Automatic mesh generation using single- and double-nodesegmentation techniques

The desired properties of quadrilateral mesh-generation techniques, well-suited for solving surface integral equations by the method of moments, are discussed. Based on this investigation, two iterative techniques for segmentation of electrically large surfaces are developed. Each iteration consists of two steps: (1) long edges are subdivided into the minimal number of short edges; and (2) large plates are subdivided by using either one interior node per long edge (the single-node technique), or two interior nodes per long edge (the double-node technique). In each of these cases, the subdivision of a large plate is performed by using three specific basic schemes, not affected by the subdivision of neighboring large plates. In addition, a constraint for segmentation of long interior edges is proposed, enabling generation of more uniform meshes. The proposed techniques are applied to the methods based on both subdomain and entire-domain approximation. It is found that, in most cases, the double-node technique is superior to the single node technique     

Automatic mesh generation using a modified Delaunay tessellation

The authors begin by discussing the Delauny triangulation and algorithms for its construction. Degeneracy and the convexity check are then considered together with the preservation of edge boundaries. Swapping in two and three dimensions, edge subdivisions, mesh smoothing techniques and the mesh generation algorithm are also discussed     

建设新一代格形城域光网络

未来光网络要解决的两大问题是如何增加网络的带宽和合理地使用这些带宽。解决城域网瓶颈和适应性的唯一出路是引入波分复用，为用户提供基于波长的服务。这就要求新一代的城域光网络能在两个垮接在不同环上的节点之间建立可管理的光路。这种可管理的光路不同于传统的静态电路，它能够根据突发性的业务动态地调配带宽，同时又具有独立于上层协议和速率的透明传输的优点。在骨干网上引入波分复用技术的好处是可以节省昂贵的光纤资源和利用一个光纤放大器同时对多个光信道进行放大。在城域网上引入波分复用，当然也能节省光纤资源，但通常不是…     

A new thresholding approach for automatic generation of polygonal approximations

The present paper proposes a new algorithm for automatic generation of polygonal approximations of 2D closed contours based on a new thresholding method. The new proposal computes the significance level of the contour points using a new symmetric version of the well-known Ramer, Douglas–Peucker method, and then a new Adaptive method is applied to threshold the normalized significance level of the contour points to generate the polygonal approximation. The experiments have shown that the new algorithm has good performance for generating polygonal approximations of 2D closed contours. Furthermore, the new algorithm does not require any parameter to be tuned.     

Automatic wall slant angle map generation using 3D point clouds

Recently, quantitative and repetitive inspections of the old urban area were conducted because many structures exceed their designed lifetime. The health of a building can be validated from the condition of the outer wall, while the slant angle of the wall widely serves as an indicator of urban regeneration projects. Mostly, the inspector directly measures the inclination of the wall or partially uses 3D point measurements using a static light detection and ranging (LiDAR). These approaches are costly, time-consuming, and only limited space can be measured. Therefore, we propose a mobile mapping system and automatic slant map generation algorithm, configured to capture urban environments online. Additionally, we use the LiDAR-inertial mapping algorithm to construct raw point clouds with gravity information. The proposed method extracts walls from raw point clouds and measures the slant angle of walls accurately. The generated slant angle map is evaluated in indoor and outdoor environments, and the accuracy is compared with real tiltmeter measurements.     

Consistent symmetric axis method for robust detection of ellipses

Ellipse detection is an interesting issue in machine vision researches and many approaches have been suggested to determine the parameters. Recently, a symmetric axis method has been proposed to determine the centre of an ellipse, but other parameters are determined otherwise. A consistent symmetric axis method is proposed that utilises the information inherent in the symmetric axes throughout the entire process to compute all of the parameters. A closed-form solution is obtained, hence the calculation of the parameters is fast. In addition, since the determination of the symmetric axes involves a set of points on the ellipse, the procedure is robust. Experiments with disjoint ellipses, interacting ellipses, defective ellipses and real objects indicate the effectiveness of the proposed method both theoretically and practically     

A unified treatment of compact symmetric FFT code generation

A method for the automatic generation of compact symmetric fast Fourier transforms (FFTs) from high-level specifications is presented. The generated code eliminates all redundant computations induced by the symmetries in the FFT data flow, minimizing storage requirements, input/output and arithmetic operations, and preserves the attractive computational feature of FFT algorithms. The code-generating method can be expressed as a simple and well-structured meta-algorithm whose inputs are the dimension and edge size of the data array and a matrix representation of the data symmetries     

Automatic generation of object recognition programs

Issues and techniques are discussed to automatically compile object and sensor models into a visual recognition strategy for recognizing and locating an object in three-dimensional space from visual data. Automatic generation of recognition programs by compilation, in an attempt to automate this process, is described. An object model describes geometric and photometric properties of an object to be recognized. A sensor model specifies the sensor characteristics in predicting object appearances and variations of feature values. It is emphasized that the sensors, as well as objects, must be explicitly modeled to achieve the goal of automatic generation of reliable and efficient recognition programs. Actual creation of interpretation trees for two objects and their execution for recognition from a bin of parts are demonstrated     

