Engineering Commons^™

Preface-Jes Focus Issue On Electrolysis For Increased Renewable Energy Penetration, B. Pivovar, M. Carmo, K. Ayers, X. Zhang, J. O'Brien

Mechanical & Aerospace Engineering Faculty Publications

(First paragraph) Today represents a particularly exciting time, as our planet’s energy system is undergoing major changes due to dramatically decreasing renewable energy prices and increasing societal concerns over greenhouse gas emissions, criteria pollutants (arsenic, mercury, NOx, particulate matter), and climate change. These factors are pushing society toward deep decarbonization of our energy system, perhaps the most challenging issue facing the planet today. Unfortunately, wind and solar energy, while both promising generation sources, come with intermittency challenges and have limitations in their abilities to impact industrial and transportation sector demands where fossil fuel energy carriers based on chemical bonds have …

Thermo-Mechanical System Identification Of A Shape Memory Alloy Actuated Mechanism, Cody Alexander Wright

Mechanical & Aerospace Engineering Theses & Dissertations

Shape memory alloy (SMA) actuators paired in an antagonistic arrangement can be used to produce mechanisms that replicate human biomechanics. To investigate this proposal, the biomechanical articulation of the elbow by means of the biceps brachii muscle is compared with that of a SMA actuated arm. This is accomplished by parametric analysis of a crank-slider kinematic mechanism actuated, first, with an experimentally characterized SMA wire and then an idealized musculotendon actuator based on actuation properties of muscles published in the literature. Next, equations of motion for the system dynamics of the SMA actuated mechanism are derived and phase portrait analysis …

Parametric Investigation Of A Laboratory Drop Test To Simulate Base Acceleration Induced By Wave Impacts Of High Speed Planing Craft, John D. Barber

Mechanical & Aerospace Engineering Theses & Dissertations

High speed operations in a small craft can be physically punishing and, in some circumstances, even dangerous for the crew. The aspect of small craft operations that make them punishing for the crew is wave slamming generated by wave impacts as the craft is traveling over the seas at high speed.

The initial step of this thesis effort was to perform a literature survey to determine what knowledge existed within the technical and academic community about wave slamming and simulating them with drop tests.

Eventually, a final experiment strongly influenced by the experiment model found in (Protocol 1, 2014) was …

Testing And Analysis Of An Exergetically Efficient 4 K To 2 K Helium Heat Exchanger, Peter N. Knudsen

Mechanical & Aerospace Engineering Theses & Dissertations

Modern experimental nuclear physics programs that utilize advanced superconducting devices require refrigeration below the lambda temperature of helium (2.1768 K) and involve sub-atmospheric helium at some point in the process. They typically operate between 1.8 and 2.1 K (16 to 40 mbar) and can require refrigeration ranging from tens to thousands of watts. These processes are very energy intensive, requiring roughly 850 W/W even for large and well-designed refrigerators, though they can easily require much more. Adiabatic expansion of sub-cooled liquid helium to these sub-atmospheric pressures will result in a two-phase mixture with a large liquid to vapor density ratio. …

Changing Trends In Wave Heights In The U.S. Mid-Atlantic Region, Hillary Lane

Civil & Environmental Engineering Theses & Dissertations

The pace and effects of climate change are an area of constant focus for coastal engineers as evolving patterns in the atmosphere worldwide affect the oceans and coasts on a regional and global scale. Surface waves respond to changing wind patterns both locally and from propagating swell, and the difficulty in predicting future wind patterns is well-established. Expectations that climate change will result in more frequent and intense coastal storms and consequently greater wave heights in the North Atlantic are still unrealized, and recent forecasts from a variety of atmosphere-ocean coupled global climate models instead predict decreasing wave heights through …

Development Of A Dsm-Based Model For Managing The Design Of Complex Systems Considering The Impact Of Technological Obsolescence, Gershom Kwaku Obeng

