对接焊缝缺陷漏磁场特征分析及识别研究

为实现钢板对接焊缝存在不同类型缺陷的识别研究,针对铁磁性焊缝的特点,探讨应用漏磁法检测钢板对接焊缝不同类型缺陷。根据漏磁检测(MFL)原理,采用有限元方法(FEM),分别建立钢板对接焊缝中可能存在的裂纹、气孔、未熔合和未焊透等缺陷的三维FEM模型。研究钢板对接焊缝包含以上不同类型缺陷时所产生的漏磁场分布特征,得到漏磁场磁感应强度水平分量和垂直分量相关对比分析曲线。仿真结果表明:漏磁法适用于钢板对接焊缝缺陷的识别研究;根据漏磁场磁感应强度分量的曲线特征,能够实现对焊缝缺陷的分类。     

考虑组织因素的液化天然气泄漏安全评价方法

为考虑组织因素对于人因失误发生的根本性影响,提出一种以贝叶斯网络(BN)为工具的人因风险分析方法,并用于液化天然气泄漏的安全评价。先将认知可靠性与失误分析方法(CREAM)的共同绩效条件(CPC)分成3层,即组织层、技术系统层和个人层。以BN为工具,利用其因果推理和诊断推理的功能,进行人因失误预测和追溯的双向分析。将考虑组织因素的人员操作失误概率引入浮式液化天然气船(FLNGV)装卸过程LNG泄漏的BN中,进行LNG泄漏的安全评价以及事故原因的重要度分析。结果表明,"执行"失误是LNG泄漏最主要的事故原因,而个人层的CPC会对执行失误产生较大的影响。     

架空及埋地天然气管道泄漏扩散数值研究

天然气在管道运输过程中,由于含硫等腐蚀性气体对管道内壁的腐蚀作用,在管内其他压力的作用下,会引起穿孔泄漏。泄漏后的天然气扩散后,可能会引发火灾、中毒或爆炸。因此,进行天然气管道泄漏扩散及数值模拟研究,对管道输送安全运营和保障人生财产安全意义重大。该文利用CFD软件对架空及埋地含硫天然气管道穿孔泄漏后的甲烷、硫化氢气体的扩散进行了数值模拟。结果表明,受土壤毛孔阻力的影响,埋地天然气管道泄漏爆炸范围比架空天然气管道泄漏要小,但其在地面的影响时间长,硫化氢的中毒范围比架空要低30m左右。为天然气的安全输送及环境保护提供了理论依据。     

细胞色素P450酶代谢新烟碱类农药N-脱烷基反应的机制研究：以噻虫嗪为例

生物转化是影响有机污染物毒性的重要过程,细胞色素P450酶在其中起着关键作用.新烟碱类农药对于哺乳动物毒性较低,但是经过P450酶的转化后,可能会产生毒性增强的代谢产物,提高环境和健康风险.本研究以噻虫嗪（TMX）为例,采用计算模拟的方法研究P450酶催化下TMX的代谢路径和产物,探讨该类污染物N-脱烷基的反应机制.计算结果表明,P450酶代谢TMX有两条不同路径：一条是经过两次O-亚甲基羟基化后通过水桥开环生成毒性减小的噻虫胺（CLO）;另一条是通过氢提取/羟基反弹羟基化甲基的过程,然后经水桥转移氢质子发生N-脱甲基反应,生成去甲基噻虫嗪（dm-TMX）,据前人实验报道该产物会导致肝肿瘤发生率的增加,具有明显的健康风险.鉴于其他烷基胺类化合物具有类似的代谢机理,进一步通过C—H键解离能(BDE_C-H)与氢提取反应的活化能（ΔE^*）建立了N-脱烷基化反应活性的预测模型,R²=0.932,平均绝对误差MAE=1.75 kcal·mol^-1,模型的稳健性良好,可以快速有效地为该类污染物的代谢活性研究提供...     

