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Articles 1 - 25 of 25
Full-Text Articles in Engineering
Measurements Of Fluvial Sediments Using A Single-Frequency Acoustic Attenuation System, Thomas Alexander Kajdan
Measurements Of Fluvial Sediments Using A Single-Frequency Acoustic Attenuation System, Thomas Alexander Kajdan
Electronic Theses and Dissertations
Suspended sediments are a global-scale pollutant that threaten the integrity of our waterways and pose an environmental threat to many aquatic ecosystems. Innovative techniques are required to continuously monitor this pollutant. Ultrasonic acoustic measurements have the potential to improve the temporal resolution of fluvial sediment data. This work investigates the use of a prototype field grade single-frequency acoustic attenuation system that was developed at the National Center for Physical Acoustics (NCPA), located at the University of Mississippi. This field-deployable unit consists of two 20 MHz immersion transducers that are aligned in a "pitch-catch" configuration at a fixed distance of 18 …
Optimized Image Compressed Sensing And Transmission Through Wireless Channels, Saheed Olanigan
Optimized Image Compressed Sensing And Transmission Through Wireless Channels, Saheed Olanigan
Electronic Theses and Dissertations
This thesis examines the robust behavior of quantized compressed sensing measurements during transmission through an additive white gaussian noise wireless channel. The poor rate-distortion performance that accompanies compressed sensing after applying quantization has led to several works in quantized compressed sensing. However, most of these works have less consideration of the effect of transmission channel on the resulting bit stream of the quantized compressed sensing measurements. For an additive white gaussian noise wireless channel model, the quantizer and bit energy signal-to-noise ratio determines the degree of the channel effect. This thesis explores the effect of quantization and channel noise during …
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 …
Environmental Degradation Of Nano Enhanced Polymers In Low Earth Orbit, Mohammed Jaradat
Environmental Degradation Of Nano Enhanced Polymers In Low Earth Orbit, Mohammed Jaradat
Electronic Theses and Dissertations
No abstract provided.
Cross-Layer Capacity Optimization In Ofdma Systems: Wimax And Lte, Bimal Paudel
Cross-Layer Capacity Optimization In Ofdma Systems: Wimax And Lte, Bimal Paudel
Electronic Theses and Dissertations
Given the broad range of applications supported, high data rate required and low latency promised; dynamic radio resource management is becoming vital for newly emerging air interface technologies such as wireless interoperability for microwave access (Wimax) and long term evolution (lte) adopted by international standards. This thesis considers orthogonal frequency division multiple access (ofdma) system, which has been implemented in both Wimax and lte technologies as their air interface multiple access mechanism. A framework for optimized resource allocation with quality of service (qos) support that aims to balance between service provider's revenue and subscriber's satisfaction is proposed. A cross-layer optimization …
Analysis And Design Of Low Profile Multiband Multifunctional Antenna Arrays, Walker F. Hunsicker
Analysis And Design Of Low Profile Multiband Multifunctional Antenna Arrays, Walker F. Hunsicker
Electronic Theses and Dissertations
Light-weight phased array antennas for aerospace and mobile applications require utilizing the same antenna aperture to provide multiple functions with dissimilar radiation pattern specifications (e.g., multiband operation for communications and tracking). Multi-functional antennas provide advantages over aggregate antenna clusters by reducing space requirements, and can aid in the optimal placement of all required apertures to provide adequate isolation between channels. Furthermore, the combination of antenna apertures into a comgeometry mitigates co-site installation issues by addressing interference within the integrated radiator design itself as opposed to the extensive analysis which is required to configure multiple radiators in close proximity. The combination …
Microstructure, Quasi-Static, And High-Strain Rate Dynamic Characterization Of Metakaolin And Fly Ash Based Geopolymers For Structural Applications, Damian Lee Stoddard
Microstructure, Quasi-Static, And High-Strain Rate Dynamic Characterization Of Metakaolin And Fly Ash Based Geopolymers For Structural Applications, Damian Lee Stoddard
Electronic Theses and Dissertations
