Mechanical Engineering Commons^™

Swelling-Etching Characterization Of Copper (I) Oxide - Pdms For The Development Of Micro/Nano - Particles Composite Mems Corrosion Sensor, Abdoul Kader Maiga

Graduate Theses and Dissertations

The primary objective for this thesis is to contribute to the understanding of the oxide removal process for a corrosion sensing device. The goal for designing such a device is for monitoring corrosion on metallic structures. The sensing material (6.35mm x 1mm discs) of the device is composed of copper (I) oxide particles mixed in some polydimethylsiloxane (PDMS). The PDMS, “housing,” is meant for controlling the oxidation rate through the sensing material. A solvent was used to facilitate the etchant diffusion through the PDMS matrix. Toluene and acetic acid were the ideal solvent and etchant, respectively, for carrying out the …

Modeling Radiation Heat Transfer For Building’S Cooling And Heating Loads: Considering The Role Of Clear, Cloudy, And Dusty Conditions In Hot And Dry Climates, Salem Ahmed Algarni

Graduate Theses and Dissertations

The influence of transient factors such as sky long wave radiation exchange and atmospheric aerosols (i.e., smog, and dust – made up of sand, clay, and silt) are not carefully considered in current building design and simulation models. Therefore, the research objective was to better understand and account for such variables, resulting in improved radiative predictive capabilities, especially important for hot and dry climates under different sky conditions including clean, cloudy, and dusty. Overall, results of this dissertation provided a better prediction method for sky long wave radiation exchange with a building’s roof and the impact of dust accumulation on …

Text-Independent Speaker Identification Using Statistical Learning, Alli Ayoola Ojutiku

Graduate Theses and Dissertations

The proliferation of voice-activated devices and systems and over-the-phone bank transactions has made our daily affairs much easier in recent times. The ease that these systems offer also call for a need for them to be fail-safe against impersonators. Due to the sensitive information that might be shred on these systems, it is imperative that security be an utmost concern during the development stages. Vital systems like these should incorporate a functionality of discriminating between the actual speaker and impersonators. That functionality is the focus of this thesis.

Several methods have been proposed to be used to achieve this system …

Maximum Power Point Tracking And Solar Power For Developing Countries Around The World, Christopher M. Plate

Electrical Engineering Undergraduate Honors Theses

Renewable energy is becoming increasingly important as more and more countries become industrialized. Using solar power as opposed to fossil fuels and coal is becoming cheaper and easier to access throughout the world, yet there are still efficiency hurdles to be overcome. Designing a cheap, easily modifiable and reparable Maximum Power Point Tracker would be a stepping stone to bringing solar power to remote parts of the globe. Once designed and made portable, these devices could be distributed throughout developing countries to enhance renewable energy output. An Arduino-based tracker was chosen for ease of use and access. This base also …

Fusion Of Short-Mid Wavelength Infrared Image And Long Wavelength Image Using Discrete Wavelet Transform For Image Quality Enhancement, Rocky Hedrick

Electrical Engineering Undergraduate Honors Theses

Infrared technology advancements have led to an expansive set of infrared applications in both the private and public sectors. New materials and manufacturing techniques have continued to reduce the cost while improving the quality of infrared cameras, but the cost is still high when compared to the cost versus quality of visible light spectrum cameras. Innovative image processing techniques can be implemented to help bridge this gap between the cost and quality of infrared cameras. The goal of this research is to improve the overall quality of infrared imaging by fusing short-mid wavelength infrared images and long wavelength images of …

Improved Methods For Identifying, Applying, And Verifying Industrial Energy Efficiency Measures, Andrew Chase Harding

Graduate Theses and Dissertations

Energy efficiency is the least expensive source of additional energy capacity for today's global energy expansion. Energy efficiency offers additional benefits of cost savings for consumers, reduced environmental impacts, and enhanced energy security. The challenges of energy efficiency include identifying potential efficiency measures, quantifying savings, determining cost effectiveness, and verifying savings of installed measures. This thesis presents three separate chapters which address these challenges. The first is a paper presented at the 2014 industrial energy technology conference (IETC) that details a compressed air system project using the systems approach to identify cost effective measures, energy intensity to project savings, and …

