Engineering Commons^™

Optimal Switch Timing For Piezoelectric-Based Semi-Active Vibration Reduction Techniques, Christopher Kelley

Electronic Theses and Dissertations

Semi-active vibration reduction techniques switch a piezoelectric transducer between an open circuit and a shunt circuit in a way that reduces vibration. The steady-state vibration amplitude is reduced by exploiting the change in stiffness between states, manipulating the converted electrical energy, or both. Semi-active techniques typically require four switches per vibration cycle. Control laws such as state switching and synchronized switch damping require switches to occur at every displacement extrema. Due to the complexity of analyzing a system with discrete switches, these control laws were developed based on intuition. The few analyses that attempt to determine an optimal switching law …

Experimental Study Of Sinkhole Failure Related To Groundwater Level Drops, Mohamed Alrowaimi

Electronic Theses and Dissertations

Sinkholes are natural geohazard phenomena that cause damage to property and may lead to loss of life. They can also cause added pollution to the aquifer by draining unfiltered water from streams, wetland, and lakes into the aquifer. Sinkholes occur in a very distinctive karst geology where carbonate, limestone, dolomite, or gypsum, are encountered as the bedrock that can naturally be dissolved by groundwater circulating through them. Sinkholes can occur gradually or suddenly with catastrophic impact depending on the geology and hydrology of the area. Predicting the formation and the collapse of a sinkhole based on the current ground investigation …

A Hybrid Simulation Framework Of Consumer-To-Consumer Ecommerce Space, Oloruntomi Joledo

Electronic Theses and Dissertations

In the past decade, ecommerce transformed the business models of many organizations. Information Technology leveled the playing field for new participants, who were capable of causing disruptive changes in every industry. "Web 2.0" or "Social Web" further redefined ways users enlist for services. It is now easy to be influenced to make choices of services based on recommendations of friends and popularity amongst peers. This research proposes a simulation framework to investigate how actions of stakeholders at this level of complexity affect system performance as well as the dynamics that exist between different models using concepts from the fields of …

Dynamic Modeling Approach To Quantify Change Orders Impact On Labor Productivity, Zain Al-Kofahi

Electronic Theses and Dissertations

In construction projects, change orders are commonly faced. These change orders, which are issued by the owner, may cause interruption to the contractor's work, resulting in damages such as loss of labor productivity, delay damages, and cost overruns which may lead to claims. The relationship between change orders and loss of labor productivity is not well understood because of the difficulty in linking the cause of the productivity loss to the change order. So, to receive compensation, the contractor needs to prove with a credible calculation that the productivity loss was a result of the change order issued by the …

Probabilistic-Based Computing Transformation With Reconfigurable Logic Fabrics, Mohammed Alawad

Electronic Theses and Dissertations

Effectively tackling the upcoming "zettabytes" data explosion requires a huge quantum leap in our computing power and energy efficiency. However, with the Moore's law dwindling quickly, the physical limits of CMOS technology make it almost intractable to achieve high energy efficiency if the traditional "deterministic and precise" computing model still dominates. Worse, the upcoming data explosion mostly comprises statistics gleaned from uncertain, imperfect real-world environment. As such, the traditional computing means of first-principle modeling or explicit statistical modeling will very likely be ineffective to achieve flexibility, autonomy, and human interaction. The bottom line is clear: given where we are headed, …

Effect Of Poisson’S Ratio On Material Properties Characterization By Nanoindentation With A Cylindrical Flat Tip Indenter, Md Mehadi Hassan

Electronic Theses and Dissertations

Nano indentation technology is commonly used to determine the mechanical properties of different kinds of engineering materials. The young’s modulus of the materials can be calculated with the load depth data obtained from an indentation test with a known Poisson’s ratio. In this investigation the NANOVEA micro/nanoindentation tester with a cylindrical flat-tip indenter will be used to find the elastic modulus, hardness and Pile up. Low carbon steel AISI1018, alloy steel AISI 4340 and aluminum alloy 6061 were selected for the case study. Finite element (FE) analysis using axisymmetric 3-D models used to establish the relationship between Poisson’s ratio and …

The Effects Of Carbon Fiber Misalignment On Composite Material Strength, Luke Stangler

