Engineering Commons^™

Microwave Nondestructive Detection Of Influenc Of Alkali-Silica Reaction (Asr) In Materials Properties Of Concrete Specimens, Reza Zoughi, John R. Gallion, Nolan W. Hayes

Electrical and Computer Engineering Faculty Research & Creative Works

Alkali-silica reaction has been identified to be a cause deterioration in concrete structures. This reaction takes place when alkalis (e.g., potassium and sodium), hydroxyl ions in the pore solution and certain siliceous minerals (present in some aggregates) are present, resulting in what is known as the ASR gel. Expansion of this gel, in the presence of heat and moisture, causes stresses that lead to microcracking and deterioration of concrete. The criticality of this problem has been particularly highlighted in recent past with respect to nuclear power plant containment concrete structures. Although there have been many studies devoted to examining and …

Impact Of Large-Scale Correlated Failures On Multilevel Virtualized Networks, Max G. Medina, Mohammed J.F. Alenazi, Egemen K. Cetinkaya

Electrical and Computer Engineering Faculty Research & Creative Works

Communication network architectures have been evolving with increased programmability and virtualization of physical infrastructures. While this evolution enables a faster introduction of new services and efficient utilization of resources, the complexities and interdependencies among the physical and virtual infrastructures, as well as the control and management planes, hinder a complete understanding of the system at hand. It is imperative, therefore, to model and study these evolving virtualized infrastructures. We propose a multilevel virtualized network embedding model and study its performance against correlated failures. Our analysis of multiple synthetic network models identified that grid-like infrastructures capture the realistic Internet2 structure the …

Bs News May/June

Building Services Engineering

No abstract provided.

The Photon Absorber And Interconnecting Layers In Multijunction Organic Solar Cell, Brishty Deb Chowdhury, Bernabe Ibarra, Federico Cesano, Yuanbing Mao, Muhammad N. Huda, Aminur Rashid Chowdhury, Carolina Olivares, M. Jasim Uddin

School of Integrative Biological & Chemical Sciences (Formerly Dept. of Chemistry)

Organic photovoltaic devices have long been considered as an important alternative for coal-based energy technologies due to their low-cost, lightweight and flexible nature. However, the power conversion efficiencies of such cells are limited by thermalization and transmission losses, which can be overcome by stacking multiple cells in a tandem configuration. This approach allows utilization of the wider spectrum of solar light, helping in attaining the theoretical limits for single cell efficiency (~30%). However, the performance of such tandem organic solar cells depends largely on several factors, including the proper design of absorber, sub-cells and interconnecting layer materials. In this review, …

Exploring The Relationship Between Sustainable Projects And Institutional Isomorphisms: A Project Typology, Rakan Alyamani, Suzanna Long, Mohammad Nurunnabi

Engineering Management and Systems Engineering Faculty Research & Creative Works

With the increase in awareness about the wide range of issues and adverse effects associated with the use of conventional energy sources came an increase in project management research related to sustainability and sustainable development. Part of that research is devoted to the development of sustainable project typologies that classify projects based on a variety of external factors that can significantly impact these projects. This research focuses on developing a sustainable project typology that classifies sustainable projects based on the external institutional influences. The typology explores the influence of the coercive, normative, and mimetic institutional isomorphisms on the expected level …

Study Of A Symmetrical Llc Dual-Active Bridge Resonant Converter Topology For Battery Storage Systems, John K. George

Graduate Theses and Dissertations

A symmetrical LLC resonant converter topology with a fixed-frequency quasi-triple phase-shift modulation method is proposed for battery-powered electric traction systems with extensions to other battery storage systems. Operation of the converter with these methods yields two unique transfer characteristics and is dependent on the switching frequency. The converter exhibits several desirable features: 1) load-independent buck-boost voltage conversion when operated at the low-impedance resonant frequency, allowing for dc-link voltage regulation, zero-voltage switching across a wide load range, and intrinsic load transient resilience; 2) power flow control when operated outside the low-impedance resonance for integrated battery charging; 3) and simple operational mode …

Investigations Of New Fault-Tolerant Methods For Multilevel Inverters, Haider Mhiesan

