In treating the motion of a fluid mathematically, it is convenient to make some simplifying assumptions. The assumptions which are made will be justifiable if they save long and laborious computations in practical problems, and if the predicted results agree closely enough with experimental results for practical use. In dealing with the flow of air about an airfoil, at subsonic speeds, the fluid will be considered as a homogeneous, incompressible, inviscid fluid.

A perda de energia de íons na matéria é um tópico importante não apenas devido à sua direta aplicação nas técnicas de análises de materiais mas também na compreensão da interação íon-átomo. O conhecimento preciso do poder de freamento de íons pesados a baixas energias é cada vez mais necessário em ciências dos materiais assim como na física nuclear básica, como por exemplo, no Método da Atenuação do Deslocamento Doppler (DSAM, na sigla em inglês). Nessa técnica, o conhecimento do poder de freamento é utilizado para determinar uma referência temporal para o decaimento nuclear enquanto em recuo em um substrato, tipicamente Au ou Pb. No entanto, o freamento de íons pesados em sólidos é ainda pouco compreendido principalmente com respeito a região de baixas energias devido às dificuldades adicionais que surgem da complicada dependência entre o estado de carga do projétil e sua velocidade instantânea no freador. Como modelos teóricos não são capazes de fornecer fornecer previsões quantitativas confiáveis, os principais modelos utilizados atualmente são de natureza semiempírica. O principal objetivo desse trabalho se concentra na obtenção de novos dados experimentais na região de energia de 100-500 keV/u.m.a., para o freamento de Ti, V, Cr, Co, Ni em Au e Ge e de Ti e Cr em Pb. Os dados experimentais com os íons de Ti, V e Cr foram obtidos utilizando a técnica de espalhamento elástico, na qual o feixe primário é espalhado por átomos de um fino alvo ( 100µg/cm²). O feixe primário espalhado produz átomos do alvo com baixas energia em recuo numa determinada direção. Os experimentais com íons de Co e Ni foram obtidos utilizando um arranjo de ToF-E (Time of Flight - Energy ) que permite a medida do freamento ao longo de uma região contínua de energia. Nesta técnica, para a produção de um feixe com ampla distribuição em energia, o feixe primário monoenergético é espalhado por substrato de Au. Os dados experimentais foram comparados com as previsões da Teoria Binária (TB) e Aproximação de Convolução Unitária (ACU) e dos modelos semiempíricos de Ziegler, Biersack e Littmark (ZBL) e de Northcliffe e Schilling (NS). Apesar dos modelos descreverem razoavelvii mente bem os freamentos de Ti, V e Cr em Au, os dados experimentais para o freamento de Ni em Au, por exemplo, chegam a ser 2 vezes maiores que as previsões de ZBL. / The energy loss of ions in materials is an important issue not only because of its direct applications on material analysis techniques, but also for the understanding of the interactions. Accurate knowledge of heavy ion stopping power at low energies is necessary in materials science as well as in basic physics, e. g. in the Doppler Shift Attenuation Method (DSAM). In this technique the knowledge of stopping power is used to determine the timescale for the decaying nuclei while slowing down in a heavy substrate, usually Au or Pb. Nevertheless, the stopping power of solids for heavy ions is still poorly known. Regarding to low energies, this is especially true due to additional difficulties arising from a complicated dependence of the projectile charge state and its istantaneous velocity in the medium. Since theoretical models are unable to produce reliable quantitative predictions, most models currently in use are of semiempirical nature. The main aim of this work is to present new experimental data in the energy range 100-500 keV/u for Ti, V, Cr, Co and Ni ions slowing down in Au and Ge, and Ti and Cr ions slowing down in Pb. Experimental data for Ti, V, Cr ions were obtained using the elastic recoil technique, where a primary beam is scattered by heavy ions from a thin target (100µg/cm²). The scattered primary beam produces recoiling atoms of the target at low energies and at a given direction, where it is placed the stoppers. Experimental data for Co and Ni ions were obtained using a ToF-E apparatus (Time of Flight - Energy detection system) which allows measuring stopping over a continuous energy range. To produce a beam of Co, for instance, with broad energy range its monoenergetic beam is scattered away by a Au substract. Our experimental data were compared to TB and UCA theories and ZBL and NS semiempical models. Although there is an overall agreement between experiment and theory for Ti, V and Cr ions, the experimental stopping power for Ni in Au, for instance, is about 2 times greater than the ZBL prediction.