Three Dimensional Simulations Of Tornado Sheltering Effect Of Man-Made Structures, Piotr Gorecki

Graduate Theses and Dissertations

A three dimensional computational fluid dynamics (CFD) model was utilized to investigate tornado-like vortex interactions with wide man-made structures. The tornado-like wind profile was approximated using Rankine vortex model. By utilizing the CFD model, it was explained why tornadoes exhibit less damage on leeward side of large structures. During the preliminary stage of this study, a perpendicular vortex-prism interaction was analyzed. The prism height and the length were equal to the vortex core radius. The prism was also 12 times wider than the vortex core radius. During the vortex-prism interaction, the near-ground portion of the vortex was blocked by the …

Characterization Of Nano-Porous Si-Cu Composites To Enhance Lubricant Retention Impacting The Tribological Properties Of Sliding Surfaces, Julius Sheldon Morehead

Graduate Theses and Dissertations

As the expectations for modern machinery's tribological and thermal performances continue to rise, the retention of lubricant on the contact surfaces of their sliding components becomes an increasingly important issue. Friction and wear cause heat-related failures which lead to catastrophic damage to machinery. Evaporation of a lubricant's volatile constituents as well as lubricant migration leads not only to a reduction in lubricant quantity but also in its quality, thus facilitating component failures. In order to enhance component reliability, the surface should incorporate features that actively retain lubricants. The unique properties of nano-porous topographies such as their high surface area-to-volume ratio …

Gui Matlab Code To Display Damped, Undamped, Forced And Unforced Mass Spring Systems, Melanie Garcia

Mechanical Engineering Undergraduate Honors Theses

Machine Dynamics and Control is the course offered at the University of Arkansas that deals with damped, undamped, forced and unforced systems. It’s important for students to understand each of these systems for future implementation in the industry and daily real life situations. The three types of damped systems, underdamped, overdamped and critically damped are analyzed in this thesis. As well as only two of the most common forced functions are analyzed, the cosine and sine functions. The objective of this thesis was to develop a GUI code in Matlab that would help students visualize the differences between undamped, damped, …

Experimental Verification And Integration Of A Next Generation Smart Power Management System, Tavis Clemmer

Graduate Theses and Dissertations

With the increase in energy demand by the residential community in this country and the diminishing fossil fuel resources being used for electric energy production there is a need for a system to efficiently manage power within a residence. The Smart Green Power Node (SGPN) is a next generation energy management system that automates on-site energy production, storage, consumption, and grid usage to yield the most savings for both the utility and the consumer. Such a system automatically manages on-site distributed generation sources such as a PhotoVoltaic (PV) input and battery storage to curtail grid energy usage when the price …

Comparison Of Evaluation, Measurement & Verification Processes: Arkansas To Bordering States, William Burgess Carlisle

Mechanical Engineering Undergraduate Honors Theses

The purpose of this paper is to compare Evaluation, Measurement, and Verification (EM&V) standards established by Arkansas and surrounding states. EM&V is the process to quantify the energy savings of an energy management project. This paper details the rules and regulation regarding the EM&V proceedings required by investor-owned utilities in providing energy-saving projects. By comparison of each state’s requirement, a clear understanding is found on where Arkansas stands in maturity of its program requirements. The reader will find Arkansas on the forefront of EM&V standardization that represents a model that surrounding states are striving to emulate.

Interface Property Of Collagen And Hydroxyapatite In Bone And Developing Bioinspired Materials, Clint Paul

Inquiry: The University of Arkansas Undergraduate Research Journal

Bone at the nanoscale consists of type I collagen and hydroxyapatite (HAP). Type I collagen and HAP [Ca10(PO4)6(OH)2] are responsible for most of the structural integrity of bone. Collagen fibrils contain HAP platelets of varying size dispersed between the collagen. We investigate heterotrimeric collagen interaction with HAP using Steering Molecular Dynamics to obtain the force-displacement relation as the collagen is undergoing shearing and peeling on the surface of HAP. Results indicate that the collagen requires 40% less force to separate form the HAP surface under peeling, when compared to shear loading conditions. In both shearing and peeling, the number of …

Utilizing Failure Information For Mission Assessment And Optimization For Complex Systems, Charlie Destefano

