冲击波作用下CHBr3/NaCl界面热弛豫特性研究

非透明材料冲击温度测量是通过对界面光辐射历史的观察实现的 ,因此对界面光辐射历史的研究是非透明材料冲击温度测量的基础。但由于冲击阻抗的失配导致界面上出现波的反射而引起温度的变化与界面热流动产生的温度变化交杂在一起 ,以及过程的瞬时性 ,使得对这一过程的实验研究显得非常困难。设计了一种界面波阻抗近似相同的特殊实验装置 ,用光辐射测量技术研究了在冲击压缩下CHBr3/NaCl界面的热弛豫过程。实验结果和理论分析表明CHBr3/NaCl界面的热弛豫时间在纳秒量级 ,与Grover等人的理论预估一致。     

钽在冲击载荷下的动态力学特性

 在对称碰撞实验中,用VISAR测试系统记录了自由面粒子速度剖面。结合材料常压弹性纵波声速的测量,利用冲击加载的双波结构,测量了钽在30 GPa以内的冲击波速度,给出了线性相关性非常好的D-u_p 关系,并与高压下的测量结果作了比较。同时对由自由面粒子速度剖面来计算层裂强度的模型进行了讨论,发现模型差异对钽的层裂强度的影响超过30%。     

JB9014钝感炸药冲击绝热线测量

 利用压力对比法,采用锰铜计测量待测炸药样品和LY12铝标准样品在LY12铝飞片同时撞击下的界面压力,运用冲击波关系式和正交回归直线拟合分析,确定了JB9014钝感炸药冲击绝热线关系式。     

一个完全守恒的格子Boltzmann模型

利用六角形格子离散的方法,使得每个六角形Cell里含有 3种不同运动速度的粒子微团,宏观物理量用这些粒子微团的矩来定义.根据微观和宏观之间的质量、动量、能量守恒准则,建立了一个二维的D2Q19格子Boltzmann模型,从该D2Q19模型出发可推导出宏观的流体力学方程组.用该模型对冲击波在障碍物组表面上的折射现象进行数值模拟,并将计算结果与实验进行了比较.     

β-delayed proton decays of 93Pd and 92Rh

β-delayed proton precursors ⁹³Pd and ⁹²Rh were produced by the irradiation of ⁵⁸Ni with a ⁴⁰Ca beam, and identified using proton-gamma coincidence measurements in combination with a helium-jet fast tape transport system. The half-lives of ⁹³Pd and ⁹²Rh were determined to be 1.3(2), 3.0(8) s, respectively. The measured energy spectrum of β-delayed protons and the estimated relative branching ratios to the final states in the daughter nuclei were fitted by a statistic model calculation, and then the ground-state spin and parity of ⁹³Pd were assigned as 9/2^±. Received: 13 April 2001 / Accepted: 22 August 2001     

CORRECTIONS TO THE COLLISION TERM IN THE BGK BOLTZMANN EQUATION

With the discrete method of the hexagonal cell and three different velocities of particle population in each cell, a two-dimensional lattice Boltzmann model is developed in this paper.^[1,2] The collision operator in the Boltzmann equation is expanded to fourth order using the Taylor expansion.^[3,4] With this model, good results have been obtained from the numerical simulation of the reflection phenomenon of the shock wave on the surface of an obstacle, and the numerical stability is also good. Thus the applicability of the D2Q 19 model is verified.     

First measurement of β-decay properties of the proton drip-line nucleus 60Ga

By using the fusion-evaporation reaction ²⁸Si(³⁶Ar,p3n) and spectroscopy of β-delayed γ-rays and charged particles on mass-separated sources, β-decay properties of the neutron-deficient isotope ⁶⁰Ga were studied for the first time. The half-life of ⁶⁰Ga was determined to be 70(15) ms, and, based on βγγ coincidences, the isobaric-analogue state in ⁶⁰Zn was identified at 4851.9(7) keV. A semiempirical proton separation energy value of 40(70) keV was deduced for ⁶⁰Ga. The experimental results on half-life, mass excess, proton separation energy, and structure of the ⁶⁰Zn daughter states are discussed in comparison with various model predictions, including large-scale shell model calculations. Received: 4 September 2001 / Accepted: 12 November 2001     

Studies on the dynamic buckling of circular plate irradiated by laser beam

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Carrier shock and frequency conversion of a few—cycle pulse laser propagating in a non—resonant two—level atom medium

We have studied the spectral behaviour of few-cycle soliton pulses in a non-resonant two-level atom medium by solving the full Maxwell－Bloch equations. It is demonstrated further that the carrier effects play an important role in the propagation of the few-cycle pulse laser. When the frequency detuning is not very large, both the population distribution and the refractive index of the medium follow the oscillatory carrier field instantaneously; in this case, carrier-wave compression or carrier shock occurs, and a supercontinuum broader than that in the resonant medium may be generated. When the frequency detuning is large, the carrier shock is weak and the spectrum is not continuous, only showing an odd harmonic radiation.     

激波管中动态相变的数值研究

用松弛模型研究了范德瓦流体中的激波管问题．当松弛参数趋于0时模型存在一个确定的黎曼解．在数值方面推导了松弛格式（relaxing）和完全松弛格式（relaxed）．在一维问题中,对于不同的剖面,数值模拟显示结果趋向于黎曼解,在理论上和数值上研究了参数的影响．对于特定的初始激波剖面,观察到了非经典的反射波．在二维问题中,研究了曲面波前的数值演化,得到一些有趣的波斑图．