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Articles 2281 - 2310 of 4180
Full-Text Articles in Engineering
Synchrotron X-Ray Diffraction And Piezospectroscopy Used For The Investigation Of Individual Mechanical Effects From Environmental Contaminants And Oxide Layer Undulations In Thermal Barrier Coatings, Sanna Siddiqui
Electronic Theses and Dissertations
The durability of Thermal Barrier Coatings (TBCs) used on the turbine blades of aircraft and power generation engines has been known to be affected by sand particle ingression comprised of Calcium-Magnesium-Alumina-Silicate (CMAS). Previous studies have shown that these effects present themselves through variations in the thermomechanical and thermochemical properties of the coating. This study investigated the impact of CMAS ingression on the Yttria Stabilized Zirconia Topcoat (YSZ) and Thermally Grown Oxide (TGO) strain in sprayed Thermal Barrier Coating (TBC) samples of varying porosity with and without CMAS ingression. In-Situ Synchrotron X-ray Diffraction measurements were taken on the sample under thermal …
Nanocomposite Coating Mechanics Via Piezospectroscopy, Gregory Freihofer
Nanocomposite Coating Mechanics Via Piezospectroscopy, Gregory Freihofer
Electronic Theses and Dissertations
Coatings utilizing the piezospectroscopic (PS) effect of alpha alumina could enable on the fly stress sensing for structural health monitoring applications. While the PS effect has been historically utilized in several applications, here by distributing the photo-luminescent material in nanoparticle form within a matrix, a stress sensing coating is created. Parallel to developing PS coatings for stress sensing, the multi-scale mechanics associated with the observed PS response of nanocomposites and their coatings has been applied to give material property measurements, providing an understanding of particle reinforced composite behavior. Understanding the nanoparticle-coating-substrate mechanics is essential to interpreting the spectral shifts for …
Processing And Characterization Of Multifunctional Thermoplastic Nanocomposite Films, Xin Wang
Processing And Characterization Of Multifunctional Thermoplastic Nanocomposite Films, Xin Wang
Electronic Theses and Dissertations
Nanoparticles reinforced polymer composite films have been widely studied for their enhanced mechanical, electrical and thermal properties compared with host polymer matrix. However, most research was conducted on incorporation of nanoparticles in polymer films to improve single property and there is a lack of research on the multifunctional polymer nanocomposite films. In this work, a scalable and continuous spray deposition process was developed for the production of nanoparticles reinforced multifunctional thermoplastic nanocomposite films. This process is capable of making a thin sheet of thermoplastic nanocomposites with high nanoparticle loadings. The smallest thickness can be 40um. The objective of this study …
Investigation Of Different Dielectric Materials As Gate Insulator For Mosfets, Ritika Oswal
Investigation Of Different Dielectric Materials As Gate Insulator For Mosfets, Ritika Oswal
Electronic Theses and Dissertations
The scaling of semiconductor transistors has led to a decrease in thickness of the silicon dioxide layer used as gate dielectric. The thickness of the silicon dioxide layer is reduced to increase the gate capacitance, thus increasing the drain current. If the thickness of the gate dielectric decreases below 2nm, the leakage current due to the tunneling increases drastically. Hence it is necessary to replace the gate dielectric, silicon dioxide, with a physically thicker oxide layer of high-k materials like Hafnium oxide and Titanium oxide. High-k dielectric materials allow the capacitance to increase without a huge leakage current. Hafnium oxide …
Automatic 3d Human Modeling: An Initial Stage Towards 2-Way Inside Interaction In Mixed Reality, Yiyan Xiong
Automatic 3d Human Modeling: An Initial Stage Towards 2-Way Inside Interaction In Mixed Reality, Yiyan Xiong
Electronic Theses and Dissertations
3D human models play an important role in computer graphics applications from a wide range of domains, including education, entertainment, medical care simulation and military training. In many situations, we want the 3D model to have a visual appearance that matches that of a specific living person and to be able to be controlled by that person in a natural manner. Among other uses, this approach supports the notion of human surrogacy, where the virtual counterpart provides a remote presence for the human who controls the virtual character's behavior. In this dissertation, a human modeling pipeline is proposed for the …
