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549 Matching Results
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Effects of Surface Texture and Porosity on the Corrosion Behavior and Biocompatibility of Pure Zinc Biomaterials for Orthopedic Applications
In this dissertation, small and large NaCl particle-derived surfaces (Ra > 40 microns) were generated on 2D Zn materials, and the surfaces were carefully studied concerning topography, corrosion behavior, and bone cell compatibility. Increases in surface roughness accelerated the corrosion rate, and cell viability was maintained. This method was then extended to 3D porous scaffolds prepared by a hybrid AM/casting technique. The scaffolds displayed a near-net shape, an interconnected pore structure, increasing porosity paralleled to an increased corrosion rate, an ability to support cell growth, and powerful antibacterial properties. Lastly, nano/micro (Rz 0.02–1 microns) topographies were generated on 2D Zn materials, and the materials were comprehensively studied with special attention devoted to corrosion behavior, biocompatibility, osteogenic differentiation, immune cell response, hemocompatibility, and antibacterial performance. For the first time, the textured nonhemolytic surfaces on Zn were shown to direct cell fate, and the micro-textures promoted bone cell differentiation and directed immune cells away from an inflammatory phenotype.
Date:
May 2021
Creator:
Cockerill, Irsalan
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
The Emergence of Receptive and Expressive Language through Stimulus-Specific Consequences
An important question in teaching language is, what accounts for the emergence of either receptive or expressive labels when teaching only one of them? The teaching procedures in the present study were intended to reproduce the natural development of bidirectional naming in which caregivers comment on the items a child is interacting with and children echo those vocalizations they hear. Thus, the only vocalizations presented by the researcher during teaching occurred after the learner pointed to a specific stimulus, and were specific to the stimulus being targeted. These vocalizations are referred to in this study as stimulus-specific consequences. The purpose of this research was to investigate if the stimulus-specific consequences could become discriminative stimuli for receptive labels, and lead to the emergence of expressive labels. Three studies were conducted, each with four adults. Results demonstrated that using a stimulus-specific consequence during teaching led to receptive labels for all participants, but led to the emergence of expressive labels for only four participants. In other words, bidirectional naming did not occur for the majority of participants. Factors that may improve interrelations between receptive and expressive labels were analyzed, but further evaluations are needed to account for the inconsistent demonstrations of naming.
Date:
May 2021
Creator:
Spurgin, Destiny
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
The Ends of Smaller Worlds
The Ends of Smaller Worlds is a collection of short stories set in Indiana. The preface is about the representation of the information age using elements of dirty realism and Gothic fiction.
Date:
May 2021
Creator:
Armes, Brett
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Engine Running: Essays
Engine Running: Essays is a collection of creative nonfiction that explores, in parts, a persona's distancing from home and self against the backdrop of an increasingly fractured family doing the same. Through a variety of forms, the essays seek to balance themes like loss, self-discovery, and manhood in reflections on the role of childhood memory, the early revelations and experimentation of sexuality, and the carving-out of personal identity in West Texas.
Date:
May 2021
Creator:
Mason, Chesley Cade
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Engineering the Uniform Lying Helical Structure in Chiral Nematic Liquid Crystal Phase: From Morphology Transition to Dimension Control
Chiral nematic liquid crystals or cholesteric liquid crystals (CLC) can be obtained by adding a chiral dopant into a nematic liquid crystal. Liquid crystal molecules spontaneously rotate along a long axis to form helical structures in CLC system. Both pitch size and orientation of the helical structure is determined by the boundary conditions and can be further tuned by external stimuli. Particularly, the uniform lying helical structure of CLC has attracted intensive attention due to its beam steering and diffraction abilities. Up to now, studies have worked on controlling the in-plane orientation of lying helix through surface rubbing and external stimuli. However, it remains challenging to achieve steady and uniform lying helical structure due to its higher energy, comparing with other helical configurations. Here, by varying the surface anchoring, uniform lying helical structure with long-range order is achieved as thermodynamically stable state without external support. Poly (6-(4-methoxy-azobenzene-4'-oxy) hexyl methacrylate) (PMMAZO), a liquid crystalline polymer, is deposited onto the silicon substrate to fine-tune the surface anchoring. By changing the grafting density of PMMAZO, both pitch size and orientation of lying helical structure are precisely controlled. As the grafting density increases, the enhanced titled deformation of helical structure suppresses the pitch size …
Date:
May 2021
Creator:
Jia, Zhixuan
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Ethnic-Racial Socialization, Ethnic-Racial Identity, and Psychosocial Functioning
The current research recruited 200 college students from the University of North Texas to explore the direct and indirect effects of familial ethnic-racial socialization on selected psychosocial variables (i.e., general self-efficacy, life satisfaction, and psychological distress) via ethnic-racial identity variables: exploration, affirmation, and resolution. The results indicated that cultural socialization from family predicted life satisfaction via exploration and resolution, predicted general self-efficacy via affirmation and resolution, and predicted psychological distress via affirmation. Additionally, patterns between exploration, affirmation, and resolution were explored through cluster analyses, and six ethnic-racial identity clusters were identified. The amount of familial ethnic-socialization and general self-efficacy reported by participants varied significantly among the identified ethnic-racial identity clusters. Implications of the findings for therapeutic interventions, university programs, and ethnic-racial identity measurement as well as limitations and future research directions are discussed.
