Dissertations / Theses on the topic 'Variable'

Latent variable models are widely used in social sciences in which interest is centred on entities such as attitudes, beliefs or abilities for which there e)dst no direct measuring instruments. Latent modelling tries to extract these entities, here described as latent (unobserved) variables, from measurements on related manifest (observed) variables. Methodology already exists for fitting a latent variable model to manifest data that is either categorical (latent trait and latent class analysis) or continuous (factor analysis and latent profile analysis). In this thesis a latent trait and a latent class model are presented for analysing the relationships among a set of mixed manifest variables using one or more latent variables. The set of manifest variables contains metric (continuous or discrete) and binary items. The latent dimension is continuous for the latent trait model and discrete for the latent class model. Scoring methods for allocating individuals on the identified latent dimen-sions based on their responses to the mixed manifest variables are discussed. ' Item nonresponse is also discussed in attitude scales with a mixture of binary and metric variables using the latent trait model. The estimation and the scoring methods for the latent trait model have been generalized for conditional distributions of the observed variables given the vector of latent variables other than the normal and the Bernoulli in the exponential family. To illustrate the use of the naixed model four data sets have been analyzed. Two of the data sets contain five memory questions, the first on Thatcher's resignation and the second on the Hillsborough football disaster; these five questions were included in BMRBI's August 1993 face to face omnibus survey. The third and the fourth data sets are from the 1990 and 1991 British Social Attitudes surveys; the questions which have been analyzed are from the sexual attitudes sections and the environment section respectively.

Statistics
Ph.D.
In this dissertation we introduce two variable selection procedures for multivariate responses. Our procedures are based on sufficient dimension reduction concepts and are model-free. In the first procedure we consider the dual marginal coordinate hypotheses, where the role of the predictor and the response is not important. Motivated by canonical correlation analysis (CCA), we propose a CCA-based test for the dual marginal coordinate hypotheses, and devise a joint backward selection algorithm for dual model-free variable selection. The second procedure is based on ordinary least squares (OLS). We derive and study the asymptotic properties of the OLS-based test under the normality assumption of the predictors as well as an asymmetry assumption. When these assumptions are violated, the asymptotic test with elliptical trimming and clustering is still valid with desirable numerical performances. A backward selection algorithm for the predictor is also provided for the OLS-based test. The performances of the proposed tests and the variable selection procedures are evaluated through synthetic examples and a real data analysis.
Temple University--Theses

Industrial processes are subject to changes that can adversely affect product quality. A change in the process that increases the variability of the output of the process causes the output to be less uniform and increases the probability that individual items will not meet specifications. Statistical control charts for monitoring process variance can be used to detect an increase in the variability of the output of a process so that the situation can be repaired and product uniformity restored. Control charts that increase the sampling rate when there is evidence the variance has changed gather information more quickly and detect changes in the variance more quickly (on average) than fixed sampling rate procedures. Several variable sampling rate procedures for detecting increases in the process variance will be developed and compared with fixed sampling rate methods. A control chart for the variance is usually used with a separate control chart for the mean so that changes in the average level of the process and the variability of the process can both be detected. A simple method for applying variable sampling rate techniques to dual monitoring of mean and variance will be developed. This control chart procedure increases the sampling rate when there is evidence the mean or variance has changed so that changes in either parameter that will negatively impact product quality will be detected quickly.
Ph. D.

The purpose of this study is to investigate the pricing of variable annuity embedded derivatives in a Lévy process setting. This is one of the practical issues that continues to face life insurers in the management of derivatives embedded within these products. It also addresses how such providers can protect themselves against adverse scenarios through a hedging framework built from the pricing framework. The aim is to comparatively consider the price differentials of a life insurer that prices its variable annuity guarantees under the more actuarially accepted regime-switching framework versus the use of a Lévy framework. The framework should address the inadequacies of conventional deterministic pricing approaches used by life insurers given the increasing complexity of the option-like products sold. The study applies finance models in the insurance context given the similarities in payoff structure of the products offered while taking into account the differences that may exist. The underlying Lévy process used in this study is the Variance-Gamma (VG) process. This process is useful in option pricing given its ability to model higher moments, skewness and kurtosis, and also incorporate stochastic volatility. The research results compare well with the regime-switching framework besides the added merit in the use of a more refined model for the underlying that captures most of the observed market dynamics.
Dissertation (MSc)--University of Pretoria, 2014.
tm2015
Mathematics and Applied Mathematics
MSc
Unrestricted

Hidden Variable is a novel that blends linear storytelling with the novel-in-stories form. It poses questions about the nature of identity as well as the feasibility of personal power, particularly with respect to disorders of the mind. Darla Pierson, the novel's protagonist, is a woman in crisis. She is steeped in self-loathing brought on by the knowledge that she has, in effect, become her dead father—a genius with an epic libido, habitually using and discarding people. Her father has another habit that Darla doesn't share: being struck by lightning. After the second strike kills him, Darla makes a conscious attempt to recreate herself. But soon the new Darla sinks into depression, and her act begins to crumble, damaging her and those around her. Throughout the years, she and her family members experience periodic clashes with nature, never fully realizing that sometimes the most powerful, most devastating opponent comes not from without, but within.
M.F.A.
Masters
English
Arts and Humanities
Creative Writing

There are many numerical methods to study the quantum mechanical three-body scattering system using the Schrodinger equation. Traditionally, a partial-wave decomposition of the total wave function is carried out first, allowing the scattering system to be solved one partial wave at a time. This is convenient when the interaction is central, causing the total angular momentum to be conserved during the collision process. This is not possible in the presence of a non-central interaction such as a laser field, where the total angular momentum is not conserved during the collision process. The Discrete Variable Representation is a new method for solving the quantum-mechanical three-body scattering problem to obtain the total cross section. The implementation of this new method for the two-body problem has been successfully applied to real systems. The extension to the three-body problem is the next logical step. For this thesis bipolar spherical harmonics are used in the implementation of the three-body Discrete Variable Representation. This Discrete Variable Representation is capable of working with any combination of interactions, including non-central interactions. The total cross section computation for a three-particle elastic-scattering numerical example is used to illustrate the potential of this Discrete Variable Representation method. The three-particle system consists of a positron scattering against a ground state hydrogen atom (an electron bound to a proton).

Semanticists, philosophers and logicians have standardly analyzed a range of natural language expressions on the model of the variables of formal languages. This dissertation explores variable- based semantic theories of pronounsand proper names. The first two chapters argue that a variable-based, presuppositional semantics for pronouns proposed by Cooper (1979, 1983) resolves an apparent trilemma arising from the conjunction of three plausible commitments concerning the semantics of pronouns: that some anaphoric pronouns with quantifier antecedents are bound variables, that referential pronouns have context-independent meanings, and that the relation between bound and referential pronouns is not ambiguity or homonymy. The first chapter argues that Cooper’s semantics is descriptively and empirically superior to alternative theories, including Kaplan’s account, which does not resolve the trilemma. The second addresses an important objection to the view that bound and referential pronouns make the same semantic contribution, involving cases where bound pronouns do not appear to trigger semantic presuppositions. I argue that this appearance is misleading: bound pronouns do trigger semantic presuppositions and have the same (Cooper-style) denotations as referential pronouns. The third chapter addresses the phenomenon of non c-command or ‘donkey’ anaphora. These anaphors appear to require a departure from Cooper’s semantics and, more generally, from the view that anaphoric pronouns correspond to (classical) bound variables. I consider D-type accounts of donkey anaphora and argue that these accounts must be revised in ways that bring the denotations of donkey anaphors closer to those of ordinary bound and referential pronouns. The last chapter asks whether proper names require a variable-based semantics. I consider a pair of recent anaphoric theories of proper names, according to which proper names have anaphoric uses and are thus better modeled as variables. I argue that there are important reasons to reject a variable-based model for proper names, in contrast with pronouns.

