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2,241 Matching Results
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Novel Phase-Chance Soft Actuators Controlled via Peltier
Soft actuation methods are a developing field of robotics deemed suitable for physical human-robot interactions due to the adaptability of materials and compliant structures. Thermo-active soft actuators are a subset of these which convert thermal energy to mechanical work in the form of elongation, bending, or twisting to conform to the environment. This study is divided into three major studies that all use actuators with a working principle of phase-change fluid vaporizing for expansion with applied heat from a Peltier. The first study evaluates the bandwidth and efficiency between (i) traditional Joule heating, and (ii) Peltier heating, finding that Peltier heating can considerably improve the operational bandwidth of the actuator. The second study uses a thin membrane actuator placed in a braided mesh to form a McKibben muscle capable of lifting 5N, and formed into a gripper capable of manipulating objects within the environment. The third study uses actuators of a solid, hollow and flexible Peltier embedded silicone structure and are evaluated and optimized in order to increase actuation speed, finding that the embedded flexible Peltier design was able to elongate over 50% of its original height in 20 seconds. The overall aim of all of these studies was to …
Date:
July 2023
Creator:
Johnson, Daniel Cody
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Pressure Controlled Topochemical Polymerization in Two-Dimensional Hybrid Perovskite
Mechanical pressure offers unique control over the energy landscape of chemical reactions, opening up pathways that are inaccessible through conventional thermochemistry. We hypothesize that the reduced dimensionality defines the conformational space of the high-pressure reaction, giving rise to new selectivity that is unavailable in 3D systems. Here, we demonstrate this concept through the pressure-controlled topochemical polymerization of the diacetylene molecule deca‐3,5‐diyn‐1‐amine (DDA) incorporated in the two-dimensional (2D) perovskite [DDA]2PbBr4. Compression at 3 GPa drives the first topochemical polymerization through 1,2 addition, forming a polyene product at room temperature. The reaction is initiated by the mechanical bending of the linear DDA molecule, a mechanism fundamentally different from the 1,4-addition in 3D solids. Importantly, pressure hinders the second 1,2-addition by disfavoring the gauche conformation between the remaining acetylene groups, allowing for the selective formation of polyene versus polyacene products. We characterize the reaction mechanisms and products using spectroscopies (Raman, X-ray photoelectron, ultraviolet-visible), X-ray diffraction and density-functional theory simulations. These results highlight the important role of dimensionality in high-pressure chemistry, and offers a new paradigm for creating low-dimensional functional materials.
Date:
December 2021
Creator:
Abu-Amara, Lama Marwan
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Remotely Controlled Magneto-Phononic Devices Achieving Nonreciprocity and Anderson Localization in Ferrofluid
Motivated by previous relevant research on phononics including both active and passive phononics, the interest of faster turnability and more functions of the active phononics of further study led to this proposing research topic: magnetic field tunable active functional phononics. The first design of magnetic field tunable reciprocal--non-reciprocal transmission acoustic device was established, material was characterized, and numerical simulation has been performed. The simulation results show clear T-symmetric breaking non-reciprocity due to energy level splitting effect with Doppler effect – an acoustic Zeeman effect. Inspired by this preliminary work, further experiments were planned to demonstrate this effective Zeeman effect in phononics and effectively charged phonons in water based ferro-fluid. The objectives of this work as the next series of tasks were to illustrate acoustic Zeeman effect and acoustic Landau levels in various strength of magnetic field to investigate a design non-reciprocal sound device with magnetic field switching, which could be controlled on the amount of non-reciprocity with the strength of magnetic field. Once this new field first discovered by the proposed study tasks, more active tunable magnetic field phononics devices could be designed and exemplified in terms of both simulations and experiments. Faster and more controllable active phononic devices could …
Date:
December 2021
Creator:
Jin, Yuqi
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
The Role of Counselor Trainees' Co-Regulated Mindfulness: A Cluster-Randomized Controlled Study
Mindfulness is a practice that has the potential to help counseling students build a variety of skills that are necessary for clinical efficacy, including therapeutic presence, attunement, empathy, cognitive flexibility, and non-reactivity. However, mindfulness is rarely taught to students in mental health training programs, which makes it an untapped possibility to improve counselor education. Additionally, rarely do researchers explore the role of counselor mindfulness and counselor trauma on clients' perceptions of therapeutic presence. Therefore, the purpose of this study is to explore the effects of a 15-week mindfulness training program for counseling students to understand its effect on client's perceptions of therapeutic presence, counselor state mindfulness development, and counselor trauma symptoms. Participants in this cluster-randomized controlled intervention were masters counseling students currently enrolled in clinical practicum accredited by the Counsel for the Accreditation of Counseling and Related Educational Programs (CACREP). Counselors provided data at three timepoints on their state mindfulness, trauma symptoms, and therapeutic presence. Clients provided data at three timepoints on their perceptions of their counselor's therapeutic presence. We analyzed data through repeated measures ANOVA and two-level longitudinal hierarchical linear models. Implications for counselor education, professional counselor development, and future research are offered and limitations are discussed.
