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Full-Text Articles in Engineering

Fully Analog Laser Driver With Robust Active Feedback Control, John Petrilli Dec 2018

Fully Analog Laser Driver With Robust Active Feedback Control, John Petrilli

Theses and Dissertations

The objective of this project was to go through a real life engineering development cycle, document and justify the design choices, and use background experience in electronic design and control systems to implement the best design possible. The laser driver implemented in this project is designed for the general use of a large variety of diodes in continuous wave mode, much like off the shelf laser drivers. The design goals included improving upon off the shelf laser drivers by decreasing steady state error, setting time, response time, and overshoot. Many different feedback control systems were evaluated, and a modified PID ...


Towards Environmentally Sustainable And Cost-Effective Food Distribution In The U.S., Jasmina Burek Dec 2018

Towards Environmentally Sustainable And Cost-Effective Food Distribution In The U.S., Jasmina Burek

Theses and Dissertations

Distribution centers (DCs) and supermarkets have an important role in food sustainability, but no previous research has accounted for their environmental impact. The purpose of this research was to assess environmental sustainability of grocery, perishables, and general merchandise DCs; to estimate food storing and retailing impact; and to provide cost-effective strategies to reduce DCs’ environmental impacts. The importance and relevance of the research is threefold: improving sustainability of DCs, food storing, and food retailing. The main method used in this research was the life cycle assessment (LCA) method. An initial study calculated environmental impacts of the Wal-Mart Stores, Inc. DCs ...


On The Development Of 8,000 Psi Geopolymer Mortar For Practical Use In Field Applications, Remington Gabriel Reed Dec 2018

On The Development Of 8,000 Psi Geopolymer Mortar For Practical Use In Field Applications, Remington Gabriel Reed

Theses and Dissertations

Although there are several perceived benefits from the use of geopolymer binder as an alternative to ordinary portland cement in concrete materials, it is not widely used in field applications. Geopolymer materials have no set guidelines for mixture design and often require heat curing to facilitate strength gain. Additionally, many geopolymers are created using carefully controlled and high quality materials and activator chemicals. These factors greatly affect the practicality of the material. The goal of this research was to create a geopolymer material capable of achieving high compressive strengths at 28 days without heat curing, and using only readily available ...


Effect Of Continuity Plate Eccentricity On The Performance Of Welded Beam-To-Column Connections, Jason Thomas Norwood Dec 2018

Effect Of Continuity Plate Eccentricity On The Performance Of Welded Beam-To-Column Connections, Jason Thomas Norwood

Theses and Dissertations

Beam-to-column connections in structural steel buildings may have varying degrees of rotational restraint and varying degrees of moment transfer. In fully restrained moment connections, shear is typically transferred through the beam web, while the moment is mostly transferred through the beam flanges which create tension/compression force couples. Column sections that are incapable of resisting these flange forces are often retrofitted with continuity plates within the connection region to improve capacity. In cases of unequal beam depths on either side of the column, an eccentricity between the framed-in beam flange and continuity plate may be required; however, limited research exists ...


Budget-Constrained Regression Model Selection Using Mixed Integer Nonlinear Programming, Jingying Zhang Dec 2018

Budget-Constrained Regression Model Selection Using Mixed Integer Nonlinear Programming, Jingying Zhang

Theses and Dissertations

Regression analysis fits predictive models to data on a response variable and corresponding values for a set of explanatory variables. Often data on the explanatory variables come at a cost from commercial databases, so the available budget may limit which ones are used in the final model.

In this dissertation, two budget-constrained regression models are proposed for continuous and categorical variables respectively using Mixed Integer Nonlinear Programming (MINLP) to choose the explanatory variables to be included in solutions. First, we propose a budget-constrained linear regression model for continuous response variables. Properties such as solvability and global optimality of the proposed ...