There exists many astronomical objects that vary in brightness. Objects such as variable stars like the Cepheids that periodically expands and contracts their outer layers, or the active galactic nuclei (AGN) where accretion of matter into a black hole generates a often varying brightness. Several candidates for being such variable objects have been identified as a result of the Vanishing and Appearing Stuff during a Century of Observations (VASCO) project. These candidates were then narrowed down to a handful that showed variability towards the infrared part of the spectrum. This bachelor’s thesis then aims to look further into these candidates using various databases and catalogues taking data from several sky surveys (SDSS, 2MASS etc). This is done to get better overview of the objects lightcurve over a bigger part of the spectrum, to establish whether the variability is real or a result from errors and to form a hypothesis of what kind of objects they could be. The result obtained from the data from the surveys points towards all the objects being real variable objects. The hypothesis is that all the objects are AGN’s that vary in brightness.
Det existerar många olika astronomiska objekt som varierar i ljusstyrka. Allt från variabla stjärnor som Cepheiderna som periodvis expanderar och kontraherar dess yttre skikt, till aktiva galaxkärnor där ackretion av materia in i ett svart hål genererar en ofta varierande ljusstyrka. Ett flertal kandidater för just sådana varierande objekt har identifierats som ett resultat av VASCO projektet. Dessa kandidater har sedan skalats ner till en handfull mängd kandidater som visade variation mot den infraröda delen av spektrumet. Detta kandidatarbete siktar på att vidare undersöka dessa kandidater genom att använda diverse astronomiska databaser och kataloger för att få data från flera kartläggningsprojekt (t.ex. SDSS, 2MASS etc). Detta är gjort för att få en bättre överblick över objektens ljuskurvor över en större del av spektrumet, att fastställa ifall objekten är riktiga variabla objekt eller uppstått på grund av diverse fel, samt att framställa en hypotes för vad det är för typ av objekt de kan vara. Resultaten från undersökningarna pekar på att alla objekten är riktiga variabla objekt. Hypotesen är att alla av objekten är aktiva galaxkärnor som varierar i ljusstyrka.

Research shows the environment affects the user both psychologically and physiologically. Teachers often alter their classrooms in order to effect these changes, for instance, by adding elements for warmth, offsetting harsh lighting, or using found objects to mark and divide space. Research and observed use communicate a need for a planned variety of spaces in function and in character. The project is a redesign of Therrell High School in southwest Atlanta seeking to complement the new movement to small learning communities, which embeds programmatic variety in the public school system. Therrell is divided into three small thematically described academies, which effectively function as three separate high schools: the School of Science, Technology, Engineering, and Math; the School of Health Sciences and Research; the School of Law, Government, and Public Policy. The design focuses on the necessary variability of spaces inherent in small learning communities. These spaces seek to address the varied instructional strategies that accompany the thematic endeavors of each school and introduce variety in architectural character, thus accommodating variable needs and desires of students. The focus of the project is on the student and the nature of space that fosters positive experiences as well as positive learning outcomes.

Spécificité légale, introduite dans notre droit positif par la loi du 24 juillet 1867, la variabilité du capital social demeure encore de nos jours trop méconnue et devrait, de fait, être érigée au rang des curiosités juridiques. On ne saurait objecter pareil constat en ce que le législateur lui-même ne semble pas lui porter un incommensurable intérêt. En effet, en ce que la variabilité du capital ne résulte que de l’adoption, par une forme sociale de droit commun, d’une simple clause statutaire, ce dernier n’a semble-t-il pas jugé indispensable d’édicter un régime juridique précis et autonome en sa faveur. Aussi, devrait-on y voir ici une renonciation certaine du législateur à la création d’une nouvelle forme sociale ne faisant, en conséquence, que renforcer la singularité dont elle fait l’objet. Toujours est-il que s’arrêter à une telle acception serait réducteur en ce que cette approche desservirait inexorablement la spécificité prévue aux articles L. 231-1 à L. 231-8 du Code de commerce et notamment quant aux nombreuses possibilités qu’elle octroie tant à la société se dotant de la spécificité légale qu’aux associés la composant
Legal specificity, introduced into our substantive law in July 24th, 1867, the variability of the share capital is still too unknown even today and should in fact be raised to the ranks of legal curiosities. We could not object such report in the fact that the legislator does not seem himself to carry him immense one interest. Indeed, the fact that the variability of the capital only results from the adoption, by a social form of common law, of a simple statutory clause, the latter does not see it necessary to enact a specific and independent legal regime in its favour. Also, should the legislator object to the creation of a new social form, it will consequently only reinforce the peculiarity of such objection. The fact remains that to stop such acceptance would be reducing in the fact that this approach would serve inexorably the specificity outlined in articles L. 231-1 in L. 231-8 of the commercial law in particular as for the numerous possibilities that she grants as long to the company being equipped with the legal specificity that to the partners making up her

The prevalence of extreme outliers in many regression data sets has led to the development of robust methods that can handle these observations. While much attention has been placed on the problem of estimating regression coefficients in the presence of outliers, few methods address variable selection. We develop and study robust versions of the forward selection algorithm, one of the most popular standard variable selection techniques. Specifically we modify the VAMS procedure, a version of forward selection tuned to control the false selection rate, to simultaneously select variables and eliminate outliers. In an alternative approach, robust versions of the forward selection algorithm are developed using the robust forward addition sequence associated with the generalized score statistic. Combining the robust forward addition sequence with robust versions of BIC and the VAMS procedure, a final model is obtained. Monte Carlo simulation compares these robust methods to current robust methods like the LSA and LAD-LASSO. Further simulation investigates the relationship between the breakdown point of the estimation methods central to each procedure and the breakdown point of the final variable selection method.

On considere la quadrique complexe q#n de dimension n qui est aussi la grassmannienne reelle des 2-plans orientes de r#n#+#2. Gasqui et goldschmidt ont montre que pour n 4 la quadrique q#n possede la propriete de rigidite infinitesimale : les seules 2-formes symetriques a energie nulle sont les derivees de lie de la metrique canonique. Les formes paires (resp. Impaires) sur la quadrique sont celles qui sont invariantes (resp. Anti-invariantes) par l'involution correspondant au changement d'orientation. Gasqui et goldschmidt ont aussi prouve que sur q#3, toute 2-forme symetrique a energie nulle et paire est une derivee de lie de la metrique. On montre que cette propriete persiste pour les formes impaires a energie nulle de q#3, ce qui etablit la rigidite infinitesimale de cet espace et regle definitivement la question de rigidite infinitesimale pour la famille des quadriques complexes non degenerees.

We propose to extend the use of penalized likelihood based variable selection methods to hierarchical generalized linear models (HGLMs) for jointly modellingboth the mean and variance structures. We are interested in applying these newmethods on multilevel structured data, hence we assume a two-level hierarchical structure, with subjects nested within groups. We consider a generalized linearmixed model (GLMM) for the mean, with a structured dispersion in the formof a generalized linear model (GLM). In the first instance, we model the varianceof the random effects which are present in the mean model, or in otherwords the variation between groups (between-level variation). In the second scenario,we model the dispersion parameter associated with the conditional varianceof the response, which could also be thought of as the variation betweensubjects (within-level variation). To do variable selection, we use the smoothlyclipped absolute deviation (SCAD) penalty, a penalized likelihood variable selectionmethod, which shrinks the coefficients of redundant variables to 0 and at thesame time estimates the coefficients of the remaining important covariates. Ourmethods are likelihood based and so in order to estimate the fixed effects in ourmodels, we apply iterative procedures such as the Newton-Raphson method, inthe form of the LQA algorithm proposed by Fan and Li (2001). We carry out simulationstudies for both the joint models for the mean and variance of the randomeffects, as well as the joint models for the mean and dispersion of the response,to assess the performance of our new procedures against a similar process whichexcludes variable selection. The results show that our method increases both theaccuracy and efficiency of the resulting penalized MLEs and has 100% successrate in identifying the zero and non-zero components over 100 simulations. Forthe main real data analysis, we use the Health Survey for England (HSE) 2004dataset. We investigate how obesity is linked to several factors such as smoking,drinking, exercise, long-standing illness, to name a few. We also discover whetherthere is variation in obesity between individuals and between households of individuals,as well as test whether that variation depends on some of the factorsaffecting obesity itself.

