UNT Theses and Dissertations - 17,209 Matching Results

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Bodies of Evidence: A Qualitative Analysis of the Lived Experiences of Female Central American and Mexican Asylum Seekers in Dallas

Description: This work addresses the experiences of female asylum seekers from Central and Mexico currently living in Dallas, TX. The main purpose is to analyze how these women engage in the gendered processes of both migrating to and accessing legal resources and protection within the United States. As the women move through male-dominated spaces in their home country, the borderlands, and the asylum court they must challenge the patriarchal institutions that attempt to silence their narratives and criminalize their bodies. Their physical wounds become evidence in the courtroom, while outside of the courtroom their movements are monitored and tracked through multiple mechanisms of state control: ankle monitors, detention centers, ICE check-ins. They face intersectional discrimination as they are targeted as both women and immigrants. However, these female asylum seekers are not victims. They constantly display agency as they represent themselves in court, find solace in their faith, and form community with each other.
Date: May 2017
Creator: Kober, Ryan Kylie
Partner: UNT Libraries

Building an Effective Piano Technique while Avoiding Injury: A Comparison of the Exercises in Alfred Cortot's "Rational Principles of Pianoforte Technique" and Carl Tausig's "Daily Studies for the Pianoforte"

Description: It is the teacher's responsibility to guide students in building an effective and injury-free piano technique. Improper technique, poor training and bad posture at the instrument all may cause problems such as lack of muscle control, weakness, or tension in the hands. Many teachers are interested in finding information about specific exercises dealing with finger strengthening, stretching, and warm-up strategies, as well as guidelines for safe practicing. It is therefore important for both teachers and students to understand how to build a technique from the earliest years of instruction. Carl Tausig (1841-1871) and Alfred Cortot (1877-1962) both contributed to the development of piano technique by writing books that include a significant number of exercises and excerpts. Their books incorporate detailed instructions on how to play each exercise effectively and without fatigue. Subsequently, Heinrich Ehrlich (1822-1899) collected and systematically arranged Tausig's notes, complementing them with detailed information on how to play Tausig's exercises without causing injury. This dissertation compares and contrasts the exercises found in Alfred Cortot's book, Rational Principles of Pianoforte Technique, and Carl Tausig's book, Daily Studies for the Pianoforte. The latter is based on the practical guidebook, How to Practise on the Piano: Reflections and Suggestions, written by Heinrich Ehrlich. Included in this study are references to the performing arts medical literature dealing with pianists' injuries. By comparing two different historical piano methods and considering their effectiveness in light of modern medical performance research, this dissertation aims to help teachers to determine which methods might be better for students to build a solid piano technique without injuring themselves.
Date: May 2017
Creator: Woo, Lae Hyung
Partner: UNT Libraries

Cardiovascular Response to a Behavioral Restraint Challenge: Urge Magnitude Influence in Men and Women

Description: Agtarap, Wright, Mlynski, Hammad, and Blackledge took an initial step in providing support for the predictive validity of a new conceptual analysis concerned with behavioral restraint, defined as active resistance against a behavioral impulse or urge. The current study was designed to partially replicate and extend findings from their study, employing a common film protocol and a procedure for inducing low- and high levels of fatigue. Analyses on key data indicated that the fatigue manipulation was ineffective. On the other hand, they supported the suggestion that behavioral restraint should be proportional to the strength of an urge being resisted so long as success is perceived as possible and worthwhile. Analyses also provided evidence of gender differences for this behavioral restraint task. Women showed relatively enhanced CV responses to my manipulation of urge magnitude, performed less well, rated the behavioral restraint challenge as harder, and rated success on the more difficult behavioral restraint task as more important. A broad indication is that men and women can differ in the strength of impulses they experience in response to stimulus presentations as well as in the importance they place on resisting the impulses.
Date: May 2017
Creator: Mlynski, Christopher
Partner: UNT Libraries