Date:
May 2023
Creator:
Warwick, Lindsey A.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Mass Spectrometry Guided Development of a Controlled Release Nanotransfersome Transdermal Drug Delivery System
Poor medical adherence attributed to patient compliance has impacted the medical community, at times, in a deleterious fashion. To combat this, the medical community has attempted to provide therapeutics in the form of absorption enhancing techniques. To improve the absorption rate techniques such as drug encapsulation using proteins, liposomes, or nanotransfersomes have been developed using mass spectrometry. These techniques, have aided in the enhanced absorption of analytes with low bioavailability, including curcumin, simvastatin, and lysozyme. Specifically, mass spectrometry allows for the development and monitoring of nanotransfersome encapsulated analytes and the permeation across the dermal membrane. This transdermal delivery would eliminate the problems encountered during first pass metabolism, while allowing for higher concentrations of analyte to be maintained in the blood serum. This can be coupled to a thermosensitive gelatin that provides for a dose control mechanism to be accomplished, allowing multiple doses to be delivered using one transdermal patch system. The novel delivery system developed using mass spectrometry, allows the analyte to be delivered into the circulatory system at a controlled dosage, via transdermal absorption. This system will aid in eliminating problems associated with patient compliance, as the patient is no longer reliant on memory to self-dose. Further, this system …
Date:
December 2020
Creator:
Kiselak, Thomas Dieter
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Developing a Pedagogical Model for Twentieth Century Flute Repertoire
Modern flute pedagogy tends to focus on repertoire which utilizes or builds upon tonal and Romantic stylistic conventions, largely ignoring works that disregard or reject these conventions until later in student's education. This lack of stylistic diversity in commonly studied works from the first half of the twentieth century can be problematic when students are approaching avant-garde or modernist repertoire for the first time, as they are unfamiliar with the style and technical needs of the pieces. This dissertation provides a style guide and progressive curriculum for the avant-garde repertoire of the early- and mid-twentieth century to help students bridge the gap from commonly-studied early-twentieth century repertoire to Post-War Modernist works. The curriculum and style guide are accompanied by an overview of avant-garde musical styles prominent in Europe and American between the 1890s and 1970s, a discussion of the pedagogical challenges of avant-garde repertoire, and two performance guides for avant-garde pieces included in the curriculum, Diaphonic Suite No. 1 by Ruth Crawford and Variations for Solo Flute by Ursula Mamlok.
Date:
August 2022
Creator:
Maker, Anne Marie Dearth
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Performing Controlled Indeterminacy in Leo Brouwer's "Sonata Mitología de las Aguas No. I, para Flauta y Guitarra"
Leo Brouwer's Sonata Mitología de las Aguas No. I for flute and guitar, first published in 2017, has taken its place as an important twenty-first-century addition to the flute and guitar duo repertory. I provide a brief historical context for the work, followed by preparation guides for guitar alone and duo passages. My preparation guides include exercises and rehearsal strategies, focusing on those passages of the work that include controlled indeterminacy. The study of indeterminacy in music is unusual in the pedagogy of the classical guitarist; this leaves guitarists unprepared for dealing with pieces, especially chamber works, that use improvisation or aleatoric music as a primary element. I take a multifaceted approach to facilitate the realization of the indeterminate sections of the work; this includes demonstrations of my traditional music notation transcriptions and other rehearsal strategies and the application of music performance study systems by James Thurmond and Marcel Tabuteau. This document aims to provide guidance to creating an organic, natural aesthetic in the actualization of Brouwer's groundbreaking work.
Date:
May 2021
Creator:
Rodriguez, Hector Javier
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Leveraging Digital Library Infrastructure to Build a Language Archive
Article introduces the collaboration between the Computational Resource for South Asian Languages (CoRSAL) group and the University of North Texas (UNT) Digital Library to build a series of interconnected digital collections for various language communities. It was presented at the 1st International Workshop on Digital Language Archives held on September 30-October 1, 2021 as part of the ACM/IEEE Joint Conference on Digital Libraries 2021.