Graduate Theses and Dissertations

The demands of power electronics with high power capability have increased in the last decades. These needs have driven the expansion of existing power electronics topologies and developing new power electronics generations. Multilevel inverters (MLI) are one of the most promising power electronics circuits that have been implemented and commercialized in high-voltage direct current (HVDC), motor drives, and battery energy storage systems (BESS). The expanding uses of the MLI have lead to creation of new topologies for different applications. However, one of the disadvantages of using MLIs is their complexity. MLIs consist of a large number of switching devices, which …

The Release, Transport, And Utilization Of Phosphorus From Bed-Sediments: A Study Of A Eutrophic Littoral Cove On Beaver Lake In Northwest Arkansas, James A. Mccarty

Graduate Theses and Dissertations

Eutrophication of surface waters not only impacts the environment but also water treatment processes, the most significant of which is from the effects of algae. During peak algal growth in many southern U.S. reservoirs, inflows that bring nutrients are at an annual minimum, and phosphorus released from bed-sediments is trapped in the hypolimnion. Littoral areas, described as the most productive zone of the lake, may be a possible source of phosphorus that fuels algal growth in the reservoir. I studied an isolated shallow cove in the War Eagle Creek arm of Beaver Lake in Northwest Arkansas to measure, quantify, and …

A Novel Three-Level Isolated Ac-Dc Pfc Power Converter Topology With Reduced Number Of Switches, Obaid Aldosari

Graduate Theses and Dissertations

The three-level isolated AC-DC power factor corrected (PFC) converter provides safe and more efficient power conversion. In comparison with two-level, three-level PFC converter has the advantages of low total harmonic distortion, low device voltage rating, low di/dt, better output performance, high power factor, and low switching losses at higher switching frequencies. The high frequency transformer (HFT) grants galvanic isolation, steps up or down secondary voltage, and limits damage in case of a fault current.

The existing three-level converter based on solid-state transformer (SST) topologies convert ac power from the electrical grid to a dc load while maintaining at least the …

Low Latency Anomaly Detection With Imperfect Models, Samrat Nath

Graduate Theses and Dissertations

The problem of anomaly detection deals with detecting abrupt changes/anomalies in the distribution of sequentially observed data in a stochastic system. This problem applies to many applications, such as signal processing, intrusion detection, quality control, medical diagnosis, etc. A low latency anomaly detection algorithm, which is based on the framework of quickest change detection (QCD), aims at minimizing the detection delay of anomalies in the sequentially observed data while ensuring satisfactory detection accuracy. Moreover, in many practical applications, complete knowledge of the post-change distribution model might not be available due to the unexpected nature of the change. Hence, the objective …

Built-In Self-Test (Bist) For Multi-Threshold Null Convention Logic (Mtncl) Circuits, Brett Sparkman

Graduate Theses and Dissertations

This dissertation proposes a Built-In Self-Test (BIST) hardware implementation for Multi-Threshold NULL Convention Logic (MTNCL) circuits. Two different methods are proposed: an area-optimized topology that requires minimal area overhead, and a test-performance-optimized topology that utilizes parallelism and internal hardware to reduce the overall test time through additional controllability points. Furthermore, an automated software flow is proposed to insert, simulate, and analyze an input MTNCL netlist to obtain a desired fault coverage, if possible, through iterative digital and fault simulations. The proposed automated flow is capable of producing both area-optimized and test-performance-optimized BIST circuits and scripts for digital and fault simulation …

Deep Learning And Polar Transformation To Achieve A Novel Adaptive Automatic Modulation Classification Framework, Pejman Ghasemzadeh

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

Automatic modulation classification (AMC) is an approach that can be leveraged to identify an observed signal's most likely employed modulation scheme without any a priori knowledge of the intercepted signal. Of the three primary approaches proposed in literature, which are likelihood-based, distribution test-based, and feature-based (FB), the latter is considered to be the most promising approach for real-world implementations due to its favorable computational complexity and classification accuracy. FB AMC is comprised of two stages: feature extraction and labeling. In this thesis, we enhance the FB approach in both stages. In the feature extraction stage, we propose a new architecture …

