Mechanical Engineering Commons^™

Synthesis Of Graphene Nanomaterials And Their Application In Electrochemical Energy Storage, Guoping Xiong

Open Access Dissertations

The need to store and use energy on diverse scales in a modern technological society necessitates the design of large and small energy systems, among which electrical energy storage systems such as batteries and capacitors have attracted much interest in the past several decades. Supercapacitors, also known as ultracapacitors, or electrochemical capacitors, with fast power delivery and long cycle life are complementing or even replacing batteries in many applications. The rapid development of miniaturized electronic devices has led to a growing need for rechargeable micro-power sources with high performance. Among different sources, electrochemical micro-capacitors or micro-supercapacitors provide higher power density …

Propagation Of Sound In The Vicinity Of Rigid Porous Interfaces, Hongdan Tao

Open Access Dissertations

Propagation of sound in the vicinity of rigid porous interfaces is investigated systematically to facilitate the acoustical characterization of sound absorption materials for noise reduction applications. Various rigid porous interfaces are considered: (1) a semi-infinite porous layer; (2) a porous hard-backed surface; and (3) a porous impedance-backed layer. A closed-form solution and numerical methods are derived with respect to each rigid porous interface condition.

A modified saddle-point method is exploited to investigate the sound field emanating from a monopole source above and below a rigid porous interface. The solutions can be expressed in a form that resembles the classical Weyl-Van …

Mechanisms Of Microstructure Formation Under The Influence Of Ultrasonic Vibrations, Milan Rakita

Open Access Dissertations

Positive effects of ultrasound on crystallization have been known for almost 90 years. Application of ultrasound has been very successful in many industries, most notably in chemistry, creating a new branch of science - sonochemistry. However, ultrasonication has not found wide commercial application in the solidification processing. The reason for that is the complexity of underlying phenomena and the lack of predicting models which correlate processing parameters with the properties of a product. The purpose of this study is to give some contribution toward better understanding of mechanisms that lead to changes in the solidifying microstructure. It has been found …

An Experimental Investigation Of Wind Turbine Aerodynamic Interaction, Brandon Lee Ennis

Open Access Dissertations

Wind turbines have become a viable component in the overall energy makeup of the United States due to improved economics where energy prices have risen and production costs dropped. For a fixed cost, the effectiveness of a wind turbine financially is highly related to its performance. Considering the size of current wind farms, a minor performance improvement will result in large additional sums of revenue. A problem that has received attention with wind farms is that while the fixed costs of the development do get spread out further to reduce the installed cost of each wind turbine, the wind turbines …

Electric Machine Differential For Vehicle Traction Control And Stability Control, Sandun Shivantha Kuruppu

Open Access Dissertations

Evolving requirements in energy efficiency and tightening regulations for reliable electric drivetrains drive the advancement of the hybrid electric (HEV) and full electric vehicle (EV) technology. Different configurations of EV and HEV architectures are evaluated for their performance. The future technology is trending towards utilizing distinctive properties in electric machines to not only to improve efficiency but also to realize advanced road adhesion controls and vehicle stability controls. Electric machine differential (EMD) is such a concept under current investigation for applications in the near future. Reliability of a power train is critical. Therefore, sophisticated fault detection schemes are essential in …

Near-Field Pressure Distributions To Enhance Sound Transmission Into Multi-Layer Materials, Andrew Martin Jessop

Open Access Dissertations

The large impedance difference between air and most solids prevents significant energy transfer from incident acoustic waves across the air-material interface. Refraction also plays a role in preventing acoustic transmission, as the wave speed difference between air and solid materials results in an increase of the resulting propagation angles, creating near-field pressure distributions in the solid material. By utilizing evanescent pressure distributions, which decay normal to the usual direction of propagation and are represented as plane waves propagating with complex angles, energy propagation through the interface can be increased in the subsonic region of wave propagation: i.e., where waves typically …

