Mechanical Engineering Commons^™

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 …

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 …

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 …

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 …

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.

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 …

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 …

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 …

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 …

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, …

Multiple Point Constraint (Mpc)-Based Variable Node Super-Element, Mohamad Eftekharjoo

Mechanical & Aerospace Engineering Theses & Dissertations

The multiple point constraint (MPC)-based variable node element is introduced in this study to handle mismatched meshes between sub-domains in finite element analysis. The MPC-variable node element is a collection of a group of elements. The compatibility condition along the interface boundary is imposed along the edge of these elements through Lagrange multipliers. The Elimination method is then used to remove the effects of the dependent nodes in these elements to produce a single MPC-based variable node element. The derived variable node elements are applied to solve two plane strain problems in order to validate the accuracy of the proposed …

Achieving Wing-Like Structural Response With Piezocomposite Unimorph Thin Plates, Francis Hauris

Mechanical & Aerospace Engineering Theses & Dissertations

This research investigates the geometric parameters that structurally influence static and dynamic bending and twisting of a wing-like plate when actuated with a surface-bonded piezoelectric material. The plate is parameterized using a finite element model that is validated by comparison with known analytical solutions. The geometric parameters analyzed for static and dynamic analysis are: the aspect ratio, actuator position, actuator angle, thickness-ratio of the active piezocomposite to the inactive substrate, and portion of the fixed end of the cantilevered structure that is fixed in the chordwise direction. For harmonically actuated cases, the resonant flapping frequency is also examined. Performance metrics …

Dynamic Project Time And Cost Evaluation Under The Combined Influence Of Contract, Quality, And Uncontrollable Change, Thomas V. Hammock

Mechanical & Aerospace Engineering Theses & Dissertations

This dissertation proposes a method that quantifies the dynamics caused by disruptions due to multiple changes that can occur during the progression of a large scale project. To begin, equations consisting of multiple parallel event sequences are derived that define the relationship between individual process events and the final project completion time. Matrix notation and a precedence matrix concept are used in this derivation to produce equations that are best suited for computer programming applications. This relationship is the foundation upon which the equations are built to calculate the variation impact on each event of a large scale project. Pursuing …

The Search For High-Impact Diagnostic And Management Tools For Low-And Middle-Income Countries: A Self-Powered Low-Cost Blood Pressure Measurement Device Powered By A Solid-State Vibration Energy Harvester, Onur Bilgen, John G. Kenerson, Muge Akpinar-Elci, Rebecca Hattery, Lisbet M. Hanson

Mechanical & Aerospace Engineering Faculty Publications

The World Health Organization has established recommendations for blood pressure measurement devices for use in low-resource venues, setting the triple A expectations of Accuracy, Affordability, and Availability. Because of issues related to training and assessment of proficiency, the pendulum has swung away from manual blood pressure devices and auscultatory techniques towards automatic oscillometric devices. As a result of power challenges in the developing world, there has also been a push towards semiautomatic devices that are not dependent on external power sources or batteries. Beyond solar solutions, disruptive technology related to solid-state vibrational energy harvesting may be the next iterative solution …

Characteristics Of Laser-Induced Plasma Flame Kernel Formation And Evolution, Wilmer Flores

Mechanical & Aerospace Engineering Theses & Dissertations

With increasing interest to engineer more efficient combustion engines, the use of laser induced ignition demonstrates to be a compelling alternative to the conventional electric spark plug. The benefits greatly outweigh those found in a conventional electric spark motor whereas research shows improvements in reduced energy consumption and harmful emissions. In addition, the ability to divert the laser beam and its reliability are advantages. Laser-based ignition is capable of generating a plasma for combustion in versatile surroundings where ignition is desired. Laser induced ignition of methane-air was investigated under diverse flow and mixture conditions. To perform this experiment three air/fuel …

Triboelectric Solar Generator Concept And Experimental Research, Elias Yazdanshenas

