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2006

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Articles 1231 - 1260 of 3391

Full-Text Articles in Engineering

Factors Affecting National Technological Absorptive Capacity, Karim Fathy Saad Jun 2006

Factors Affecting National Technological Absorptive Capacity, Karim Fathy Saad

Archived Theses and Dissertations

No abstract provided.

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Leadership In Student Distance Education Teams, Leroy Cox, Susan L. Murray, David Spurlock Jun 2006

Leadership In Student Distance Education Teams, Leroy Cox, Susan L. Murray, David Spurlock

Engineering Management and Systems Engineering Faculty Research & Creative Works

Interactive video technology has become a widely used medium for education. A prominent implementation of this technology, interactive distance learning, involves groups of students at local and remote sites connected by audio and video teleconferencing. This approach has made the task of delivering vital undergraduate and graduate engineering courses to distributed audiences much easier. As this approach has permeated more curricula, distance education instructors have increasingly assigned projects that require distance learners to work together as an element of the final course grade. This trend presents an interesting opportunity for researchers to understand the nature of interactions among course participants …

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Adaptive Neural Network Control And Wireless Sensor Network Based Localization For Uav Formation, H. Wu, Jagannathan Sarangapani Jun 2006

Adaptive Neural Network Control And Wireless Sensor Network Based Localization For Uav Formation, H. Wu, Jagannathan Sarangapani

Electrical and Computer Engineering Faculty Research & Creative Works

We consider a team of unmanned aerial vehicles (UAV's) equipped with sensors and motes for wireless communication for the task of navigating to a desired location in a formation. First a neural network (NN)-based control scheme is presented that allows the UAVs to track a desired position and orientation with reference to the neighboring UAVs or obstacles in the environment. Second, we discuss a graph theory-based scheme for discovery, localization and cooperative control. The purpose of the NN cooperative controller is to achieve and maintain the desired formation shape in the presence of unmodeled dynamics and bounded unknown disturbances. Numerical …

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The Effect Of Sample Size And Ground Granulated Blast-Furnace Slag On Hydration Temperature In Hot Climates, Mariam Eissa Saeed Al-Harrasi Jun 2006

The Effect Of Sample Size And Ground Granulated Blast-Furnace Slag On Hydration Temperature In Hot Climates, Mariam Eissa Saeed Al-Harrasi

Theses

Heat of hydration of Portland cement mixes is of great importance to civil engineers. While there is great deal of work being carried out on the hydration temperature of OPC-slag mixes, there is a lack in the literature of research work on the effect of such materials in real hot climates. The current research examines the influence of ground granulated blast-furnace slag (ggbs) as a partial cement replacement on temperature evolution during hydration in winter and summer in AI-Ain (interior region of the United Arab Emirates). Evolution of temperature inside the concrete was recorded by the aid of a Labview …

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A Time-To-First Spike Cmos Image Sensor With Coarse Temporal Sampling, Qiang Luo, John G. Harris, Zhiliang J. Chen Jun 2006

A Time-To-First Spike Cmos Image Sensor With Coarse Temporal Sampling, Qiang Luo, John G. Harris, Zhiliang J. Chen

Electrical and Computer Engineering Faculty Research & Creative Works

Conventional voltage-based CMOS image sensors inherently have a dynamic range of about 60 dB. To extend the dynamic range, a two-degree of freedom time-based CMOS image sensor is proposed. Instead of reading analog voltages off chip, a time representation is used to record when the photodetector voltage passes a timing-varying threshold. The time measurements are combined with the reference voltage waveform to reconstruct the image. Experimental results on a prototype 32 x 32-pixel array CMOS image sensor verify that the two-degree of freedom sampling technique is feasible for ultra-wide dynamic range imaging. A measured 115 dB dynamic range at 30 …

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Lock-Based Cache Coherence Protocol For Chip Multiprocessors, Ihab Ismail Jun 2006

