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Articles 2821 - 2850 of 4180
Full-Text Articles in Engineering
Global Secure Sets Of Trees And Grid-Like Graphs, Yiu Yu Ho
Global Secure Sets Of Trees And Grid-Like Graphs, Yiu Yu Ho
Electronic Theses and Dissertations
Let G = (V, E) be a graph and let S ⊆ V be a subset of vertices. The set S is a defensive alliance if for all x ∈ S, |N[x] ∩ S| ≥ |N[x] − S|. The concept of defensive alliances was introduced in [KHH04], primarily for the modeling of nations in times of war, where allied nations are in mutual agreement to join forces if any one of them is attacked. For a vertex x in a defensive alliance, the number of neighbors of x inside the alliance, plus the vertex x, is at least the number …
Vision Based Trajectory Tracking Of Space Debris In Close Proximity Via Integrated Estimation And Control, Ni Li
Electronic Theses and Dissertations
Since the launch of the first rocket by the scientists during the World War II , mankind continues their exploration of space. Those space explorations bring the benefits to human, such as high technology products like GPS, cell phone, etc. and in-depth insight of outside of the earth. However, they produce millions of debris with a total estimated mass of more than 3,000,000 kg in the space around the earth, which has and will continue to threat the safety of manned or unmanned space exploration. According to the research, at least tens of spacecraft were considered been damaged or destroyed …
Ultra-High Performance Fiber Reinforced Concrete In Bridge Deck Applications, Jun Xia
Ultra-High Performance Fiber Reinforced Concrete In Bridge Deck Applications, Jun Xia
Electronic Theses and Dissertations
The research presented in this dissertation focuses on the material characterization of ultrahigh performance fiber reinforced concrete (UHP-FRC) at both the microscopic and macroscopic scales. The macroscopic mechanical properties of this material are highly related to the orientation of the steel fibers distributed within the matrix. However, the fiber orientation distribution has been confirmed to be anisotropic based on the flow-casting process. The orientation factor and probability density function (PDF) of the crossing fiber (fibers crossing a cutting plane) orientation was obtained based on theoretical derivations and numerical simulations with respect to different levels of anisotropy and cut planes oriented …
Process-Dependent Microstructure And Severe Plastic Deformation In Sicp?? Reinforced Aluminum Metal Matrix Composites, Catalina Uribe-Restrepo
Process-Dependent Microstructure And Severe Plastic Deformation In Sicp?? Reinforced Aluminum Metal Matrix Composites, Catalina Uribe-Restrepo
Electronic Theses and Dissertations
Discontinuously reinforced MMCs with optimized microstructure are sought after for exceptional high strain rate behavior. The microstructure evolution of a stir-cast A359 aluminum composite reinforced with 30 vol.% SiCp after isothermal anneal, successive hot-rolling, and high strain rate deformation has been investigated. Quantitative microstructural analysis was carried out for the as-cast, annealed (470°C, 538°C and 570°C) and successively hot rolled specimens (64, 75, 88, and 96% rolling reductions). Selected composites were also examined after high strain rate deformation. X-ray diffraction, optical microscopy, scanning electron microscopy and transmission electron microscopy were employed for microstructural characterization. The strength and ductility of the …
Thermomechanical Behavior Of High-Temperature Shape Memory Alloy Ni-Ti-Pd-Pt Actuators, Douglas E. Nicholson
Thermomechanical Behavior Of High-Temperature Shape Memory Alloy Ni-Ti-Pd-Pt Actuators, Douglas E. Nicholson
Electronic Theses and Dissertations
To date the commercial use of shape memory alloys (SMAs) has been mostly limited to binary NiTi alloys with transformation temperatures approximately in the -100 to 100 ºC range. In an ongoing effort to develop high-temperature shape memory alloys (HTSMAs), ternary and quaternary additions are being made to binary NiTi to form NiTi-X (e.g., X: Pd, Pt, Au and Hf) alloys. Stability and repeatability can be further increased at these higher temperatures by limiting the stress, but the tradeoff is reduced work output and stroke. However, HTSMAs operating at decreased stresses can still be used effectively in actuator applications that …
Low Noise, Narrow Optical Linewidth Semiconductor-Based Optical Comb Source And Low Noise Rf Signal Generation, Ibrahim Tuna Ozdur
Low Noise, Narrow Optical Linewidth Semiconductor-Based Optical Comb Source And Low Noise Rf Signal Generation, Ibrahim Tuna Ozdur
Electronic Theses and Dissertations
Recently optical frequency combs and low noise RF tones are drawing increased attention due to applications in spectroscopy, metrology, arbitrary waveform generation, optical signal processing etc. This thesis focuses on the generation of low noise RF tones and stabilized optical frequency combs. The optical frequency combs are generated by a semiconductor based external cavity mode-locked laser with a high finesse intracavity etalon. In order to get the lowest noise and broadest bandwidth from the mode-locked laser, it is critical to know the free spectral range (FSR) of the etalon precisely. First the etalon FSR is measured by using the modified …
