The method of testing of XLPE cable insulation resistance to partial discharges and electrical treeing

The paper gives a method of model XLPE medium voltage cable insulation testing for partial discharges and electrical treeing with a point to plane test geometry. Based on this method, a comparative estimate of insulation resistance to treeing and partial discharges have been made. XLPE crosslinked by different methods (steam medium and hot nitrogen medium) and with varying contents of inorganic filler kaolin were tested. The characteristics of partial discharges were measured by means of a pulse height analyser characterized with a microscope. The data have been analysed statistically.     

Explosive Random‐Coefficient AR(1) Processes and Related Asymptotics for Least‐Squares Estimation

Abstract. Large sample properties of the least‐squares and weighted least‐squares estimates of the autoregressive parameter of the explosive random‐coefficient AR(1) process are discussed. It is shown that, contrary to the standard AR(1) case, the least‐squares estimator is inconsistent whereas the weighted least‐squares estimator is consistent and asymptotically normal even when the error process is not necessarily Gaussian. Conditional asymptotics on the event that a certain limiting random variable is non‐zero is also discussed.     

THE ANALYSIS OF THE SEPARATED LAYERS ALGORITHM BY DOMAIN DECOMPOSITION METHOD

From the principle of of the Domain Decomposition Method (DDM), we analyse the 2nd-order linear elliptic partial differential problems and link the Separated-Layers Algorithm (SLA) with DDM. The mathematical properties of SLA and numerical example are presented to obtain satisfactory computation results. For general linear differential ones, also are the structure of SLA and its characteristics discussed.     

CXFTV2: A Fortran subroutine for the discrete least squares convex approximation

A Fortan subroutine calculates the least squares approximation to n data values containing random errors subject to non-negative second divided differences (convexity). The method employs a dual active set quadratic programming technique that allows several concavities of an iterate to be corrected simultaneously, which is a distinctive feature of this calculation. A B-spline representation of the iterates reduces each active set calculation to an unconstrained minimization with fewer variables that requires only O(n) computer operations. Details in these techniques including the data structure that establishes the implementation of the method are specified. Numerical testing on a variety of data sets indicates that the subroutine is particularly efficient, terminating after a small number of active set changes, the subroutine being suitable for large numbers of data. A numerical example and its output is provided to help the use of the software.     

用偏微分方程构造过渡面

用偏微分方程的构造曲面是一种新兴的方法，本文借若干算例说明如何用偏微分方程构造两已知曲面之间的过渡面。论文着重讨论用四阶方程构造一阶连续的过渡面。     

次生伽马能谱分析方法的实验研究

本文指出一种地化学闭合模型的热中子瞬发活化伽马分析方法，它是地球化学测井的核心技术，标准谱的获得，基于标准谱的加权最小二乘解谱方法、灵敏度刻度及地球化学闭合模型是这一方法的关键环节。     

初至波走时层析成像中的正则化方法

 波场的等效性、观测数据的有限性和观测误差等因素导致地球物理反演本身具有严重的多解性，降低这种多解性的一种重要途径就是对反演过程进行约束。传统的初至波走时层析成像方法，通常是在外部对模型空间施加显式的约束和平滑处理，这样就会破坏模型参数与传播算子之间的相关性，难以达到有效利用先验信息的目的, 甚至会影响反演的稳定性。针对这一问题，本文将先验信息分为三类，在此基础上阐述了通过正则化手段将各种先验信息纳入到反演方程当中，替代传统的外部约束模式。理论试验结果表明，正则化方法比外部约束方法有效地提高了反演的精度和分辨率；将该正则化方法应用于实际二维资料处理，也得到了比较好的反演结果。     

液压支架设计及制作过程中的优化

主要介绍液压支架设计和使用过程中局部结构上的缺陷,经过优化设计从而实现安装、拆卸方便,维护量减少,检修便利。制作过程中部分零部件改变工艺过程实现通用化、系列化。     

Performance analysis of the forgetting factor RLS algorithm

An analysis is given of the performance of the standard forgetting factor recursive least squares (RLS) algorithm when used for tracking time-varying linear regression models. Three basic results are obtained: (1) the ‘P-matrix’ in the algorithm remains bounded if and only if the (time-varying) covariance matrix of the regressors is uniformly non-singular; (2) if so, the parameter tracking error covariance matrix is of the order O(μ + γ²/μ), where μ = 1 - λ, λ is the forgetting factor and γ is a quantity reflecting the speed of the parameter variations; (3) this covariance matrix can be arbitrarily well approximated (for small enough μ) by an expression that is easy to compute.