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A massively parallel hardware architecture for ray-tracing

International Journal of High Performance systems Architecture 2009年第1期2卷 26-34页

作者： Nery, A.S. Nedjah, N. França, F.M.G. Computer Architecture and Microelectronics Laboratory Systems Engineering and Computer Science Program COPPE P.O. Box 68511 21941-972 Rio de Janeiro Brazil Department of Electronics Engineering and Telecommunications Faculty of Engineering Universidade do Estado do Rio de Janeiro Rua Sao Francisco Xavier 524 Sala 5145-F Maracana 20.550-900 Rio de Janeiro RJ Brazil Universidade Federal do Rio de Janeiro Rio de Janeiro Brazil Department of Electronics Engineering and Telecommunications Faculty of Engineering State University of Rio de Janeiro Brazil Brazil

Real time performance of non-interactive rendering of three-dimensional scenes is usually unachievable. Ray tracing is one of the methods used for rendering such scenes. The performance achieved by a sequential software-based implementation of ray tracing is far from satisfactory. In contrast, many parallel implementations of ray tracing have been enabling real time performance, as the underlying algorithm can be massively parallelised. Thus, it is expected that a custom parallel design in hardware is likely to achieve the acceptable performance standards. In this paper, we propose a hardware architecture, which we call GridRT, capable of dealing with the main desirable features of ray tracing, such as shadows and reflections effects, imposing low requirements in terms of silicon area while achieving acceptable performance in terms of rendering time. This architecture achieves is efficient yet compact as it explores the massive parallelism offered by the intrinsic structure of the algorithm. The design exploits the usage the spatial data structure of regular grids. Copyright © 2009 Inderscience Enterprises Ltd.

关键词： Ray tracing

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Mediating process adaptation through a goal-oriented context-aware approach

Mediating process adaptation through a goal-oriented context...

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International Conference on computer Supported Cooperative Work in Design

作者： Vanessa Tavares Nunes Cláudia M. Lima Werner Flávia Maria Santoro COPPE/PESC-Systems Engineering and Computer Science Program UFRJ Rio de Janeiro Brazil NP2Tec and Postgraduate Information Systems Program UNIRIO Rio de Janeiro Brazil

Complexity and dynamism of day-to-day activities in organizations are inextricably linked, one impacting the other, increasing the challenges for constant adaptation on the way to organize work to address emerging demands. Market is demanding systems that are aware of organizations processes and able to evolve and adapt to new situations in everyday working activities. We argue that flexibility in processes could be managed in real time, by PAIS (Process-aware Information systems), using context information collected in the work environment. This paper proposes CGAdapt, a context management architecture approach that aims to improve and automate dynamic process adaptation. We explain how process adaptation may occur in real time through an existent scenario using this proposal and discuss the value of context-awareness to reason about process alternative adaptations in a goal oriented approach.

关键词： Context Materials Business Adaptation models Analytical models

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Dynamic process adaptation: A context-aware approach

Dynamic process adaptation: A context-aware approach

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International Conference on computer Supported Cooperative Work in Design

作者： Vanessa Tavares Nunes Cláudia M. Lima Werner Flávia Maria Santoro COPPE PESC-Systems Engineering and Computer Science Program UFRJ Rio de Janeiro Brazil NP2Tec and Postgraduate Information Systems Program UNIRIO Rio de Janeiro Brazil

Dynamism of day-to-day activities in organizations is inextricably linked and there is a variety of information, insight and reasoning being processed between people and systems, in carrying out a business process. We argue that flexibility in processes could be managed in real time, using context information collected in the work environment. This paper proposes a context management architecture approach that aims to improve and automate dynamic process adaptation. We explain how process adaptation may occur in real time and discuss a scenario for this proposal.

关键词： Context Adaptation models Organizations Cognition Context modeling Uncertainty

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Attitude control without angular velocity measurement: a passivity approach

Attitude control without angular velocity measurement: a pas...

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IEEE International Conference on Robotics and Automation (ICRA)

作者： F. Lizarralde J.T. Wen Department of Electrical Engineering COPPE UFRJ Rio de Janeiro Brazil Center for Advanced Technology in Automation and Robotics Department of Electrical Computer and Systems Engineering Rensselaer Polytechnic Institute Troy NY USA

It is well known that the linear feedback of the quarternion of the attitude error and angular velocity globally stabilizes the attitude of a rigid body. In this note, we show that the angular velocity feedback can be replaced by a nonlinear filter of the quarternion, thus removing the need of direct angular velocity measurement. In contrast to other approaches, this design exploits the inherent passivity of the system; a dynamic observer reconstructing the velocity is not needed. An application of the proposed scheme is illustrated for the robot control problem. Simulation results are included to illustrate the theoretical results.

