Engineering Commons^™

High Temperature Oxidation Characteristics Of Nb-10w-Xcr Alloys, Maria Del Pilar Moricca

Open Access Theses & Dissertations

The use of refractory metals in high temperature applications has been attractive for several years. Systems based on niobium represent a potential new generation of refractory materials systems because of their low density, high melting points, and strength at elevated temperatures. Despite these desirable characteristics, the widespread use of niobium-based alloys is limited because its oxidation resistance is still inadequate for structural applications. Understanding the oxidation kinetics of Nb-based alloys and the role of the different phases in the oxidation process is of crucial importance to improve the oxidation resistance of these materials.

The effect of Cr content on the …

Design Of A Low Voltage Analog To Digital Converter, Praveen Kumar Palakurthi

Open Access Theses & Dissertations

For the past 40 years, the number of transistors per chip has been increasing at an exponential rate confirming Moore's Law regarding the growth of chip complexity. Increases in transistor count have led to enhancements in functionality and made possible products with features that were unimaginable ten years ago. Consequently, the resulting increase in digitization in all electronics, across a wide range of applications, requires the Analog-to-Digital Converters (ADCs) with a higher resolution and lower power consumption. The evolution of the integrated circuit technologies and scaling methodologies partially helps in providing faster circuits and allowing complex functionalities in a given …

Electric Power Distribution Optimization Using Evolutionary Algorithms, Sowmya Parimi

Open Access Theses & Dissertations

In the present research, a new evolutionary algorithm is developed to solve the component allocation problem in electricity distribution systems. The problem addresses the upgrade/design of an electricity distribution system with the objective of minimizing expected system downtime subject to cost and repair time constraints. The algorithm is tested on the Dual Element Spot Network (DESN) configuration which is one of the most commonly used configurations by the power industry. This algorithm is demonstrated with two examples.

Microstructural Characterization Of Overaged Gtd-111 Hp Turbine Buckets, Oscar Quintero

Open Access Theses & Dissertations

Superalloys are metallic materials that exhibit excellent mechanical strength and creep resistance at high temperatures. They have good surface stability and are corrosion resistant. Superalloys are mostly used in the aerospace industry, gas turbine engines and blades (hot zones of gas turbines), and where extreme heat is encountered. The focus of this research was on the GTD-111 Ni-base superalloy, which is a General Electric (GE) proprietary superalloy mostly used in gas turbine blades with the form of high pressure or first stage buckets. This alloys features better mechanical properties, creep resistance, and a higher stress rupture temperature than the commonly …

Discrete Element Modelling Of Silicon Nitride Ceramics: Crack Formation And Propagation In Indentation Test And Four Point Bending Test, Rajeev Senapati

Open Access Theses & Dissertations

Advanced ceramic materials have been extensively used in aerospace, automobile and other industries. However, the reliability of the advanced ceramics is the major concern because of the brittle nature of the materials. This work aims to model silicon nitride ceramics using Discrete Element Method (DEM) and simulating the crack formation and propagation. DEM software package PFC2D is used to simulate indentation test and four point bending test on silicon nitride ceramics and the behaviour of crack formation and propagation is identified. The numerical representation of ceramic materials is done by generating a densely packed particle system using the specimen genesis …

Integrated Finite Element Analysis Program To Evaluate Pavement Performance And Predict Non-Destructive Testing Response, Cesar Tirado

Open Access Theses & Dissertations

The response of a pavement system under wheel loading has been a subject of research for many decades. Several models have been developed to predict pavement performance based on layer deformation and fatigue cracking. Among them stand out computer programs based on linear elasto-static layered systems and viscoelastic-plastic models; however, newer or more advanced constitutive models cannot be rigorously incorporated into them. In contrast, finite element techniques allow incorporation of nonlinear and viscoelastic-plastic behavior of the pavement materials but licensing of software and the need to train personnel greatly limits its use by highway agencies. A mechanistic-empirical (M-E) approach for …