Lock-Based Cache Coherence Protocol For Chip Multiprocessors, Ihab Ismail

Archived Theses and Dissertations

Chip multiprocessor (CMP) is replacing the superscalar processor due to its huge performance gains in terms of processor speed, scalability, power consumption and economical design. Since the CMP consists of multiple processor cores on a single chip usually with share cache resources, process synchronization is an important issue that needs to be dealt with. Synchronization is usually done by the operating system in case of shared memory multiprocessors (SMP). This work studies the effect of performing synchronization by the hardware through its integration with the cache coherence protocol. A novel cache coherence protocol, called Lock-based Cache Coherence Protocol (LCCP) was …

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A Three Core Type Heterogeneous Chip Multiprocessor: Towards An Optimized Cmp Architecture, Ali Yehia Ali Jun 2006

A Three Core Type Heterogeneous Chip Multiprocessor: Towards An Optimized Cmp Architecture, Ali Yehia Ali

Archived Theses and Dissertations

No abstract provided.

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Bs News Jun 2006

Bs News

Building Services Engineering

No abstract provided.

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Infrared Optical Properties Of MgX-1Zn1-XO Thin Films (0≤X≤1): Long-Wavelength Optical Phonons And Dielectric Constants, C. Bundemann, A. Rahm, M. Lorenz, M. Grundmann, Mathias Schubert Jun 2006

Infrared Optical Properties Of MgX-1Zn1-XO Thin Films (0≤X≤1): Long-Wavelength Optical Phonons And Dielectric Constants, C. Bundemann, A. Rahm, M. Lorenz, M. Grundmann, Mathias Schubert

Nebraska Center for Materials and Nanoscience: Faculty Publications

Infrared spectroscopic ellipsometry in the spectral range from ω =360 cm-1 to ω =1500 cm-1 and Raman scattering spectroscopy are applied to study the long-wavelength optical phonon modes and dielectric constants of MgxZn1-xO thin films in the composition range 0≤x≤1. The samples were grown by pulsed laser deposition on sapphire substrates. X-ray diffraction measurements of the thin film samples reveal the hexagonal wurtzite crystal structure for x≤0.53 and the cubic rocksalt crystal structure for x≥0.67. A systematic variation of the phonon mode frequencies with Mg-mole fraction x is found …

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Investigating The Impact Of Remotely Sensed Precipitation And Hydrologic Model Uncertainties On The Ensemble Streamflow Forecasting, Hamid Moradkhani, K. Hsu, Y. Hong, S. Sorooshian Jun 2006

Investigating The Impact Of Remotely Sensed Precipitation And Hydrologic Model Uncertainties On The Ensemble Streamflow Forecasting, Hamid Moradkhani, K. Hsu, Y. Hong, S. Sorooshian

Civil and Environmental Engineering Faculty Publications and Presentations

In the past few years sequential data assimilation (SDA) methods have emerged as the best possible method at hand to properly treat all sources of error in hydrological modeling. However, very few studies have actually implemented SDA methods using realistic input error models for precipitation. In this study we use particle filtering as a SDA method to propagate input errors through a conceptual hydrologic model and quantify the state, parameter and streamflow uncertainties. Recent progress in satellite-based precipitation observation techniques offers an attractive option for considering spatiotemporal variation of precipitation. Therefore, we use the PERSIANN-CCS precipitation product to propagate input …

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Estimating Open-Ocean Barotropic Tidal Dissipation: The Hawaiian Ridge, Edward D. Zaron, Gary D. Egbert Jun 2006

Estimating Open-Ocean Barotropic Tidal Dissipation: The Hawaiian Ridge, Edward D. Zaron, Gary D. Egbert

Civil and Environmental Engineering Faculty Publications and Presentations

The generalized inverse of a regional model is used to estimate barotropic tidal dissipation along the Hawaiian Ridge. The model, based on the linear shallow-water equations, incorporates parameterizations for the dissipation of energy via friction in the bottom boundary layer and form drag due to internal waves generated at topographic slopes. Sea surface height data from 364 orbit cycles of the Ocean Topography Experiment (TOPEX)/Poseidon satellite mission are used to perform inversions at eight diurnal and semidiurnal tidal frequencies. It is estimated that the barotropic M2 tide loses energy at a rate of 19 GW, of which 88% is lost …

