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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
81

Identification and Analysis of Illegal States in the Apoptotic Discrete Transition System Model using ATPG and SAT-based Techniques

Shrivastava, Anupam 14 November 2008 (has links)
Programmed Cell Death, or Apoptosis, plays a critical role in human embryonic development and in adult tissue homeostasis. Recent research efforts in Bioinformatics and Computational Biology focus on gaining deep insight into the Apoptosis process. This allows researchers to clearly study the relation between the dysregulation of apoptosis and the development of cancer. Research in this highly interdisciplinary field of bioinformatics has become much more quantitative, using tools from computational sciences to understand the behavior of Biological systems. Previously, an abstracted model has been developed to study the Apoptosis process as a Finite State Discrete Transition Model. This model facilitates the reutilization of the digital design verification and testing techniques developed in the Electronic Design Automation domain. These verification and testing techniques for hardware have become robust over the past few decades. Usually simulation is the cornerstone of the Design Verification industry and bulk of states are covered by simulation. Formal verification techniques are then used to analyze the remaining corner case states. Techniques like Genetic Algorithm guided Logic Simulation (GALS) and SAT-based Induction have already been applied to the Apoptosis Discrete Transition Model. However, the Apoptosis model presents some unique problems. The simulation techniques have shown to be unable to cover most of the states of the Apoptosis model. When SAT-based Induction is applied to the Apoptosis model, in particular to find illegal states, very few illegal states are identified. It particularly suffers from the fact that the Apoptosis Model is rather complex and the formulation for testing and verification is hard to tackle at larger bounds greater than 20 or so. Consequently, the state space of the Apoptosis model largely lies in the unknown region, meaning that we are unable to either reach those states or prove that they are illegal. Unless we know whether these states are reachable or illegal, it is not feasible to infer information about the model such as what protein concentrations can be reached under what kind of input stimuli. Questions such as whether certain protein concentrations can be reached or not in this model can only be answered if we have a clear picture of the reachability of state space. In this thesis, we propose techniques based on ATPG and SAT based image computation of the Apoptosis finite transition model. Our method leverages the results obtained in previous research work. It uses the reachable states obtained from the simulation traces of the previous work as initial states for our technique. This enables us to identify more illegal states in less number of iterations; in other words, we are able to reach the fixed point in image computation faster. Our experimental analysis illustrates that the proposed techniques could prove most of the former unknown states as illegal states. We are able to extend our analysis to obtain clearer picture of the interaction of any two proteins in the system considered together. / Master of Science
82

Lower Semicontinuity and Young Measures for Integral Functionals with Linear Growth

Johan Filip Rindler, Johan Filip January 2011 (has links)
No description available.
83

