Engineering Commons^™

Reliability Of Heterogeneous Distributed Computing Systems In The Presence Of Correlated Failures, Jorge E. Pezoa, Majeed M. Hayat

Electrical and Computer Engineering Faculty Research and Publications

While the reliability of distributed-computing systems (DCSs) has been widely studied under the assumption that computing elements (CEs) fail independently, the impact of correlated failures of CEs on the reliability remains an open question. Here, the problem of modeling and assessing the impact of stochastic, correlated failures on the service reliability of applications running on DCSs is tackled. The service reliability is modeled using an integrated analytical and Monte-Carlo (MC) approach. The analytical component of the model comprises a generalization of a previously developed model for reliability of non-Markovian DCSs to a setting where specific patterns of simultaneous failures in …

Position/Speed Sensorless Control For Permanent-Magnet Synchronous Machines, Yue Zhao

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

Permanent-magnet synchronous machines (PMSMs) are widely used in industrial applications owing to their distinctive advantages, such as high efficiency, high power density, and wide constant power region. To achieve high-performance field oriented control, accurate rotor position information, which is usually measured by rotary encoders or resolvers, is indispensable. However, the use of these sensors increases the cost, size, weight, and wiring complexity and reduces the mechanical robustness and the reliability of the overall PMSM drive systems. The goal of the research for this dissertation was to develop a rotor position/speed sensorless control system with performance comparable to the sensor-based control …

Towards A Sustainable Modular Robot System For Planetary Exploration, S. G. M. Hossain

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

This thesis investigates multiple perspectives of developing an unmanned robotic system suited for planetary terrains. In this case, the unmanned system consists of unit-modular robots. This type of robot has potential to be developed and maintained as a sustainable multi-robot system while located far from direct human intervention. Some characteristics that make this possible are: the cooperation, communication and connectivity among the robot modules, flexibility of individual robot modules, capability of self-healing in the case of a failed module and the ability to generate multiple gaits by means of reconfiguration. To demonstrate the effects of high flexibility of an individual …

Active Control Of Aerial Refueling Drogue, Taeseung Kuk

Dissertations

An active stabilization method for an aerial refueling drogue used in probe-drogue refueling system is presented in this study. The present refueling drogue exhibits an unstable motion due to various turbulent natures, which results in high failure rates and sometimes catastrophic accidents. Although it is considered a routine procedure for human pilot, the workload for mid-air refueling is highly demanding and autonomous operation is by no means a simple task. With rapidly growing use of unmanned aerial vehicles, autonomous aerial refueling is identified as one of essential technologies in future aviation. The present research is a pioneering work in active …

Real-Time Control Of Shunt Active Power Filter Under Distorted Grid Voltage And Unbalanced Load Condition Using Self Tuning Filter, Samet Biricik, Soydan Redif, Ozgur Ozerdem, Shafiuzzaman K. Khadem, Malabika Basu

Articles

In this paper, an alternative control method is proposed to improve the harmonic suppression efficiency of the active power filter in a distorted and an unbalanced power system to compensate for the perturbations caused by the unbalanced non-linear loads. The proposed method uses a self-tuning filter (STF) to process the grid voltage in order to provide a uniform reference voltage to obtain the correct angular position of the phase locked loop. Moreover, the required compensation currents are obtained by implementing another STF in the transformed set of currents in order to separate the fundamental and the harmonic currents. This allows …

Differential Effects Of Refractive Blur On Day And Nighttime Driving Performance, Joanne M. Wood, Michael J. Collins, Alex Chaparro, Ralph Marszalek, Trent Carberry, Philippe Lacherez, Byoung Sun Chu

Publications

PURPOSE. To investigate the effect of different levels of refractive blur on real-world driving performance measured under day and nighttime conditions.