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Enhancing Targeted Traffic Enforcement Efforts In Portland, Oregon, Max Coffman, Christopher Monsere Jun 2006

Enhancing Targeted Traffic Enforcement Efforts In Portland, Oregon, Max Coffman, Christopher Monsere

Civil and Environmental Engineering Faculty Publications and Presentations

Enforcement is a key component of any comprehensive traffic safety program, and through a unique effort the Portland Office of Transportation (PDOT) partners with schools, the court system, community groups and the Police Bureau to develop a coordinated citywide program to improve traffic safety. However, like many government agencies, the Police Bureau faces constraints that limit the resources it can devote to traffic safety. In response, PDOT and the Police Bureau’s Traffic Division have instituted a program of Strategic and Focused Enforcement (SAFE) to better allocate limited traffic safety personnel and resources. Using historical crash data, PDOT identified 30 high …

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Molecular Characterization Of Wetland Soil Bacterial Community In Constructed Mesocosms, Ethan C. Bishop Jun 2006

Molecular Characterization Of Wetland Soil Bacterial Community In Constructed Mesocosms, Ethan C. Bishop

Theses and Dissertations

The use of wetlands to effectively remediate aquifers contaminated with chlorinated solvents is an emerging technique, which shows high promise. In order to better understand this process and test its legitimacy, a treatment wetland was constructed at Wright-Patterson AFB, Dayton, Ohio and, in a joint effort with Wright State University (WSU), has previously shown the effective removal of PCE. The purpose of this research was to characterize the soil bacterial community, pre-PCE injection, among three wetland plant species from the sedge family (Cyperaceae) within constructed wetland mesocosms and to identify any bacterial dominance. Carex comosa, Scirpus atrovirens, and Eleocharis erythropoda …

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Effects Of Frequency And Environment On Fatigue Behavior Of An Oxide-Oxide Ceramic Matrix Composite At 1200°C, Griffin Hetrick Jun 2006

Effects Of Frequency And Environment On Fatigue Behavior Of An Oxide-Oxide Ceramic Matrix Composite At 1200°C, Griffin Hetrick

Theses and Dissertations

Advances in aeronautical engineering in the 21st century depend upon materials that can perform well in extreme environments such as high temperatures and oxidizing conditions. Nextel™720/Alumina (N720/A) is an oxide/oxide ceramic matrix composite with a porous alumina matrix that has been identified as a candidate material for such applications. This research investigated the effects of frequency on fatigue response of N720/A at 1200°C in both air and steam environment. Prior investigation of this material by Eber [8] in 2005 studied fatigue behavior at 1200°C in air and in steam environments at the frequency of 1.0 Hz. The current research focused …

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Theoretical Modeling Of The Transient Effects Of A Towline Using The Method Of Characteristics, Christopher A. Hill Jun 2006

Theoretical Modeling Of The Transient Effects Of A Towline Using The Method Of Characteristics, Christopher A. Hill

Theses and Dissertations

The use of decoys in combat has become more advanced in recent years. Some of the newest military aircraft, such as the US Navy's F/A-18E/F Superhornet, have the capability to deploy a towline with an attached decoy when entering hostile territory as a defense mechanism against enemy threats. In steady state, the towline extends behind and below the aircraft. A major concern is the position of the towline, as aircraft maneuvers can cause the line to enter the engine plume. The high exhaust heat can cause problems, such as damaging electrical equipment and severing the line. In order to better …

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Characterization Of Uav Performance And Development Of A Formation Flight Controller For Multiple Small Uavs, Patrick A. Mccarthy Jun 2006

Characterization Of Uav Performance And Development Of A Formation Flight Controller For Multiple Small Uavs, Patrick A. Mccarthy