The estimation of latent variable models with ordinal and continuous, or ranking variables is the research focus of this thesis. The existing estimation methods are discussed and a composite likelihood approach is developed. The main advantages of the new method are its low computational complexity which remains unchanged regardless of the model size, and that it yields an asymptotically unbiased, consistent, and normally distributed estimator. The thesis consists of four papers. The first one investigates the two main formulations of the unrestricted Thurstonian model for ranking data along with the corresponding identification constraints. It is found that the extra identifications constraints required in one of them lead to unreliable estimates unless the constraints coincide with the true values of the fixed parameters. In the second paper, a pairwise likelihood (PL) estimation is developed for factor analysis models with ordinal variables. The performance of PL is studied in terms of bias and mean squared error (MSE) and compared with that of the conventional estimation methods via a simulation study and through some real data examples. It is found that the PL estimates and standard errors have very small bias and MSE both decreasing with the sample size, and that the method is competitive to the conventional ones. The results of the first two papers lead to the next one where PL estimation is adjusted to the unrestricted Thurstonian ranking model. As before, the performance of the proposed approach is studied through a simulation study with respect to relative bias and relative MSE and in comparison with the conventional estimation methods. The conclusions are similar to those of the second paper. The last paper extends the PL estimation to the whole structural equation modeling framework where data may include both ordinal and continuous variables as well as covariates. The approach is demonstrated through an example run in R software. The code used has been incorporated in the R package lavaan (version 0.5-11).

Recently, covering arrays have been the subject of considerable research attention as they hold both theoretical interest and practical importance due to their applications to testing. In this thesis, we perform the first comprehensive study of a generalization of covering arrays called variable strength covering arrays, where we dictate the interactions to be covered in the array by modeling them as facets of an abstract simplicial complex. We outline the necessary background in the theory of hypergraphs, combinatorial testing, and design theory that is relevant to the study of variable strength covering arrays. We then approach questions that arise in variable strength covering arrays in a number of ways. We demonstrate their connections to hypergraph homomorphisms, and explore the properties of a particular family of abstract simplicial complexes, the qualitative independence hypergraphs. These hypergraphs are tightly linked to variable strength covering arrays, and we determine and identify several of their important properties and subhypergraphs. We give a detailed study of constructions for variable strength covering arrays, and provide several operations and divide-and-conquer techniques that can be used in building them. In addition, we give a construction using linear feedback shift registers from primitive polynomials of degree 3 over arbitrary finite fields to find variable strength covering arrays, which we extend to strength-3 covering arrays whose sizes are smaller than many of the best known sizes of covering arrays. We then give an algorithm for creating variable strength covering arrays over arbitrary abstract simplicial complexes, which builds the arrays one row at a time, using a density concept to guarantee that the size of the resultant array is asymptotic in the logarithm of the number of facets in the abstact simplicial complex. This algorithm is of immediate practical importance, as it can be used to create test suites for combinatorial testing. Finally, we use the Lovasz Local Lemma to nonconstructively determine upper bounds on the sizes of arrays for a number of different families of hypergraphs. We lay out a framework that can be used for many hypergraphs, and then discuss possible strategies that can be taken in asymmetric problems.

Thesis (S.M.)--Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and the Woods Hole Oceanographic Institution), 2009.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 111-112).
Over the past 20 years, underwater vehicle technology has undergone drastic improvements, and vehicles are quickly gaining popularity as a tool for numerous oceanographic tasks. Systems used on the vehicle to alter buoyancy, or variable buoyancy (VB) systems, have seen only minor improvements during the same time period. Though current VB systems are extremely robust, their lack of performance has become a hinderance to the advancement of vehicle capabilities. This thesis first explores the current status of VB systems, then creates a model of each system to determine performance. Second, in order to quantitatively compare fundamentally different VB systems, two metrics, [beta]m and [beta]vol, are developed and applied to current systems. By determining the ratio of performance to size, these metrics give engineers a tool to aid VB system development. Finally, the fundamental challenges in developing more advanced VB systems are explored, and a couple of technologies are investigated for their potential use in new systems.
by Harold Franklin Jensen III.
S.M.

Doctor of Philosophy
Department of Mathematics
Charles N. Moore
The reader will recall that the classical $p$-Lebesgue spaces are those functions defined on a measure space $(X, \mu)$ whose modulus raised to the $p^{\rm th}$ power is integrable. This condition gives many quantitative measurements on the growth of the function, both locally and globally. Results and applications pertaining to such functions are ubiquitous. That said, the constancy of the exponent $p$ when computing $\int_X \abs{f}^p d\mu$ is limiting in the sense that it is intrinsically uniform in scope. Speaking loosely, there are instances in which one is concerned with the $p$ growth of a function in a region $A$ and its $q$ growth in another region $B$. As such, allowing the exponent to vary from region to region (or point to point) is a reasonable course of action. The task of developing such a theory was first taken up by Wladyslaw Orlicz in the 1930's. The theory he developed, of which variable Lebesgue spaces are a special case, was only intermittently studied and analyzed through the end of the century. However, at the turn of the millennium, several results and their applications sparked a focused and intense interest in variable $L^p$ spaces. It was found that with very few assumptions on the exponent function many of the classical structure and density theorems are valid in the variable-exponent case. Somewhat surprisingly, these results were largely proved using intuitive adaptations of well-established methods. In fact, this methodology set the tone for the first part of the decade, where a multitude of ``affirmative'' results emerged. While the successful adaptation of classical results persists to a large extent today, there are nontrivial situations in which one cannot hope to extend a result known for constant $L^p$. In this paper, we wish to explore both of the aforementioned directions of research. We will first establish the fundamentals for variable $L^p$. Afterwards, we will apply these fundamentals to some classical $L^p$ results that have been extended to the variable setting. We will conclude by shifting our attention to Littlewood-Paley theory, where we will furnish an example for which it is impossible to extend constant-exponent results to the variable case.

International Telemetering Conference Proceedings / October 17-20, 1994 / Town & Country Hotel and Conference Center, San Diego, California
This paper describes a ferrite antenna that can produce any polarization on the Poincaré sphere over the frequency range of 9.0 to 11.4 GHz by utilizing Faraday rotation and a quarter-wavelength phase shifter. All possible polarizations of the electromagnetic wave are achievable with this antenna which includes linear, circular and elliptical polarizations. Any tilt angle of elliptical polarization and any orientation of the linear polarization can be achieved as well. The polarization of the ferrite antenna can be electronically switched to a different polarization instantly without the use of moving parts. An automatic data acquisition system was designed and built to fully analyze the antenna' s characteristics.

Master of Agribusiness
Department of Agricultural Economics
Jeffery R. Williams
Production agriculture is constantly evolving to become more efficient and productive. Crop residue serves as a valuable source of nutrients for the soil, but it is increasingly abundant with today’s enhanced crop genetics. If new technology can effectively provide a way to micro-manage crop residue levels within a field, the benefits will go beyond soil health. Surplus crop residue can be collected for secondary income while leaving the optimum amounts in the field to maintain the environment and soil health as well as promote future crop growth. The main objective of this study is to create a budget model that will determine the economic impact of crop residue removal on a controlled basis. The goals are to determine crop residue removal practices that are sustainable for the long-term, while also enhancing soil quality and increasing grain yield in future years. A sub-objective is to build a business case for producers to invest in variable crop residue management. The hypothesis presented in this study is that the increased complexity and price of a variable rate system is offset by more supplemental profits, increased crop yields, and better management of soil health and nutrients. The negative perceptions of crop residue removal include the fear of soil erosion or loss of soil organic matter. By developing a budget model that is easy to use, takes advantage of existing field data for inputs, and allows producers the ability to look at their operations on a sub-field level, this study aims to provide the necessary motivation to invest in new technology that will increase their productivity. By entering their site-specific crop residue return rate data into a budget model, along with prices and costs related to combine and auxiliary equipment, corn and corn stover, transportation and logistics, and nutrient replacement, they will come up with a return per acre for both constant rate and variable rate collection. The budget model determines whether it is economically viable to harvest crop residue from a continuous corn rotation at a variable rate across a field, rather than at a constant rate, using a producer’s own specific field data. To validate the concept, data from a joint study between John Deere and Iowa State is entered into the model. Prescriptions for corn stover return rates are provided from the study for pre-defined grid areas. Prescriptions are derived from a combination of data including grain yield, soil loss due to wind and water erosion, climate, topography, and soil sample data at time of planting (Nelson, et al. 2004). The average corn stover removal percentage was less for variable rate collection than constant rate collection, 26.05% to 31.85%. However, the assumption that grain yield and corn stover yield are positively correlated did not prove to be true in this case study. The variable rate plots had a lower average grain yield of 158.84 bushel/acre, compared to 160.46 for the constant rate plots, but they had more total corn stover available and therefore a higher return rate of 3.70 tons/acre, compared to 3.05 for the constant rate plots. This case study illustrates that less corn stover can be returned to the field through constant or variable rate collection while sustaining higher grain yields than a conventional harvest that would return all of the corn stover to the field. This case study demonstrates that variable rate collection can be more expensive than constant rate, but not in every situation. Every unique field site will require a specific crop residue management recommendation that is determined by both economic and environmental factors.

