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Full-Text Articles in Engineering
Natural Polymer Based Composite Scaffolds For Tissue Engineering Applications, Marcos R. Villarreal
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
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
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
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 …
Investigation Of Slective Laser Melting Of Mecanically Alloyed Metastable Al5fe2 Powder, Hugo Montiel
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 …
Wind Tunnel Flow Characterization Utilizing Turbulence Spheres, David Omar Cano
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 …
Two Dimensional Inverse Dynamics Model Of Human Knee Dynamics During The Moderate Squat Exercise, Ricardo Gomez Jr.
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
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 …
Development Of Metallic And Ceramic Nanotubes Via Magnetron Sputtering, Hillario Cortez
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 Study Of The Selective Laser Alloying Of Elemental Titanium And Boron Powder, Yingbin Hu
A Study Of The Selective Laser Alloying Of Elemental Titanium And Boron Powder, Yingbin Hu
Theses and Dissertations - UTB/UTPA
To better understand the selective laser alloying process of elemental titanium and boron powder, theoretic models are created which takes material related, reaction related, laser related, and other affecting factors into consideration. These models do help interpret the corresponding experiment results. In turn, the related experiment results validate the theoretic models created. In practice, the experiments with two different molar ratios of 1:2 and 4:1 between titanium and boron are carried out. The huge amount of energy released because of reaction between titanium and boron during laser irradiation makes it hard to understand and control the alloying process. At the …
Computational Prediction Of Remodeling Of Collagen Fiber Network In Articular Cartilage Under Dynamic Unconfined Compression, Juan Andres Coello Amado
Computational Prediction Of Remodeling Of Collagen Fiber Network In Articular Cartilage Under Dynamic Unconfined Compression, Juan Andres Coello Amado
Theses and Dissertations - UTB/UTPA
A poroelastic finite element model of a heterogeneous cartilage disk was created based on previous studies and experimental setups; this allows us to study cartilage behavior under dynamic unconfined compression. Previous studies have used a Post Hoc approach, which consist of searching for patterns or relationships between predicted mechanical parameters obtained through computational and experimental results. Our goal in this study is to take the same Post-Hoc approach and identify patterns between predicted mechanical parameters, such as fiber strain or stress, and experimentally-measured collagen fiber distribution (i.e. reorientation of fibers under dynamic unconfined compression). After computational predictions were obtained, it …
Aerodynamic Flow Field Characterization Of Airfoils With And Without Leading Edge Modifications, Oscar Hernandez
Aerodynamic Flow Field Characterization Of Airfoils With And Without Leading Edge Modifications, Oscar Hernandez
Theses and Dissertations - UTB/UTPA
Recently, much focus has been on comprehending the aerodynamic properties associated with the humpback whales pectoral fin. The perturbations found on its leading edge are believed to attribute to the humpbacks maneuverability significantly. These tubercles are assumed to be analogous to strakes on an aircraft, which generate large-scale vortices. More specifically, the vortices prompted by the leading edge increase the momentum exchange within the boundary layer, allowing the flow to remain attached at higher angles of attack, thus delaying stall and in turn increase lift by a passive means of reducing drag. The focus of this investigation is on characterizing …
Proper Orthogonal Decomposition For Incompressible And Compressible Flows, Seyed Milad Rafieinaini
Proper Orthogonal Decomposition For Incompressible And Compressible Flows, Seyed Milad Rafieinaini
Theses and Dissertations - UTB/UTPA
In this project, reduced order modelling technique has been used to investigate incompressible and compressible flows. At first, Proper Orthogonal Decomposition (POD), Singular Value Decomposition (SVD) and Principal Component Analysis (PCA) have been used to analyze pulsed jet flow as an incompressible flow and supersonic impinging jet as a compressible flow. Then, two flows have been investigated from physics point of view and finally the link between physics of flows and modes have been studied. All investigations have been done based on the given data from Particle Image Velocimetry (PIV). These data have been analyzed by using MATLAB®. Finally, the …
Surface Characterization Of 316l Stainless Steel For Biomedical Applications, Lawrence Cano
Surface Characterization Of 316l Stainless Steel For Biomedical Applications, Lawrence Cano
Theses and Dissertations - UTB/UTPA
Stainless steel alloys play an important role in the field of biomaterials due to their exceptional corrosion resistance and biocompatibility. These alloys have the capability to enhance the quality of a human life by altering various structures of human physiology. The close proximity these alloys have with destructive body fluids, ion dissolution is a detrimental cause from the corrosion initiative and may cause unfavorable reactions. A view on developing an improved compatible surface for the human body leads to implementation of different chemical surface modifications used for creating features that must be corrosion resistant and biologically active without changing the …
A Preventive Maintenance Framework In Dairy Production Operations, Maria F. Vargas
