Thesis (Ph. D.)--University of Texas at Austin, 2005. / Supervisor: Carl S. Blyth. Vita. Includes bibliographical references.

This study addresses a familiar challenge in corpus pragmatic research: the search for functional phenomena in large electronic corpora. Speech acts are one area of research that falls into this functional domain and the question of how to identify them in corpora has occupied researchers over the past 20 years. This study focuses on apologies as a speech act that is characterised by a standard set of routine expressions, making it easier to search for with corpus linguistic tools. Nevertheless, even for a comparatively formulaic speech act, such as apologies, the polysemous nature of forms (cf. e.g. I am sorry vs. a sorry state) impacts the precision of the search output so that previous studies of smaller data samples had to resort to manual microanalysis. In this study, we introduce an innovative methodological approach that demonstrates how the combination of different types of collocational analysis can facilitate the study of speech acts in larger corpora. By first establishing a collocational profile for each of the Illocutionary Force Indicating Devices associated with apologies and then scrutinising their shared and unique collocates, unwanted hits can be discarded and the amount of manual intervention reduced. Thus, this article introduces new possibilities in the field of corpus-based speech act analysis and encourages the study of pragmatic phenomena in large corpora.

The renewed academic interest in using solar sails as a source of spacecraft propulsion has been accompanied by a recent fervor of investigations into non-ideal and off-nominal sail performance considerations. One of the most influential considerations, uncertain optical degradation, has been shown to present significant trajectory design difficulties. This paper investigates the potential of using a mid-course degradation model update to mitigate the risk of missing the target destination in a sample 300 day Earth-Venus trajectory. Using a range of potential degradation profiles, it is shown that correcting in the first half of the mission is highly likely to result in a trajectory that arrives sufficiently close to Venus at the end of the mission timeframe. Depending on the exact extent of the uncertainty, the data suggests that the latest a correction should take place ranges from 150 to 240 days into the mission. The influence of two different parameters, the extent and rate of degradation, are compared to show that the former of the two is more impactful on correcting timing than the latter.

Accelerating the convergence rate of Krylov subspace methods with parallelizable preconditioners is essential for obtaining effective iterative solvers for very large linear systems of equations. Substructuring provides a framework for constructing robust and parallel preconditioners for linear systems arising from the discretization of boundary value problems. Although collocation is a very general and effective discretization technique for many PDE problems, there has been relatively little work on preconditioners for collocation problems. This thesis proposes two preconditioning methods for solving linear systems of equations arising from Hermite bicubic collocation discretization of elliptic partial differential equations on square domains with mixed boundary conditions. The first method, called <i>edge preconditioning</i>, is based on a decomposition of the domain in parallel strips, and the second, called <i>edge-vertex preconditioning</i>, is based on a two-dimensional decomposition. The preconditioners are derived in terms of two special rectangular grids -- a coarse grid with diameter <i>H</i> and a hybrid coarse/fine grid -- which together with the fine grid of diameter <i>h</i> provide the framework for approximating the interface problem induced by substructuring. We show that the proposed methods are effective for nonsymmetric indefinite problems, both from the point of view of the cost per iteration and of the number of iterations. For an appropriate choice of <i>H</i>, the edge preconditioner requires <i>O(N)</i> arithmetic operations per iteration, while the edge-vertex preconditioner requires <i>O(N^4/3)</i> operations, where <i>N</i> is the number of unknowns. For the edge-vertex preconditioner, the number of iterations is almost constant when <i>h</i> and <i>H</i> decrease such that <i>H/h</i> is held constant and it increases very slowly with <i>H</i> when <i>h</i> is held constant. For both the edge- and edge-vertex preconditioners the number of iterations depends only weakly on <i>h</i> when <i>H</i> is constant. The edge-vertex preconditioner outperforms the edge-preconditioner for small enough <i>H</i>. Numerical experiments illustrate the parallel efficiency of the preconditioners which is similar or even better than that provided by the well-known PETSc parallel software library for scientific computing. / Ph. D.

