求解水下纵向加肋无限长非圆柱壳声辐射问题的一种新的半解析方法

基于齐次扩容精细积分法和复数矢径虚拟边界谱方法，利用Fourier积分变换和稳相法，提出了一种具有较高效率和精度的新的求解水下纵向加肋无限长非圆柱壳声辐射问题的半解析方法．考虑了非圆柱壳和肋骨之间同时存在多种相互作用力和力偶矩，较已往很多学者仅计及法向相互作用力更加符合实际．不仅比较了该文方法和精确解计算纵向加肋圆柱壳在集中点力激励下的声辐射计算结果，同时还研究了肋骨数量、大小以及椭圆柱壳横截面椭圆度对声辐射特性的影响．数值计算结果表明该文方法较已有的混合FE-BE法更为有效．     

Theoretical model of acoustic emission under mechanical loading of rocks in the maximum compaction region

A theoretical model of changes in acoustic emission activity in a geomaterial under continuous or stepwise mechanical loading is justified. Based on this model, the experimentally found laws of emission in the region of the maximum compaction of rock samples with different rates of mechanical loading of these samples are analyzed. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 4, pp. 145–152, July–August, 2006.     

气体爆轰波在声学吸收壁下游的再加强过程

实验研究了爆轰波在声学吸收段下游发生的再恢复过程。利用声学吸收段首先将一个稳定的爆轰波衰减,于是产生一个非稳定爆轰波,速度降为 45% ~60?J。该非稳定爆轰波传出声学吸收段后再次加强,并在距声学吸收段出口端一定距离处突然发展成超驱动爆轰。实验利用烟迹技术捕捉了爆轰波从发生衰减到再次加强的全过程,获得了爆轰波再加强距离随初压变化的实验规律。由此,本文建立了再加强段内加速传播火焰的理论模型,称为激波 -爆燃波复合态,并解释了火焰加速和超驱动爆轰形成的机理。     

任意段变模量桩纵向振动的解析解

建立了均质土中考虑桩端土和桩侧土作用的任意段变模量桩，讨论了在桩顶受纵向激励时的定解问题，并用拉氏变换（Laplace)求得桩顶速度频域响应的解析解，然后利用卷积定理和拉氏逆变换求得桩顶速度时域响应的解析解，并将其运用到桩基质量的动力检测中。对弹性模量突变桩以及模量连续变化桩的振动特性作了进一步的研究，并将理论曲线与实测曲线进行了拟合对比，结果表明，两者吻合较好。     

导管对动脉中脉动流生理参数的影响

导管在循环生理学和临床医学中已得到广泛的应用。血管中介入导管后必然会影响测量的准确性和受检者的正常生理状态。许多学者讨论过导管的介入对压力测量结果的影响,但还未见有讨论导管介入对正常生理状态影响的文章报导。本文基于动脉中血液流的刚性管分析模型,从理论上讨论了血流量和纵向阻抗等生理状态参数在导管介入前后的变化情况,为进一步全面分析导管介入对动脉中血液脉动流的影响提供了理论基础。     

Numerical simulation of receptivity of a hypersonic boundary layer to acoustic disturbances

Direct numerical simulations of the evolution of disturbances in a viscous shock layer on a flat plate are performed for a free-stream Mach number M _∞ = 21 and Reynolds number Re _L = 1.44 · 10⁵. Unsteady Navier-Stokes equations are solved by a high-order shock-capturing scheme. Processes of receptivity and instability development in a shock layer excited by external acoustic waves are considered. Direct numerical simulations are demonstrated to agree well with results obtained by the locally parallel linear stability theory (with allowance for the shock-wave effect) and with experimental measurements in a hypersonic wind tunnel. Mechanisms of conversion of external disturbances to instability waves in a hypersonic shock layer are discussed. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 3, pp. 84–91, May–June, 2007.     

Gas-dynamic approach in the nonlinear theory of ion acoustic waves in a plasma: An exact solution

An exact solution of the problem of the acoustic wave structure in a plasma is obtained. Both plasma component are treated as gases with specified initial temperatures and adiabatic exponents. The system of equations describing the wave profile is solved using an original method consisting of reducing the system to the Bernoulli equation. A numerical example of the obtained general solution of the problem of the wave profile for arbitrary parameters is given. Curves are constructed that bound the region of existence of a stationary solitary ion acoustic wave in the parameter space. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 5, pp. 3–11, September–October, 2007.     

气体非稳定爆轰波在具有声学吸收壁的直角三通弯管中传播特性研究

本文实验研究了丙烷、氧气和空气的预混气体非稳定爆轰波在具有声学吸收壁的直角三通弯管中传播特性，分析了声学吸收材料厚度对非稳定爆轰波传播特性的影响．实验结果表明，在直角三通弯管中安装声学吸收材料对气体非稳定爆轰波有明显的衰减作用，在弯管前后非稳定爆轰波的传播速度和压力都有很大程度的减小．而且随着声学吸收材料厚度的增加，气体非稳定爆轰波强度衰减幅度增大．这一实验结论对工业安全具有重要的参考价值．     

Reproducible time-of-flight measurements with a piezoelectric transducer for acoustoelastic stress evaluation

The acoustic coupling of a piezoelectric transducer to the specimen by means of a viscous couplant proves to be a weak link in performing acoustoelastic experiments. Measurements reveal that an increased coupling layer thickness potentially leads to a more reproducible time-of-flight determination. To assess the consequences of this approach, a model is developed for the pulse-echo configuration. Diffraction in the specimen is taken into account and a viscoelastic model is used to describe wave propagation in shear wave couplant. The results clearly show the advantages of an increased coupling layer thickness. Paper was presented at the 1994 SEM Spring Conference on Experimental Mechanics held in Baltimore, MD on June 8–10.     

Internal streamwise action of saw-tooth sound waves on turbulent jets

The results of an experimental investigation of the acoustic field produced by turbulent subsonic jets under internal acoustic excitation are presented. It is shown that under the action of saw-tooth finite-amplitude waves the turbulent jets can radiate Mach waves into the ambient medium due to compact acoustic disturbances traveling along the jet at a velocity greater than the speed of sound in the surrounding space.Translated from Izvestiya Rossiiskoi Academii Nauk, Mekhanika Zhidkosti i Gaza, No. 5, 2004, pp. 153–158. Original Russian Text Copyright © 2004 by Pimshtein.