Volatility is a measure of the risk of an investment and plays an essential role in several areas of finance, including portfolio management and pricing of options. In this thesis, we have implemented and evaluated several so-called GARCH models for volatility prediction based on historical price series. The evaluation builds on different metrics and uses a comprehensive data set consisting of many assets of various types. We found that more advanced models do not, on average, outperform simpler ones. We also found that the length of the historical training data was critical for GARCH models to perform well and that the length was asset-dependent. Further, we developed and tested a method for taking exogenous variables into account in the model to improve the predictive performance of the model. This approach was successful for some of the large US/European indices such as Russell 2000 and S&P 500. / Volatilitet är ett mått på risken i en investering och spelar en viktig roll inom flera olika områden av finans, såsom portföljteori och prissättning av optioner. I det här projektet har vi implementerat och utvärderat olika, så kallade, GARCH modeller för prediktering av volatiliteten givet historisk prisdata. Utvärderingen av modellerna bygger på olika metriker och använder ett omfattande dataset med prishistorik för tillgångar av olika typer. Vi fann att mer komplexa modeller inte i allmänhet ger bättre resultat än enklare modeller. Vidare fann vi att en kritisk parameter för att erhålla goda resultat är att välja rätt längd på tidshistoriken av data som används för att träna modellen, och att den längden skiljer sig mellan olika tillgångar. Slutligen, vidareutvecklade vi modellen genom att inkorporera exogena variabler på olika sätt. Vi fann att det gick att förbättra GARCH modellerna främst med hjälp av några av de stora amerikanska och europeiska index som Russell 2000 och S&P 500.

Software systems are today a part of more or less every organization. The varieties of software used in organizations are ranging from simple log-keeping applications to advanced decision support systems. The task of a priori valuation of software investments has attracted a lot of research for a long time. One of the main themes of this research has been which types of consequences software investments result in and how these consequences can be incorporated in the a priori valuation of the investment. Much of this research has stated the problem as how to incorporate intangible consequences in the valuation since intangible costs and benefits are assumed to represent a large part of the consequences from a software investment. These consequences are therefore highly relevant in the appraisal of software investments. This thesis is concerned with the question of how intangible consequences can be incorporated in the a priori valuation of a software investment. To answer this question, this thesis presents a theoretical model for the valuation of a software investment based upon a discounted cash flow model in continuous time. The general model argued for in this thesis is that usage results in consequences which must be translated into cash flows to be incorporated in a discounted cash flow model. The software usage is chosen as the underlying value creating function since it is the basic underlying function that creates all consequences specific to the software investment. This thesis develops a stochastic cash flow model to incorporate the uncertainty and characteristics of when the intangible conse quences have an effect on the cash flow by adopting a Brownian motion into the valuation model. To find an analytic model for the problem, the expectations of the future cash flows is transformed into risk-neutral expectations. This allows us to use the risk-free rate of return as a discount factor in the model.

Markov processes have a long history of being used to model safety critical systems. However, with the development of autonomous vehicles and their increased complexity, Markov processes have been shown to not be sufficiently precise for reliability calculations. Therefore there has been the need to consider a more general stochastic process, namely the Semi-Markov process (SMP). SMPs allow for transitions with general distributions between different states and can be used to precisely model complex systems. This comes at the cost of increased complexity when calculating the reliability of systems. As such, methods to increase the interpretability of the system and allow for appropriate approximations have been considered and researched. In this thesis, a novel classification approach for transitions in SMP has been defined and complemented with different conjectures and properties. A transition is classified as good or bad by comparing the reliability of the original system with the reliability of any perturbed system, for which the studied transition is more likely to occur. Cases are presented to illustrate the use of this classification technique. Multiple suggestions and conjectures for future work are also presented and discussed. / Markovprocesser har länge använts för att modellera säkerhetskritiska system. Med utvecklingen av autonoma fordon och deras ökade komplexitet, har dock markovprocesser visat sig vara otillräckliga exakta för tillförlitlighetsberäkningar. Därför har det funnits ett behov för en mer allmän stokastisk process, nämligen semi-markovprocessen (SMP). SMP tillåter generella fördelningar mellan tillstånd och kan användas för att modellera komplexa system med hög noggrannhet. Detta innebär dock en ökad komplexitet vid beräkningen av systemens tillförlitlighet. Metoder för att öka systemets tolkningsbarhet och möjliggöra lämpliga approximationer har därför övervägts och undersökts. I den här masteruppsatsen har en ny klassificeringsmetod för övergångar i SMP definierats och kompletteras med olika antaganden och egenskaper. En övergång klassificeras som antingen bra eller dålig genom en jämförelse av tillförlitligheten i det ursprungliga systemets och ett ändrat system, där den studerade övergången har högre sannolikhet att inträffa. Fallstudier presenteras för att exemplifiera användningen av denna klassificeringsteknik. Flera förslag och antaganden för framtida arbete presenteras och diskuteras också.

