功率失配误差限的几种表达方式

不确定度评定中常需对功率失配的不确定度进行评定,这就需要我们了解其误差限。实际情况中,有多种功率失配误差限的表达方式,它们的本质相同,形式不同,故在此做一下分析和总结。     

线性模拟量数据采集系统准确度的一种评价方法

采用一种新的准确度表述方法来评价数据采集系统的准确度；同时讨论了该方法的数据采集系统各种误差与现有指标的兼容性问题。     

对JJG577—94中基本误差限和检定流量点规定的探讨

新规程ＪＪＧ５７７－９４中的基本误差限规定与标准不符，检定Ｑｍｉｎ流量点的规定与实际情况不符。建议修改。     

Helmholtz方程基于变限积分法的数值求解

Helmholtz方程是一类描述电磁波的椭圆型偏微分方程，在力学、声学和电磁学等领域应用广泛。为了消除因高波数引起的污染效应，数值求解Helmholtz方程的传统方法是对网格进行加密，网格加密不仅增加了时间复杂度，且离散后的矩阵通常是病态的。因此，寻求对任意波数都有效的方法是必要的。在有限体积法的基础上，引入变限因子，将微分方程完全转换成积分方程，利用一元三点和二元九点Lagrange插值公式，构造含三对角矩阵的离散格式，分别对一维和二维Helmholtz方程进行变限积分法的数值求解。该方法适用于任意波数，求解过程物理意义明确，数值格式简单。对于一维Helmholtz方程研究了变限因子对误差的影响，利用Taylor展式及Lagrange插值余项公式进行误差估计，证明离散格式的截断误差达到二阶。数值实例表明该离散格式的变限因子和步长相等时，误差阶较低。对二维Helmholtz方程，探究不同波数对数值解的影响，证明离散格式的截断误差达到三阶。数值实例表明，对于不同的波数，数值格式都有较好的精度，高波数没有引起污染效应。     

GPS-RTK高程测量代替四等水准测量的实践

本文简要介绍了GPS高程测量的基本原理、GPS-RTK测量原理以及坐标转换方法等,在此基础上,讨论分析了运用GPS-RTK技术进行高程测量精度的评定方法。分别采用GPS和水准仪对校园网进行测量,得到RTK高程和水准高程数据,计算出点间高差较差和高差较差中误差,并依照评定方法进行比较,分析得出GPS-RTK高程测量能够满足四等水准测量精度要求的结论。运用GPS-RTK技术进行高程测量对测区要求较高,但是其作业效率高,数据精确,所以在部分地区可以代替水准测量,具有很好的应用前景。     

GPS-RTK接收机定位误差的检定方法

GPS实时动态差分定位模式(简称GPS-RTK)现已得到了广泛的应用,针对厂家给出的GPS-RTK接收机能否达到标称定位精度指标,实际定位误差如何检定,现行的检定规程中又没有明确规定的实际。本文结合工作实践,探讨了GPS-RTK接收机定位误差的检定方法、过程和限差规定。     

检定电子式无功电能表的建议

指出了电子式无功电能表没有对应的检定规程,提出了检定电子式无功电能表时,判定合格与否的基本误差限,以及测定基本误差应调定的负载功率。     

大坝有限元分析应力取值的研究

提出了基于误差控制下的自适应网格的有限元应力取值标准:即给定一全局误差限作为自适应有限元网格剖分的准则,以此网格计算所得应力即为有限元应力取值。应用适用于工程计算的Z2后验误差估计方法以及h-型自适应策略,对一个典型的重力坝剖面进行了线弹性自适应有限元计算。计算结果表明:给定一个全局误差限,网格剖分调整若干次后即可满足误差要求,不会出现因角缘应力集中出现剖分不收敛的情况;存在一个全局误差限,使得当继续降低误差限时,坝踵和坝趾的角缘应力趋于稳定值。     

激光测振仪误差限的测量不确定度

介绍了评价激光测振仪误差限指标时,测量结果的不确定度分析和评价过程;讨论了影响评价结果不确定度的几个主要误差来源,包括信号源误差、测量仪器的测量误差、测量重复性的影响等等.在一个实际评价例子上,给出了误差限指标不确定度分析和评价结果;该过程及结论可应用在对于计量标准进行误差限指标的不确定度分析上,也可用于估计误差限指标本身的测量不确定度.     