Date:
October 7, 2021
Creator:
Phillips, Mark Edward; Burke, Mary; Tarver, Hannah & Zavalina, Oksana
Object Type:
Article
System:
The UNT Digital Library
Using existing metadata standards and tools for a digital language archive: a balancing act
Article discusses how building a digital language archive requires a number of steps to ensure collecting, describing, preserving and providing access to language data in effective and efficient ways. This paper introduces the reader to the background of this project and discusses some of the areas important for representing language materials where both University of North Texas Libraries (UNTL) metadata and CoRSAL metadata practices were adapted to better fit the needs of intended audiences.
Date:
June 16, 2022
Creator:
Burke, Mary; Tarver, Hannah; Phillips, Mark Edward & Zavalina, Oksana
Object Type:
Article
System:
The UNT Digital Library
Exploring the Effects of Cultural Consequences Identified through a Ranking Task on the Interlocking Behavioral Contingencies of Ethically Self-Controlled Responses with Participants with Pre-Existing Relationships
This study explored the effects of cultural consequences identified through a ranking task on the selection of interlocking behavioral contingencies and aggregate products constituting ethically self-controlled responses when participants had pre-existing relationships. Two experiments were conducted to explore these effects. Experiment 1 had two triads of three participants each recruited from a university-based autism center. Experiment 2 had three triads of three participants each; participants in Triads 3 and 4 were recruited from a university-based rock-climbing club while participants in Triad 5 were recruited from the same university-based autism center as in Experiment 1. All participants were exposed to a task that involved choosing odd or even rows from a matrix displayed throughout the experimental session. Individual contingencies were programmed in all conditions while metacontingencies were programmed in some conditions. Participants selected the topography of the cultural consequence through a pre-experimental ranking task prior to the onset of the experimental session. A change was made to the experimenter's verbal behavior in all operant and metacontingency conditions for Experiment 2. The results of both experiments indicate that identification of the cultural consequence through a ranking task with participants having pre-existing relationships did have an effect on the continued selection of the …
Date:
May 2022
Creator:
Elwood, Chelsea Christina
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Toward an Experimental Analysis of a Competition between Dimensions of Cultural Consequences
The exponential growth of the human population has contributed to the overuse and degradation of common pool resources. Using science as a tool for informed policy-making can improve the management of our common pool resources. Understanding the conditions that influence groups of individuals to make ethical self-controlled choices may help solve problems related to the overuse and degradation of common pool resources. Ethical self-control involves the conflict of choice between one that will benefit the individual versus one that will benefit the group. The cumulative effect of many individuals behaving in an ethically self-controlled manner with common resource use may offset some of the harm posed by overuse of common pool resources. Metacontingency arrangements involving ethical self-control may provide some insight as to if and how groups may cooperate to manage a common pool resource. This manuscript proposes an experimental preparation and methodology to evaluate the effects of competing magnitudes of cultural consequences on culturants and their cumulative effect on common pool resources; and provides an analysis and discussion of five trends that might result from such a line of research.
Date:
August 2020
Creator:
Guerrero, Maria Brenda
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
How is the Volatility Priced by the Stock Market?
Traditional portfolio theory suggests that, in equilibrium, only the market risk is priced in the cross-section of expected stock returns. However, if the market is not perfect and investors are constantly changing investing behaviors based on their perceptions about future market outlook, then non-traditional risk factors could potentially provide significant power of describing the expected stock returns. This dissertation has two essays on the pricing of volatility, in which the market is not assumed to be frictionless or perfect. Essay 1 focuses on the pricing of individual volatility in penny stocks. Empirical results show that individual volatility plays an important role in describing the average cross-sectional returns of penny stocks. Resorting to the rolling portfolio approach, evidences indicate that portfolios consisting of penny stocks with high individual volatilities, on average, earned much higher returns than portfolios consisting of penny stocks with low individual volatilities. This effect is statistically significant when multiple factors are controlled simultaneously. Essay 2 focuses on the pricing of the market volatility among individual stocks. Following the rolling portfolio method, Essay 2 constructs portfolios that consist of individual stocks with various market volatility exposures. Traditional risk factors such as market beta, size, book-to-market, and momentum are controlled …
Date:
August 2020
Creator:
Yu, Huaibing
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Impact of Processing Parameters and Forces on Channels Created by Friction Stir Bobbin Tools
In this thesis, friction stir channeling (FSC) and its process parameters influence on geometry, surface quality and productivity are explored. The probe of the friction stir processing (FSP) tool used to perform these tests was a modified submerged bobbin tool made of MP 159 Co-Ni alloy. The body was made from H13 tool steel. To find the optimal channel conditions for a targeted range of process parameters, multiple 6061 aluminum samples were prepared with a U shape guide to test the effects of different spindle speeds and feed rates. Using a gantry-type computer numerical control (CNC) friction stir welding (FSW) machine, the aluminum coupons were subjected to calibration experiments, force control tests, and an increased production rate to test these effects. It was found through experimentation that the programmed feed rates, spindle speeds and forces produced by the machine had an impact on the channel geometry. It was determined from the force-controlled setup that 8.46 mm/s at 750 RPM was the best combination of results for the four conditions tested on a CNC friction stir processing-machine. It was then tested at 10.58 mm/s at 800 RPM, which had comparable results with the best combination of input parameters from the force-controlled …
Date:
May 2022
Creator:
Koonce, James G
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Interim Committee Charges: Texas House or Representatives, 87th Legislature
List of committees in the Texas House of Representatives with updated charges for the interim period of the 87th session.
