Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2008. / Horizon sensing is an effective way to determine the pitch and roll of a LEO satellite and Earth horizon sensors that operate in the visible range of the electromagnetic spectrum are commonly used. These sensors have the disadvantage that they cannot operate when the satellite is in eclipse. Earth horizon sensors that operate in the infrared spectral range are a solution to take attitude measurements when the satellite is in eclipse. Until recently infrared detectors could only operate at very low temperatures and needed to be cryogenically cooled. The result was that their power consumption and physical characteristics (like dimensions and mass) were such that they were not suitable for use in small and medium LEO satellites. As a result of technology expansion in the field of infrared imagers the past few years, infrared imagers were developed which do not require cooling. The scope of this project was to develop and implement an Earth horizon sensor by using a low-cost, uncooled infrared imager. The performance and physical characteristics of various imager were evaluated and it was decided to select a low resolution thermopile imager mainly as a result of the cost limitations of the project. Software algorithms were then evaluated and selected for horizon detection and attitude determination. The Earth horizon sensor that was developed did not comply with the accuracy requirement (3s < 0.1o) that was set for the project because of the low resolution of the sensor. Methods to improve the accuracy were investigated and finally a sub-pixel edge estimation algorithm was developed and implemented which resulted in an improvement of 69% in the pitch accuracy and 49% in roll accuracy. With the sub-pixel edge estimation algorithm implemented the horizon sensor almost met the accuracy requirements (s < 0.0811o for pitch and s < 0.2944o for roll). This project confirms that, with further improvement to the design and test facilities, developing a low-cost, uncooled infrared Earth horizon sensor that meets the accuracy requirements is feasible.

The objective of this thesis was to understand the factors that affect the selection of remedial treatments for the complex staining of masonry materials on cultural resources located in environmentally sensitive sites such as Fort Livingston, Louisiana, on the Gulf Coast of the United States and other locations impacted by pollutants including crude oil. After the Deepwater Horizon oil spill in April 2010, the brick-and-tabby Fort was stained by crude oil. The EPA recommends SWA for removal of oil from solid surfaces such as masonry; however, limited research has been conducted into SWA effective for removal of crude oil from masonry, particularly in remote and environmentally sensitive locations. Research was conducted collaboratively at NCPTT and UT-Austin to identify a series of suitable SWA and to develop methods for evaluating SWA effectiveness in the laboratory. Products were selected for laboratory evaluation that do not require long dwell times, are easy to transport to the site, can be applied with portable equipment, produce effluent that can be collected for off-site disposal, and are listed on the EPA-published NCP Product Schedule. Two sets of 36 brick samples each were soiled with crude oil from the Fort. One set of samples was artificially weathered and one set was unweathered prior to being cleaned with selected six SWA. Laboratory evaluation shows that the primary factor affecting cleaner selection for remediation of brick masonry stained by light crude oil is the extent of weathering of oil on the masonry. For light crude oil, such as that spilled in the Gulf, organic solvent-based cleaners may be most effective if cleaning is possible soon after the staining occurs. Aqueous surfactant cleaners are most effective for removing weathered light crude oil from masonry. The following SWA listed in order of performance are recommended for field trials at Fort Livingston: 1. Cytosol; 2. SC-1000; 3. De-Solv-It APC; 4. De-Solv-It Industrial followed by De-Solv-It APC; 5. De-Solv-It Industrial followed by SC-1000. / text