数据采集系统误差限的测量不确定度

本文介绍了评价数据采集系统误差限指标时 ,测量结果的不确定分析和评价过程 ,该过程及结论可应用在对计量标准进行误差限指标的不确定分析上 ,也可用于估计误差限指标本身的测量不确定度     

保税港区出口集运三级供应链博弈分析

基于随机需求,针对出口集运模型下一个国内供应商、一个国内分销商和一个国外零售商组成的三级供应链,运用博弈理论的逆向归纳法,定量比较分析有无保税港区情形下供应链上各成员的最优利润。结果表明：有保税港区后,供应链上成员达到了三方共赢;国外消费者的消费福利提高;供应商可获单位价值退税额与分销商可获单位价值利益的增加,有利于供应链三方利润的增加和消费者福利的提高。     

一类动力系统的稳定性及镇定

本文定义了一类新的动力系统-HCTD系统,利用矩阵迹的不等式理论研究了这类系统的稳定性,并给出了该系统稳定的充分必要条件。讨论了当Lyapunov方程的解P是HCTD阵时,动力系统稳定的充分条件。提出了用解矩阵迹的不等式设计动力系统镇定控制器的一种新方法。     

Bayesian calculation of cost optimal burn-in test durations for mixed exponential populations

The burn-in process is a part of the production process whereby manufactured products are operated for a short period of time before release. In this paper, a Bayesian method is developed for calculating the optimal burn-in duration for a batch of products whose life distribution is modeled as a mixture of two (denoted ‘strong’ and ‘weak’) exponential sub-populations. The criteria used is the minimization of a total expected cost function reflecting costs related to the burn-in process and to product failures throughout a warranty period. The expectation is taken with respect to the mixed exponential failure model and its parameters. The prior distribution for the parameters is constructed using a beta density for the mixture parameter and independent gamma densities for the failure rate parameters of the sub-populations. It is assumed that the optimal burn-in time is selected in advance and remains fixed throughout the burn-in process. When additional failure information is available prior to the burn-in process, the minimization of posterior total cost is used as the criteria for selecting the optimal burn-in time. Expressions for the joint posterior distribution and cost are provided for the case of both complete and truncated data. The method is illustrated with an example.     

An evolutionary algorithm for global optimization based on self-organizing maps

In this article, a new population-based algorithm for real-parameter global optimization is presented, which is denoted as self-organizing centroids optimization (SOC-opt). The proposed method uses a stochastic approach which is based on the sequential learning paradigm for self-organizing maps (SOMs). A modified version of the SOM is proposed where each cell contains an individual, which performs a search for a locally optimal solution and it is affected by the search for a global optimum. The movement of the individuals in the search space is based on a discrete-time dynamic filter, and various choices of this filter are possible to obtain different dynamics of the centroids. In this way, a general framework is defined where well-known algorithms represent a particular case. The proposed algorithm is validated through a set of problems, which include non-separable problems, and compared with state-of-the-art algorithms for global optimization.     

基于精细积分法的结构碰撞动力系数谱研究

将精细积分法引入结构碰撞问题研究中,并借鉴已有反应谱定义提出结构碰撞加速度动力系数谱的概念,采用精细积分法对相邻结构进行了Ⅰ类、Ⅱ类和Ⅲ类场地下碰撞加速度动力系数谱研究。结果表明,精细积分法用于结构的碰撞分析,计算精度和效率较高,对求解结构碰撞问题是适用的;不同场地类型的地震动输入下,结构的碰撞响应有差异,总体上Ⅱ类场地结构碰撞力响应最大;结构碰撞力对初始间隙大小并不敏感,阻尼比的增加使结构的碰撞力响应降低。     

Diffraction Laser-Electronic Fourier Thickness Gage for Monitoring the Thickness of a Large Diameter Lens

The methodology of synthesizing a model for a diffraction laser-optical system for measuring the thickness of large diameter lenses within the framework of engineer-graph procedures for the design, manufacture, and study of a laser-electronic Fourier thickness gage is developed. Nine stages are identified for model synthesis based on successive-parallel sorting of models when considering statement of the problem in designing a laser-electronic Fourier thickness gage. The task of creating a fundamentally new method and provisions for measuring lens thickness is solved by means of an automatic diffraction-geometric-optical method for recording the space-frequency spectrum of the measuring aperture. Schematic analysis is performed and a functional optical scheme is constructed for a two-channel diffraction laser-optical system for measuring lens thickness. A measurement procedure is developed and the Fourier thickness gage developed is studied by experiment. __________ Translated from Izmeritel'naya Tekhnika, No. 10, pp. 30–35, October, 2005.     

