声波测井存储模块的快速检测系统和补偿方法*

筛选高温下稳定的存储器并设计有效的温度补偿算法是实现井下声波测井数据存储的关键。为了快速测试不同存储器在高温下的故障情况以及错误校验纠错算法的温度补偿效果,该文设计了基于通用测试座的硬件系统,编写了基于MSComm控件的上位机控制软件,开发了模拟实际测井温度环境的测试策略,并对几种存储器进行了高温老化实验。结果表明,存储器在高温下(175℃)会出现彻底损坏、比特位翻转等故障,错误校验纠错算法可以提高存储器的使用温度。该设计不仅可以对符合开放NAND闪存接口协议的同类存储器进行快速的高温老化与筛选,而且对井下存储系统的设计有重要的参考意义。     

冷绝缘超导电缆绝缘材料测试综述

绝缘材料在液氮中的各种性能将直接影响到冷绝缘高温超导(HTS)超导电缆的质量。对四种绝缘材料:电缆纸、聚丙烯层压纸、聚酰亚胺薄膜和低密度聚乙烯薄膜在常温和低温下的电阻率、介电常数、介质损耗角正切、低温介电强度和局部放电进行实验研究和对比,得到了有价值的数据。     

高通量研磨-X射线荧光光谱法测定不同植源性食品中硒含量北大核心

为了提高食品的样品检验效率,采用高通量研磨制备样品,利用X射线荧光光谱法对食品中硒含量进行检测。重点研究了样品含水率、样品颗粒粒径、研磨条件、检测条件等因素对检测结果的影响。结果表明:样品干基含水量小于20%,样品颗粒粒径小于100μm;高通量研磨条件为装样量3 g,频率30 Hz,研磨3 min;高精度X射线荧光光谱仪检测条件为检装样量0.2 g,PP膜压紧,检测90 s时的情况下,硒的检出限0.01 mg/kg,仪器的精密度小于5%,与粉碎法进行对比,相对偏差在-10.37%~8.05%。说明高通量研磨-X射线荧光光谱法检测食品中硒含量的方法快速、准确,可以满足批量样品现场检测分析需求。     

软件模块测试中的动态资源分配问题

为有效利用测度过程中投入的测试资源,提高测试效率,本文考虑将测试过程为多个阶段并为各个阶段动态分配测试资源的方法,为此提出两种动态分配测试资源模型,当测试资源总数一定时,测试约束时各软件模块中剩余错误平均数量小的模型;当给定测试约束时各软件模块中剩余错误平均数要达到的预定指标时,所用的测试资源最少的模型。     

Detection of fatigue damage in steel using laser speckle

We investigated a method to detect fatigue damage of steels without contact using laser speckle. In the earlier stage of fatigue in steels, slipbands appear on the surface and microscopic shear strain is stored in the slipbands. The slipbands appear more densely with progress of fatigue damage. When a laser illuminates the surface of the fatigued steel, light intensity distribution of the laser speckle pattern formed by the reflected light changes with the change of surface properties caused by slipbands. It has been clarified that the width of the speckle pattern broadens corresponding to spatial frequency distribution of the surface profile and thus it is presumed that speckle pattern broadens with increase of slipband density. This shows that we can detect fatigue damage by observing the laser speckle pattern on material surface. The method presented in this paper is based on this phenomenon. We observed change of the speckle pattern during fatigue loading under constant stress amplitude using a steel specimen and the relation between speckle pattern, number of loading cycles and also magnitude of loading was considered. We investigated the possibility of detection of fatigue damage using this method and also proposed a method to estimate fatigue life by observing change tendency of the speckle pattern depending on the number of loading cycles in the earlier stage of fatigue before crack initiation.     

The effects of nonnormality on asymptotic distributions of some likelihood ratio criteria for testing covariance structures under normal assumption

This paper examines asymptotic distributions of the likelihood ratio criteria, which are proposed under normality, for several hypotheses on covariance matrices when the true distribution of a population is a certain nonnormal distribution. It is well known that asymptotic distributions of test statistics depend on the fourth moments of the true population's distribution. We study the effects of nonnormality on the asymptotic distributions of the null and nonnull distributions of likelihood ratio criteria for covariance structures.     

Solitary waves for Non-Destructive Testing applications: Delayed nonlinear time reversal signal processing optimization

An original signal processing method called delayed Time Reversal-Nonlinear Elastic Wave Spectroscopy is introduced in the present paper. The method could be used to amplify signal in certain regions of the material under Non Destructive Testing. It allows to optimize and change the shape of the received focused wave in the material, either by making the focusing sharper by decreasing the side lobes or making it wider by modifying the actual focusing peak. It is also possible to use the focused signal as a delta-basis to construct a signal with arbitrary envelope or reduce the side lobes of the focused signal. These concepts are shown to work well in the simulations and the physical experiments. This signal processing method is particularly promising for nonlinear and solitary wave analysis, since it allows to create an interaction of sharp and solitary wave peaks just underneath the receiving transducer. Due to simple and accurate linear prediction of the received interaction signal, any differences of measurements and predictions could indicate the presence of nonlinearities.     

Relative sensitization efficiency of fluorescent probes/sensitizers for monitoring and acceleration of cationic photopolymerization of monomers

The performance of a series of 1-amino-2,6-dicyano-3,5-diphenylbenzene derivatives (i.e., meta-terphenyls) as fluorescent molecular probes for monitoring cationic photopolymerization of monomers by the Fluorescence Probe Technique (FPT) was studied. It was found that the m-terphenyls accelerate the cationic photopolymerization initiated with diphenyliodonium photoinitiators at the wavelength where the photoinitiator alone does not work. Consequently, application of the m-terphenyls in a dual role: (a) as fluorescent probes for monitoring the cationic polymerization progress, and (b) as long-wavelength sensitizers for diphenyliodonium photoinitiators is proposed. Next, a precise method for determination of relative sensitization efficiency of the sensitizers has been devised and applied for evaluation of the performance of the m-terphenyl sensitizers in comparison to that of a commercial sensitizer: 2,4-diethyl-9H-thioxanthen-9-one.     

Wald意义下的局部π-Bayes最优决策

本文在某些必要的适当条件下,采用一种独特的方式证明Wald意义下的最优决策的存在性.并表明:Wald意义下的最优决策作为一种π-Bayes最优决策实际上是局部的.     

The role of Nordtest in testing and quality assurance

 This article describes on the idea behind Nordtest, the results of its activities and how Nordtest has influenced testing and quality assurance. By financing projects in the field of technical testing Nordtest has been able to utilise the best available Nordic knowledge and resources to respond to Nordic needs and has gained acceptance in all Nordic countries. During Nordtest's 25 years of operation its projects have resulted in over 500 test methods and over 350 technical reports that are widely used both within and outside the Nordic countries. Examples of some project results are given. Important issues in testing and quality assurance are expressed in Nordtest position papers. Nordtest's active participation in the European and global co-operation in testing and quality assurance is also described.