Finite-difference methods for computing the derivative of a function with respect to an independent variable require knowledge of the perturbation step size for that variable. Although rules of thumb exist for determining the magnitude of the step size, their effectiveness diminishes for complicated functions or when numerically solving difficult optimization problems. This dissertation investigates the problem of determining the step size that minimizes the total error associated with finite-difference derivative approximations. The total error is defined as the sum of errors from numerical sources (roundoff error) and mathematical approximations (truncation error). Several finite-difference approximations are considered, and expressions are derived for the errors associated with each approximation. Analysis of these errors leads to an algorithm that determines the optimal perturbation step size that minimizes the total error. A benefit of this algorithm is that the computed optimal step size, when used with neighboring values of the independent variable, results in approximately the same magnitude of error in the derivative. This allows the same step size to be used for several successive iterations of the independent variable in an optimization loop. A range of independent variable values for which the optimal step size can safely remain constant is also computed. In addition to roundoff and truncation errors within the finite-difference method, numerical errors within the actual function implementation are also considered. It is shown that the optimal step size can be used to compute an upper bound for these condition errors, without any prior knowledge of the function implementation. Knowledge of a function's condition error is of great assistance during the debugging stages of simulation design. Although the fundamental analysis assumes a scalar function of a scalar independent variable, it is later extended to the general case of a vector function of a vector independent variable. Several numerical examples are shown, ranging from simple polynomial and trigonometric functions to complex trajectory optimization problems. In each example, the step size is computed using the algorithm developed herein, a rule-of-thumb method, and an alternative statistical algorithm, and the resulting finite-difference derivatives are compared to the true derivative where available. / text

In this thesis I estimate a monetary value of the risk attached to living near a hazardous waste site in the town of Teckomatorp. This site is the result of hundreds of rusty leaking barrels of toxins being buried in the ground by the company BT Kemi in the 1970’s. Ever since then the site has been remediated in several steps and is still contaminated today. For estimating the perceived risk of living near this site I use a hedonic price model (HP) which is a form of a revealed preference approach. In a HP model the price of a market good is a function of different utility-bearing characteristics and the estimated parameters can be used to calculate the implicit prices of these characteristics. In this case I use a data set from the National Swedish Institute for Building Research (IBF) and regress property price on a number of housing characteristics. I compare an estimated town-effect for Teckomatorp with the estimates for two control towns: Billeberga and Anderslöv. I can confirm my hypothesis that, after controlling for housing characteristics, there is a negative effect on prices of property in Teckomatorp. I find that property prices are on average 46878 SEK lower in Teckomatorp than in the two control towns.

I denna studie undersöks om nedläggningen av Uddevallavarvet och bilsätesfabriken i Bengtsfors påverkade andelen sjukskrivningar i respektive kommun. För att estimera effekten av företagsnedläggningarnas påverkan på sjukskrivningarna i de två olika kommunerna har jag valt att använda mig av difference-in-difference-metoden. Andelen sjukskrivningar utvalda veckor under året då företagsnedläggningarna inträffade i de två olika kommunerna kommer att jämföras med tidsperioder före och efter nedläggningen. Andelen sjukskrivningar utvalda veckor i Uddevalla och Bengtsfors kommun kommer även att jämföras med andelen sjukskrivningar motsvarande veckor i en annan jämförbar kommun, nämligen Köpings kommun. Genom tillämpning av difference-in-differencemetoden erhålls två signifikanta och positiva resultat som tyder på att andelen sjukskrivningar ökat i samband med nedläggningen av Uddevallavarvet.