Hybrid And Smart Topologically Interlocking Materials, Somesh Khandelwal

Open Access Dissertations

This thesis explores the mechanical properties of a new class of multifunctional architectured materials, Topologically Interlocking Materials (TIMs). These materials are created as an assembly of unit elements arranged in an interlocking pattern such that the load transfer between unit elements occurs by contact only. In the absence of adhesive interaction, the tensile component of the load is carried by complementary tensile elements in the form of external constraints or integrated filaments. By virtue of the bottom up design used in creating these materials, their mechanical properties are influenced by a number of controllable parameters including shape, confinement force, scale, …

Multiscale Simulation Of Thermocline Energy Storage For Concentrating Solar Power, Scott Michael Flueckiger

Open Access Dissertations

Concentrating solar power (CSP) is a renewable and demonstrated technology for large-scale power generation but requires multiple engineering advancements to achieve grid parity with conventional fossil fuels. Part of this advancement includes novel and inexpensive thermal energy systems to decouple daily power production from intermittent solar collection. Dual-media thermocline tanks, composed of molten salt and solid rock filler, offer low-cost storage capability but the concept has experienced limited deployment in CSP plants due to unresolved concerns about long-term thermal and structural stability. The main objective of the present work is to advance the understanding of thermocline storage design and operation …

Graphene Decorated Substrates And Their Interfacial Characteristics, Anurag Kumar

Open Access Dissertations

Carbon nanotubes and graphene have been extensively studied for their excellent properties. As research on carbon expands, two major issues face the scientific community: (i) Expanding the scale of synthesis and (ii) Integration of different carbon structures for improved functionality. While significant advancements have been made in large-scale synthesis, room for improvement remains. As the scale of production increases, issues such as time, cost and energy that may otherwise not be very significant, begin to play greater roles. Thus, in order to effectively transition from laboratory prototypes to industrial products, a synthesis method that can address these issues is strongly …

Subgrid Scale Modeling For Large Eddy Simulation Of Buoyant Turbulent Flows, Niranjan Shrinivas Ghaisas

Open Access Dissertations

Buoyancy effects due to small density differences commonly exist in turbulent fluid flows occurring in nature and in engineering applications. The large eddy simulation (LES) technique, which is being increasingly used for simulating buoyant turbulent flows, requires accurate modeling of the subgrid sclae (SGS) momentum and buoyancy fluxes. This thesis presents a series of LES and direct numerical simulation (DNS) studies towards a priori and a posteriori evaluation of existing SGS models, and development of new SGS models for the buoyancy flux. This thesis also presents the application of LES, in elucidating qualitative physical features and accurate measures of important …

Solution To Certain Problems In The Failure Of Composite Structures, Jonathan Goodsell

Open Access Dissertations

The present work contains the solution of two problems in composite structures. In the first, an approximate elasticity solution for prediction of the displacement, stress and strain fields within the m-layer, symmetric and balanced angle-ply composite laminate of finite-width subjected anticlastic bending deformation is developed. The solution is shown to recover classical laminated plate theory predictions at interior regions of the laminate and thereby illustrates the boundary layer character of this interlaminar phenomenon. The results exhibit the anticipated response in congruence with the solutions for uniform axial extension and uniform temperature change, where divergence of the interlaminar shearing stress is …

Numerical Techniques For The Noninvasive Assessment Of Material Properties And Stresses In Soft Biomaterials, Kent David Butz

Open Access Dissertations

The noninvasive measurement of finite displacements and strains in biomaterials by magnetic resonance imaging (MRI) may be shown to enable mathematical estimates of stress distributions and material properties within structures of the body such as articular cartilage or the intervertebral disc. Such methods will allow for non-contact and patient-specific modeling in a manner not currently possible with traditional mechanical testing or finite element techniques. Therefore, the objective of this thesis was to develop computational methods incorporating imaging-based measures of deformation, composition, and local microstructure to permit nondestructive analysis of a range of complex biomechanical systems.

