Engineering Commons^™

High Temperature Oxidation Behavior Of Nb-20si-20cr Alloys With Hafnium Additions, Alma Rosa Vazquez

Open Access Theses & Dissertations

Advances in aircraft and gas turbine engine technology have steadily increased the operating temperatures, and even the state of the art materials can not meet the requirements for the new challenges. Efforts are under way to study the possibility of substituting nickel-based alloys with niobium-based alloys that offer higher melting points and excellent mechanical properties. Notwithstanding these good properties, the utilization of Nb-based alloys is limited since oxidation resistant is still a serious problem. Therefore understanding the corrosion behavior of Nb-based alloys is a crucial step to enhancing oxidation resistance.

The oxidation behavior of two alloys from the Nb-Si-Cr system …

Evaluation And Recommendation Of Mix Design For Emulsion Stabilized Bases, Samuel Franco

Open Access Theses & Dissertations

Asphalt emulsion has been used for base material stabilization in a few TxDOT districts. Results from these practices were quite different. The initial performance of two projects on US287 constructed around 2000 in the Amarillo District has been found to be satisfactory. However, the Yoakum District has reported problems with asphalt emulsion for base work in a project on FM 237. The preliminary conclusion from these trials has been that asphalt emulsion may not perform well in the high humidity/high rainfall areas like east Texas. On the other hand, using calcium-based additives to stabilize base courses in road construction has …

The Effect Of Mmod Porosity On Crater Depth After Hypervelocity Impact, David Ledesma

Open Access Theses & Dissertations

A significant amount of research has been conducted in the last decades on the design of spacecraft shielding for the impacts of Micro Meteoroid and Orbital Debris (MMOD). Through the use of hydrocodes, empirical data, and physical testing, researchers have been successful in studying a wide range of shielding configurations. However, a very limited amount of research has been conducted to understand the effect that the porosity and irregular shape of MMOD has on the damage they create on spacecraft components.

The work presented in this thesis addresses the modeling of MMDO porosity by using the CTH hydrocode to investigate …

Evaluation Methods For Health Monitoring Of Aerospace Structure Rotary Joints, Sergio Armando Navarro

Open Access Theses & Dissertations

In September 2007, the excessive vibrations played a significant role in the station operation since one of the rotary joints, which provides the station electrical energy, presented an anomaly. The replacement of its bearing components and re-lubrication were necessary to reduce the problem. To avoid a new anomaly, the inspection of the rotary joints performance continues by using the accelerometers data. This thesis presents three new approaches to monitor the vibrations at the International Space Station based on Root-Mean-Square, kurtosis, and Approximate Entropy (ApEn). MATLAB functions and codes were necessary to implement the three monitoring techniques results from the provided …

Development Of A Gis Fiber Optics Assetmanagement System For The City Of El Paso, Luis Fernando Quintana

Open Access Theses & Dissertations

The GIS Fiber Optics Asset Management System (GFOAMS) was developed for the City of El Paso, to manage the public fiber optics infrastructure. Using a map-driven interface, the GFOAMS is composed of three modules: inventory, documents, and images. Its interactive multilayer data structure contains information for Junction Boxes, Conduit Runs, and Cables for twelve fiber optic systems across the city. The fiber optics network stored in the GFOAMS connects city buildings and facilities such as police departments, fire departments, municipal courts, health administration building, public transportation facilities/Sun Metro, libraries and others. Applications of the GFOAMS include tools to easy access …

Analysis Of Indoor And Outdoor Particulate Matter At Various Residences In The El Paso Region, Joseph Christopher Pinon

Open Access Theses & Dissertations

This thesis is a presentation of particulate matter data collected from February 2007 to June 2008. Personal environment monitors (PEM), which measured 7-day PM2.5 concentrations, had been deployed at 14 homes during the 2007 year and deployed in 16 different homes during the 2008 sampling year. Within each sampling year, sampling occurred for two one-week (7-day) periods during each season. In addition to PEM sampling, a tapered element oscillating microbalance (TEOM) continuous sampler had been deployed in both indoors and outdoors at one pre-selected household per week. Gravimetric, chemical, and black carbon analysis had been performed on the PEM PM2.5 …