Thinking of difference in this dissertation is presented by a philosophical reconstruction of the notion of “ontological difference” in the philosophy of Martin Heidegger, and of the notion of ethical difference in the philosophy of Emmanuel Levinas. It is shown that while in Western philosophy even before Heidegger there was research and intellectual developments regarding difference, difference itself was not considered a philosophical problem. It is in Heidegger’s philosophy that one first finds formulated the problem of difference or the philosophical problem of difference as the founding principle of philosophy and Western spirituality itself. Through an analysis of Dasein (“being there”), temporality, and the two different ways of being of entities, as found elaborated in his early work Being and Time, it is shown that the notion of ontological difference is first of all the perspective of thinking from which Heidegger raises the question of the meaning of being. Further, by discussing other fundamental problems of philosophy, such as those which arise with the concepts of time, truth, ground, and identity, it is shown how in Heidegger’s philosophy the problem of ontological difference is formulated. The latter problem opens the possibility of rethinking the essence of metaphysical thinking, which is seen by Heidegger as a forgetfulness of being and difference. The dissertation shows that there is an ambiguity in Heidegger’s conception of ontological difference:... [to full text] / Disertacijoje skirties mąstymas pristatomas rekonstruojant ontologinio skirtumo plėtotę Heideggerio filosofijoje bei etinio skirtumo plėtotę Levino filosofijoje. Parodoma, kad nors Vakarų filosofijoje iki Heideggerio ir brėžiami bei svarstomi įvairūs „skirtumai“, filosofine problema skirtumas čia taip ir netampa. Tuo tarpu Heideggerio filosofijoje suformuluojama filosofinė skirties, kaip steigiančio principo, problema. Atliekant štai-būties, laikiškumo, esinių skirtingo buvimo būdų analizę parodoma, kad ontologinis skirtumas visų pirma yra mąstymo perspektyva iš kurios Heideggeris kelia būties prasmės klausimą. Aptariant kitas fundamentalias filosofijos problemas – laiko, tiesos, pagrindo, tapatybės, atskleidžiama, kaip Heideggerio filosofijoje suformuluojama ontologinio skirtumo problema. Tai atveria galimybę permąstyti metafizinio mąstymo esmę, kuri Heideggerio pamatoma kaip būties, o drauge ir kaip skirtumo užmarštis. Ontologinio skirtumo dviprasmiškumas atskleidžiamas parodant ontologinį skirtumą kaip pačią metafizikos prielaidą bei numatant metafizikos įveikos galimybę. Pereinant prie Levino skirties sampratos analizės, parodoma, kad skirties mąstymas yra, viena vertus, tai kas jungia šiuos du mąstytojus, antra vertus, tai kas juos labiausiai ir atskiria. Disertacijoje analizuojama, kuria prasme ontologinis skirtumas yra Levino skirties mąstymo išeities taškas bei atskleidžiama, kaip performuluojama skirties problema. Būties ir esinio skirtumo radikalizavimas ir... [toliau žr. visą tekstą]

Disertacijoje skirties mąstymas pristatomas rekonstruojant ontologinio skirtumo plėtotę Heideggerio filosofijoje bei etinio skirtumo plėtotę Levino filosofijoje. Parodoma, kad nors Vakarų filosofijoje iki Heideggerio ir brėžiami bei svarstomi įvairūs „skirtumai“, filosofine problema skirtumas čia taip ir netampa. Tuo tarpu Heideggerio filosofijoje suformuluojama filosofinė skirties, kaip steigiančio principo, problema. Atliekant štai-būties, laikiškumo, esinių skirtingo buvimo būdų analizę parodoma, kad ontologinis skirtumas visų pirma yra mąstymo perspektyva iš kurios Heideggeris kelia būties prasmės klausimą. Aptariant kitas fundamentalias filosofijos problemas – laiko, tiesos, pagrindo, tapatybės, atskleidžiama, kaip Heideggerio filosofijoje suformuluojama ontologinio skirtumo problema. Tai atveria galimybę permąstyti metafizinio mąstymo esmę, kuri Heideggerio pamatoma kaip būties, o drauge ir kaip skirtumo užmarštis. Ontologinio skirtumo dviprasmiškumas atskleidžiamas parodant ontologinį skirtumą kaip pačią metafizikos prielaidą bei numatant metafizikos įveikos galimybę. Pereinant prie Levino skirties sampratos analizės, parodoma, kad skirties mąstymas yra, viena vertus, tai kas jungia šiuos du mąstytojus, antra vertus, tai kas juos labiausiai ir atskiria. Disertacijoje analizuojama, kuria prasme ontologinis skirtumas yra Levino skirties mąstymo išeities taškas bei atskleidžiama, kaip performuluojama skirties problema. Būties ir esinio skirtumo radikalizavimas ir... [toliau žr. visą tekstą] / Thinking of difference in this dissertation is presented by a philosophical reconstruction of the notion of “ontological difference” in the philosophy of Martin Heidegger, and of the notion of ethical difference in the philosophy of Emmanuel Levinas. It is shown that while in Western philosophy even before Heidegger there was research and intellectual developments regarding difference, difference itself was not considered a philosophical problem. It is in Heidegger’s philosophy that one first finds formulated the problem of difference or the philosophical problem of difference as the founding principle of philosophy and Western spirituality itself. Through an analysis of Dasein (“being there”), temporality, and the two different ways of being of entities, as found elaborated in his early work Being and Time, it is shown that the notion of ontological difference is first of all the perspective of thinking from which Heidegger raises the question of the meaning of being. Further, by discussing other fundamental problems of philosophy, such as those which arise with the concepts of time, truth, ground, and identity, it is shown how in Heidegger’s philosophy the problem of ontological difference is formulated. The latter problem opens the possibility of rethinking the essence of metaphysical thinking, which is seen by Heidegger as a forgetfulness of being and difference. The dissertation shows that there is an ambiguity in Heidegger’s conception of ontological difference:... [to full text]

