Página 5 dos resultados de 100905 itens digitais encontrados em 0.144 segundos

‣ Recuperação de informação: análise sobre a contribuição da ciência da computação para a ciência da informação; Information Retrieval: analysis about the contribution of Computer Science to Information Science

Ferneda, Edberto
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 15/12/2003 Português
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Desde o seu nascimento, a Ciência da Informação vem estudando métodos para o tratamento automático da informação. Esta pesquisa centrou-se na Recuperação de Informação, área que envolve a aplicação de métodos computacionais no tratamento e recuperação da informação, para avaliar em que medida a Ciência da Computação contribui para o avanço da Ciência da Informação. Inicialmente a Recuperação de Informação é contextualizada no corpo interdisciplinar da Ciência da Informação e são apresentados os elementos básicos do processo de recuperação de informação. Os modelos computacionais de recuperação de informação são analisados a partir da categorização em “quantitativos” e “dinâmicos”. Algumas técnicas de processamento da linguagem natural utilizadas na recuperação de informação são igualmente discutidas. No contexto atual da Web são apresentadas as técnicas de representação e recuperação da informação desde os mecanismos de busca até a Web Semântica. Conclui-se que, apesar da inquestionável importância dos métodos e técnicas computacionais no tratamento da informação, estas se configuram apenas como ferramentas auxiliares, pois utilizam uma conceituação de “informação” extremamente restrita em relação àquela utilizada pela Ciência da Informação; Since its birth...

‣ Understanding expressive action

Wren, Christopher R. (Christopher Richard)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 120 p.; 1445846 bytes; 1445561 bytes; application/pdf; application/pdf
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We strain our eyes, cramp our necks, and destroy our hands trying to interact with computer on their terms. At the extreme, we strap on devices and weigh ourselves down with cables trying to re-create a sense of place inside the machine, while cutting ourselves off from the world and people around us. The alternative is to make the real environment responsive to our actions. It is not enough for environments to respond simply to the presence of people or objects: they must also be aware of the subtleties of changing situations. If all the spaces we inhabit are to be responsive, they must not require encumbering devices to be worn and they must be adaptive to changes in the environment and changes of context. This dissertation examines a body of sophisticated perceptual mechanisms developed in response to these needs as well as a selection of human-computer interface sketches designed to push the technology forward and explore the possibilities of this novel interface idiom. Specifically, the formulation of a fully recursive framework for computer vision called DYNA that improves performance of human motion tracking will be examined in depth. The improvement in tracking performance is accomplished with the combination of a three-dimensional...

‣ Interactive maintenance terminal fault isolation program

Bulat, Michael Henry
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: [51] leaves; 2802156 bytes; 2801915 bytes; application/pdf; application/pdf
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by Michael Henry Bulat.; Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1981.; MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.; Bibliography: leaves 40-41.

‣ Formal specification of a specification library

Atreya, Sriram K
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 108 leaves; 6267324 bytes; 6267084 bytes; application/pdf; application/pdf
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by Sriram K. Atreya.; Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1982.; MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING; Bibliography: leaves 101-103.

‣ A garbage-collecting associative memory for database systems

Ross, Richard Alan
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 66 leaves; 4656218 bytes; 4655974 bytes; application/pdf; application/pdf
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by Richard Alan Ross.; Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1982.; MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.; Bibliography: leaves 64-66.

‣ Computational genomics : mapping, comparison, and annotation of genomes

Batzoglou, Serafim
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 191 leaves; 16436794 bytes; 16436554 bytes; application/pdf; application/pdf
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The field of genomics provides many challenges to computer scientists and mathematicians. The area of computational genomics has been expanding recently, and the timely application of computer science in this field is proving to be an essential component of the large international effort in genomics. In this thesis we address key issues in the different stages of genome research: planning of a genome sequencing project, obtaining and assembling sequence information, and ultimately study, cross-species comparison, and annotation of finished genomic sequence. We present applications of computational techniques to the above areas: (1) In relation to the early stages of a genome project, we address physical mapping, and we present results on the theoretical problem of finding minimum superstrings of hypergraphs, a combinatorial problem motivated by physical mapping. We also present a statistical and simulation study of "walking with clone-end sequences", an important method for sequencing a large genome.; (cont.) (2) Turning to the problem of obtaining the finished genomic sequence, we present ARACHNE, a prototype software system for assembling sequence data that are derived from sequencing a genome with the "shotgun" method. (3) Finally...