Geopolymers are a class of rapid setting cementing systems that have been used as mortar or additives in concrete mixes to improve properties. Several types of geopolymer systems such as metakaolin and fly ash based geopolymers are widely used, and are available in different mixture proportions [1, 2]. Metakaolin (Al2Si2O7), a dehydroxylated form of Kaolinite (Al2Si2O5(OH)4) clay readily available from many sources, provides several benefits whenadded to a concrete mix design or used as a mortar system, including durability, freeze/thaw, acid resistance, and high temperature resistance [3]. Class F fly ash-based mortar geopolymers provide added fire retardation, reduces crack formation, …
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 …
Reconfigurable Microstrip Antennas With Tunable Radiation Pattern Characteristics, Ahmed Khidre
Reconfigurable Microstrip Antennas With Tunable Radiation Pattern Characteristics, Ahmed Khidre
Electronic Theses and Dissertations
Reconfigurable beam antenna systems are capable of changing their radiation characteristics in real time, such as beam direction, beam shape, beamwidth, etc. Such antenna system is desired for various wireless applications because of many reasons among them; it helps to enhance signal strength received from an intended target, mitigates interference, and accommodates sudden changes in traffic demand of wireless networks. It might also help to reduce the deployment cost of wireless networks infrastructures. In this dissertation, designs for reconfigurable beam microstrip antennas with tunable radiation characteristics have been proposed. The method to achieve these designs is the reconfigurable parasitic element …
Adaptive Relay-Selection In Decode-And-Forward Cooperative Systems, Adham Ahmed Hagag
Adaptive Relay-Selection In Decode-And-Forward Cooperative Systems, Adham Ahmed Hagag
Electronic Theses and Dissertations
In the past few years adaptive decode-and-forward cooperative diversity systems have been studied intensively in literature. Many schemes and protocols have been proposed to enhance the performance of the cooperative systems while trying to alleviate its drawbacks. One of the recent schemes that had been shown to give high improvements in performance is the best-relay selection scheme. In the best-relay selection scheme only one relaying nodes among the relays available in the system is selected to forward the source's message to the destination. The best relay is selected as the relay node that can achieve the highest end-to-end signal-to-noise ratio …
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 …
Evaluation Of Cotton Valley "D" Sand Production In Stampede Field, Mississippi, U.S.A., Patrick Lawrence Murphy
Evaluation Of Cotton Valley "D" Sand Production In Stampede Field, Mississippi, U.S.A., Patrick Lawrence Murphy
Electronic Theses and Dissertations
No abstract provided.
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 …
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 …
Three-Dimensional Numerical Modeling Of Multiple-Sized Sediment Transport Modeling Under Current And Waves, Qianru Lin
Three-Dimensional Numerical Modeling Of Multiple-Sized Sediment Transport Modeling Under Current And Waves, Qianru Lin
Electronic Theses and Dissertations
In this study, a three-dimensional numerical model of multiple-sized sediment transport under current and waves is developed. The coastal circulations are described by a three-dimensional hydrodynamic model, which is governed by the three-dimensional phase-averaged shallow water flow equations coupled with wave radiation stresses. Methods are also developed to determine the bed shear stress due to current only, waves only, and coexistence of current and waves, accounting for the nonlinear interaction of the current and waves on bed shear stresses. Meanwhile, empirical formulas for bed-load transport capacity, suspended-load transport capacity, and near-bed suspended-load concentration under current and waves are established for …
Rss Based Localization In A Rayleigh Fading Environment, Rojina Adhikary
Rss Based Localization In A Rayleigh Fading Environment, Rojina Adhikary
Electronic Theses and Dissertations
The objective of this thesis is to quantify the improvement that can be obtained in sensor agent localization accuracy as a function of the number of multipath components that can be resolved. We assume that a known number sensor agents are located at unknown coordinates within a rectangular grid having anchors at the corner locations, whose locations are known. Further, we assume fading is Rayleigh and that the propagation constant is constant but unknown. Also, we assume that modulation is spread spectrum and that either the sensors or agents are capable of resolving multipath components down to the chip level …
Xqx Based Modeling For General Integer Programming Problems, Vijay P. Ramalingam
Xqx Based Modeling For General Integer Programming Problems, Vijay P. Ramalingam
Electronic Theses and Dissertations