Date:
May 2021
Creator:
Hasan, Faraha
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Examining the Links between Attachment Style, Psychopathic Traits, and Sexuality
Previous literature has identified links between psychopathic trait severity and disturbed styles of attachment on sexual outcomes in adulthood. However, few studies have investigated these domains within one design. Therefore, it is unclear how they may influence each other, given that an association between attachment styles and psychopathic traits has also been previously documented. This study sought to explore the possible role of psychopathic traits upon the association between attachment and sexual outcomes. Participants were sampled from an undergraduate student population at a large university. Data were analyzed using correlational and hierarchical regression analyses, as well as two exploratory path models. Analyses suggested that aspects of attachment and psychopathic trait severity were significantly associated with each other and differentially predicted certain sexual outcomes. Furthermore, results indicated that the effects of attachment avoidance on sexual outcomes were mediated by Factor 1 traits of psychopathy, while the effects of attachment anxiety were mediated by Factor 2 traits. Additionally, it was found that attachment style was linked with contempt, and this was further linked to disturbances in sexual outcomes, which is a novel finding. Implications of the findings, limitations, and future directions are discussed.
Date:
May 2021
Creator:
Bubeleva, Katherine V
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Examining the Role of Gendered Racial Identity in the Relationship Between Gendered Racism and Psychological Distress in Black Women
Racism, sexism, and other forms of oppression are consequential to Black women's mental health. The current research examines the psychological impact of gendered racism, which is oppression on the basis of both gender and race, and the extent to which gendered racial identity may buffer the association between gendered racism and psychological distress (i.e., anxiety and depressive symptoms) among U.S. Black women. The study includes a sample of 150 Black women (at least 18 years of age or older, mean age = 39.11) recruited using Qualtrics panel service. Women were administered measures of gendered racism, gendered racial identity, and mental health (i.e., anxiety and depression). Data was analyzed through a series of bivariate correlations and moderation analyses using PROCESS macro. Results revealed that gendered racial identity did not moderate the association between gendered racism and mental health. This study advances our understanding of the oppression Black women contend with on the basis of their race and gender and offers insight about the factors that may mitigate the psychological impact of this phenomenon on Black women.
Date:
May 2021
Creator:
Doty, Dominique C.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Exploring Critical Thinking Support for K-12 Education in the Internet Age
This dissertation uses a three-manuscript style, and the ultimate purpose was to support critical thinking teaching in K-12 education from a systematic view concerning the lack of critical thinking in the young generation. The three manuscripts included in this dissertation were entirely or partly adapted based on three published or submitted research papers. The first research paper is a literature review article with an introduction to a development framework of nine principles, which provided a new view to developing critical thinking in younger children based on conceptual understanding of critical thinking. The second research paper is a study I coauthored with J. Michael Spector, which calls for more attention to the development of human intelligence given the rapid development of artificial intelligence and proposed that developing inquiry and critical thinking is a key to develop human intelligence. The third research paper reports an investigation over middle school educators' conceptualization of critical thinking and its alignment with the established theory and research. The major purpose was to connect the established theory and research with educational practices regarding what critical thinking constitutes. The significance of this study is to reveal the issues behind the abstract understanding of critical thinking and address the …
Date:
May 2021
Creator:
Ma, Shanshan
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Exploring Factors Affecting Public Service Motivation: An Investigation of Public Service Motivation in Saudi Arabia
This research builds on social exchange theory and self-determination theory to better understand the relationships between employee engagement, demographic and personal attributes, and public service motivation (PSM). It hypothesizes that employee engagement and demographic and personal characteristics (education, income, gender, and parents working in civil service) will directly affect PSM. I also hypothesize that education, income, and gender will have an indirect effect and moderate the relationship between employee engagement and PSM. This dissertation uses a quantitative approach to investigate the hypotheses introduced with the conceptual model. This research uses structural equation modeling as a data analysis technique. Based on 704 valid questionnaires distributed to Saudi public employees in Riyadh, Jeddah, Dammam, and Assir, the analysis shows that a higher level of employee engagement will lead to a higher level of public service motivation. It also reveals that a higher level of education will lead to a higher level of PSM.; the hypothesis that income positively affects PSM is not supported. Thus, this study finds that there is no significant relationship between income and PSM. Being female is found to be negatively associated with PSM. Therefore, the hypothesis that females are lower PSM than males is supported. Parents of public …