‣ Radar tracking system development

Chin, Yue Hann
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 65 leaves; 738663 bytes; 761184 bytes; application/pdf; application/pdf
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The Airborne Seeker Test Bed (ASTB) is an airborne sensor testing platform operated by the Tactical Defense Systems group at MIT Lincoln Laboratory. The Instrumentation Head (IH) is a primary sensor on the ASTB. It is a passive X-band radar receiver located on the nose of the plane. The IH serves as a truth sensor for other RF systems on the test bed and is controlled by an onboard tracking system, the Seeker Computer. The Seeker Computer processes IH data in real-time to track targets in Doppler, angle, and range. From these tracks it then produces angle-error feedback signals that command the IH gimbals, keeping targets centered along the antenna boresight. Over three years, a new Seeker Computer was built to replace an old system constrained by obsolete hardware. The redevelopment project was a team effort and this thesis presents a systems-level analysis of the design process, the new Seeker Computer system, and the related team and individual contributions to software and digital signal processing research that took place during development.; by Yue Hann Chin.; Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.; This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.; Includes bibliographical references (leaf 65).

‣ rMPI : an MPI-compliant message passing library for tiled architectures; MPI-compliant message passing library for tiled architectures

Psota, James Ryan
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 115 leaves; 6753474 bytes; 7102742 bytes; application/pdf; application/pdf
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Next-generation microprocessors will increasingly rely on parallelism, as opposed to frequency scaling, for improvements in performance. Microprocessor designers are attaining such parallelism by placing multiple processing cores on a single piece of silicon. As the architecture of modern computer systems evolves from single monolithic cores to multiple cores, its programming models continue to evolve. Programming parallel computer systems has historically been quite challenging because the programmer must orchestrate both computation and communication. A number of different models have evolved to help the programmer with this arduous task, from standardized shared memory and message passing application programming interfaces, to automatically parallelizing compilers that attempt to achieve performance and correctness similar to that of hand-coded programs. One of the most widely used standard programming interfaces is the Message Passing Interface (MPI). This thesis contributes rMPI, a robust, deadlock-free, high performance design and implementation of MPI for the Raw tiled architecture.; (cont.) rMPIs design constitutes the marriage of the MPI interface and the Raw system, allowing programmers to employ a well understood programming model to a novel high performance parallel computer. rMPI introduces robust...

‣ POSH : a generalized CAPTCHA with security applications; Generalized CAPTCHA with security applications

Daher, Waseem S. (Waseem Sebastian)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 53 p.
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A puzzle only solvable by humans, or POSH, is a prompt or question with three important properties: it can be generated by a computer, it can be answered consistently by a human, and a human answer cannot be efficiently predicted by a computer. In fact, a POSH does not necessarily have to be verifiable by a computer at all. One application of POSHes is a scheme proposed by Canetti et al. that limits on-line dictionary attacks against password-protected local storage, without the use of any secure hardware or secret storage. We explore the area of POSHes, implement several candidate POSHes and have users solve them, to evaluate their effectiveness. Given these data, we then implement the above scheme as an extension to the Mozilla Firefox web browser, where it is used to protect user certificates and saved passwords. In the course of doing so, we also define certain aspects of the threat model for our implementation (and the scheme) more precisely.; by Waseem S. Daher.; Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.; This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.; Includes bibliographical references (p. 51-53).

‣ A Flexible Brain-Computer Interface

Bayliss, Jessica D. ; Ballard, Dana H.
Fonte: University of Rochester. Computer Science Department. Publicador: University of Rochester. Computer Science Department.
Tipo: Tese de Doutorado
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Thesis (Ph. D.)--University of Rochester. Dept. of Computer Science, 2001. Simultaneously published in the Technical Report series.; Recent advances in computer hardware and signal processing have made it feasible to use human EEG signals or "brain waves" to communicate with a computer. Locked-in patients now have a means to communicate with the outside world. Even with modern advances, such systems still suffer from communication rates on the order of 2-3 items/minute. In addition, existing systems are not likely to be designed with flexibility in mind, leading to slow systems that are difficult to improve. This dissertation presents a flexible brain-computer interface that is designed to facilitate changes in signal processing methods and user applications. In order to show the flexibility of the system, several applications, ranging from a brain-body actuated video game played with eye movements to a brain-computer interface for environmental control in a virtual apartment, are shown. The P3 evoked potential is a positive wave in the EEG signal peaking at around 300 milliseconds after task-relevant stimuli and it can be used as a binary control signal. A virtual driving experiment shows that the P3 can be reliably detected within a virtual environment. Several on-line algorithms for processing single trial P3 evoked potentials are presented and compared. It is important that actual EEG signals rather than signal artifacts are being recognized and thus false recognition of artifacts is shown to be small. Results from an environmental control application within a virtual apartment are presented. Subjects do not perform significantly different between controlling the application from a computer monitor and when fully immersed in the virtual apartment and subjects like the immersive VR environment better. This highlights the fact that the P3 component of the evoked potential is robust over different environments and that usability does not depend solely on performance...

