Engineering Commons^™

Fusion Of Imaging And Inertial Sensors For Navigation, Michael J. Veth

Theses and Dissertations

The motivation of this research is to address the limitations of satellite-based navigation by fusing imaging and inertial systems. The research begins by rigorously describing the imaging and navigation problem and developing practical models of the sensors, then presenting a transformation technique to detect features within an image. Given a set of features, a statistical feature projection technique is developed which utilizes inertial measurements to predict vectors in the feature space between images. This coupling of the imaging and inertial sensors at a deep level is then used to aid the statistical feature matching function. The feature matches and inertial …

Graph Theoretical Analysis Of Network Centric Operations Using Multi-Layer Models, Ann Wong-Jiru

Theses and Dissertations

As the Department of Defense continues its transformations to a network centric force, evaluating DoD's progression towards net-centricity remains a challenge. This research proposes to extend the Network Centric Operation Common Framework Version 2.0 (draft) with the metrics based in graph theory and, specifically addresses, among other metrics, the measurement of a net-centric force's mission effectiveness. The research incorporates the importance of understanding network topology for evaluating an environment for net-centricity and using network characteristics to help commanders assess the effects of network changes on mission effectiveness. The multi-layered model of Network Centric Operations and interlayer mapping are introduced to …

Factors Influencing Engineering Students' Decisions To Cheat By Type Of Assessment, Honor J. Passow, Mathew J. Mayhew, Cynthia J. Finelli, Trevor S. Harding, Donald D. Carpenter

Materials Engineering

Academic dishonesty (cheating) has been prevalent on college campuses for decades, and the percentage of students reporting cheating varies by college major. This study, based on a survey of 643 undergraduate engineering majors at 11 institutions, used two parallel hierarchical multiple regression analyses to predict the frequency of cheating on exams and the frequency of cheating on homework based on eight blocks of independent variables: demographics, pre-college cheating behavior, co-curricular participation, plus five blocks organized around Ajzen's Theory of Planned Behavior (moral obligation not to cheat, attitudes about cheating, evaluation of the costs and benefits of cheating, perceived social pressures …

Modeling Fracture In Z-Pinned Composite Co-Cured Laminates Using Smeared Properties And Cohesive Elements In Dyna3d, Jason K. Freels

Theses and Dissertations

The purpose of the present research was three-fold: 1) gain a more sophisticated understanding of the response of co-cured composite joints with and without through-thickness reinforcement (TTR), 2) compare the behavior of specimens reinforced with various sizes and densities of reinforcement, and 3) use experimental data to verify the existing DYNA3D smeared property model. Double cantilever beam, end-notch flexure and T-section specimens reinforced with 0.011" diameter z-pins at 2% and 4% volume densities were tested to determine the mode I, mode II and mixed mode (I and II) behavior. Results were added to preliminary research in which tests were conducted …

Rate Dependence Of Tensile Properties And Stress-Strain Behavior Of An Oxide/Oxide Ceramic Matrix Composite At Elevated Temperature And The Effects Of Low-Magnitude Sustained Loading On Composite Microstructure, Andrew T. Radzicki

Theses and Dissertations

Advanced aerospace structures and components require materials that exhibit high strength at high operating temperatures. Nextel ™ 720/Alumina (N720/A) is an oxide/oxide, porous-matrix ceramic-matrix composite developed for load bearing applications at elevated temperatures. The current research investigates the rate dependence of tensile properties of the N720/A CMC at 1200°C as well as the creep behavior of this composite under applied stresses in the 1-25 MPa range. In addition, influence of prior loading rate on the creep response of N720/A under applied stresses above 50 MPa was evaluated at 1200°C. Tensile tests conducted at loading rate of 0.0025 and 25 MPa/s …

Effects Of Environment On Creep Behavior Of Two Oxide-Oxide Ceramic Matrix Composites At 1200°C, Pavlos Koutsoukos

