两种不同冷却方式在高压变频应用中的对比分析

本文介绍了两种不同冷却方式在600MW机组一次风机变频节能改造中的应用实例，对空一水冷却系统和密闭冷却系统两种冷却方式进行技术方案和经济效益对比分析，阐述了其中存在的差异和特点。为高压变频节能改造中降低冷却系统能耗，提高系统安全可靠性，提供重要的可借鉴经验。     

Layer‐By‐Layer Electropeeling of Organic Conducting Material Imaged In Real Time

Soft materials comprising low‐molecular‐weight organic molecules are attracting increasing interest because of their importance in the development of a number of emerging areas in nanoscience and technology, including molecular electronics, nanosystems for energy conversion, and devices in the widest sense. Their interaction with electrodes and their behavior under electric fields is a topic of vital significance for these areas, and about which very little is known. Here unprecedented evidence is presented for the controlled peeling of organic molecular material when a voltage is applied between the conducting system and the conducting probe of a scanning force microscope. The rate of removal of the material from the surface of the bulk conducting supramolecular material can be tuned. It depends on the potential applied and is initiated only above a threshold value of 200 mV. The results indicate the importance of electric fields on the stability and performance of conducting organic systems at the nanoscale.     

基于DSP的连续可调高压直流电源的研究

本文研制了以DSP为控制核心,集中实现了移相全桥逆变技术、电源输出调压和过压过流保护等功能的新型直流高压发生器。该新型直流高压发生器使用高频开关技术和集成驱动芯片,使装置的体积小,调压响应平稳、快速;输出电压稳定度高,纹波系数小,电路抗干扰能力强;实际应用达到了预期的设计效果。     

Effect of high-voltage electrostatic field on quality of carrot juice during refrigeration

In the present study, carrot juice was used as the experimental material and stored in a 100 kV/m high-voltage electrostatic field (HVEF; E-group) which was used as a freshness-retention system. The changes in the biological properties were investigated relative to those juices which were stored in a common refrigerator (R-group) and controlled at the same temperature (4 °C). The results showed that the extent of color difference (ΔE), amount of total phenolics, tannins, and total plate counts of carrot juice were increased during the storage period, whereas the turbidity and amount of total carotenoids decreased under all treatment conditions. These factors remained relatively constant during storage in the E-group, whereas a significant difference (p < 0.05) was observed in the R-group. The HVEF treatment yielded better physicochemical properties and prolonged the shelf-life of the carrot juice. The application of HVEF at low temperature has the potential of imparting freshness and a high nutritional value to the products.     

锂离子电池用聚合物电解质的最新进展I.干态聚合物电解质

聚合物锂离子电池的发展对聚合物电解质提出了更高的要求,促使人们开发性能优良的干态聚合物电解质。综述了近年来干态聚合物电解质的研究进展,包括:(1)以改性聚氧化乙烯-锂盐复合体系为代表的耦合体系;(2)导电机理完全不同的解耦合体系;(3)阴离子移动受限的单离子体系。其中,解耦合体系与单离子体系的研究得到了特别的关注。     

Theoretical approaches to superionic conductivity

Recent theoretical approaches to the understanding of superionic conductivity in polycrystalline, glassy and polymeric materials are briefly reviewed. Phase transitions to the superionic conducting state in the AgI family are apparently triggered by cluster formation and strong mobile ion interaction within the clusters. Anomalous conductivity and related physical properties are explained in the cluster induced distortion model. Ionic composites such as AgX : Al₂O₃ (X = Cl, Br and I) involve conducting and non-conducting phases and the all-important interface between the two whose space charge enhances the conductivity and also trigger phase transitions to exotic polymorphic phases, for which the mechanisms are yet to be explored. Ion hopping dynamics controls the conductivity of superionic glasses. Mode coupling and jump relaxation theories account for the non-Debye relaxation observed in a.c. conductivity of these glasses. The theory of conductivity in polymer electrolytes—still in its infancy—involves their complex structure and glass transition behaviour. Preparative and thermal history, composition and crystallinity control ionic conductivity. New approaches to the synthesis of optimal polymer electrolytes such as rubbery electrolytes, crystalline polymers and nanocomposites must be considered before achieving a comprehensive theoretical understanding. Based on an invited talk given by the first author at the National Workshop on Solid State Ionics and its Applications, Bharatiar University, Coimbatore, 18–23 January 2002.     

A Strategy for Analysis and Modelling of Impedance Spectroscopy Data of Electroceramics: Doped Lanthanum Gallate

Modelling of impedance spectroscopy (IS) data of electroceramics depends critically on the correct choice of equivalent electrical circuit so that the extracted parameters have physical significance. The strategy proposed to choose the correct circuit involves analysis of IS data in several of the four complex formalisms: impedance, electric modulus, admittance and permittivity together with consideration of the frequency and temperature dependence of data and the magnitude and temperature dependence of extracted resistance and capacitance values. This is demonstrated using IS data from oxide-ion conducting La_0.80Sr_0.20Ga_0.83Mg_0.17O_2.82 ceramics over the range 182 to 280°C. Low temperature data are fitted first, to allow a full characterisation of the bulk response; some of the bulk parameters may then be fixed to enable fitting of the higher temperature data which increasingly feature lower frequency phenomena such as grain boundary impedances. The most appropriate circuit in this case is found to consist of a parallel combination of a resistor, capacitor and constant phase element (CPE) for the bulk response in series with a resistor and capacitor in parallel for a constriction resistance. The origin of the constriction resistance may be associated with the presence of plate-like LaSrGaO₄ secondary phase within the grains and/or with the presence of pores at the grain boundaries. The importance of choosing (a) the correct equivalent circuit and (b) approximately correct input values for the various circuit parameters to be fitted and refined are demonstrated.     

Superconducting Busline Design for HT—7U Tokamak

Superconducting (SC) tokamak HT-7U has seven pairs of buslines connecting toroidal/Poloidal coils and the current leads,These SC buslines(SCBLs) share a common cryostat and are made of the calbe in conduit conductors(CICCs) arranged as a decoupling configuration.In order to reduce the heat loads conducted from the seven current leads with a capacity of 15kA during the magnets cooldown.the buslines with a much lower thermal conduction were employed in comparison with the current leads,and a special cooling loop was designed.     

高性能结型场效应对管及其在ASIC中的应用

采用结型场效应管作为输入级的专用集成电路,一般都具有高速宽带以及高输入阻抗的特点。场效应管与双极型器件相结合,已成为新型专用型集成运算放大器的主要发展方向之一。国内在这些专用集成电路的研制工作中所面临的主要困难,是高耐压高频结型场效应对管的工艺制作。本文在介绍高性能结型场效应对管在ASIC中的应用及其工艺试验情况。