Vegetation is commonly modelled as emergent arrays of rigid, circular cylinders. However, the drag coefficient (CD) of real stems or trunks is closer to that of cylinders with a square cross-section. In this thesis, vegetation has been idealised as square cylinders in laboratory experiments with a turbulence intensity of the order of 10% which is similar to that of typical river flows. These cylinders may also represent other obstacles such as architectural structures. This research has determined CD of an isolated cylinder and cylinder pairs as a function of position as well as the average drag coefficient (CDv) of larger arrays. A strain gauge was used to measure CD whilst CDv was computed with a momentum balance which was validated by strain gauge measurements for a regularly spaced array. The velocity and turbulence intensity surrounding a pair of cylinders arranged one behind the other with respect to mean flow (in tandem) were also measured with an Acoustic Doppler Velocimeter. The isolated cylinder CD was found to be 2.11 in close agreement with other researchers. Under fixed flow conditions CD for a cylinder in a pair was found to be as low as -0.40 and as high as 3.46 depending on their relative positioning. For arrays, CDv was influenced more by the distribution of cylinders than the flow conditions over the range of conditions tested. Mean values of CDv for each array were found to be between 1.52 and 3.06. This new insight therefore suggests that CDv for vegetation in bulk may actually be much higher than the typical value of 1 which is often assumed to apply in practice. If little other information is available, a crude estimate of CDv = 2 would be reasonable for many practical applications. The validity of a 2D realizable k-epsilon turbulence model for predicting the flow around square cylinders was evaluated. The model was successful in predicting CD for an isolated cylinder. In this regard the model performed as well as Large Eddy Simulations by other authors with a significant increase in computational efficiency. However, the numerical model underestimates CD of downstream cylinders in tandem pairs and overestimates velocities in their wake. This suggests it may be necessary to expand the model to three-dimensions when attempting to simulate the flow around two or more bluff obstacles with sharp edges.