Finite strain-based models were developed …

A Novel Multiblock Immersed Boundary Method Enabling High Order Large Eddy Simulation Of Pathological And Medical Device Hemodynamics, Anupindi Kameswararao

Open Access Dissertations

Computational fluid dynamics (CFD) simulations are becoming a reliable tool in understanding disease progression, investigating blood flow patterns and evaluating medical device performance such as stent grafts and mechanical heart valves. Previous studies indicate the presence of highly disturbed, transitional and mildly turbulent flow in healthy and pathological arteries. Accurate simulation of the transitional flow requires high order numerics together with a scale resolving turbulence model such as large eddy simulation (LES). This in turn limits one to use a structured fluid flow solver on which complex, branching arterial domains that are typical in the human blood circulatory system could …

A New Angle On Microscopic Suspension Feeders Near Boundaries, Rachel E. Pepper, Marcus Roper, Sangjin Ryu, Nobuyoshi Matsumoto, Moeto Nagai, Howard A. Stone

Department of Mechanical and Materials Engineering: Faculty Publications

Microscopic sessile suspension feeders are a critical component in aquatic ecosystems, acting as an intermediate trophic stage between bacteria and higher eukaryotic taxa. Because they live attached to boundaries, it has long been thought that recirculation of the feeding currents produced by sessile suspension feeders inhibits their ability to access fresh fluid. However, previous models for the feeding flows of these organisms assume that they feed by pushing fluid perpendicular to surfaces they live upon, whereas we observe that sessile suspension feeders often feed at an angle to these boundaries. Using experiments and calculations, we show that living suspension feeders …

Sequential Structural And Fluid Dynamics Analysis Of Balloon-Expandable Coronary Stents., David Martin

Doctoral

As in-stent restenosis following coronary stent deployment has been strongly linked with stent-induced arterial injury and altered vessel hemodynamics, the sequential numerical analysis of the mechanical and hemodynamic impact of stent deployment within a coronary artery is likely to provide an excellent indication of coronary stent performance. Despite this observation, very few numerical studies have considered both the mechanical and hemodynamic impact of stent deployment. In light of this observation, the aim of this research is to develop a robust numerical methodology for investigating the performance of balloon-expandable coronary stents in terms of their mechanical and hemodynamic impact within a …

Theoretical Analysis Of Torsionally Vibrating Microcantilevers For Chemical Sensor Applications In Viscous Liquids, Tao Cai

Dissertations (1934 -)

Dynamically driven microcantilevers excited in the transverse (or out-of-plane) direction are widely used as highly sensitive chemical sensing platforms in various applications. While these devices work very well in air, their performance in liquids is not efficient because of the combination of increased viscous damping and effective fluid mass. In order to improve the characteristics of microcantilevers in liquid environments, some other vibration modes such as the torsional mode and lateral (or in-plane) flexural mode have been proposed.
In this work, the characteristics of torsionally vibrating rectangular microcantilevers with length L, width b and thickness h in viscous liquids are …

Application Of Machine Learning And Parametric Nurbs Geometry To Mode Shape Identification, Robert Mceuen Porter

Theses and Dissertations

In any design, the dynamic characteristics of a part are dependent on its geometric and material properties. Identifying vibrational mode shapes within an iterative design process becomes difficult and time consuming due to frequently changing part definition. Although research has been done to improve the process, visual inspection of analysis results is still the current means of identifying each vibrational mode determined by a modal analysis. This research investigates the automation of the mode shape identification process through the use of parametric geometry and machine learning.In the developed method, displacement results from finite element modal analysis are used to create …

Design Exploration And Analysis Of Carbon-Infiltrated Carbon Nanotube Vascular Stents, Darrell John Skousen

