移动基站无线传感器网络2个参数的优化

针对一种移动基站协助数据收集模式,研究移动基站最佳缓冲区位置的设计问题,得出节点在发射半径r=R的情况下,当移动基站缓冲区的中心位于2／3R时,网络的总能量消耗最小,当中心位于1／2R时,网络的寿命最长。在r〈〈R的情况下,节点的发射功率可选择{l..k}中的一种传送数据,并给出通过插值作图法得到最佳基站缓冲区位置的设置与节点最佳发射功率的计算方法,相比采用固定功率发射方法,能够将网络寿命提高5倍。     

特种电动机高压阀门准确制动的仿真计算

对于特种异步电动机拖动的高压阀门 ,切断电动机交流供电电源后 ,在电机的定子绕组中通入适当的直流电流 ,产生直流磁场 ,使电机进行能耗制动 ,让阀心和电机转子的能量 ,包括动能消耗在转子的绕组中 ,达到准确停车的目的。介绍了这一过程的计算机仿真计算     

水煤浆添加剂的研究进展

随着世界原油资源的日渐减少及燃煤污染的日趋严重，水煤浆作为一种新型的环保型煤基流体燃料日益受到人们的重视。从70年代至今，国内外学都研究过多种添加剂，目前制浆用添加剂主要分为阴离子表面活性和非离子表面活性剂两大类，但高效、价廉、适用性广的添加剂为数并不多。     

A private versus a public space: Anonymity and buying decorative symbolic goods for avatars in a virtual world

The virtual world has become a new channel in which people can contact with others, and organizations can provide service to their customers. Selling symbolic virtual goods has also emerged as a new economy in the virtual world. Such symbolic goods cannot facilitate people to accomplish any specific tasks; people buy them simply to decorate their avatars. This study is based on the theories of symbolic consumption, self-presentation, and computer-mediated environment, to investigate why people buy decorative symbolic goods in the virtual world. The results show that people buy symbolic virtual goods for both emotional and social values. While user perceived social presence and telepresence affect both social and emotional value of symbolic goods, individual self-presentation motivation affects only social value. Besides, anonymous users in the virtual world show behaviors that differ with non-anonymous ones.     

基于龙虎山水电站水轮机选型设计

根据龙虎山水电站的工程概况,对该电站的设计参数进行选择分析,综合考虑各种因素,对比国内能量指标较优的转轮,从各个方面对各型号进行了比较,确定了“4大+1小”为最优方案,选择了最适合于本电站的水轮机的机型.     

Performance of Sewage Sludge Treatment and Electricity Generation by Different Configuration Microbial Fuel Cells

This paper compared the degradation efficiency of sludge organic matters and electric-production by two typical microbial fuel cells——dual-chamber microbial fuel cell(DMFC)and single chamber air cathode microbial fuel cell(SAMFC),and the variations of sludge protein,polysaccharide and ammonia nitrogen within the systems were also investigated.The results showed that the concentration of sludge soluble chemical oxygen demand,protein and carbohydrate of DMFC are higher than these of SAMFC during the systems operation,while DMFC can achieve a better ammonia nitrogen removal than SAMFC.Under the same operation condition,the stable voltage output of DMFC and SAMFC is 0.61 V and 0.37 V;the maximum power density of DMFC and SAMFC is 2.79 W/m3and 1.25 W/m3;TCOD removal efficiency of DMFC and SAMFC is 34.14%and 28.63%for 12 d,respectively.Meanwhile,DMFC has a higher coulomb efficiency than SAMFC,but both are less than5%.The results showed that DMFC present a better performance on sludge degradation and electric-production.     

Dynamics of polymer electrolyte fuel cells undergoing load changes

Numerical simulations are carried out for a single-channel polymer electrolyte fuel cell (PEFC) undergoing a step increase in current density. The objective is to elucidate profound interactions between the cell voltage response and water transport dynamics occurring in a low-humidity PEFC where the membrane hydration and hence resistance hinges upon the product water. Detailed results are presented to show that a step increase in the current density leads to anode dryout due to electroosmotic drag, while it takes several seconds for water back-diffusion and anode humidified gas to re-wet the anode side of the polymer membrane. The water redistribution process is controlled by water production, membrane hydration, electroosmotic drag, and water diffusion in the membrane. The anode dryout results in a substantial drop in cell voltage and hence temporary power loss. Under extreme situations such as dry anode feed, large step increase in the current density, and/or lower temperatures, the cell voltage may even reverse, resulting in not only power loss but also cell degradation. Finally, the dynamics of current distribution after a step change in gas humidification is numerically examined.     

燃料乙醇发展现状和前景展望

介绍了国内外燃料乙醇的发展现状以及我国对于发展燃料乙醇的相关政策,从成本、原料、粮食安全、市场及经济性方面进行了分析,建议应借助人大立法,保证燃料乙醇推广的顺利进行;政府应制定补贴、免征税收等政策并及时落实;积极推进燃料乙醇新技术的开发工作;扩大燃料乙醇应用范围,推进燃料乙醇的应用进程;开展乙醇化工的研究。     

Electro-oxidation of dimethyl ether on Pt/C and PtMe/C catalysts in sulfuric acid

The electro-oxidation of dimethyl ether (DME) on PtMe/Cs (Me = Ru, Sn, Mo, Cr, Ni, Co, and W) and Pt/C electro-catalysts were investigated in an aqueous half-cell, and compared to the methanol oxidation. The addition of a second metal enhanced the tolerance of Pt to the poisonous species during the DME oxidation reaction (DOR). The PtRu/C electro-catalyst showed the best electro-catalytic activity and the highest tolerance to the poisonous species in the low over-potential range (<0.55 V, 50 °C) among the binary electro-catalysts and the Pt/C, but at the higher potential (>ca. 0.55 V, 50 °C), the Pt/C behaved better than PtRu/C. The apparent activation energy for the DOR decreased in the order: PtRu/C (57 kJ mol⁻¹) > Pt₃Sn/C (48 kJ mol⁻¹) ≈ Pt/C (46 kJ mol⁻¹). On the other hand, the activation energy for the MOR showed a different turn, decreased in the following order: Pt/C (43 kJ mol⁻¹) > Pt₃Sn/C (35 kJ mol⁻¹) ≈ PtRu/C (34 kJ mol⁻¹). The temperature dependence of the DOR was greater than that of the oxidation of methanol (MOR) on the PtRu/C.