Evaluation Of Rsaf Airworthiness And Applicability, Majed M. Altowairqi Sep 2018

Evaluation Of Rsaf Airworthiness And Applicability, Majed M. Altowairqi

Theses and Dissertations

This research focuses on evaluation of Royal Saudi Air Force (RSAF) airworthiness processes and their applicability. The current RSAF airworthiness process is in accordance with internationally recognized best practice in the area of military aviation, this is achieved by benchmarking against European Aviation Safety Agency (EASA) and International Organization for Standardization (ISO) standards. Airworthiness policy for the RSAF is developed on the basis that it will be as civil as possible and as military as necessary. For the purpose of this research, the current RSAF airworthiness process will be benchmarked against the United States Air Force (USAF) airworthiness process. That ...


Operational Squadron Scheduling, Khaled A. Almannaei Sep 2018

Operational Squadron Scheduling, Khaled A. Almannaei

Theses and Dissertations

The 28th Operational Weather Squadron (28th OWS) is responsible for producing and disseminating mission planning and execution weather analyses and forecasts. The squadron must prepare schedules that meet the needs of their mission while dealing with real-world constraints such as time windows, task priorities, and intermittent recurring missions. The 28th OWS's manning consists of active duty, deployed in-place, reserve, civilian and contract personnel. In this research, a scheduling model and algorithm are provided as an approach to crew scheduling for the 28th Operational Weather Squadron. Scheduling in the 28th OWS is complex and can be time consuming. This model ...


Distributed Methods For Composite Optimization: Communication Efficiency, Load-Balancing And Local Solvers, Chenxin Ma Sep 2018

Distributed Methods For Composite Optimization: Communication Efficiency, Load-Balancing And Local Solvers, Chenxin Ma

Theses and Dissertations

The scale of modern datasets necessitates the development of efficient distributed opti- mization methods for composite problems, which have numerous applications in the field of machine learning. A critical challenge in realizing this promise of scalability is to develop efficient methods for communicating and coordinating information between distributed ma- chines, taking into account the specific needs of machine learning algorithms. Recent work in this area has been limited by focusing heavily on developing highly specific methods for the distributed environment. These special-purpose methods are often unable to fully leverage the competitive performance of their well-tuned and customized single machine counterparts ...


Multi-Level Multi-Objective Programming And Optimization For Integrated Air Defense System Disruption, Aaron M. Lessin Sep 2018

Multi-Level Multi-Objective Programming And Optimization For Integrated Air Defense System Disruption, Aaron M. Lessin

Theses and Dissertations

The U.S. military's ability to project military force is being challenged. This research develops and demonstrates the application of three respective sensor location, relocation, and network intrusion models to provide the mathematical basis for the strategic engagement of emerging technologically advanced, highly-mobile, Integrated Air Defense Systems. First, we propose a bilevel mathematical programming model for locating a heterogeneous set of sensors to maximize the minimum exposure of an intruder's penetration path through a defended region. Next, we formulate a multi-objective, bilevel optimization model to relocate surviving sensors to maximize an intruder's minimal expected exposure to traverse ...


Investigation Of A Pressure Wave Supercharger For An Industrial Diesel Engine, Brian A. Beasley Sep 2018

Investigation Of A Pressure Wave Supercharger For An Industrial Diesel Engine, Brian A. Beasley

Theses and Dissertations

Internal combustion engines suffer from decreased performance as altitude is in- creased. This performance decrease can be overcome by increasing the pressure in the engine's intake manifold. Typically, this is accomplished with a turbocharger or supercharger. However, mechanical compression devices such as these suffer from decrease compression efficiency as the size of the device decreases. The size of the compression device scales with the amount of mass ow through the device, and the amount of mass ow is proportional to the size of the engine. This means a small turbocharger for a small engine is less efficient than a ...


Application Of Spectral Solution And Neural Network Techniques In Plasma Modeling For Electric Propulsion, Joseph R. Whitman Sep 2018

Application Of Spectral Solution And Neural Network Techniques In Plasma Modeling For Electric Propulsion, Joseph R. Whitman

Theses and Dissertations

A solver for Poisson's equation was developed using the Radix-2 FFT method first invented by Carl Friedrich Gauss. Its performance was characterized using simulated data and identical boundary conditions to those found in a Hall Effect Thruster. The characterization showed errors below machine-zero with noise-free data, and above 20% noise-to-signal strength, the error increased linearly with the noise. This solver can be implemented into AFRL's plasma simulator, the Thermophysics Universal Research Framework (TURF) and used to quickly and accurately compute the electric field based on charge distributions. The validity of a machine learning approach and data-based complex system ...