Fatigue Lifetime Approximation Based On Quantitative Microstructural Analysis For Air Plasma Sprayed Thermal Barrier Coatings, Carmen Bargraser
Fatigue Lifetime Approximation Based On Quantitative Microstructural Analysis For Air Plasma Sprayed Thermal Barrier Coatings, Carmen Bargraser
Electronic Theses and Dissertations
The durability of thermal barrier coatings (TBCs) affects the life of the hot section engine components on which they are applied. Fatigue is the general failure mechanism for such components and is responsible for most unexpected failures; therefore it is desirable to develop lifetime approximation models to ensure reliability and durability. In this study, we first examined the microstructural degradation of air plasma sprayed ZrO2-8wt.%Y2O3 TBCs with a low-pressure plasma sprayed CoNiCrAlY bond coat on an IN 738LC superalloy substrate. The durability of TBCs were assessed through furnace thermal cyclic tests carried out in air at 1100°C with a 1-, …
Nutrient Removal From Urban Stormwater Using Floating Treatment Wetland System, Md Kamrul Islam
Nutrient Removal From Urban Stormwater Using Floating Treatment Wetland System, Md Kamrul Islam
Electronic Theses and Dissertations
Despite the technology advancement, degradation of water quality due to stormwater continues to be a significant threat to the water and ecosystems due to the exponential growth of industries and agricultural enterprises that discharge stormwater. These anthropogenic activities are the sources of high nitrogen and phosphorus quantities in stormwater, which is responsible for eutrophication phenomena and deterioration of public health. Floating Treatment Wetlands (FTWs) are a potential solution to this problem. Both microcosm and mesocosm level studies were conducted for the effective removal of nutrients in stormwater wet detention ponds with different sorption media under varying nutrient concentrations and weather …
Harmony An Architecture For Network Centric Heterogeneous Terrain Database Re-Generation, Benito Graniela
Harmony An Architecture For Network Centric Heterogeneous Terrain Database Re-Generation, Benito Graniela
Electronic Theses and Dissertations
Homogeneous proprietary online terrain databases are prolific. So also is the one directional generation and update process for these terrain databases. The existence of architectures and common ontologies that enable consistent and harmonious outcomes between distributed, multi-directional, heterogeneous terrain databases are lacking. Further due to technological change that empowers end-users, the expectations for immediate terrain database update are constantly increasing. As an example, a variety of incompatible synthetic environmental representations are used for military Modeling and Simulation applications. Regeneration and near-real-time update of compiled synthetic environments in a distributed, heterogeneous run time environment is an issue that is relevant to …
A Contextual Approach To Learning Collaborative Behavior Via Observation, Cynthia L. Johnson
A Contextual Approach To Learning Collaborative Behavior Via Observation, Cynthia L. Johnson
Electronic Theses and Dissertations
This dissertation describes a novel technique to creating a simulated team of agents through observation. Simulated human teamwork can be used for a number of purposes, such as expert examples, automated teammates for training purposes and realistic opponents in games and training simulation. Current teamwork simulations require the team member behaviors be programmed into the simulation, often requiring a great deal of time and effort. None are able to observe a team at work and replicate the teamwork behaviors. Machine learning techniques for learning by observation and learning by demonstration have proven successful at observing behavior of humans or other …
Correlating Microstructural Development And Failure Mechanisms To Photo Stimulated Luminescence Spectroscopy And Electrochemical Impedance Spectroscopy In Thermal Barrier Coatings, Balaji Jayaraj
Electronic Theses and Dissertations
Thermal barrier coatings (TBCs) are widely used for thermal protection of hot section components in turbines for propulsion and power generation. Applications of TBCs based on a clearer understanding of failure mechanisms can help increase the performance and life-cycle cost of advanced gas turbine engines. Development and refinement of robust nondestructive evaluation techniques can also enhance the reliability, availability and maintainability of hot section components in gas turbines engines. In this work, degradation of TBCs was non-destructively examined by photostimulated luminescence spectroscopy (PSLS) and electrochemical impedance spectroscopy (EIS) as a function of furnace thermal cycling carried out in air with …
A 2009 Mobile Source Emissions Inventory Of The University Of Central Florida, Johanna Marie Clifford
A 2009 Mobile Source Emissions Inventory Of The University Of Central Florida, Johanna Marie Clifford
Electronic Theses and Dissertations