Catastrophe in Permanence: Benjamin's Natural History of Environmental Crisis

Description: Walter Benjamin warned in 1940 of a certain inconspicuous threat to political thinking, not least of all to materialism, that takes progress as an historical norm. Implicit in this conception is what he describes as an empty continuum of time along which the prevailing tradition chronicles its own mythic development and drains everyday life of genuine historical experience. The myth of progressive history advances insidiously today in consumeristic and technocratic attempts at reconciling cultural imagery with organic nature. In this dissertation, I pursue the contradictions of such images as they crystallize around the natural history of twenty-first century commodity society, where promises of ecological remediation, sustainable urban development, and climate change mitigation have yet to introduce a true crisis of historical experience to the ongoing environmental crisis of capitalism. A more radical way of seeing the cultural representation of nature would, I argue, penetrate its mythic determination by market forces and bear witness to the natural-historical ruins and traces that constitute, in Benjamin's terms, a single "catastrophe" where others perceive historical continuity. I argue that Benjamin's critique of progress is instructive to interpreting those utopian dreams, ablaze in consumer life and technological fantasy, that recent decades of growing environmental concern have channeled into the recovery of an experience of the natural world. His dialectics of nature and alienated history confront the wish-image of organic abundance with the transience of its appropriated expression in the commodity-form. Drawing together this confrontation with a varied literature on collective memory, nature, and the city, I suggest that our poverty of experience is more than simply a technical, economic, or even ecological problem, but rather follows from the commodification of history itself. The goal of this work is to reflect upon the potentiality of communal politics that subsist not in rushing headlong into a progressive ...
Date: May 2017
Creator: Bower, Matthew S
Partner: UNT Libraries

The Civic Roles of Neighborhood Associations in Seoul, Korea: Implications for Urban Governance

Description: This dissertation answers three research questions: "What differences and similarities exist among neighborhood associations in the United States, Japan, and Seoul, South Korea?," "What are the civic roles of neighborhood associations in apartment complexes in Seoul, South Korea?," and "What factors promote neighborhood associations to play civic roles in urban governance?" To answer the first question, this research analyzes the purposes, governance structures, roles, and legal substance of neighborhood associations by reviewing previous studies, public and legal documents, court cases in the U.S., and by conducting interviews. To answer the second and the third questions, a 2016 survey, "Understanding the Roles of Neighborhood Associations in Urban Governance" was conducted with 154 representatives of neighborhood associations in Seoul. Social capital theory, government failure theory, and third party government theory were used to create hypotheses that test proposed relationships about neighborhood interactions, community characteristics, and the civic roles played by neighborhood associations. The findings show that neighborhood associations have adopted several roles including service provider, partner in public service delivery for local government, and advocate for residents in urban governance. The findings also show that social capital created by neighborhood interactions and community characteristics facilitates neighborhood associations to play civic roles in urban governance.
Date: May 2017
Creator: Kim, Jung Wook
Partner: UNT Libraries

A Cognitive Radio Application through Opportunistic Spectrum Access

Description: In wireless communication systems, one of the most important resources being focused on all the researchers is spectrum. A cognitive radio (CR) system is one of the efficient ways to access the radio spectrum opportunistically, and efficiently use the available underutilized licensed spectrum. Spectrum utilization can be significantly enhanced by developing more applications with adopting CR technology. CR systems are implemented using a radio technology called software-defined radios (SDR). SDR provides a flexible and cost-effective solution to fulfil the requirements of end users. We can see a lot of innovations in Internet of Things (IoT) and increasing number of smart devices. Hence, a CR system application involving an IoT device is studied in this thesis. Opportunistic spectrum access involves two tasks of CR system: spectrum sensing and dynamic spectrum access. The functioning of the CR system is rest upon the spectrum sensing. There are different spectrum sensing techniques used to detect the spectrum holes and a few of them are discussed here in this thesis. The simplest and easiest to implement energy detection spectrum sensing technique is used here to implement the CR system. Dynamic spectrum access involves different models and strategies to access the spectrum. Amongst the available models, an interweave model is more challenging and is used in this thesis. Interweave model needs effective spectrum sensing before accessing the spectrum opportunistically. The system designed and simulated in this thesis is capable of transmitting an output from an IoT device using USRP and GNU radio through accessing the radio spectrum opportunistically.
Date: May 2017
Creator: Bhadane, Kunal Ashok Ashok
Partner: UNT Libraries