We present a new way to model general integer programming (IP) problems with in- equality and equality constraints using XQX. We begin with the definition of IP problems folloby their practical applications, and then present the existing XQX based models to handle such problems. We then present our XQX model for general IP problems (including binary IP) with equality and inequality constraints, and also show how this model can be applied to problems with just inequality constraints. We then present the local optima based solution procedure for our XQX model. We also present new theorems and their proofs for our …
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 …
Critical Analysis Of Transmitarray Antenna Design, Ahmed H. Abdelrahman
Critical Analysis Of Transmitarray Antenna Design, Ahmed H. Abdelrahman
Electronic Theses and Dissertations
In recent years, transmitarray antenna concept attracts growing interests of many scientists in the antenna area. It combines the favorable features of the lens antenna that are based on optical theory and the microstrip arrays that are based on array theory, leading to a low profile design with high gain, high radiation efficiency, and flexible radiation performance. Transmitarrays are now emerging as a new generation of high-gain antennas for long-distance communications. In this dissertation, comprehensive analysis, new methodologies, and novel designs of transmitarray antennas are presented. * detailed analysis of the design of planar space fed array antennas is presented. …
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 …
Pretreatment Of Cellulosic Biomass By Iron-Containing Magnetic Ionic Liquid Dissolution, Christopher Roth Riley
Pretreatment Of Cellulosic Biomass By Iron-Containing Magnetic Ionic Liquid Dissolution, Christopher Roth Riley
Electronic Theses and Dissertations
The focus of this project is to determine the effectiveness in the preprocessing of biomass when magnetic ionic liquids (MIL) (1-butyl-3-methylimidazolium tetrachloroferrate (Bmim[FeCl4]) and 1-ethyl-3-methylimidazolium tetrachloroferrate (Emim[FeCl4])) are used as a green solvent. Lignocellulose is a promising starting material for a plethora of products, ranging from biofuels to custom chemicals; however, lignocellulose is resistant to enzymatic degradation. Various biomass-preprocessing techniques such as microbial, mechanical, and chemical pretreatment are used for enhancing the digestibility of biomass to sugars for ethanol production. Varieties of ionic liquids have demonstrated the ability to fragment lignocellulose. However, after fragmentation, separation of biomass and ionic liquids …
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 …
Development And Validation Of The Structural Health Evaluation (SheTm) Program, Steven Worley
Development And Validation Of The Structural Health Evaluation (SheTm) Program, Steven Worley
Electronic Theses and Dissertations
No abstract provided.
Broadband Approaches And Beam-Scanning Techniques For Reflectarray Antenna, Yilin Mao
Broadband Approaches And Beam-Scanning Techniques For Reflectarray Antenna, Yilin Mao
Electronic Theses and Dissertations
Reflectarray antennas combine the numerous advantages of reflector antennas and phased array antennas and create a hybrid high-gain antenna with a low-profile, low-mass, easy-fabrication, and diversified radiation performance. However, it still has some inherent drawbacks, such as limited bandwidth and scanning range, which are targeted in this dissertation. At first, the array theory approach for radiation analysis of reflectarray antennas is described and implemented. Numerical results are then presented and compared with reference results to confirm its reliability. As the most critical influential factor to the reflectarray bandwidth, the element bandwidth was studied at first, and the effects of element …
High-Strain Rate Tensile Characterization Of Graphite Platelet Reinforced Vinyl Ester Based Nanocomposites Using Split-Hopkinson Pressure Bar, Brahmananda Pramanik
High-Strain Rate Tensile Characterization Of Graphite Platelet Reinforced Vinyl Ester Based Nanocomposites Using Split-Hopkinson Pressure Bar, Brahmananda Pramanik
Electronic Theses and Dissertations
The dynamic response of exfoliated graphite nanoplatelet (xGnP) reinforced and carboxyl terminated butadiene nitrile (CTBN) toughened vinyl ester based nanocomposites are characterized under both dynamic tensile and compressive loading. Dynamic direct tensile tests are performed applying the reverse impact Split Hopkinson Pressure Bar (SHPB) technique. The specimen geometry for tensile test is parametrically optimized by Finite Element Analysis (FEA) using ANSYS Mechanical APDL®. Uniform stress distribution within the specimen gage length has been verified using high-speed digital photography. The on-specimen strain gage installation is substituted by a non-contact Laser Occlusion Expansion Gage (LOEG) technique for infinitesimal dynamic tensile strain measurements. …