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Amino acid-derived Lewis basic catalysts for asymmetric allylation of aldehydes and silylation of alcoholsZhao, Yu January 2008 (has links)
Thesis advisor: Marc L. Snapper / Chapter 1. Review of concept and methodology development for asymmetric allylation of carbonyls and imines. Chapter 2. Description of the catalytic asymmetric addition of allyltrichlorosilane to aldehydes catalyzed by a proline-based N-oxide catalyst. Chapter 3. Introduction of the first catalytic asymmetric silylation of alcohols for desymmetrization of meso-diols. Chapter 4. Presentation of asymmetric silylation for synthesis of chiral syn-1,2-diols by kinetic resolution or divergent reaction on a racemic mixture. / Thesis (PhD) — Boston College, 2008. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.
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Computing automorphism groups of projective planesUnknown Date (has links)
The main objective of this thesis was to find the full automorphism groups of
finite Desarguesian planes. A set of homologies were used to generate the automorphism
group when the order of the plane was prime. When the order was a prime
power Pa,a ≠ 1 the Frobenius automorphism was added to the set of homologies,
and then the full automorphism group was generated. The Frobenius automorphism
was found by using the planar ternary ring derived from a coordinatization of the
plane. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2013.
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Fast pattern matching and its applications. / CUHK electronic theses & dissertations collectionJanuary 2011 (has links)
After that, strip sum and orthogonal Haar transform are proposed. The sum of pixels in a rectangle can be computed by one addition using the strip sum. Then this thesis proposes to use the orthogonal Haar transform (OHT) for pattern matching. Applied for pattern matching, the fast OHT algorithm using strip sum requires O(log u) additions per pixel to project input data of size N1 x N2 onto u 2-D OHT bases. Experimental results show the efficiency of pattern matching using OHT. / Firstly, this thesis proposes a fast algorithm for Walsh Hadamard Transform (WHT) on sliding windows which can be used to implement pattern matching efficiently. / Support vector machine (SVM) is a widely used classification approach. Direct computation of SVM is not desirable in applications requiring computationally efficient classification. To relieve the burden of high computational time required for computing SVM, this thesis proposes a transform domain SVM (TDSVM) using pruning that computes SVM much faster. Experimental results show the efficiency in applying the proposed method for human detection. / Then this thesis analyzes and compares state-of-the-art algorithms for full search equivalent pattern matching. Inspired by the analysis, this thesis develops a new family of transforms called the Kronecker-Hadamard Transform (KHT) of which the GCK family is a subset and WHT is a member. Thus, KHT provides more choices of transforms for representing images. Then this thesis proposes a new fast algorithm that is more efficient than the GCK algorithm. All KHTs can be computed efficiently using the fast KHT algorithm. Based on the KHT, this thesis then proposes the segmented KHT (SegKHT). By segmenting input data into Ls parts, the SegKHT requires 1/Ls the computation required by the KHT algorithm in computing basis vectors. Experimental results show that the proposed algorithm can significantly accelerate the pattern matching process and outperforms state-of-the-art methods. / This thesis aims at improving the computational efficiency in pattern matching. / Ouyang, Wanli. / Adviser: Wai Kuen Cham. / Source: Dissertation Abstracts International, Volume: 73-04, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 143-147). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.
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Extremal semi-modular functions and combinatorial geometriesNguyen, Hien Quang January 1975 (has links)
Thesis. 1975. Ph.D.--Massachusetts Institute of Technology. Dept. of Mathematics. / Vita. / Bibliography: leaves 132-133. / by Nguyen Quang Hien. / Ph.D.
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Matrix correspondences and the enumeration of plane partitions.Gansner, Emden Robert January 1978 (has links)
Thesis. 1978. Ph.D.--Massachusetts Institute of Technology. Dept. of Mathematics. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Bibliography: p. 213-217. / Ph.D.
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Getting Things in Order: An Introduction to the R Package seriationHahsler, Michael, Hornik, Kurt, Buchta, Christian 18 March 2008 (has links) (PDF)
Seriation, i.e., finding a suitable linear order for a set of objects given data and a loss or merit function, is a basic problem in data analysis. Caused by the problem's combinatorial nature, it is hard to solve for all but very small sets. Nevertheless, both exact solution methods and heuristics are available. In this paper we present the package seriation which provides an infrastructure for seriation with R. The infrastructure comprises data
structures to represent linear orders as permutation vectors, a wide array of seriation methods using a consistent interface, a method to calculate the value of various loss and merit functions, and several visualization techniques which build on seriation. To illustrate how easily the package can be applied for a variety of applications, a comprehensive collection of examples is presented.
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A local relative trace formula for spherical varietiesFilip, Ioan January 2016 (has links)
Let F be a local non-Archimedean field of characteristic zero. We prove a Plancherel formula for the symmetric space GL(2,F)\GL(2,E), where E/F is an unramified quadratic extension. Our method relies on intrinsic geometric and combinatorial properties of spherical varieties and constitutes the local counterpart of the global computation of the Flicker-Rallis period as a residue of periods against Eisenstein series. We also give a novel derivation of the Plancherel formula for the strongly tempered variety T\PGL(2) over F (with maximal split torus T) using a canonical smooth asymptotics morphism and a contour shifting method. In this rank one local setting, our proof is similar to Langlands' proof over global fields describing the spectrum of a reductive group in terms of residues of Eisenstein series. Finally, using both L2-decompositions, we develop a local relative trace formula and outline a comparison result in the setting of the unitary rank one Gan-Gross-Prasad conjecture.
