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  Partner: UNT Libraries
 Collection: UNT Theses and Dissertations
Corrosion Protection of Low Carbon Steel By Cation Substituted Magnetite (Fe3o4)

Corrosion Protection of Low Carbon Steel By Cation Substituted Magnetite (Fe3o4)

Date: May 2013
Creator: Phadnis, Ameya
Description: Surfaces of low carbon steel sheet were modified by exposure to highly caustic aqueous solutions containing either chromium or aluminum cations. Corrosion resistances of such surfaces were compared with that of steel surfaces exposed to plain caustic aqueous solution. In all cases a highly uniform, black coating having a spinel structure similar to magnetite (Fe3O4) was obtained. The coated steel surfaces were characterized using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and Fourier transform infrared spectrophotometry (FTIR). Polarization resistances (Rp) of modified steel surfaces were measured and compared with that of bare steel surfaces. Results indicate that chromium (Fe2+ Fe3+x Cr3+1-x) or aluminum (Fe2+ Fe3+x Al3+1-x) substituted spinel phases formed on steel surfaces showed higher Rp values compared to only magnetite (Fe2+ 2Fe3+O4) phase formed in the absence of either chromium or aluminum cations. Average Rp values for steel surfaces with chromium containing spinel phase were much higher (21.8 k?) as compared to 1.7 k? for bare steel surfaces. Steel surfaces with aluminum containing spinel phase and steels with plain magnetite coated samples showed average Rp values of 3.3 k? and 2.5 k? respectively. XPS and EDS analysis confirmed presence of cations of chromium and ...
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Design of a Dual Band Gan Pa Utilizing Dual Band Impedance Transformers

Design of a Dual Band Gan Pa Utilizing Dual Band Impedance Transformers

Date: May 2013
Creator: Poe, David R.
Description: This thesis discusses the design, fabrication, and testing of a high efficiency, dual band radio frequency power amplifier. While it is difficult to demonstrate an exact mode of operation for power amplifiers at radio frequencies, based on the characteristics of the transistor itself, the argument can be made that our high efficiency performance is due to an approximation to class E operation. The PA is designed around a CGH40025 transistor manufactured by Cree, Inc, which has developed a very useful nonlinear model of its transistor, which allows use of software load/source pull methods to determine optimum impedances to be presented to the gate and drain (hereafter referred to as source and load) of the transistor at each band of operation. A recent work on dual-band impedance matching is then used to design distributed element networks in order to present conjugate matches of these impedances to the transistor. This is followed by a careful layout, after which the PA is then fabricated on a low-impedance substrate using a LPKF Protomat S63 rapid prototyping machine. Measurements of gain and drain current provide values for power-added-efficiency. Simulated gains were 21 and 18 dB at 800 MHz and 1.85 GHz, respectively, with PAE around ...
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Supply Chain Network Planning for Humanitarian Operations During Seasonal Disasters

Supply Chain Network Planning for Humanitarian Operations During Seasonal Disasters

Date: May 2013
Creator: Ponnaiyan, Subramaniam
Description: To prevent loss of lives during seasonal disasters, relief agencies distribute critical supplies and provide lifesaving services to the affected populations. Despite agencies' efforts, frequently occuring disasters increase the cost of relief operations. The purpose of our study is to minimize the cost of relief operations, considering that such disasters cause random demand. To achieve this, we have formulated a series of models, which are distinct from the current studies in three ways. First, to the best of our knowledge, we are the first ones to capture both perishable and durable products together. Second, we have aggregated multiple products in a different way than current studies do. This unique aggregation requires less data than that of other types of aggregation. Finally, our models are compatible with the practical data generated by FEMA. Our models offer insights on the impacts of various parameters on optimum cost and order size. The analyses of correlation of demand and quality of information offer interesting insights; for instance, under certain cases, the quality of information does not influence cost. Our study has considered both risk averse and risk neutral approaches and provided insights. The insights obtained from our models are expected to help agencies reduce ...
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Data Transmission in Quantized Consensus

Data Transmission in Quantized Consensus

Date: May 2013
Creator: Parvez, Imtiaz
Description: In the world of networked system, average consensus is an important dimension of co-ordinate control and cooperation. Since the communication medium is digital, real value cannot be transmitted and we need to perform quantization before data transmission. But for the quantization, error is introduced in exact value and initial average is lost. Based on this limitation, my 16 bit quantization method (sending MSB in 1-4 cycle and MSB+LSB in 5th cycle) reduces error significantly and preserves initial average. Besides, it works on all types of graphs (star, complete, ring, random geometric graph). My other algorithm, distributing averaging algorithm (PQDA) with probabilistic quantization also works on random geometric graph, star, ring and slow co-herency graph. It shows significant reduced error and attain strict consensus.
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The Politics of Grading: a Comparative Study of High School English Teachers' Personal Beliefs, Self-reported Systems, and Actual Practices

The Politics of Grading: a Comparative Study of High School English Teachers' Personal Beliefs, Self-reported Systems, and Actual Practices

