Mechanical Engineering Commons^™

Three-Dimensional Scaffolds Of Graphene, Carbon Nanotubes And Transition-Metal Oxides For Applications In Electronics, Sensors And Energy Storage, Gilbert N. Mbah

Department of Chemistry: Dissertations, Theses, and Student Research

Electronics, sensors and energy storage devices are the new waves behind economic development, security and communication¹. Engineering small sizes of electronic, sensors and energy storage devices is the hurdle limiting efficient, portable and vast applications of Nano-devices for economic, security and communication advancement². Silicon the major material used in transistors has approached its limit to fabricated Nano-devices³. The discovery of free standing, one atomic layer thick and two-dimensional graphene sheets with high conductivity, inert, high specific surface area, stable and high tensile strength material in 2004 has shown capabilities to replaced silicon in electronics, …

Performance Analysis Of A Copper Ii Sulfate Pentahydrate Based Thermogalvanic Cell., Steffen Krebs

Electronic Theses and Dissertations

Low grade heat recovery systems are more relevant today due to the rising costs in energy and transition to non-fossil fuel energy sources. Thermogalvanic cells show potential due to low cost and scalability. In this study the performance of a Copper II Sulfate Pentahydrate based electrolyte was evaluated. The effects of electrolyte concentration, electrode separation, and electrode surface area were studied experimentally. Conductive heat transfer within the electrolyte was simulated via SolidWorks. All experimental thermocell testing was conducted to find the maximum power production of a particular cell design. The base cell had a six inch electrode separation with two …

Mechanics Of Electrode Materials In Lithium Battery Applications., Jubin Chen

Electronic Theses and Dissertations

During lithiation and detlithiation, substantial volumetric changes occur within the electrode materials used for rechargeable lithium batteries. The magnitude of these deformations is inherently linked to the electrical capacity of the battery electrical capacity, which tends to degrade with repeated cycling. In this dissertation, the relationship between electrical discharge capacity and mechanical deformation state is examined using in-situ imaging of the working electrode surface within a custom CR2032 coin cell lithium battery. Digital image correlation is used to quantify electrode strains throughout the discharge-charge process. The effect of constraint due to substrate stiffness is investigated for two film materials: traditional …

On The Selection Of A Good Shape Parameter For Rbf Approximation And Its Application For Solving Pdes, Lei-Hsin Kuo

Dissertations

Meshless methods utilizing Radial Basis Functions~(RBFs) are a numerical method that require no mesh connections within the computational domain. They are useful for solving numerous real-world engineering problems. Over the past decades, after the 1970s, several RBFs have been developed and successfully applied to recover unknown functions and to solve Partial Differential Equations (PDEs).
However, some RBFs, such as Multiquadratic (MQ), Gaussian (GA), and Matern functions, contain a free variable, the shape parameter, c. Because c exerts a strong influence on the accuracy of numerical solutions, much effort has been devoted to developing methods for determining shape parameters which provide …

Jet And Droplet Impingement On Superhydrophobic Surfaces, Jonathan Glenn Stoddard

Theses and Dissertations

The effect of superhydrophobicity on liquid water impingement on a flat horizontal surface was explored. The surfaces combined a hydrophobic surface chemistry with a patterned microstucture in order to produce high contact angles with water. Three sets of experiments were performed, one for jet impingement and two for droplet impingement, which advance previous work in characterizing the interaction of water and superhydrophobic surfaces.Jet impingement experiments were performed to characterize a transitional regime between an unsubmerged and a completely submerged superhydrophobic surface by varying an imposed downstream depth. For low downstream depths, the surface remained unsubmerged and displayed only break up …

Non-Intrusive Second Law Performance Evaluation Of A Domestic Freezer, Jim Mcgovern, S. Oladunjoye

Conference Papers

This paper describes non-intrusive performance testing and second law, exergy-based, performance evaluation of a small, contemporary domestic freezer that used R600a refrigerant. The methodology presented is associated with logging of temperatures and the instantaneous power consumption. It gives a ‘second law of thermodynamics’ perspective on operating performance by providing rational efficiency values and by localizing and quantifying the instantaneous exergy destruction rates. This approach is compared to a more conventional ‘first law’ energy analysis. Suggestions are made for the standardization of such an approach in order to enhance the sustainability of domestic freezers. Keywords: Domestic freezer, Performance testing, Performance evaluation, …

Wind Tunnel Flow Characterization Utilizing Turbulence Spheres, David Omar Cano

Theses and Dissertations - UTB/UTPA

When it comes to designing products that will be highly subjected to the aerodynamics of the atmospheric freestream, it’s vital to take into consideration parameters such as geometry and surface smoothness. The optimization of the performance of certain products may be done so with the usage of wind tunnel testing. In order to utilize this tool to its full potential, the flow quality must be pre-determined before running tests. In determining the flow quality there are two main parameters needed to obtain this value. These parameters are referred to as the Turbulence Factor (TF) and Turbulence Intensity (TI). To calculate …

