The coupling of real-time measurements and numerical models will be important in overcoming the challenges in environmental and oceanographic assessments in surface waters. Continuous monitoring will take advantage of current state-of-the-art in sensor development, remote sensing technology. The numerical modeling tools available exist in many different forms and varying levels of complexity from depth integrated one-dimensional (1-D) models to full three-dimensional (3-D) models. Common to all are the constraints and forcing required in driving the models. These include hydrodynamic and barometric information, which are relatively difficult to obtain given the time scale of the bio-chemical and physical processes governing the fate and transport of the constituents of interest. This study is focused on the development of a framework that couples real-time measurements and numerical simulation for tracking constituents in surface waters. The parameterization of the mixing and turbulent diffusion impacts the formulation of the constituent-transport governing equations to the extent that the numerical model is being driven by near real-time observations of hydrodynamic data and the consequent evaluation of model coefficients. The effects of shear-augmented diffusion processes in shallow embayment and near-shore waters are investigated in order to develop algorithms for obtaining a shear diffusion coefficient, Ke from shear-current measurements and turbulent diffusion-coefficient, Kz measured by the auto-correlation function, Rτ of the velocity time-series. Typically, the diffusion coefficients are measured through tracer experiments as determined by the time rate of change of the variance of a growing patch (K = ½ dσ2 /dt), which introduces the concept of diffusion length-scale (or time-scale). In this study, the dye-tracer experiment was used, not so much in the context of evaluation of a diffusion coefficient, but within a modeling framework to validate a numerical scheme driven by real-time hydrodynamic observations. Overall, the effect of shear-currents in shallow wind-driven estuaries is studied using a prototype bay typical of the Texas Gulf-coast. A numerical model was developed and used in testing these hypotheses through a series of dye-tracer experiments under varying meteorological conditions.

<p>This essay deals with wage dispersion, the Burdett-Mortensen model is applied to a set of data collected from the year 1973 – 1989. The Burdett-Mortensen model aims to explain the reasons for wage dispersion between similar able individuals. The purpose of this essay is to test the Burdett-Mortensen model accuracy in explaining wage dispersion between similar able people, by applying it to male supervisors in Sweden between 1973 and 1989. The results of this test are mixed, meaning that no clear judgment can be done to validate or reject the accuracy of the assumptions made by the authors of this model. These results leads to the conclusion that further more expansive test of this model is required to make such a judgement.</p>

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 145-148).

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references (leaves 130-137). Available also in a digital version from Dissertation Abstracts.

Not available / text

There is significant interest in understanding and exploiting the extraordinary property enhancements of polymers, enabled by adding small concentrations of nanoparticles to polymer hosts to create polymer nanocomposites (PNCs). Thin film PNCs hold potential for novel technological applications in areas such as optoelectronics or photovoltaic devices. One of the key challenges that limits the potential of PNC-based technologies is the control of nanofiller dispersion throughout the matrix. This requires a fundamental understanding of the energetic interactions that affect dispersion. Thin film PNCs pose a greater challenge than bulk PNCs, largely because interfacial interactions become increasingly important as the material is confined. It is equally important to find effective processing schemes that promote nanofiller dispersion in a manner that can be readily scalable for industrial operations. Accordingly, the last few years have seen an upsurge in processing schemes involving supercritical solvents, due in part to their tunable solvent strength. To this end, our research is aimed at gaining control of nanoparticle dispersion within thin film hosts using supercritical CO₂ (scCO₂) as a processing aid. This research examined a series of related problems. For the first project, we investigated the effects of scCO₂ sorption on the structural stability and kinetics of destabilization of homopolymer films. We showed that the films are metastable under these conditions, and the barrier to nucleation is larger than that encountered in air/vaccum. We also examined the issue of nanofiller dispersion within homopolymer thin films. In a model athermal mixture, polystyrene-coated gold nanoparticles in polystyrene hosts, interfacial segregation was generally observed, and was shown to be a function of the wetting characteristics of the brush-matrix interface and the ratio of the size of the particles to the unperturbed dimensions of the host chains. In a separate system, we show how scCO₂ can serve to prevent coarsening, which is ubiquitous in air/vacuum environments at elevated temperatures, for these nanofillers. Finally, we made nanocomposite micellar structures from block copolymers, with a fluorinated block. Gold nanoparticles were sequestered within the discontinuous domain. We then showed how scCO₂ could be used to invert the structure, placing the nanoparticles in the continuous phase.

The Swedish defence agency (FOI) has developed a particle model (called Pello) that simulates the dispersion of aerosols and gases. At the boundaries, such as the ground, the particles can either reflect back into the domain (the atmosphere) or be absorbed. Which of the events that occurs is decided by a certain probability, which in the present model depends on mere physical properties. In this thesis we have investigated a newly proposed boundary behaviour which also depends on the time step used in the numerical simulations. We verified the accuracy of the new model by using a dispersion model with an explicit solution. To gain a better understanding of how important parameters at the boundary influence each other, we performed a sensitivity analysis. Simulations showed an overall improving concentration profile as the time step became smaller and the new model working well. The convergence order of the simulations was found to be close to 0.5. In this thesis we have shown that there exist an upper limit for the time step, which depends on the specific model. The present used time step at FOI does not have this versatile property. But having this upper limit for the time step close to the boundary, and a uniform time step can be time demanding. This lead us to the conclusion that an adaptive time step should be implemented.

A study is made of the problem of metamaterial homogenization, which is the attempt to represent an artificially fabricated inhomogeneous periodic structure as a homogeneous medium with an electromagnetic response described by a number of constitutive parameters (permittivity, permability, etc.) In particular, the importance of spatial dispersion in metamaterials and the need to characterize metamaterials with wavevector dependent constitutive parameters is explained an examined. A brief survey of important previous attempts at metamaterial homogenization is presented. This is followed by a discussion of spatial dispersion in metamaterial crystals. The importance of spatial dispersion in metamaterials is justified and some manifestations of spatial dispersion described. In particular the little known phenomenon of bianisotropy in centrosymmetric crystals due to spatial dispersion is explained. Also, the effects of spatial dispersion on physical quantities such as energy flux and dissipation are identified. We then describe a new method for solving for the free eigenmodes of a metamaterial crystal with a complex wavevector eigenvalue simulation. Next, two different theoretical attempts by the author at metamaterial homogenization are described, both accompanied by tests of the calculated constitutive parameters and critical examination of the strengths and weaknesses of each approach. Finally, strong evidence of the presence and importance of spatial dispersion in metamaterials is presented. / text

published_or_final_version / Mechanical Engineering / Master / Master of Philosophy