新型高k栅介质材料研究进展

随着半导体技术的不断发展，MOSFET（metal-oxide-semiconductor field effect transistor）的特征尺寸不断缩小，栅介质等效氧化物厚度已小至nm数量级。这时电子的直接隧穿效应将非常显著，将严重影响器件的稳定性和可靠性。因此需要寻找新型高k介质材料，能够在保持和增大栅极电容的同时，使介质层仍保持足够的物理厚度来限制隧穿效应的影响。本文综述了研究高k栅介质材料的意义；MOS栅介质的要求；主要新型高k栅介质材料的最新研究动态；展望了高k介质材料今后发展的主要趋势和需要解决的问题。     

Network topology and the theory of rubber elasticity

The earliest investigations on rubber elasticity, commencing in the 19th century, were necessarily limited to phenomenological interpretations. The realisation that polymers consist of very long molecular chains. commencing c. 1930, gave impetus to the molecular theory of rubber elasticity (1932-). according to which the high deformability of an elastomer, and the elastic force generated by deformation, stem from the configurations accessible to long molecular chains. Theories of rubber elasticity put forward from 1934-1946 relied on the assumption that the junctions of the rubber network undergo displacements that are affine in macroscopic strain. The theory of James and Guth (1947) dispensed with this premise, and demonstrated instead that the mean positions of the junctions of a ‘phantom’ network consisting of Gaussian chains devoid of material properties are affine in the strain. The vital significance of the distinction between the actual distribution of chain vectors in a network and their distribution if the junctions would be fixed at their mean positions went unnoticed for nearly 30 years. Experimental investigations, commencing with the incisive work of Gee in 1946. revealed large departures from the relationship of stress to strain predicted by the theories cited. This discrepancy prompted extensive studies, theoretical and experimental, during succeeding years. Inquiry into the fundamentals of polymer networks, formed for example by interlinking very long polymer molecules, exposed the need to take account of network imperfections, typically consisting of chains attached at only one end to a network junction. Various means were advocated to make corrections for these imperfections. The cycle rank ζ of the network has been shown (1976) to be the fundamental measure of its connectivity, regardless of the junction functionality and pattern of imperfections. Often overlooked is the copious interpenetration of the chains comprising typical elastomeric networks. Theories that attempt to represent such networks on a lattice are incompatible with this universal feature. Moreover, the dense interpenetration of chains may limit the ability of junctions in real networks to accommodate the fluctuations envisaged in the theory of phantom networks. It was suggested in 1975 that departures from the form predicted for the elastic equation of state are due to constraints on the fluctuations of junctions whose effect diminishes with deformation and with dilation. Formulation of a self-consistent theory based on this suggestion required recognition of the non-affine connection between the chain vector distribution function and the macroscopic strain in a real network, which may partake of characteristics of a phantom network in some degree. Implementation of the idea was achieved through postulation of domains of constraint affecting the equilibrium distribution of fluctuations of network junctions from their mean positions. This led in due course to a theory that accounts for the relationship of stress to strain virtually throughout the ranges of strain accessible to measurement. The theory establishes connections between structure and elastic properties. This is achieved with utmost frugality in arbitrary parameters.     

Structural acrylic adhesives for the sheet steel fabrication industries

Recent developments in rubber-toughened structural acrylic adhesives now offer sheet steel fabricators the opportunity to replace conventional metal fastening techniques such as spot welding with lower cost, durable, more versatile structural adhesive bonding. These developments, in particular much improved ability to bond oily/waxy surfaces common to the motor car industry and improved retention of fracture toughness after exposure to paint stoving temperatures, are discussed in this paper.     

瓷质抛光砖批量色差产生的原因与对策

从原料与生产工艺过程分析了瓷质势光砖批量色差产生的原因，并提出了相应对策，为生产质量佳化提供一定的参考。     

国外农用非织造布覆盖材料的应用

非织造布在现代农业生产中占有重要地位 ,非织造布作为农用覆盖材料在柑橘、草莓、茶叶、花卉、水稻和玉米育苗以及人参栽培等多方面应用较为广泛 ,本文对国外农用非织造布覆盖材料的特点、性能以及应用情况作了介绍     

The effect of doubly tapered strut morphology on the plastic yield surface of cellular materials

Although the literature on the mechanics of cellular materials is vast, there is no theoretical model to account for the effects of axial yielding of struts aligned to the applied loading direction on the plastic yield surface under multiaxial loading conditions. An anisotropic hexagonal model having tapered strut morphology is developed to show these effects on the plastic yield surface under multiaxial tensile loading condition. This model covers several types of cellular structure such as two-dimensional (2D) hexagonal and square cellular materials, and three-dimensional (3D) hexagonal and rhombic cellular materials of rod-like columnar structure. A tetrahedral element with tapered strut morphology is also used for a foam model to illustrate these effects on the yield surface under axisymmetric loading condition. Plastic collapse due to bending moment in the inclined struts is a dominant mode. However, under multiaxial tensile loading, the collapse due to axial yielding of struts parallel to the loading direction is found to be an important mode. The shape of plastic yield surface was found to depend not only on relative density but also on the strut morphology.     

土工合成材料在防汛抢险中的应用

土工合成材料具有整体性强、抢险速度快、适应性强、储运方便、造价低、经久耐用和可废物利用的优点，在防汛抢险中主要起到排水、反滤和防渗的作用，常用于堤岸崩塌、基础管涌、堤身跌窝与漏洞、背水坡散浸、背水面脱坡、洪水浸顶和防风浪淘刷、涵闸及堵口等方面，可及时排队险情。     

PTC热敏电阻的现状与发展趋势(续一)

基于对1995年以来,国内外PTC热敏电阻的研究,介绍了PTC热敏电阻用原料(BaCO3、TiO2、BaTiO3、SrCO3、PbO、Pb3O4、SrTiO3、PbTiO3、Y2O3、Nb2O5、CaCO3、SiO2等);材料(BaTiO3系、V2O3系及高分子);生产技术(瓷粉制造、烧成、芯片制造、质量评定、理化分析、片式PTC生产);重点产品(消磁、马达启动、限流及加热等用)以及基础研究(相变应力模型、表面势垒模型)等方面的现状及今后的发展趋势。     

半功率点法估计阻尼的一种改进

为了提高半功率点法估计阻尼的精度，探讨了快速傅立叶变换（FFT）离散谱线之间函数值的意义，基于这种连续性理解，构造了半功率点估计阻尼的新算法，采用理论分析与数值仿真相结合的方法研究了半功率点法的主要误差因素和各自特性，特别是其中窗阻尼变化规律，给出了保证阻尼误差小于10％，5％和1％对窗长的要求。