Date:
March 2022
Creator:
Texas. Legislature. House of Representatives.
Object Type:
Pamphlet
System:
The Portal to Texas History
Role of microRNAs and their downstream target transcription factors in zebrafish thrombopoiesis
Article describes how previous studies have shown that human platelets and megakaryocytes carry microRNAs suggesting their role in platelet function and megakaryocyte development. In their laboratory, the authors identified 15 microRNAs in thrombocytes using single-cell RNA sequencing.
Date:
September 26, 2023
Creator:
Qaryoute, Ayah Al; Fallatah, Weam; Dhinoja, Sanchi; Raman, Revathi & Jagadeeswaran, Pudur
Object Type:
Article
System:
The UNT Digital Library
Grass, Weed and WIldflower Guide
Field guide to plants found in Texas, organized into sections for grasses, weeds, and wildflowers, with a page for each species with photos and basic information about when it grows, whether it is native, rough size, and a list of characteristics for identification. Index starts on page 168.
Date:
2020
Creator:
Texas. Department of Transportation.
Object Type:
Book
System:
The Portal to Texas History
Using a microprocessor knee (C-Leg) with appropriate foot transitioned individuals with dysvascular transfemoral amputations to higher performance levels: a longitudinal randomized clinical trial
Article evaluating whether advanced prostheses can provide better safety and performance capabilities to maintain and improve quality of life in individuals who are predominantly designated MFCL level K2. This study used a 13 month longitudinal clinical trial to determine the benefits of using a C-Leg and 1M10 foot in individuals at K2 level with transfemoral amputation due to vascular disease.
Date:
May 25, 2021
Creator:
Jayaraman, Chandrasekaran; Mummidisetty, Chaithanya K.; Albert, Mark; Lipschutz, Robert; Hoppe-Ludwig, Shenan; Mathur, Gayatri et al.
Object Type:
Article
System:
The UNT Digital Library
[Commencement Program for University of North Texas, Fall 2020]
Commencement program for the fall 2020 graduating class of the University of North Texas, held at Apogee Stadium on Sunday, November 22, 2020. The program contains the order of service and a list of graduates for the baccalaureate, master's, and doctoral degrees.
Date:
November 22, 2020
Creator:
University of North Texas
Object Type:
Pamphlet
System:
The UNT Digital Library
Air Corridors: Concept, Design, Simulation, and Rules of Engagement
Air corridors are an integral part of the advanced air mobility infrastructure. They are the virtual highways in the sky for transportation of people and cargo in the controlled airspace at an altitude of around 1000 ft. to 2000 ft. above the ground level. This paper presents fundamental insights into the design of air corridors with high operational efficiency as well as zero collisions. It begins with the definitions of air cube, skylane or track, intersection, vertiport, gate, and air corridor. Then, a multi-layered air corridor model is proposed. Traffic at intersections is analyzed in detail with examples of vehicles turning in different directions. The concept of capacity of an air corridor is introduced along with the nature of distribution of locations of vehicles in the air corridor and collision probability inside the corridor are discussed. Finally, the results of simulations of traffic flows are presented.
Date:
December 2021
Creator:
Muna, Sabrina Islam
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Increasing the Effectiveness of Location-Based Advertising
Location-based ads are defined as any ads that are sent by an identified source to consumers' mobile devices when they are around the advertised product/store. Although mobile ad spending is said to have accounted for 68% of all digital ad spending in 2020, knowledge of how businesses can use mobile and location-based technology to reach their customers effectively is limited. Thus, the purpose of this three-essay format dissertation is to review the literature on LBA and identify the gaps in the literature and attempt to address a few of these gaps in the remaining two essays. The second essay tests an integrated model by examining the effects of the various retailer and consumer-controlled factors on two retail performances. In the third essay, we explore how LBA affects different dimensions of consumer-brand engagement. The results and findings provide important implications for retailers and brands to increase their performances.
