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Articles 2821 - 2850 of 2901

Full-Text Articles in Engineering

Design Of A Supersonic Wind Tunnel, Jay Pascual May 2007

Design Of A Supersonic Wind Tunnel, Jay Pascual

Mechanical Engineering Undergraduate Honors Theses

A supersonic wind tunnel was to be designed using the existing compressed air tank at the Mechanical Engineering building at the University of Arkansas. A throat area of 0.000375 m2 was used in the design process. The properties of the air were calculated using various Mach numbers. These results are used to determine if a wind tunnel of Mach numbers between one and five can be built at the University of Arkansas and can run for a sufficient amount of time. Also, the dimensions of the supersonic wind tunnel were calculated for these various Mach numbers.


Improvement To The Data Logging Capability Of A Cough Monitoring System, Matthew Barlow Jan 2007

Improvement To The Data Logging Capability Of A Cough Monitoring System, Matthew Barlow

Inquiry: The University of Arkansas Undergraduate Research Journal

Data logging capability of a previously developed self contained cough recorder using an accelerometer as the sensing element is improved by using a secure digital memory card for later retrieval on a computer. Firmware is developed to enhance the functionality of the cough recorder. Existing libraries are modified for increased write rates. Increased writing speed allows 8-bit sampling at rates exceeding 8kHz, allowing for detailed time and frequency domain analysis. Additional features have also been developed to enable easy management of recordings, such as a file system compatibility with Microsoft Windows., and unique file names for each recording.


Measurement And Modeling Of Light Transmission Through Turbid Media, Alois (Al) J. Adams, Michael Fahrenwald, Long Do Jan 2007

Measurement And Modeling Of Light Transmission Through Turbid Media, Alois (Al) J. Adams, Michael Fahrenwald, Long Do

Journal of the Arkansas Academy of Science

No abstract provided.


Design Of Novel Experimental Techniques To Investigate The Formation Of Nanoparticle-Based Tribofilms, Corey Thompson Dec 2006

Design Of Novel Experimental Techniques To Investigate The Formation Of Nanoparticle-Based Tribofilms, Corey Thompson

Mechanical Engineering Undergraduate Honors Theses

Nano-engineered lubricant additives such as organically-active nanoparticles of molybdenum disulphide (Hybrid-milled MoS2) are becoming increasingly popular in the fight against harsh friction and wear that occurs during boundary-layer lubrication. A previous paper (Verma, 2007), has reported improvements in both coefficient of friction and wear scar diameter; however, there exists very little data concerning the methods through which this improvement is achieved. Using techniques such as atomic force microscopy (AFM), nanoindentation, scanning electron microscopy (SEM), focused ion beam (FIB), high resolution transmission electron microscopy (HRTEM) as well as tribometery, the chemical and mechanical characteristics of the nanoparticle based tribofilm are characterized. …


Ultrafiltration Membrane Process For Pyrogen Removal In The Preparation Of Water For Injection (Wfi), Thet N. Soe Jan 2006

Ultrafiltration Membrane Process For Pyrogen Removal In The Preparation Of Water For Injection (Wfi), Thet N. Soe

Inquiry: The University of Arkansas Undergraduate Research Journal

An artificial kidney process based on ultrafiltration (called hemodiafiltration) more effectively removes blood toxins, particularly those of higher molecular weight, than conventional dialysis. In hemodiafiltration, replacement liquid must be added directly to the patient's blood to replace liquid filtered out of the blood in the ultrafiltration cartridge. This replacement liquid is made up of' "water for injection" (WFI) and other components such as salts and glucose. WFI is produced either by distillation or reverse osmosis and has a cost of $1.00 per liter. A patient with kidney problems would require three hemodiafiltration treatments per week, each requiring 70-80 liters of …


Evaluation Of Rice Hulls As A Lignocellulosic Substitute In Wood Plastic Composites, P. Jack Bourne Jan 2006