Impacting Testing Of High Temperature Ceramics Through The Use Of A Vitiated Heater For Hot And Cold Fire Collisions, Adrian Trejo

Open Access Theses & Dissertations

Material testing is a crucial step during the design process as particular materials serve as safety and life saving conditions. In this study, a MoSi2 is chosen as the target specimen to undergo impact under high temperatures. An impact apparatus is designed and constructed for the purpose of propelling alumina particles at high velocities. A nozzle using compressed nitrogen gas is used to fire the particle at the desired velocities. Due to the possibility of thermal shock occurring at higher temperatures, a separate nozzle utilizing vitiation heating is designed to fire the particle at equally higher temperatures to prove the …

An Experimental Study Of The Hydrodynamics Of Multiphase Flow In Fluidized Beds, Gerardo Vargas

Open Access Theses & Dissertations

Fluidized bed reactors have been widely used as a gasifier in coal gasification processes to convert coal into other forms of energy. At this stage, full fluidization is required to attain the best thermochemical reaction within the fluid-solid mixture. This can only be achieved if the fluid is maintained between minimum fluidization and terminal velocities. To better understand the hydrodynamics of multiphase flow, a fluidized bed was designed and constructed to carry out the investigation. Compressed air and 1-mm glass beads were used to determine gas minimum fluidization and terminal velocities at three different particle concentrations. The solids were enclosed …

Methodology To Develop A Minimum Cost Acceptance Sampling Plan For Highway Construction, Gandhar Wazalwar

Open Access Theses & Dissertations

Quality Assurance has always been a part of manufacturing processes. Since World War II, Acceptance Sampling has been introduced and implemented for quality control and improvement. Since statistical methods are applied for quality assurance, especially in acceptance sampling, various methods are becoming popular among the highway agencies over the period of time. As a result, several specifications have been designed to date based upon different statistical theories, each with its own advantages and shortcomings. Acceptance is a form of quality assurance which is employed as an audit tool for decision making to accept or reject the product based on its …

Vision-Based Virtual Mouse System, Tom Wanjala Watiti

Open Access Theses & Dissertations

This thesis describes a virtual mouse system that utilizes machine vision technology to enable a user to navigate through software window screens on a standard personal computer, access and control software, and/or peripheral devices attached to the personal computer. Utilizing the virtual mouse, the user can execute the standard control functions of the system mouse required to perform software application selection functions and navigation tasks without physical interface with the controlled computer. The machine vision algorithm utilizes a set of four simulated photoelectric sensors, with Gaussian filter sensitivities, to compute and track the mouse location. By utilizing Gaussian filters, instead …

Estimating Variation In Stiffness And Volume Change Of Clays From Geochemical And Index Properties, Cynthia Roxanna Zuniga

Open Access Theses & Dissertations

Clayey soils from six different locations in Texas were analyzed and evaluated with respect to their expansion and shrinkage and change in stiffness associated with moisture content variation. These soils consist of five high plasticity-index (PI) clays (PI greater than 25) and one low-PI clay (PI = 17). The behavior of the clays changes dramatically with moisture content fluctuation, thus causing stiffness and volume changes throughout the year. Total or differential volume movements caused by swell or shrinkage strains of expansive soils and reduction in modulus can exert enough pressure to damage the pavements and cause maintenance problems.

The intent …

Laminar Burning Velocities Of Gas Mixtures, Vishwanath Reddy Ardha

Open Access Theses & Dissertations

In this study, burning velocities of hydrogen-carbon monoxide (H2-CO) mixtures, which are primary constituents of syngas fuels, are measured. The effect of different burner systems, H2 concentration, and different measurement techniques on the burning velocities of H2-CO mixtures is also discussed. The burning velocities of H2-CO mixtures increase with the increase in H2 content in the mixture. When compared with different burner systems using different methods, the burning velocity data almost coincide in the lean condition, but at rich condition the data stray away from each other. The burning velocities of actual syngas compositions (based on different sources of coal) …

Failure Analysis And Materials Characterization Of Hip Implants, Amanda Marie Bastidos