Date:
August 2022
Creator:
Thapa, Sajani
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Aerodynamic Optimization of a 2D Airfoil for Rotary-Wing Aircraft at Mars Atmospheric Conditions
The interest toward Mars exploration has been considerably increasing due to also the successful deployment of the Perseverance rover and the continuous tests developed by SpaceX's launch vehicle, Starship. While the Mars 2020 mission is currently in progress, the first controlled flight on another planet have been proven in April 2021 with the vertical take-off and landing of the Ingenuity rotorcraft on Mars. In addition, the rotorcraft Dragonfly is expected to achieve the same endeavor in Titan, the largest moon of Saturn, by 2036. Continuous efforts have been oriented toward the development of new technologies and aircraft configurations to improve the performance of current proposed designs to achieve powered flight in different planetary bodies. This thesis work is a preliminary study to develop a comprehensive analysis over the generation of optimum airfoil geometries to achieve vertical flight in environments where low Reynolds numbers and Mach number equal to 0.2 and 0.5.
Date:
December 2021
Creator:
Saez, Aleandro G.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Stimulus Control Effects of Changes in Schedules of Reinforcement
Sometimes, changes in consequences are accompanied by a clear stimulus change explicitly arranged by the experimenter. Other times when new consequences are in effect, there is little or no accompanying stimulus change explicitly arranged by the experimenter. These differences can be seen in the laboratory as multiple (signaled) schedules and mixed (unsignaled) schedules. The current study used college students and a single-subject design to examine the effects of introducing signaled and unsignaled schedules, and the transitions between them. In one phase, a card was flipped from purple to white every time the schedule was switched from VR-3 to FT-10. In another phase, the schedule still changed periodically, but the card always remained on the purple side. Results showed that the participants' responding was controlled by the schedule of reinforcement, by the color of the card, or both. These results suggest that changes in patterns of reinforcement lead to changes in stimulus control. In addition, the stimulus control for a behavior can come from several different sources. During teaching, it may facilitate the development of stimulus control to change the environment when a new behavior is required.
Date:
August 2020
Creator:
Abdel-Jalil, Awab
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Fabrication of the Novel Asymmetric Polymeric Materials via Bottom-Up Approach
Asymmetric polymeric materials can be formed by either top-down or bottom-up methods. Bottom-up methods involve assembling the atoms and molecules to form small nanostructures by carefully controlled synthesis, which results in a reduction of some of the top-down limitations. In this dissertation, thermal, tribological and antireflective properties of polymeric materials have been enhanced by introducing structural asymmetry. The overall performance of commercial polymeric coatings, e.g. epoxy and polyvinyl chloride, has been improved by conducting the blending methods, specifically, chemical modification (α,ω-dihydroxydimethyl(methyl-vinyl)oligoorganosiloxane), cross-linking (triallyl isocyanurate), and antioxidant (tris(nonylphenyl) phosphite) incorporation. The nonequilibrium polymeric structures (moth-eye and square array) have been developed for the ultrahigh molecular weight block copolymers via the short-term solvent vapor annealing self-assembly. The large domain size of the moth eye structure allows for improvement of the light transmittance particularly in the visible and near infrared ranges, while the square arrangement of the block copolymer opens the possibility of magnetic data storage application by the large magnetic nanoparticles' embedment or masking of the superconductors.
Date:
May 2022
Creator:
Hnatchuk, Nataliia
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Engineering a Microfluidic Blood-Brain Barrier on a Silicon Chip
The blood-brain barrier (BBB) is composed of brain microvascular endothelial cells (BMECs), pericytes, and astrocytic endfeet, which regulate the transport of molecules into and out of the brain. BMECs possess intrinsic barrier properties that limit the passage of approximately 98% of small molecules into the brain in healthy individuals. However, in some brain diseases, the BBB undergoes structural and functional alterations, which can contribute to disease progression. In this study, we aimed to investigate the BBB by exploring the effects of endothelial cell stretching and the optimal dimensionality of stretching to enhance endothelium barrier tightness in Chapter 2. Subsequently, we developed an endothelium gradient stretching device to further examine the stretching effect in Chapter 3. Additionally, we investigated the promotion of endothelium tightness through the use of electrospun fibers, wherein we controlled the pore size. Based on these findings, we designed and fabricated an organ chip model that incorporates mechanical stretching, microfluidic techniques, electrospun fibers, and hydrogel extracellular matrix (ECM). The results of permeability testing demonstrated that this chip significantly improved the tightness of microvascular selective transport ability and has the potential to be used in drug sorting for central nervous system (CNS) diseases.
Date:
July 2023
Creator:
Liu, Jiafeng
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library