[pt] Sistemas pneumáticos são equipamentos leves, baratos, limpos e de baixo risco, sendo apropriados para aplicações que necessitem de força e rapidez de resposta. Por outro lado, esse tipo de sistema apresenta restrições devido à principal característica do ar: sua compressibilidade confere efeitos não lineares ao sistema, desde um escoamento turbulento pelas válvulas de controle até sua atuação dentro do cilindro – a qual inclui alta sensibilidade ao atrito e volumes inativos durante o curso do pistão. Essas características particulares dificultam seu controle e posicionamento preciso e limitam sua aplicação, principalmente considerando seu emprego em um mecanismo tipo Plataforma de Stewart em escala reduzida. No presente trabalho apresenta-se a modelagem, simulação computacional e análise experimental do comportamento dinâmico de um sistema de atuação pneumático que inclui uma válvula de controle de vazão não convencional, composta de quatro válvulas proporcionais, e um atuador com haste simples de dupla ação. O objetivo deste trabalho é, baseado nos resultados experimentais, determinar as características desses componentes para desenvolver estratégias de controle em tempo real capazes de minimizar os efeitos das não linearidades típicas, visando sua utilização no mecanismo anteriormente mencionado. / [en] Pneumatic equipment is lightweight, cheap, clean and low-risk, being suitable for applications that require strength and high responsiveness. Nevertheless, this type of system has some limitations due to the air main feature: its compressibility results in nonlinear effects in the system, from the turbulent flow control valves to its performance inside the cylinder - which includes high sensitivity to friction and dead volumes during the stroke piston. These particular characteristics make its control and precise positioning difficult, limiting its application, especially when considered its use in a mechanism such as a Stewart Platform in a reduced scale. The present paper presents the modeling, computational simulation and experimental analysis of the dynamic behavior of a pneumatic actuation system that includes an unconventional flow control valve, consisting of four proportional valves, and a double acting single rod actuator. The final goal of this work is to, based on experimental results, determine the characteristics of these components in order to develop real-time control strategies which can minimize the effects of those typical nonlinearities for their use in the mechanism mentioned above.

The main goal of this thesis is comparison of FEDs monetary policy in times of Great Depression and financial crisis 2007 -- 2009. Both of them began when the speculative bubble burst (in the first case it was in stock market, in the second one it occurred in real estate market). The effect of speculative bubbles bursting had very negative impact on global economic system. The FEDs monetary reaction to the both crises was very different. It differentiates in many aspects -- in times of Great Depression FED acted passive -- did not provide large open market purchases, did not lowered the interest rate quick enough to avoid the money stock fall-down. In current crisis, FED did not repeat mistakes made during Great Depression. In response to the market pressure, FED created several unconventional tools to support liquidity of depository institutions, primary dealers and commercial paper market. Via these new-invented programs, FED did not allow the money stock to fall and as the financial strains eased, they slowly disappeared. Besides these liquidity programs, FED supported economy with fast interest rate lowering and providing quantitative easing. Steps taken by FED helped to stabilize financial markets.