Mechanical & Aerospace Engineering Theses & Dissertations

Obsolescence has been a constant issue for process planners and designers and if not properly accounted for, obsolescence can become an expensive issue. As systems become more complex, interconnected, and nonhomogeneous, separate studies of single groups of equipment are no longer sufficient in modeling the obsolescence of the systems that they make up. The purpose of this dissertation is to model the likelihood of a process's design becoming obsolescent given the obsolescent behavior of the equipment used to complete the process. The methodology discussed in this work is based on a combination of using a systems engineering tool called the …

An Examination Of The Indentation Size Effect In Fcc Metals And Alloys From A Kinetics Based Perspective Using Nanoindentation, David Earl Stegall

Mechanical & Aerospace Engineering Theses & Dissertations

The indentation size effect (ISE) in metals is described as the rise in hardness with decreasing depth of indentation and contradicts conventional plasticity behavior. The goal of this dissertation is to further examine the fundamental dislocation mechanisms that may be contributing to the so-called indentation size effect. In this work, we examined several metals and alloys including 99.999% Aluminum (SFE ~200 mJ/m²), 99.95% Nickel (SFE ~125 mJ/m²), 99.95% Silver (SFE ~22 mJ/m²⁾, and three alloys, alpha brass 70/30 (SFE >10 mJ/m²), 70/30 nickel copper (SFE ~100 mJ/ …

A Comparison Of Microstructure And Uniaxial Compressive Response Of Ice-Templated Porous Alumina Scaffolds Fabricated From Two Different Particle Sizes, Nikhil D. Dhavale

Mechanical & Aerospace Engineering Theses & Dissertations

Development of bio-inspired highly porous (>50 vol.%) cellular ceramics is crucial to meet the demand of high-performance lightweight and damage-tolerant materials for a number of cutting-edge applications including impact energy absorption, biomedical implants, and energy storage. A key design feature that is observed in many natural materials (e.g., nacre, bamboo, wood, etc.) is the presence of hierarchical microstructure that results in an excellent synergy of various material properties, which are otherwise considered as mutually exclusive in current paradigm of materials design. To this end, development of multilayered, interconnected and anisotropic cellular ceramics could benefit the aforementioned applications. However, mimicking …

Carbon Deposition During Oxygen Production Using High Temperature Electrolysis And Mitigation Methods, Timothy Adam Bernadowski

Mechanical & Aerospace Engineering Theses & Dissertations

Carbon dioxide in the Martian atmosphere can be converted to oxygen during high temperature electrolysis for use in life-support and fuel systems on manned missions to the red planet. During electrolysis of carbon dioxide to produce oxygen, carbon can deposit on the electrolysis cell resulting in lower efficiency and possibly cell damage. This would be detrimental, especially when the oxygen product is used as the key element of a space life support system. In this thesis, a theoretical model was developed to predict hazardous carbon deposition conditions under various operating conditions within the Martian atmosphere. The model can be used …

Constrained-Energy Cross-Well Actuation Of Bistable Structures, Masoud Zarepoor

Mechanical & Aerospace Engineering Theses & Dissertations

Bistable structures have two stable equilibrium positions and can be utilized to maintain a specific static shape with no energy consumption. This dissertation focuses on the minimum required energy for performing snap-through of a bistable structure. Snap-through is the motion of a bistable structure from one stable equilibrium position to the other. This research uses the Duffing-Holmes equation as a one-degree-of-freedom representative model of a bistable structure, and this nonlinear equation is solved to calculate the required energy for cross-well oscillation. The research identifies several unique features of the response of a bistable system subjected to force and energy constraints. …

Development Of The Compact Jet Engine Simulator From Concept To Useful Test Rig, Henry H. Haskin

Mechanical & Aerospace Engineering Theses & Dissertations

Two Compact Jet Engine Simulator (CJES) units were designed for integrated wind tunnel acoustic experiments involving a Hybrid Wing Body (HWB) vehicle. To meet the 5.8% scale of the HWB model, Ultra Compact Combustor technology from the Air Force Research Laboratory was used. The CJES units were built and integrated with a control system in the NASA Langley Low Speed Aero acoustic Wind Tunnel. The combustor liners, plug—vane and flow conditioner components were built in-house at Langley Research Center. The operation of the CJES units was mapped and fixes found for combustor instability tones and rig flow noise. The original …

Bunch Splitting Simulations For The Jleic Ion Collider Ring, R. Gamage, T. Satogata

Physics Faculty Publications

We describe the bunch splitting strategies for the proposed JLEIC ion collider ring at Jefferson Lab. This complex requires an unprecedented 9:6832 bunch splitting, performed in several stages. We outline the problem and current results, optimized with ESME including general parameterization of 1:2 bunch splitting for JLEIC parameters.

