Printed slot antennas for various wideband applications using shape blending

This article presents a novel design of wide slot antenna for various wideband applications created using a shape‐blending algorithm. The proposed printed antenna consists of a wide rectangular slot and a tuning stub, which is formed by blending the shapes of from a cross and a square. Various bandwidths can be obtained based on the structure with different blended shapes. The impact of the antenna geometry on the antenna performance has been investigated and analyzed in detail. To verify the proposed designs, six prototypes of slot antennas with various tuning stub shapes are designed, fabricated, and measured. The simulated results are compared with the measured performance and show good agreement. A bandwidth range from 38.5 to 126.4% for voltage standing wave ratio (VSWR) less than 2 is exhibited by selecting different blended shapes, which can be served as an antenna design guideline. Moreover, the proposed type of antenna has a compact size and a simple structure, which make it an excellent candidate for wideband applications. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:3–12, 2016.     

Local control of interval tension using weighted splines

Cubic spline interpolation and B-spline sums are useful and powerful tools in computer aided design. These are extended by weighted cubic splines which have tension controls that allow the user to tighten or loosen the curve on intervals between interpolation points. The weighted spline is a C¹ piecewise cubic that minimizes a variational problem similar to one that a C² cubic spline minimizes. A B-spline like basis is constructed for weighted splines where each basis function is nonnegative and nonzero only on four intervals. The basis functions sum up identically to one, thus curves generated by summing control points multiplied by the basis functions have the convex hull property. Different weights are built into the basis functions so that the control point curves are piecewise cubics with local control of interval tension. If all weights are equal, then the weighted spline is the C² cubic spline and the basis functions are B-splines.     

Adaptive mesh refinement using piecewise-linear shape functions based on the blending function method

Use of quadrilateral elements for finite element mesh refinement can lead either to so-called irregular meshes or the necessity of adjustments between finer and coarser parts of the mesh necessary. In the case of irregular meshes, constraints have to be introduced in order to maintain continuity of the displacements. Introduction of finite elements based on blending function interpolation shape functions using piecewise boundary interpolation avoids these problems. This paper introduces an adaptive refinement procedure for these types of elements. The refinement is anh-method. Error estimation is performed using the Zienkiewicz-Zhu method. The refinement is controlled by a switching function representation. The method is applied to the plane stress problem. Numerical examples are given to show the efficiency of the methodology.     

Hand shape recognition based on coherent distance shape contexts

In this paper, we propose a novel hand shape recognition method named as Coherent Distance Shape Contexts (CDSC), which is based on two classical shape representations, i.e., Shape Contexts (SC) and Inner-distance Shape Contexts (IDSC). CDSC has good ability to capture discriminative features from hand shape and can well deal with the inexact correspondence problem of hand landmark points. Particularly, it can extract features mainly from the contour of fingers. Thus, it is very robust to different hand poses or elastic deformations of finger valleys. In order to verify the effectiveness of CDSC, we create a new hand image database containing 4000 grayscale left hand images of 200 subjects, on which CDSC has achieved the accurate identification rate of 99.60% for identification and the Equal Error Rate of 0.9% for verification, which are comparable with the state-of-the-art hand shape recognition methods.     

Bicubic B-spline blending patches with optimized shape

Two constructions of bicubic B-spline patches with fixed boundary conditions are described. Their goal is to minimize functionals taken for measures of patch badness. The first construction is numerically solving the triharmonic equation . The functional minimized in the second construction is the sum of a term determined by the surface shape (the distribution of mean curvature) and a term introduced to overcome the problem of ambiguity of minimum of the first term. In addition to boundary conditions one can impose constraints, e.g. fix constant parameter curves of the patch.     

Curvature weighted gradient based shape orientation

Determining the orientation of a shape is a common task in many image processing applications. It is usually part of the image preprocessing stages and further processing may rely on an adequate method to determine the orientation. There are several methods for computing the orientation of a shape, each of them with its own strengths and weaknesses; a method which performs outstandingly for one application may have a poor performance for a different application. In this paper we present a new method for computing shape orientation based on the projection of the tangent vectors of a shape onto a line and weighting them using a function of the curvature. Some of the results from ?uni? (2008) [14] are particular cases of the results presented here.     

Local shape approximation from shading

Shading can be used as an independent cue for exact shape recovery, or it can be used as a supplementary cue for shape interpolation between features whose depths are known from other cues. Exact shape cannot be inferred from a local analysis of shading. However, for shape interpolation a crude local approximation may be sufficient. This paper explores the limits of such local approximations that are easy to compute. In particular, the shape of shading is used to approximate the surface in areas of monotonic change of intensity. This analysis is accompanied by a method for computing the direction of a single-point light source from the shading on occluding contours. A qualitative classification of shape near shading singularities is also discussed.This work was performed at the Massachusetts Institute of Technology, Center for Biological Information Processing.     

