Engineering Commons^™

Growth And Characterization Of Zno For The Front Contact Of Cu(In,Ga)Se2, Rita Bhatt

USF Tampa Graduate Theses and Dissertations

ZnO window layers for CIGS solar cells are grown with a DC sputtering technique instead of a conventional RF sputtering technique. Transparent window layers and buffer layers are sputtered from the Zn target in the presence of Oxygen. The window layer is doped with Aluminum in order to achieve high electrical conductivity and thermal stability. The effect of different sputtering parameters on the electrical and optical properties of the films is elaborately studied. Sets of annealing experiments are also performed. Combinations of different deposition parameters are examined to design the optimum fabrication conditions. We are able to deposit 85% transparent, …

Combined Loading Of Composite Box-Beams With Linearized Differential Equations Of Motion, Michael Alan Dupuis

Master's Theses - Daytona Beach

The purpose of the following analysis is to develop a method for determining vertical, horizontal, and torsional displacements of arbitrarily laminated, cantilevered composite box-beam under static, transverse loading. Small deflections are assumed and the differential equations of motion have been linearized for ease of calculation. The Smith and Chopra stiffness matrix is used in the equations of motion, and software was written to solve for the stiffness matrix elements. Comparisons are made with bending slope solutions from previously published results, and the presented analysis is compared to empirical results of a composite box-beam under tip loading. Finally, an example solution …

The Determination Of Failure Occurring In The Stator Coil Winding Due To The Over-Voltage Using Matlab Software, Ali Reza Alavizadeh

Morehead State Theses and Dissertations

A thesis presented to the faculty of the College of Science & Technology at Morehead State University in partial fulfillment of the requirements for the degree of Master of Science in Vocational Education & Technology by Ali Reza Alavizadeh on December 1, 2000.

Localized Corrosion Behaviour Of Molybdenum Bearing And Stabilized Stainless Steels In Saline Media, Hany Mohamed Sabry Ahmed

Archived Theses and Dissertations

No abstract provided.

Deformation And Limit Strain Analysis Of Superplastic Materials Using Finite Elements, Noha Mohamed Hassan

Archived Theses and Dissertations

No abstract provided.

An Experimental Study Of Low Speed Open Cavity Flows, Abraham J. Meganathan

Masters Theses

The experimental work is part of an ongoing study aimed at understanding and controlling of cavity instabilities by passive or active steady or unsteady fluid injection. An experimental setup has been designed to quantitatively visualize the flow-field inside the cavity for varying relative dimensions (L/D ratios of 2.0, 2.67, 3.5 and 4.5, W/D of 3.33) at low subsonic speeds ranging from 55 ft/sec to 214 ft/sec using Particle Image Velocimetry (PIV).

The results showed that PIV could provide instantaneous velocity and other flow field data inside and above the cavity. The quality of data is good and may be used …

Prediction Of Airfoil Stall In Icing Conditions Using Wing Surface Pressures, Erik Pederson

Masters Theses

This thesis presents work on a Normalized Lift Coefficient instrumentation system that predicts airfoil stall in icing conditions. The system uses four surface pressures, measured aft of the ice formation, from which the aircraft's normalized lift coefficient is determined. The pressure port locations were selected such that the calibration algorithm remains nearly constant as the leading edge ice shape and thickness change. Data collected in the Western Michigan University Wind Tunnel is presented for three ice formations varying in both shape and thickness. The ice and no ice conditions were compared and a set of four ports was found that …

Texture And Young’S Modulus Of Nickel/Gamma-Alumina Composites, Abdulaziz Alamr

Masters Theses

To improve Young's modulus of 2024-T3 rolled aluminum specimens, it was electroplated with nickel reinforced with nano-particles of γAl₂O₃. Taguchi method was used to investigate the effect of coating variables, which were current density, coating time, and mixing rate, on the coating thickness. The coatings were tested for crystallographic texture, using pole figures of (200) and (111) for nickel and (400) for γAl₂O₃. Surface topography was measured using WYKO Vertical Interference Microscope. The crystallographic texture of nickel in the coating depended on the coating conditions. A universal testing machine was- used to …

Residual Stress And Wear Resistance Of Composite Coatings Of Nickel/Gamma-Alumina, Khaled Abdulrahman Al-Ogab

Masters Theses

Nickel reinforced with nanoparticles of γ−Al₂O₃ have been successfully codeposited on 2024-T3 cold rolled aluminum alloy by electrodeposition with direct current. The effects of current density, particle concentration in the nickel sulfamate bath, air agitation, and coating time on Ni/γ−Al₂O₃ composite have been investigated. The residual stresses and wear resistance of the Ni/γ−Al₂O₃ composite have been measured using X-ray diffractometer and pin-on-disk techniques respectively. The residual stress and wear resistance behavior of the composite were compared with those of nickel-only deposits. An annealed ground nickel, which was mechanically removed from the …

