Open Access. Powered by Scholars. Published by Universities.®

Mechanical Engineering Commons™

Open Access. Powered by Scholars. Published by Universities.®

University of Arkansas, Fayetteville

Discipline
Keyword
Publication Year
Publication
Publication Type

Articles 271 - 300 of 310

Full-Text Articles in Mechanical Engineering

Development Of Mems-Based Corrosion Sensor, Feng Pan Dec 2012

Development Of Mems-Based Corrosion Sensor, Feng Pan

Graduate Theses and Dissertations

This research is to develop a MEMS-based corrosion sensor, which is used for monitoring uniform, galvanic corrosion occurring in infrastructures such as buildings, bridges. The corrosion sensor is made up of the composite of micro/nano metal particles with elastomers. The mechanism of corrosion sensor is based on the mass transport of corrosive species through the sensor matrix. When the metal particles in the matrix corrode, the electrical resistivity of the material increases due to increasing particle resistances or reduction of conducting pathways. The corrosion rate can be monitored by detecting the resistivity change in sensing elements. The life span of …

Go to article

Distribution Map Of Multi-Walled Carbon Nanotubes In A Refrigerant/Oil Mixture Within A 2.5 Ton Unitary Air-Conditioner, Warren Russell Long Dec 2012

Distribution Map Of Multi-Walled Carbon Nanotubes In A Refrigerant/Oil Mixture Within A 2.5 Ton Unitary Air-Conditioner, Warren Russell Long

Graduate Theses and Dissertations

In recent years, nanoparticles have received considerable attention as a potential additive to heat transfer fluids (i.e. refrigerant) in order to increase the heat transfer capabilities of these fluids. The potential of carbon nanotubes (CNTs) to exit the compressor, migrate throughout a vapor compression air conditioning system, and possibly foul the components of such a system was experimentally investigated in this research. Six grams of CNTs were dispersed in the polyol ester oil used by a 2.5 ton (8.79 kW) unitary air conditioning system, which was continuously operated for 168 hours. After this time, the unit was shut down and …

Go to article

Design, Fabrication, Testing Of Cnt Based Isfet And Characterization Of Nano/Bio Materials Using Afm, Zhuxin Dong Dec 2012

Design, Fabrication, Testing Of Cnt Based Isfet And Characterization Of Nano/Bio Materials Using Afm, Zhuxin Dong

Graduate Theses and Dissertations

A combination of Carbon Nanotubes (CNTs) and Ion Selective Field Effect Transistor (ISFET) is designed and experimentally verified in order to develop the next generation ion concentration sensing system. Micro Electro-Mechanical System (MEMS) fabrication techniques, such as photolithography, diffusion, evaporation, lift-off, packaging, etc., are required in the fabrication of the CNT-ISFET structure on p-type silicon wafers. In addition, Atomic Force Microscopy (AFM) based surface nanomachining is investigated and used for creating nanochannels on silicon surfaces. Since AFM based nanomanipulation and nanomachining is highly controllable, nanochannels are precisely scratched in the area between the source and drain of the FET where …

Go to article

Evaluation Of Shock Induced Spallation In Nanocrystalline Copper, Chase Philpot Dec 2012

Evaluation Of Shock Induced Spallation In Nanocrystalline Copper, Chase Philpot

Mechanical Engineering Undergraduate Honors Theses

This research uses atomistic simulations to examine the behavior of nanocrystalline Cu under impact at ballistic speeds. The advantage of using atomistic simulations to study shock induced deformation is that a real-time picture of the evolution of the microstructure can be attained, whereas experimentally this is not possible. Specifically, molecular dynamics simulations are used to build models of the material and run the simulations. Six cases are explored: Single crystal Cu loaded along the <100>, <110>, and <111> directions, and nanocrystalline samples with average grain diameters of 5, 10, and 15 nm. The target to flyer ratio is varied to generate …

Go to article

Computational Design Of The Electrical And Mechanical Performance Of Steerable Mems Antennas, Morgan Andrew Roddy Dec 2012

Computational Design Of The Electrical And Mechanical Performance Of Steerable Mems Antennas, Morgan Andrew Roddy

