A UNIVERSAL MODULATION FUNCTION AND A GENERALIZED ANALYTICAL SOLUTION FOR PHOTOREFRACTIVE TWO WAVE COUPLING

We proposed a universal form of the modulation function,and derived a generalized analytical solution of the two wave coupled equation in transmission geometry in photorefractive crystal corresponding to the universal modulation function. The generalized analytical solution can be transformed into different analytical solutions reported in previous works on different conditions.In addition, other new analytical solutions can be obtained from the generalized analytical so lution,and an example is given in the present paper.     

INVESTIGATION OF PHOTOREFRACTIVE TWO-WAVE COUPLING IN Cr-DOPED STRONTIUM BARIUM NIOBATE CRYSTAL

We present here the experimental results of photorefractive two-wave coupling in the congruent strontium barium niobate (SBN:61) crystal doped with 1000ppm Cr. Employing a He－Ne laser (632.8nm), we observed the coupling characteristics under different conditions. The crystal shows excellent photorefractive properties, with a high coupling coefficient nearly 6cm^-1 as the beam intensity ratio m is less than 100. The saturated coupling coefficient of SBN:61:Cr shows a maximum at a certain external beam crossing angle 2θ_peak, which varies with different m, showing a nearly linear dependence on m. The saturated coupling response time τ is measured to be less than 0.8 s. The response time decreased with increasing beam crossing angles no matter how large m is. We also observed the behaviour of the probe beam in reversed experimental procedures. We found that the probe beam shows a bistable state in both procedures.     

伽玛函数与一个力学问题的解析解

本文借助质心系动能定理、质心运动定理和伽玛函数Γ(a)的性质,不用计算机和数学软件,得出一个力学问题的解析解.     

TWO-WAVE COUPLING IN PHOTOREFRACTIVE TRANSITION METAL DOPED POTASSIUM SODIUM BARIUM STRONTIUM NIOBATE CRYSTALS

Large values of the exponential gain coefficient are obtained (Γ= 8-20cm^-1) in photorefractive potassium sodium barium strontium niobate crystals doped with transition metal elements: Co, Gu, Fe, Cr and Ni by using two-wave coupling experiments with argon ion laser (λ = 488nm). The response time is measured to be 60-1000ms at an intensity of 5W/cm² for various samples. We find that in all the crystals electrons are the dominant photorefractive charge carriers, and the typical density of carriers is 10¹⁶-10¹⁷ cm^-3.     

OPTICAL BISTABILITY IN A RING CAVITY WITH A PHOTOREFRACTIVE TWO-WAVE MIXER

We observed the phenomenon of optical bistability in a ring cavity with a photorefractive two-wave mixer. The experimental results are in agreement with those of theory.     

APPROXIMATION ANALYTICAL SOLUTION FOR A CURRENT-CARRYING ION SHEATH AND ITS CHAOS CONTROL

A higher-order approximation analytical solution for a current-carrying ion sheath is automatically derived in computer by decomposition method. Chaos behaviors in the system driven by an external periodic oscillation are controlled using feedback control strategy. Its effectiveness is verified by numerical simulations.     

He—HF体系的结构和分析势能函数

利用Ｇｕａｓｓｉａｎ９４程序和ＱＣＩＳＤ／６－３１１＋＋Ｇ方法得到Ｈｅ－ＨＦ和Ｈｅ－ＦＨ两种线性平衡结构,计算出了这两种弱结合分子的结构参数、离解能和二阶力常数。在此基础上,利用多体项展式方法民出Ｈｅ－ＨＦ（Ｘ＾１Σ＾＋）体系的分析势能函数,得到的势能面准确地再现了Ｈｅ－ＨＦ和Ｈｅ－ＦＨ两种线性结构。     

Ar—HF体系的结构,性质和分析势能函数

利用Ｇａｕｓｓｉａｎ９２程序和ＣＩＤ／６—３１１Ｇ＊方法优化得到ＡｒＨＦ和ＡｒＦＨ两种线性平衡结构，计算出了这两种弱结合分子的结构参数和离解能，并使用该程序和ＭＰ２／６—３１１Ｇ＊方法计算得到它们的力常数。在此基础上，利用多体项展式方法导出ＡｒＨＦ（Ｘ１Σ＋）体系的分析势能函数，得到的势能面正确地再现了ＡｒＨＦ和ＡｒＦＨ两种线性结构，预测出ＡｒＨＦ有Ｃｓ结构存在。     

