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Abbasian, Houman. "Inner Ensembles: Using Ensemble Methods in Learning Step." Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31127.
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A pivotal moment in machine learning research was the creation of an important new
research area, known as Ensemble Learning. In this work, we argue that ensembles are
a very general concept, and though they have been widely used, they can be applied in
more situations than they have been to date. Rather than using them only to combine
the output of an algorithm, we can apply them to decisions made inside the algorithm
itself, during the learning step. We call this approach Inner Ensembles. The motivation
to develop Inner Ensembles was the opportunity to produce models with the similar
advantages as regular ensembles, accuracy and stability for example, plus additional
advantages such as comprehensibility, simplicity, rapid classification and small memory
footprint. The main contribution of this work is to demonstrate how broadly this idea
can be applied, and highlight its potential impact on all types of algorithms. To support
our claim, we first provide a general guideline for applying Inner Ensembles to different algorithms. Then, using this framework, we apply them to two categories of learning
methods: supervised and un-supervised. For the former we chose Bayesian network, and
for the latter K-Means clustering. Our results show that 1) the overall performance of
Inner Ensembles is significantly better than the original methods, and 2) Inner Ensembles
provide similar performance improvements as regular ensembles.
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Benkaddour, Saïd. "Relation entre ensembles totalement flous et ensembles ordonnés." Lyon 1, 1986. http://www.theses.fr/1986LYO11714.
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Le present travail fait suite aux recherches menees sur la theorie des ensembles flous. D. Ponasse a defini la categorie jtf des j-ensembles totalement flous. Dans sa these de 3eme cycle g. Mycek a demontre que cette categorie est un topos lorsque j est un anti-ordinal (c. A. D. : j est un ordinal lorsqu'il est muni de l'ordre inverse). Il a exhibe tous les objets elementaires de ce topos. Wu tao, lui, a fait une etude detaillee de ce topos avec j antiordinal. Dans leurs articles j. Coulon et j. L. Coulon montrent que pour j un treillis de heyting complet la categorie jtf est equivalente a la categorie jtf et que jtf n'est pas un topos lorsque j n'est pas un anti-ordinal. Dans la premiere partie de ce travail je continue l'etude de la categorie jtf. Je demontre qu'elle est isomorphe a la categorie notee jid dont les objets sont des ensembles ordonnes et les morphismes sont des applications verifiant certaines conditions. J'ai traduit les notions de mono, epi et iso (morphisme) dans jid en notions de surjection, injection et bijection. Dans la deuxieme partie j'etudie les proprietes categoriques de jid: objet final (resp. Initial), produit (resp. Coproduit), pulback (resp. Pushout), noyau de paire (resp. Conoyau) et l'exponentielle. 1**(o)) je demontre que la plus grande famille de monomorphismes qu'on peut classer c'est la famille des monomorphismes dits forts. 2**(o)) je prouve que dans le cas ou j est un anti-ordinal tout monomorphisme est fort donc jid est un topos. 3**(o)) lorsque j n'est pas un anti-ordinal il existe des monomorphismes non forts donc non classifiables. Donc jid n'est pas un topos.
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Benkaddour, Saïd. "Relation entre les ensembles totalement flous et ensembles ordonnés." Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb37595915s.
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Andrle, Miroslav. "Ensembles modèles et analyse en ondelettes adaptées." Paris 7, 2002. http://www.theses.fr/2002PA077202.
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Khatib, Souad El. "Espaces métriques dans la théorie des ensembles flous." Lyon 1, 1986. http://www.theses.fr/1986LYO10060.
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Cette these est composee de trois chapitres. Le premier est un rappel des travaux de michael erceg, sur la definition d'un espace metrique flou: metric spaces in fuzzy set theory, j. M. A. , 69, 1979 (205-230). Dans cet article l'auteur a defini un ecart (une distance), flou(e) sur un ensemble flou, prenant ses valeurs dans l'ensemble des reels positif. Dans le deuxieme chapitre on introduit l'ensemble des reels flous positifs, c'est l'ensemble des applications de l'ensemble des reels dans l'intervalle unite, qui sont continues a gauche, croissantes et qui prennent la valeur zero a zero et telles la borne superieure est egale a un. Puis on decrit l'operation d'addition cet ensemble definie par sherwood et m. D. Taylor dans leur article "some pm structures on the set of distribution functions". Le troisieme chapitre constitue le but premier de cette these et consiste a donner une definition d'un quasi-ecart (ecart) flou, sur un ensemble flou, prenant ses valeurs non pas dans l'ensemble des reels positifs, mais dans l'ensemble des reels flous positifs. Puis on definit une uniformite floue sur un espace pseudometrique flou, en utilisant la definition d'une uniformite floue donnee par hutton: "uniformities on fuzzy topological spaces". En completant les resultats de hutton, on obtient des resultats sur l'engendrement des topologies floues sur les ensembles flous par des quasi-ecarts flous, on definit encore l'ecart flou conjugue, puis la distance floue
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De, Jongh Albert. "Neural network ensembles." Thesis, Stellenbosch : Stellenbosch University, 2004. http://hdl.handle.net/10019.1/50035.
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Thesis (MSc)--Stellenbosch University, 2004.ENGLISH ABSTRACT: It is possible to improve on the accuracy of a single neural network by using an ensemble of diverse and accurate networks. This thesis explores diversity in ensembles and looks at the underlying theory and mechanisms employed to generate and combine ensemble members. Bagging and boosting are studied in detail and I explain their success in terms of well-known theoretical instruments. An empirical evaluation of their performance is conducted and I compare them to a single classifier and to each other in terms of accuracy and diversity.
AFRIKAANSE OPSOMMING: Dit is moontlik om op die akkuraatheid van 'n enkele neurale netwerk te verbeter deur 'n ensemble van diverse en akkurate netwerke te gebruik. Hierdie tesis ondersoek diversiteit in ensembles, asook die meganismes waardeur lede van 'n ensemble geskep en gekombineer kan word. Die algoritmes "bagging" en "boosting" word in diepte bestudeer en hulle sukses word aan die hand van bekende teoretiese instrumente verduidelik. Die prestasie van hierdie twee algoritmes word eksperimenteel gemeet en hulle akkuraatheid en diversiteit word met 'n enkele netwerk vergelyk.
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Dromey, Christopher. "The Pierrot ensembles." Thesis, King's College London (University of London), 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.682572.
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The ‘Pierrot’ ensemble of mixed single strings, winds and piano has become standard in contemporary music, yet it is a genre that had neither been categorised nor explored analytically. This novel line-up, derived from Arnold Schoenberg’s Pierrot lunaire, Op. 21 (1912), inspired a new, British-led repertory that influenced composition as much as concert life. I chronicled this lineage of Pierrot ensembles to offer an alternative reading of twentieth-century music and culture. The thesis included analysis of salient works by Peter Maxwell Davies, Elisabeth Lutyens and Humphrey Searle, and drew on research in the Paul Sacher Stiftung (Basel) and Britten-Pears Archive (Aldeburgh), rediscovering previously unpublished works by Harrison Birtwistle and Benjamin Britten.
