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Articles 1 - 30 of 121
Full-Text Articles in Engineering
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 …
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 …
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 …
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 …
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 …
Improving Queueing Implementation On High Speed Switches, Wendy Hernandez
Improving Queueing Implementation On High Speed Switches, Wendy Hernandez
Theses and Dissertations - UTB/UTPA
In this thesis two different conventional shared memory allocation schemes - Dynamic Threshold (DT) and Threshold-based Filtering (TF) - are evaluated under varied traffic conditions in order to determine the optimal configuration for each tested scenario. The effect that a changing ABL, load, and ratio between buffer size and ports have on the packet loss is observed for buffer sharing schemes DT and TF schemes. This allowed to easily determining the Alpha and Thresholds required by DT and TF schemes respectively to obtain an optimal configuration under each of the different tested scenarios. A new shared memory allocation scheme referred …
Pdms Microchannel Scaffolds For The Isolation Of Individual Axon Regeneration, Bong Kyun Kim
Pdms Microchannel Scaffolds For The Isolation Of Individual Axon Regeneration, Bong Kyun Kim
Theses and Dissertations - UTB/UTPA
Injuries to the peripheral nervous system often result in the loss of sensory or motor function within the effected nerve. Nerve scaffolds provide the mechanical support and topographical cues to axon regeneration such that the gap within the injured nerve is bridged and functional recovery is restored. The Microchannel Peripheral Nerve Scaffold, µPNS, was fabricated from PDMS using micromachining techniques that allow for the unprecedented control of microchannel dimensions and paths and therefore, the production of highly customizable Nerve scaffolds for peripheral nerve regeneration applications. The device was then implanted within the sciatic nerves of a series of Lewis rats, …
Security Integrity Of Ekg Signal Monitoring Under Different Network Attack Conditions, Raghava Teja Pingali
Security Integrity Of Ekg Signal Monitoring Under Different Network Attack Conditions, Raghava Teja Pingali
Theses and Dissertations - UTB/UTPA
This thesis focuses on issues related with monitoring of EKG signals under different network attack traffic conditions. It is becoming common for modern hospitals to monitor real time EKG signals of patients on computers that are usually connected to networks. If the network suffers with attack conditions, it can affect connected computers and alter EKG signals monitoring, hence raising false alarms. Denial of Service attacks may silently affect the real time monitoring of EKG signals. Altering of EKG signals may result in loss of integrity and it can violate CIA triad of security. In this thesis, different attack conditions were …
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 …
Evaluation Of Security Vulnerabilities Of Popular Computer And Server Operating Systems Under Cyber Attacks, Rodolfo Baez Jr.
Evaluation Of Security Vulnerabilities Of Popular Computer And Server Operating Systems Under Cyber Attacks, Rodolfo Baez Jr.
Theses and Dissertations - UTB/UTPA
Nowadays many operating systems are including security features in order to prevent network attacks, and since one of the roles of the OS is to manage the resources as efficient as possible. It is imperative to investigate the protection that is provided. Therefore, the scientific significance of this thesis was to evaluate, what type of built-in defense mechanisms that different OS’s had in place in order to mitigate these network attacks. In this thesis, we considered the security of the following globally deployed computer OS’s: Microsoft’s Windows 7, Apple’s OS X Lion, and Ubuntu 13.10. Furthermore, we also tested four …
Distributed Coordinate Tracking Control Of Multiple Wheeled Mobile Robots, Yifan Xing
Distributed Coordinate Tracking Control Of Multiple Wheeled Mobile Robots, Yifan Xing
Theses and Dissertations - UTB/UTPA
In this thesis, distributed coordinate tracking control of multiple wheeled-mobile robots is studied. Control algorithms are proposed for both kinematic and dynamic models. All vehicle agents share the same mechanical structure. The communication topology is leader-follower topology and the reference signal is generated by the virtual leader. We will introduce two common kinematic models of WMR and control algorithms are proposed for both kinematic models with the aid of graph theory. Since it is more realistic that the control inputs are torques so dynamic extension is studied following by the kinematics. Torque controllers are designed with the aid of backstepping …
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 …
Electrocardiogram Data Collection Under Network Attacks On The Mac Platform, Golshan Famitafreshi
Electrocardiogram Data Collection Under Network Attacks On The Mac Platform, Golshan Famitafreshi
Theses and Dissertations - UTB/UTPA
Increasing heart disease among human beings needs more precise treatment, which requires monitoring of electrocardiogram (ECG). In many cases, real time monitoring of ECG is needed via wireless or wireline networks. Use of network-connected computers for monitoring proposes can raise security issues, which can be created by viruses, worms, or external agents such as DoS attack traffic. Any alteration of this biomedical signal can lead to wrong diagnosis and wrong treatment. Furthermore, in healthcare industry, HIPAA rules require health information to be kept secure by providing confidentiality, integrity, and availability. This thesis investigates how integrity and availability of remotely monitored …