Small Below-Endurance-Limit Cycle Damage Contributions In Variable Sequence Loading For 2024-T351 Aluminum Alloy, Christopher M. Ngiau

Masters Theses

It is a common practice in industry today to totally discard the presence of small below-endurance/fatigue limit cycles while calculating damage accumulation using the Palmgren-Miner rule. However, it was experimentally found in a number of studies that small cycles with stress amplitudes below the fatigue/endurance limit do in fact contribute significantly to the damage accumulation in all types of materials. There was a need to investigate cases where small cycles would only be present for a certain percentage of the material's life. An experimental study was done on 2024- T351 aluminum alloy. Loading was done in low and high cyclic …

The Viscoelastic Behavior Of Pigmented Latex Coating Films, Katharina Prall

Electronic Theses and Dissertations

The mechanical properties of paper coatings are essential for use performance of coated paper (e.g. calendering, printing degradation during printing operations, pick). This study investigates the microscopic and macroscopic mechanisms that determine the viscoelastic behavior of pigmented latex coating films. Pigmented coating layers were prepared with different microstructures. This was achieved by using different pigment types and shapes (polystyrene plastic pigment - spheres, precipitated calcium carbonate - rhombs, clay - plates), and changing pigment volume concentration (PVC). Two styrene-butadiene latices with different degree of carboxylation (acidic level 0.3% and 4.5%) were evaluated to determine effect of adhesion. The viscoelastic material …

Modeling Of A Meat Cooking Process For On-Line Monitoring And Control, Oralia Garcia

Theses and Dissertations - UTB/UTPA

A heat transfer model is developed to predict cooking time of meat patties given the initial temperature of meat, oven temperature, and meat properties to monitor and control a cooking process on-line. Experiments were performed to find the cause of variability in cooked weight and raw temperature effects in forming and final cooked temperature. Advanced charting techniques concluded that only common causes of variability were present in the process. Thermal conductivity experiments were performed to determine the thermal conductivity of meat (k), which was compared with the properties of meat published in literature to validate the experiment. Oven design analysis …

Computer-Based Methods For Constructing Two-Level Fractional-Factorial Experimental Designs With A Requirement Set, Steven L. Forsythe

Theses and Dissertations

This dissertation developed four methodologies for computer-aided experimental design of two-level fractional factorial designs with requirement sets (DOE/RS). The requirement sets identify all the experimental factors and the appropriate interaction terms to be evaluated in the experiment. Taguchi graphs and similar manual methods provide techniques for solving the DOE/RS problem. Unfortunately, these methods are limited because they become difficult to use as the number of factors or interaction terms exceeds ten. This research showed that the DOE/RS problem belongs to a class of difficult-to-solve problems known as NP-Complete. It is the combinatorial nature of NP-Complete problems that causes them to …

Estimating Budget Relationships With A Leontief Input-Output Model, Guenever L. R. Shariff

Theses and Dissertations

Forty years ago, the Office of the Secretary of Defense proposed using the Leontief input-output model to assess tradeoffs in the Department of Defense's (DoD) budget. We demonstrate that the Leontief input-output model can assess tradeoffs in the Air Force's budget. To increase one part of the Air Force's budget, we need to know the interrelationships between that budget area and the other areas. In this research, we look at different methods of how the functional areas might interact. We demonstrate our methodology on two data sets - DoD and the Air Force aggregate budget data. By looking at how …

Covalidation Of Dissimilarly Structured Models, Samuel A. Wright

Theses and Dissertations

A methodology is presented which allows comparison between models constructed under different modeling paradigms. Consider the following situation: Two models are constructed to study different aspects of the same system. One model simulates a fleet of aircraft moving a given combination of cargo and passengers from an onload point to an offload point. A second model is a linear programming model that optimizes the aircraft and route selection required for the same scenario. We develop a methodology to structure the comparison between large-scale models such as these. Models that compare favorably using this methodology are deemed covalid. Models that perform …

Optimal Design Of Beams Undergoing Harmonic Bending And Torsion Using Finite Elements, Arnoldo Garcia

Theses and Dissertations - UTB/UTPA

In this study, the objective is to determine the natural frequency of an Euler-Bernoulli beam with an intermediate mass and inertial component. The beam is studied with fixed and relaxed end conditions. The beam is also modeled with an intermediate support. The models are then compared with an approximate closed form solution for the natural frequency. Results show that the closed form equation is within 2% percent when compared to the exact natural frequency equation.