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Al-Razgan, Muna Saleh. "Weighted clustering ensembles." Fairfax, VA : George Mason University, 2008. http://hdl.handle.net/1920/3212.
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Thesis (Ph.D.)--George Mason University, 2008.Vita: p. 134. Thesis director: Carlotta Domeniconi. Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Information Technology. Title from PDF t.p. (viewed Oct. 14, 2008). Includes bibliographical references (p. 128-133). Also issued in print.
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Daigle, Elise. "Examining Music Ensemble Recruitment and Retention through Student Persistence into College Performing Ensembles." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1523523995130136.
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Zajicek, Daniel J. "A rhetorical guide to Ebb." connect to online resource, 2006. http://www.unt.edu/etd/all/May2006/zajicek%5Fdaniel/index.htm.
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Thesis (M.M.)--University of North Texas, 2006.For flute, oboe, clarinet, contrabassoon, horn , tuba, percussion (2 players), 2 violins, viola, cello, double bass, 1 laptop computer, and 2 or more loudspeakers. System requirements: Adobe Acrobat Reader. Duration: 10:00. Includes performance notes by the composer (p. 1-23). Includes bibliographical references (p. 23-24).
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Shoemaker, Larry. "Ensembles for distributed data." [Tampa, Fla.] : University of South Florida, 2005. http://purl.fcla.edu/fcla/etd/SFE0001296.
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Dubbs, Alexander. "Beta-ensembles with covariance." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/90185.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mathematics, 2014.67
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 73-79).
This thesis presents analytic samplers for the [beta]-Wishart and [beta]-MANOVA ensembles with diagonal covariance. These generalize the [beta]-ensembles of Dumitriu-Edelman, Lippert, Killip-Nenciu, Forrester-Rains, and Edelman-Sutton, as well as the classical [beta] = 1, 2,4 ensembles of James, Li-Xue, and Constantine. Forrester discovered a sampler for the [beta]-Wishart ensemble around the same time, although our proof has key differences. We also derive the largest eigenvalue pdf for the [beta]-MANOVA case. In infinite-dimensional random matrix theory, we find the moments of the Wachter law, and the Jacobi parameters and free cumulants of the McKay and Wachter laws. We also present an algorithm that uses complex analysis to solve "The Moment Problem." It takes the first batch of moments of an analytic, compactly-supported distribution as input, and it outputs a fine discretization of that distribution.
by Alexander Dubbs.
Ph. D.
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Roberts, Ekaterina Sergeevna. "Tailored random graph ensembles." Thesis, King's College London (University of London), 2014. https://kclpure.kcl.ac.uk/portal/en/theses/tailored-random-graph-ensembles(daefc925-24a3-4f7f-8c79-21b9136c636b).html.
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Tailored graph ensembles are a developing bridge between statistical mechanics and biological networks. In this thesis, this concept is used to generate a suite of rigorous mathematical tools to quantify and compare the topology of cellular signalling networks. Earlier published results to quantify the entropy of constrained random graph ensembles are extended by looking at constraints relating to directed graphs, bipartite graphs, neighbourhood compositions and generalised degrees. To incorporate constraints relating to the average number of short loops, a number of innovative techniques are reviewed and extended, moving the analysis beyond the usual tree-like assumption. The generation of unbiased sample networks under some of these new constraints is studied. A series of illustrations of how these concepts may be applied to systems biology are developed. Topological observables are obtained from real biological networks and the entropy of the associated random graph ensemble is calculated. Certain studies on over-represented motifs are replicated and the influence of the choice of null model is considered. The correlation between the topological role of each protein and its lethality is studied in yeast. Throughout, this document aims to promote looking at a network as a realisation satisfying certain constraints rather than just as a list of nodes and edges. This may initially seem to be an abstract approach, but it is in fact a more natural viewpoint within which to consider many fundamental questions regarding the origin, function and design of observed real networks.
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Llerena, Nils Ever Murrugarra. "Ensembles na classificação relacional." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/55/55134/tde-18102011-095113/.
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Em diversos domínios, além das informações sobre os objetos ou entidades que os compõem, existem, também, informaçõoes a respeito das relações entre esses objetos. Alguns desses domínios são, por exemplo, as redes de co-autoria, e as páginas Web. Nesse sentido, é natural procurar por técnicas de classificação que levem em conta estas informações. Dentre essas técnicas estão as denominadas classificação baseada em grafos, que visam classificar os exemplos levando em conta as relações existentes entre eles. Este trabalho aborda o desenvolvimento de métodos para melhorar o desempenho de classificadores baseados em grafos utilizando estratégias de ensembles. Um classificador ensemble considera um conjunto de classificadores cujas predições individuais são combinadas de alguma forma. Este classificador normalmente apresenta um melhor desempenho do que seus classificadores individualmente. Assim, foram desenvolvidas três técnicas: a primeira para dados originalmente no formato proposicional e transformados para formato relacional baseado em grafo e a segunda e terceira para dados originalmente já no formato de grafo. A primeira técnica, inspirada no algoritmo de boosting, originou o algoritmo KNN Adaptativo Baseado em Grafos (A-KNN). A segunda ténica, inspirada no algoritmo de Bagging originou trê abordagens de Bagging Baseado em Grafos (BG). Finalmente, a terceira técnica, inspirada no algoritmo de Cross-Validated Committees, originou o Cross-Validated Committees Baseado em Grafos (CVCG). Os experimentos foram realizados em 38 conjuntos de dados, sendo 22 conjuntos proposicionais e 16 conjuntos no formato relacional. Na avaliação foi utilizado o esquema de 10-fold stratified cross-validation e para determinar diferenças estatísticas entre classificadores foi utilizado o método proposto por Demsar (2006). Em relação aos resultados, as três técnicas melhoraram ou mantiveram o desempenho dos classificadores bases. Concluindo, ensembles aplicados em classificadores baseados em grafos apresentam bons resultados no desempenho destesIn many fields, besides information about the objects or entities that compose them, there is also information about the relationships between objects. Some of these fields are, for example, co-authorship networks and Web pages. Therefore, it is natural to search for classification techniques that take into account this information. Among these techniques are the so-called graphbased classification, which seek to classify examples taking into account the relationships between them. This paper presents the development of methods to improve the performance of graph-based classifiers by using strategies of ensembles. An ensemble classifier considers a set of classifiers whose individual predictions are combined in some way. This combined classifier usually performs better than its individual classifiers. Three techniques have been developed: the first applied for originally propositional data transformed to relational format based on graphs and the second and the third applied for data originally in graph format. The first technique, inspired by the boosting algorithm originated the Adaptive Graph-Based K-Nearest Neighbor (A-KNN). The second technique, inspired by the bagging algorithm led to three approaches of Graph-Based Bagging (BG). Finally the third technique, inspired by the Cross- Validated Committees algorithm led to the Graph-Based Cross-Validated Committees (CVCG). The experiments were performed on 38 data sets, 22 datasets in propositional format and 16 in relational format. Evaluation was performed using the scheme of 10-fold stratified cross-validation and to determine statistical differences between the classifiers it was used the method proposed by Demsar (2006). Regarding the results, these three techniques improved or at least maintain the performance of the base classifiers. In conclusion, ensembles applied to graph-based classifiers have good results in the performance of them
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Rosaz, Laurent. "Ensembles inevitables de mots." Paris 7, 1993. http://www.theses.fr/1993PA077093.