L'objet d'étude de la présente recherche est la notion de « collocation fondamentale ». Nous calquons ce terme sur celui de « vocabulaire fondamental », issu de la dénomination Français fondamental utilisée par Gougenheim et al. (1964) pour désigner le vocabulaire de base de la langue française. Dans la thèse, les collocations fondamentales sont envisagées comme des unités polylexicales significatives (unies par des liens collocationnels) fréquentes (dans l'usage) ou non fréquentes (lorsqu'elles sont pertinentes pour la communication) qui représentent pour les locuteurs natifs les contextes de cooccurrence les plus essentiels et les plus typiques d'un mot pivot donné. Les études descriptives ou acquisitionnelles sur les collocations sont assez récentes et, à notre connaissance, ne se sont pas encore intéressées à cette notion, qui devrait pourtant constituer une étape préliminaire cruciale dans toute approche didactique destinée aux apprenants de langue étrangère. La présente étude se veut une recherche qualitative et quantitative d'un échantillon de collocations fondamentales constitué à partir de dix substantifs pivots représentant des « événements sociaux ». Le corpus que nous avons analysé est frWac (Baroni et al., 2010), un très vaste corpus écrit issu du Web analysé à l'aide de scripts Perl développés par Olivier Kraif (2011). A partir des pivots choisis, nous avons extrait de ce corpus les associations candidates au statut de collocations fondamentales ; puis nous avons demandé à 90 locuteurs natifs du français de sélectionner celles qui leur apparaissaient essentielles pour la communication. L'objectif a été d'évaluer, à l'aide de l'intuition de locuteurs natifs, la validité de l'échantillon automatiquement constitué, et de comprendre de quoi dépendait l'assignation du caractère fondamental de la part des enquêtés. Nous avons obtenu deux résultats principaux : - En premier lieu, nous avons constaté l'existence d'une corrélation faiblement positive, mais non systématique, entre la fréquence des associations dans le corpus et le score obtenu pour les associations sélectionnées par les locuteurs natifs. - En second lieu, nous avons constaté que lorsque la fréquence ne jouait pas de rôle, pour les enquêtés, dans l'attribution du caractère fondamental, alors la cause était à chercher dans le figement. En effet, dans des cas singuliers, les associations peu fréquentes sont sélectionnées parce qu'elles comportent un certain degré de figement ; à l'inverse, les associations les plus fréquentes sont exclues parce qu'elles sont perçues comme libres. Enfin, nous avons présenté la notion de collocation fondamentale en vue d'une exploitation didactique : à travers l'analyse de la structuration du domaine sémantique des « événements sociaux » qui nous a servi d'exemple, nous avons montré l'importance du repérage des « collocations fondamentales » afin d'opérer la sélection du vocabulaire à enseigner en classe de FLE. / The focus of the present study is the concept of core collocation. This term is defined with reference to the core vocabulary list produced by Gougenheim et al. (1964), Le Français Fondamental. Despite the fact that the importance of this list is broadly acknowledged, a critical point is that the analysis of the syntagmatic level was neglected. From this awareness, we develop the main focus of the present research and our basic assumption that the criteria applied to define core vocabulary, mainly frequency and availability, should be equally applied to define core collocations, a key concept in L2 teaching. We define core collocations as significative (the collocational relation), frequent (the usage) or available (essential for accomplishing basic communicative tasks) units representing the most basic co-occurrences of a word. This study aims to define core collocations through the investigation of a sample of collocations associated with ten basic nouns in a lexical area of interest for second language learners, the one of social relations. The corpus that we investigated is frWaC (Baroni et al., 2010), a lemmatized web-derived corpus assembled through automated procedures crawling the Web. The corpus was analyzed using a tool based on programming scripts Perl developed by Olivier Kraif (2011). The extraction tool makes use of frequency, dispersion and four associative measures (mutual information, log likelihood, t-score and z-score) and produces concordance lines. We chose the ten pivot nouns, we extracted the most frequent and available collocations and we evaluated the extracted sample through a comparison between 90 native speakers' intuitions about core collocations with statistical data. The results of the present research can be summarized as follows: - Since the most frequent collocations also received the highest number of votes by the tested subjects, we claim that frequency is a crucial feature in dictating the lexical choices made by speakers. However, some associations represent outliers: they are deviating points from the normal distribution of correlation between frequency and coreness attributed by native speakers. We might conclude that there is a certain linear correlation between the two variables but that this correlation is not systematic. - What is core is not only a matter of frequency, but it also depends on units' fixedness. Native speakers sometimes ignore frequent associations since they have a loose degree of fixedness, being rather free combinations; whereas other times they chose low frequent associations that they perceive as being very fixed. This study finally draws important pedagogical implications. The analysis of core collocations in the semantic area of “social relations” served us to explain which criteria can be adopted to run a filter across the wide set of phraseological units a given word produces, helping L2 teachers to find criteria to select the essential items to be taught first.

