低碳贝氏体钢的研究现状与发展前景

综述了低碳贝氏体钢的国内外研究现状,指出低碳贝氏体钢性能优良且成本低廉.并结合低碳贝氏体钢的市场需求和邯钢品种钢的研发方向,展望了低碳贝氏体钢的发展前景,提出低碳贝氏体钢产品品种的开发及其控轧控冷工艺的研制是其研究方向.     

Laser direct writing of β-Co/Ga and Mn/Ga alloy microstructures from organometallic single-source precursors

β-Co/Ga and Mn/Ga alloys have been deposited on various substrates by laser direct write chemical vapour deposition (LCVD) from novel single-source precursors. The preformed alloy stoichiometry of 1:1 defined by the metal ratio of the precursors, (CO)₄Co-GaEt₂(NMe₃) (1) and (CO)₅Mn-GaEt₂(NMe₃) (2), is retained within the deposited structures. The depositions were up to 1.5 μm thick and the lateral dimension (4 μm) was determined by the diameter of the laser focus. The deposited structures were contaminated with ∼10 at. % C and O (by AES).     

An analysis of the heat transfer rate and efficiency of TE (thermoelectric) cooling systems

The heat transfer rate and efficiency of TE (thermoelectric) cooling systems were investigated. The emphasis of the present study is focused on the use of large-scale TE refrigerators for air conditioning applications. A one-dimensional heat transfer analysis was performed to determine the cooling power and electricity consumption of the TE elements. The constant-property results are in good agreement with the variable-property solutions for TE materials and temperatures typical for air conditioning applications. A heat transfer analysis was also carried out for TE refrigerators equipped with a heat exchanger. Both parallel- and counter-flow heat exchangers were considered. Fluid temperature variations of these two flow arrangements were found to be quite different, but the efficiencies and cold fluid exit temperatures differed only slightly when a uniform current was used for all TE elements. If the length of the heat exchanger exceeds an optimal value, the cold fluid temperature begins to rise and the efficiency drops for both parallel- and counter-flow arrangements. The second law of thermodynamics was applied to the optimization of TE refrigerators operating between two constant-temperature reservoirs and between two flowing fluids. It was found that if a TE cooling system incorporates a heat exchanger, a nonuniform current distribution should be used to achieve the maximum efficiency and the lowest cold fluid temperature. The optimization results for TE refrigerators operating between two constant-temperature reservoirs are not applicable to TE cooling systems between two flowing fluids. The most energy-efficient current distribution for the parallel-flow arrangement is the one which increase in the direction of the cold fluid.     

Developments in iron and steel making

A survey is presented of the direct reduction processes which are presently in commercial operation for the production of iron and steel as an alternative to the classical blast furnace route. The relative advantages and disadvantages of each technology are presented and their relative energy efficiencies discussed.     

Gas-based direct reduction processes for iron and steel production

Gas-based processes for the direct reduction of iron are discussed and compared in terms of their costs and energy effectiveness. Possible future lines of development are presented.     

粉末冶金多孔材料性能研究

为了研究多孔结构的渗透特性和机械性能,采用粉末冶金模压烧结技术制备微孔尺寸约5μm不锈钢、高温合金和铜合金非等厚回转体多孔发汗结构,研究了其微孔分布均匀性、气体渗透性能和力学性能与孔隙率的关系,渗透率随孔隙率增大而增大,强度随孔隙率增大而降低,除铜合金外,延伸率随孔隙率增大而降低。金属粉末冶金多孔材料可用于热防护结构的发汗冷却。     

溅射法制备Al/Pb金属多层膜

通过直流二极溅射法制备了具有不同调制波长和周期的Al／Pb金属多层膜。分别通过扫描电镜、X-射线衍射试验以及能谱对多层膜的表面形貌、断面形貌、结构和组成进行了分析。结果表明,所制备的Al／Pb纳米多层膜既无新相生成也无非晶相产生;在亚微米尺寸范围内,铝和铅的微粒分布均匀;在纳米尺寸范围内,形成了Pb对Al的包覆。     

异步电动机直接转矩控制分析与展望

直接转矩控制技术是目前一种先进的异步电动机变频调速新技术。文中详尽分析了直接转矩控制的数学模型和控制原理,并讨论了其存在的缺陷,提出了相应的改进措施。在此基础上预测了直接转矩控制技术的发展趋势。     

基于人工神经网络的交流感应电机控制系统

讨论了用径向基函数网络(radialbasisfunction,简称RBF)方法所设计的交流异步电机直接转矩控制系统的自适应电机的u-n模型。该模型实时性好,能够克服电机在低速状态下定子电阻的变化及参数变化所带来的影响。仿真表明所设计的系统具有良好的控制性能。     

ModBus协议在无线监控系统中的应用

本文介绍了ModBus协议的原理和在信号无线监控系统上的应用,提出了可有效延长通信距离的中继地址编码方案和传输实现方法,提出了用VC编程通过串行口直接控制数传模块的方案。并讨论了无线数据传输抗干扰措施的一些关键技术问题和解决方法。