In the automotive industry one of the methods used in accelerating the design, testing and development of a system or a vehicle is the use of virtual vehicle simulations. The simulations cut costs in the form of fewer prototypes required for actual testing and accelerated fault finding in the design of a system. The simulation results are very dependent on the model used for the simulation and the inputs to the system. Feasible results can often be obtained with a simplified model if the correct input data is supplied to the simulation. In South Africa, the commercial, military and off-road vehicle industries mainly use the test tracks at the Gerotek Test Facilities for ride comfort and durability tests over repeatable terrains. Terrain profiles of these tracks are not available and cannot be measured using commercially available inertial profilometers due to the severe roughness of the terrain. This study concentrates on obtaining the input data in the form of the terrain profile used for vehicle simulations and field tests in which a vehicle is driving on rough terrains. The input data is referred to as the profile of the terrain and the profiled terrains are the actual terrains used for testing. Three different methods are used in measuring the profile of the terrain namely a mechanical profilometer, photogrammetry and a 3-D scanner using a laser displacement sensor. These methods are evaluated by profiling the same section of the Belgian paving and calculating the Displacement Spectral Densities. The most efficient method is used to profile additional terrains. The terrain profiles thus obtained is used as input to an existing off-road vehicle simulation model built in MSC Adams View. This model has previously been verified over discrete obstacles where excellent correlation with experimental results was obtained. Comparison between simulated and measured results over the terrains profiled in this study also gives good correlation, establishing further confidence in the measured terrain profiles. / Dissertation (MEng)--University of Pretoria, 2009. / Mechanical and Aeronautical Engineering / unrestricted

While stepping in place without vision, individuals displace linearly and rotate, without perceiving these displacements. The aims of this study were to evaluate the effect of a concomitant cognitive task and the influence of knee height on these displacements in stepping in place for 50 steps. Sixteen adults (mean age = 22 years) performed four conditions of stepping: normal knee height and high knee height with and without a cognitive task. Antero-posterior (AP) displacement was significantly smaller in dual task than in single task at normal knee height, and AP and medio-lateral displacements were significantly larger at high than at normal knee height for single and dual task. No changes in body rotation were found. These findings suggest that automaticity is involved in the control of stepping in place with a concurrent cognitive task and that one’s attentional capacity is exceeded when stepping in place with high knees and a cognitive task.

The use of enzymes, nature´s own catalysts, both isolated or as whole cells to perform chemical transformations is called biocatalysis. As a complement to classical chemical catalysis, biocatalysis can be an environmentally friendly and more economical option in the production and synthesis of chemicals. Research on the application of amine transaminases in synthesis of chiral amines have exploded over the last two decades and interest from the industry is increasing. Amine transaminases are promising catalysts due to their ability to perform reductive amination of ketones with excellent enantioselectivity. For a process to be efficient, high substrate specificity of the applied enzyme is an important factor. A variant of Chromobacterium violaceum amine transaminase that was obtained through rational design has an increased specific activity toward (S)-1-phenylethylamine and a set of 4´-substituted acetophenones. This result makes this variant a promising catalyst for the asymmetric synthesis of similar amines. Amine transaminase catalyzed asymmetric synthesis of amines generally suffers from unfavorable equilibrium. Two methods that include spontaneous tautomerization and biocatalytic amidation for equilibrium displacement have therefore been developed. Efficient assays and screening methods are demanded for the discovery and development of novel amine transaminases. For this purpose, a sensitive fluorescence-based assay that holds promise as a high-throughput screening method was developed. One of the major obstacles for application of enzymes in industrial processes is the instability of the enzyme toward harsh conditions. The stability of Chromobacterium violaceum amine transaminase was investigated and improved using co-solvents and other additives. Co-lyophilization with surfactants was also applied to improve the performance of the same enzyme in organic solvents. / <p>QC 20161017</p>

