The design of a high temperature thermoelectric generator element using silicon carbide

This report presents the design of an optimum, high temperature silicon carbide thermoelectric generator element. The analytical efforts have been divided into three basic parts, the development of the theory, the accumulation of the data, and the optimization of the design. The first step in the theory development was the derivation of accurate design equations. With this done, the design philosophy and computer program were constructed, the latter utilizing a subroutine to contain the design equations. The data was obtained from a survey of many references and, for the most part, was found to be inexact, requiring the consideration of ranges of loosely bounded values. In evaluating the data and optimizing the designs, both graphical and numerical methods were used. The actual calculations during the optimization process were performed on the IBH 360/50 system, and entailed some twenty computer runs, encompassing sixty designs. The final result was an element that would produce electrical power at a power density of 9.2 Megawatts/H3 and an efficiency of 9.17 Percent --Abstract, page ii

Ecology of Small Insectivorous Birds in a Bottomland Hardwood Forest.

Changes in species composition and abundance, habitat use patterns and foraging behavior of 19 bird species in a bottomland hardwood forest in Louisiana were studied during the 1984-1989 breeding seasons. Species that used only one macrohabitat included the Yellow-throated Warbler along oxbow lake margins and the American Redstart, Swainson\u27s Warbler, and Hooded Warbler in non-flooded oak-gum-elm forest. The Northern Parula and Kentucky Warbler used 2 macrohabitats--non-flooded forest and oxbow lake margins. Thirteen species used 3 macrohabitats (non-flooded forest, seasonally flooded forest, and oxbow lake margins). I distinguished 6 groups of species that used similar microhabitat and foraging behavior. Ecological partitioning occurred primarily by (1) foraging height and height-related characters, (2) foraging locations within the forest canopy, and (3) differential use of foraging substrates and foraging maneuvers. Vegetation structure and height may be important in determining the abundance and combination of insectivorous birds existing at Tensas. Implications for management and conservation are discussed. To conserve migrant insectivorous birds, we must know the ranges, habitats, and patterns of habitat use. I selected a representative species, the Hooded Warbler, and compared habitat use and foraging ecology at a breeding and wintering site. Hooded Warbler winter distribution is concentrated along the Gulf of Mexico coast and Caribbean slope from southcentral Veracruz to Honduras. Winter habitat is typically undergrowth of humid forest; second-growth habitats are also important. At Tensas, hoodeds preferred dense foliage in the shrub and subcanopy layers, and captured prey primarily from the lower surfaces of leaves. At Los Tuxtlas, they were more generalized and captured prey from air and leaves, used a variety of other substrates, and foraged in open portions of the lower levels of the forest. Macro- and microhabitat use by Hooded Warblers were different at my study sites in the breeding and non-breeding ranges. I believe, the use of habitats varies between locations such as the wintering and breeding grounds for many species; to evaluate the relative importance of any proposed habitat changes, we must know how the changes will affect macro- and microhabitat and how the species use macro- and microhabitat

The availability of social studies reference books in thirty-five New England libraries

Thesis (Ed.M.)--Boston University This item was digitized by the Internet Archive

Tensor-multi-scalar theories from multidimensional cosmology

Inhomogeneous multidimensional cosmological models with a higher dimensional space-time manifold M=M_0 x M_1 x ... M_n are investigated under dimensional reduction to tensor-multi-scalar theories. In the Einstein conformal frame, these theories take the shape of a flat sigma-model. For the singular case where M_0 is 2-dimensional, the dimensional reduction to dilaton gravity is preformed with different distinguished representations of the action.Comment: 14 pages, latex, to appear in Phys. Rev.

2d Stringy Black Holes and Varying Constants

Motivated by the recent interest on models with varying constants and whether black hole physics can constrain such theories, two-dimensional charged stringy black holes are considered. We exploit the role of two-dimensional stringy black holes as toy models for exploring paradoxes which may lead to constrains on a theory. A two-dimensional charged stringy black hole is investigated in two different settings. Firstly, the two-dimensional black hole is treated as an isolated object and secondly, it is contained in a thermal environment. In both cases, it is shown that the temperature and the entropy of the two-dimensional charged stringy black hole are decreased when its electric charge is increased in time. By piecing together our results and previous ones, we conclude that in the context of black hole thermodynamics one cannot derive any model independent constraints for the varying constants. Therefore, it seems that there aren't any varying constant theories that are out of favor with black hole thermodynamics.Comment: 12 pages, LaTeX, to appear in JHE

Taming the Runaway Problem of Inflationary Landscapes

A wide variety of vacua, and their cosmological realization, may provide an explanation for the apparently anthropic choices of some parameters of particle physics and cosmology. If the probability on various parameters is weighted by volume, a flat potential for slow-roll inflation is also naturally understood, since the flatter the potential the larger the volume of the sub-universe. However, such inflationary landscapes have a serious problem, predicting an environment that makes it exponentially hard for observers to exist and giving an exponentially small probability for a moderate universe like ours. A general solution to this problem is proposed, and is illustrated in the context of inflaton decay and leptogenesis, leading to an upper bound on the reheating temperature in our sub-universe. In a particular scenario of chaotic inflation and non-thermal leptogenesis, predictions can be made for the size of CP violating phases, the rate of neutrinoless double beta decay and, in the case of theories with gauge-mediated weak scale supersymmetry, for the fundamental scale of supersymmetry breaking.Comment: 31 pages, including 3 figure

Lifetimes of spherically symmetric closed universes

It is proven that any spherically symmetric spacetime that possesses a compact Cauchy surface $\Sigma$ and that satisfies the dominant-energy and non-negative-pressures conditions must have a finite lifetime in the sense that all timelike curves in such a spacetime must have a length no greater than $10 \max_\Sigma(2m)$, where $m$ is the mass associated with the spheres of symmetry. This result gives a complete resolution, in the spherically symmetric case, of one version of the closed-universe recollapse conjecture (though it is likely that a slightly better bound can be established). This bound has the desirable properties of being computable from the (spherically symmetric) initial data for the spacetime and having a very simple form. In fact, its form is the same as was established, using a different method, for the spherically symmetric massless scalar field spacetimes, thereby proving a conjecture offered in that work. Prospects for generalizing these results beyond the spherically symmetric case are discussed.Comment: 12 pages (uuencoded postscript; self-unpacking), NCSU-MP-940