All systems are unreliable in the sense that they degrade with age and usage and eventually fail. The degradation depends on the load (or stress) on the system and the maintenance actions. With higher load the productivity increases but this is achieved at the expense of faster degradation and more frequent failures. This in turn reduces the availability of the system. The yield (expected output per unit time), expected operational cost and the expected profit are functions of the load and the availability. The relationship between load and yield is a complicated function and depends on system reliability and maintenance actions. The thesis deals with determining the optimal load and maintenance actions to maximise the yield (or expected profit) or to minimise the expected cost. The thesis comprises of two parts (Parts I and II). Part I is theoretical in nature and looks at the modelling, analysis and optimisation issues. Part II deals with a real case study involving a dragline used in open cut mining. Part I starts with stress-life models which link the load on the system with the reliability of the system. It examines the empirical data in the form of S-N and P-S-N curves, and as WPP plots reported in the literature. The salient features are identified so as to assess the suitability of different models to model the stress-life data. Various Weibull models are assessed to determine their suitability to model stress-life data at the component level. This is followed by a discussion of the modelling at the system level. Optimal maintenance actions are derived based on component level and system level stress-life models. For the component level models, the optimal maintenance actions are derived for a variety of maintenance strategies (such as the age, block and periodic policies) for a specified load to minimise the asymptotic expected cost per unit time. Following this, the joint optimal choice of load and maintenance is examined. For the system level model, the optimal load is obtained to minimise the expected cost per unit time over the life of the system taking into account different actions such as minor and major preventive maintenance actions and corrective maintenance actions. Part II deals with a case study involving a BE1370W dragline. The dragline is used in open cut coal mining to remove the dirt (overburden) on top of the coal seam. This involves dragging the bucket, which is suspended from the boom, through the muckpile until full and then hoisting and swinging the bucket to the dumping point. The capacity of the bucket size determines the load on the dragline. The system level model studied in Part I is used to determine the optimal load to maximise the yield. The dragline was modelled as comprising of 25 components (or sub-systems). Each component was modelled using a system level model of Part I. The model parameters were estimated using real operating and maintenance data over two years. The optimal load to maximise the yield was derived and a sensitivity study carried out.

Estudos anteriores têm relatado um decremento na capacidade de produção de força com a idade. Mudanças estruturais e funcionais nos músculos esqueléticos tal como a sarcopenia (perda de massa muscular), diminuição da ativação das unidades motoras, co-contração aumentada da musculatura antagonista, diminuição da tensão da fibra muscular e rigidez do tendão são referidos para explicar a funcionalidade motora reduzida em indivíduos idosos. Este estudo objetivou investigar as mudanças ligadas à idade na produção de torque voluntário isométrico e isocinético (TVM), como também as respostas eletromiográficas (EMG). Hipotetizamos, como conseqüências do envelhecimento: a) uma redução da capacidade de produção de TVM; b) deslocamento da curva torque-ângulo (para a esquerda) na direção de menores comprimentos musculares; c) deslocamento da curva torque-velocidade (para a esquerda) na direção de menores velocidades; d) que uma menor ativação muscular seria observada. Quarenta indivíduos saudáveis, do gênero masculino, divididos igual e randomizadamente em quatro grupos (15-30; 31-45; 46-60 e 61-75 anos), participaram neste estudo como sujeitos, aos quais foram solicitados produzir torques máximos de extensão de joelho em um dinamômetro isocinético (Byodex®) em diferentes ângulos (15º; 30º;45º; 60º; 75º; 90º e 105º) e velocidades (60º/s; 120º/s; 180º/s; 240º/s; 300º/s e 360º/s) Sinais da EMG dos músculos da coxa, como vasto lateral, reto femoral e vasto medial foram simultaneamente registrados. O nível de atividade física foi avaliado pelo