Browsing by Subject "WAVE"
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Item Computer simulations of a hydrogen fueled internal combustion engine(2005-05) Halmari, Jaakko Jalmari; Maxwell, Timothy T.; Parten, Michael E.; Ertas, AtilaRicardo WAVE was used to simulate the hydrogen internal combustion engine used in Texas Tech University’s FutureTruck Ford Explorer. Initially, a naturally aspirated gasoline engine was simulated, followed by the supercharged hydrogen engine. The objective of these simulations was to maximize power of the hydrogen engine, while minimizing the emissions and fuel consumption. Among the variables which were changed, were the equivalence ratio, compression ratio, throttle opening, camshaft timing, and exhaust size. The simulation results studied included the volumetric efficiency, fuel consumption, as well as NO emissions. Several results were compared to the gasoline baseline model.Item Experimental study on rectangular barge in beam sea(Texas A&M University, 2005-08-29) Jung, Kwang-HyoThis study presents laboratory observations of flow characteristics for regular waves passing a rectangular barge in a two dimensional wave tank. The rectangular barge was fixed and free to roll (one degree of freedom) in a beam sea. Particle image velocimetry (PIV) was employed to measure the velocity field in the vicinity of the structure. The mean velocity and turbulence properties were obtained by phase-averaging the velocity profiles from repeated test runs. The quantitative flow characteristics were represented to elucidate the coupled interactions between the regular wave and the barge in roll motion or fixed condition. Additionally, the turbulence properties including the turbulence length scale and the turbulent kinetic energy budget were investigated to characterize the flow pattern due to the wave interaction. Because all the data including wave elevations, roll motion, and dynamic pressure were synchronized with velocity profiles, the results between the roll motion and the fixed condition were compared. The viscous effects due to the flow separation depend on the relative relation between the wave water particle motion and the roll motion of the barge. The viscous damping mechanism that reduces the roll motion at the roll natural period wave is illustrated. It shows that the vortex flow was mainly induced by the roll motion. For wave periods longer than the roll natural period, the flow was separated in different directions accompanying the roll natural period wave. The longer waves may help the roll motion with the vortex flow predominantly separated by the wave water particle motion rather than the barge motion. This may be called the viscous exciting effect. Moreover, the variations of dynamic pressures near the corners were measured and analyzed along with the viscous effect for both the roll motion and the fixed barge cases.Item HEM-protein regulates cell migration and asymmetric cell division during development of the ventral nerve cord in Drosophila melanogaster(2010-07-08) Zengrong Zhu; Krishna M. Bhat; Pomila Singh; Ping Wu; Kathleen M. Beckingham; Javier V. NavarroCell migration and asymmetric cell division are two of the key events during development of the nervous system. I have focused on a typical neuronal lineage, NB4-2→GMC-1→RP2/sib, in the ventral nerve cord (VNC) of the Drosophila embryo to investigate the regulation of neuronal migration and asymmetric cell division during development of the nervous system. I have discovered a migration defect of RP2 neurons in HEM-protein (Hem) mutants: RP2 neurons cross the midline and migrate from the initial hemi-segment to the opposite hemi-segment. The same migration defect is observed in WASP-family verprolin-homologous protein (WAVE/SCAR) and Abl tyrosine kinase (Abl) mutants, suggesting that these three genes might act together to regulate neuronal migration in the VNC. I have found that Hem is required for maintaining the protein level of WAVE in vivo and is necessary for its proper localization in the cell. In Hem mutants, WAVE is down regulated and mis-localized in RP2 neurons, resulting in the migration defect of RP2 neurons. Abl on the other hand negatively regulates the protein level of WAVE. When Abl is ectopically expressed, WAVE protein is down regulated. In Abl mutants, WAVE is up regulated and its hyperactivity may be responsible for the migration defect of RP2 neurons. Meanwhile, instead of asymmetric division in wild type embryos, a symmetric division of GMC-1 is observed in the “strong phenotype embryo†of HemJ4-48 mutants. It was not observed in other Hem mutants and Hem deficiency alleles. The truncated Hem protein (∆HemJ4-48) in HemJ4-48 allele may behave as a neomorphic protein, resulting in the symmetric division of GMC-1. In HemJ4-48 mutants, the apical localization of Inscuteable (Insc) is disrupted, suggesting that regulation of the asymmetric division of GMC-1 by Hem is mediated by Insc. The same symmetric division of GMC-1s was also observed in Abl mutants but not WAVE mutants, suggesting that Abl may act together with Hem to regulate the asymmetric division of GMC-1s. This study uses the Drosophila VNC as a model system and describes how neuronal migration and asymmetric cell division are regulated by Hem during development of the nervous system.