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Apres l'introduction des definitions de base, je definis les ensembles inevitables de mots, je donne des exemples, j'introduis des outils (les coupures et des automates), puis je donne mes resultats: les ensembles inevitables peuvent etre decrits, les ensembles inevitables reduits sont en nombre fini, un contre-exemple est donne a la conjecture de l'extension de mot, le probleme de l'extension d'un ensemble est donne (et resolu) les coupures sont etudiees et les equivalences introduites, des methodes sont donnees pour ameliorer les descriptions. Je finis par donner des problemes qui restent ouverts.
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Pruniéras, Jean. "Ensembles [oméga] et applications." Paris 13, 2001. http://www.theses.fr/2001PA132024.
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La thèse définit le concept d'ensemble [oméga] et propose son application à des problèmes sans lien direct apparentThis thesis defines the set concept [omega] and proposes its application to problems which are not directly linked to each other
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Swanzy, David Paul. "The wind ensemble and its music during the French Revolution (1789-1795) /." Ann Arbor : UMI, 2000. http://catalogue.bnf.fr/ark:/12148/cb370598520.
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Matsukevich, Dzmitry. "Quantum networking with atomic ensembles." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-07072006-173336/.
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Thesis (Ph. D.)--Physics, Georgia Institute of Technology, 2007.Kennedy, Brian, Committee Member ; Chapman, Michael, Committee Member ; Kuzmich, Alex, Committee Chair ; Raman, Chandra, Committee Member ; Voss, Paul, Committee Member.
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Nunn, Joshua. "Quantum Memory in Atomic Ensembles." Thesis, University of Oxford, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.526095.
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Hornik, Kurt. "A CLUE for CLUster ensembles." Institut für Statistik und Mathematik, WU Vienna University of Economics and Business, 2005. http://epub.wu.ac.at/1690/1/document.pdf.
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Cluster ensembles are collections of individual solutions to a given clustering problem which are useful or necessary to consider in a wide range of applications. The R package clue provides an extensible computational environment for creating and analyzing cluster ensembles, with basic data structures for representing partitions and hierarchies, and facilities for computing on these, including methods for measuring proximity and obtaining consensus and "secondary" clusterings. (author's abstract)Series: Research Report Series / Department of Statistics and Mathematics
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Fisher, Charles. "Statistical Characterization of Protein Ensembles." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10223.
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Conformational ensembles are models of proteins that capture variations in conformation that result from thermal fluctuations. Ensemble based models are important tools for studying Intrinsically Disordered Proteins (IDPs), which adopt a heterogeneous set of conformations in solution. In order to construct an ensemble that provides an accurate model for a protein, one must identify a set of conformations, and their relative stabilities, that agree with experimental data. Inferring the characteristics of an ensemble for an IDP is a problem plagued by degeneracy; that is, one can typically construct many different ensembles that agree with any given set of experimental measurements. In light of this problem, this thesis will introduce three tools for characterizing ensembles: (1) an algorithm for modeling ensembles that provides estimates for the uncertainty in the resulting model, (2) a fast algorithm for constructing ensembles for large or complex IDPs and (3) a measure of the degree of disorder in an ensemble. Our hypothesis is that a protein can be accurately modeled as an ensemble only when the degeneracy of the model is appropriately accounted for. We demonstrate these methods by constructing ensembles for K18 tau protein, \(\alpha\)-synuclein and amyloid beta - IDPs that are implicated in the pathogenesis of Alzheimer's and Parkinson's diseases.
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Siegert, Stefan. "Rank statistics of forecast ensembles." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-102152.
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Ensembles are today routinely applied to estimate uncertainty in numerical predictions of complex systems such as the weather. Instead of initializing a single numerical forecast, using only the best guess of the present state as initial conditions, a collection (an ensemble) of forecasts whose members start from slightly different initial conditions is calculated. By varying the initial conditions within their error bars, the sensitivity of the resulting forecasts to these measurement errors can be accounted for. The ensemble approach can also be applied to estimate forecast errors that are due to insufficiently known model parameters by varying these parameters between ensemble members.
An important (and difficult) question in ensemble weather forecasting is how well does an ensemble of forecasts reproduce the actual forecast uncertainty. A widely used criterion to assess the quality of forecast ensembles is statistical consistency which demands that the ensemble members and the corresponding measurement (the ``verification\'\') behave like random independent draws from the same underlying probability distribution. Since this forecast distribution is generally unknown, such an analysis is nontrivial. An established criterion to assess statistical consistency of a historical archive of scalar ensembles and verifications is uniformity of the verification rank: If the verification falls between the (k-1)-st and k-th largest ensemble member it is said to have rank k. Statistical consistency implies that the average frequency of occurrence should be the same for each rank.
A central result of the present thesis is that, in a statistically consistent K-member ensemble, the (K+1)-dimensional vector of rank probabilities is a random vector that is uniformly distributed on the K-dimensional probability simplex. This behavior is universal for all possible forecast distributions. It thus provides a way to describe forecast ensembles in a nonparametric way, without making any assumptions about the statistical behavior of the ensemble data. The physical details of the forecast model are eliminated, and the notion of statistical consistency is captured in an elementary way. Two applications of this result to ensemble analysis are presented.
Ensemble stratification, the partitioning of an archive of ensemble forecasts into subsets using a discriminating criterion, is considered in the light of the above result. It is shown that certain stratification criteria can make the individual subsets of ensembles appear statistically inconsistent, even though the unstratified ensemble is statistically consistent. This effect is explained by considering statistical fluctuations of rank probabilities. A new hypothesis test is developed to assess statistical consistency of stratified ensembles while taking these potentially misleading stratification effects into account.
The distribution of rank probabilities is further used to study the predictability of outliers, which are defined as events where the verification falls outside the range of the ensemble, being either smaller than the smallest, or larger than the largest ensemble member. It is shown that these events are better predictable than by a naive benchmark prediction, which unconditionally issues the average outlier frequency of 2/(K+1) as a forecast. Predictability of outlier events, quantified in terms of probabilistic skill scores and receiver operating characteristics (ROC), is shown to be universal in a hypothetical forecast ensemble. An empirical study shows that in an operational temperature forecast ensemble, outliers are likewise predictable, and that the corresponding predictability measures agree with the analytically calculated ones.
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Dumitriu, Ioana 1976. "Eigenvalue statistics for beta-ensembles." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/29347.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mathematics, 2003.Includes bibliographical references (p. 155-163) and index.
