Página 1 dos resultados de 8908 itens digitais encontrados em 1.687 segundos

‣ Determining molecular conformation from distance or density data

Wang, Cheuk-san, 1971-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 130 p.; 2400582 bytes; 2400339 bytes; application/pdf; application/pdf
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The determination of molecular structures is of growing importance in modern chemistry and biology. This thesis presents two practical, systematic algorithms for two structure determination problems. Both algorithms are branch-and-bound techniques adapted to their respective domains. The first problem is the determination of structures of multimers given rigid monomer structures and (potentially ambiguous) intermolecular distance measurements. In other words, we need to find the the transformations to produce the packing interfaces. A substantial difficulty results from ambiguities in assigning intermolecular distance measurements (from NMR, for example) to particular intermolecular interfaces in the structure. We present a rapid and efficient method to simultaneously solve the packing and the assignment problems. The algorithm, AmbiPack, uses a hierarchical division of the search space and the branch-and-bound algorithm to eliminate infeasible regions of the space and focus on the remaining space. The algorithm presented is guaranteed to find all solutions to a pre-determined resolution. The second problem is building a protein model from the initial three dimensional electron density distribution (density map) from X-ray crystallography. This problem is computationally challenging because proteins are extremely flexible.; (cont.) Our algorithm...

‣ Displaying data structures for interactive debugging

Myers, Brad Allen
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 103 leaves; 9650252 bytes; 9650011 bytes; application/pdf; application/pdf
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by Brad Allen Myers.; Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1980.; MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.; Vita.; Bibliography: leaves 98-102.

‣ Predicting the beta-trefoil fold from protein sequence data

Menke, Matthew Ewald, 1978-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 47 p.; 1848213 bytes; 1848021 bytes; application/pdf; application/pdf
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A method is presented that uses [beta]-strand interactions at both the sequence and the atomic level, to predict the beta-structural motifs in protein sequences. A program called Wrap-and-Pack implements this method, and is shown to recognize β-trefoils, an important class of globular β-structures, in the Protein Data Bank with 92% specificity and 92.3% sensitivity in cross-validation. It is demonstrated that Wrap-and-Pack learns each of the ten known SCOP β-trefoil families, when trained primarily on β-structures that are not β-trefoils, together with 3D structures of known β-trefoils from outside the family. Wrap-and-Pack also predicts many proteins of unknown structure to be β-trefoils. The computational method used here may generalize to other β-structures for which strand topology and profiles of residue accessibility are well conserved.; by Matthew Ewald Menke.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.; Includes bibliographical references (p. 45-47).

‣ An analysis of different data base structures and management systems on Clickstream data collected for advocacy based marketing strategies experiments for Intel and GM

Wang, Yufei, 1981-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 83 leaves; 3834009 bytes; 3837420 bytes; application/pdf; application/pdf
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Marketing on the Internet is the next big field in marketing research. Clickstream data is a great contribution to analyze the effects of advocacy based marketing strategies. Handling Clickstream data becomes a big issue. This paper will look at the problems caused by Clickstream data from a database perspective and consider several theories to alleviate the difficulties. Applications of modern database optimization techniques will be discussed and this paper will detail the implementation of these techniques for the Intel and GM project.; by Yufei Wang.; Thesis (M. Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.; Includes bibliographical references (leaves 82-83).

‣ Representation and analysis of real-time control structures

Archer, Rowland Frank
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 111 pages; 5152965 bytes; 5152777 bytes; application/pdf; application/pdf
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by Rowland Frank Archer, Jr.; Thesis. 1978. M.S.--Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science.; MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.; Bibliography: p. 110-111.

‣ Data structure repair using goal-directed reasoning

Demsky, Brian Charles, 1975-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 207 p.; 11058649 bytes; 11071885 bytes; application/pdf; application/pdf
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Software errors, hardware faults, and user errors can cause data structures in running applications to become damaged so that they violate key consistency properties. As a result of this violation, the application may produce unacceptable results or even crash. This dissertation presents a new data structure repair system that accepts a specification of key data structure consistency constraints, then generates repair algorithms that dynamically detect and repair violations of these constraints, enabling the application to continue to execute productively even in the face of otherwise crippling errors. We have successfully applied our system to five benchmarks: CTAS, an air traffic control tool; AbiWord, an open source word processing application; Freeciv, an online game; a parallel x86 emulator; and a simplified Linux file system. Our experience using our system indicates that the specifications are relatively easy to develop once one understands the data structures. Furthermore, for our set of benchmark applications, our experimental results show that our system can effectively repair inconsistent data structures and enable the application to continue to operate successfully.; by Brian C. Demsky.; Thesis (Ph. D.)--Massachusetts Institute of Technology...