This thesis reports on the results of a mobile source emissions inventory for the University of Central Florida (UCF). For a large urban university, the majority of volatile organic compounds (VOC), oxides of nitrogen (NOx), and carbon dioxide (CO2) emissions come from onroad sources: personal vehicles and campus shuttles carrying students, faculty, staff, and administrators to and from the university, as well as university business trips. In addition to emissions from daily commutes, non-road equipment such as lawnmowers, leaf blowers, small maintenance vehicles, and other such equipment utilized on campus contributes to a significant portion to the total emissions from …
An Experimental Investigation On The Dynamics Of Bubbles Utilizing Refrigerant R134a Under Pressurized Flow Boiling Conditions, Keon Vereen
Electronic Theses and Dissertations
Flow boiling heat transfer allows for the dissipation of large amounts of heat. In this work, the effect of heat flux and pressure on flow boiling of liquid refrigerant R-134a is studied in a vertical thin channel. The experimental setup mimics a refrigeration cycle and specifically looks at the effect of pressure and wall heat flux on the departure size and bubble generation rate. The experimental setup consists of a closed loop which includes a vertical narrow rectangular channel and two synchronized high speed cameras for optical measurements at either sides of the channel. The setup is built to employ …
The Implications Of Virtual Environments In Digital Forensic Investigations, Farrah M. Patterson
The Implications Of Virtual Environments In Digital Forensic Investigations, Farrah M. Patterson
Electronic Theses and Dissertations
This research paper discusses the role of virtual environments in digital forensic investigations. With virtual environments becoming more prevalent as an analysis tool in digital forensic investigations, it’s becoming more important for digital forensic investigators to understand the limitation and strengths of virtual machines. The study aims to expose limitations within commercial closed source virtual machines and open source virtual machines. The study provides a brief overview of history digital forensic investigations and virtual environments, and concludes with an experiment with four common open and closed source virtual machines; the effects of the virtual machines on the host machine as …
Infrared Phased-Array Antenna-Coupled Tunnel Diodes, Brian Alan Slovick
Infrared Phased-Array Antenna-Coupled Tunnel Diodes, Brian Alan Slovick
Electronic Theses and Dissertations
Infrared (IR) dipole antenna-coupled metal-oxide-metal (MOM) tunnel diodes provide a unique detection mechanism that allows for determination of the polarization and wavelength of an optical field. By integrating the MOM diode into a phased-array antenna, the angle of arrival and degree of coherence of received IR radiation can be determined. The angular response characteristics of IR dipole antennas are determined by boundary conditions imposed by the surrounding dielectric or conductive environment on the radiated fields. To explore the influence of the substrate configuration, single dipole antennas are fabricated on both planar and hemispherical lens substrates. Measurements demonstrate that the angular …
Design And Analysis Of A Cylindrical Dielectric Resonator Antenna Array And Its Feed Network, John Ashmore
Design And Analysis Of A Cylindrical Dielectric Resonator Antenna Array And Its Feed Network, John Ashmore
Electronic Theses and Dissertations
There is an ever increasing need for smaller, lighter, more efficient antennas for commercial and military applications. One such antenna that meets these requirements is the dielectric resonator antenna (DRA). In recent years there has been an abundance of research on the utilization of the DRA as a radiating element. However, its practical application - especially pertaining to DRA arrays - is still considered to be at its infancy. The purpose of this work is to present a systematic process to be used in the design, simulation, optimization, fabrication, and testing of a cylindrical DRA array including its associated feed …
Co2 Adsorption On Solid Sorbents, Bingyu Li
Co2 Adsorption On Solid Sorbents, Bingyu Li
Electronic Theses and Dissertations
Sorbent-based CO2 capture technology is considered as one of the potential scientific techniques for mitigating greenhouse gas emission. Major advantages of sorbent based adsorption are its low regeneration energy coupled with the elimination of corrosion and equipment degradation characteristic of amine based solvent CO2 capture systems which are the preferred industrial methods. Different CO2 capture configurations, processes, and operational parameters for different sorbents were revieand summarized. Efficient industrial applications for CO2 capture require that solid sorbents possess an adsorption capacity between 1000-2000µmol/g or more together with a long-term regeneration capacity. Economical consideration necessitates that the cost of CO2 sequestration be …
Substrate Integrated Waveguide Horn Slot Antenna Array, Saritha Muguti
Substrate Integrated Waveguide Horn Slot Antenna Array, Saritha Muguti
Electronic Theses and Dissertations
Substrate integrated waveguide (SIW) is a rectangular dielectric-filled waveguide, which is synthesized in a planar substrate with arrays of metallic vias to realize bilateral side walls and its transitions with planar structures. These vias act as walls of the waveguide supporting current flow, thus allowing for waveguide mode propagation. Substrate integrated waveguide is suggested for low-loss, low-cost and high density integration applications. SIW preserves the advantages from both the traditional rectangular waveguide and microstrip for easy integration. It is used in designing passive circuits such as resonators, couplers, filters, power dividers, circulators, and antennas. Here, full wave analysis is used …