Date:
May 2021
Creator:
Alotaibi, Saud G.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Exploring the Impacts of COVID-19 on Hotel Booking Intentions: An Application of the Protection Motivation Theory
After the hit of the COVID-19 pandemic, the hotel industry's efforts need to focus on recovering travelers' confidence by introducing new safe and clean programs or seals. However, there is a lack of guidelines regarding which hotel safety/cleaning programs and what communication strategies are more effective when approaching guests. This study aims to address this gap by using a 2 (COVID-19 Message Type: Fear Appeals vs. Hope Appeals) × 2 (Hotel Safety/Cleaning Program Type: Internal vs. Third-Party) between-subject experiment design. Specifically, it applies the protection motivation theory in investigating the effects of different messages (hope vs. fear) along with different types of hotel safety/cleaning programs (internal vs. third-party) on guests' booking intentions. The moderating role of risk propensity was also explored. The data were collected in a public university located south of the U.S. Different ANOVA and MANOVA tests were conducted. The results suggest that hope appeal messages and hotel internal cleaning programs arouse higher booking intentions. When presenting COVID-19 related information provided by hotels, hope appeals represent a better communication strategy. In addition, the coping and threat appraisals showed to be correlated with hotel guests' booking intentions. Moreover, response efficacy was the strongest predictor with a positive correlation, whereas …
Date:
May 2021
Creator:
Calderon, Araceli Hernandez
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Exploring Turkish American Fathers: Father Involvement, Father's Perception of Maternal Gatekeeping, Competence, and Conservatism
There has been an increase in the fatherhood studies with minority groups in the United States in the past decades; however, these studies rarely included Turkish American fathers. To the best of the authors knowledge, current study was the first to explore father involvement in relation to fathers' perception of mothers' gate-keeping, fathers' competence as a parent, and their cultural stance as related to conservatism among a sample of Turkish American fathers with children between the ages of 3 to 6 years (n = 103). An exploratory factor analysis was conducted to examine the factor loadings of gate-closing and gate-opening items. The results yielded a two-factor solution with one suppressed item, and two cross-loading items with factor loadings bigger than .32. A path analysis was conducted to determine whether father's competence in relation to gate-closing and gate-opening, and father's conservatism adequately described father involvement through regression paths. The results of the chi-square goodness-of-fit test were not significant, χ2(3) = 1.84, p = .607, suggesting that the model fit the data well. Father's competency significantly predicted father involvement (B = 0.56, SE = .211, p = .008). Gate-closing (B = -30.48, SE = 15.340, p = .047) and gate-opening (B = …
Date:
May 2021
Creator:
Soyer, Gonca Feyza
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
An Extensible Computing Architecture Design for Connected Autonomous Vehicle System
Autonomous vehicles have made milestone strides within the past decade. Advances up the autonomy ladder have come lock-step with the advances in machine learning, namely deep-learning algorithms and huge, open training sets. And while advances in CPUs have slowed, GPUs have edged into the previous decade's TOP 500 supercomputer territory. This new class of GPUs include novel deep-learning hardware that has essentially side-stepped Moore's law, outpacing the doubling observation by a factor of ten. While GPUs have make record progress, networks do not follow Moore's law and are restricted by several bottlenecks, from protocol-based latency lower bounds to the very laws of physics. In a way, the bottlenecks that plague modern networks gave rise to Edge computing, a key component of the Connected Autonomous Vehicle system, as the need for low-latency in some domains eclipsed the need for massive processing farms. The Connected Autonomous Vehicle ecosystem is one of the most complicated environments in all of computing. Not only is the hardware scaled all the way from 16 and 32-bit microcontrollers, to multi-CPU Edge nodes, and multi-GPU Cloud servers, but the networking also encompasses the gamut of modern communication transports. I propose a framework for negotiating, encapsulating and transferring data …
Date:
May 2021
Creator:
Hochstetler, Jacob Daniel
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Factors Impacting Multicultural Teaching Competence among Counselor Educators: Ethnic/Racial Identity Development and Social Justice Orientation
Multicultural (MC) counseling and social justice (SJ) are foundational parts of counselors' professional identity, and they are fostered through a developmental process that counselor educators facilitate. The purpose of this study was to explore the relationship between counselor educators' ethnic/racial identity development (ERI), their social justice orientation (SJO) and their multicultural teaching competence (MCTC). MCTC was examined using the constructs of knowledge and sensitivity. Data was collected from a nationally distributed online survey. Data were analyzed using four hierarchical regression models in order to control for socially desirable responding. Results indicated that ERI was a significant predictor of MCTC-Knowledge (p < .001) and that SJO was a significant predictor of MCTC-Sensitivity (p < .001). Socially desirable responding was not significantly related to MCTC. Results suggest the importance of attending to ERI and SJO as separate processes in training future counselor educators.