Three-Dimensional Wall Effects In A Scramjet Cavity Flameholder, Evan P. Oren Sep 2018

Three-Dimensional Wall Effects In A Scramjet Cavity Flameholder, Evan P. Oren

Theses and Dissertations

Scramjets, or supersonic combustion ramjets, are a key component for the development of powered hypersonic vehicles. The flameholding strategy used in this engine creates a recirculation region by creating a cavity in one side of the combustor. This highly unsteady region is difficult to interrogate through conventional means. A novel optical observation technique called hyperspectral imaging has been developed to examine the scramjet combustion chamber. The hyperspectral camera is capable of generating an interferogram at hundreds to thousands of wavelengths. These data are integrated across the line-of-sight with no information on three-dimensional (3D) location of origin. A model must be ...


Flightline Simulation Model Of A Squadron, Huseyin Mert Sep 2018

Flightline Simulation Model Of A Squadron, Huseyin Mert

Theses and Dissertations

Military flight training is a long and costly process. Ensuring that the training aircraft are ready for flight is critical in processing pilots through training courses on schedule. Maintaining a high mission capable rate for training aircraft requires scheduled periodic maintenance and maintenance between sorties. Aircraft Ground Equipment (AGE) is used to service each aircraft to make it ready for the following flight. Having a sufficient amount of AGE available is critical, as cancelling or delaying sorties due to lack of AGE generally has a significant impact on the training schedule. This work analyzes the AGE support equipment used in ...


Development Of A Subsurface Landfill Fire Risk-Index, Samain Sabrin Aug 2018

Development Of A Subsurface Landfill Fire Risk-Index, Samain Sabrin

Theses and Dissertations

Landfill subsurface fires create environmental hazards by emitting potentially dangerous particulates into the atmosphere and damaging liners, potentially contaminating surrounding soil and groundwater aquifers with leachate. Currently, the only means of detecting underground fires are physical tests. This paper is used to describe an index that can be employed to track fire risk across a landfill. The landfill parameters analyzed for fire risk susceptibility in Chapter 1 include residual nitrogen concentration, oxygen exceedance, methane concentration, carbon monoxide level, methane and carbon dioxide ratio and monitoring well temperature. Incorporating these factors, a landfill fire index ranging from 1 to 10 was ...


Geophysical Assessment Of Subsurface Soil Conditions Using Capacitively Coupled Resistivity, Folaseye Coker Aug 2018

Geophysical Assessment Of Subsurface Soil Conditions Using Capacitively Coupled Resistivity, Folaseye Coker

Theses and Dissertations

The purpose of this research is to explore the applicability of Capacitively-Coupled Resistivity (CCR) as an improvement on traditional drilling and sampling methods for subsurface soil investigations. The CCR method could be used to identify critical locations for drilling and sampling such as expansive clay layers and anomalies (sinkholes, unknown landfills, etc.) rather than uniformly sampling across a site. CCR surveys were performed at Alpena, Arkansas along a highway expansion project changing US 62 from a two lane to four lane highway, and at Alton, Illinois along the Mel Price Levee, a 5.2 mile levee along a portion of ...


Determining The Effect Of Locally Delivered Bioactive Modulators On Macrophage Activation At The Implantation Site Of Different Biomaterials In Rats, Kamel Alkhatib Aug 2018

Determining The Effect Of Locally Delivered Bioactive Modulators On Macrophage Activation At The Implantation Site Of Different Biomaterials In Rats, Kamel Alkhatib

Theses and Dissertations

Altering the foreign body reaction by targeting macrophages has been of interest in the biomaterials field to improve the integration of longevity of implanted biomedical devices. The objective of this dissertation was to study the effect of locally delivered bioactive modulators on macrophage activation at the implantation site of different biomaterials in rats. Iloprost, a prostacyclin analog, was tested for its ability to direct macrophages to their pro-wound healing phenotype after the implantation of microdialysis probe in the subcutaneous space of male Sprague Dawley rats. This study showed that iloprost can shift macrophage activation states in vivo to the pro-wound ...


