半平面压电体的Green函数及其应用

本文研究半平面压电体在线力、电荷和位错作用下的弹性场和电场，即Green函数．基于各向异性弹性力学中的Stroh方法和解析延拓理论，推导了Green函数的封闭形式的解．作为解的应用，分析了含半无限裂纹的无限大压电介质的机电耦合场，给出了应力和电位移强度因子的解析表达式．     

在热压缩态中测量相位算符的涨落

利用热场动力学的方法计算了热压缩态中测量相位算符的涨落，引入了两种类型的基础量子涨落，一种是与测量相位的两个正交分量相联系，另一种是与一个测量相位分量和光子数相联系。由此，研究了热压缩压中测量相位涨落的两种压缩及其与温度的关系。     

Penny-shaped crack in a piezoelectric cylinder under electro-mechanical loads

Summary The fracture behavior of a penny-shaped crack in a axisymmetrical piezoelectric ceramic cylinder of finite radius under mechanical and electrical loads is analyzed under electric continuous boundary conditions on the crack surface. The potential theory and Hankel transform are used to obtain a system of dual integral equations, which is then expressed as a Fredholm integral equation. Singular mechanical and electrical fields and field intensity factors of mode I are obtained. The numerical values of various field intensity factors for PZT-6B piezoelectric ceramics are graphically shown for a uniform load and a ring-shaped load, respectively. The effects of the radius of the cylinder on the field intensity factors are investigated. This work was supported by the Korea Research Foundation Grant (KRF-2001-041-E00057).     

偏置信号调制下色关联噪声驱动的单模激光的光强相对涨落

采用线性化近似，计算了由具有色关联的受偏置信号调制的色泵噪声和色量子噪声驱动 的单模激光增益模型的光强相对涨落，发现相对涨落随噪声强度的变化曲线中存在极小值，分析了偏置信号的强度、周期信号频率、噪声间的互关联强度和互关联时间对曲线的影响； 对单模激光增益模型在偏置信号调制和直接信号调制两种方式下的输出光强相对涨落进行了比较，发现光强涨落与偏置信号的强度密切相关. 关键词： 偏置信号调制 光强相对涨落 线性化近似     

光强对短脉冲在准周期光学超晶格中传输的影响

 在考虑自相位调制和高阶群速色散的情况下，分析了超短脉冲在准周期Fibonacci超晶格中传输时，入射光强对脉冲传输特性的影响。结果表明：入射光强度对脉冲传输特性影响很大，不但使频谱展宽，而且限制超晶格的有效长度，是超短脉冲进行频率转换的主要考虑因素之一。     

ZnO纳米管的拉曼光谱学研究

通过对ZnO纳米管样品的拉曼光谱研究,发现ZnO纳米管拉曼频率和体材料拉曼频率相同,在不同波长激发下,ZnO纳米管拉曼谱峰的频率也保持不变,从而得到了极性晶体拉曼谱不同于以往非极性拉曼谱的特性:在纳米体系中没有出现明显的尺寸限制效应。     

The gauged O(3) sigma model: Schrödinger representation and Hamilton-Jacobi formulation

We first study a free particle on an (n−1)-sphere in an extended phase space, where the originally second-class Hamiltonian and constraints are now in strong involution. This allows for a Schrödinger representation and a Hamilton-Jacobi formulation of the model. We thereby obtain the free particle energy spectrum corresponding to that of a rigid rotator. We extend these considerations to a modified version of the field theoretical O(3) nonlinear sigma model, and obtain the corresponding energy spectrum as well as BRST Lagrangian.     

Image feature based automatic correction of low-frequency spatial intensity variations in MR images

An automatic method of compensating for low-frequency variations in magnetic resonance images is presented. Small variations within a tissue type are modelled and a correction function is generated. The methods is based completely on image features and does not need a phantom or user interaction to generate the compensation function. This image correction simplifies digital image analysis and may enhance clinical evaluation. As a result, the correction technique reduces inhomogeneity and improves contrast. Our results show that the radiofrequency response variation of coils can be reduced. The segmentation process, even with a simple threshold method, produces more reliable results when corrected images are used. The presented method is most useful for images acquired in the sagital and coronal planes with circular local coils, or using surface coils, e.g., spine coils.     

An extension of CVDV model to Zeldovich exchange reactions for hypersonic non-equilibrium air flows

A new preferential vibration-dissociation-exchange reactions coupling model – labelled CVDEV – resulting from an extension of the well-known Treanor and Marrone CVDV model, has been derived to take into account the coupling between the vibrational excitation of the and molecules and the two Zeldovich exchange reactions. Analytical expressions for the exchange reactions coupling factor and for the average vibrational energy lost – or gained – by a molecule through an exchange reaction have been developed. The influence of such a coupling has been shown by means of numerical simulations of hypersonic air flows through normal and bow shock waves. Code-to-code comparisons between our model and other recent approaches have been conducted. The infrared radiation of nitric oxide behind a normal shock wave resulting from computations with the CVDEV model has been compared with other coupling model results and to recent shock tube experimental data. These comparisons have shown a good agreement of our model results with the experimental data. In this context, the results show the prominent influence of vibration coupling on the first Zeldovich reaction, and the absence of vibration coupling effects on the second Zeldovich reaction. Received 30 June 1997 / Accepted 3 December 1997     

二步幂零Lie群上sub-Laplace算子的谱

本文首先研究包括Ｇｒｅｉｎｅｒ算子和二步幂零Ｌｉｅ群上ｓｕｂ Ｌａｐｌａｃｅ算子Ｌ在内的广义齐次线性偏微分算子的谱，然后利用酉表示理论确定了算子Ｌ的谱结构，并深化了Ｋ．Ｆｕｒｕｔａｎｉ，Ｋ．Ｓａｇａｍｉ，Ｎ．Ｏｔｓｕｋｉ关于Ｌａｐｌａｃｅ算子的有关结果．