Graduate Theses and Dissertations

This paper presents a new failure analysis method, Failure Identification for Mission Analysis (FIMA), which performs a general failure analysis for the overall state of a system, as well as a mission-specific analysis that identifies how failures may have differing effects on the various mission tasks that a system must complete. The FIMA method is capable of being implemented at any point in the design process. During early design stages, the FIMA method will identify various qualitative failure scenarios based on programmed functional relationships and any number of initial failures wished to be simulated. The functional relationships for this method …

Wear Resistant Polydopamine/Ptfe Nanoparticle Composite Coating For Dry Lubrication Applications, Samuel George Beckford

Graduate Theses and Dissertations

This dissertation presents an investigation into the effect of nanoparticle fillers and a polydopamine adhesive primer on the tribological performance of thin PTFE films. The principal objective of this investigation was to reduce wear in PTFE films, an issue which precludes the use of PTFE films in tribological applications requiring high durability. The friction and wear of the composite films were evaluated using a ball-on-flat configuration in linear reciprocating motion. It was found that the use of a polydopamine adhesive primer reduces the wear of PTFE films more than 600 times. X-ray photoelectron spectroscopy (XPS) results show that a tenacious …

Highly Transparent, Self-Cleaning, And Antireflective Nanoparticle Coatings, Corey Seth Thompson

Graduate Theses and Dissertations

Current solar panel technologies require a sheet of glass to serve as both mechanical support and to protect the cells from the environment. The reflection from the glass sheet can reflect up to 8% of the incident light, reducing the power output of the panel. Antireflective coatings can be used to allow more light to enter the panel to be converted into usable electricity. However, no solid thin film materials exhibit a low enough index of refraction to serve as antireflective coatings for common solar glass. The main goal of this research was to investigate the self-cleaning, antifogging, and antireflective …

Atomistic Simulation And Virtual Diffraction Characterization Of Alumina Interfaces: Evaluating Structure And Stability For Predictive Physical Vapor Deposition Models, Shawn Patrick Coleman

Graduate Theses and Dissertations

The objectives of this work are to investigate the structure and energetic stability of different alumina (Al₂O₃) phases using atomistic simulation and virtual diffraction characterization. To meet these objectives, this research performs molecular statics and molecular dynamics simulations employing the reactive force-field (ReaxFF) potential to model bulk, interface, and surface structures in the θ-, γ-, κ-, and α-Al₂O₃ system. Simulations throughout this study are characterized using a new virtual diffraction algorithm, developed and implemented for this work, that creates both selected area electron diffraction (SAED) and x-ray diffraction (XRD) line profiles without assuming …

Electroencephalography(Eeg) Data Collection And Processing Through Machine Learning, Jayshree Desai

Graduate Theses and Dissertations

Machine learning methods are an excellent way for understanding the neural basis of human decision making. Some machine learning systems try to eradicate the need for human intuition in data analysis whereas others embrace a collective approach between humans and machines. The objective of this project is to collect Electroencephalography (EEG) signals through wireless sensors, and the process the collected signals through machine learning methods. The EEG data is collected using three EEG electrodes, each being the positive, negative and ground terminals respectively. Since the signal measures in the unit of micro-volts it needs to be amplified using amplifier circuit. …

Phase Transformation In Monolayer Molybdenum Disulphide With And Without Defects Under Tension Predicted By Atomistic Simulations, Khanh Quoc Dang

Graduate Theses and Dissertations

In addition to its use as a solid lubricant, molybdenum disulphide (MoS2) has gained recent attention as a possible substitute for silicon as it is increasingly difficult to keep shrinking down electronic devices made of silicon, the conventional electronic material. When thinned down to atomic thickness, monolayer MoS2 possesses very unique and promising electronic and electrical properties. Unlike electronic and electrical properties, knowledge of the mechanical properties and role of structural defects on these properties of monolayer MoS2 is unexplored. For this thesis, the two main objectives are (1) to gain insight about the failure mechanism of monolayer MoS2 by …

Ultrathin Ptfe Coating For Hypodermic Needles Enabled By Mussel-Inspired Pda Adhesive Layer, Spencer A. Foust