Computational fluid dynamics (CFD) simulation is a computational tool for exploring flow applications in science and technology. Of central importance in many flow scenarios is the accurate modelling of the boundary layer phenomenon. This is particularly true in the aerospace industry, where it is central to the prediction of drag. Modern CFD codes as applied to modelling aerodynamic flows have to be fast and efficient in order to model complex realistic geometries. When considering viscous flows, the boundary layer typically requires the largest part of computational resources. To simulate boundary layer flow with most current CFD codes, requires extremely fine mesh spacing normal to the wall and is consequently computationally very expensive. Boundary layer modelling approaches offer considerable computational cost savings. One boundary layer method which proved to be very accurate is the two-integral method of Drela (1985). Coupling the boundary layer solution to inviscid external flow, however, is a challenge due to the Goldstein singularity, which occurs as separation is approached. This research proposed to develop a new method to couple Drela‟s two-integral equations to a generic outer flow solver in an iterative fashion. The study introduced an auxiliary equation, which was solved along with the displacement thickness to overcome the Goldstein singularity without the need to solve the entire flow domain simultaneously. In this work, the incompressible Navier-Stokes equations were used for the outer flow. In the majority of previous studies, the boundary layer thickness was simulated using a wall transpiration boundary condition at the interface between viscous and inviscid flows. This boundary condition was inherently non-physical since it added extra mass into the system to simulate the effects of the boundary layer. Here, this drawback was circumvented by the use of a mesh movement algorithm to shift the surface of the body outward without regridding the entire mesh. This replaced the transpiration boundary condition. The results obtained show that accurate modelling is possible for laminar incompressible flow. The predicted solutions obtained compare well with similarity solutions in the case of flat and inclined plates, and with the results of a NACA0012 airfoil produced by the validated XFOIL code (Drela and Youngren, 2001). Copyright / Dissertation (MEng)--University of Pretoria, 2012. / Mechanical and Aeronautical Engineering / unrestricted