Theses and Dissertations

The Air Force Institute of Technology's (AFIT) Advanced Navigation Technology (ANT) Center has recently delved into the research topic of small Unmanned Aerial Vehicles (UAV). One area of particular interest is using multiple small UAVs cooperatively to improve mission efficiency, as well as perform missions that couldn't be performed using vehicles independently. However, many of these missions require that the UAVs operate in close proximity of each other. This research lays the foundation required to use the ANT Center's UAVs for multi-vehicle missions (e.g. cooperatively) by accomplishing two major goals. First, it develops test procedures that can be used to …

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Experimental Investigation Of The Aerodynamic Ground Effect Of A Tailless Lambda-Shaped Ucav With Wing Flaps, Jason T. Mostaccio Jun 2006

Experimental Investigation Of The Aerodynamic Ground Effect Of A Tailless Lambda-Shaped Ucav With Wing Flaps, Jason T. Mostaccio

Theses and Dissertations

This experimental study adequately identified the ground effect region of a lambda-shaped unmanned combat air vehicle (UCAV). The lambda planform used in this study was originally tested in a previous experiment to determine the stability and control characteristics generated out-of-ground-effect. The following study extends the existing database by analyzing the inherent aerodynamic behavior that is produced by employing trailing edge flap deflections while flying in-ground-effect (IGE). To accomplish this objective, static ground effect tests were performed in the AFIT 3? x 3? subsonic wind tunnel where a ground plane was used to simulate the forces and moments on the UCAV …

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A Bimodular Theory For Finite Deformations: Comparison Of Orthotropic Second-Order And Exponential Stress Constitutive Equations For Articular Cartilage, Stephen M. Klisch Jun 2006

A Bimodular Theory For Finite Deformations: Comparison Of Orthotropic Second-Order And Exponential Stress Constitutive Equations For Articular Cartilage, Stephen M. Klisch

Mechanical Engineering

Cartilaginous tissues, such as articular cartilage and the annulus fibrosus, exhibit orthotropic behavior with highly asymmetric tensile–compressive responses. Due to this complex behavior, it is difficult to develop accurate stress constitutive equations that are valid for finite deformations. Therefore, we have developed a bimodular theory for finite deformations of elastic materials that allows the mechanical properties of the tissue to differ in tension and compression. In this paper, we derive an orthotropic stress constitutive equation that is second-order in terms of the Biot strain tensor as an alternative to traditional exponential type equations. Several reduced forms of the bimodular second-order …

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A Wind Tunnel Investigation Of Joined Wing Scissor Morphing, Christopher C. Dike Jun 2006

A Wind Tunnel Investigation Of Joined Wing Scissor Morphing, Christopher C. Dike

Theses and Dissertations

The Air Force Research Laboratory's Munitions Directorate has been looking to extend the range of its small smart bomb. Corneille [6] has conducted tests to determine the aerodynamic characteristics of joined wings on a missile and determine if joined wings are more beneficial than a single wing configuration. The concept of retrofitting wings on the bomb introduced an interesting problem: storage before deployment. This study conducted steady-state low speed wind tunnel testing of a joined wing configuration that morphed from a compact configuration for storage to a full extension. These steady-state tests examine differing sweep angles of the same joined …

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Situational Awareness And Synthetic Vision For Unmanned Aerial Vehicle Flight Testing, Joseph M. Dugan Jun 2006

Situational Awareness And Synthetic Vision For Unmanned Aerial Vehicle Flight Testing, Joseph M. Dugan

Theses and Dissertations

The Advanced Navigation Technology (ANT) Center at the Air Force Institute of Technology (AFIT) is currently exploring ways to develop and advance the employment of autonomous Unmanned Aerial Vehicles (UAV) by the Department of Defense for military purposes. The research in this thesis describes the development of a tool that enhances situational awareness and provides synthetic vision in a program called the Aviator Visual Display Simulator (AVDS) during UAV flight. During flight testing, the Situational Awareness and Synthetic Vision Relay Tool (SASVRT) developed provides the test coordinator and pilot, as well as the safety observers, with the most pertinent information …

