应用优化技术计算船舶斜浪中的扭矩外力

从实用角度出发,应用优化技术,确定船舶斜浪中的平衡浮态,在传统方法基础上更接近实际状态. 提出了一种船舶斜置于波浪上的外力计算方法,编制了计算机程序. 另外,特别针对大开口船舶其剖面扭心在基线以下的特点,计及了左右舷不对称横向力对扭矩的贡献.     

冲击波对含水炸药减敏作用的实验研究

对水胶炸药和乳化炸药在冲击波作用后的爆炸性能作了对比实验研究,结果表明水胶炸药的抗压性能明显优于乳化炸药,分析认为造成这种差别的原因是两种炸药不同的结构组分和敏化方式。用示波器捕捉两种炸药受冲击波作用前后的水中爆炸冲击波,利用冲击波参数计算炸药的减敏程度,将炸药的压力减敏作用数量化,克服了以往的研究方法只能用半爆率、拒爆率等概念计数表述的不足。     

广义特征坐标系计算膨胀波与激波优越性的数值验证

最近提出的以流体速度和声速的线性组合为速度而运动的广义特征坐标系,是-个更为-般的坐标系统,当参数取不同特殊值的时候,就可以得到其他经典的坐标系统.这种坐标系的最大特点是,它能跟随膨胀波(当然也可以跟随激波和接触间断)运动,从而在使用同-计算格式的前提下,使得膨胀波的计算精度更高.对膨胀波和激波进行数值试验,结果显示广义特征坐标系在计算膨胀波和激波时明显优于传统的坐标系.     

非线性力学与计算

本文阐述了计算在非线性力学中的地位与作用,并分析了在非线性力学计算中可能遇到的数学问题。列举了在非线性力学若干研究领域中的前沿课题,还探讨了如何充分利用计算机功能与资源的问题。     

纵横波测已紧固螺栓轴向应力

本提出了用纵横波声时测已紧固螺栓轴向应力的一种新方法,解决了用超声精确地测已紧固螺栓应力问题,并且利用超声波沿轴向传播的波速同轴向应力以及三阶弹性常数的关系导出了螺栓应力同其材料声速特性、夹紧距离、温度及纵、横波声时的一种新关系,考虑了受应力作用时温度对声速的影响,简化了测量及计算过程,本还介绍了材料的声速特性实验及测量方法;实验结果表明应力低于２５０ＭＰａ,夹紧距离大于３０ｍｍ时,应力超声测     

强地震的前兆次声波研究

利用在北京昌平安装的次声三点阵,对强地震前兆次声波进行了5年的连续观测。统计分析结果表明:强震前约10天内常能测到振幅很强的前兆次声。其三维动态频谱的特点是,振幅由弱逐渐加强,达到极值后变弱;先为长周期波(10-20分),紧跟着短周期波(5-10分),然后又出现更长的周期波,最后长短周期波一起出现。提前时间与三点阵到震中距离之间没有明显的关系,与震级之间也没有明显的关系。     

Study of the saturation effect and output power of optically pumped FIR laser

In this paper, the density matrix equation of a six-level system has been solved, in case of the FIR wave signals in the system were not small enough to be neglected. The output power density of the laser system has been calculated by means of the iteration method. The saturation effect of the system has been revenled by the numerical calculation. Several sets of curves of laser output power vs, the length of laser with defferent pumping detuning and the optimum operating pressure under certain condition have been obtained. These calculated values were in good agresment with the data provided in the literatures.     

Computation of waves generated by submarine landslides

Waves generated by submarine landslides are treated as three-dimensional flows of a perfect incompressible fluid. For the solution of the Cauchy-Poisson problem a time-discretization is applied which leads at each time step to a non-homogeneous free surface condition; the solution is then divided into two parts. The first part, subject to the true free surface condition, is computed in a simplified domain with constant depth. The second part involves a homogeneous free surface condition, a corrected bottom condition and the true bathymetry. In the case of constant depth, unconditional stability of the time discretization is derived. In the case of variable depth, mass and energy conservation is derived. Numerical results are presented. Comparison is made with other methods for the generation of axisymmetric waves. The transient propagation along a rectilinear coast is studied, including a comparison between two different bathymetries; trapping of energy is observed.     

Ion acoustic turbulence and anomolous transport

Theoretical interpretation of ion acoustic turbulence is shown to require the use of renormalized turbulence theory for calculating the turbulent spectra and transport coefficients. The physics of solitons, double layers, and ion phase space holes have an impact on the one-dimensional problem.     

Ordinary and extraordinary cyclotron waves in metals

Dispersion equations for the ordinary and extraordinary cyclotron waves propagating perpendicular to the magnetic field in metals in the critical region where the wavelength is comparable to the electron Larmor radius are derived as an infinite but rapidly converging power series expansion in δ( = Ω/Ω-M). Numerical studies for the cyclotron wave propagation near the first seven resonances are carried out. The non-local behaviour of those waves in the critical region 01 ⩽ kR ⩽ 3-0 is studied. For the ordinary waves the first few resonances show significant dispersion than those near higher resonances which are dispersion-free. Only one extraordinary wave propagates near the fundamental cyclotron frequency. For the higher resonances, two modes propagate near each of the resonant frequencies, of which one mode remains constant for all values ofkR whereas the second mode shows significant dispersion. But beyond the fifth resonance both the modes are dispersion free.