The purpose of this paper is to examine some basic topics in category theory. A category consists of a class of mathematical objects along with a morphism class having an associative composition. The paper is divided into two chapters. Chapter I deals with intrinsic properties of categories. Various "sub-objects" and properties of morphisms are defined and examples are given. Chapter II deals with morphisms between categories called functors and the natural transformations between functors. Special types of functors are defined and examples are given.

An integral domain D is weakly integrally closed if whenever there is an element x in the quotient field of D and a nonzero finitely generated ideal J of D such that xJ J2, then x is in D. We define weakly integrally closed numerical monoids similarly. If a monoid algebra is weakly integrally closed, then so is the monoid. A pattern F of finitely many 0's and 1's is forbidden if whenever the characteristic binary string of a numerical monoid M contains F, then M is not weakly integrally closed. Any stretch of the pattern 11011 is forbidden. A numerical monoid M is weakly integrally closed if and only if it has a forbidden pattern. For every finite set S of forbidden patterns, there exists a monoid that is not weakly integrally closed and that contains no stretch of a pattern in S. It is shown that particular monoid algebras are weakly integrally closed. / by Mary E. Hopkins. / Thesis (Ph.D.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

In this thesis, we focus on the the comparison of treatments with ordered categorical responses. The three cases of treatment comparisons will all be studied. The main objective of this thesis is to develop more effective comparison methods for treatments with ordinal responses and to address some important issues involved in different comparison problems. Our major statistical approach is to consider ordinal responses as manifestations of some underlying continuous random variables. / The comparison of treatments to detect possible treatment effects is a very important topic in statistical research. It has been drawing significant interests from both academicians and practitioners. Important research work on treatment comparisons dates back several decades. For treatment comparisons, the following three cases are very common: the comparison of two independent treatments; the comparison of treatments with repeated measurements; and the multiple comparison of several treatments. For different cases, the involved research issues are usually different. In many fields of study, the level of measurement for responses of the treatments is ordinal. Many examples can be found in areas such as biostatistics, psychology, sociology, and market research, where the ordered categorical variables play an important role. / This thesis consists of three main parts. In the first part, we consider the modeling of treatments with longitudinal ordinal responses by a latent growth curve. On the basis of such a latent growth curve, we achieve a comprehensive flexible model with straightforward interpretations and a variety of applications including treatment comparison, the analysis of covariates, and equivalence test of treatments. In the second part, we consider the comparison of several treatments with a control for ordinal responses. By considering the ordinal responses as manifestations of some underlying normal random variables, a latent normal distribution model is utilized and the corresponding parameter estimation method is proposed. Further, we also derive testing procedures that compare several treatments with a control under an analytical framework. Both single-step and stepwise procedures are introduced, and these procedures are compared in terms of average power based on a simulation study. In the last part of this thesis, we establish a unified framework for treatment comparisons with ordinal responses, which allows various treatment comparison methods be comprehended using a unified perspective. The latent variable model is also utilized, but the underlying random variables are allowed to have any member of the location-scale distribution family. This latent variable model under such a specification of underlying distributions subsumes many existing models in the literature. A two-step procedure to identify the model and produce the parameter estimates is proposed. Based on this procedure, many important statistical inferences can be conveniently conducted. Furthermore, the sample size determination method based on the latent variable method is also proposed. The proposed latent variable method is compared with the existing methods in terms of power and sample size. / Lu, Tongyu. / Adviser: Wai-Yin Poon. / Source: Dissertation Abstracts International, Volume: 73-06, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 94-101). / 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.