The Poincare equations, also known as Lagrange's equations in quasi coordinates, are revisited with special attention focused on a diagonal form. The diagonal form stems from a special choice of quasi velocities that were first introduced by Georg Hamel nearly a century ago. The form has been largely ignored because the quasi velocities create so-called Hamel coefficients that appear in the governing equations and are based on the partial derivative of the mass matrix factorization. Consequently, closed-form expressions for the Hamel coefficients can be difficult to obtain and relying on finite-dimensional, numerical methods are unattractive. In this thesis we use a newly developed operator overloading technique to automatically generate the Hamel coefficients through exact partial differentiation together with numerical evaluation. The equations can then be numerically integrated for system simulation. These special Poincare equations are called the Hamel Form and their usefulness in dynamic modeling and control is investigated. Coordinated control algorithms for an automatic retargeting system are developed in an attempt to protect an area against direct assaults. The scenario is for a few weapon systems to suddenly be faced with many hostile targets appearing together. The weapon systems must decide which weapon system will attack which target and in whatever order deemed sufficient to defend the protected area. This must be performed in a real-time environment, where every second is crucial. Four different control methods in this thesis are developed. They are tested against each other in computer simulations to determine the survivability and thought process of the control algorithms. An auction based control algorithm finding targets of opportunity achieved the best results.

A perda de energia de íons na matéria é um tópico importante não apenas devido à sua direta aplicação nas técnicas de análises de materiais mas também na compreensão da interação íon-átomo. O conhecimento preciso do poder de freamento de íons pesados a baixas energias é cada vez mais necessário em ciências dos materiais assim como na física nuclear básica, como por exemplo, no Método da Atenuação do Deslocamento Doppler (DSAM, na sigla em inglês). Nessa técnica, o conhecimento do poder de freamento é utilizado para determinar uma referência temporal para o decaimento nuclear enquanto em recuo em um substrato, tipicamente Au ou Pb. No entanto, o freamento de íons pesados em sólidos é ainda pouco compreendido principalmente com respeito a região de baixas energias devido às dificuldades adicionais que surgem da complicada dependência entre o estado de carga do projétil e sua velocidade instantânea no freador. Como modelos teóricos não são capazes de fornecer fornecer previsões quantitativas confiáveis, os principais modelos utilizados atualmente são de natureza semiempírica. O principal objetivo desse trabalho se concentra na obtenção de novos dados experimentais na região de energia de 100-500 keV/u.m.a., para o freamento de Ti, V, Cr, Co, Ni em Au e Ge e de Ti e Cr em Pb. Os dados experimentais com os íons de Ti, V e Cr foram obtidos utilizando a técnica de espalhamento elástico, na qual o feixe primário é espalhado por átomos de um fino alvo ( 100µg/cm²). O feixe primário espalhado produz átomos do alvo com baixas energia em recuo numa determinada direção. Os experimentais com íons de Co e Ni foram obtidos utilizando um arranjo de ToF-E (Time of Flight - Energy ) que permite a medida do freamento ao longo de uma região contínua de energia. Nesta técnica, para a produção de um feixe com ampla distribuição em energia, o feixe primário monoenergético é espalhado por substrato de Au. Os dados experimentais foram comparados com as previsões da Teoria Binária (TB) e Aproximação de Convolução Unitária (ACU) e dos modelos semiempíricos de Ziegler, Biersack e Littmark (ZBL) e de Northcliffe e Schilling (NS). Apesar dos modelos descreverem razoavelvii mente bem os freamentos de Ti, V e Cr em Au, os dados experimentais para o freamento de Ni em Au, por exemplo, chegam a ser 2 vezes maiores que as previsões de ZBL. / The energy loss of ions in materials is an important issue not only because of its direct applications on material analysis techniques, but also for the understanding of the interactions. Accurate knowledge of heavy ion stopping power at low energies is necessary in materials science as well as in basic physics, e. g. in the Doppler Shift Attenuation Method (DSAM). In this technique the knowledge of stopping power is used to determine the timescale for the decaying nuclei while slowing down in a heavy substrate, usually Au or Pb. Nevertheless, the stopping power of solids for heavy ions is still poorly known. Regarding to low energies, this is especially true due to additional difficulties arising from a complicated dependence of the projectile charge state and its istantaneous velocity in the medium. Since theoretical models are unable to produce reliable quantitative predictions, most models currently in use are of semiempirical nature. The main aim of this work is to present new experimental data in the energy range 100-500 keV/u for Ti, V, Cr, Co and Ni ions slowing down in Au and Ge, and Ti and Cr ions slowing down in Pb. Experimental data for Ti, V, Cr ions were obtained using the elastic recoil technique, where a primary beam is scattered by heavy ions from a thin target (100µg/cm²). The scattered primary beam produces recoiling atoms of the target at low energies and at a given direction, where it is placed the stoppers. Experimental data for Co and Ni ions were obtained using a ToF-E apparatus (Time of Flight - Energy detection system) which allows measuring stopping over a continuous energy range. To produce a beam of Co, for instance, with broad energy range its monoenergetic beam is scattered away by a Au substract. Our experimental data were compared to TB and UCA theories and ZBL and NS semiempical models. Although there is an overall agreement between experiment and theory for Ti, V and Cr ions, the experimental stopping power for Ni in Au, for instance, is about 2 times greater than the ZBL prediction.

