Engineering Commons^™

Analytical Model Of A Thermomechanical Hot Channel Coupled To A Friction Stir Welding Process, Saptarshi Mandal

Mechanical & Aerospace Engineering Theses & Dissertations

Although fusion welding techniques are well established, recent developments in solid state joining techniques have produced high quality welds in materials that are difficult to fusion weld. Friction Stir Welding (FSW) was developed in 1991 as a robust solid-state joining technique that uses a specially shaped rotating tool to generate heat and plasticize material around the tool. The tool then mixes plasticized material along the joint line to produce the weld. Over the last decade, FSW has become increasingly popular for welding aluminum. The combination of attractive properties of the weld and cost-efficiency has led researchers to investigate the feasibility …

Hypersonic Boundary-Layer Stability Across A Compression Corner, Hongwu Zhao

Mechanical & Aerospace Engineering Theses & Dissertations

Stability of a hypersonic boundary-layer over a compression corner was investigated numerically. The three-dimensional compressible Navier-Stokes equations were solved using a fifth-order weighted essentially non-oscillating (ArENO) shock capturing scheme to study the shock wave and boundary-layer interactions. The boundary-layer stability was studied in three distinct regions: upstream of the separation region, inside the separation region and downstream of the separation region. After the mean flow field was computed, linear stability theory was employed to predict the unstable disturbance modes in different flow regions and also to find the most amplified disturbance frequency across the compression corner. Gortler instability computations were …

Optimization-Based Architecture For Managing Complex Integrated Product Development Projects, Hisham Mohamed El-Sayed Abdelsalam

Mechanical & Aerospace Engineering Theses & Dissertations

By the mid-1990's, the importance of early introduction of new products to both market share and profitability became fully understood. Thus, reducing product time-to-market became an essential requirement for continuous competition. Integrated Product Development (IPD) is a holistic approach that helps to overcome problems that arise in a complex product development project. IPD emphasis is to provide a framework for an effective planning and managing of engineering projects. Coupled with the fact that about 70% of the life cycle cost of a product is committed at early design phases, the motivation for developing and implementing more effective methodologies for managing …

Piezoelectric Sensor In The Application Of Rolling Bearing Health Monitoring, Yinyin Liu

Mechanical & Aerospace Engineering Theses & Dissertations

A condition-based monitoring concept for rolling element bearings in machinery utilizing a piezoelectric load sensor is investigated in this thesis. The radially polarized cylindrical piezoelectric sensor is modeled in its specific coordinates. The sensor registers the stress occurring in all directions around it. The sensor's behavior due to several typical loads is analyzed. Based on the induced stresses in the sensor, the sensor's output as an electric charge can be obtained using the method of integration.

Considering both the normal and tangential loads distributed on the rolling beating's roller-raceway contact surface, the dynamic stress distribution in the outer raceway was …

Photonic Crystals: Modeling And Simulation, Shangping Guo

Electrical & Computer Engineering Theses & Dissertations

Photonic crystals are periodic electromagnetic media in optical wavelength scale. They possess photonic band gaps (PBGs) that inhibit the existence of light within the crystals in certain wavelength range. Such band gaps produce many interesting optical phenomena. In this dissertation, the frequency (plane wave method, PWM) and time domain (finite difference time domain method, FDTD) methods are developed for their modeling and simulation.

The theory and algorithm of plane wave method are studied in detail and implemented in a unique and efficient approach. PWM is used to obtain the gap and mode information of ideal and defective photonic crystals. Several …

Diode Laser Crystallization Of Hydrogenated Amorphous Silicon Thin Films For Solar Cell Applications, Brian A. Eaton

Mechanical & Aerospace Engineering Theses & Dissertations

The research objectives were to prove the crystallization of hydrogenated amorphous silicon (a-Si:H) thin films using a diode laser operating at an 805 nm wavelength and to provide morphology trends in laser crystallized samples. This work was primarily intended for solar cell applications.