This thesis is centrally concerned with the texts of Jacques Derrida that have addressed directly the theme of sexual difference. Yet to say the thesis is centrally concerned with a philosophy that positions itself clearly as one that deconstructs centrality and its trajectory of return, is to face the crisis or chiasmus of my concern. The thesis is not returned to Derrida. If the question of feminism for Derrida is a question from the margins, from interruptions, of the trace and of la cendre, ashes, the question of sexual difference is primordially and originarily that of the undecidability of the name, signatory, and textual border. She would not have appeared here. Therefore she cannot return. There are two frames to this research that can be recognized in the chapter sequence of the thesis. Initially I develop a preparatory engagement to a questioning of the ontology of sexual difference, with Chapters 2 and 3, with a questioning that broaches the metaphysics of the feminine with respect to the texts of Derrida, Heidegger and Cixous in particular and further engages with Écriture Féminine, Levinas and feminist responses to Heidegger and Levinas. However, this broader questioning is undertaken in order to develop a sharper focus on the writings of Derrida that address Heidegger’s ontological difference, Levinas’s ethics before being, and a more originary questioning of sexual difference. The second frame and predominant focus of the thesis is on Derrida’s approach to the metaphysics of the feminine with four pivotal texts by Derrida from the late 1970s and early 1980s examined in Chapters 4 to 7. Each addresses a questioning of difference and the metaphysical tradition, under difference’s many names: ontological difference, sexual difference, différance, and engages deconstruction’s encounters with Nietzsche & Heidegger (Spurs); the psychoanalysts Abraham & Torok (“Fors”); Levinas (“At This Very Moment in This Work Here I Am”) and Hegel (Glas). In bringing together these four texts, my aim is to emphasize the significance of a double deconstructive movement of transgression and restoration, as this research’s politico-ethical acts of writing and reading for an otherwise discourse on sexual difference. This otherwise discourse has always already been produced with phallogocentrism and remains critical for the inventing of thresholds across philosophy, literature and their others. The ashen Preface enkindles a paradigmatic figure as deconstructive trace of sexual difference in writing and reading practices. A Postscript questions the binding to institutional laws constitutive of disciplinary practice while the fiery trace in Derrida’s writing on Kafka’s law concludes on the ash-laden edges of Blanchot’s unavowable work.