Resource-Bounded Reasoning about Knowledge

Ho, Ngoc Duc 28 November 2004 (has links) (PDF)
Der Begriff ``Agent'' hat sich als eine sehr nützliche Abstraktion erwiesen, um verschiedene Problembereiche auf eine intuitive und natürliche Art und Weise zu konzeptualisieren. Intelligente Agenten haben daher Anwendung gefunden in verschiedenen Teilbereichen der Informatik. Zur Modellierung werden intelligente Agenten meist als intentionale Systeme aufgefaßt und mit Hilfe von mentalistischen Begriffen wie Wissen, Glauben (oder Überzeugung), Wunsch, Pflicht, Intention usw. beschrieben. Unter diesen mentalen Begriffen gehören die epistemischen Begriffe (d.h., Wissen und Glauben) zu den wichtigsten und wurden auch am intensivsten untersucht. Zur Modellierung von Wissen und Glauben werden in der Regel modale epistemische Logiken verwendet. Solche Systeme sind aber nicht geeignet, um ressourcenbeschränkte Agenten zu beschreiben, weil sie zu starke Annahmen bezüglich der Rationalität von Agenten machen. Zum Beispiel wird angenommen, daß Agenten alle logischen Wahrheiten sowie alle Konsequenzen seines Wissens kennen. Dieses Problem ist bekannt als das Problem der logischen Allwissenheit (``logical omniscience problem''). Da alle Agenten grundsätzlich nur über begrenzte Ressourcen (wie z.B. Zeit, Information, Speicherplatz) verfügen, können sie nur eine begrenzte Menge von Informationen verarbeiten. Daher müssen alternative Modelle entwickelt werden, um Agenten realistisch modellieren zu können (siehe Kapitel 2). Daß modale epistemische Logik für die Formalisierung des ressourcenbeschränkten Schließens (``resource-bounded reasoning'') nicht geeignet ist, wird als ein offenes Problem der Agententheorien anerkannt. Es gibt bisher aber keine brauchbaren Alternativen zur Modallogik. Die meisten Ansätze zur Lösung des logischen Allwissenheitsproblems versuchen, Wissen und Glauben mit Hilfe schwacher Modallogiken zu beschreiben. Solche Versuche sind nicht befriedigend, da sie eine willkürliche Einschränkung der Rationalität der Agenten zur Folge haben (siehe Kapitel 3). Mein Ziel ist es, einen Rahmen für das ressourcenbeschränktes Schließen über Wissen und Glauben zu entwickeln. Damit soll eine solide Grundlage für Theorien intelligenter Agenten geschaffen werden. Als Nebenergebnis wird das logische Allwissenheitsproblem auf eine sehr intuitive Art und Weise gelöst: obwohl Agenten rational sind und alle logischen Schlußregeln anwenden können, sind sie nicht logisch allwissend, weil ihnen nicht genügend Ressourcen zu Verfügung stehen, um alle logischen Konsequenzen ihres Wissens zu ziehen. Im Kapitel 4 wird eine Reihe von Logiken vorgestellt, die den Begriff des expliziten Wissens formalisieren. Es wird eine Lösung des Problems der logischen Allwissenheit der epistemischen Logik vorgeschlagen, die die Rationalität der Agenten nicht willkürlich einschränkt. Der Grundgedanke dabei ist der folgende. Ein Agent kennt die logischen Konsequenzen seines Wissens nur dann, wenn er sie tatsächlich hergeleitet hat. Wenn ein Agent alle Prämissen einer gültigen Schlußregel kennt, kennt er nicht notwendigerweise die Konklusion: er kennt sie nur nach der Anwendung der Regel. Wenn er den Schluß nicht ziehen kann, z.B. weil er nicht die notwendigen Ressourcen dazu hat, wird sein Wissen nicht um diese herleitbare Information erweitert. Die Herleitung neuer Informationen wird als die Ausführung mentaler Handlungen aufgefaßt. Mit Hilfe einer Variante der dynamischen Logik können diese Handlungen beschrieben werden. Im Kapitel 5 werden Systeme für das ressourcenbeschränkte Schließen über Wissen und Glauben entwickelt, die auch quantitative Bedingungen über die Verfügbarkeit von Ressourcen modellieren können. Mit Hilfe dieser Logiken können Situationen beschrieben werden, wo Agenten innerhalb einer bestimmten Zeitspanne entscheiden müssen, welche Handlungen sie ausführen sollen. Der Ansatz besteht darin, epistemische Logik mit Komplexitätstheorie zu verbinden. Mit Hilfe einer Komplexitätsanalyse kann ein Agent feststellen, ob ein bestimmtes Problem innerhalb vorgegebener Zeit lösbar ist. Auf der Grundlage dieses Wissens kann er dann die für die Situation geeignete Entscheidung treffen. Damit ist es gelungen, eine direkte Verbindung zwischen dem Wissen eines Agenten und der Verfügbarkeit seiner Ressourcen herzustellen. / One of the principal goals of agent theories is to describe realistic, implementable agents, that is, those which have actually been constructed or are at least in principle implementable. That goal cannot be reached if the inherent resource-boundedness of agents is not treated correctly. Since the modal approach to epistemic logic is not suited to formalize resource-bounded reasoning, the issue of resource-boundedness remains one of the main foundational problems of any agent theory that is developed on the basis of modal epistemic logic. My work is an attempt to provide theories of agency with a more adequate epistemic foundation. It aims at developing theories of mental concepts that make much more realistic assumptions about agents than other theories. The guiding principle of my theory is that the capacities attributed to agents must be empirically verifiable, that is, it must be possible to construct artificial agents which satisfy the specifications determined by the theory. As a consequence, the unrealistic assumption that agents have unlimited reasoning capacities must be rejected. To achieve the goal of describing resource-bounded agents accurately, the cost of reasoning must be taken seriously. In the thesis I have developed a framework for modeling the relationship between knowledge, reasoning, and the availability of resources. I have argued that the correct form of an axiom for epistemic logic should be: if an agent knows all premises of a valid inference rule and if he performs the right reasoning, then he will know the conclusion as well. Because reasoning requires resources, it cannot be safely assumed that the agent can compute his knowledge if he does not have enough resources to perform the required reasoning. I have demonstrated that on the basis of that idea, the problems of traditional approaches can be avoided and rich epistemic logics can be developed which can account adequately for our intuitions about knowledge.
84

