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A numerical study of coastal stratus cloud in a two-dimensional meso-scale modelLee, Tae Young 01 November 1983 (has links)
A two-dimensional numerical mesoscale model, which ic1udes
radiative and turbulent transfers, has been constructed to study the
formation, development and dissipation of coastal stratus cloud
under an inversion. In the model, the delta-Eddington and emissivity
approximations are used for the solar and thermal radiative
transfers, respectively. K-theory parameterization is adopted for
the turbulent transfer. Ground surface temperature and moisture are
predicted using the methods of Deardorff (1977, 1978). This model
is applied to a domain which extends 180 km into sea and 240 km
inland horizontally and about 2 km from the earth1s surface vertically.
A bare, flat soil surface is assumed.
As a prelude to the study of the stratus cloud, sea breeze
circulations with and without a temperature inversion have been
investigated. The model without an inversion yields speeds of the
sea breeze front which are close to the values that have been
observed under insolation and other meteorological conditions
similar to those used in the model. The presence of an inversion
causes the depth of sea breeze circulation to be shallower and its
inland penetration during the evening hours to be weaker compared to
the case without inversion; however, the basic structure of the sea
breeze circulation is unaffected by the inversion.
The model has been used to study the growth, development and
dissipation of stratus cloud under an inversion in the west coast
region of the United States. The effects of large scale motions on
these processes have also been examined. Cloud parameters such as
the times of initial formation and of dissipation inland, the maximum
distance of inland penetration, the maximum liquid water path
and the cloud-top height are affected in the presence of such large
scale motions; for example, both the maximum liquid water path and
the cloud-top height are appreciably enhanced - by about a factor of
two - when large scale westerly winds (U[subscript g]=5mfs, V[subscript g]=0) are present
compared to the case when U[subscript g]=V[subscript g]=0. The cloud parameters
predicted by the model are in close correspondence with existing
observations in southern California.
It is found that the sea breeze circulation is not appreciably
affected by the presence of moderate amounts of stratus cloud.
While advection plays a dominant role in the horizontal development
of the stratus cloud inland, radiative processes (cooling
and heating) are observed to govern the vertical growth and dissipation
of the cloud layer. Vertical growth is influenced by the rate
of radiative cooling at cloud-top. Because of the combined effects
of solar and surface heating, the stratus inland is observed to
dissipate more rapidly during the morning hours than the cloud over
the ocean where surface heating is minimal. / Graduation date: 1984
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Mathematical modeling and kinematics a study of emerging themes and their implications for learning mathematics through an inquiry-based approach /Carrejo, David John, Marshall, Jill Ann, Petrosino, Anthony J. January 2004 (has links) (PDF)
Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisors: Jill Marshall and Anthony Petrosino. Vita. Includes bibliographical references. Available also from UMI company.
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Minimising the calculation time of the cluster program by choosing theminimum convergent cluster size and the best relaxation factorLau, Wai-ping, 劉偉平 January 1999 (has links)
published_or_final_version / abstract / toc / Physics / Master / Master of Philosophy
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A numerical study of the effect of cloud nuclei on the initiation of rain from warm cloudsLee, Seung-Man January 1978 (has links)
Typescript. / Theses (Ph. D.)--University of Hawaii at Manoa, 1978. / Bibliography: leaves 85-89. / Microfiche. / viii, 89 leaves ill
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The development of time-dependent mean-field theory for ion-metal interactions.Schafer, Kenneth Joseph. January 1989 (has links)
The development of time-dependent mean-field theory (TDMF) for the treatment of ion-metal interactions is detailed. By allowing for the time-dependent, nonlinear response of the conduction electrons, TDMF provides a self-consistent description that is free of the adiabatic and linear response approximations that have conventionally been used to treat dynamical processes in simple metals. We present the first results of three-dimensional simulations of a bare proton passing through a thin metallic foil. The nonlinear-induced electron density, dynamical screening potential, and electronic stopping power are all displayed as functions of time for several proton velocities ranging from one-half to eight times the Fermi velocity of a simple metal (sodium). We find that a sizable induced density forms behind the proton and that this density is carried along in the wake of the proton with very little dispersion as it traverses the foil. At proton velocities comparable to or above the Fermi velocity, these wake-riding electrons are shaken off as the proton passes through the rear surface of the foil. We find no evidence that the proton forms a stable hydrogen atom as it traverses the foil. At the velocities studied, the conduction electrons provide a weak, asymmetric screening of the proton, with some regions behind the proton actually being overscreened at the higher velocities. A comparison of our results with a standard linear response treatment of the problem reveals both qualitative and quantitative differences in the calculated time-dependent electron density and screening length. We find that the basic assumption underlying the linear response approximation is not justified in this case, due to the strongly nonlinear nature of the conduction electrons' response. These results are illustrative of the kinds of calculations that can be carried out with the simulation package that we have developed and we describe several applications that are planned for the near future. Several innovations in numerical technique, developed in the course of this work, are also detailed.