A Preventive Maintenance Framework In Dairy Production Operations, Maria F. Vargas
Theses and Dissertations - UTB/UTPA
Dairy operations suffer frequent stops. Product shrinkage is a consequence of downtime, which includes losses of packaging material, scraped finish product and capacity. This work proposes a troubleshooting methodology to identify causes of downtime, estimation of waste cost, and minimization of operation disruptions by applying a combination of a cost function to assess waste, and performance measurements. The drinkable yogurt process is evaluated to find the principal areas for wasted bottles and yogurt. In order to make a decision about which of those sources to address, a General Cost Function is used to estimate waste cost which include measurements that …
Low Speed Water Tunnel Testing, John J. Taylor
Low Speed Water Tunnel Testing, John J. Taylor
Theses and Dissertations - UTB/UTPA
Water tunnels are ideal for studying flow patterns for hydrodynamic effects. The functionality of the University of Texas-Pan American water tunnel was limited by not being able to measure forces and moments corresponding to flow patterns. This report delivers an experimental set-up for calibrating the velocity of the water and development of a load measuring system to relate simultaneous visual investigation. An in-depth parts breakdown of the SST-model pump and the dye injection system for flow visualization will be reviewed. Few balances have been made for water tunnels due to small and difficult to measure flow-induced forces. The motive is …
Effects Of Vapor Grown Carbon Nanofibers On Electrical And Mechanical Properties Of A Thermoplastic Elastomer, Daniel Thomas Basaldua
Effects Of Vapor Grown Carbon Nanofibers On Electrical And Mechanical Properties Of A Thermoplastic Elastomer, Daniel Thomas Basaldua
Theses and Dissertations - UTB/UTPA
Carbon nanofiber (CNF) reinforced composites are exceptional materials that exhibit superior properties compared to conventional composites. This paper presents the development of a vapor grown carbon nanofiber (VGCNF) thermoplastic polyurethane (TPU) composite by a melt mixing process. Dispersion and distribution of CNFs inside the TPU matrix were examined through scanning electron microscopy to determine homogeneity. The composite material underwent durometer, thermal gravimetric analysis, differential scanning calorimetry, heat transfer, hysteresis, dynamic modulus, creep, tensile, abrasion, and electrical conductivity testing to characterize its properties and predict behavior. The motivation for this research is to develop an elastomer pad that is an electrically …
A Decision Support Model For Process Planning In Remanufacturing Using Fuzzy Set Theory And Genetic Algorithm, Juan C. Martinez
A Decision Support Model For Process Planning In Remanufacturing Using Fuzzy Set Theory And Genetic Algorithm, Juan C. Martinez
Theses and Dissertations - UTB/UTPA
The environmental awareness and resources preservation has boosted the use of remanufacturing processes. Many important studies have been made in this area, but there are still pitfalls and opportunities that have not been explored yet. Specifically, the cleaning processes play a critical role in remanufacturing. It is among the top of most costly processes and it plays a key step in remanufacturing because delivers a free of contaminant product ready for reprocessing. Understanding and selecting the best processes to meet the need and goals of remanufacturers are important for effective and efficient remanufacturing. Due to variables and high uncertainty associated …
A Study Comparing The Pedagogical Effectiveness Of Virtual Worlds And Of Traditional Training Methods, Benjamin Peters
A Study Comparing The Pedagogical Effectiveness Of Virtual Worlds And Of Traditional Training Methods, Benjamin Peters
Theses and Dissertations - UTB/UTPA
This experiment tests whether a virtual world is a more suitable alternative to classical paper and pen case studies for teaching people how to disarm improvised explosive devices (IED). Following preliminary training, the subjects are separated into a group of 32 and one of 33. The odd-numbered subjects receive case studies while the even-numbered subjects receive training in the virtual world, Second Life. After their training, each subject is put into a simulated test where they attempt to properly disarm a mock IED attached to a victim played by an actor/actress. The results of the experiment show no significant difference …
A Decision Support System To Measure Product Suitability For Additive Manufacturing Processes, Cynthia De Vasconcellos Barros
A Decision Support System To Measure Product Suitability For Additive Manufacturing Processes, Cynthia De Vasconcellos Barros
Theses and Dissertations - UTB/UTPA
Additive Manufacturing (AM) technologies started arising around 1980’s and they are currently considered to be the third industrial revolution. With improvements in computers, materials, and automated machines, manufacturers across several types of industries are becoming more familiar with AM processes, and it has become more common to see products that are being fabricated by using this new technology. However, there are still questions regarding when it is suitable to use Additive Manufacturing or conventional manufacturing processes depending on different factors. The purpose of this thesis is to create a Decision Support System (DSS) that will help users measure product suitability …
Nanostructured Transition Metal Oxides For Energy Storage And Conversion, Qiang Li
Nanostructured Transition Metal Oxides For Energy Storage And Conversion, Qiang Li
Theses and Dissertations - UTB/UTPA