An Evolutionary Approach Based On Viral Replication For Solving Combinatorial Optimization Problems, Claudia Evangelina Valles Sosa

Open Access Theses & Dissertations

A new multi-objective evolutionary algorithm that mimics the way viruses replicate is presented. The purpose of viral replication is to allow the reproduction and survival of its kind. The algorithm is able to produce a large number of solutions to be evaluated by imitating the way viral replication and the infection process work. The well-known multi-objective redundancy allocation problem is used to show the performance of this new viral-based evolutionary approach. The algorithm considers the maximization of system reliability, the minimization of system cost, and the minimization of system weight to be optimized simultaneously. The solution to the multi-objective optimization …

Indentifying And Understanding User Preferences In Generic Planning Tools, Grisel Ventura

Open Access Theses & Dissertations

Planning is an important cognitive work activity. To support this complex task, the development of planning tools is important to support people during decision-making and problem-solving tasks. Nowadays, a large number of manual and electronic tools support this complex activity; manual and electronic planning tools aid people in creating strategies for effective work performance. However, there is limited information on the design of generic planning tools people use for their activities, and why people choose to use the planning tool they do. Some examples of generic tools for planning are calendars, checklists, agendas, etc.

To answer this question, this research …

An Ultra Low Power Subthreshold Delta Sigma Digital To Analog Converter, Ricardo Baca

Open Access Theses & Dissertations

Abstract

In the last four decades the incorporation of analog, digital and mixed-signal integrated circuits (IC) using Complementary Metal Oxide Semiconductor (CMOS) technology has been dramatically increasing and is improving almost every aspect of modern life. Furthermore, the continuous advances in CMOS Very Large System Integration (VLSI) technology allow higher integration densities and the increasing number of subsystems in a single chip results in higher speed execution and lower power consumption. Therefore, the increasing digitalization in electronic circuits across a wide range of battery-operated applications where reliability and power dissipation are critical requires Digital to Analog Converters (DACs) with higher …

Design And Cfd Optimization Of Methane Regenerative Cooled Rocket Nozzles, Christopher Linn Bradford

Open Access Theses & Dissertations

Liquid rocket engines benefit in life cycle from the active regenerative cooling method which passes the fuel as the coolant through channels surrounding the combustion chamber. These channels are designed and optimized using structural considerations as well as heat transfer theory, then CFD simulations with the software FLUENT are performed for the final analysis. The difficulty in using methane as the fuel/coolant is addressed, and requires the use of the ideal gas numerical model in preliminary CFD simulations. Comparison to real gas numerical models is made, and results also given for one channel design. The techniques utilized herein allow the …

Asphaltene As Light Harvesting Material In Dye Sensitized Solar Cell, Rajab Emhemed Abujnah

Open Access Theses & Dissertations

This Dissertation characterizes the first asphaltene DSSC (dye-sensitized solar cell), in which light to electricity conversion efficiency has improved from 0 % to 1.8 %. Four natural organic asphaltene factions, namely, un-fractionated asphaltene, Fr. 1 Asphaltene, Fr.2 asphaltene, Fr.3 and Fr.4 were extracted and tested for various solar cell parameters of TiO2 based dye-sensitized solar cell DSSC. DSSCs were fabricated using the four individual asphaltene dyes. The photovoltaic performance of the cells was examined by determining the various parameters such as open-circuit voltage, short-circuit current, fill factor, and series resistance. The overall energy conversion efficiency was also measured to correlate …

Designing, Understanding, And Analyzing Unconventional Computation: The Important Role Of Logic And Constructive Mathematics, Vladik Kreinovich

Departmental Technical Reports (CS)

In this paper, we explain why, in our opinion, logic and constructive mathematics are playing -- and should play -- an important role in the design, understanding, and analysis of unconventional computation.

