非均匀变厚度梁的动力响应的一般解

在本文中提出一个新方法——阶梯折算法来研究在任意载荷下任意非均匀和任意变厚度伯努利-欧拉梁的动力响应问题.研究了自由振动和强迫振动.新方法需要将区间离散为一定数目的元素,每个元素可看作是均匀和等厚度的.因此均匀、等厚度梁的一般解可在每个元素上应用.然后用初参数表示的整个梁的一般解使之满足相邻二元素间的物理和几何连续条件,这样就可以得到解析形式的自由振动的频率方程和解析形式的强迫振动的最终解,它化为求解二元线性代数方程,与离散元素的数目无关.现在的方法可推广应用至任意非均匀及任意变厚度有粘滞性和其他种类的梁以及其他结构元件问题上去.     

Discrete-event dynamic systems: The strictly convex case

Given the observed outputg _j of a discrete-event system, a classical problem is to find a matrix realisationg _j =cA ^jb withA of least possible dimension. When the sequenceg _j is convex and ultimately 1-periodic, a linear-time algorithm suffices to construct such a realisation over the algebra (R, max, +). When the transient is strictly convex, this realisation is minimal-dimensional.     

Stress intensity factors for corner cracks at a hole under remote tension

The three-dimensional weight function method recently developed by the authors is used to determine stress intensity factors for two symmetric quarter-elliptical corner cracks at a hole in a wide finite-thickness plate subjected to remote tensile loading. The geometry parameters considered arer/t=0.5, 1, 2;a/c=0.2, 0.5, 1, 2;a/t=0.2, 0.5 withinc/r=2. The results are compared, where possible, with other solutions available in the literature. Generally good agreement is observed. The effect of an approximation of the two-dimensional unflawed stress distribution on the accuracy of stress intensity factors by the weight function method is discussed.     

非线性RL电路的暂态特性

对一个可解的非线性ＲＬ电路模型的暂态过程进行了研究，得到非线性ＲＬ电路的一些普遍特性，加深了加ＲＬ电路中的有关概念的理解，对教学有一定的参考价值。     

Morse势函数和钼单晶等的临界切应力的温度依赖性

综述了以往钼、铁、铝、镁等单晶临界切应力温度依赖性的实验；指出：在滑移系统不变的条件下，在一定的温度范围内，临界切应力和温度呈近似指数关系是相当普遍的规律。Ｍｏｒｓｅ势函数应用和实验的吻合说明原子间力对屈服应力的重要作用。结合近来发展讨论今后的发展，指出金属范性的本质深入到电子结构层次研究的重要意义。     

厚环壳的渐近求解方程和作用弯矩M0的解

本文从三维弹性力学基本方程出发，利用几何小参数ａ＝ｒ＿０／Ｒ＿摄动展开，得到了任意载荷下，厚环壳的各级渐近求解方程。它可以分成两组类似平面应变问题和扭转问题的独立方程组。用此方程求得了厚环壳受弯矩Ｍ＿０作用的两级渐近解。     

Determination of Soot Particle Size in a Premixed Flame: a Static and Dynamic Light Scattering Study

In this contribution we report upon our static and dynamic light scattering experiments to characterize soot particles in flames. We studied sooting laminar premixed flame with acetylene as fuel mixed with air as oxidizer. The air equivalence ratio of the combustion was larger than one. We used a Kaskan type burner with circular geometry and a stabilizing flow of nitrogen around the flame. We focused on the determination of the size of the soot particles in the center of the flame as a function of height above burner. In addition we investigated the influence of the mixing ratio of the gases on the size of the particles. Our results show that static light scattering is better suited than dynamic light scattering for a fast and reliable characterization of soot particles in flames. The latter needs detailed a priori information about the flame to allow the unique determination of sizes from the diffusion measurements. The soot particles grow monotonously with height above burner and with decreasing air equivalence ratio. The aggregates have a fractal dimension lower than two.     

CUT ELIMINATION FOR PROPOSITIONAL DYNAMIC LOGIC WITHOUT

The aim of this paper is to extend the semantic analysis of tense logic in Rescher/Urquhart [3] to propositional dynamic logic without*. For this we develop a nested sequential calculus whose axioms and rules directly reflect the steps in the semantic analysis. It is shown that this calculus, with the cut rule omitted, is complete with respect to the standard semantics. It follows that cut elimination does hold for this nested sequential calculus. MSC: 03B45.     

Light level control in birefringent fibres through thermal stress effects caused by the absorption of broadside incident light: a single-ended fibre-optic system

In this paper, light level control is demonstrated using optically induced thermal stress effects in a polarization-maintaining optical fibre. The controlling light beam is absorbed by a blackened segment of the fibre and produces local heating. Light control is demonstrated in the single-ended sensor configuration, which displays a response that cannot be explained from phase delays only, but requires the addition of the coupled mode theory.     

一种基于碳纳米管的随机存储器

利用碳纳米管之间范德瓦耳斯力,设计了一种基于碳纳米管的可读写的随机存储器,研究了系统的双稳性,讨论了存储器的优点和可行性,并得出系统具有良好存储效应所应满足的条件 关键词： 碳纳米管 范德瓦耳斯力 动态随机存储器