基于整数编码粒子群算法的树状供水管网优化

以管网年费用折算值为目标函数,以管网布置形式及管径为优化参数,建立了树状供水管网的优化设计模型.利用基于整数编码的粒子群算法对这一模型进行了求解,该方法以某一管网连接状态及各管段管径作为粒子群个体,采用整数编码,通过不断地更新粒子的位置来搜索最优的管网结构及管径值,实现了对管网布置形式及管径的同时优化.优化过程中,对进化过程中产生的不可行解进行处理,提高了优化效率.实例表明,将粒子群算法应用于树状管网优化设计中可以获得更好的优化结果和效率.     

高强冷弯薄壁型钢卷边槽形截面轴压柱畸变屈曲试验研究

本文对550MPa高强冷弯薄壁型钢卷边槽形截面轴压构件畸变屈曲性能进行了试验研究,17根试件的试验结果表明:由于试件局部屈曲一般发生在畸变屈曲之前,促使畸变屈曲提前出现,这种相关作用减弱了构件整体刚度,降低了构件承载力;澳洲规范AS/NZS 4600:1996及北美规范NAS 2004中关于发生畸变屈曲构件承载力的计算方法没有考虑局部屈曲和畸变屈曲相关作用的不利影响。依据试验结果本文提出了一种修正直接强度法的建议计算方法,该法计算结果与试验结果较为接近且偏安全。     

Application of an effective strategy for optimizing the design of air curtains for open vertical refrigerated display cases

This paper presents a novel strategy for optimizing the design of air curtains for open vertical refrigerated display cases which is based on an air curtain two-fluid of cooling loss (CLTF) model and a support vector machine (SVM) algorithm. A model for air curtain cooling loss, one important performance factor of display cases, is proposed. To verify the air curtain cooling loss and determine which design parameters significantly influence the performance of air curtains in open vertical display cases, the CLTF model was built to study the flow and transfer of heat through air curtains used in such display cases. After the object function for cooling loss is constructed, it is solved using an SVM algorithm with different input design parameter combinations. As a result, the predicted cooling loss is reduced by 19.6%. After being validated using experimental data, the TEC/TDA of optimum display case is found to be reduced by 17.1%. The experimental results show this strategy to be an effective method of optimizing the air curtain design.     

The role of ambient conditions on the performance of a planar,air-breathing hydrogen PEM fuel cell

This paper presents experimental data on the effects of varying ambient temperature (10–40 °C) and relative humidity (20–80%) on the operation of a free-breathing fuel cell operated on dry-hydrogen in dead ended mode. We visualize the natural convection plume around the cathode using shadowgraphy, measure the gas diffusion layer (GDL) surface temperature and accumulation of water at the cathode, as well as obtain polarization curves and impedance spectra. The average free-convection air speed was 9.1 cm s⁻¹ and 11.2 cm s⁻¹ in horizontal and vertical cell orientations, respectively. We identified three regions of operation characterized by increasing current density: partial membrane hydration, full membrane hydration with GDL flooding, and membrane dry-out. The membrane transitions from the fully hydrated state to a dry out regime at a GDL temperature of approximately 60 °C, irrespective of the ambient temperature and humidity conditions. The cell exhibits strong hysteresis and the dry membrane regime cannot be captured by a sweeping polarization scan without complete removal of accumulated water after each measurement point. Maximum power density of 356 mW cm⁻² was measured at an ambient temperature of 20 °C and relative humidity of 40%.     

Electrochemical impedance spectroscopy study of methanol oxidation on nanoparticulate PtRu direct methanol fuel cell anodes: Kinetics and performance evaluation

Electrochemical impedance spectroscopy (EIS) along with cyclic voltammetry (CV) has been applied as a tool for the mechanistic investigation of methanol oxidation on nanoparticulate PtRu fuel cell anodes of a commercially available state of the art membrane electrode assembly (MEA). The spectra could be fitted to a circuit derived analytically for multi-step single adsorbed intermediate reactions. The analysis has indicated that methanol adsorption and surface blocking occur below the onset and the surface is ‘poisoned’ to the highest degree just before the onset, implying that the removal of residues before the onset, if any, is slower compared to the formation. The onset potential is marked by a sudden change in the mechanism as the impedance becomes pseudoinductive. It has also been demonstrated that EIS can be applied for analyzing and singling out different contributions behind electrode performance for methanol oxidation reaction under fuel cell operating condition.     

Protues仿真时值得注意的几个问题

针对单片机Protues仿真时出现的发光管限流电阻、ADC0808芯片的时钟信号、AT24C01芯片地址码等问题进行了必要的说明。     

NaHSO_4在有机合成中的新应用

近年来,硫酸氢钠(NaHSO4)作为一种稳定的、廉价的试剂,被广泛的应用在有机合成中。其可在不同的温和条件下高产率的催化氧化反应,C—O的形成与断裂等反应类型,根据硫酸氢钠的不同形式综述了其在有机合成中的其它新应用。     

Interfacial microstructure and strength of steel/aluminum alloy joints welded by resistance spot welding with cover plate

We joined aluminum alloy A5052 to cold-rolled steel SPCC (Steel Plate Cold Commercial) and austenitic stainless steel SUS304 using resistance spot welding with a cover plate. The interfacial microstructure was observed using transmission electron microscopy. A thick two-layered reaction layer contains Fe₂Al₅ and FeAl₃ and a thin serration reaction layer contains Fe₂Al₅ and FeAl₃ were observed at the A5052/SPCC and A5052/SUS304 interface, respectively. Mechanical property analysis suggested that the reaction layer has no effect on the tensile shear strength of the A5052/SUS304 joint and that the tensile shear strength of the A5052/SPCC joint is influenced by the reaction layer formed at its interface.     

基于本体的车身设计知识库的构建方法研究

在研究本体、知识库相关理论,分析车身设计领域知识形态结构的基础上,建立了车身设计知识本体,并将本体论引入到车身设计知识的管理系统中,提出了构建基于本体的可重构的车身设计知识库,并在理论上提出了该系统的框架结构。