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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
91

Characterization of Syntactic Foams and Their Sandwich Composites: Modeling and Experimental Approaches

Gupta, Nikhil 27 June 2003 (has links)
Hollow particle filled polymers known as syntactic foams are lightweight and highly damage tolerant. Syntactic foams are used as core materials in sandwich composites. The use of such materials in aeronautical and space structures make it necessary to understand their characteristics for various environmental and loading conditions. The first part of the present work takes modeling and finite element analysis approach to understand and predict the deformation behavior of syntactic foams. Contact analysis is performed on single particle models by the finite element analysis approach. In the second part extensive experiments are carried out to characterize syntactic foams for hygrothermal and compressive properties, and syntactic foam core sandwich composites for compressive and flexural properties. Flexural tests are carried out in three and four point bending and short beam shear configurations. Syntactic foams are tested in three different specimen sizes and orientations to characterize them as per the recommendations of various ASTM standards. Effect of specimen aspect ratio on the measured mechanical properties can be determined by such an approach. The effect of change in the internal radius of hollow particles, called cenospheres, on mechanical properties is studied for all these loading conditions. Five different types of cenospheres are selected for the study of the internal radius dependence of mechanical properties of syntactic foams and their sandwich composites. All selected types of cenospheres have the same outer radius, however, their internal radius is different. Hence, difference in mechanical properties of syntactic foams is caused due to a difference in only one parameter, the cenosphere internal radius. Such unique approach made it possible to identify the individual contribution of matrix resin and cenospheres in the mechanical properties of syntactic foams. Specimen deformation behavior and fracture features are correlated to deformation curves obtained during the testing.
92

Finite-Horizon Operations Planning for a Lean Supply Chain system

Diponegoro, Ahmad 08 July 2003 (has links)
This dissertation studies an operational policy for a lean supply chain system consisting of a manufacturer, multiple suppliers and multiple buyers. The manufacturer procures raw materials from the suppliers and converts them into finished products, which are then shipped in batches to the buyers at certain intervals of times. Three distinct but inseparable problems are addressed: single supplier and single buyer with fixed delivery size (FD), multiple suppliers and multiple buyers with individual delivery schedule (MD), and time dependent delivery quantity with trend demand (TD). The mathematical formulations of these supply systems are categorized as mixed-integer, nonlinear programming problems (MINLAP) with discrete, non-convex objective functions and constraints. The operations policy determines the number of orders of raw material, beginning and ending times of cycles, production batch size, production start time, and beginning and ending inventories. The goal is to minimize the cost of the two-stage, just-in-time inventory system that integrates raw materials ordering and finished goods production system. The policy is designed for a finite planning horizon with various phases of life cycle demands such as inception (increasing), maturity (level) and phasing out (declining). Analytical results that characterize the exact, optimal policy for the problems described above are devised to develop efficient and optimal computational procedures. A closed-form heuristic that provides a near-optimal solution and tight lower bound is proposed for the problem FD. A network model to represent the problems is proposed and network-based algorithms are implemented to solve the problems FD, MD and TD optimally. The computational complexities of the algorithms are Θ(N<sup>2</sup>) or O(N<sup>3</sup>) where N is the total number of shipments in the planning horizon. Numerical tests to assess the robustness and quality of the methods show that the present research provides superior results. Production and supply chain management play an important role in ensuring that the necessary amounts of materials and parts arrive at the appropriate time and place. A manager, using the models obtained in this research, can quickly respond to consumers' demand by effectively determining the right policies to order raw materials, to deliver finished goods, and to efficiently manage their production schedule.
93