IPAQforma curta (International questionnaire of physical activity ). Valores de TVM, valores RMS do sinal EMG e nível de atividade física foram usados como medidas dependentes. Os resultados demonstraram uma diminuição no TVM com a idade. Particularmente, menores valores de TVM foram encontrados durante as maiores velocidades em condições isocinéticas. Nenhuma mudança foi observada nas curvas torque-ângulo e torque-velocidade e nenhuma mudança ligada à idade foram encontradas nas respostas da EMG. Concluímos que a idade afeta a produção de TVM, particularmente em maiores velocidades. Além disso, os resultados permitemnos apontar que os altos níveis de atividade física e demandas funcionais possam explicar a similaridade encontrada nas respostas EMG entre os diferentes grupos. / Previous studies have reported a decrease in force production ability with age. Structural and functional changes on the skeletal muscles such as sarcopenia (loss of muscle mass), decreased ability of motor unit firing, increased co-activation of antagonist muscle, decreased muscle fiber tension and tendon’s rigidity are taken into account for the reduced motor functionality in elderly individuals. This study aimed to investigate age-related changes of maximum voluntary isometric and isokinetic torque production (MVT), as well as electromyography (EMG) responses. We hypothesized that as consequence of aging: a) a reduced ability of MVT production; b) a torque/angle curve displacement (left side) towards the lowers muscle lengths; c) a torque/velocity curve displacement (left side) towards smaller velocities; d) and decreased muscle activation will be observed. Forty healthy male individuals, evenly and randomly divided in four age groups (15–30; 31– 35; 45– 60; 60–75 years old), participated in this study as subjects. The subjects were asked to produce maximum knee extension torques on the isokinetic dynamometer (Cybex ®) in different angles (15º; 30º; 45º; 60º; 75º; 90º and 105º) and velocities (60º/s; 120º/s; 180º/s; 240º/s; 300º/s and 360º/s) EMG signals from the upper leg muscles such as, vatsus lateralis, rectus femoris, vastus medialis, were simultaneously recorded. The level of physical activity was evaluated by the QIAF–short form (International questionnaire of physical activity). MVT values, RMS values from EMG signals and level of physical activity were used as dependent measures. The results showed a decrease in MVT with age. Particularly, lower values of MVT were found during higher velocities under isokinetic condition. No changes were observed for torque/angle and torque/velocity curves and no age-related changes were found on the EMG responses. We conclude that aging affects MVT production, particularly during high velocities. In addition, the results allowed us to point out that higher levels of physical activity and functional demand, showed by the older groups, could explain the similarities found on EMG responses among the different age groups.

Estudos anteriores têm relatado um decremento na capacidade de produção de força com a idade. Mudanças estruturais e funcionais nos músculos esqueléticos tal como a sarcopenia (perda de massa muscular), diminuição da ativação das unidades motoras, co-contração aumentada da musculatura antagonista, diminuição da tensão da fibra muscular e rigidez do tendão são referidos para explicar a funcionalidade motora reduzida em indivíduos idosos. Este estudo objetivou investigar as mudanças ligadas à idade na produção de torque voluntário isométrico e isocinético (TVM), como também as respostas eletromiográficas (EMG). Hipotetizamos, como conseqüências do envelhecimento: a) uma redução da capacidade de produção de TVM; b) deslocamento da curva torque-ângulo (para a esquerda) na direção de menores comprimentos musculares; c) deslocamento da curva torque-velocidade (para a esquerda) na direção de menores velocidades; d) que uma menor ativação muscular seria observada. Quarenta indivíduos saudáveis, do gênero masculino, divididos igual e randomizadamente em quatro grupos (15-30; 31-45; 46-60 e 61-75 anos), participaram neste estudo como sujeitos, aos quais foram solicitados produzir torques máximos de extensão de joelho em um dinamômetro isocinético (Byodex®) em diferentes ângulos (15º; 30º;45º; 60º; 75º; 90º e 105º) e velocidades (60º/s; 120º/s; 180º/s; 240º/s; 300º/s e 360º/s) Sinais da EMG dos músculos da coxa, como vasto lateral, reto femoral e vasto medial foram simultaneamente registrados. O nível de atividade física foi avaliado pelo IPAQforma curta (International questionnaire of physical