Dentre os vários radioisótopos existentes, o 99mTc e o 188Re apresentam propriedades físicoquímicas bastante específicas que os qualificam para utilização em Medicina Nuclear nas áreas de diagnóstico e terapia, respectivamente. Além disso, estes radiofármacos podem ser distribuídos à classe médica sob a forma de sistemas geradores de 99Mo-99mTc e 188W-188Re, garantindo autonomia e praticidade em sua utilização. O presente projeto de mestrado tem por objetivo determinar a capacidade de alguns materiais adsorvedores para retenção de molibdênio e tungstênio, visando o preparo de sistemas geradores de 99Mo-99mTc e de 188W- 188Re com características adequadas para aplicação em Medicina Nuclear. Quantidades conhecidas, em massa, de molibdênio (Mo) e tungstênio (W) foram adicionadas às soluções carga previamente preparadas, com valores de pH ajustados entre 1 e 7, e estas por sua vez foram então percoladas ao longo de diferentes dispositivos contendo em seu interior alumina, resina ou composto de poli-zircônio também denominado PZC. As eluições foram realizadas com um intervalo de tempo de aproximadamente 24 horas entre uma outra para os sistemas geradores de 99Mo-99mTc e de cerca de 48 horas para os sistemas geradores de 188W-188Re em função da diferença da meia-vida física existente entre os elementos pai e filho envolvidos em ambas as reações. As amostras eluídas dos sistemas geradores contendo tanto 99mTc quanto 188Re foram submetidas a testes de controle de qualidade visando-se determinar o grau de pureza radionuclídica, radioquímica e química de cada uma delas, mas nenhuma contaminação significativa por 99Mo, 188W, tecnécio ou rênio nos estados coloidais assim como zircônio foi detectada tanto nas soluções carga eluídas quanto nas soluções extraídas com solução salina para qualquer valor de pH estudado. Os cartuchos comerciais de alumina do tipo Sep Pak Ácida retiveram de maneira mais eficiente o molibdênio presente nas soluções carga eluídas quando comparados aos demais dispositivos comerciais de retenção utilizados. Entretanto, quando esta comparação estende-se as colunas cromatográficas de alumina, conclui-se que o emprego da alumina ácida como adsorvedor é ainda mais eficaz do que a utilização dos cartuchos do tipo Sep Pak Ácida e da própria alumina calcinada convencional, porém ainda assim não supera a performance apresentada pelo PZC. Os experimentos realizados com tungstênio, os quais envolveram a utilização de cartuchos comerciais de retenção de Sep Pak Ácida, assim como o emprego de alumina sob as formas calcinada convencional e ácida, revelaram que a alumina ácida constitui o melhor material adsorvedor. Quanto ao pH das soluções carga, observou-se que este deve ser ajustado de modo a ser mantido sempre que possível por volta de 5 (pH ácido) para as soluções preparadas contendo molibdênio sob a forma não radioativa como carregador, enquanto que para as soluções carga preparadas com tungstênio o pH deve ser neutro. / Amongst some existing radioisotopes, 99mTc and 188Re present adequate physicalchemical properties for use in Nuclear Medicine in the areas of diagnosis and therapy, respectively. Moreover, these radioisotopes can be distributed to medical centers in the form of generator systems of 99Mo-99mTc and 188W-188Re, allowing autonomy and practicity in use. The objective of this work consists of determining the capacity of some adsorbent materials for retention of molibdenium and tungsten, aiming the optimization of generator systems of 99Mo- 99mTc and 188W-188Re with suitable characteristics for application in Nuclear Medicine. Known amounts, in mass, of molybdenum (Mo) and tungsten (W) were added to the loading solutions previously prepared, with values of pH adjusted between 1 and 7, and these were then percolated through different devices containing in its interior alumina, resin or poly-zirconium compound also known as PZC. The elutions were carried out within an interval of time of approximately 24 hours for the generator systems of 99Mo -99mTc and 48 hours for the generator systems of 188W-188Re due to the difference between the half-lives of radionuclides involved in the reactions. The eluted samples from both generator systems containing 99mTc or 188Re were submitted to quality control tests aiming to evaluate the radionuclidic, radiochemical and chemical purity, but no significant contamination for 99Mo, 188W, technetium or rhenium in the colloidal states and zirconium were detected in the eluted solutions and in the solutions extracted with saline solution for any value of pH studied. The commercial alumina cartridges known as Acid Sep Pak were more efficient in retaining the molybdenum in the loading solutions when compared with the others commercial retention devices employed. However, when this comparison extends to the chromatographic alumina columns, the use of acid alumina as adsorbent is more efficient when compared to the Acid Sep Pak cartridges and to calcinated alumina column but still does not overcome the performance shown by PZC. The experiments carried out with tungsten, which involved the use of commercial cartridges of Acid Sep Pak, as well as alumina in the calcinated and acid forms, showed that acid alumina was the best adsorbent material. Concerning the pH of the loading solutions, it was observed that it must be adjusted to 5 (acid) for the prepared solutions containing molybdenum, whereas for the loading solutions prepared with tungsten the pH must be neutral.