Configuring Traditional Multi-Dock, Unit-Load Warehouses, Mahmut Tutam Aug 2018

Configuring Traditional Multi-Dock, Unit-Load Warehouses, Mahmut Tutam

Theses and Dissertations

The development of expected-distance formulas for multi-dock-door, unit-load warehouse configurations is the focus of the dissertation. From formulations derived, the width-to-depth ratios minimizing expected distances are obtained for rectangle-shaped, unit-load warehouse configurations. Partitioning the storage region in the warehouse into three classes, the performance of a multi-dock-door, unit-load warehouse is studied when storage regions can be either rectangle-shaped or contour-line-shaped. Our first contribution is the development of formulas for expected distance traveled in storing and retrieving unit loads in a rectangle-shaped warehouse having multiple dock doors along one warehouse wall and storage racks aligned perpendicular to that wall. Two formulations ...


Evaluation Of A Solar Powered Variable Flow Tail Water Recovery System For Furrow Irrigation, Vaishali Kandpal Aug 2018

Evaluation Of A Solar Powered Variable Flow Tail Water Recovery System For Furrow Irrigation, Vaishali Kandpal

Theses and Dissertations

Furrow irrigation is a very common irrigation method for growing crops like soybean, cotton and corn in Arkansas. A major portion of this irrigation water is lost as runoff from the field significantly reducing the irrigation application efficiency. There are various methods of improving irrigation efficiency and one of the methods is using tail-water recovery. A tail-water recovery system utilizes tail-water recovery ditches or pits to collect tail-water which can be re-used for irrigation. However, this method is very labor intensive and has been found to be economically non-feasible for some farms in the past research studies. In order to ...


Characterizing Targeted Therapeutic Delivery And Cellular Dynamics Using In Vitro Cancer Disease Models, Christopher George Uhl Aug 2018

Characterizing Targeted Therapeutic Delivery And Cellular Dynamics Using In Vitro Cancer Disease Models, Christopher George Uhl

Theses and Dissertations

Cancer is a significant health risk to people living in developed and developing countries, which continues to prove difficult to treat. Common treatment options of cancers include surgical removal, radiation, and chemotherapies, which are often used in combination to improve the likelihood of successful treatment. Such combinatory approaches towards treatment are often taken because each approach is not targeted enough to function perfectly on its own. Being able to delivery therapeutic loads in a more targeted manner to sites of cancer has the capability of improving therapeutic efficiency and improving patient responses. The development of improved therapeutic delivery vehicles and ...


Grain Size Effects On Viscoelastic Relaxation Of Sub-Micron Thickness Fcc Metallic Films, Jeffrey Smyth Aug 2018

Grain Size Effects On Viscoelastic Relaxation Of Sub-Micron Thickness Fcc Metallic Films, Jeffrey Smyth

Theses and Dissertations

Sub-micron thickness metallic thin films are known to exhibit mechanical size effects, where the thin film mechanical behavior can differ significantly from that of a bulk version of the same material. One such mechanical behavior, and the focus of this work, is the unique thin film viscoelastic deformation response to sub-yield, low-strain stimuli in near-ambient temperature environments. In engineering components using bulk materials, strains within the elastic regime are generally considered instantaneous. It is only at higher operating temperatures that temporal deformation processes, such as creep, are considered in bulk component design. However, in Micro-Electro-Mechanical Systems (MEMS), specifically Radio Frequency ...


