焊管内裂纹电磁激励红外无损检测数值模拟

研究ANSYS有限元模拟下基于电磁激励红外热像的直缝焊管内部裂纹检测,为实践提供有价值的参考依据。根据感应加热原理,建立了电磁场和温度场的数学模型,进行两个场的顺序耦合分析,通过改变裂纹埋藏深度、线圈位置、材料物性、感应加热时间,探讨其对内部裂纹可检测规律的影响。仿真结果表明,内部裂纹的存在影响试件表面的温度场,并且随着埋藏深度的增加以及线圈位置偏离越远,表面获得的温度也随之下降,铁磁性材料更容易被检测出来,通过选择合适激励频率或电流强度、线圈位置,红外热像仪能够探测到内部裂纹的存在。     

抗PCM A/μ律压缩及其转换的语音密写

该文提出一种在数字语音信号中嵌入隐蔽信息的方法.根据PCM A/μ律压缩及其转换特性,采用对某些宿主语音样本预修改和动态选择嵌入比特位的方法,使密写信号不仅没有感知失真,而且经A/μ律压缩及其相互转换处理后仍可无误提取嵌入的隐蔽数据,因此含密语音信号不仅可在Internet上传输,还可在跨国PSTN中传输.实验结果表明了该方法的有效性.     

浅谈对21世纪初我国“神医”事件的思考

本文概述了21世纪初我国几个典型的＂神医＂事件,初步分析了21世纪初我国＂神医＂的基本特征,并在法律层面和科技工作者层面上提出了相关对策,指出：在法律层面上,应进一步完善相关法律法规;而在科技工作者层面上,应进一步加强媒体、科技工作者、政府的合作。     

On spatially explicit models of cholera epidemics

We generalize a recently proposed model for cholera epidemics that accounts for local communities of susceptibles and infectives in a spatially explicit arrangement of nodes linked by networks having different topologies. The vehicle of infection (Vibrio cholerae) is transported through the network links that are thought of as hydrological connections among susceptible communities. The mathematical tools used are borrowed from general schemes of reactive transport on river networks acting as the environmental matrix for the circulation and mixing of waterborne pathogens. Using the diffusion approximation, we analytically derive the speed of propagation for travelling fronts of epidemics on regular lattices (either one-dimensional or two-dimensional) endowed with uniform population density. Power laws are found that relate the propagation speed to the diffusion coefficient and the basic reproduction number. We numerically obtain the related, slower speed of epidemic spreading for more complex, yet realistic river structures such as Peano networks and optimal channel networks. The analysis of the limit case of uniformly distributed population sizes proves instrumental in establishing the overall conditions for the relevance of spatially explicit models. To that extent, the ratio between spreading and disease outbreak time scales proves the crucial parameter. The relevance of our results lies in the major differences potentially arising between the predictions of spatially explicit models and traditional compartmental models of the susceptible–infected–recovered (SIR)-like type. Our results suggest that in many cases of real-life epidemiological interest, time scales of disease dynamics may trigger outbreaks that significantly depart from the predictions of compartmental models.     

麦克斯韦的尾模型方程的守恒律

研究麦克斯韦的尾模型方程的守恒律.运用直接方法以及解空间上的变分方法讨论方程的守恒律.给出了麦克斯韦尾模型方程形如(T1(x,t,u,ux,ut),T2(x,t,u,ux,ut))的守恒向量.利用2种方法得到了麦克斯韦的尾模型方程的3个守恒律.     

糕点生产现场检查的要点

深入理解食品生产相关法令法规和标准,逐步统一各级执行者的认识,通过不断学习和实践提高基层监管的专业水平,是食品安全监管工作发展的当前迫切要求。本文整合了国内各标准和法规对糕点生产现场各要素的具体要求,同时罗列了该类产品生产的主要污染源、控制方式以及标签标识,为监管人员和审核人员从实际工作需求角度去理解各标准和法规提供参考,从而实现在监管工作更加专业高效、重点突出的目标,也可为糕点生产企业现场布局和内审具体工作实施提供技术参考。     

Analysis of factors related to illegal tobacco sales to young people in Ontario

OBJECTIVE: To identify and to discuss factors influencing illegal merchant sales of tobacco to underage people in Ontario, Canada. DESIGN: Results were obtained through random retail compliance checks of tobacco merchants. A multivariate analysis specified the relationship between selected independent variables and the willingness of tobacco merchants to sell to minors. The selected independent variables included retail operation type, community population size, the presence of tobacco production, signage, sex and age of volunteers, smoking prevalence rates, and enforcement rates. PARTICIPANTS: A random, stratified sample of 438 tobacco retailers in 186 communities in Ontario. MAIN OUTCOME MEASURE: Willingness of merchants to sell tobacco to minors. RESULTS: Older youths and girls were more likely to be sold tobacco products. Purchase attempts carried out in tobacco-producing regions were also statistically related to illegal sales. CONCLUSIONS: Policy efforts to control youth access to tobacco in Canada may need to invoke legislation requiring merchants to request proper identification from customers who appear to be under the age of 25, and who seek to purchase tobacco products. Further attention could also be directed at tobacco control policies and enforcement strategies that need to consider the unique challenges faced by jurisdictions where the tobacco industry is a powerful presence.     

胶原蛋白肽产业现状及发展趋势

胶原蛋白肽作为一种新兴的功能性蛋白配料近年来在国内外发展迅速。文中综述了胶原蛋白肽的定义、特性、制备工艺以及国内外胶原蛋白肽产业的发展现状,厘清了胶原蛋白肽推广过程中下游生产企业和消费者关注的3方面问题,包括胶原蛋白肽产品品质与原料来源间关系,胶原蛋白肽功效与分子量间关系以及胶原蛋白肽应用法规,展望了胶原蛋白肽产品的研究发展趋势,以期科学引导从事和关注胶原蛋白肽产业人群,促进国内胶原蛋白肽产业的健康持续发展。     

国内外纺织品标准、法规生态安全要求差异

为使国内相关企业能系统地了解国内外标准和技术法规中对纺织品生态安全性的要求,以便准确、及时地应对国外相关贸易技术壁垒,简述了国内外纺织品生态安全要求相关标准和技术法规,分析了各国、各地区标准与技术法规中对纺织品生态安全要求的差异。     

我国特殊食品法律法规和标准体系现状研究

《食品安全法》第七十四条规定,国家对保健食品、特殊医学用途配方食品和婴幼儿配方食品等特殊食品实行严格监督管理。我国以《食品安全法》作为法律依据,以相关的法规和规章作为补充,建立较为完善的法律法规体系,保障特殊食品的生产经营在约束范围内进行。本文对近年来特殊食品颁布的法律、法规、规章和标准进行系统阐述,总结我国特殊食品的法规体系和标准体系现状。