‣ High performance photodetectors for multimode optical data links

Giziewicz, Wojciech Piotr, 1977-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 240 p.
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The majority of photodetectors presented in the literature, or available commercially, have dimensions on the order of 50 Ym or smaller, suitable for glass multimode or single mode fibre applications. The recent successful commercialisation of very large core diameter plastic optical fibre in systems based around 650 nm emitters, as well as the recent emergence of new polymer materials enabling relatively low loss at the more standard 780 nm and 850 nm wavelengths, has exposed the need for integrated photodetectors with dimensions well above 100 /m and capable of bitrates from 250 Mb/s for low-cost consumer applications to multiple Gb/s for high performance short reach interconnects. This size-performance regime has been largely ignored until now. This work examines interdigitated detector structures in multiple material systems by measurement and simulation. An optoelectronic frequency response measurement system was designed and implemented for this work, allowing measurement up to 8 GHz using 850 nm or 1550 nm sources. The full expression for frequency response of diffusion current under different illumination scenarios was derived, a topic normally omitted in the discussion of photodetectors, and applied to the analysis of device measurements.; (cont.) Silicon detectors of various geometries were fabricated...

‣ Modular data structure verification

Kuncak, Viktor (Viktor Jaroslav), 1977-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 166 p.
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This dissertation describes an approach for automatically verifying data structures, focusing on techniques for automatically proving formulas that arise in such verification. I have implemented this approach with my colleagues in a verification system called Jahob. Jahob verifies properties of Java programs with dynamically allocated data structures. Developers write Jahob specifications in classical higher-order logic (HOL); Jahob reduces the verification problem to deciding the validity of HOL formulas. I present a new method for proving HOL formulas by combining automated reasoning techniques. My method consists of 1) splitting formulas into individual HOL conjuncts, 2) soundly approximating each HOL conjunct with a formula in a more tractable fragment and 3) proving the resulting approximation using a decision procedure or a theorem prover. I present three concrete logics; for each logic I show how to use it to approximate HOL formulas, and how to decide the validity of formulas in this logic. First, I present an approximation of HOL based on a translation to first-order logic, which enables the use of existing resolution-based theorem provers. Second, I present an approximation of HOL based on field constraint analysis, a new technique that enables decision procedures for special classes of graphs (such as monadic second-order logic over trees) to be applied to arbitrary graphs.; (cont.) Third...

‣ The integration of InP /InGaAsP ridge waveguide structures with dielectric waveguides on silicon

Barkley, Edward R. (Edward Robert)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 271 p.
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Chip-to-chip optical interconnect technology, which is being explored as a potential replacement for copper chip-to-chip interconnects at data transmission rates exceeding 10 Gb/s, is one of several technologies that could be enabled by the monolithic integration of III-V optoelectronic devices on a silicon integrated circuit. Two significant capabilities required to achieve this monolithic integration were addressed: the assembly of III-V device structures on silicon and the fabrication of the waveguides that perform the intra-chip routing of the optical signal to and from these integrated device structures. These waveguides, consisting of a silicon oxynitride core (n = 1.6) and a silicon dioxide cladding (n = 1.45) were deposited via plasma-enhanced chemical vapor deposition (PECVD). The integrated InP/InGaAsP structures were fabricated using an existing novel technique for preparing very thin (on the order of 5 pm thick) substrate free rectangular structures (approximately 145 pm wide by 300 pm long) with cleaved facets. Using a pick-and-place method, the InP/InGaAsP structures were assembled in 6 pm deep rectangular wells formed by etching through the waveguide stack. The resulting configuration of the integrated devices in the wells facilitated end-fire coupling with the silicon oxynitride waveguides.; (cont.) Transmission spectrum measurements for this configuration verified the desired end-fire optical coupling through the integrated InP/InGaAsP device structures with a total coupling loss of 17.75 dB. This loss was shown through measurements and finite difference time domain (FDTD) simulations to be a function of integrated device misalignment...

