Vibro-acoustic modelling of a railway bridge crossed by a train

This paper presents a vibro-acoustic modelling of a railway bridge excited by a moving train. The modelling of the bridge-train system is carried out by the modal superposition method taking into account the train mass, the viscoelastic suspension of the vehicles with an unlimited number of trucks and spans of the bridge. The numerical resolution of the coupled equations of motion is carried out by the Newmark’s method with an iterative process. we studied on one hand the influence of the track irregularities on the dynamic behaviour of the bridge-train system on the other hand the noise radiated by the bridge due to the passage of the train. The acoustic pressure is obtained by solving the wave equation which has as excitations source the bridge acceleration, they are considered as acoustic monopoles.     

Test for parameter change based on the estimator minimizing density-based divergence measures

In this paper we consider the problem of testing for a parameter change based on the cusum test proposed by Leeet al. (2003,Scandinavian Journal of Statistics,30, 781–796). The cusum test statistic is constructed via employing the estimator minimizing density-based divergence measures. It is shown that under regularity conditions, the test statistic has the limiting distribution of the sup of standard Brownian bridge. Simulation results demonstrate that the cusum test is robust when outliers exist.     

至多一个分布变点的非参数检验及其渐近性质

本文研究了连续分布函数变点的假设检验问题,通过秩统计量和次序统计量方法,得到了相应的检验统计量及其渐近性质.     

Asymptotic behaviour of solutions to cable stayed bridge equations

Asymptotic behaviour of solutions to the nonlinear variational equations of the two basic types of cable stayed bridges is studied. The equations describe vertical and torsional oscillations of the center span, which is the part of road bed between pylons. Due to damping, amplitude and velocity of oscillations remain bounded if wind force is bounded as well. Moreover, the solution to the nonlinear equations converges to the solution of the steady state problem if wind drops. If the center span has certain aerodynamical properties and the initial state is near to the solution of the steady state problem, then the solution converges to the steady state solution even if the forces representing wind do not vanish.     

水浮力对浮桥动力响应特性的分析

为了研究水介质的浮力对桥梁静态响应、特别是动态响应的影响,了解水浮力在桥梁动力响应上的作用及其大小,利用虚功原理和振型叠加法对桥梁运动的控制方程进行求解,并编制了通用的求解程序,通过对比简支梁桥和浮桥各阶振型的传播速度、静力作用、单阶荷载作用以及移动荷载作用下的动力响应,得出水浮力的存在大大降低了浮桥的挠度,使得浮桥的动力响应存在临界长度,即简支梁桥的运动整体性强,而浮桥的运动局部性强,对浮桥进行动力分析时,可以在临界长度以内进行处理,而不必对整个桥梁进行求解.     

Theory of nonadiabatic electron transitions in symmetrical two-center tunnel electrochemical contact

Passage of current through two-center bridge contact is studied theoretically for a nonadiabatic mechanism of electron transfer. General expressions for steady-state current as a function of overvoltage and bias voltage are obtained. For a symmetrical contact, a simple approximate expression is derived for current in the limit when electron transfer between bridge redox-groups is the slow stage. It is shown that the current as a function of overvoltage passes through a maximum near the equilibrium potential. The shape of the maximum does not depend on the medium reorganization energy.     

Synthesis,structure determination and chemoselective catalytic studies of amino acids complexes of osmium(II)

The two new half sandwich amino acids complexes of osmium, i.e. [Os(η6‐p‐cymene)(κ1‐N‐(rac)‐phenylglycine methylester)Cl₂] ( A ) and [Os(η6‐p‐cymene)(κ1‐N,N′‐(S)‐phenylalanineamido)Cl] ( B ) have been synthesized and employed for chemoselective reduction of ketones (nine α,β‐unsaturated ketones and three saturated ketones). The complexes were characterized by spectroscopic as well as analytical methods; their solid structures were confirmed by single‐crystal X‐ray analysis. Both of the osmium complexes catalyze the reduction of α,β‐unsaturated ketones to saturated ketones via isomerization of the initially produced allylic alcohols. The reducible substrates were studied to obtain information on the steric and electronic factors which may affect the interaction of the substrate with the metal center and, thus, control the selectivity of the hydrogen‐transfer reductions. Copyright © 2008 John Wiley & Sons, Ltd.     

不对称入口速度剖面对两种类型颈动脉分又模型外侧壁切应力的影响

在定常流不对称人口速度剖面条件下,对健康型和致病型颈动脉分叉TF-AHCB模型进行实验和数值模拟研究,发现不对称人口速度剖面的形状对模型外侧壁的低切应力和切应力速度分布有明显影响。在50°模型窦前部的壁面切应力梯度比20°模型高出数倍,当人口速度剖面向颈内动脉偏斜时更可高出10倍以上。这些结果对认识导致动脉粥样硬化斑块的血流动力学因子的影响因素有重要参考价值。     

掺杂Sr8 CaRe3 Cu4 O24:一种可能具有半金属性和大的氧磁矩的材料

用密度泛函理论方法仔细研究了新型钙钛矿铜氧材料Sr8CaRe3Cu4O24的电子结构和磁性性质，发现掺杂将使得这种材料表现出非常奇特的性质：（1）用W或Mo替代Re，将使得材料变成半金属，同时它的磁转变温度仍然很高；（2）对Sr8CaRe3Cu4O24进行空穴掺杂，也将使它变为具有高磁转变温度的半金属材料。更为奇特的是，空穴掺杂将导致O原子上有很大的磁矩。因此，Sr8CaRe3Cu4O24很有可能是一种有广阔应用前景的磁性材料。