基于几何法立体图像校正的研究

立体视觉图像校正是加速立体匹配简单而常用的技术之一。采用几何法对使用棱镜的单镜头立体视觉系统图像进行校正,根据成像原理,从图像平面像素点反推到三维实体点的分析运算,利用成像光线几何关系求解虚拟相机外部参数,实现极线的校正,避免了复杂相机标定过程。同时,该算法可以从双棱镜应用推广到多面棱镜的单棱镜立体视觉系统图像校正。实验结果表明,基于几何法对使用棱镜的单镜头立体视觉系统图像校正是有效的。     

A GLCM-Feature-Based Approach for Reversible Image Transformation

Recently, a reversible image transformation (RIT) technology that transforms a secret image to a freely-selected target image is proposed. It not only can generate a stego-image that looks similar to the target image, but also can recover the secret image without any loss. It also has been proved to be very useful in image content protection and reversible data hiding in encrypted images. However, the standard deviation (SD) is selected as the only feature during the matching of the secret and target image blocks in RIT methods, the matching result is not so good and needs to be further improved since the distributions of SDs of the two images may be not very similar. Therefore, this paper proposes a Gray level co-occurrence matrix (GLCM) based approach for reversible image transformation, in which, an effective feature extraction algorithm is utilized to increase the accuracy of blocks matching for improving the visual quality of transformed image, while the auxiliary information, which is utilized to record the transformation parameters, is not increased. Thus, the visual quality of the stego-image should be improved. Experimental results also show that the root mean square of stego-image can be reduced by 4.24% compared with the previous method.     

Convex optimization and limit analysis: Application to Gurson and porous Drucker-Prager materials

First, we summarize our convex optimization method to solve the static approach of limit analysis. Then, we present the main features of a quadratic extension of a recently proposed mixed finite element method of the kinematic approach. Both methods are applied to obtain precise solutions to a forming problem with Gurson and Drucker-Prager materials. Finally, in order to analyze the criterion of “Porous Drucker-Prager” materials, the Gurson micro-macro model involving a Drucker-Prager matrix containing cylindrical cavities is investigated. Comparing previous results shows, among other things, a similarity in the compression case not always observed for the “Porous von Mises” material between cylindrical and spherical cases.     

序列图象目标的一种特殊数字跟踪方法

介绍了在数,模检测相结合的电视跟踪器的一项关键技术－指寅区域的位置和大小的序列图象的实时捕获和处理,并以ＡＤＳＰ２１８１为核心实现了一实际的系统,分析了其中的关键硬件技术介绍了可编程器件ＥＰＬＤ在其中的应用,给出了实时采集处理的结果。     

An Algorithm for the Proximity Operator in Hybrid TV-Wavelet Regularization,with Application to MR Image Reconstruction

Total variation (TV) and wavelet $L_1$ norms have often been used as regularization terms in image restoration and reconstruction problems. However, TV regularization can introduce staircase effects and wavelet regularization some ringing artifacts, but hybrid TV and wavelet regularization can reduce or remove these drawbacks in the reconstructed images. We need to compute the proximal operator of hybrid regularizations, which is generally a sub-problem in the optimization procedure. Both TV and wavelet $L_1$ regularisers are nonlinear and non-smooth, causing numerical difficulty. We propose a dual iterative approach to solve the minimization problem for hybrid regularizations and also prove the convergence of our proposed method, which we then apply to the problem of MR image reconstruction from highly random under-sampled k-space data. Numerical results show the efficiency and effectiveness of this proposed method.     