A Retrospective Study Of Amusement Ride Restraint And Containment Systems: Identifying Design Challenges For Statistically Rare Anthropometric Cases, Paula M. Stenzler

Engineering Management & Systems Engineering Theses & Dissertations

The intent of this project was to conduct a retrospective study of amusement ride restraint and containment systems’ failures to identify the challenges associated with existing design criteria to safely accommodate statistically rare groups that fall outside amusement industry standards. Innovations in ride technology provide an opportunity for injuries to occur if restraint and containment systems cannot properly accommodate unique patron anthropometry. It is paramount to understand how anthropometric features contribute to the patron’s ability to defeat ride restraint and containment systems. A systemic perspective was used based on industry accident data to frame the problem associated with restraint and …

Experimental Investigation Of Turbulent Structures And Non-Equilibrium Effects In Axial Wake Vortices Via Particle Image Velocimetry, Jeffry William Ely

Mechanical & Aerospace Engineering Theses & Dissertations

Vortices are a common phenomenon in fluid flows that arise as kinetic energy dissipates into heat via viscous interaction. They arise naturally at large scales in the form of dust devils, tornadoes, and as a counter-rotating vortex pair in the wake of aircraft. It is important to understand the conditions leading to their formation, their duration, and their dissipation in order to forecast or prevent undesirable effects. Among these deleterious effects is a decrease in safety of aircraft operations in the wake of other aircraft, an extremely common situation at airports around the world. A large number of mathematical models …

Secondary Electron Emission From Plasma Processed Accelerating Cavity Grade Niobium, Miloš Bašović

Mechanical & Aerospace Engineering Theses & Dissertations

Advances in the particle accelerator technology have enabled numerous fundamental discoveries in 20th century physics. Extensive interdisciplinary research has always supported further development of accelerator technology in efforts of reaching each new energy frontier.

Accelerating cavities, which are used to transfer energy to accelerated charged particles, have been one of the main focuses of research and development in the particle accelerator field. Over the last fifty years, in the race to break energy barriers, there has been constant improvement of the maximum stable accelerating field achieved in accelerating cavities. Every increase in the maximum attainable accelerating fields allowed for higher …

Thin Film Studies Toward Improving The Performance Of Accelerator Electron Sources, Md Abdullah Al Mamun

Mechanical & Aerospace Engineering Theses & Dissertations

Future electron accelerators require DC high voltage photoguns to operate beyond the present state of the art to conduct new experiments that require ultra-bright electron beams with high average current and higher bunch charge. To meet these demands, the accelerators must demonstrate improvements in a number of photogun areas including vacuum, field emission elimination in high voltage electrodes, and photocathodes. This dissertation illustrates how these improvements can be achieved by the application of suitable thin-films to the photogun structure for producing ultra-bright electron beams.

This work is composed of three complementary studies. First, the outgassing rates of three nominally identical …

Concurrent Spatial Mapping Of The Viscoelastic Behavior Of Heterogeneous Soft Materials Via A Polymer-Based Microfluidic Device, Wenting Gu

Mechanical & Aerospace Engineering Theses & Dissertations

This dissertation presents a novel experimental technique, namely concurrent spatial mapping (CSM), for measuring the viscoelastic behavior of heterogeneous soft materials via a polymer-based microfluidic device. Comprised of a compliant polymer microstructure and an array of electrolyte-enabled distributed resistive transducers, the microfluidic device detects both static and dynamic distributed loads. Distributed loads deform the polymer microstructure and are recorded as resistance changes at the locations of the transducers.