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A Comparative Analysis Of Single-Stage-To-Orbit Rocket And Air-Breathing Vehicles, Benjamin S. Orloff Jun 2006

A Comparative Analysis Of Single-Stage-To-Orbit Rocket And Air-Breathing Vehicles, Benjamin S. Orloff

Theses and Dissertations

This study compares and contrasts the performance of a variety of rocket and air breathing, single-stage-to-orbit, reusable launch vehicles. Fuels considered include bi-propellant and tri-propellant combinations of hydrogen and hydrocarbon fuels. Astrox Corporation's HySIDE code was used to model the vehicles and predict their characteristics and performance. Vehicle empty mass, wetted area and growth rates were used as figures of merit to predict the procurement, operational and maintenance cost trends of a vehicle system as well as the system's practicality. Results were compared to those of two-stage-to-orbit reusable launch systems using similar modeling methods. The study found that single-stage-to-orbit vehicles …

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An Experimental Study Of A Pulsed Dc Plasma Flow Control Actuator, Jennifer D. Wall Jun 2006

An Experimental Study Of A Pulsed Dc Plasma Flow Control Actuator, Jennifer D. Wall

Theses and Dissertations

An experiment on the effects of a pulsed DC plasma actuator on a separated flow in a low speed wind tunnel was conducted. The actuator consisted of two asymmetric copper electrodes oriented normal to the flow separated by a dielectric barrier and mounted on a flat plate in the center of the tunnel. A contoured insert was constructed and used to create an adverse pressure gradient in the test section comparable to a Pak-B low pressure turbine blade distribution. Suction was applied from the upper wall to induce separation along the flat plate over the electrodes. The DC power supply …

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Characterizing A Co-Flow Nozzle For Use In A Filtered Rayleigh Scattering System, David S. Miceli Jun 2006

Characterizing A Co-Flow Nozzle For Use In A Filtered Rayleigh Scattering System, David S. Miceli

Theses and Dissertations

Research was conducted on the flow field exiting a co-annular flow nozzle for use in filtered Rayleigh scattering flow visualizations. More specifically, the flow visualizations were of the flow field exiting a coflow nozzle and illuminated by a tunable, nominal 4.2 watt narrow line width Argon laser operating at 514.5nm. ND:YAG lasers are typically used in this application, but some of the properties of a tunable Argon laser make it an attractive alternative. Before generating flow visualizations, the coflow nozzle was characterized both experimentally and computationally. Due to a flow asymmetry in the outer annulus flow field, the nozzle was …

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Effect Of Environment On Creep Behavior Of An Oxide/Oxide Cfcc With ±45° Fiber Orientation, Gregory T. Siegert Jun 2006

Effect Of Environment On Creep Behavior Of An Oxide/Oxide Cfcc With ±45° Fiber Orientation, Gregory T. Siegert

Theses and Dissertations

Aerospace applications require materials capable of maintaining superior mechanical properties while operating at high temperatures and oxidizing environments. Nextel™ 720/A (N720/A), an oxide/oxide ceramic matrix composite (CMC) with a porous alumina matrix was developed specifically to provide improved long-term properties and performance at 1200°C. This research evaluated the creep behavior of N720/A with a ±45° fiber orientation at 1200°C in: laboratory air, steam, and argon environments. Creep-rupture tests at the creep stress levels of: 45, 40, 35, and 15 MPa were conducted in each environment.
The ultimate tensile strength of N720/A with ±45° fiber orientation was 55 MPa, the elastic …

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High Altitude Airship Station-Keeping Analysis, Douglas P. Kondrack Jun 2006

High Altitude Airship Station-Keeping Analysis, Douglas P. Kondrack

Theses and Dissertations

Lighter-than-air vehicles were once widely utilized by most major militaries. The airship’s extended range and flight endurance made them the optimal vehicle for surveillance and reconnaissance. These flight characteristics have created new interest in using lighter-than-air vehicles as high altitude surveillance and communications platforms. Future Department of Defense plans include high altitude airships that will operate at near space altitudes and take advantage of the low wind region in the upper atmosphere located at approximately 24 km. A high altitude airship could provide 24-hour coverage of a target area if operated in this low wind region. This study investigated the …

