On the stability of plates under combined compression and in-plane bending

The conventional stability analysis of plates under combined compression and in-plane bending is based on the assumption that the plate is free to move laterally and, hence, the restraints imposed by the attached elements against this motion are ignored. The paper explores the influence of these restraints on the plate under this type of loading. The unloaded edges are assumed to be partially restrained against in-plane translation while remaining straight and the distributions of the resulting forces acting on the plate are shown. The stability analysis is done numerically using the Galerkin method and various strategies that economize the numerical implementation are presented. The results are obtained showing the variation of the buckling load, from free edge translation to fully restrained, for simply supported and clamped unloaded edges for various plate aspect ratios and stress gradient coefficients. An apparent decrease in the buckling load is observed due to these destabilizing forces acting in the plate and changes in the buckling mode are observed by increasing the intensity of the lateral restraint. A comparison is made between the buckling loads predicted from various formulae in stability standards based on free edge translation and the values derived from the present investigation. A difference of about 34% in the predicted buckling load and different buckling load were found.     

确定两个任意简单多边形空间关系的算法

阐述了把简单多边形的边分为奇偶边的新思想,根据一多边形的边与另一多边形的拓朴关系,划分边为5种拓朴类型:内边、外边、重叠边、相交边、复杂边,进而给出了确定两个多边形空间关系的算法,算法的时间复杂度为O((n+m)log(n+m)),其中n、m分别是两输入多边形的顶点数。该算法建立在数学理论基础之上,没有奇异情况需要处理,易于编程实现。算法的主要思想对确定两个简单多面体空间关系亦有参考价值。     

确定两个任意简单多边形交、并、差的算法

提出了把多边形的边分为奇偶边的新思想，根据输入多边形A，B之间边的拓扑关系，划分A，B边为内边、外边、重叠边3种，揭示A，B与它们的交、并、差之间边的本质联系，进而描述了确定任意两个简单多边形交、并、差算法．算法的时间复杂度为O((n m k)log(n m k))，其中n，m分别是A，B的顶点数，k是两多边形的交点数．算法建立在数学理论基础之上，很好地处理了布尔运算的奇异情形，比如重叠边，边与边相交于边的顶点等情形．本算法易于编程实现。     

Edge quality metrics for image enhancement

The paper presents a new adaptive full reference method for quality measurement of image enhancement algorithms. The method is based on the analysis of basic edges??sharp edges which are distant from another edges. The proposed basic edges metrics calculates error values in two areas related to typical artifacts of image enhancement algorithms: basic edges area and basic edges neighborhood. The metrics are illustrated with an application to image resampling and image deblurring but it is also applicable for image deringing and image denoising.     

基于边界提升变换的图像压缩

为获得图像中光滑边界的稀疏表达和克服传统量化离散小波系数造成的边界失真,提出了一种基于边界的提升变换。其主要思想是将图像分为边界带和剩余区域两部分,然后对这两部分分别应用一维和二维基于边界的小波变换。边缘的前处理是这种方法的一个重要部分。为了提高编码性能,对两条平行或近似平行的边界线用一条脊线表示,并且对脊线和边界线按照光滑尖锐比进行修剪。最后根据边界小波变换系数的特点给出了合适的编码方法。本方法针对富含边界的图像在峰值信噪比和视觉质量方面比JPEG2000均有明显的提高。     

Authenticating edges produced by zero-crossing algorithms

It is shown that zero-crossing edge detection algorithms can produce edges that do not correspond to significant image intensity changes. Such edges are called phantom or spurious. A method for classifying zero crossings as corresponding to authentic or phantom edges is presented. The contrast of an authentic edge is shown to increase and the contrast of phantom edges to decrease with a decrease in the filter scale. Thus, a phantom edge is truly a phantom in that the closer one examines it, the weaker it becomes. The results of applying the classification schemes described to synthetic and authentic signals in one and two dimensions are given. The significance of the phantom edges is examined with respect to their frequency and strength relative to the authentic edges, and it is seen that authentic edges are denser and stronger, on the average, than phantom edges     

Computer‐aided diagnosis of lossy microwave coupled resonators filters

A method is presented for extracting the coupling matrix (CM) and the unloaded Q from the measured (or electromagnetic simulated) scattering parameters of a lossy coupled resonators bandpass filter. The method can be used for computer‐aided tuning of a microwave filter. The method consists of two elements: 1) a three‐parameter optimization method is proposed to obtain the unloaded Q (assuming all the resonators with the same unloaded Q) and to remove the phase shift of the measured S‐parameters caused by the phase loading and the transmission lines at the input/output ports of a filter; 2) the Cauchy method is used for determining characteristic polynomial models of the S‐parameters of a microwave filter in the normalized low‐pass frequency domain. Once the characteristic polynomials of the S‐parameters without phase‐shift effects are determined, the CM of a filter with a given topology can be extracted using well‐established techniques. Three diagnosis examples illustrate the validity of the proposed method. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