Mechanical & Aerospace Engineering Theses & Dissertations

In this thesis, a novel concept, a triboelectric solar generator (TSG ), is proposed for generation of high voltage direct current (HVDC) electricity from solar radiation. An experimental investigation was conducted to prove the concepts of charge generation through the triboelectric effect and charge transmission using semiconductors. The triboelectric effect, also known as the contact electrification, is a well-known physical phenomenon that electrostatic charges are generated by rubbing dissimilar materials. However, traditional triboelectric generators had never been commercialized due to their poor power output. Physically, it is due to the difficulty of charge transmission from insulators, which generate charges. The …

Nano Scale Mechanical Analysis Of Biomaterials Using Atomic Force Microscopy, Diganta Dutta

Mechanical & Aerospace Engineering Theses & Dissertations

The atomic force microscope (AFM) is a probe-based microscope that uses nanoscale and structural imaging where high resolution is desired. AFM has also been used in mechanical, electrical, and thermal engineering applications. This unique technique provides vital local material properties like the modulus of elasticity, hardness, surface potential, Hamaker constant, and the surface charge density from force versus displacement curve. Therefore, AFM was used to measure both the diameter and mechanical properties of the collagen nanostraws in human costal cartilage. Human costal cartilage forms a bridge between the sternum and bony ribs. The chest wall of some humans is deformed …

Constrained Discrete Phase Control Of A Heaving Wave Energy Converter In Irregular Seas Using Reinforcement Learning, Praveen D. Malali

Mechanical & Aerospace Engineering Theses & Dissertations

Designed for offshore deployment in irregular seas, the point absorber wave energy conversion (WEC) system is promisingly attractive amongst the currently available WEC technologies. The effectiveness of phase control when applied to a heaving point absorber through a hydraulic power take-off (PTO) system is systematically investigated in both regular and irregular waves. For this purpose, two phase control accumulators are utilized in the hydraulic PTO system. Simulations are performed in MATLAB® using the Cummins equation to model the dynamics of the heaving point absorber in the time domain.

For a given sea state, the opening instant of the control valves …

Development Of Analytical Sensitivity Analysis For Ahp Applications, Marie L. Ivanco

Mechanical & Aerospace Engineering Theses & Dissertations

Decision makers often face complex problems, which can seldom be addressed without the use of structured analytical models. Mathematical models have been developed over the last 50 years to streamline and facilitate decision making activities. The Analytic Hierarchy Process constitutes one of the most utilized Multi-Criteria Decision Analysis Methods. While AHP has been thoroughly researched and applied, the method still shows limitations in terms of integrating profile disparities of Subject Matter Experts (SMEs). This thesis develops an analytical sensitivity analysis method for AHP based on local partial derivatives to address these limitations. Four examples are presented to demonstrate and validate …

Design Of Timing Circuit For Fuel Injection Conversion And Development Of Laboratory To Analyze Engine Performance Using A Dynamometer, Aditi Jayram Limaye

Mechanical & Aerospace Engineering Theses & Dissertations

A fundamental facility was built to analyze some of the basic parameters involved in engine performance, namely torque and power output of the engine. One of the objectives was to convert a carbureted engine into a fuel injection or (Fl) engine. This was achieved by designing and creating a timing circuit that is required to trigger the electronic fuel injector or (EFI). The facility was designed around a dynamometer and a fuel delivery system; that provided a specialized tool to analyze engines and injectors.