Theses and Dissertations

Previous studies by the advisor and graduate students examined creep behavior of the Nextel720/Alumina CMC in air and in 100% steam environments at 1200 and 1330°C. Results showed that while this oxide/oxide system exhibits an exceptionally high fatigue limit at 1200°C it also experiences substantial strain accumulation under sustained loading conditions. Furthermore, these earlier investigations revealed a significant degrading effect of 100% steam environment on material performance under both static and cyclic loadings. The present effort will investigate creep rupture behavior of Nextel720/Alumina composite in the inert gas environment. In addition, creep rupture behavior of Nextel720/Aluminosilicate CMC will be investigated …

Parameter Estimation Of A Tactical Missile Using Linear Regression, Kelly S. Powers

Theses and Dissertations

This research presents the method of Linear Regression as a parameter identification method to determine the longitudinal dimensional stability derivatives of a tactical missile. Missile flight histories are characterized by rapid accelerations, rapidly changing mass property characteristics with often short flight times. These characteristics make accurate parameter estimation of the missile aerodynamics more challenging than for aircraft. The simulation used for this research was created in MATLAB/SIMULINK based on the missile trajectory program, TRAP. The aerodynamic data for the 6- DoF missile model was based on a supersonic, tail controlled missile similar to an AIM-9X missile. Two command input types …

Design And Numerical Simulation Of Two Dimensional Ultra Compact Combustor Model Sections For Experimental Observation Of Cavity-Vane Flow Interactions, David S. Moenter

Theses and Dissertations

An improved computational fluid dynamics (CFD) model was developed for numerical simulation of the Ultra Compact Combustor (UCC) concept to enhance turbulent flow characterization of the circumferentially traveling, centrifugal-force enhanced combustion, cavity flow into the engine main flow passage via a radial cavity in the turbine axial guide vanes. The CFD model uses a dense grid on a 60° periodic, axisymmetric combustor section, with the RNG κ-ε turbulence model to resolve turbulent flow details. An overall analysis and performance evaluation of the experimentally tested UCC configuration and an axially shortened cavity baseline configuration was conducted at various experimentally documented operating …

Natural Frequencies And Mode Shapes Of A Nonlinear, Uniform Cantilevered Beam, Daniel J. Marquez-Chisolm

Theses and Dissertations

A series of experiments in 1975, referred to as the Princeton Beam Experiments, were performed to measure natural frequencies and create a nonlinear elastic deformation model to improve helicopter main beam designs. These experiments used a homogeneous 7075 aluminum beam and have been referenced as a baseline for the past thirty years to validate computer models and theories in an effort to build beams capable of withstanding aero-elastic, static, and dynamic loading. The purpose of this study is to measure the dynamic nonlinear bending and torsion response of a cantilever beam. The natural frequencies are measured in the flatwise and …

Three Component Velocity Measurements In The Tip Vortex Of A Micro-Air-Vehicle, Hong-Joon Park

Theses and Dissertations

The purpose of this research was to improve the MAV that will be used for battle damage assessment and reconnaissance or local surveillance through the experiments in AFIT wind tunnel. The experiments were performed to investigate the wing displacement and wing tip vortex interaction. To conduct the experiments, telescopic survey tool and tri-axial hot-wire anemometer was utilized. The results indicate that wing tip displacement of the flexible wing was approximately 8 times that of the rigid wing in an unstalled condition and data suggests that flexible wing has a denser core-distribution of velocity within the wing tip vortex and delays …

Fast Scene Based Nonuniformity Correction With Minimal Temporal Latency, Christopher A. Rice

Theses and Dissertations

The focus of this research was to derive a new algorithm for correction of gain nonuniformities in LIDAR focal plane arrays using as few frames as possible. Because of the current low production rate of LIDAR focal plane arrays there is a natural tendency for extreme nonuniformities to exist on a pixel by pixel basis as the manufacturing technique has not yet been perfected. Generally, nonuniformity correction techniques require a large number of frames and/or have obscure requirements on the translational shifts in the input image frames. This thesis presents a solution for finding multiplicative nonuniformities that exist in a …

Structural Analysis Of The Rigidizable Inflatable Get-Away-Special Experiment, Anna E. Gunn-Golkin