activity ). Valores de TVM, valores RMS do sinal EMG e nível de atividade física foram usados como medidas dependentes. Os resultados demonstraram uma diminuição no TVM com a idade. Particularmente, menores valores de TVM foram encontrados durante as maiores velocidades em condições isocinéticas. Nenhuma mudança foi observada nas curvas torque-ângulo e torque-velocidade e nenhuma mudança ligada à idade foram encontradas nas respostas da EMG. Concluímos que a idade afeta a produção de TVM, particularmente em maiores velocidades. Além disso, os resultados permitemnos apontar que os altos níveis de atividade física e demandas funcionais possam explicar a similaridade encontrada nas respostas EMG entre os diferentes grupos. / Previous studies have reported a decrease in force production ability with age. Structural and functional changes on the skeletal muscles such as sarcopenia (loss of muscle mass), decreased ability of motor unit firing, increased co-activation of antagonist muscle, decreased muscle fiber tension and tendon’s rigidity are taken into account for the reduced motor functionality in elderly individuals. This study aimed to investigate age-related changes of maximum voluntary isometric and isokinetic torque production (MVT), as well as electromyography (EMG) responses. We hypothesized that as consequence of aging: a) a reduced ability of MVT production; b) a torque/angle curve displacement (left side) towards the lowers muscle lengths; c) a torque/velocity curve displacement (left side) towards smaller velocities; d) and decreased muscle activation will be observed. Forty healthy male individuals, evenly and randomly divided in four age groups (15–30; 31– 35; 45– 60; 60–75 years old), participated in this study as subjects. The subjects were asked to produce maximum knee extension torques on the isokinetic dynamometer (Cybex ®) in different angles (15º; 30º; 45º; 60º; 75º; 90º and 105º) and velocities (60º/s; 120º/s; 180º/s; 240º/s; 300º/s and 360º/s) EMG signals from the upper leg muscles such as, vatsus lateralis, rectus femoris, vastus medialis, were simultaneously recorded. The level of physical activity was evaluated by the QIAF–short form (International questionnaire of physical activity). MVT values, RMS values from EMG signals and level of physical activity were used as dependent measures. The results showed a decrease in MVT with age. Particularly, lower values of MVT were found during higher velocities under isokinetic condition. No changes were observed for torque/angle and torque/velocity curves and no age-related changes were found on the EMG responses. We conclude that aging affects MVT production, particularly during high velocities. In addition, the results allowed us to point out that higher levels of physical activity and functional demand, showed by the older groups, could explain the similarities found on EMG responses among the different age groups.

Determinar curvas a partir de uma série da pontos é uma tarefa importante e muito utilizada em CAD. Este trabalho propõe um algoritmo para determinar uma curva aproximadora representada por diversas curvas de Bézier em sequência a partir de uma sequência de pontos. É utilizada uma abordagem de curvas de Bézier por trechos, onde cada trecho possui continuidade C1-fraca. A otimização é feita pelo recozimento simulado com vizinhança adaptativa que minimiza a soma das distâncias de cada ponto da sequência à curva aproximadora e utiliza o comprimento da curva aproximadora como um fator de regularização. Adicionalmente, é utilizado o recozimento simulado multi-objetivo que avalia a influência da soma das distâncias de cada ponto à curva e do comprimento da curva separadamente. Também é feita uma comparação entre a técnica de ajuste de curvas e a técnica de interpolação de curvas. / The task of determining a curve from a set of points is very important in CAD. This work proposes an algorithm to determine a sequence of Bézier curves that approximate a sequence of points. The piecewise Bézier curve is used, where each curve has C1- weak continuity. The optimization is done using the simulated annealing with adaptive neighborhood aiming at minimizing the sum of the distances from each point of the sequence to the generated curve. The length of this curve is used as a regularization factor. In addition, it is used a multi-objective simulated annealing that evaluates the influence of the sum of the distances from each point to the generated curve, and the curves length. It is also done a comparison between curve fitting and curve interpolation techniques.

