A general method for the connection of a component thermal model to a board

In this paper, a generalized method for the connection of a thermal component model in board- and system-level thermal simulations is presented. The method allows for the definition of uniform heat flow connections as well as the standard uniform temperature interface regions. The use of uniform heat flow ports will be shown to better handle cases where large temperature gradients are present in the base model. The two methods of connecting the component model will be evaluated using two different models. First, a simple example will be presented to illustrate the nonphysical behavior introduced by the use of uniform temperature connections. Second, a model of an electronic package will be used to evaluate the relative merits of the two connection methods with respect to board thermal conductivity and boundary conditions present on the board and the package. It will be shown that the results from use of uniform heat flow connections are generally better than from use of uniform temperature regions with respect to predicting junction and board temperatures.     

Dynamic void formation in a DD-copper-structure with different metallization geometry

In this study the degradation phenomena in dual-damascene copper (DD-Cu) metallizations will be investigated due to high current densities and substrate temperatures by finite element modeling. The static and dynamic simulations and calculations will show the suitability of the method in comparison to experimental results from the literature. Different geometry variations, like overlap and via height as well as a variation of the stress free temperature of the metallization will be carried out. It will be found, that if the maximum temperature in the metallization is near the stress free temperature the electromigration is dominant. If the temperatures differ from the stress free level stress migration will be predominant. Out of this it will be found that the knowledge of the stress free temperature in the metallization is very important for a sufficient migration determination.     

基于一种混合语言模型的自动文本分类技术研究

随着Internet以及Intranet中大量可利用信息的爆炸式增长,文本分类成为处理和组织大量文档数据的关键技术之一。该文提出一种本体论和统计方法相结合的混合语言模型,用以解决自动文本分类问题。首先,通过学习不同类别的训练语料,分别获得各自类别的语言本体知识库,构造成为不同类别的分类器。对于实际文档,将基于不同类别的语言本体知识库分别获得对文档的评价值,并以所获得的最高评价值决定该文档的类别归属。与Bayes,k-nearest neighbor,support vector machine等3种典型的文本分类器进行了比较。实验结果表明,该文方法的分类性能均胜于其上述3种方法。     

Synthesis of the fields of a transverse feed for a spherical reflector

The problem of designing a transverse feed for a spherical reflector is considered and a method is presented for synthesizing the fields on a surface of a sphere enclosing a feed that will produce a specified reflected field at the surface of a spherical reflector. The method identifies the reflector and a spherical surface enclosing the feed as a boundary value problem and uses a finite set of spherical waves to approximate the boundary conditions. A feed designed to excite this field will in turn produce the desired reflected field at the surface of the reflector, under the condition that that portion of the reflected field which is scattered by the feed may be neglected. It is shown that the feed need produce only a small part of the synthesized field to obtain an antenna efficiency of more than 70 percent. Some typical field distributions will be shown so as to indicate a method for designing a feed and to point out the correlation between the polarization of the synthesized field and the polarization of the reflected field at the surface of the reflector.     

Noise reduction method using a variance map of the phase differences in digital holographic microscopy

The phase reconstruction process in digital holographic microscopy involves a trade-off between the phase error and the high-spatial-frequency components. In this reconstruction process, if the narrow region of the sideband is windowed in the Fourier domain, the phase error from the DC component will be reduced, but the high-spatial-frequency components will be lost. However, if the wide region is windowed, the 3D profile will include the high-spatial-frequency components, but the phase error will increase. To solve this trade-off, we propose the high-variance pixel averaging method, which uses the variance map of the reconstructed depth profiles of the windowed sidebands of different sizes in the Fourier domain to classify the phase error and the high-spatial-frequency components. Our proposed method calculates the average of the high-variance pixels because they include the noise from the DC component. In addition, for the nonaveraged pixels, the reconstructed phase data created by the spatial frequency components of the widest window are used to include the high-spatial-frequency components. We explain the mathematical algorithm of our proposed method and compare it with conventional methods to verify its advantages.     