As shown by the Macondo blowout, a deepwater well control event can result in loss of life, harm to the environment, and significant damage to company and industry reputation. Consistent adherence to safety regulations is a recurring issue in deepwater well construction. The two federal entities responsible for offshore U.S. safety regulation are the Department of the Interior’s Bureau of Safety and Environmental Enforcement (BSEE) and the U.S. Coast Guard (USCG), with regulatory authorities that span well planning, drilling, completions, emergency evacuation, environmental response, etc. With such a wide range of rules these agencies are responsible for, safety compliance cannot be comprehensively verified with the current infrequency of on-site inspections. Offshore regulation and operational safety could be greatly improved through continuous remote real-time data monitoring. Many government agencies have adopted monitoring regimes dependent on real-time data for improved oversight (e.g. NASA Mission Control, USGS Earthquake Early Warning System, USCG Vessel Traffic Services, etc.). Appropriately, real-time data monitoring was either re-developed or introduced in the wake of catastrophic events within those sectors (e.g. Challenger, tsunamis, Exxon Valdez, etc.). Over recent decades, oil and gas operators have developed Real-Time Operations Centers (RTOCs) for continuous, pro-active operations oversight and remote interaction with on-site personnel. Commonly seen as collaborative hubs, RTOCs provide a central conduit for shared knowledge, experience, and improved decision-making, thus optimizing performance, reducing operational risk, and improving safety. In particular, RTOCs have been useful in identifying and mitigating potential well construction incidents that could have resulted in significant non-productive time and trouble cost. In this thesis, a comprehensive set of recommendations is made to BSEE and USCG to expand and improve their regulatory oversight activities through remote real-time data monitoring and application of emerging real-time technologies that aid in data acquisition and performance optimization for improved safety. Data sets and tools necessary for regulators to effectively monitor and regulate deepwater operations (Gulf of Mexico, Arctic, etc.) on a continuous basis are identified. Data from actual GOM field cases are used to support the recommendations. In addition, the case is made for the regulator to build a collaborative foundation with deepwater operators, academia and other stakeholders, through the employment of state-of-the-art knowledge management tools and techniques. This will allow the regulator to do “more with less”, in order to address the fast pace of activity expansion and technology adoption in deepwater well construction, while maximizing corporate knowledge and retention. Knowledge management provides a connection that can foster a truly collaborative relationship between regulators, industry, and non-governmental organizations with a common goal of safety assurance and without confusing lines of authority or responsibility. This solves several key issues for regulators with respect to having access to experience and technical know-how, by leveraging industry experts who would not normally have been inaccessible. On implementation of the proposed real-time and knowledge management technologies and workflows, a phased approach is advocated to be carried out under the auspices of the Center for Offshore Safety (COS) and/or the Offshore Energy Safety Institute (OESI). Academia can play an important role, particularly in early phases of the program, as a neutral playing ground where tools, techniques and workflows can be tried and tested before wider adoption takes place. / text

Le silence — ou plutôt la grande variété de ce que l’on appelle “silences” — est un phénomène complexe qui prend une part directe dans la dynamique du langage et la création du sens linguistique, mais aussi dans la production du sens symbolique et des effets poétiques. Le travail est organisé en deux parties: la première traite la question de l'acte de silence dans l'expérience linguistique du monde, tandis que la deuxième analyse l'expérience poétique des silences en appliquant les résultats précédemment obtenus au Coup de dés de Stéphane Mallarmé. Plus précisément, dans la partie linguistique, on passe en revue différentes théories pour dégager la place que le silence s’y voit reconnaître. On l’étudie successivement en tant que signe linguistique, en tant qu’acte linguistique, comme élément pertinent, comme procédé rhétorique, comme phénomène symbolique. La partie poétique se fonde sur la théorie de l'évocation pour aboutir, en passant par un chapitre consacré à la poésie moderne dans son ensemble, à l'œuvre de Stéphane Mallarmé, le premier poète qui ait créé une véritable poétique des silences, tant dans ses ouvrages poétiques (dont le Coup de dés est l'exemple le plus radical) que dans ses écrits théoriques.

Waterflooding is a common type of oil recovery techniques where water is pumped into the reservoir for increased productivity. Reservoir states change with time, as such, different injection and production settings will be required to lead the process to optimal operation which is actually a dynamic optimization problem. This could be solved through optimal control techniques which traditionally can only provide an open-loop solution. However, this solution is not appropriate for reservoir production due to numerous uncertain properties involved. Models that are updated through the current industrial practice of ‘history matching’ may fail to predict reality correctly and therefore, solutions based on history-matched models may be suboptimal or non-optimal at all. Due to its ability in counteracting the effects uncertainties, direct feedback control has been proposed recently for optimal waterflooding operations. In this work, two feedback approaches were developed for waterflooding process optimization. The first approach is based on the principle of receding horizon control (RHC) while the second is a new dynamic optimization method developed from the technique of self-optimizing control (SOC). For the SOC methodology, appropriate controlled variables (CVs) as combinations of measurement histories and manipulated variables are first derived through regression based on simulation data obtained from a nominal model. Then the optimal feedback control law was represented as a linear function of measurement histories from the CVs obtained. Based on simulation studies, the RHC approach was found to be very sensitive to uncertainties when the nominal model differed significantly from the conceived real reservoir. The SOC methodology on the other hand, was shown to achieve an operational profit with only 2% worse than the true optimal control, but 30% better than the open-loop optimal control under the same uncertainties. The simplicity of the developed SOC approach coupled with its robustness to handle uncertainties proved its potentials to real industrial applications.

