Effect of Annealing on the Surface Microstructure of Y-Ba-Cu-O Superconducting Ceramics

Precusors to the YBa₂Cu₃O_7-δ material were prepared by both the oxalate precipitation method and conventional ceramic processing. Second-phase grains were observed to develop on the exposed fracture surface during annealing at 500° to 600°C in an ambient atmosphere. The second-phase grains were identified to be BaCO₃ using EDX and XRD. The liquid phase, which was formed because of local chemical inhomogeneity in the Y-Ba-Cu-O system, contributed to the formation of second-phase grains as a source of Ba.     

A new voltage control equipment using fuzzy inference

Power system control equipment needs higher sensitivity and operational reliability. Advanced voltage control equipment is needed for reducing the frequency of tap changes and improving the characteristics (the relationship between the actual voltage and reference voltage) of the voltage to meet today's power system requirements. However, these objectives are in a trade-off relationship. Studies of voltage control derived from a knowledge base suitable for electric power systems can satisfy these objectives using fuzzy inference. Compared with corresponding conventional equipment, the new equipment improved the deviation of 30 min average voltage of 30 percent. This paper describes the design concept of new voltage control equipment using fuzzy inference. In addition, field test results are described along with rules of fuzzy inference, membership functions, and the deviation of 30 min average voltage through detailed simulation.     

Interconnected power systems with superconducting magnetic energy storage

The objective of this work is to discuss the concept of back‐to‐back interconnection systems with energy storage, especially with a Superconducting Magnetic Energy Storage (SMES) incorporated into a back‐to‐back DC link. In this case, each converter of the back‐to‐back system is used as a power conditioning system for the SMES coils. Since the AC–DC converter can be designed independently of the frequency of the power system, a two‐way switch is connected to the AC side of each converter. This two‐way switch can select the interconnected power systems. By using the two‐way switches, this system can provide the stored energy in the SMES system to each interconnected power system through two AC–DC converters. For instance, lower‐cost power of each power network can be stored through two converters during the off‐peak hours and made available for dispatch to each power network during periods of demand peak. Then this system increases the reliability of electric power networks and enables the economical operations depending on the power demand. This paper describes the unique operations of the back‐to‐back interconnection with SMES and discuses the optimal SMES configuration for a 300‐MW‐class back‐to‐back interconnection. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(2): 37–43, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20482     

科研项目管理信息系统的设计

介绍了用自顶向下的结构化方法进行科研项目管理信息系统设计的过程。该系统的应用节省了大量人力、物力和财力,提高了企业科研项目管理水平。     

DSP技术在液压混合动力汽车能源控制方面的应用

文章分析了液压混合动力汽车的发展趋势,简述数字信号处理器(DSP)作为控制器的优势和DSP作为控制器对并联式混合动力液压车的能源控制的工作原理,给出了能源控制系统DSP信号流程图和主程序流程图。测试结果表明,DSP能源控制系统能够比较精确的对液压混合动力车的能量消耗与分配进行控制,具有很好的应用前景。     

凤滩水电厂自动发电控制策略

介绍了凤滩水电厂自动发电控制(AGC)策略的实现方法,重点介绍了修正等容量比例有功分配方法及相应措施.程序设计的原则是,机组紧跟目标负荷的情况下,在最佳效率下运行,同时减少机组开/停机次数、有功调节频率和跨越振动区次数,从而减少机组磨损,兼顾运行效率和机组运行安全.     