METHODS. Participants included 12 visually normal, young adults (mean age = 25.+- 5.2 years) who drove an instrumented research vehicle around a 4 km closed road circuit with three different levels of binocular spherical refractive blur (+0.50 diopter sphere [DS], +1.00 DS, +2.00 DS) compared with a baseline condition. The subjects wore optimal spherocylinder correction and the additional blur lenses were mounted in modified fullfield goggles; the order of testing of the blur conditions was randomized. Driving …

Unattended Remotely Operated Deep-Water Sediment Oxygen Demand Chambers, Drake Theodore Mailes

Theses and Dissertations

Dissolved oxygen (DO) depletion in a water body is governed by two primary mechanisms: biological oxygen demand (BOD) from the water column, and sediment oxygen demand (SOD) from sediments. SOD is the dominant oxygen sink in many water bodies; measurements show as much as 95% of oxygen consumption as attributable to SOD (Truax, Shindala, & Sartain, 1996). Measuring SOD in surface water impoundments is an essential component in evaluating and an important input for modeling the health of a water body. Traditional SOD measurement methods are difficult in deeper waters, such as in reservoirs or lakes, because traditional SOD measurement …

Staged Data Warehousing With Gigabytes Of Longitudinal Data, Tyson Spoelma

2014 Conference Presentations

The GVSU Offshore Wind Assessment Project buoy generates approximately 20 gigabytes of raw, longitudinal data each year. It has been running from the end of 2011 to early 2014 with potentially continuing operation for several years. Our data warehousing measures receives the data as unindexed files with loosely defined variable sets to an organized database with standardized message types and date span folders. In order to utilize and share our large data most efficiently, we created a streamlined database file structure for internal analytical use and a web based data retrieval system for portable external environment use.

Predictive Analytics For Outpatient Appointments, Nang Laik Ma, Khataniar Seemanta, Dan Wu, Serene Seng Ying Ng

Research Collection School Of Computing and Information Systems

Healthcare is a very important industry where analytics has been applied successfully to generate insights about patients, identify bottleneck and to improve the business efficiency. In this paper, we aim to look at the patient appointment process as the hospital is experiencing high volume of ?no shows. ?No shows have a high impact on longer appointment lead time for patients, poor patient satisfaction and loss of revenue for hospital. We use data analytics to identify pattern of ?no shows, develop a statistical model to predict the probability of ?no shows and finally operationalizing the model to embed the analytics solution …

Where Am I? : Studying Users’ Indoor Navigation Location Needs, Kartik Muralidharan, Archan Misra, Rajesh Krishna Balan

Research Collection School Of Computing and Information Systems

Location has emerged as the single-most important context whilst building pervasive mobile applications. Several mobile applications have appeared that use location to provide a host of services such as location-specific advertising as well as navigation. As a result, the key challenge of positioning techniques has been to provide the most precise location of the user (device) and much effort has been put in computing this fine grained location in indoor environments. This is under the assumption that highly accurate location is crucial for all indoor services. To understand the location accuracy, that should prove sufficient, for users to navigate to …

An Investigation Of Business Transformation Disruptors At The Military Strategic Command Level, Thomas Bock

Engineering Management & Systems Engineering Theses & Dissertations

This dissertation contributes an empirical research on business transformation disruption in the military. Specifically, this exploratory research seeks a better understanding of disruption of business transformation and some of the factors that are likely to impact the transformation process at the military strategic command level. A lack of empirical studies existing in the literature, coupled with the continuous transformation challenges faced by military organizations, make it necessary to conduct this empirical study of business transformation disruption in the military.

This research was carried out utilizing a two-phase mixed-methods approach. The first phase included qualitative data gathering through a series of …

Characterization Of An Impulse Radiating Antenna In The Near Field, Chandra Barjracharya

Electrical & Computer Engineering Theses & Dissertations

The biological effects of intense sub-nanosecond pulses on tissues or cells are in the dielectric domain and not based on thermal loading as in the conventional microwave radiation, which may lead to an entirely new approach of modifying cell functions. Moreover, the resulting cell functional change may be detected with higher resolution by broadband, sub-nanosecond pulses than conventional narrowband systems. The delivery of intense sub-nanosecond pulses to near-field biological tissues, however, has not been studied, not mentioning the focal depth and volume. In this dissertation, for the first time, an impulse radiating antenna with a balanced feed structure is studied …

A Systems-Based Framework For The Assessment Of Performance Measurement System Implementations In R&D Organizations, Kenneth S. Baggett Jr.

