电流相加,即得补偿后原边电流。在学习过程中,所建补偿器的各柔性神经元柔性地改变其形状以适应各自的角色,高度柔性特点增强了网络学习能力,不但可减少网络节点数,而且可减少迭代学习时间。仿真研究中,应用一个900:5A的CT测试所提出的补偿器,测试时考虑了CT原边电流不同直流分量、CT剩磁大小与CT负载特性的影响。仿真结果验证了所提补偿方法的高精度,而且不受CT负载特性、CT剩磁情况及原边电流直流成分的影响。     

Dielectric properties of alternative refrigerants

This paper gives an overview of our research, from experimental measurements of the relative permittivity on new and alternative refrigerants, to theoretical interpretation of the data and density functional and density functional self-consistent reaction field calculations for a series of HFC molecules. Experimental measurements were obtained as a function of temperature and pressure for Class B refrigerants-HCFC-123, HCFC-142b, HCFC-141b, Class A refrigerants-HFC-32, HFC-134a, HFC-152a, HFC-143a, HFC-227ea, HFC-245fa, HFC-365mfc and some mixtures of them: HFC-125/143a/134a (R-404A), HFC-32/125/134a (R-407C), HFC-125/143a (R-507), HFC-32/125 (R-410A). Density functional and density functional self-consistent reaction field calculations were performed for CHF2CF3 (HFC-125), CH2FCF3 (HFC-134a), CH3CF3 (HFC-143a), CH2F2 (HFC-32), and CHF2CH3 (HFC-152a). A particular emphasis has been given to the calculation of dimerisation energies, rotational potentials, polarisabilities and dipole moments.     

苏共执政模式的失败及其启示

苏共在执政的74年中，形成了鲜明的苏共执政模式。这种执政模式以计划经济、高度集权、意识形态教条为基本特点。苏共执政模式曾使苏联取得了诸多成就，但这种执政模式内在的结构缺陷，最终导致了苏共的彻底失败。从党与指导思想、党与组织制度、党与政、党与民等角度分析了苏共执政模式失败的必然性。这些为推进我党新时期的建设提供了许多有益的启示。     

中国武术文化特性及对世界体育文化的影响

从哲理、技击、健身、娱乐等方面阐述了中国武术的文化特性,并综述了中国武术在世界范围内传播、推广与发展的过程中,以优秀的民族文化表现形式对世界体育文化生活、体育健身观念、体育保健、体育美学等方面具有直接的影响.     

Comment on "From the summation-by-parts algorithm to Pi"

Comments on the paper by Mosig (IEEE Antennas and Propagation Magazine, vol.47, p.38-40, 2005 December). The paper by Mosig discussed acceleration of convergence of series. Without commenting on either the validity or efficiency of his method, the present author would like to draw attention to an existing method, published long ago by D. Shanks (1955). Briefly stated, this method takes a sequence and defines partial sums, which is described in this paper.     

A Lumped Parameter Model for Product Flow Times in Manufacturing Lines

Based upon basic drivers for the flow time, a lumped parameter model for a manufacturing line has been derived by using Kingman's approximation. The lumped parameter model for the flow time consists of a workstation and delay time. The workstation is characterized by the effective process time of the bottleneck workstation and the weighted sum of the coefficients of variation of all workstations. The delay time is determined by the sum of all effective process times of the nonbottleneck workstations. The advantage of the application of the lumped parameter model is that the variability of the total line is determined by a measurement at the operating point of the actual manufacturing line. This variability depends upon the operating point. Examples show that this dependency is not too strong for lines with a distinct bottleneck workstation in the actual line. From the derivation of the lumped parameter model it can be concluded that an improvement of the effective process time of the bottleneck workstation of the line results in an increase of the total variability of the line. This variability can be reduced by either reducing the variability of all workstations or the effective process times of the nonbottleneck workstations     

Measurements and simulations of transient characteristics of heat pipes

The rejection of heat generated by components and circuits is a very important aspect in design of electronics systems. Heat pipes are very effective, low cost elements, which can be used in cooling systems. This paper presents the modelling and measurements of the heat and mass transfer in heat pipes. The physical model includes the effects of liquid evaporation and condensation inside the heat pipe. The internal vapour flow was fully simulated using computational fluid dynamics. The theory has been compared with experimental measurements using thermographic camera and contact thermometers. The main purpose of this study is to determine the effective heat pipe thermal conductivity in transient state during start up the pipe operation and temperature increase.     

Selecting Significant Effects in Factorial Designs Taking Type II Errors into Account

When analysing the effects of a factorial design, it is customary to take into account the probability of making a Type I error (the probability of considering an effect significant when it is non‐significant), but not to consider the probability of making a Type II error (the probability of considering an effect as non‐significant when it is significant). Making a Type II error, however, may lead to incorrect decisions regarding the values that the factors should take or how subsequent experiments should be conducted. In this paper, we introduce the concept of minimum effect size of interest and present a visualization method for selecting the critical value of the effects, the threshold value above which an effect should be considered significant, which takes into account the probability of Type I and Type II errors. Copyright © 2006 John Wiley & Sons, Ltd.     

提高500 kV电网向北京输送能力的措施

为确保北京电网经济、可靠地供电,文章从规划的角度论述了已经使用与即将规划使用的各种提高电网输送能力的措施,主要包括改善500kV电网结构,加强和扩大以北京电网为中心的受端电网;送端适当互联;加强北京电网中的无功电源建设;在北京电网中建设电源以提供电压支撑;采用串联补偿技术和紧凑型线路送电等.并对应用柔性交流输电（FACTS）技术和缩短保护动作时间以提高电网输送能力进行了展望.