Theses and Dissertations

The purpose of this research was to validate the structural integrity of the Rigidizable Inflatable Get-Away-Special Experiment (RIGEX) and make appropriate improvements to the design, motivated by static and dynamic analysis results. RIGEX is designed to advance the use of rigidizable inflatable structures in the space environment by providing three sets of on-orbit test data on the structural characteristics of three thermoplastic composite tubes. This thesis discusses the RIGEX structural analysis. The term structural analysis refers to the development of a detailed finite element model and the tests for which the model was used. The finite element model provided an …

Scaling Flight Tests Of Unmanned Air Vehicles, Jeevani I. Abeygoonewardene

Theses and Dissertations

Increasing technological advances and research interest in unmanned air vehicles (UAVs), have led to the need for having safe, inexpensive and effective means of experimenting with their fight performance and surveillance capabilities. Work has previously been done in areas of controlling, analyzing, and predicting cooperative and autonomous operations of UAVs and other vehicles. In addition, there are well established guidelines for scaling experiments in fluid mechanics, where geometric, kinematic and dynamic similarity is obtained by formulating problems in terms of non dimensional variables using dimensional analysis. However, little or no work has been done in developing experiments or guidelines for …

Effects Of Phase Difference Between Axial And Contact Loads On Fretting Fatigue Behavior Of Titanium Alloy, Mohammad Almajali

Theses and Dissertations

Fretting fatigue is the surface damage that occurs at the interface between two components that are undergoing a small amplitude oscillatory movements. It results in a reduction of the material life as compared to the plain fatigue. Most of the previous works were accomplished under a constant applied normal load and a little effort was done under a variable contact load, while none of these studies has considered the phase difference between the axial load and the contact load. The primary goal of this study is to investigate the effect of phase difference between axial and contact loads on fretting …

Fault And Defect Tolerant Computer Architectures: Reliable Computing With Unreliable Devices, George R. Roelke Iv

Theses and Dissertations

This research addresses design of a reliable computer from unreliable device technologies. A system architecture is developed for a "fault and defect tolerant" (FDT) computer. Trade-offs between different techniques are studied and yield and hardware cost models are developed. Fault and defect tolerant designs are created for the processor and the cache memory. Simulation results for the content-addressable memory (CAM)-based cache show 90% yield with device failure probabilities of 3 x 10(-6), three orders of magnitude better than non fault tolerant caches of the same size. The entire processor achieves 70% yield with device failure probabilities exceeding 10(-6). The required …

Efficacy Of Virtual Models In A Production Systems Course, Lawrence Whitman, Barbara Chaparro

Publications

Wichita State University has developed an integrated set of virtual reality models of an aircraft assembly line. These models are intended to provide students an ‘artifact’ of industrial and manufacturing engineering by providing a realistic environment for initial learning and application. By utilizing a virtual model of the line, students are able to view the process and interrogate the process details, make changes and observe the effects, and gain a better understanding of the concepts and their interrelationships. This paper presents the method used to assess if virtual models (computer models of a real factory) lead to: improved perception of …

Grain Growth Behavior At Absolute Zero During Nanocrystalline Metal Indentation, F. Sansoz, V. Dupont

Aerospace Engineering - Daytona Beach

The authors show using atomistic simulations that stress-driven grain growth can be obtained in the athermal limit during nanocrystalline aluminum indentation. They find that the grain growth results from rotation of nanograins and propagation of shear bands. Together, these mechanisms are shown to lead to the unstable migration of grain boundaries via process of coupled motion. An analytical model is used to explain this behavior based on the atomic-level shear stress acting on the interfaces during the shear band propagation. This study sheds light on the atomic mechanism at play during the abnormal grain coarsening observed at low temperature in …

Modulation Of Stretch Reflexes Of The Finger Flexors By Sensory Feedback From The Proximal Upper Limb Poststroke, Gilles Hoffmann, Derek G. Kamper, Jennifer H. Kahn, William Zev Rymer, Brian D. Schmit