Random matrix theory is a maturing discipline with decades of research in multiple fields now beginning to converge. Experience has shown that many exact formulas are available for certain matrices with real, complex, or quaternion entries. In random matrix jargon, these are the cases β = 1, 2 and 4 respectively. This thesis explores the general P > 0 case mathematically and with symbolic software. We focus on generalizations of the Hermite distributions originating in physics (the "Gaussian" ensembles) and the Laguerre distributions of statistics (the "Wishart" matrices). One of our main contributions is the construction of tridiagonal matrix models for the general (β > 0) 0 β-Hermite and (β > 0, a > β(m - 1)/2) β-Laguerre ensembles of parameter a and size m, and investigate applications of these new ensembles, particularly in the areas of eigenvalue statistics. The new models are symmetric tridiagonal, and with entries from real distributions, regardless of the value of β. The entry distributions are either normal or X, so "classical", and the independence pattern is maximal, in the sense that the only constraints arise from the symmetric/semi-definite condition. The β-ensemble distributions have been studied for the particular 1, 2, 4 values of p as joint eigenvalue densities for full random matrix ensembles (Gaussian, or Hermite, and Wishart, or Laguerre) with real, complex, and quaternion entries (for references, see [66] and [70]). In addition, general -ensembles were considered and studied as theoretical distributions ([8, 51, 50, 55, 56]), with applications in lattice gas theory and statistical mechanics (the parameter being interpreted as an arbitrary inverse temperature of a Coulomb gas with logarithmic potential).
(cont.) Certain eigenvalue statistics over these general β-ensembles, namely those expressible in terms of integrals of symmetric polynomials with corresponding Hermite or Laguerre weights, can be computed in terms of multivariate orthogonal polynomials (Hermite or Laguerre). We have written a Maple Library (MOPs: Multivariate Orthogonal Polynomials symbolically) which implements some new and some known algorithms for computing the Jack, Hermite, Laguerre, and Jacobi multivariate polynomials for arbitrary. This library can be used as a tool for conjecture-formulation and testing, for statistical computations, or simply for getting acquainted with the mathematical concepts. Some of the figures in this thesis have been obtained using MOPs. Using the new β-ensemble models, we have been able to provide a unified perspective of the previously isolated 1, 2, and 4 cases, and prove generalizations for some of the known eigenvalue statistics to arbitrary β. We have rediscovered (in the Hermite case) a strong version of the Wigner Law (semi-circle), and proved (in the Laguerre case) a strong version of the similar law (generalized quarter-circle). We have obtained first-order perturbation theory for the P large case, and we have reason to believe that the tridiagonal models in the large n (ensemble size) limit will also provide a link between the largest eigenvalue distributions for both Hermite and Laguerre for arbitrary P (for β = 1, 2, this link was proved to exist by Johannson [52] and Johnstone [53]) ...
by Ioana Dumitriu.
Ph.D.
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Moupila-Mapépé, Aurélien. "Hyperbolicité et ensembles invariants isolés." Mémoire, Université de Sherbrooke, 2001. http://savoirs.usherbrooke.ca/handle/11143/4529.
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Certains processus dynamiques en physique, chimie et biologie peuvent être décrits par des équations différentielles dépendant des paramètres qui ne peuvent être déterminés avec un degré arbitraire de précision. Il est important donc, pour l'étude de ces systèmes, de déterminer des structures qui restent stables pour des petites perturbations. Plusieurs de ces structures peuvent être décrites en termes de la théorie de l'indice de Conley. Ce mémoire consiste en une présentation des méthodes utilisées dans la théorie des systèmes dynamiques pour prouver la stabilité des voisinages isolants, des blocs isolants et des paires pour l'indice, des structures indispensables pour le calcul de l'indice de Conley, qui lui même est non seulement porteur de l'information sur la stabilité, mais permet aussi dans certains cas, de prouver l'existence de certaines solutions remarquables des équations différentielles. Il s'agit principalement d'une analyse comparative de deux méthodes: une première méthode fondée sur les blocs isolants (voisinages isolants spéciaux dont les frontières peuvent être"tangentes" au flot seulement dans des régions spéciales) et les fonctions de Lyapunov (les fonctions à valeurs réelles qui sont définies dans un voisinage d'un ensemble compact invariant et dont les dérivées première et seconde en direction du champ vectoriel ont des propriétés spéciales); la deuxième méthode est basée sur les flots multivoques, totalement différente de l'autre, et représente en fait une alternative à la première.
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Brown, Gavin. "Diversity in neural network ensembles." Thesis, University of Birmingham, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410855.
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Fernandes, Everlandio Rebouças Queiroz. "Evolutionary ensembles for imbalanced learning." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/55/55134/tde-30102018-101256/.
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In many real classification problems, the data set used for model induction is significantly imbalanced. This occurs when the number of examples of some classes is much lower than the other classes. Imbalanced datasets can compromise the performance of most classical classification algorithms. The classification models induced by such datasets usually present a strong bias towards the majority classes, tending to classify new instances as belonging to these classes. A commonly adopted strategy for dealing with this problem is to train the classifier on a balanced sample from the original dataset. However, this procedure can discard examples that could be important for a better class discrimination, reducing classifier efficiency. On the other hand, in recent years several studies have shown that in different scenarios the strategy of combining several classifiers into structures known as ensembles has proved to be quite effective. This strategy has led to a stable predictive accuracy and, in particular, to a greater generalization ability than the classifiers that make up the ensemble. This generalization power of classifier ensembles has been the focus of research in the imbalanced learning field in order to reduce the bias toward the majority classes, despite the complexity involved in generating efficient ensembles. Optimization meta-heuristics, such as evolutionary algorithms, have many applications for ensemble learning, although they are little used for this purpose. For example, evolutionary algorithms maintain a set of possible solutions and diversify these solutions, which helps to escape out of the local optimal. In this context, this thesis investigates and develops approaches to deal with imbalanced datasets, using ensemble of classifiers induced by samples taken from the original dataset. More specifically, this theses propose three solutions based on evolutionary ensemble learning and a fourth proposal that uses a pruning mechanism based on dominance ranking, a common concept in multiobjective evolutionary algorithms. Experiments showed the potential of the developed solutions.Em muitos problemas reais de classificação, o conjunto de dados usado para a indução do modelo é significativamente desbalanceado. Isso ocorre quando a quantidade de exemplos de algumas classes é muito inferior às das outras classes. Conjuntos de dados desbalanceados podem comprometer o desempenho da maioria dos algoritmos clássicos de classificação. Os modelos de classificação induzidos por tais conjuntos de dados geralmente apresentam um forte viés para as classes majoritárias, tendendo classificar novas instâncias como pertencentes a essas classes. Uma estratégia comumente adotada para lidar com esse problema, é treinar o classificador sobre uma amostra balanceada do conjunto de dados original. Entretanto, esse procedimento pode descartar exemplos que poderiam ser importantes para uma melhor discriminação das classes, diminuindo a eficiência do classificador. Por outro lado, nos últimos anos, vários estudos têm mostrado que em diferentes cenários a estratégia de combinar vários classificadores em estruturas conhecidas como comitês tem se mostrado bastante eficaz. Tal estratégia tem levado a uma acurácia preditiva estável e principalmente a apresentar maior habilidade de generalização que os classificadores que compõe o comitê. Esse poder de generalização dos comitês de classificadores tem sido foco de pesquisas no campo de aprendizado desbalanceado, com o objetivo de diminuir o viés em direção as classes majoritárias, apesar da complexidade que envolve gerar comitês de classificadores eficientes. Meta-heurísticas de otimização, como os algoritmos evolutivos, têm muitas aplicações para o aprendizado de comitês, apesar de serem pouco usadas para este fim. Por exemplo, algoritmos evolutivos mantêm um conjunto de soluções possíveis e diversificam essas soluções, o que auxilia na fuga dos ótimos locais. Nesse contexto, esta tese investiga e desenvolve abordagens para lidar com conjuntos de dados desbalanceados, utilizando comitês de classificadores induzidos a partir de amostras do conjunto de dados original por meio de metaheurísticas. Mais especificamente, são propostas três soluções baseadas em aprendizado evolucionário de comitês e uma quarta proposta que utiliza um mecanismo de poda baseado em ranking de dominância, conceito comum em algoritmos evolutivos multiobjetivos. Experimentos realizados mostraram o potencial das soluções desenvolvidas.
