排序方式: 共有30条查询结果,搜索用时 31 毫秒
1.
Glaucio H. Paulino Ivan F. M. Menezes Marcelo Gattass Subrata Mukherjee 《International journal for numerical methods in engineering》1994,37(9):1511-1530
A Finite Element Graph (FEG) is defined here as a nodal graph (G), a dual graph (G*), or a communication graph (G˙) associated with a generic finite element mesh. The Laplacian matrix ( L (G), L (G*) or L (G˙)), used for the study of spectral properties of an FEG, is constructed from usual vertex and edge connectivities of a graph. An automatic algorithm, based on spectral properties of an FEG (G, G* or G˙), is proposed to reorder the nodes and/or elements of the associated finite element mesh. The new algorithm is called Spectral PEG Resequencing (SFR). This algorithm uses global information in the graph, it does not depend on a pseudoperipheral vertex in the resequencing process, and it does not use any kind of level structure of the graph. Moreover, the SFR algorithm is of special advantage in computing environments with vector and parallel processing capabilities. Nodes or elements in the mesh can be reordered depending on the use of an adequate graph representation associated with the mesh. If G is used, then the nodes in the mesh are properly reordered for achieving profile and wavefront reduction of the finite element stiffness matrix. If either G* or G˙ is used, then the elements in the mesh are suitably reordered for a finite element frontai solver, A unified approach involving FEGs and finite element concepts is presented. Conclusions are inferred and possible extensions of this research are pointed out. In Part II of this work,1 the computational implementation of the SFR algorithm is described and several numerical examples are presented. The examples emphasize important theoretical, numerical and practical aspects of the new resequencing method. 相似文献
2.
In this paper we present a method for the calibration of multiple cameras based on the extraction and use of the physical characteristics of a one-dimensional invariant pattern which is defined by four collinear markers. The advantages of this kind of pattern stand out in two key steps of the calibration process. In the initial step of camera calibration methods, related to sample points capture, the proposed method takes advantage of using a new technique for the capture and recognition of a robust sample of projective invariant patterns, which allows to capture simultaneously more than one invariant pattern in the tracking area and recognize each pattern individually as well as each marker that composes them. This process is executed in real time while capturing our sample of calibration points in the cameras of our system. This new feature allows to capture a more numerous and robust set of sample points than other patterns used for multi-camera calibration methods. In the last step of the calibration process, related to camera parameters' optimization, we explore the collinearity feature of the invariant pattern and add this feature in the camera parameters optimization model. This approach obtains better results in the computation of camera parameters. We present the results obtained with the calibration of two multi-camera systems using the proposed method and compare them with other methods from the literature. 相似文献
3.
This paper uses the geostatistical function - semivariogram and a set of 3D geometric measures - sphericity index, convexity index, extrinsic and intrinsic curvature index and surface type, to characterize lung nodules as malignant or benign in computerized tomography images. Based on a sample of 31 nodules, 25 benign and 6 malignant, these methods are first analyzed individually and then jointly, with techniques for classification and analysis (stepwise discriminant analysis, leave-one-out and ROC curve). We have concluded that the individual measures and their combinations produce good results in the diagnosis of lung nodules. 相似文献
4.
This paper focuses on computer-aided analysis of three-dimensional buildings with 32-bit, virtual-memory minicomputers. Various floor, inertial, geometry, stiffness, and displacement models of three-dimensional buildings are discussed with respect to implications for computational efficiency. From this discussion a model for three-dimensional buildings is selected for use with virtual-memory minicomputers. This paper also treats the use of symbolic manipulation, dynamic allocation of memory, and matrix storage and manipulation to achieve computational efficiency. Examples with computational statistics illustrate the ideas presented. 相似文献
5.
Engineering with Computers - This work presents a new efficient array-based algorithm for adaptive mesh refinement capable of interactively generating millions of triangles. The new refinement... 相似文献
6.