‣ Research in Computer Science and Computer Engineering

Feldman, J. A. ; Merriam, C. W.
Fonte: University of Rochester. Computer Science Department. Publicador: University of Rochester. Computer Science Department.
Tipo: Relatório
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This report describes many of the computer related research efforts at the University of Rochester. The Department of Computer Science is involved in research in automatic programming, including very high level languages and data structures; machine perception; and in problem solving using combinations of traditional heuristic methods, artificial intelligence, and utility theory. The research of the Department of Electrical Engineering includes basic computer engineering research in the construction of computer systems and operating systems, research in image processing and in numerical methods, and research in production automation which is concerned with mechanical manufacturing and assembly, and is currently developing mathematical models of parts, raw materials and tools. In conjunction with other departments, Electrical Engineering is also using computers for biomedical applications including ultrasound diagnostic techniques for heart disease, and pattern recognition techniques for detection of cancer from PAP smears.

‣ Research in Computer Science and Computer Engineering

Feldman, J. A. ; Merriam, C. W.
Fonte: University of Rochester. Computer Science Department. Publicador: University of Rochester. Computer Science Department.
Tipo: Relatório
Português
Relevância na Pesquisa
66.67459%
This report describes many of the computer related research efforts at the University of Rochester. The Department of Computer Science is involved in research in automatic programming, including very high level languages and data structures; machine perception; and in problem solving using combinations of traditional heuristic methods, artificial intelligence, and utility theory. The research of the Department of Electrical Engineering includes basic computer engineering research in the construction of computer systems and operating systems, research in image processing and in numerical methods, and research in production automation which is concerned with mechanical manufacturing and assembly, and is currently developing mathematical models of parts, raw materials and tools. In conjunction with other departments, Electrical Engineering is also using computers for biomedical applications including ultrasound diagnostic techniques for heart disease, and pattern recognition techniques for detection of cancer from PAP smears.

‣ Research in Computer Science and Computer Engineering

Feldman, J. A. ; Merriam, C. W.
Fonte: University of Rochester. Computer Science Department. Publicador: University of Rochester. Computer Science Department.
Tipo: Relatório
Português
Relevância na Pesquisa
66.67459%
This report describes many of the computer related research efforts at the University of Rochester. The Department of Computer Science is involved in research in automatic programming, including very high level languages and data structures; machine perception; and in problem solving using combinations of traditional heuristic methods, artificial intelligence, and utility theory. The research of the Department of Electrical Engineering includes basic computer engineering research in the construction of computer systems and operating systems, research in image processing and in numerical methods, and research in production automation which is concerned with mechanical manufacturing and assembly, and is currently developing mathematical models of parts, raw materials and tools. In conjunction with other departments, Electrical Engineering is also using computers for biomedical applications including ultrasound diagnostic techniques for heart disease, and pattern recognition techniques for detection of cancer from PAP smears.

‣ Refinement composition using doubly labeled transition graphs

Martinsen, Thor
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado Formato: xxii, 53 p.
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Process Algebra forms a cornerstone in the formal methods area of Computer Science. Among the more widely used approaches is Milner's Communication and Concurrency Systems (CCS). Recently CCS has been extended by Schmidt and Bibighaus through the introduction of Doubly Labeled Transition Systems. This framework has enhanced the model's ability to capture security and availability properties. In this thesis we reformulate, simplify, and extend Bibighaus' work using a graph theoretic framework. The intent is that this abstract mathematical view will make the results more accessible and stimulate additional research. Existing definitions and theorems are redefined and proved using Labeled and Doubly Labeled Transition Graphs (LTG and DLTG). CCS simulation concepts are recast as graph morphisms and the notion of abstraction and refinement are explained through the use of graphs. Bibighaus' work is extended by showing how to carry out non-atomic DLTG refinement, and by developing a form of graph composition involving graph refinements that share a common abstract graph. This type of composition is proven to always be possible with DLTG refinements, and we demonstrate that the composite graph is both a refinement of the abstract graph, and an abstract graph for the refinements from which it was made.; US Navy (USN) author.

‣ Design & implementation of a wireless sensor prototyping kit; Wireless sensor prototyping kit

Hope, Jamison Roger
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 237 p.; 11435381 bytes; 11451039 bytes; application/pdf; application/pdf
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In recent years, wireless sensor networks (WSN) has become an active area of research among computer scientists. In this work, JONA, a prototyping kit for wireless sensors, will be described. The intention of this kit is to open WSN research to interested parties outside of the electrical engineering and computer science communities, who may wish to use wireless sensor networks in their own work. The kit's hardware and software are based upon de facto standards for academic research (Crossbow and TinyOS), with an emphasis on low cost and ease of development. This research has the dual goals of describing a classroom kit and developing a self-contained document providing background material suitable for an introductory project-based class on WSN.; by Jamison Roger Hope.; Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.; Includes bibliographical references (p. 231-234) and index.