Theses and Dissertations

The purpose of this research was to design, develop, and test coronary stent designs composed of carbon-infiltrated carbon nanotubes (CI-CNTs). Coronary stents currently have two major complications: restenosis and thrombosis. CI-CNT stents have potential to address both of these issues, and therefore may provide improved clinical outcomes. CI-CNT stent geometry is patterned using high-resolution photolithography that provide advantages in design possibilities.To develop a coronary stent, a standard design process was followed including: background, design specifications, concept generation, development, analysis, and testing. Background research was first completed and general design specifications for coronary stent performance were compiled. Multiple design concepts were …

Energy And Economic Optimization To Achieve Near Zero Energy Homes In Europe: Implications Of Inclusion Of Lighting And Appliances, Florida Solar Energy Center, Danny Parker

FSEC Energy Research Center®

Achieving annual net zero energy use in homes has been demonstrated as feasible in dozens of monitored projects in the United States.[1] In particular, very low energy use homes in Europe have been proven within the Passivhaus approach.[2] Achieving 'nearly zero energy buildings' (NZEB) has also been established as a vital objective over the next decade within the European Union (EU) (Boermans et al., 2011). However, reaching this result at the lowest possible cost remains a key challenge around the world. Balancing renewable power generation with energy efficiency will be vital in Europe as anticipated by Voss, Musall and Lichtmeß.[4] …

Technical Subtopic 2.1: Modeling Variable Refrigerant Flow Heat Pump And Heat Recovery Equipment In Energyplus, Florida Solar Energy Center, Richard Raustad

FSEC Energy Research Center®

The University of Central Florida/Florida Solar Energy Center, in cooperation with the Electric Power Research Institute and several variable-refrigerant-flow air conditioning (VRF AC) manufacturers, provided a detailed computer model for a VRF AC system in the United States Department of Energy's (U.S. DOE) EnergyPlus' building energy simulation tool. No other simulation tool currently has the capability to accurately model this state-of-the-art VRF heating, ventilating, and air conditioning (HVAC) equipment. Detailed laboratory testing and field demonstrations were performed to measure equipment performance and compare this performance with that predicted by the use of this new model through computer simulation.

This project …

Bipedal Locomotion, Jamie Nichol, Dr. Paul Eastman

Journal of Undergraduate Research

Creating an artificial biped (two legged machine) has proven a challenge. The first stage of the project, designing and building the mechanical frame, has required that I study several engineering disciplines. I have also learned many lessons by trial and error.

Enhanced Reducibility And Conductivity Of Na/K-Doped Srti0.8Nb0.2O3, Guoliang Xiao, Sirikanda Nuansaeng, Lei Zhang, Suwit Suthirakun, Andreas Heyden, Hans-Conrad Zur Loye, Fanglin Chen

Faculty Publications

Donor and acceptor co-doped SrTiO₃ materials have shown interesting features in their conductivity and reducibility. In this work, 10 mol% Na⁺ or K⁺ as acceptor dopants have been introduced into the A-site of donor-doped strontium titanate, SrTi_0.8Nb_0.2O₃, and the doping impact on their properties has been studied. By doping with Na or K, the sinterability of SrTi_0.8Nb_0.2O₃ in reducing atmospheres has been improved. Na_0.1Sr_0.9Ti_0.8Nb_0.2O₃ and K_0.1Sr_0.9Ti_0.8Nb_0.2O₃ show metallic …

Flame Jet Impingement Heat Transfer, Todd Moss, Dr. Brent Webb

Journal of Undergraduate Research

Impinging flame jets are used widely in industry and manufacturing because of their high heat transport characteristics and tight spatial control of the heating. The technique is used in heating or re-heating of stock in the metals and glass industries, and in welding and soldering operations. However, these impinging flame jets are not well understood, and few studies reporting local and average heat transfer characteristics exist in the open literature which might be used by designers (Baukal and Gebhart, 1995a, 199b). The purpose of this research is to experimentally characterize and correlate the local and average heat transfer behavior of …

Design Of An Aerospike Rocket Nozzle For Integration With A Hybrid Rocket Motor, Jeffrey L. Smith, Dr. Paul F. Eastman

Journal of Undergraduate Research

Safe, reliable, technologies are needed to launch a new generation of astronauts and space tourists into space. The aerospike nozzle is more efficient than traditional bell shaped nozzles and is safer because of lower combustion chamber pressure. These excellent performance characteristics have never before been tested in conjunction with a hybrid rocket motor. This paper presents the design and testing method for an aerospike rocket.