Mechanical Engineering Undergraduate Honors Theses

Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene, commonly known by its brand name Teflon®, which has many desirable properties such as a low coefficient of friction, high temperature resistance, anti-microbial properties, hydrophobicity, biocompatibility, and chemical resistance. One of the major challenges caused by the non-stick property of PTFE is its poor adhesion to substrates: PTFE coatings can be easily detached from surfaces under frictional forces and shear. The molecule polydopamine (PDA) was discovered as the key protein for adhesion between polytetrafluoroethylene and substrates of many materials, including steel, and thus has been used as a unique approach for coatings. …

The Design And Implementation Of A Multi-Chip Power Module Layout Synthesis Tool, Brett W. Shook

Graduate Theses and Dissertations

This thesis presents the design and implementation of a software tool, referred to as PowerSynth, which is used to synthesize multi-chip power module (MCPM) layouts and also aids in the overall design process. MCPMs allow power electronics systems to achieve higher efficiencies and reduced size, weight, and cost through the compact integration of devices into a single package. MCPM design is highly multidisciplinary which involves electrical, thermal, and mechanical performance considerations. Conventionally, the design process may require several iterations and multiple software modeling tools to create high performance MCPMs. The layout of an MCPM consists of a pattern of metal …

High Temperature Ltcc Based Sic Double-Sided Cooling Power Electronic Module, Hao Zhang

Graduate Theses and Dissertations

This objective of this dissertation research is to investigate a module packaging technology for high temperature double-sided cooling power electronic module application. A high-temperature wire-bondless low-temperature co-fired ceramic (LTCC) based double-sided cooling power electronic module was designed, simulated and fabricated. In this module, the conventional copper base plate is removed to reduce the thermal resistance between the device junctions to the heat sink and to improve the reliability of the module by eliminating the large area solder joint between the power substrate and the copper base plate. A low-temperature co-fired ceramic (LTCC) substrate with cavities and vias is used as …

Crack Growth Behavior Under Creep-Fatigue Conditions Using Compact And Double Edge Notch Tension-Compression Specimens, Santosh B. Narasimha Chary

Graduate Theses and Dissertations

The American Society for Testing and Materials (ASTM) has recently developed a new standard for creep-fatigue crack growth testing, E 2760-10, that supports testing compact specimens, C(T), under load controlled conditions. C(T) specimens are commonly used for fatigue and creep-fatigue crack growth testing under constant-load-amplitude conditions. The use of these specimens is limited to positive load ratios. They are also limited in the amount of crack growth data that can be developed at high stress intensity values due to accumulation of plastic and/or creep strains leading to ratcheting in the specimen. Testing under displacement control can potentially address these shortcomings …

Design And Construction Of An Experiment For The Investigation Of The Effects Of Gust On Flapping Wing Micro Air Vehicle Power Consumption, Brett Hiller

Mechanical Engineering Undergraduate Honors Theses

In recent years, the promising nature of flapping wing flight has led researchers to investigate the wing morphology and unsteady wing aerodynamics found in insects to aid in the design of modern micro air vehicles (MAVs). A high-fidelity flapping wing MAV could achieve high mobility, hovering stability, increased stealth, and efficient flight at low speeds. These characteristics offer a viable solution to the operational requirements for the typical hazardous and dynamic environments encountered during flight. While the kinematics and morphology of flapping wings are well-understood, significant research has yet to be completed with respect to the control and power requirements …

Optimization Of Automated Temperature Measurement System For Formed Meat Products, Tyler Norman

Mechanical Engineering Undergraduate Honors Theses

The Federal Safety and Inspection Services in accordance with United States Department of Agriculture require that formed meat products be cooked to a specified minimum internal temperature in order to eliminate the possible presence of harmful bacteria. The current system of verifying the internal temperatures of formed meat products consists of manually inserting a temperature probe into the selected sample as it exits the oven. Creating an automated system that measures and records the internal temperatures of formed meat samples as they exit the oven along a meat processing line has been the topic of an ongoing research. The most …

Exploration Into Properties Of Molybdenum Disulfide Using Atomistic Simulation, Joseph Simpson