Date:
May 2021
Creator:
Laird, Amber N
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Factors that Affect HIPAA Compliance: A Bibliometrics Study
According to the U.S. Department of Health and Human Services (HHS), patients and providers do not understand the Health Information Privacy and Accountability Act (HIPAA). Non-compliance with HIPAA is primarily due to confusion, along with insufficient understanding. HSS has taken measures to simplify the language they use to communicate HIPAA, however, they have not taken steps that consider if one's culture, religious and social perspectives, institutional training, credentials, and comprehension of legal terminology affects medical providers and non-clinical administrative personnel's abilities to understand HIPAA. This research uses bibliometrics to examine the literature from January 2010 – September 2020 that addresses HIPAA's use of legal terminology, literacy level, and institutional training, along with religious and social perspectives, and credentials of medical providers and non-clinical administrative personnel. A total of 107 articles were examined, 42 were assigned article influence scores with values that were less than 1.00, which is a below-average influence score for the article. There were 29 articles with values equal to or above 1.00, which translates to an equal or above-average influence score. The remaining 36 articles did not have article influence scores and were assigned values as not available. Results of the review of the literature indicate that …
Date:
May 2021
Creator:
Drayden, Craig M.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Faculty Response to Academic Dishonesty in the Classroom at a Four-Year Public Institution
Academic dishonesty is prevalent in institutions of higher education. Faculty are at the forefront of this issue as they are in the classroom with the students. However, faculty may be hesitant to address academic dishonesty for a myriad of reasons. The purpose of this qualitative exploratory case study was to explore how faculty members viewed their roles in addressing academic dishonesty. Study participants were 11 full-time faculty from a Southern University who had taught for at least two years and had experienced academic dishonesty in the classroom. Artifacts were also gathered from three documentary sources. Four major themes emerged from the data: (a) faculty investment in academic integrity, (b) faculty-student relationship impact on interaction, (c) personal values guiding faculty response, and (d) deterrents preventing faculty action. Several implications included the need for: (i) ongoing professional development opportunities for faculty, (ii) the creation of shared ownership and governance of academic integrity between faculty and university leadership; (iii) consistent prevention and enforcement of academic dishonesty according to university guidelines, and (iv) the creation of a partnership between the conduct office and the various faculty departments.