Made available in DSpace on 2014-12-17T15:15:01Z (GMT). No. of bitstreams: 1 MariaLC_TESE.pdf: 10138137 bytes, checksum: 77bd9c3c6dc76faa3f4dc70c892af4b1 (MD5) Previous issue date: 2014-04-07 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Stellar differential rotation is an important key to understand hydromagnetic stellar dynamos, instabilities, and transport processes in stellar interiors as well as for a better treatment of tides in close binary and star-planet systems. The space-borne high-precision photometry with MOST, CoRoT, and Kepler has provided large and homogeneous datasets. This allows, for the first time, the study of differential rotation statistically robust samples covering almost all stages of stellar evolution. In this sense, we introduce a method to measure a lower limit to the amplitude of surface differential rotation from high-precision evenly sampled photometric time series such as those obtained by space-borne telescopes. It is designed for application to main-sequence late-type stars whose optical flux modulation is dominated by starspots. An autocorrelation of the time series is used to select stars that allow an accurate determination of spot rotation periods. A simple two-spot model is applied together with a Bayesian Information Criterion to preliminarily select intervals of the time series showing evidence of differential rotation with starspots of almost constant area. Finally, the significance of the differential rotation detection and a measurement of its amplitude and uncertainty are obtained by an a posteriori Bayesian analysis based on a Monte Carlo Markov Chain (hereafter MCMC) approach. We apply our method to the Sun and eight other stars for which previous spot modelling has been performed to compare our results with previous ones. The selected stars are of spectral type F, G and K. Among the main results of this work, We find that autocorrelation is a simple method for selecting stars with a coherent rotational signal that is a prerequisite to a successful measurement of differential rotation through spot modelling. For a proper MCMC analysis, it is necessary to take into account the strong correlations among different parameters that exists in spot modelling. For the planethosting star Kepler-30, we derive a lower limit to the relative amplitude of the differential rotation. We confirm that the Sun as a star in the optical passband is not suitable for a measurement of the differential rotation owing to the rapid evolution of its photospheric active regions. In general, our method performs well in comparison with more sophisticated procedures used until now in the study of stellar differential rotation / A rota??o diferencial superficial ? um importante par?metro para a compreens?o do d?namo hidromagn?tico estelar, instabilidades e processos de transportes no interior estelar, bem como fornece subs?dios para um melhor tratamento das mar?s em bin?rias pr?ximas e sistemas estrela-planeta. As miss?es espaciais MOST, CoRoT e Kepler t?m fornecido uma grande e homog?nea quantidade de dados fotom?tricos. O que permite, pela primeira vez, o estudo da rota??o diferencial em amostras estatisticamente robustas cobrindo quase todos os est?gios da evolu??o estelar. Nesta tese, n?s desenvolvemos e apresentamos um m?todo para medir o limite inferior para a amplitude da rota??o diferencial a partir de s?ries fotom?tricas igualmente espa?adas, tais como aquelas obtidas pelas miss?es espaciais supracitadas. O modelo foi concebido para ser aplicado em estrelas do tipo solar cuja modula??o ?tica ? dominada pelo efeito das manchas estelares. As estrelas s?o selecionadas a partir de uma autocorrela??o das s?ries temporais, o que permite uma determina??o precisa dos per?odos de rota??o das manchas. Um modelo simples de duas manchas ? aplicado juntamente com crit?rios de informa??o bayesiana para selecionar, preliminarmente, os intervalos das s?ries temporais que mostram evid?ncias de rota??o diferencial com manchas de ?rea quase constante. A signific?ncia da rota??o diferencial detectada e as medidas de sua amplitude e incertezas s?o obtidas por an?lise a posteriori bayesiana, em uma aproxima??o Monte Carlo via cadeias de Markov (MCMC). Aplicamos nosso m?todo para o Sol e outras oito estrelas para as quais a modelagem de manchas foi anteriormente realizada. As estrelas selecionadas s?o de tipo espectral F, G e K. Obtivemos ent?o a rota??o diferencial e comparamos os resultados obtidos pelo nosso m?todo com aqueles j? conhecidos na literatura. Entre os principais resultados deste trabalho, encontramos que autocorrela??o ? um m?todo simples e eficaz para sele??o de estrelas com um sinal rotacional coerente, pr?-requisito para uma medida de rota??o diferencial por meio de modelagem de manchas. Para uma an?lise adequada de MCMC ? necess?rio levar em considera??o a forte correla??o entre diferentes par?metros existentes na modelagem de manchas. Para a estrela hospedeira de planeta Kepler-30, encontramos um baixo limite para uma amplitude relativa de rota??o diferencial. Tamb?m, confirmamos ainda que o nosso modelo n?o ? adequado para medir a rota??o diferencial do Sol como uma estrela, na banda ?tica, devido ? r?pida evolu??o de suas regi?es fotosf?ricas ativas. Em geral, o nosso modelo funciona bem em compara??o com os mais sofisticados procedimentos at? agora utilizados no estudo da rota??o diferencial estelar