Many engineering problems are naturally posed as optimal control problems. It may involve moving between two points in the fastest possible way, or to put a satellite into orbit with minimum energy consumption. Many optimal control problems are too difficult to be solved analytically and therefore require the use of numerical methods. The numerical methods that are the most widespread are the so-called direct methods. However, there is one major drawback with these. If the problem is non-convex, the solution is not guaranteed globally optimal, that is, the absolute best, instead it is guaranteed locally optimal, that is the best in its vicinity. To compensate for this, the problem should be solved several times, under different conditions, in order to investigate whether the solution is a good candidate for the global optimum. CasADi is a software specifically designed for dynamic optimization. It has gained wide spread in recent years because it provides all the necessary building blocks for dynamic optimization. This has given individual engineers and scientists the ability to independently formulate and solve all sorts of optimal control problems. However, this requires good theoretical knowledge of the necessary numerical methods. The advantage of a toolbox, which solves general optimal control problems, is that the underlying numerical methods have been tested and shown to function on optimal control problems with known solutions. This means that the user does not need exhaustive knowledge of the numerical methods involved, but can focus on formulating and solving optimal control problems. The main contribution of this thesis is an optimal control toolbox for MATLAB based on CasADi. The toolbox does not require expert knowledge of the numerical methods, but provides an alternative lower level abstraction that allows for more complex problem formulations. The toolbox implements two direct methods, direct multiple shooting and direct collocation. This allows a problem formulation with many degrees of freedom. The most important property of the toolbox is that the discretization can be changed, without the problem formulation needing to be altered. This way the user can easily change the conditions for his/her problem. The thesis describes how the two implemented direct methods work, and the design choices made. It also describes what remains to test and evaluate, and the problems that have been used as a reference during the development process.

Thesis. 1976. M.S.--Massachusetts Institute of Technology. Dept. of Ocean Engineering. / Microfiche copy available in Archives and Engineering. / Includes bibliographical references. / M.S.

<p>The purpose of this paper is to examine the adverbs <em>mainly</em>, <em>mostly</em>, <em>chiefly</em> and <em>principally</em> for their level of synonymity. Dictionaries commonly lists synonyms to their main entries without providing information about commonality, contexts or level of formality or even sample sentences. More often than not this is done in a circular fashion, one main entry is listed as synonym to another which in turn is listed as a synonym to the first. This is confusing to persons not knowing what word to use and when to use it. The adverbs <em>mainly</em>, <em>mostly</em>, <em>chiefly</em> and <em>principally</em> are listed as synonyms to each other in several dictionaries in this circular fashion. By using corpus research I have shown that these adverbs are not the absolute synonyms dictionaries indicate, but differ greatly in usage, context and level of formality. I have investigated real samples of how <em>mainly</em>, <em>mostly</em>, <em>chiefly</em> and <em>principally</em> are used in a British newspaper. From the results I have obtained, I have analyzed the usage of the adverbs and suggested new and improved definitions.</p>

This thesis examines the transient performance of packed bed heat regenerators when very large temperature differences are involved. The effects of gas temperature on the key gas physical properties of velocity, density and heat capacity were studied via simulation. Three models were developed and compared. The first model (HRKDV) considers heat balances for both solid and gas phases, the second (HRVDV) considers mass balances in addition to the heat balances set up in the first model and the third one (HRASO) considers that the only significant rate of accumulation term is that of the energy of the solid phase. The governing partial differential equations were solved by the method of lines with the spatial discretization accomplished by the method of orthogonal collocation. The findings of this work reveal that whereas the effects of large temperature changes on the gas velocity and density are completely negligible, the effects of temperature on the gas heat capacity must be considered "continuously" when large temperature swings occur. Considering the heat capacity as a constant, even at an average value, leads to significant errors in temperature profiles. / Graduation date: 1992

The major contributions of this thesis are categorized into three areas: (i) magnetic modeling, (ii) optimal performance assessment and (iii) multi-objective design methodology of the linear permanent-magnet (LPM) and linear variable reluctance (LVR) motors for manufacturing automation applications. The target application is to perform repetitive point-to-point positioning tasks on a continuous basis under temperature constraints. Through simplification, the constraint on temperature rise may be replaced by a constraint on average power dissipation, provided that the thermal resistance is constant and known. The basic framework of analysis is first introduced for a class of idealized linear synchronous (LS) motors, where magnetic saturation and spatial harmonics are neglected, to provide clarity and insight. The physics-based force models for the LPM and LVR motors, including spatial harmonics and magnetic saturation as appropriate, are then developed. Due to magnetic linearity, the force model of the LPM motor is derived from the analytical solution of the Poisson Equation. A nonlinear magnetic circuit analysis model is developed for the LVR motor that includes both spatial harmonics and magnetic saturation. The accuracy of both force models are verified by finite element analysis. Applying those force models, the optimal performance assessment of the LPM and LVR motors is explored using the mathematical framework discussed for the idealized LS motors. In particular, the relationship between travel time and travel distance is characterized in terms of average power dissipation. The performance assessment methodologies developed here may be applied to any motor technology used in manufacturing automation applications. The multi-objective design optimization problem is then defined and software for its solution is developed using Monte-Carlo synthesis, the performance assessment tools and dominance-based sorting. Design results for the LPM and LVR motors are then presented. Future research is discussed as the conclusion of the thesis.