多子阵子空间拟合波达方向估计

提出了考虑阵元互耦的子空间拟合波达方向估计方法。用一带状、对称Toeplitz矩阵对均匀线阵的互耦矩阵建模。根据互耦矩阵自由度,去除部分两边阵元,研究了子空间拟合算法中ESPRIT算法的理论性能。在大快拍的情况下,均匀线阵的MCLS-ESPRIT算法的角度估计误差是一个零均值的联合高斯分布,同时给出了分布的协方差表达式。由方差的数值计算可知,在阵元数和信源数确定的情况下,存在估计标准差最小的子阵;与不存在互耦的理想情况相比,除了估计标准差少许增加外,性能接近。本文的方法已应用于高分辨率测深侧扫声呐,获得了好结果。在声呐阵阵元数增加的条件下,用本文的方法,能抑制均匀线阵的互耦的影响。     

PERFORMANCE CHARACTERIZATION AND MODELING OF A COMPOSITE HIP PROSTHESIS

Hip prostheses made from thick laminated composite material were cyclically tested under biaxial compressive loading. Fatigue damage was studied using X-ray radiography, a surface replication, and sectioning of the specimens. It has been shown that damage in the neck region occurred predominantly in form of matrix cracking along fiber directions in the major load-carrying plies. These matrix cracks initiated from the surface of the medial-posterior corner, as a result of local high compressive stress, extended to the lateral side, and distributed toward the anterior side, with an increase of applied cycles. We also briefly outlined a life-prediction model for predicting the remaining life and strength of the composite prosthesis based on a "critical element" concept, as well as how laboratory test results can be used in the model.     

A laser micro-chopper approach for molecular beam probe

A laser micro-chopper has been designed to respond fast to a molecular beam. A method of spectral structure measurement is established to analyse the responding signals. In experiments, the minimum detectable signals correspond to an air molecular-beam intensity of 5 × 10⁸/s     

THE NECESSARY AND SUFFICIENT CONDITIONS FOR THE SOLVABILITY OF A CLASS OF THE MATRIX INVERSE PROBLEM

Censider the solutions of the matrix inverse problem, which are symmetric positive semide finite on a subspace. Necessary and sufficient conditions for the solvability, as well as the general solution are obtained. The best approximate solution by the above solution set is given. Thus the open problem in [1] is solved.     

基于小波变换及布朗分形模型的纹理分割

在研究小波变换及布朗分形模型的基础上，定义了水平分维数，垂直分维数，对角分维数，并将它们作为纹理特征量来实现纹理的分割．实验结果表明，这些特征量能够很好地反映纹理特征，从而分割时不需有关图象中纹理类别的先验信息，较以往方法在准确度和计算复杂程度上都有很大提高．     

Least‐squares finite element method on adaptive grid for PDEs with shocks

We apply the least‐squares finite element method with adaptive grid to nonlinear time‐dependent PDEs with shocks. The least‐squares finite element method is also used in applying the deformation method to generate the adaptive moving grids. The effectiveness of this method is demonstrated by solving a Burgers' equation with shocks. Computational results on uniform grids and adaptive grids are compared for the purpose of evaluation. The results show that the adaptive grids can capture the shock more sharply with significantly less computational time. For moving shock, the adaptive grid moves correctly with the shock. © 2005 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2006     

Wormhole solution in Bergmann-Wagoner scalar-tensor gravitational theory

We give a Euclidean wormhole solution in the vacuum Bergmann-Wagoner scalar-tensor gravitational theory. We show that this wormhole, unlike others, has complex charge and is a baby universe (half a wormhole).     

退火处理对SnO2薄膜光致发光性质的影响

实验研究表明,SnO2薄膜经过退火处理后其光致发光谱有明显的变化。在氧和氮两种不同气氛中进行热处理,其变化也有差异。这种变化主要是由于SnO2膜中氧空位和自由载流于浓度变化所致。     

N,N′-乙二水杨酰胺合铜(Ⅱ)酸根的Cu(Ⅱ)-Co(Ⅱ)配合物的合成与磁性

本文报道了2个新的Cu(Ⅱ)-Co(Ⅱ)双核配合物的制备。经元素分析和红外、电子光谱以及变温磁化率的测定,研究了配合物的某些性质。     

应用晶体结构数据进行化学反应途径研究 Ⅰ. 五配位钼化合物Mo(L)5的动态立体化学

The principle of structure correlation is applied to 28 crystal structures which contain 44 different five-coordinate molybdenum fragments. The data derived map the reaction pathway for a bimolecular ligand substitution reaction at tetrahedral molybdenum centers. The dihedral-angle method from Muetterties and Guggenberger is employed in order to describe the interconversion between the trigonal bipyramidal (TBP) and the square pyramidal (SQP) conformations via the Berry pseudorotation mechanism in the system of Mo(L)_5 complexes. This structure correlation method provides a convincing mapping of the Berry pathway in this paper.