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Modeling A Reparable Supply Chain And Applying Cpfr Concepts, Sandra A. Mayhall Jun 2006

Modeling A Reparable Supply Chain And Applying Cpfr Concepts, Sandra A. Mayhall

Theses and Dissertations

The Air Force supply chain includes parts required to build, fix, or maintain aircraft delivered to the warfighter to carry out missions. Industry has shown that following Collaborative Planning, Forecasting, and Replenishment (CPFR) concepts, particularly reducing inventory through accurate demand forecasts, has increased profits in part by lowering the holding costs of inventory and increasing sales. This is analogous to the Air Force increasing aircraft availability. There is scant evidence that demand forecasts generated at any level in the Air Force are shared with the intent of coordinating replenishment. This thesis uses a simple discrete-event stochastic simulation model to show …

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Evaluation Of The Effects Of Predicted Associativity On The Reliability And Performance Of Mobile Ad Hoc Networks, Esteban Francisco Sanchez Jun 2006

Evaluation Of The Effects Of Predicted Associativity On The Reliability And Performance Of Mobile Ad Hoc Networks, Esteban Francisco Sanchez

Theses and Dissertations

Routing in Mobile Ad Hoc Networks (MANETs) presents unique challenges not encountered in conventional networks. Predicted Associativity Routing (PAR) is a protocol designed to address reliability in MANETs. Using associativity information, PAR calculates the expected lifetime of neighboring links. Nodes use this expected lifetime, and their neighbor's connectivity to determine a residual lifetime. The routes are selected from those with the longest residual lifetimes. In this way, PAR attempts to improve the reliability of discovered routes. PAR is compared to AODV using a variety of reliability and performance metrics. Despite its focus on reliability, PAR does not provide more reliable …

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Mitigating Insider Threat Using Human Behavior Influence Models, Anthony J. Puleo Jun 2006

Mitigating Insider Threat Using Human Behavior Influence Models, Anthony J. Puleo

Theses and Dissertations

Insider threat is rapidly becoming the largest information security problem that organizations face. With large numbers of personnel having access to internal systems, it is becoming increasingly difficult to protect organizations from malicious insiders. The typical methods of mitigating insider threat are simply not working, primarily because this threat is a people problem, and most mitigation strategies are geared towards profiling and anomaly detection, which are problematic at best. As a result, a new type of model is proposed in this thesis, one that incorporates risk management with human behavioral science. The new risk-based model focuses on observable influences that …

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Maneuver Estimation Model For Geostationary Orbit Determination, Brian J. Hirsch Jun 2006

Maneuver Estimation Model For Geostationary Orbit Determination, Brian J. Hirsch

Theses and Dissertations

As an increasing number of geostationary satellites fill a limited number of orbital slots, collocation of satellites leads to a risk of close approach or misidentification. The ability to detect maneuvers made by these satellites using optical observations can help to prevent these problems. Such a model has already been created and tested using data from the Air Force Maui Optical and Supercomputing site. The goal of this research was to create a more robust model which would reduce the amount of data needed to make accurate maneuver estimations. The Clohessy-Wiltshire equations were used to model the relative motion of …

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Fast Video Stabilization Algorithms, Mohammed A. Alharbi Jun 2006

Fast Video Stabilization Algorithms, Mohammed A. Alharbi

Theses and Dissertations

A fast and robust electronic video stabilization algorithm is presented in this thesis. It is based on a two-dimensional feature-based motion estimation technique. The method tracks a small set of features and estimates the movement of the camera between consecutive frames. It is used to characterize the motions accurately including camera rotations between two imaging instants. An affine motion model is utilized to determine the parameters of translation and rotation between images. The determined affine transformation is then exploited to compensate for the abrupt temporal discontinuities of input image sequences. Also, a frequency domain approach is developed to estimate translations …

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