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Logarithmic fidelity and adiabatic requirement in the LMG model. / Logarithmic fidelity and adiabatic requirement in the Lipkin-Meshkov-Glick model / LMG模型中的保真度對數和絶熱要求 / Lipkin-Meshkov-Glick模型中的保真度對數和絶熱要求 / Logarithmic fidelity and adiabatic requirement in the LMG model. / LMG mo xing zhong de bao zhen du dui shu he jue re yao qiu / Lipkin-Meshkov-Glick mo xing zhong de bao zhen du dui shu he jue re yao qiuJanuary 2010 (has links)
Leung, Ching Yee = LMG模型中的保真度對數和絶熱要求 / 梁靜儀. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 53-58). / Abstracts in English and Chinese. / Leung, Ching Yee = LMG mo xing zhong de bao zhen du dui shu he jue re yao qiu / Liang Jingyi. / Chapter 1 --- Quantum phase transition and fidelity --- p.1 / Chapter 1.1 --- What is a quantum phase transition --- p.1 / Chapter 1.2 --- Use of fidelity in describing QPT --- p.3 / Chapter 1.3 --- Quantum fidelity versus classical fidelity --- p.5 / Chapter 1.4 --- Motivation of the project --- p.8 / Chapter 2 --- Introduction to LMG model --- p.11 / Chapter 2.1 --- The LMG model --- p.11 / Chapter 2.2 --- General ground-state solution of LMG model --- p.13 / Chapter 2.3 --- Analytical solution of ground-state fidelity of LMG model --- p.16 / Chapter 2.4 --- Numerical diagonalization of the Hamiltonian --- p.23 / Chapter 3 --- Scaling dependence of logarithmic fidelity in the LMG model --- p.26 / Chapter 3.1 --- Symmetry-broken phase --- p.26 / Chapter 3.2 --- Polarized phase --- p.29 / Chapter 3.3 --- Scaling behavior of logarithmic fidelity around the critical point --- p.30 / Chapter 4 --- Quench dynamics --- p.35 / Chapter 4.1 --- Introduction to quench dynamics --- p.35 / Chapter 4.2 --- Quantum adiabatic theorem --- p.35 / Chapter 4.3 --- Ground-state quench dynamics --- p.37 / Chapter 4.4 --- Motivation --- p.38 / Chapter 4.5 --- "Adiabaticity, residue energy and fidelity" --- p.39 / Chapter 4.6 --- Adiabatic requirement --- p.40 / Chapter 5 --- LMG model in quench dynamics --- p.42 / Chapter 5.1 --- Numerical analysis method --- p.42 / Chapter 5.2 --- Loss of adiabaticity --- p.44 / Chapter 5.3 --- The adiabatic requirement in the symmetry-broken phase --- p.45 / Chapter 5.4 --- The adiabatic requirement in the polarized phase --- p.46 / Chapter 5.5 --- In the critical region --- p.47 / Chapter 6 --- Summary --- p.50 / Chapter 6.1 --- Scaling dependence of logarithmic fidelity --- p.50 / Chapter 6.2 --- Scaling dependence of duration time in quench dynamics --- p.52 / Bibliography --- p.53
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Rebound predictions of mechanical collisionsLai, Liang-Ju 02 February 1999 (has links)
Predictions of mechanical collisions between two bodies frequently cannot be completed by the impulse-momentum equation together with a complete description of the motion of the system at the initial contact. Additional account must be taken of the deformations and frictional interaction induced by the impulsive reaction force, where the bodies contact one another, as these play an important role in the outcome of the collision.