O Clostridium perfringens é um microrganismo anaeróbio que está presente no solo e no trato intestinal dos mamíferos. Provoca intoxicação alimentar nos seres humanos, doenças enterotoxêmicas nos animais domésticos e gangrena gasosa em ambos os grupos. O C. perfringens é classificado em cinco tipos (A, B, C, D e E) mediante a produção de quatro toxinas principais (alfa, beta, épsilon e iota). Neste trabalho foi possível padronizar a técnica de PCR para detectar a presença dos genes cpa, cpb e etx a partir de culturas de C. perfringens. A sensibilidade analítica da técnica de PCR a partir de culturas de C. perfringens foi de 2,27 ng/µL para o gene cpa, 22,7 pg/µL para o gene cpb e 22,7 pg/µL para o gene etx. A pesquisa dos genes cpa, cpb e etx partir de 35 amostras de C. perfringens isoladas de bovinos revelou que 16 (45,7%) eram do tipo A; 18 (51,4%) eram do tipo C e 1 (2,9%) era do tipo B. Não foi observada nenhuma amostra do tipo D. A metodologia de PCR revelou-se útil na tipificação de amostras de C. perfringens isoladas de bovinos, contribuindo para o diagnóstico dessa bacteriose neste país, eliminando as dificuldades de tipificação oriundas do alto custo e da indisponibilidade de anti-soros para a tipificação pela reação de soroneutralização e evitando a utilização de animais de laboratório. / Clostridium perfringens is an anaerobic micro-organism that is present in the soil and gastrointestinal tract of mammals. It causes food poisoning in humans, enterotoxemic diseases in domestic animals and gas gangrene in both. C. perfringens is classified into five types (A, B, C, D and E) according to the production of four major toxins (alpha, beta, epsilon and iota). In this trial was possible to standardize the PCR?s technique to detect cpa, cpb and etx genes from cultures of C. perfringens. PCR?s analythical sensibility was 2.27 ng/µL for cpa gene, 22.7 pg/µL for cpb gene and 22.7 pg/µL for etx gene. The research of cpa, cpb and etx genes from 35 samples of C. perfringens isolated from cattle reveals that 16 (45.7%) were classified as type A, 18 (51.4%) as type C and 1 (2.9%) as type B. No sample of type D was observed. PCR?s technique reveals to be usefull to typify samples of C. perfringens isolated from cattle, contributing to diagnose of this bacterial disease in this country and solving typifing problems represented by the high costs of the process and by the lack of antiserum that is required to typify the micro-organism by seroneutralization. PCR?s technique avoid the use of laboratory animals, too.

Magister Artium - MA / The purpose of this investigation is to determine how a group of selected institutionalized alcoholics react to a broad-spectrum model in regard to their perception of treatment, re-integration into community life and general rehabilitation. The method that was employed to achieve this goal is fivefold. Firstly alcoholics were placed within a theoretical perspective by focusing on the etiology, nature, extent and consequences thereof. Secondly the existing methods of treatment and the existing facilities available in South Africa were investigated. These two objectives were realized by means of a comprehensive literature study. Thirdly an empirical investigation was carried out of the policy and philosophical approach as well as the application of the multi-disciplinary methods of treatment at the Avalon Treatment Centre. Information in this regard was gained during visits to the Centre by means of personal interviews with the team applying the treatment as well as the respondents reacted to the treatment model by means of case studies. Data was obtained by conducting unstructured in-depth interviews with the respondents. By this means respondents were identified in terms of their personality configuration, marital, scholastic, professional, religious and socio-economic status. The respondents' drinking behaviour is focused on in order to determine patterns and tendencies in the development of the respondents' drinking problem. The researcher also followed up the respondents' behaviour over a period of two years to determine their re-integration within the community as well as their total rehabilitation. Valuable information about the respondents was gained during group therapy sessions and also meetings of Alcoholics Anonymous by means of participant observation. As member of Alcoholics Anonymous the researcher was part of the group and on an equal footing with the respondents. The advantage this held was that the researcher was accepted by the group and information was passed on without inhibitions. Fifthly the findings, conclusions and recommendations resulting from the whole investigation are set out. From the investigation it would appear that the problem of alcoholism, especially in South Africa is serious and escalating. In the light of this, there is a growing need for effective treatment. In spite of intensive treatment with complete abstinence general, degenerate as the aim of the treatment, the respondents, in because of denial, resistance to treatment, personality and social configuration and also poor re-integration, reacted poorly to treatment. The present specifically be sharpened establishment study shows that institutional treatment and as applied by the Avalon Treatment Centre can in order to be more effective. The of a more realistic perception of alcoholism among alcoholics per se is foremost. A more "enlightened" view of alcoholism is pleaded in terms of which alcoholism would be viewed as a non-stigmatised illness responding to treatment. The possibility that there will be a greater willingness on the part of alcoholics to submit to treatment is visualised. A more positive image of treatment centres should be created while the problem of alcoholism must be approached with a greater measure of sensitivity. Treatment should be of such a nature that it should emphasize and reinforce a positive self-image, pride in oneself and dignity. A more extensive programme of treatment that would include an exploratory project and longitudinal research is pleaded. The desirability of involving other key figures, important persons in the alcoholics life, and institutions as well as community organizations proposed with The traditional emphasis should helping fall services is re-orientation and education in order on sensitising, to achieve a more positive perception and understanding of alcoholism within the community. This study will hopefully stimulate further research in this direction. / South Africa