An Introductory Study Of The Dynamics Of Autorotation For Wind Energy Harvesting, Bilal Salih
An Introductory Study Of The Dynamics Of Autorotation For Wind Energy Harvesting, Bilal Salih
Electronic Theses and Dissertations
Wind turbines have been used for decades to harvest wind energy. They are suitable only to work on close to ground, and have several drawbacks that are related to the availability of the wind and the amount of extracted power compared with the cost of construction. On the other hand, there is an abundant wind power that is available at high altitudes. The wind jet streams at high elevations 8 - 12 kms are pervasive and persistent, and can potentially produce immense wind energy. Even at moderate elevations of 4 - 5 kms, wind power densities are much higher than …
A Continuous Hydrologic Model Structure For Applications At Multiple Time Scales, Jonathan Griffen
A Continuous Hydrologic Model Structure For Applications At Multiple Time Scales, Jonathan Griffen
Electronic Theses and Dissertations
There are many different controlling factors on the partitioning of rainfall into runoff. However, the influence of each of these controls varies across different temporal scales. Consequently, numerous water balance models have been developed in the literature for application across various time scales. These models are usually developed for a particular time scale so that the controls with the greatest influence on rainfall partitioning are captured. For example, the SCS curve number method was developed to simulate direct runoff at the event scale; the "abcd" model was developed as a monthly water balance model; and the Budyko model was developed …
Evaluating The Effectiveness Of Conversion Of Traditional Five Section Head Signal To Flashing Yellow Arrow (Fya) Signal, Meshal Almoshaogeh
Evaluating The Effectiveness Of Conversion Of Traditional Five Section Head Signal To Flashing Yellow Arrow (Fya) Signal, Meshal Almoshaogeh
Electronic Theses and Dissertations
In the United States, there are two schemes of operating traffic signal controls for permitted protected left turns (PPLT) namely the traditional five-section head system (known as Dog-House) and the flashing yellow arrow system (FYA). Past studies have agreed that these controls lead to decrease the average delay per left turn vehicle, decrease the protected green time, increase the left turn capacity, and enhance the intersection overall operation. The flashing yellow arrow (FYA) has been approved by the Federal Highway Administration as the national standard for the PPLT operations at signalized intersections. So, the Florida Department of Transportation also approved …
Exploring Sparsity, Self-Similarity, And Low Rank Approximation In Action Recognition, Motion Retrieval, And Action Spotting, Chuan Sun
Electronic Theses and Dissertations
This thesis consists of 4 major parts. In the first part (Chapters 1-2), we introduce the overview, motivation, and contribution of our works, and extensively survey the current literature for 6 related topics. In the second part (Chapters 3-7), we explore the concept of "Self-Similarity" in two challenging scenarios, namely, the Action Recognition and the Motion Retrieval. We build three-dimensional volume representations for both scenarios, and devise effective techniques that can produce compact representations encoding the internal dynamics of data. In the third part (Chapter 8), we explore the challenging action spotting problem, and propose a feature-independent unsupervised framework that …
Non-Hydrostatic Models For Wave Propagation, Breaking, And Run-Up, Zhangping Wei
Non-Hydrostatic Models For Wave Propagation, Breaking, And Run-Up, Zhangping Wei
Electronic Theses and Dissertations
This dissertation develops a series of non-hydrostatic pressure wave models based on the finite element free surface flow model, CCHE2D, for simulating propagation, breaking, and run-up of coastal wave processes. The first non-hydrostatic formulation presented in this dissertation directly introduces a non-hydrostatic pressure module into CCHE2D. An edge-based pressure allocation method is implemented, and a depth-integrated vertical momentum equation is introduced. The depth-integrated horizontal momentum equations are solved for a provisional velocity field, and then the non-hydrostatic pressure is obtained by satisfying the divergence-free velocity field condition, subsequently the velocity field is corrected by the non-hydrostatic pressure. Finally the free …
