Vibration analysis of a beam with PCLD Patch

An analytical approach for vibration response analysis of a beam with single passive constrained layer damping (PCLD) patch is presented. The governing equation of motion of the beam is firstly derived on the basis of an energy approach and the Lagrange equation. The noval contribution is that a third admissible function is introduced to represent the longitudinal displacements of the constraining layer in the PCLD patch when the assumed-modes method is applied for discretizing the governing equation. In conventional analytical approaches, only two admissible functions are used together with a longitudinal static equilibrium equation of a section of base beam or constraining layer. Comparison of the computational results from the proposed analytical approach and the conventional analytical approach as well as a commercial FEM code reveals that the proposed analytical approach can describe the vibration responses of the damped beam more accurately for commonly used viscoelastic material (VEM) layer in the PCLD patch while the conventional analytical approach, in general, overestimates the damping effects of the PCLD patch. The advantages and disadvantages of the proposed analytical approach and conventional analytical approach are discussed through some case studies.     

A boundary element method for the calculation of noise barrier insertion loss in the presence of atmospheric turbulence

Atmospheric turbulence is an important factor that limits the amount of attenuation a barrier can provide in the outdoor environment. It is therefore important to develop a reliable method to predict its effect on barrier performance. The boundary element method (BEM) has been shown to be a very effective technique for predicting barrier insertion loss in the absence of turbulence. This paper develops a simple and efficient modification of the BEM formulation to predict the insertion loss of a barrier in the presence of atmospheric turbulence. The modification is based on two alternative methods: (1) random realisations of log-amplitude and phase fluctuations of boundary sources and (2) de-correlation of source coherence using the mutual coherence function (MCF). An investigation into the behaviours of these two methods is carried out and simplified forms of the methods developed. Some systematic differences between the predictions from the methods are found. When incorporated into the BEM formulation, the method of random realisations and the method of MCF de-correlation provide predictions that agree well with predictions by the parabolic equation method and by the scattering cross-section method on a variety of thin barrier configurations.     

障碍平方期权的定价

本讨论了一种变异期权——收益结构为平方的障碍期权，在股票价格服从几何布朗运动的模型下，由带单侧吸收壁的布朗运动的密度和分布函数得到连续障碍平方期权的定价公式．     

On the role of the interface charge in non-ideal metal–semiconductor contacts

The bias dependent interface charge is considered as the origin of the observed non-ideality in current–voltage and capacitance–voltage characteristics. Using the simplified model for the interface electronic structure based on defects interacting with the continuum of interface states, the microscopic origin of empirical parameters describing the bias dependent interface charge function is investigated. The results show that in non-ideal metal–semiconductor contacts the interface charge function depends on the interface disorder parameter, density of defects, barrier pinning parameter and the effective gap center. The theoretical predictions are tested against several sets of published experimental data on bias dependent ideality factor and excess capacitance in various metal–semicoductor systems.     

高温超导体的结构组装

 在总结铜氧化物高温超导体晶体结构特点的基础上，提出了以无限层结构Cu-O钙钛矿为核心的结构组装概念，通过和相关结构的外延组合，衍生出了高温超导体的主要晶体构型。进一步运用此观念，建立了新的三元数命名法，并对高温超导体的晶体结构进行了归类。     

Moisture barrier of AlxOy coating on poly(ethylene terephthalate), poly(ethylene naphthalate) and poly(carbonate) substrates

The moisture barrier property of Al_xO_y coated poly(ethylene terephthalate) (PET), poly(ethylene naphthalate) (PEN) and poly(carbonate) (PC), have been investigated. The differences in the morphology of the Al_xO_y sputtered grown on these substrate were investigated using atomic force microscopy (AFM). The initial growth of the Al_xO_y followed closely the topology of the substrate and an amplified roughness was observed. In the fully grown Al_xO_y, the comparative roughness followed that of the substrates. It has been found that a single layer Al_xO_y improved the moisture barrier of PET by an order of magnitude, PC by two orders of magnitude while no improvement was observed for PEN. UV-ozone treatment on PC further improved the moisture barrier, while no improvement was observed for PET and PEN. The comparative effects of the substrate surface roughness and surface energy on the moisture barrier are discussed.     

Constructing Solutions of an Ill-Posed Nonlinear Singularly Perturbed Problem for an Equation of Elliptic Type

Mathematical Notes -     

氩气介质阻挡放电的发光特性

本文使用水电极介质阻挡放电装置,采用光学方法测量了氩气介质阻挡放电的发光特性。发现在驱动电压处于一定的范围内时,放电处于丝极模式,在驱动电压的每半周期内,无论是放电的总光还是单个微通道的放电发光均只有一次脉冲,单个微放电的时间为2μs,而总放电时间为2.4μs,这表明在氩气的丝极模式中,各单丝产生与熄灭的时间极其接近,各个放电丝之间有着很好的时间相关性。最后将本文的结果与空气中介质阻挡放电丝极模式的发光特性相比较,空气放电在每半周内的总光信号由多个脉冲组成,而每一个脉冲对应多个放电丝,因而氩气中各个放电微通道之间的时间相关性远强于空气的情况。     

超重核266Hs形成截面的入射道依赖

计算和比较了²⁶Mg+²⁴⁴Cm, ²⁷Al+²⁴³Am和³²S+²³⁸U3个反应系统的俘获截面和复合核²⁷⁰Hs形成截面. 在俘获截面计算中, 考虑了靶核形变效应. 穿越库仑势垒后, 反应系统由熔合谷进入不对称裂变谷. 只有越过不对称裂变谷中的条件鞍点的事件才进入复合核组态. 我们用考虑中子流动和径向运动的二参量Smoluchowski扩散方程来处理中间阶段的动力学过程. 此外, 还计算了经4n蒸发形成超重核²⁶⁶Hs的截面. 研究表明, 入射道的势垒分布, 中间阶段的条件鞍点高度对俘获截面, 复合核形成几率, 以及最终的超重核形成截面有显著影响.     

Time dependent analysis of finite buffer fluid flows and risk models with a dividend barrier

Based on the matrix-analytic approach to fluid flows initiated by Ramaswami, we develop an efficient time dependent analysis for a general Markov modulated fluid flow model with a finite buffer and an arbitrary initial fluid level at time 0. We also apply this to an insurance risk model with a dividend barrier and a general Markovian arrival process of claims with possible dependencies in successive inter-claim intervals and in claim sizes. We demonstrate the implementability and accuracy of our algorithms through a set of numerical examples that could also serve as test cases for comparing other solution approaches.