Die vorliegende Arbeit beschäftigt sich mit dem Problem der zufälligen Wärmeausbreitung in beschränkten Gebieten. Dieses Phänomen wird dabei durch eine lineare parabolische Randanfangswertaufabe beschrieben, wobei die Anfangsbedingung und die Neumannrandbedingung als zufällige Felder mit gegebener Wahrscheinlichkeitsverteilung angenommen werden. Des Weiteren werden die zufälligen Felder als homogen und epsilon-korreliert mit einer kleinen Korrelationslänge epsilon > 0 vorausgesetzt und sollen glatte Realisierungen besitzen. Zur Lösung der Randanfangswertaufgabe werden sowohl die klassische Formulierung als auch die Variationsformulierung herangezogen und in diesem Zusammenhang die Fourier Methode sowie die Finite-Elemente Methode betrachtet. Die Finite-Elemente Methode und die Fourier-Methode führen auf einen expliziten funktionalen Zusammenhang zwischen der zufälligen Lösung der betrachteten Randanfangswertaufgabe und den Einflussgrößen, so dass Momentenfunktionen davon abgeleitet werden können. Das Hauptinteresse dieser Arbeit liegt auf der Berechnung dieser Momentenfunktionen, welche durch die gewählten Eigenschaften der stochastischen Einflußgrößen bestimmt werden. Basierend auf dem Finite-Elemente Ansatz bzw. dem Fourier Ansatz werden verschiedene Approximationsmöglichkeiten insbesondere für die Korrelationsfunktion erörtert. Des Weiteren wird die Möglichkeit der Simulation des zufälligen Randanfangswertproblems betrachtet. Hierzu wird zur Simulation der zufälligen Einflussgrößen auf die Theorie von Moving Average Feldern zurückgegriffen. Der letzte Teil der Arbeit widmet sich dem Vergleich der erhaltenen analytischen Resultate anhand konkreter numerischer Beispiele.

Im Mittelpunkt dieser Arbeit steht die Untersuchung des stochastischen Verhaltens von Lösungen parabolischer Randanfangswertprobleme mit zufälligen Koeffizienten. Aufgaben dieser Art entstehen beispielsweise bei der mathematischen Modellierung von Wärmeleitprozessen in Materialien, deren Wärmeleitfähigkeit als zufällige Größe bzw. als zufällige Funktion angesehen werden kann. Die Modellierung dieser stochastischen Einflüsse erfolgt u. a. mit Hilfe von epsilon-korrelierten Funktionen. Um stochastische Charakteristiken wie Erwartungswert-, Korrelations- und Varianzfunktion der Lösung des Randanfangswertproblems näherungsweise zu ermitteln, werden die Ansätze der Finite-Elemente-Methode (FEM), der Fouriermethode sowie der Stochastischen Simulation gewählt. Die beiden erstgenannten Verfahren erfahren eine Kombination mit der Methode der Störungsrechnung, wodurch sich jeweils Entwicklungen der gesuchten Charakteristiken bis zur zweiten Ordnung bezüglich eines Störungsparameters ergeben. Konkrete Ergebnisse werden für einfache ein- und zweidimensionale Gebiete ermittelt. Die Anwendung der Störungsrechnung wird im Fall der FEM zudem analytisch gerechtfertigt. Die Methode der Stochastischen Simulation nutzt die Approximation der eingehenden zufälligen Funktion durch Moving-Average-Felder. Für die Auswertung der auftretenden Integrale bei Anwendung der FEM werden explizite Formeln angegeben. Für einige Beispiele im ein- und zweidimensionalen Fall erfolgt die numerische Umsetzung sowie die grafische Präsentation der Ergebnisse sowie deren Vergleich für die verschiedenen eingesetzten Methoden. / This work focuses on the stochastic behavior of solutions of parabolic initial value problems with random coefficients. This sort of tasks is a result of modeling heat conduction processes on material whose heat conductivity can be considered as a random value or a random function. Stochastic influences are modeled, among others, by epsilon correlated functions. In order to determine stochastic characteristics like expectation value function, correlation function, and variance function of the problems solution approximately, the finite element method (FEM), the Fourier method, and the Monte Carlo Simulation are chosen. The first two methods are combined with perturbation techniques. This leads to expansions of the characteristics up to the second order with respect to a perturbation parameter. Results are determined for cases of one and two dimensional domains. The applicability of perturbation methods is verified for the FEM-based solution. The Monte Carlo Simulation uses the approximation of random functions by moving average fields. Explicit formulas are given for the evaluation of integrals which appear by applying the FEM. The work ends with the presenting of numerical examples for the one and two dimensional case.