Optimization Of Wind Fence Enclosures For Infrasonic Wind Noise Reduction, Johnpaul Russell Abbott
Optimization Of Wind Fence Enclosures For Infrasonic Wind Noise Reduction, Johnpaul Russell Abbott
Electronic Theses and Dissertations
A large porous wind barrier enclosure has been built and tested to optimize wind noise reduction at infrasonic frequencies between 0.01-10 Hz in order to develop a technology that is simple, cost effective, and improves upon the limitations of pipe and porous hose arrays. The effects of varying the fence's porosity, modifying its top condition and bottom gap, doubling the height and diameter, and adding a secondary wind barrier were investigated. A simple mathematical model which estimates the wind noise measured at the center of the enclosure was derived based on the measured turbulence and velocity profiles measure outside the …
A Complex-Envelope Fdtd Formulation Using Real-Valued Field-Variables, Qi Liu
A Complex-Envelope Fdtd Formulation Using Real-Valued Field-Variables, Qi Liu
Electronic Theses and Dissertations
Use of the complex-envelope (CE) representation of band-pass limited sources and their resulting fields increases the allowable time-step in finite-difference time-domain (FDTD) simulations. The complex envelope representation transforms band-pass limited fields and sources to complex-valued low-pass limited form and Maxwells equations from real-valued partial differential equations (PDEs) to complex-valued PDEs. Previous CE FDTD schemes have used complex valued difference equations in terms of complex valued field quantities to approximate these complex PDEs. This choice requires the use of complex numbers and complex operations in the computer program implementing the solution. An alternative CE FDTD scheme using only real numbers and …
Relaxation Adaptive Memory Programming For The Resource Constrained Project Scheduling Problem, Robert Christopher-Lee Riley
Relaxation Adaptive Memory Programming For The Resource Constrained Project Scheduling Problem, Robert Christopher-Lee Riley
Electronic Theses and Dissertations
The resource constrained project scheduling problem (RCPSP) is one of the most intractable problems in operations research; it is NP-hard in the strong sense. Due to the hardness of the problem, exact solution methods can only tackle instances of relatively small size. For larger instances commonly found in real applications heuristic solution methods are necessary to find near-optimal solutions within acceptable computation time limits. In this study algorithms based on the relaxation adaptive memory programming (RAMP) method (Rego, 2005) are developed for the purpose of solving the RCPSP. The RAMP algorithms developed here combine mathematical relaxation, including Lagrangian relaxation and …
Parametric Scramjet Analysis, Jongseong Choi
Parametric Scramjet Analysis, Jongseong Choi
Electronic Theses and Dissertations
The performance of a hypersonic flight vehicle will depend on existing materials and fuels; this work presents the performance of the ideal scramjet engine for three different combustion chamber materials and three different candidate fuels. Engine performance is explored by parametric cycle analysis for the ideal scramjet as a function of material maximum service temperature and the lower heating value of jet engine fuels. The thermodynamic analysis is based on the Brayton cycle as similarly employed in describing the performance of the ramjet, turbojet, and fanjet ideal engines. The objective of this work is to explore material operating temperatures and …
Design And Analysis Of Reconfigurable Sensing Antennas For Wireless Sensing Applications, Qian Qiao
Design And Analysis Of Reconfigurable Sensing Antennas For Wireless Sensing Applications, Qian Qiao
Electronic Theses and Dissertations
Reconfiguration sensing antenna (rsa) is a novel antenna concept, which not only can transmit or receive radio waves but also can sense the surrounding environment. The environment sensing is realized by reconfiguring the antenna's characteristics, such as resonant frequency, and radar cross section (rcs). The rsas possess the advantages of passive and low cost, which make them suitable for the large-scale wireless sensing networks (wsns) deployment. In this dissertation, the rsas concept is demonstrated, and two sensing mechanisms performed in the rsas are investigated. In order to verify these sensing mechanisms, four rsas are designed, analyzed, and measured. All the …