Esta dissertação de mestrado apresenta um estudo sobre os efeitos de diferentes funções de recompensa, aplicadas em aprendizado por reforço multiagente, para o problema de roteamento de veículos, em redes de tráfego. São abordadas duas funções de recompensas que diferem no alinhamento do sinal numérico enviado do ambiente ao agente. A primeira função, chamada função individual, é alinhada à utilidade individual do agente (veículo ou motorista) e busca minimizar seu tempo de viagem. Já a segunda função, por sua vez, é a chamada difference rewards, essa é alinhada à utilidade global do sistema e tem por objetivo minimizar o tempo médio de viagem na rede (tempo médio de viagem de todos os motoristas). Ambas as abordagens são aplicadas em dois cenários de roteamento de veículos que diferem em: quantidade de motoristas aprendendo, topologia e, consequentemente, nível de complexidade. As abordagens são comparadas com três técnicas de alocação de tráfego presentes na literatura. Resultados apontam que os métodos baseados em aprendizado por reforço apresentam desempenho superior aos métodos de alocação de rotas. Além disso, o alinhamento da função de recompensa à utilidade global proporciona uma melhora significativa nos resultados quando comparados com a função individual. Porém, para o cenário com maior quantidade de agentes aprendendo simultaneamente, ambas as abordagens apresentam soluções equivalentes. / This dissertation presents a study on the effects of different reward functions applyed to multiagent reinforcement learning, for the vehicles routing problem, in traffic networks. Two reward functions that differ in the alignment of the numerical signal sent from the environment to the agent are addressed. The first function, called individual function is aligned with the agent’s (vehicle or driver) utility and seeks to minimize their travel time. The second function, is called difference rewards and is aligned to the system’s utility and aims to minimize the average travel time on the network (average travel time of all drivers). Both approaches are applied to two routing vehicles’ problems, which differ in the number of learning drivers, network topology and therefore, level of complexity. These approaches are compared with three traffic assignment techniques from the literature. Results show that reinforcement learning-based methods yield superior results than traffic assignment methods. Furthermore, the reward function alignment to the global utility, provides a significant improvement in results when compared with the individual function. However, for scenarios with many agents learning simultaneously, both approaches yield equivalent solutions.

Esta dissertação de mestrado apresenta um estudo sobre os efeitos de diferentes funções de recompensa, aplicadas em aprendizado por reforço multiagente, para o problema de roteamento de veículos, em redes de tráfego. São abordadas duas funções de recompensas que diferem no alinhamento do sinal numérico enviado do ambiente ao agente. A primeira função, chamada função individual, é alinhada à utilidade individual do agente (veículo ou motorista) e busca minimizar seu tempo de viagem. Já a segunda função, por sua vez, é a chamada difference rewards, essa é alinhada à utilidade global do sistema e tem por objetivo minimizar o tempo médio de viagem na rede (tempo médio de viagem de todos os motoristas). Ambas as abordagens são aplicadas em dois cenários de roteamento de veículos que diferem em: quantidade de motoristas aprendendo, topologia e, consequentemente, nível de complexidade. As abordagens são comparadas com três técnicas de alocação de tráfego presentes na literatura. Resultados apontam que os métodos baseados em aprendizado por reforço apresentam desempenho superior aos métodos de alocação de rotas. Além disso, o alinhamento da função de recompensa à utilidade global proporciona uma melhora significativa nos resultados quando comparados com a função individual. Porém, para o cenário com maior quantidade de agentes aprendendo simultaneamente, ambas as abordagens apresentam soluções equivalentes. / This dissertation presents a study on the effects of different reward functions applyed to multiagent reinforcement learning, for the vehicles routing problem, in traffic networks. Two reward functions that differ in the alignment of the numerical signal sent from the environment to the agent are addressed. The first function, called individual function is aligned with the agent’s (vehicle or driver) utility and seeks to minimize their travel time. The second function, is called difference rewards and is aligned to the system’s utility and aims to minimize the average travel time on the network (average travel time of all drivers). Both approaches are applied to two routing vehicles’ problems, which differ in the number of learning drivers, network topology and therefore, level of complexity. These approaches are compared with three traffic assignment techniques from the literature. Results show that reinforcement learning-based methods yield superior results than traffic assignment methods. Furthermore, the reward function alignment to the global utility, provides a significant improvement in results when compared with the individual function. However, for scenarios with many agents learning simultaneously, both approaches yield equivalent solutions.

