Engineering Commons^™

Zinc Telluride Deposition Using Close Space Sublimation, Luis Carlos Romo

Open Access Theses & Dissertations

This thesis presents the optimization process of the close space sublimation (CSS) technique to deposit zinc telluride (ZnTe) on thin-film cadmium telluride (CdTe) solar cells. Previous research has demonstrated that creating a heavily doped ZnTe intermediate layer between the absorber-CdTe and the back contacts produces low-resistive CdTe contacts that overcome the Schottky barrier created at the interface of a metal and a semiconductor [11]. ZnTe interlayer forms a tunnel barrier at the contact interface so the positive charges created at the p-CdTe/n-cadmium sulfide (CdS) junction can be easily collected at the back contact maximizing the current collection process. However, ZnTe …

E-Quality Control: A Support Vector Machines Approach, Kalyan Reddy Aleti

Open Access Theses & Dissertations

The web-enabled quality control process presents many benefits to industry, such as universal access, remote control capability, and integration of production equipment into information networks for improved efficiency. This capability has a great potential, since engineers can access and control the equipment anytime, anywhere as the design stages evolve. In this context, this work uses innovative methods in remote part tracking and quality control with the aid of the modern equipment and application of Support Vector machine learning approach to predict the outcome of the quality control process. The classifier equations are built on the data obtained from the experiments …

Stochastic Gaussian And Non-Gaussian Signal Modeling, Madhu Kishore Yerramothu

Open Access Theses & Dissertations

This thesis introduces a methodology for modeling stochastic signals that have either Gaussian or approximately bell-shaped non-Gaussian distribution. The synthesized model can be used to generate stochastic signals that approximate both the power spectral density (PSD) and the probability density function (pdf) of the original stochastic signal. The new methodology is based on non-linear transformations, filter banks and autoregressive-moving average (ARMA) models. Because the stochastic signals modeled can have Gaussian distribution or approximately bell shaped non-Gaussian distribution, normality tests such as sample skewness, sample kurtosis, Kolmogorov-Smirnov test, and Shapiro-Wilk test are also used.

Many methods have been proposed in the …

Stereolithography Of Poly(Ethylene Glycol) Hydrogels With Application In Tissue Engineering As Peripheral Nerve Regeneration Scaffolds, Karina Arcaute

Open Access Theses & Dissertations

In recent years, rapid prototyping (RP) technologies initially developed to create prototypes prior to production for the automotive, aerospace, and other industries, have found applications in tissue engineering (TE). Several different RP technologies are being used to fabricate biocompatible 3D structures with controlled micro- and macro-scale characteristics. The focus of this research was to explore the capabilities of the RP technology, stereolithography (SL), for creating complex, 3D scaffolds with applications in TE using a photocrosslinkable biopolymer, poly(ethylene glycol) (PEG). The primary objective was to create an implantable multi-lumen nerve guidance conduit (NGC) for the regeneration of peripheral nerves.

Studies of …

Quantifying Anisotropy In Asphalt Concrete Pavements Using An Ultrasonic Method, Monica C. Jurado

Open Access Theses & Dissertations

Asphalt concrete is a bonded granular material whose internal structure is anisotropic. Such anisotropy is due to anisotropic particles and void's structure, particle distribution and orientation, and restrain and force pattern used during compaction. Even with this knowledge asphalt concrete design is made considering asphalt concrete as an isotropic material. The biggest difference between an isotropic and anisotropic material is that, an isotropic material is characterized by two independent constants and an anisotropic material could be characterized by up to 81 constants. An extensive research to characterize and quantify anisotropy is only available for some composite materials. Based on the …

Evaluation Of An Image Processing Algorithm For Scene Change Detection, Daniel Flores

Open Access Theses & Dissertations

Despite the efforts to reduce traffic accidents by government entities and automobile manufactures, the numbers of accidents are not considerably reduced. An evaluation of an algorithm based on the fly's eye is done on this research applying its principles to detect scene change on images for printed circuit boards providing initial steps to implement this algorithm on vehicular traffic to keep track of objects moving on the field for collision avoidance purposes. The effectiveness of the algorithm is addressed through a comparison of its performance with that found in experimental data.

Allocating Emergency Response Vehicles To Cover Critical Infrastructures, Hao Lei

Open Access Theses & Dissertations

Optimal deployment of limited emergency response service units in a metropolitan area is of interests to public agencies. The limited emergency units not only have to respond to the demand for service by residents and businesses, but also cover Critical Infrastructures (CIs). This Thesis formulates an improved optimization model to allocate different types of Emergency Response Service (ERS) units among their candidate base stations. The allocation of units must ensure maximum coverage to CIs, subject to the capacities of the base stations, service standard in terms of time to reach the CIs, and the availability of the ERS units (when …

Quality Evaluation Of Portland Cement Concrete At Early Age With Free-Free Resonant Column, Gilberto Wenglas

Open Access Theses & Dissertations

At early age, the behavior and mechanical properties of portland cement concrete changes rapidly with time due to hydration. The hydration process consists of a series of chemical reactions that accelerate nonlinearly with the rise in temperature. The hydration process consists of three stages: the dormant period, the setting time, and the hardening time. Timely opening of roads and resumption of constructions depend of the knowledge of these stages. The initial and final setting times are arbitrarily determined by a standard test (ASTM C 403). Although the setting time has been studied for many decades, the new technologies allow making …

Expert System Design Guide For Lower Classification Roads Over High Pi Clays, Yaqi Wanyan