Placement Of Mode And Wavelength Converters For Throughput Enhancement In Optical Networks, Ruaa Abdulrahman
Placement Of Mode And Wavelength Converters For Throughput Enhancement In Optical Networks, Ruaa Abdulrahman
Electronic Theses and Dissertations
The success of recent experiments to transport data using combined wavelength division multiplexed (WDM) and mode-division multiplexed (MDM) transmission has generated optimism for the attainment of optical networks with unprecedented bandwidth capacity, exceeding the fundamental Shannon capacity limit attained by WDM alone. Optical mode converters and wavelength converters are devices that can be placed in future optical nodes (routers) to prevent or reduce the connection blocking rate and consequently increase network throughput. In this thesis, the specific problem of the placement of mode converters (MC) and mode-wavelength converters (MWC) in combined mode and wavelength division multiplexing (MWDM) networks is investigated. …
Treatment-Specific Approaches For Analysis And Control Of Left Ventricular Assist Devices, George Faragallah
Treatment-Specific Approaches For Analysis And Control Of Left Ventricular Assist Devices, George Faragallah
Electronic Theses and Dissertations
A Left Ventricular Assist Device (LVAD) is a mechanical pump that helps patients with heart failure conditions. This rotary pump works in parallel to the ailing heart and provides an alternative path for blood flow from the weak left ventricle to the aorta. The LVAD is controlled by the power supplied to the pump motor. An increase in the pump motor power increases the pump speed and the pump flow. The LVAD is typically controlled at a fixed setting of pump power. This basically means that the controller does not react to any change in the activity level of the …
Multifunctional, Multimaterial Particle Fabrication Via An In-Fiber Fluid Instability, Joshua Kaufman
Multifunctional, Multimaterial Particle Fabrication Via An In-Fiber Fluid Instability, Joshua Kaufman
Electronic Theses and Dissertations
Spherical micro- and nano-particles have found widespread use in many various applications from paint to cosmetics to medicine. Due to the multiplicity of desired particle material(s), structure, size range, and functionality, many approaches exist for generating such particles. Bottom-up methods such as chemical synthesis have a high yield and work with a wide range of materials; however, these processes typically lead to large polydispersity and cannot produce structured particles. Top-down approaches such as microfluidics overcome the polydispersity issue and may produce a few different structures in particles, but at lower rates and only at the micro-scale. A method that can …
Quantifying Ultra-High Performance Concrete Flexural System Mechanical Response, Yulin Xiao
Quantifying Ultra-High Performance Concrete Flexural System Mechanical Response, Yulin Xiao
Electronic Theses and Dissertations
The research and application of Ultra-high Performance Concrete (UHPC) has been developed significantly within the last 1-2 decades. Due to the specific property of high strength capacity, it is potential to be used in bridge deck system without shear reinforcement so that it provides even lighter self-weight of the deck. However, one of the shear component, dowel action, has not been adequately investigated in the past. In this dissertation, a particular test was designed and carried out to fully investigate the dowel action response, especially its contribution to shear resistance. In addition, research on serviceability and fatigue behaviors were expanded …
Functional Scaffolding For Musical Composition: A New Approach In Computer-Assisted Music Composition, Amy K. Hoover
Functional Scaffolding For Musical Composition: A New Approach In Computer-Assisted Music Composition, Amy K. Hoover
Electronic Theses and Dissertations
While it is important for systems intended to enhance musical creativity to define and explore musical ideas conceived by individual users, many limit musical freedom by focusing on maintaining musical structure, thereby impeding the user's freedom to explore his or her individual style. This dissertation presents a comprehensive body of work that introduces a new musical representation that allows users to explore a space of musical rules that are created from their own melodies. This representation, called functional scaffolding for musical composition (FSMC), exploits a simple yet powerful property of multipart compositions: The pattern of notes and rhythms in different …