一种新的用于图象拼接的颜色融合方法

基于图象的虚拟现实是实现虚现实系统的一种新方法，对于该方法而言，全景图的制作是至关重要的，全景图制作中的一项关键技术是颜色融合，即在接接图象时，如何使颜色能平滑过度，对此，本文提出了一种基于塔形结构的颜色融合算法，首先，它将图象分解成一组带通图象，然后在第五个频率带内使用没的加权函数进行颜色融合。在每一个频率带内，加权函数的系数以及颜色融合区域的大小，是由两幅图象的图象特征在该频率带内的差异决定的     

A Geometric Approach to Archetypal Analysis and Nonnegative Matrix Factorization

Archetypal analysis and nonnegative matrix factorization (NMF) are staples in a statistician's toolbox for dimension reduction and exploratory data analysis. We describe a geometric approach to both NMF and archetypal analysis by interpreting both problems as finding extreme points of the data cloud. We also develop and analyze an efficient approach to finding extreme points in high dimensions. For modern massive datasets that are too large to fit on a single machine and must be stored in a distributed setting, our approach makes only a small number of passes over the data. In fact, it is possible to obtain the NMF or perform archetypal analysis with just two passes over the data.     

孔径测量中CCD瞄准方法与图像处理

探讨了在孔径测量过程中使用CCD摄像机对孔径工作面进行瞄准的方法,介绍了图像的处理方法。     

基于白色与黑色像素区域相间明显的快速边界获取的方法

在实现工业机器视觉系统时,边界获取成为必不可少的一环。为了提高边界获取的速度和生产效率,介绍了一种边界获取的简单有效的新方法,该方法是基于白色与黑色像素区域相间明显的条件下提出的。方法的主要思路是通过计算连续黑白像素宽度及相关处理,获得边界。该方法检测目标时快速,稳定;通过选取不同的像素宽度阀值,可以方便地检测出相应的不同的边界。此方法适用于处理速度要求非常高的工业机器视觉中特征边界的边界获取。     

基于支持向量机的油封缺陷图像检测方法

提出一种基于支持向量机分类的油封缺陷图像检测方法,把油封外观中的有无缺陷看作两种不同的类别模式,应用支持向量机对两类不同的样本采样学习,然后进行分类判断。采集油封各部位图像并进行预处理,利用算法切割出各个检测区域图像,根据油封主要部位的各类缺陷特点,选取不同特征参数。应用径向基核函数建立支持向量机识别模型,并通过实验实现核函数参数寻优。实验结果表明,该方法具有检测成本低、可靠性高、泛化能力强、容易在线实施等特点,具有实用推广价值。     

A Knowledge Based Approach to Integrated Battle Damage Assessment and Repair Analysis

1IntroductionBDARanalysisisacomPlexworkaildakindofanalysistechniquewhichcanbeusedtodetenninebattledaInagemodeanditsrecoverysotgyHavingnoeffectivewaysfordeteninningBDARinfonnationcurrently,wehavetodirechytakeoraPplysomeresearchmethodswhichareuscdinreliabilitymaintainability,survivability,vulnerability,weaponefficiencyandsoon,suchasFMEA/DMEA,MA,FTA,andvulnerabilityanalysis.Theseinfonnationandanalysisresultscomefromtheexperienceandki1owledgeofthedomainexpertS.Therefore,thispaPerprovides…     

Test Case Prioritization in Unit and Integration Testing: A Shuffled-Frog-Leaping Approach

Both unit and integration testing are incredibly crucial for almost any software application because each of them operates a distinct process to examine the product. Due to resource constraints, when software is subjected to modifications, the drastic increase in the count of test cases forces the testers to opt for a test optimization strategy. One such strategy is test case prioritization (TCP). Existing works have propounded various methodologies that re-order the system-level test cases intending to boost either the fault detection capabilities or the coverage efficacy at the earliest. Nonetheless, singularity in objective functions and the lack of dissimilitude among the re-ordered test sequences have degraded the cogency of their approaches. Considering such gaps and scenarios when the meteoric and continuous updations in the software make the intensive unit and integration testing process more fragile, this study has introduced a memetics-inspired methodology for TCP. The proposed structure is first embedded with diverse parameters, and then traditional steps of the shuffled-frog-leaping approach (SFLA) are followed to prioritize the test cases at unit and integration levels. On 5 standard test functions, a comparative analysis is conducted between the established algorithms and the proposed approach, where the latter enhances the coverage rate and fault detection of re-ordered test sets. Investigation results related to the mean average percentage of fault detection (APFD) confirmed that the proposed approach exceeds the memetic, basic multi-walk, PSO, and optimized multi-walk by 21.7%, 13.99%, 12.24%, and 11.51%, respectively.     