关键词： Angular velocity Velocity measurement PD control Feedback Quaternions Robot control Orbital robotics Robotics and automation Space vehicles Proportional control

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Thoth: improving experiences reuses in the scientific environment through workflow management system

Thoth: improving experiences reuses in the scientific enviro...

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International Conference on computer Supported Cooperative Work in Design

作者： E. Bomfim J. Oliveira J.M. de Souza J. Strauch COPPE/UFRJ-Computer Science Department Graduate School of Engineering Federal University of Rio de Janeiro Brazil DCC-IM/UFRJ-Computer Science Department Mathematics Institute Federal University of Rio de Janeiro Brazil ENCE-National Statistics College Brazil

The activities executed in the scientific environment are extremely dependent on knowledge from their performers. Thus, knowledge management initiatives are very important in this environment. One of the possibilities for improving the knowledge flow is to explore past experiences, resulting from the modeling and execution of previous scientific activities and handled by a workflow management system. This work presents Thoth, a system which aims at knowledge reuse in the scientific environment, during the planning, design and execution of scientific activities. This approach is integrated with a CBR approach, also described in this paper, with workflow systems and the use of ontologies.

关键词： Workflow management software Knowledge management computer science Ontologies Collaborative work Knowledge engineering Mathematics Statistics Educational institutions Production

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An empirical methodology for introducing software processes

An empirical methodology for introducing software processes

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8th Eiropean engineering Conference (ESEC) and 9th ACM SIGSOFT Symposium on the Foundations of Software engineering (FSE-9)

作者： Shull, Forrest Carver, Jeffrey Travassos, Guilherme H. Fraunhofer Center - Maryland University of Maryland 4321 Hartwick Road College Park MD 20742 United States Exp. Software Engineering Group Department of Computer Science University of Maryland College Park College Park MD 20742 United States Computer Science Department COPPE UFRJ C.P. 68511 - Ilha do Fundão Rio de Janeiro - RJ - 21945-180 Brazil

There is a growing interest in empirical study in software engineering, both for validating mature technologies and for guiding improvements of less-mature technologies. This paper introduces an empirical methodology, based on experiences garnered over more than two decades of work by the Empirical Software engineering Group at the University of Maryland and related organizations, for taking a newly proposed improvement to development processes from the conceptual phase through transfer to industry. The methodology presents a series of questions that should be addressed, as well as the types of studies that best address those questions. The methodology is illustrated by a specific research program on inspection processes for Object-Oriented designs. Specific examples of the studies that were performed and how the methodology impacted the development of the inspection process are also described.

关键词： Software engineering

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DIRECTIONAL DECOMPOSITION BASED TOTAL VARIATION IMAGE RESTORATION

DIRECTIONAL DECOMPOSITION BASED TOTAL VARIATION IMAGE RESTOR...

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European Signal Processing Conference

作者： Daniel R. Pipa Stanley H. Chan Truong Q. Nguyen Universidade Federal do Rio de Janeiro (COPPE/UFRJ) Harvard University - School of Engineering and Applied Science University of California San Diego - Department of Electrical and Computer Engineering

ISBN: (纸本)9781467310680

This paper proposes an extension of total variation (TV) image deconvolution technique that enhances image quality over classical TV while preserving algorithm speed. Enhancement is achieved by altering the regularization term to include directional decompositions before the gradient operator. Such decompositions select areas of the image with characteristics that are more suitable for a certain type of gradient than another. Speed is guaranteed by the use of the augmented Lagrangian approach as basis for the algorithm. Experimental evidence that the proposed approach improves TV deconvolution is provided, as well as an outline for a future work aiming to support and substantiate the proposed method.

关键词： Total variation Augmented Lagrangian Pmage deconvolution Image restoration Directional decompositions DIRECTIONAL image restoration technique Basis algorithms Television decomposition Imagery (Psychotherapy) images Outlines deconvolution Image quality

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The Use of Support Vector Machine and Genetic Algorithms to Predict Protein Function

The Use of Support Vector Machine and Genetic Algorithms to ...

