超声场中硬壁凹坑空化空蚀特性研究

利用高速摄影技术对超声场中硬壁凹坑的空化空蚀特性进行了实验研究,重点研究了凹坑的驻气特性,微泡散逸特性以及空泡对蚀坑发展过程的影响.对直径为1mm的玻璃凹坑进行了空化实验,分别对金属铝和金属铜试件进行了为期60min和240min的空蚀实验,发现硬壁凹坑开始驻留游移空泡是凹坑进入空蚀加速阶段的标志.凹坑倾向于会聚较大的游移空泡并从驻留空泡顶端散逸微泡,这使凹坑成为一个空化核的发生源.在确定的实验条件下,蚀坑直径存在一个确定的稳定值,达到这个稳定值之后蚀坑直径不再增加.     

高职院校旅游专业英语听力教学现状分析与对策研究

目前,我国高职院校旅游专业英语听力教学现状不容乐观,尚存在不少问题。本文全面客观地总结出高职院校旅游专业英语听力教学中存在的问题,并深入分析问题形成的原因,进而提出改进的对策,以期对高职院校英语教学改革提供一些借鉴和启示。     

The concept of ＇respect＇ in the relationship between participant and researcher in a research project

Introduction Educational research is the scientific research applied to educational matters. Some principles should be given to apply tO research with human participants, for the research may bring both benefits and burdens. The research may contribute to the educational betterment of those being studied or even promote educational development of a country. On the other hand, research can be a burden, principally to the participants. It can physically harm them, or invade their privacy, or offend them, and so on （Wilkinson, 2001）. Therefore, ethics of research should be discussed. ＂＇ Research ethics＇ refers to the moral principles guiding research, from its inception through to its completion and publication of results and beyond - for example the curation of data and physical samples after the research has been published＂ （Busher, 2005, p.3）. In this article, I shall explain respect for participants by linking it to the understanding of respect, the notions of informed consent, protection of participants from harm and confidentiality.     

舌形挑流鼻坎水力特性研究

基于拱坝表孔泄洪的水槽实验,分析了舌形挑坎曲率和挑角的变化对水流横向扩散及下游水垫塘底板时均压力的影响。在不同泄流量和下游水深条件下,对不同曲率和挑角的舌形挑坎以及常规挑坎进行了比较研究。结果表明,水流经过舌形挑坎时流态稳定,水舌横向扩散明显。在挑坎末端高程相同的条件下,下泄流量较小时,曲率和挑角越大,水舌单宽流量的横向分布越均匀,水垫塘底板最大时均压力越小;大泄流量时,曲率和挑角不宜过大,以保证水舌扩散效果。     

上市公司经营者股票期权行权价格的确定

经营者股票期权激励的强度和绩效取决于其行权价格的科学测定。针对上市公司探讨了行权价格的确定。     

VOF模型在有支流汇入的河道复杂流场中的应用

采用VOF模型对大渡河与楠桠河交汇处的护堤工程区及其影响范围进行了三维数值模拟计算分析.结果表明:楠桠河与大渡河交汇口处的流态主要受大渡河流态的影响.护堤工程扩建后,断面平均流速在局部的增大,会增加对河岸的冲刷,因此在护堤建设过程中,应加强固岸措施.工程现场的原位试验观察与模拟计算结果吻合较好,加之工程多年来的安全运行,均说明VOF模型是一种处理复杂自由表面的有效方法,可在天然河道,特别是在有支流汇入的复杂河道流场研究中推广应用.