An application of the J-Q model for estimating cleavage stress in the brittle-to-ductile transition

A recent model was proposed by the authors to predict cleavage failure for steels based on a weak link mechanism and a crack tip stress field modified for planar constraint by the J – Q theory. The model uses the distribution of toughness results at a single temperature to predict a toughness distribution at a different temperature and/or geometry. In this model a material cleavage stress is needed to predict when the weak link fracture is triggered. This cleavage stress is a key input for the application of the model but it is not a property that is routinely measured and it is hence not available for most steel alloys. In this paper, a method to estimate the average value of the cleavage stress is presented, based on a characteristic of the model to predict cleavage failure. Examples of cleavage stress are given for several steels and these results are used to predict the toughness distributions for structural component models.     

Singularity-reduced integral equations for displacement discontinuities in three-dimensional linear elastic media

A systematic procedure is followed to develop singularity-reduced integral equations for displacement discontinuities in homogeneous linear elastic media. The procedure readily reproduces and generalizes, in a unified manner, various integral equations previously developed by other means, and it leads to a new stress relation from which a general weakly-singular, weak-form traction integral equation is established. An isolated discontinuity is treated first (including, as special cases, cracks and dislocations) after which singularity-reduced integral equations are obtained for cracks in a finite domain. The first step in the development is to regularize Somigliana's identity by utilizing a stress function for the stress fundamental solution to effect an integration by parts. The resulting integral equation is valid irrespective of the choice of stress function (as guaranteed by a certain ‘closure condition’ established for the integral operator), but certain particular forms of the stress function are introduced and discussed, including one which admits an interpretation as a ‘line discontinuity’. A singularity-reduced integral equation for the displacement gradients is then obtained by utilizing a relation between the stress function and the stress fundamental solution along with the closure condition. This construction does not rely upon a particular choice of stress function, and the final integral equation (which is a generalization of Mura's (1963) formula) has a kernel which is a simple function of the stress fundamental solution. From this relation, singularity-reduced integral equations for the stress and traction are easily obtained. The key step in the further development is the construction of an alternative stress integral equation for which a differential operator has been ‘factored out’ of the integral. This is accomplished by, in essence, establishing a stress function for the stress field induced by the discontinuity. A weak-form traction integral equation is then readily obtained and involves a kernel which is only weakly-singular. The nonuniqueness of this kernel is discussed in detail and it is shown that, at least in a certain sense, the kernel which is given is the simplest possible. The results for an isolated discontinuity are then adapted to treat cracks in a finite domain. In doing so, emphasis is given to the development of weakly-singular, weak-form displacement and traction integral equations since these form the basis of an effective numerical procedure for fracture analysis (Li et al., 1998), and such equations are presented for both elastostatics and elastodynamics. A noteworthy aspect of the development is that there is no need to introduce Cauchy principal value integrals much less Hadamard finite part integrals. Finally, the utility of the systematic procedure presented here for use in obtaining singularity-reduced integral equations for other unbounded media (viz. the half-space and bi-material) is indicated. This revised version was published online in July 2006 with corrections to the Cover Date.     

Exact solution of the displacement boundary-value problem of elasticity for a torus

This paper presents an exact analytical solution to the displacement boundary-value problem of elasticity for a torus. The introduced form of the general solution of elastostatics equations allows to solve exactly a broad class of boundary-value problems in coordinate systems with incomplete separation of variables in the harmonic equation. The original boundary-value problem for a torus is reduced to infinite systems of linear algebraic equations with tridiagonal matrices. An analytical technique for solving systems of diagonal form is developed. Uniqueness of the solutions of vector boundary-value problems involving the generalized Cauchy-Riemann equations is investigated, and it is shown that the obtained solution for the displacement boundary-value problem for a torus is unique due to the specific properties of the suggested general solution. The analogy between problems of elastostatics and steady Stokes flows is demonstrated, and the developed elastic solution is used to solve the Stokes problem for a torus.     

Entwicklung und Anwendung von mathematischen Optimierungsmethoden zur Ableitung von vereinfachten Prüfungen für Fahrwerksbauteile

Testing the fatigue life time of chassis components is necessary during the development process and for quality supervision during the period of series production. In many cases a simplified test is done to reduce the complexity of the test. The development engineer has to develop the specification of those simplified tests. According to the task different approaches are possible: Looking for an adaquate test load or for a simplified mounting ore both. This paper deals with several numerical methods for test specification development. Especially a numerical optimization routine is presented for detection of a signifcant load case. Also the iterative searching for a simplified mounting in combination with damage based selection of load channel is shown. Exemplary the application of the routines is demonstrated by Porsche PANAMERA wheel carrier and a suspension‐strut receiving. The actual stage of development of the numerical routines is presented. In addition intended upgrades of the software are shown.