Development Of Full Surface Transient Thermochromic Liquid Crystal Technique For Internal Cooling Channels, Lucky Tran
Development Of Full Surface Transient Thermochromic Liquid Crystal Technique For Internal Cooling Channels, Lucky Tran
Electronic Theses and Dissertations
Proper design of high performance industrial heat transfer equipment relies on accurate knowledge and prediction of the thermal boundary conditions. In order to enhance the overall gas turbine efficiency, advancements in cooling technology for gas turbines and related applications are continuously investigated to increase the turbine inlet temperature without compromising the durability of the materials used. For detailed design, local distributions are needed in addition to bulk quantities. Detailed local distributions require advanced experimental techniques whereas they are readily available using numerical tools. Numerical predictions using a computational fluid dynamics approach with popular turbulence models are benchmarked against a semi-empirical …
A Framework For Workforce Management An Agent Based Simulation Approach, Mario Marin
A Framework For Workforce Management An Agent Based Simulation Approach, Mario Marin
Electronic Theses and Dissertations
In today's advanced technology world, enterprises are in a constant state of competition. As the intensity of competition increases the need to continuously improve organizational performance has never been greater. Managers at all levels must be on a constant quest for finding ways to maximize their enterprises' strategic resources. Enterprises can develop sustained competitiveness only if their activities create value in unique ways. There should be an emphasis to transfer this competitiveness to the resources it has on hand and the resources it can develop to be used in this environment. The significance of human capital is even greater now, …
Synthesis, Processing And Characterization Of Polymer Derived Ceramic Nanocomposite Coating Reinforced With Carbon Nanotube Preforms, Hongjiang Yang
Synthesis, Processing And Characterization Of Polymer Derived Ceramic Nanocomposite Coating Reinforced With Carbon Nanotube Preforms, Hongjiang Yang
Electronic Theses and Dissertations
Ceramics have a number of applications as coating material due to their high hardness, wear and corrosion resistance, and the ability to withstand high temperatures. Critical to the success of these materials is the effective heat transfer through a material to allow for heat diffusion or effective cooling, which is often limited by the low thermal conductivity of many ceramic materials. To meet the challenge of improving the thermal conductivity of ceramics without lowering their performance envelope, carbon nanotubes were selected to improve the mechanical properties and thermal dispersion ability due to its excellent mechanical properties and high thermal conductivity …
Decentralized Power Management In Microgrids, Amit Bhattacharjee
Decentralized Power Management In Microgrids, Amit Bhattacharjee
Electronic Theses and Dissertations
A large number of power sources, operational in a microgrid, optimum power sharing and accordingly controlling the power sources along with scheduling loads are the biggest challenges in modern power system. In the era of smart grid, the solution is certainly not simple paralleling. Hence it is required to develop a control scheme that delivers the overall power requirements while also adhering to the power limitations of each source. As the penetration of distributed generators increase and are diversifi ed, the choice of decentralized control becomes preferable. In this work, a decentralized control framework is conceived. The primary approach is …
Synthetic Generators For Simulating Social Networks, Awrad Mohammed Ali
Synthetic Generators For Simulating Social Networks, Awrad Mohammed Ali
Electronic Theses and Dissertations
An application area of increasing importance is creating agent-based simulations to model human societies. One component of developing these simulations is the ability to generate realistic human social networks. Online social networking websites, such as Facebook, Google+, and Twitter, have increased in popularity in the last decade. Despite the increase in online social networking tools and the importance of studying human behavior in these networks, collecting data directly from these networks is not always feasible due to privacy concerns. Previous work in this area has primarily been limited to 1) network generators that aim to duplicate a small subset of …