Fine-Grained Visual Representation Learning With Deep Neural Networks, Tao Xu Aug 2018

Fine-Grained Visual Representation Learning With Deep Neural Networks, Tao Xu

Theses and Dissertations

Representation learning is about learning representative features of the data that make it easier to extract useful information for the subsequent learning task. Due to the great success of deep learning, representations learned by deep neural networks have shown significant improvement than handcrafted features on most learning tasks. However, it is still very challenging to learn fine-grained visual representations, which refer to highly localized features extracted from images that are useful for image understanding tasks, such as fine-grained recognition, image generation and semantic segmentation. Fine-grained recognition identifies subtle visual differences to distinguish among subordinate categories; image generation learns fine-grained visual ...


The Mechanical Performance And Microstructure Development Of Laser Beam Welds And Post Weld Heat Treatment Of Ti 1023 Alloy, Meng Fu Huang Aug 2018

The Mechanical Performance And Microstructure Development Of Laser Beam Welds And Post Weld Heat Treatment Of Ti 1023 Alloy, Meng Fu Huang

Theses and Dissertations

Titanium alloys are widely used in the aerospace industry. For example, most components of the Boeing 777 landing gear are made of the Ti-10V-2Fe-3Al (Ti1023) alloy due to its lighweight and superior mechanical strength. In addition, because Titanium is chemicaly active element, when jointing the Ti alloy components, the laser beam welding (LBW) has been selected for avoiding the eventual contaminations and narrowing the heat affected zone by the presence of its protected atmosphere and low heat input. However, there is a lack of reported research results about welded Ti1023 alloy, particularly laser beam welding. Therefore, the microstructure and mechanical ...


Sustainability Of Utilizing Renewable And Nuclear Energy In Saudi Arabia Using Different Types Of Life Cycle Assessment, Kamel Almutairi Aug 2018

Sustainability Of Utilizing Renewable And Nuclear Energy In Saudi Arabia Using Different Types Of Life Cycle Assessment, Kamel Almutairi

Theses and Dissertations

Evaluating the global environmental impacts of the current and future energy policies in Saudi Arabia using Life cycle assessment (LCA) method was the main objective of this dissertation. First, the attributional life cycle assessment (ALCA) framework was used to evaluate the Saudi’s air conditioning systems, as they are responsible for about 70% of the total Saudi residential electricity consumption. The ALCA’s results showed that the AC use phase produces the largest share of the environmental impact and the magnitude of the environmental impacts is influenced by the type of primary fuel used for electricity generation.

Emerging non-fossil sources ...


Aberration Corrected Analytical Electron Microscopy Studies Of Nanometallic Catalysts, Sultan Althahban Aug 2018

Aberration Corrected Analytical Electron Microscopy Studies Of Nanometallic Catalysts, Sultan Althahban

Theses and Dissertations

Catalysis by nanoscopic metal structures, ranging from nanoparticles to sub-nm clusters and even individual atoms, is amongst the most intensely studied topics in nanoscience. The catalytic performance of supported metal nanoparticles is governed by their crysallographic structure, shape, size, composition and interaction with the support. Aberration-corrected scanning transmission electron microscopy (AC-STEM), with its ultra-high spatial resolution for imaging and compositional analysis, is an ideal tool for characterizing such features in metallic nanocatalysts. In this thesis, five case studies are presented where AC-STEM has been invaluable in elucidating synthesis route - structure - performance relationships in some technologically important catalyst systems.


Computational Study Of Free Jets Emanating From Circular And Lobed Orifice-Lattice Boltzmann Method, Yang Chen Aug 2018

Computational Study Of Free Jets Emanating From Circular And Lobed Orifice-Lattice Boltzmann Method, Yang Chen

Theses and Dissertations

The Lattice Boltzmann method is an effective computational fluid dynamics tool to study complex flows. Unlike conventional numerical schemes based on discretization of macroscopic continuum equations, the Lattice Boltzmann method is based on particles and mesoscopic kinetic equations. Single-Relaxation Time Lattice Boltzmann Method (SRTLBM) with Smagorinsky LES model is applied to simulate high Reynolds number jet flows of single and multiphase flows emanating. The multi-block approach is implemented to refine the mesh when the high resolution is needed in the region around the core jet. An 2nd order accurate interface treatment between neighboring blocks is derived to satisfy the conservation ...