‣ Lower bound techniques for data structures

Pǎtraşcu, Mihai
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 143 p.
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We describe new techniques for proving lower bounds on data-structure problems, with the following broad consequences: * the first [omega](lg n) lower bound for any dynamic problem, improving on a bound that had been standing since 1989; * for static data structures, the first separation between linear and polynomial space. Specifically, for some problems that have constant query time when polynomial space is allowed, we can show [omega](lg n/ lg lg n) bounds when the space is O(n - polylog n). Using these techniques, we analyze a variety of central data-structure problems, and obtain improved lower bounds for the following: * the partial-sums problem (a fundamental application of augmented binary search trees); * the predecessor problem (which is equivalent to IP lookup in Internet routers); * dynamic trees and dynamic connectivity; * orthogonal range stabbing. * orthogonal range counting, and orthogonal range reporting; * the partial match problem (searching with wild-cards); * (1 + [epsilon])-approximate near neighbor on the hypercube; * approximate nearest neighbor in the l[infinity] metric. Our new techniques lead to surprisingly non-technical proofs. For several problems, we obtain simpler proofs for bounds that were already known.; by Mihai Pǎtraşcu.; Thesis (Ph. D.)--Massachusetts Institute of Technology...

‣ Custom Memory Placement for Parallel Data Mining

Parthasarathy, Srinivasan ; Zaki, Mohammed Javeed ; Li, Wei
Fonte: University of Rochester. Computer Science Department. Publicador: University of Rochester. Computer Science Department.
Tipo: Relatório
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A lot of data mining tasks, such as Associations, Sequences, and Classification, use complex pointer-based data structures that typically suffer from sub-optimal locality. In the multi-processor case shared access to these data structures may also result in false-sharing. Most of the optimization techniques for enhancing locality and reducing false sharing have been proposed in the context of numeric applications involving array-based data structures, and are not applicable for dynamic data structures due to dynamic memory allocation from the heap with arbitrary addresses. Within the context of data mining it is commonly observed that the building phase of these large recursive data structures, such as hash trees and decision trees, is random and independent from the access phase which is usually ordered and typically dominates the computation time. In such cases locality and false sharing sensitive memory placement of these structures can enhance performance significantly. We evaluate a set of placement policies over a representive data mining application (association rule discovery) and show that simple placement schemes can improve execution time by more than a factor of two. More complex schemes yield an additional 5-20% gain.

‣ Eliminating Amortization: On Data Structures with Guaranteed Response Time

Raman, Rajeev ; Dietz, Paul F.
Fonte: University of Rochester. Computer Science Department. Publicador: University of Rochester. Computer Science Department.
Tipo: Technical Report; Thesis
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Thesis (Ph. D.)--University of Rochester. Dept. of Computer Science, 1992. Simultaneously published in the Technical Report series.; An efficient amortized data structure is one that ensures that the average time per operation spent on processing any sequence of operations is small. Amortized data structures typically have very non-uniform response times, i.e., individual operations can be occasionally and unpredictably slow, although the average time over the sequence is kept small by completing most of the other operations quickly. This makes amortized data structures unsuitable in many important contexts, such as real-time systems, parallel programs, persistent data structures and interactive software. On the other hand, an efficient (single-operation) worst-case data structure guarantees that every operation will be processed quickly. The construction of worst-case data structures from amortized ones is a fundamental problem which is also of pragmatic interest. Progress has been slow so far, both because the techniques used were of a limited nature and because the resulting data structures had much larger hidden constant factors. I try to address both these issues in this thesis. I consider several inter-related dynamic data structuring problems for which only efficient amortized solutions were known and obtain new worst-case algorithms for them using a unified framework...

‣ Algorithms and Data Structures for an Expanded Family of Matroid Intersection Problems

Frederickson, Greg N. ; Srinivas, Mandayam A.
Fonte: University of Rochester. Computer Science Department. Publicador: University of Rochester. Computer Science Department.
Tipo: Relatório
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Consider a matroid of rank n in which each element has a real-valued cost and one of d > 1 colors. A class of matroid intersection problems is studied in which one of the matroids is a partition matroid that specifies that a base have qj elements of color j, for j = 1, 2, ... , d. Relationships are characterized among the solutions to the family of problems generated when the vector (q1, q2, ... , qd) is allowed to range over all values that sum to n. A fast algorithm is given for solving such matroid intersection problems when d is small. A characterization is presented for how the solution changes when one element changes in cost. Data structures are given for updating the solution on-line each time the cost of an arbitrary matroid element is modified. Efficient update algorithms are given for maintaining a color-constrained minimum spanning tree in either a general or a planar graph. An application of the techniques to finding a minimum spanning tree with several degree-constrained vertices is described.

‣ 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
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87.65053%
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.