Graduate Theses and Dissertations

This thesis describes the origins, improvements, and variations of a broadband microwave antenna that can be beam-steered by a micro-electromechanical system (MEMS). The steerable MEMS antenna of this work was comprised of a planar antenna on top of a Silicon membrane. The membrane is etched to create a gimbal hinge structure and a platform which supported the antenna and gave it one or two degrees of freedom of rotation. The antennas presented were broadband and fed by a coplanar waveguide (CPW) transmission line which traversed the hinge structure. The antenna's orientation in space was designed to be changed through electrostatic …

Go to article

A Study On The Effects Of Solar Power, Jonathan Hayes May 2012

A Study On The Effects Of Solar Power, Jonathan Hayes

Electrical Engineering Undergraduate Honors Theses

The utilization of new and alternative energy sources, specifically solar energy, has been on the rise and will continue to grow as we attempt to diminish our use and dependency on older, nonrenewable energy sources. One of the biggest challenges involved with the use of solar energy, or renewable energy in general, is how to provide this energy for general public use. Some of the limiting factors to this are the efficiency in which solar power can be harvested and converted into usable energy, and the cost of the technology to do this. Recent technological developments have included the microinverter, …

Go to article

Energy Consumption And Greenhouse Gas Emissions From Commercial And Manufacturing Sectors Specific Studies On Hvac Equipment And Dairy Processing, Aik Jong Tan May 2012

Energy Consumption And Greenhouse Gas Emissions From Commercial And Manufacturing Sectors Specific Studies On Hvac Equipment And Dairy Processing, Aik Jong Tan

Graduate Theses and Dissertations

Commercial and manufacturing sectors in United States consumed approximately 50% of the total End use energy in 2010. In 2009, 81.5% of the greenhouse gas (GHG) emitted in the United States was energy related. From the broad aspects of commercial and manufacturing sectors; two relatively narrow and specific topics, commercial building's HVAC equipment and dairy processing were chosen to increase the understanding of the energy use and GHG emission in these two sectors. Few published studies related to these two specific areas are available. The first study in this thesis discussed the energy use and GHG emissions by HVAC equipment …

Go to article

Computer Modeling Of The Influence Of Structure Plan Areas On Tornado Forces, Nashmi Hassan M Alrasheedi May 2012

Computer Modeling Of The Influence Of Structure Plan Areas On Tornado Forces, Nashmi Hassan M Alrasheedi

Graduate Theses and Dissertations

The study of the conventional Straight Line (SL) wind flow dominates research into wind loads on structures. Most structure design takes into account only research into SL flow. Few researchers have studied tornado forces on buildings and attempted to distinguish between tornadic wind loads and SL flow loads. Using a computer simulation, this research addresses and distinguishes between the tornadic forces and SL forces on structures. In the numerical simulation, tornado forces and SL forces will be compared on large structure plan areas and on thin structure plan areas. Additionally this research investigates how the increase in the vortex strength …

Go to article

Design And Implementation Of A Small Electric Motor Dynamometer For Mechanical Engineering Undergraduate Laboratory, Aaron Farley May 2012

Design And Implementation Of A Small Electric Motor Dynamometer For Mechanical Engineering Undergraduate Laboratory, Aaron Farley

Graduate Theses and Dissertations

This thesis set out to design and implement a new experiment for use in the second lab of the laboratory curriculum in the Mechanical Engineering Department at the University of Arkansas in Fayetteville, AR. The second of three labs typically consists of data acquisition and the real world measurements of concepts learned in the classes at the freshman and sophomore level. This small electric motor dynamometer was designed to be a table top lab setup allowing students to familiarize themselves with forces, torques, angular velocity and the sensors used to measure those quantities, i.e. load cells and optical encoders. The …

Go to article

Design Of Orbital Maneuvers With Aeroassisted Cubesatellites, Stephanie Clark May 2012