Verificação e comprovação de erros em códigos C usando bounded model checker

Rocha, Herbert Oliveira 04 February 2011 (has links)
Made available in DSpace on 2015-04-11T14:03:20Z (GMT). No. of bitstreams: 1 HERBERT OLIVEIRA.pdf: 512075 bytes, checksum: acc5d05442df938abdfa025f9db23367 (MD5) Previous issue date: 2011-02-04 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The use of computer-based systems in several domains has increased significantly over the last years, one of the main challenges in software development of these systems is to ensure the correctness and reliability of these. So that software verification now plays an important role in ensuring the overall product quality, aimed mainly the characteristics of predictability and reliability. In the context of software verification, with respect to the use of model checking technique, Bounded Model Checkers have already been applied to discover subtle errors in actual systems projects, contributing effectively in this verification process. The value of the counterexample and safety properties generated by Bounded Model Checkers to create test case and to debug these systems is widely recognized. When a Bounded Model Checking (BMC) finds an error it produces a counterexample. Thus, the value of counterexamples to debug software systems is widely recognized in the state-of-the-practice. However, BMCs often produce counterexamples that are either large or difficult to be understood and manipulated mainly because of both the software size and the values chosen by the respective solver. In this work we aim to demonstrate and analyze the use of formal methods (through using the model checking technique) in the process of developing programs in C language, exploring the features already provided by the model checking as the counterexample and the identification and verification of safety properties. In view of this we present two approaches: (i) we describe a method to integrate the bounded model checker ESBMC with the CUnit framework. This method aims to extract the safety properties generated by ESBMC to generate automatically test cases using the rich set of assertions provided by the CUnit framework and (ii) a method aims to automate the collection and manipulation of counterexamples in order to instantiate the analised C program for proving the root cause of the identified error. Such methods may be seen as a complementary technique for the verification performed by BMCs. We show the effectiveness of our proposed method over publicly available benchmarks of C programs. / A utilização de sistemas baseados em computador em diversos domínios aumentou significativamente nos últimos anos. Um dos principais desafios no desenvolvimento de software de sistemas críticos é a garantia da sua correção e confiabilidade. Desta forma, a verificação de software exerce um papel importante para assegurar a qualidade geral do produto, visando principalmente características como previsibilidade e confiabilidade. No contexto de verificação de software, os Bounded Model Checkers estão sendo utilizados para descobrir erros sutis em projetos de sistemas de software atuais, contribuindo eficazmente neste processo de verificação. O valor dos contra-exemplos e propriedades de segurança gerados pelo Bounded Model Checkers para criar casos de testes e para a depuração de sistemas é amplamente reconhecido. Quando um Bounded Model Checking (BMC) encontra um erro ele produz um contra-exemplo. Assim, o valor dos contra-exemplos para depuração de software é amplamente reconhecido no estado da prática. Entretanto, os BMCs frequentemente produzem contra-exemplos que são grandes ou difíceis de entender ou manipular, principalmente devido ao tamanho do software e valores escolhidos pelo solucionador de satisfabilidade. Neste trabalho visamos demonstrar e analisar o uso de método formal (através da técnica model checking) no processo de desenvolvimento de programas na linguagem C, explorando as características já providas pelo model checking como o contra-exemplo e a identificação e verificação de propriedades de segurança. Em face disto apresentamos duas abordagens: (i) descrevemos um método para integrar o Bounded Model Checker ESBMC como o framework de teste unitário CUnit, este método visa extrair as propriedades geradas pelo ESBMC para gerar automaticamente casos de teste usando o rico conjunto de assertivas providas pelo framework CUnit e (ii) um método que visa automatizar a coleta e manipulação dos contra-exemplos, de modo a instanciar o programa C analisado, para comprovar a causa raiz do erro identificado. Tais métodos podem ser vistos como um método complementar para a verificação efetuada pelos BMCs. Demonstramos a eficácia dos métodos propostos sobre benchmarks públicos de código C.
85