RECONSTRUCTION OF ONE DIMENSIONAL MULTI-LAYERED MEDIA BY USING A TIME DOMAIN SIGNAL FLOW GRAPH TECHNIQUE

A novel inverse scattering method to reconstruct the permittivity profile of one-dimensional multi-layered media is proposed in this paper.Based on the equivalent network ofthe medium,a concept of time domain signal flow graph and its basic principles are introduced,from which the reflection coefficient of the medium in time domain can be shown to be a series ofDirac δ-functions(pulse responses).In terms of the pulse responses,we will reconstruct both thepermittivity and the thickness of each layer will accurately be reconstructed.Numerical examplesverify the applicability of this method     

基于噪声-纹理检测算子的图像去噪方法

利用能量泛函极小化方法对图像进行滤波时,通常用分段常数函数来近似图像,在滤除噪声的同时也丢失了许多纹理和细节信息.基于这一不足,本文提出一个噪声—纹理检测算子,利用这一算子对滤掉的信息作进一步检验,从而尽可能多的抽取出被误滤掉的纹理信息,将这些纹理信息补充回滤波后的图像中得到最终的去噪图像.实验表明,本文提出的算子对去噪后图像纹理信息的保留具有明显效果.     

Road extraction from aerial images using a region competition algorithm.

In this paper, we present a user-guided method based on the region competition algorithm to extract roads, and therefore we also provide some clues concerning the placement of the points required by the algorithm. The initial points are analyzed in order to find out whether it is necessary to add more initial points, and this process will be based on image information. Not only is the algorithm able to obtain the road centerline, but it also recovers the road sides. An initial simple model is deformed by using region growing techniques to obtain a rough road approximation. This model will be refined by region competition. The result of this approach is that it delivers the simplest output vector information, fully recovering the road details as they are on the image, without performing any kind of symbolization. Therefore, we tried to refine a general road model by using a reliable method to detect transitions between regions. This method is proposed in order to obtain information for feeding large-scale Geographic Information System.     

Technological analysis of integrated circuits as a part of a manufacturing lines agreement for France Telecom: Methodology and examples of potential reliability problems

France Telecom is now introducing, for integrated circuits, a manufacturing lines agreement instead of the classical individual types procedure. This new method will be briefly described. We shall then develop particularly one step of this methodology: the construction or technological analysis made on a circuit representative of the process which has to be agreed by the partners. Procedure developed for this analysis will be described and examples of potential reliability problems presented. Finally, we shall discuss the way in which the problems observed during construction analysis complete the other steps of the general line and process agreement.     

Imaging of biomedical data using a multiplicative regularizedcontrast source inversion method

In this paper, the recently developed multiplicative regularized contrast source inversion method is applied to microwave biomedical applications. The inversion method is fully iterative and avoids solving any forward problem in each iterative step. In this way, the inverse scattering problem can efficiently be solved. Moreover, the recently developed multiplicative regularizer allows us to apply the method blindly to experimental data. We demonstrate inversion from experimental data collected by a 2.33-GHz circular microwave scanner using a two-dimensional (2-D) TM polarization measurement setup. Further some results of a feasibility study of the present inversion method to the 2-D TE polarization and the full-vectorial three-dimensional measurement will be presented as well     

Comments on `Quarter-wave transformer for a digital phase shifter?

In a recent publication, Hering describes a method to match a ferrite-loaded waveguide. It will be shown here that this approach leads to erroneous results for most cases of interest.     

舰载雷达发现目标的效能概率

舰载雷达发现目标的效能概率是表征舰载雷达保障武器系统完成某一单项作战任务的重要指标之一。首先研究了舰载雷达能够保障舰炮射击时发现目标的效能 ,并给出了效能概率的计算方法 ,然后就典型的雷达保障舰炮射击情况作了定量数学计算 ,计算结果表明 ,该算法是有效的 ,其结果对于提高舰载雷达的作战效能具有重要应用价值。     

BI-FDTD: a novel finite-difference time-domain formulation for modeling wave propagation in bi-isotropic media

This paper presents a newly developed finite-difference time-domain (FDTD) technique, referred to as BI-FDTD, for modeling electromagnetic wave interactions with bi-isotropic (BI) media. The theoretical foundation for the BI-FDTD method will be developed based on a wavefield decomposition. The main advantage of this approach is that the two sets of wavefields are uncoupled and can be viewed as propagating in an equivalent isotropic medium, which makes it possible to readily apply conventional FDTD analysis techniques. The BI-FDTD scheme will also be extended to include the dispersive nature of chiral media, an important subclass of bi-isotropic media. This extension represents the first of its kind in the FDTD community. Validations of this new model are demonstrated for a chiral half-space and a chiral slab.     