Membranas auto-sustentáveis compostas por filmes finos com múltiplas camadas SiO2/ ( 30 nm)/CdSe( 3,0nm)/SiO2 (18 nm) e SiO2( 30 nm)/PbSe( 3,0nm)/SiO2( 18 nm) foram produzidas por magnetron sputtering e submetidas à irradiação com feixe de elétrons em microscópios de transmissão eletrônica convencionais na faixa de energia de 80 a 300 keV em densidades de corrente de 0,3 a 8,0 A cm-2. Variações de contraste observadas em micrografias adquiridas com diferentes doses de elétrons sinalizam uma considerável redistribuição atômica nos filmes semicondutores, tal redistribuição é restrita às regiões iluminadas e possui maior dependência em relação à dose do que à densidade de corrente do feixe. Medidas de difração com área selecionada (Select Area Diffraction - SAD), observações em condição de alta resolução (High Resolution Transmission Microscopy - HRTEM) e medidas de dispersão em energia de Raio-X característico (Energy Dispersive Spectroscopy - EDS) indicam que ambos semicondutores mantém a estrutura cristalina e a quantidade de átomos de Cd, Se e Pb durante irradiação. As membranas SiO2/CdSe/SiO2 apresentam uma retração contínua e homogênea das interfaces CdSe/SiO2 ao longo da superfície irradiada, a nucleação e crescimento de regiões com apenas SiO2 dá origem a uma rede percolada de CdSe que é desmembradas em nanofios nodulares e nanopartículas isoladas. Os filmes de PbSe não apresentam um processo homogêneo e contínuo durante irradiação. Inicialmente, as interfaces PbSe/SiO2 apresentam perda das arestas de alto ângulo Neste caso, as modificações microestruturais são mais intensas após uma dose limite e em regiões específicas, próximas a buracos de SiO2 previamente existentes na amostra como depositada. Medidas SAD, micrografias em condição de campo escuro e análises de imagem HRTEM mostram que a irradiação no PbSe causa separação de fases, identificada por distribuições de nanopartículas de Pb interfaceadas com uma rede planar percolada de PbSe. A conservação de matéria nos sistemas permitiu determinar os fluxos atômicos durante irradiação, o que foi realizado pelo tratamento numérico das micrografias adquiridas em diferentes doses. A investigação do aquecimento da amostra e do comportamento dos sistemas quando irradiados em diferentes energias e densidades de corrente sugerem que os deslocamentos atômicos podem ser correlacionados com as probabilidades de interação entre elétrons e átomos alvo. Isto permitiu a comparação entre fluxos atômicos experimentais, obtidos pelo tratamento numérico das micrografias TEM, com fluxos atômicos deduzidos em função das seções de choque para deslocamentos atômicos diretos, induzidos por colisões elásticas entre elétrons e átomos alvo, e deslocamentos indiretos, causados por radiólise. Os fluxos teóricos consideram variações nas taxas de deslocamento dos átomos de Cd, Se e Pb ao longo da interface semicondutor/SiO2, tais variações são entendidas como consequência de mudanças na energia de coesão das interfaces, que foram calculadas em função da curvatura e energia de superfície através do modelo de gota líquida (Líquid Drop Model - LDM) Comparações entre os fluxos atômicos inferidos das micrografias com os fluxos teóricos, obtidos das seções de choque para espalhamento elástico e inelástico de elétrons, permitiram estimar as energias de deslocamento dos átomos na interfaces e elaborar possíveis mecanismos para as mudanças microestruturais durante a irradiação. Os valores calculados de energia de deslocamento são inferiores às energias necessárias para deslocar átomos na superfície ou no interior da rede cristalina, mas podem ser aproximados às energias de migração atômica em interfaces. Os resultados mostram que os mecanismos de deslocamento atômico nos filmes finos de CdSe e PbSe não são os mesmos. As mudanças microestruturais observadas nos filmes finos de CdSe não podem ser explicadas apenas em termos de colisões balísticas dos elétrons, mas poderiam ocorrer por deslocamentos radiolíticos, principalmente se houverem estados de interface e meia banda que permitam excitações com energias transferidas menores que a largura de banda do CdSe. Já os resultados das irradiações no PbSe podem ser explicados como decorrentes de deslocamentos diretos, causados pela colisão balística dos elétrons nos átomos de Pb e Se pouco coesos nos planos PbSe{111}. Contudo, este estudo não permite excluir um possível processo de múltiplas ionizações como causa dos fluxos atômicos durante irradiação de ambas membranas. / Self-standing membranes compounded for multilayers SiO2/( 30 nm)/CdSe ( 3.0nm) /SiO2 (18 nm) and SiO2( 30 nm)/PbSe( 3.0nm)/SiO2( 18 nm) were irradiated in conventional Transmission Electron Microscopes (TEM) at energy range of 80 - 300 keV, current densities 0.3 - 8.0 A cm-2. The image contrasts of the micrographs acquired at different electron doses show an intense atomic redistribution in the semiconductor films. The effects of irradiation are restricted on the irradiated regions and show a dose dependence instead electric current dependence. Select Area Diffraction (SAD), Energy Dispersive Spectroscopy (EDS) measurements and High Resolution Electron Transmission Microscopy (HRTEM) micrographs show that the both semiconductors mantained the crystal structure and quantity of Cd, Se and Pb atoms after irradiation. The SiO2/CdSe/SiO2 membranes have a homogeneously and continuous retraction of the CdSe/SiO2 interfaces along the irradiated regions. The SiO2 holes grow to produce a percolated planar network of CdSe. In larger doses this network is disrupted, producing nodular nanowires and isolated nanoparticles. Otherwise, the PbSe thin films did not show a homogeneous and continuous process. In the first minutes of irradiation, the SiO2 holes lost the edges of high angles, the retraction of the interfaces PbSe/SiO2 occurs only at a specific electron dose, after which there are growth and nucleation of new holes around the previous ones SAD measurements, dark field micrographs and HRTEM images attest phase separation during electron beam irradiation of the PbSe, the results show isolated Pb nanoparticles connected to a planar percolated network of PbSe. The matter conservation at the systems allowed the calculation of an atomic flux during the irradiation, what was made by the numerical treatment of the micrographs acquired at different electron doses. The investigation of the sample heating and the behavior of the systems when irradiated at different energies and current densities suggest that the atomic displacements can be correlated with the probabilities of electron-atom interactions. This allowed the comparison between the inferred atomic fluxes with atomic fluxes deduced by the cross sections for the ballistic displacement induced by elastic collision of the electrons and the atomic fluxes deduced by the inelastic cross sections, which show the probability of the indirect displacements induced by radiolysis. These fluxes consider changes in the displacement rates of the Cd, Se, and Pb atoms along the semiconductor/SiO2 due to changes in the cohesion energy at the interfaces, what was calculated in function of the curvature and surface energy using the Líquid Drop Model - LDM The comparison between the atomic fluxes inferred by the TEM micrographs with the theoretical fluxes obtained by the elastic and inelastic scaterring cross sections allowed extimations of the displacement energies of the Cd, Se e Pb atoms at the interfaces, what was used to argue some possibles mechanisms for the microstructural changes during the irradiation. The calculated displacement energies are lower than the bulk or surface displacement energies, but can be approximated with the migration energies for the atomic diffusion at the interfaces. The results suggest that the mechanisms of atomic displacement can not be the same for the thin films of CdSe and PbSe. The microstructural changes observed in the CdSe thin films can not be explained only in terms of ballistic displacements, but can be explained by indirect displacements induced by the radiolysis, especially if there are intermediate and middle band states that allow excitations with energies below the CdSe band-gap. In other way, the results of the PbSe can be explained by direct displacements caused by the ballistic collision of the electrons at the Pb and Se atoms placed in the unstable PbSe{111} planes. However, this study can not rule out the possibility of a multiple ionization process as the cause of the atomic fluxes in both membranes.