Biomedical Engineering Faculty Research and Publications

Neural coupling of proximal and distal upper limb segments may have functional implications in the recovery of hemiparesis after stroke. The goal of the present study was to investigate whether the stretch reflex response magnitude of spastic finger flexor muscles poststroke is influenced by sensory input from the shoulder and the elbow and whether reflex coupling of muscles throughout the upper limb is altered in spastic stroke survivors. Through imposed extension of the metacarpophalangeal (MCP) joints, stretch of the relaxed finger flexors of the four fingers was imposed in 10 relaxed stroke subjects under different conditions of proximal sensory input, …

Melt Detection In Antarctic Ice Shelves Using Scatterometers And Microwave Radiometers, David G. Long, Lucas B. Kunz

Faculty Publications

Ku-band dual-polarization radar backscatter measurements from the SeaWinds-on-QuikSCAT scatterometer are used to determine periods of surface freeze and melt in the Antarctic ice shelves. The normalized horizontal-polarization radar backscatter (sigmao) and backscatter polarization ratio are used in maximum-likelihood estimation of the ice state. This method is used to infer the daily ice-surface conditions for 25 study locations located on the Ronne, Ross, Larsen, Amery, Shackleton, and other ice shelves. The temporal and spatial variations of the radar response are observed for various neighborhood sizes surrounding each given location during the study period. Criteria for determining the dates of melt onset …

Maximizing Miniature Aerial Vehicles, Stephen Griffiths, Jeffery Brian Saunders, Andrew Curtis, Blake Barber, Timothy W. Mclain, Randal W. Beard

Faculty Publications

Despite the tremendous potential demonstrated by miniature aerial vehicles (MAV) in numerous applications, they are currently limited to operations in open air space, far away from obstacles and terrain. To broaden the range of applications for MAVs, methods to enable operation in environments of increased complexity must be developed. In this article, we presented two strategies for obstacle and terrain avoidance that provide a means for avoiding obstacles in the flight path and for staying centered in a winding corridor.

Comparison Of Microcantilever Hg Sensing Behavior With Thermal Higher Order Modes For As-Deposited Sputtered And Thermally Evaporated Au Films, Gregory P. Nordin, Michael A. George, Ashwini R. Kadam

Faculty Publications

As-deposited sputtered and thermally evaporated Au films are studied for Hg sensing with rectangular Si microcantilevers. Microcantilever deflection and frequency shifts in the first four thermally induced flexural modes are measured for each type of Au film as a function of Hg exposure. All thermally induced higher order modes show shifts in their frequencies for Hg exposures when the Au is sputter deposited whereas typically only the third and fourth order modes show frequency shifts when the Au is thermally evaporated. A technique is employed in order to vary Au coverage along a microcantilever surface. The shifts in the thermal …

On Mitigating Distributed Denial Of Service Attacks, Zhiqiang Gao

Dissertations

Denial of service (DoS) attacks and distributed denial of service (DDoS) attacks are probably the most ferocious threats in the Internet, resulting in tremendous economic and social implications/impacts on our daily lives that are increasingly depending on the wellbeing of the Internet. How to mitigate these attacks effectively and efficiently has become an active research area. The critical issues here include 1) IP spoofing, i.e., forged source lIP addresses are routinely employed to conceal the identities of the attack sources and deter the efforts of detection, defense, and tracing; 2) the distributed nature, that is, hundreds or thousands of compromised …

Unified Architecture Of Mobile Ad Hoc Network Security (Mans) System, Li Ling

Dissertations

In this dissertation, a unified architecture of Mobile Ad-hoc Network Security (MANS) system is proposed, under which IDS agent, authentication, recovery policy and other policies can be defined formally and explicitly, and are enforced by a uniform architecture. A new authentication model for high-value transactions in cluster-based MANET is also designed in MANS system. This model is motivated by previous works but try to use their beauties and avoid their shortcomings, by using threshold sharing of the certificate signing key within each cluster to distribute the certificate services, and using certificate chain and certificate repository to achieve better scalability, less …

Constitutive Modeling Of The Thermo-Mechanics Associated With Crystallizable Shape Memory Polymers, Gautam Barot