Towards Gross-Pitaevskiian Description Of Solar System & Galaxies, Florentin Smarandache, Victor Christianto, Yunita Umniyati

Branch Mathematics and Statistics Faculty and Staff Publications

In this paper, we argue that Gross-Pitaevskii model can be a more complete description of both solar system and spiral galaxies, especially taking into account the nature of chirality and vortices in galaxies. We also hope to bring out some correspondence among existing models, e.g., the topological vortex approach, Burgers equation in the light of KAM theory, and the Cantorian Navier-Stokes approach. We hope further investigation can be done around this line of approach.

Delineating The Relationship Between Cardiovascular Physiology And Subject Characteristics Using Computational Modeling And Systemic Review, Aseem Pradhan

All Theses

Lumped Parameter Networks (LPN) are computational models that can capture the systemic responses of the cardiovascular system. An LPN describes the systemic behavior by providing outputs such as the blood pressure, flowrate, and heart chamber volume at the points defined in the network. To use the LPN for medical applications, it needs to provide output values that represent the physiology of realistic subjects. The cardiovascular system exhibits short-term and long-term adaptations to factors such as aging, weight gain, exercise, etc. Therefore, subject characteristics such as age, height, weight, etc. affect the output values of the LPN. Current literature reports the …

General Aviation Airport Runway Incursions: A Qualitative Approach To Examining Reasons For, Barriers To Addressing, And Lessons Learned From Airport Managers' First-Hand Experiences, Indira Maharaj

Theses and Dissertations

The purpose of the study was manifold: (a) to understand the reasons for runway incursions (RIs) at general aviation (GA) airports, (b) to describe the barriers to addressing runway incursions at GA airports, and (c) to describe the lessons learned from addressing runway incursions at GA airports. This study was based primarily on a phenomenological research design, which led to a set of inductively derived conjectures. The study’s sample consisted of 10 GA airports that had at least 10 times the number of GA operations than the number of air carrier (commercial) operations as reported in the Air Traffic Activity …

Flight Testing Of The Piper J4a Cub Coupe, Kenneth Burton Connick

Theses and Dissertations

Flight testing is an important part of in the airplane design process. This testing is performed to ensure that the airplane complies with the established requirements and regulations for flight safety, as well as to ensure it meets its mission objectives. The Federal Aviation Administration (FAA) currently governs these requirements and regulations for civilian aircraft and provides airworthiness certifications. The FAA regulations were introduced in 1965. Prior to that, civilian aircraft were certified through the Civil Aeronautics Administration using Civil Air Regulations (CARs).

Thermal Management Design Of A 6u Cubesat With A High-Power Additive Manufacturing Payload Using Analytical Modeling With Experimental Validation, Todd Wayne Fennell Jr.

Theses and Dissertations

As the capacity of compact battery technology for spacecraft missions continue to improve, small payloads are less constrained by power limitations, thus relatively high-power applications may be considered. AddCube is a mission to develop a platform, conforming to the 6U CubeSat Standard capable of demonstrating on-orbit Additive Manufacturing technology. A critical concern is the development and demonstration of a thermal management design that is capable of handling the significant waste heat generated by the high-power Additive Manufacturing payload while maintaining component temperatures throughout the spacecraft within an acceptable range. This effort includes a trade study for the evaluation of candidate …

A Study On Reaction Rate Factors Of A Single-Step Combustion Mechanism For Gasoline Hcci Combustion, Pakawat Panuwatsuk

Theses and Dissertations

Homogeneous Charge Compression Ignition (HCCI) engine has been invented to achieve the advantages of both diesel and gasoline engines. HCCI engine can run with a higher compression ratio like diesel engine in order to achieve high thermal efficiency. Meanwhile, like gasoline engine, the engine produces less NOx gas and particulate matters than diesel engine. However, there are several difficulties associated with HCCI combustion, which still require further development to the engine. The most important issues are autoignition timing and narrow operational range. In order to develop an HCCI engine, a numerical simulation can significantly save cost, time and resources over …