Improving Sample Collection Of Trace Particles Of Mock Explosive On Nano Coated Sensor, Daniel Woldemichael Yebo
Improving Sample Collection Of Trace Particles Of Mock Explosive On Nano Coated Sensor, Daniel Woldemichael Yebo
Electronic Theses and Dissertations
In protection against explosive-based terrorism, development and mass deployment of miniature sensors can play a tremendous role. In trace explosive detection, one of the challenges is bringing explosive vapor samples from the environment to the sensor element. Such collection of a selective and sufficient amount of air sample will enable the device detect the explosive at lower concentration. This can be done by adsorption of the explosive vapor on a substrate. This research implements the idea by developing a nano coated sensor on a lead zirconate titanate (PZT) substrate. The effects of varying the amount of polyethyleneimine in the nano …
A Field Validation Of Dam Indexing Methods In Mississippi, Steven Thomas Fox
A Field Validation Of Dam Indexing Methods In Mississippi, Steven Thomas Fox
Electronic Theses and Dissertations
Indexing methods are applied to dam inventories throughout the United States to assist in prioritizing resources to maintain aging dam structures. Three published indexing methods and one proposed method were applied to 24 dams through Mississippi. The majority of dams in Mississippi have little to no information concerning the performance records or design specifics of a given dam. Field assessments were conducted to determine the physical condition of each dam, identify potentially deficiencies at dams, and calculate a consequence in the event of a dam failure. The results of the four indexing methods will be compared and advantages and disadvantages …
Voice Call Capacity Over Wireless Mesh Networks, Pradeep Gunda Bhat
Voice Call Capacity Over Wireless Mesh Networks, Pradeep Gunda Bhat
Electronic Theses and Dissertations
The goal of this thesis is to understand the voice call carrying capacity of an IEEE 802.11b/e based ad hoc network. We begin with the modelling of conversational speech and define a six state semi-Markov voice model based on ITU-T P59 recommendation. We perform a theoretical analysis of the voice model and compare it with results obtained via simulations. Using a Java based IEEE 802.11 medium access layer simulator, we determine the upper-bound for the number of voice calls carried by an ad hoc network. We use a linear topology with the ideal carrier sensing range and evaluate the number …
Effects Of A Heated Turbulent Boundary Layer On Surface Pressure Fluctuations, David William Rich
Effects Of A Heated Turbulent Boundary Layer On Surface Pressure Fluctuations, David William Rich
Electronic Theses and Dissertations
Recent work has shown that spatial correlation of surface pressure fluctuations in a fully turbulent atmospheric boundary layer (ABL) can give information about the velocity field and turbulence. This is of particular importance to the future of wind energy to predict the incoming velocity flow field of wind turbines so as to actively control them for peak operating efficiency and damage reduction. All of the environmental effects on the surface pressure fluctuations need to be fully understood before a suitable flow prediction algorithm can be constructed. One such environmental effect which has not been previously studied is the effect of …
Freeze-Thawing Of Polyester/E-Glass As An Evaluation Of An Astm International Test Standard Proposal, Stefan Mauritz Strandlund
Freeze-Thawing Of Polyester/E-Glass As An Evaluation Of An Astm International Test Standard Proposal, Stefan Mauritz Strandlund
Electronic Theses and Dissertations
American Composites Manufacturers Association (ACMA) reported in 2009 that the four major sectors currently utilizing fiber reinforced polymers (FRP) are construction, corrosion, marine, and transportation in descending order of total FRP shipped. All of these sectors are known to be billion dollar industries and they are all involved with applications subjected to freezing and thawing. FRP encompass many characteristics that are beneficial to these sectors and also in resisting this exposure. ASTM International has yet not developed a standard to test FRP materials resistance to freeze-thaw (FT) cycling exposure. The D20.18.02 committee of the ASTM is in the process of …
Lt Code Equations, Stanley Truitt
Lt Code Equations, Stanley Truitt
Electronic Theses and Dissertations
The LT Code equations describe the process of encoding input symbols into an error correcting code that requires no feedback from the receiver. The mathematical process involved the development of LT Codes is important. This thesis address the issue of improving the understanding of the LT Code equations presented in the original paper. This task is accomplished by inserting the mathematical details when possible, providing graphical results to the equations, and comparing the equations results against random computer generated simulations results. This thesis will improve the understanding of how LT Codes equations related to actual results.