In this thesis, we introduce Irregular Variable Length Coding (IrVLC) and investigate its applications, characteristics and performance in the context of digital multimedia broadcast telecommunications. During IrVLC encoding, the multimedia signal is represented using a sequence of concatenated binary codewords. These are selected from a codebook, comprising a number of codewords, which, in turn, comprise various numbers of bits. However, during IrVLC encoding, the multimedia signal is decomposed into particular fractions, each of which is represented using a different codebook. This is in contrast to regular Variable Length Coding (VLC), in which the entire multimedia signal is encoded using the same codebook. The application of IrVLCs to joint source and channel coding is investigated in the context of a video transmission scheme. Our novel video codec represents the video signal using tessellations of Variable-Dimension Vector Quantisation (VDVQ) tiles. These are selected from a codebook, comprising a number of tiles having various dimensions. The selected tessellation of VDVQ tiles is signalled using a corresponding sequence of concatenated codewords from a Variable Length Error Correction (VLEC) codebook. This VLEC codebook represents a specific joint source and channel coding case of VLCs, which facilitates both compression and error correction. However, during video encoding, only particular combinations of the VDVQ tiles will perfectly tessellate, owing to their various dimensions. As a result, only particular sub-sets of the VDVQ codebook and, hence, of the VLEC codebook may be employed to convey particular fractions of the video signal. Therefore, our novel video codec can be said to employ IrVLCs. The employment of IrVLCs to facilitate Unequal Error Protection (UEP) is also demonstrated. This may be applied when various fractions of the source signal have different error sensitivities, as is typical in audio, speech, image and video signals, for example. Here, different VLEC codebooks having appropriately selected error correction capabilities may be employed to encode the particular fractions of the source signal. This approach may be expected to yield a higher reconstruction quality than equal protection in cases where the various fractions of the source signal have different error sensitivities. Finally, this thesis investigates the application of IrVLCs to near-capacity operation using EXtrinsic Information Transfer (EXIT) chart analysis. Here, a number of component VLEC codebooks having different inverted EXIT functions are employed to encode particular fractions of the source symbol frame. We show that the composite inverted IrVLC EXIT function may be obtained as a weighted average of the inverted component VLC EXIT functions. Additionally, EXIT chart matching is employed to shape the inverted IrVLC EXIT function to match the EXIT function of a serially concatenated inner channel code, creating a narrow but still open EXIT chart tunnel. In this way, iterative decoding convergence to an infinitesimally low probability of error is facilitated at near-capacity channel SNRs.

The primary aims of this thesis, is to provide a body of knowledge on variable structure system theory and to apply the developed design concepts to control practical systems. It introduces the concept of a structure. The main aim in designing variable structure controllers, is to synthesize a variable structure system from two or more single structure systems, in such a way that the ensuing system out-performs its component structures. When a sliding mode is defined, the ensuing closed loop behaviour of the system is invariant to plant parameter changes and external disturbances. A variable structure controller was designed for a servo motor and successfully applied to the system. In practice, the phase plane representative point does not slide at infinite frequency with infinitesimal amplitude along the switching surface(s). Thus, the concept of a quasi-sliding regime was introduced. For high performance system specifications, the phase plane representative point could cycle about the origin. In some instances, sliding could be lost. For high speed applications, a novel design modification ensured that the system did not lose sliding. In addition, the controller could track a rapidly changing set point. Successful results support the developed theory.

Dèveloppement d'un modèle de loi de comportement élastoviscoplastique a température variable pour la prévision du comportement des structures métalliques soumis a des chargements thermomécaniques variables. Identification de ce modèle sur le superalliage inco718 soumis a des essais uniaxiaux isothermes entre 20 et 800c

This thesis presents inference for the multiple linear regression model Y = beta_1 x_1 + ... + beta_p x_p + e after model or variable selection, including prediction intervals for a future value of the response variable Y_f, and testing hypotheses with the bootstrap. If n is the sample size, most results are for n/p large, but prediction intervals are developed that may increase in average length slowly as p increases for fixed n if the model is sparse: k predictors have nonzero coefficients beta_i where n/k is large.

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Mecânica, Florianópolis, 2016.
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Os motores de taxa de compressão variável (VCR) têm se tornado uma oportunidade para a adequação frente às novas leis de redução de consumo de combustível e emissão de poluentes. Acredita-se que os motores VCR são capazes de unir tanto eficiência quanto alto desempenho. É objetivo desta pesquisa investigar as oportunidades de desenvolvimentos futuros no âmbito dos motores de taxa de compressão variável. A seguir, um breve resumo do trabalho e suas seções são apresentadas. Introdução: A introdução tem por objetivo apresentar a tecnologia de motores de taxa de compressão variável, suas características e justificativas para a pesquisa. Além disso, discutem-se os objetivos, as delimitações do trabalho e, brevemente, a metodologia adotada. Revisão de Bibliografia: Neste capítulo apresenta-se a metodologia de desenvolvimento de produtos conhecida por modelo PRODIP (BACK et al.,2008). Todas as etapas e características são discutidas e criticadas em relação ao trabalho que se almeja desenvolver. Metodologias de projeto de mecanismos também são apresentadas focando-se nos trabalhos de Yan (1999) e Tsai (2000). Além disso, discute-se a respeito da metodologia proposta por Murai (2013), a qual foi desenvolvida junto ao Laboratório de Robótica da UFSC e tem se mostrado muito importante para o desenvolvimento de novos mecanismos. Por último, uma metodologia de pesquisa de patentes também é apresentada. Esta metodologia também foi desenvolvida junto ao Laboratório de Robótica da UFSC e está de acordo com os escritórios internacionais de patentes. Juntamente à metodologia de busca de patentes, encontra-se uma breve explicação sobre a estrutura de uma patente e características gerais de uma pesquisa de patentes. Motores de Taxa de Compressão Variável: O terceiro capítulo é dedicado ao levantamento de estado da arte dos motores VCR. Primeiramente mostra-se uma classificação de motores reconfiguráveis e o enquadramentos dos motores VCR nessa classificação. Então, aborda-se a literatura (livros e artigos) para investigar testes experimentais e simulações a respeito do tema além de classificações anteriores deste tipo de motor. O levantamento de estado da arte continua analisando produtos lançados no mercado e as principais empresas por trás desta tecnologia. Por último os resultados da pesquisa de patentes são mostrados. Foram analisadas 1163 patentes resultando em 127 conceitos diferentes de motores VCR. Baseando-se nesta pesquisa e a comparando com outros autores, este trabalho propõe uma nova classificação para os motores VCR, os quais podem ser divididos em 7 grandes classes. As cadeias cinemáticas de todas as classes de motores VCR são analisadas com o objetivo de investigar suas respectivas características estruturais e funcionais. Além disso, a reconfigurabilidade em motores VCR é discutida. Desenvolvimento de Motores VCR: No quarto capítulo são definidos os requisitos estruturais e funcionais por meio do levantamento do estado da arte e por comparação com os trabalhos de Freudenstein and Maki (1983) e Tsai (2000). Os requisitos são então utilizados para enumerar e selecionar cadeias cinemáticas com potencial de se desenvolver motores de taxa de compressão variável. Por fim, discute-se o potencial para inovação destes motores. Estudos de Caso: Neste capítulo, três cadeias cinemáticas em potencial definidas no capítulo anterior são estudadas com o objetivo de exemplificar o desenvolvimento de novos motores VCR de acordo com a abordagem sistemática do Laboratório de Robótica da UFSC.

