Crack Tip Field and J-Integral with Strain Gradient Effect

The mode I plane strain crack tip field with strain gradient effects is presented in this paper based on a simplified strain gradient theory within the framework proposed by Acharya and Bassani. The theory retains the essential structure of the incremental version of the conventional J_2 deformation theory No higher-order stress is introduced and no extra boundary value conditions beyond the conventional ones are required. The strain gradient effects are considered in the constitutive relation only through the instantaneous tangent modulus. The strain gradient measures are included into the tangent modulus as internal parameters. Therefore the boundary value problem is the same as that in the conventional theory Two typical crack Problems are studied: (a) the crack tip field under the small scale yielding condition induced by a linear elastic mode-I K-field and (b) the complete field for a compact tension specimen. The calculated results clearly show that the stress level near the crack tip with strain gradient effects is considerable higher than that in the classical theory The singularity of the strain field near the crack tip is nearly equal to the square-root singularity and the singularity of the stress field is slightly greater than it. Consequently, the J-integral is no longer path independent and increases monotonically as the radius of the calculated circular contour decreases.

Seismic Responses of a Hemispherical Alluvial Valley to SV Waves: A Three-Dimensional Analytical Approximation

An analytical solution to the three-dimensional scattering and diffraction of plane SV-waves by a saturated hemispherical alluvial valley in elastic half-space is obtained by using Fourier-Bessel series expansion technique. The hemispherical alluvial valley with saturated soil deposits is simulated with Biot's dynamic theory for saturated porous media. The following conclusions based on numerical results can be drawn: (1) there are a significant differences in the seismic response simulation between the previous single-phase models and the present two-phase model; (2) the normalized displacements on the free surface of the alluvial valley depend mainly on the incident wave angles, the dimensionless frequency of the incident SV waves and the porosity of sediments; (3) with the increase of the incident angle, the displacement distributions become more complicated; and the displacements on the free surface of the alluvial valley increase as the porosity of sediments increases.

基于LBM方法的高速列车空气动力学计算

利用格子波尔兹曼方法计算了高速列车的空气动力学问题.计算采用真实非简化列车几何,千万量级空间网格.不同工况的结果均真实反应实际情况,表明格子波尔兹曼方法在实际工程计算中有非常广阔的应用空间.

Method for measuring the lateral aberrations of a lithographic projection system with mirror-symmetric FOCAL marks

A novel method for measuring the imaging quality of a projection system with mirror-symmetric FOCAL marks is proposed, and the principle of the method is described. Through experiments, it is demonstrated that not only the axial aberrations but also the lateral aberrations can be measured with high accuracy by the method. The advantages of the method include obtaining more aberrations than the FOCAL technique and making it much simpler to perform a full-scale measurement of the imaging quality of a lithographic projection system. (C) 2006 Society of Photo-Optical Instrumentation Engineers.

基于镜像焦面检测对准标记的套刻性能原位测量技术

套刻性能是现代高精度步进扫描投影光刻机的重要性能指标之一。提出了一种基于镜像焦面检测对准标记（简称“镜像焦面检测对准标记”）的光刻机套刻性能原位测量技术。该技术通过对曝光在硅片上的镜像焦面检测对准标记图形进行光学对准，利用标记图形对准位置与理想位置偏差实现套刻性能的原位检测。实验结果表明该技术在进行套刻误差的精确测量的同时还可以全面、定量地计算影响光刻机单机套刻误差的场内参量及场间参量。与目前套刻性能原位测量技术相比，该技术有效地避免了测量精度对轴向像质限制的依赖，简化了光刻机整机性能检测的过程。

一种高效热调谐共振腔增强型探测器及其制作方法

一种高效热调谐共振腔增强型探测器及其制作方法

一种电刺激噪声消除仪

本发明公开了一种电刺激噪声消除仪，包括两根用于采集生物电信号的微电极，所述微电极的信号输出端经噪声抑制电路后输出，所述噪声抑制电路包括差分放大电路和电阻电容补偿电路，所述微电极采集的电信号经电阻电容补偿电路，分别输入差分放大电路的两个输入端，经差分放大之后输出。利用本发明所述电刺激噪声(伪迹)消除仪，可以消除大于生物电信号本身约40倍以上的电刺激噪声，从而有利于实现将电刺激和单位放电记录这两项重要的神经电生理研究技术有机的结合起来，对神经电生理的研究具有积极的促进作用。