The classical Nevanlinna-Pick interpolation theorem, proved in 1915 by Pick and in 1919 by Nevanlinna, gives a condition for when there exists an interpolating function in H∞(D) for a specified set of data in the complex plane. In 1967, Sarason proved his commutant lifting theorem for H∞(D), from which an operator theoretic proof of the classical Nevanlinna-Pick theorem followed. Several competing noncommutative generalizations arose as a consequence of Sarason's result, and two strategies emerged for proving generalized Nevanlinna-Pick theorems: via a commutant lifting theorem or via a resolvent, or displacement, equation. We explore the difference between these two approaches. Specifically, we compare two theorems: one by Constantinescu-Johnson from 2003 and one by Muhly-Solel from 2004. Muhly-Solel's theorem is stated in the highly general context of W*-correspondences and is proved via commutant lifting. Constantinescu-Johnson's theorem, while stated in a less general context, has the advantage of an elegant proof via a displacement equation. In order to make the comparison, we first generalize Constantinescu-Johnson's theorem to the setting of W*-correspondences in Theorem 3.0.1. Our proof, modeled after Constantinescu-Johnson's, hinges on a modified version of their displacement equation. Then we show that Theorem 3.0.1 is fundamentally different from Muhly-Solel's. More specifically, interpolation in the sense of Muhly-Solel's theorem implies interpolation in the sense of Theorem 3.0.1, but the converse is not true. Nevertheless, we identify a commutativity assumption under which the two theorems yield the same result. In addition to the two main theorems, we include smaller results that clarify the connections between the notation, space of interpolating maps, and point evaluation employed by Constantinescu-Johnson and those employed by Muhly-Solel. We conclude with an investigation of the relationship between Theorem 3.0.1 and Popescu's generalized Nevanlinna-Pick theorem proved in 2003.