Abstract : The variable compression ratio (VCR) engine has become an opportunity to overcome the new consumption and emissions laws. Researchers believe that the VCR engine can unite both efficiency and performance. This research aims to investigate the opportunity of further developments within the VCR field. In order to accomplish that, a review of design methodology is provided. First an overview of product development methodology is presented focusing on the PRODIP Model (BACK et al., 2008). Then, it is discussed the mechanism design methodologies such as Yan (1999) and Tsai (2000). Also, the methodology proposed by Murai (2013) is applied. In addition, a patent survey methodology is provided. A state of the art survey analysed the information available in the literature, the market and the patents database. The patent survey was conducted analysing 1163 patents and resulting in 127 different VCR engine designs. Based on that survey and comparing with several authors, this research proposes an enhanced classification of the VCR engines, which contains 7 major classes. The kinematic chains from all classes of VCR engines are analysed in order to investigate the structural and functional characteristics which are compared with previous works from Freudenstein and Maki (1983) and Tsai (2000). This information is used to discuss the reconfigurability of VCR engines, to define the proper design requirements and to generate new potential kinematic chains for innovative designs of VCR engines. At last, three case studies are presented with the objective of exemplifying the development of novel VCR engines using the UFSC Robotics Lab systematic approach.

Latent variable model is a common probabilistic framework which aims to estimate the hidden states of observations. More specifically, the hidden states can be the position of a robot, the low dimensional representation of an observation. Meanwhile, various latent variable models have been explored, such as hidden Markov models (HMM), Gaussian mixture model (GMM), Bayesian Gaussian process latent variable model (BGPLVM), etc. Moreover, these latent variable models have been successfully applied to a wide range of fields, such as robotic navigation, image and video compression, natural language processing. So as to make the learning of latent variable more efficient and robust, some approaches seek to integrate latent variables with related priors. For instance, the dynamic prior can be incorporated so that the learned latent variables take into account the time sequence. Besides, some methods introduce inducing points as a small set representing the large size latent variable to enhance the optimization speed of the model. Though those priors are effective to facilitate the robustness of the latent variable models, the learned latent variables are inclined to be dense rather than diverse. This is to say that there are significant overlapping between the generated latent variables. Consequently, the latent variable model will be ambiguous after optimization. Clearly, a proper diversity prior play a pivotal role in having latent variables capture more diverse features of the observations data. In this thesis, we propose diversified latent variable models incorporated by different types of diversity priors, such as single/dual diversity encouraging prior, multi-layered DPP prior, shared diversity prior. Furthermore, we also illustrate how to formulate the diversity priors in different latent variable models and perform learning, inference on the reformulated latent variable models.

Dans un anneau de polynômes à n indéterminées A[n]=A[y1,. . . ,yn] à coefficients dans un anneau commutatif unitaire A on dit qu'un polynôme p=p(y1,. . . ,yn) est une variable ou A-variable s'il existe un (A-)automorphisme α de A[n] tel que p=α(y1). Dans cette thèse, on donne une construction assez générale de variables de A\n par conjugaison d'automorphismes de A\n avec des automorphismes de (QuotA)\n. On définit les variables résiduelles qui désigne des polynômes qui sont des variables modulo \Max pour tout idéal ma\-xi\-mal \Max de A, en particulier, lorsque A=\C\x=\C[x1\trxk], on parle de variables \xb-résiduelles. Bien entendu les variables sont des variables résiduelles mais la réciproque est-elle vraie? On montre, grâce à un résultat de Daigle et Freudenburg, que les variables \xb-résiduelles de \C\x[y,z] sont bien des \xb-variables. Les variables interviennent également dans les problèmes d'hyperplans plongés d'Abhyankar-Sathaye; un polynôme p de A\n est un (A-)hyperplan si le quotient de A\n par l'idéal principal engendré par p, (p) est isomorphe à A[n−1]. Les variables sont des hyperplans et on étudie là encore la réciproque. Dans l'article co-écrit avec M. M. Kaliman et Zaidenberg qui fait partie de cette thèse on étudie les hyperplans de \C[x,y,z,u] de la forme p=f(x,y)u+g(x,y,z). À un changement des variables x et y près on montre que ces hyperplans sont aussi des variables x-résiduelles et partant de là on montre que ce sont des x−plans (i. E. A-plans où A=\C[x]) de \Cx[y,z,u] et même qu'il existe un automorphisme α de A[y,z,u,v] tel que α((p,v))=(y,v). Dans certains cas, par exemple lorsque g est de degré un en z, on parvient à prouver que ce sont des x-variables. On donne aussi une généralisation d'un théorème de Wright en montrant qu'un x-plan de la forme f(x,y,z)un+g(x,y,z) où n≥2 est une x-variable. Cependant le problème reste irrésolu concernant, par exemple, le polynôme y+x[xz+y(yu+z2)] qui, bien qu'étant un x-plan et une variable x-résiduelle ne semble pas être une x-variable
In a polynomial ring in n variables A\n=A[y1\tryn] with coefficients in a commutative ring A, a polynomial p=p(y1\tryn) is called a variable or an A-variable if there exists an (A-)automorphism α of A\n such that p=α(y1). In this thesis we give a quite general construction of variables of A\n conjugating automorphisms of A\n with automorphisms of (\QuotA)\n. We define residual variables which refer to polynomials that are variables modulo \Max for every maximal ideal \Max of A; in particular, when A=\C\x=\C[x1\trxk], one says \xb-residual variables. Of course, variables are residual variables, but what about the inverse implication? Using a Daigle and Freudenburg's result, we show that \xb-residual variables of \C\x[y,z] are actually \xb-variables. Variables naturally appear in Abhyankar-Sathaye's embedding problem. A polynomial p in A\n is called an (A-)hyperplane if the quotient of A\n by the principal ideal (p) generated by p is isomorphic to A[n−1]. Variables are hyperplanes and the problem consists in studying the inverse implication. In an article, written jointly with M. Kaliman and M. Zaidenberg and which is the last part of this thesis, we study hyperplanes of \C[x,y,z,u] of the form p=f(x,y)u+g(x,y,z). Up to a change of the variables x and y we show that those hyperplanes are also x-residual variables. Moreover we prove that they are x-planes of \Cx[y,z,u] and, that there exists an automorphism α of A[y,z,u,v] such that α((p,v))=(y,v). In some cases, for example when g has degree one in z, we manage to prove that they are x-variables. We also give a generalization of Wright's theorem showing that an x-plane of the form f(x,y,z)un+g(x,y,z), where n≥2, is an x-variable. However the problem remains unsolved when we consider, for instance, the polynomial y+x[xz+y(yu+z2)] which, although being an x-plane and an x-residual variable, does not seem to be an x-variable

Nous proposons dans cette thèse la méthode STREE de construction d'arbres de décision avec des données symboliques. Ce type de données permet de caractériser des individus de niveau supérieur qui peuvent être des classes ou catégories d’individus ou des concepts au sens des treillis de Galois. Les valeurs des variables, appelées variables symboliques, peuvent être des ensembles, des intervalles ou des histogrammes. Le critère de partitionnement récursif est une combinaison d'un critère par rapport aux variables explicatives et d'un critère par rapport à la variable à expliquer. Le premier critère est la variation de la variance des variables explicatives. Quand il est appliqué seul, STREE correspond à une méthode descendante de classification non supervisée. Le second critère permet de construire un arbre de décision. Il s'agit de la variation de l'indice de Gini si la variable à expliquer est nominale et de la variation de la variance si la variable à expliquer est continue ou bien est une variable symbolique. Les données classiques sont un cas particulier de données symboliques sur lesquelles STREE peut aussi obtenir de bons résultats. Il en ressort de bonnes performances sur plusieurs jeux de données UCI par rapport à des méthodes classiques de Data Mining telles que CART, C4.5, Naive Bayes, KNN, MLP et SVM. STREE permet également la construction d'ensembles d'arbres de décision symboliques soit par bagging soit par boosting. L'utilisation de tels ensembles a pour but de pallier les insuffisances liées aux arbres de décisions eux-mêmes et d'obtenir une décision finale qui est en principe plus fiable que celle obtenue à partir d'un arbre unique
In this thesis, we propose the STREE methodology for the construction of decision trees with symbolic data. This data type allows us to characterize individuals of higher levels which may be classes or categories of individuals or concepts within the meaning of the Galois lattice. The values of the variables, called symbolic variables, may be sets, intervals or histograms. The criterion of recursive partitioning is a combination of a criterion related to the explanatory variables and a criterion related to the dependant variable. The first criterion is the variation of the variance of the explanatory variables. When it is applied alone, STREE acts as a top-down clustering methodology. The second criterion enables us to build a decision tree. This criteron is expressed as the variation of the Gini index if the dependant variable is nominal, and as the variation of the variance if thedependant variable is continuous or is a symbolic variable. Conventional data are a special case of symbolic data on which STREE can also get good results. It has performed well on multiple sets of UCI data compared to conventional methodologies of Data Mining such as CART, C4.5, Naive Bayes, KNN, MLP and SVM. The STREE methodology also allows for the construction of ensembles of symbolic decision trees either by bagging or by boosting. The use of such ensembles is designed to overcome shortcomings related to the decisions trees themselves and to obtain a finaldecision that is in principle more reliable than that obtained from a single tree

