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Articles 2881 - 2910 of 4566

Full-Text Articles in Engineering

Vacancy Engineered Doped And Undoped Nanocrystalline Rare Earth Oxide Particles For High Temperature Oxidation Resistant Coating, Ranjith Thanneeru Jan 2007

Vacancy Engineered Doped And Undoped Nanocrystalline Rare Earth Oxide Particles For High Temperature Oxidation Resistant Coating, Ranjith Thanneeru

Electronic Theses and Dissertations

Rare earth oxides with trivalent lattice dopants have been of great interest to researchers in the recent years due to its potential applications in catalysis and high temperature protective coatings. The ability to store oxygen in rare earths is the basis for catalysis because of the ability to change valence states which causes the presence of intrinsic oxygen vacancies in the crystal lattice. Although, several doped-rare earth oxide systems in micron scale have been investigated, the doping effect in cerium oxide nanoparticles with well characterized particle size has not been studied. The doping of ceria at that small size can …

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Infrared Antenna-Coupled Phased-Array, Christopher Middlebrook Jan 2007

Infrared Antenna-Coupled Phased-Array, Christopher Middlebrook

Electronic Theses and Dissertations

Phased-array antennas are commonplace in the radiofrequency portion of the electromagnetic spectrum. Exploitation of phasing effects between multiple antennas facilitates a wide range of applications, including synthetic-aperture radar, beam forming, and beam scanning. For the first time, the phased addition of multiple dipole antennas is demonstrated in the infrared, at a wavelength of 10.6 micrometers. Coplanar strip lines are used to interconnect the antennas, preserving the phase of the individual contributions. Several different proof-of-concept experiments are performed, using planar antennas fabricated with direct-write electron-beam lithography. Infrared-frequency currents from two dipole antennas are summed together at a common feedpoint and dissipated …

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High-Speed Modelocked Semiconductor Lasers And Applications In Coherent Photonic Systems, Wangkuen Lee Jan 2007

High-Speed Modelocked Semiconductor Lasers And Applications In Coherent Photonic Systems, Wangkuen Lee

Electronic Theses and Dissertations

1.55-µm high-speed modelocked semiconductor lasers are theoretically and experimentally studied for various coherent photonic system applications. The modelocked semiconductor lasers (MSLs) are designed with high-speed (>5 GHz) external cavity configurations utilizing monolithic two-section curved semiconductor optical amplifiers. By exploiting the saturable absorber section of the monolithic device, passive or hybrid mode-locking techniques are used to generate short optical pulses with broadband optical frequency combs. Laser frequency stability is improved by applying the Pound-Drever-Hall (PDH) frequency stabilization technique to the MSLs. The improved laser performance after the frequency stabilization (a frequency drifting of less than 350 MHz), is extensively studied …

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Medium Access Control Protocols And Routing Algorithms For Wireless Sensor Networks, Anirban Bag Jan 2007

Medium Access Control Protocols And Routing Algorithms For Wireless Sensor Networks, Anirban Bag

Electronic Theses and Dissertations

In recent years, the development of a large variety of mobile computing devices has led to wide scale deployment and use of wireless ad hoc and sensor networks. Wireless Sensor Networks consist of battery powered, tiny and cheap "motes", having sensing and wireless communication capabilities. Although wireless motes have limited battery power, communication and computation capabilities, the range of their application is vast. In the first part of the dissertation, we have addressed the specific application of Biomedical Sensor Networks. To solve the problem of data routing in these networks, we have proposed the Adaptive Least Temperature Routing (ALTR) algorithm …

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Scalable Volumetric Three-Dimensional Up-Conversion Display Medium, Jung-Hyun Cho Jan 2007

Scalable Volumetric Three-Dimensional Up-Conversion Display Medium, Jung-Hyun Cho

Electronic Theses and Dissertations

There are many different techniques to display 3D information. However, not many of them are able to provide sufficient depth cues to the observers to sense or feel the images as real three-dimensional objects. Volumetric three-dimensional displays generate images within a real 3D space, so they provide most of the depth cues automatically. This thesis discusses the basic notions required to understand three-dimensional displays. Also discussed are different techniques used to display 3D information and their advantages and disadvantages as well as their current limitations. Several rare-earth doped fluoride crystals that are excited to emit visible light by sequential two …

