Engineering Commons^™

Development Of Wide Band Gap Semiconductor Materials For Renewable Energy, S.M. Sarif Masud

Open Access Theses & Dissertations

Several new wide band gap semiconductor nanocomposite photocatalytic materials have been synthesized from HTiNbO5 and HNb3O8 for solar energy conversion. As a source of renewable energy, the materials are being tested to produce hydrogen fuel from water via photolysis. The materials have high surface areas, are macroporous, and have flatband potentials suitable for reducing water to create hydrogen. Under visible or ultra violet light, the materials were found to be very promising as hydrogen evolving photocatalysts. As part of the synthesis of the composites, the catalysts also exhibited excellent catalytic activity under UV light for reducing ionic platinum and gold …

Combustion Characteristics Of Alh3 Flame, Sudipa Sarker

Open Access Theses & Dissertations

The combustion characteristics of Al hydride and Al were compared using a combustion chamber. Burning rate, ignition energy and temperature at atmospheric temperature and pressure in carbon dioxide and O2 were tested with a volumetric flow rate that ranged from 10 to 50% in Ar. A spark ignition system was used to ignite the Alane and Aluminum. The combustion rate was measured using a high speed camera. Results showed the combustion rate of Alane and Aluminum decreases with increasing volumetric flow rate of oxidizer. And the combustion rate of Alane is higher than that of Aluminum. Alane needs more ignition …

Scaffold Based In-Vitro Osteodistraction For Bone Tissue Engineering, Cesar Adrian Terrazas

Open Access Theses & Dissertations

Engineering of hard tissues such as bone is a challenge because of the limited ability of the body to heal large defects. Current treatment options, such as employing bone sections from the patient or a deceased donor have been utilized for some time now with various degrees of success. However, these methods still exhibit many limitations such as limited supply and the possibility of transmission of disease.

To address the many limitations of bone grafts, synthetic engineered substitutes have been developed and widely researched for nearly three decades. Generally termed scaffolds, these are matrices that serve the purpose of temporary …

Categorization Of Functional Impairments In Human Locomotion Using The Methods Of The Fusion Of Multiple Sensors And Computational Intelligence, Huiying Yu

Open Access Theses & Dissertations

The main aim of this dissertation work was to develop an intelligent system to monitor, quantify and differentiate variances in human gait with high reliability and efficiency using the fusion of multiple sensor data and the methods of fuzzy inferential logic.

Gait disorders are heterogeneous and produce disabilities that vary substantially from individual to individual. The recognition, quantification and analysis of gait dysfunction is complex and, requires the integration of large amounts of data across multiple domains (kinetic, kinematic and electromyographic). Current systems for gait analysis generally require space and complex imaging equipment, as well as prolonged processing time, rendering …

Development Of A Land Use Regression Model To Predict Nitrogen Dioxide Concentrations, Teresa Sosa

Open Access Theses & Dissertations

Air pollution is a major environmental concern in the El Paso-Juárez region. According to the Ministry of Environment and Natural Resources (Secretaría de Medio Ambiente y Recursos Naturales, SEMARNAT) the city of Juárez is one of the city's in México with the highest atmospheric levels of pollution because of its accelerated and unplanned urban growth. One air pollutant of concern is nitrogen dioxide (NO2) due to its detrimental health effects that have been associated with airway inflammation in healthy people and increased respiratory symptoms in people with asthma. Land use regression modeling is a GIS based approach that seeks to …

An Ab-Initio Study Of The Elastic Properties Of Important Group Iv Diborides At High Temperatures, Manny Gonzales

Open Access Theses & Dissertations

Presented is an ab-initio Molecular Dynamics (MD) study, employing the Density Functional Theory (DFT), of the lattice parameter, thermal expansion coefficients and elastic constants of ZrB₂, TiB₂ and HfB₂ as a function of temperature. The MD trajectories provide the equilibrium lattice parameters at finite temperatures, and the gradient of the energy from these equilibrium solutions is then used to calculate the components of the stiffness tensor. The results for ZrB₂ are shown to agree well with reported experimental results for the lattice parameters and elastic constants as a function of temperature.

