Engineering Commons^™

Microstructure And Mechanical Properties Of Sputter-Deposited Nanocrystalline W1-Ymoyo3 Thin Films, Gabriel Lopez

Open Access Theses & Dissertations

Currently, there is a wide-spread interest in the design and development of indium (In) free transparent conductive oxides (TCOs) for utilization in photovoltaics and optoelectronics. Tungsten oxide (WO3)-based materials are being explored for their utilization in solar cells, photo-electrochemical cells (PECs), electrochromic (EC) "smart windows," information displays, variable reflectance mirrors, and photo-detector materials. Designing ternary compounds or composite/hybrid structures coupled with tailoring the nano-architectures of WO3-based materials has been considered to be attractive develop potential candidates with enhanced performance. In this context, in this Thesis work, an attempt is made to prepare W-Mo-O nanocomposite films, which can be considered as …

Supplier Evaluation And Selection In Automotive Industry Using Conditional Probability, Anand Raj

Open Access Theses & Dissertations

Supplier evaluation and selection is one very important factor for the success of a company. There are many supplier evaluation and selection tools and software available in the market. But this approach is different from the others. Here a comprehensive list of suppliers selection criteria is selected and they are divided in 3 supplier selection group. This group of criteria is done based on the relationship among them. All the suppliers are evaluated based on these 3 supplier selection group. The supplier with the highest value is selected. The probability associated with that factor is assigned and at the end …

Influence Of Overlay Thickness On Interface Bonding, Aliasghar Dormohammadi

Open Access Theses & Dissertations

Overlaying is an efficient and proven pavement preservation approach for flexible pavements. The overlay thickness varies from 1 in. to 4 in. depending on the conditions of the existing pavement, financial resources, etc. In the recent decade, financial constraints in conjunction with the push for pavement preservation, the overlay thickness is being reduced to less than an in. The ultra-thin overlay is a new cost-effective method that can be used to preserve functional pavement problems and provide satisfactory ride quality. Although studies have been conducted to evaluate pavement systems using numerical simulation, the research in the area of evaluating existing …

Molecular Dynamics Studies Of Crystal Growth Phenomena In Cdte Based Heterostructures, Rodolfo Aguirre Ii

Open Access Theses & Dissertations

Cadmium telluride (CdTe) is a material used to make solar cells because it absorbs the sunlight very efficiently and converts it into electricity. However, CdTe modules suffer from degradation of 1% over a period of 1 year. Improvements on the efficiency and stability can be achieved by designing better materials at the atomic scale. Experimental techniques to study materials at the atomic scale, such as Atomic Probe Tomography (APT) and Transmission Electron Microscope (TEM) are expensive and time consuming. On the other hand, Molecular Dynamics (MD) offers an inexpensive and fast computer simulation technique to study the growth evolution of …

Development And Verification Of A Lab-Scale Green Propellant Hybrid Motor System, Shyamal Patel

Open Access Theses & Dissertations

Hybrid rocket propulsion offers the potential to combine advantages of both solid and liquid propellant systems, but low regression rates hinder their practicality. The suggested use of hydroxylammonium nitrate (HAN) based propellants in hybrids offers the potential for developing high impulse motors with low development and production costs. In this paper, I present the development of a small-scale system used to measure the regression rate of a hybrid motor. The system can accommodate fuel grains 5 cm long with an outer diameter of 6 cm and can implement the various decomposition gases needed for HAN. The motor firings of hydroxyl …

Development And Integration Of The Janus Robotic Lander: A Liquid Oxygen - Liquid Methane Propulsion System Testbed, Raul Ponce

Open Access Theses & Dissertations

Initiatives have emerged with the goal of sending humans to other places in our solar system. New technologies are being developed that will allow for more efficient space systems to transport future astronauts. One of those technologies is the implementation of propulsion systems that use liquid oxygen and liquid methane (LO2-LCH4) as propellants.