红尾副鳅的亚种分化及其动物地理分析

红尾副鳅（Paracobitis variegtus）广泛分布于黄河、长江和南盘江水系的上游。其背鳍分枝鳍条数目、前鼻孔的形态、头部斑纹、须的长度和前躯的被鳞程度等特征均表明红尾副鳅已分化为两个亚种。两个亚种的分布在地理上是相互隔离的:红尾副鳅指名亚种（P.variegatus variegatus）的分布范围限于黄河、长江水系的上游;而新亚种长鳍副鳅（P.variegatus longidorsalis）则仅分布于南盘江的上游。亚种的分化可能与晚更新世时滇东高原的急剧抬升有关。本文还讨论了Nemachilus berezowskii Gunther 1896和Nemacheilusoxygnathus Regan 1908的分类地位。经查看其模式标本,认为上述两个名称应为红尾副鳅指名亚种的同物异名。

用微卫星指纹识别天鹅洲保护区长江江豚个体

DNA指纹个体识别技术是保护遗传学研究中的一种非常重要的手段。为了准确地识别天鹅洲保护区中的每一头长江江豚以开展保护遗传学及其它相关研究 ,并实施有效的种群管理 ,本研究应用 4个微卫星座位初步构建了该群体的DNA指纹图谱 ,并利用此图谱成功地对不同时期在保护区捕获的江豚进行了个体识别研究。结果显示微卫星指纹技术是一种适用于长江江豚个体识别研究的可靠手段

Characteristic study of maximum modal gain of p-doped 1.3 mu m InAs/GaAs quantum dot lasers

We report an experimental and theoretical study of maximum modal gain of p-doped 1.3 mu m InAs/GaAs quantum dot (QD) lasers. The maximum modal gain of the QD laser with five stacks of QDs is as high as 17.5 cm(-1) which is the same as that of the undoped laser with identical structures. The expression of the maximum modal gain is derived and it is indicated that p-doping has no effect to the maximum modal gain. We theoretically calculated the maximum modal gain of the QD lasers and the result is in a good agreement with the experimental data. Furthermore, QDs with lower height or smaller aspect ratio are beneficial to achieving a greater maximum modal gain that leads to lower threshold current density and higher differential modal gain, which is good for the application of p-doped 1.3 mu m InAs/GaAs QD lasers in optical communications systems.

Application of plane wave method to the calculation of electronic states of nano-structures

The electronic states of nano-structures are studied in the framework of effective-mass envelope-function theory using the plane wave basis. The barrier width and the number of plane waves are proposed to be 2.5 times the effective Bohr radius and 15(n), respectively, for n-dimensional nano-structures (n = 1,2,3). Our proposals can be widely applied in the design of various nano-structure devices.

基于有序标记的IP包追踪方案

包标记方案是一种针对DoS攻击提出的数据包追踪方案，由于其具有响应时间快、占用资源少的特点，近年来受到了研究者的广泛关注．但由于包标记方案标记过程的随机性，使得受害者进行路径重构时所需收到的数据包数目大大超过了进行重构所必需收到的最小数据包数目，从而导致重构误报率的提高和响应时间的增长．本文提出了一种基于有序标记的IP包追踪方案，该方案通过存储每个目标IP地址的标记状态，对包标记的分片进行有序发送，使得在DoS发生时，受害者重构路径所需收到的标记包的数目大大降低，从而提高了对DoS攻击的响应时间和追踪准确度．该算法的提出进一步提高了包标记方案在实际应用中的可行性．

DCT变换域乘嵌入图像水印的检测算法

目前大多数水印算法采用线性相关的方法检测水印，但是，当原始媒体信号不服从高斯分布，或者水印不是以加嵌入方式嵌入到待保护的媒体对象中时，该方法存在一定的问题．数字水印的不可感知性约束决定了水印检测是一个弱信号检测问题，利用这一特性，首先从图像DCT（discrete cosine transfom）交流变换系数的统计特性出发，应用广义高斯分布来建立其统计分布模型，然后将水印检测问题转化为二元假设检验问题，以非高斯噪声中弱信号检测的基本理论作为乘嵌入水印的理论检测模型，推导出优化的乘嵌入水印检测算法，并对检测算法进行了实验．结果表明，对于未知嵌入强度的乘水印的盲检测，提出的水印检测器具有良好的检测性能．因此，该检测器能在数字媒体数据的版权保护方面得到了实际的应用．