Design Of Orbital Maneuvers With Aeroassisted Cubesatellites, Stephanie Clark

Graduate Theses and Dissertations

Recent advances within the field of cube satellite technology has allowed for the possible development of a maneuver that utilizes a satellite's Low Earth Orbit (LEO) and increased atmospheric density to effectively use lift and drag to implement a noncoplanar orbital maneuver. Noncoplanar maneuvers typically require large quantities of propellant due to the large delta-v that is required. However, similar maneuvers using perturbing forces require little or no propellant to create the delta-v required. This research reported here studied on the effects of lift on orbital changes, those of noncoplanar types in particular, for small satellites without orbital maneuvering thrusters. …

Go to article

Comparative Fatigue Analysis Of Metals And Polymers For Engineering Applications, Monica Jones May 2012

Comparative Fatigue Analysis Of Metals And Polymers For Engineering Applications, Monica Jones

Mechanical Engineering Undergraduate Honors Theses

Rapid prototype polymers are becoming increasingly popular for engineering applications, particularly during the design phase as a quick check for size and fit; however they are not currently widely-used for load-bearing applications. Current research at the University of Arkansas Department of Mechanical Engineering focused on rapid prototyped polymers by doing cyclical tensile testing. The results were analyzed for strain energy and fatigue data. When cycling at lower percentages of ultimate stress, unusual strain energy patterns were observed. This research details testing of metals in order to compare strain energy patterns to those of the rapid prototype polymers.

Go to article

Enhanced Tribological Properties Of Surfaces Patterned With Dlc/Su8 Microstructures, Luke Osborn May 2012

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

Mechanical Engineering Undergraduate Honors Theses

Textured surfaces can reduce friction due to decreased contact area between two surfaces, and could therefore increase the reliability of micro-electro-mechanical systems (MEMS). The problem with some microtextures is their inability to withstand significant amounts of wear, often deforming or breaking, thus limiting their potential uses and overall effectiveness. In this study, connected and isolated SU8 microstructures with and without diamond-like coating (DLC) were designed to investigate the effects of these microstructures on the tribological performance of a surface. Friction studies were conducted using a tribometer, while surface topography and wear were characterized by scanning electron microscopy (SEM), optical microscope, …

Go to article

Surface Wetting And Friction Studies Of Nano-Engineered Surfaces On Copper Substrate, Julius Sheldon Morehead Dec 2011

Surface Wetting And Friction Studies Of Nano-Engineered Surfaces On Copper Substrate, Julius Sheldon Morehead

Graduate Theses and Dissertations

Nano-engineered-textures on a material surface can dramatically improve the wetting and non-wetting properties of a surface, and they also show promise to address friction issues that affect surfaces in contact. In this work, aluminum-induced crystallization (AIC) of amorphous silicon (a-Si) was used to produce nano-textures on copper (Cu) substrates. A study was performed to examine the effects of changing the annealing conditions and a-Si thickness on nano-texture formation. The creation of various nano-topographies and chemically modifying them using octafluorocyclobutane (C4F8) was performed to control hydrophilicity, hydrophobicity, and oil affinity of nano-textured surfaces. A video-based contact angle measurement system was used …

Go to article

Development Of A Structured Concrete Thermocline Thermal Energy Storage System, Bradley M. Brown Dec 2011

Development Of A Structured Concrete Thermocline Thermal Energy Storage System, Bradley M. Brown

Graduate Theses and Dissertations

The past couple of decades have shown a concern when considering the way the world obtains its power. The focus has been switching from fossil fuels that have been used for hundreds of years to renewable energy sources, such as the sun. Solar energy is readily and infinitely available for harnessing. One problem with solar energy, though, is its inability to be used during the night time and during cloud covered weather. A solution to this problem is the use of energy storage mechanisms. For solar plants that use solar thermal energy (concentrating solar power plants), thermal energy storage (TES) …

Go to article

Development Of Spray Cooling For High Heat Flux Electronics, Jeremy Scott Junghans Dec 2011

Development Of Spray Cooling For High Heat Flux Electronics, Jeremy Scott Junghans

Graduate Theses and Dissertations

The thermal demands of modern day electronic systems require innovative thermal solutions. Spray cooling has proven to be able to cool heat fluxes orders of magnitude higher than traditional cooling methodologies. This work includes a comparison of spray cooling to standard thermal management methodologies. Key system parameters and considerations are discussed. The properties of available packaging materials and their effect on the reliability of a spray cooled system are presented. Parameters such as fluid temperature, droplet size, fluid velocity and flow rate all directly impact performance and are detailed in this work. Finally, results from of a wide range of …