Dentre os vários radioisótopos existentes, o 99mTc e o 188Re apresentam propriedades físicoquímicas bastante específicas que os qualificam para utilização em Medicina Nuclear nas áreas de diagnóstico e terapia, respectivamente. Além disso, estes radiofármacos podem ser distribuídos à classe médica sob a forma de sistemas geradores de 99Mo-99mTc e 188W-188Re, garantindo autonomia e praticidade em sua utilização. O presente projeto de mestrado tem por objetivo determinar a capacidade de alguns materiais adsorvedores para retenção de molibdênio e tungstênio, visando o preparo de sistemas geradores de 99Mo-99mTc e de 188W- 188Re com características adequadas para aplicação em Medicina Nuclear. Quantidades conhecidas, em massa, de molibdênio (Mo) e tungstênio (W) foram adicionadas às soluções carga previamente preparadas, com valores de pH ajustados entre 1 e 7, e estas por sua vez foram então percoladas ao longo de diferentes dispositivos contendo em seu interior alumina, resina ou composto de poli-zircônio também denominado PZC. As eluições foram realizadas com um intervalo de tempo de aproximadamente 24 horas entre uma outra para os sistemas geradores de 99Mo-99mTc e de cerca de 48 horas para os sistemas geradores de 188W-188Re em função da diferença da meia-vida física existente entre os elementos pai e filho envolvidos em ambas as reações. As amostras eluídas dos sistemas geradores contendo tanto 99mTc quanto 188Re foram submetidas a testes de controle de qualidade visando-se determinar o grau de pureza radionuclídica, radioquímica e química de cada uma delas, mas nenhuma contaminação significativa por 99Mo, 188W, tecnécio ou rênio nos estados coloidais assim como zircônio foi detectada tanto nas soluções carga eluídas quanto nas soluções extraídas com solução salina para qualquer valor de pH estudado. Os cartuchos comerciais de alumina do tipo Sep Pak Ácida retiveram de maneira mais eficiente o molibdênio presente nas soluções carga eluídas quando comparados aos demais dispositivos comerciais de retenção utilizados. Entretanto, quando esta comparação estende-se as colunas cromatográficas de alumina, conclui-se que o emprego da alumina ácida como adsorvedor é ainda mais eficaz do que a utilização dos cartuchos do tipo Sep Pak Ácida e da própria alumina calcinada convencional, porém ainda assim não supera a performance apresentada pelo PZC. Os experimentos realizados com tungstênio, os quais envolveram a utilização de cartuchos comerciais de retenção de Sep Pak Ácida, assim como o emprego de alumina sob as formas calcinada convencional e ácida, revelaram que a alumina ácida constitui o melhor material adsorvedor. Quanto ao pH das soluções carga, observou-se que este deve ser ajustado de modo a ser mantido sempre que possível por volta de 5 (pH ácido) para as soluções preparadas contendo molibdênio sob a forma não radioativa como carregador, enquanto que para as soluções carga preparadas com tungstênio o pH deve ser neutro. / Amongst some existing radioisotopes, 99mTc and 188Re present adequate physicalchemical properties for use in Nuclear Medicine in the areas of diagnosis and therapy, respectively. Moreover, these radioisotopes can be distributed to medical centers in the form of generator systems of 99Mo-99mTc and 188W-188Re, allowing autonomy and practicity in use. The objective of this work consists of determining the capacity of some adsorbent materials for retention of molibdenium and tungsten, aiming the optimization of generator systems of 99Mo- 99mTc and 188W-188Re with suitable characteristics for application in Nuclear Medicine. Known amounts, in mass, of molybdenum (Mo) and tungsten (W) were added to the loading solutions previously prepared, with values of pH adjusted between 1 and 7, and these were then percolated through different devices containing in its interior alumina, resin or poly-zirconium compound also known as PZC. The elutions were carried out within an interval of time of approximately 24 hours for the generator systems of 99Mo -99mTc and 48 hours for the generator systems of 188W-188Re due to the difference between the half-lives of radionuclides involved in the reactions. The eluted samples from both generator systems containing 99mTc or 188Re were submitted to quality control tests aiming to evaluate the radionuclidic, radiochemical and chemical purity, but no significant contamination for 99Mo, 188W, technetium or rhenium in the colloidal states and zirconium were detected in the eluted solutions and in the solutions extracted with saline solution for any value of pH studied. The commercial alumina cartridges known as Acid Sep Pak were more efficient in retaining the molybdenum in the loading solutions when compared with the others commercial retention devices employed. However, when this comparison extends to the chromatographic alumina columns, the use of acid alumina as adsorbent is more efficient when compared to the Acid Sep Pak cartridges and to calcinated alumina column but still does not overcome the performance shown by PZC. The experiments carried out with tungsten, which involved the use of commercial cartridges of Acid Sep Pak, as well as alumina in the calcinated and acid forms, showed that acid alumina was the best adsorbent material. Concerning the pH of the loading solutions, it was observed that it must be adjusted to 5 (acid) for the prepared solutions containing molybdenum, whereas for the loading solutions prepared with tungsten the pH must be neutral.