Engineering Management & Systems Engineering Theses & Dissertations

Performance measurement is utilized by organizations in all industries, including research and development (R&D). Measures are developed, data are collected, and the measurement results are used to drive the organization. The implicit hope is, of course, that the measures drive the organization to improve. However, literature identifies high failure rates directly related to performance measurement system (PMS) implementations. Establishing the fundamental operational characteristics associated with successful PMSs would provide a significant contribution towards the establishment of PMS assessment criteria. This research addresses this gap through the use of a grounded theory method employed to identify these operational characteristics, assesses the …

Assessing The Impact Of Electronic Health Record Systems Implementation On Hospital Patient Perceptions Of Care, Katherine Sofia Palacio Salgar

Engineering Management & Systems Engineering Theses & Dissertations

The delivery of health care services has been impacted by advances in Knowledge Management Information Systems (KMIS) and Information Technology (IT). The literature reveals that Electronic Health Records Systems (EHRs) are a comprehensive KMIS. There is a wide recognition in the body of knowledge that demonstrates the potential of EHRs to transform all aspects of health care services and, in consequence, the performance of Health Care Delivery Organizations (HCDO). Authors of published research also agree that there is a need for more empirical contributions that demonstrate the impact of EHRs upon HCDO. It is argued that in most cases, studies …

The Relationship Among Hfacs Levels And Analysis Of Human Factors In Unmanned And Manned Air Vehicles, Veysel Yesilbas

Engineering Management & Systems Engineering Theses & Dissertations

This dissertation analyzes the structural relationships among the Human Factors Accident Classification System levels for unmanned air vehicle and manned air vehicle accidents and the common relationships between unmanned air vehicle and manned air vehicle accident causes. The study acquired DOD HFACS accident classification data from 347 United States Air Force Class A accident reports for the years between 2000 and 2013.

The dissertation utilized a set of analysis that is considered to contribute substantially to the respective domain of the study. The correlations found among categorical levels were applied to HFACS taxonomy based on the Reason Model via path …

Assessing Organizational Effectiveness Through The Competing Values Framework A Data Envelopment Approach, Raghavender Macherla

Engineering Management & Systems Engineering Theses & Dissertations

This study proposes a model to diagnose organizations using the mathematical principles of data envelopment analysis (DEA) to the variables generated using competing values framework (CVF) in order to evaluate overall organizational effectiveness. The notion of organizational effectiveness is abstract and difficult to measure due to its complexity and multi-functional nature. Over the years, measurement of organizational effectiveness has remained a challenge due to the lack of agreement on the factors that should be assessed to determine effectiveness. This research is aimed at shedding some light into this topic by using data envelopment analysis as a tool to measure relative …

An Adaptive Kalman Filter For Voltage Sag Detection In Power Systems, Hisham Odeh Alrawashdeh

Dissertations

The exact values of the noise covariance matrix of the Kalman filter state vector Q and the measured signal noise covariance matrix R must be obtained in order to achieve the optimal performance of the Kalman filter. There have been many techniques and assumptions made to evaluate and compute Q and R. The effects of Q and R are investigated in detail in this dissertation. Based on these investigations, the Kalman filter has been modeled to detect the fundamental signal amplitude variations of power system signals. This technique helps in evaluating voltage sags in power systems.

Two algorithms are …

A Metaevaluation Of Energy Efficiency Evaluations, Brandy Brown

Dissertations

This study systematically reviews the methodological characteristics of energy efficiency evaluations and uses metaevaluation to assess its quality. Metaevaluation is used to systematically assess the quality of evaluation products, confirm that evaluations deliver sound findings and conclusions, are useful to the client, are credible, are ethically conducted, and are done as cost-effective as possible. The results of this study show that the ability to accurately assess evaluation for methodological quality using evaluations reports as a primary data source depends on the presence of detailed descriptions of evaluation methods. Furthermore, the study suggests that methodological variations of energy efficiency evaluations coalesce …

Numerical And Experimental Investigation Of Orthopaedic Fracture Fixation, Bipinchandra Patel