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 …
Applications Of Magnetostrictive Materials In The Real-Time Monitoring Of Vehicle Suspension Components, Raul Estrada
Applications Of Magnetostrictive Materials In The Real-Time Monitoring Of Vehicle Suspension Components, Raul Estrada
Theses and Dissertations - UTB/UTPA
The purpose of this project is to explore applications of magnetostrictive materials for real-time monitoring of railroad suspension components, in particular bearings. Monitoring of such components typically requires the tracking of temperature vibration and load. In addition, real-time, long-term monitoring can be greatly facilitated through the use of wireless, self-powered sensors. Magnetostrictive materials, such as Terfenol-D, have the potential to address both requirements. Currently, piezoelectrics are used for many load and energy harvesting applications; however, they are fragile and are difficult to use for static load measurements. Magnetostrictive metals are tougher, and their property of variable permeability when stressed can …
Characterization Of Gan Thin Films Grown By Rf Magnetron Sputtering For Fabrication Of An Algan/Gan Hemt Biosensor, Rocio Yolanda Garza
Characterization Of Gan Thin Films Grown By Rf Magnetron Sputtering For Fabrication Of An Algan/Gan Hemt Biosensor, Rocio Yolanda Garza
Theses and Dissertations - UTB/UTPA
Radio-Frequency (RF) Magnetron Sputtering has been used to grow GaN thin films for future fabrication of an AlGaN/GaN HEMT biosensor. A GaN target was sputtered at various parameters on silicon and sapphire substrates, at room temperature and at elevated temperature using substrate heating and post deposition annealing treatment. The research conducted investigates the effects of sputtering gas (Argon or Nitrogen gas), RF power (40W or 50W), and pressure (4mT – 30mT) on the structural properties of the thin films. Imaging tools such as the Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), X-ray Diffractometer (XRD), and …
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 …
Seeds Of Solutions™: An Economical & Efficient Approach Towards Power Engineering Education, Eli Alvarez
Seeds Of Solutions™: An Economical & Efficient Approach Towards Power Engineering Education, Eli Alvarez
Theses and Dissertations - UTB/UTPA
Power demands are set to increase over the next twenty years; however, research shows that there may be a shortage of power engineers due to an appreciable percentage of the current power engineer workforce retiring, insufficient enrollment in power engineering programs and a lack of emphasis in power engineering at the university level. This thesis provides supporting research for future power demands, workforce and faculty shortages. Using temporary research in modern learning / teaching styles, student / teacher perceptions, educational trends and regional course offerings, this thesis describes a learning approach towards power engineering education. Designed specifically for universities with …
A 129nw Neural Amplifier And Gm-C Filter For Eeg Using Gm/Id Methodology, Samuel A. Gallegos
A 129nw Neural Amplifier And Gm-C Filter For Eeg Using Gm/Id Methodology, Samuel A. Gallegos
Theses and Dissertations - UTB/UTPA
This Thesis presents a low-power analog front-end amplifier and Gm-C filter for biomedical sensing applications, specifically for Electroencephalogram (EEG) use. The proposed neural amplifier uses a supply voltage of 1.8V, it has a mid-band gain of 40.75dB, and consumes a total current of 71.82nA, for a total dissipated power of 129.276nW. Also presented is the design of a 3rd order Butterworth Low Pass Gm-C Filter which makes use of 14.7nS transconductors; the proposed filter has a pass band suitable for EEG recording use (1-100Hz). The amplifier and filter utilize current sources without bias resistances which provide 56nA and (1.154nA x …
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 Dual Band High Impedance Antenna For Rf Harvest Applications, Andres J. Medina
A Dual Band High Impedance Antenna For Rf Harvest Applications, Andres J. Medina
Theses and Dissertations - UTB/UTPA
A design for a compact dual band very high impedance antenna for RF Harvest applications is presented. The antenna is designed to present a very high input impedance at its feed point at 900 MHz and 1.8 GHz. The design incorporates the folding concept into a customized bowtie antenna to achieve high input impedance. The design methodology and simulations are presented, as well as a comparison of the measured results against the simulation results. A rectifier circuit and dual band matching network are also simulated and presented.
Cluster Computer Simulation Of Buffer Sharing Schemes Under Bursty Traffic Load, Javier Castillo
Cluster Computer Simulation Of Buffer Sharing Schemes Under Bursty Traffic Load, Javier Castillo
Theses and Dissertations - UTB/UTPA
In this thesis it is first analyzed the effect that different Average Burst Length, buffer size or number of ports have on the performance in terms of packet loss ratio on shared memory network switches using Complete Sharing as baseline for the memory allocation scheme. Three different shared memory allocation schemes - Sharing with a Minimum Allocation (SMA), Sharing with Maximum Queue lengths (SMXQ), and Dynamic Threshold (DT) - are then analyzed under varied traffic conditions in order to determine the best configuration for each tested scenario. Having determined the best configuration for each individual scheme under all the tested …