Tensile Strength and Bonding Characteristics of Self-Compacting Concrete

Druta, Cristian 08 July 2003 (has links)
Self-compacting concrete, also referred to as self-consolidating concrete, is able to flow and consolidate under its own weight and is deaerated almost completely while flowing in the formwork. It is cohesive enough to fill the spaces of almost any size and shape without segregation or bleeding. This makes SCC particularly useful wherever placing is difficult, such as in heavily-reinforced concrete members or in complicated workforms. The objectives of this research were to compare the Splitting Tensile Strength and Compressive Strength values of self-compacting and normal concrete specimens and to examine the bonding between the coarse aggregate and the cement paste using the Scanning Electron Microscope. Cylinder specimens (8" by 4") were tested for Splitting Tensile and Compressive Strength after 28 days of standard curing, in order find out if self-compacting concrete would show an increase in these strengths and a better bonding between aggregate and cement paste, compared to normal concrete. The mix design used for making the concrete specimens was based on previous research work from literature. The water - cement ratios varied from 0.3 to 0.6 while the rest of the components were kept the same, except the chemical admixtures, which were adjusted for obtaining the self-compactability of the concrete. All SCC mixtures exhibited greater values in both splitting tensile and compressive strength after being tested, compared to normal concrete. The splitting tensile strength increased by approximately 30%, whilst the compressive strength was around 60% greater. In addition, the SCC tensile strengths after 7 days were almost as high as those obtained after 28 days for normal concrete. This was possible due to the use of mineral and chemical admixtures, which usually improve the bonding between aggregate and cement paste, thus increasing the strength of concrete. Images taken from concrete samples having water-cement ratios of 0.3, 0.4, and 0.6, using the Scanning Electron Microscope, have shown that the widths of the physical interface microcracks were greater for normal concrete than for self-compacting concrete, which implies that the aggregate-cement bonds were better for SCC than for normal concrete.
94

High Strain Rate Properties of Polymer Matrix Composites

Jadhav, Amol 08 July 2003 (has links)
The vast differences in strength, ultimate strain and modulus during high strain rate (HSR) deformation of materials have been a very long-standing subject of engineering interest. This thesis deals with characterization of mechanical properties of two composite materials, balanced angle-ply graphite epoxy laminates (fibrous composite) and syntactic foams (particulate composite). The focus of this study is to compare the mechanical properties of these composite materials at high strain rates and quasi-static conditions and to find out the effects of failure modes on HSR mechanical properties of these materials. Split Hopkinson Pressure Bar (SHPB) apparatus is used for the HSR testing of balanced angle-ply IM7/8551-7 graphite/epoxy laminates and syntactic foams at varying strain rates, ranging from 500 s<sup>-1</sup> to 1700 s<sup>-1</sup>. Graphite/epoxy laminates with seven different fiber orientations including longitudinal and transverse are used in this study. Syntactic foams of four different densities are used in order to observe the density effect on the HSR properties. The aspect ratio (L/D) of all the specimens is kept equal to one. Failed specimens are consequently observed under optical and scanning electron microscope in order to understand the fracture modes of these materials. The results of the tests on both materials demonstrate considerable increase in peak strength and the elastic modulus under HSR. It is also observed that the failure strain values vary considerably with increasing strain rate. Fiber orientation, in case of balanced angle-ply graphite epoxy laminates and density in case of syntactic foams are found to influence the HSR mechanical properties and strain rate sensitivity of peak stress. Delamination caused by edge effects is the prominent mechanism of failure for graphite/epoxy specimens whereas vertical cracking through cenospheres is recognized to be the dominant mode of failure for syntactic foam specimens under HSR testing conditions. These results are essential for conducting realistic numerical simulations for safe design of structures.
95

Five Films of Steven Soderbergh

Beale, Donald 09 July 2003 (has links)
This study examines five films of Steven Soderbergh: <em>sex, lies, and videotape</em> (1989), <em>The Underneath</em> (1995), <em>Out of Sight</em> (1998), <em>The Limey</em> (1999), and <em>Traffic</em> (2000). For each film, themes and cinematic form and technique are analyzed with the intent of demonstrating a consistent authorial voice of the director. The investigation reveals that common themes include the protagonist at odds with the world about him, journey, ambiguities and uncertainties in the characters' worlds, and the nondichotomous nature of reality, especially in regard to morality. The study also argues that Soderbergh has evolved a style that favors a nonlinear narrative and parallel editing, frequent use of a hand-held camera, and systematic uses of color. It is concluded that such commonalities in theme and style provide evidence for an evolving artistic vision.
96

Optimization of a Skewed Logistic Distribution with Respect to the Kolmogorov-Smirnov Test