Natural Polymer Based Composite Scaffolds For Tissue Engineering Applications, Marcos R. Villarreal

Theses and Dissertations - UTB/UTPA

The fabrication, characterization, and bio-assessment of two types of perspective tissue engineering (TE) scaffolds are presented. Principally derived of biopolymers, both types of scaffolds generally followed porous scaffold methodologies for synthesis. Differentiating the two scaffold varieties was chiefly driven by crosslinking attainment, where crosslinking is argued to add structural stability and aid in regulating biodegradability rates in TE scaffolds. Microwave irradiation via conventional microwave was one method used to prospectively crosslink cornstarch to chitosan and sodium alginate. Triethyl orthoformate, was used to prospectively crosslink collagen and chitosan. After the scaffolds were “crosslinked” they were subjected to freeze drying techniques in …

Two-Dimensional Dynamics Model Of The Lower Limb To Include Viscoelastic Knee Ligaments, Eduardo Granados

Theses and Dissertations - UTB/UTPA

A dynamic, 2D, anatomical knee joint model has been developed to simulate knee reactions to external input forces. A deformable contact area approach is used to find contact forces and moments, and a method of applying nonlinear viscoelastic ligament strain rate response was also developed and implemented on the model to account for the effects of viscoelasticity on the ligament fibers. The ligaments were then tested for various deficiencies to identify their effects on the natural frequency of the knee. Internal knee forces from ligaments, muscles, and contacting surfaces are modeled and then numerically found for different exercises. Static and …

Development, Optimization, And Implementation Of A Vibration Based Defect Detection Algorithm For Railroad Bearings, Amy Gonzalez

Theses and Dissertations - UTB/UTPA

Of the three main rail accident types in the United States, derailments are the most common. Studies have shown that derailments occurring above 25 mph are caused by equipment failures such as bearing failures. As a preventative measure, condition-monitoring systems are required to detect defective bearings in the field. Based on data compiled from multiple experiments of healthy and defective bearings at UTPA, an algorithm has been devised to identify bearing abnormalities. Vibration analysis techniques are utilized to potentially determine whether a bearing is defective and the defect type and size using the acquired vibration signatures. Implementation of a defect …

Onboard Load Sensor Prototype For Use In Freight Railcar Service, Thomas Michael Diedrich

Theses and Dissertations - UTB/UTPA

Determining the exact load carried by an individual railcar is crucial in the railroad industry. With an accurate load measurement, the filling process can be optimized to provide maximum cargo load without exceeding the loading thresholds set by the Association of American Railroads (AAR). In addition to optimizing the cargo load, an accurate load measurement will make it possible to identify any load imbalance in the railcar which has detrimental effects on bearing. Previous work conducted with a strain-gauge-based load sensor suspended between a thermoplastic steering pad and a bearing adapter provided accurate load data in the laboratory setting. This …

Two Dimensional Inverse Dynamics Model Of Human Knee Dynamics During The Moderate Squat Exercise, Ricardo Gomez Jr.

Theses and Dissertations - UTB/UTPA

The purpose of this research is to investigate the internal forces on the human knee joint during moderate squat exercise. An inverse dynamics, two dimensional, anatomic dynamic knee model is developed. The model describes the motion in the sagittal plane of human leg, and includes tibia, femur, ligamentous knee structures, tendons and muscles. The software package Matlab is used to solve the inverse dynamics model. Numerical simulations are conducted for walking (the stance phase of the gait cycle) in order to validate the model, and for moderate squatting in order to predict ligament, contact and muscle forces during this exercise.

Nonlinear Dynamics Of Electrostatically Actuated M/Nems Plates To Include Casimir And Van Der Waals Effects, Reynaldo Oyervides

Theses and Dissertations - UTB/UTPA

The amplitude-frequency response and voltage-amplitude response of electrostatically actuated micro and nano-electromechanical systems (M/NEMS) clamped circular plates are investigated. The system is actuated by soft AC voltage at frequency near half natural frequency of the plate, and another case near natural frequency of the plate, they resulting in primary and parametric resonances of the system, respectively. The system is first analytically modeled using the Method of Multiple Scales (MMS). MMS results are then compared to Reduced Order Model (ROM) method frequency response numerical simulations. Besides MMS and ROM, time response simulations are conducted. The agreement of the frequency responses of …

Investigation Of Slective Laser Melting Of Mecanically Alloyed Metastable Al5fe2 Powder, Hugo Montiel