The context of this thesis is derived categories in algebraic geometry and geo- metric quotients. Specifically, we prove the embedding of the derived category of a smooth curve of genus greater than one into the derived category of the moduli space of semistable pairs over the curve. We also describe closed cover conditions under which the composition of a pullback and a pushforward induces a fully faithful functor. To prove our main result, we give an exposition of how to think of general Geometric Invariant Theory quotients as quotients by the multiplicative group.

by Leung Chi Kwan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 133-135). / Preface --- p.ii / Chapter 1 --- Introduction to Module Equivalence --- p.1 / Chapter 1.1 --- Introduction and Preliminaries --- p.1 / Chapter 2 --- Some Classical Results --- p.12 / Chapter 2.1 --- Morita Theorem --- p.12 / Chapter 2.2 --- Puller Theorem --- p.13 / Chapter 2.3 --- The Equivalence Mod-A ~Im(TP) --- p.29 / Chapter 2.4 --- The Equivalence Im(HP)~Im(Tp) --- p.33 / Chapter 3 --- *-modules and Tilting Modules --- p.39 / Chapter 3.1 --- The Equivalence Cogen(KA)~Gen(PR) --- p.39 / Chapter 3.2 --- Torsion Theories and *-modules --- p.56 / Chapter 3.3 --- The Structure of *-modules --- p.60 / Chapter 3.4 --- Characterizations of Tilting Modules --- p.65 / Chapter 4 --- Equivalences and Dualities --- p.85 / Chapter 4.1 --- The Equivalence PA~IR --- p.85 / Chapter 4.2 --- The Equivalence FGP-A ~FCI-R --- p.93 / Chapter 5 --- Torsion Theories Induced by Tilting Modules --- p.100 / Chapter 5.1 --- The Tilting Theorem --- p.100 / Chapter 5.2 --- Tilting Torsion Theories --- p.113 / Chapter 5.3 --- Isomorphisms of Endomorphism Rings of Tilting Modules --- p.122 / References --- p.133

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (p. 79-80).

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (p. 177-179).

The purpose of this study is to investigate and understand data which are grouped into categories. At the onset, the study presents a review of early research contributions and controversies surrounding categorical data analysis. The concept of sparseness in a contingency table refers to a table where many cells have small frequencies. Previous research findings showed that incorrect results were obtained in the analysis of sparse tables. Hence, attention is focussed on the effect of sparseness on modelling and analysis of categorical data in this dissertation. Cressie and Read (1984) suggested a versatile alternative, the power divergence statistic, to statistics proposed in the past. This study includes a detailed discussion of the power-divergence goodness-of-fit statistic with areas of interest covering a review on the minimum power divergence estimation method and evaluation of model fit. The effects of sparseness are also investigated for the power-divergence statistic. Comparative reviews on the accuracy, efficiency and performance of the power-divergence family of statistics under large and small sample cases are presented. Statistical applications on the power-divergence statistic have been conducted in SAS (Statistical Analysis Software). Further findings on the effect of small expected frequencies on accuracy of the X2 test are presented from the studies of Tate and Hyer (1973) and Lawal and Upton (1976). Other goodness-of-fit statistics which bear relevance to the sparse multino-mial case are discussed. They include Zelterman's (1987) D2 goodness-of-fit statistic, Simonoff's (1982, 1983) goodness-of-fit statistics as well as Koehler and Larntz's tests for log-linear models. On addressing contradictions for the sparse sample case under asymptotic conditions and an increase in sample size, discussions are provided on Simonoff's use of nonparametric techniques to find the variances as well as his adoption of the jackknife and bootstrap technique. / Thesis (M.Sc.)-University of Natal, Durban, 1998.

Note: / Butler's Theorems, with one minor exception, are resolved: in a 2-categorical setting. His Adjointness theorems are all proved correct, after one tiny modification. Then, using a condition on adjoint squares, twenty-two of his Tripleability theorems are proved correct; th~ee are proved false. The other theorem is still unresolved, but it is of very minor importance. / Les theoremes de Butler, a l'exception d'un seul de peu d'importance, sont resulus dans un contexte 2-categorique.Tous ses theoremes d'adjonction sont demontres etre valides apres une modification minime. Ensuit~ utilisant une condition de carres adjoints, vingt-deux de ses Theoremes de monadicite sont demontres et trois autres sont refutes. La validation ou refutation d'un seul de ses +heoremes, de peu d'importance, demeure en suspense.

Butler's Theorems, with one minor exception, are resolved: in a 2-categorical setting. His Adjointness theorems are all proved correct, after one tiny modification. Then, using a condition on adjoint squares, twenty-two of his Tripleability theorems are proved correct; three are proved false. The other theorem is still unresolved, but it is of very minor importance.