Coming Out: The Lived Experiences of LGB College Students who Feel Supported by Their Parents

Description: The purpose of this phenomenological study was to explore how LGB college students created meaning out of their coming out process to their parents. I recruited LGB college students who perceived support from their parents during their coming out process and asked the following research question: What are the lived experiences of LGB college students who have experienced support from their parents during the coming out process? Seven White (n = 4), African American (n = 2), and Hispanic (n = 1) college students, three men and four women aged 18-24 years, shared narratives that included time periods before, during, and after their coming out disclosures to their parents. Using an adapted phenomenological analysis, I identified nine major themes: awareness of feeling different, positive relationship with parents prior to coming out, college impacting the coming out process, feeling unsure of how parents would respond to disclosure, parents assuring continued loved and acceptance, parents affirming LGB identity, increased relational depth with parents, increased sense of authenticity, and an appreciation for family's response and support. The findings provide insight into how counselors might work most beneficially with LGB college students and their parents around the coming out process. Opportunities for future research and limitations of the study are discussed.
Date: May 2017
Creator: Price, Eric W
Partner: UNT Libraries

A Community Based Assessment: An Analysis of Community Based Tourism in Kalache and Hulgol, India

Description: This study incorporated a community based assessment with a focus on community based tourism in Kalache and Hulgol, India. Kalache and Hulgol are two agrarian based communities located in the environmentally significant region of the Western Ghats. Each of these communities has considered community based tourism as a means to reduce urban youth outmigration, to diversify economic resources, and to encourage the empowerment of women. The primary goals of this study were to understand the community issues and objectives, to determine the level of support for tourism development, to determine participant attitudes toward tourism, and to determine the obstacles to tourism development. The findings of this project address the complexity of operating in the tourism industry, the impacts of tourism, and the use of community based tourism models in support of sustainable tourism.
Date: May 2017
Creator: Schutz, Michael
Partner: UNT Libraries

A Comparative Evaluation of Matrix Training Arrangements

Description: A common goal of instructional techniques is to teach skills effectively and efficiently. Matrix training techniques are both effective and efficient as they allow for the emergence of untrained responding to novel stimulus arrangements, a phenomenon known as recombinative generalization. However, it is unclear which type of matrix arrangement best promotes recombinative generalization. The current study compared two common matrix training approaches, an overlapping (OV) design and a non-overlapping (NOV) design, with respect to arranging relations targeted for training. We conducted a replication evaluation of a Wilshire and Toussaint study, and taught two typically-developing preschoolers compound object-action labels in Spanish and used either an OV or NOV matrix training design. Results from both studies demonstrated the participant trained with an OV design produced recombinative generalization and participants trained with a NOV design produced significantly low levels of emergence or none at all. These results suggest that an OV matrix design facilitates recombinative generalization more effectively than a NOV design. Implications for instructional arrangements are discussed.
Date: May 2017
Creator: Cliett, Terra N
Partner: UNT Libraries

Comparing Media Usage of Binary and Non-Binary Transgender Individuals when Discovering and Describing Gender Identity

Description: This study was conducted through in-depth interviews to examine potential differences between binary-aligned transgender individuals and non-binary individuals in regards to media usage when learning about, articulating, and explaining their gender identity. Results showed numerous differences between transgender people with binary-aligned and non-binary gender identifications in regards to social media preferences and differences in perceived media importance and effects. Additional information was found in regards to the age at which gender identity is articulated and the importance of individuality in comparison to one's gender identity.
Date: May 2017
Creator: Laljer, David B
Partner: UNT Libraries

Composer/Performer Collaboration as Seen in the Solo Piano Part of Percy Grainger's Edition of the Edvard Grieg Piano Concerto in A Minor, Opus 16