Comprehensive rehabilitation projects of dam spillways are made in Sweden, due to stricter dam safety guidelines for their discharge capacity. The Piano Key Weir (PKW) is an innovative design which has proven effective through several renovation projects made in many countries including France. In this study we investigate the flow patterns around a prototype PKW, located in Escouloubre dam in southern France, with numerical simulations through three different flow cases in Ansys Fluent. A computational domain containing the PKW is created in the CAD software Ansys SpaceClaim for the simulations. Three polyhexcore meshes are further generated using Ansys Fluent Meshing. The three flow cases are then simulated with a Reynolds-averaged Navier-Stokes (RANS) model, coupled with realizable k-epsilon and volume of fluid models. Through an assessment of the discretization error between three meshes, a relative error of one percent is obtained for the discharge rate. The numerical results are qualitatively compared with results from previously conducted physical experiments on this PKW. The RANS model does not capture the water surface undulations (due to turbulence) around the PKW. The effects from under modelled surface undulations are alleviated by inserting an air vent to the PKW, which results in a flow behaviour in good agreement with the physical experiments. Through this alteration, water discharge rates are computed with a maximum discrepancy of five percent compared with the corresponding experimental values. A large eddy simulation should be conducted in the future, to bring further light on air exchange and water interaction phenomena present in the PKW flow pattern.

<p>One of the longstanding goals of photonics research has been to obtain strong optical nonlinearities. A promising method to achieve this goal is to operate in the so-called epsilon near zero (ENZ) spectral regime, where the real part of the dielectric permittivity changes sign. If accompanied by low losses, this region enables a platform to achieve extraordinarily high nonlinear response, along with many other interesting optical phenomena. In this work, some of the common all-optical switching structures employing homogeneous ENZ materials are investigated under varying conditions of frequency, incidence angle, and polarization. The optimum switching conditions have been highlighted to pave the way forward to the best experimental configurations in future studies. Moreover, the properties of some of the emerging novel plasmonic materials such as aluminum-doped zinc oxide (AZO) and titanium nitride (TiN) are investigated, specifically for ENZ applications. Their thickness-dependent crystalline structure and carrier densities are employed as a method to control their optical properties. A near-perfect absorption scheme is demonstrated utilizing the Ferrell-Berreman mode occurring at the ENZ region of ultrathin AZO and TiN film. The ENZ frequency and the associated absorption peak of AZO are engineered through thickness-dependence to cover most of the telecom range. This work covers the theoretical background for ENZ nonlinearities and looks into the materials aspect for better control of nonlinearities in experimental realizations.</p>

Various anomalous effects that emerge when the interfaces between media are involved in sound-matter or light-matter interactions are studied. The three specific systems examined are a fluid channel between elastic metal plates, a linear chain of metallic perforated cylindrical shells in air, and a metal-dielectric slab with the interfaces treated as finite regions of smoothly changing material properties. The scattering of acoustic signals on the first two is predicted to be accompanied by the effects of redirection and splitting of sound. In the third system, which supports the propagation of surface plasmons, it is discovered that the transition region introduces a nonradiative decay mechanism which adds to the plasmon dissipation. The analytical results are supported with numerical simulations. The outlined phenomena provide the ideas and implications for applications involving manipulation of sound or excitation of surface plasmons.

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