The benefits of a LO2-LCH4 propulsion system are plenty. One of the main advantages is the possibility of manufacturing the propellants at the destination body. A space vehicle which relies solely on liquid oxygen and liquid methane for its main propulsion and reaction control engines is necessary …

Design Of A Feed System For An Oxy-Methane High Pressure Combustor, Jorge Arturo Rosero

Open Access Theses & Dissertations

With growing concern over the effects that fossil fuels are having on the environment and the expected increases in energy demand in the coming decades, it is becoming increasingly more important to find cleaner and more efficient ways to generate energy. Natural gas has grown in popularity in the last decade thanks to a drastic drop in price and its lower carbon emissions compared to coal. With enough natural gas reserves in the United States to last over 90 years, natural gas is expected to be a large part of the future energy outlook.

Increased demand from growing populations also …

Evaluation Of Mechanical Parameters Of Contaminated Road Base And Railway Ballast, Prajwol Tamrakar

Open Access Theses & Dissertations

This Dissertation comprises two topics in the area of transportation geotechnics that focus on the evaluation of stiffness parameters of contaminated road base and railway ballast. The abstracts of these two studies are provided in the following two paragraphs.

The performance of a flexible pavement depends on the mechanical characteristics of its unbound granular base layer. The mechanical characteristics such as stiffness and deformation resistance depend on many factors such as the material gradation, fines content, moisture content, physical properties of coarse aggregate and more. The base materials are often contaminated by the excessive fines that is caused by improper …

Process-Structure-Property Relationship In Magnesium-Based Biodegradable Alloy For Biomedical Applications, Pramanshu Trivedi

Open Access Theses & Dissertations

Magnesium alloys are considered to be the next generation of biomaterials because of their ability to degrade in the physiological environment. We elucidate here the impact of multiaxial forging of Mg-2Zn-2Gd alloy on grain refinement to sub-micron regime and relate the structure to mechanical properties and biological functionality. As-cast and annealed samples were multiaxial forged (MAF) for a total number of two passes with a true strain of ~2/pass. Considering that the microstructure governs the biological response of materials, we studied the constituents of the microstructure in conjunction with the mechanical behavior. The antimicrobial behavior in a Mg-2Zn-2Gd alloy with …

Improving The Regression Rate Of An Htpb Hybrid Rocket Fuel Grain, Travis Wesley Belcher

Open Access Theses & Dissertations

Hybrid rockets are the combination of liquid and solid propellant systems. The University of Texas at El Paso (UTEP) is currently researching combining Hydroxyl-Terminated Polybutadiene (HTPB) and Hydroxyl Ammonium Nitrate (HAN) in preparation for conducting testing using an Air Force developed monopropellant known as AF-M315E as an oxidizer. A new system was developed to conduct this testing based in the Goddard Laboratory at UTEP. This system was subjected to a series of tests to ascertain its performance characteristics, which are detailed in this Thesis.

Characterization Of Electrically Conductive Inks In Simulated Space Environment, Kazi Md Masum Billah

Open Access Theses & Dissertations

Increasing numbers of satellite missions necessitate a standalone power supply with self-recovery capabilities in case of failure in the space environment. A self-repairing kit was developed with the capabilities to repair the damaged solar array by dispensing conductive inks. Dispensing of conductive materials using direct writing technology to the space environment not only repairs damaged electronic components but also demonstrates the possibilities of manufacturing in outer space. For earth application, properties of direct writing inks have been evolved. In space application, direct writing inks or conductive inks have some issues such as outgassing, vapor pressure, curing etc.Therefore, having the properties …

Electronic Structure Studies On Transition Metal Containing Endohedral Fullerenes, Carbon Onions And Zinc Sulfide Cages, Shusil Bhusal

Open Access Theses & Dissertations

We present the most stable structures for VXSc3-XN@C2n (where X=1-3 and 2n=70, 76, 78 and 80) using a systematic procedure that involves all possible isomers of the host fullerene cages. Subsequently, a detailed investigation of structural and electronic properties of the lowest energy isomers is performed using density functional theory in combination with large polarized Gaussian basis sets. The search procedure developed involved structural optimizations of thousands of fullerenes and correctly identifies the experimentally observed VSc2N@C80 and V2ScN@C80 isomer as the most stable structures. The structural analysis shows that a few V-doped endohedral fullerenes do not follow the isolated pentagon …