Turbulence Modelling Of Thick Axisymmetric Wall-Bounded Flows And Axisymmetric Plume

Dewan, Anupam 03 1900 (has links) (PDF)
No description available.
86

O síle slabých rozšíření teorie V0 / On the Power of Weak Extensions of V0

Müller, Sebastian Peter January 2013 (has links)
Název práce: O síle slabých rozšírení teorie V0 Autor: Sebastian Müller Katedra: Katedra Algebry Vedoucí disertační práce: Prof. RNDr. Jan Krajíček, DrSc., Katedra Algebry. Abstrakt: V predložené disertacní práci zkoumáme sílu slabých fragmentu arit- metiky. Činíme tak jak z modelově-teoretického pohledu, tak z pohledu důkazové složitosti. Pohled skrze teorii modelu naznačuje, že malý iniciální segment libo- volného modelu omezené aritmetiky bude modelem silnější teorie. Jako příklad ukážeme, že každý polylogaritmický řez modelu V0 je modelem VNC. Užitím známé souvislosti mezi fragmenty omezené aritmetiky a dokazatelností v ro- zličných důkazových systémech dokážeme separaci mezi rezolucí a TC0 -Frege systémem na náhodných 3CNF-formulích s jistým poměrem počtu klauzulí vůci počtu proměnných. Zkombinováním obou výsledků dostaneme slabší separační výsledek pro rezoluci a Fregeho důkazové systémy omezené hloubky. Klíčová slova: omezená aritmetika, důkazová složitost, Fregeho důkazový systém, Fregeho důkazový systém omezené hloubky, rezoluce Title: On the Power of Weak Extensions of V0 Author: Sebastian Müller Department: Department of Algebra Supervisor: Prof. RNDr. Jan Krajíček, DrSc., Department of Algebra....
87