Go to article

Understanding The Role Of A Bio-Inspired Surface Modification For Delayed Icing, Clayton Schenk Aug 2011

Understanding The Role Of A Bio-Inspired Surface Modification For Delayed Icing, Clayton Schenk

Graduate Theses and Dissertations

Atmospheric icing event is problematic for outdoor structures because it can damage, slow, impede, and danger general routine. For a wind turbine blade, it can damage, disrupt movement, and cause potentially dangerous ice throw. Anti-icing based on a surface texture is advantageous due to the low cost of maintenance and there is no additional requirement of energy output for preventing the icing problem. This work is based on the biomimicry of the superhydrophobic nature of the lotus leaf, whereas the limited wettability supports the water to flow freely from the surface structure. The phenomenon is based on a morphology and …

Go to article

A Solid State Nitrogen Gas Generating Chip And Applications For Picosatellites, Kyle Godin Aug 2011

A Solid State Nitrogen Gas Generating Chip And Applications For Picosatellites, Kyle Godin

Graduate Theses and Dissertations

A microscale gas generating chip has many applications; in this study, applications relating to picosatellites have been considered. Cube satellites, a type of picosatellite, are of mass around one kilogram and side length 10cm x 10cm x 10cm. Their launches are becoming more numerous since their debut ten years ago. Their low cost and deployment system makes space accessible to agencies hitherto barred from it, such as universities and small governments. However, their power, mass, and volume budget is extremely tight. A microscale gas chip could compete with other designs for attitude control devices, most not flown yet as cube …

Go to article

Gimbaled Permanent Magnet-Based Attitude Control For Pico/Nano-Satellites, Rex Bair May 2011

Gimbaled Permanent Magnet-Based Attitude Control For Pico/Nano-Satellites, Rex Bair

Mechanical Engineering Undergraduate Honors Theses

As man-made satellites grow continually smaller and smaller, new, lower mass, volume, and power solutions must be devised to give these satellites the same performance capabilities as larger satellites. One subsystem that is especially difficult to shrink is the Attitude Determination and Control System (ADACS), which is used to position the satellite in a given orientation with respect to a specific reference frame. This paper explores a novel mechanism which combines both of these functions into one device. A permanent magnet is used in conjunction with the geomagnetic reference frame to provide magnetic torque to change the spacecraft's attitude. By …

Go to article

Carbon Nanotube Based Ion Sensitive Field Effect Transistor, Matthew Margis May 2011

Carbon Nanotube Based Ion Sensitive Field Effect Transistor, Matthew Margis

Mechanical Engineering Undergraduate Honors Theses

Carbon nanotubes (CNTs) have been the subject of much research in the past two decades. Due to their extraordinary mechanical and electrical properties, CNTs are ideal candidates for various sensors and electronic device applications. The purpose of this research is to overcome the difficulties in separating and aligning CNTs so that they can be implemented in an ion sensitive field effect transistor (ISFET). A solution to the alignment process has been presented that involves cutting nano channels on a microelectrode chip with an Atomic Force Microscope (AFM) in order to nanomanipulate the CNTs into the nano channels. Upon successfully cutting …

Go to article

Spectral Characterization Of Venusian Surface Mineralogy, Johnathon Conley May 2011

Spectral Characterization Of Venusian Surface Mineralogy, Johnathon Conley

Mechanical Engineering Undergraduate Honors Theses

While the atmospheric chemical composition of the Venusian atmosphere has been characterized at length by probes and ground-based equipment, the surface mineralogy of Venus is not yet well understood. The extremely thick atmosphere of Venus shields the surface from direct observation. While radar imaging of the surface reveals surface morphology, surface composition is difficult to characterize at a distance. Observation is also difficult due to the intense temperature (approximately 480°C) and pressure (approximately 90 atm) found on the surface. This has prompted NASA and other institutions around the world to begin planning for new missions to land on the surface …