计算电大尺寸目标物理光学散射场的快速算法

电大尺寸目标高频散射场的仿真一般使用物理光学（physical optics, PO）方法,该方法要求对目标使用尺寸为八分之一倍波长的三角网格进行剖分。然而,随着入射波频率增加,网格数目呈指数增长。本文提出基于一倍波长的二次曲面网格的快速PO（fast PO,FPO）方法,该方法使用线性多项式拟合振幅函数,能够有效降低面片数目。与二次多项式拟合振幅函数的快速物理光学方法相比,本文方法避免了菲涅尔积分的求解,且计算速度快1.22倍。为了进一步降低网格数目,提出了自适应网格技术的快速物理光学（FPO based on the adaptive mesh technique, AFPO）方法,允许使用比标准奈奎斯特采样率更少的网格数目对目标进行离散。通过后验误差估计和数值算例对所提出算法的精度和速度进行了验证,结果表明与采用均匀网格剖分的方法相比,AFPO方法所需的面片数目降低89.58%。     

The automatic generation of the finite element mesh for realization of ricatti transformation

Computer techniques for solving electro-magnetic scattering problems of dielectric cylinders of arbitrary cross sections by the unimoment method are investigated. In the solution of the fields inside the mathematical circle, a computer program for the realization of Ricatti transformation in solving the linear algebraic equations is programmed. With the case of a rectangular cylinder as an example, automatic generation of finite element mesh for Ricatti transformation is achieved. It is shown that both the memory capacity and the computing time of the computer are greatly saved by using these techniques. The previous procedure of the finite element method is also greatly simplified.     

可控内存写漏洞自动利用生成方法

针对现有漏洞自动利用生成方法无法实现从“可控内存写”到“控制流劫持”的自动构造问题,提出一种可控内存写漏洞的自动利用生成方法。首先,基于内存地址控制力度的动态污点分析方法检测可控内存写漏洞;然后,基于漏洞利用模式进行利用要素搜索,通过约束求解自动构造可控内存写漏洞的利用。实验结果表明,所提方法可以有效检测可控内存写漏洞,搜索漏洞利用要素,自动生成从可控内存写到控制流劫持的利用。     

可控内存写漏洞自动利用生成方法

针对现有漏洞自动利用生成方法无法实现从“可控内存写”到“控制流劫持”的自动构造问题,提出一种可控内存写漏洞的自动利用生成方法。首先,基于内存地址控制力度的动态污点分析方法检测可控内存写漏洞;然后,基于漏洞利用模式进行利用要素搜索,通过约束求解自动构造可控内存写漏洞的利用。实验结果表明,所提方法可以有效检测可控内存写漏洞,搜索漏洞利用要素,自动生成从可控内存写到控制流劫持的利用。     

Query-enabled sensor networks using the cyclic symmetric wakeup design

The problem of conserving energy under multiple constraints of query waiting delays and sensing coverage preservation in query-based wireless sensor networks is addressed. We propose a network architecture based on the cyclic symmetric block design class of wakeup schemes. Using a target tracking application as an example, specific requirements of the application translates to design parameters in our proposed solution. Our proposal demonstrates good delay performances, high target tracking accuracies and low target identification errors, without the need for costly double-radio channels while increasing network lifetimes by a factor of four to eight over traditional methods.     

Automatic generation of error control codes for computerapplications

This paper proposes a methodology, implemented in a tool, to automatically generate the main classes of error control codes (ECC's) widely applied in computer memory systems to increase reliability and data integrity. New code construction techniques extending the features of previous single error correcting (SEC)-double error detecting (DED)-single byte error detecting (SBD) codes have been integrated in the tool. The proposed techniques construct systematic odd-weight-column SEC-DED-SBD codes with odd-bit-per-byte error correcting (OBC) capabilities to enhance reliability in high speed memory systems organized as multiple-bit-per-chip or card     

Automatic generation of boundary conditions using demons nonrigid image registration for use in 3-D modality-independent elastography

Modality-independent elastography (MIE) is a method of elastography that reconstructs the elastic properties of tissue using images acquired under different loading conditions and a biomechanical model. Boundary conditions are a critical input to the algorithm and are often determined by time-consuming point correspondence methods requiring manual user input. This study presents a novel method of automatically generating boundary conditions by nonrigidly registering two image sets with a demons diffusion-based registration algorithm. The use of this method was successfully performed in silico using magnetic resonance and X-ray-computed tomography image data with known boundary conditions. These preliminary results produced boundary conditions with an accuracy of up to 80% compared to the known conditions. Demons-based boundary conditions were utilized within a 3-D MIE reconstruction to determine an elasticity contrast ratio between tumor and normal tissue. Two phantom experiments were then conducted to further test the accuracy of the demons boundary conditions and the MIE reconstruction arising from the use of these conditions. Preliminary results show a reasonable characterization of the material properties on this first attempt and a significant improvement in the automation level and viability of the method.     