Description: The purpose of this document is threefold. First, it demonstrates what Grieg contributes to the musical text compared with the original Peters edition, particularly, those additions that refer to expression, interpretation, and style. Second, this document focuses on presenting Grainger's changes that were approved by Grieg. Third, the document evaluates Grainger's own suggestions for pedaling, hand redistribution and fingering, addition of notes, tempo markings, and other performance guidelines.
Date: May 2017
Creator: Lee, Sung Yo
Partner: UNT Libraries

Consequences of Coworker Bullying: A Bystander Perspective

Description: Previous research on workplace bullying primarily focuses on two main actors – the bully and the victim – while neglecting a third actor: the bystander of the bullying. The prevalence of workplace bullying is increasing across organizations, resulting in more employees becoming subjected to the effects of workplace bullying. Furthermore, witnessing coworker-on-coworker bullying is likely to influence the relationships that the bystander has with the two coworkers involved in the bullying episode. Two areas are proposed to investigate their effect on the coworker bystander: coworker interpersonal justice and personal identification with coworkers. Coworker interpersonal justice involves the perceived fairness between coworkers, while personal identification refers to how these bystanders identify with the specific actors of the bullying event. In addition to work-related outcomes, bystanders are affected at a personal level. That is, being exposed to bullying situations causes these bystanders to alter their anxiety levels and their core affect, with core affect being a precursor to moods and emotions. In addition to the aforementioned outcomes of witnessing a coworker bullying incident, there are also contextual aspects which may influence these relationships. Personal-level factors, such as a bystander's empathy and sense of coherence (i.e., coping mechanisms), may influence the effect of witnessing a coworker being bullied. Similarly, the gender of the victim in relation to the gender of the bystander may also play a role. Using affective events theory, I investigate how witnessing coworker bullying in the workplace effects bystanders. This research employs a 2 x 2 experimental design with multi-wave data collection and an in-person lab session to test the proposed hypotheses. AET is operationalized by creating a fictional coworker bullying situation in which observers are either exposed to the bullying situation or not. This research offers several contributions to the management literature as well as to practitioners. First, it ...
Date: May 2017
Creator: Medina, Michele Nicole
Partner: UNT Libraries

Construct Validation and Measurement Invariance of the Athletic Coping Skills Inventory for Educational Settings

Description: The present study examined the factor structure and measurement invariance of the revised version of the Athletic Coping Skills Inventory (ACSI-28), following adjustment of the wording of items such that they were appropriate to assess Coping Skills in an educational setting. A sample of middle school students (n = 1,037) completed the revised inventory. An initial confirmatory factor analysis led to the hypothesis of a better fitting model with two items removed. Reliability of the subscales and the instrument as a whole was acceptable. Items were examined for sex invariance with differential item functioning (DIF) using item response theory, and five items were flagged for significant sex non-invariance. Following removal of these items, comparison of the mean differences between male and female coping scores revealed that there was no significant difference between the two groups. Further examination of the generalizability of the coping construct and the potential transfer of psychosocial skills between athletic and academic settings are warranted.
Date: May 2017
Creator: Sanguras, Laila Y
Partner: UNT Libraries

A Constructional Approach to Establishing and Maintaining Calm Canine Behavior

Description: Very few behavior-change programs with canines produce effects that persist beyond the training condition. The present study is an experimental demonstration of a constructional program that established calm patterns of behavior as alternatives to hyperactive ones. Three dogs that exhibited hyperactive patterns were chosen as subjects. Seven conditions common to canine-caretaker relationships were used to determine which factors resulted in the hyperactive patterns. Then, sitting and lying down were taught as beginning points using touch as a reinforcer. The final behavior, maintained by naturally occurring reinforcers, was established errorlessly. The study used a control-analysis strategy of behavior change with a changing-criterion design. The intervention resulted in an immediate reduction in hyperactivity and an increase in sitting and lying down for all dogs.
Date: May 2017
Creator: Owens, Chase
Partner: UNT Libraries