A Point‐wise Approach to the Analysis of Complex Composite Structures Using Digital Image Correlation and Thermoelastic Stress Analysis

Thermoelastic stress analysis (TSA) and digital image correlation (DIC) are used to examine the stress and strain distributions around the geometric discontinuity in a composite double butt strap joint. A well‐known major limitation in conducting analysis using TSA is that it provides a metric that is only related to the sum of the principal stresses and cannot provide the component stresses/strains. The stress metric is related to the thermoelastic response by a combination of material properties known as the thermoelastic constant (coefficient of thermal expansion divided by density and specific heat). The thermoelastic constant is usually obtained by a calibration process. For calibration purposes when using orthotropic materials, it is necessary to obtain the thermoelastic constant in the principal material directions, as the principal stress directions for a general structure are unknown. Often, it is assumed that the principal stress directions are coincident with the principal material directions. Clearly, this assumption is not valid in complex stress systems, and therefore, a means of obtaining the thermoelastic constants in the principal stress directions is required. Such a region is that in the neighbourhood of the discontinuities in a bonded lap joint. A methodology is presented that employs a point‐wise manipulation of the thermoelastic constants from the material directions to the principal stress directions using full‐field DIC strain data obtained from the neighbourhood of the discontinuity. A comparison of stress metrics generated from the TSA and DIC data is conducted to provide an independent experimental validation of the two‐dimensional DIC analysis. The accuracy of a two‐dimensional plane strain finite element model representing the joint is assessed against the two experimental data sets. Excellent agreement is found between the experimental and numerical results in the adhesive layer; the adhesive is the only component of the joint where the material properties were not obtained experimentally. The reason for the discrepancy is discussed in the paper.     

局部非线性刚度阻尼系统参数识别的一种新方法

研究了具有平方非线性刚度和平方非线性阻尼的两自由度局部非线性振动系统，采用空间法来识别该系统模型的参数。利用该方法对非线性频响函数进行估计，并利用最小二乘法对模型的非线性刚度系数和非线性阻尼系数进行了优化，实验结果表明了该方法的可行性，在识别和优化汽车等局部非线性系统的物理参数方面具有一定的参考价值。     

A Local Approach to Brittle Fracture Analysis and Its Physical Interpretation

The paper presents a review of studies dedicated to the development of a local approach to brittle fracture in metals and alloys. To work out a statistical criterion of local fracture in a metal in the vicinity of a stress concentrator is shown to be the key task of the local approach. The author substantiates a possibility of describing the process of brittle (quasibrittle) fracture in metals ahead of the notch on the basis of primary principles, i.e., on the basis of the analysis of the processes of formation and catastrophic growth of crack nuclei. The physical effects have been established, which must be allowed for in the development of the local fracture criterion. The author considers the main factors that govern the size of the process zone. This parameter has been found to depend on the value of the relative gradient of the local plastic strain intensity. The appropriateness of using the Weibull distribution to describe quasibrittle fracture of metals is analyzed. It is demonstrated that the Weibull parameters are not material's constants as postulated in the conventional variant of the local approach. Their values depend on the local plastic strain and the metal stress state in the vicinity of the stress concentrator.     

A variationally consistent αFEM (VCαFEM) for solution bounds and nearly exact solution to solid mechanics problems using quadrilateral elements

A variationally consistent alpha finite element method (VC αFEM) for quadrilateral isoparametric elements is presented by constructing an assumed strain field in which the gradient of the compatible strain field is scaled with a free parameter α. The assumed strain field satisfies the orthogonal condition and the Hellinger–Reissner variational principle is used to establish the discretized system of equations. It is shown that the strain energy is a second‐order continuous function of α, and the VC αFEM can produce both lower and upper bounds to the exact solution in the strain energy for all elasticity problems by choosing a proper α∈[0, α_upper]. Based on this bound property, an exact‐α approach has been devised to give an ultra‐accurate solution that is very close to the exact one in the strain energy. Furthermore, the exact‐α approach also works well for volumetric locking problems, by simply replacing the strain gradient matrix by a stabilization matrix. In addition, a regularization‐α approach has also been suggested to overcome possible hourglass instability. Intensive numerical studies have been conducted to confirm the properties of the present VC αFEM, and a very good performance has been found in comparing to a large number of existing FEM models. Copyright © 2010 John Wiley & Sons, Ltd.     