Les courbes remplissant l'espace sont connues pour la capacité d'ordonner les points multidimensionnels sur une ligne en tout conservant la localité, i.e. les points proches sont toujours proches sur la ligne. La conservation de la localité est beaucoup recherchée dans plusieurs applications. La courbe de Hilbert est la courbe remplissant l'espace qui conserve le mieux la localité. Cette courbe est originalement proposée en 2D, i.e. n'est qu'applicable aux points dans un espace 2D. Pour une perspective d'application dans le cas multidimensionnel, nous proposons dans cette thèse une généralisation de la courbe de Hilbert. La courbe généralisée est définie en s'appuyant sur la propriété essentielle de la courbe de Hilbert qui crée son niveau de conservation de la localité : l'adjacence. Ainsi, elle évite la dépendance du motif primitif RBG qui est le seul motif primitif de la courbe étendu par les recherches précédentes. Le résultat est donc une famille de courbe conservant bien la localité. L'optimisation de la conservation de la localité est aussi abordée pour permettre de retrouver la courbe qui conserve le mieux la localité. Pour cet objectif, nous proposons une mesure de la conservation de la localité. En s'appuyant sur les paramètres, cette mesure peut adapter aux différentes situations applicatives comme le changement de métrique ou de taille de localité. La construction est une partie importante de la thèse, elle est la base du calcul de l'index utilisé dans l'application. Pour un calcul de l'index rapide, la courbe de Hilbert autosimilaire est utilisée. La courbe de Hilbert satisfaisant les conditions de la courbe fait l'objet du chapitre 4. La courbe généralisée est enfin appliquée dans la recherche d'image. Il s'agit d'une recherche par le contenu où chaque image est caractérisée par un vecteur multidimensionnel. Les images sont ordonnées par la courbe sur une ligne ; ainsi, la recherche est simplifiée en une recherche sur une liste ordonnée. En donnant une image d'entrée, les images similaires sont celles correspondantes aux index voisins de l'index de l'image d'entrée. La conservation de la localité garantit que ces index correspondent aux images similaires. / The space-filling curves are known for the ability to order the multidimensional points on a line while preserving the locality, i.e. the close points are closely ordered on the line. The locality preserving is wished in many applications. Hilbert curve is the best locality preserving space-filling curve. This curve is originally proposed in 2D, i.e. it is only applied to points in a 2D space. For application in the multidimensional case, we propose in this thesis a generalization of Hilbert curve. Generalized curve is based on the essential property of Hilbert curve that creates its level of locality preserving: the adjacency. Thus, it avoids the dependence on the pattern RBG, which is the only pattern of the curve extended by previous researches. The result is a family of curves preserving well the locality. The optimization of the locality preserving is also addressed to find out the best locality preserving curve. For this purpose, we propose a measure of the locality preserving. Based on the parameters, this measure can adapt to different application situations such as the change of metric or locality size. The curve construction is an important part of the thesis. It is the basis of the index calculation used in application. For a rapid index calculation, the self-similar Hilbert curves is used. They are Hilbert curves satisfying the self-similar conditions specified in chapitre 4. The generalized curve is finally applied in image search. It is the question of the content-based image search (CBIR) where each image is characterized by a multidimensionalvector. Images are ordered by the curve of a line, and the search is simplified to the search on an ordered list. By giving an input image, similar images are those corresponding to neighbors of the index of the input. The locality preserving ensures that these indexes correspond to similar images.

This thesis investigates errors on speech sounds (or phonemes) produced in laboratory speech stimuli designed to generate phonological onset errors. The present study adds to the literature on phonological speech errors with an instrumental analysis of tongue posture during speech error production and an investigation of the nature of speech errors as unintended variation in articulation. This study utilized ultrasound instrumentation to visualize speech errors made on velar and alveolar stop consonants at the point of stop closure. Two types of errors were of interest, categorical errors and gradient errors. Categorical errors are those that are heard by the listener and instrumentally appear to be a correct production of an incorrect target. Gradient errors are those that are usually heard to be the correct target, but on instrumental examination display characteristics of an incorrect production. Six participants repeated eight tongue twisters in both a baseline and an experimental condition. This study was interested in errors produced on the onset stop consonant pairs /t, d/ and /k, g/. Recordings were transcribed to determine the perceptual identity of each target. Ultrasound videos were then analyzed and an individual frame representing the articulatory posture for each closure was extracted. These frames were fit with a smoothing spline curve using Edgetrak software. A curve-to-curve analysis based on the methods of Zharkova (2009) was conducted as a means of further investigating variation in individual speakers as well as providing a quantitative measure of errors. Results from the six speakers showed that all produced both categorical and gradient errors. The speakers showed individual variation in the stability of their productions and overall rate of errors. There was an observable trend for speakers who were more stable in their baseline productions to produce fewer errors, both gradient and categorical, in the experimental portion. Conversely, those speakers who exhibited more variation in their baseline productions had a higher rate of error under the experimental condition.