Open Access Theses & Dissertations

This research focused on the microstructural characterization and failure analysis of hip implant components. The main hip components analyzed were the femoral heads and the ultra-high molecular weight polyethylene (UHMWPE) liners. Previous research has shown that hip implants tend to fail by the PE liners due to adhesive and abrasive wear, delamination, and third body particles (metals, ceramics, and PE). The methods and procedures for analyzing the said failures consisted of non-destructive and destructive evaluations. Non-destructive evaluations included of techniques such as visual characterization and dye penetrant inspection (DPI)-which displayed macroscopic surface details and presented initial clues as to the …

Observed Superspin-Glass Behavior In Ni0.5zn0.5fe2o4 Nanoparticles, Antony Adair

Open Access Theses & Dissertations

In this investigation we seek to identify the magnetic behavior of Ni0.5Zn0.5Fe2O4 nanoparticles though AC-susceptibility and DC-magnetization measurements. Powder x-ray diffraction was performed to determine the purity and average diameter ( ~ 9nm) of the particles. Aditionally, structure was confirmed by comparison through the International Centre for Diffraction Data's Powder Diffraction File [52] (PDF # 08-0234).

Zero-field cooled and field cooled DC magnetization measurements (bifurcation and blocking temperature), as well as M(H) hysteresis (below and above the blocking temperature) lead us to initially suggest that the material may in fact be superparamagnetic. However, further investigation of the real AC susceptibility …

Application Of Sensor Fusion To Human Locomotor System, John Kweku Avor

Open Access Theses & Dissertations

This research study proposes a multi-sensor data fusion technique to determine the complex interactions between the sensory, muscular and mechanical components of the human locomotor systems (neuromechanics). The object in this work is to demonstrate the viability in using inertial sensors for accurate gait phase determination and to present the acceleration effect specific body segment contributes in order to establish a functional gait. The current method used in determining gait phases consist of combining ground reaction force and angular data, this method is time consuming and cannot be totally reliable. We found out that gait phases can be determined distinctively …

Temperature-Induced Phenomena In Systems Of Magnetic Nanoparticles, Abdul Wazed Bhuiya

Open Access Theses & Dissertations

Magnetic nanoparticle ensembles have received a lot of attention, stemming in part from their current and potential applications in biomedicine and in the development of high-density magnetic storage media. Key to the functionality of these systems are microscopic structures and mechanisms that make them exhibit unique properties and behave differently from their bulk counterparts.

We studied microscopic structures and processes that dictate macroscopic properties, behavior and functionality of magnetic nanoparticle ensembles. As the temperature T strongly influences the magnetic behavior of these systems, we studied temperature dependent magnetic properties using AC-susceptibility and DC-magnetization measurements carried out over a broad range …

Experimental Investigation Of A Meso-Scale Axial Flow Pump, Jonathon Ray Bice

Open Access Theses & Dissertations

The scope of this work involves the testing of an experimental meso-scale axial flow pump intended for use in micro-spacecraft and micro-satellites. A setup was implemented to test pressure and flow characteristics at different velocities for three configurations of the pump. In addition, an alternate setup was used to test torque and efficiency. Computational fluid dynamics simulations were also conducted. The results are presented and analyzed to determine whether the pump is a viable alternative for the space industry.

Microstructural Characterization And Heat Treatment Of A-286 Turbine Buckets, Christopher Michael Bradley

Open Access Theses & Dissertations

A-286 is an iron-based superalloy used extensively in land-based gas turbines for 2nd stage (low pressure) buckets and 1st and 2nd stage wheels. Although A-286 may appear to some as just another austenitic stainless steel, its elevated temperature properties are attributed to ' precipitate structures, effective distributions of alloy carbides in the forms of M23C6, M6C and MC, and solid solution strengthening. Unfortunately over the course of these components service lives microstructural degradation develops in the form of η-phase formation. The presence of η-phase, especially in large quantities, can have a negative effect on stress rupture properties. Resistance to creep …