Dissertations

Poor bone fracture fixation leads to malunion, delayed union, non-union, or infection. These malunited fractures affect a bone’s ability to carry loads. Patient outcomes regarding fixation quality can be affected by the healing environment and human factors such as bone quality and surgeons’ perception. Furthermore, the stiffness and strength of the screw-plate construct affect the healing environment. Therefore, this dissertation investigates the stiffness and strength of the non-locking (conventional) and locking (fixed angle) type screw-plate constructs and the factors that contribute to them, such as screw-plate interface, screw design, bone density, cortical bone thickness and load orientation. Additionally, the surgeon’s …

State Variable Model For Unsteady Two Dimensional Axial Vortex Flow With Pressure Relaxation, Mazin Mohammed Elbakri Abuharaz

Mechanical & Aerospace Engineering Theses & Dissertations

This research has utilized a state variable model for unsteady two dimensional axial vortex flows experiencing non-equilibrium pressure gradient forces. The model was developed successfully using perturbed radial and azimuthal momentum equations and a pressure Poisson's equations. Three main regions of the axial vortex flow were highlighted in this study including: a laminar core region, a non-equilibrium pressure envelope, and an outer potential vortex.

Linear stability theory was utilized to formulate the model and the perturbation functions were assumed to be of the Fourier type. The flow parameters considered were the Reynolds numbers, ranging between 6,000 and 14,000, and a …

Systems Theory Based Framework For Competency Models, Joseph M. Bradley

Engineering Management & Systems Engineering Theses & Dissertations

The purpose of this research was to develop and apply a systems theoretic framework for design, analysis and transformation of competency models using an inductive research design. This research examines the origins and development of competency models from a systems theoretic perspective. Competency models have been largely developed by a comparative method first proposed by McClelland, or the use of Delphi method survey techniques. The assumption that a population containing an exemplar and fully successful members would enable population of a holistic competency model has reported numerous failures. Similarly, reporting on the use of Delphi methods has focused on attempting …

An Investigation Into The Analysis Of Truncated Standard Normal Distributions Using Heuristic Techniques, John Walter Ralls

Engineering Management & Systems Engineering Theses & Dissertations

Standard normal distributions (SND) and truncated standard normal distributions (TSND) have been widely used and accepted methods to characterize the data sets in various engineering disciplines, financial industries, medical fields, management, and other mathematic and scientific applications. For engineering managers, risk managers and quality practitioners, the use of the standard normal distribution and truncated standard normal distribution have particular relevance when bounding data sets, evaluating manufacturing and assembly tolerances, and identifying measures of quality. In particular, truncated standard normal distributions are used in areas such as component assemblies to bound upper and lower process specification limits.

This dissertation presents a …

Transparent Spectrum Co-Access In Cognitive Radio Networks, Jonathan Daniel Backens

Electrical & Computer Engineering Theses & Dissertations

The licensed wireless spectrum is currently under-utilized by as much as 85%. Cognitive radio networks have been proposed to employ dynamic spectrum access to share this under-utilized spectrum between licensed primary user transmissions and unlicensed secondary user transmissions. Current secondary user opportunistic spectrum access methods, however, remain limited in their ability to provide enough incentive to convince primary users to share the licensed spectrum, and they rely on primary user absence to guarantee secondary user performance. These challenges are addressed by developing a Dynamic Spectrum Co-Access Architecture (DSCA) that allows secondary user transmissions to co-access transparently and concurrently with primary …

Stormwater Infrastructure Optimization On Conjunctive Improvements, Mohammad Hussin Shar

Civil & Environmental Engineering Theses & Dissertations

The studied drainage system is located in the downtown of the City of Newport News, in a basin known as Anderson Park. The drainage system collects and conveys rainfall runoffs to the system outfall located at the shoreline of the Hampton Roads body of water, which is located south of the study area. The aim of this study is to analyze the area's drainage system, determine maximum capacities, identify system deficiencies and generate the most possible, practical and economical solution for fixing the system deficiencies.