A Content Analysis of Medical School Problem-Based Learning Cases

Description: Problem-based learning (PBL) was developed for use in medical education to incorporate more active, learner-centered instruction. Central to problem-based learning is the problem, which in medical education is usually case a case presentation, revealed in stages to allow learners to form and research learning objectives. The purpose of this study was to identify themes present across the PBL cases, including the patient-centeredness of the cases. Content analysis was used to examine 62 PBL cases that comprised the first and second years' core curriculum at a public medical school. The cases included a patient population similar to the local population, but care was more hospital-centric than would be expected from the actual patterns of medical utilization in the United States. Analyzing along two axes of patient-centeredness, the PBL cases demonstrated a good understanding of the patient (knowing the patient), but other qualities such as shared decision making was not as exemplified. Medical educators can use the results to understand elements that contribute to patient-centeredness and apply the analysis framework to evaluate future cases.
Date: May 2017
Creator: Kinkade, Scott Edward
Partner: UNT Libraries

Content and Temporal Analysis of Communications to Predict Task Cohesion in Software Development Global Teams

Description: Virtual teams in industry are increasingly being used to develop software, create products, and accomplish tasks. However, analyzing those collaborations under same-time/different-place conditions is well-known to be difficult. In order to overcome some of these challenges, this research was concerned with the study of collaboration-based, content-based and temporal measures and their ability to predict cohesion within global software development projects. Messages were collected from three software development projects that involved students from two different countries. The similarities and quantities of these interactions were computed and analyzed at individual and group levels. Results of interaction-based metrics showed that the collaboration variables most related to Task Cohesion were Linguistic Style Matching and Information Exchange. The study also found that Information Exchange rate and Reply rate have a significant and positive correlation to Task Cohesion, a factor used to describe participants' engagement in the global software development process. This relation was also found at the Group level. All these results suggest that metrics based on rate can be very useful for predicting cohesion in virtual groups. Similarly, content features based on communication categories were used to improve the identification of Task Cohesion levels. This model showed mixed results, since only Work similarity and Social rate were found to be correlated with Task Cohesion. This result can be explained by how a group's cohesiveness is often associated with fairness and trust, and that these two factors are often achieved by increased social and work communications. Also, at a group-level, all models were found correlated to Task Cohesion, specifically, Similarity+Rate, which suggests that models that include social and work communication categories are also good predictors of team cohesiveness. Finally, temporal interaction similarity measures were calculated to assess their prediction capabilities in a global setting. Results showed a significant negative correlation between the Pacing Rate and ...
Date: May 2017
Creator: Castro Hernandez, Alberto
Partner: UNT Libraries

A Content Originality Analysis of HRD Focused Dissertations and Published Academic Articles using TurnItIn Plagiarism Detection Software

Description: This empirical exploratory study quantitatively analyzed content similarity indices (potential plagiarism) from a corpus consisting of 360 dissertations and 360 published articles. The population was defined using the filtering search criteria human resource development, training and development, organizational development, career development, or HRD. This study described in detail the process of collecting content similarity analysis (CSA) metadata using Turnitin software (www.turnitin.com). This researcher conducted robust descriptive statistics, a Wilcoxon signed-rank statistic between the similarity indices before and after false positives were excluded, and a multinomial logistic regression analysis to predict levels of plagiarism for the dissertations and the published articles. The corpus of dissertations had an adjusted rate of document similarity (potential plagiarism) of M = 9%, (SD = 6%) with 88.1% of the dissertations in the low level of plagiarism, 9.7% in the high and 2.2% in the excessive group. The corpus of published articles had an adjusted rate of document similarity (potential plagiarism) of M = 11%, (SD = 10%) with 79.2% of the published articles in the low level of plagiarism, 12.8% in the high and 8.1% in the excessive group. Most of the difference between the dissertations and published articles were attributed to plagiarism-of-self issues which were absent in the dissertations. Statistics were also conducted which returned a statistically significant justification for employing the investigative process of removing false positives, thereby adjusting the Turnitin results. This study also found two independent variables (reference and word counts) that predicted dissertation membership in the high (.15-.24) and excessive level (.25-1.00) of plagiarism and published article membership in the excessive level (.25-1.00) of plagiarism. I used multinomial logistic regression to establish the optimal prediction model. The multinomial logistic regression results for the dissertations returned a Nagelkerke pseudo R2 of .169 and for the published articles a Nagelkerke pseudo R2 ...
Date: May 2017
Creator: Mayes, Robin James
Partner: UNT Libraries