PURPOSE: Controlling and monitoring volume load (VL) and training intensity (TI) is essential to managing injuries, fatigue and the recovery-adaptation process in competitive athletes. Conventional calculations of VL (sets x reps x load) and TI (VL/reps) give no consideration to barbell displacement during resistance training exercises. The purpose of this investigation was to determine whether the inclusion of displacement in VL and TI calculations would provide substantial benefits over conventional calculations of VL and TI. METHODS: Eight trained weightlifters (5 male, 3 females, 173.6 cm and 88.6 kg), 7 of which were national level, participated in the study. For each subject, a V-scope 120 was used to measure the concentric phase displacement of 24 different exercises performed during the study. VL, TI, VL with displacement (VLwD) and TI with displacement (TIwD) were calculated on a daily basis (VLwD= VL x displacement, TIwD = VLwD/reps). Loads and repetition counts were recorded for each exercise performed over 21 weeks of training which allowed for the calculation of VL, VLwD, TI and TIwD across several training phases. RESULTS: VL correlated strongly to VLwD (r=0.98) while TI also correlated strongly with TIwD (r=0.88). CONCLUSIONS: Results suggest that if exercise selection remains consistent, measuring VL and TI without displacement can illustrate workloads similar to measuring VL and TI while factoring in displacement.

Please note: creative writing theses are permanently embargoed in OpenBU. No public access is forecasted for these. To request private access, please click on the lock icon and filled out the appropriate web form. / A collection of short stories. / 2031-01-01T00:00:00Z

Flash photolysis techniques were applied to studies of solvent displacement by Lewis bases (L) from solvated metal carbonyl complexes of Cr, Mo, and W. On the basis of extensive studies of the reaction rate laws, activation parameters , and linear-free-energy-relationships, it was concluded that the mechanisms of solvent displacement reactions depend on the electronic and steric properties of the solvents and L, as well as the identities of the metal atoms. The strengths of solvent-metal bonding interactions, varying from ca. 7 to 16 kcal/mol, and the bonding "modes" of solvents to metals are sensitive to the structures of the solvent molecules and the identities of the metal centers. The results indicate dissociative desolvation pathways for many arene solvents in (solvent)Cr(CO)_5 (solvent = benzene, fluorobenzene, toluene, etc.) complexes, and are consistent with competitive interchange and dissociative pathways for (n-heptane)M(CO)_5. Different types of (arene)-Cr(CO)_5 interactions were suggested for chlorobenzene (CB) vs. fluorobenzene and other non-halogenated arenes, i.e. via σ-halogen-Cr bond formation in the CB solvate vs. π-arene-Cr bond formation through "isolated" double bonds in solvates of the other arenes. The data also indicate the increasing importance of interchange pathways for solvent displacement from the solvates of Mo and W vs. that of Cr.

Reproductive isolation can be achieved through multiple types of barriers and is essential for speciation. In flowering plants, pre-pollination barriers (e.g. differentiation in pollination niches) are believed to be the most efficient at preventing gene flow across species boundaries. In closely related species that come into secondary contact, such barriers can evolve to prevent competition for pollinator service and/or interspecific pollen transfer, which can have fitness costs. Hence pollination niche differentiation should be stronger in sympatric populations than in allopatric populations (i.e. character displacement). To investigate the differences in pollination niches and to see if it is consistent with a hypothesis of character displacement, I used the two closely related and phenotypically similar orchid species, Gymnadenia conopsea and G. densiflora. I sampled mixed and pure populations of G. conopsea and G. densiflora on Öland during the summer of 2020. In these populations, I used video cameras and pollinator catches to record pollinator activity and characterize the composition of pollinator communities. Estimation of pollinator efficiency was also assessed by analyzing the number of pollinia carried by each pollinator. Contrary to my expectations, I found that both orchids had their visitation peak during the night and that the most frequent and efficient pollinators were Autographa gamma or Deilephila porcellus for both of them. Furthermore, no increased differentiation between the two species was found in mixed compared to pure populations. My results suggest that plant-pollinator interactions do not act as efficient pre-pollination barriers in these two orchid species, and that competition for pollinator service and through interspecific pollen transfer seem to be too weak to drive pollination niche partitioning.