Magmas experiencing pressure changes can follow equilibrium or nonequilibrium degassing paths that determine the rate of gas exsolution and the composition of gases exsolved. Many variables influence timescales of equilibration between vapor and melt after a perturbation in pressure, temperature, or other factors, and the magnitude of this equilibration time determines whether the system experiences equilibrium degassing or not. In order to create a simplified framework for assessing degassing regime, we constructed a numerical diffusion model to test the sensitivity of equilibration time to variables such as bubble size, spacing, melt temperature, initial and final system pressures, and water content. We then determined the degassing regime for a range of bubble-spacing and decompression rates as an initial simplified framework to build on. We also attempted the first mixed-volatile continuous decompression experiments in order validate our model and further improve analyses and interpretations of volatile gradients in natural samples.

Tese de doutoramento. Engenharia do Ambiente. Faculdade de Engenharia. Universidade do Porto, Departamento de Engenharia Química. Instituto Superior de Engenharia do Porto. 2010

Bibliography: leaves 210-223.

Thesis (M.Ch.E.)--University of Delaware, 2007. / Principal faculty advisor: Brian G. Willis, Dept. of Chemical Engineering. Includes bibliographical references.

Typical power outputs of commercially available diode lasers are on the order of 5 milliwatts. This thesis discusses the growth, processing and fabrication of high power (lOO's of milliwatts) diode lasers. Devices were grown by Molecular Beam Epitaxy (MBE) and by Metal Organic Chemical Vapor Deposition (MOCVD). The MOCVD diode lasers demonstrated room temperature laser operation with peak output powers of 450 mW/facet pulsed mode. The MBE diode lasers demonstrated room temperature pulsed laser operation of 110 mW/facet. The dynamics of the quantum well structure were studied. The carrier concentration, threshold current density and coatings were modeled. It was demonstrated through transmission line analogies that, depending on the thickness of the high reflective coating, the result would be a high output power diode laser or a superluminescent device. The MBE device was coated with a high power coating resulting in a peak power of 450 mW. The MOCVD device was used to study the superluminescence resulting from specific coatings. / Graduation date: 1992

No description available.

This study employed a commercial code to simulate a chemical vapor deposition process in a rectangular chamber for deposition of a silicon dioxide layer on a rectangular substrate. We focus on the deposition rate on the substrate surface. We discuss the effects of the Reynolds number, the distance from inlet to substrate, the size of inlet region, the temperature of the inlet region, and the temperature of substrate. The results show that as the temperature increase, the deposition rate on the substrate grows highly. This effect will decrease if the temperature is above the specific range. Besides, it is easily deposited unequally on the edge and corner region of the substrate. However, the central region on the substrate is still uniform. We could get bigger uniform area to adjust the proper conditions.

Low pressure chemical vapor deposition (LPCVD) is one of the important technics in the semiconductor process recently. The computer simulation is the best efficient method on the process research. This research use numerical method to study the performance of showerhead parameters, and to confer the flow field distribution and deposition rate under different design parameters in LPCVD of silicon (Si). In this simulation, the CVD reactor modelings are constructed and discredited by using implicit finite volume method. The grids are arranged in a staggered manner for the discretization of the governing equations. Then the SIMPLE-type algorithm is used to solve all of the discretized algebra equations. The variable parameters are: (1) the inlet velocity, (2) the holes diameter of showerhead, (3) the showerhead size. The results show that using the showerhead can adjust the flow filed distribution and it is better for film thickness uniformity. The holes diameter and distribution density have relations with film uniformity. We also proved that the growth rate increase with the inlet velocity under the some conditions.

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: Deposition rate; zirconia; TBC; texture; microstructure; EB-PVD. Includes bibliographical references (p. 78-79).

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also from UMI Company.