Digital Commons Network^™

Flow Vision For Autonomous Underwater Vehicles Via An Artificial Lateral Line, Nam Nguyen, Douglas L. Jones, Yingchen Yang, Chang Liu

Mechanical Engineering Faculty Publications and Presentations

Most fish have the capability of sensing flows and nearby movements even in dark or murky conditions by using the lateral line organs. This enables them to perform a variety of underwater activities, such as localizing prey, avoiding predators, navigating in narrow spaces, and schooling. To emulate this capability for Autonomous Underwater Vehicles, we developed an artificial lateral line using an array of Micro-Electro-Mechanical-Systems (MEMS) flow sensors. The signals collected via the artificial lateral line are then processed by an adaptive beamforming algorithm developed from Capon's method. The system produces 3D images of source locations for different hydrodynamic activities, including …

A Study Of The Effect Of Vibration On Railroad Bearing Temperature, Bertha Alicia Gonzalez

Theses and Dissertations - UTB/UTPA

An on-track collaborative field test and laboratory experiments were conducted in order to determine the relationship between abrupt rises in surface temperature of a railroad bearing and vibration signatures captured during the experiments. The collaborative field test was conducted in order to investigate the root cause for this abrupt temperature change known as bearing temperature trending. The research presented in this thesis will show that temperature trending is correlated to an increase in the magnitude of vibration within the bearing and the fundamental frequencies that are generated by the internal components of a rotating bearing assembly. Distinct vibration mechanisms are …

Photonic Crystal Design And Fabrication Assisted By Tunable Femtosecond Oscillator Laser, Kristofer B. Ohlinger

Theses and Dissertations - UTB/UTPA

Photonic Crystals have the potential for engineered light interaction as directed by the photonic bandgap, a property that details the prohibited propagation region and ultimately the ability to guide light. A so called, photonics-on-chip, would incorporate arbitrary light guiding with functional elements in one package. The realization of such a device is subject to the fabrication paradigms implemented and this thesis is concerned with holographic lithography as a means for creating polymer photonics crystal templates and two-photon polymerization for incorporating light guiding pathways.

In this thesis, the design of the to-be-fabricated structures has been co-opted by computational exploration of the …

Design And Implementation Of An Actively Adjustable Spring Mechanism Via Redundant Actuation, Eleazar Marquez

Theses and Dissertations - UTB/UTPA

This study presents the theoretical results and experimental validation of an adjustable stiffness mechanism. The use of redundant actuation is emphasized in the design of a one-degree-of-freedom Watt II mechanism capable of independently controlling the effective stiffness without a change in equilibrium position. This approach is in contrast to previous spring mechanism designs unable to actively control the spring rate independent of deflection, and has potential applications in various types of suspension and assembly systems. Results indicate that driving the redundantly actuated, unidirectional, spring mechanism requires attaching two direct brush-type direct current motors on each of the two grounded revolute …

Surface Optimization Of High Density Polyethylene And Carbon Nanofiber Composites For The Improvement Of Electromagnetic Shielding Effectiveness, Brandon C. Jarvis

Theses and Dissertations - UTB/UTPA

Nanoreinforced composites of High Density Polyethylene (HDPE) and Carbon Nanofibers (CNF) of varying nanofiber concentration were fabricated via melt mixing. Following fabrication, various metal and metal-nitride thin films were sputter deposited upon the substrates. Volume resistivity measurements of the composite substrates, as well as four point probe analysis of the composites and the deposited films were performed and are reported. Electromagnetic Interference (EMI) Shielding Effectiveness (SE) measurements were performed upon all samples in order to gauge the effects of percolation and the presence of the deposited film(s) upon overall SE. Comparisons of experimental measurements with analytical models available in the …

Electrospinning To Forcespinning™, Kamal Sarkar, Carlos Gomez, Steve Zambrano, Michael Ramirez, Eugenio De Hoyos, Horacio Vasquez, Karen Lozano

