Hydrodynamic and thermal development of compressible oscillatory flow inside circular channel

In order to study the hydrodynamic and thermal development of compressible oscillatory flow inside a circular channel, the coefficient of hydrodynamic development (CHD) and the coefficient of thermal development (CTD) are proposed as index parameters, based on the temporal–spatial profile characteristics of the velocity and the temperature field. CHD expresses the variation rate of velocity profile along the axial direction at the phase of centerline velocity reaching its maximum, while CTD denotes the variation rate of temperature profile along the axial direction at the phase of maximum temperature difference between the centerline fluid and the wall. Numerical computations are conducted for a given physical model to validate the effectiveness of these two index parameters. The CHD and CTD as a function of the normalized distance from the entrance into the channel are computed and presented. CHD = 0.1 and CTD = 0.1 are suggested to determine the hydrodynamic and thermal entrance lengths, respectively, which is proved acceptable by comparing the velocity and temperature profiles at various positions along the channel axis.     

Switching memory cells constructed on plastic substrates with silver selenide nanoparticles

Programmable metallization cell (PMC) memory is a kind of next generation non-volatile memory that has attracted increasing attention in recent years as a possible replacement for flash memory. In spite of the considerable amount of research focused on the fabrication of non-volatile memories on plastic substrates with lightweight, thin, and bendable characteristics, there have been few studies on the fabrication of PCM memory on flexible substrates. In this study, we synthesized Ag₂Se nanoparticles (NPs) by a positive-microemulsion method and constructed PMC memories on plastic substrates with programmable layers formed by the spin-coating of the Ag₂Se NPs. To the best of the knowledge, this is the first attempt to construct PMC memory on plastic substrates by the spin-coating of Ag₂Se NPs. The Ag₂Se NPs synthesized in this study had a uniform size of 2 nm and interestingly showed α-phase (high temperature phase) stability at room temperature. Switching behaviors were observed through the voltage scanning on the fabricated memories with applicable switching voltages. However, the resistance ratios of the off-state to the on-state were quite small. The possible reasons for the α-phase stability of the Ag₂Se NPs at room temperature and the detailed memory characteristics will be described in this article.     

Facile synthesis of hypercrosslinked resins via chloromethylation and continuous condensation of simple aryl molecules

A sort of non-polystyrene type hypercrosslinked resin was firstly synthesized through chloromethylation of simple aryl molecules (benzene, toluene, naphthalene, diphenyl), succedent continuous Friedel-Crafts alkylation polymerization and post-crosslinking reaction. The chemical and porous structures of these novel resins were characterized with BET, FT-IR and elementary analysis, respectively. The results showed that these novel adsorptive materials possessing abundant crosslinked networks had high specific surface areas (up to 1191.26 m²/g), large pore volumes (0.2–1.4 ml/g), narrow pore size distributions (mainly in the range of micropores and small mesopores).     

A finite element analysis of ship sections subjected to underwater explosion

This paper presents numerical simulations of dynamic responses of a ship section to non-contact underwater explosion using ABAQUS. The finite element model of the ship section including the size of fluid mesh, initial and boundary conditions etc. has been built up. Comparisons of the acceleration and velocity response between the experimental and numerical results have been investigated. The numerical results agree well with the measured results. Furthermore, the effect of the mass proportional damping factor on the velocity response have been investigated numerically. The dynamic response modes of the ship section subjected to a side-on non-contact underwater explosion are discussed.     

劳动密集型企业社会责任核心要素研究

企业履行社会责任是全球性新趋势。自本世纪初开始,社会责任问题逐渐成为国际社会关注的焦点,一些国家和组织开始研究和制定有关社会责任标准,并推动这些标准的实施。为了满足国际社会对企业社会责任规范化和统一化的需     

硫铝酸钙改性硅酸盐水泥应用研究进展

硫铝酸钙改性硅酸盐水泥熟料兼具硅酸盐水泥熟料和硫铝酸盐水泥熟料的优良性能,同时该种水泥熟料对粉煤灰等火山灰类材料具有超强的活性激发效果,这使得硫铝酸钙改性硅酸盐水泥具有广阔的应用前景。主要概括了硫铝酸盐改性硅酸盐水泥的性能及水化特性,综述了该种水泥与不同矿物掺合料的复合性能以及与化学外加剂的适应性,提出了硫铝酸钙改性硅酸盐水泥存在的问题及改善措施。     

Equilibrium States of Liquid, Solid, and Vapor and the Configurations for Copper, Tungsten, and Pores in Liquid-Phase Sintering

The equilibrium state of the liquid–solid structure during liquid-phase sintering (LPS) is pondered with respect to minimum energy geometries. Besides the solid–liquid ratio, several interfacial energies determine the most stable geometric configuration. In this study, we rely on the attributes of the copper or nickel as the liquid, tungsten as the solid, and vapor to solve for terminal configurations that include liquid pools inside the solid grains. Surface evolution is enabled using a stepwise computer program[1] to rearrange and reshape small grain clusters reflective of LPS based on a preset combination of wetting and dihedral angles. The findings show how different interfacial energies, as a result of oxidation or impurity segregation, play a role in determining the final geometry. The specific concern is identification of situations in which a liquid is stable inside the solid, as observed in some LPS materials.     

基于模范用户的改进协同过滤算法

针对传统协同过滤算法普遍存在的稀疏性和扩展性问题,在传统协同过滤算法的基础上提出一种基于模范用户的协同过滤算法。通过对用户空间的聚类,自动选取模范用户聚类的最优粒度,利用模范用户产生推荐。实验结果表明,与传统协同过滤算法和其他基于聚类策略的算法相比,该算法在明显提高推荐效率的同时对推荐精度和稳定性都有所改进。     

Ag-TCNQ金属/有机双层膜中的扩散机制

研究了用真空分层蒸镀法获得的金属/有机双层膜(Ag-TCNQ)中的层间扩散行为.根据Cu、Ag在与TCNQ形成络合物时表现出的相似性,建立了异质元素标志法,以Cu为标志元素,研究了金属有机络合物Ag-TCNQ形成过程中Ag扩散的微观机制.使用二次离子质谱(SIMS)分析了Cu、Ag元素在不同样品膜中的浓度分布及变化情况.结果表明,不同于纯金属薄膜中Cu、Ag清晰的界面,在络合物中的Cu与Ag之间存在交叉,说明两种离子之间存在着交换现象.由此可以推断,薄膜中的扩散机制是Ag离子在Ag-TCNQ络合物中的换位扩散.