Finney, James Charles 18 May 2004 (has links)
The four-parameter kappa distribution (Hosking 1994) was analyzed with respect to the various possible shapes of the probability density function. The general form for the cumulative distribution function when both h and k are non-zero is: F(x) = { 1 - h [ 1 - k ( x - ξ ) / α ]<sup>1/k</sup> }<sup>1/h</sup>. The parameters h and k work together to define the function's shape, ξ affects location, and α is the scale parameter. A method of selecting parameters to minimize the Kolmogorov-Smirnov test statistic, D, was developed. The technique was first described for the logistic distribution, which is the special case of the kappa distribution with k = 0 and h = -1. Then the more general case, k = 0 and h ≠ 0, was further explored as a possibility for expanding the optimization technique. The optimization method was shown to provide the parameters h, ξ, and α such that the Kolmogorov-Smirnov test statistic, D, was minimized. This optimization was applied to several example data sets and found to produce distributions that fit the empirical data much better than the normal or lognormal distribution functions. The results have potential applications in describing the distributions of many types of real data, including, but not limited to, weather, hydrologic and other environmental data. Matching empirical data to an invertible probability distribution makes it convenient to simulate random data that follow closely the characteristics of the natural data. Preliminary inquiry suggested that the technique might be expanded to allow non-zero values of k. This would improve the shape flexibility slightly and produce slightly better fits to empirical data.
97

The Attack Will Go on: The 317th Infantry Regiment in World War II

Dominique, Dean James 10 July 2003 (has links)
The 317th Infantry Regiment was reactivated on July 15, 1942 as a subordinate element of the 80th Infantry Division. The regiment trained for two years in Tennessee, Kansas, Arizona, California, and finally New Jersey before departing for England in June 1944. Entering the European continent after D-Day, the regiment experienced its first combat in August 1944 when it assisted in closing the gap at Falaise and spearheaded Third Army's attack on Nancy. The 317th sat through the logistics shortfall that stopped the Third Army's advance during the "October Pause" in the fall of 1944. But then in November the regiment moved through the Maginot Line and prepared to attack Hitler's West Wall. In mid-December, German forces launched the famous Battle of the Bulge with a surprise attack in the Ardennes forest with twenty-five divisions. The 317th was one of the first units to begin the movement north to relieve the beleaguered American troops in the Ardennes. The regiment continued fighting through January 1945 until some units were exhausted. When Third Army resumed the offensive in February, so did the regiment. On Valentine's Day, 1945, it entered the Reich, moved rapidly through the Eifel and Palatinate regions, and crossed the Rhine River. During this time, the 317th overran some of the concentration camps that were Hitler's answer to the "Jewish question." The regiment moved through Nuremberg and into Austria, where, as it prepared for what loomed as a ferocious battle, the war ended. After serving as an occupation force, the unit officially deactivated in January 1946, after three and a half yearsof valiant service. The 317th had fought its way from Evron, France to Kirchdorf, Austria,participants in the horror and glory of war. It left behind on the battlefields of Europe 312 officers and 7392 enlisted men - fallen comrades in the struggle to free Europe from Nazi tyranny.
98

An Africanist-Orientalist Discourse: The Other in Shakespeare and Hellenistic Tragedy

Jeoung, Haegap 29 August 2003 (has links)
The main aim of this dissertation is to show how the discourse of the psychoanalytical other--femininity, death, madness, disorder, and impiety--overlaps with colonial discourse in some plays from Shakespearean and Greek-Roman tragedy, and what difference or similarity there is between the two ages. The hypothesis is that foreigners are allegories of the psychoanalytical other. For this purpose, the research tries to grasp the concept of the other, from the viewpoint of psychoanalysis, and to analyze the core of colonial discourse on the basis of the concept of the psychoanalytical other. The starting point of the dissertation is that the other is related to the "uncanny other" within ourselves, which is "the hidden face of our identity," arising from the dialectic between desire and anxiety. The dissertation puts emphasis on the fact that colonial imagination relates the imagination of the colonial other to that of the "uncanny other" within. In relation to Greek tragedy, the psychological tendency is called "basic tendency" by Frank Snowden, which develops into "power relations" in Shakespeare's plays, where the psychological other becomes the object of politics--that is, the politicization of the other. For instance, the color black is psychologically related to death in some of Hellenistic tragedy, which is as natural as even Africans equate blackness with evil. But since the Mediaeval Ages, the black-evil equation was established as a frame of politics of a theatre-state. However, the dissertation doesn't ignore the possibility that Shakespeare debunks the colonial imagination of the Renaissance Europeans.
99