Evaluation Of Rice Hulls As A Lignocellulosic Substitute In Wood Plastic Composites, P. Jack Bourne

Inquiry: The University of Arkansas Undergraduate Research Journal

Rising raw material costs and shortage of woody materials necessitate alternative sources for lignocellulosic material in wood plastic composites (WPC). This study was conducted to evaluate rice hull (RH), an agricultural residue, as a cellulosic substitute in WPC. Samples were fabricated with approximately 4% zinc stearate, 48% high-density polyethylene obtained from recycled plastics and 48% lignocellulosic material by mass. The composition of the lignocellulosic material was changed from 0 to 100% RH at 20% increments while the remainder was wood flour. The extruded sampled were tested for mechanical properties such as specific gravity, water absorption, linear coefficients of thermal expansion, …


A Study Of The Impact Of Prognostic Errors On System Performance, Mauricio Carrasco Jan 2006

A Study Of The Impact Of Prognostic Errors On System Performance, Mauricio Carrasco

Inquiry: The University of Arkansas Undergraduate Research Journal

Condition-based maintenance is growing in popularity as a means of improving equipment maintenance efficiency. Whether it be the maintenance of an airplane, a computer system, or any type of physical system, the prognostic tools associated with condition-based maintenance are subject to statistical error. These errors can lead to unnecessary preventive maintenance due to underestimation of system remaining life and unnecessary system failures due to overestimation of system remaining life. What is not clear is if these statistical errors outweigh the benefits of a condition-based maintenance policy. This study attempts to address this concern through the evaluation and comparison of three …


Use Of Calcium Hypochlorite As A Sanitizer For Seeds Used For Sprouting: Task #2; Impact: Improved Alfalfa Decontamination Technologies, Emily Damron, Carrie Klein, Melissa Leach, Jordan Mourot, Tom Murphy, Amy Seamans, Ryan Wilson Jan 2005

Use Of Calcium Hypochlorite As A Sanitizer For Seeds Used For Sprouting: Task #2; Impact: Improved Alfalfa Decontamination Technologies, Emily Damron, Carrie Klein, Melissa Leach, Jordan Mourot, Tom Murphy, Amy Seamans, Ryan Wilson

Inquiry: The University of Arkansas Undergraduate Research Journal

Consumption of raw or lightly cooked alfalfa sprouts has been a concern of the U.S. Food and Drug Administration (FDA) in recent years due to connections between sprouts and foodborne illnesses. Researchers have identified, contaminated seeds as the primary source of alfalfa sprouts contamination. Contamination of alfalfa seeds can originate in the field, harvesting, storing, or sprouting. Two pathogens of particular concern on alfalfa seeds are Escherichia coli 0157:H7 (E. coli) and Salmonella. These pathogens are capable of producing biofilms that provide protection for individual cells and allow for survival in otherwise hostile environments, including some disinfectant washes. Other factors …


Parameter Extraction Software For Silicon Carbide Schottky, Merged Pin Schottky And Pin Power Diode Models, Edgar Cilio Jan 2004

Parameter Extraction Software For Silicon Carbide Schottky, Merged Pin Schottky And Pin Power Diode Models, Edgar Cilio

Inquiry: The University of Arkansas Undergraduate Research Journal

A software program for on-state parameter extraction is presented for the realization of a high quality model for SiC Schottky, Merged PiN Schottky, and PiN Power diodes based on McNutt and Mantooth's Comprehensive SiC Diode model [ 1 ].