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Kirchner, Ulrich. "Approaches to ensembles of universes." Doctoral thesis, University of Cape Town, 2003. http://hdl.handle.net/11427/4898.
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Includes bibliographical references.This thesis consists of three parts - each of them focusing on different aspects relating to ensembles of universes and causally disconnected regions. In the first part I investigate possible measures over the space of FLRW models. In the second part I examine the behaviour of such transition regions for spherically symmetric space-times. In the last part of this thesis I discuss philosophical, physical, and probabilistic issues related to the concept of a multiverse - an ensemble of universes. The difference between ensembles of really existing universes and ensembles of possible universes is emphasized.
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Berglund, Filip. "Asymptotics of beta-Hermite Ensembles." Thesis, Linköpings universitet, Matematisk statistik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-171096.
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In this thesis we present results about some eigenvalue statistics of the beta-Hermite ensembles, both in the classical cases corresponding to beta = 1, 2, 4, that is the Gaussian orthogonal ensemble (consisting of real symmetric matrices), the Gaussian unitary ensemble (consisting of complex Hermitian matrices) and the Gaussian symplectic ensembles (consisting of quaternionic self-dual matrices) respectively. We also look at the less explored general beta-Hermite ensembles (consisting of real tridiagonal symmetric matrices). Specifically we look at the empirical distribution function and two different scalings of the largest eigenvalue. The results we present relating to these statistics are the convergence of the empirical distribution function to the semicircle law, the convergence of the scaled largest eigenvalue to the Tracy-Widom distributions, and with a different scaling, the convergence of the largest eigenvalue to 1. We also use simulations to illustrate these results. For the Gaussian unitary ensemble, we present an expression for its level density. To aid in understanding the Gaussian symplectic ensemble we present properties of the eigenvalues of quaternionic matrices. Finally, we prove a theorem about the symmetry of the order statistic of the eigenvalues of the beta-Hermite ensembles.I denna kandidatuppsats presenterar vi resultat om några olika egenvärdens-statistikor från beta-Hermite ensemblerna, först i de klassiska fallen då beta = 1, 2, 4, det vill säga den gaussiska ortogonala ensemblen (bestående av reella symmetriska matriser), den gaussiska unitära ensemblen (bestående av komplexa hermitiska matriser) och den gaussiska symplektiska ensemblen (bestående av kvaternioniska själv-duala matriser). Vi tittar även på de mindre undersökta generella beta-Hermite ensemblerna (bestående av reella symmetriska tridiagonala matriser). Specifikt tittar vi på den empiriska fördelningsfunktionen och två olika normeringar av det största egenvärdet. De resultat vi presenterar för dessa statistikor är den empiriska fördelningsfunktionens konvergens mot halvcirkel-fördelningen, det normerade största egenvärdets konvergens mot Tracy-Widom fördelningen, och, med en annan normering, största egenvärdets konvergens mot 1. Vi illustrerar även dessa resultat med hjälp av simuleringar. För den gaussiska unitära ensemblen presenterar vi ett uttryck för dess nivåtäthet. För att underlätta förståelsen av den gaussiska symplektiska ensemblen presenterar vi egenskaper hos egenvärdena av kvaternioniska matriser. Slutligen bevisar vi en sats om symmetrin hos ordningsstatistikan av egenvärdena av beta-Hermite ensemblerna.
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Baffoe, Nana Ama Appiaa. "Diagnostic Tools for Forecast Ensembles." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case1522964882574611.
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Rahman, Md Ahsanur. "Unstable Communities in Network Ensembles." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/78290.
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Ensembles of graphs arise naturally in many applications, for example, the temporal evolution of social contacts or computer communications, tissue-specific protein interaction networks, annual citation or co-authorship networks in a field, or a family of high-likelihood Bayesian networks inferred from systems biology data. Several techniques have been developed to analyze such ensembles. A canonical problem is that of computing communities that are persistent across the ensemble. This problem is usually formulated as one of computing dense subgraphs (communities) that are frequent, i.e., appear in many graphs in the ensemble.
In this thesis, we seek to find "unstable communities" which are the antithesis of frequent, dense subgraphs. Informally, an unstable community is a set of nodes that induces highly-varying subgraphs in the ensemble. In other words, the graphs in the ensemble disagree about the precise pairwise connections among these nodes. The primary contribution of this dissertation is to introduce the concept of unstable communities as a novel problem in the field of graph mining. Specifically, it presents three approaches to mathematically formulate the concept of unstable communities, devises algorithms for computing such communities in a given ensemble of networks, and shows the usefulness of this concept in a variety of settings.
Our first definition of unstable community relies on two parameters: the first ensures that a node set induces several different subgraphs in the ensemble and the second guarantees that each of these subgraphs occurs in a large number of graphs in the ensemble. We present two algorithms to enumerate unstable communities that match this definition. The first approach, ClustMiner, is a heuristic that transforms the problem into one of computing dense subgraphs in a single graph that summarizes the ensemble. The second approach, UCMiner, is guaranteed to enumerate all maximal unstable communities correctly. We apply both approaches to systems biology datasets to demonstrate that UCMiner is superior to ClustMiner in the sense that ClustMiner's output contains node sets that are not unstable while also missing several communities computed by UCMiner. We find several node sets that capture the uncertain connectivity of genes in relevant protein complexes, suggesting that further experiments may be required to precisely discern their interaction patterns.
Our second and third definitions of unstable community rely on a novel concept of (scaled) subgraph divergence, a formulation that uses the concept of relative entropy to measure the instability of a community. We propose another algorithm, SDMiner, that can exactly enumerate all maximal unstable communities with small (scaled) subgraph divergence. We perform extensive experiments on social network datasets to show that we can discover UCs that capture the main structural variations of the given set of networks and also provide us with interesting and relevant insights about these datasets.Ph. D.
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Grumbach, Stéphane. "Ensembles et fonctions en Datalog." Paris 11, 1990. http://www.theses.fr/1990PA112003.
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Tardivel, Valérie. "Ensembles coanalytiques en analyse harmonique." Paris 6, 1986. http://www.theses.fr/1986PA066096.