Theses and Dissertations - UTB/UTPA

Selective Laser Melting (SLM), an Additive Manufacturing (AM) technology, enables the production of complex structured metal products. Aluminum alloys are used in SLM as high-strength lightweight materials for weight reduction in structural components. Previous investigations report high laser powers (300 W) and slow scanning speeds (500 mm/s) to process aluminum alloys under SLM. This research investigates the SLM processing of Al-Fe alloy by utilizing metastable Al5Fe2 powder system produced by mechanical alloying. Metastable systems are thermodynamically activated with internal energy that can generate an energy shortcut when processing under SLM. The optimum laser power, scan speeds and scan distances were …

Development Of Metallic And Ceramic Nanotubes Via Magnetron Sputtering, Hillario Cortez

Theses and Dissertations - UTB/UTPA

Nanotechnology has been extensively studied throughout the years and has allowed for the development of new structures and technologies. Nanofibers in particular have intrinsically unique properties such as large surface area to volume ratio. Nanofiber structures have a wide range of applications that include: catalysts, sensors, biomedical scaffolds, filtration devices, high performance textiles, energy storage systems, sensitized solar cells, photonics, nanocomposites, membranes, drug delivery systems, and electronics. The objective of this work is to fabricate nanotubular structures by employing the template approach. The template approach consists in the fabrication of circular shaped templates, nanofibers, and then coating the template fibers …

A Concept Validation Of A Magnetometry-Based Technology For Detecting Concealed Weapons In Vehicle Door Panels, Nar Vang

Master's Theses

Acts of insurgency have become an increasing threat resulting in extensive measures being taken by the law enforcement authorities to mitigate their devastating effects on human life and infrastructure. This thesis introduces a magnetometry-based information, and signal processing methodology for detecting concealed ferrous objects in vehicle body panels. From extensive literature research, it was observed that while magnetic sensors have been used in a variety of related applications, but they have not been extensively applied to the on-road detection of firearms and explosives concealed in vehicles. This study utilized an extensive experimental protocol for preliminary concept validation. The main idea …

Reactive Motions In A Fully Autonomous Crs Catalyst 5 Robotic Arm Based On Rgbd Data, Arad Haselirad

Theses and Dissertations

This study proposes a method to perform velocity estimation using motion blur in a single image frame along x and y axes in the camera coordinate system and intercept a moving object with a robotic arm. It will be shown that velocity estimation in a single image frame improves the system's performance. The majority of previous studies in this area require at least two image frames to measure the target's velocity. In addition, they mostly employ specialized equipments which are able to generate high torques and accelerations.

The setup consists of a 5 degree of freedom robotic arm and a …

Mechanical Properties Of Laser-Sintered-Nylon Diamond Lattices, Clayton Neff

USF Tampa Graduate Theses and Dissertations

Additive manufacturing offers a manufacturing technique to produce complex geometry prototypes at a rapid pace and low cost. These advantages advocate additive manufacturing for the design and production of cellular structures. Cellular structures are interesting because they contain a large amount of porosity (void space of air) to manifest a lightweight structure. Designs of cellular structures generate a periodic pattern; often of complex geometry, called a lattice.

There has been a significant amount of research to maximize specific stiffness of lattice structures but little to evaluate low-stiffness lattices. Low-stiffness structures benefit energy absorbance through bending of the lattice. This research …

Feasibility Of Wireless Power Transfer For Electrification Of Transportation: Techno-Economics And Life Cycle Assessment, Jason C. Quinn, B. J. Limb, P. Barr

Mechanical and Aerospace Engineering Faculty Publications

Integration of wireless power transfer (WPT) systems in roadways and vehicles represents a promising alternative to traditional internal combustion transportation systems. The economic feasibility and environmental impact of WPT applied to the transportation system is evaluated through the development of engineering system models. For a 20% penetration of the WPT technology in vehicles, results show a 20% reduction in air pollutants, 10% reduction in energy use and CO2 emissions and a societal level payback (defined as total cost of ownership savings compared to a traditional vehicle equal to roadway infrastructure) of 3 years. The modeled system covers 86% of all …

Simulation And Validation Of Radio Frequency Heating Of Shell Eggs, Soon Kiat Lau

Department of Food Science and Technology: Dissertations, Theses, and Student Research

Finite element models were developed with the purpose of finding an optimal radio frequency (RF) heating setup for pasteurizing shell eggs. Material properties of the yolk, albumen, and shell were measured and fitted into equations that were used as inputs for the model. When the egg was heated by itself, heating tend to be focused at the air cell to result in a “coagulation ring.” The focused heating near the air cell of the egg prevented satisfactory pasteurization of the egg, but deeper analysis of the simulation results offered a new perspective on how non-uniform RF heating could occur in …