Date: May 2013
Creator: Thibodeaux, Lisa M.
Description: The purpose of this study was to attain and analyze data regarding high school English teachers' beliefs about grading practices and their self-reported grading practices, to identify and understand disparities that exist between teachers' beliefs and self-reported practices, to identify discrepancies between the same self-reported practices and evidence of the practices actually utilized, and to consider teachers' perceptions as to the causes for these discrepancies. Instrumentation for this study included two surveys with both Likert and Likert-like items and an interview/portfolio analysis of teachers' grading systems. A combined total of 204 high school English-language arts teachers representing thirty-eight states and eighty-five schools comprised the sample. Corresponding pairs of Likert-type items were analyzed using studies of the mode, median, mean rank, and the Mann-Whitney U Test to study a comparison of the medians, and comparisons of true Likert scale item results were completed using studies of the means and an independent samples t-test. Interview/portfolio analysis data were analyzed both descriptively and inferentially including the calculation of 95% confidence intervals for generalizability. All open-ended items were considered qualitatively through a process of identifying and categorizing trends in language and over-arching themes. Results indicate that the sample finds grading practices recommended by experts ...
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Estimation of Aircraft Emissions for the Corpus Christi International Airport, Corpus Christi, Texas

Estimation of Aircraft Emissions for the Corpus Christi International Airport, Corpus Christi, Texas

Date: May 2013
Creator: Thomas, Gregson Johann
Description: Commercial aviation is a vital part of the United States economy. It generates over $1 trillion annually, which is more than 5% of the U.S. GDP, and produces approximately 10 million jobs. Every year there is an increase in commercial air traffic. This is attributed to expanding trade between states and other countries, which requires larger amounts of cargo aircraft in operation, and also catering to the growing number of middle and upper class passengers who travel for business and pleasure purposes. A rise in commercial aviation leads to the use of more aviation fuel on a monthly and annual basis. This in turn leads to escalated levels of combustion by-products from jet and turbofan engines into the atmosphere. The negative effects of these by-products range from producing poor air quality and consequent health hazards to contributing to global warming. This study is aimed at assessing the impacts of aircraft emissions on the local air quality in Corpus Christi using the Emissions and Dispersion Modeling System. Flight data for the study was obtained from the Department of Transportation's Research and Innovative Technology Administration. Analyses of the emissions were compared on monthly, annual, engine type and airline provider bases. Climatic, economic ...
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Federal Funds Target Rate Surprise and Equity Duration

Federal Funds Target Rate Surprise and Equity Duration

Date: May 2013
Creator: Tee, Kienpin
Description: In this paper I use an equity duration framework to develop and empirically test the hypothesis that returns on growth stock portfolios react more strongly to Federal Funds target rate change announcements, as compared to value stock portfolios. When I decompose the Federal Funds rate change, I find that portfolio returns are only sensitive to rate shocks, as opposed to the predictable component of rate change. Since growth stocks are expected to have higher duration than value stocks, I further explore the well documented polarity between value and growth stocks, by examining the interest rate sensitivities of portfolios that diverge along four fundamental-to-prices ratios: dividend yield, book-to-market value, earnings-to-price and cashflows-to-price. In each case, I find that price reactions are more pronounced for portfolios with high growth characteristics. I also document that portfolio returns react asymmetrically to positive and negative target rate surprises, and that this reaction is conditional on the state of business cycles - periods of economic expansions and recessions. To improve the robustness of my results, several statistical applications have been applied. First, I include Newey-west estimators to examine significant levels of regression estimates. Second, I check if there is any contemporaneous correlation across target rate shocks ...
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The Influence of Business Intelligence Components on the Quality of Decision Making

The Influence of Business Intelligence Components on the Quality of Decision Making

Date: May 2013
Creator: Visinescu, Lucian L.
Description: Decision makers require the right information at the right time, in the right place and in the right format so that they can make good decisions. Although business intelligence (BI) has the potential to improve decision making, there is little empirical evidence of how well this has been achieved. The purpose of this dissertation is to examine the quality of decisions made using BI. The research question it addresses is what are the key antecedents of decision quality for users of business intelligence systems? The theoretical support for the model is developed based on the literature review that draws on decision support systems (DSS), group decision support systems (GDSS), and BI. Grounded on this literature review, the antecedents of decision quality are operationalized in this dissertation through independent variables such as the problem space complexity, the level of BI usage, the BI user experience, and information quality. The dependent variable is operationalized as decision quality and it captures the self-satisfaction with a decision made by users in a BI environment. The research model was tested using a survey of BI users whose names were provided by a marketing company. This research suggests that BI user experience is a more complex ...
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Determinacy-related Consequences on Limit Superiors

Determinacy-related Consequences on Limit Superiors

Date: May 2013
Creator: Walker, Daniel
Description: Laczkovich proved from ZF that, given a countable sequence of Borel sets on a perfect Polish space, if the limit superior along every subsequence was uncountable, then there was a particular subsequence whose intersection actually contained a perfect subset. Komjath later expanded the result to hold for analytic sets. In this paper, by adding AD and sometimes V=L(R) to our assumptions, we will extend the result further. This generalization will include the increasing of the length of the sequence to certain uncountable regular cardinals as well as removing any descriptive requirements on the sets.
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The Ways of Reflection: Heidegger, Science, Reflection, and Critical Interdisciplinarity

The Ways of Reflection: Heidegger, Science, Reflection, and Critical Interdisciplinarity

Date: May 2013
Creator: Toole, Toby Houston
Description: This thesis argues that there is a philosophical attempt directed at combating the fragmentation of the sciences that starts with Heidegger and continues today through Trish Glazebrook's interpretations of the former's concept of "reflection," and Carl Mitcham and Robert Frodeman's concept of "critical interdisciplinarity" (CID). This is important as the sciences are both more implicated in our lives and more fragmented than ever. While scientific knowledge is pursued for its own sake, the pertinent facts, meaning, and application of the science is ignored. By linking Heidegger's views on the fragmentation of the sciences to Glazebrook's interpretations of reflection and Mitcham and Frodeman's CID, I show that CID is a concrete realization of Heidegger's reflection.
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