小议烯烃和炔烃的加成反应

烯烃和炔烃在结构上的共同点都表现在碳碳双键、碳碳叁键的不饱和性上。在一定条件下都能和氢、卤素等试剂发生一系列的加成反应。但是两者又有较明显的区别,炔烃比烯烃难发生亲电加成,易发生亲核加成反应。本文从烯烃和炔烃的结构上进行比较来寻找性质差别的原因。     

Conversion of CO<Subscript>2</Subscript> to useful substances with composite iron,nickel, and copper catalysts

Composite materials of Fe/Al₂O₃, which consist of small particles of iron supported by thermally stable alumina even at 500–700 °C, have been widely used in the water-gas shift reaction for natural gas reforming. Therefore, Fe/Al₂O₃ is one of the promising candidates for re-transformation of exhausted CO₂ into fuels such as alcohols and hydrocarbons. The development of a CO₂ reforming system using the composite materials of Fe/Al₂O₃ through CO₂ reduction to CO, dissociation of water into hydrogen, and methanol synthesis has been investigated. It was found that dry and steam (i.e. wet) reforming of CO₂ produced almost the same amount of CO. At a temperature above 500 °C, maximal and saturated yields of CO and H₂ from CO₂ and water were obtained. However, this CO₂ reforming system requires higher-pressure conditions from several tens to hundreds standard atmospheric pressure in order to achieve high yield and selectivity for methanol production. In this study we developed the modified CO₂ reforming system by the utilization of Ni and/or Cu instead of Fe in order to obtain other types of useful products such as CO, CH₄, and carbon, more efficiently and selectively under atmospheric pressure. When Ni or Cu was used, conversion of CO₂ was reduced to 76%, while 9% of methane was detected in the case of Ni. On the other hand, though the CO₂ conversion reduced half of the Fe, the selectivity of CO from CO₂ increased to 95% in the case of Cu.     

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)     

树立正确政绩观,打造务实亲民政府

领导干部的政绩观正确与否,直接关系到领导干部能取得什么样的政绩,关系到政府的办事效率,关系到政府在人民群众心里的形象。领导干部要树立正确的政绩观,打造亲民政府,实现和谐社会。     

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.     

大学诊断的理念与实践

大学诊断是国外最近兴起的针对大学开展评价和咨询服务的一种新的形式,它类似于企业诊断。大学诊断是在多种指标数据和调查研究的基础上,采用各种计量方法、定性分析和比较方法对大学的现状、水平和前景竞争力等各个方面进行全面系统地分析,提出判断性的评价意见和发展对策。以武汉大学社会科学研究竞争力评价为例,在中国高校人文社会科学研究竞争力评价的指标数据和评价结果的基础上,通过同类高校之间的比较分析,揭示武汉大学社会科学研究的优势与差距,提出有针对性的发展对策和建议。     

证明责任规范的本质论 --对"不适用规范说"的修正

证明责任规范的本质是事实“真”“伪”不明时法官是经证明责任规范的指示后是不适用实体规范,还是根据证明责任规范直接作出裁判。“不适用规范说”具有特定的优越性,对解决刑事诉讼及行政诉讼中的证明责任问题也具有重大意义。     

关于信息论与课件评价标准的探讨

课件是教育信息的集合，课件的设计与运行是教育信息的获取、加工、处理、传递和反馈的过程。信息论是研究信息的产生、获取、度量、变换、传输、处理、识别及其应用的科学。因而它对课件的设计、课件的评价和课件的完善具有重要的意义。本文以信息论的观点对课件的评价标准问题进行探讨。