A Theoretical Approach for Estimating Fracture Toughness of Ductile Metals

Fracture toughness is very important when applying Damage Tolerance Design and Assessment Techniques. The traditional testing approach for obtaining fracture toughness values is costly and time consuming. In order to estimate the fracture toughness of ductile metals, the fracture mechanics theory, materials plastic deformation theory and materials constructive relationships are employed here. A series of formulae and a theoretical approach are presented to calculate fracture toughness values of different materials in the plane stress and plane strain conditions. Compared with test results, evaluated values have a good agreement.     

Testing and Evaluation for Web Usability Based on Extended Markov Chain Model

As the increasing popularity and complexity of Web applications and the emergence of their new characteristics. the testing and maintenance of large, complex Web applications are becoming more complex and difficult. Web applications generally contain lots of pages and are used by enormous users. Statistical testing is an effective way of ensuring their quality. Web usage can be accurately described by Markov chain which has been proved to be an ideal model for software statistical testing. The results of unit testing can b eutilized in the latter stages, wbich is an important strategy for bottom-to-top integration testing, and the other improvement of extended Markov chain model (FMM) is to present the error type vector which is treated as a part of page node. This paper also proposes the algorithm for generating test cases of usage paths. Finally, optional usage reliability evaluation methods and an incremental usability regression testing model for testing and evaluation are presented.     

大学英语分级教学之改革与探索

本文结合大学英语教学现状及分级教学的理论依据,提出了大学英语教学改革--分级教学的必要性和科学性,并进一步就分级教学的模式构想进行了探讨,旨在倡导实行分级教学,以提高大学英语教学水平和质量,为大学英语教学跃上一个新台阶提供一种新思路。     

铆接结构中缺陷的脉冲远场涡流定量评估技术

针对飞机机身铆接结构检测中难以对缺陷进行定量评估的问题,将脉冲远场涡流检测技术运用于铆接结构缺陷检测之中。利用脉冲激励频谱成分丰富、可提取特征信息较多的优势对铆接结构中缺陷的定量评估技术展开研究。首先,建立铆接结构脉冲远场涡流三维检测模型,对缺陷进行检测,从而确定缺陷位置。在此基础上,分析缺陷类型、尺寸对检测信号的影响发现直接耦合分量幅值与上下表面缺陷深度之间具有不同的变化关系,从而实现对缺陷的分类识别。最终,利用信号的过零时间变化量实现对缺陷深度的定量,在缺陷深度已知的情况下,进一步利用直接耦合分量幅值变化对上表面缺陷长度进行定量;利用间接耦合分量幅值变化对下表面缺陷长度进行定量。     

油田埋地碳钢管道外腐蚀行为研究

针对大庆油田龙虎泡作业区埋地碳钢管道外腐蚀较为严重的情况,通过检测埋管防护层破损点周围土壤的物理、化学性质和硫酸盐还原菌（SRB）数量,分析土壤的腐蚀性。采用扫描电镜能谱（SEM-EDS）、X射线衍射（XRD）和红外光谱（IR）等技术对管道外壁腐蚀物的形貌、元素组成和矿物成分等进行了表征和分析。借助动电位极化曲线和电化学阻抗谱（EIS）进一步研究了埋地碳钢管道外壁在土壤浸出液中的腐蚀行为。结果表明,作业区潮湿的盐碱性土壤环境和复杂多变的土壤性质使该地区埋地碳钢管道发生腐蚀;腐蚀产物主要包括Fe₃O₄和FeOOH,其中FeOOH位于外层,Fe₃O₄位于内层;腐蚀产物通过参与阴极反应或充当大阴极来加剧管道腐蚀。     

基于二进制熵的加解密函数定位方法

针对二进制程序模糊测试中加解密函数定位准确率低的问题,提出一种基于二进制熵的加解密函数定位方法.该方法对二进制程序的控制流信息进行模型构建以定位程序关键代码,提取关键代码前后的数据流并计算其二进制熵,通过前后二进制熵的关系确定被测代码中是否存在加解密函数.实验结果表明,该方法能够有效发现程序中的加解密函数,准确率大于99%;该方法可以用于提高模糊测试发现漏洞的能力,具有一定的实用价值.      

Damage evolution and failure mechanism of thermal barrier coatings under Vickers indentation by using acoustic emission technique

Acoustic emission(AE) technique was adopted to monitor the damage evolution of air plasma-sprayed(APS) yttria-partially-stabilized zirconia(YSZ) thermal barrier coatings(TBCs) during instrumented indentation testing, and then the failure mechanisms were investigated by cluster analysis and wavelet transform methods.The results of cluster analysis showed that there were three classes associated with distinct failure types for the 8YSZ coatings under Vickers indentation. Based on wavelet transform, these three clusters could be clearly distinguished from their dominant frequency bands, which were concentrated on levels A5(0–156.25 kHz), D5(156.25–312.5 kHz) and D4(312.5–625 kHz), respectively. Thus, the failure mechanism of 8YSZ coatings under Vickers indentation could be clarified by the distribution of different failure types in indentation depth. To sum up, as indentation load increases, the 8YSZ coatings can accommodate the indenter by elastic or little plastic deformation, microcracks propagation and then debonding at the splat boundaries. By comparing the distribution of AE signals induced by different failure types in indentation depth for samples with different thermal exposure time, it can be inferred that thermal exposure treatment can accelerate the degradation of APS 8YSZ TBCs.     

石油化工给排水管道常用API标准制造阀门的试验

该文介绍了石油化工给排水管道常用API标准制造阀门—闸阀、截止阀、蝶阀的试验项目及试验比例,通过在某大型石油化工项目的成功实践,证明了严格执行该阀门试验项目及试验比例对保证石油化工给排水管道施工质量的必要性、合理性。     

市售饮用纯净水微生物污染状况检测与分析

对2009-2011年360份饮用纯净水进行检测。结果显示饮用纯净水总合格率为93.1%。影响饮用纯净水卫生质量的主要微生物指标为菌落总数，微生物合格率春冬季高于夏秋季。2009-2011年连续3年饮用纯净水微生物检测合格率呈上升趋势。     

喷泉测试技术的推广应用

随着国民经济和城市建设的迅速发展及人民生活水平的不断提高,水景喷泉得到了广泛应用,市场的推动使许多企业从事水景喷泉工程安装和相关产品的生产,现已形成了行业规模,并得到了较快的发展。介绍了喷泉的发展历史,阐述了喷泉测试技术的内容,列举了喷泉测试技术的推广成果。