Esta dissertação de mestrado apresenta um estudo sobre os efeitos de diferentes funções de recompensa, aplicadas em aprendizado por reforço multiagente, para o problema de roteamento de veículos, em redes de tráfego. São abordadas duas funções de recompensas que diferem no alinhamento do sinal numérico enviado do ambiente ao agente. A primeira função, chamada função individual, é alinhada à utilidade individual do agente (veículo ou motorista) e busca minimizar seu tempo de viagem. Já a segunda função, por sua vez, é a chamada difference rewards, essa é alinhada à utilidade global do sistema e tem por objetivo minimizar o tempo médio de viagem na rede (tempo médio de viagem de todos os motoristas). Ambas as abordagens são aplicadas em dois cenários de roteamento de veículos que diferem em: quantidade de motoristas aprendendo, topologia e, consequentemente, nível de complexidade. As abordagens são comparadas com três técnicas de alocação de tráfego presentes na literatura. Resultados apontam que os métodos baseados em aprendizado por reforço apresentam desempenho superior aos métodos de alocação de rotas. Além disso, o alinhamento da função de recompensa à utilidade global proporciona uma melhora significativa nos resultados quando comparados com a função individual. Porém, para o cenário com maior quantidade de agentes aprendendo simultaneamente, ambas as abordagens apresentam soluções equivalentes. / This dissertation presents a study on the effects of different reward functions applyed to multiagent reinforcement learning, for the vehicles routing problem, in traffic networks. Two reward functions that differ in the alignment of the numerical signal sent from the environment to the agent are addressed. The first function, called individual function is aligned with the agent’s (vehicle or driver) utility and seeks to minimize their travel time. The second function, is called difference rewards and is aligned to the system’s utility and aims to minimize the average travel time on the network (average travel time of all drivers). Both approaches are applied to two routing vehicles’ problems, which differ in the number of learning drivers, network topology and therefore, level of complexity. These approaches are compared with three traffic assignment techniques from the literature. Results show that reinforcement learning-based methods yield superior results than traffic assignment methods. Furthermore, the reward function alignment to the global utility, provides a significant improvement in results when compared with the individual function. However, for scenarios with many agents learning simultaneously, both approaches yield equivalent solutions.

nÃo hà / The present study sets out this issue, in order to investigate the impacts of electronic invoice in the collection of VAT in the State of CearÃ, more precisely in the pioneering activities in their use. It was intended to achieve this purpose by researching the history, legislation, the operational model and the benefits of this new tool, with a descriptive and econometric analysis of the activities of VAT collections required and not required in the periods before and after the fiscal policy. We used the methodological âdifference in differenceâ, which results indicated that, in a general context, the binding nature of the invoice electronically provided an effect on the collection of VAT, on average, much higher than the observed in sectors that were not included in the policy. The intersection of information more efficiently by computerized means contributed such to reduce tax evasion as well as to improve a control over the movement of goods and services that culminated in a result of effective policy. It is noteworthy that there are other variables that affect the level of collection of VAT. However, their unavailability aggregated by the sector made it impossible to insert them in the model. So what can be said in this work is that eletronic invoice promoted a positive impact on the collection of VAT and that politics is only partly responsible for the observed growth. / O presente trabalho se propÃs a estudar este tema, tendo como objetivo investigar os impactos da Nota Fiscal EletrÃnica na arrecadaÃÃo do ICMS no Estado do CearÃ, mais precisamente nas atividades pioneiras na sua utilizaÃÃo. Pretendeu-se atingir essa finalidade, pesquisando o histÃrico, a legislaÃÃo, o modelo operacional e os benefÃcios dessa nova ferramenta, complementando com uma anÃlise descritiva e economÃtrica das arrecadaÃÃes de ICMS das atividades obrigadas, comparativamente as nÃo obrigadas, nos perÃodos prà e pÃs a polÃtica fiscal. Utilizou-se a metodologia economÃtrica diferenÃa em diferenÃa, cujos resultados apontam que num contexto geral, a compulsoriedade da nota fiscal de forma eletrÃnica proporcionou um efeito sobre a arrecadaÃÃo do ICMS, em mÃdia, bem superior aquele observado para os setores que nÃo foram contemplados com a polÃtica. O cruzamento de informaÃÃes de forma mais eficiente por meios informatizados contribuÃram tanto para reduÃÃo da sonegaÃÃo como para uma melhor fiscalizaÃÃo na circulaÃÃo de mercadorias e serviÃos que culminaram num resultado de eficÃcia da polÃtica em questÃo. Vale ressaltar, que existem outras variÃveis que afetam o nÃvel de arrecadaÃÃo do ICMS, contudo, a indisponibilidade das mesmas agregadas por setores impossibilitaram suas inserÃÃes no modelo. Portanto, o que se pode afirmar neste trabalho à que a NF-e promoveu um impacto positivo sobre a arrecadaÃÃo do ICMS e que a polÃtica somente à responsÃvel por parte do crescimento observado.