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)     

二元二次Jacobi猜想的求逆公式

利用行列式的基本知识和计算技巧,给出了复数域上一次与二元二次Jacobi猜想的一个简明的求逆公式,验证了Abhyankar多元幂级数在上述情形下的形式求逆公式。     

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.     

新形势下高校开展思想政治教育的几点思考

新形势下,加强和改进大学生思想政治教育工作,探索思想政治教育的有效途径和方法,既是高校和高校思想政治教育工作者的一项重大课题,也是一项紧迫任务。只有发掘课堂教学的主导作用,发挥宿舍在育人中的重要阵地作用,加强校园网络的建设和管理,牢牢把握这块新阵地,运用社会实践这一重要手段,将社会主义荣辱观教育贯穿于大学生的思想政治教育中,才能增强思想政治教育的针对性和实效性,提高大学生思想政治素质。     

本体性游戏与幼儿元认知发展的研究

元认知在个体的发展中起着重要的作用。在不同的个体身上,元认知有成熟与次成熟之别,整体与局部之分。幼儿具有局部的次成熟的元认知。在本体性游戏的影响下,幼儿的元认知将获得较快的发展。     

研究生遥感处理类课程的创新改革与实践研究

结合遥感处理类课程的特点和我校研究生教学的实际需求,本文基于我校研究生《SAR图像处理与解译》课程建设开展改革探索,从教学内容更新、教学方式改革、教学资源优化等方面出发,有机融合课堂研讨式教学、实践开发式教学、教学资源优化、科研成果分享等多元教学模式,在实践中取得了较好的效果,能够激发学生学习和研究的兴趣,提高学生的主动性和创新能力,充分满足遥感技术的发展及研究型专业人才培养的需要。     

从“观音”形态之流变看中国佛教美术世俗化、本土化的过程

在中国佛教美术发展的历史进程中，经历了一个外来艺术本土化、宗教艺术世俗化的过程。这一过程，突出地反映在不同历史时期观音造像的形态变化之中，体现了中国佛教艺术走向世俗的必然趋势。     

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.