Gis-Based Tool For Assessing Hydraulic Performance Of Drainage Infrastructure System In El Paso, Gema L. Camacho

Open Access Theses & Dissertations

Maintaining a city's storm-water drainage infrastructure system can be an overwhelming effort, especially when data is inaccurate, incomplete, or located in disparate sources. This was the case for the City of El Paso. This research was part of a project funded by the City of El Paso to enhance their GIS storm drainage infrastructure system. For the first task of the project, the GIS software was used to store stormwater drainage data into one convenient GIS file. A GIS framework was created during the first phase of the project. This GIS database contained drainage data (such as location, material, dimensions, …

Using The Taguchi Design And The Central Composite Design To Increase The Robustness Of A Process From Its Raw Material Variability, Alvaro Cuevas

Open Access Theses & Dissertations

This research presents an experimental study where four controllable and one noise factor are analyzed using the Taguchi approach and the Central Composite Design (CCD) in order to induce robustness in a process that is being designed to treat residual grease from small restaurants. Three response variables are analyzed separately to establish the parameters conditions to obtain the most robust process output. These suggested conditions are validated conducting confirmation runs that are compared statistically to the predictions from the Taguchi prediction model for the Taguchi approach, and the Response optimizer for the CCD. The accuracy of each method is measured …

Retention And Productivity In Industrial Search And Scan Tasks, Camilo Aguilera

Open Access Theses & Dissertations

An experiment was developed in order to study the interaction between individual factors (gender and mood) and the retention ability in search and scan activities. 54 subjects between 18 and 30 years old participated in a computer-based memory test from the North of Mexico area. A full factorial design was used to analyze the variables. Two factors, one with two levels (gender: male and female), and the second factor with three levels (mood: positive, neutral, and negative) were used in the analysis. The output was measured as the amount of characters memorized in a string of random alphanumeric characters. Data …

Microstructure And Electrical Performance Of Sputter-Deposited Hafnium Oxide (Hfo2) Thin Films, Brandon Adrian Aguirre

Open Access Theses & Dissertations

Hafnium oxide (HfO2) based dielectrics have been currently considered as the possible replacements for the traditional gate-oxide (SiO2) of the complementary metal-oxide semiconductor (CMOS) devices. The high dielectric constant, wide band gap, and thermal stability in contact with Si make HfO2 a potential material for application in CMOS devices. The performance of HfO2 as a gate oxide material, however, depends on its quality and interface structure with Si. In this work, HfO2 thin films have been deposited by rf sputtering onto Si(100) substrates under varying growth temperatures (Ts). The objective of the work is to understand the growth and microstructure …

Flashback Propensity Of Gas Mixtures, Bidhan Kumar Dam

Open Access Theses & Dissertations

In this study, experimental measurements of flashback propensity of hydrogen (H2)-carbon monoxide (CO) mixtures, which are the primary constituents of syngas fuels, are described. The effects of H2 concentration, diluents and swirl on the flashback propensity of H2 CO flames are discussed. For boundary layer type flashback, the critical velocity gradient (gF) values of 5 to 95%, 15 to 85%, and 25 to 75% H2-CO mixtures somewhat agree with the scaling relation (g_F=c (S_L^2)/α) and yield an average c value of 0.038. At a lower SL2/α ratio, burner diameters have small effects on critical velocity gradient measurements; however, the effect …

Treatment Of Ro Concentrate Using Vsep Technology, Guillermo Guadalupe Delgado

Open Access Theses & Dissertations

The city of El Paso has the largest inland brackish desalination plant in the world. The Kay Bailey Hutchison (KBH) Desalting plant produces 15 million of permeate water every day. Due to the excellent quality of the water, the permeate water is blended with brackish water producing a final volume of 27.5 million gallons of water every day. With an average recovery rate of 80%, the KBH plant produces an average of 3 million gallons of concentrated brackish water that is disposed of via injection wells 23 miles from the plant.