Constructing a wire-frame from views on arbitrary view planes for objects with conic sections inclined to all view planes

A new and efficient approach to construct a 3D wire-frame of an object from its orthographic projections is described. The input projections can be two or more and can include regular and complete auxiliary views. Each view may contain linear, circular and other conic sections. The output is a 3D wire-frame that is consistent with the input views.The approach can handle auxiliary views containing curved edges. This generality derives from a new technique to construct 3D vertices from the input 2D vertices (as opposed to matching coordinates that is prevalent in current art). 3D vertices are constructed by projecting the 2D vertices in a pair of views on the common line of the two views. The construction of 3D edges also does not require the addition of silhouette and tangential vertices and subsequently splitting edges in the views. The concepts of complete edges and n-tuples are introduced to obviate this need. Entities corresponding to the 3D edge in each view are first identified and the 3D edges are then constructed from the information available with the matching 2D edges. This allows the algorithm to handle conic sections that are not parallel to any of the viewing directions. The localization of effort in constructing 3D edges is the source of efficiency of the construction algorithm as it does not process all potential 3D edges.Working of the algorithm on typical drawings is illustrated.     

Weighted graphs with fixed vertex degrees and network flows

Classes of weighted graphs (with or without loops) that are realizations of nonnegative vectors are considered. The set of vertices is divided into two subsets, and the sums of weights of edges in each subset and the sum of weights of edges that are incident to vertices of the two subsets are considered. Lower and upper (attainable) estimates are obtained for these sums. Since the division into two subsets specifies a cut in the network and the sum of weights of edges “connecting” these subsets is the cut capacity, the results can be applied in the theory of network flows.     

Clamping a polygon

Aclamping hand has two opposing parallel edges; the distance between them can vary. We define what it means for the edges of a clamping hand and some edges of a polygon to form aclamp on the polygon. We conjecture that any polygon can be clamped by a hand if its edges are of positive length, but only provide proofs that clamps must exist for convex polygons and for certain polygons composed of two convex chains. The proofs involve extensive case analyses, and it is not obvious how to generalize them.     

传感器网络的可定位性条件

针对两个节点集合,提出了一组可定位性条件.可定位性条件包含两部分:两个集合之间需要的连接边的数目,以及如何布置这些连接边.本文将每组节点和它们的内部连接边刻画成一个距离图.两个节点集合之间的可定位性判定等同于两个融合图的全局刚性测试.针对两个融合图的可定位性,给出了一系列的充要条件.     

一种改进型Canny边缘检测算法

边缘检测是提取图像特征的首要条件。文章提出了一种改进型Canny边缘检测算法。首先在边缘梯度计算时,将二维滤波模板分解为两个一维滤波模板,实现并行处理,提高运算速度;引入双阈值法则同时保证图像中强边缘点和弱边缘点的提取,并基于非局部最大值抑制原理检测边缘点,大大提高了边缘检测的精度和准确度;最后采用形态学算子实现对检测边缘进行细化处理,实现了单像素级细化边缘提取。实验结果表明,该算法在保证实时性的同时,具有很好的检测精度和准确度。     

On the hop-constrained survivable network design problem with reliable edges

In this paper, we study the hop-constrained survivable network design problem with reliable edges. Given a graph with non-negative edge costs and node pairs Q, the hop-constrained survivable network design problem consists of constructing a minimum cost set of edges so that the induced subgraph contains at least K edge-disjoint paths containing at most L edges between each pair in Q. In addition, we consider here a subset of reliable edges that are not subject to failure. We study two variants: a static problem where the reliability of edges is given, and an upgrading problem where edges can be upgraded to the reliable status at a given cost. We adapt for the two variants an extended formulation proposed in Botton, Fortz, Gouveia, Poss (2011) [1] for the case without reliable edges. As before, we use Benders decomposition to accelerate the solving process. Our computational results indicate that these two variants appear to be more difficult to solve than the original problem (without reliable edges). We conclude with an economical analysis which evaluates the incentive of using reliable edges in the network.     