Date:
May 2021
Creator:
Smith, Laura Trahan
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Foreign Direct Investment and Sustainable Peace During/After Civil Conflicts
This dissertation examines the impact of FDI on peace in civil conflict-experienced states. While economic grievances have often been pointed out as a major cause of civil war within the literature, scholarship on post-conflict peace has focused mainly on political settlements, such as one-sided victories or power sharing, largely ignoring the importance of economic conditions. Thus, this dissertation aims to examine how FDI can affect sustainable peace in conflict-experienced states in terms of prevention of conflict recurrence and regime stability. FDI can be conducive to peace during/after civil conflicts, as it can bring capital which can be used for economic reconstruction and development in conflict-experienced states. Furthermore, this dissertation focuses on the impact of bilateral FDI. When a third party intervenes in a conflict management process and the third party has a great deal of economic interaction with the conflict experienced state, this economic interdependency will affect the third party's motivation to make the conflict-experienced state stable. It also provides third-party with greater leverage over peace efforts. Eventually, this third-party leverage will affect peace during/after civil conflicts. This dissertation is built around three interrelated empirical chapters: (1) determinants of FDI in conflict-experienced states, (2) the impact of FDI on conflict …
Date:
May 2021
Creator:
Jeong, Bora
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Francis Bacon's New Atlantis: The Quiet Revolution of Science, Religion, and Politics
Francis Bacon (1561-1626) is recognized as a founder of the modern scientific project and a forerunner of the modern era of political thought. He advocated the development of an active science that would enable human beings to control nature in order to relieve man's estate. To accomplish this, Bacon argues that we must reconstruct all arts and sciences upon a more solid foundation. In reconstructing the arts and sciences, Bacon subtly changes the meaning of foundational religious, political, and scientific notions in order to better suit his project of progress. As the inheritors of his vision, turning to Bacon helps recover foundational considerations that have been forgotten as a result of his success. This dissertation approaches Bacon's thought through an analysis of his New Atlantis, a fable that envisions the completion of his project. I also turn to his other political, scientific, and religious works as appropriate to supply what is omitted in the fable. I find that although his revision of religious, scientific, and political foundations is conducted subtly they are nevertheless revolutionary, and essential for preparing the various outlooks that characterize the modern world.
Date:
May 2021
Creator:
Lowe, Evan M.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
François Couperin's Neuvième Concert, "Ritratto Dell' Amore": A Performance Guide and Edition for Flute and Keyboard
François Couperin (1668-1733) was one of the earliest French Baroque composers to merge the Italian style into the French tradition. He had great influence on the development of French Baroque music from the end of the seventeenth century until his death. Couperin's four Concerts Royaux and the ten Concerts Nouveaux (published in 1722 and 1724) were written for the enjoyment of Louis XIV. Those suites were popular in the court before they were published, as they were requested to be performed every Sunday during the years 1714 and 1715 to give pleasure to the king. Rittrato dell'amore is the ninth suite out of the fourteen suites. The purpose of this study is to provide a performance guide and a practical edition of François Couperin's Neuvième Concert Ritratto dell' amore. It also contrasts Italian style and French tradition in the Baroque period, and how Couperin blended both styles together in his Neuvième Concert. In addition, this dissertation summarizes the general principles of Baroque performance practice that one may encounter in Neuviéme Concert, including notes inégales (unequal notes), ornamentation, over-dotting, and other issues. It is especially important for one to understand the performance style of French Baroque music in order to perform …
Date:
May 2021
Creator:
Wong, Ieng Wai
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Freight Forwarder Satisfaction: A Conceptualization and an Empirical Test of Effect on Airport Customer Loyalty and Competitiveness
In 2018, global gross domestic product (GDP) was US$86.3 trillion, and almost a quarter of that value was due to international trade with a value of US$19.6 trillion. Air cargo accounts for about 35 percent of that trade value (approximately US$6.86 trillion). Moreover, from the perspective of the airport sector, air cargo revenue contributes between 20 to 70 percent of airport revenue. The global airport revenue for freight in 2018 was US$250 billion. Despite the interest and research activities surrounding competition and competitiveness of airports and specifically among airlines and passengers, it appears scholars have overlooked research concerning the competitiveness of airports when it comes to air cargo. This study attempts to fill the gap in the supply chain and logistics literature by putting forward a framework and ultimately operationalizing the framework highlighting the pivotal role of air cargo in the supply chain domain and within the global economy. Specifically, the framework is operationalized within the freight forwarding air cargo supply chain domain – providing insight into this important yet understudied phenomenon. The population of interest is freight forwarders from the Dubai International Airport, United Arab Emirates. The Middle East represents 18 percent of the world's air cargo volume and …
Date:
May 2021
Creator:
Almofeez, Sarah Ibraheem
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Gabriel Pierné's Sonata in D Minor, op. 36: A Study of the Work's Compositional Language and Context, Focusing on the Composer's Transcription for Flute