Theoretical Acoustic Absorber Design Approach For Lox/Lch4 Pintle Injector Rocket Engines, Jonathan Candelaria

Open Access Theses & Dissertations

Liquid rocket engines, or LREs, have served a key role in space exploration efforts. One current effort involves the utilization of liquid oxygen (LOX) and liquid methane (LCH4) LREs to explore Mars with in-situ resource utilization for propellant production. This on-site production of propellant will allow for greater payload allocation instead of fuel to travel to the Mars surface, and refueling of propellants to travel back to Earth. More useable mass yields a greater benefit to cost ratio. The University of Texas at El Paso's (UTEP) Center for Space Exploration and Technology Research Center (cSETR) aims to further advance these …

Organic-Inorganic Graphite And Transition Metal Dichalcogenide Based Composites For 3d Printing, Jorge Alfredo Catalan Gonzalez

Open Access Theses & Dissertations

This project was multipronged to help fuse together topics of additive manufacturing and two-dimensional (2D) layered materials, and studying the mechanical and electrical properties of the composites produced. The composites are made from the thermoplastic polymer acting as a matrix and the graphite and 2D transition metal dichalcogenides (TMDs) serving as the filler or reinforcement. Different concentrations of TMD's were added to the matrix to study the effect of composition on the mechanical and electrical properties. To shed insights into the mechanical properties, test coupons were produced as "dog bone" structures for tensile testing using the ASTM D638 type 5 …

Mechanically Activated Magnesiothermic Combustion Synthesis Of Zirconium And Hafnium Diborides, Sergio Cordova

Open Access Theses & Dissertations

Magnetohydrodynamic (MHD) generation of electric power has the potential to increase the thermal efficiency of fossil-fuel burning power plants. Electrode materials in MHD generators must possess a high melting point, high electrical and thermal conductivities, chemical stability, and resistance to thermal shock, oxidation, and plasma sparks/arcs. Ultra-high temperature ceramics based on diborides of zirconium and hafnium (ZrB2 and HfB2) are promising materials for this application. Self-propagating high-temperature synThesis (SHS) is an attractive method for their large-scale fabrication, but SHS of ZrB2 and HfB2 from elemental Zr, Hf, and B is not economically viable because of the high cost of the …

Design And Development Of A High Pressure Oxy-Methane Combustor, Jaime Cruz Gurrola

Open Access Theses & Dissertations

Most of the greenhouse gas emissions in the US comes from the electricity sector by burning fossil fuels. Environmental regulations have been implemented to reduce the amount of CO2 emitted into the atmosphere. One method to reduce the greenhouse gas emissions to the atmosphere is oxy-fuel technology. One of the biggest challenges of oxy-fuel combustion is thermal management due to the elevated temperature combustion. The main objective of this Thesis was to design and develop a steady-state high pressure combustor that uses oxygen and methane with a thermal power input of 500 kW and operation at 20 bar pressure. An …

Advances In Chemical Vapor Deposition Growth Of Molybdenum Disulfide For Photodetectors And Flexible Electronics, Carlos Francisco De Anda Orea

Open Access Theses & Dissertations

The conversion of light into electrical signals is at the basis of technologies that affect our daily lives. Applications, including video imaging, optical communications, biomedical imaging, security, night-vision, gas sensing and motion detection have reached a high level of maturity due to the development of high-performance materials, large-scale production, and integration technologies. Currently conventional photodetectors made of Silicon (Si) or III-V compounds are about to reach their maximum efficiency, and every time it is harder to get a noticeable improvement in performance of sensors based on these materials, not to mention the complicated fabrication methods to achieve just a few …

Methods For Producing Graphene From Petroleum By-Products, Eva M. Deemer

Open Access Theses & Dissertations

N/A

First Level Design And System Design Of Janus Liquid Oxygen-Liquid Methane Lander, Jahir Fernandez