A Subthreshold Reconfigurable Architecture For Harsh Environments, Ameet O. Chavan

Open Access Theses & Dissertations

Energy harvesting and functional reconfigurability are necessary features in order to simultaneously achieve longer operating lifetimes and versatility in application for many next generation electronic systems. The presented research incorporates capabilities that not only enable applications to self-power from ambience but also permit change in functionality based on real-time application requirements. Currently, many applications are battery powered with custom hardware, which severely confines the application platform. Moreover, maintenance and upgrades are prohibitively expensive, particularly in the case of remote locations with limited accessibility. For harsh environments like Space or the battlefield, apart from features such as low power and econfigurability, …

Sensitivity Analysis Of The Johnson-Cook Plasticity Model For Hypervelocity Impacts: A Hydro-Code Study, Carlos David Castellanos

Open Access Theses & Dissertations

Computer simulations have been in use for decades in the modeling of hypervelocity impacts and general large deformation problems. Several computer codes have been developed to simulate this type of problems under a variety of geometric configurations and for any number of materials. These codes make use of several constitutive material models to simulate the response of the material under a variety of thermo-mechanical conditions. The Johnson-Cook constitutive model is widely used in the simulation hypervelocity impacts for the simulation of crater formation and even perforation of target structures. This thesis presents the results of a sensitivity study of this …

Synthesis And Manufacture Of Photocrosslinkable Poly(Caprolactone)-Based 3d Scaffolds For Tissue Engineering Applications, Nathan Jonathan Castro

Open Access Theses & Dissertations

It is known that the body can efficiently repair hard tissue (bone) micro fractures by suturing the defect through the deposition of minerals resulting in an area that is stronger post-injury. Larger defects, however, generally cause more trouble since the body is incapable of repairing them. Bone defects can occur as a result of congenital abnormalities, trauma, or disease. Traditional methods for addressing these defects have involved the use of acellular cadaverous bone or autologous bone. Both contain innate problems associated with them; the former method can result in disease transmission, as well as very low integration with the host …

Multidisciplinary Collaborative Model For Complex, Angel Ernesto Delgado

Open Access Theses & Dissertations

Nowadays, most devices with advanced technology require the development of embedded systems with mechanical and electrical components as well as software including more than one discipline. These are devices that are usually complex in terms of composition and functionality and that design must follow a methodology in order to successfully design and launch a device of this nature. Hence, the assembly of a multidisciplinary engineering group is required to carry out such complex devices and develop a fully functional product. The group may also need an expert on the field that can provide guidance and knowledge where needed. This is …

Assessing Annual And Seasonal Spatial Variability Of Ambient Pm10 Using Linear Regression Analysis In A United States-Mexico Urban Sprawl, Mario Ivan Garcia

Open Access Theses & Dissertations

As air quality issues grow progressively in the consciousness of the global community, stakeholders are pressing for epidemiologic studies of air pollution. The effects of chronic exposure to ambient air pollution remain a difficult challenge due to its substantial small-scale spatial variation. Recent approaches to assess intra-urban exposure have employed the use of proximity-based assessment, interpolation methods, emission-meteorological models, dispersions models, and land-use regression (LUR) models.

This thesis assesses the spatial variability of ambient particulate matter (PM10) obtained by five self-governing models for the area of El Paso. Using multiple linear regression analysis five regression-based equations were developed to predict …

Automated Fluid Handling And Leveling System For Multiple Material Stereolithography, Yinko I. Grajeda

Open Access Theses & Dissertations

This work addresses the development of an automated multiple material fluid handling and leveling system for its implementation into a Multiple-Material Stereolithography (MMSL) apparatus. A patent filed by Wicker et al. (US Patent 7,556,490) disclosing a MMSL apparatus served as the basis for the development of this work. The system is designed to operate in a variety of MMSL apparatus configurations. Fluid vats are designed to meet the enclosure constraints, facilitate the interface to the pump and sensor, and support the handling of the fluids. Due to its fluid isolation and bi-directional flow capabilities, a digital drive peristaltic pump is …