Creating Discussion: An Auteur Analysis of Films Directed by Adrian Lyne

Description: This thesis examines the various "signature" threads that are present within the "oeuvre" of the Hollywood filmmaker Adrian Lyne. The goal of this thesis is to showcase both how and why Lyne can be thought of as an auteur and to open up his films to new and previously unexplored meanings. Lyne's eight feature films are analyzed in-depth individually and in comparison to one another from a variety of theoretical frameworks and points of focus in each of the body chapters.
Date: May 2017
Creator: Oliver, Stephanie Renee
Partner: UNT Libraries

Culturally Competent Evaluations

Description: Significant growth in the number of English language learners (ELLs) in U.S. schools is anticipated to continue, demanding that educators and evaluators have the skills necessary to distinguishing language difference from disability and provide appropriate services to these students. However, little research exists examining the role of evaluator's cultural competence in evaluating ELLs for special education; furthermore, what does exist shows that many evaluators report low levels of self-efficacy as it relates to assessing ELLs. The first chapter of the dissertation reports on a review of 21 articles conducted to address best practices for evaluating culturally and linguistically diverse (CLD) learners, evaluator self-efficacy, and recommendations for conducting culturally competent assessments and evaluations. The majority of the articles identified in this review focused on recommendations for best practices for conducting evaluations rather than reporting empirical findings related to the topic. Only one study was identified that focused on appropriate training needed by evaluation staff to effectively discriminate between language difference and a disability. Based on the findings of this review, additional research, using a rigorous methodology is needed. Addressing that need, the second chapter reports the results of a study conducted to examine the effectiveness of Project PEAC3E (Preparing Evaluators to Accurately Conduct Culturally Competent Evaluations), a reform-oriented professional development model, using case-based activities designed to increase evaluators' sense of self-efficacy, cultural competence, and the accuracy of evaluator eligibility decisions for English language learners (ELLs). The study found that Project PEAC3E was effective in increasing evaluator self-efficacy.
Date: May 2017
Creator: Chen, Cristina Rodriguez
Partner: UNT Libraries

Design, Modeling, and Experiment of a Piezoelectric Pressure Sensor based on a Thickness-Shear Mode Crystal Resonator

Description: This thesis presents the design, modeling, and experiment of a novel pressure sensor using a dual-mode AT-cut quartz crystal resonator with beat frequency analysis based temperature compensation technique. The proposed sensor can measure pressure and temperature simultaneously by a single AT-cut quartz resonator. Apart from AT-cut quartz crystal, a newly developed Langasite (LGS) crystal resonator is also considered in the proposed pressure sensor design, since LGS can operate in a higher temperature environment than AT-cut quartz crystal. The pressure sensor is designed using CAD (computer aided design) software and CAE software - COMSOL Multiphysics. Finite element analysis (FEA) of the pressure sensor is performed to analyze the stress- strain of the sensor's mechanical structure. A 3D printing prototype of the sensor is fabricated and the proposed sensing principle is verified using a force-frequency analysis apparatus. Next to the 3D printing model verification, the pressure sensor with stainless steel housing has been fabricated with inbuilt crystal oscillator circuit. The oscillator circuit is used to excite the piezo crystal resonator at its fundamental vibrational mode and give the frequency as an output signal. Based on the FEA and experimental results, it has been concluded that the maximum pressure that the sensor can measure is 45 (psi). The pressure test results performed on the stainless steel product shows a highly linear relationship between the input (pressure) and the output (frequency).
Date: May 2017
Creator: Pham, Thanh Tuong
Partner: UNT Libraries

Design of a Lower Extremity Exoskeleton to Increase Knee ROM during Valgus Bracing for Osteoarthritic Gait