Dissertations

This research addresses issues central to material modeling and process simulations. Here, issues related for developing constitutive model for crystallizable shape memory polymers are addressed in details. Shape memory polymers are novel material that can be easily formed into complex shapes, retaining memory of their original shape even after undergoing large deformations. The temporary shape is stable and return to the original shape is triggered by a suitable mechanism such heating the polymer above a transition temperature. Crystallizable shape memory polymers are called crystallizable because the temporary shape is fixed by a crystalline phase, while return to the original shape …

Characterization Of Hypertension Through Multivariate Analysis Utilizing Linear And Nonlinear Methods, Diane L. Donnelly

Dissertations

Analysis of blood pressure by nonlinear methods is vastly underutilized in current research. As such, 24-hour ambulatory blood pressure data from a small cohort of borderline hypertensive and normotensive subjects were analyzed using linear and nonlinear methods. Data were collected and provided by researchers from Columbia University. The cohort size was twelve subjects, consisting of two groups of six each. Although disease state was known, group membership for individual subjects was not. Therefore, one aspect of this research was to separate the cohort, a-priori, into two distinct, evenly sized groups, based solely on analysis results. Separation was accomplished by the …

Automatic Modulation Classification Of Communication Signals, Zaihe Yu

Dissertations

The automatic modulation recognition (AMR) plays an important role in various civilian and military applications. Most of the existing AMR algorithms assume that the input signal is only of analog modulation or is only of digital modulation. In blind environments, however, it is impossible to know in advance if the received communication signal is analogue modulated or digitally modulated. Furthermore, it is noted that the applications of the currently existing AMR algorithms designed for handling both analog and digital communication signals are rather restricted in practice. Motivated by this, an AMR algorithm that is able to discriminate between analog communication …

Analytical Model For Staging Emergency Evacuations, Vivek V. Korikanthimath

Dissertations

Disaster response in areas of high population density is centered on the efficient evacuation of people and possibly goods. Developing evacuation plans suitable for different levels of urgency based on the intensity of threat is a challenging task. In case of densely populated cities (e.g., New York, Los Angeles), the level of threat is enhanced by the congestion of their transportation systems, and the decision to evacuate a region simultaneously or by dividing it into multiple stages (or zones) affects the required evacuation time and associated delays.

The evolution of the traffic conditions on the evacuation route can vary significantly …

Evaluation Of Environmental Carrying Capacity And Application Of The Sustainability Target Method, Chatpet Yossapol

Dissertations

The environmental carrying capacity (CC) is defined as the capacity of the earth to absorb or tolerate potentially stressful burdens imparted at various scales and locations, that is, to accommodate the ecological stresses without showing permanent damage. The CC can be used as a reference dataset for Life Cycle Assessment (LCA) purposes and as a baseline for other environmental studies.

In this research, a set of impact-oriented U.S. CC is developed for both input- and output-related impacts. CC for eight common impact categories is evaluated: resource depletion, global warming, ozone depletion, acidification, eutrophication, photochemical ozone formation, human toxicity, and eco-toxicity. …

The Impact Of Abiotic And Biogenic Mn Oxide Coatings On Contaminant Mobility, Bioavailability, And Attenuation, Thipnakarin Boonfueng

Dissertations

Abiotic and biogenic manganese oxide coatings significantly impact the mobility and bioavailability of metals in soils and sediments. While sorption to discrete Mn oxides has been investigated in a number of studies, coatings have not received as much attention. Abiotic nanocrystalline (hydrous manganese oxide (HMO)) and crystalline Mn oxides (bimessite and pyrolusite) coated on montmorillonite were studied for formation, structure, stability, and surface properties. Coatings dominated the clay surface characteristics where the surface charge behaved similar to that of the discrete oxide and the local structure was consistent with the pure oxide phase. Furthermore, in sorption studies, Zn and Pb …

Field Monitoring And Hourly Simulation Modeling Of The Melink Intellihood Exhaust Control System At Two Supermarkets, One Restaurant, And One Fast Food Restaurant; Final Report, Florida Solar Energy Center, Lixing Gu

FSEC Energy Research Center®

Monitoring of variable speed control of exhaust and make-up air on four Florida buildings is performed. Computer modeling is used to determine energy and demand savings on a yearly basis.