广义势和耗散函数

介绍广义势和耗散函数的概念，并举例说明存在广义势和耗散函数力学体系Ｌａｇｒａｎｇｅ方程的应用。     

广义四维谐振子位势的B-S波函数

关键词：     

C_（60k~2）π－能谱的群论解析计算

本文推导出正二十面体（Ｉ＿ｈ）对称的同系碳簇Ｃ＿（６０ｋ￣２）π－轨道的群约化通式；在紧束缚（Ｈｕｃｋｅｌ）方案下，应用Ｌａｎｃｚｏｓ三对用比方法，对每一类不可约表示仅需造出一个基函数作为起始态，便可使６０ｋ￣２×６０ｋ￣２久期方程达到理想的方块化，系统地求出了Ｃ＿（６０）—Ｃ＿（２１６０）（ｋ＝１—６）按不可约表示分类的方块本证多项式和能级的解析形式（但五次以上代数方程只能求数值报）。文中叙述本方法的梗概，示范Ｃ＿（６０），Ｃ＿（２４０）及Ｃ＿（５４０）的计算结果。     

12MeV LIA X射线斑点测试及其调制传递函数

 介绍了测试12MeV LIA X光斑点的测试系统,利用刀口法和大孔成像法测出所成像的黑密度分布, 获得X光斑点大小结果; 根据该光源的近乎轴对称特点和大孔所成像的密度分布,经数值处理拟合出斑点强度的空间分布;利用该系统,获得了判断12MeV LIA X光成像空间分辨能力的调制传递函数。     

C2分子的分析势能函数与垂直电离势

用ａｂｉｎｉｔｉｏ计算方法和实验光谱数据分别导出Ｃ２分子基态Ｘ１Σ＋ｇ和激发态ｄ３Πｇ的Ｍｕｒｅｌ－Ｓｏｒｂｉｅ函数，同时用ＱＣＩＳＤ／６－３１１Ｇ方法优化出Ｃ－２、Ｃ＋２、Ｃ２＋２分子离子基态的平衡核间距，算出Ｃ２分子的垂直电离势，计算数据与实验光谱数据进行了比较。     

广义含时谐振子的精确解和Berry相因数

本文利用Lewis-Riesenfeld的量子理论,求出广义含时谐振子的精确解。研究了此精确解的绝热渐近极限,并求出广义谐振子在量子绝热情形的Berry相因数。进而利用此精确解构造了广义含时谐振子的相干态,并得到相应的经典Hannay角。     

强激光辐照下窗口材料靶传热及热应力破裂的解析分析

用有限Ｈａｎｋｅｌ积分变换法对轴对称强激光束辐照下平面薄靶（或薄膜）传热及热应力分布进行了解析推导，得到了随时间演变的温度场及相应的热应力场的解析解。对比有关实验，对强激光束辐照窗口材料（例如ＭｇＦ２晶体、Ｋ９玻璃）靶引起其脆性热应力破裂进行了分析，详细讨论了激光强度、激光－靶能量耦合系数、辐照时间及光斑尺寸等因素对靶的破坏的影响。     

从截面上晶粒大小的面密度分布计算体密度分布

在截面上可以测定晶粒依直径大小分布的面密度。利用夏耳和萨尔忒可夫方法可以将面密度换算到体密度。这些方法主要是解多元联立一次方程。本文提出一个新的方法;直接解积分方程,利用拉普拉斯变换求出体密度的解。将所得结果和以前的结果对照,发现有一些差异;即过去的计算的结果一般使密度偏低,并且在变化较大的区间无法正确地估计及计算出来。本文的方法是严格的,可以知道各处的精确程度。在一个具体的例中来表示出这一点。     

板翅式换热器的动态特性分析解

本文用四个连接矩阵描述多股流换热器通道的连接方式、流体的分流和旁通,获得了多股流换热器及其网络动态特性的通用分析解。应用Pingaud模型对板翅式换热器翅片的动态特性进行简化,从而使该通用解可用来求解多股流板翅式换热器的动态特性。通过计算结果和实验的比较,证明此通用解适用于板翅式换热器动态特性求解。