CN Paiva MT Castelo-Branco J Lannes-Vieira CR Gattass 《Canadian Metallurgical Quarterly》1999,91(1):7-19
Currently, there is no vaccine available against Chagas' disease. Immune abnormalities induced by T. cruzi pose particular difficulties for vaccine development, since immunological memory must be able to overcome them to prevent spread of infection/sequelae. We have previously demonstrated that experimental vaccination with live CL-14 trypomastigotes does not induce polyclonal lymphocyte activation, immunosuppression, or pathology and efficiently immunizes against virulent T. cruzi. Herein we show that: (1) expansion of CD4+ and CD8+ subsets peaks 2 weeks after infective challenge in both challenged-vaccinated mice and infected controls, but the former exhibit a smaller increase in blastogenesis and in the numbers of activated CD11a(hi)CD4+ and CD11a(hi)CD8+ cells; (2) in long-term-vaccinated mice, expansion of activated subsets (CD62Llo/- and CD11a(hi)) is accelerated among CD8+ PBL 1 week after challenge; (3) challenged-vaccinated mice retract the CD8+-activated subset 5 weeks after challenge, different from infected controls; (4) protection conferred by CL-14 immunization can be adoptively transferred to na?ve recipients with lymphocyte suspensions, and prior depletion of CD8+ (but not of CD4+) cells abolishes protective immunity. Our findings indicate that protective immunity generated by CL-14 immunization involves a transient CD8+ recall response and is capable of preventing the signs of polyclonal lymphocyte activation induced by virulent challenge. 相似文献
7.
Marcelo Gattass John F. Abel 《International journal for numerical methods in engineering》1987,24(11):2119-2141
Bathe and co-workers'1,2 updated Lagrangian formulation is reviewed for a two-dimensional beam-column element. From this review a physical interpretation and properties are derived for the matrices of the method. A variant of Argyris and co-workers'4,5 natural concept is introduced in the updated Lagrangian formulation, and a new method to derive element matrices arises. A detailed derivation of the matrices of the twodimensional beam-column element is presented to clarify further the UL formulations. Explicit expressions for these matrices, computed with the use of symbolic manipulation,17 are also presented to illustrate the concepts discussed. Finally, numerical results are shown to compare and evaluate different methods and matrices. 相似文献
8.
Araújo José Denes Lima Souza Johnatan Carvalho Neto Otilio Paulo Silva de Sousa Jefferson Alves de Almeida João Dallyson Sousa de Paiva Anselmo Cardoso Silva Aristófanes Corrêa Junior Geraldo Braz Gattass Marcelo 《Multimedia Tools and Applications》2019,78(10):12987-13004
Multimedia Tools and Applications - Glaucoma is the second major cause of vision loss worldwide. It is usually caused by the increase in the intraocular pressure, which damages the optic nerve... 相似文献
9.
Leonardo de Oliveira Martins Aristófanes Corrêa Silva Anselmo Cardoso de Paiva Marcelo Gattass 《Journal of Signal Processing Systems》2009,55(1-3):77-90
Breast cancer is a serious public health problem in several countries. Computer-aided detection/diagnosis systems (CAD/CADx) have been used with relative success in aid of health care professionals. The goal of such systems is not to replace the professionals, but to join forces in order to detect the different types of cancer at an early stage. The main contribution of this work is the presentation of a methodology for detecting masses in digitized mammograms using the growing neural gas algorithm for image segmentation and Ripley’s K function to describe the texture of segmented structures. The classification of these structures is accomplished through support vector machines which separate them in two groups, using shape and texture measures: masses and non-masses. The methodology obtained 89.30% of accuracy and a rate of 0.93 false positives per image. 相似文献
10.
Diniz João O. B. Quintanilha Darlan B. P. Santos Neto Antonino C. da Silva Giovanni L. F. Ferreira Jonnison L. Netto Stelmo M. B. Araújo José D. L. Da Cruz Luana B. Silva Thamila F. B. da S. Martins Caio M. Ferreira Marcos M. Rego Venicius G. Boaro José M. C. Cipriano Carolina L. S. Silva Aristófanes C. de Paiva Anselmo C. Junior Geraldo Braz de Almeida João D. S. Nunes Rodolfo A. Mogami Roberto Gattass M. 《Multimedia Tools and Applications》2021,80(19):29367-29399
Multimedia Tools and Applications - At the end of 2019, the World Health Organization (WHO) reported pneumonia that started in Wuhan, China, as a global emergency problem. Researchers quickly... 相似文献