Open Access Theses & Dissertations

Taking humans to space has always been a fantastic feat, but taking humans to another planet in our solar system is the new goal. Technology has come a long way and with that, so has our knowledge of space and what can be done with current technology to accomplish our goal. These technologies allow for a more efficient space system to transport future astronauts using liquid oxygen and liquid methane (LO2-LCH4) as propellants. This combination of propellants, LO2-LCH4, brings a variety of benefits. One of the main advantages is that they can be recovered or created from local resources, using …

Development Of Post-Pareto Optimality Methods For Multiple Objective Optimization, Juan Valentin Fernandez

Open Access Theses & Dissertations

In the past years, multiple objective optimization has been considered, as an important research area since in many real life problems there exists multiple criteria that need to be optimized simultaneously. The use of evolutionary algorithms or metaheuristic methods as solution methodologies lead to a large number of Pareto solutions rather than a single unique optimum. This Pareto-optimal set most of the time tends to be very large and the decision maker now faces the challenge of reducing its size to analyze a feasible number of solutions, thus deciding the best possible solution. In this work, two methods will be …

Behavior Of Sandwich Composite Cores Under Extreme Conditions, Carlos Daniel Garcia Perez

Open Access Theses & Dissertations

The use of composite structures for diverse applications have become of great interest for scientists and engineers thanks to the advantages that they may offer in comparison to conventional materials. In the case of sandwich composite structures, its mechanical properties can be tailored according to the necessities through the correct selection of a core and facesheets. In combination, this "new" material will have superior properties compared to traditional materials such as steel and aluminum. For arctic exploration, a core with low moisture absorption, low density, and resistance to extreme, low temperatures is desirable for this type of application. This Thesis …

Test Methods For The Fracture And Fatigue Crack Growth Behavior Of Hot Mix Asphalts, Eduardo Garcia

Open Access Theses & Dissertations

The service life and mechanical properties of bituminous mixtures are greatly affected by distress problems such as fracture, thermal cracking, and fatigue cracking of the asphalt layers. The fracture and fatigue crack growth (FCG) behavior of bituminous mixtures are difficult to quantify due to material-, test-, and equipment-related uncertainties. The goal of this study is to introduce a systematic fracture and fatigue crack growth testing approach for hot mix asphalts (HMAs). The objective is to experimentally evaluate the fracture resistance and fracture toughness behavior of a dense-graded HMA material at different temperatures and varying thicknesses. The effect of thickness on …

Studies On Woven Carbon/Vinyl Ester Composites: Environmental Effects, Joining And Hybridization, Ricardo Garcia

Open Access Theses & Dissertations

The incessant demand for fiber reinforced polymer composites, or FRPCs, in industrial applications which desire materials that possess high strength-to-weight ratios, generates a theory-to-practice void which must be filled with scientific research. In this Thesis, woven carbon/vinyl ester composites are studied under a wide spectrum of settings and conditions. The adverse effects of sea water environment and arctic temperatures on such mentioned composites are explored in the form of moisture uptake, impact on flexural modulus, strength and structural damage. It was found that sea water saturation in general degrades the flexural strength up to 19.45%, and arctic exposure and combined …

Asset Management Support Tools To Assist Agencies In The Development Of Guardrail Preservation Programs, Sandra N. Gutierrez

Open Access Theses & Dissertations

The purpose of this Thesis is to develop a Guardrail Asset Management Framework and a Condition-Based Model to assist agencies in the development of guardrail preservation programs. Both of the guardrail asset management tools can be incorporated into an existing asset management program to assist agencies in utilizing guardrail inventory to forecast key asset management parameters such as the guardrail condition, funds necessary for maintenance and repair, backlogged funding, guardrail system value, and the guardrail sustainability ratio. Each of these parameters is described and determined for a case study involving six scenarios modeling funding and maintenance constraints that can arise …

Integrating Manufacturing Geometric Imperfections In The Inelastic Behavior Modeling Of Joints Used In Three-Dimensional Structures, Alfonso Andres Garcia

