Engineering Commons^™

Development Of A Micro-Catbed For Miniature Thrusters, Chance Paul Garcia

Open Access Theses & Dissertations

The goal of this work is to develop a micro catalytic bed for miniature thrusters. A test bed was constructed for experimental testing to characterize several parts of the micro catalytic bed. The reactant fluid studied is 90% Hydrogen Peroxide (H2O2) by weight. Three different cross sectional area designs were tested to determine decomposition efficiency, temperature reaction propensity, optimum flow rate, and temperature distribution across each bed. The products of decomposition were condensed to measure the oxygen released from decomposition. The results will be used to develop the basis for a micro catalytic bed design to implement into future miniature …

Generation Of High Resolution Radar Signals Using Three Dimensional Chaotic Flows, Chandra Sekhar Pappu

Open Access Theses & Dissertations

The purpose of this project is to investigate the system parameter and certain signal processing techniques to achieve wide bandwidth and frequency agility in order to build a high resolution radar. The technique relies on the output of an n-dimensional (n>2) non-linear system that exhibits chaotic behavior.

Firstly, the compressed Lorenz attractor is considered which has a set of three state variables x, y and z and three control parameters &rho, &beta, and &sigma. By varying &rho and &beta as function of time highly chaotic parameter space region is simulated such that chaotic signal behaves optimally.

For comparison purpose …

A Subthreshold Reconfigurable Architecture For Harsh Environments, Ameet 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 reconfigurability, …

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, …

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 …

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 …

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) …

Quality Assesment In Bone Scaffolds Through Internet Based Robotic Using Intelligent Data Mining, Aditya Chilukuri

Open Access Theses & Dissertations

Optimization of design in fabricating scaffolds in an important step in obtaining tissue engineering scaffolds with appropriate shape and inner microstructure. Different shapes & sizes of scaffolds are modeled using UGS NX 6.0 modeling software with variable pore sizes. The quality issue we are concerned is about scaffold porosity, because of fabrication errors the porosity is not be very high for few models. There is lot of research ongoing for characterization using scanning electron microscope, but this study will introduce a new technique to characterize the scaffolds using network based robots, machine vision system and conveyor facility using which the …

Decision Support Tools For Bus Rapid Transit Corridor Planning, Luis David Galicia

Open Access Theses & Dissertations

Bus Rapid Transit (BRT) Systems have been gained popularity in the United States and worldwide as a cost-effective solution of mass transit. There are certain elements and characteristics that such a system should accomplish to be considered a BRT. However, a uniform definition, defined phases to be deployed, and a reliable methodology to estimate ridership are not well structured and clear yet. The purpose of this research was to help BRT stakeholders with an effective method to plan and assess BRT projects. The first goal of this research was to provide a comprehensive description of the essential characteristics of BRT …

Optimization Models For The Economic And Non-Economic Level Of Repair Analysis, Carlos Marco Ituarte-Villarreal

Open Access Theses & Dissertations

Every component, equipment or system will eventually fail. All failures produce a maintenance cost and, repair costs are especially hard to estimate ahead of time. Research shows that maintenance costs are the most substantial costs of development and use of equipment, reason why the cost of the product or equipment through its life is a major concern. Therefore, the main objective of this thesis is to provide a new optimization model to determine the minimum cost maintenance policy for complex systems.

Renewable Energy Integration: An Approach For Micro-Grid Optimization., Nicolas Lopez

Open Access Theses & Dissertations

This thesis explores the Renewable Energy Integration Problem beginning with a literature review on the different sources of electrical energy classified as Non-Renewable and Renewable, stating that the integration of renewable sources within the pre-existing Power-Grids is a current worldwide problem that is being addressed with different approaches.

The impossibility to exactly model the different equations relating the electric output of the renewable energy sources as they relate with meteorological factors, makes the renewable sector a stochastic component of the overall mathematical model, where it can be concluded that most of the problem is in the area of the forecast. …

Microstructure And Property Evaluation Of Lifepo4 Thin Films For Application In Microbatteries, Jose Marcos Mares

Open Access Theses & Dissertations

The shortage of fossil fuels and the requirements to produce clean, environmental friendly, efficient, and economical energy are the principal problems in the context of energy technology for current and future generations. Therefore, advanced energy storage and conversion capabilities with higher capacity and efficiency are desired. Currently, there is an enormous interest in the development of high energy density rechargeable batteries for use in domestic applications, automotive industries and portable electronic applications. The present research focuses on the development of LiFePO4 thin films for solid-state thin-film microbatteries. The present effort was performed with a specific purpose of understanding the effect …

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 …

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 …

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

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 …

A Tool To Improve And Preserve Flexible Pavement At Intersections, Carlos Jesus Solis

Open Access Theses & Dissertations

Rural intersections originally constructed with thin untreated flexible base and hot mix or a two-course surface treatment tend to experience severe pushing, shoving and rutting. These failures cause an extremely rough surface that can cause damage to small vehicles and potentially cause motorists to lose control of their vehicles. These distresses almost always result in complete failure of the existing pavement that must be repaired several times during the life of the roadway by maintenance forces. In most cases, pavements constructed with the same materials and cross-sections adjacent to the intersection perform adequately.