A domain coupling method for finite element digital image correlation with mechanical regularization: Application to multiscale measurements and parallel computing

A general method is proposed to couple two subregions analyzed with finite element digital image correlation even when using a mechanical regularization (regularized digital image correlation). A Lagrange multiplier is introduced to stitch both displacements fields in order to recover continuity over the full region of interest. Another interface unknown is introduced to ensure, additionally, the equilibrium of the mechanical models used for regularization. As a first application, the method is used to perform a single measurement from images at two different resolutions. Secondly, the method is also extended to parallel computing in regularized digital image correlation. The problem is formulated at the interface and solved with a Krylov‐type algorithm. A dedicated preconditioner is proposed to significantly accelerate convergence. The resulting method is a good candidate for the analysis of large data sets. Copyright © 2016 John Wiley & Sons, Ltd.     

一种新的基于粗糙集的数学形态学算法及其在图像边缘检测中的应用

从粗糙集的角度出发来研究数学形态学,指出经典数学形态学模型是不符合实际的,引入粗糙集中的粗糙度的概念改进了形态学模型,通过动态的选择结构元素来对图像进行处理.实验显示,基于粗糙集的数学形态学方法较好地解决了经典形态学处理中图像目标边界线条较粗的缺点.相比经典梯度算子,文中提出的方法又较好地保证了图像边界的连续性,同时还避开了结构元素的选择问题.     

A complete automated algorithm for segmentation of tissues and identification of tumor region in T1, T2, and FLAIR brain images using optimization and clustering techniques

Tissues in brain are the most complicated parts of our body, a clear examination and study are therefore required by a radiologist to identify the pathologies. Normal magnetic resonance (MR) scanner is capable of producing brain images with bounded tissues, where unique and segregated views of the tissues are required. A distinguished view upon the images is manually impossible and can be subjected to operator errors. With the assistance of a soft computing technique, an automated unique segmentation upon the brain tissues along with the identification of the tumor region can be effectively done. These functionalities assist the radiologist extensively. Several soft computing techniques have been proposed and one such technique which is being proposed is PSO‐based FCM algorithm. The results of the proposed algorithm is compared with fuzzy C‐means (FCM) and particle swarm optimization (PSO) algorithms using comparison factors such as mean square error (MSE), peak signal to noise ratio (PSNR), entropy (energy function), Jaccard (Tanimoto Coefficient) index, dice overlap index and memory requirement for processing the algorithm. The efficiency of the PSO‐FCM algorithm is verified using the comparison factors.     

A dislocation and point force approach to the boundary element method for mixed mode crack analysis of plane anisotropic solids

Abstract

This study investigates the feasibility of enhancing steam‐driven ejector performance. Initially, a one‐dimensional ejector theory is used to examine the effects on ejector performance of three isentropic efficiencies: nozzle efficiency η_m , mixing efficiency η_m, and diffuser efficiency η_m . Theoretical analysis demonstrates that mixing efficiency profoundly affects ejector performance, but that the other two efficiencies have slightly influenced ejector performance. This finding suggests that efficient mixing can promote ejector performance. This study also attempts to improve mixing efficiency using a petal nozzle. The behavior and characteristics of a petal nozzle are investigated by testing the nozzle under various operating conditions, i.e. primary pressure, secondary pressure, and back pressure. In addition, the study compares the experimental and theoretical results. These results prove that using a petal nozzle can improve ejector performance. The shadowgraph method was used to visualize the inner flow field of an ejector. The flow patterns observed should help to further improve ejector performance.