L'objectif de la thèse est de concevoir des compensateurs discrets qui permettent de compenser les non-linéarités introduites par les différents éléments dans la boucle de commande numérique, tout en maintenant des performances dynamiques élevées, des temps de développement rapide, et une structure reconfigurable. Ces compensateurs discrets doivent également avoir des temps de réponse rapide, avoir une déviation de la tension minimale et avoir, pour un étage de puissance donné, un temps de récupération rapide de la tension. Ces performances peuvent être atteintes par des compensateurs discrets conçus sur la base de techniques de contrôle linéaires et non linéaires. Pour obtenir une réponse rapide et stable, la thèse propose deux solutions : La première consiste à utiliser des techniques de contrôle linéaires et de concevoir le compensateur discret tout en gardant la bande passante la plus élevée possible. Il est communément admis que plus la bande passante est élevée, plus la réponse transitoire est rapide. L‘obtention d’une bande passante élevée, en utilisant des techniques de contrôle linéaires, est parfois difficile. Toutes ces situations sont mises en évidence dans la thèse. La seconde consiste à combiner les techniques de contrôle linéaires avec les techniques de contrôles non linéaires tels que la logique floue ou les réseaux de neurones. Les résultats de simulations ont permis de vérifier que la combinaison des contrôleurs non-linéaires avec les linéaires ont un meilleur rendement dynamique que les contrôleurs linéaires lorsque le point de fonctionnement varie. Avec l'aide des deux méthodes décrites ci-dessus, la thèse étudie également la technique de l’annulation des pôles-zéros (PZC) qui annule la fonction de transfert du convertisseur. Quelques modifications des techniques classiques de contrôle sont également proposées à partir de contrôleurs numériques afin d’améliorer les performances dynamiques. La thèse met également en évidence les non-linéarités qui dégradent les performances, propose les solutions permettant d'obtenir les meilleures performances, et lève les mystères du contrôle numérique. Une interface graphique est également introduite et illustrée dans le cas de la conception d'un convertisseur abaisseur de tension synchrone. En résumé, cette thèse décrit principalement l'analyse, la conception, la simulation, l’optimisation la mise en œuvre et la rentabilité des contrôleurs numériques. Une attention particulière est portée à l'analyse et l'optimisation des performances dynamique à haute fréquence et pour de faibles puissances des convertisseurs DC-DC abaisseur de tension. Ces convertisseurs fonctionnent en mode de conduction continue (CCM) à une fréquence de commutation de 1 MHz et s’appuie sur des techniques de contrôle linéaires et non linéaires de façon séquentielle. / The objective of the thesis is to design the discrete compensators which counteract the nonlinearities introduced by various elements in the digital control loop while delivering high dynamic performance, fast time-to-market and scalability. Excellent line and fast load transient response, which is a measure of the system response speed, with minimal achievable voltage deviation and a fast voltage recovery time for a given power stage can be achieved through the discrete compensators designed on the basis of linear and nonlinear control techniques. To achieve a stable and fast response, the thesis proposes two ways. One way is to use linear control techniques to design the discrete compensator while keeping the bandwidth higher. It is well-known fact that the higher the bandwidth, the faster is the transient response. Achieving higher bandwidth through linear control techniques sometimes becomes tricky. All those situations are highlighted in the thesis. The other way is to hybridize the linear control techniques with the nonlinear control techniques such as fuzzy logic or neural network based control techniques. Simulation results verify that hybridization of nonlinear controllers with the linear ones have better dynamic performance over linear controllers under the change of operating points. Along with using the two methodologies described above, the thesis also investigates the pole-zero cancellation (PZC) technique in which the poles and zeros of the compensator are placed in such a way that they cancel the effect of the poles or zeros of the buck converter to boost the phase margin at the required bandwidth. Some modifications are also suggested to the classical control techniques based digital controllers to improve the dynamic performance. The thesis highlights the nonlinearities which degrade the performance, a cost-effective solution that achieves good performance and the mysteries of digital control system. A graphical user interface is introduced and demonstrated for use with the design of a synchronous-buck converter. In summary, this thesis mainly describes the analysis, design, simulation, optimization, implementation and cost effectiveness of digital controllers with particular focus on the analysis and the optimization of the dynamic performance for high-frequency low-power DC-DC buck converter working in continuous conduction mode (CCM) operating at a switching frequency of 1 MHz using linear and nonlinear control techniques in a very sequential and comprehensive way.