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All-Optical Regeneration For Phase-Shift Keyed Optical Communication Systems, Kevin Croussore Jan 2007

All-Optical Regeneration For Phase-Shift Keyed Optical Communication Systems, Kevin Croussore

Electronic Theses and Dissertations

All-optical signal processing techniques for phase-shift keyed (PSK) systems were developed theoretically and demonstrated experimentally. Nonlinear optical effects in fibers, in particular four-wave mixing (FWM) that occurs via the ultra-fast Kerr nonlinearity, offer a flexible framework within which numerous signal processing functions can be accomplished. This research has focused on the regenerative capabilities of various FWM configurations in the context of processing PSK signals. Phase-preserving amplitude regeneration, phase regeneration, and phase-regenerative wavelength conversion are analyzed and demonstrated experimentally. The single-pump phase-conjugation process was used to regenerate RZ-DPSK pulse amplitudes with different input noise distributions, and the impact on output phase …

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Process Development For The Fabrication Of Mesoscale Electrostatic Valve Assembly, Shailini Rajiv Dhru Jan 2007

Process Development For The Fabrication Of Mesoscale Electrostatic Valve Assembly, Shailini Rajiv Dhru

Electronic Theses and Dissertations

This study concentrates on two of the main processes involved in the fabrication of electrostatic valve assembly, thick resist photolithography and wet chemical etching of a polyamide film. The electrostatic valve has different orifice diameters of 25, 50, 75 and 100 µm. These orifice holes are to be etched in the silicon wafer with deep reactive ion etching. The photolithography process is developed to build a mask of 15 µm thick resist pattern on silicon wafer. This photo layer acts as a mask for deep reactive ion etching. Wet chemical etching process is developed to etch kapton polyamide film. This …

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Understanding The Low Temperature Electrical Propertiesof Nanocrystalline Sno2 For Gas Sensor Applications, Christina Drake Jan 2007

Understanding The Low Temperature Electrical Propertiesof Nanocrystalline Sno2 For Gas Sensor Applications, Christina Drake

Electronic Theses and Dissertations

Nanocrystalline metal/metal oxide is an important class of transparent and electronic materials due to its potential use in many applications, including gas sensors. At the nanoscale, many of the phenomena observed that give nanocrystalline semiconducting oxide enhanced performance as a gas sensor material over other conventional engineering materials is still poorly understood. This study is aimed at understanding the low temperature electrical and chemical properties of nanocrystalline SnO2 that makes it suitable for room temperature gas detectors. Studies were carried out in order to understand how various synthesis methods affect the surfaces on the nano-oxides, interactions of a target gas …

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Parameter Estimation Using Sensor Fusion And Model Updating, Kevin Francoforte Jan 2007

Parameter Estimation Using Sensor Fusion And Model Updating, Kevin Francoforte

Electronic Theses and Dissertations

Engineers and infrastructure owners have to manage an aging civil infrastructure in the US. Engineers have the opportunity to analyze structures using finite element models (FEM), and often base their engineering decisions on the outcome of the results. Ultimately, the success of these decisions is directly related to the accuracy of the finite element model in representing the real-life structure. Improper assumptions in the model such as member properties or connections, can lead to inaccurate results. A major source of modeling error in many finite element models of existing structures is due to improper representation of the boundary conditions. In …

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Rigorous Analysis Of Wave Guiding And Diffractive Integrated Optical Structures, Andrew Greenwell Jan 2007

Rigorous Analysis Of Wave Guiding And Diffractive Integrated Optical Structures, Andrew Greenwell