A Comparative Evaluation Of .Net Remoting And Java Rmi, Taneem Ibrahim Jan 2004

A Comparative Evaluation Of .Net Remoting And Java Rmi, Taneem Ibrahim

Inquiry: The University of Arkansas Undergraduate Research Journal

Distributed application technologies such as Micrososoft.NET Remoting, and Java Remote Method Invocation (RMI) have evolved over many years to keep up with the constantly increasing requirements of the enterprise. In the broadest sense, a distributed application is one in which the application processing is divided among two or more machines. Distributed middleware technologies have made significant progress over the last decade. Although Remoting and RMI are the two of most popular contemporary middleware technologies, little literature exists that compares them. In this paper, we study the issues involved in designing a distributed system using Java RMI and Microsoft.NET Remoting. In …


Investigation On How To Improve Latent Semantic Analysis Performance, Thao Doan Jan 2003

Investigation On How To Improve Latent Semantic Analysis Performance, Thao Doan

Inquiry: The University of Arkansas Undergraduate Research Journal

Latent Semantic Analysis (LSA) is a matching technique capable of recognizing the semantic relationships of data that ordinary techniques such as string matching cannot. This is especially valuable for data integration applications, like those of Acxiom, where data items are usually related by context, rather than in a literal match. Even though it has been shown that LSA is 30% more effective in finding and ranking relevant pieces of information than existing string-by-string matching techniques (Deerwester et al., 1990; Dumais, 1995), the performance of the LSA seems to be affected by the presence of shared words, or “noise”, in data. …


Computer Modeling Of Tornado Forces On A Cubic Building Using Large Eddy Simulation, R. Panneer Selvam, Paul C. Millett Jan 2003

Computer Modeling Of Tornado Forces On A Cubic Building Using Large Eddy Simulation, R. Panneer Selvam, Paul C. Millett

Journal of the Arkansas Academy of Science

A tornado changes its wind speed and direction rapidly; therefore, it is difficult to study the effects of a tornado on buildings in a wind tunnel. The status of the tornado-structure interaction and various models of the tornado wind field found in literature are surveyed. Three dimensional computer modeling work using the turbulence model based on large eddy simulation is presented. The effect of a tornado on a cubic building is considered for this study. The Navier-Stokes (NS) equations are approximated by the finite difference method and solved by an implicit procedure. The force coefficients are plotted in time to …


Interpolation Techniques For Overset Grids, Paul S. Sherman, Nathan B. Edgar Jan 2003

Interpolation Techniques For Overset Grids, Paul S. Sherman, Nathan B. Edgar

Journal of the Arkansas Academy of Science

The use of finite difference schemes in computational aeroacoustics requires the use of structured grids incomputational space. Complex geometries in the physical space can be modeled using multiple overlapping grids that are transformed into computational space. In this work, finite difference schemes are used that necessitate the addition of psuedo- or ghost-points in the overlap region of the grids for closure of the difference stencil. The functional values at these ghost points must be approximated from the values at the original grid points. This paper investigates interpolation techniques for these overset grids. An n th order interpolation scheme using Lagrange …


Novel High Frequency Silicon Carbide Static Induction Transistor-Based Test-Bed For The Acquisition Of Sic Power Device Reverse Recovery Characteristics, Kevin M. Speer, Ty R. Mcnutt, Alexander B. Lostetter, H. Alan Mantooth, Kraig J. Olejniczak Jan 2003

Novel High Frequency Silicon Carbide Static Induction Transistor-Based Test-Bed For The Acquisition Of Sic Power Device Reverse Recovery Characteristics, Kevin M. Speer, Ty R. Mcnutt, Alexander B. Lostetter, H. Alan Mantooth, Kraig J. Olejniczak

Journal of the Arkansas Academy of Science

A test system is presented that utilizes a high-frequency Silicon Carbide (SiC) Static Induction Transistor (SIT) in place of the traditional MOSFET to test reverse recovery characteristics for the new class of SiC power diodes. An easily implementable drive circuit is presented that can drive the high-frequency SIT. The SiC SIT is also compared to a commonly used Si MOSFET in the test circuit application.