Spatio-Temporal Cardiac Pacing Sites Localization And Time Varying Pericardium Potential Maps Projection Using Ecg Precordial Leads And A Single Moving Dipole Model, Jaime R. De La Cruz

Open Access Theses & Dissertations

A novel non-invasive method for the spatiotemporal localization of the sites of strongest cardiac activity, and for the creation of time varying Pericardium Potential Maps (PPM), with the use of patients' ECG precordial leads, is proposed in this Thesis study. Compared to previous studies, which analyze electrocardiograms in either time domain or spatial domain, the proposed method has the advantage of a simultaneous spatiotemporal electrocardiograph analysis and a 3-D visualization of pericardium potentials maps, as well as, the pericardium surface polarization patterns during the cardiac cycle. The spatial properties added to the electrocardiogram allow for the analysis of specific regions …

Photocatalytic Destruction Of Halogenated Organic Compounds In Water With A New Photocatalyst, Mabruka Hadidan

Open Access Theses & Dissertations

In this research, a newly developed high surface area semiconductor porous material was synthesized from potassium titanium niobium mixed oxide (KTiNbO5) to be used as a photo catalyst in the presence of UV light to degrade halogenated organic compounds in water. The goal of the project was to investigate the catalytic activity of the material for its effectiveness in the degradation of the halogenated organic compounds, and it is the first investigation of this new photocatalyst with halogenated compounds. Model compounds dichloromethane, 1-chlorobutane, chlorobenzene, and trifluoroacetic acid in aqueous solutions were tested with the photocatalyst under ultraviolet light irradiation, using …

Modeling Impulse Oscillometry Data: Using Augmented-Ric And Extended-Ric Respiratory Impedance Model Paramaters To Track Pulmonary Health And Disease, Carlos Domingo Ramos Rocha

Open Access Theses & Dissertations

Respiratory diseases are a great health concern. Early detection of disease could greatly improve quality of life and yet the most common pulmonary function test can be an unreliable diagnostic method, especially in the case of children. A reliable method of detecting and assessing small airway impairment could greatly help with timely diagnosis. This research approaches this problem by taking Impulse Oscillometry (IOS) data and its model-derived parameters and assessing their utility in tracking respiratory function and more specifically, small airway function.

This research first describes the use of electric circuits as models to describe lung properties at distinct regions …

Mixed-Signal Distributed Feature Extraction For Classification Of Wide-Band Acoustic Signals On Sensor Networks, Humberto Santacruz

Open Access Theses & Dissertations

This thesis proposes a distributed/collaborative scheme for the classification of wide-band acoustic events within the context wireless sensor networks (WSNs). The proposed method is characterized by a mixed-signal processing scheme for the extraction of feature vectors which reduces the processing, memory allocation, and power requirements of the sensor nodes. The mixed-signal scheme assumes that nodes have an analog frontend consisting of a microphone, a bandpass filter, a squaring element and an integrator. This chain of components produces an estimate of the energy over the frequency subband extracted by the filter. The WSN has the ability to form a distributed filter …

A Framework For Strategic Sustainable Supply Chain Design, Abril Paola Vazquez

Open Access Theses & Dissertations

Sustainable supply chain management has raised interest considerably in recent years; due to environmental concerns from society as well industries. There is a high interest in the industries to solve this problem but many of the frameworks are directed to specific situation or structure. A strategic sustainable supply chain design framework is presented with the purpose of providing many companies, including small and big industries, the means to maintain an eco-friendly operation. These include; industry plants, distribution centers, and retailers.

Experimental Investigation Of Magnesium/Regolith Combustion For In-Situ Production Of Materials On The Moon, Christopher White

Open Access Theses & Dissertations

Future settlements on the Moon will require that strong, cost-effective structural materials be developed in whole or in part from locally available resources. Such materials can be created in-situ from the lunar regolith using self-propagating high-temperature synthesis (SHS). By mixing the lunar regolith with metal additives, such as aluminum or magnesium, a combustible mixture is formed which, when ignited, can reach temperatures high enough to allow combustion to be self-sustaining, sintering the lunar regolith without further energy input and without the need for atmospheric oxygen. The resulting products may be strong enough for some structural applications, such as radiation shielding, …