Electronic Theses and Dissertations

Nondestructive Evaluation (NDE) is an effective way for determining material properties. More specifically, ultrasonic waves along with visual measurements from a microscope can be used to systematically determine the elastic modulus of single ply composites that are subject to an altered manufacturing process. In this approach, the magnitude of specific ultrasonic wave velocities is applied through Chirstoffel's equations to determine the necessary five elastic constants that describe the elastic modulus of transversely isotropic composites. On the other hand, fiber misalignment measurements are taken through via digital microscopy to satisfy a statistical approach for the determination of the same elastic modulus. …

Understanding The Impact Of Non-Thermal Processing And Co2 Assisted Extrusion On Antioxidant, Textural And Functional Properties Of Corn, Sorghum And Apple Pomace Based Extrudates, Umesh Chandra Lohani

Electronic Theses and Dissertations

Currently, there is a worldwide demand for antioxidant rich foods in diet, especially ready to eat foods, i.e. cereals and snacks. In recent years, the research has got momentum to valorize the underutilized crops, i.e. millet, sorghum and industrial food by-products, i.e. fruit pomace to incorporate into main stream of human diet due to their enrichment in nutritional as well as bioactive compounds like phenolic and flavonoid antioxidants. However, most of the phenolic compounds in plant are present in the bound form with the carbohydrates, lignin, pectin and proteins which reduces their ability to function as good antioxidants. Therefore, in …

Sensing Using Specialty Optical Fibers, Amy Van Newkirk

Electronic Theses and Dissertations

Fiber optic based sensing is a growing field with many applications in civil and aerospace engineering, oil and gas industries, and particularly in harsh environments where electronics are not able to function. Optical fibers can be easily integrated into structures, are immune to electromagnetic interference, can be interrogated from remote distances, and can be multiplexed for distributed measurements. Because of these properties, specialty fiber designs and devices are being explored for sensing temperature, strain, pressure, curvature, refractive index, and more. Here we show a detailed analysis of a multicore fiber (MCF) for sensing, including its design and optimization in simulation, …

Electrical Parasitic Bandwidth Limitations Of Oxide-Free Lithographic Vertical-Cavity Surface-Emitting Lasers, Xu Yang

Electronic Theses and Dissertations

Nowadays, Vertical-Cavity Surface-Emitting Lasers (VCSELs) are the most popular optical sources in short-reach data communications. In the commercial oxide VCSEL technology, an oxide aperture is created inside resonant cavity in realizing good mode and current confinement, however, high electrical resistance comes along with forming the oxide aperture and the electrical parasitic bandwidth becomes the main limitation in modulation speed. In this report, electrical bandwidths of oxide-free lithographic VCSELs have been studied along with their general lasing properties. Due to the new ways of fabricating the aperture, record low resistances have been achieved in oxide-free lithographic VCSELs with various sizes, while …

Improved Interpolation In Sph In Cases Of Less Smooth Flow, Oddny Brun

Electronic Theses and Dissertations

We introduced a method presented in Information Field Theory (IFT) [Abramovich et al., 2007] to improve interpolation in Smoothed Particle Hydrodynamics (SPH) in cases of less smooth flow. The method makes use of wavelet theory combined with B-splines for interpolation. The idea is to identify any jumps a function may have and then reconstruct the smoother segments between the jumps. The results of our work demonstrated superior capability when compared to a particular challenging SPH application, to better conserve jumps and more accurately interpolate the smoother segments of the function. The results of our work also demonstrated increased computational efficiency …

The Impact Of Automation Reliability And Fatigue On Reliance, Ryan Wohleber

Electronic Theses and Dissertations

The objective of this research is to inform the design of dynamic interfaces to optimize unmanned aerial vehicle (UAV) operator reliance on automation. A broad goal of the U.S. military is to improve the ratio of UAV operators to UAVs controlled. Accomplishing this goal requires the use of automation; however, the benefits of automation are jeopardized without appropriate operator reliance. To improve reliance on automation, this effort sought to accomplish several objectives organized into phases. The first phase aimed to validate metrics that could be used to gauge operator fatigue online, to understand how the reliability of automated systems influences …

Computer Vision Based Structural Identification Framework For Bridge Health Mornitoring, Tung Khuc