>Magister Scientiae - MSc / Velocity modelling forms an integral part of the seismic interpretation process initially completed in two-way time. In order for a representative depth conversion, it is obligatory to construct a velocity model that serves the bridge between velocity and respective two-way time. This study deals with the investigation of subsurface heterogeneities and its impact on the variation of velocities. Interpretation of time domain reflection data results in one or more seismic horizons, however these horizons should represent the variation in subsurface geology as a result of acoustically different layers displaying varying reflection amplitudes. The purpose of this study was fulfilled by examining the variation of these velocities in relation to the geology and its significance towards building a velocity model. It is evident that complexities, such as an existing heterogeneous subsurface is present in the study area. Using velocities only considered at formation well tops, as a result, does not completely honour the variation in these velocities. The velocity profile as calculated from the sonic log was characterized into zones representing unique velocity trends. The analyses to understand the impact of subsurface heterogeneities on the velocities was completed by the application of seismic facies analysis which entailed the study of the seismic reflector patterns and amplitudes; a study of the lithologies present and the generation of mineral plots using available wireline logs, all of which in close relation to the variation in velocities. The characterized zones, as a result have shown that shaly sediments are typically associated with higher velocities (~2800 – 4600m/s) compared to sandstones of lower densities. Mineral plots however, have also indicated that where quartz minerals were present (specifically zone L), sandstones as a result have shown higher velocities (~4800m/s) as compared to the shales (~3600m/s). These higher velocities are also associated with more organised seismic reflectors with brighter amplitudes and strong contrasts in acoustic impedance as shown by the seismic. Uniform velocities were observed in zones such as zone Ia, typically associated with a low acoustic impedance contrast and minimal variation in its lithological make-up. The integrated investigation of subsurface heterogeneities has shown that velocities vary to a substantial degree as a result of existing subsurface heterogeneities. The variation of these velocities are hence significant enough that it should be considered when constructing a velocity model which aims to respect the geology of the study area. The result of understanding the relation between the geology and resultant velocities may prove to advance the results of the velocity model in a manner that it is more complete and representative of the subsurface.

The marimba is rapidly achieving greater importance as a solo percussion instrument. Solo compositions for the marimba have been commissioned and performed only in the last sixty years. The 1986 National Endowment for the Arts Solo Marimba Commission is considered one of the most important commissioning projects in the history of marimba literature. Two compositions created through this project, Velocities by Joseph Schwantner and Reflections on the Nature of Water by Jacob Druckman have become two of the most influential works in contemporary marimba music. This thesis will focus on a historical perspective of the project, as well as theoretical aspects and performance issues related to these two compositions. The National Endowment for the Arts (NEA) issued a consortium commissioning grant through the Percussive Arts Society (PAS) in 1986 to three internationally renowned marimbists, William Moersch, Leigh Howard Stevens and Gordon Stout. Three Pulitzer Prize winners were brought together to compose three new works for the marimba. The resulting pieces were: Reflections on the Nature of Water by Jacob Druckman, Velocities by Joseph Schwantner, and Islands from Archipelago: Autumn Island by Roger Reynolds. A brief history of the classical concert marimba and the development of solo marimba literature is provided in the second chapter. The fourth and fifth chapters provide individual information about the pieces, including concise biographical information about the composers and an analysis of the two compositions.

No description available.

In this study the elastic properties of a fcc Fe0.87Mn0.13 random alloy are studied by ab initio calculations. Ground state lattice parameters and elastic properties are calculated with Density Functional Theory using the Exact Muffin-Tin Orbital method and the Coherent Potential Approximation. Several magnetic models, approximations and distortion techniques are evaluated for optimized results, which are obtained by a Disordered Local Moment model with the Frozen Core and Generalized Gradient approximations using volume-conserving distortions.  Conclusively the longitudinal sound velocities are calculated from second order elastic stiffness constants and visualized by two different codes. The importance of magnetism for elastic properties is confirmed, as is the usefulness of the optimized computational scheme; all quantities obtained via the scheme is in accord with earlier theoretical and experimental results. Volume-conserving distortions are found to be more precise than volume-altering for calculation of elastic constants but also to be highly dependent on the precision of bulk modulus determination. The two sound-velocity codes are in complete agreement.