The conventional film configuration of electrochemical electrodes hardly fulfills the high energy and efficiency requirements because heavy electroactive material deposition restricts ion diffusion path, and lowers power density and fault tolerance. In this thesis, I demonstrate that novel nanoarchitectured transition metal oxides (TMOs), e.g. MnO2, V2O5, and ZnO, and their relevant nanocomposites were designed, fabricated and assembled into devices to deliver superior electrochemical performances such as high energy and power densities, and rate capacity. These improvements could be attributed to the significant enhancement of surface area, shortened ion diffusion distances and facile penetration of electrolyte solution into open structures of …
Corrosion Assessment And Enhanced Biocompatibility Analysis Of Biodegradable Magnesium-Based Alloys, Luis Enrique Pompa
Corrosion Assessment And Enhanced Biocompatibility Analysis Of Biodegradable Magnesium-Based Alloys, Luis Enrique Pompa
Theses and Dissertations - UTB/UTPA
Magnesium alloys have raised immense interest to many researchers because of its evolution as a new third generation material. Due to their biocompatibility, density, and mechanical properties, magnesium alloys are frequently reported as prospective biodegradable implant materials. Moreover, magnesium based alloys experience a natural phenomena to biodegrade in aqueous solutions due to its corrosive activity, which is excellent for orthopedic and cardiovascular applications. However, major concerns with such alloys are fast and non-uniform corrosion degradation. Controlling the degradation rate in the physiological environment determines the success of an implant. In this investigation, three grades of magnesium alloys: AZ31B, AZ91E and …
Manufacture And Characterization Of Silver And Copper Nanostructures Produced Via Forcespun Nylon 6 Nanofibers, Wenqian Zhao
Manufacture And Characterization Of Silver And Copper Nanostructures Produced Via Forcespun Nylon 6 Nanofibers, Wenqian Zhao
Theses and Dissertations - UTB/UTPA
Nylon 6 nanofibers were produced using the Forcespinning® method and were deposited with silver or copper thin films using the high vacuum thermal evaporation technique for surface functionalization of nanostructures. The changes in surface composition, morphology and surface energy of native and metallic coated Nylon 6 nanofibers were examined. Their antibacterial properties of native, silver or copper coated Nylon 6 nanofibers were tested. Furthermore, the Nylon 6 nanofibers were used as templates in order to obtain silver or copper nanotubes where the polymer was removed after high temperature calcination. The metallic coated Nylon 6 nanofibers and metallic nanotubes morphology and …
Influence Of Surface Modification On Corrosion And Biocompatibility Of Titanium Alloys, Zia Ur Rahman
Influence Of Surface Modification On Corrosion And Biocompatibility Of Titanium Alloys, Zia Ur Rahman
Theses and Dissertations - UTB/UTPA
Titanium alloys enhance the quality and longevity of human life by replacing or treating various parts of the body. However, the aggressive body fluids lead to corrosion and metal ions dissolution. These ions leach to the adjacent tissues and causes adverse reactions. Surface modifications improve corrosion resistance and biological activity. In this investigation, electropolishing, magnetoelectropolishing, titanium coating and hydroxyapatite coating were carried out on commercially pure titanium (CPTi), Ti6Al4V and Ti6Al4V-ELI (Extra Low Interstitials). These surface modifications are known to affect surface chemistry, morphology, wettability, corrosion resistance and biocompatibility of these materials. In vitro cyclic potentiodynamic polarization tests were conducted …
Thermal Analysis Of Carbon Nanofiber Reinforced Isotactic Polypropylene, Anna Alicia Hernandez
Thermal Analysis Of Carbon Nanofiber Reinforced Isotactic Polypropylene, Anna Alicia Hernandez
Theses and Dissertations - UTB/UTPA
Isotactic Polypropylene (IPP) is a commonly known thermoplastic that has unique properties include being light weight, high performance, impact strength, tensile strength, elongation, and high temperature properties. The use of vapor grown carbon nanofiber (VGCNF) reinforcements on polypropylene has shown to produce high specific modulus, strength, electrical and thermal properties on specimens. Thermogravimetric (TGA) investigations on the thermal degradation of isotactic polypropylene – vapor grown carbon nanofibers composites in nitrogen were reported. The mass evolution as a function of temperature is a single sigmoid for both polypropylene and polypropylene loaded with VGCNF. The inflection temperature of these sigmoids increases as …
Mass Production Of Β-Silicon Carbide Nanofibers By The Novel Method Of Forcespinning, Alfonso Salinas
Mass Production Of Β-Silicon Carbide Nanofibers By The Novel Method Of Forcespinning, Alfonso Salinas
Theses and Dissertations - UTB/UTPA
Non-oxide Ceramics such as silicon carbide have very unique properties, for example high toughness, thermal stability, wear resistant, and thermal shock resistance these properties make these ceramic fibers excellent for high temperature applications. Here we present the development of Silicon Carbide nanofibers utilizing a Polystyrene/Polycarbomethylsilane solution as the precursor materials. The Forcespinning ® was performed under a controlled nitrogen environment to prevent fiber oxidation. Characterization was conducted using scanning electron microscopy, x-ray diffraction, and thermogravimetric analysis. The results show successful formation of high yield, long continuous bead-free nanofibers with diameters ranging from 280nm to 2 micron depending on the selected …
Design And Optimization Of A Railroad Conductive Suspension Element Pad Composed Of Thermoplastic Polyurethane And Carbon Black, Ruben Suarez Jr.