Electronic Theses and Dissertations

The objective of this dissertation is to develop a comprehensive Structural Identification (St-Id) framework with damage for bridge type structures by using cameras and computer vision technologies. The traditional St-Id frameworks rely on using conventional sensors. In this study, the collected input and output data employed in the St-Id system are acquired by series of vision-based measurements. The following novelties are proposed, developed and demonstrated in this project: a) vehicle load (input) modeling using computer vision, b) bridge response (output) using full non-contact approach using video/image processing, c) image-based structural identification using input-output measurements and new damage indicators. The input …

Low Impact Development Analysis And Comparative Assessment Of Wet Detention Ponds With Floating Treatment Wetlands, Nicholas Hartshorn

Electronic Theses and Dissertations

The aim of this thesis is to examine, develop, and assess innovative best management practices (BMPs) in stormwater management for pollutant reduction, flood control, and environmental sustainability. Previous research has clearly shown that urban stormwater runoff quickly transports pathogens, metals, sediment, and chemical pollutants to receiving waterbodies, resulting in the degradation of receiving waters and disruption of ecological networks. In response to this growing concern, regulatory agencies, such as the Environmental Protection Agency (EPA) and the Florida Department of Environmental Protection (FDEP), have set forth regulations aimed at protecting and restoring waterbodies. These regulations include numeric nutrient criteria (NNC) and …

Global Data Association For Multiple Pedestrian Tracking, Afshin Dehghan

Electronic Theses and Dissertations

Multi-object tracking is one of the fundamental problems in computer vision. Almost all multi-object tracking systems consist of two main components; detection and data association. In the detection step, object hypotheses are generated in each frame of a sequence. Later, detections that belong to the same target are linked together to form final trajectories. The latter step is called data association. There are several challenges that render this problem difficult, such as occlusion, background clutter and pose changes. This dissertation aims to address these challenges by tackling the data association component of tracking and contributes three novel methods for solving …

Methods And Implementation Of Fluid-Structure Interaction Modeling Into An Industry-Accepted Design Tool, Donn R. Sederstrom

Electronic Theses and Dissertations

Fluid-structure interaction (FSI) modeling is a method by which fluid and solid domains are coupled together to produce a single result that cannot be produced if each physical domain was evaluated individually. The work presented in this dissertation is a demonstration of the methods and implementation of FSI modeling into an industry-appropriate design tool. Through utilizing computationally inexpensive equipment and commercially available software, the studies presented in this work demonstrate the ability for FSI modeling to become a tool used broadly in industry.

To demonstrate this capability, the cases studied purposely include substantial complexity to demonstrate the stability techniques required …

Finite Element And Probabilistic Analysis Of Soft Tissue Structures Of The Human Lumbar Spine, Dana Joseph Coombs

Electronic Theses and Dissertations

Human lumbar spine mechanics are influenced by soft tissue structures. Understanding and properly modeling these structures can help determine pathology, treatment, and implant design and performance. Finite element models of the L4-L5 level of the lumbar spine are often used, which include a representation of the intervertebral disc and spinal ligaments. Validation of these models are typically based on torque rotation data from a single subject or the models use average properties reported in literature. However, experimental testing reports variation up to 40% in ligament stiffness and even greater variability for annulus fibrosis properties. Probabilistic approaches enable consideration of the …

Statistical Modeling To Investigate Anatomy And Function Of The Knee, Lowell Matthew Smoger

Electronic Theses and Dissertations

The natural knee is a hinge joint with significant functional requirements during activities of daily living; as a result, acute and chronic injuries can occur. Pathologies are influenced by joint anatomy and may include patellar maltracking, cartilage degeneration (e.g. osteoarthritis), or acute injuries such as meniscal or ligamentous tears. Population variability makes broadly applicable conclusions about etiology of these conditions from small-scale investigations challenging. The work presented in this dissertation is a demonstration of statistical modeling approaches to evaluate population variability in anatomy of the knee and function of its tibiofemoral (TF) and patellofemoral (PF) joints. Three-dimensional (3D) computational models …