Open Access Theses & Dissertations

Three-dimensional structures follow design practices on the common assumption that joints are either rigid, or pinned. However, the non-linear behavior of engagement of the joints is required to be incorporated into the analysis. This research is intended to incorporate manufacturing geometric imperfections into the mechanical analysis of reticulated space structures jointing systems. Imperfect jointing systems deviate from the as-designed models in such a way that the location of the connecting surfaces does not follow the designed interaction path between the component elements. However, current structural analysis methodologies do not consider manufacturing geometric imperfections and often fail to consider the stresses …

On Demand 3d Printed Hybrid Scaffolds For Tissue Engineering Applications, Ivan D. Hernandez

Open Access Theses & Dissertations

A composite 3D printed polymer scaffold with inbuilt porosity and filled with a hydrogel can provide an ideal support system for cell growth, proliferation, and vascularization. Therefore, a hybrid system of 3D printed polycaprolactone (PCL) scaffold and a hydroxyapatite-based hydrogel was developed for application in the reconstruction of bone defects, which are inherently difficult to repair without any guided therapies. In the present study, a 3D printed gyroid structure of PCL allowed the loading of a higher amount of hydrogel as compared to conventionally used 3D printed mesh structure of the same volume and strut thickness. The hydrogel was composed …

Ac Susceptibility And Epr Investigations Of Superspin Dynamics In Manganese Oxide Nanoparticles, Mahesh Koirala

Open Access Theses & Dissertations

We have investigated the superspin dynamics of 5 nm and 10 nm mixed state Mn3O4 nanoparticles utilizing ac-susceptibility and electron paramagnetic resonance measurements. The out of phase component of the ac-susceptibility measurements show a magnetic anomaly below (T

Cost-Effective Recovery Of Concentrated Cooling Tower Blowdown Using The Cerro Process, Lindsey Nicole Larson

Open Access Theses & Dissertations

The Concentrate Enhanced Recovery Reverse Osmosis (CERRO) process is a seawater-RO unit that can cost-effectively achieve extremely high recoveries from water high in silica, carbonate and sulfate concentrations. This relatively new technology takes advantage of the induction time of potential foulants to recover more water than what is normally achievable with a conventional desalination system. The scope of the project was to evaluate the efficiency of the CERRO process as a pilot study using cooling tower blowdown which varied in water quality parameters daily. It was found that the CERRO pilot could successfully achieve 85% recovery, and the main limitation …

Quantification Of The Impact Of Asphalt Pavement Conditions On Gas Emissions, Oscar Daniel Gonzalez Calvo

Open Access Theses & Dissertations

This research develops a methodology to quantify the impact of asphalt pavement conditions on vehicular gas emissions based on statistical analysis to correlate the relationship between asphalt pavement roughness and gas emissions. ANOVA (Analysis of Variance) hypoThesis tests were used to compare the factors affecting the results. The roughness was measured with the International Roughness Index (IRI) using a profilometer provided by TxDOT and the gas emissions were measured with a Portable Emission Measurement System (PEMS).

This research also presents the savings obtained in gas emissions using different maintenance and rehabilitation strategies established by TxDOT (Preventive Maintenance, Light Rehabilitation, Medium …

Design Of A 2000 Lbf Lox/Lch4 Throttleable Rocket Engine For A Vertical Lander, Israel Lopez

Open Access Theses & Dissertations

Liquid oxygen (LOX) and liquid methane (LCH4) has been recognized as an attractive rocket propellant combination because of its in-situ resource utilization (ISRU) capabilities, namely in Mars. ISRU would allow launch vehicles to carry greater payloads and promote missions to Mars. This has led to an increasing interest to develop spacecraft technologies that employ this propellant combination.

The UTEP Center for Space Exploration and Technology Research (cSETR) has focused part of its research efforts to developing LOX/LCH4 systems. One of those projects includes the development of a vertical takeoff and landing vehicle called JANUS. This vehicle will employ a LOX/LCH4 …