¡@¡@¡@¡@¡@¡@¡@­^¡@¤å¡@ºK¡@­n¡@¡@¡@¡@¡@¡@¡@ Heat transfer of a molten splat to a thin layer rapidly solidified on a cold substrate and the heat transfer coefficient at the bottom surface of a splat is extensively and self-consistently investigated. Rapid freezing in the splat is governed by a nonequilibrium kinetics at the solidification front in contrast to the melting in the substrate simulated by the traditional phase change problem. Solving one-dimensional unsteady heat conduction equations and accounting for distinct properties between phases and splat and substrate, the results show the effects of dimensionless parameters such as the dimensionless kinetic coefficient, stefan number, latent heat ratio, initial, equilibrium melting, and nucleation temperature, and conductivity, density, and specific heat ratios between solid and liquid and splat and substrate on unsteady temperature fields and freezing and melting rates in the splat and substrate and on unsteady variation of Biot number are presented. The unsteady variation of the heat coefficient or Biot number can be divided by five regimes: liquid splat-solid substrate, liquid splat-liquid substrate, solid splat-solid substrate, solid splat-liquid substrate, and the nucleation of the splat. Appropriate choices of dimensionless parameters to control the time for freezing and melting of the splat and substrate and an understanding and estimation of the heat coefficient at the bottom surface of the splat therefore are presented. The velocity distribution function and transport variables of the positive ions and electrons in the collisionless presheath and sheath of a plasma near a wall partially reflecting ions and electrons are determined from a kinetic analysis. Since velocities of the ions and electrons near the wall are highly non-Maxwell-Boltzmann distributions, accurate predictions of transport variables such as density, fluid velocity, mean pressure, fluidlike viscous stress and conduction require kinetic analysis. The result find that dimensionless transport variables of ions and electrons in the presheath and sheath can be exactly expressed in terms of transcendental functions determined by dimensionless independent parameters of ions and electrons reflectivities of the wall, ion-to-electron mass ratio, charge number and electron-to-ion temperature ratio at the presheath edge. The effects of the parameters on transport variables at the wall are also obtained. The computed transport variables in the presheath and sheath show agreement with available theoretical data for a completely absorbing wall.

Thesis (Ph.D.)--Drexel University, 2010. / Includes abstract and vita. Includes bibliographical references (leaves 159).

Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references (leaves 122-129). Also available in electronic version. Access restricted to campus users.

Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 123-135).

Thesis (Ph.D.)--Drexel University, 2008. / Includes abstract and vita. Includes bibliographical references (leaves 97-118).

Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 163-168).

Thesis (Ph. D.)--Drexel University, 2007. / Includes abstract and vita. Includes bibliographical references.

Thesis (M.S.)--Drexel University, 2007. / Includes abstract. Includes bibliographical references (leaves 36-38).

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第19474号 / 理博第4134号 / 新制||理||1595(附属図書館) / 32510 / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)准教授 荒木 武昭, 教授 佐々 真一, 教授 山本 潤 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

Vortex motion plays an important role in the transport properties of high Tc superconductors. In the presence of a sufficiently large applied current vortices will drift creating an ohmic resistance in the material, while defects in the material will tend to inhibit their motion. Some types of material defects are more effective at pinning then others, and therefore, above the depinning threshold, may effect the motion of vortices differently. To investigate their motion, voltage noise generated by moving vortices is studied for different material defect types using a nonequilibrium Metropolis Monte Carlo simulation. The current-voltage (I-V) characteristics obtained from the simulation for various vortex densities and defect types show features similar to those obtained in experiments. The power spectra generated for point and columnar disorder are then compared for increasing vortex density. Above, but near the depinning threshold, broadband noise associated with plastic vortex flow is observed for columnar defects at low vortex densities, while for higher densities a triangular lattice is obtained along with a washboard signal and higher harmonics. For point defects a washboard signal with higher harmonics is always observed in the region investigated. These results suggest that power spectra for both point and columnar defects are qualitatively similar for higher vortex densities (larger magnetic fields). A second comparison is made by observing, on the one hand, the power spectra for finite linear defects increasing in length and, on the other hand, increasing point defect strength. Power spectra and structure factor results are very similar for these results as well. Both show a trend from an ordered to a disordered system with a washboard peak first increasing and then decreasing in power with increasing pinning efficiency. For both defect types the power spectrum is eventually dominated by broadband noise indicating the approach to the pinned glassy phases. / Ph. D.