Heat Transfer Mechanisms In Water-Based Nanofluids., Masoudeh Ahmadi

Electronic Theses and Dissertations

Nanofluids are a class of heat transport fluids created by suspending nano-scaled metallic or nonmetallic particles into a base fluid. Some experimental investigations have revealed that the nanofluids have remarkably higher thermal conductivities than those of conventional pure fluids and are more suited for practical application than the existing techniques of heat transfer enhancement using millimeter and/or micrometer-sized particles in fluids. Use of nanoparticles reduces pressure drop, system wear, and overall mass of the system leading to a reduction in costs over existing enhancement techniques. In this work, the heat transfer coefficient is determined experimentally using copper oxide (CuO) based …

Assessing The Water Quality Benefits Of Green Infrastructure Stormwater Control Measures., Sam Abdollahian

Electronic Theses and Dissertations

Permeable pavements systems and tree boxes are a common type of Green Infrastructure (GI) Stormwater Control Measures (SCMs) that are often used for mitigating the stormwater runoff. In this study two permeable pavement systems and a tree box installed along parking lanes of an urban street in Louisville, KY, were investigated to evaluate their performance on improving stormwater runoff quality. The water quality monitoring was accomplished by analysis of samples collected from stormwater runoff and the captured stormwater volume at the bottom of the permeable pavements’ sub-base reservoir and by a drain gauge (lysimeter) installed in the tree box. Pollutants …

Development Of A Vascularized, Induced Pluripotent Stem Cell-Derived Liver-Tissue Mimic For Therapeutic Applications., Venkat Madhav Ramakrishnan

Electronic Theses and Dissertations

This dissertation describes the incorporation of several technologies (stem cells, gene therapy, tissue engineering and regenerative medicine) into a single project that aims to produce a liver-tissue mimic for therapeutic applications. The liver is arguably one of the most complex organs in the body. In addition to its remarkable capacity to regenerate, it performs a host of vital functions. As a result, its impairment has widespread systemic consequences. The work described herein focused on the liver in the context of cardiovascular disease and used the heritable disorder Familial Hypercholesterolemia (FH) as a clinical disease model. As (a) the only definitive …

Exclusive-Or Preprocessing And Dictionary Coding Of Continuous-Tone Images., Takiyah K. Cooper

Electronic Theses and Dissertations

The field of lossless image compression studies the various ways to represent image data in the most compact and efficient manner possible that also allows the image to be reproduced without any loss. One of the most efficient strategies used in lossless compression is to introduce entropy reduction through decorrelation. This study focuses on using the exclusive-or logic operator in a decorrelation filter as the preprocessing phase of lossless image compression of continuous-tone images. The exclusive-or logic operator is simply and reversibly applied to continuous-tone images for the purpose of extracting differences between neighboring pixels. Implementation of the exclusive-or operator …

Application Of The Aeroacoustic Analogy To A Shrouded, Subsonic, Radial Fan., Bryan Buccieri

Electronic Theses and Dissertations

A study was conducted to investigate the predictive capability of computational aeroacoustics with respect to a shrouded, subsonic, radial fan. A three dimensional unsteady fluid dynamics simulation was conducted to produce aerodynamic data used as the acoustic source for an aeroacoustics simulation. Two acoustic models were developed: one modeling the forces on the rotating fan blades as a set of rotating dipoles located at the center of mass of each fan blade and one modeling the forces on the stationary fan shroud as a field of distributed stationary dipoles. Predicted acoustic response was compared to experimental data. The blade source …

Plasma Catalysis Using Low Melting Point Metals., Maria Carreon

Electronic Theses and Dissertations

Plasma catalysis is emerging as one of the most promising alternatives to carry out several reactions of great environmental importance, from the synthesis of nanomaterials to chemicals of great interest. However, the combined effect of a catalyst and plasma is not clear. For the particular case of 1-D nanomaterials growth, the low temperatures synthesis is still a challenge to overcome for its scalable manufacturing on flexible substrates and thin metal foils. Herein, the use of low-melting-point metal clusters under plasma excitation was investigated to determine the effectiveness in their ability to catalyze the growth of 1-D nanomaterials. Specifically, plasma catalysis …

Novel Biomechanical Test Method For Cancellous Bone Screws And Screw Augmentation With Cement., Kevin Lancaster