Electronic Theses and Dissertations

The realization of wavelength scale and sub-wavelength scale fabrication of integrated optical devices has led to a concurrent need for computational design tools that can accurately model electromagnetic phenomena on these length scales. This dissertation describes the physical, analytical, numerical, and software developments utilized for practical implementation of two particular frequency domain design tools: the modal method for multilayer waveguides and one-dimensional lamellar gratings and the Rigorous Coupled Wave Analysis (RCWA) for 1D, 2D, and 3D periodic optical structures and integrated optical devices. These design tools, including some novel numerical and programming extensions developed during the course of this work, …

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Decision-Maker Trade-Offs In Multiple Response Surface Optimization, Alicia Hawkins Jan 2007

Decision-Maker Trade-Offs In Multiple Response Surface Optimization, Alicia Hawkins

Electronic Theses and Dissertations

The focus of this dissertation is on improving decision-maker trade-offs and the development of a new constrained methodology for multiple response surface optimization. There are three key components of the research: development of the necessary conditions and assumptions associated with constrained multiple response surface optimization methodologies; development of a new constrained multiple response surface methodology; and demonstration of the new method. The necessary conditions for and assumptions associated with constrained multiple response surface optimization methods were identified and found to be less restrictive than requirements previously described in the literature. The conditions and assumptions required for a constrained method to …

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Recognizing Teamwork Activity In Observations Of Embodied Agents, Linus Jan Luotsinen Jan 2007

Recognizing Teamwork Activity In Observations Of Embodied Agents, Linus Jan Luotsinen

Electronic Theses and Dissertations

This thesis presents contributions to the theory and practice of team activity recognition. A particular focus of our work was to improve our ability to collect and label representative samples, thus making the team activity recognition more efficient. A second focus of our work is improving the robustness of the recognition process in the presence of noisy and distorted data. The main contributions of this thesis are as follows: We developed a software tool, the Teamwork Scenario Editor (TSE), for the acquisition, segmentation and labeling of teamwork data. Using the TSE we acquired a corpus of labeled team actions both …

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Micro-Optic-Spectral-Spatial-Elements (Mosse), Alok Ajay Mehta Jan 2007

Micro-Optic-Spectral-Spatial-Elements (Mosse), Alok Ajay Mehta

Electronic Theses and Dissertations

Over a wide range of applications, optical systems have utilized conventional optics in order to provide the ability to engineer the properties of incident infra-red fields in terms of the transmitted field spectral, spatial, amplitude, phase, and polarization characteristics. These micro/nano-optical elements that provide specific optical functionality can be categorized into subcategories of refractive, diffractive, multi-layer thin film dichroics, 3-D photonic crystals, and polarization gratings. The feasibility of fabrication, functionality, and level of integration which these elements can be used in an optical system differentiate which elements are more compatible with certain systems than others. With enabling technologies emerging allowing …

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Stress, Fatigue And Workload: Determining The Combined Affect On Human Performance, Jessica Mock-Mclaughlin Jan 2007

Stress, Fatigue And Workload: Determining The Combined Affect On Human Performance, Jessica Mock-Mclaughlin

Electronic Theses and Dissertations

This research generated a model that will help to predict, prevent, control and mitigate the occurrence of task related factors that negatively influence stress, fatigue, and workload; thus enhancing human performance. Past research efforts involving stress, fatigue and workload identified factors that influence a change in performance (Lan, Ji and Looney, 2003, and Hancock & Warm, 1989). Also, while some mathematical models have been developed within each respective area, however, there is no evidence of an integrated model describing the combined affect of stress, fatigue and workload. To respond to this research gap, a quantitative model representing the state of …

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Effects Of Polarization And Coherence On The Propagation And The Detection Of Stochastic Electromagnetic Beams, Mohamed Fouad Salem Jan 2007

Effects Of Polarization And Coherence On The Propagation And The Detection Of Stochastic Electromagnetic Beams, Mohamed Fouad Salem

Electronic Theses and Dissertations

Most of the physically realizable optical sources are radiating in a random manner given the random nature of the radiation of a large number of atoms that constitute the source. Besides, a lot of natural and synthetic materials are fluctuating randomly. Hence, the optical fields that one encounters, in most of the applications are fluctuating and must be treated using random or stochastic functions. Within the framework of the scalar-coherence theory, one can describe changes of the properties of any stochastic field such as the spectral density and the spectral degree of coherence on propagation in any linear medium, deterministic …