材料疲劳裂纹门槛值测定方法研究

目的研究快速简便的金属材料疲劳裂纹扩展门槛值测定方法。方法利用原位观察技术,通过对裂纹扩展的精确捕捉获得材料裂纹扩展门槛值。结果利用原位技术测量获得的LY12CZ铝合金材料疲劳裂纹门槛值与Bucci采用升降法获得的门槛值数据相近,并且测量简便。结论利用扫描电镜原位技术可以快速获得裂纹扩展门槛值,是一项具有工程应用前景的裂纹扩展门槛值测量手段。     

室内环境污染问题现状研究

首先介绍了室内环境污染问题的历史沿革,以及关于室内环境污染物质的种类、浓度及污染源的研究状况,并对国内外在室内环境污染物质的毒理学和室内环境污染的治理与控制的研究现状进行了综述,指出了中国进行室内环境污染系统研究的必要性。最后,通过分析综述的国内外关于室内环境污染和治理的研究进展,提出两个室内大气污染学科方面未来的研究重点;开展地域性的室内环境污染物分布情况的基础性研究;研制新的模块型的室内空气污染物处理系统。     

Computer Professionals and Carpal Tunnel Syndrome (CTS)

Carpal Tunnel Syndrome (CTS) is an important problem among computer professionals. Hence the prevalence of CTS among computer professionals and risk factors were studied. 648 subjects were selected from 4,276 computer professionals from 21 companies with a simple random sampling method. CTS was diagnosed based on clinical features.

The prevalence of CTS was found to be 13.1% (95% CI 10.5–15.7%). Subjects with over 8 years of computer work, over 12 hrs of work per day and system administrators were at a higher risk for CTS (OR 3.3, 4.9 and 2.5 respectively). Flexed or extended hand position had higher risk for CTS.

Higher risk for CTS was found with higher exposure to computer work. Ergonomic considerations are important in facilitating proper positioning of hand while working with a computer. Further studies on CTS risk factors among computer professionals are essential for planning prevention.     

Mental Symptoms and the Use of New Technical Equipment

The aim of this paper was to present how mental symptoms are connected to the use of desktop, portable or minicomputers (communicators and hand-held computers), mobile phones, and background information such as age and gender in the Finnish working-age population. The study was carried out as a cross-sectional study by posting a questionnaire to 15 000 working-age (18-65) Finns. The mental symptoms of 6121 respondents were analysed using the model factors age, gender, the use of computers and the use of mobile phones. In all data, the use of desktop computers was related to mental symptoms. However, the results of our data are not highly reliable, because the nonresponse rate was over 50%. Nevertheless, it may be essential to take into account in the future that working with computers can increase workers’ mental symptoms, and it is important to observe their mental health.     

Coincidence and Upgrade: A Typical Case Study of Rural Ecotourism Development

Abstract

At present, internal rural tourism is at the stage of upgrading and renewing, and ecotourism has been considered to be the main direction. This paper discussed the concepts and criteria of rural tourism and ecotourism, analyzed a typical case of Nongke Village of Chengdu City-being considered to be the first rural tourism site in China, went deep into the problems of the contents and criteria of the development of rural ecotourism, and tried to probe into the principles of the development of rural ecotourism both theoretically and practically so as to understand the rules of the development of rural ecotourism.     

Progress in Enclave Tourism Study of Overseas: A Literature Review

Abstract

In response to the “isolated island” phenomenon emerging from the development of tourist resorts in China, this paper reviews the study of enclave tourism overseas, which has similar features to the resort “island”. Based on the literatures related to enclave tourism from Tourism Management and Annals of Tourism Research, this paper reviews the study of enclave tourism from the following aspects: definition discussion, theories used, causation of enclaves, characteristics and impacts of enclave tourism. The understanding of the overseas researches on enclave tourism would provide instructions for the study on the problems of Chinese resorts, such as enclavity and “island effects”, and suggest measures for the sustainable development of resorts in China. This paper is divided into three sections. Section 1 briefly introduces the development of enclave tourism in developing countries and the outline of enclave tourism study. Section 2 elaborates on the contents of enclave tourism research and gives deep insights into the study on concepts, characteristics, causations and effects respectively, which is the key part of this paper; Section 3 concludes the review and proposes suggestions for the enclave tourism study in China.