一种结构紧凑的毫米波波导滤波器的设计

提出了一种新颖的毫米波波导滤波器的设计方法,以常用的H面膜片波导滤波器为基础,配合并不常用的基于磁耦合原理的波导同轴转换,从波导短路端面引入E面耦合环,使输入输出方向在一条直线上,并将两者做一体化设计,在保证良好性能指标的情况下,结构设计更为紧凑,体积更小。该设计保证了在星载或机载设备上空间结构受限的情况下,器件安装与电缆连接的便利。借助HFSS全波电磁场仿真,成功地运用在中心频率30GHz毫米波波导带通滤波器的设计上,使设计方法更为简便实用。     

一种宽带圆形阵列天线的矩量法分析

利用矩量法对宽带圆形阵列天线的互耦特性进行分析。为了对较粗线天线进行精确分析,矩量法采用正弦差值基函数与点配法,并采用全域线天线积分核计算Pocklington方程,得到天线的广义散射矩阵,实现互耦分析。为了验证其计算结果,对所设计阵列天线进行了CST软件仿真和实验测试。仿真和测试结果表明：矩量法计算与CST仿真结果基本相同,实验测试结果在主波束方向、主波瓣宽度、副瓣电平等特性上与计算和仿真结果近似一致,说明此方法能够有效的对宽带阵列天线进行互耦分析。     

容差网络可及点优化方法的研究

容差网络可及点的合理选择,是模拟电路故障诊断理论中一个急待研究的课题,它涉及故障的可诊断性,易觉察性和故障可测度等诸方面问题。本文在文献＾「１,２」的基础上,应用区间分析法探讨容差网络可及点的优化选择。文中提出一系列优化选择可及点的方法和公式,它对工程实际网络的应用都具有一定指导意义。     

用校正片确定激光测距机中接收光栏的位置

对于YAG、Gasb等非可见波长的激光测距机,在其装校期间,经常碰到确定接收(视场)光栏位置的问题.这里介绍一种用校正片确定接收光栏位置的方法.通过校正片,利用可见光(D光)便可定出非可见波长光的焦点位置,从而接收光栏的位置便得以确定.     

一种新的基于对应像素距离度量的图像相关匹配方法

传统的图像相关匹配方法中,由于实时图和参考图之间存在着灰度差异和一定程度的几何形变以及对目标的局部遮挡,使得利用求取对应像素灰度差累加和来进行相似性度量算法的性能很容易受到影响。文中从另一角度提出了一种新的图像相关匹配算法。该方法改变了原先匹配算法中求取模块图像和目标图像的像素灰度差的和的方法,而改为求取两幅图像之间相接近的点的个数,从而使匹配算法的稳定性大大提高,因为 局部出现的大片噪声点将不会影响匹配的结果,而这样的情况在传统的相关算法中将会显著影响匹配结果。实验结果表明了该方法的有效性。     

结合单双行人DPM模型的交通场景行人检测

针对日常交通场景下,行人目标易被遮挡,影响行人检测效果的问题,提出一种结合单行人和双行人DPM模型的交通场景行人检测方法.该方法首先从INRIA、ETH等行人数据集中提取训练样本的DPM特征,通过LatentSVM方法训练得到单、双人DPM模型;然后采用分类检测方法,将交通场景行人分为单独分布行人和混合分布行人两类.检测时首先使用双行人模型SDP-DPM对目标图像进行目标匹配,如果没有检测到双行人目标,则判定为单独分布行人情况,转而使用单行人模型SP-DPM进行检测,并保存检测结果;如果检测到双行人目标,则判定为混合分布行人情况,此时先保存对应的双行人滤波响应,再使用单行人模型进行二次检测,并将两次检测的结果进行加权结合.实验结果表明,本文算法能够在行人相互遮挡严重的交通环境下,有效检测出行人,整体精度优于传统的DPM算法和当前行人检测的主要流行算法.     

Electrostatic Shielding of a Charged Conducting Sphere by a Fine-Mesh Grounded Screen

The physical system considered is a charged conducting sphere held at a fixed absolute potential via a battery or some other power source. Another sphere, concentric with and larger than the first, is fabricated out of a fine-mesh screen and this outer screen is grounded. The objective is to calculate the effectiveness of the screen in reducing the electrostatic field at points outside of the system. A derivation based on elementary principles of electrostatics will show that the shielding effectiveness of the screen can be expressed in terms of the separation between the two spheres and another quantity, represented in the paper by B, that is an intrinsic property of the screen. Approximations will be used that require the screen to have a mesh size that is fine compared to other dimensions of the system. In particular, characteristic distances between mesh wires must be smaller (by an amount that was not numerically evaluated in this paper) than the separation between the charged sphere and the spherical screen shield. For a sufficiently simple mesh weave, B can be calculated. More generally, B for a given screen can be measured by measuring the capacitance per unit area and separation between a flat piece of the screen and a parallel metal plate. This method of measuring B is described in the report.