Numerical investigation of cavitating flow behind the cone of a poppet valve in water hydraulic system

Computational Fluid Dynamics (CFD) simulations of cavitating flow through water hydraulic poppet valves were performed using advanced RNGk-epsilon turbulence model. The flow was turbulent, incompressible and unsteady, for Reynolds numbers greater than 43000. The working fluid was water, and the structure of the valve was simplified as a two dimensional axisymmetric geometrical model. Flow field visualization was numerically achieved. The effects of inlet velocity, outlet pressure, opening size as well as poppet angle on cavitation intensity in the poppet valve were numerically investigated. Experimental flow visualization was conducted to capture cavitation images near the orifice in the poppet valve with 30° poppet angle using high speed video camera. The binary cavitating flow field distribution obtained from digital processing of the original cavitation image showed a good agreement with the numerical result. Project supported by the National Natural Science Foundation of China (No. 59835160) and Scientific Research Foundation for Returned Overseas Chinese Scholars, State Education Ministry of China (No. 50175097)     

抽象函数的一致强可导性问题

文中指出从区域G包括于K(K是数域)到Banach空间内的抽象函数x(t)的强一致连续性、强(弱)可导性及一致强(弱)可导性、强囿变之间的关系，并且给出一致强可导的条件。     

Operationalizing and validating disciplinary literacy in secondary education

The goal of this study was to define the construct and establish the validity of disciplinary literacy, which has recently gained attention from the implementation of the Common Core State Standards (National Governors Association Center for Best Practices & Council of Chief State School Officers in Common Core State Standards for English language arts & literacy in history/social studies, science, and technical subjects [PDF]. Authors, Washington, DC, 2010). After defining disciplinary literacy in the four core disciplines of English language arts, science, history and social studies, and mathematics, scales were developed and administered to a snowball sample of professionals nationwide, with 857 respondents. The data showed evidence of disciplinary literacy as a multidimensional construct with three related factors: source literacy, analytic literacy, and expressive literacy. Based on EFA and CFA results, we can conclude that there are at least three types of literacy in operation among the four core disciplines. The three factors of literacy varied significantly by the four core disciplines of English/language arts (ELA), science, history and social studies, and mathematics, supporting the notion that each discipline uses literacy uniquely. This is the first study of its kind to attempt to define, quantify, and validate the construct of disciplinary literacy.     

Classifications of college students’ protean and boundaryless orientation to work

Increasingly, individuals navigate their own careers in self-directed (protean) and boundaryless contexts. These concepts have been applied to adult employees but have seen limited application with young adults. Therefore, 205 college students were assessed on the Protean and Boundaryless Career Attitudes scales (Briscoe, Hall, and DeMuth, 2006); i.e., self-directed career management, values-driven, boundaryless mindset, and organizational mobility preferences. Scale items were reworded to focus on college experience. Cluster analysis organized respondents into five distinct protean-boundaryless career types. Three types were similar to those hypothesized for adults, while two types were unique to our sample.     

Modeling water and carbon fluxes above summer maize field in North China Plain with back-propagation neural networks

INTRODUCTION Dynamics of carbon and water vapor fluxesexchange between the atmosphere and the ecosystembiosphere, depend on complex and non-liner interplayamong physiological, ecological, biochemical andedaphic factors and meteorological conditions (Jarvis,1995; Leuning et al., 1995). There are many studiesquantifying the fluxes across different time and spacescales as well as assessing the environment con-straints on them by some kinds of biophysical orempirical models whose resul…     

会计信息法律规定的缺陷与完善

会计信息是一种商品，是价值运动及其属性的一种客观表达。会计信息的特征，可以概括为可靠性、相关性、可比性与可理解性(清晰性)。我国企业会计信息存在的问题主要是会计信息虚假，但在我国现行法律法规中，缺乏对虚假会计信息的具体认定以及由虚假会计信息所产生的其他法律问题的规定。完善我国企业会计信息法律规范，法律必须对于会计信息及虚假会计信息作出明确界定，对提供虚假会计信息的单位和人员的责任作出细化规定，对提供虚假会计信息的损害赔偿作出具体规定，建立专门对会计问题进行司法鉴定的职业——法务会计。     

信息技术与课程整合不等同于CAI

该文从历史发展背景、内涵、目标、教学过程以及对教师和学生的要求等方面对信息技术与课程整合、计算机辅助教学加以区分,并对二者的发展前景做出展望。     

教育与生产劳动相结合的历史发展

本文叙述了教育与生产劳动相结合思想的历史发展,从而归纳出其与经济发展的关系。     

西北民族地区高等理科教育改革初探

本文首先从历史的角度,分析了西北民族地区高等理科教育发展状况,并深入探讨了西北民族地区高等理科教育存在的主要问题,然后结合民族地区社会经济发展特点和民族学生学习特征,有针对性地提出了西北民族地区高等理科教育改革思路.