‣ A continuous-wave second harmonic gyrotron oscillator at 460 GHz

Hornstein, Melissa K. (Melissa Kristen), 1977-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 266 p.
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We report the short pulse and CW operation of a 460 GHz gyrotron oscillator both at the fundamental (near 230 GHz) and second harmonic (near 460 GHz) of electron cyclotron resonance. During operation in a complete CW regime with 12.4 kV beam voltage and 135 mA beam current, the gyrotron generates a record 8 W of power in the second harmonic TE0,6,1 mode at 458.6 GHz. Design at high frequency, second harmonic, and low beam power is challenging because the latter two involve lower gain than at fundamental modes and all three necessitate higher Q cavities. Under complete computer control, the gyrotron has stably operated continuously for over an hour near 460 GHz. Diagnostic radiation pattern measurements of the beam using an array of pyroelectric sensors show a bi-Gaussian beam with 4% ellipticity. Operation in the fundamental modes, including the TE₀ ₃ ₁ mode at 237.91 GHz and the TE₂ ₃ ₁ at 233.15 GHz, is observed at peak output powers up to 70 W. CW studies of the fundamental TE₂ ₃ mode at low voltage reveal that the mode can be excited with less than 7 W of beam power at less than 3.5 kV. Further, we demonstrate broadband continuous frequency tuning of the fundamental modes of the oscillator over a range of more than 2 GHz through variation of the magnetic field alone.; (cont.) We interpret these results in terms of smooth transitions between higher order axial modes of the resonator. In a related experiment...

‣ Authorship Patterns in Computer Science Research in the Philippines

Pabico, Jaderick P.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 22/07/2015 Português
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We studied patterns of authorship in computer science~(CS) research in the Philippines by using data mining and graph theory techniques on archives of scientific papers presented in the Philippine Computer Science Congresses from 2000 to 2010 involving 326~papers written by 605~authors. We inferred from these archives various graphs namely, a paper--author bipartite graph, a co-authorship graph, and two mixing graphs. Our results show that the scientific articles by Filipino computer scientists were generated at a rate of 33~papers per year, while the papers were written by an average of 2.64~authors (maximum=13). The frequency distribution of the number of authors per paper follows a power-law with a power of $\varphi=-2.04$ ($R^2=0.71$). The number of Filipino CS researchers increases at an annual rate of 60~new scientists. The researchers have written an average of 1.42~papers (maximum=20) and have collaborated with 3.70~other computer scientists (maximum=54). The frequency distribution of the number of papers per author follows a power law with $\varphi=-1.88$ ($R^2=0.83$). This distribution closely agrees with Lotka's {\em law of scientific productivity} having $\varphi\approx -2$. The number of co-authors per author also follows a power-law with $\varphi=-1.65$ ($R^2=0.80$). These results suggest that most CS~papers in the country were written by scientists who prefer to work alone or at most in small groups. These also suggest that few papers were written by scientists who were involved in large collaboration efforts. The productivity of the Philippines' CS researchers...

‣ The cost of reading research. A study of Computer Science publication venues

Cohen, Joseph Paul; Aravena, Carla; Ding, Wei
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 30/11/2015 Português
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What does the cost of academic publishing look like to the common researcher today? Our goal is to convey the current state of academic publishing, specifically in regards to the field of computer science and provide analysis and data to be used as a basis for future studies. We will focus on author and reader costs as they are the primary points of interaction within the publishing world. In this work, we restrict our focus to only computer science in order to make the data collection more feasible (the authors are computer scientists) and hope future work can analyze and collect data across all academic fields.

‣ Collaboration in computer science: a network science approach. Part II

Franceschet, Massimo
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 21/04/2011 Português
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We represent collaboration of authors in computer science papers in terms of both affiliation and collaboration networks and observe how these networks evolved over time since 1960. We investigate the temporal evolution of bibliometric properties, like size of the discipline, productivity of scholars, and collaboration level in papers, as well as of large-scale network properties, like reachability and average separation distance among scientists, distribution of the number of scholar collaborators, network clustering and network assortativity by number of collaborators.

‣ Modal logic in computer science

Lambert, Leigh
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Masters Project Formato: 337492 bytes; 157531 bytes; application/pdf; application/pdf
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Modal logic is a widely applicable method of reasoning for many areas of computer science. These areas include artificial intelligence, database theory, distributed systems, program verification, and cryptography theory. Modal logic operators contain propositional logic operators, such as conjunction and negation, and operators that can have the following meanings: "it is necessary that," "after a program has terminated," "an agent knows or believes that," "it is always the case that," etc. Computer scientists have examined the difficulty of problems in modal logic, such as satisfiability. Satisfiability determines whether a formula in a given logic is satisfiable. The complexity of satisfiability in modal logic has a wide range. Depending on how a modal logic is restricted, the complexity can be anywhere from NP-complete to highly undecidable. This project gives an introduction to common variations of modal logic in computer science and their complexity results.