Automatic generation of noise-free time-activity curve with gated blood-pool emission tomography using deformation of a reference curve

This paper describes a new method for assessing clinical parameters from a noisy regional time-activity curve (TAC) in tomographic gated blood-pool ventriculography. This method is based on a priori knowledge on the shape of a TAC, and shape approximation. The rejection method was used to generate different random Poisson deviates, covering standard count levels, of six representative TACs in order to test and compare the proposed method with harmonic and multiharmonic reconstruction methods. These methods were compared by evaluating four clinical parameters: time of end systole, amplitude, peak ejection and filling rates. Overall, the accuracy of assessment of these parameters was found to be better with the method described in this paper than with standard multiharmonic fits.     

Image filtering in the block DCT domain using symmetric convolution

Processing of images in the transform domain saves computation by avoiding inverse and re-transform operations. In this paper, we present a technique for filtering of images in the transform domain using symmetric convolution in the block DCT space. Due to the application of convolution-multiplication property in the DCT domain, the filtering operation requires significantly less computation than its equivalent in the original signal/image space. To take care of discontinuities along boundaries of blocks, filtering is performed on a larger DCT block composed from adjacent blocks. Subsequently, the filtered DCT block is obtained by decomposing it. The proposed filtering technique achieves the same results of linear convolution in the spatial domain with reduced cost. With the proposed filtering, it is possible to significantly speedup the operation by ignoring some elements in the filtering matrices whose magnitudes are smaller than a threshold value. Typical sparseness of DCT domain input blocks is also considered for further reduction of computational cost. The proposed method uses simple linear operations such as matrix multiplication, which is appropriate for efficient hardware implementations. We also demonstrate its applications in image sharpening and removal of blocking artifacts directly in the compressed domain.     

Overlay multicast for MANETs using dynamic virtual mesh

Overlay multicast protocol builds a virtual mesh spanning all member nodes of a multicast group. It employs standard unicast routing and forwarding to fulfill multicast functionality. The advantages of this approach are robustness and low overhead. However, efficiency is an issue since the generated multicast trees are normally not optimized in terms of total link cost and data delivery delay. In this paper, we propose an efficient overlay multicast protocol to tackle this problem in MANET environment. The virtual topology gradually adapts to the changes in underlying network topology in a fully distributed manner. To save control overhead, the participating nodes only keep a fisheye view of the dynamic mesh. The multicast tree is progressively adjusted according to the latest local topology information. Simulations are conducted to evaluate the tree quality. The results show that our approach solves the efficiency problem effectively. This research was supported in part by the National Science Foundation under the grants CCR-0296070 and ANI-0296034. The preliminary results of this work is presented in “Efficient Overlay Multicast in Mobile Ad Hoc Networks,” Proc. IEEE WCNC 2003. Chao Gui is a Technical Research Staff at Kiyon Inc (www.kiyon.com). His research interests include wireless networking and mobile computing. His current efforts are on industrial implementation of wireless mesh networks and embedded systems. Dr. Gui has received Ph.D. in Computer Science from University of California at Davis in 2005. Prasant Mohapatra is currently a Professor in the Department of Computer Science at the University of California, Davis. He has also held various positions at Iowa State University, Michigan State University, Intel Corporation, Panasonic Technologies, Institute of Infocomm Research, Singapore, and the National ICT, Australia. Dr. Mohapatra received his Ph.D. in Computer Engineering from the Pennsylvania State University in 1993. He was/is on the editorial boards of the IEEE Transactions on computers, ACM/Springer WINET, and Ad hoc Networks Journal. He has served on numerous technical program committees for international conferences, and served on several panels. He was the Program Vice-Chair of INFOCOM 2004, and the Program Co-Chair of the First IEEE International Conference on Sensor and Ad Hoc Communications and Networks, (SECON-2004). Dr. Mohapatra’s research interests are in the areas of wireless networks, sensor networks, Internet protocols and QoS.     

Watermarking 3D models using spectral mesh compression

We propose a robust and imperceptible spectral watermarking method for high rate embedding of a watermark into 3D polygonal meshes. Our approach consists of four main steps: (1) the mesh is partitioned into smaller sub-meshes, and then the watermark embedding and extraction algorithms are applied to each sub-mesh, (2) the mesh Laplacian spectral compression is applied to the sub-meshes, (3) the watermark data is distributed over the spectral coefficients of the compressed sub-meshes, (4) the modified spectral coefficients with some other basis functions are used to obtain uncompressed watermarked 3D mesh. The main attractive features of this approach are simplicity, flexibility in data embedding capacity, and fast implementation. Extensive experimental results show the improved performance of the proposed method, and also its robustness against the most common attacks including the geometric transformations, adaptive random noise, mesh smoothing, mesh cropping, and combinations of these attacks.