During the time the bodies are in contact, elastic, friction and inertia properties combine to produce a complex variation of sliding and sticking through out the contact surface. For accurately predicting the impulse and velocity changes during contact, a considerably simplified, coupled, conservative model, which captures the essential characteristics of the elastic-friction interaction during contact loading, is investigated in this thesis. In this simplified model, the interface between two colliding bodies resembles the behavior of a pair of mutually perpendicular, non-linear springs which react independently with the exception that the stiffness of the tangential "spring" is influenced by the normal displacement. These elastic properties, in combination with
inertial properties derived from generalized impulse-momentum laws, form a "spring-mass" system for which numerical integration yields the prediction of rebound velocities.
For comparison, an explicit non-linear finite element code, DYNA3D, developed at Lawrence Livermore National Laboratory for analyzing the transient dynamic response of three-dimensional solids, is used to predict the responses of an elastic sphere and elastic rod, each colliding with a rigid plane with varying initial velocities and configurations. Results are also compared with results of a complex analysis of collisions of spheres by Maw, Barber, and Fawcett (1976). / Graduation date: 1999
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Modeling and simulation of CF���/O��� microwave plasma afterglowsCamara, Amadou Tidiane 05 December 1997 (has links)
A gas phase kinetic model for the CF���/O��� microwave discharge plasma and afterglow of our laboratory has been developed. A reaction pathway identifying the major chemical reactions is proposed. The rate coefficients of the electron impact dissociation reactions are determined at three different plasma powers using both published electron molecule collision cross section data and plug flow analysis of data collected in our system. Agreement between calculated and experimental rate coefficients is better than 20%. Fluid simulations of a two-dimensional mathematical model were performed using computational fluid dynamics. It is found that the model reproduced qualitatively the general trends of the experimental data. The effects of plasma power, feed gas composition, residence time and pressure on the product distribution of the system are studied. CF��� conversion increases with power and residence time. The variation of CF��� conversion and carbon containing species
distribution falls into two regimes. In the oxygen rich regime (below 25 mole % CF��� in the feed), CO��� is found to be the major product of CF��� decomposition; homogeneous recombination reactions between atomic oxygen and the free radicals are found to be the dominant mechanism in the afterglow region resulting in high CF��� conversions. Homogeneous reactions convert CO to CO���. In the CF��� rich regime (above 50 mole % CF���), COF��� is found to be the major product of CF��� decomposition. Recombination reactions of CF��� with atomic fluorine dominate in the afterglow region and limit conversion. Lowering pressures result in increased conversion of CF��� and increased concentration of the carbon containing species. / Graduation date: 1998
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Ab initio calculations of silicon clusters黃新祥, Wong, Sun-cheung. January 1998 (has links)
published_or_final_version / Physics / Master / Master of Philosophy
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Computational modeling of a liquid crystal phase transitionWincure, Benjamin, 1966- January 2007 (has links)
This thesis numerically solves the tensor order parameter continuum theory equations for nematic liquid crystals to investigate liquid crystal texturing mechanisms during an isotropic to nematic phase transition in a bulk unstable isotropic phase and next to solid surfaces. The Time Dependent Ginsburg Landau equation with a Landau de Gennes Helmholtz free energy density description is used to predict the shapes, textures and defect mechanisms that occur in the expanding droplets and films of a 4'-pentyl-4-cyanobiphenyl (5CB) nematic phase immediately after their nucleation from an unstable isotropic phase, due to a temperature quench. To create a robust simulation method able to tackle high curvature, defect nucleation, heterogeneous substrates and phase ordering interfaces, particular attention was paid to adapting the mathematical model and computational methods to what was previously known about the nucleation and growth events that occur experimentally during a bulk 5CB isotropic to nematic phase transition and next to decorated solid surfaces. The numerical simulations provide detailed predictions about (i) growth rates for different temperature quenches, (ii) structure of the isotropic-nematic interface, (iii) shapes of expanding nano and submicron nematic droplets, (iv) texturing within growing nano and submicron nematic droplets, (v) a new defect formation mechanism called "interfacial defect shedding", and (vi) the effect of contact angle and interface curvature next to a solid surface with anchoring switches. The main contributions of this thesis are its detailed predictions that emerge from the liquid crystal simulation results, the careful adaptation of the mathematical model and numerical method to what is currently known about early stage growth in a nematic liquid crystal phase, and the validation of new theory by the simulation results.
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