Parameter Extraction Software For Compact Diode Model, Maruf Hossain, Edgar Cilio, Ty R. Mcnutt, Alexander B. Lostetter, H. Alan Mantooth Jan 2003

Parameter Extraction Software For Compact Diode Model, Maruf Hossain, Edgar Cilio, Ty R. Mcnutt, Alexander B. Lostetter, H. Alan Mantooth

Journal of the Arkansas Academy of Science

No abstract provided.


Testing And Modeling Electrical Characteristics Of Novel Silicon Carbide (Sic) Static Induction Transistors (Sits), Avinash S. Kashyap, Sharmila D. Mangan Lal, Ty R. Mcnutt, Alexander B. Lostetter, H. Alan Mantooth Jan 2003

Testing And Modeling Electrical Characteristics Of Novel Silicon Carbide (Sic) Static Induction Transistors (Sits), Avinash S. Kashyap, Sharmila D. Mangan Lal, Ty R. Mcnutt, Alexander B. Lostetter, H. Alan Mantooth

Journal of the Arkansas Academy of Science

No abstract provided.


The Need For Pfc Abatement In Semiconductor Manufacturing, Mohsen Manesh, Brian Kendrick Jan 2002

The Need For Pfc Abatement In Semiconductor Manufacturing, Mohsen Manesh, Brian Kendrick

Inquiry: The University of Arkansas Undergraduate Research Journal

Perfluorocompounds (PFCs) are highly stable chemical compounds used in two integral steps of semiconductor manufacturing: chemical vapor deposition (CVD) chambers and etch chambers. Unfortunately, PFCs are also greenhouse gases linked to global warming. This, combined with their long atmospheric lifetimes gives them global warming potentials much higher than C02 the principal greenhouse gas. In a series of voluntary agreements with the United States and other national governments, the worldwide semiconductor industry has set a goal of reducing PFC emissions to 90% of their 1995 levels. To reach this goal, researchers have explored four main methods of reduction: substitution of PFCs, …


Extraction Of Silymarin Compounds From Milk Thistle (Silybum Marianum) Seed Using Hot, Liquid Water As The Solvent, J.F. Alvarez Barreto Jan 2002

Extraction Of Silymarin Compounds From Milk Thistle (Silybum Marianum) Seed Using Hot, Liquid Water As The Solvent, J.F. Alvarez Barreto

Inquiry: The University of Arkansas Undergraduate Research Journal

High value specialty chemicals are usually obtained from natural products by extracting with generally regarded as safe (GRAS) solvents. Because organic solvents are quite often used, high operating and disposal costs often occur. When compared to traditional solvents, water can be viewed as an interesting alternative because of its low operating and disposal costs. Milk thistle contains compounds (taxifolin, silychristin, silydianin, silybinin A and silybinin B) that display hepatoxic protection properties. This paper examines the batch extraction of silymarin compounds from milk thistle seed meal in 50'C, 70'C, 85'C and 100'C water as a function of time. For taxifolin, silychristin, …


Stability And Optimization Of Photoconductivity In Thermally Vacuum Evaporated Indium (Iii) Sulfide Thin Films, Gustavo Rehder, Robert Engelken, Randy Stidham, Richard Tanner, Lee Ketchum, Anil Baral Jan 2002

Stability And Optimization Of Photoconductivity In Thermally Vacuum Evaporated Indium (Iii) Sulfide Thin Films, Gustavo Rehder, Robert Engelken, Randy Stidham, Richard Tanner, Lee Ketchum, Anil Baral

Journal of the Arkansas Academy of Science

Long term stability of photosensitivity versus time in indium (III) sulfide thin films thermally vacuum evaporated onto photocell-patterned printed circuit boards varies sensitively with several factors including contact metal type, contact metal diffusion and electromigration into the semiconductor, doping, and encapsulation method. Because of the significant photoconductivity and relative low toxicity and environmental impact of this compound semiconductor, it is important to better characterize these dependences toward commercial applications. We will report on measurements of photoconductivity vs. time as functions of such factors and evolving methods to stabilize this photoconductivity.


