Conventionally the size of the back clearance played a great importance on reducing the axial clearance by utilizing the concept that the decreased axial clearance results in lower axial force acting on the impeller. However, from the previous works on the effect of the back clearance on the hydrodynamic forces upon the semi-open impeller showed the opposite trend: increasing the back clearance results in the reduced axial loading. In this work, the CFD simulation of an entire pump and detailed analysis on the back clearance flow are performed. By utilizing the commercially available software, meshing and CFD simulations are performed. LDA data, unsteady pressure data, and pressure distributions on the housing are used to validate the CFD model. The flow field prediction of the back clearance flow is then compared with other researcher’s works of the gap flow analysis between the rotating and stationary disks. The flow field inside the impeller passage, which is very sensitive to the back clearance size, is also studied. The empirical equation for the leakage loss through the balance holes is produced using the CFD predictions.

none

Thesis (Ph.D.)--Virginia Commonwealth University, 2009. / Prepared for: Dept. of Public Policy and Administration. Title from title-page of electronic thesis. Bibliography: leaves 230-254.

Thesis (Ph. D.)--Yale University, 1977. / Includes bibliographical references (p. 210-212).

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references. Available also from UMI Company.

Thesis--M. Phil., University of Hong Kong, 1980.

Zugl.: Marburg, Univ., veränd. Diss., 2009

Understanding possible variations in muscle activation patterns and its functional implications to movement control is crucial for rehabilitation. Inter-/intra-subject variability is often observed in muscle activity used for performing the same task in both healthy and impaired individuals. However, the extent to which muscle activation patterns can vary under specific neuromuscular conditions and differ in function are still not well understood. Current musculoskeletal modeling approaches using optimization techniques to identify a unique solution cannot adequately address such questions. Here I developed a novel computational framework using detailed musculoskeletal model to reveal the latitude the nervous system has in selecting muscle activation patterns for a given task regarding neuromechanical constraints. I focused on isometric hindlimb endpoint force generation task relevant to balance behavior in cats. By identifying the explicit bounds on activation of individual muscles defined by biomechanical constraints, I demonstrate ample range of feasible activation patterns that account for experimental variability. By investigating the possible neuromechanical bases of using the same muscle activation pattern across tasks, I demonstrate that demand for generalization can affect the selection of muscle activation pattern. By characterizing the landscape of the solution space with respect to multiple functional properties, I demonstrate a possible trade-off between effort and stability. This framework is a useful tool for understanding principles underlying functional or impaired movements. We may gain valuable insights to developing effective rehabilitation strategies and biologically-inspired control principles for robots.

The water balance equation is one of the most fundamental concepts in hydrology. How much precipitation a river basin receives, and where that water goes, defines what flora, fauna, and industry the basin can support. Models for solving this equation originally relied only on precipitation, air temperature, and day length, but have adapted as new data becomes available. Recent advances in technology, especially remote sensing and web services, make it cheaper and easier than ever to obtain hydrological data, including many variables that were previously impossible to measure. This thesis will examine the water balance of the San Marcos River Basin and demonstrate how remote sensing and web services can improve our understanding of the basin's hydrology. It was found that 72% of precipitation in the San Marcos Basin is lost to evapotranspiration. This percentage varies from year to year as a function of precipitation, but the annual volume of evapotranspiration stays almost constant. It was only during the second consecutive year of drought that there was an appreciable change in evapotranspiration. This suggests that annual evapotranspiration can be thought of as a property inherent to a watershed's hydrology, and so long as there is enough stored water in the soil, that demand will be met. The water left over after ET takes its share can either flow out of the basin through a river channel or stay within the basin as storage. After examining methods for partitioning the available water between outflow and storage, it was found that lumped water balance models cannot be used in the San Marcos River Basin because of its complex interactions with the Edwards Aquifer. In order to better model soil moisture dynamics and groundwater infiltration, a distributed model will have to be developed that accounts for flow in and out of the aquifer. / text

Obesity is a known risk factor for many types of cancer including pancreatic. Calorie restriction (CR), an anti-obesity diet regimen, has potent anticancer effects that may be mediated through its ability to reduce serum metabolic hormones and protumorigenic cytokines such as insulin-like growth factor (IGF)-1. IGF-1 is a metabolic hormone responsive to nutrient status that activates the inflammatory, cancer-related pathway, nuclear factor (NF)-[kappa]B. For this report, we tested the hypothesis that CR, via regulation of IGF-1, inhibits pancreatic tumor cell growth through modulation of NF-kB activation and protumorigenic gene expression. Male athymic nude mice were randomized to either a control diet consumed ad libitum (n=15) or a 30% CR diet (n=15) for 17 weeks, at which time, mice were injected with human pancreatic cancer cells (MiaPaca) and tumor growth was monitored for 6 weeks. Translocation of p65, a regulatory element of NF-[kappa]B, and expression of its downstream gene targets were analyzed in excised tumors. CR mice weighed less, (p<0.05), and had smaller tumors (p=0.022) relative to controls. Tumors from CR mice, relative to controls, demonstrated significant decreases in NF-[kappa]B downstream genes CCND1, RELA, Survivin, VEGF, and XIAP. These findings parallel our previous studies in pancreatic tumors from mouse origin, and suggest that the inhibitory effects of CR on MiaPaca pancreatic tumor growth are associated with decreased NF-kB activation. / text