‣ Automatic Representation Selection for Associative Data Structures

Rovner, Paul D.
Fonte: University of Rochester. Computer Science Department. Publicador: University of Rochester. Computer Science Department.
Tipo: Thesis; Technical Report
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Thesis (Ph. D.)--Harvard University. Division of Engineering and Applied Physics, 1976.; The selection of efficient storage representations for high-level data structures is a design problem that is ready for systematic analysis. This thesis is about automating such low-level design for the associative data structures of a given program. To develop intuitions and guidelines for future work, we chose to study how to select in-core storage representations for the associative data structures (triples) of SAIL. SAIL is an ALGOL-60 based artificial intelligence language. The high-level data structures of SAIL include ITEMS (abstract objects), SETS of items, LISTS (sequences) of items, and TRIPLES (associations) of items. We developed an experimental system (the Storage Structure Selection System) which runs on a PDP-lO computer and analyzes a given SAIL program to determine good representations for its associative data structures. This required methods for determining the ways that the program uses its data structures, the properties of typical storage structure representations, and the development of strategies for estimating computation cost. In this thesis, we introduce new analysis methods for the following special problems of selecting good representations for associative data structures: characterizing storage structures that provide multiple access paths to data ("sharing" )...

‣ Quadtree representation and compression of spatial data

Yin, Xiang
Fonte: Brock University Publicador: Brock University
Tipo: Electronic Thesis or Dissertation
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Spatial data representation and compression has become a focus issue in computer graphics and image processing applications. Quadtrees, as one of hierarchical data structures, basing on the principle of recursive decomposition of space, always offer a compact and efficient representation of an image. For a given image, the choice of quadtree root node plays an important role in its quadtree representation and final data compression. The goal of this thesis is to present a heuristic algorithm for finding a root node of a region quadtree, which is able to reduce the number of leaf nodes when compared with the standard quadtree decomposition. The empirical results indicate that, this proposed algorithm has quadtree representation and data compression improvement when in comparison with the traditional method.

‣ Classification of semantic relations in different syntactic structures in medical text using the MeSH hierarchy

Bhooshan, Neha
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 39 leaves; 2414432 bytes; 2414074 bytes; application/pdf; application/pdf
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Two different classification algorithms are evaluated in recognizing semantic relationships of different syntactic compounds. The compounds, which include noun- noun, adjective-noun, noun-adjective, noun-verb, and verb-noun, were extracted from a set of doctors' notes using a part of speech tagger and a parser. Each compound was labeled with a semantic relationship, and each word in the compound was mapped to its corresponding entry in the MeSH hierarchy. MeSH includes only medical terminology so it was extended to include everyday, non-medical terms. The two classification algorithms, neural networks and a classification tree, were trained and tested on the data set for each type of syntactic compound. Models representing different levels of MeSH were generated and fed into the neural networks. Both algorithms performed better than random guessing, and the classification tree performed better than the neural networks in predicting the semantic relationship between phrases from their syntactic structure.; by Neha Bhooshan.; Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.; Includes bibliographical references (leaf 38).

‣ The Representation of symmetric patterns using the quadtree data structure

Lodolini, Lucia
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
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Hierarchical data structures for image representation have been widely explored in recent years. These data structures are based on the principle of "recursive decomposition" of an image region. The most commonly mentioned picture data structure for two-dimensional data is referred to as a "quadtree". The purpose of this thesis is to investigate the use of a general quadtree scheme as a means of representing symmetric images. Specifically, images are generated according to the rules of selected two-dimensional plane symmetry groups.

‣ Efficient geographic information systems: Data structures, Boolean operations and concurrency control

Sheng, James Min
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
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Geographic Information Systems (GIS) are crucial to the ability of govern mental agencies and business to record, manage and analyze geographic data efficiently. They provide methods of analysis and simulation on geographic data that were previously infeasible using traditional hardcopy maps. Creation of realistic 3-D sceneries by overlaying satellite imagery over digital elevation models (DEM) was not possible using paper maps. Determination of suitable areas for construction that would have the fewest environmental impacts once required manual tracing of different map sets on mylar sheets; now it can be done in real time by GIS. Geographic information processing has significant space and time require ments. This thesis concentrates on techniques which can make existing GIS more efficient by considering these issues: Data Structure, Boolean Operations on Geographic Data, Concurrency Control. Geographic data span multiple dimensions and consist of geometric shapes such as points, lines, and areas, which cannot be efficiently handled using a traditional one-dimensional data structure. We therefore first survey spatial data structures for geographic data and then show how a spatial data structure called an R-tree can be used to augment the performance of many existing GIS. Boolean operations on geographic data are fundamental to the spatial anal ysis common in geographic data processing. They allow the user to analyze geographic data by using operators such as AND...