The sources of and solutions for failure …

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 …

Acoustic Reflectometry Using Gaussian-Modulated Sinusoidal Waves And The Ware-Aki Algorithm, Ernesto Rodrigo Vazquez Ceron

Open Access Theses & Dissertations

Acoustic reflectometry, a non invasive technique, consists of solving, the inverse problem of estimating the cross sectional area as function of the distance of a cylindrical cavity by impacting an audible acoustic pulse of high amplitude and short duration, and analyzing the reflected wave. The technique has been applied in Biomedical Engineering to estimate both the area of a human upper airway and the patency of endotracheal tubes as a function of distance. Several ways have been tested to improve the quality of an acoustic pulse and different algorithms have been tested to reduce the losses. However, an acoustic pulse …

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.

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 …

12 Bit Charge Redistribution Digital To Analog Converter For The Residence Time Fluxgate Magnetometer, Miguel Angel Alamillo

Open Access Theses & Dissertations

The continuous advances in CMOS VLSI technology have culminated in high speed, low voltage CMOS digital circuits with gate delays below 50 ps at 1.5 V supply. At the same time, high voltage analog signal processing has fallen behind to the high flexibility and high reliability of DSP. However, the main drawback of DSP is the need for high accuracy low distortion data converters and as a consequence of the persistent efforts of reducing size, cost and power of solid-state components the field of CMOS Mixed-Signal circuit design has become of the utmost importance.

The obvious functionality of data converters …

Probabilistic Analysis Of Concrete Fracture, Mustafa Abushaala Aldalinsi

Open Access Theses & Dissertations

It is well known to civil engineers that fatigue leads to the bulk of structural failures. In plain and reinforced concrete structures, fatigue might account for excessive deformation, excessive of crack widths, de-bonding of reinforcement and rupture of the reinforcement, all of these can lead to structural collapse. Fatigue crack propagation can be a method to predict a remaining life of a structures. Herein will show some works that have been done in order to analyze the fatigue crack growth for plain concrete specimen. The goals of this study are to estimate the critical crack length and remaining life of …

Effects Of Unbalanced Approach Volumes On Roundabout Operations, Marilyn Valdez

Open Access Theses & Dissertations

Modern roundabouts are increasingly popular in the United States due to their advantages in improving safety and reducing delay at intersections. A roundabout is an intersection in which traffic enters the intersection and travels in a circular counterclockwise motion around a center island. In a roundabout, priority is given to vehicles traveling in the circular roadway, and incoming traffic at the roundabout approach must yield to the circulating traffic. If there is an unbalance in approach volume, the approaches with higher input volumes may dominate the circulating flow preventing vehicles the other approaches to enter the roundabout. This may consequently …

Observer-Dependent Model For Analyzing Subjective Parameters In Epidemiology, Milad Zarei

Open Access Theses & Dissertations

Although medical technologies for preventing the contagion and spread of infectious diseases have improved steadily throughout the last century, new infectious diseases are still emerging and spreading swiftly. The modeling of infectious disease spread is crucial in addressing the lack of predictive ability in epidemiology. Managing the spread of infectious diseases requires processing quantitative epidemiological data and the ability to capture the dynamics of the infectious disease in order to provide a measure of control.

In this thesis, I have introducing cognitive biases in diseases spread modeling. For the first time, to the author's knowledge, the human subjective experience has …

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, …

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 …

Simulation And Optimization Of Ultra Thin Photovoltaics, Jose Luis Cruz-Campa

Open Access Theses & Dissertations

Sandia National Laboratories (SNL) conducts pioneering research and development in Micro-Electro-Mechanical Systems (MEMS) and solar cell research. This dissertation project combines these two areas to create ultra-thin small-form-factor crystalline silicon (c-Si) solar cells. These miniature solar cells create a new class of photovoltaics with potentially novel applications and benefits such as dramatic reductions in cost, weight and material usage.

At the beginning of the project, unusually low efficiencies were obtained in the research group. The intention of this research was thus to investigate the main causes of the low efficiencies through simulation, design, fabrication, and characterization.

Commercial simulation tools were …