One industry goal was to produce a high-efficiency and low-cost solar cell capable of competing economically with other energy sources at large scale in the world market. Excimer laser crystallization was one very promising technique. However, two important problems still hindered economic competition. This research addressed the problems associated with excimer laser crystallization by utilizing a diode …

A Numerical Analysis Of A Non-Porous, Flexible Upper Airfoil Surface, Asao Omura

Mechanical & Aerospace Engineering Theses & Dissertations

The aerodynamic behavior of the early Wright brothers' airfoils is an important element of the history of aeronautics. Their fabric-covered wings were not constrained to maintain the airfoil shape of their wooden rib substructures and therefore differences in performance between rigid and flexible Wright airfoil shapes can be expected. The purpose of this thesis was to develop a systematic numerical approach that allows an assessment of the influence of the fabric on the overall aerodynamic behavior of the Wright Model B airfoil. The Model B airfoil was chosen because it is the earliest "production" airfoil and has sufficient documentation to …

Development Of A Multicriteria Spatial Decision Support System With Application To The Economic Optimization Of Aircraft Based Weather Data Collection, Ganzague Erol Osman Ozan

Engineering Management & Systems Engineering Theses & Dissertations

This research is motivated by the economic optimization of the Troposherical Airborne Meteorological Data Reporting (TAMDAR), an aircraft-based meteorological data collection system. In the envisioned TAMDAR system, meteorological data collected by the onboard sensors of selected aircraft are transmitted to the ground as aircraft fly their missions. The data is processed by a national center, which disseminates the data to diverse users such as weather forecasters and aviation control centers. Substantial government funding is required for the implementation and operation of this new data acquisition system and data transmission expenditures constitute the largest portion of the costs. To achieve economic …

Nonlinear Response And Fatigue Estimation Of Aerospace Curved Surface Panels To Acoustic And Thermal Loads, Adam Przekop

Mechanical & Aerospace Engineering Theses & Dissertations

This work presents a finite element modal formulation for large amplitude free vibration of arbitrary laminated composite shallow shells. The system equations of motion are formulated first in the physical structural-node degrees of freedom (DOF). Then, the system is transformed into general Duffing-type modal equations with modal amplitudes of coupled linear bending-inplane modes. The linear bending-inplane coupling is due to the shell curvature as well as unsymmetric lamination stacking. Multiple modes, inplane inertia, and the first-order transverse shear deformation for composites are considered in the formulation. A triangular shallow shell finite element is developed from an extension of the triangular …

Information System Product Development By Integration Of Kano's Customer Satisfaction Model With Quality Function Deployment, Afife Yesim Sireli

Engineering Management & Systems Engineering Theses & Dissertations

Product development of complex, innovative information technology related systems presents difficult challenges for technology managers, and new product failures are a significant problem. The main reason for this is insufficient decision-making due to the lack of a customer-oriented product development process in the information system (IS) companies, which is often related to deficiencies in cooperation between R&D and marketing departments. Integrating consumer requirements into the product design phase is an important factor for improving market success. Therefore, a product development decision model is needed for the managers of information system companies to make more accurate decisions about the characteristics of …

Evolution Of The Band Structure Of Β-In2 S3−3x O3x Buffer Layer With Its Oxygen Content, N. Barreau, S. Marsillac, J. C. Bernède, L. Assmann

Electrical & Computer Engineering Faculty Publications

The evolution of the band structure of β-In2 S3−3x O3x (BISO) thin films grown by physical vapor deposition, with composition x, is investigated using x-ray photoelectron spectroscopy. It is shown that the energy difference between the valence-band level and the Fermi level remains nearly constant as the optical band gap of the films increases. As a consequence, the difference between the conduction band level and the Fermi level increases as much as the optical band gap of the films. The calculation of the electronic affinity [ ] of the BISO thin films shows that it decreases linearly from 4.65 …

The Effects Of Intense Submicrosecond Electrical Pulses On Cells, Jingdong Deng, Karl H. Schoenbach, E. Stephen Buescher, Pamela S. Hair, Paula M. Fox, Stephen J. Beebe