This thesis consists of two parts. The first part reviews a Variable Search, a variable selection procedure for mean modeling. The second part deals with variance modeling for robust parameter design in computer experiments. In the first chapter of my thesis, Variable Search (VS) technique developed by Shainin (1988) is reviewed. VS has received quite a bit of attention from experimenters in industry. It uses the experimenters' knowledge about the process, in terms of good and bad settings and their importance. In this technique, a few experiments are conducted first at the best and worst settings of the variables to ascertain that they are indeed different from each other. Experiments are then conducted sequentially in two stages, namely swapping and capping, to determine the significance of variables, one at a time. Finally after all the significant variables have been identified, the model is fit and the best settings are determined. The VS technique has not been analyzed thoroughly. In this report, we analyze each stage of the method mathematically. Each stage is formulated as a hypothesis test, and its performance expressed in terms of the model parameters. The performance of the VS technique is expressed as a function of the performances in each stage. Based on this, it is possible to compare its performance with the traditional techniques. The second and third chapters of my thesis deal with variance modeling for robust parameter design in computer experiments. Computer experiments based on engineering models might be used to explore process behavior if physical experiments (e.g. fabrication of nanoparticles) are costly or time consuming. Robust parameter design (RPD) is a key technique to improve process repeatability. Absence of replicates in computer experiments (e.g. Space Filling Design (SFD)) is a challenge in locating RPD solution. Recently, there have been studies (e.g. Bates et al. (2005), Chen et al. (2006), Dellino et al. (2010 and 2011), Giovagnoli and Romano (2008)) of RPD issues on computer experiments. Transmitted variance model (TVM) proposed by Shoemaker and Tsui. (1993) for physical experiments can be applied in computer simulations. The approaches stated above rely heavily on the estimated mean model because they obtain expressions for variance directly from mean models or by using them for generating replicates. Variance modeling based on some kind of replicates relies on the estimated mean model to a lesser extent. To the best of our knowledge, there is no rigorous research on variance modeling needed for RPD in computer experiments. We develop procedures for identifying variance models. First, we explore procedures to decide groups of pseudo replicates for variance modeling. A formal variance change-point procedure is developed to rigorously determine the replicate groups. Next, variance model is identified and estimated through a three-step variable selection procedure. Properties of the proposed method are investigated under various conditions through analytical and empirical studies. In particular, impact of correlated response on the performance is discussed.

A study has been performed to determine the advantages and disadvantages of variable thrust and variable specific impulse (Isp) trajectories for solar system exploration. There have been several numerical research efforts for variable thrust, variable Isp, power-limited trajectory optimization problems. All of these results conclude that variable thrust, variable Isp (variable specific impulse, or VSI) engines are superior to constant thrust, constant Isp (constant specific impulse, or CSI) engines. However, most of these research efforts assume a mission from Earth to Mars, and some of them further assume that these planets are circular and coplanar. Hence they still lack the generality. This research has been conducted to answer the following questions: - Is a VSI engine always better than a CSI engine or a high thrust engine for any mission to any planet with any time of flight considering lower propellant mass as the sole criterion? - If a planetary swing-by is used for a VSI trajectory, is the fuel savings of a VSI swing-by trajectory better than that of a CSI swing-by or high thrust swing-by trajectory? To support this research, an unique, new computer-based interplanetary trajectory calculation program has been created. This program utilizes a calculus of variations algorithm to perform overall optimization of thrust, Isp, and thrust vector direction along a trajectory that minimizes fuel consumption for interplanetary travel. It is assumed that the propulsion system is power-limited, and thus the compromise between thrust and Isp is a variable to be optimized along the flight path. This program is capable of optimizing not only variable thrust trajectories but also constant thrust trajectories in 3-D space using a planetary ephemeris database. It is also capable of conducting planetary swing-bys. Using this program, various Earth-originating trajectories have been investigated and the optimized results have been compared to traditional CSI and high thrust trajectory solutions. Results show that VSI rocket engines reduce fuel requirements for any mission compared to CSI rocket engines. Fuel can be saved by applying swing-by maneuvers for VSI engines, but the effects of swing-bys due to VSI engines are smaller than that of CSI or high thrust engines.

Durant les dernières décennies, la quantité de données disponibles en génétique a consi-dérablement augmenté. D’une part, une amélioration des technologies de séquençage demolécules a permis de réduire fortement le coût d’extraction du génome humain. D’autrepart, des consortiums internationaux d’institutions ont permis la mise en commun de lacollecte de données sur de larges populations. Cette quantité de données nous permetd’espérer mieux comprendre les mécanismes régissant le fonctionnement de nos cellules.Dans ce contexte, l’épidémiologie génétique est un domaine cherchant à déterminer larelation entre des caractéristiques génétiques et l’apparition d’une maladie. Des méthodesstatistiques spécifiques à ce domaine ont dû être développées, en particulier à cause desdimensions que les données présentent : en génétique, l’information est contenue dans unnombre de variables grand par rapport au nombre d’observations.Dans cette dissertation, deux contributions sont présentées. Le premier projet appeléPIGE (Pathway-Interaction Gene Environment) développe une méthode pour déterminerdes interactions gène-environnement. Le second projet vise à développer une méthode desélection de variables adaptée à l’analyse de données provenant de différentes études etprésentant une structure de groupe de variables.Le document est divisé en six parties. Le premier chapitre met en relief le contexte,d’un point de vue à la fois biologique et mathématique. Le deuxième chapitre présente lesmotivations de ce travail et la mise en œuvre d’études en épidémiologie génétique. Le troi-sième chapitre aborde les questions relatives à l’analyse d’interactions gène-environnementet la première contribution de la thèse y est présentée. Le quatrième chapitre traite desproblématiques de méta-analyses. Le développement d’une nouvelle méthode de réductionde dimension répondant à ces questions y est présenté. Le cinquième chapitre met en avantla pertinence de la méthode dans des cas de pleiotropie. Enfin, le sixième et dernier chapitredresse un bilan du travail présenté et dresse des perspectives pour le futur
During the last decades, the amount of available genetic data on populations has growndrastically. From one side, a refinement of chemical technologies have made possible theextraction of the human genome of individuals at an accessible cost. From the other side,consortia of institutions and laboratories around the world have permitted the collectionof data on a variety of individuals and population. This amount of data raised hope onour ability to understand the deepest mechanisms involved in the functioning of our cells.Notably, genetic epidemiology is a field that studies the relation between the geneticfeatures and the onset of a disease. Specific statistical methods have been necessary forthose analyses, especially due to the dimensions of available data: in genetics, informationis contained in a high number of variables compared to the number of observations.In this dissertation, two contributions are presented. The first project called PIGE (Pathway-Interaction Gene Environment) deals with gene-environment interaction assessments.The second one aims at developing variable selection methods for data which has groupstructures in both the variables and the observations.The document is divided into six chapters. The first chapter sets the background of this work,where both biological and mathematical notations and concepts are presented and gives ahistory of the motivation behind genetics and genetic epidemiology. The second chapterpresent an overview of the statistical methods currently in use for genetic epidemiology.The third chapter deals with the identification of gene-environment interactions. It includesa presentation of existing approaches for this problem and a contribution of the thesis. Thefourth chapter brings off the problem of meta-analysis. A definition of the problem and anoverview of the existing approaches are presented. Then, a new approach is introduced.The fifth chapter explains the pleiotropy studies and how the method presented in theprevious chapter is suited for this kind of analysis. The last chapter compiles conclusionsand research lines for the future

This study extends the idea and the technique of realizing 2ⁿᵈ-order state variable filters to the realization of single block nᵗʰ-order state variable filters and introduces a modified realization with different design procedures. The effects of gain-bandwidth on the performance of state variable filter realizations with respect to properties, such as, magnitude and phase characteristics and the actual pole locations are investigated and discussed. Various methods of compensation for these effects are also addressed.