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機率過程（Stochastic Process）是統計學應用的一個領域，而等候系統模型是機率 過程的一個特例。舉凡能適切劃分顧客及服務者的問題，都可用恰當的等候模型尋求 效益上最佳平衡。 對於M/G/r，GI/M/r及GI/G/r 模型，在分析上不易，且現實生活中，穩定（Stationa ry）及獨立（Independence）的假設均難完全符合，因此在這些假設下所導出的確切 模型（Explicit Model），應算是現實狀況的「概略」模型。對於既複雜又無確切結 果的上述模型，利用運作方便的近似值模型來替代，是本篇論文的主要目的。 全文共六章。第一章緒論；第二章等候理論的幾個基本觀念；第三章確切等候系統模 型，討論M/G/I及GI/M/1 模型，及所遭遇的困難；第四章近似值等候系統模型，討論 GI/G/I模型及由此發展出的近似值與上下界（Bound ）；第五章模擬印證；第六章結 論。

The performance modelling of large-scale systems using discrete-state approaches is fundamentally hampered by the well-known problem of state-space explosion, which causes exponential growth of the reachable state space as a function of the number of the components which constitute the model. Because they are mapped onto continuous-time Markov chains (CTMCs), models described in the stochastic process algebra PEPA are no exception. This thesis presents a deterministic continuous-state semantics of PEPA which employs ordinary differential equations (ODEs) as the underlying mathematics for the performance evaluation. This is suitable for models consisting of large numbers of replicated components, as the ODE problem size is insensitive to the actual population levels of the system under study. Furthermore, the ODE is given an interpretation as the fluid limit of a properly defined CTMC model when the initial population levels go to infinity. This framework allows the use of existing results which give error bounds to assess the quality of the differential approximation. The computation of performance indices such as throughput, utilisation, and average response time are interpreted deterministically as functions of the ODE solution and are related to corresponding reward structures in the Markovian setting. The differential interpretation of PEPA provides a framework that is conceptually analogous to established approximation methods in queueing networks based on meanvalue analysis, as both approaches aim at reducing the computational cost of the analysis by providing estimates for the expected values of the performance metrics of interest. The relationship between these two techniques is examined in more detail in a comparison between PEPA and the Layered Queueing Network (LQN) model. General patterns of translation of LQN elements into corresponding PEPA components are applied to a substantial case study of a distributed computer system. This model is analysed using stochastic simulation to gauge the soundness of the translation. Furthermore, it is subjected to a series of numerical tests to compare execution runtimes and accuracy of the PEPA differential analysis against the LQN mean-value approximation method. Finally, this thesis discusses the major elements concerning the development of a software toolkit, the PEPA Eclipse Plug-in, which offers a comprehensive modelling environment for PEPA, including modules for static analysis, explicit state-space exploration, numerical solution of the steady-state equilibrium of the Markov chain, stochastic simulation, the differential analysis approach herein presented, and a graphical framework for model editing and visualisation of performance evaluation results.