Modeling Of Electrofusion Coils For Performance Optimization, Steve Farmer, Robert A. Sims Jan 2002

Modeling Of Electrofusion Coils For Performance Optimization, Steve Farmer, Robert A. Sims

Journal of the Arkansas Academy of Science

Modeling physical parameters provides a virtual design environment allowing the confirmation and optimization of electrofusion characteristics. Finite element incorporate physical parameters and their interactions along common boundaries defined within a model geometry. The electrofusion of polymeric piping is a widely accepted means of assembling piping systems with zero-leakage integrity. The key parameters in the fusion process are the coil resistance, the current passing through the coil and the time the current is applied. Modeling the coil and applying current to the model is accomplished using the MATLABpartial differential equations (PDE) toolbox. This paper presents the method of modeling and the …


Co-Polymers Of Furan With Pyrrole Or Thiophene: A Synthetic Study, Rose M. Mcconnell, Walter E. Godwin, Susan E. Baker, Kenya Powell, Martha Baskett, Amy Morara, Xiadong Ma Jan 2002

Co-Polymers Of Furan With Pyrrole Or Thiophene: A Synthetic Study, Rose M. Mcconnell, Walter E. Godwin, Susan E. Baker, Kenya Powell, Martha Baskett, Amy Morara, Xiadong Ma

Journal of the Arkansas Academy of Science

The use of conductive polymers as a substitute for metallic conductors and semiconductors has attracted much attention in the literature. In particular, aromatic heterocyclic polymers constitute an important class since they possess chemical and electrical stability in both the oxidized (doped) and neutral (undoped) state. Doping a polymer allows one to vary its electrical, mechanical, optical, and thermal properties. The properties of these polymers are promising for their many technological uses such as antistatic coatings, solar cells, and electronic devises. Polyfuran is among the least common heterocyclic polymers. Polyfuran has been reported to be much less stable that either polypyrrole …


Pressure And Flow Validation Of A Second Generation Gas Extraction Probe For A Hybrid Rocket Gas Extraction System, Constance Meadors, Andrew B. Wright Jan 2002

Pressure And Flow Validation Of A Second Generation Gas Extraction Probe For A Hybrid Rocket Gas Extraction System, Constance Meadors, Andrew B. Wright

Journal of the Arkansas Academy of Science

A gas extraction system (GES) has been designed for use with the hybrid rocket facility at the University of Arkansas at Little Rock (UALR) for spectroscopic analysis of rocket plumes. While monitoring gas flow-rate and pressure, the GES extracts gases from the hybrid rocket plume and transports them to a mass spectrometer. This paper describes design and construction of a gas extraction probe (GEP) prototype capable of extracting gases directly from the plume. Gas dynamics equations were used to design two venturi-type GEP, converging and converging-diverging. The probe was tested with air to verify design assumptions. Flow rate through the …


A Method Of Implementing The Interleaver In 3g Wireless Communication Systems For Randomization Of Burst Errors, Eric Duquette Jan 2001

A Method Of Implementing The Interleaver In 3g Wireless Communication Systems For Randomization Of Burst Errors, Eric Duquette

Inquiry: The University of Arkansas Undergraduate Research Journal

In less than a year or two, third generation ( 3G) wireless communication systems will be replacing the currently existing second generation (2G) wireless systems and be used worldwide. The 3G systems will have a higher data transfer capacity, which allows for simultaneous data, voice, and video transfer (e.g., multimedia applications) while most of 2G systems only allow for low-rate data and voice transfer. The wireless communications industry has set standards for 3G, which detail various operations of the technology. It should be noted that the 3G standards outline only the different operations and not the processes for the production …


Analysis Of Wireless Networking On The University Of Arkansas Campus, Julia Lincoln Jan 2000

Analysis Of Wireless Networking On The University Of Arkansas Campus, Julia Lincoln