Tungsten Oxide (Wo3) Thin Films For H2s Sensor Application In Energy Systems, Satya Kiran Gullapalli

Open Access Theses & Dissertations

The sulfur containing emissions in coal gasification systems to produce energy are devastating and hostile to the requirements of clean, environmental friendly, efficient, and economical energy. Therefore, hydrogen sulfide (H₂S) emissions in coal gasification plants must be monitored, controlled and effectively removed before the syngas is used for energy production. The present research focuses on the development and utilization of tungsten oxide (WO₃) thin films and nanostructures for H₂S application in the coal gasification systems. As a part of that overall goal, the present work was performed with a specific objective of understanding the …

Controlling Features And Processes For Radionuclide Release From Unsaturated Zone Geological Repositories, Lubna K. Hamdan

Open Access Theses & Dissertations

In the long run, nuclear waste packages will fail gradually due to localized and general corrosion and radionuclides will be transported to the accessible environment by ground water.

Two main failure scenarios are expected for the waste packages: Flow-through model and bathtub model; in the flow-through model water flows through the waste container, while in the bathtub model water pools inside the waste package. The Department of Energy, in their performance assessment of the proposed repository at Yucca Mountain, excluded the bathtub model from their analysis and assumed the diffusion and advection to be in the same direction in the …

Selection Process, Modified Impact Testing And Failure Analysis Of An Electron-Beam-Melted Ti-6al-4v 3d Tessellation Based On The Eulerian Path Of The First Stellation Of The Rhombic Dodecahedron Open Unit Cell, Hugo Lopez

Open Access Theses & Dissertations

Ti-6Al-4V lattice block structures manufactured through the electron beam melting (EBM) process are a promising field in design and research due to great advantages that the alloy, the process and the final product offer. Three lattice block structures were manufactured through the electron beam process using an ARCAM A2 machine. The structures were designed using the MATERIALIZE^TM software and were designed around different types of unit cells. Compression testing was performed and one unit cell was selected due to its anisotropic behavior for modified impact testing. The same unit cell was used and it was scaled up to add …

Dynamic Modeling Of Human Gait And Motor, Chad Everett Joshua Macdonald

Open Access Theses & Dissertations

The simulation of gait, impairments and the outcomes of rehabilitation strategies is an important area of research. The ability to study the efficacy of treatment options before applying them to patients has the potential to improve the efficiency of the rehabilitation process. Any such simulations must incorporate some model of the motor learning process to properly anticipate the responses of patients.This dissertation presents initial work on the modeling of gait and the study of motor adaptation with a view towards simulating the motor adaptation process during gait.

Specifically, an inverse dynamic model of gait incorporating sagittal plane limb and torso …

Processing Of Zrb2-Zrc-Zrxsiy Ceramic By Reactive Metal Penetration, Nischel B. Maheswaraiah

Open Access Theses & Dissertations

The processing of ZrB2-ZrC-ZrxSiy composite by reactive metal penetration was investigated as a successor to the ZrB2-SiC composites for hypersonic vehicles application, which cannot be used for extended time at temperatures greater than 1600C due to formation of SiO and CO gases. Zirconium (Zr), zirconium disilicide (ZrSi2), and boron carbide (B4C) were reacted in graphite crucibles for 60, 120, 180, and 240 minutes. Microscopy and x-ray diffraction (XRD) deduced the formation of a heterogeneous microstructure of ZrB2-ZrC-ZrxSiy precipitates surrounded by a solidified Zr-Si melt. Unreacted boron carbide was observed in samples held at 1860C for 60 minutes and 120 minutes, …

A New Green Chemistry Method Based On Plant Extracts To Synthesize Gold Nanoparticles, Milka Odemariz Montes Castillo

Open Access Theses & Dissertations

Extraordinary chemical and physical properties exhibited by nanomaterials, as compared to their bulk counterparts, have made the area of nanotechnology a growing realm in the past three decades. It is the nanoscale size (from 1 to 100 nm) and the morphologies of nanomaterials that provide several properties and applications not possible for the same material in the bulk. Magnetic and optical properties, as well as surface reactivity are highly dependent on the size and morphology of the nanomaterial. Diverse nanomaterials are being widely used in molecular diagnostics as well as in medicine, electronic and optical devices. Among the most studied …

