Effects of stator bending on pressure field and loss of transonic turbine stage

To study effects of the upstream flow field changing on the downstream flow field of transonic turbine, different three-dimensional bowed blades, which are the stator blades of transonic turbine stage, were designed in this paper. And then numerical calculations were carried out. The effects on downstream flow field were studied and analyzed in detail. Results show that, at the middle of stator blades, although the increasing Mach number causes the increase of shock-wave strength and friction, the middle flow field of downstream rotors is improved obviously. It is an important change in transonic condition. This causes the loss of the rotor’s middle part decreased greatly. Correspondingly, efficiency of the whole transonic stage can be increased.     

基于蒙特卡罗方法的复合材料辐射屏蔽设计北大核心CSCD

在乏燃料后处理厂的工作环境中可能存在着低能中子-γ射线混合辐射,严重威胁工作人员的人身安全。本文针对上述混合辐射环境,利用蒙特卡罗程序Geant4模拟计算了一种钨/硼纤维增强含硼/铋聚合物复合材料中不同材料参数对低能中子和γ射线综合防护效果的影响。结果显示,此种钨/硼纤维复合材料对低能中子和γ射线均具有良好的屏蔽效果。文章证实了纤维垂直排布方式具有比平行排布方式更优的屏蔽效果,且垂直排布方式下透过粒子束的强度分布更加均匀。此外,在聚合物基体中掺杂一定质量分数的硼/铋可以进一步增强复合材料的辐射屏蔽效果。依据这些结果我们认为此种复合材料可以为后处理厂等辐射环境中的防护服及相关防护用具提供参考。     

Employing user profiles to test a new version of a GUI component in its context of use

Advancement in reusable component technology has had a significant impact on the development of complex graphical user interfaces (GUIs), which are front-ends to most of today’s software. Software developers can, with very little effort, integrate components into their software’s GUI. Problems, however, arise when new versions of GUI components replace their predecessors in an implementation. Often, the inclusion of a new version of a component breaks some part of the software, i.e., tasks that end-users were able to perform before modifications were made can no longer be performed. Software developers (who also happen to be component users) are unable to perform adequate regression testing in this context because of several factors, including lack of source code, environmental side-effects on GUI rendering, event-driven nature of GUIs, and large number of possible permutations of events. This paper presents a new technique that end-users’ quality assurance (QA) teams can employ to test the new version of a component in its application context by using the existing version as a baseline. The technique combines lightweight event-level dynamic profiling to collect user profiles in a transparent manner, GUI reverse engineering to extract the structure of the component’s GUI, test case execution to replay the collected profiles on the new version, and GUI oracles that collect properties from the existing version. Empirical studies demonstrate the practicality, usefulness, and limitations of the technique. Atif M. Memon is an Assistant Professor at the Department of Computer Science, University of Maryland. He received his BS, MS, and Ph.D. in Computer Science in 1991, 1995, and 2001 respectively. He was awarded a Gold Medal in BS. He was awarded Fellowships from the Andrew Mellon Foundation for his Ph.D. research. He received the NSF CAREER award in 2005. His research interests include program testing, software engineering, artificial intelligence, plan generation, reverse engineering, and program structures. He is a member of the ACM and the IEEE Computer Society.     

复杂流场特征区域模糊描述与提取方法

引入模糊理论对流场特征的描述,提出了一种流场特征区域描述与提取算法.通过采用模糊理论对流场特征区域进行描述,从基本属性φ、衍生属性Υ、关联属性Ⅱ这3个层次建立了测度规则,然后对各规则分析建立了相应的特征向量,并基于特征向量偏差给出了模糊测度隶属度的确定方法.理论分析表明,该描述与提取算法在最小平方和准则下是对流场区域的...     

并发垃圾收集器及其调度方法的研究

垃圾收集技术被广泛地应用于现代高级编程语言环境中,它在解决内存泄露等问题的同时也影响了应用程序的响应时间.为了减小甚至消除由于垃圾收集所造成的应用程序停顿,设计并实现了能与应用程序并发运行的垃圾收集器Tick.在研究过程中,使用Snapshot-at-the-Beginning算法解决了"一致性丢失"的问题;并动态地对垃圾收集线程进行调度,从而更加有效地利用系统资源.测试结果表明,Tick能有效地消除应用程序因垃圾收集所造成的停顿并减少应用程序的执行时间.     

海洋噪声中舰船辐射噪声的一种检测方法

利用高阶谱分析的方法对实际的海洋环境噪声和舰船辐射噪声的高斯性和线性特性进行了检测,发现在一般情况下,短时间内的海洋环境噪声是高斯信号,而舰船辐射噪声信号则是非高斯和非线性的。它们的这些差异性可以用来进行舰船辐射噪声的检测,以及提高舰船噪声的各种处理的精度。     

浅论高校计算机网络实验室的建设与管理

本文分析了计算机网络实验室建设的需求和管理现状,在此基础上指出了建设管理的目标及网络化管理的实现,目的在于提高教育教学质量。     

基于通用MODEM区域水文资料遥测系统设计

介绍一种简单的区域水位,雨量遥测系统。系统由ＰＩＣ１６Ｃ７３单片机、普通调制解器及工业级ＰＣ机构成。ＰＣ机能通过共用电话网实时和实时查询各水文站点的水文数据,为文水预报提供依据。     

安全支付协议的设计与验证研究

安全支付协议是实现电子商务在线支付的关键。目前缺乏同时支持电子商品和实物商品的在线支付协议,基于此,该文给出了一种同时支持这两类商品交易的安全支付协议,最后使用SMV工具对协议的原子性进行了分析并验证了其可行性。     

基于模拟退火遗传算法的测试数据生成研究

在软件测试中,如何才能生成高效的测试用例一直是人们研究的热点.提出了一种基于模拟退火的遗传算法,用于测试数据的生成.该算法有效克服了传统GA局部搜索能力差和早熟现象.同时也有效改善了SA全局搜索能力差的问题.随后提出了一个基于模拟退火遗传算法的测试数据自动生成的系统框架结构.并重点介绍了如适应度函数选取问题、编码问题和遗传算子改进问题等关键技术.实验结果表明.该苒法运用在测试数据自动生成领域.其效率和效果都优于传统的遗传算法.