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 Collection: UNT Theses and Dissertations
Effect of Dispersed Particles and Branching on the Performance of a Medium Temperature Thermal Energy Storage System

Effect of Dispersed Particles and Branching on the Performance of a Medium Temperature Thermal Energy Storage System

Date: August 2013
Creator: Hasib, A. M. M. Golam
Description: The main objective of my thesis is to develop a numerical model for small-scale thermal energy storage system and to see the effect of dispersing nano-particles and using fractal-like branching heat exchanger in phase change material for our proposed thermal energy storage system. The associated research problems investigated for phase change material (PCM) are the low thermal conductivity and low rate of heat transfer from heat transfer fluid to PCM in thermal energy storage system. In this study an intensive study is carried out to find the best material for thermal storage and later on as a high conductive nano-particle graphite is used to enhance the effective thermal conductivity of the mixed materials. As a thermal storage material molten solar Salt (60% NaNO3+40%KNO3) has been selected, after that detailed numerical modeling of the proposed design has been done using MATLAB algorithm and following the fixed grid enthalpy method. The model is based on the numerical computation of 1-D finite difference method using explicit scheme. The second part of the study is based on enhancing the heat transfer performance by introducing the concept of fractal network or branching heat exchanger. Results from the numerical computation have been utilized for the comparison ...
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The Contribution of Mira Behn and Sarala Behn to Social and Environmental Transformation in the Indian State of Uttarakhand

The Contribution of Mira Behn and Sarala Behn to Social and Environmental Transformation in the Indian State of Uttarakhand

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Date: May 2014
Creator: Mallik, Bidisha
Description: The influence of Mohandas K. Gandhi on social and environmental movements in post-colonial India has been widely acknowledged. Yet, the contributions of two European associates of Gandhi, Madeleine Slade and Catherine Mary Heilemann, better known in India as Mira Behn and Sarala Behn, have not received the due attention of the academic community. This dissertation is an examination of the philosophy and social activism of Mira Behn and Sarala Behn and their roles in the evolution of Gandhian philosophy of socioeconomic reconstruction and environmental conservation in the present Indian state of Uttarakhand. Instead of just being acolytes of Gandhi, I argue that these women developed ideas and practices that drew upon from an extensive intellectual terrain that cannot be limited to Gandhi’s work. I delineate the directions in which Gandhian thought and experiments in rural development work evolved through the lives, activism, and written contributions of these two women. Particularly, I examine their influence on social and environmental movements, such as the Chipko and the Anti-Tehri Dam movements, and their roles in promoting grassroots social development and environmental sustainability in the mountain communities of Uttarakhand. Mira Behn and Sarala Behn’s integrative philosophical worldviews present epistemological, sociopolitical, ethical, and metaphysical principles ...
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The Impact of Teacher Perception of Cultural Competence on the Instructional Decision Making of English As Second Language (Esl) Students

The Impact of Teacher Perception of Cultural Competence on the Instructional Decision Making of English As Second Language (Esl) Students

Date: May 2014
Creator: Lim, Okyoung
Description: Recent research suggests that culturally responsive teaching (CRT) practices have the potential to increase student educational outcomes, as well as to reduce unnecessary or inappropriate placement referrals. Examination of the core components in CRT, teacher efficacy and cultural competence, is proposed to be a critical step to reduce unwarranted referrals of culturally and linguistically diverse students. However, there is limited empirical support for the relationship between CRT and instructional referrals, and even among existing studies there is inconsistency regarding the relation of these constructs. The purpose of this study is to examine teacher factors (i.e., teacher role, degree earned, years of teaching, ESL certification held, language proficiency and ethnicity) as a predictor of teacher competence, and the role these factors play in teachers’ referral decision making. To investigate these relationships, a national sample of elementary teachers (N = 258) completed a survey addressing their background, profession endorsements, sense of teaching efficiency, and the instructional decisions they would make in the scenarios presented. The results of this study revealed that teacher role (i.e., general, ESL or special educator) and ESL certification were important predictors of teacher competency. A statistically significant mean difference in teacher competency was found between teachers with and ...
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From Development of Semi-empirical Atomistic Potentials to Applications of Correlation Consistent Basis Sets

From Development of Semi-empirical Atomistic Potentials to Applications of Correlation Consistent Basis Sets