Open Access Theses & Dissertations

This research was focused on low-volume roads over expansive clayey soils in Texas. In spite of the redundant pavement designs recommended and widely used in Texas for roads in high PI clay areas, these pavements often fail prematurely. This failure occurs primarily because of the highly variable properties of the clayey subgrade throughout the year due to moisture fluctuations. The problematic nature of high PI clays, despite the fact that volumetric changes such as heaving are sometime considered in the design, is of concern since they contribute to roughness and longitudinal shrinkage cracking of the road, and as such the …

A Distributed Reconstruction Of Ekg Signals, Gabriel Cordova

Open Access Theses & Dissertations

In this Thesis the parallel computing methodology is applied to an algorithm used in the reconstruction of electrocardiographic (EKG) measurements. The reconstructions are being performed to obtain a better understanding of the source and behavior of the electrical activity that generates the EKG measurements. The contribution of this Thesis is to identify and eliminate inefficiencies present in the current reconstruction algorithm. Additionally, this Thesis reduces the computation times of the EKG reconstruction by applying distributed computing through the use of Remote Procedure Calls (RPC). Lastly, it provides an analysis of the speed-up and efficiency of the distribution implemented using parallel …

Homography Based Multiple Camera Detection Of Camouflaged Targets, Jesus Flores Guerra

Open Access Theses & Dissertations

This Thesis proposes an improvement on segmentation of camouflaged objects by combining information from multiple static cameras with overlapping views onto a common reference plane. Previous camouflage detection work relies on a single camera and focuses on pattern recognition, gray level co-occurrence matrix (GLCM) computation, convexity detection and operations such as connected components or morphology. These methods make real-time implementation computationally expensive. The proposed work diverges from these techniques, taking advantage of the added information from several viewpoints. Background subtraction is performed on each individual camera and then, the segmentation result is transformed onto a common plane using homography. A …

Guidelines For Using Local Material For Roadway Base And Subbase, Biraj Gautam

Open Access Theses & Dissertations

Flexible base materials that meet TxDOT specifications are getting more difficult to purchase in many TxDOT Districts. As a result, higher quality materials have to be hauled long distances, sometimes from other States. This act would significantly increase the costs associated with the construction of roads and subsequent maintenance and rehabilitation of them. Lower quality (i.e., out-of-specification) materials are normally available. If through appropriate modifications of the materials (adjusting the gradation or/and stabilization) or structural design (specifying thicker layers of base and/or hot mix) the use of the local materials can be permitted, the construction can be accelerated and significant …

Screening The Phytoremediation Potential Of Native Plants Growing On Mine Tailings In Arizona, Usa, Md Nazmul Haque

Open Access Theses & Dissertations

Mining companies have been playing an important role for the utilization of the Earth's natural resources for the prosperity of human society. However, the mining of resources has generated solid wastes called tailings that have become a serious environmental threat worldwide. Technologies such as soil caping have been used to remediate the problem. Nevertheless, the remediation of mine tailings using conventional technologies is costly and environmentally unpleasant. Since the last few decades, a plant based technology known as phytoremediation has appeared as a promising alternative. Several plant species have demonstrated to have phytoremediation capabilities; though, best results have been obtained …

Phase Change Cooling Applications - Engine Cooling, Kiran Kumar Katta

Open Access Theses & Dissertations

Waste heat recovery system composed of two phase cooling system, exhaust heat exchanger, and mini-turbine has been proposed by Henry Works, Inc to generate auxiliary power via harvesting engine cooling and exhaust heat loss from heavy duty vehicles. The objective of this research is to evaluate the two phase cooling system through the engine dynamometer test and obtain initial test data for the development of the waste heat recovery system. Engine dynamometer experiment for evaluating two phase cooling has been conducted using Perkins diesel engine. During two phase cooling phase, the coolant temperature showed less than 1 °C variation in …

Assessment Of Human Muscle Fatigue From Surface Emg Signals Recorded During Isometric Voluntary Contractions By Using A Cosine Modulated Filter Bank, Cristhian Mauricio Potes

Open Access Theses & Dissertations

Human muscle fatigue involves both a decrease in the frequency and increase in the amplitude of a surface electromyographic (EMG) signal. Muscle fatigue is also related to a decrease of the force impeding to reach the same initial level of the maximum voluntary contraction (MVC). To determine muscle fatigue indices, a method is proposed by decomposing a surface EMG signal into 32-subbands. This decomposition was attained by using a cosine modulated filter bank. The

surface EMG signals analyzed during this research were recorded during isometric voluntary contractions. Both the instantaneous mean frequency (IMF) and the instantaneous amplitude (IA) are estimated …

A Study Of The Interaction Of Thioindigo Dye, With Several Inorganic Host Materials, Alejandra Ramirez

Open Access Theses & Dissertations

Maya Blue has been the focus of numerous studies and is believed to be a mixture of palygorskite clay and indigo dye.^1,2 Several derivatives of this pigment have been developed with intriguing properties. For instance, the dye thioindigo reacts with the palygorskite clay to exhibit a broad range of colors from red to blue under UV-Vis excitation. Based on FT-Raman and computer simulation, previous work performed in our group could relate indigo and thioindigo interaction to the aluminum sites in the framework. super>3,4

The work performed with other inorganic host materials such as, layer structures and zeolites have …

Analysis Of Number And Mass Concentration Of Coarse And Fine, Nancy Garcia

Open Access Theses & Dissertations

There is currently much concern over particles suspended in the ambient air, their effects on people and the environment throughout the world. The suspended particles can cause adverse health effects, reduce visibility and over the course of time wear buildings. Primary air quality concerns are of particles, their effects and their key characteristics. Particle number concentration (NC) of traffic emissions is an important element of the study, specifically heavy duty diesel engine emissions. Particle number concentration is the number of particles of a specific size in a unit of air; in this study they are measured by the number of …