The general goal of this thesis is to analyze, in some European countries, the connections of Variable Pay Systems with company behaviour, collective bargaining, wage determination and wage inequality. We introduce three different approaches to Variable Pay Systems. First, a company-industry approach in the case of Spain, using a qualitative methodology and analyzing competitiveness, productivity, unit labor cost and collective agreements. Second, a country-collective bargaining approach in the case of some European countries and using a quantitative methodology. And third, a country-wage determination and wage-inequality approach in the case of some European countries and using a quantitative methodology. A multidisciplinary point of view is used, combining tools from Industrial Relations and from Labor Economics. Wage determination is a commonplace in Labor Economics literature, but considering wages as a “black box”, without taking into account any breakdowns like variable forms of remuneration. Industrial Relations analyze factors which are determining Variable Pay Systems without their impact in wage determination or in wage inequality. Some literature justifies the introduction of Variable Pay Systems with the improvement in motivation employees, assuming that it will imply an improvement in productivity level. But our general research question is if there are other factors which are explaining the use of Variable Pay Systems and if there are other implications arising. This thesis is divided in four different chapters. In Chapter 1 we offer a literature review about definition and classification of variable pay schemes. On the one hand, Variable Pay Systems would be linked with globalization and its consequences and with last economic crisis, in terms of different elements like searching for improvements in competitiveness by companies and financialization; so, they would be a consequence of the changes in general economic framework of world economy. And, on the other hand, Variable Pay Systems would be the cause of the improving in motivation employees, in productivity and in competitiveness of the firms. In Chapter 2, we do an analysis of Variable Pay Systems in the case of nine companies from Spanish Automotive industry. We combine information from interviews and from collective agreements legal text with companies economic information, from Sabi database. Using a qualitative methodology (Multi Value Qualitative Comparative Analysis), our main conclusion is that the introduction of Variable Pay Systems would be closer to the strategies of multinational companies looking for higher level of competitiveness (decreasing unit labor cost) than to their strategies looking for improvement in employees motivation. In Chapter 3, we analyze the connection between Variable Pay Systems and collective bargaining regimes. We use three waves (2002, 2006 and 2010) from SES (Structure Earnings Survey) and we chose six different European countries (Finland, Spain, Portugal, France, Romania and Poland) with available data and with different collective bargaining regimes. As a proxy of Variable Pay Systems we use “Annual Bonuses” and its breakdown in Regular bonuses, Productivity bonuses and Profit sharing premiums. We evaluate the probability of earning bonuses (as dependent variable) and if this probability has any kind of pattern connected with collective bargaining regimes. Our main conclusion is as bargaining regimes become much more decentralized, bonuses depend on a larger number of variables (statistically significant), because in these situations they are not included in collective agreements; so, bonuses become much more variable. In Chapter 4, we take the same three waves from SES to analyze the main relevant variables of wage determination, through OLS (Ordinary Least Square) regression applied to a Mincerian wage equation, which includes a proxy of Variable Pay Systems (as independent variable). We use a decomposition of wage variance through difference of the R2 coefficient, in order to look what is the contribution of bonuses to wage variance. Moreover, we introduce Fields decomposition to evaluate which is the contribution of bonuses to wage inequality. One conclusion is that in countries with higher level of decentralization in collective bargaining, are countries with higher percentage in wage variance explanation by productivity bonuses and profit sharing premium. And, other conclusion, is that in countries in which bonuses are explaining the most important part of wage variance are the same countries in which bonuses have highest incidence in wage inequality, through Fields decomposition. In 2010, these countries were Spain, Portugal and Romania.
L’objectiu general d’aquesta tesi és analitzar, en alguns països europeus, les connexions dels Sistemes de Retribució Variable amb el comportament de l’empresa, la negociació col.lectiva, la determinació salarial i la desigualtat salarial. Introduïm tres diferents aproximacions als Sistemes de Retribució Variable. La primera és una aproximació des del punt de vista de l’empresa i el sector, en el cas d’Espanya, utilitzant una metodologia qualitativa i analitzant la competitivitat, la productivitat, els costos laborals unitaris i els convenis col.lectius. La segona és una aproximació des del punt de vista de la negociació col.lectiva i de país, en el cas d’alguns països europeus i utilitzant una metodologia quantitativa . La tercera és una aproximació des del punt de vista de la determinació salarial i la desigualtat salarial a nivell de país, en el cas d’alguns països europeus i utilitzant una metodologia quantitativa. S’utilitza un punt de vista multidisciplinar, combinant elements de Relacions Laborals amb elements d’Economia Laboral. La determinació salarial és un lloc comú en la literatura de l’Economia Laboral, però considerant els salaris com una “caixa negra”, sense tenir en compte cap desglós com les formes de remuneració variables. Les Relacions Laborals analitzen els factors que estan determinant els Sistemes de Retribució Variable sense el seu impacte en la determinació salarial i en la desigualtat salarial. Alguna literatura justifica la introducció de Sistemes de Retribució Variable amb la millora en la motivació dels treballadors, considerant que aquest fet implicarà una millora en el nivell de productivitat. Però la nostra pregunta general de recerca és si hi ha d’altres factors que estan explicant la utilització dels Sistemes de Retribució Variable i si hi ha d’altres implicacions que se’n deriven. Aquesta tesi està dividida en quatre capítols diferents. En el capítol 1 oferim una revisió de la literatura sobre la definició i la classificació dels esquemes de retribució variable. D’una banda, els Sistemes de Retribució Variable estarien relacionats amb la globalització i amb les seves conseqüències i amb la darrera crisi econòmica, en termes de diferents elements com la recerca de millores en la competitivitat per part de les empreses i la financialització; per tant, serien una conseqüència dels canvis en el marc econòmic general de l’economia mundial. I, d’altra banda, els Sistemes de Retribució Variables serien la causa de la millora en la motivació dels treballadors, en la productivitat i en la competitivitat de les empreses. En el capítol 2, fem una anàlisi dels Sistemes de Retribució Variable en el cas de nou companyies del sector de l’automoció a Espanya. Combinem informació provinent d’entrevistes i dels textos legals dels convenis col.lectius amb informació econòmica de les empreses, provinent de la base de dades Sabi. Utilitzant una metodologia qualitativa, la conclusió principal és que la introducció de Sistemes de Retribució Variable es deuria més a les estratègies de les empreses multinacionals buscant nivells de competitivitat superiors (costos laborals unitaris decreixents) que a una estratègia de recerca d’una millora en la motivació dels treballadors. En el capítol 3, analitzem la connexió entre els Sistemes de Retribució Variable i els règims de negociació col.lectiva. Utilitzem tres onades (2002, 2006 i 2010) de la Enquesta d’Estructura Salarial i hem triat sis països diferents (Finlàndia, Espanya, Portugal, França, Romania i Polònia) amb dades disponibles i amb diferents règims de negociació col.lectiva. Com a “proxy” dels Sistemes de Retribució Variable utilitzem els Bonus anuals i el seu desglòs entre Regular bonus, Bonus de la productivitat i les primes de Participació en els beneficis. Nosaltres avaluem la probabilitat de guanyar un bonus (com a variable depenent) i si aquesta probabilitat segueix algun tipus de patró relacionat amb els règims de negociació col.lectiva. La nostra conclusió principal és que a mesura que els règims de negociació col.lectiva esdevenen molt més descentralitzats, els bonus depenen d’un conjunt de variables (estadísticament significatives) més gran, perquè en aquestes situacions no estan inclosos en els convenis col.lectius; així, els bonus esdevenen molt més variables. En el capítol 4, prenem les mateixes tres onades de l’Enquesta d’Estructura Salarial per a analitzar les variables més rellevants en la determinació salarial, mitjançant una regressió amb Mínims Quadrats Ordinaris aplicats a una equació salarial Minceriana que inclou una “proxy” dels Sistemes de Retribució Variable (com a variable independent). Utilitzem una descomposició de la variança salarial a través de la diferència del coeficient R2, amb l’objectiu de veure quina és la contribució dels bonus a la variança salarial. A més a més, introduïm la descomposició de Fields per a avaluar quina és la contribució dels bonus a la desigualtat salarial. Una conclusió és que els països amb alts nivells de decentralització en la negociació col.lectiva són països amb un percentatge més alt en l’explicació de la variança salarial a través dels Bonus de productivitat i de la prima de Participació en els beneficis. I, una altra conclusió, és que els països en els quals els bonus estan explicant la part més important de la variança salarial són els mateixos països en els quals els bonus tenen la incidència més gran en la desigualtat salarial, mitjançant la descomposició de Fields. L’any 2010 aquests països van ser Espanya, Portugal i Romania.