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O problema de minimização de pilhas abertas - novas contribuições / The minization of open stacks problem - new contribuctionsFink, Claudia 19 October 2012 (has links)
O Problema de Minimização do Número Máximo de Pilhas Abertas (MOSP, do inglês minimization of open stacks problem) é um problema de otimização combinatória da família NP-Difícil que vem recebendo grande atenção na literatura especializada. Este trabalho apresenta novas contribuições em termos de modelos e técnicas de resolução para o problema. A primeira parte deste trabalho lidou com modelos matemáticos, sendo analisados os modelos existentes que se baseiam em programação inteira mista. Variações de um modelo da literatura foram propostas, com o objetivo de tentar diminuir o tempo de execução necessário para se obter uma solução exata com a utilização de pacotes comerciais. Os resultados mostraram que as propostas são capazes de acelerar a solução de algumas classes de instâncias mas, que de maneira geral, métodos baseados em relaxação linear encontram dificuldade em provar a otimalidade devido à baixa qualidade dos limitantes inferiores. Uma outra contribuição deste trabalho foi o desenvolvimento de um modelo conjunto para o problema MOSP e para o problema de minimização da duração de pedidos (MORP, do inglês minimization of order spread problem). Este modelo propõe um framework unificado em que os dois problemas podem ser resolvidos ao mesmo tempo, tendo suas funções objetivo individuais ponderadas através de pesos definidos pelo usuário. A segunda parte do trabalho voltou-se para o desenvolvimento de métodos heurísticos para o MOSP. Duas estratégias de solução foram desenvolvidas. O primeiro método propõe uma transformação heurística entre o problema MOSP e o clássico problema do caixeiro viajente (TSP, do inglês traveling salesman problem). A partir de uma representação em grafo do MOSP, o TSP é definido por meio de uma regra de atribuição de distâncias baseadas nos graus dos nós. Nos testes computacionais, a estratégia proposta mostrou-se eficiente em relação às heurísticas específicas para o MOSP, obtendo a solução ótima do MOSP em 80,42% das instâncias testadas e sendo competitiva em termos de tempo computacional com algumas das melhores heurísticas da literatura. O segundo método heurístico proposto utilizou a ideia de decomposição. De fato, neste método, um corte no grafo associado ao problema original divide-o em problemas menores, que são resolvidos. A solução global é obtida através da junção das soluções dos subproblemas e, em alguns casos, é possível demonstrar a otimalidade da solução obtida. Testes computacionais indicam a validade da proposta e apontam caminhos para pesquisas futuras / The minimization of open stacks problem (MOSP) is a well known NP-hard combinatorial optimization problem that has been extensively discussed in the specialized literature. This study presents some new contributions in terms of models and solution methods for this problem. The first part of this thesis dealt with mathematical models. The existing mixedinteger models have been analyzed and variants of a well known model have been proposed, with the goal of reducing the time needed by commercial packages to obtain proved-optimal solutions. The results of computational tests on a widely used set of instances have indicated that the modifications proposed are able to reduce the time needed to obtain optimal solutions for some classes of instances. Nevertheless, a conclusion has been the fact that mixed-integer programming models have difficulty in obtaining convergence due to the low quality linear relaxation bounds. Another contribution of this thesis is the proposal of a single model that is able to deal with both the MOSP and with the Minimization of Order Spread Problem (MORP). This unified framework allows both problems to be jointly solved, by using a weighted objective function that included both original objectives. The second part of this thesis dealt with the development of heuristic strategies. Two solution strategies have been proposed. The first method proposes a heuristic conversion between MOSP and Traveling Salesman Problem (TSP) instances. This conversion relies the assignment distances to the TSP instance based on the degree of the vertices of the associated MOSP graph. Computational tests have shown that the proposed methodology is efficient, both in terms of solution quality (optimal solutions were obtained for 80.42% of the tested instances) and computational effort. The second method uses a decomposition idea. A cut is made in the graph associated with the original MOSP problem, yielding two smaller problems, which are solved. In some cases, the obtained combined solution can be prover optimal. Computational tests have shown the validity of the proposal and indicate new research opportunities
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Combinatorial Proofs Using Complex WeightsChen, Bo 30 May 2010 (has links)
In 1961, Kasteleyn, Fisher, and Temperley gave a result for the number of possible tilings of a 2m 2n checkerboard with dominoes. Their proof involves the evaluation of a complicated Pfaffian. In this thesis we investigate combinatorial strategies to evaluate the sum of evenly spaced binomial coefficients, and present steps towards a purely combinatorial proof of the 1961 result.
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A Combinatorial Analog of the Poincaré–Birkhoff Fixed Point TheoremCloutier, John 01 May 2003 (has links)
Results from combinatorial topology have shown that certain combinatorial lemmas are equivalent to certain topologocal fixed point theorems. For example, Sperner’s lemma about labelings of triangulated simplices is equivalent to the fixed point theorem of Brouwer. Moreover, since Sperner’s lemma has a constructive proof, its equivalence to the Brouwer fixed point theorem provides a constructive method for actually finding the fixed points rather than just stating their existence. The goal of this research project is to develop a combinatorial analogue for the Poincare ́-Birkhoff fixed point theorem.
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