Translating "Hebrew" into "Greek": The Discursive Hermeneutics of Emmanuel Levinas's Talmudic Readings

Guy, Matthew Wayne 03 September 2003 (has links)
This dissertation examines Emmanuel Levinass Talmudic readings and the hermeneutics employed to translate the Talmud into modern language. Levinas claims to be translating Hebrew into Greek by rendering into a universal, philosophical language (Greek) the ethical structure of subjectivity (Hebrew) within the Talmud. Since they investigate the structure of subjectivity, extensive use of his philosophical works and the influential works of others are used to analyze his Talmudic readings. Chapter One places Levinass project against the background of the Talmud, Judaic tradition, and projects like Rudolf Bultmanns New Testament readings and Thorleif Bomans comparative study of Greek and Hebrew. A brief abstract of Levinass philosophy emphasizing his understanding of the hermeneutics of subjectivity is given. Chapters Two and Three examine Husserl and Heideggers formative influences, especially their hermeneutics of everyday experience, wherein Levinas locates the essential flaw of Western philosophy, which begins with an already constituted subjectivity. Although all three view the structure of hermeneutics as essentially discursive, Levinas insists that the subject is not the source for these discursive structures, or even for its own subjectivity. Rather, that source, where any philosophical understanding must start, is the Other. Levinas sees exhortations against things like sorcery and temptation as the Talmuds mode of resisting and restraining subjectivitys natural tendency to seek out its own freedom and power. Western philosophy, however, actually tends to either start from this condition or work toward it. Chapter Four discusses the idea of infinity according to Levinas and Descartes, and its role in founding consciousness. In this respect, infinity coincides with the idea of God . Chapter five looks at ethics and its relation to the structure of subjectivity. Levinas reads the Talmud in light of the ethical situation confronting the subject in the encounter with the Other. The Other actually establishes subjectivity and its discursive hermeneutical structures, so subjectivity begins and continues as an ethical response. The Conclusion looks at the idea of messianic politics, showing how Levinas describes the structure of subjectivity as a unique chosenness, revealing its discursive hermeneutical structures to be orientating the subject to future ethical responses.
100

Rotary Kiln Incineration of Hazardous Wastes: Pilot-Scale Studies at Louisiana State University

Earle, John Sutherland 19 September 2003 (has links)
Studies of incineration of surrogates for hazardous wastes are conducted in the pilot-scale rotary kiln incinerator (RKI) at Louisiana State University (LSU) in Baton Rouge, Louisiana. The purpose of the research is to investigate methods of treating and destroying hazardous wastes in a cost-effective and environmentally sound way. The objective is to provide process data that will contribute to increased knowledge for RKI design and operation. The LSU facility is a College of Engineering Combustion Laboratory that is unique in its large size as a university laboratory. It is equipped with individual instruments for analysis of O<sub>2</sub>, CO, CO<sub>2</sub>, HCl, SOx and NOx and a mass spectrometer to continuously monitor products of combustion for rigorous evaluation of efficiencies of operation. Experiments conducted to investigate parameters and variables affecting the design and operation of the kiln substantiate mathematical treatment of material and energy balances. These investigations add new and useful data to be used in design of rotary kilns, a major objective of this research. One of the principal contributions of this dissertation relates to the effects of batch feeding on instability of the combustion process. Surges in temperature, pressure, and their effects on products of incomplete combustion are discussed. Other activities of the combustion laboratory are described: Incineration of still bottoms to recover byproduct potash produced by the Audubon Sugar Institute; burning of synthetic fireplace logs; study of incinerator stack gases; and determination of rates of fugitive emissions from flanges and valves. Economics of operation and maintenance of the facility are calculated, tabulated, and related to contract charges for combustion studies on behalf of industrial clients. Future prospects for the laboratory as a research and teaching facility are discussed.

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