In this thesis, first we study the unique classical solution of quasi-linear second order parabolic partial differential equations (PDEs). For this, we study the existence and uniqueness of the $L^2_{\rho}( \mathbb{R}^{d}; \mathbb{R}^{d}) \otimes L^2_{\rho}( \mathbb{R}^{d}; \mathbb{R}^{k})\otimes L^2_{\rho}( \mathbb{R}^{d}; \mathbb{R}^{k\times d})$ valued solution of forward backward stochastic differential equations (FBSDEs) with finite horizon, the regularity property of the solution of FBSDEs and the connection between the solution of FBSDEs and the solution of quasi-linear parabolic PDEs. Then we establish their connection in the Sobolev weak sense, in order to give the weak solution of the quasi-linear parabolic PDEs. Finally, we study the unique weak solution of quasi-linear second order elliptic PDEs through the stationary solution of the FBSDEs with infinite horizon.

Abstract The purpose of this study was to explore the impact of the BP Deepwater Horizon oil spill on students of two coastal Louisiana secondary schools. Bronfenbrenner’s (1979) ecological systems theory was used as a framework to understand how exposure, gender, socioeconomic status, and resilience interact to influence the impact of the spill on students. Cross-sectional questionnaires were administered to 155 high school students in May 2012 and 225 middle school students in January 2013 out of 1247 possible for a return rate of about 30%. Results showed that exposure groups differed significantly on students’ Impact of Event Scale (IES; Horowitz, Wilner, & Alvarez, 1979) scores. Students with high exposure to the oil spill had significantly higher IES scores than those with no exposure and low exposure. Logistic regression results indicated that exposure was a significant predictor of higher IES scores and as exposure increased by 1, students were 1.46 times more likely to experience higher impact. Males were found to have significantly higher IES scores than females, with a low effect size. Students did not differ significantly across resilience levels. In the entire sample, lower-SES students did not score significantly different on IES scores than higher-SES students. However, in the high school significant differences were found between SES groups and SES was a significant predictor of higher IES scores. Implications are provided for counselor educators interested in disaster mental health. Conclusions include suggestions for counselors servicing areas affected by the oil spill and how individual and environmental characteristics of students can influence risk factors. Keywords: Disaster mental health, crisis intervention counseling, ecological systems theory, BP Deepwater Horizon oil spill, secondary school students, resilience, risk factors