Go to article

Tribological Behavior Of Lubricants With And Without Nanoadditives: A Compartive Study, Kevin Carlson May 2011

Tribological Behavior Of Lubricants With And Without Nanoadditives: A Compartive Study, Kevin Carlson

Mechanical Engineering Undergraduate Honors Theses

Nano particle based additives have become a main focal point in the design of new lubricants, in order to better achieve reduction in both friction and wear. Previous research has led to the development of one such lubricant known as NanoGlide® by a company called NanoMech, Inc. The success of this initial lubricant design encouraged the research and potential development of new formulations of nano particle based lubricants by NanoMech, Inc. Using tribological testing, and Scanning Electron Microscopy (SEM), this research analyzed the behavior and performance of three new nano additives (NanoGlide 1, NanoGlide2, and NanoGlide3) in three different lubricant …

Go to article

The Effects Of Roof Solar Absorptance On Building Energy Performance In A Variety Of U.S. Climate Zones, Zachary Eubanks Dec 2010

The Effects Of Roof Solar Absorptance On Building Energy Performance In A Variety Of U.S. Climate Zones, Zachary Eubanks

Mechanical Engineering Undergraduate Honors Theses

The solar absorptance of a roof surface directly affects the solar heat gain through the roof. It has been shown that buildings in hot climates benefit from roofs with low absorptance. Cold and moderate climates have received less attention in previous studies. This paper simulates the effects on annual energy use, carbon dioxide emission, and utility cost of varying the solar absorptance of warehouse and small office building roofs in a wide variety of U.S. climate zones using EnergyPlus software and the DOE Commercial Building Benchmark Models. Results show that the optimum absorptance not only depends on the climate zone, …

Go to article

Factors Affecting Redox Magnetohydrodynamics For Flow In Small Volumes, Matthew D. Gerner Aug 2009

Factors Affecting Redox Magnetohydrodynamics For Flow In Small Volumes, Matthew D. Gerner

Graduate Theses and Dissertations

Lab-on-a-chip technologies offer the possibility of developing analytical devices that are low-cost, portable, disposable, fast, and operable by non-technical personnel. Such devices require automated methods to manipulate ultra-small volumes (picoliters) of samples and solution, including pumping, stirring, and positioning. Current methods for ultra-small volume microfluidics have limitations that restrict their use including high voltage requirements, disadvantageous flow profiles or rates, and relatively complicated fabrication due to mechanical parts. Redox magnetohydrodyanmics (RMHD) that utilizes permanent magnets for portability shows promise as a micropump with ease of switching flow direction, no moving parts, compatibility with both aqueous and non-aqueous solutions, low voltages …

Go to article

Automated Flight Through Inertial Navigation And Digital Fly-By-Wire Systems, Aaron French May 2009

Automated Flight Through Inertial Navigation And Digital Fly-By-Wire Systems, Aaron French

Mechanical Engineering Undergraduate Honors Theses

With technology advancing by leaps and bounds by the year, the uses of Unmanned Aerial Vehicles are becoming more apparent. The possibilities for an aerial vehicle that is fully autonomous are endless. Such aerial vehicles could divert manpower to humanitarian efforts, airlift, and other non‐attack operations. Leaders can put their focus elsewhere on the battlefield with the knowledge that the skies over their heads will be well guarded. These desires give life to projects such as this. No advancement in civilization has ever been made without the collective revolutionary research of great minds, trial by fire, and daring to dream.

Go to article

Free Fridays: An Alternative Way To Conserve Energy, Lauren Kuenzel May 2009

Free Fridays: An Alternative Way To Conserve Energy, Lauren Kuenzel

Mechanical Engineering Undergraduate Honors Theses

In February 2007, the University of Arkansas at Fayetteville (UAF) signed the President's Climate Commitment to set a goal of becoming climate neutral. A large part of any strategy to become climate neutral includes energy conservation. In light of that, a four-day school week is proposed for UAF as an alternative energy savings possibility. This reduced schedule has been applied to K-12 schools and state government institutions, but not yet to universities. Along with numerous benefits such as energy conservation of buildings on the free day, a more effective use of time and building space and the positive emotional repercussions …

