Critical Speed Control of a Solar Car

The World Solar Challenge is a 3000 km race for solar powered cars across the Australian continent from Darwin to Adelaide. Each car is powered by a panel of photovoltaic cells which convert sunlight into electrical power. The power can be used directly to drive the car or stored in a battery for later use. Previous papers (P. Howlett, P. Pudney, T. Tarnopolskaya, and D. Gates, IMA Journal of Mathematics Applied in Business and Industry vol. 8, pp. 59–81, 1997; P.G. Howlett and P.J. Pudney, Dynamics of Continuous, Discrete and Impulsive Systems vol. 4, pp. 553–567, 1998) using a simplified model of the battery, have shown that the optimal strategy is essentially a speedholding strategy. In this paper, with a more realistic model of the battery, we show that the optimal driving strategy is a critical speed strategy. For an optimal journey with no beginning and no ending the solar car must always travel at the critical speed. For an optimal journey of finite length the speed must be close to the critical speed for most of the journey. The critical speed depends on the solar power and will normally vary slowly with time.     

混合信号芯片设计处理关键的转折阶段

通过简单地剪切和粘贴知识产权(IP)内核可以加快无工厂半导体公司的系统级芯片(SOC)设计。 过去十年中,涌现出大量的为系统制造商提供专用芯片(ASIC)的小型IC设计公司。这些被称为无工厂企业(因为他们将IC制造过程转交给商业芯片制造工厂),需要的启动资金较少,而且如果市场接受他们的产品的话,能够获得丰厚的回报。在大量设计工具的支持下,这些无工厂设计企业在历史悠久的大型芯片制造商,如IBM、Intel、Motorola和德州仪器公司所主导的市场中赢得了一席之地。     

Buchbesprechungen

Ohne Zusammenfassung     

Analytic models for multistage interconnection networks

Central to all parallel architectures is a switching network which facilitates the communication between a machine's components necessary to support their cooperation. Multistage interconnection networks (MINs) are classified and analytic models are described for both packet-switched and circuit-switched MINs with asynchronous transmission mode. Under strong enough assumptions, packet switching can be modeled by standard queuing methods, hence providing a standard against which to assess approximate models. We describe one such approximate model with much weaker assumptions which is more widely applicable and can be implemented more efficiently. To model circuit switching requires a different approach because of the presence of passive resources, namely multiple links through the MIN which must be held before a message can be transmitted and throughout its transmission. An approximate analysis based upon the recursive structure of a particular MIN topology which yields accurate predictions when compared with simulation is described.     

Hydrogenation of brown coal: 6. Reactions of coal-derived products with hydrogen in the presence of metal-based catalysts

The product from the hydrogenation of an iron-tin treated Morwell, Victorian coal was separated into a number of fractions by solvent separation. Each of these fractions (tetrahydrofuran-insoluble materials, asphaltols, asphaltenes and oils) was reacted separately with hydrogen in tetralin both with and without added catalysts. The effect of added catalyst and of temperature, pressure, time and solvent on the hydrocracking and repolymerization reactions is discussed. The interconvertibility of the brown coal-derived products is clearly established, reinforcing the importance of incorporating reversibility of reactions in mechanistic models developed to describe coal hydroliquefaction.     

Phase Studies Concerning Sintering in Aluminas Doped with Ti4+

Previous solid state analyses of sintering in Ti⁴⁺-doped-commercial alumina are shown to be in error because a liquid phase exists in the appropriate region of the Al₂O₃−TiO₃−Na₂Ophase diagram at least by 1350^°C, a temperature lower than that at which "solid state" studies were conducted. It is suggested that liquid-phase sintering is a much more common occurrence than was realized formerly.     

Finite‐Element Implementation of a Self‐consistent Texture Model with a Hardening Law Based on Dislocation Densities

A self‐consistent texture model is implemented in the finite‐element code ABAQUS/Explicit®. Hardening of the slip systems is described by evolution laws for dislocation densities, and the Bauschinger effect is included. With these ingredients the cold rolling of an IF‐steel is simulated and the evolution of texture and anisotropy is examined. The use of the dislocation based hardening law is found to have a significant effect on the evolution of the anisotropic yield surface, but only very little influence on the texture. Furthermore, the hardening model is used to investigate the evolution of dislocation densities in differently oriented grains during plane strain compression. It is found that the dislocation density varies greatly depending on orientation, an observation which can help to explain the orientation dependence of recrystallization.     

Effect of preparation technique on the properties of Mo-containing Al-MCM-41

The Al-MCM-41 has been used as support to prepare Mo-containing catalysts. The 12- molybdophosphoric heteropoly acid (HPMo) is used as initial compound. The catalysts are synthesized by two different methods: incipient impregnation with aqueous solution of the acid and mechanochemical synthesis. The samples were tested in the reaction of the thiophene hydrodesulfurization after activation with mixture H₂ + H₂S. The effect of the preparation method of the catalysts on their physicochemical and catalytic properties has been studied. A partial destruction of the loaded compound is observed in mechanochemically treated sample whereas the aggregates are formed from the particles of different size in the impregnated sample. The specific surface area of the sample prepared by mechanical–chemical treatment decreases 2–3 times, while the total pore volume is about four times lower. The HDS activity is higher on the impregnated sample than on the mechanochemically treated one.     

最快晶体管的频率接近太赫兹

Robert J.Mears是用于宽带互联网的铒掺杂光纤放大器(EDFA)的发明者。他在寻找将光器件和波导结合到硅中的方法时,发现了一个有趣的结果:一种特殊的硅超晶格结构可以加速某一个