Correlating Skin Vibration With Radiated Sound During Speech, Jason Schulthess, Dr. Scott Thomson

Journal of Undergraduate Research

The intent of this research was to study correlation between the sound that is radiated during human speech and the resulting vibrations that occur in the skin in regions of the head and neck. This report includes results from two parts of this research. First are the measurement results and the comparisons of frequency content obtained from the vibration of the skin at various locations on the head and neck. The second is a presentation of the results examining the frequency content of the measurement device; this study was motivated by preliminary testing results that revealed possible interference due to …

Design Of Compliant Prosthetic Ankle Joints Using A Kinematic Model, Jason M. Wiersdorf, Robert Robins, Spencer P. Magleby, Larry L. Howell, Robert H. Todd

Journal of Undergraduate Research

The complex system of bones, muscles, ligaments and tendons in the human ankle allow it to withstand high compression impacts, to move in multiple degrees of freedom, and to transfer energy from the leg to the foot while walking or running.

Use Of Signal Processing Methods To Improve Speech Intelligibility In Throat Microphones, Daniel J. Andelin, Dr. Scott Thomson

Journal of Undergraduate Research

Effective communication, vital to successful operations in many sectors, including military, business, and industry, depends largely on the receiver’s ability to accurately interpret the transmitted signal, generally referred to as speech intelligibility (SI). The presence of elevated noise can be seriously detrimental to SI. To reduce ambient noise in communication through audio microphones, it is possible to use a throat microphone (TM), which senses vocal fold vibrations through the skin on the speaker’s neck, as opposed to detecting the airborne sound wave emanating from the speaker’s mouth, as in standard microphones . Unfortunately, the position of the TM on the …

Synthetic Model Of Vocal Folds, Todd C. Groesbeck, Dr. Scott Thomson

Journal of Undergraduate Research

The influence and treatment of human vocal fold scarring is a topic of great interest to the speech community (clinicians, surgeons, educators, etc). Understanding how voice production occurs “is sought in order to improve predictive, diagnostic, and corrective practices related to vocal fold health” . When a patient undergoes vocal fold surgery, scarring frequently occurs. The same surgery intended to heal the vocal fold thus leaves it damaged; scarring results in impaired vibration and prevents the individual from normal, healthy voice use.

Terrain Following In Unmanned Air Vehicles Using Optic Flow Sensors, Blake Barber, Dr. Tim Mclain

Journal of Undergraduate Research

A key enabling technology that will allow the U.S. Military to maintain information superiority in the 21st century is the development and implementation of Unmanned Air Vehicle (UAV) technology. Especially critical to the support of the small special operations units conducting the asymmetric warfare of the 21st century will be the development of mini and micro UAV technology. Mini and micro UAV technology will enable foot soldiers to hand launch and recover small, robust reconnaissance aircraft capable of providing real-time video surveillance and real-time target acquisition. These capabilities will allow soldiers to have the full situational awareness they need for …

Frequency Response Of Skin Vibration On The Head And Neck During Speech, Ben Pence, Dr. Scott Thomson

Journal of Undergraduate Research

During speech, the vocal folds vibrate resulting in audible sounds. In addition to being transmitted through the vocal tract these vibrations are also transmitted through several layers of various types of tissue throughout the head and neck, resulting in small, but measurable, skin surface vibration. Contact microphones sense these skin surface vibrations for speech transmission as opposed to acoustic microphones that sense air vibrations that radiate from the mouth.