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IEEE International Conference on systems, Man, and Cybernetics

作者： Walkiria K. Resende Renato A. Nascimento Carolina R. Xavier Iara F. Lopes Cristianc N. Nobre Department of Computer Science Universidade Federal de Sao Joao del Rei - UFSJ Department of Computer Science Pontificia Universidade Catolica de Minas Gerais PUC/MG Civil Engineering Program COPPE - UFRJ

ISBN: (纸本)9781467317139

In Bio informatics, the prediction of protein function is considered a very important task but also difficult. Using a set of enzymes represented by Hydrolase, Isomerase, Ligase, Lyase, Transferase and Oxidoreductase classes, previously used by Dobson et ah, this paper proposes a self-learning process able to predict their classes, based on their primary and secondary structures, through a Support Vector Machine (SVM) classifier and genetic algorithm. An SVM can he characterized as a supervised machine learning algorithm capable of resolving linear and non-linear classification problems. During the learning process, both the training data and the corresponding output are presented to the SVM to allow its parameters to he adjusted. This study utilized genetic algorithms - optimization heuristics often used to estimate parameters - to adjust the main parameters of the classifier such as kernel function type and parameter C, which provides the relationship between the training error and the margin of separation between classes. In this specific prediction problem, the results indicate that the best function is an RBF where width is 6.1 and C is 6.9. Using these parameters, the classifier obtains an average accuracy of 79.74%.

关键词： Component: Proteins Prediction Support Vector Machine Genetic Algorithms protein structure function Support Vector Network Genetic Algorithm (GA) Classifiers Learning processes secondary structures

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Perspectives on creativity in web learning

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2nd International Conference on Web-Based Learning, ICWL 2003

作者： Vivacqua, Adriana Mattos, Francisco Tornaghi, Alberto De Souza, Jano M. Cukierman, Henrique COPPE/UFRJ – Computer Science Department Graduate School of Engineering PO Box 68511 Rio de JaneiroRJ21941-972 Brazil Institute of Mathematics Federal University of Rio de Janeiro PO Box 68511 Rio de JaneiroRJ21941-972 Brazil

ISBN: (纸本)3540407723

Creativity is an important asset in today’s fast changing environment. We believe it can and should be stimulated in educational environments, through the use of tools and careful design of activities and work groups. In this paper, we present and briefly discuss a checklist of eight activities to support creativity and should be applied when designing educational courses. We discuss the benefits of group work and present some educational perspectives to support it. We then relate creativity and collaborative learning and analyze a dynamic geometry system in relation to this checklist. © Springer-Verlag Berlin Heidelberg 2003.

关键词： computers

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Using Distributed-Shared Memory Mechanisms for Agents Communication in a Distributed System

Using Distributed-Shared Memory Mechanisms for Agents Commun...

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International Conference on Intelligent systems Design and Applications (ISDA)

作者： Thiago Gonzaga Cristina Bentes Ricardo Farias Maria Clicia S. de Castro Ana Cristina Garcia Department of Systems Engineering University of State of Rio de Janeiro Brazil Department of Systems Engineering – UERJ Maracanã COPPE – Systems Engineering – UFRJ Cidade Universitária Fundão Brazil Institute of Mathematics and Statistics - UERJRua S˜ao Francisco Xavier 524 - Maracan˜a Department of Computer Science – UFF Niterói Brazil

In multi-agent systems, blackboard communication provides an easy way for agents to communicate. However, in a distributed architecture, the blackboard is commonly implemented in a single node, that is the "blackboard server". This approach may work well for a small number of agents. Nevertheless, when the number of agents increases, the blackboard server becomes the bottleneck for the system scalability. In this work we propose a novel agent communication system based on distributed-shared mechanisms that allows the implementation of a shared address space on a distributed system, without centralizing the blackboard. Our idea is to distribute the shared data over the nodes and use a message passing sub-system, totally transparent to the agents. We implemented this idea in a multi-agent system based on social laws, and used a distributed-shared memory system to handle the messaging. We created a conflict simulator, and showed that the distributed-shared mechanisms easy the implementation of a truly distributed blackboard.

关键词： computer architecture Design engineering systems engineering and theory Multiagent systems Scalability Message passing Programming profession Read-write memory Personal communication networks Space technology

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