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)     

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.     

Filtration of micro-particles within multi-fiber arrays by adhesive DEM-CFD simulation

A 3D multi-time scale discrete element method-computational fluid dynamic (DEM-CFD) coupling approach was applied to investigate the filtration of micron-sized particles by different types of fiber arrays. Both the pressure drop and the filtration efficiency were examined to indicate the filtration performance of the fiber arrays. Fibers that were uniformly arrayed in a parallel or staggered manner were compared. Results showed that the staggered array showed a better performance than the parallel array in terms of both pressure drop and filtration efficiency. Further, we compared the performance of different staggered arrays, i.e. a regular case, one densified in the front layers and another densified in the back layers. The front densified array was found to enter the clogging and cake filtration stage in the shortest time, leading to the highest filtration efficiency, but the highest pressure drop. The back densified array still achieved a much higher filtration efficiency, despite a much lower pressure drop comparable to that of the regular array. The results suggest that the two kinds of densified arrays may be suited for different purposes, e.g. baghouse filters or breathing masks.     

A novel multi-objective optimization method for the pressurized reservoir in hydraulic robotics

The pressurized reservoir is a closed hydraulic tank which plays a significant role in enhancing the capabilities of hydraulic driven robotics. The spring pressurized reservoir adopted in this paper requires comprehensive performance, such as weight, size, fluid volume, and pressure, which is hard to balance. A novel interactive multi-objective optimization approach, the feasible space tightening method, is proposed, which is efficient in solving complicated engineering design problems where multiple objectives are determined by multiple design variables. This method provides sufficient information to the designer by visualizing the performance trends within the feasible space as well as its relationship with the design variables. A step towards the final solution could be made by raising the threshold on performance indicators interactively, so that the feasible space is reduced and the remaining solutions are more preferred by the designer. With the help of this new method, the preferred solution of a spring pressurized reservoir is found. Practicability and efficiency are demonstrated in the optimal design process, where the solution is determined within four rounds of interaction between the designer and the optimization program. Tests on the designed prototype show good results.     

实施六项举措提升六大作用--浙江大学宁波理工学院开展大学生党员旗帜工程的探索与实践

大学生党员的先进性应落实在大学生的学习、生活和工作诸方面。浙江大学宁波理工学院通过实施以大学生党员挂牌为核心的学生党员旗帜工程,使大学生党员在政治思想、业务学习、班团建设、社会活动、校园文明建设和联系群众等方面的作用都得到了充分的发挥,同时也探索出了一条学生党员做学生思想政治教育工作带头人的新路。     

论非公有制经济宪法地位的确立与提升

非公有制经济的合宪性是其宪法地位确立的前提条件,社会主义市场经济制度的确立是非公有制经济合宪性的基础.我国非公有制经济的宪法地位是随着社会主义市场经济体制逐步建立,在1982宪法的基础上,经过1988年、1993年两次修改后,逐步确立起来的,而随后的1999年、2004年两次修宪则实现了非公有制经济的宪法地位的提升.     

Florida and Puerto Rico Secondary Science Teachers’ Knowledge and Teaching of Climate Change Science

Misconceptions about climate change science are pervasive among the US public. This study investigated the possibility that these misconceptions may be reflective of science teachers’ knowledge and teaching of climate change science. Florida and Puerto Rico secondary science teachers who claim to teach extensively about climate change were surveyed in regard to their conceptions of climate change science and the climate change-related topics they teach. Results show that many teachers hold naïve views about climate change (e.g. that ozone layer depletion is a primary cause of climate change) and climate change science (e.g. that it must be based on controlled experiments for it to be valid). In addition, teachers in both groups neglect crucial topics such as how evidence for climate change is developed and the social, political, and economic dimensions of climate change. Our results suggest the need for teachers to understand how to teach climate change and the nature of climate change science using authentic contexts that promote effective socioscientific decision-making and climate change mitigation.     

Integrating Tinbergen's inquiries: Mimicry and play in humans and other social mammals

Visual signals convey emotions and intentions between individuals. Darwin underlined that human facial expressions represent a shared heritage between our species and many other social mammals. Social play is a fertile field to examine the role and the potential communicative function of facial expressions. The relaxed open-mouth (or play face) is a context-specific playful expression, which is widespread in human and non-human mammals. Here, we focus on playful communication by applying Tinbergen’s four areas of inquiry: proximate causation, ontogeny, function, and evolution. First of all we explore mimicry by focusing on its neural substrates and factors of modulation within playful and non-playful context (proximate causation). Play face is one of the earliest facial expressions to appear and be mimicked in neonates. The motor resonance between infants and their caregivers is essential later in life when individuals begin to engage in increasingly complex social interactions, including play (ontogeny). The success of a playful session can be evaluated by its duration in time. Mirroring facial expressions prolongs the session by favoring individuals to fine-tune their own motor sequences accordingly (function). Finally, through a comparative approach we also demonstrate that the elements constituting play communication and mimicry are sensitive to the quality of interindividual relationships of a species, thus reflecting the nature of its social network and style (evolution). In conclusion, our goal is to integrate Tinbergen’s four areas of ethological inquiry to provide a broader framework regarding the importance of communication and mimicry in the play domain of humans and other social mammals.