Uno de los motivos de este trabajo es hacer una reflexión sobre el concepto actual de "confort en la arquitectura", sobre la dirección dominante que en este sentido han tomado los diseñadores contemporáneos y sobre las implicaciones sociales y de consumo energético.
Actualmente la mayoría de índices de confort que se utilizan son de tipo cuantitativo y sin variabilidad temporal, horaria, diaria y estacional. Desde principios de la década de los ochentas algunos autores han expuesto sus reflexiones sobre la necesidad de incorporar las variantes cualitativas y de variabilidad temporal en los índices de confort. Por lo que este trabajo abordará un tema que esta por definirse y que se discute y se investiga actualmente.
La hipótesis que se plantea en este trabajo es la siguiente: el ambiente térmico dentro de un espacio arquitectónico debe tener variaciones temporales y espaciales parecidas, aunque en diferente escala, a las que se dan en el ambiente exterior. Esto para no generar estrés térmico por una exposición a condiciones demasiado estáticas, evitar contrastes térmicos excesivos entre el interior y el exterior y no perder la capacidad de adaptación o la tolerancia a los cambios en el ambiente. Además de que nuestra percepción del espacio y del tiempo se basa en buena parte en la percepción de los cambios de los estímulos.
Para lo que es necesario un modelo de confort térmico que tome en cuenta las condiciones térmicas del exterior junto con todos los fenómenos y características del edificio y del usuario relacionados con el ambiente térmico.
Con la consecuencia directa de que al ser menores las exigencias de acondicionamiento, esto representaría un ahorro de energía por este concepto en el mantenimiento y uso de los edificios.
El objetivo central de este trabajo es sustentar teóricamente la hipótesis planteada, es decir, la necesidad y conveniencia de la variabilidad del ambiente térmico dentro de lo edificios, teniendo como principal referencia la oscilación de la temperatura exterior del aire, como principal indicador del clima exterior, además la circunstancias fisiológicas, físicas e incluso psicológicas del ocupante y algunas de las características del edificio.
Un segundo objetivo es, realizar el planteamiento teórico de un modelo de confort térmico que integre el mayor número posible de las condicionantes del confort térmico, estas condicionantes serán las características del ambiente exterior, las condiciones particulares de los ocupantes y las características del edificio que tengan una influencia directa en ambiente térmico y en la percepción de éste por el ocupante.
Y el tercer objetivo es, diseñar una herramienta informática que permita comprobar de una manera ágil el comportamiento de éste al modificar las variantes que lo integran y sus valores y que a su vez permita aplicar el modelo de confort térmico a la evaluación del ambiente térmico en los edificios.
Las conclusiones centrales de este trabajo son sobre la variabilidad del ambiente térmico, de la que mediante el estudio realizado sobre del entorno térmico en la Sala de Ordenadores de la E.T.S.A.B. se observó lo siguiente, primero, que la oscilación de las componentes del entorno térmico: temperatura del aire, temperatura radiante, humedad relativa y velocidad del aire; existe en este tipo de espacios aún cuando no se desean.
Por otra parte, pudo observarse que la aplicación de sistemas mecánicos de acondicionamiento ambiental no garantiza la obtención de un ambiente que ofrezca confort térmico a los ocupantes, siendo éste un entorno controlado, en el que la variación de sus componentes son mínimas y que se encuentran dentro de lo que se considera confort térmico.
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One of the motives of this work is to make a reflection on the current concept of "comfort in the architecture", on the dominant direction that in this sense the contemporary designers have taken and on the social implications and of energy consumption.
At the moment most of indexes of comfort that are used are of quantitative type and without temporary variability, horary, daily and seasonal. From principles of the decade of the 80 some authors have exposed their reflections about the necessity of incorporating the qualitative variants and of temporary variability in the indexes of comfort. For what this work will approach a topic that this to be defined and that you discusses and it is investigated at the moment.
The hypothesis that thinks about in this work is the following one: the thermal environment inside an architectural space should have similar temporary and space variations, although in different scale, to those that are given in the external environment. This for not generating thermal stress for an exhibition to too static conditions, to avoid excessive thermal contrasts between the interior and the external one and not to lose the capacity of adaptation or the tolerance to the changes in the environment. Besides that our perception of the space and of the time it is based on good part in
the perception of the changes of the stimuli.
For what is necessary a model of thermal comfort that takes into account the thermal conditions of the exterior together with all the phenomena and characteristic of the building and of the user related with the thermal environment.
With the direct consequence that to the smallest being the environment demands, this would represent an energy saving for this concept in the maintenance and use of the buildings.
The central objective of this work is to sustain the outlined hypothesis theoretically, that is to say, the necessity and convenience of the variability of the thermal environment inside the buildings, having as main reference the oscillation of the external temperature of the air, as main indicator of the external climate, moreover the physiologic circumstances, physical and even psychological of the occupant and some of the characteristics of the building.
A second objective is, to carry out the theoretical position of a model of thermal comfort that integrates the biggest number possible of the conditions of the thermal comfort, these conditions will be the characteristics of the external environment, the conditions peculiar of the occupants and the characteristics of the building that have a direct influence in thermal atmosphere and in the perception of this for the occupant.
And the third objective is, to design a computer tool that allows to check in an agile way the behavior from this when modifying the variants that integrate it and its values and that in turn it allows to apply model el of thermal comfort to the evaluation of the thermal environment in the buildings.
The conclusions centrals of this work are about the variability of the thermal environment, of the one that by means of the study carried out on of the thermal environment in the Room of Computers of the E.T.S.A.B. the following, first was observed that the oscillation of the components of the thermal environment: temperature of the air, radiant temperature, relative humidity and speed of the air; it still exists in this type of spaces when they are not wanted.
On the other hand, it could be observed that the application of mechanical conditioning systems of environment doesn't guarantee the obtaining of an environment that offers thermal comfort to the occupants, being this a controlled environment, in which the variation of its components is minimum and that they are inside what is considered thermal comfort.

This study begins with a review of economic and industrial relations literature to identify changes to the workplace that will make industry more productive and competitive. It identifies the measures necessary for industry to take advantage of technological development and to make the workplace more flexible. Specifically it focuses on variable or flexible compensation plans. After identifying the key features of various forms of flexible compensation, it examines approximately 30 plans being used in British Columbia. The case studies assist in identifying the advantages and disadvantages of each type of plan, from the perspectives of the employer, the employees and the trade union. Finally it suggests steps that can be taken by government to encourage variable compensation.
Law, Peter A. Allard School of
Graduate

Generalized Linear Models (GLMs) (McCullagh and Nelder, 1989) provide a unified framework for fixed effect models where response data arise from exponential family distributions. Much recent research has attempted to extend the framework to include random effects in the linear predictors. Different methodologies have been employed to solve different motivating problems, for example Generalized Linear Mixed Models (Clayton, 1994) and Multilevel Models (Goldstein, 1995). A thorough review and classification of this and related material is presented. In Item Response Theory (IRT) subjects are tested using banks of pre-calibrated test items. A useful model is based on the logistic function with a binary response dependent on the unknown ability of the subject. Item parameters contribute to the probability of a correct response. Within the framework of the GLM, a latent variable, the unknown ability, is introduced as a new component of the linear predictor. This approach affords the opportunity to structure intercept and slope parameters so that item characteristics are represented. A methodology for fitting such GLMs with latent variables, based on the EM algorithm (Dempster, Laird and Rubin, 1977) and using standard Generalized Linear Model fitting software GLIM (Payne, 1987) to perform the expectation step, is developed and applied to a model for binary response data. Accurate numerical integration to evaluate the likelihood functions is a vital part of the computational process. A study of the comparative benefits of two different integration strategies is undertaken and leads to the adoption, unusually, of Gauss-Legendre rules. It is shown how the fitting algorithms are implemented with GLIM programs which incorporate FORTRAN subroutines. Examples from IRT are given. A simulation study is undertaken to investigate the sampling distributions of the estimators and the effect of certain numerical attributes of the computational process. Finally a generalized latent variable model is developed for responses from any exponential family distribution.