Conventional reverse osmosis (RO) systems are not capable of …

Characterization Of A Mems Accelerometer For A Highway Health Monitoring Ultra-Low Power Sensor, Karla Cecilia Enriquez

Open Access Theses & Dissertations

With the 2009 American Recovery and Reinvestment Act, government officials recognized the need to implement automated methods that reduce the cost of assessment projects and provide a long-term solution to monitor the structural health of bridges and highways. Although important research exists in the area of non-destructive evaluation, current road health monitoring efforts continue to be costly and time consuming. This Thesis focuses on the characterization of a MEMS accelerometer intended to be the basis of a novel ultra-low power sensing system to remotely asses the condition of highways. The architecture of a sensor prototype built to validate an algorithm …

Autonomous Vehicle Navigation: A Comparative Study Of Classical Logic And Neural Network Technique, Javier Alejandro Flores

Open Access Theses & Dissertations

Today is an era in which humans need the help of automated machines to facilitate their hectic lives. Over the past few decades, robotics has been one of the most researched areas in the world. One area of this research is obstacle avoidance for autonomous vehicles. In order to avoid an obstacle, the system may include two important characteristics: obstacle detection and avoidance control. In this Thesis a classical logic system and artificial neural network approach is presented. With the help of an Integrated Development Environment, a virtual robot was able to negotiate a maze and avoid obstacles according to …

Spectroscopic Characterizations Of Organic/Inorganic Nanocomposites, Jayesh Rasikalal Govani

Open Access Theses & Dissertations

Inorganic potassium dihydrogen phosphate (KDP) is widely known for its value as a nonlinear optical material. In this study, pure and l-arginine-doped KDP single crystals were grown by the slow solvent evaporation technique and further subjected to infrared absorption and Raman studies for the confirmation of chemical group functionalization and possible bonding between the organic and inorganic materials. The appearance in the infrared absorption spectra of additional vibrational lines, which mostly originate from disturbed N-H, C-H, and C-N bonds of the l-arginine-doped salt, confirm the interaction between KDP and the organic material. This affirmation is supported by more evidence from …

Identification Of Human Gait Using Genetic Algorithm Tuned Fuzzy Logic, Abdallah Abdel-Rahman Hassan Mahmoud

Open Access Theses & Dissertations

Data mining is concerned with the discovery of useful hidden information in large databases. Classification is a data mining task producing rules in which a set of attributes in data predict the value of a class attribute. Classifiers usually produce a large number of rules, most of which are not interesting to the user. Rule interestingness is a decisive factor. However, evaluating rule interestingness is challenging as it involves both objective (data-driven) and subjective (user-driven) aspects.

In this research, a fuzzy genetic algorithm is proposed to discover classification rules that are both accurate and interesting. Continuous attributes are fuzzified so …

Comparison Of Older Mexican American Upper Extremity Reach Capabilities To Older Anglo Americans, Odi Mike Ikpe

Open Access Theses & Dissertations

The study aimed to investigate if there are upper extremity reach capability differences in older Mexican Americans and older Anglo Americans. The subjects were recruited and corresponded to the 2000 census track. Upper extremity reach capability was determined by analysis of 20 range of motion variables. A MANOVA analysis utilizing SPSS software was performed with age, gender and ethnicity as independent variables while height and 20 range of motion anthropometric measurements servings as dependent variables (responses). Ethnicity as a function of age was found to be significant in height, horizontal distance from buttock to hand, rotation of head to the …

Reduced Dimensionality Hyperspectral Classification Using Finite Mixture Models, Vikram Jayaram

Open Access Theses & Dissertations

Classification of HSI data is a challenging problem for two main reasons. First, with limited spatial resolution of HSI sensors and/or the distance of the observed scene, the images invariably contain pixels composed of several materials. It is desirable to resolve the contributions of the constituents from the observed image without relying on high spatial resolution images. Remote sensing cameras have been designed to capture a wide spectral range motivating the use of post-processing techniques to distinguish materials via their spectral signatures. Secondly, available training data for most pattern recognition problems in HSI processing is severely inadequate. Under the framework …