No Brasil, a alta produtividade das plantações florestais tem despertado grande interesse em relação à nutrição das árvores. Diante disso, este trabalho tratou de 2 estudos sobre a absorção de nutrientes pelas árvores de Eucalyptus grandis. O primeiro avaliou o potencial de absorção de N, K e Ca pelas árvores de E. grandis (6 anos de idade - 25 m de altura média) em função da profundidade, da textura e da umidade do solo. Através de tubos de plástico, aplicou-se conjuntamente os marcadores NO3 --15N, Rb+ (análogo ao K+) e Sr2+ (análogo ao Ca2+) nas profundidades de 10, 50, 150 e 300 cm, num Latossolo vermelho textura média e num Latossolo vermelho argiloso. Utilizou-se o delineamento experimental inteiramente casualizado com 3 repetições de pares de árvores por profundidade de injeção e por tipo de solo. Após a injeção dos marcadores nas quatro profundidades, coletou-se dessas árvores folhas recém expandidas em vários períodos do verão, sendo o experimento repetido no período do inverno. O conteúdo de água foi monitorado continuamente em diferentes profundidades dos dois solos. A partir das quatro profundidades de injeção dos marcadores, a determinação das concentrações foliares de Rb, de Sr e da percentagem de átomo de 15N permitiu estimar a potencial absorção relativa (PAR) e a potencial absorção relativa específica (PARE), definida na divisão da PAR pela densidade de raízes finas em cm cm-3 (DRF), na camada de solo correspondente. O segundo, através de microeletrôdos seletivos de íons, mediu os fluxos de NH4 +, NO3 -, K+ e H+ (nmol m-2 s-1) em soluções de NH4NO3 (50 µM) e KNO3 (50 µM). Os microeletrôdos foram posicionados ao longo da raiz desde a ponta (0 cm) até 0,5; 1,0; 1,5; 2,0; 3,0; 5,0; e 8,0 cm de distância da ponta da raiz. Os fluxos foram medidos na raiz fina de 4 mudas de E. grandis que permaneceram numa solução pré-tratamento menos concentrada (50 µM) e na raiz fina de 4 mudas que permaneceram numa solução pré-tratamento mais concentrada (500 µM). No primeiro estudo, os resultados sugeriram que as raízes finas de E. grandis apresentaram um contraste entre as taxas potenciais de absorção e a profundidade, dependendo do nutriente. No segundo estudo, a tendência de maior absorção K+ e NH4 + em relação ao NO3 - pôde ter ocorrido devido às células das raízes de E. grandis serem mais permeáveis ao K+ e a forma preferencial de absorção de nitrogênio desta espécie ser o NH4 +. Os padrões distintos de absorção de NH4 +, K+ e NO3 -, desde a ponta da raiz das mudas de E. grandis até 8 cm de distância, puderam resultar das diferenças morfológicas, como: maior absorção de íons entre a zona de diferenciação e elongação celular das raízes e a zona de maturação celular (zona branca até 2 cm de distância da ponta); e diminuição da absorção na zona em que as células do córtex começaram a morrer ou já estavam mortas (zona escura entre 2 e 8 cm de distância da ponta da raiz). / The high productivity of forest plantations in Brazil has attracted great interest in relation to the nutritional aspect of trees. Therefore, this work deals with two studies on nutrient uptake by trees of Eucalyptus grandis. The first assessed the potential uptake of N, K and Ca by E. grandis trees (6 years of age 25 m mean height), in Brazil, as a function of soil depth, texture and water content. We injected NO3 --15N, Rb+ (analogue of K+) and Sr2+ (analogue of Ca2+) tracers simultaneously in a solution through plastic tubes at 10, 50, 150 and 300 cm in depth in a sandy and a clayey Ferralsol soil. A complete randomized design was set up with 3 replicates of paired trees per injection depth and soil type. Recently expanded leaves were sampled at various times after tracer injection in the summer, and the experiment was repeated in the winter. Soil water contents were continuously monitored at the different depths in the two soils. Determination of foliar Rb and Sr concentrations and 15N atom% made it possible to estimate the relative uptake potential (RUP) of tracer injections from the four soil depths and the specific relative uptake potential (SRUP), defined as RUP, per unit of fine root length density (RLD) in the corresponding soil layer. The second, in solutions of NH4NO3 (50 µM) and KNO3 (50 µM) were measured the flows of NH4 +, NO3 -, K+ and H+ (nmol m-2 s-1) through microelectrodes selective ions. Along the root, the microelectrodes were positioned at the root tip (0 cm) to 0.5, 1.0, 1.5, 2.0, 3.0, 5.0, and 8.0 cm away of the root tip. The flows were measured in fine roots of 4 E. grandis seedlings that remained in a pretreatment solution less concentrated (50 µM) and fine root of 4 seedlings that remained in pretreatment solution more concentrated (500 µM) through ion selective microelectrode. In the first study, the results suggest that the fine roots of E. grandis trees exhibit contrasting potential uptake rates with depth depending on the nutrient. In the second, the trend towards greater uptake K+ and NH4 + in relation to NO3 - may be due to the root cells of E. grandis are more permeable to K+ and to the preferred form of nitrogen absorption of this species is NH4 +. The different absorptions patterns of NH4 +, K+ and NO3 - along the roots of E. grandis seedlings from the root tip up to 8 cm away can be the result of morphological differences, such as higher absorption of ions between the zone of cell differentiation and elongation of the roots and cell maturation zone (white zone up to 2 cm away from tip), and decreased absorption in the area where the cortical cells start dying or already are dead (dark zone between 2 and 8 cm away from the root tip).