Large Eddy Simulations Of Ventilated Micro-Hydrokinetic Turbine And Pump-Turbines, Cosan Daskiran Aug 2018

Large Eddy Simulations Of Ventilated Micro-Hydrokinetic Turbine And Pump-Turbines, Cosan Daskiran

Theses and Dissertations

Large eddy simulations of ventilated hydrokinetic turbine and pump-turbine are conducted. The mathematical modeling of oxygen dissolution and the flow model employed were validated by comparing predicted dissolved oxygen concentration against reported experimental measurements. A parametric study is performed to investigate the influence of interfacial forces, surface tension and bubble breakage and coalescence terms. It is demonstrated that aeration via hydrokinetic turbines can be used to improve the dissolved oxygen level in rivers for better water quality. It is also shown that aeration can effectively be achieved via the pump-turbine system to provide the desired dissolved oxygen level for the ...


Privacy In Dynamical Systems And Networks: Anonymous Routing And Retail Competition, Omid Javidbakht Aug 2018

Privacy In Dynamical Systems And Networks: Anonymous Routing And Retail Competition, Omid Javidbakht

Theses and Dissertations

Tradeoffs between privacy and utilities, and privacy preserving control mechanisms in dynamical systems and networks are studied in this dissertation. Despite security mechanisms and data encryption, these systems are still vulnerable to timing analysis, wherein an eavesdropper can use these observations to interpret the identity of individuals. Motivated by this vulnerability, the first three topics of this dissertation investigates privacy preserving mechanisms in dynamical systems and network. The last chapter studies the effect of privacy awareness of consumers on retail competition.The first topic of this dissertation studies the tradeoff between delay and packet source anonymity in a network of ...


Hybrid Ion Exchange Processes For Sustainable Softening And Marcellus Flowback Treatment, Jinze Li Aug 2018

Hybrid Ion Exchange Processes For Sustainable Softening And Marcellus Flowback Treatment, Jinze Li

Theses and Dissertations

Hybrid ion exchange technology has been applied in many environmental aspects nowadays due to its high treatment efficiency, reusability, customizable selectivity, operational stability, and low cost. Under certain circumstances, ion exchange technology is a favorable substitute for traditional treatment process, and its applications in industries are continually growing.Water hardness is a concern for many industrial and municipal unit operations, which could result in surface scaling of heat transfer equipment or membranes. Sodium exchange softening, although commonly used, has caused serious pollution to local ecological and water environments due to its discharge of high salinity spent regenerant. Many arid areas ...


A Service System With On-Demand Agents, Stochastic Gradient Algorithms And The Sarah Algorithm, Lam Nguyen Aug 2018

A Service System With On-Demand Agents, Stochastic Gradient Algorithms And The Sarah Algorithm, Lam Nguyen

Theses and Dissertations

We consider a system, where a random flow of customers is served by agents invited on-demand. Each invited agent arrives into the system after a random time, and leaves it with some probability after each service completion. Customers and/or agents may be impatient. The objective is to design a real-time adaptive invitation scheme that minimizes customer and agent waiting times.We study some aspects of the SGD method with a fixed, large learning rate and propose a novel assumption of the objective function, under which this method has improved convergence rates. We also propose a convergence analysis of SGD ...


The Resilience Of Smart Energy Systems Against Adversarial Attacks, Operational Degradation And Variabilities, Parth Pradhan Aug 2018

The Resilience Of Smart Energy Systems Against Adversarial Attacks, Operational Degradation And Variabilities, Parth Pradhan

Theses and Dissertations

The presented research investigates selected topics concerning resilience of critical energy infrastructures against certain types of operational disturbances and/or failures whether natural or man-made. A system is made resilient through the deployment of physical devices enabling real-time monitoring, strong feedback control system, advanced system security and protection strategies or through prompt and accurate man-made actions or both. Our work seeks to develop well-planned strategies that act as a foundation for such resiliency enabling techniques.The research conducted thus far addresses three attributes of a resilient system, namely security, efficiency, and robustness, for three types of systems associated with current ...