After collecting all of required data, the drainage system was modeled and calibrated using the …

Generation Of Bipolar Nanosecond Pulses, Sambasiva Rao Rajulapati

Electrical & Computer Engineering Theses & Dissertations

Bipolar pulse generation has been studied using transmission line technology, which was mainly used for monopolar pulse generation. In this thesis, low impedance, high current, nanosecond pulse generators were designed, constructed and tested. Five transmission lines were connected in parallel, so the impedance was 10 n. The transmission lines were switched by a spark gap switch operated in air. The closing of the switch creates a matched condition on one side of the transmission lines and a short circuit on the other side of the transmission lines. When the transmission lines are precharged, one of the two waves in opposite …

Synthesis Of Nanolaminate Structures Of Alternating Layers Of Lead Telluride And Lead Selenide By Atomic Layer Deposition For Thermoelectric Applications, Arun Deepak Ramalingom Pillai

Electrical & Computer Engineering Theses & Dissertations

Alloys composed of lead, telluride and selenide compounds exhibit very high figure of merit ZT values at intermediate temperatures, making them exceptional thermoelectric materials in a particular temperature range. Advancement in thermoelectric devices and applications hinges on increasing ZT, which is a ratio of the thermoelectric power factor to the thermal conductivity. One of the proposed avenues to achieving this goal is the use of low dimensional structures such as quantum wells, quantum dots, superlattices (SL) and nanolaminates to affect heat transport. SL structures can effectively confine charge carriers as well as scatter phonons which contribute significantly to thermal conductivity. …

Fluid-Structure Interaction Modeling Of A F/A-18 Twin-Tail Buffet Using Non-Linear Eddy Viscosity Models, Ahmed M. Nagib M. Elmekawy

Mechanical & Aerospace Engineering Theses & Dissertations

When turbulent flow generates unsteady differential pressure over an aircraft's structure, this may generate buffeting, a random oscillation of the structure. The buffet phenomenon is observed on a wide range of fighter aircraft, especially fighters with twin-tail. More research is needed to better understand the physics behind the vortical flow over a delta wing and the subsequent tail buffet.

This dissertation reports the modeling and simulation of a steady-state one-way fluid-structure interaction for the tail buffet problem observed on a F/A-18 fighter. The time-averaged computational results are compared to available experimental data. Next, computations are extended to simulate an unsteady …

Simulation Modeling And Analysis Of Customs-Regulated Container Terminal Operations With Multimodal Transportation, Mariam A. Kotachi

Engineering Management & Systems Engineering Theses & Dissertations

World trade has been increasing dramatically in the past two decades and, as a result, container exchange has grown significantly. Consequently and to meet this increase, several container terminals are expanding and many new ones are being established. A port with one or more container terminals is considered a complex system in which many entities interact to accomplish seamless handling of containers inbound and outbound. The level of complexity is drastically heightened for container terminals containing multimodal transportation systems as they typically involve ships, rail, and trucks arriving to one or more terminals delivering containers of different sizes to several …

System Identification Of An Autonomous Surface Vehicle, Christopher John Cook

Mechanical & Aerospace Engineering Theses & Dissertations

The modeling and system identification of a small pontoon based marine craft, without rudder control, in a controlled environment. Old Dominion University's autonomous surface vehicle was modeled using the Observer/Kalman System Identification method. The experimental position data was collected using a laser positioning system along with Arduino based sensors on board the boat to collect the motor speeds of the dual outboard motors. The data was then compiled using the System/ Observer/Controller Identification Toolbox to derive a dynamic model that is capable of providing path estimation and prediction information to the autonomous robotic system.

Design And Construction Of A Reconfigurable Pilot-In-The-Loop Aircraft Simulation Workstation, John J. Miller

Mechanical & Aerospace Engineering Theses & Dissertations

This thesis presents and explains the methodology used to design and construct an aircraft dynamics simulation workstation. Beginning from an outdated Navy T-34 training simulator, a gift to the school by the Naval Aerospace Medical Research Laboratory via a previous student, a new system was created to allow an engineer and/or pilot to manually control and evaluate vehicle characteristics for the purposes of research, development, and testing. Retaining only the superstructure of the original T-34 trainer, the entire system was re-engineered to provide a functional, immersive, and expandable simulation environment, complete with a five-screen visual system covering 97.5 deg of …