Development Of An Astm Draft Standard For The Elevated Temperature Moisture Conditioning Of Pultruded Fiber Reinforced Polymer Composites, Tunji Adejumo
Electronic Theses and Dissertations
No abstract provided.
The Fev Frontend: A Terrain And Water Simulation Client, Donald Brent Sharrow
The Fev Frontend: A Terrain And Water Simulation Client, Donald Brent Sharrow
Electronic Theses and Dissertations
The FEV (Flood Emergency Visualizer) Frontend is a Java and OpenGL-based 3D vi- sualizer of flood simulation results in real-time. Simulations can be recomputed based on user-defined terrain edits made directly on the rendering surface. The frontend is the client software of the FEV system that includes a backend for solving water flow equations using CUDA. To render large datasets, level-of-detail and other optimizations are needed to render terrain and water surfaces with interactive frame rates.
Quantification Of An Ultrasound Test Apparatus And Its Potential Use To Control Nuisance Species In Commercial Aquaculture Settings, Bradley T. Goodwiller
Quantification Of An Ultrasound Test Apparatus And Its Potential Use To Control Nuisance Species In Commercial Aquaculture Settings, Bradley T. Goodwiller
Electronic Theses and Dissertations
As one step in the investigation of using acoustics to improve aquaculture production, work was pursued on the possible use of ultrasound to control the Bolbophorus trematode in commercial catfish ponds. The trematode population can be controlled by eliminating the host ram's horn snail via exposure to high amplitude ultrasound. Initial laboratory tests indicated that a commercially available sonicator (operating at 20 kHz) is capable of killing individual snails in fish tanks. More thorough testing indicated efficiency rates of approximately 35% on batches of 10 snails. In addition to the snails killed immediately, there was evidence that the sonication technique …
Characteristics Of Different Focusing Antennas In The Near Field Region, Shaya Karimkashi
Characteristics Of Different Focusing Antennas In The Near Field Region, Shaya Karimkashi
Electronic Theses and Dissertations
Focusing antennas are of interest in many application including microwave wireless power transmission, remote (non-contact) sensing, and medical applications. Different kinds of antennas such as array antennas, reflector antennas and Fresnel zone plate (FZP) antennas have been used for these applications. Here, first, a new scheme in designing focused array antennas with desired sidelobe levels (SLLs) in the near field region is presented. The performance of the large focused array antennas is predicted based on the knowledge of the mutual admittances of a smaller array. The effects of various focal distances on the near field pattern of these antennas are …
Theoretical Study Of Beam Transformations By Volume Diffraction, Sergiy V. Mokhov
Theoretical Study Of Beam Transformations By Volume Diffraction, Sergiy V. Mokhov
Electronic Theses and Dissertations
Laser beams can be manipulated by volume diffractive elements in addition to conventional optical elements like mirrors, lenses, and beam splitters. Conventional optical elements can be described by applying the basic laws of reflection and refraction at the surfaces of the elements. Even diffraction by surface gratings utilizes relatively simple mathematics. This is to be contrasted with the volume diffraction, which requires coupled wave theory in the slowly varying envelope approximation (SVEA) to obtain accurate results. Efficient spatially distributed diffraction of laser beams is possible due to the high coherence of laser light, and it occurs at specific resonant Bragg …
Electromagnetic Propagation Anomalies In Waveguiding Structures And Scattering Systems, Alessandro Salandrino
Electromagnetic Propagation Anomalies In Waveguiding Structures And Scattering Systems, Alessandro Salandrino
Electronic Theses and Dissertations
The effects related to diffraction and interference are ubiquitous in phenomena involving electromagnetic wave propagation, and are accurately predicted and described within the framework of classical electrodynamics. In the vast majority of the cases the qualitative features of the evolution of a propagating wave can be inferred even without detailed calculations. A field distribution will spread upon propagation, will accumulate phase along the direction of power flow, will exert mechanical forces upon scattering objects in the direction of propagation etc. When such predictions fail, counterintuitive effects and new functionalities can be engineered. In this work a series of exceptional cases …