The main goal of the thesis is to explore selected economical hypotheses through theoretical conception applying macroeconomics data from the Czech Republic. This thesis includes the following hypotheses: budget deficits solved by increasing taxes, compromise between unemployment and inflation, low impact of budget deficits. To verify these hypotheses, there is a comparison with economic theories such as Laffer curve, which has showed that Laffer peak is at the level of 22 % taxation. Other used theory is the Phillips curve where correlation between inflation and unemployment rate is stronger based on yearly data than on monthly data. Theoretical model IS-LM has confirmed that multiplication effect could have caused the positive economic growth in 2010 and 2011. Even if economical hypothesizes are partially correct, they are not recommended for the government to determine their decisions. There are more efficient long-term solutions that can be used to solve challenges of the recent economic situation.

O problema de seleção de características, no contexto de Reconhecimento de Padrões, consiste na escolha de um subconjunto X de um conjunto S de características, de tal forma que X seja \"ótimo\" dentro de algum critério. Supondo a escolha de uma função custo c apropriada, o problema de seleção de características é reduzido a um problema de busca que utiliza c para avaliar os subconjuntos de S e assim detectar um subconjunto de características ótimo. Todavia, o problema de seleção de características é NP-difícil. Na literatura existem diversos algoritmos e heurísticas propostos para abordar este problema; porém, quase nenhuma dessas técnicas explora o fato que existem funções custo cujos valores são estimados a partir de uma amostra e que descrevem uma \"curva em U\" nas cadeias do reticulado Booleano (P(S),<=), um fenômeno bem conhecido em Reconhecimento de Padrões: conforme aumenta-se o número de características consideradas, há uma queda no custo do subconjunto avaliado, até o ponto em que a limitação no número de amostras faz com que seguir adicionando características passe a aumentar o custo, devido ao aumento no erro de estimação. Em 2010, Ris e colegas propuseram um novo algoritmo para resolver esse caso particular do problema de seleção de características, que aproveita o fato de que o espaço de busca pode ser organizado como um reticulado Booleano, assim como a estrutura de curvas em U das cadeias do reticulado, para encontrar um subconjunto ótimo. Neste trabalho estudamos a estrutura do problema de minimização de funções custo cujas cadeias são decomponíveis em curvas em U (problema U-curve), provando que o mesmo é NP-difícil. Mostramos que o algoritmo de Ris e colegas possui um erro que o torna de fato sub-ótimo, e propusemos uma versão corrigida e melhorada do mesmo, o algoritmo U-Curve-Search (UCS). Apresentamos também duas variações do algoritmo UCS que controlam o espaço de busca de forma mais sistemática. Introduzimos dois novos algoritmos branch-and-bound para abordar o problema, chamados U-Curve-Branch-and-Bound (UBB) e Poset-Forest-Search (PFS). Para todos os algoritmos apresentados nesta tese, fornecemos análise de complexidade de tempo e, para alguns deles, também prova de corretude. Implementamos todos os algoritmos apresentados utilizando o arcabouço featsel, também desenvolvido neste trabalho; realizamos experimentos ótimos e sub-ótimos com instâncias de dados reais e simulados e analisamos os resultados obtidos. Por fim, propusemos um relaxamento do problema U-curve que modela alguns tipos de projeto de classificadores; também provamos que os algoritmos UCS, UBB e PFS resolvem esta versão generalizada do problema. / The feature selection problem, in the context of Pattern Recognition, consists in the choice of a subset X of a set S of features, such that X is \"optimal\" under some criterion. If we assume the choice of a proper cost function c, then the feature selection problem is reduced to a search problem, which uses c to evaluate the subsets of S, therefore finding an optimal feature subset. However, the feature selection problem is NP-hard. Although there are a myriad of algorithms and heuristics to tackle this problem in the literature, almost none of those techniques explores the fact that there are cost functions whose values are estimated from a sample and describe a \"U-shaped curve\" in the chains of the Boolean lattice o (P(S),<=), a well-known phenomenon in Pattern Recognition: for a fixed number of samples, the increase in the number of considered features may have two consequences: if the available sample is enough to a good estimation, then it should occur a reduction of the estimation error, otherwise, the lack of data induces an increase of the estimation error. In 2010, Ris et al. proposed a