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Optimization Models For Emergency Relief Shelter Planning For Anticipated Hurricane Events, Abeer Tarief Sharawi Jan 2007

Optimization Models For Emergency Relief Shelter Planning For Anticipated Hurricane Events, Abeer Tarief Sharawi

Electronic Theses and Dissertations

Natural disasters, specifically hurricanes, can cause catastrophic loss of life and property. In recent years, the United States has endured significant losses due to a series of devastating hurricanes (e.g., Hurricanes Charley and Ivan in 2004, and Hurricanes Katrina and Wilma in 2005). Several Federal authorities report that there are weaknesses in the emergency and disaster planning and response models that are currently employed in practice, thus creating a need for better decision models in emergency situations. The current models not only lack fast communication with emergency responders and the public, but are also inadequate for advising the pre-positioning of …

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Three-Dimensional Micron-Scale Metal Photonic Crystals Via Multi-Photon Direct Laser Writing And Electroless Metal Deposition, Amir Tal Jan 2007

Three-Dimensional Micron-Scale Metal Photonic Crystals Via Multi-Photon Direct Laser Writing And Electroless Metal Deposition, Amir Tal

Electronic Theses and Dissertations

Three-dimensional (3D) metal photonic crystals (MPCs) can exhibit interesting electromagnetic properties such as ultra-wide photonic or "plasmonic" band gaps, selectively tailored thermal emission, extrinsically modified absorption, and negative refractive index. Yet, optical-wavelength 3D MPCs remain relatively unexplored due to the challenges posed by their fabrication. This work explores the use of multi-photon direct laser writing (DLW) coupled with electroless metallization as a means for preparing MPCs. Multi-photon DLW was used to prepare polymeric photonic crystal (PC) templates having a targeted micron-scale structure and form. MPCs were then created by metallizing the polymeric PCs via wet-chemical electroless deposition. The electromagnetic properties …

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Liquid Crystal Thermography Studies In Water Pool Boiling At Subatmospheric Pressures, Kiran Talari Jan 2007

Liquid Crystal Thermography Studies In Water Pool Boiling At Subatmospheric Pressures, Kiran Talari

Electronic Theses and Dissertations

A pool boiling experimental facility has been designed and built to investigate nucleate pool boiling in water under sub atmospheric pressure. Liquid crystal thermography, a non intrusive technique, is used for the determination of surface temperature distributions. This technique uses encapsulated liquid crystals that reflect definite colors at specific temperatures and viewing angle. Design of the test section is important in this experimental study. Since a new TLC is required for every new set of test conditions, a permanently sealed test section is not an option. The real challenge is to design a leak proof test section which is flexible …

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A Multi-Layer Fpga Framework Supporting Autonomous Runtime Partial Reconfiguration, Heng Tan Jan 2007

A Multi-Layer Fpga Framework Supporting Autonomous Runtime Partial Reconfiguration, Heng Tan

Electronic Theses and Dissertations

Partial reconfiguration is a unique capability provided by several Field Programmable Gate Array (FPGA) vendors recently, which involves altering part of the programmed design within an SRAM-based FPGA at run-time. In this dissertation, a Multilayer Runtime Reconfiguration Architecture (MRRA) is developed, evaluated, and refined for Autonomous Runtime Partial Reconfiguration of FPGA devices. Under the proposed MRRA paradigm, FPGA configurations can be manipulated at runtime using on-chip resources. Operations are partitioned into Logic, Translation, and Reconfiguration layers along with a standardized set of Application Programming Interfaces (APIs). At each level, resource details are encapsulated and managed for efficiency and portability during …

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Plasma Processing For Retention Of Nanostructures, Viswanathan Venkatachalapathy Jan 2007

