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．     

A Method for Determining the Viscoelastic Characteristics of Composites

An efficient method for determining the deformation function of a composite is discussed. The method is based on a fractional exponential representation of the deformation functions of the composite components. The viscoelastic solution is obtained using the Volterra principle. The deformation function is represented as a function of a base operator. Thus, the problem is solved by approximating the deformation function by a continued fraction and applying the method of operator continued fractions. A computational procedure is detailed and illustrated using data on longitudinal relaxation of polymethylmethacrylate. As an example, the deformation of a polymethylmethacrylate-based fibrous composite with viscoelastic properties is analyzed__________Translated from Prikladnaya Mekhanika,Vol. 41, No. 5, pp. 9–21, May 2005.     

大迎角细长体绕流背涡结构与气动特性分析

结合实验成果，对大迎角细长体绕流结构及其气动特征进行了分析。利用势流理论，探讨了大迎角下非对称侧向力沿物体轴线的变化特征与分离背涡结构之间的关系，得出截面侧向力系数沿轴向呈现正弦型曲线的变化特征是由轴向旋涡不断脱落所形成的多涡系统诱导的结果。对于三涡以上的多涡系统中，对称的物面压强分布并非一定对应对称的涡结构。     

超薄膜磁头滑块气动力特性

采用有限差分法对广义润滑方程进行数值求解,计算出计算机磁头滑块压强场的分布情况。分析、研究了其稳态和动态气动力特性,并将计算结果分别与求解一阶、二阶修正雷诺方程所得到的结果进行了比较,得到如下三个结论:(1)当飞行高度很小,飞行速度较低时,必须采用广义润滑方程进行磁头滑块的气动力计算,(2)与广义润滑方程结果比较,求解一阶修正雷诺方程所得到的计算结果总是偏高,而求解二阶修正雷诺方程所得到的计算结果总是偏低。此外,还解决了大压缩数下数值失稳问题,使得压缩数可以计算到120万,足以适应任何实际工程的需要。     

复合地基承载特性的弹塑性分析

对桩及承台采用线弹性有限元模型,对承台下桩周土采用弹塑性有限元模型,对群桩以外的土体采用线弹性无限元模型,在桩土接触面上设置接触面单元,利用三维弹塑性有限元对桩%D土%D承台相互作用进行了分析。得出了如下结论 :承台下桩顶反力总体表现出角桩最大,边桩次之,中桩最小的分布规律,随着作用在承台上的荷载增大,桩顶反力趋于均匀分布,承台下桩侧摩阻力是由桩端向桩顶逐渐发展的,承台对桩上部侧摩擦阻力存在“削弱作用”。为了验证本文方法的可行性,对承台下有九桩的情况进行了静载试验,将试验结果与本文计算结果进行了比较。     

Effect of boundary conditions on turbulence characteristics in two-phase jet flows with phase transitions

It is shown that there are no self-similarity and similarity of transverse fields of correlation moments of fluctuating parameters of phases in two-phase jets, in contrast to one-phase jets. The influence of the initial values of a number of parameters of a two-phase jet (gas temperature, volume concentration of droplets in the initial cross section, and radius of the initial cross section of the jet) on turbulence characteristics is analyzed on the basis of numerical simulations. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 46, No. 3, pp. 29–40, May–June, 2005.     

Magnetic shielding for DAMPE electromagnetic calorimeter PMTs

The magnetic characteristics of R5610A-01 photomultiplier tubes are studied in this paper. The experimental data shows that the gain of R5610A-01 loses about 53% when the magnetic field is 3 Gs along its +X axis. A cylinder of one-layer permalloy strip is able to reduce the effect of a 3 Gs magnetic field on the PMT gain to less than 1%.     

Destruction of polylactic acid microcapsules under ultrasound irradiation

Hollow microcapsules have been considered for potential applications as drug or gene carriers. This paper describes an investigation into the mechanical properties of microcapsules with a biocompatible polylactic acid (PLA) shell that can be destroyed using ultrasound irradiation. The microcapsules had a radius of 1 to 25 μm and a shell thickness of 100 nm to 3 μm, and their response to ultrasound pulses with a center frequency of 700 kHz to 2 MHz was investigated. It was found that approximately 50% of capsules with a radius of 20 μm were destroyed using pulses with a pressure amplitude of 50 kPa and a frequency of 700 kHz, which is close to the resonance frequency of the capsules.     

Study on the bend characteristics of single mode-multimode-single mode optical fiber structure

In this paper, the bend characteristics of the single mode-multimode-single mode (SMS) fiber structure are experimentally investigated. SMS fiber structure is very sensitive to the bend. The central wavelength shifts to shorter wavelength with the increasing of fiber bend angle. The central wavelength shift changes with the changing of multimode fiber(MMF) bend section length. The shorter bend MMF has higher sensitivity to the bend angle.