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Lachièze-Rey, Raphaël. "Ensembles convexes et mosaïques aléatoires." Thesis, Lille 1, 2010. http://www.theses.fr/2010LIL10084/document.
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Cette thèse s'occupe de différents problèmes de géométrie stochastiques, inspirés plus particulièrement de la géométrie convexe. On s'occupe tout d'abord des points extrêmaux du graphe de certains processus Markoviens. Dans un second chapitre, on s'intéresse au réarrangement convexe de certains champs aléatoires Gaussiens centrés. Le chapitre trois est consacré à l'ergodicité des mosaïques aléatoire de type STIT. On s'intéresse enfin à l'épluchage d'un processus ponctuel, avec une généralisation de la notion d'enveloppe convexe à celle d'enveloppe L-convexe, ou L est une famille de fermés arbitraireThis thesis is concerned with various problems of stochastic geometry, more particularly inspired from convex geometry. The first chapter is devoted to the study of extreme points of the graph of some Markov processes. Then we are interestd in the convex rearrangement of centered Gaussian fields. In the third chapter we study the ergodicity of STIT tessellations, a particular class of random mosaics in R^d. Finally, we the study the peeling of a Point process, with the generalisation of the notion of convex hull to that of L-enveloppe, with L an arbitrary class of closed sets
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Cadena, Carlos. "Evolutionary feature creation for ensembles." Thèse, Montréal : École de technologie supérieure, 2008. http://proquest.umi.com/pqdweb?did=1472144241&sid=4&Fmt=2&clientId=46962&RQT=309&VName=PQD.
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Thèse (M. Ing.) -- École de technologie supérieure, 2008."by Cadena, Carlos" -- p. de. t. "Thesis presented to École de technologie supérieure in partial fulfillment of the requirements for the degree of master of engineering." CAQMUQET CaQMUQET Bibliogr. : f.[223]-229. Également disponible en version électronique. CaQMUQET
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Moupila-Mapépé, Aurélien. "Hyperbolicité et ensembles invariants isolés." Sherbrooke : Université de Sherbrooke, 2001.
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Tardivel, Valérie. "Ensembles coanalytiques en analyse harmonique." Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb37601475m.
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Lupu, Titus. "Ensembles poissoniens de boucles markoviennes." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112066/document.
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L'objet d'étude de cette thèse est une mesure infinie sur les boucles (lacets) naturellement associée à une large classe de processus de Markov et les processus ponctuels de Poisson d'intensité proportionnelle à cette mesure (paramètre d'intensité alpha>0). Ces processus ponctuels de Poisson portent le nom d'ensembles poissoniens de boucles markoviennes ou de soupes de boucles. La mesure sur les boucles est covariante par un certain nombre de transformations sur les processus de Markov, par exemple le changement de temps.Dans le cadre de soupe de boucles brownienne à l'intérieur d'un sous-domaine ouvert propre simplement connexe de C, il a été montré que les contours extérieurs des amas extérieurs de boucles sont, pour alpha<=1/2, des Conformal Loop Ensembles CLE(kappa), kappa dans (8/3,4]. D'autre part il a été montré pour une large classe de processus de Markov symétriques que lorsque alpha=1/2, le champ d'occupation d'une soupe de boucle (somme des temps passés par les boucles aux dessus des points) est le carré du champ libre gaussien. J'ai étudié d'abord les soupes de boucles associés aux processus de diffusion unidimensionnels, notamment leur champ d'occupation dont les zéros délimitent dans ce cas les amas de boucles. Puis j'ai étudié les soupes de boucles sur graphe discret ainsi que sur graphe métrique (arêtes remplacés par des fils continus). Sur graphe métrique on a d'une part une géométrie non triviale pour les boucles et d'autre part on a comme dans le cas unidimensionnel continu la propriété que les zéros du champ d'occupation délimitent les amas des boucles. En combinant les graphes métriques et l'isomorphisme avec le champ libre gaussien j'ai montré que alpha=1/2 est le paramètre d'intensité critique pour la percolation par soupe de boucles de marche aléatoire sur le demi plan discret Z*N (existence ou non d'un amas infini) et que pour alpha<=1/2 la limite d'échelle des contours extérieurs des amas extérieurs sur Z*N est un CLE(kappa) dans le demi-plan continuIn this thesis I study an infinite measure on loops naturally associated to a wide range of Markovian processes and the Poisson point processes of intensity proportional to this measure (intensity parameter alpha>0). This Poissson point processes are called Poisson ensembles of Markov loops or loop soups. The measure on loops is covariant with some transformation on Markovian processes, for instance the change of time. In the setting of Brownian loop soups inside a proper open simply connected domain of C it was shown that the outer boundaries of outermost clusters of loops are, for alpha1/2, Conformal Loop Ensembles CLE(kappa), kappa in (8/3,4]. Besides, it was shown for a wide range of symmetric Markovian processes that for alpha=1/2 the occupation field of a loop soup (the sum of times spent by loops over points) is the square of the Gaussian free field. First I studied the loop soups associated to one-dimensional diffusions, and particularly the occupation field and its zeroes that delimit in this case the clusters of loops. Then I studied the loop soups on discrete graphs and metric graphs (edges replaced by continuous lines). On a metric graph on one hand the loops have a non-trivial geometry and on the other hand one has the same property as in the setting of one-dimensional diffusions that the zeroes of the occupation field delimit the clusters of loops. By combing metric graphs and the isomorphism with the Gaussian free field I have shown that alpha=1/2 is the critical parameter for random walk loop soup percolation on the discrete half-plane Z*N (existence or not of an infinite cluster of loops) and that for alpha<= 1/2 the scaling limit of outer boundaries of outermost clusters on Z*N is a CLE(kappa) on the continuum half plane
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Zagorski, Marcus. "And drown the wakeful anguish of the soul." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0007/MQ43989.pdf.
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Lecomte, Dominique. "Classes de Wadge potentielles et théorèmes d'uniformisation partielle." Paris 6, 1993. http://www.theses.fr/1993PA066591.
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Lors de l'étude des relations d'équivalence borélienne, le problème suivant apparaît: peut-on diminuer la complexité d'un borélien d'un produit de deux espaces polonais en enrichissant les topologies sur chacun des facteurs ? D'où l'introduction de la notion de classe de Wadge potentielle. On cherche à savoir si certains résultats vrais pour les classes de Wadge peuvent être adaptés aux classes de Wadge potentielles. En l'occurrence, il s'agit d'une part de voir si cette notion correspond à une réduction, comme dans le cas des classes de Wadge classiques, et on verra que non. On cherchera ensuite à̀ savoir si on peut obtenir des résultats de type Hurewicz, c'est à dire: Ne pas être d'une classe donnée, c'est être au moins aussi compliqué que des exemples de référence n'étant pas de cette classe. On obtiendra des résultats partiels pour les petites classes de Wadge (notamment, on caractérisera les boréliens potentiellement fermes parmi les boréliens à coupes dénombrables, à l'aide d'ensembles localement a projections ouvertes). Ceci nous amènera à des résultats d'uniformisation, pour des ensembles à coupes maigres, à coupes non maigres, des intersections dénombrables d'ouverts denses, et des intersections dénombrables d'ouverts, localement à projections ouvertes. En étudiant les limites de ces résultats, on montrera que l'analogie entre ensembles maigres et ensembles de mesure 0 n'est pas parfaite. Le dernier résultat d'uniformisation évoque fournira une caractérisation plus parlante que celle évoquée ci-dessus
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Colangelo, Giorgio. "Quantum measurements with cold atomic ensembles." Doctoral thesis, Universitat Politècnica de Catalunya, 2016. http://hdl.handle.net/10803/404449.