Negative effect of [bmim][PF6] on the catalytic activity of alcohol dehydrogenase: mechanism and prevention

BACKGROUND: [bmim][PF₆] is a hydrophobic ionic liquid which could be considered as an environmentally friendly solvent for biocatalysis. In pure [bmim][PF₆], however, alcohol dehydrogenase from yeast (YADH) has no catalytic activity. The aim of the present work was (1) to quantitatively study the negative effect of [bmim][PF₆] on the catalytic activity of YADH and the related mechanism and (2) to made an attempt to lessen the negative effect of [bmim][PF₆] on YADH by microemulsifying [bmim][PF₆]. RESULTS: The activity of YADH in the homogeneous solution formed by H₂O, CH₃CH₂OH and [bmim][PF₆] decreased rapidly with the increase of the molar fraction of [bmim][PF₆]. The inhibitory effect of [bmim][PF₆] on YADH was probably caused by the competition of the imidazole group of [bmim][PF₆] with the coenzyme NAD⁺ for the binding sites on YADH. In a water‐in‐[bmim][PF₆] microemulsion, YADH was catalytically active due to the formation of the interfacial membrane of the nonionic surfactant TritonX‐100, which separated YADH from [bmim][PF₆] and avoided the direct inactivation of [bmim][PF₆] on YADH. Under optimal conditions, the activity of YADH was as high as 51 µmol L^?1 min^?1. CONCLUSION: [bmim][PF₆] was an inhibitor of YADH and its negative effect on YADH could be lessened by its microemulsification. Copyright © 2008 Society of Chemical Industry     

On a responsive replenishment system: a fuzzy logic approach

In today's competitive business environment, it is important that customers are able to obtain their preferred items in the shops they visit, particularly for convenience store chains such as 7–Eleven where popular items are expected to be readily available on the shelves of the stores for buyers. To minimize the cost of running such store chains, it is essential that stocks be kept to a minimum and at the same time large varieties of popular items are available for customers. In this respect, the replenishment system needs to be able to cope with the taxing demands of minimal inventory but at the same time keeping large varieties of needed items. This paper proposes a replenishment system which is able to respond to the fluctuating demands of customers and provide a timely supply of needed items in a cost–effective way. The proposed system embraces the principle of fuzzy logic which is able to deal with uncertainties by virtue of its fuzzy rules reasoning mechanism, thereby leveraging the responsiveness of the entire replenishment system for the chain stores. To validate the feasibility of the approach, a case study has been conducted in an emulated environment with promising results.     

Effect of spray nozzle design on liquid-solid contact in fluidized beds

In industrial fluid cokers the feedstock, consisting of heavy bituminous hydrocarbons, is atomized with steam and injected into a hot fluidized bed of coke. Good and uniform contact of the liquid droplets with the solid particles is required to provide heat for the cracking reactions while minimizing mass transfer effects. Experiments in a pilot plant coker have suggested that the initial particle/liquid mixing, in the spray jet, is rather poor. Experiments in a X-ray scanner showed that liquid droplets and entrained particles accumulate just below the tip of the jet plume to form agglomerates.An experimental technique was used to quantitatively determine the quality of mixing with a variety of nozzle configurations including several novel designs. By improving spray stability, redistributing liquid droplets to the solids-rich region of the jet and increasing the surface area of the gas-liquid jet-fluidized bed interface, liquid/solid contact is improved.     

Experimental and analytical study on the spray characteristics of dimethyl ether (DME) and diesel fuels within a common-rail injection system in a diesel engine

This paper investigates the effect of injection parameters on the characteristics of dimethyl ether (DME) as an alternative fuel in a diesel engine with experimental and analytical models based on empirical equations. In order to study macroscopic and microscopic characteristics of DME fuel, this work focuses on the atomization characteristics of DME and compares experimental and predicted results for spray development obtained by empirical models for diesel and DME fuel. Detailed comparisons of spray tip penetration from three different empirical correlations and from visualization experiments of diesel and DME fuels were conducted under various fuel injection conditions. In comparison with the results of different empirical equations for measured spray tip penetration, the experimental results of this study provide good agreement with the calculation results based on empirical equations, except during the earliest stage of the injected spray sequence. The results of atomization characteristics indicate that DME showed better spray characteristics than conventional diesel fuel. Also, the fuel injection delay and maximum injection rate of DME fuel are shorter and lower than those of diesel fuel at the same injection conditions, respectively.