There are very few significant sonatas for flute and piano written between 1880 and 1918, a period of unusually rich stylistic diversity. Gabriel Pierné composed his Sonata in D Minor, Op. 36 for piano and violin in 1900, and later transcribed it for flute and piano. Unfortunately, the work has not been embraced to a significant extent by either violinists or flutists. The wealth of violin sonatas from this period might explain it not becoming part of the canon for violinists, but this is not the case for the flute repertoire, where it seems that it should hold a place of genuine importance. Since little has been written about Pierné as a composer or about this piece in either of its versions, this project is intended to promote an understanding of the work in its historical and theoretical context and to advocate for more frequent performances. This document also suggests an alternate version of several particular passages so it can better represent the characteristics of today's flute and its modern techniques. This research will help other flutists and flute professors to introduce and spread an awareness of its existence and ideally helping to establish its place in the flute repertoire. …
Date:
May 2021
Creator:
Le, Huong Thu
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
A Genetic Assessment of the Mating System of a Suburban Red-Shouldered Hawk Population in Southwest Ohio
Considering the high reproductive investment of the social male and the cost to the female of losing this benefit by soliciting copulations outside the social pair bond, it is expected that most raptor populations would exhibit low to no occurrence of extra-pair paternity (EPP). This holds true for the majority of raptor species studied to date with only one exception of an urban Cooper's hawk (Accipiter cooperii) study which reported an unexpectedly high extra-pair young frequency of 19.29%. In our study we examined the frequency of EPP within a red-shouldered hawk (Buteo lineatus) population residing in the suburban/urban matrix of southwest Ohio. During the breeding seasons of 2018 and 2019, 181 breeding age and nestling individuals were color-banded and sampled for genetic analysis using nine microsatellite loci. After genotyping a total of 40 broods (with at least two nestlings per brood) and both presumptive parents of each brood, no clear evidence of EPP was detected. However, at one nest site, the entire brood of four chicks was not sired by the adult male observed during the courtship period, nor another adult male observed tending the chicks later in the season. We suspect that this particular nest represented two instances of …
Date:
May 2021
Creator:
Wrona, Anna Maria
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
High Strain Rate Deformation Behavior of Single-Phase and Multi-Phase High Entropy Alloys
Fundamental understanding of high strain rate deformation behavior of materials is critical in designing new alloys for wide-ranging applications including military, automobile, spacecraft, and industrial applications. High entropy alloys, consisting of multiple elements in (near) equimolar proportions, represent a new paradigm in structural alloy design providing ample opportunity for achieving excellent performance in high strain rate applications by proper selection of constituent elements and/or thermomechanical processing. This dissertation is focused on fundamental understanding of high strain-rate deformation behavior of several high entropy alloy systems with widely varying microstructures. Ballistic impact testing of face centered cubic Al0.1CoCrFeNi high entropy alloy showed failure by ductile hole growth. The deformed microstructure showed extensive micro-banding and micro-twinning at low velocities while adiabatic shear bands and dynamic recrystallization were seen at higher velocities. The Al0.7CoCrFeNi and AlCoCrFeNi2.1 eutectic high entropy alloys, with BCC and FCC phases in lamellar morphology, showed failure by discing. A network of cracks coupled with small and inhomogeneous plastic deformation led to the brittle mode of failure in these eutectic alloys. Phase-specific mechanical behavior using small-scale techniques revealed higher strength and strain rate sensitivity for the B2 phase compared to the L12 phase. The interphase boundary demonstrated good stability without any …
Date:
May 2021
Creator:
Muskeri, Saideep
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Hybrid Optimization Models for Depot Location-Allocation and Real-Time Routing of Emergency Deliveries
Prompt and efficient intervention is vital in reducing casualty figures during epidemic outbreaks, disasters, sudden civil strife or terrorism attacks. This can only be achieved if there is a fit-for-purpose and location-specific emergency response plan in place, incorporating geographical, time and vehicular capacity constraints. In this research, a comprehensive emergency response model for situations of uncertainties (in locations' demand and available resources), typically obtainable in low-resource countries, is designed. It involves the development of algorithms for optimizing pre-and post-disaster activities. The studies result in the development of four models: (1) an adaptation of a machine learning clustering algorithm, for pre-positioning depots and emergency operation centers, which optimizes the placement of these depots, such that the largest geographical location is covered, and the maximum number of individuals reached, with minimal facility cost; (2) an optimization algorithm for routing relief distribution, using heterogenous fleets of vehicle, with considerations for uncertainties in humanitarian supplies; (3) a genetic algorithm-based route improvement model; and (4) a model for integrating possible new locations into the routing network, in real-time, using emergency severity ranking, with a high priority on the most-vulnerable population. The clustering approach to solving dept location-allocation problem produces a better time complexity, and the …
Date:
May 2021
Creator:
Akwafuo, Sampson E
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library