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This thesis describes quantum measurements of an ensemble of cold rubidium-87 atoms.
We extend the covariance matrix formalism to spin-1 systems, including effects of decoherence, losses due to probing and atom number fluctuations.
We show that the model can reproduce perimental results of both the mean and variance of a Faraday rotation measurement of the free induction decay signal of a coherent spin state precessing in an inhomogeneous magnetic field.
We derive linearization procedures for Faraday measurements with high rotation angles and develop a fast differential photodetector that allows high dynamic range detection. We also study how to experimentally calibrate the reference quantum noise level under inhomogeneous
light-atom interaction. We show that two non-commuting collective spin observables describing
the atomic ensemble can be simultaneously known with sensitivity beyond classical limits, producing a planar quantum squeezed state. We theoretically study this state's metrological advantages and we find optimal conditions for its realization.
Finally, using quantum non-demolition (QND) measurements of an atomic coherent state precessing under an orthogonal magnetic field, we track the radial and the angular component of the collective spin of the atomic ensemble below Poisson statistics and below the projection
noise level by 7.0 dB and 2.9 dB respectively.
The final topic of this thesis is the investigation of measurement backaction as a genuine quantum signature through the violation of Leggett-Garg inequalities. The use of QND measurements, which does not perturb the measured quantity, provide a way to certify such violations as due to true quantum effects rather than other possible classical disturvbance caused by the measurement. The use of Gaussian states described by covariance matrix calculations indicates these techniques can be applied to truly macroscopic systems.Esta tesis describe medidas cuánticas en una nube de átomos fríos de rubidio-87. Extendemos el formalismo de matriz de covariancia a sistemas de espin-1, incluyendo decoherencias, pérdidas debidas a la luz de prueba y fluctuaciones del número de átomos. Mostramos que el modelo puede reproducir los resultados experimentales de medias y variancias de medidas de rotación de Faraday de una señal de decaimiento libre de inducción de un estado coherente de spin rotando en un campo magnético. Derivamos procedimientos de linearizacion para medidas de Faraday con ángulos de rotación grandes y desarrollamos un fotodetector rápido que permite la detección en rango dinámico alto. En esta tesis estudiamos también el problema de interacción luz-átomos en el caso de acoplamiento inhomogéneo y calibramos experimentalmente el nivel de ruido cuántico. Demostramos que dos observables colectivas de espín que describen la nube atómica que no conmutan se pueden conocer simultáneamente con precisión más allá de los límites clásicos, produciendo un estado cuántico planar comprimido. Estudiamos teóricamente sus ventajas metrológicas y encontramos condiciones óptimas para su realización. Así mismo, utilizando medidas cuánticas no desctructivas (QND) en un estado atómico coherente rotando en un campo magnético ortogonal, monitorizamos las componentes radial y angular del spin colectivo de la nube de átomos 7.0 dB por debajo de la estadística Poissoniana y 2.9 dB por debajo del nivél del ruido de proyección. El último resultado de esta tesis es la investigación del contra-efecto de la medida como un auténtico efecto cuántico a través de la violación de las desigualdades de Leggett-Garg. El uso de las medidas QND, que no perturban la observable medida, permite considerar las violaciones como en verdadero efecto cuántico en lugar de otros posibles efectos clásicos causados por la medida. Por otro lado el uso de estados Gaussianos usado en los cálculos de matriz de covariancia puede ser aplicado también a sistemas verdaderamente macroscópicos.
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Montbrió, i. Fairen Ernest. "Synchronization in ensembles of nonisochronous oscillators." [S.l. : s.n.], 2004. http://pub.ub.uni-potsdam.de/2004/0049/mtbrio.pdf.
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Zell, Thierry. "Etude quantitative des ensembles semi-pfaffiens." Phd thesis, Université Rennes 1, 2003. http://tel.archives-ouvertes.fr/tel-00008488.
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Dans la présente thèse, on établit des bornes supérieures sur les nombres de Betti des ensembles définis à l'aide de fonctions pfaffiennes, en fonction de la complexité pfaffienne (ou format) de ces ensembles. Les fonctions pfaffiennes ont été définies par Khovanskii, comme solutions au comportement quasi-polynomial de certains systèmes polynomiaux d'équations différentielles. Les ensembles semi-pfaffiens satisfont une condition de signe booléene sur des fonctions pfaffiennes, et les ensembles sous-pfaffiens sont projections de semi-pfaffiens. Wilkie a démontré que les fonctions pfaffiennes engendrent une structure o-minimale, et Gabrielov a montré que cette structure pouvait etre efficacement décrite par des ensembles pfaffiens limites. A l'aide de la théorie de Morse, de déformations, de recurrences sur le niveau combinatoire et de suites spectrales, on donne dans cette thèse des bornes effectives pourtoutes les catégories d'ensembles pré-citées.
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Zhou, Da Sheng. "Eigenvalues statistics for restricted trace ensembles." Thesis, University of Macau, 2010. http://umaclib3.umac.mo/record=b2182958.
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Montbrió, i. Fairen Ernest. "Synchronization in ensembles of nonisochronous oscillators." Phd thesis, Universität Potsdam, 2004. http://opus.kobv.de/ubp/volltexte/2005/158/.
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Diese Arbeit analysiert Synchronisationsphaenomene, die in grossen Ensembles von interagierenden Oszillatoren auftauchen. Im speziellen werden die Effekte von Nicht-Isochronizitaet (die Abhaengigkeit der Frequenz von der Amplitude des Oszillators) auf den makroskopischen Uebergang zur Synchronisation im Detail studiert. Die neu gefundenen Phaenomene (Anomale Synchronisation) werden sowohl in Populationen von Oszillatoren als auch zwischen Oszillator-Ensembles untersucht.This thesis analyses synchronization phenomena occurring in large ensembles of interacting oscillatory units. In particular, the effects of nonisochronicity (frequency dependence on the oscillator's amplitude) on the macroscopic transition to synchronization are studied in detail. The new phenomena found (Anomalous Synchronization) are investigated in populations of oscillators as well as between oscillator's ensembles.
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Pisetta, Vincent. "New Insights into Decision Trees Ensembles." Thesis, Lyon 2, 2012. http://www.theses.fr/2012LYO20018/document.