This thesis is titled The influence of a nonlinear Power Take Off on a Wave Energy Converter. It looks at the effect that having a nonlinear Power Take Off (PTO) has on an inertial referenced, slack moored, point absorber, Wave Energy Converter (WEC). The generic device studied utilizes relative heave motion between an axi-symmetric cylinder and an internal mass, for the PTO to operate between. The PTO is the part of the WEC that transforms the relative motion into electricity. In this work, three different types of nonlinear PTO and a linear PTO are presented, tested, analysed and compared. The three nonlinear PTO types are: • A PTO that extracts energy in only one direction, either in relative compression or expansion. • A linear PTO and an additional endstop or peripheral PTO, that can only extract energy when the relative position of the internal mass has reached a pre-determined position. • A PTO that has damping forces that are quadratically proportional to the relative velocity. A numerical simulation has been built based upon a Runge-Kutta time series progression. The model uses the summation of the excitation force from the waves, the radiation force from the movement of the cylinder, the buoyancy force and the PTO forces. These combine to cause acceleration of the mass of the external cylinder, with an equal and opposite PTO force acting on the internal mass. The excitation force and added mass values are obtained from the boundary element method software, WAMIT. Prony’s method is used to obtain an approximate radiation force, based upon the radiation time force history. This numerical model operates on both a 1:40 scale and a full sized model. The numerical model finds the optimal PTO parameters, for different PTO setups, in irregular sea states. This optimum is based on the power extracted as well as indications of the reliability and lifetime of the system. The numerical simulation presents results showing how the nonlinearity of the PTO influences the motions of the WEC, resulting in dissimilarities between the Response Amplitude Operator (RAO) results, obtained from regular seas, and the Linear Transfer Function (LTF), found from irregular sea testing. The experimental model has been tested in the Curved Wave Tank facility at the University of Edinburgh, with a 1:40 scaled model. It used a central rod both as a support structure and to limit the movement of the cylinder and internal mass to heave. Between the cylinder and internal mass a spring and pneumatic damper operate in parallel, in various setups. It was tested in regular and irregular sea states and the position of the internal mass and cylinder was monitored. The experimental model was tested to ascertain the time series motions, RAO, LTF, the relative phase between the bodies and the power extracted for different wave climates. The numerical and experimental work were compared to allow confidence in both models. They showed relatively good agreement for the RAOs, LTFs and predictions of the relative phase but there was discrepancies in the predicted power for both regular and irregular seas. This difference is due to the difficulties in obtaining the relative velocities in the experimental model, resulting in a significant error in power prediction, since the power is proportional to the square of the relative velocities. The conclusions show that having a mono-directional PTO as opposed to a bi-directional PTO results in an approximately equal or greater power extraction in a variety of different sea states. An additional endstop or peripheral damper can increase the total power that a WEC extracts, in some situations, and may be advantageous depending upon the other potential benefits it brings to the WEC.

The laminar burning velocity of a fuel is the rate of normal propagation of a 1D flame front relative to the movement of the unburned gas. This is a fundamental property of a fuel that affects many aspects of its combustion behaviour. Experimental values are required to validate kinetic simulations, and also to provide input for models of flashback, minimum ignition energy and turbulent combustion. Burning velocity affects burn duration and consequently power output in spark ignition engines. Burning velocities are affected by pressure, temperature, equivalence ratio, residuals, additives, and stretch rates. The constant volume vessel has been used as it is considered both the most versatile and accurate method of measuring laminar burning velocities. An existing combustion vessel and oven were refurbished and new systems built for fuel injection, ignition, experiment control, data acquisition and high speed schlieren photography. An existing multi-zone model was used to allow calculation of burning velocity from pressure and schlieren data, allowing the user to select data uncorrupted by heat transfer or cellularity. A twelve term correlation for burning velocity was validated using methane modelling data. The chosen data from all the experiments was then fitted to the correlation. Methane, n-butane, n-heptane, iso-octane, toluene, ethylbenzene and ethanol were tested over a wide range of initial pressures (0.5, 1, 2 and 4 barA), temperatures (289-450 K) and equivalence ratios (0.7-1.4). For liquid fuels, tests with real residuals at mole fractions of up to 0.3 were also conducted. Stoichiometric mixture tests were performed at two initial temperatures (380 and 450 K) and the same four initial pressures. For mixtures of iso-octane and ethylbenzene, percentage volumes of 12.5, 25, 50 and 75% iso-octane were tested. It was found that the the percentage of iso-octane affected burning velocity non-linearly. For iso-octane/ethanol, a single 50:50% mixture was tested.