Electronic Theses and Dissertations

It is often difficult to achieve adequate screw fixation for plate constructs in fractures with poor quality bone or in metaphyseal bone with extensive bone loss or comminution[7][17]. Furthermore, rescuing or augmenting failed screw fixation in inadequate bone with various cement products has yielded mixed results when tested with pure axial pullout loading[20][21]. In most cases, plate/screw constructs experience both vertical (translational) and horizontal (pullout) forces during physiologic loading[17][20][21]. The increased use of locked screws in plate constructs has also changed the loading patterns of bone screws. For this study, a novel “toggle-out” testing method was developed to more realistically …

Solar Powered Picnic Table For Charging Cellphones And Other Small Devices, Casey B. Potts

Electronic Theses and Dissertations

Solar panels are used in many different applications for generating sustainable energy. Many countries use solar power as a power generation method. It is also, an excellent option for getting power to difficult areas. There are three main systems used when generating solar power: grid-tied, battery banked, and direct driven systems. Most systems use a combination of grid-tied and battery banked so any unused power can be fed back into the main grid for compensation. The solar power application suggested in this thesis will provide USB power to a picnic table enabling students to charge cellphones and other small devices …

Synthesis And Functional Evaluation Of Peptide Modified Poly (Lactic-Co-Glycolic Acid) Nanoparticles To Inhibit Porphyromonas Gingivalis Biofilm Formation., Paridhi Kalia

Electronic Theses and Dissertations

Periodontal disease is an oral inflammatory disorder that afflicts roughly 46% of the adults in the U.S. Currently, treatment of periodontal disease involves the removal of plaque from the gingival pocket (with possible antibiotic treatment) and if necessary, gingival surgery. To our knowledge, no therapeutic approach exists that promotes host-biofilm homeostasis by limiting pathogen recolonization of the oral cavity after prophylaxis or treatment. The interaction of the pathogen Porphyromonas gingivalis with commensal streptococci is critical for initiation of periodontitis and represents a target for limiting P. gingivalis colonization of the oral cavity. Previous studies showed that a synthetic peptide …

New Visible Light Absorber For Solar Fuels : Ga(Sbx)N1-X Alloys., Swathi Sunkara

Electronic Theses and Dissertations

Solar energy conversion to fuels via photoelectrochemical water splitting is one of the most important technological directions toward meeting the global energy and environmental challenge. However, till date, there are no suitable semiconductor materials available that can absorb visible light, possess right kind of band edge energetics and are stable in aqueous environments. In this work, a new III-V alloy material Ga(Sbx)N1-x with dilute antimony concentration is proposed and developed for photoelectrochemical water splitting. Experimental studies were conducted first to synthesize the proposed alloy materials to understand structure-property relationships and compare them to those obtained using first principles computations. Finally, …

Spare Parts On Demand Using Additive Manufacturing : A Simulation Model For Cost Evaluation., Stefan Jedeck

Electronic Theses and Dissertations

Little is known about the impact of additive manufacturing in the spare part supply chain. A few studies are available, but they focus on specific parts and their applications only. A general model, which can be adapted to different applications, is nonexistent. This dissertation proposes a decision making framework that enables an interested practitioner/manager to decide whether using additive manufacturing to make spare parts on demand is economical when compared to conventional warehousing strategy. The framework consists of two major components: a general discrete event simulation model and a process of designing a wide range of simulation scenarios. The goal …

Evaluation Of Two-Phase Evaporation Pressure Drop Correlations For Low Refrigerant Mass Flux., Anna Fenko

Electronic Theses and Dissertations

This study was conducted to evaluate three currently popular two-phase pressure drop models for extremely low velocity refrigerant flow through smooth circular evaporators in household refrigeration systems. Experimental data was taken at mass fluxes under 70 kg/m²s for two refrigerants, R134A and R600A, internal diameters of aluminum evaporators ranging from 0.186 to 0.317 inches, U-bend internal radii ranging from 0.342 to 0.750 inches in horizontal and vertical orientations of evaporators. The geometry of the samples closely resembled a commonly used serpentine shape with multiple U-bends experiencing both, up- and down-flow of the refrigerant. Two empirical models, Müller-Steinhagen & …