Set Your Sights High: The Effect Of Heads-Up Displays On Situation Awareness And Performance For Small Unmanned Aircraft Systems, Summer Lindsey Rebensky

Theses and Dissertations

The purpose of the current study was to examine the effect of two interface designs—traditional and heads-up displays (HUDs)—on situation awareness (SA), performance, and workload for sUAS operations. The study utilized an experimental repeated measures design to determine the relationship between interface design on the various dependent variables through a simulated search and rescue mission. Participants flew two simulated search and rescue missions to find missing persons utilizing traditional and HUD displays. During the missions, participants took pictures of human targets and were queried on their SA using the freeze probe SAGAT approach. Then participants rated their subjective SA using …

Voltage Controlled Laser Scribed Graphene (Lsg) Microstrip Attenuator, Nathaniel Michael D’Agati

Theses and Dissertations

In this paper, a preliminary design of a voltage-tunable microstrip attenuator using Laser Scribed graphene (LSG) is proposed. The paper will demonstrate that the fabrication of LSG from graphene oxide on standard doubled-sided FR-4 Copper-clad Substrate can be used as a voltage-controlled resistor that results in a tunable microstrip attenuator across the microwave frequencies from 50MHz to 5.5GHz. The measured attenuation ranges from 2.6 dB to 11.5dB at 4 GHz with a DC bias voltage ranging from 0V (minimum attenuation) to 6.0V (maximum attenuation). Graphene is a unique material with interesting electromagnetic and mechanical properties. Graphene conducts electricity better than …

Revisiting Elliptic Curve Cryptography With Applications To Post-Quantum Sidh Ciphers, Wesam Nabil Eid

Theses and Dissertations

Elliptic Curve Cryptography (ECC) has positioned itself as one of the most promising candidates for various applications since its introduction by Miller and Kolbitz in 1985 [53, 44]. The core operation for ECC is the scalar multiplication [k]P where many efforts have addressed its computation speed. Here we introduce an efficient approach for calculating elliptic curve operations by a novel regrouping of terms and creating new projective representation operators and increasing parallelism. These operators and the corresponding projective coordinate representations are shown to lead to adjusted versions of scalar multiplication algorithms that are evaluated. These techniques enable more opportunities for …

Improving Wake-Up-Word And General Speech Recognition Systems, Gamal Mohamed Bohouta

Theses and Dissertations

Automatic Speech Recognition (ASR), a technology that allows a machine to recognize the utterances spoken into a microphone by a person and then converts it to text, is commonly used for different types of applications, such as command and control systems, personal assistant systems, medical systems, disabilities systems, dictation systems, telephony systems, and embedded applications. Due to its extensive use, interest in ASR technology has surged among inventors and researchers alike. They have worked diligently to improve the performance of the ASR systems by developing several techniques or approaches in different aspects,such as enhancing features, training an acoustic model, enhancing …

Microgravity Emergency Medical Containment System – A Concept Of Architecture, Prototyping, And Usability Research, Keith Elliott Crisman

Theses and Dissertations

Exploration is intrinsic to human nature but is well understood to be accompanied by inherent risks to the explorer. This is particularly evident in the exploration of extreme environments such as long-duration space habitation; in which risk is increased due in particular to the distance from assistance, services, and replenishment of consumables. One of the major risks to extreme environment survivability is lack of access to emergency medical care. This risk is further amplified in the microgravity environment where terrestrial non-life-threatening conditions can become life threatening due to lack of next-level-care capabilities. The question posed within this research asks, ‘What …

Model Optimization For Edge Devices, Adolf Anthony D’Costa

Theses and Dissertations

Edge devices are undergoing groundbreaking computing transformation, which lets us tap into artificial intelligence, quantum computing, 5th generation network capability, fog networking, and computing complex algorithms. Edge systems have substantial advantages over the conventional system in terms of scalability, optimized resources, reliability, and security. The proliferation of such resource-constrained devices in recent years has resulted in the generation of a large quantity of data; these data-producing devices are attractive targets for applications of machine learning. Machine learning models, especially deep learning neural networks, produced models that have high accuracy and prediction capability, but it comes at the cost of computation …