Mechanical Engineering Faculty Publications and Presentations

A new process called Forcespinning™ has been developed to make nanofibers from a wide range of materials. This new method uses centrifugal force, rather than electrostatic force as in the electrospinning process. The Forcespinning™ method uses either solutions or solid materials that are solution or melt spun into nanofibers. Key parameters to control the geometry and morphology of the nanofibers include rotational speed of the spinneret, collection system and temperature. Orifices of the spinneret can have arbitrary geometric shapes to provide corresponding cross-section of nanofibers. The Forcespinning™ method has been successfully used to make nanofibers of poly-ethylene …

A Stochastic Product Priority Optimization Method For Remanufacturing System Based On Genetic Algorithm, Xiong Xiong

Theses and Dissertations - UTB/UTPA

Increasing number of manufacturers are developing remanufacturing facilities to recover end-of-life products for product/component reuse and material recycling while the high uncertainty pattern of returned products complicates the production planning. In this thesis a stochastic production priority optimization method, considering various priority concerns for remanufacturing systems is developed. Priority ranking and matching algorithm is developed to determine the priority rule, using thirteen weighting factors. Queueing models are developed to formulate the objective function, a genetic algorithm is then developed to search optimal solution under different business configurations. Result of this research will provide insights to priority assignment mechanism, which in …

Design And Testing Of Orifice Valves For Use In Freight Railcars Hydraulic Suspension System, Awni K. Alshakhshir

Theses and Dissertations - UTB/UTPA

The work presented in this thesis describes the specific steps undertaken to design and test two spool type control valves that will be part of Amsted Rail’s innovative vertical hydraulic damper system. The design challenge lies in the requirement that these spool valves must maintain a linear relation between pressure drop, flow rate, and position, during the extension and retraction cycles of the hydraulic damper. To this end, a series of laboratory experiments were conducted on spools having different land geometries in order to acquire the optimum apertures that will produce the desired performance based on simulation data provided by …

On Nonlinear Response Of Micro And Nano Capacitive Resonators, Martin William Knecht

Theses and Dissertations - UTB/UTPA

The nonlinear response of an electrostatically actuated micro/nano-resonator is investigated. The resonator is parametrically actuated using an electrostatic force with a first order fringe correction. Viscous damping and the Casimir effect are included. The resonator is studied using the Method of Multiple Scales in a direct approach of the problem and then compared numerically using a Reduced Order Model based on the application of a Galerkin procedure. In addition to primary resonance (ω0), parametric resonances are found at half (½ω0), twice (2ω 0), and three-halves ([special characters omitted]ω0) natural frequency. The frequency response is investigated for excitations near primary and …

Electrorheological Fluid Effect Of Polymer Coated Carbon Nanofibers And/Or Fullerenes In Liquid Crystals, Steven S. French

Theses and Dissertations - UTB/UTPA

An ER fluid is a ‘smart’ visco-elastic material, with flow properties influenced by external electric fields, whereby its viscosity increases within the field and returns to its inherent viscosity without the field present. This unique behavior opens many possibilities for new technologies. The optimization of ER fluid performance depends on the chemical and structural compositions of the particles in suspension and the suspension itself. Recent inclusion of nano-particles within ER fluids has shown a relationship to favorable ER trends. Therefore, this research involved nano-laden ER fluid samples of fullerenes (C60) and/or polymer coated carbon nano-fibers as the dispersed phases. These …

An Analytic Hierarchy Process Approach To Assess Health Service Quality, Yan Li

Theses and Dissertations - UTB/UTPA

While improving quality in health care is currently at the forefront of professional, political, and managerial attention, the key dimensions constituting health-care quality have not been fully understood. Also, few valid approaches have been proposed to the measurement of health-care quality. In this research, the Analytic Hierarchy Process (AHP) approach is applied to study the structure of health-care quality and deducted relative importance weights for each of the quality elements. A statistical quality model is derived to assess medical equipment quality which is an important part constituting the general health-care quality. Finally, the application of the AHP model to assess …

Development And Implementation Of An Introduction To Stem Course For Dual-Enrollment Programs, Horacio Vasquez, Arturo Fuentes, Javier Macossay-Torres, Martin W. Knecht, Robert Freeman