The CSM technique identifies the elastic modulus of soft materials by applying a precisely controlled indentation depth using a rigid probe to a sample placed on the device. The spatially-varying elastic modulus …

A Hybrid Position Feedback Controller For Bistable Structures, Mehmet R. Simsek

Mechanical & Aerospace Engineering Theses & Dissertations

Bistability is the property of structures showing the ability to attain two statically stable states. Due to dynamic and static advantages such as no energy demand at stable positions and providing higher deflections compared to a monostable structure, bistability may be appealing in control surface design for aircraft structures and load alleviation for wind turbine blades. The dynamics of bistable structures is nonlinear because of the snap-through occurring during the cross-well oscillation between two stable states. A new control strategy called hybrid position feedback control is developed based on the conventional positive position control to exploit linear dynamics of bistable …

The Reconfigurable Machinery Efficient Workspace Analysis Based On The Twist Angles, Ana M. Djuric, Vukica Jovanovic, Mirjana Filipovic, Ljubinko Kevac

Engineering Technology Faculty Publications

A novel methodology for the calculation, visualisation and analysis of the Reconfigurable Machinery Efficient Workspace (RMEW), based on the twist angles, is presented in this paper. The machinery's kinematic parameters are used for calculating the workspace, while the efficient workspace is associated with the machinery's path and includes the end-effector position and orientation. To analyse and visualise many different machinery efficient workspaces at the same time, the calculation is based on the previously developed and validated complex reconfigurable machinery's kinematic structure named n-DOF Global Kinematic Model (n-GKM). An industrial robot is used as an example to demonstrate …

Regression Analysis Of Pem Fuel Cell Transient Response, Russell L. Edwards, Ayodeji Demuren

Mechanical & Aerospace Engineering Faculty Publications

To develop operating strategies in polymer electrolyte membrane (PEM) fuel cell-powered applications, precise computationally efficient models of the fuel cell stack voltage are required. Models are needed for all operating conditions, including transients. In this work, transient evolutions of voltage, in response to load changes, are modeled with a sum of three exponential decay functions. Amplitude factors are correlated to steady-state operating data (temperature, humidity, average current, resistance, and voltage). The obtained time constants reflect known processes of the membrane heat/water transport. These model parameters can form the basis for the prediction of voltage overshoot/undershoot used in computational-based control systems, …

Computational Assessment Of Neural Probe And Brain Tissue Interface Under Transient Motion, Michael Polanco, Sebastian Bawab, Hangsoon Yoon

Mechanical & Aerospace Engineering Faculty Publications

The functional longevity of a neural probe is dependent upon its ability to minimize injury risk during the insertion and recording period in vivo, which could be related to motion-related strain between the probe and surrounding tissue. A series of finite element analyses was conducted to study the extent of the strain induced within the brain in an area around a neural probe. This study focuses on the transient behavior of neural probe and brain tissue interface with a viscoelastic model. Different stages of the interface from initial insertion of neural probe to full bonding of the probe by astro-glial …

Electrokinetic Phenomena In Pencil Lead-Based Microfluidics, Yashar Bashirzadeh, Venkat Maruthamuthu, Shizhi Qian

Mechanical & Aerospace Engineering Faculty Publications

Fabrication of microchannels and associated electrodes to generate electrokinetic phenomena often involves costly materials and considerable effort. In this study, we used graphite pencil-leads as low cost, disposable 3D electrodes to investigate various electrokinetic phenomena in straight cylindrical microchannels, which were themselves fabricated by using a graphite rod as the microchannel mold. Individual pencil-leads were employed as the micro-electrodes arranged along the side walls of the microchannel. Efficient electrokinetic phenomena provided by the 3D electrodes, including alternating current electroosmosis (ACEO), induced-charge electroosmosis (ICEO), and dielectrophoresis (DEP), were demonstrated by the introduced pencil-lead based microfluidic devices. The electrokinetic phenomena were characterized …

A Pilot Program For The Recruitment And Education Of Navy Veterans Based On System-Level Technical Expertise And Leadership Maturation Developed During Service, Anthony W. Dean, Connor Schwalm, Patrick S. Heaney, Linda Vahala, Yuzhong Shen, Jennifer G. Michaeli