[pt] O objetivo da presente dissertação é capturar o valor da flexibilidade que uma planta XTL oferece na entrada do sistema produtivo, onde podem ser utilizados diversos tipos de insumos como matéria-prima. A saída do sistema produtivo também permite que diferentes produtos sejam produzidos. Desta forma, o autor considera que a metodologia das opções reais é a mais indicada para se avaliar tais flexibilidades, sendo o objeto principal deste estudo a análise da opção de conversão (Input/Output Switch option) através da utilização do processo estocástico de reversão à média com saltos. Os resultados desta dissertação podem auxiliar a tomada de decisão dos gestores da área de petróleo e energia, onde outros projetos já foram avaliados através dessa mesma metodologia, no entanto, não existe qualquer interesse em comprovar a eficiência da teoria das opções reais frente às metodologias de avaliação financeira usuais. / [en] The objective of this dissertation is to value the operational flexibility that a GTL plant can offer at the entrance of the productive process where multiples inputs can be used as row material. Different products also can be produced. The real options theory is considered by the author as the most indicated financial methodology to value theses flexibilities and the main goal of the present study is to value the Input/Output switch option and the mean reversion with jumps stochastic process. The aim of this study is also to support manager´s investment decision from oil and energy field, where others projects has been already valuated with real options theory so the proof of the theory efficiency against traditional valuation methodologies is not object from this study.

[pt] O objetivos desta dissertação é fazer uma análise de investimentos usando a teoria das Opções Reais de uma planta GTL. Está análise é a mais indicada, pois se verificam várias flexibilidades nesta planta em relação aos inputs (pode ser usado mais de um produto como matéria- prima) e em relação aos outputs (existem várias combinações possíveis de produção). Torna-se de grande importância neste caso saber calcular o valor destas opções e verificar se vale a pena ou não a construção de uma planta que possa usar como matéria prima mais de um produto e/ou que possa produzir mais de uma possível combinação de produção. A construção de uma planta que possua a possibilidade de trocar de insumo e/ou trocar a combinação de produção só será viável caso o valor criado pela flexibilidade seja maior do que o custo necessário para implementá-la (investimento adicional e custos operacionais extras). Sendo assim, o objetivo desta dissertação é calcular até quanto a Petrobras estaria disposta a pagar para ter uma planta que possua a opção de swicth use dos inputs e/ou outputs, o valor que ela teria que investir para usufruir desta flexibilidade, e através da diferença entre estes valores verificar se vale a pena ou não a construção da planta com flexibilidade de input e/ou output. / [en] The objective of this dissertation is to do a analysis of investiment using the real option theory for the plant GTL. This analysis is the best because there are many flexibilities in this plant in relation the inputs (the plant can operate with several inputs) and in relation the outputs (there are many possible combination of production). In this case is very important to know how to calculate the value of these options and to verify if it is worthwhile or not the construction of a plant that could use two inputs and/or is able to procuce several possible combinations of production. The construction of the plant that change the input abd /or can changer the production combination is viable if the value created by flexibility is large than the necessary cost to implement its (additional investiment and extra operational costs). So, the objective of this dissertation is to calculate until hen Petrobras would be avaible to pay in order to have a plant that has the option of swicth use of inputs and/or outputs, the value it would have to invest to use this flexibility, and through the difference between these values verify if is worthwhile or not the construction of the plant with the flexibility of input and/or output.

Neste trabalho estudamos um modelo estocástico com simetria Ising e dois estados absorventes em três dimensões com uma rede cúbica e em duas dimensões através de uma rede triangular. O estudo levou em conta cálculos de aproximação de campo médio e simulações de Monte Carlo. Os resultados mostraram que o modelo tem transição de segunda ordem de uma fase paramagnética para uma fase ferromagnética, uma transição da fase ferromagnética para uma fase absorvente, também de segunda ordem, e ainda uma transição de primeira ordem da fase paramagnética para a fase absorvente. No espaço de parâmetros as três linhas de transição se encontram no diagrama de fases em um ponto onde o modelo se comporta como o modelo do votante. / In this work we studied a stochastic model with ising symmetry and two simmetric absorbing configurations in a three-dimensional cubic lattice and in two dimensions using a triangular lattice. The study took into account simple mean-field approximations and Monte Carlo simulations. The results showed that the model has a second-order transition from a paramagnetic phase to a ferromagnetic phase and second-order transition from ferromagnetic phase to the absorbing one. A first-order phase transition from the paramagnetic phase to the absorbing phase is observed too. In the phase diagram the two second-order transition lines aproaches to the point where the model behaves like the voter model.