Design And Optimization Of A Railroad Conductive Suspension Element Pad Composed Of Thermoplastic Polyurethane And Carbon Black, Ruben Suarez Jr.
Theses and Dissertations - UTB/UTPA
The AdapterPlus™ Pad, made from thermoplastic polyurethane (TPU), is used to enhance steering and prevent metal-to-metal contact between the railcar side frame and the bearing adapter. Although the AdapterPlus™ Pad acts as a pedestal liner in the suspension assembly, it must allow electric current to flow from the rail, through the bearing adapter wall to the side frame in order to activate a solenoid air valve that releases cargo gates. Currently, the pad uses copper inserts that allow current through. Because the Adapter Plus™ Pad is subject to large dynamic loads, the copper inserts permanently deform losing contact and cutting …
Development Of Hydrodynamic Channel Routing Model Of The Lower Rio Grande River To Assist In Flood And Stormwater Management, Andrew W. Leeper
Development Of Hydrodynamic Channel Routing Model Of The Lower Rio Grande River To Assist In Flood And Stormwater Management, Andrew W. Leeper
Theses and Dissertations - UTB/UTPA
Flooding and stormwater management of the Lower Rio Grande River (LRG) has become a major issue throughout the years with local entities along the river. The purpose of this study is to develop a hydrodynamic channel routing model to predict water surface elevation changes due to flooding. The study area consists of the LRG from Los Ebanos to Brownsville, Texas. This hydrodynamic model displays the hydraulics of the water flow through the LRG and determines where potential flood hazards exist. To verify the accuracy of the model a series of calculated output hydrographs were established at the Progreso Bridge and …
Nonlinear Dynamics Of Carbon Nanotubes Under Soft Alternating Current Actuation, Le Luo
Nonlinear Dynamics Of Carbon Nanotubes Under Soft Alternating Current Actuation, Le Luo
Theses and Dissertations - UTB/UTPA
This thesis work deals with electrostatically actuated Carbon Nanotubes (CNTs) cantilevers. Four forces are acting on the CNTs cantilever, namely damping, elastic, electrostatic and van der Waals forces. The van der Waals force is significant for values of 50 nm or lower of the gap between the CNTs and the ground substrate. As both electrostatic and van der Waals forces are nonlinear, and the CNTs electrostatic actuation is given by alternating current (AC) voltage, the CNTs undergo nonlinear parametric dynamics. The Method of Multiple Scales (MMS) and Reduced Order Model (ROM) are employed to investigate the system under soft excitation …
Calibration And Optimization Of A Load Sensor Embedded In A Railroad Bearing Adapter, Lorenzo Saenz Iv
Calibration And Optimization Of A Load Sensor Embedded In A Railroad Bearing Adapter, Lorenzo Saenz Iv
Theses and Dissertations - UTB/UTPA
Freight railcars rely heavily on weigh bridges and stations to determine cargo load. As a consequence, all load measurements are limited to certain locations and specified prices. To this end, this study presents work performed to develop one of the first economical, reliable sensors for keeping track of both dynamic and static loads on a freight railcar. Preliminary testing provided a strain-gauge based sensor that delivered load information in the laboratory environment. Federal Railroad Association (FRA) protocol testing was met and consistent results were obtained from the sensing device. The latter allowed for an optimized sensor that could potentially deliver …