The Effects Of Diffusion, Capillary Heterogeneity, And Porous Media Morphology On Co2 Migration In Porous Media, Oluseye Babafemi Adeyemi
The Effects Of Diffusion, Capillary Heterogeneity, And Porous Media Morphology On Co2 Migration In Porous Media, Oluseye Babafemi Adeyemi
Electronic Theses and Dissertations
The Modified Invasion Percolation (MIP) model was used to simulate the invasion of CO2 into a medium initially saturated with water and the style of capillary heterogeneity in combination with buoyancy and viscous forces were varied to yield 105 different simulation scenarios. Thereafter, the invasion of the CO2 gas is simulated using a finite difference model and the effective mass transfer coefficient is determined and linked to various styles of capillary heterogeneity. Results show that an increase in saturation does not result in an increase in mass transfer coefficient rather, the surface area, which in turn is controlled by the …
Finite Element Analysis Of Shear Resistant Mechanisms For Biolaminate Interfaces, Matthew Nelms
Finite Element Analysis Of Shear Resistant Mechanisms For Biolaminate Interfaces, Matthew Nelms
Electronic Theses and Dissertations
The Alligator gar possesses a flexible dermal armor consisting of overlapping ganoid scales. Each scale is a bilayer hydroxyapatite and collagen-based bio-laminate for protection against predation. The exoskeleton fish scale is comprised of a stiff outer ganoine layer, a characteristic "sawtooth" pattern at the interface and a compliant bone inner layer with all materials exhibiting a decreasing elastic modulus, yield strength and density through the thickness. Experiments on ganoid scales revealed properties such as damage mitigation and energy dissipation that are unique to biological dermal armor. The objective of this investigation is to develop a fundamental understanding of the stress …
Processing And Characterization Of Continuous Basalt Fiber Reinforced Ceramic Matrix Composites Using Polymer Derived Ceramics, Sarah Cox
Electronic Theses and Dissertations
The need for high performance vehicles in the aerospace industry requires materials which can withstand high loads and high temperatures. New developments in launch pads and infrastructure must also be made to handle this intense environment with lightweight, reusable, structural materials. By using more functional materials, better performance can be seen in the launch environment, and launch vehicle designs which have not been previously used can be considered. The development of high temperature structural composite materials has been very limited due to the high cost of the materials and the processing needed. Polymer matrix composites can be used for temperatures …
Non-Oxide Porous Ceramics From Polymer Precursor, Xueping Yang
Non-Oxide Porous Ceramics From Polymer Precursor, Xueping Yang
Electronic Theses and Dissertations
Non-oxide porous ceramics exhibit many unique and superior properties, such as better high-temperature stability, improved chemical inertness/corrosive resistance, as well as wide band-gap semiconducting behavior, which lead to numerous potential applications in catalysis, high temperature electronic and photonic devices, and micro-electromechanical systems. Currently, most mesoporous non-oxide ceramics (e.g. SiC) are formed by two-step templating methods, which are hard to adjust the pore sizes, and require a harmful etching step or a high temperature treatment to remove the templates. In this dissertation, we report a novel technique for synthesizing hierarchically mesoporous non-oxide SiC ceramic from a block copolymer precursor. The copolymer …
Photonic Filtering For Applications In Microwave Generation And Metrology, Marcus Bagnell
Photonic Filtering For Applications In Microwave Generation And Metrology, Marcus Bagnell
Electronic Theses and Dissertations
This work uses the photonic filtering properties of Fabry-Perot etalons to show improvements in the electrical signals created upon photodetection of the optical signal. First, a method of delay measurement is described which uses multi-heterodyne detection to find correlations in white light signals at 20 km of delay to sub millimeter resolution. By filtering incoming white light with a Fabry-Perot etalon, the pseudo periodic signal is suitable for measurement by combining and photodetecting it with an optical frequency comb. In this way, optical data from a large bandwidth can be downconverted and sampled on low frequency electronics. Second, a high …