The results from the carbureted experiments and the FI experiments were compared to the rated specifications …

Isogeometric Analysis For Electromagnetism, Tahsin Khajah

Mechanical & Aerospace Engineering Theses & Dissertations

The combination of numerical analysis with the scanning technology has been seeing increased use in many research areas. There is an emerging need for high-fidelity geometric modeling and meshing for practical applications. The Isogeometric Analysis (IGA) is a comprehensive computational framework, which integrates geometric modeling and meshing with analysis. Different from other existing numerical methods, the IGA can generate analysis ready models without loss of geometrical accuracy. In IGA, the continuity and the quality of a solution can be conveniently controlled and refined. These features enable IGA to integrate modeling, analysis, and design in a unified framework, the root idea …

Validation Of Open Chain Model During Kinematic Analysis Of Joint Mobilization Of The Foot: An In Vitro Study, Anthony Ross Mcnally

Mechanical & Aerospace Engineering Theses & Dissertations

Joint mobilization techniques have been shown to improve dorsiflexion range of motion after ankle injury in multiple in vivo studies; however, the underlying arthrokinematic effects of this treatment still require clarification. Therefore, the purpose of this preliminary study was to determine the viability of an open kinetic chain in vitro model for applying Maitland Grade III anterior/posterior joint mobilizations to the talocrural joint while examining the osteokinematic and arthrokinematic changes at the talocrural, subtalar and hindfoot joints. Three fresh frozen cadaver lower legs had Maitland Grade III anterior-to-posterior joint mobilization applied to the talocrural joint in 2 sessions of 200 …

Correlation Of Csk2sb Photocathode Lifetime With Antimony Thickness, M. A. Mamun, C. Hernandez-Garcia, M. Poelker, A. A. Elmustafa

Mechanical & Aerospace Engineering Faculty Publications

CsK₂Sb photocathodes with quantum efficiency on the order of 10% at 532 nm, and lifetime greater than 90 days at low voltage, were successfully manufactured via co-deposition of alkali species emanating from an effusion source. Photocathodes were characterized as a function of antimony layer thickness and alkali consumption, inside a vacuum chamber that was initially baked, but frequently vented without re-baking. Photocathode lifetime measured at low voltage is correlated with the antimony layer thickness. Photocathodes manufactured with comparatively thick antimony layers exhibited the best lifetime. We speculate that the antimony layer serves as a reservoir, or sponge, for …

Multi-Scale Visualization Of Molecular Architecture Using Real-Time Ambient Occlusion In Sculptor, Manuel Wahle, Willy Wriggers

Mechanical & Aerospace Engineering Faculty Publications

The modeling of large biomolecular assemblies relies on an efficient rendering of their hierarchical architecture across a wide range of spatial level of detail. We describe a paradigm shift currently under way in computer graphics towards the use of more realistic global illumination models, and we apply the so-called ambient occlusion approach to our opensource multi-scale modeling program, Sculptor. While there are many other higher quality global illumination approaches going all the way up to full GPU-accelerated ray tracing, they do not provide size-specificity of the features they shade. Ambient occlusion is an aspect of global lighting that offers great …

A Simulation-Based Approach To Risk Assessment And Mitigation In Supply Chain Networks, Mamadou Seck, Ghaith Rabadi, Christian Koestler

Engineering Management & Systems Engineering Faculty Publications

We present in this paper a simulation-based approach to evaluate the risk associated with supply chain disruptions caused by failures in some supply chains nodes and measure the impact of such disruptions on supply chain key performance measures (KPIs) of interest. The proposed framework enables analysts and managers to repeatedly assess the risk to their supply chains based on various simulated scenarios and identify the most critical nodes whose disruption will have the highest impact on the KPIs of interest. As a result, companies can focus on the most critical supply chain assets and develop targeted mitigation plans that minimize …

Addressing New Skills Needed For The Automotive Industry Through A Motorsports Educational Pathway, Vukica M. Jovanovic, Mileta M. Tomovic, Alok K. Verma, Nathan Luetke, Steve Branch

Engineering Technology Faculty Publications

The automotive industry has higher-skilled positions available that need engineers and engineering technologists qualified and capable to work in a high-paced, advanced manufacturing sector. Various educational programs across the country offer programs related to the motorsports area at the Associate of Science level. There are also various articu-lation agreements that enable students to continue their education to the baccalaureate level. These programs try to fill in the gap related to the skills shortage in systems and new design methods and processes. The main strength of such educational pathways is that students, who are trained to work as technicians with an …