Resource-Bounded Reasoning about Knowledge

Ho, Ngoc Duc 28 November 2004 (has links)
Der Begriff ``Agent'''' hat sich als eine sehr nützliche Abstraktion erwiesen, um verschiedene Problembereiche auf eine intuitive und natürliche Art und Weise zu konzeptualisieren. Intelligente Agenten haben daher Anwendung gefunden in verschiedenen Teilbereichen der Informatik. Zur Modellierung werden intelligente Agenten meist als intentionale Systeme aufgefaßt und mit Hilfe von mentalistischen Begriffen wie Wissen, Glauben (oder Überzeugung), Wunsch, Pflicht, Intention usw. beschrieben. Unter diesen mentalen Begriffen gehören die epistemischen Begriffe (d.h., Wissen und Glauben) zu den wichtigsten und wurden auch am intensivsten untersucht. Zur Modellierung von Wissen und Glauben werden in der Regel modale epistemische Logiken verwendet. Solche Systeme sind aber nicht geeignet, um ressourcenbeschränkte Agenten zu beschreiben, weil sie zu starke Annahmen bezüglich der Rationalität von Agenten machen. Zum Beispiel wird angenommen, daß Agenten alle logischen Wahrheiten sowie alle Konsequenzen seines Wissens kennen. Dieses Problem ist bekannt als das Problem der logischen Allwissenheit (``logical omniscience problem''''). Da alle Agenten grundsätzlich nur über begrenzte Ressourcen (wie z.B. Zeit, Information, Speicherplatz) verfügen, können sie nur eine begrenzte Menge von Informationen verarbeiten. Daher müssen alternative Modelle entwickelt werden, um Agenten realistisch modellieren zu können (siehe Kapitel 2). Daß modale epistemische Logik für die Formalisierung des ressourcenbeschränkten Schließens (``resource-bounded reasoning'''') nicht geeignet ist, wird als ein offenes Problem der Agententheorien anerkannt. Es gibt bisher aber keine brauchbaren Alternativen zur Modallogik. Die meisten Ansätze zur Lösung des logischen Allwissenheitsproblems versuchen, Wissen und Glauben mit Hilfe schwacher Modallogiken zu beschreiben. Solche Versuche sind nicht befriedigend, da sie eine willkürliche Einschränkung der Rationalität der Agenten zur Folge haben (siehe Kapitel 3). Mein Ziel ist es, einen Rahmen für das ressourcenbeschränktes Schließen über Wissen und Glauben zu entwickeln. Damit soll eine solide Grundlage für Theorien intelligenter Agenten geschaffen werden. Als Nebenergebnis wird das logische Allwissenheitsproblem auf eine sehr intuitive Art und Weise gelöst: obwohl Agenten rational sind und alle logischen Schlußregeln anwenden können, sind sie nicht logisch allwissend, weil ihnen nicht genügend Ressourcen zu Verfügung stehen, um alle logischen Konsequenzen ihres Wissens zu ziehen. Im Kapitel 4 wird eine Reihe von Logiken vorgestellt, die den Begriff des expliziten Wissens formalisieren. Es wird eine Lösung des Problems der logischen Allwissenheit der epistemischen Logik vorgeschlagen, die die Rationalität der Agenten nicht willkürlich einschränkt. Der Grundgedanke dabei ist der folgende. Ein Agent kennt die logischen Konsequenzen seines Wissens nur dann, wenn er sie tatsächlich hergeleitet hat. Wenn ein Agent alle Prämissen einer gültigen Schlußregel kennt, kennt er nicht notwendigerweise die Konklusion: er kennt sie nur nach der Anwendung der Regel. Wenn er den Schluß nicht ziehen kann, z.B. weil er nicht die notwendigen Ressourcen dazu hat, wird sein Wissen nicht um diese herleitbare Information erweitert. Die Herleitung neuer Informationen wird als die Ausführung mentaler Handlungen aufgefaßt. Mit Hilfe einer Variante der dynamischen Logik können diese Handlungen beschrieben werden. Im Kapitel 5 werden Systeme für das ressourcenbeschränkte Schließen über Wissen und Glauben entwickelt, die auch quantitative Bedingungen über die Verfügbarkeit von Ressourcen modellieren können. Mit Hilfe dieser Logiken können Situationen beschrieben werden, wo Agenten innerhalb einer bestimmten Zeitspanne entscheiden müssen, welche Handlungen sie ausführen sollen. Der Ansatz besteht darin, epistemische Logik mit Komplexitätstheorie zu verbinden. Mit Hilfe einer Komplexitätsanalyse kann ein Agent feststellen, ob ein bestimmtes Problem innerhalb vorgegebener Zeit lösbar ist. Auf der Grundlage dieses Wissens kann er dann die für die Situation geeignete Entscheidung treffen. Damit ist es gelungen, eine direkte Verbindung zwischen dem Wissen eines Agenten und der Verfügbarkeit seiner Ressourcen herzustellen. / One of the principal goals of agent theories is to describe realistic, implementable agents, that is, those which have actually been constructed or are at least in principle implementable. That goal cannot be reached if the inherent resource-boundedness of agents is not treated correctly. Since the modal approach to epistemic logic is not suited to formalize resource-bounded reasoning, the issue of resource-boundedness remains one of the main foundational problems of any agent theory that is developed on the basis of modal epistemic logic. My work is an attempt to provide theories of agency with a more adequate epistemic foundation. It aims at developing theories of mental concepts that make much more realistic assumptions about agents than other theories. The guiding principle of my theory is that the capacities attributed to agents must be empirically verifiable, that is, it must be possible to construct artificial agents which satisfy the specifications determined by the theory. As a consequence, the unrealistic assumption that agents have unlimited reasoning capacities must be rejected. To achieve the goal of describing resource-bounded agents accurately, the cost of reasoning must be taken seriously. In the thesis I have developed a framework for modeling the relationship between knowledge, reasoning, and the availability of resources. I have argued that the correct form of an axiom for epistemic logic should be: if an agent knows all premises of a valid inference rule and if he performs the right reasoning, then he will know the conclusion as well. Because reasoning requires resources, it cannot be safely assumed that the agent can compute his knowledge if he does not have enough resources to perform the required reasoning. I have demonstrated that on the basis of that idea, the problems of traditional approaches can be avoided and rich epistemic logics can be developed which can account adequately for our intuitions about knowledge.
88

Val av Cookies : - En kvantitativ studie om förekomsten av privacy paradox och bounded rationality vid en användares val av cookies.