Engineering Technology Faculty Publications

The project, Stern2STEM, aims to advance STEM (Science, Technology, Engineering, and Mathematics) education through the preparation of student veterans to pursue baccalaureate STEM degrees and support the re-employment of these veterans into the Department of Defense (DoD) and the wider defense support industry. The program builds on the training that veterans have received in highly skilled technical areas, both in the classroom and “on-the-job”, to develop system level expertise in their respective technical disciplines. Key components of the program include: (1) establishing a mechanism for outreach and recruitment; (2) providing leveling, tutoring, mentoring, and support for students; (3) teaching …

Applications Of Digital Manufacturing In Manufacturing Process Support, Vukica Jovanovic, Mihael Debevec, Niko Herakovic, Alok Verma, Mileta Tomovic

Engineering Technology Faculty Publications

In this study, the authors developed three new approaches and models for improvements related to manufacturing processes. The main focus was on planning in a digital environment before the actual manufacturing process is carried out. The first approach is digital manufacturing, which gives affords the opportunity for performing an entire manufacturing process in a virtual environment. In this way, engineers virtually define, plan, create, monitor, and control all production processes. The planning phase can be done simultaneously, while other manufacturing processes are already in place. In this way, processes can continue with no interruption. Various product lifecycle management tools have …

Modeling Social, Economic, Technical & Environmental Components In An Energy System, Ange-Lionel Toba, Mamadou Seck

Engineering Management & Systems Engineering Faculty Publications

Energy system models have become the main supporting tool for energy policy. Modern challenges in energy policy require energy systems models that integrate technical, environmental and societal aspects of the energy systems. In this paper, we introduce a conceptual model for an energy system model that specifies the relationships between social, technical, environmental, and economic aspects of an energy system. This conceptual model presented in the IDEF0 language will serve as a basis for a computational energy systems model. © 2016 The Authors.

Period Batch Control - A Production Planning System Applied To Virtual Manufacturing Cells, Z. Tesic, B. Stevanaov, V. Jovanovic, M. Tomic, C. Kafol

Engineering Technology Faculty Publications

Period Batch Control (PBC) system has been known for its implementation with the classical group technology (GT) cells, and it has been known for its simplicity. The main production planning decisions concern the choice of the period length and the stage number and contents. Also, in order to better integrate the production planning with the application of GT cells at the shop floor, the concept of virtual manufacturing cells has been applied. Since virtual cells configurations are changing periodically, a model for implementing the PBC system into virtual manufacturing cells environment is developed. The model enables alignment of the PBC …

Backward Dijkstra Algorithms For Finding The Departure Time Based On The Specified Arrival Time For Real-Life Time-Dependent Networks, Gelareh Bakhtyar, Vi Nguyen, Mecit Cetin, Duc Nguyen

Civil & Environmental Engineering Faculty Publications

A practical transportation problem for finding the “departure” time at “all source nodes” in order to arrive at “some destination nodes” at specified time for both FIFO (i.e., First In First Out) and Non-FIFO “Dynamic ” Networks is considered in this study. Although shortest path (SP) for dynamic networks have been studied/documented by various researchers, contributions from this present work consists of a sparse matrix storage scheme for efficiently storing large scale sparse network’s connectivity, a concept of Time Delay Factor (TDF) combining with a “general piece- wise linear function” to describe the link cost as a function of time …

Analyses Of 476 Mhz And 952 Mhz Crab Cavities For Jlab Electron Ion Collider, Hyekyoung Park, A. Castilla, J. R. Delayen, S. U. De Silva, V. Morozov

Physics Faculty Publications

Center for Accelerator Science at ODU has designed, fabricated and successfully tested a crab cavity for MEIC at Jefferson Lab*. This proof of principle cavity was based on the earlier MEIC design which used 748.5 MHz RF system. The updated MEIC design** utilizes the components from PEP-II. It results in the change on the bunch repetition rate of stored beam to 476.3 MHz. The ion ring collider will eventually require 952.6 MHz crab cavity. This paper will present the analyses of crab cavities of both 476 MHz and 952 MHz options. It compares advantages and disadvantages of the options which …