Novel Control Technique For Cadmium Sulfide, Rafael Ordonez

Open Access Theses & Dissertations

Cadmium sulfide Chemical-Bath-Deposition parameters are modified to allow, for the first time, real time monitoring of cadmium ion molarity using a commercially available cadmium ion Ion-Selective-Electreode at 60°C. This modification involves alterations to typical deposition parameters that eliminate the formation of cadmium hydroxide and keep cadmium ion molarity above 10-7M. The new or atypical parameters developed are pH values below 8.9 and lower moralities for all chemicals. In order to have complexation of cadmium ion driven mainly by ammonia, parameters that minimized complexation by other chemicals are found. Cadmium acetate concentration below 2mM and ammonium acetate concentration below 10mM minimize …

Impact Of Moisture Content And Density On Stiffness-Based Acceptance Of Geomaterials, Lourdes Guadalupe Pacheco

Open Access Theses & Dissertations

Modulus-based quality management of compacted layers has been considered by a number of highway agencies. Even though simple in concept, the paradigm shift from density to modulus for quality acceptance has generated some technical and institutional challenges. One of these complications is that for a given density, the modulus can vastly vary depending on the moisture content at the time of compaction and at the time of acceptance. The results of a systematic study carried out to qualify and quantify the impact of compaction moisture content, moisture content at the time of field testing and density on the modulus and …

Microstructure Investigation Of Al-Rich Titanium Aluminum Alloys, David Pham

Open Access Theses & Dissertations

The microstructures of Ti-Al alloys with 70-80 wt% Al were investigated. Aluminum wire (99.999%) and TiH₂ powder (99.7%) were used to produce the sample compositions inside a vertical tube furnace at 1600^oC in an Ar atmosphere. Argon is purified through a dehumidification and deoxidation system. Magnesium perchlorate Mg(ClO₄)₂ acts as a desiccant and titanium sponge pulls oxygen from the Ar in furnaces operating at 800^oC and 750^oC. X-ray diffraction and an optical microscope are used to identify phases and compositions

Theoretical Exploratory Investigation On Reliability Of Advanced Ceramics By Discrete Element Simulation, Ana Laura Quezada Lara

Open Access Theses & Dissertations

The increasing application of silicon nitride in biomedical and other engineering fields has elevated the necessity to understand its reliability. Due to the complexity of producing pure material researchers have been analyzing the behavior of the material with flaws. In this thesis several scenarios are simulated with the support of PFC2D to analyze microcrack propagation depending on the position, quantity and size of the voids to understand the effect each of the cases have on the material. A four point bending test was applied to each case twice recording the loading force. Having two runs allows doing a statistical analysis …

Spectroscopic Study Of The Inhibition Of Calcium Oxalate Calculi By Larrea Tridentata, Luis Alonso Pinales

Open Access Theses & Dissertations

The causes of urolithiasis include such influences as diet, metabolic disorders, and genetic factors which have been documented as sources that aggravate urinary calculi depositions and aggregations, and, implicitly, as causes of urolithiasis. This study endeavors to detail the scientific mechanisms involved in calcium oxalate calculi formation, and, more importantly, their inhibition under growth conditions imposed by the traditional medicinal approach using the herbal extract, Larrea tridentata. The calculi were synthesized without and with Larrea tridentata infusion by employing the single diffusion gel technique. A visible decrease in calcium oxalate crystal growth with increasing amounts of Larrea tridentata herbal infusion …

Fabrication Of Miniature Drug Screening Platform Using Low Cost Bioprinting Technology, Jorge Ivan Rodriguez