Bioelectrics Publications

A simple electrical model for living cells predicts an increasing probability for electric field interactions with intracellular substructures of both prokaryotic and eukaryotic cells when the electric pulse duration is reduced into the submicrosecond range. The validity of this hypothesis was verified experimentally by applying electrical pulses (durations 100 μs– 60 ns, electric field intensities 3–150 kV/cm) to Jurkat cells suspended in physiologic buffer containing propidium iodide. Effects on Jurkat cells were assessed by means of temporally resolved fluorescence and light microscopy. For the longest applied pulses, immediate uptake of propidium iodide occurred consistent with electroporation as the cause of …

Dynamics Of Phase Transitions On Low-Index Metal Surfaces, Bo Lin

Electrical & Computer Engineering Theses & Dissertations

The surface superheating and phase transitions at the low-index surface of metal were investigated using conventional continuous and 100-ps time-resolved reflection high-energy electron diffraction. Three metal surfaces, In(111), Au(110) and Pb(111), have been investigated in this work. The high temperature behavior of the In(111) surface was investigated using reflection high-energy electron diffraction with 100-ps temporal resolution. The change of surface vacancy density on In(111) is observed from 300 K to near the bulk melting point. The vacancy-formation energy of In(111) surface is estimated from experimental results. The surface vacancy density is observed to increase with temperature; however, the average random …

Parallel Implementation Of A Face Recognition [Sic] System Based On Modular Pca Approach, Rajkiran Gottumukkal

Electrical & Computer Engineering Theses & Dissertations

This thesis describes research in automated methods for the recognition of human faces. The research is driven by the need to design a method, which would ensure high accuracy under the conditions of facial expression, illumination and pose variations. The resulting method is able to cope with uncontrolled nature of facial expression, illumination and head rotations. The main novelty of this work is the idea that some of the local facial features do not vary even when the facial expression, illumination and pose vary. This idea is applied to the existing principle component analysis lPCA) method to arrive at a …

A Pipelined Architecture For Real Time Correction Of Barrel Distortion In Wide-Angle Camera Images, Hau Trung Ngo

Electrical & Computer Engineering Theses & Dissertations

Images captured by wide-angle cameras show barrel type spatial distortion due to wide-angle configuration of the camera lens where image regions farther from the center are compressed in a nonlinear fashion. The barrel distortion correction technique based on least squares estimation attempts to correct a distorted image by expanding it nonlinearly so that straight lines in the object space remain straight in the image space. The intensity value of a pixel in the expanded image is calculated by back mapping its position to the corresponding position in the distorted image and performing linear interpolation on the neighboring pixels. Distorted images …

Analysis Of Ingaassb/Aigaassb Photodetectors For Applications At The 2.0 Micron Wavelengths, Phani Pendyala

Electrical & Computer Engineering Theses & Dissertations

The study of an InGaAsSb-based heterojunction avalanche photo detector has been carried out for 2-μm applications. A separate absorption and multiplication structure was used because it minimizes the tunneling component of the dark current in the absorption region, and also provides single-carrier injection into the multiplication region. This is a well-known requirement for reducing the multiplication noise. The primary goal was to evaluate the potential of InGaAsSb-AlGaAsSb photo-detectors for photodetection at the two-micron wavelength.

InGaAsSb is a relatively new material, and, therefore, characterization and photodetector response analysis based on this material are not available in the literature. In this thesis …

Adaptive Segmentation Techniques For Object Region Extraction From Images With Complex Lighting Environment, Deepthi P. Valaparla

Electrical & Computer Engineering Theses & Dissertations

Automated image segmentation of objects in complex lighting environments is a difficult task since it is not possible to pre-define a threshold to distinguish the object from the background. It is ascertained that an effective threshold citation for such objects depends on the negative binomial distribution of the object region with respect to the background lighting. Based on this concept, a novel adaptive threshold selection method for automatic segmentation of the lumen region in endoscopic images is presented in this thesis. More precise lumen region and boundary are obtained by an integrated neighborhood search based region growing procedure whose speed …

Implementation And Testing Of Unsteady Reynolds-Averaged Navier-Stokes And Detached Eddy Simulation Using An Implicit Unstructured Multigrid Scheme, Juan A. Palaez