Go to article

Nickel-Induced Crystallization Of Amorphous Silicon, Robert Fleming May 2009

Nickel-Induced Crystallization Of Amorphous Silicon, Robert Fleming

Mechanical Engineering Undergraduate Honors Theses

One- and two-dimensional silicon nanostructures, such as nanodots, nanowires, and surface topography, have potential uses in a variety of fields, including microelectronics, photonics, and tribology. In this thesis research, nickel-induced crystallization (NIC) of amorphous silicon (a-Si) was investigated to determine the suitability of NIC of a-Si to produce silicon nanostructures on silicon substrates. The results show that formation of both surface topography and nanowires is possible with NIC of a-Si. In addition, the formation of nanostructures is very sensitive to Ni thickness, and the resulting nanostructures and films display a high degree of repeatability. The results obtained from this research …

Go to article

Development Of Miniature Hybrid Rockets For Orbital Upkeep And Transfer Applications In Nano/Pico-Satellites, Derek Willingham May 2008

Development Of Miniature Hybrid Rockets For Orbital Upkeep And Transfer Applications In Nano/Pico-Satellites, Derek Willingham

Mechanical Engineering Undergraduate Honors Theses

This research has developed and constructed a successful miniature hybrid rocket test assembly for research into hybrid rocket scaling issues. It is hoped that such systems will find eventual integration into small satellites. The test assembly houses 3" fuel grains and provides an inlet for gaseous oxidizer. Although far from complete, preliminary data were taken with PMMA and GOx and some useful conclusions were drawn that will benefit future research into this topic. Fuel grains with combustion chambers whose diameters range from 1/16" to 3/8" were tested at different flow rates and thrust data gathered. Maximum flow information was gathered …

Go to article

Benefits Of Leed Designs In Arkansas K-12 Schools, Philip Thrift May 2008

Benefits Of Leed Designs In Arkansas K-12 Schools, Philip Thrift

Mechanical Engineering Undergraduate Honors Theses

This paper provides and evaluation of an existing LEED certified sustainable green building for energy-efficiency, environmental impact, economic value, and occupant health. The new Bethel Middle School located in Bryant, Arkansas was the first LEED (Leadership in Energy and Environmental Design) certified public school building in the state. Based on actual building specifications and validated with the first year's utility bills, a simulation model was used to evaluate various design aspects of the school building. The building's baseline energy usage was compared with numerous energy and environmental scenarios. Results include both environmental and economic assessments. Overall, the study found that …

Go to article

Restart Capabilities Of Hybrid Rocket Motor Utilizing Gaseous Propane And Oxygen Injection System, Joseph Gracy May 2008

Restart Capabilities Of Hybrid Rocket Motor Utilizing Gaseous Propane And Oxygen Injection System, Joseph Gracy

Mechanical Engineering Undergraduate Honors Theses

Hybrid rockets have become an increasingly popular application in professional and amateur rocketry for their outstanding performance and reliability. An issue pressing the marketability and functionality of these rockets is the ability to restart with an exclusive system after primary ignition. Research and development of a system that can be used reliably in either application to achieve restart under various conditions has been made recently using dual injection of GOX and C3H8 using a 200kV ignition system while implementing a polymethylmethacrylate (PMMA) formable polymer as primary fuel. The system used a manual valve arrangement for control. The design features most …

Go to article

Numerical Thermal-Fluid Analysis Of A Liquid Cooled Novel 3-D Electronic Package, Aron Meyer May 2008

Numerical Thermal-Fluid Analysis Of A Liquid Cooled Novel 3-D Electronic Package, Aron Meyer

Mechanical Engineering Undergraduate Honors Theses

The need for smaller and more powerful processors has become more and more important in recent times. This need is nowhere more evident than in the military where the ability to process large amounts of data quickly and accurately can save lives. So the University of Arkansas has been researching a new chip design, the 3-D stack-up thru-silicon via chip. This has several benefits over the traditional chip designs, but comes at the price of having more heat to be dissipated. Due to the need to dissipate up to 20 watts per wafer a liquid cooling system was used with …

Go to article

First Prev Next Last