Mechanical Engineering Faculty Publications and Presentations

A new Introduction to Science, Technology, Engineering, and Mathematics (STEM) course was developed and taught for the first time during the summer in 2009 to dual enrollment college students at South Texas College (STC). The new Introduction to STEM course was developed in collaboration between STEM Faculty members at the University of Texas-Pan American (UTPA) and STC, with the objective of creating, supporting and strengthening STEM pathways for students in the Dual-Enrollment Engineering Academy (DEEA) and other dual-enrollment or similar programs. The course was offered to two groups of students, at two different campuses in the DEEA program at STC. …

An Information Technology Suitability Index For Mass Customization, Oscar Leonardo Barrenechea

Theses and Dissertations - UTB/UTPA

In today’s manufacturing world, high competitive markets are pushing companies to find better ways to satisfy their customer’s needs using several Mass Customization (MC) approaches. Consequently, new Information Technologies (IT) have taken a very important role in order to manage the increasing amount of data generated from those customers. The purpose of this thesis is to develop an IT suitability index for MC that would help to identify the critical IT factors to be addressed in order to efficiently support MC. A linear programming regression model was utilized to generate index values. Finally, the results of this model could be …

Thermal Analysis Of Railroad Bearings: Effect Of Wheel Heating, Lariza A. Navarro

Theses and Dissertations - UTB/UTPA

Catastrophic bearing failure is a major concern for the railroad industry because it can lead to costly train stoppages. Excessive heat buildup within the bearing is one of the main factors that can warn of impending failure. The work presented in this thesis is motivated by the need to understand the heat transfer paths to the bearing when wheel heating occurs. A series of experiments and finite element analyses were conducted in order to quantify the different heat transfer mechanisms, with emphasis on radiation. The results indicate that the effect of thermal radiation is minimal when the wheel tread temperature …

Gas-Assisted Powder Injection Molding: A Comparison Of Residual Wall Thickness Between Metal Cavity Vs. Sla Cavity And Effect Of Mold Temperature On Residual Wall Thickness, Donghan Kim

Theses and Dissertations - UTB/UTPA

The effects of processing variables on gas penetration depth and Residual Wall Thickness (RWT) in an aluminum (Al) cavity of Gas-Assisted Injection Molding (GAIM) were investigated with Polypropylene (PP) and Stainless Steel Powder Feedstock (SSPF). The selected processing variables were melt temperature, shot size, gas pressure, and gas delay time. By using a Taguchi L9 array, the results were compared with previous work. For PP, there were no significant differences on gas penetration depth. However, the significance of gas delay time was relatively higher in an Al cavity as compared to a Stereolithography (SLA) cavity from previous work with SSPF. …

Thermal Models Of Railroad Wheels And Bearings, Kevin D. Cole, Constantine Tarawneh, Arturo A. Fuentes, Brent Wilson, Linda Navarro

Mechanical Engineering Faculty Publications and Presentations

The rolling surface for railroad wheels can be a heat source that may have an impact on the performance of the wheel bearing. In this study, experimental data from an electrically-heated railroad wheel set is analyzed by constructing thermal models of the wheel set. A steady finite-element model, a steady-analytical model, and a transient lumped-parameter model are discussed. Model parameters are determined from careful comparisons with the experimental data. The lumped-parameter model given here is intended as a simple predictive tool for determining when wheel heating caused by rail operations will have an impact on bearing temperature. The model parameters …

Recovery Of Rectified Signals From Hot-Wire/Film Anemometers Due To Flow Reversal In Oscillating Flows, Yingchen Yang, Douglas L. Jones, Chang Liu

Mechanical Engineering Faculty Publications and Presentations

Hot-wire/film anemometers have been broadly used in experimental studies in fluid mechanics, acoustics, and ocean engineering. Yet, it is well known that hot-wire/film anemometers rectify the signal outputs due to the lack of sensitivity to flow direction. This main drawback, in turn, makes them less useful for diverse fluctuating flow measurements. To solve this issue, a rectification recovery method has been developed based on reconstruction of the Fourier series expansion in conjunction with signal-squaring approach. This signal recovery method was experimentally examined and proven to be successful for both conventional and microfabricated hot-wire/film anemometers. The method was further applied to …