小型高效蒸汽轮机主汽阀的优化设计

数值模拟了某小型高效汽轮机主调阀内的全三维复杂蒸汽流场,给出了阀门的整体流量特性曲线,分析了阀门内部流场细节,指出调节阀的喉道附近流场分布不均匀是造成阀门损失的主要原因。接着对阀碟型线进行优化,优化后的阀门通流量减小,流场内部涡流区大大减小,速度分布不均匀性得到改善,湍动能范围和幅值大幅度下降,这一切表明阀门的效率和稳定性得到很大的提高。最后,实验验证了阀门的通流特性和安全性,为阀门的结构优化设计提供了重要依据。     

光滑工件尺寸的测量与检验及其计算机实现

在生产实践中，对光滑工件的测量与检验需要查找国家标准规定的数据表格，然后经过一定的数值计算，才能选择出合适的计量器具并给出相应的验收尺寸。手工的查找和计算数据既浪费时间，又易出错。这里采用最新的国家标准GB／T3177—1997（光滑工件尺寸的检验），改变了以往单一的内缩验收方式。根据工件的功能要求，同时考虑到实际的加工工艺能力和现场拥有的仪器现状综合选择计量器具，并应用VB6．0语言开发了应用软件，将以上工作由计算机来完成，提高了检验效率和检验的准确率，降低了检验成本。     

实施大学生职业资格证书制度的实践与探索

本文阐述了在大学生中实施职业资格鉴定,推行学历证书与国家职业资格证书并举制度,介绍了大学生职业资格鉴定考核在高校的实践,提出做好职业资格鉴定工作和加强实训教学、提高学生操作技能的建议.     

一种基于Petri网的时间工作流模型的研究与验证

时间管理是工作流管理软件的重要部分,针对目前工作流系统对时间管理的需求,通过对传统Petri网扩展时间信息来描述时间模型,提出了一种静态验证方法,对模型进行基本验证和任务间的依赖约束验证;实例分析表明,该方法在减少工作量的同时提高了验证的有效性。     

闸门流激振动全水弹性模型试验的原型验证

由于弹性结构与其周围流场存在着复杂的相互作用,单纯数值方法还不能正确预报这种水弹性振动,因此,水弹性模型试验已成为预报流场中结构原型行为的唯一方法.在对水弹性振动模型相似准则和研制的闸门水弹性振动模型材料性质简要介绍的基础上,对三峡大坝导流底孔弧形闸门全水弹性模型振动试验成果和其原型振动观测成果作了多方面对比分析.结果表明:全水弹性模型试验预报的原型闸门的动力特性、振动加速度、结构动静应力与原型闸门在相近条件下的实测成果颇为一致,从而验证了闸门全水弹性模型对原型闸门流激振动行为预报的可靠性.     

某柴油机过热故障分析

某水冷柴油机在进行耐久性考核试验过程中,出现曲轴箱废气压力突然升高,排温升高的故障现象。经拆检分析确定了该故障产生的原因是整机过热造成的。为了分析整机过热原因,建立了相应的故障树,通过逐条排查分析,找出了故障发生的根本原因是:由于冷却系统膨胀水箱蒸汽阀密封不严,造成闭式冷却循环系统失效,冷却液汽化,循环系统产生气阻,并最终导致水泵供水量不足,引发柴油机过热故障。故障排除后,整机重新进入考核试验,并顺利通过了耐久性考核,验证了故障定位合理性和所采取措施的可行性。     

Towards Test Purpose Generation from CTL Properties for Reactive Systems

This paper presents an approach for the generation of test purposes in the form of labelled transition systems from specifications of properties in CTL. The approach is aimed at adapting the model checking process, by extending search algorithms to perform further analysis so that examples and counter-examples can be extracted. An algorithm for the generation of test purposes through analysis over the examples and counter-examples is presented, along with a case study to show the correspondence between the CTL properties and the generated test purposes.     

Estimators of sensitivity and specificity in the presence of verification bias: A Bayesian approach

Verification bias can occur if some of the patients with test results are not selected to receive the gold standard procedure. Unverified cases frequently are not suggestive to be positives. Consequently, the set of verified cases overestimates the number of true positives and underestimates the number of true negatives. The sensitivity and specificity estimates based only on the patients with verified disease are often biased. In this article we derive estimators for sensitivity and specificity not subject to verification bias using a Bayesian approach. Marginal posterior densities of all parameters are estimated using the Gibbs sampler algorithm. An application to the study of accuracy of Hybrid Capture II in the diagnosis of cervical intraepithelial neoplasia grades 2 and 3 illustrates the proposed methodology.     

从示值超差谈水泥压力试验机的设计/检定及修理

从水泥压力试验机检验水泥的几个实例，展现了由于水泥压力试验机的示值超差而造成的危害以及现场如何排除这些示值超差的方法；并从水泥检验的特殊性以及笔者在长期实际工作中的经验，介绍了水泥压力试验机示值超差的几种主要表现形式、示值误差图线，分析了产生示值超差的原因。进而指出了在设计时应如何避免产生示值超差、在检定及修理时应如何发现示值超差及排除示值超差的问题。     

Abstractions of data types

The use of abstraction in the context of abstract data types, is investigated. Properties to be checked are formulas in a first order logic under Kleene's 3-valued interpretation. Abstractions are defined as pairs consisting of a congruence and a predicate interpretation. Three types of abstractions are considered,∀∀, ∀∃ and ∃^0,1∀, and for each of them corresponding property preservation results are established. An abstraction refinement property is also obtained. It shows how one can pass from an existing abstraction to a (less) finer one. Finally, equationally specified abstractions in the context of equationally specified abstract data types are discussed and exemplified.On leave from the Department of Computer Science, “Al. I. Cuza” University, Iaşi 740083, RomaniaThe research reported in this paper was partially supported by the program ECO-NET 08112WJ/2004-2005 and by the National University Research Council of Romania, grants CNCSIS 632(28)/2004 and CNCSIS 632(50)/2005.