Dahlgren, Carl, Lundkvist, Elias January 2023 (has links)
Data räknas idag som en av världens värdefullaste resurser. I takt med att internet har blivit mer etablerat och utökat sina användningsområden, har insamlingen av information om dess användare ökat. Genom att använda sig av cookies kan företag analysera sina kunders vanor på internet och på så sätt tillgodose personligt riktad reklam och specialanpassade flöden. Tidigare studier visar att internetanvändare är oroliga över deras personliga integritet på nätet men att de inte tar åtgärder för att skydda den. Fenomenet kallas för privacy paradox och det finns rapporter som tyder på att detta fenomen inte är närvarande hos svenska internetanvändare. Studiens syfte är att undersöka om privacy paradox finns hos svenska internetanvändare och om fenomenet kan förklaras via en avsaknad av kunskap inom området, även kallat bounded rationality. Studiens datamängd samlades in via en internetbaserad enkät och analyserades utifrån studiens teoretiska modell som utgår ifrån det teoretiska ramverket Knowledge-Attitude-Behaviour(KAB). Univariat-, bivariat- och multivariat statistik användes för att beskriva datamängden och besvara forskningsfrågan. SmartPLS användes för att konstruera och analysera PLS-SEM modellerna som användes i den multivariata analysen. Det statistiska programmeringsspråket R användes vid den univariata och bivariata analysen. Resultatet visade att privacy paradox inte kunde fastställas i studiens datamängd. Det kunde även fastställas att datamängden påvisade en hög kunskap gällande cookies, vilket talar emot en förekomst av bounded rationality. / Data is now considered one of the world's most valuable resources. As the internet has become more established and expanded its uses, the collection of user information has increased. By using cookies, companies can analyze their customers' habits on the internet and thus provide personalized advertising and customized feeds. Previous studies show that internet users are concerned about their online privacy but do not take steps to protect it. The phenomenon is called the privacy paradox and there are reports that suggest that this phenomenon is not present among Swedish internet users. The purpose of the study is to investigate whether the privacy paradox is present among Swedish internet users and whether the phenomenon can be explained by a lack of knowledge in the area, also known as bounded rationality. The study's data set was collected via an Internet-based questionnaire and analyzed in the study's theoretical model, a model based on the theoretical framework Knowledge-Attitude-Behavior (KAB). Univariate, bivariate and multivariate statistics were used to describe the data set and answer the research question. SmartPLS was used to construct and analyze the PLS-SEM models used in the multivariate analysis. The statistical programming language R was used for the univariate and bivariate analysis. The results showed that privacy paradox could not be established in the study's data set. It was also determined that the data set showed a high level of knowledge about cookies which is contradicting bounded rationality.
89

[en] OPTIMIZATION OF GEOMETRICAL CONFIGURATION OF RIGID RISERS / [pt] OTIMIZAÇÃO DA CONFIGURAÇÃO GEOMÉTRICA DE RISERS RÍGIDOS