Date: May 2014
Creator: Gibson, Joshua S.
Description: The development of the semi-empirical atomistic potential called the embedded atom method (EAM) has allowed for the efficient modeling of solid-state environments, at a lower computational cost than afforded by density functional theory (DFT). This offers the capability of EAM to model the energetics of solid-state phases of varying coordination, including defects, such as vacancies and self-interstitials. This dissertation highlights the development and application of two EAMs: a Ti potential constructed with the multi-state modified embedded atom method (MS-MEAM), and a Ni potential constructed with the fragment Hamiltonian (FH) method. Both potentials exhibit flexibility in the description of different solid-states phases and applications. This dissertation also outlines two applications of DFT. First, a study of structure and stability for solid-state forms of NixCy (in which x and y are integers) is investigated using plane-wave DFT. A ground state phase for Ni2C is elucidated and compared to known and hypothesized forms of NixCy. Also, a set of correlation consistent basis sets, previously constructed using the B3LYP and BLYP density functionals, are studied. They are compared to the well-known to the correlation consistent basis sets that were constructed with higher-level ab initio methodologies through computations of enthalpies of formation and combustion enthalpies. ...
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Development of Enabling Technologies to Visualize the Plant Lipidome

Development of Enabling Technologies to Visualize the Plant Lipidome

Date: August 2013
Creator: Horn, Patrick J.
Description: Improvements in mass spectrometry (MS)-based strategies for characterizing the plant lipidome through quantitative and qualitative approaches such as shotgun lipidomics have substantially enhanced our understanding of the structural diversity and functional complexity of plant lipids. However, most of these approaches require chemical extractions that result in the loss of the original spatial context and cellular compartmentation for these compounds. To address this current limitation, several technologies were developed to visualize lipids in situ with detailed chemical information. A subcellular visualization approach, direct organelle MS, was developed for directly sampling and analyzing the triacylglycerol contents within purified lipid droplets (LDs) at the level of a single LD. Sampling of single LDs demonstrated seed lipid droplet-to-droplet variability in triacylglycerol (TAG) composition suggesting that there may be substantial variation in the intracellular packaging process for neutral lipids in plant tissues. A cellular and tissue visualization approach, MS imaging, was implemented and enhanced for visualizing the lipid distributions in oilseeds. In mature cotton seed embryos distributions of storage lipids (TAGs) and their phosphatidylcholine (PCs) precursors were distribution heterogeneous between the cotyledons and embryonic axis raising new questions about extent and regulation of oilseed heterogeneity. Extension of this methodology provides an avenue for understanding metabolism ...
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Leadership Styles and Cultural Sensitivity of Department Chairs at Texas Public Universities

Leadership Styles and Cultural Sensitivity of Department Chairs at Texas Public Universities

Date: May 2014
Creator: Hernańdez-Katz, Melissa
Description: As the U.S. population diversifies, so do its higher education institutions. Leadership at these institutions should be prepared for this diversification of students, faculty, and staff. The purpose of this study was to gain greater knowledge about the leadership styles and cultural sensitivity of department chairs. Survey research was used to determine if department chairs’ leadership styles correlated with their cultural sensitivity. The target population was department chairs from public universities in the state of Texas. The survey was distributed to 406 randomly selected department chairs. The participants completed three measures: Leadership Behavior Description Questionnaire (LDBQ) for leadership style, the Intercultural Sensitivity Scale (ISS) for cultural sensitivity, and a demographic questionnaire (gender, age range, race/ethnicity, and years of service as department chair). The sample included 165 usable surveys (40% return rate). The department chairs were primarily male (72%), White (78%), and over 50 (71%) years of age. First, a statistically significant negative correlation (r = -.431, p < .0001) occurred between LBDQ overall scores and overall ISS scores: As chairs scored higher on leadership ability, they scored lower on intercultural sensitivity. Second, leadership style by demographic variable displayed mixed results. No significant difference was found for leadership style by age, ...
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Development of a Cost Effective Wireless Sensor System for Indoor Air Quality Monitoring Applications

Development of a Cost Effective Wireless Sensor System for Indoor Air Quality Monitoring Applications