Dans la première partie, nous présentons les résultats de l'étude du supraconducteur sans inversion de symétrie LaRhSi3 par spectroscopie muonique. En champ nul, nous n'avons pas détecté de champ interne. Ceci indique que la fonction d'onde de l'état supraconducteur n'est pas dominée par l'état triplet. Les mesures en champ transverse de 35G présentent une transition en accord avec la transition de phase attendue sous le champ critique Hc1. Nous avons répété ces mesures pour un champ entre Hc1 et Hc2, 150G. Le spectre obtenu pour ces mesures conserve l'asymétrie et relaxe rapidement à basse température tel que prédit pour un supraconducteur dans la phase d'Abrikosov. Néanmoins, les relaxations produites par ce balayage en température présentent une transition à près de 2 fois la température critique attendue. Dans la deuxième partie de ce mémoire, nous donnons l'interprétation des résultats de la diffraction neutronique inélastique par l'étude des champs électriques cristallins. Ces mesures ont été effectuées sur des aimants frustrés SrHo2O4 et SrDy2O4 sous la forme de poudre. L'étude des niveaux produits par les champs cristallins par la méthode des opérateurs de Stevens indique une perte du moment cinétique dans les deux matériaux. Pour le SrDy2O4, l'état fondamental serait constitué de quatre états dégénérés quasi accidentellement qui portent un moment magnétique total non-nul. Toute fois, nos mesures de susceptibilité magnétique ne montrent aucun ordre au-dessus de 50mK. Pour le SrHo2O4, le fondamental est formé d'une paire accidentelle. Nous obtenons un moment magnétique de 6.94(8)$\mu_B$ ce qui s'accorde avec les données expérimentales. / In the first part of this thesis, we present our muon spectroscopy results of the non-centrosymmetric superconductor LaRhSi3. Zero magnetic field measurements showed no internal field, suggesting at most a very small triplet component in the superconducting wave function. A temperature scan taken in 35G transverse-field geometry showed a phase transition at Hc1. The asymmetry of the muon relaxation spectrum measured at 20mK and field of 150G, which is between the lower and upper critical fields, shows a faster relaxation rate compared to the spectrum obtained at 4K, a behaviour expected in the presence of vortices in the type II superconductor. However, the temperature dependence of the relaxation rate begins to increase all the way to a temperature twice Tc of LaRhSi3 in a field of 150G. In the second part of this document, we present the interpretation of inelastic neutron scattering by crystalline electric fields. These measurements were carried out on powder samples of frustrated quantum magnets SrHo2O4 and SrDy2O4. Using Stevens operators method, we determined the level scheme du to crystalline electric field effects using a point charge model and fitted it to the experimental data. For the SrDy2O4 we found a ground state that appears to be composed of four quasi-accidental degenerate states that carry a non zero magnetic moment even though susceptibility measurements did not indicate magnetic order above 50mK. For the SrHo2O4, the ground state is a pair with a 6.98(8)$\mu_B$ magnetic moment. This lat value fots with experimental data.

Technologies such as horizontal wells and multi-stage hydraulic fracturing have made ultra-low permeability shale and tight gas reservoirs productive but the industry is still on the learning curve when it comes to addressing various production issues. Some of the problems encountered while hydraulically fracturing these reservoirs are the absence of frac barriers, thinner shales and the increased presence of geological hazards. Induced vertical fractures sometimes extend to an underlying aquifer and become a conduit to the well. We have developed a low-concentration, low-viscosity and delayed-crosslink polymeric gel system as a water shutoff agent for hydraulically-fractured tight gas and shale reservoirs, where some fractures might connect to water rich zones. The system also is a significant improvement over traditional flowing gels for fracture water shutoff in conventional reservoirs because of these features. The gel uses high molecular weight hydrolyzed polyacrylamide (HPAM) at low polymer concentrations with a delayed organic crosslinker. This crosslinker is more environmentally benign and provides much longer gelation time and stronger final gels than comparable polymer loadings with chromium carboxylate crosslinkers at higher temperatures. The low viscosity system allows low-pressure extrusion of gelant into the narrow-aperture fractures present in unconventional gas reservoirs. The gelant can be pumped at low pressures due to lower polymer concentrations and delayed gelation point. This allows the potential to seal problem zones that are producing excess water even when the fractures conducting water have very narrow apertures. By impeding water production, the gel system developed here can effectively delay water loading thereby avoiding abandonment or installation of expensive equipment with increased operational costs, thus extending life and reserves of unconventional gas wells.

Thesis (M.A.)--University of Kansas, 2008. / Title from title page of PDF document (viewed on: Dec 18, 2009). Includes bibliographical references.

Thesis (Master of Military Studies)-Marine Corps Command and Staff College, 2008. / Title from title page of PDF document (viewed on: Feb 2, 2010). Includes bibliographical references.

Thesis (Master of Military Studies)-Marine Corps Command and Staff College, 2008. / Title from title page of PDF document (viewed on: Feb 11, 2010). Includes bibliographical references.

Thesis (Master of Military Studies)-Marine Corps Command and Staff College, 2008. / Title from title page of PDF document (viewed on: Dec 29, 2009). Includes bibliographical references.

Thesis (Master of Military Studies)-Marine Corps Command and Staff College, 2008. / Title from title page of PDF document (viewed on: Dec 29, 2009). Includes bibliographical references.

Thesis (Master of Military Studies)-Marine Corps Command and Staff College, 2008. / Title from title page of PDF document (viewed on: Dec 29, 2009). Includes bibliographical references.