Shape optimization of a dielectric resonator for improving its unloaded quality factor

A novel approach for shape optimization of dielectric resonators is presented with an objective of improving their unloaded quality factor. Shape (level‐set) and topology (topology gradient) optimization methods coupled with finite element method are utilized together, which as a result, relaxes the traditional trade‐off made between the spurious‐free band (isolation) and the high unloaded quality factor of the resonators. The defined cost function is minimized by the proposed iterative coupling between the level‐set method and the topology gradient method. The optimized resonator, which improves the unloaded quality factor of about 65% compared with the reference, is then approximated for fabrication. The reference, optimized, and approximated resonators are fabricated and measured. Results from the simulated and the fabricated resonators validate the optimization approach presented in this work. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

三维模型轮廓线抽取算法

虽然三维模型的轮廓线在图形交流中起着重要的作用,但由于轮廓线是视点依赖的,当物体在空间运动时,用现有算法从复杂的三维模型中抽取轮廓线需耗费大量时间,为了提高抽取轮廓线的速度,提出了两种新的抽取三维模型轮廓线算法,这两种算法是先利用轮廓线的局部极值特性来获得部分轮廓边,然后利用轮廓线的连通性,通过简单的比较运算,即可获得三维模型的外部轮廓线,实验结果表明,该两种算法都可快速获得三维模型的外围轮廓线,最后还将本算法与相关算法进行了详细的比较分析。     

基于自适应多尺度焊缝X光图像缺陷分割研究

焊缝X光图像中的缺陷包括近似圆形和近似条形缺陷。由多尺度边缘检测理论可知：在适当尺度下,圆形缺陷在相互正交的两个方向上都是屋脊边缘,而条形缺陷只在一个方向上是屋脊边缘。利用区域一致性测度自适应确定小波滤波尺度。并在缺陷存在区域自适应确定LOG算子和方向可调滤波器的滤波尺度用以分割两种缺陷。理论分析和实验结果表明,算法有较好的分割效果。     

纹理边缘引导的深度图像超分辨率重建

目的 深度图像作为一种普遍的3维场景信息表达方式在立体视觉领域有着广泛的应用。Kinect深度相机能够实时获取场景的深度图像,但由于内部硬件的限制和外界因素的干扰,获取的深度图像存在分辨率低、边缘不准确的问题,无法满足实际应用的需要。为此提出了一种基于彩色图像边缘引导的Kinect深度图像超分辨率重建算法。方法 首先对深度图像进行初始化上采样,并提取初始化深度图像的边缘;进一步利用高分辨率彩色图像和深度图像的相似性,采用基于结构化学习的边缘检测方法提取深度图的正确边缘;最后找出初始化深度图的错误边缘和深度图正确边缘之间的不可靠区域,采用边缘对齐的策略对不可靠区域进行插值填充。结果 在NYU2数据集上进行实验,与8种最新的深度图像超分辨率重建算法作比较,用重建之后的深度图像和3维重建的点云效果进行验证。实验结果表明本文算法在提高深度图像的分辨率的同时,能有效修正上采样后深度图像的边缘,使深度边缘与纹理边缘对齐,也能抑制上采样算法带来的边缘模糊现象;3维点云效果显示,本文算法能准确区分场景中的前景和背景,应用于3维重建等应用能取得较其他算法更好的效果。结论 本文算法普遍适用于Kinect深度图像的超分辨率重建问题,该算法结合同场景彩色图像与深度图像的相似性,利用纹理边缘引导深度图像的超分辨率重建,可以得到较好的重建结果。     

用最小回路求两个简单多边形的交、并、差集

针对求两个简单多边形交、并、差集问题,提出一种基于最小回路的新算法。首先,将初始多边形P和Q初始化为逆时针方向,并将两个多边形交点处的关联边排序。然后,从各个交点出发利用最小转角法搜索最小回路,并根据这些最小回路中包含P和Q边的方向性对它们进行分类。最终,不同类别的最小回路将对应P和Q的交、并、差集。算法的时间复杂度为O((n+m+k)logd),其中n、m 分别是P和Q的顶点数,k是两多边形的交点数,d为将多边形分割的单调链数。算法几何意义明显,对于多边形布尔运算中的重合顶点、重合边等奇异情形,具有较好的适应性。     

一种区域边界的识别和区域标记算法与应用

本文介绍了一种区域边界的识别算法和一种区域标记的算法,前者在有若干区域的多条边界相交及存在边界公用的情况下,通过直线生成的方法能寻找出每一个最小区域的完整的区域边界;后者则能在识别出区域边界的基础上进行区域的标记,把区域分割出来,这两个算法已用于电脑刺绣编程系统的图象预处理系统,效果良好。文中并通过实例说明了这两个算法的特点。