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  • Thesis

  • Scalable cooperative multiagent reinforcement learning in the context of an organization

    • Authors: Abdallah, Sherief (2006)

  • Reinforcement learning techniques have been successfully used to solve single agent optimization problems but many of the real problems involve multiple agents, or multi-agent systems. This explains the growing interest in multi-agent reinforcement learning algorithms, or MARL. To be applicable in large real domains, MARL al¬gorithms need to be both stable and scalable. A scalable MARL will be able to perform adequately as the number of agents increases. A MARL algorithm is stable if all agents (eventually) converge to a stable joint policy. Unfortunately, most of the previous approaches lack at least one of these two crucial properties. This dissertation proposes a scalable and stable MARL framework using a network of mediator agents. The network connections restrict the space of ...
  • Thesis

  • Statistical LTAG parsing

    • Authors: Shen, Libin (2006)

  • In this work, we apply statistical learning algorithms to Lexicalized Tree Adjoining Grammar (LTAG) parsing, as an effort toward statistical analysis over deep structures. LTAG parsing is a well known hard problem. Statistical methods successfully applied to LTAG parsing could also be used in many other structure prediction problems in NLP. For the purpose of achieving accurate and efficient LTAG parsing, we will investigate two aspects of the problem, the data structure and the algorithm. 1. We introduce LTAG-spinal, a variant of LTAG with very desirable linguistic, computational and statistical properties. It can be shown that LTAG-spinal with adjunction constraints is weakly equivalent to the traditional LTAG. For the purpose of statistical processing, we extract an LTAG-spinal...
  • Thesis

  • Stochastic delay equations and invariant measure for the wave equation with noise

    • Authors: Zhao, Xi (2006)

  • This thesis is divided into two major parts. First we study the moment stability of the trivial solution of a linear differential delay equation in the presence of additive and multiplicative white noise. The stability of the first moment for the solutions of a linear differential delay equation under stochastic perturbation is identical to that of the unperturbed system. However, the stability of the second moment is altered by the perturbation. We obtain, using Laplace transform tech¬niques, necessary and sufficient conditions for the second moment to be bounded. Then we establish the stability criteria for stochastic differential equations with Markovian switching using the comparison principle. These criteria include sta¬bility in probability, asymptotic stability in probability...
  • Thesis

  • Supporting on-the-fly data integration for bioinformatics

    • Authors: Zhang, Xuan (2006)

  • The use of computational tools and on-line data knowledgebases has changed the way the biologists conduct their research. The fusion of biology and information science is expected to continue. Data integration is one of the challenges faced by bioinformatics. In order to build an integration system for modern biological research, three problems have to be solved. A large number of existing data sources have to be incorporated and when new data sources are discovered, they should be utilized right away. The variety of the biological data formats and access methods have to be addressed. Finally, the system has to be able to understand the rich and often fuzzy semantic of biological data. Motivated by the above challenges, a system and a set of tools have been implemented to support o...
  • Thesis

  • Synthesis, structure, and reactivity of terminal cobalt imido complexes

    • Authors: Shay, Daniel Travis (2006)

  • The synthesis and structural characterization of imido ligated cobalt complexes that employ the sterically hindered hydrotris(3-`Bu-5-Me-pyrazolyl)borate ligand, i. e., TptBu,MeCoNR (R = Me, Et, `Bu, Ad) have been accomplished. These terminal imido complexes possess relatively short Co-N bond distances in the range of 1.64-1.67 A, indicating a multiple bond to the metal. Reactivity studies have been undertaken with a variety of substrate ranging from protonation using acids such as HC1 and lutidinium-BARF (BARF = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate) to ligand transfer of the imido fragment to carbon monoxide. Kinetic studies of the thermal decomposition of Tp'Bu,MeCoNAd which undergoes C-H activation of the Tp ligand yielding BptBu,Me(Me-pz-CMe2CH22N(Ad)H)Co, have b...
  • Thesis

  • Tate-Shafarevich groups of Jacobians of Fermat curves

    • Authors: Levitt, Benjamin (2006)

  • For a fixed rational prime p and primitive p-th root of unity (, we consider the Jacobian, J, of the complete non-singular curve give by equation yP = xa(1 - x)b. These curves are quotients of the p-th Fermat curve, given by equation xP+yP = 1, by a cyclic group of automorphisms. Let k = Q(() and ks be the maximal extension of k unramified away from p inside a fixed algebraic closure of k. We produce a formula for the image of certain coboundary maps in group cohomology given in terms of Massey products, applicable in a general setting. Under specific circumstance, stated precisely below, we can use this formula and a pairing in the Galois cohomology of ks over k studied by W. McCallum and R. Sharifi in [MS02] to produce non-trivial elements in the Tate-Shafarevich group of J. In pa...
  • Thesis

  • Techniques for incorporating data quality assessments into learning algorithms for Bayesian networks

    • Authors: Sessions, Valerie Kay (2006)

  • The field of Bayesian Networks (BNs) has had much success in developing structure learning algorithms to learn BNs directly from data. However, research has normally started with the assumption that the data given to the learning algorithm is accurate. This assumption is a naive one and can lead to very biased and unrealistic decision making frameworks. If we are to use decision making algorithms to their full potential we must design them with the capability to account for data quality. Our research lays the foundation for the development of new algorithms that incorporate data quality assessments into traditional BN learning algorithms - specifically the PC algorithm. We begin by reviewing Bayesian networks, learning algorithms, and data quality measures. We then quantify the effe...
  • Thesis

  • Texture- and structure-based image representation with applications to image retrieval and compression

    • Authors: He, Zhihua (2006)

  • The design of an efficient image representation methods using small numbers of features can facilitate image processing tasks such as compression of images and content-based retrieval of images from databases. In this dissertation, three methods for capturing and concisely representing two distinguishing characteristics of images, namely texture and structure, are developed. Applications of these compact representations of image characteristics to image compression as well as retrieval of images and hand-sketches of images from databases are given and performance is compared with other compression and retrieval methods. The first method to be introduced is a directional, hidden-Markov-model-based method for succinctly describing image texture using a small number of features. This ...