Mechanical & Aerospace Engineering Theses & Dissertations

Investigation and development of the Detached Eddy Simulation (DES) technique for the computation of unsteady flows on unstructured grids are presented. The motivation of the research work is driven by the ultimate goal of predicting separated flows of aerodynamic importance, such as massive stall or flows over complex non-streamlined geometries. These cases, in which large regions of massively separated flow are present, represent a challenge for conventional Unsteady Reynolds-Averaged Navier-Stokes (URANS) models, that in many cases, cannot produce solutions accurate enough and/or fast enough for industrial design and applications. A Detached Eddy Simulation model is implemented and its performance compared …

Field Emission Based Sensors Using Carbon Nanotubes, Changkun Dong

Physics Theses & Dissertations

A number of sensitive applications would be greatly benefited by the development of better cold cathodes that employ the electron field emission process. Among the many kinds of field emitters that could be tried, carbon nanotubes (CNT) have a number of distinct advantages because of their unique geometrical structure, chemical inertness, mechanical stiffness, and high thermal and electrical conductivities. This dissertation describes research in which CNT cathodes were fabricated and their emission characteristics were measured.

Multi-walled carbon nanotubes (MWNT) were grown by chemical vapor deposition (CVD) on various substrates: Ni and Hastelloy gauze, 304 stainless steel (SS) plates, and Ni-coated …

A Combinatorial Technique For Face Detection Based On Color And Statistical Analysis, Harishwaran Hariharan

Electrical & Computer Engineering Theses & Dissertations

Automatic detection of faces from video sequences is an important task in security applications. The number, location, size and orientation of human faces in a video frame are unpredictable and can vary from frame to frame. A face detection algorithm for color images in the presence of varying lighting conditions and complexity in background relying upon color and statistical analysis is presented in this thesis. The new method detects skin regions over the entire image and then classifies the skin regions as faces and non-faces. Segmentation of skin regions is performed by a novel color space merging procedure named Integrated …

Creating Enterprise Simulations Using High Level Architecture, Anton R. Lidums

Electrical & Computer Engineering Theses & Dissertations

Despite an established need, there are two remaining roadblocks to building distributed simulations and enterprise simulation systems. First, commercial simulation packages and engineering modeling tools are not readily distributable across multiple computers and have traditionally had very little impetus for utilizing a distributable format. Second, although HLA simulations have been built and there are tools to facilitate those efforts, very little has been done or written that specifically describes a "non-standard" integration implementation in sufficient detail to make the process reusable or repeatable. This thesis introduces a proof of concept prototype that was developed to integrate simulations. The paper presents …

Two Dimensional Numerical Simulation Of Highly-Strained Hydrogen-Air Opposed Jet Laminar Diffusion Flames, Kyu C. Hwang

Mechanical & Aerospace Engineering Theses & Dissertations

In this study, a detailed 2-D numerical technique is utilized to investigate the structure, and flame extinction and restoration characteristics of laminar hydrogen-air opposed jet diffusion flames, using both plug (uniform) and parabolic inflow boundary conditions for 3 millimeter jet tubes, spaced 6 millimeters apart and imbedded in low velocity coflows.

First, by using the most recent of two chemical kinetic models, excellent agreement was obtained between calculated distributions of temperature and major species, and published UV laser Raman scattering measurements, for 50% and 100% hydrogen-air flames over a range of input strain rates. Agreement with measured OH profiles was …

Use Of Eps-Filled Tires As Lightweight Construction Material, Sethapong Sethabouppha

Civil & Environmental Engineering Theses & Dissertations

The purpose of this research is to study the possibility of recycling discarded automobile tires as a lightweight construction material by injecting expanded polystyrene (EPS) into the hollow space of the tires. The observation from compression tests on used tires revealed that the tread wall of these tires bent toward their own center. This inward deformation should provide confining stress to the contained EPS, and thus the compressive strength of EPS-tire composite was expected to be higher than that of EPS.

