探求高效裂解生产乙烯的新途径

乙烯是裂解反应过程中的中间产物，其收率随反应时间变化．在最佳反应时间，收率最高．裂解反应温度愈高，峰值收率愈高，最佳反应时间则愈短．当前通用的竖管裂解炉难以满足大幅度提高乙烯收率并降低生产成本的要求．评述了几种激波加热方法的优缺点．简要描述了我们目前正在研究中的反向射流混合加热方法．     

Experimental Study of the Dynamic Effect of an Internal Solitary Wave on a Submerged Circular Cylinder

The hydrodynamic loads due to the interaction of a small-amplitude internal solitary wave with a submerged circular cylinder in a two-layer system of miscible fluids were studied experimentally. The dependence of the internal-wave transmission coefficient on the position of the center of the cylinder relative to the pycnocline and on the ratio of the cylinder diameter to the fluid-layer thickness was obtained. The effects of the pycnocline thickness and the depth of the center of the cylinder on the value of the hydrodynamic loads were studied. Visualization of the flow structure was performed. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 46, No. 6, pp. 36–44, November–December, 2005.     

隐式Newmark法分析波动问题精度的探讨

本文研究了用平均加速度的Newmark积分格式求解一维平面弹性波动问题的精度。由于平均加速度的Newmark积分格式没有振幅衰减、不产生数值阻尼,因此采用此法分析波动问题会产生较强的高频振荡,尤其是加速度的计算值误差甚大。本文对防护工程中常见的平台型荷载和升压三角形荷载作用下的波动问题,应用有限元分析的实例表明:采用有数值阻尼的Newmark积分格式是改进有限元求解波动问题的一个有效方法,可以大大地提高应力和加速度求解精度。文中推荐的有数值阻尼Newmark积分格式的积分参数(=0.9,=0.49)可供工程中土与结构动力分析时参考使用。     

Atmospheric pressure waves in the field of volcanology

Atmospheric pressure waves are a notable phenomenon associated with explosive volcanic eruptions. They can provide us with information about eruption processes that are useful both scientifically and practically. In this paper, we give a brief review of studies that have been carried out on this phenomenon in the field of volcanology. Then, we introduce a prototype tool called ‘MOVE’ (Mobile Observatory for Volcanic Explosions). It is a remote-controlled vehicle carrying various instruments to observe pressure waves and the eruption processes. PACS 91.40.Dr · 91.40.Ft · 93.65.+e · 93.85.+qThis paper was based on work presented at the 2nd International Symposium on Interdisciplinary Shock Wave Research, Sendai, Japan on March 1–3, 2005.     

Three-Dimensional Dynamic Contact Problem for an Elliptic Crack Interacting with a Normally Incident Harmonic Compression–Expansion Wave

The paper deals with the three-dimensional dynamic problem for an elliptic crack interacting with a normally incident harmonic compression–expansion wave, considering the contact interaction of the crack faces. An asymmetric solution is obtained using an iteration algorithm developed earlier. Numerical results are presented     

周期波导中弹性波局部化问题的研究

基于弹性波传递矩阵方法，对周期波导中弹性波局部化问题进行了分析研究。根据互易性原理和能量地恒定律，给出了结构弹性波传递矩阵的一般表达式。采用两种求解局部化因子的计算方法，分别计算了谐和与失谐周期波导中的局部化因子，并对其进行了分析讨论。本文对周期波导中波传播与振动局部化的分析方法和计算结果可用于结构的优化设计。     

单侧摩擦约束夹杂物的瞬态弹性波散射的时域边界元分析--反平面情况

应用时域边界元法研究了瞬态SH波对单侧摩擦约束夹杂物的散射问题，假设摩擦遵守库仑定量，当入射SH波足够强时界面会出现局部滑移，发现了一种有效的迭代技术以确定边界上的未知区域（滑移和粘着区）。算例计算了无限域中圆柱埋置夹杂物对瞬态SH波的散射问题。     

Elastic impact on finite Timoshenko beam

In this paper the analytical solutions of the impact of a particle on Timoshenko beams with four kinds of different boundary conditions are obtained according to Navier's idea, which is further developed. The initial values of the impact forces are exactly determined by the momentum conservation law. The propagation of the longitudinal and transverse waves along the beam, especially, the effects of boundary conditions on the characteristics of the reflected waves, are investigated in detail. Some results are compared with those by MSC/NASTRAN.     

An optimisation method for separating and rebuilding one-dimensional dispersive waves from multi-point measurements. Application to elastic or viscoelastic bars

When using a classical SHPB (split Hopkinson pressure bar) set-up, the useful measuring time is limited by the length of the bars, so that the maximum strain which can be measured in material testing applications is also limited. In this paper, a new method with no time limits is presented for measuring the force and displacement at any station on a bar from strain or velocity measurements performed at various places on the bar. The method takes the wave dispersion into account, as must inevitably be done when making long time measurements. It can be applied to one-dimensional and single-mode waves of all kinds propagating through a medium (flexural waves in beams, acoustic waves in wave guides, etc.). With bars of usual sizes, the measuring time can be up to 50 times longer than the time available with classical methods. An analysis of the sensitivity of the results to the accuracy of the experimental data and to the quality of the wave propagation modelling was also carried out. Experimental results are given which show the efficiency of the method.     

Hyperbolicity and one-dimensional waves in compressible two-phase flow models

Hyperbolic models for compressible two-phase flows including a conservative symmetric hyperbolic model are reviewed. The basis for a theory of shock waves is developed within the framework of the latter. The analysis of small amplitude discontinuities allows us to conclude that in general there are two types of shocks corresponding to two sound waves. The problem of transition between a pure phase and a mixture (the phase vacuum problem) is analysed. It is proved that for some models the smooth centred wave solution can not provide such a transition. Within the framework of our conservative model there is the possibility of constructing discontinuous solutions which can resolve the phase vacuum problem.PACS: 47.55Kf, 47.40.-xE. Romenski: On leave from Sobolev Institute of Mathematics, Russian Academy of Sciences, Novosibirsk 630090, Russia