Plasma Processing For Retention Of Nanostructures, Viswanathan Venkatachalapathy

Electronic Theses and Dissertations

Plasma spray processing is a technique that is used extensively in thermal barrier coatings on gas and steam turbine components, biomedical implants and automotive components. Many processing parameters are involved to achieve a coating with certain functionality. The coating could be required to function as thermal barrier, wear resistant, corrosion resistant or a high temperature oxidation resistant coating. Various parameters, such as, nozzle and electrode design, powder feeding system, spray distances, substrate temperature and roughness, plasma gas flow rates and others can greatly alter the coating quality and resulting performance. Feedstock (powder or solution precursor) composition and morphology are some …

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Design And Modeling Of Radiation Hardened Ldmosfet For Space Craft Power Systems, Patrick Shea Jan 2007

Design And Modeling Of Radiation Hardened Ldmosfet For Space Craft Power Systems, Patrick Shea

Electronic Theses and Dissertations

NASA missions require innovative power electronics system and component solutions with long life capability, high radiation tolerance, low mass and volume, and high reliability in space environments. Presently vertical double-diffused MOSFETs (VDMOS) are the most widely used power switching device for space power systems. It is proposed that a new lateral double-diffused MOSFET (LDMOS) designed at UCF can offer improvements in total dose and single event radiation hardness, switching performance, development and manufacturing costs, and total mass of power electronics systems. Availability of a hardened fast-switching power MOSFET will allow space-borne power electronics to approach the current level of terrestrial …

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Modeling And Digital Control Of High Frequency Dc-Dc Power Converters, Yangyang Wen Jan 2007

Modeling And Digital Control Of High Frequency Dc-Dc Power Converters, Yangyang Wen

Electronic Theses and Dissertations

The power requirements for leading edge digital integrated circuits have become increasingly demanding. Power converter systems must be faster, more flexible, more precisely controllable and easily monitored. Meanwhile, in addition to control process, the new functions such as power sequencing, communication with other systems, voltage dynamic programming,load line specifications, phase current balance, protection, power status monitoring and system diagnosis are going into today's power supply systems. Digital controllers, compared withanalog controllers, are in a favorable position to provide basic feedback control as well as those power management functions with lower cost and great flexibility. The dissertation gives an overview of …

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A User Interactive Calibration Program For An Object Tracking System Using A Triaxial Accelerometer, Richard A. Elliott Jan 2007

A User Interactive Calibration Program For An Object Tracking System Using A Triaxial Accelerometer, Richard A. Elliott

HIM 1990-2015

A major method in object tracking systems and other inertial measurement devices resolves around the use of one, two, or three axis accelerometers. A leader in the field such devices is Microstrain Incorporated. They have developed a three axis accelerometer that uses a three axis magnetic sensor array to compute the pitch, roll, and yaw of a compact inertial measurement unit. In researching such devices, it became apparent that data collected using such units is extremely sensitive both to local magnetic fields and human interactions with the devices. It is therefore of great importance to ensure the device or devices …

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Tunable Nanostructure Anti-Reflective Coatings, Erik Brinley Jan 2007

Tunable Nanostructure Anti-Reflective Coatings, Erik Brinley

Electronic Theses and Dissertations

Research was conducted on broadband, anti-reflective coatings for fused silica and chalcogenide substrates in the infrared region of light. Using chemical preparation to create nano-porous through nano-particle based sol-gel solutions, the alteration of optical properties including refractive index and optical thickness was conducted. The nano-particles can modify the coating surface to allow only zero-order diffracted wave propagation reducing scattering while a partially graded profile of refractive index due surface evaporation lessened the precise phase relations of typical homogeneous coatings. My study of silica and titania sol-gel, and hybrid mixtures of the two were used to obtain the optical properties of …

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Developing A Spatial Interface For Information Visualization And Management In A Crisis Response Scenario, Anthony Costello Jan 2007

Developing A Spatial Interface For Information Visualization And Management In A Crisis Response Scenario, Anthony Costello