PAULO HENRIQUE DA SILVA CARDOSO 23 October 2019 (has links)
[pt] A crescente demanda pela explotação de óleo em águas cada vez mais profundas representa um desafio para o projeto seguro e eficiente de risers. Tipicamente, o projeto deste elemento estrutural exige um elevado número de análises numéricas e, muitas vezes, se baseia na experiência do projetista, especificamente no que diz respeito à obtenção de uma configuração inicial estruturalmente viável. A automação de tarefas nas fases preliminares de projeto pode proporcionar uma maior eficiência e segurança na seleção de configurações viáveis, além de reduzir o tempo necessário para a realização desta tarefa. Este trabalho propõe uma ferramenta computacional para a otimização de configurações iniciais de risers, satisfazendo requisitos estruturais, operacionais e econômicos. A ferramenta se baseia no método Globalized Bounded Nelder-Mead (GBNM), que não requer o cálculo de gradientes, demanda poucas avaliações da função objetivo por iteração, ou seja, reduz o número de análises dinâmicas realizadas usando o Método dos Elementos Finitos, e permite a implementação de uma estratégia eficiente de paralelização do problema. Para validar e demonstrar a eficiência da ferramenta proposta, são apresentados estudos de caso que reproduzem as condições encontradas em fases iniciais de projetos de risers, bem como uma comparação dos resultados com os obtidos utilizando outros métodos de otimização conhecidos na literatura. / [en] The increasing demand for oil exploitation in deeper water represents a challenge for the safe and efficient design of risers. Typically, the design of this structural member requires a large number of numerical analyses and is often based on the designer’s experience, specifically with respect to obtaining a structurally feasible initial configuration. The automation of tasks in the preliminary stages of design can provide greater efficiency and safety in the selection of feasible configurations, in addition to reducing the time required to perform this task. This work proposes a computational tool to optimize initial riser configurations, satisfying structural, operational and economic requirements. The tool is based on the Globalized Bounded Nelder-Mead method (GBNM), which does not require the computation of gradients, it requires few evaluations of the objective function per iteration, i.e., it reduces the number of dynamic analyses performed using the Finite Element Method, and allows the implementation of an efficient strategy to parallelize the problem. In order to validate and demonstrate the efficiency of the proposed tool, case studies that reproduce the conditions found during the initial stages of the design of risers are presented, as well as a comparison of the results with those obtained using other optimization methods established in the literature.
90

Asymmetrisk Information i Värderingsprocessen : Hur kompenserar värderare för bristande information på den kommersiellafastighetsmarknaden. / Asymmetric Information in the Valuation Process : The way property appraisers compensate for the asymmetric information on the real estatemarket.

Sjöö, Tim, Ahlqvist, Linus January 2022 (has links)
Den svenska fastighetsmarknaden är en högaktuell och attraktiv marknad med en högefterfrågan. Det finns därför ett stort intresse av värdering av fastigheter, vilket är en viktigdel av en fastighetsförsäljning, ett fastighetsköp eller belåning. Hur arbetar då en värderarepå den kommersiella fastighetsmarknaden för att värdera en fastighet, på en marknad därasymmetrisk information gör att de olika aktörerna sitter på olika mycket information? Syftet med detta arbete är att undersöka hur en värderare på den kommersiellafastighetsmarknaden arbetar för att kompensera för den asymmetriska information som blandannat en försäljning genom fastighetspaketering medför. Studien kommer även undersöka omdet finns någon skillnad i processen om värderingen utförs av ett företag med entransaktionsavdelning kopplad till den, eller då värderingsföretaget inte har entransaktionsavdelning. Syftet uppnås i denna studie genom intervjuer utförda med några avde mer etablerade aktörerna inom fastighetsvärdering på den kommersiellafastighetsmarknaden. Studien visar på att det finns klara likheter i hur arbetsprocessen vid värdering av enkommersiell fastighet ser ut, men den visar även på att det finns skillnader företagen emellan,framför allt skillnader mellan företagen med en transaktionsavdelning och de utan en sådanavdelning. Värderare på ett företag med en transaktionsavdelning verkar förlita sig i en relativtstor utsträckning på sin egen transaktionsavdelning vid insamlandet av information,någonting som kan leda till psykologiska begränsningar i informationsinsamlandet. Värderarepå företag som inte har en transaktionsavdelning tenderar att gå mer informella vägar vidinsamlingen av information. / The Swedish property market is a highly current and attractive market with a high demand.Therefore there is a high interest in valuation of properties, which is an important part of realestate sales, buying property or taking loans from the bank. How does a property appraiserwork on the commercial property market, which is known for its asymmetric informationwhere the parties have different amounts of information? The purpose of this study is to examine how a property appraiser on the commercial real estatemarket compensates for the asymmetric information which real estate packaging brings. Thisstudy will also look into whether there is any difference in the process if the valuation isperformed by a company which has a transaction department or if it ́s performed by acompany which does not have a transaction department. The purpose in this study is fulfilledthrough interviews with some of the more established commercial property appraisers. The study shows similarities in the process of valuing a commercial property between thedifferent companies, however, it also shows differences in the process. The differences mainlyshow between the companies with a transaction department and the companies that doesn ́thave this department. Appraisers in a company with a transaction department seems to relyto a wider extent on its own transaction department, when it comes to gather information,something that may lead to psychological restraints in the information gathering. Theappraisers in the companies without a transaction department, take more informal ways togather the information.

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