In the present work, novel dewatering aids and a novel centrifuge configuration were developed and applied for the purpose of dewatering fine particles. Three different types dewatering reagents were tested in different filtration and centrifugation units. These chemicals included low-HLB surfactants, naturally occurring lipids, and modified lipids. Most of these reagents are insoluble in water; therefore, they were used in solutions of appropriate solvents, such as light hydrocarbon oils and short-chain alcohols. The role of these reagents was to increase the hydrophobicity of the coal and selected mineral particles (chalcopyrite, sphalerite, galena, talc, clay, phosphate, PCC and silica) for the dewatering. In the presence of these reagents, the water contact angles on the coal samples were increased up to 90o. According to the Laplace equation, an increase in contact angle with the surfactant addition should decrease the capillary pressure in a filter cake, which should in turn increase the rate of dewatering and help reduce the cake moisture. The use of the novel dewatering aids causes a decrease in the surface tension of water and an increase in the porosity of the cake, both of which also contribute to improved dewatering. A series of batch-scale dewatering tests were conducted on a variety of the coal and mineral samples using the novel dewatering aids. The results obtained with a Buchner funnel and air pressure filters showed that cake moistures could be reduced substantially, the extent of which depends on the particle size, cake thickness, drying time, reagent dosage, conditioning time, reagent type, sample aging, water chemistry, etc. It was determined that use of the novel dewatering aids could reduce the cake formation time by a significant degree due to the increased kinetics of dewatering. At the same time, the use of the dewatering aids reduced the cake moistures by allowing the water trapped in smaller capillaries of the filter cake. It was found that final cake moistures could be reduced by 50% of what can be normally achieved without using the reagents. However, the moisture reduction becomes difficult with increasing cake thickness. This problem can be minimized by applying a mechanical vibration to the cake, spraying a short-chain alcohol on the cake and by adding a small amount of an appropriate coagulant, such as alum and CaCl2 to the coal and mineral slurries. The novel dewatering aids were also tested using several different continuous filters, including a drum filter, disc filter and horizontal belt filter (HBF). The results obtained with these continuous filtration devices were consistent with those obtained from the batch filters. Depending on the coal and mineral samples and the type of the reagent, 40 to 60% reductions in moisture were readily achieved. When using vacuum disc filters, the cake thickness increased substantially in the presence of the novel dewatering aids, which could be attributed to the increased kinetics of dewatering. A dual vacuum system was developed in the present work in order to be able to control the cake thickness, which was necessary to achieve lower cake moistures. It was based on using a lower vacuum pressure during the cake formation time, while a full vacuum pressure was used during the drying cycle time. Thus, use of the dual vacuum system allowed the disc filter to be used in conjunction with the novel dewatering aids. Its performance was similar to that of HBF, which is designed to control cake thickness and cake formation time independently. The effectiveness of using the novel dewatering aids were also tested in a full-continuous pilot plant, in which coal samples were cleaned by a flotation column before the flotation product was subjected to the disc filter. The tests were conducted with and without using novel dewatering aids. These results were consistent with those obtained from the laboratory and batch-scale tests. The novel centrifuge developed in the present work was a unit, which combined a gravity force and air pressure. The new centrifuge was based on increasing the pressure drop across the filter cake formed on the surface of the medium (centrifuge wall). This provision made it possible to take advantage of Darcy s law and improve the removal of capillary water, which should help lower the cake moisture. A series of tests were conducted on several fine coal and mineral particles and obtained more than 50% moisture reduction even at very fine particle size (2 mm x 0). Based on the test results obtained in the present work, two proof-of-concept (POC) plants have been designed. The first was for the recovery of cyclone overflows that are currently being discarded in Virginia, and the other was for the recovery of fines from a pond in southern West Virginia. The former was designed based on the results of the plant tests conducted in the present work. Cost vs. benefit analyses were conducted on the two POC plants. The results showed very favorable internal rates of return when using the novel dewatering aids. Surface chemistry studies were conducted on the coal samples based on the results obtained in the present investigation. These consisted mainly of the surface characterization of the coal samples (surface mineral composition, surface area, zeta potential, x-ray photoelectron microscopy (XPS)), acid-base interactions of the solids and liquids, dewatering kinetic tests, contact angle measurements of the coal samples and surface force measurements using AFM. In addition, carbon coating on a silica plate using palsed laser deposition (PLD) and Langmuir-Blodgett (LB) film deposition tests were conducted on the sample to better understand the surfactant adsorption and dewatering processes. The test results showed that the moisture reductions on the fine particles agree well with the surface chemistry results. / Ph. D.