The beam is modeled with a finite element software. The goal is to minimize the weight of a beam structure subject to harmonic excitation. Results …

Pd/Ni Metal-Oxide-Semiconductor Hydrogen Sensor Utilizing A Segregated Pd-Ti Adhesion Layer, Mark Wayne Jenkins

Electrical and Computer Engineering ETDs

A novel technique has been developed that incorporates an adhesion layer into a hydrogen sensor that is based on a MOS structure. Previous structures containing no adhesion layer exhibited long-term drift and device failure due to delamination of the gate. While devices that did incorporate a normal adhesion layer lost all of their sensitivity. This is the first demonstration of combining virtues of an adhesion layer for a noble metal on insulator while retaining hydrogen sensitivity in a field effect sensor. The design issues related to utilizing Pd films for hydrogen sensors are presented. The recipes for fabricating the sensors …

Fish Cage Physical Scale Modeling, Michael J. Palczynski

Master's Theses and Capstones

Scale model tests were completed in the University of New Hampshire (UNH) Wave/Tow tank to determine the movements and forces on two different fish cage models. The results of the testing were used to validate a finite element analysis and also were scaled up to that of a full sized, deployed fish cage used for aquaculture purposes.

The first model was a “skeleton” cage (without nets) rectangular in shape. This model was moored submerged in front of a viewing window and subjected to various regular waves. The motions were then recorded nonintrusively by means of an optical system acting through …

An Ameliorated Prediction Of The Empennage In-Flight Gust Loads For A General Aviation Aircraft, Philippe Marchand

Master's Theses - Daytona Beach

Airplanes often operate beyond their original design load profiles. Aviation opens so many new possibilities and wide variety of possible activities that it is hard for designers to foresee all loading spectra that the airplane structure will experience throughout its life. Nevertheless, the aircraft structures are required to be designed to failsafe or safe-life criteria to be certified by the FAA. AFS-120 provides a database of normal accelerations that can be used to derive airplane wing loads. ACE-100 describes an acceptable method for determining the fatigue life of an empennage based on the same normal acceleration data provided in AFS-120. …

Modifications To An Existing Glycol Retention Pond And Alternative Technologies Review For Aircraft Deicing Operations And Glycol Recovery And Treatment: Dane County Regional Airport, Steven J. Sletten

Master's Theses - Daytona Beach

The purpose of this study was to review new aircraft deicing technologies and developments and surmise which approach may be the most appropriate for the Dane County Regional Airport’s (KMSN) expansion plans, size, available funds, and environmental impact reduction efforts. This paper focuses on the emerging glycol source reduction issues that may be most suitable for this particular airport. A new deicing technology at KMSN would reduce the amount of aircraft deicing fluid used, allow for effacing flight operations, limit environmental impact, and lessen the costs of maintaining and operating the current glycol fluid recovery and treatment system.

Storm water …

Determination Of Anisotropy Of Granular Materials And Its Relation To Liquefaction Resistance Under Cyclic Loading, Omer Faruk Capar

Civil & Environmental Engineering Theses & Dissertations

Granular materials such as sand deposits have anisotropic characteristics due to the gravitational forces during depositional process and various stress histories. These anisotropic characteristics make evaluation of liquefaction resistance of soil very complex. Since obtaining undisturbed soil specimens for laboratory tests from discrete elements like sandy soils is very laborious, the soil specimens are reconstituted in laboratory with regards to the in-situ density of soil. Reconstituting the soil changes the soil fabric or anisotropic characteristics in comparison with field conditions. Many researchers have pointed out that liquefaction resistance is highly influenced by differences in the structure of the soil (or …

Fourier Transform Raman Spectroscopy For Process Control In The Petroleum Industry, Kent Lawson Wise

Chemistry & Biochemistry Theses & Dissertations

As early as 1950, Raman spectroscopy was proposed as a method to determine aromatics and olefins in hydrocarbon mixtures. Until recently, extensive use of Raman spectroscopy in the characterization of hydrocarbons has not been practical due to several limitations. One early limitation to Raman analysis was the absence of a high intensity and stable excitation source. This problem has been overcome with the advent of lasers. Another limitation was the presence of fluorescence in hydrocarbon fuels when excited by visible lasers. However, the development of Fourier-transform Raman spectrometers now allows Raman spectra to be collected using near-IR lasers (e.g …

Turbulent Mixing And Chemical Reaction In Baffled Stirred Tank Reactors : A Comparison Between Experiments And A Novel Micromixing-Based Computational Fluid Dynamics Model, Otute Akiti

Dissertations

The optimization of reaction processes to maximize the yield of a desired product while minimizing the formation of undesired by-products is one of the most important steps in process development for drug manufacturing or fine chemical production. In many situations the kinetics of product formation can be quite complex and involve a number of intermediate steps as well as parallel and serial reactions. This renders the systems sensitive to the operating conditions. Often, upon scale-up, a decrease in the yield of the desired product is experienced, while more undesired by-products are produced. A large number of interrelated variables influence the …

Feasibility Study To Extract Iron And Chromium From Chromium Contaminated Soils, Wiwat Kamolpornwijit

Dissertations

Chromium contaminated soils, besides being recognized for toxic and hazardous hexavalent chromium, contain high iron concentrations. At some sites, concentrations of iron oxide are higher than 30%. Both iron and chromium in soils have recyclable value provided they can be either concentrated in the oxide form or separated as metal. The concentrated oxide can be used as a substitute for the iron ore. The extracted metal can also be recycled in the steel industry. The objective of this study is to study the feasibility of extracting iron and chromium from soils.