Date: May 2014
Creator: Abraham, Sherin
Description: Poor air quality can greatly affect the public health. Research studies indicate that indoor air can be more polluted than the outdoor air. An indoor air quality monitoring system will help to create an awareness of the quality of air inside which will eventually help in improving it. The objective of this research is to develop a low cost wireless sensor system for indoor air quality monitoring. The major cost reduction of the system is achieved by using low priced sensors. Interface circuits had to be designed to make these sensors more accurate. The system is capable of measuring carbon dioxide, carbon monoxide, ozone, temperature, humidity and volatile organic compounds. The prototype sensor node modules were developed. The sensor nodes were the connected together by Zigbee network. The nodes were developed in such a way that it is compact in size and wireless connection of sensor nodes enable to collect air quality data from multiple locations simultaneously. The collected data was stored in a computer. We employed linear least-square approach for the calibration of each sensor to derive a conversion formula for converting the sensor readings to engineering units. The system was tested with different pollutants and data collected was ...
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Synthesis Strategies and a Study of Properties of Narrow and Wide Band Gap Nanowires

Synthesis Strategies and a Study of Properties of Narrow and Wide Band Gap Nanowires

Date: May 2014
Creator: Sapkota, Gopal
Description: Various techniques to synthesize nanowires and nanotubes as a function of growth temperature and time were investigated. These include growth of nanowires by a chemical vapor deposition (CVD) system using vapor-liquid-solid (VLS) growth mechanism and electro-chemical synthesis of nanowires and nanotubes. Narrow band gap InSb Eg = 0.17 eV at room temp) nanowires were successively synthesized. Using a phase diagram, the transition of the nanowire from metallic- semiconducting- semi-metallic phase was investigated. A thermodynamic model is developed to show that the occurrence of native defects in InSb nanowires influenced by the nanowire growth kinetics and thermodynamics of defect formation. Wide band gap ZnO (Eg = 3.34 eV) and In2O3 (3.7 eV) were also synthesized. ZnO nanowires and nanotubes were successfully doped with a transition metal Fe, making it a Dilute Magnetic Semiconductor of great technological relevance. Structural and electronic characterizations of nanowires were studied for different semiconducting, metallic and semi-metallic nanowires. Electron transport measurements were used to estimate intrinsic material parameters like carrier concentration and mobility. An efficient gas sensing device using a single In2O3 nanowire was studied and which showed sensitivity to reducing gas like NH3 and oxidizing gas like O2 gas at room temperature. The efficiency of the ...
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A Quantitative Assessment of Site Formation at the Dmanisi Archaeological Site, Republic of Georgia

A Quantitative Assessment of Site Formation at the Dmanisi Archaeological Site, Republic of Georgia

Date: August 2013
Creator: Crislip, Peter S.
Description: The focus of this thesis was to gather and analyze micromorphological and petrographic data on soils at the archaeological site of Dmanisi in order to better understand the extent to which the deposition and alteration of the sediments has affected the preservation of artifacts and faunal remains. A major goal of this research was to test hypothesis related to why bone material is discovered in some strata and not in others. This research focuses on the application of micromorphology (supplemented with other methods) to the soils through the use of petrographic analysis of thin sections and scanning electron microscopy. These techniques complement previous field analyses by providing a quantitative assessment of individual strata through point counting and chemical mapping. The results of this research support the hypothesis that the sediments are predominantly mafic ashes, while showing that there is very little soil development in the strata. This suggests quick episodic burial in a relatively dry climate, confirming the hypothesis for a short time sequence in the strata. Additionally, differential weathering probably did not play a significant role in the differential abundance of bone remains among the strata at Dmanisi.
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Autonomic Failure Identification and Diagnosis for Building Dependable Cloud Computing Systems

Autonomic Failure Identification and Diagnosis for Building Dependable Cloud Computing Systems

Date: May 2014
Creator: Guan, Qiang
Description: The increasingly popular cloud-computing paradigm provides on-demand access to computing and storage with the appearance of unlimited resources. Users are given access to a variety of data and software utilities to manage their work. Users rent virtual resources and pay for only what they use. In spite of the many benefits that cloud computing promises, the lack of dependability in shared virtualized infrastructures is a major obstacle for its wider adoption, especially for mission-critical applications. Virtualization and multi-tenancy increase system complexity and dynamicity. They introduce new sources of failure degrading the dependability of cloud computing systems. To assure cloud dependability, in my dissertation research, I develop autonomic failure identification and diagnosis techniques that are crucial for understanding emergent, cloud-wide phenomena and self-managing resource burdens for cloud availability and productivity enhancement. We study the runtime cloud performance data collected from a cloud test-bed and by using traces from production cloud systems. We define cloud signatures including those metrics that are most relevant to failure instances. We exploit profiled cloud performance data in both time and frequency domain to identify anomalous cloud behaviors and leverage cloud metric subspace analysis to automate the diagnosis of observed failures. We implement a prototype of the ...
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