Dans cette thèse, nous considérons des problèmes de stabilité et de commande robuste pour une classe de systèmes linéaires à sauts aléatoires. Dans la première partie, nous nous intéressons d'une part à l'analyse de la de systèmes linéaires à sauts Markoviens non-Homogènes en temps, et ceci en temps discret. En particulier, nous considérons le cas où la matrice de probabilité de transition de la chaîne de Markov non-Homogène varie dans un intervalle. En nous appuyons sur des outils issus de l'analyse par intervalles ainsi que de la théorie des graphes, nous obtenons une condition suffisante de stabilité en moyenne quadratique de cette classe de systèmes. D'autre part, nous considérons le problème de stabilité stochastique de systèmes linéaires à temps continu et à sauts aléatoires dépendant de l'état du système. En utilisant une version stochastique de la deuxième méthode de Lyapunov et la formule de Dynkin adaptée à cette classe de systèmes, nous établissons des conditions suffisantes de stabilité en termes d'inégalités matricielles linéaires. Dans la seconde partie de cette thèse, nous étudions le problème de commande prédictive des systèmes à sauts aléatoires sujets à des contraintes de type probabilistes. Nous étudions dans un premier temps un problème de commande à horizon glissant d'un système linéaire discret à sauts dépendant de l'état, soumis à des perturbations aléatoires éventuellement non bornées et à des contraintes de type probabilistes sur l'état du système. Dans un deuxième temps, nous relaxons l'hypothèse d'accessibilité de l'état du système et considérons le problème de commande à horizon glissant basée sur une estimation de l'état du système / We address stability and control problems of random jump linear systems (JLSs) that consists of a set of linear systems and the switching among them is governed by a random jump process. In the first part, we consider second moment stability and stabilization of random JLSs. We first consider discrete-Time inhomogeneous Markov JLSs with interval transition probability matrix and obtain a sufficient condition in terms of a spectral radius of a matrix by using results of interval analysis and graph theory. Alternatively, we obtain a convex hull representation of the interval transition probability matrix and give a sufficient condition in terms of linear matrix inequalities, using which we deal with stabilization. Next, we consider a continuous-Time state-Dependent JLS, where the transition rates of the random jump process depend on the state variable and address the problem of stochastic stability and stabilization. Then, we consider the presence of external disturbances and extend our results to H infinity stabilization problem. In the second part, we consider control of random JLSs subject to constraints. We use receding horizon control approach to handle constraints. We first investigate a receding horizon control of discrete-Time state-Dependent JLSs subject to stochastic disturbances and probabilistic constraints. For the same system, we try to extend our approach to the case of imperfect state availability. However, the unavailability of the state makes the formulation of state-Dependent jump process complex. Thus we confine ourselves to discrete-Time homogeneous Markov JLSs with process noise and noisy measurements and address the receding horizon control problem

Crude oil causes both lethal and sublethal effects on marine organisms, but the impact upon sensory function remains unexplored. Elasmobranchs rely upon the effective functioning of their sensory systems for use in feeding, mating, and predator avoidance. The objective of this study was to test the effect of crude oil upon the olfactory and electroreceptive sensitivity of the Atlantic stingray, Dasyatis sabina. The magnitudes of the electro-olfactogram (EOG) responses were significantly depressed by 26% (Glutamic Acid) to 157% (Cysteine) for all amino acids when stingrays were exposed to crude oil. The shapes of the EOG responses when exposed to oil were also significantly different, exhibiting a more protracted response compared to un-exposed stingrays. Oil exposed stingrays exhibited a significant decrease in orientation distance to prey-simulating electric fields. This study is the first to quantify the effects of crude oil on olfactory and electrosensory sensitivity of marine predators. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection