<p>Non-pulsatile and pulsatile flow in bent pipes and radial turbine has been assessed with numerical simulations. The flow field in a single bent pipe has been computed with different turbulence modelling approaches. A comparison with measured data shows that Implicit Large Eddy Simulation (ILES) gives the best agreement in terms of mean flow quantities. All computations with the different turbulence models qualitatively capture the so called Dean vortices. The Dean vortices are a pair of counter-rotating vortices that are created in the bend, due to inertial effects in combination with a radial pressure gradient. The pulsatile flow in a double bent pipe has also been considered. In the first bend, the Dean vortices are formed and in the second bend a swirling motion is created, which will together with the Dean vortices create a complex flow field downstream of the second bend. The strength of these structures will vary with the amplitude of the axial flow. For pulsatile flow, a phase shift between the velocity and the pressure occurs and the phase shift is not constant during the pulse depending on the balance between the different terms in the Navier- Stokes equations.</p><p>The performance of a radial turbocharger turbine working under both non-pulsatile and pulsatile flow conditions has also been investigated by using ILES. To assess the effect of pulsatile inflow conditions on the turbine performance, three different cases have been considered with different frequencies and amplitude of the mass flow pulse and different rotational speeds of the turbine wheel. The results show that the turbine cannot be treated as being quasi-stationary; for example, the shaft power varies with varying frequency of the pulses for the same amplitude of mass flow. The pulsatile flow also implies that the incidence angle of the flow into the turbine wheel varies during the pulse. For the worst case, the relative incidence angle varies from approximately −80° to +60°. A phase shift between the pressure and the mass flow at the inlet and the shaft torque also occurs. This phase shift increases with increasing frequency, which affects the accuracy of the results from 1-D models based on turbine maps measured under non-pulsatile conditions.</p><p>For a turbocharger working under internal combustion engine conditions, the flow into the turbine is pulsatile and there are also unsteady secondary flow components, depending on the geometry of the exhaust manifold situated upstream of the turbine. Therefore, the effects of different perturbations at the inflow conditions on the turbine performance have been assessed. For the different cases both turbulent fluctuations and different secondary flow structures are added to the inlet velocity. The results show that a non-disturbed inlet flow gives the best performance, while an inflow condition with a certain large scale eddy in combination with turbulence has the largest negative effect on the shaft power output.</p>

Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 95-98). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 95-98). Also available on the Internet.

This work studies the effects of radial flow on the aerodynamic phenomena occurring on a retreating blade with a focus on dynamic stall and reverse flow as applied to both a helicopter rotor in forward flight and a wind turbine operating at a yaw angle. While great progress has been made in understanding the phenomenon of two-dimensional dynamic stall, the effect of rotation on the dynamic stall event is not well understood. Experiments were conducted on a rigid two bladed teetering rotor at high advance ratios in a low speed wind tunnel. Particle image velocimetry (PIV) measurements were used to quantify the flow field at several azimuthal angles on the rotating blade during the dynamic stall event. The effect of centrifugal forces induced ``pure'' radial velocity on the dynamic stall event at 270 degrees azimuth was studied in detail. Further investigation of the radial flow field suggested that the mean radial velocity attenuated on moving outboard due to an apparent shear layer instability and it was demonstrated to be of first order importance in the flow field. These radial flow results prompted an exploration of the flow over a rotating disk to establish similarities of the radial flow over rotating blade in separated flow to that over a rotating disk in separated flow. While a greater part of this work focused on aspects of dynamic stall on the retreating blade, the final parts focus on the exotic flow regime of reverse flow (characterized by flow from the trailing edge to the leading edge of the blade). Aerodynamic loads measurement and surface flow visualization via tufts are used to first quantify the behavior of a static yawed blade in reverse flow. PIV measurements are then used on a static yawed blade and a rotating blade in reverse flow conditions to ascertain the effects of rotation on reverse flow.

Retrospective studies suggest that lifestyle activities may provide protection against Alzheimer s Disease (AD). However, such studies can be inaccurate and prospective longitudinal studies investigating lifestyle protection against AD are both impractical and impossible to control for. Transgenic (Tg+) AD mice offer a model in a well controlled environment for testing the potential for environmental factors to impact AD development. In an initial study, Tg+ and non-transgenic (Tg-) mice were housed in either environmentally enriched (EE) or standard housing (SH) from 2-6 months of age, with a behavioral battery given during the last 5 weeks of housing. In the Morris maze, platform recognition, and radial arm water maze tasks, Tg+/EE mice were completely protected from cognitive impairment present in Tg+/SH mice and comparable to control Tg-/SH mice in cognitive performance. The current study utilized the same cognitive-based behavioral battery and multimetric statis statistical analysis to investigate the protective effects of "complete" environment enrichment (EE) versus several of its components (physical activity, social interactions) in AD transgenic mice. The AD transgenic mice utilized develop beta-amyloid (AB) deposition and cognitive impairment by 6-7 months of age. Similar to our initial study, results show that "complete" EE (physical, social, and cognitive activities) from 2 to 8 months of age completely protected AD transgenic mice from cognitive impairment in tasks representing different cognitive domains - working memory, reference learning, and search/recognition. In strong contrast, Tg+ mice reared in environments that included physical activity and social interaction, or only social interaction, were not protected from cognitive impairment in adulthood -- enhanced cognitive activity was required over and above that present in these other environments. Through use of discriminant function analysis, EE and/or NT mice were consistently discriminated from the poorer performing other housing groups. The cognitive benefits observed in EE-housed Tg+ mice occurred without significant changes in cortical AB levels, plasma cytokine levels, or plasma corticosterone levels, suggesting involvement of mechanisms independent of these endpoints. However, EE-housed Tg+ mice did have decreased dendritic length of neurons in the parietal cortex (but not hippocampus). Noteworthy is that plasma cytokine levels and hippocampal dendritic length consistently correlated with cognitive measures, suggesting their involvement in underlying mechanisms of cognitive performance. The present work provides the first evidence that "complete" EE (including enhanced cognitive activity) is needed to provide cognitive protection against AD in a Tg+ model of the disease, while the physical and social activity components of EE do not alone lead to protection. These results suggest that humans desiring to gain maximal environmental protection against AD should live a lifestyle high in cognitive, social, and physical activities together.

Analytical solutions for aquifer response to pumping are commonly used to infer the hydraulic properties of aquifers. This dissertation develops new analytical solutions for the analysis of pumping test data from confined and unconfined aquifer.An analytical solution for flow to a partially penetrating well of infinitesimally small radius in a compressible unconfined aquifer is developed that allows inferring its saturated and unsaturated hydraulic properties from drawdowns recorded in the saturated and/or the unsaturated zone. The effects of unsaturated zoneconstitutive parameters and thickness on drawdowns in the saturated and unsaturated zones as functions of position and time is investigated; the solution is validated against numerical simulations of drawdown in a synthetic aquifer having unsaturated properties described by the van Genuchten (1980) - Mualem (1976)constitutive model; used to analyze drawdown data from a pumping test conducted by the US Geological Survey at Cape Cod,Massachusetts; and corresponding estimates of van Genuchten - Mualem parameters are compared with laboratoryvalues obtained for similar materials in the area.Drawdowns generated by extracting water from a large diameter (e.g. water supply) well are affected by wellbore storage. An analytical solution in Laplace transformed space for drawdown in a uniformanisotropic confined aquifer caused by withdrawing water at a constant rate from a partially penetrating well with storage is developed. When the pumping well is fully penetrating the solution reduces to that of Papadopulos and Cooper (1967); to that of Hantush (1964) when the pumping well has no wellbore storage; to the solution of Theis (1935) when both conditions are fulfilled; and to that of Yang et al. (2006) when the pumping well is partially penetrating, having finite radius but lacking storage. The solutionis validated against synthetic pumping test data and used to explore graphically the effects of partial penetration, wellbore storage and anisotropy on time evolutions of drawdown in the pumping well and in observation wells.The analytical solution for unconfined aquifers is extended to the case of a finite diameter pumping well with storage. The extended analytical solution is used to investigate the effects of storage in the pumping well and delayed piezometer response on drawdowns in the saturated and unsaturated zones as functions of position and time. The solution is validated against numerical simulations of drawdown in a synthetic aquifer having unsaturated properties described by the van Genuchten (1980) - Mualem (1976) model. It is then used to analyze a seven-day pumping test conducted by University of Waterloo researchers at the Canadian Forces Base Borden in Ontario, Canada; and to compare our results with those ofMoench (2008).

Approximation and interpolation employing radial basis functions has found important applications since the early 1980's in areas such as signal processing, medical imaging, as well as neural networks. Several applications demand that certain physical properties be fulfilled, such as a function being divergence free. No such class of radial basis functions that reflects these physical properties was known until 1994, when Narcowich and Ward introduced a family of matrix-valued radial basis functions that are divergence free. They also obtained error bounds and stability estimates for interpolation by means of these functions. These divergence-free functions are very smooth, and have unbounded support. In this thesis we introduce a new class of matrix-valued radial basis functions that are divergence free as well as compactly supported. This leads to the possibility of applying fast solvers for inverting interpolation matrices, as these matrices are not only symmetric and positive definite, but also sparse because of this compact support. We develop error bounds and stability estimates which hold for a broad class of functions. We conclude with applications to the numerical solution of the Navier-Stokes equation for certain incompressible fluid flows.

Tese de Mestrado Integrado. Engenharia Mecânica. Faculdade de Engenharia. Universidade do Porto. 2013

Neurogenesis occurs in exclusive regions in the adult nervous system, the subventricular zone and dentate gyrus in the brain, and olfactory epithelium (OE) in the periphery. Cell replacement after death or injury, occurs to varying degrees in neural tissue, and is thought to be dependent upon the biological responses of stem and/or progenitor cells. Despite the progress made to identify adult OE and central nervous system (CNS) progenitors and lineage trace their progeny, our spatial and temporal understanding of embryonic OE neuroglial progenitors has been stalled by the paucity of identifiable genes able to distinguish individual candidate progenitors. In the developing CNS, radial glia serve as both neural progenitors and scaffolding for migrating neuroblasts and are identified by the expression of a select group of antigens, including nestin. Here, I show that the embryonic OE contains a novel radial glial-like progenitor (RGLP) that is not detected in adult OE. RGLPs express the radial glial antigens nestin, GLAST and RC2, but not brain lipid binding protein (BLBP), which, distinct from CNS radial glia, is instead found in olfactory ensheathing cells, a result confirmed using lineage tracing with BLBP-cre mice. Nestin-cre-mediated lineage tracing with three different reporters reveals that only a subpopulation of nestin-expressing RGLPs activate the “CNS-specific” nestin regulatory elements, and produce spatially restricted neurons in the OE and vomeronasal organ. The dorsal-medial restriction of transgene-activating cells is also seen in the embryonic OE of Nestin-GFP transgenic mice, where GFP is found in a subpopulation of GFP+ Mash1+ neuronal progenitors, despite the fact that endogenous nestin expression is found in RGLPs throughout the OE. In vitro, embryonic OE progenitors produce three biologically distinct colony subtypes, that when generated from Nestin-cre/ZEG mice, produce GFP+ neurons, recapitulating their in vivo phenotype, and are enriched for the most neurogenic colony subtype. Neurogenesis in vitro is driven by the proliferation of nestin+ progenitors in response to FGF2. I thus provide evidence for a novel neurogenic precursor, the RGLP of the OE, that can be regulated by FGF2, and provide the first evidence for intrinsic differences in the origin and spatiotemporal potential of distinct progenitors during OE development.

Zentall, Steirn, and Jackson-Smith (1990) found evidence for dual coding in pigeons in a radial maze analog task. Specifically, they found that pigeons used retrospective coding in which previously chosen keys were remembered when a delay was interpolated early in a trial and prospective coding in which to-be-visited keys were remembered when a delay was interpolated late in a trial. An alternative explanation, the criterion shift hypothesis proposed by Brown, Wheeler, and Riley (1989), suggests that these data are consistent with dual coding because of an artifact of the correction procedures used by Zentall et al. The criterion hypothesis suggests that retrospective coding is used and that pigeons make choices more carefully after many choices have been made on delay trials as compared to control trials, which creates the appearance of prospective coding later in a trial. The present experiments tested this hypothesis using a new testing trial procedure and new, more conservative control trials. In experiment 1, the results of Zentall et al. were replicated using a fixed delay procedure instead of their original progressive delay procedure. Experiment 2 used a forced choice procedure after the delay to make the probability of making an error 50% on each trial type. Control trials also included a forced choice procedure to eliminate the assumptions required by the corrections procedure used by Zentall et al. The results were inconsistent with the retrospective coding account predicted by the criterion shift hypothesis and with the dual coding hypothesis. Instead, the results were consistent with a prospective coding account in which to-be-visited keys were remembered. These results were replicated in Experiment 3 using the pigeons from Experiment 1. The present findings have important implications for the field of comparative cognition.