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Les ensembles d’arbres constituent à l’heure actuelle l’une des méthodes d’apprentissage statistique les plus performantes. Toutefois, leurs propriétés théoriques, ainsi que leurs performances empiriques restent sujettes à de nombreuses questions. Nous proposons dans cette thèse d’apporter un nouvel éclairage à ces méthodes. Plus particulièrement, après avoir évoqué les aspects théoriques actuels (chapitre 1) de trois schémas ensemblistes principaux (Forêts aléatoires, Boosting et Discrimination Stochastique), nous proposerons une analyse tendant vers l’existence d’un point commun au bien fondé de ces trois principes (chapitre 2). Ce principe tient compte de l’importance des deux premiers moments de la marge dans l’obtention d’un ensemble ayant de bonnes performances. De là, nous en déduisons un nouvel algorithme baptisé OSS (Oriented Sub-Sampling) dont les étapes sont en plein accord et découlent logiquement du cadre que nous introduisons. Les performances d’OSS sont empiriquement supérieures à celles d’algorithmes en vogue comme les Forêts aléatoires et AdaBoost. Dans un troisième volet (chapitre 3), nous analysons la méthode des Forêts aléatoires en adoptant un point de vue « noyau ». Ce dernier permet d’améliorer la compréhension des forêts avec, en particulier la compréhension et l’observation du mécanisme de régularisation de ces techniques. Le fait d’adopter un point de vue noyau permet d’améliorer les Forêts aléatoires via des méthodes populaires de post-traitement comme les SVM ou l’apprentissage de noyaux multiples. Ceux-ci démontrent des performances nettement supérieures à l’algorithme de base, et permettent également de réaliser un élagage de l’ensemble en ne conservant qu’une petite partie des classifieurs le composantDecision trees ensembles are among the most popular tools in machine learning. Nevertheless, their theoretical properties as well as their empirical performances are subject to strong investigation up to date. In this thesis, we propose to shed light on these methods. More precisely, after having described the current theoretical aspects of three main ensemble schemes (chapter 1), we give an analysis supporting the existence of common reasons to the success of these three principles (chapter 2). This last takes into account the two first moments of the margin as an essential ingredient to obtain strong learning abilities. Starting from this rejoinder, we propose a new ensemble algorithm called OSS (Oriented Sub-Sampling) whose steps are in perfect accordance with the point of view we introduce. The empirical performances of OSS are superior to the ones of currently popular algorithms such as Random Forests and AdaBoost. In a third chapter (chapter 3), we analyze Random Forests adopting a “kernel” point of view. This last allows us to understand and observe the underlying regularization mechanism of these kinds of methods. Adopting the kernel point of view also enables us to improve the predictive performance of Random Forests using popular post-processing techniques such as SVM and multiple kernel learning. In conjunction with random Forests, they show greatly improved performances and are able to realize a pruning of the ensemble by conserving only a small fraction of the initial base learners
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Ardeshir, G. "Decision tree simplification for classifier ensembles." Thesis, University of Surrey, 2002. http://epubs.surrey.ac.uk/843022/.
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Design of ensemble classifiers involves three factors: 1) a learning algorithm to produce a classifier (base classifier), 2) an ensemble method to generate diverse classifiers, and 3) a combining method to combine decisions made by base classifiers. With regard to the first factor, a good choice for constructing a classifier is a decision tree learning algorithm. However, a possible problem with this learning algorithm is its complexity which has only been addressed previously in the context of pruning methods for individual trees. Furthermore, the ensemble method may require the learning algorithm to produce a complex classifier. Considering the fact that performance of simplification methods as well as ensemble methods changes from one domain to another, our main contribution is to address a simplification method (post-pruning) in the context of ensemble methods including Bagging, Boosting and Error-Correcting Output Code (ECOC). Using a statistical test, the performance of ensembles made by Bagging, Boosting and ECOC as well as five pruning methods in the context of ensembles is compared. In addition to the implementation a supporting theory called Margin, is discussed and the relationship of Pruning to bias and variance is explained. For ECOC, the effect of parameters such as code length and size of training set on performance of Pruning methods is also studied. Decomposition methods such as ECOC are considered as a solution to reduce complexity of multi-class problems in many real problems such as face recognition. Focusing on the decomposition methods, AdaBoost.OC which is a combination of Boosting and ECOC is compared with the pseudo-loss based version of Boosting, AdaBoost.M2. In addition, the influence of pruning on the performance of ensembles is studied. Motivated by the result that both pruned and unpruned ensembles made by AdaBoost.OC have similar accuracy, pruned ensembles are compared with ensembles of single node decision trees. This results in the hypothesis that ensembles of simple classifiers may give better performance as shown for AdaBoost.OC on the identification problem in face recognition. The implication is that in some problems to achieve best accuracy of an ensemble, it is necessary to select base classifier complexity.
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Nagel, Uwe [Verfasser]. "Analysis of Network Ensembles / Uwe Nagel." Konstanz : Bibliothek der Universität Konstanz, 2013. http://d-nb.info/1030479054/34.
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Ahmad, Amir. "Data Transformation for Decision Tree Ensembles." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508528.
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Plumpton, Catrin Oliver. "Classifier ensembles for streaming fMRI data." Thesis, Bangor University, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540419.
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Bilgic̦, Berkin. "Fast human detection with cascaded ensembles." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/57684.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 75-78).
Detecting people in images is a challenging task because of the variability in clothing and illumination conditions, and the wide range of poses that people can adopt. To discriminate the human shape clearly, Dalal and Triggs [1] proposed a gradient based, robust feature set that yielded excellent detection results. This method computes locally normalized gradient orientation histograms over blocks of size 16x16 pixels representing a detection window. The block histograms within the window are then concatenated. The resulting feature vector is powerful enough to detect people with 88% detection rate at 10 -4 false positives per window (FPPW) using a linear SVM. The detection window slides over the image in all possible image scales; hence this is computationally expensive, being able to run at 1 FPS for a 320x240 image on a typical CPU with a sparse scanning methodology. Due to its simplicity and high descriptive power, several authors worked on the Dalal-Triggs algorithm to make it feasible for real time detection. One such approach is to implement this method on a Graphics Processing Unit (GPU), exploiting the parallelisms in the algorithm. Another way is to formulate the detector as an attentional cascade, so as to allow early rejections to decrease the detection time. Zhu et al. [2] demonstrated that it is possible to obtain a 30x speed up over the original algorithm with this methodology.
(cont.) In this thesis, we combine the two proposed methods and investigate the feasibility of a fast person localization framework that integrates the cascade-of-rejectors approach with the Histograms of Oriented Gradients (HoG) features on a data parallel architecture. The salient features of people are captured by HoG blocks of variable sizes and locations which are chosen by the AdaBoost algorithm from a large set of possible blocks. We use the integral image representation for histogram computation and a rejection cascade in a sliding-windows manner, both of which can be implemented in a data parallel fashion. Utilizing the NVIDIA CUDA framework to realize this method on a Graphics Processing Unit (GPU), we report a speed up by a factor of 13 over our CPU implementation. For a 1280x960 image our parallel technique attains a processing speed of 2.5 to 8 frames per second depending on the image scanning density, with a detection quality comparable to the original HoG algorithm.
by Berkin Bilgic̦.
S.M.