new algorithm to solve this particular case of the feature selection problem: their algorithm takes into account the fact that the search space may be organized as a Boolean lattice, as well as that the chains of this lattice describe a U-shaped curve, to find an optimal feature subset. In this work, we studied the structure of the minimization problem of cost functions whose chains are decomposable in U-shaped curves (the U-curve problem), and proved that this problem is actually NP-hard. We showed that the algorithm introduced by Ris et al. has an error that leads to suboptimal solutions, and proposed a corrected and improved version, the U-Curve-Search (UCS) algorithm. Moreover, to manage the search space in a more systematic way, we also presented two modifications of the UCS algorithm. We introduced two new branch-and-bound algorithms to tackle the U-curve problem, namely U-Curve-Branch-and-Bound (UBB) and Poset-Forest-Search (PFS). For each algorithm presented in this thesis, we provided time complexity analysis and, for some of them, also proof of correctness. We implemented each algorithm through the featsel framework, which was also developed in this work; we performed optimal and suboptimal experiments with instances from real and simulated data, and analyzed the results. Finally, we proposed a generalization of the U-curve problem that models some kinds of classifier design; we proved the correctness of the UCS, UBB, and PFS algorithms for this generalized version of the U-curve problem.

This dissertation emphasizes the security aspects of real-time media. The problems of existing real-time media protections are identified in this research, and viable solutions are proposed. First, the security of real-time media depends on the Secure Real-time Transport Protocol (SRTP) mechanism. We identified drawbacks of the existing SRTP Systems, which use symmetric key encryption schemes, which can be exploited by attackers. Elliptic Curve Cryptography (ECC), an asymmetric key cryptography scheme, is proposed to resolve these problems. Second, the ECC encryption scheme is based on elliptic curves. This dissertation explores the weaknesses of a widely used elliptic curve in terms of security and describes a more secure elliptic curve suitable for real-time media protection. Eighteen elliptic curves had been tested in a real-time video transmission system, and fifteen elliptic curves had been tested in a real-time audio transmission system. Based on the performance, X9.62 standard 256-bit prime curve, NIST-recommended 256-bit prime curves, and Brainpool 256-bit prime curves were found to be suitable for real-time audio encryption. Again, X9.62 standard 256-bit prime and 272-bit binary curves, and NIST-recommended 256-bit prime curves were found to be suitable for real-time video encryption.The weaknesses of NIST-recommended elliptic curves are discussed and a more secure new elliptic curve is proposed which can be used for real-time media encryption. The proposed curve has fulfilled all relevant security criteria, but the corresponding NIST curve could not fulfill two such criteria. The research is applicable to strengthen the security of the Internet of Things (IoT) devices, especially VoIP cameras. IoT devices have resource constraints and thus need lightweight encryption schemes for security. ECC could be a better option for these devices. VoIP cameras use a similar methodology to traditional real-time video transmission, so this research could be useful to find a better security solution for these devices.

The purpose of this paper is to investigate the relationship between economic development and pollution in the middle- and high-income countries for the period between 1960 and 2014. The study is conducted by first testing the environmental Kuznets curve, an economic theory that income has an inverted U-shape relationship with environmental degradation. Later, the Revised environmental Kuznets curve is tested, an economic theory that countries undergoing economic development at a later period will have a lower peak of environmental degradation compared to countries undergoing economic development at an earlier period. Empirical tests of carbon dioxide (CO2) per capita and income (GDP per capita) were conducted in two different panel tests containing middle-income countries in one and high-income countries in the other. The observed relationship shows that a country's early economic development degrades the environment until what is called the turning point is reached, after which the environment improves with further economic development. Thus, the expected inverted U-shape is observed for both MIE and HIE. Furthermore, the tests tell us that the turning point for MIE is significantly lower than for HIE, which is the expected result.