Mechanical Engineering Undergraduate Honors Theses

Molybdenum disulfide (MoS2) has a lamellar crystal structure, which makes it ideal for use as a solid lubricant. Transmission electron microscope (TEM) images have shown that line defects exist within the lattice of mechanically deformed MoS2, but the physical mechanisms which lead to the formation of these defects are unknown. The two central objectives of this research are to use molecular dynamics simulations to study the effects of tensile deformation on both single layer and bulk MoS2 and explore the properties of line defects in an otherwise perfect lattice of MoS2. Under tensile loading, molecular dynamics simulations show a multi-stage …

Development Of A Pdms Based Micro Total Analysis System For Rapid Biomolecule Detection, Balaji Srinivasan Venkatesh

Graduate Theses and Dissertations

The emerging field of micro total analysis system powered by microfluidics is expected to revolutionize miniaturization and automation for point-of-care-testing systems which require quick, efficient and reproducible results. In the present study, a PDMS based micro total analysis system has been developed for rapid, multi-purpose, impedance based detection of biomolecules. The major components of the micro total analysis system include a micropump, micromixer, magnetic separator and interdigitated electrodes for impedance detection. Three designs of pneumatically actuated PDMS based micropumps were fabricated and tested. Based on the performance test results, one of the micropumps was selected for integration. The experimental results …

Design And Fundamental Understanding Of Minimum Quantity Lubrication (Mql) Assisted Grinding Using Advanced Nanolubricants, Parash Kalita

Graduate Theses and Dissertations

Abrasive grinding is widely used across manufacturing industry for finishing parts and components requiring smooth superficial textures and precise dimensional tolerances and accuracy. Unlike any other machining operations, the complex thermo-mechanical processes during grinding produce excessive friction-induced energy consumption, heat, and intense contact seizures. Lubrication and cooling from grinding fluids is crucial in minimizing the deleterious effects of friction and heat to maximize the output part quality and process efficiency. The conventional flood grinding approach of an uneconomical application of large quantities of chemically active fluids has been found ineffective to provide sufficient lubrication and produces waste streams and pollutants …

Enhanced Tribological Properties Of Surfaces Patterned With Su8/Dlc Microstructures, Luke Osborn

Inquiry: The University of Arkansas Undergraduate Research Journal

In tribology (the study of friction, wear, and lubrication), it is known that micro-textured surfaces can reduce friction due to decreased contact area between two surfaces. The problem with many micro-textures, however, is their inability to withstand significant amounts of wear, thus limiting their potential uses and overall effectiveness. In this study, connected and isolated microstructures of SU8, a negative tone photoresist, coated with and without diamond-like carbon (DLC), were designed to investigate the effects of these microstructures and DLC coating on the tribological performance of a surface. Friction and wear studies were conducted using a tribometer; surface topography and …

Valence-Length Correlations For Chemical Bonds From Atomic Orbital Exponents, F. D. Hardcastle

Journal of the Arkansas Academy of Science

Pauling’s empirical bond valence-length correlation has proven valuable because it offers a quick and convenient way of checking and evaluating molecular structures and determining oxidation states from measured bond lengths. In this study, a simplified quantum-mechanical approach was used to derive Pauling’s empirical bond valence-length relationship by considering overlap of hydrogen-like orbitals. An expression for the b “empirical” fitting parameter was derived in terms of atomic-orbital exponents. A new set of orbital exponents is presented using published atomic/covalent radii and a continuous function for the effective principal quantum. The b parameters calculated from the orbital exponents are consistent with bond …

Trajectory Generation For Stair Ascent Walking Using Rayleigh Oscillator, T. Afzal, Andrew B. Wright, Kamran Iqbal

Journal of the Arkansas Academy of Science

This paper describes a trajectory generation technique for stair-ascent walking. The knee, hip and ankle joint trajectory during stair ascent are generated using mutually coupled, nonlinear oscillators. The parameters of the oscillators are tuned using the harmonic balance method, which converts the nonlinear differential equations to a set of algebraic equations. Fourier analysis of data generated by stair-ascent walking is performed to extract the amplitude and the phase of the dominant frequency components for each joint trajectory. The solution for the oscillator is assumed to be a sinusoidal wave and then by harmonic balance method the parameters of the oscillator …