To produce EPS-filled tire prototypes for this study, EPS type II, with density of 24 kg/m3, was injected into …

Output Analysis Of Configurable Port Simulation, Ravikiran Jogu

Electrical & Computer Engineering Theses & Dissertations

The Configurable Port Simulation (CPortS) is a simulation of military cargo moving through a commercial seaport during a force deployment. CPortS simulates cargo at the individual entity level of detail. Simulation at the individual entity level generates huge amounts of output data making the output analysis difficult. To understand the reasons as to why bottlenecks occur in the process of cargo clearance, an analyst needs to be able to partition the data during analysis, not a priori. This makes the estimation of required graph generation impossible, which demands a very dynamic output analysis tool that can enable the analyst to …

Automatic Speaker Identification Using Reusable And Retrainable Binary-Pair Partitioned Neural Networks, Ashutosh Mishra

Electrical & Computer Engineering Theses & Dissertations

This thesis presents an extension of the work previously done on speaker identification using Binary Pair Partitioned (BPP) neural networks. In the previous work, a separate network was used for each pair of speakers in the speaker population. Although the basic BPP approach did perform well and had a simple underlying algorithm, it had the obvious disadvantage of requiring an extremely large number of networks for speaker identification with large speaker populations. It also requires training of networks proportional to the square of the number of speakers under consideration, leading to a very large number of networks to be trained …

Numerical Studies On Supersonic Mixing And Combustion Phenomena, Tarek M. Abdel-Salam

Mechanical & Aerospace Engineering Theses & Dissertations

A numerical study is conducted to investigate the mixing, combustion, and flow characteristics of different scramjet-combustor configurations. Three-dimensional models for the combustors have been used. Numerical results are obtained using a finite volume computational fluid dynamics (CFD) code with unstructured grids with sizes between 200,000 and 400,000 cells.

In the first part of the current study, the effects of the side angle of the fuel injectors in both mixing and combustion processes are investigated. Raised (compression) and relieved (expansion) wall-mounted ramps are used with side angles of 0 (unswept), 5, and 10 degrees. Results are obtained for nonreacting flows as …

Fuzzy System Identification Based Upon A Novel Approach To Nonlinear Optimization, Raymond Scott Starsman

Electrical & Computer Engineering Theses & Dissertations

Fuzzy systems are often used to model the behavior of nonlinear dynamical systems in process control industries because the model is linguistic in nature, uses a natural-language rule set, and because they can be included in control laws that meet the design goals. However, because the rigorous study of fuzzy logic is relatively recent, there is a shortage of well-defined and understood mechanisms for the design of a fuzzy system. One of the greatest challenges in fuzzy modeling is to determine a suitable structure, parameters, and rules that minimize an appropriately chosen error between the fuzzy system, a mathematical model, …

Common Data Administration, Data Management, And Data Alignment As A Necessary Requirement For Coupling C4isr Systems And M&S Systems, Andreas Tolk

Computational Modeling & Simulation Engineering Faculty Publications

Within the application domain of military simulation systems, training and exercises as well as support to real operations require the coupling of the simulation system delivering the needed functionality with the Command, Control, Computing, Communications, Intelligence, Surveillance, and Reconnaissance (C4ISR) system providing the necessary data. The solution to this challenge is to build appropriate interfaces. Although in long term a more integrated approach will be necessary, in short and mid term, gateways and interfaces are likely to remain the standard. However, in order to succeed with the respective efforts, at least on the data level of interoperability, a common solution …

Identifying Critical Knowledge For Projects, Timothy Kotnour, Rafael Landaeta

Engineering Management & Systems Engineering Faculty Publications

This article is the result of an investigation of the challenge faced by project managers in identifying critical knowledge for projects. Five major areas of project knowledge are identified. The literature defines knowledge as information that has been given meaning.

The critical knowledge for projects was identified through the literature and by our experience as applied researchers. Managers of multi-project organizations can use this article as a guide for identifying the critical knowledge that is vital for their projects.

An Experimental Study Of Flow Control Techniques On A Multi-Element Airfoil, Ira James Walker

Mechanical & Aerospace Engineering Theses & Dissertations

The results of a wind tunnel experiment are reported, which investigated two different flow control techniques that demonstrated the potential of increasing the lift coefficient on a multi-element airfoil. The data also indicated that boundary-layer separation on the trailing-edge flap could be reduced significantly. Results of the investigation revealed that for some test conditions an increased amount of suction occurred on the upper surface of the main element where the flow was attached. One of the techniques that was tested in this investigation involved the use of a pair of piezoelectric devices attached to the model to provide oscillatory motion …