Open Access Theses & Dissertations

In the pharmaceutical industry, new chemicals and substances are being tested to find appropriate compounds or mix for treating a specific disease. The demand for screening large compound collections against and increasing number of therapeutic targets has stimulated technology development in the areas of assay automation and miniaturization. Current methods for evaluating the reactions of cells use a volume in the range of microliters. We have developed a new and low-cost deposition method to fabricate miniature drug screening platform that can realistically and inexpensively evaluate biochemical reactions up to 4 substances per trial in a picoliter-scale volume. This paper describes …

The Reactivity Of A Zr-Si Melt With B4c At Ultrahigh Temperatures, Alvaro Vega Sandate

Open Access Theses & Dissertations

Surfaces with exceptional properties are needed for next generation materials. Hypersonic re-entry space vehicles or turbines are subjected to both oxidizing and neutral environments and nose-caps or wings on such vehicles could easily reach operating temperatures of over 2000°C. Ultrahigh temperature ceramics like ZrB2 and HfB2 have melting temperatures of 3245°C and 3380°C respectively. However, these materials need to be protected from oxidation, usually with an oxide layer. Zirconium is more affordable and will be used to study its reaction with B4C and ZrSi2.

Experimentation was conducted by melting Zr slugs into a B4C and ZrSi2 packed bed at 1860°C …

A Risk Analysis Framework For Toll Road Revenue Forecasts, Gabriel Alejandro Valdez Ceniceros

Open Access Theses & Dissertations

In the United States, the shortage for traditional public sector funding sources for a safer and more effective highway infrastructure has made it more increasingly difficult for transportation agencies to keep up with the increasing demand. As a consequence, transportation agencies are considering a number of alternatives to raise funds such as charging tolls or cooperating with the private sector. One of the most important steps when analyzing the feasibility of a toll road is the traffic forecast process. However, the uncertainty of the traffic forecast has become apparent across the U.S. as evident in the common overestimation of traffic …

Resistive Switching Of Tin Dioxide (Sno2) For Memristor Applications, Sergio Fabian Almeida

Open Access Theses & Dissertations

In the last decades new electrical devices have been investigated in order to overcome problems caused by integrated circuit shrinking. Within these devices there is one that has attracted much attention due to its high scalability and simple structure. This device was proposed theoretically by Leon Chua in 1971 who gave it the name of "Memristor". In the recent years thin films structures composed of a metal/oxide/metal (MOM) stack have been linked to this new device, also known as "Resistive switching". There are several applications for the memristor; one of the most important is for resistive random access memory (ReRAM) …

Reclamation Of Salt From Brine Springs, Tejaswini Anand

Open Access Theses & Dissertations

Sodium-chloride brine underlies the shallow subsurface and discharges in springs and streams at numerous locations in Kent and Stonewall Counties in Central Texas. These discharges eventually flow into the Salt Fork of the Brazos River, lowering the quality of this important surface water resource. One potentially cost effective solution for the problem of excess salt loading to the Brazos River by brine spring discharge is to intercept brine groundwater discharges and either treat or evaporate the water. We have examined the energetic of desalinating and evaporating the water from the brine to produce marketable salt products and distilled water. Our …

Component Replacement Analysis For Electricity Distribution Systems Using Evolutionary Algorithms, Vasukumar Chenna

Open Access Theses & Dissertations

The main objective of the electric power grid is to supply economical and reliable electricity to industrial, commercial, household, transportation, and other end-users, including agricultural, educational institutions and hospitals. The power system is a very large and complex network consisting of generation, transmission, and distribution systems. The main focus of the present research is in the area of power distribution systems. Almost all the areas of the power grid uses simpler radial distribution systems to distribute electricity to the end consumer, it is the final and therefore vital link between the consumer and the rest of the power grid. Therefore …

E-Quality: Using Dimensional Index Values Towards Improving Classification Accuracy, Prashanth Devaram

Open Access Theses & Dissertations

E-quality is a process through which inspection of the process and quality of the part produced is done online resulting in the improvement of the process and reduction in the amount of time consumed for the overall process. Automated quality control involves using a methodology to classify the parts based on the dimensions of the features on a part. However, achieving 100% classification accuracy is not an easy task, especially in area of quality control where small differences in dimensions result in part fall into a different category. In this study, a novel approach for modifying the data before being …