基于四元素插值的空间曲线边界约束变形方法

曲线形状的变形技术在计算机动画和产品造型设计中有着重要的应用。以单位球面四元素插值为基础建立非线性的局部变换,通过在中间帧重构方程引进边界控制条件,提出了具有边界约束的空间曲线和平面曲线形状的变形方法。该方法在曲线形状渐变序列中具有保周长的线性变化,适合一般曲线的渐变和骨架行走的特征。还给出了建立渐变序列的边界曲线算法,通过实例说明了造型和编辑边界曲线能得到良好的拼接效果。实验表明,该算法在空间曲线变形中具有良好的视觉效果和应用前景,算法具有简易性和统一性。     

Shape blending using the star-skeleton representation

Shape blending, the metamorphosis of one shape into another, is a central problem in two-dimensional computer animation. In spite of impressive uses of morphing in film and video productions, the problem is far from solved. In particular, shape blending still requires considerable manual effort. By decomposing two polygons into equivalent star-shaped pieces and a connecting skeleton, the paper presents a blending method which can represent polygon interiors, not just boundaries, and generate high-quality results with minimal user intervention     

Efficient shape matching using shape contexts

We demonstrate that shape contexts can be used to quickly prune a search for similar shapes. We present two algorithms for rapid shape retrieval: representative shape contexts, performing comparisons based on a small number of shape contexts, and shapemes, using vector quantization in the space of shape contexts to obtain prototypical shape pieces.     

辅助身份认证的局部形状上下文手形认证算法

随着技术的发展和对安全性要求的提高,单一生物特征已经很难满足高度机密身份认证的需求,需要进行多特征身份认证,因此提出一种可以用做辅助认证的手形认证算法.该算法不限制图像采集背景,实验中采用了相对难处理的白色背景.先粗分割提取手形样本,后根据样本特征细分割得到手形轮廓,该分割算法能够在含阴影的图像中准确地提取手形轮廓,具有高自适应性和可移植性;同时提出了局部形状上下文手形认证算法,采用局部均匀采样,在局部范围内提取手形的形状上下文特征,根据该特征进行匹配认证.该方法的认证等错误率为3.15％,与其他形状上下文算法相比,在相同时间代价下,等错误率降低了1.5％ ～5％.     

Measuring biological shape using geometry-based shape transformations

This paper presents a methodology for shape analysis of anatomical structures. A template shape is used as a unit, and a shape transformation mapping the template to a particular structure is used to quantify the shape of the structure with respect to the template. The geometric characteristics of the boundaries of the template and the individual structure are used to define point correspondences between the template and the structure. These correspondences are then used to determine the shape transformation, which is based on an elastic adaptation of the template. Regional inter-subject and inter-population shape differences are then identified by comparing the corresponding shape transformations point-wise. Validation using simulation experiments is also presented.     

Local shape of offsets to algebraic curves

In this paper we introduce the notion of local shape to describe the behavior of a real place of an algebraic curve around its center. We analyze how the local shape is affected by the offsetting process, and we relate this phenomenon to the curvature of the curve. Furthermore, we characterize the situations when the offsetting process behaves locally well, so that the local shape is preserved.     

多帧相参积累的检测前跟踪方法

针对现有检测前跟踪（TBD）算法在多帧间积累时都使用非相参积累,积累效率较低的问题,对相参积累的TBD方法进行了研究。该方法在多帧回波数据下通过数据拼接、回波方位选取、噪声置零及走动补偿后利用FFT实现了帧间相参积累。仿真实验表明,相对现有的TBD方法,该方法能在较少帧的回波数据下实现良好的检测性能。     

Local bifurcations and feasibility regions indifferential-algebraic systems

The dynamics of a large class of physical systems such as the general power system can be represented by parameter-dependent differential-algebraic models of the form x˙=f and 0=g. Typically, such constrained models have singularities. This paper analyzes the generic local bifurcations including those which are directly related to the singularity. The notion of a feasibility region is introduced and analyzed. It consists of all equilibrium states that can be reached quasistatically from the current operating point without loss of local stability. It is shown that generically loss of stability at the feasibility boundary is caused by one of three different local bifurcations, namely the saddle-node and Hopf bifurcations and a new bifurcation called the singularity induced bifurcation which is analyzed precisely here for the first time. The latter results when an equilibrium point is at the singular surface. Under certain transversality conditions, the change in the eigenstructure of the system Jacobian at the equilibrium is established and the local dynamical structure of the trajectories near this bifurcation point is analyzed