Flight Path Control During Hypersonic Atmospheric Entry Using Active Magnetic Arrays, Matthew Tyler Austin

Theses and Dissertations

The purpose of this thesis is to study the reaction to the Lorentz force induced during the hypersonic regime of flight by an active magnetic field. The effect that a magnetic array has on the flight characteristics of a blunt body during Earth atmospheric entry is characterized and isolated for independent analysis. This is done to show that mission-specific benefits to utilizing this method of entry control exist and therefore warrant further study. To conduct this analysis, a 1000 kg blunt body test case was used. This craft contains three separate magnets located behind the nose with two of them …

Use Of Garmin Autopilot Envelope Protection System For Simplified Vehicle Operations In General Aviation, Stephen Sullivan

Theses and Dissertations

The general aviation industry suffers from high rates of fatalities and accidents occurring due to loss of control while in flight. This thesis research aims to implement a simple yet effective simplified vehicle operations (SVO) scheme that uses a Garmin autopilot system to create a pilot-on-the-loop controller to help prevent loss of control incidents from occurring. With this scheme, the pilot is controlling turns and climb rates instead of elevator and aileron deflections and is protected from the risk of under-speed and stall through the Garmin autopilots built-in limits. To interface with the autopilot system, a Raspberry Pi and Pythonbased …

Examining The Impact Of Student Motivation On Performance In Mechanical Engineering Design Courses, Elisabeth Kames

Theses and Dissertations

Design courses are an integral component of undergraduate engineering education. Design is recognized as one of the primary responsibilities of an engineer in industry. New designs are responsible for stimulating sales and company growth.1 This dissertation outlines a study seeking to explore the impact of student motivation factors on course performance of mechanical engineering students in design courses. The first design course, cornerstone design, takes place during the first semester of freshman year. The second course, capstone design, takes place during the student’s final year of undergraduate study. An adapted version of the Motivated Strategies for Learning Questionnaire (MSLQ) is …

Design, Analysis, And Demonstration Of A Multipurpose Fluid Tank Dynamics Characterization Platform, Cameron Ian Hume

Theses and Dissertations

The development of a highly versatile multiphase fluid tank characterization platform is essential to the analysis and improvement of propellant storage tanks. The performance of these tanks is highly critical to the safety and performance of their carriers, especially in the space industry where the propellant makes up the overwhelming majority of the mass of the vehicle. This thesis outlines the design and development of a linear stage used to test and validate the characteristic of multiphase fluids inside moving specific tanks. This document will walk through the steps taken to bring a new linear stage to life, from the …

Analysis Of Polyester Interleafs For Toughness Enhancement In Composite Structures, Adnan Gheryani

Theses and Dissertations

Delamination between composite layers is one of primary weaknesses in composite material structure. Various researchers have developed techniques to control delamination in laminated structures. One of these techniques is “interleaving,” adding high toughness material to key interfaces in a laminate. This research studies using polyester veil as a low-cost interleaf alternative to other materials and focuses on a non-woven, polyester spunbond material. Two different interleaf thicknesses, 0.18 mm and 0.74 mm are primarily used. In addition, fine 4 g/m2 polyester was also compared. Carbon/epoxy composites are manufactured using 2x2 Twill 24”-12k carbon fibers embedded in an epoxy resin, with polyester …

Estimation Of Interior And Contents Damage Due To Wind Driven Rain Ingress Into Mid/High-Rise Buildings, Zhuoxuan Wei

Theses and Dissertations

Hurricanes can lead to the loss of millions of dollars and the death of hundreds of people. The increasing concentration of people in coastal cities, exacerbates this problem and results in greater hurricane damage to residential buildings. In particular, recent hurricanes in Florida have shown the vulnerability of mid/high-rise buildings (MHRB) to hurricane-induced water ingress. However, few damage models are able to produce realistic estimates of interior damage. To accurately estimate the interior and contents damage of mid/high-rise buildings due to water ingress during hurricanes, this thesis proposes a new physics-based methodology, which extends the results of previous work on …