Description: Knee osteoarthritis (KOA) is the primary cause of chronic immobility in populations over the age of 65. It is a joint degenerative disease in which the articular cartilage in the knee joint wears down over time, leading to symptoms of pain, instability, joint stiffness, and misalignment of the lower extremities. Without intervention, these symptoms gradually worsen over time, decreasing the overall knee range of motion (ROM) and ability to walk. Current clinical interventions include offloading braces, which mechanically realign the lower extremities to alleviate the pain experienced in the medial compartment of the knee joint. Though these braces have proven effective in pain management, studies have shown a significant decrease in knee ROM while using the brace. Concurrently, development of active exoskeletons for rehabilitative gait has increased within recent years in efforts to provide patients with a more effective intervention for dealing with KOA. Though some developed exoskeletons are promising in their efficacy of fostering gait therapy, these devices are heavy, tethered, difficult to control, unavailable to patients, or costly due to the number of complicated components used to manufacture the device. However, the idea that an active component can improve gait therapy for patients motivates this study. This study proposes the design of an adjustable lower extremity exoskeleton which features a single linear actuator adapted onto a commercially available offloading brace. This design hopes to provide patients with pain alleviation from the brace, while also actively driving the knee through flexion and extension. The design and execution of this exoskeleton was accomplished by 3D computer simulation, 3D CAD modeling, and rapid prototyping techniques. The exoskeleton features 3D printed, ABS plastic struts and supports to achieve successful adaptation of the linear actuator to the brace and an electromechanical system with a rechargeable operating capacity of 7 hours. Design validation was ...
Date: May 2017
Creator: Cao, Jennifer M
Partner: UNT Libraries

Design Principle on Carbon Nanomaterials Electrocatalysts for Energy Storage and Conversion

Description: We are facing an energy crisis because of the limitation of the fossil fuel and the pollution caused by burning it. Clean energy technologies, such as fuel cells and metal-air batteries, are studied extensively because of this high efficiency and less pollution. Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are essential in the process of energy storage and conversion, and noble metals (e.g. Pt) are needed to catalyze the critical chemical reactions in these devices. Functionalized carbon nanomaterials such as heteroatom-doped and molecule-adsorbed graphene can be used as metal-free catalysts to replace the expensive and scarce platinum-based catalysts for the energy storage and conversion. Traditionally, experimental studies on the catalytic performance of carbon nanomaterials have been conducted extensively, however, there is a lack of computational studies to guide the experiments for rapid search for the best catalysts. In addition, theoretical mechanism and the rational design principle towards ORR and OER also need to be fully understood. In this dissertation, density functional theory calculations are performed to calculate the thermodynamic and electrochemical properties of heteroatom-doped graphene and molecule-adsorbed graphene for ORR and OER. Gibb's free energy, overpotential, charge transfer and edge effect are evaluated. The charge transfer analysis show the positive charges on the graphene surface caused by the heteroatom, hetero-edges and the adsorbed organic molecules play an essential role in improving the electrochemical properties of the carbon nanomaterials. Based on the calculations, design principles are introduced to rationally design and predict the electrochemical properties of doped graphene and molecule-adsorbed graphene as metal-free catalysts for ORR and OER. An intrinsic descriptor is discovered for the first time, which can be used as a materials parameter for rational design of the metal-free catalysts with carbon nanomaterials for energy storage and conversion. The success of the design principle provides a better ...
Date: May 2017
Creator: Zhao, Zhenghang
Partner: UNT Libraries

Determining Whether and When People Participate in the Events They Tweet About

Description: This work describes an approach to determine whether people participate in the events they tweet about. Specifically, we determine whether people are participants in events with respect to the tweet timestamp. We target all events expressed by verbs in tweets, including past, present and events that may occur in future. We define event participant as people directly involved in an event regardless of whether they are the agent, recipient or play another role. We present an annotation effort, guidelines and quality analysis with 1,096 event mentions. We discuss the label distributions and event behavior in the annotated corpus. We also explain several features used and a standard supervised machine learning approach to automatically determine if and when the author is a participant of the event in the tweet. We discuss trends in the results obtained and devise important conclusions.
Date: May 2017
Creator: Sanagavarapu, Krishna Chaitanya
Partner: UNT Libraries