Electronic Theses and Dissertations

The focus of this study was to investigate how a spatial interface can be effectively utilized to support information presentation and information integration via human-centric data visualization, leading to decreased cognitive load, more accurate situation awareness, and subsequently, improved task performance. In high tempo, information intensive environments like those managed by an emergency operations center (EOC), information organization tools are essential. Though users can be trained to use conventional email software applications efficiently, the constraints of the information management paradigms inherent to conventional systems may limit a user's ability to gather context and create an accurate picture of the situation. …

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Using Surrogate Measures To Predict Patient Satisfaction In The Emergency Department, Erica Egri Jan 2007

Using Surrogate Measures To Predict Patient Satisfaction In The Emergency Department, Erica Egri

Electronic Theses and Dissertations

With healthcare organizations struggling to remain competitive and financially stable in a market where minimizing costs is a priority, hospital administrators feel the sense of urgency when it comes to keeping patients satisfied with services in order to expand volume and market share. The Emergency Department is considered the front door of a healthcare organization, and keeping its visitors satisfied in order to guarantee a future visit or a referral to a friend or family member is a must. While patient input on the services received in a healthcare facility is essential to improving quality of care, the costs associated …

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Wall Heat Transfer Effects In The Endwall Region Behind A Reflected Shock Wave At Long Test Times, Corey Frazier Jan 2007

Wall Heat Transfer Effects In The Endwall Region Behind A Reflected Shock Wave At Long Test Times, Corey Frazier

Electronic Theses and Dissertations

Shock-tube experiments are typically performed at high temperatures (≥1200K) due to test-time constraints. These test times are usually ~1 ms in duration and the source of this short, test-time constraint is loss of temperature due to heat transfer. At short test times, there is very little appreciable heat transfer between the hot gas and the cold walls of the shock tube and a high test temperature can be maintained. However, some experiments are using lower temperatures (approx. 800K) to achieve ignition and require much longer test times (up to 15 ms) to fully study the chemical kinetics and combustion chemistry …

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Heat Transfer In Multi-Layer Energetic Nanofilm On Composites Substrate, Manesh Navid Amini Jan 2007

Heat Transfer In Multi-Layer Energetic Nanofilm On Composites Substrate, Manesh Navid Amini

Electronic Theses and Dissertations

The main purpose of this work is the physical understanding and the numerical description of the reaction of the dense metastable intermolecular composition (MIC). Energy density of MIC is much higher than conventional energetic material; therefore, MIC finds more applications in the propellant and explosive system. The physical model includes the speed of propagation and rate of reaction, and the relationship between the layer thickness, heat rate, and length of the flame based on physical model. In Part I of this thesis, a one-dimensional model based on Weihs was developed for 20 pairs of a multi-layer of aluminum and copper …

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Maximum Energy Harvesting Control Foroscillating Energy Harvesting Systems, John Elmes Jan 2007

Maximum Energy Harvesting Control Foroscillating Energy Harvesting Systems, John Elmes

Electronic Theses and Dissertations

This thesis presents an optimal method of designing and controlling an oscillating energy harvesting system. Many new and emerging energy harvesting systems, such as the energy harvesting backpack and ocean wave energy harvesting, capture energy normally expelled through mechanical interactions. Often the nature of the system indicates slow system time constants and unsteady AC voltages. This paper reveals a method for achieving maximum energy harvesting from such sources with fast determination of the optimal operating condition. An energy harvesting backpack, which captures energy from the interaction between the user and the spring decoupled load, is presented in this paper. The …

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On The Incorporation Of The Personality Factors Into Crowd Simulation, Sivakumar Jaganathan Jan 2007

On The Incorporation Of The Personality Factors Into Crowd Simulation, Sivakumar Jaganathan

Electronic Theses and Dissertations

Recently, a considerable amount of research has been performed on simulating the collective behavior of pedestrians in the street or people finding their way inside a building or a room. Comprehensive reviews of the state of the art can be found in Schreckenberg and Deo (2002) and Batty, M., DeSyllas, J. and Duxbury, E. (2003). In all these simulation studies, one area that is lacking is accounting for the effects of human personalities on the outcome. As a result, there is a growing emphasis on researching the effects of human personalities and adding the results to the simulations to make …

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