Chromium contaminated soils, can be classified into two groups, …

Axisymetric Vibrations Of Homogeneous And Sandwich Spherical Shells With A Hole At The Center, Wai-Kwong Wong

Dissertations

Based on Hamilton's principle and the theory of elasticity, both linear and nonlinear governing equations of motion are derived for elastic spherical shells. Most of the analysis is focused on the free axisymmetric vibrations of homogeneous and sandwich shallow spherical shells. The nonlinear behavior, which allows for small deflections, is also discussed.

The linear vibrations of homogeneous and sandwich shallow spherical shells with a hole at the center are investigated with emphasis placed on the effect of thickness-shear deformation and rotatory inertia. The effects of curvature and the size of the central hole are studied for free axisymmetric motions of …

Nanoporous Sio2/Vycor Membranes For Air Separation, Mihir Tungare

Theses

Porous Vycor tubes with 40Å initial pore diameter were modified using low pressure chemical vapor deposition (LPCVD) of silicon dioxide N0₂). Diethylsilane (DES) in conjunction with nitrous oxide (N₂O) was used as a precursor to synthesize these SiO₂ films. The aim of this study was to obtain a considerable selectivity between species of comparable size and hence N₂O was used. The use of N₂O was believed to make the process self-limiting. DES was allowed to flow through the tube and N₂O on the outside in the chamber at 550°C …

Reduction Of Peak To Average Power Ratio In Ofdm And Ofdm-Cdma System, Jie Cheng

Theses

High Peak to Average Power Ratio is a main problem in Orthogonal Frequency Division Multiplexing(OFDM) system and Orthogonal Frequency Division Multiplexing -Code Division Multiple Access (OFDM-CDMA) system. Considering a compensated High Power Amplifier(HPA), in order to keep linearity for amplification, Input Back-Off(IBO) of the HP-A, has to be increased for handling a high PAPR. Higher 1130 will make HPA less efficient. Additionally, a signal with high PAPR will suffer clipping when PAPR is larger than 1130 of the HPA. Clipping can cause the distortion of the signal and deteriorate the performance of the system. Reduction of PAPR is a main …

Autonomic Activity In Gulf War Veterans Using Heart Rate And Systolic Blood Pressure Variability, Maryann S. Fam

Theses

Heart rate variability (HRV) describes variations of heart rate and is attributed to cyclic fluctuations in autonomic tone. The different methods of heart rate variability analysis allow for a non-invasive assessment of autonomic activity. This study analyzes the heart rate variability through both frequency domain methods and joint time-frequency domain methods which were executed through the LabVJEW graphical programming language. These algorithms were utilized to assess autonomic nervous system activity in Gulf War veterans with no health complaints versus Gulf War veterans with chronic fatigue syndrome. The heart rate variability analysis was obtained from acquired measurements of heart rate and …

Preparation And Properties Of Tantalum Silicide Films On Silicon Substrates, Lei Jin

Theses

Tantalum silicide (TaSi₂) thin films were sputter deposited on p- type and n- type silicon substrates using VARIAN 3125 magnetron DC sputtering system with TaSi₂ target. The thicknesses of TaSi₂ thin films considered in this study are 200Å, 600Å and 1000Å, respectively. The TaSi₂/Si wafers were annealed at temperatures in the range of 400 to 900°T. The sheet resistances of TaSi₂ thin films with various thicknesses were measured by four-point probe before and after annealing. The sheet resistance decreases with increase in annealing temperature and decreases with the increase in thickness of TaSi …

Drowsy Driver Data Acquisition System, Rafael Norat

Theses

This thesis focuses on detecting the drowsiness of a driver based on differentiation of the EEG signal activity between the eyes open and eyes closed states. Here, it is observed that there is a significant increase 'in a 10 Hz component of the alpha rhythm activity when the subject under test closes his / her eyes. This phenomenon was observed when electrodes were attached to the occipital region. A more desirable approach is to develop a non-intrusive measurement based on a multiturn differential coil combination utilizing a low noise high gain amplifier. The system developed here used an 80,000 turn …