Inquiry: The University of Arkansas Undergraduate Research Journal

Wireless communication has already begun to change the way business and research is done today. Development of the wireless network for digital cellular phone has already improved the area of voice communications. The area of portable and mobile connectivity for computers and other devices is beginning to emerge. The research analyzes and compares a few of these wireless networks. Physical aspects such as range, interference factors, and frequency capabilities and restrictions are assessed. Capacity analysis including round trip times, latency, and throughput are done as well. Issues of authentication and addressing protocols are researched to determine optimal performance and convenience …


Field Interpretation Of Latitude And Longitude In Arkansas: A Portable Coordinate Projection, William R. Teague Jan 2000

Field Interpretation Of Latitude And Longitude In Arkansas: A Portable Coordinate Projection, William R. Teague

Journal of the Arkansas Academy of Science

Two- and three-dimensional coordinate systems are fundamental to most quantitative mapping applications. The Geodetic, Universal Transverse Mercator (UTM),and State Plane systems have traditional roles in various science, surveying, and government agency engineering applications. The coordinates of three-dimensional Geodetic system are latitude, longitude, and height above ellipsoid (HAE).Because of its ability to cope with the intrinsically three dimensional character of the earth's surface, the Geodetic system is capable of supporting precise relative positioning and very high accuracy computations of distance between any two positions on or near the earth's surface. The two-dimensional UTMand State Plane systems are extremely useful for the …


Mechatronic Design Of A Treaded Mobile Robot For Mine Sweeping, Andrew B. Wright Jan 2000

Mechatronic Design Of A Treaded Mobile Robot For Mine Sweeping, Andrew B. Wright

Journal of the Arkansas Academy of Science

Autonomous mobile robots, which can be programmed to exhibit cooperative behaviors, are ideal mechanisms for sweeping land mines. They can spread out to hunt for the mines, using a dispersal rule. Once a mine is located, they can congregate to surround it using a clustering rule. Should a robot be destroyed by tripping an unseen mine, the cost is minimal compared to a human life. UALR has been experimenting with coupled oscillator based rule generators for several years using fragile, indoor robots in a laboratory setting to validate the clustering and dispersal behaviors. In order to accomplish outdoor trials, a …


Derivation Of Equations Of Motion For A Four Link Robotic Leg For A Walking Vehicle, Andrew B. Wright Jan 1999

Derivation Of Equations Of Motion For A Four Link Robotic Leg For A Walking Vehicle, Andrew B. Wright

Journal of the Arkansas Academy of Science

A four degree of freedom leg for a walking robot has been modeled using Newton's method. Unlike robot manipulators, which have a fixed base, a leg model must include inertial forces due to base motion. These forces have been included in the formulation. These equations can be used for design, simulation, and control. The inverse kinematics for this leg are also presented. This allows the joint angles to be computed from a desired foot-hold position.


Thin Film Deposition Of Silicon For Solar Cell Applications, Sailesh Kumar, Roger M. Hawk Jan 1997

Thin Film Deposition Of Silicon For Solar Cell Applications, Sailesh Kumar, Roger M. Hawk

Journal of the Arkansas Academy of Science

Thin films of silicon have been formed using a patented electrostatic deposition method which utilizes charged particle motion in an electric field. After deposition, the films are heat treated for varying times and temperatures in a programmable furnace maintained under a purified argon atmosphere. X-ray diffraction (XRD) confirmed that these films were polycrystalline in nature. These films were found to have grain sizes of about 50 microns. Solar cells were fabricated using these large grained polycrystalline silicon films by sputtering pure gold as both front and back contacts. The cells have shown efficiencies of 1.8%. This paper reports on the …


Preparation Of Powder Precursors And Evaporation Of Photoconductive Indium Sulfide Films, Chris Barber, Robert Engelken, Brandon Kemp, Wasim Aleem, Imran Khan, Chris Edrington, Michael Buck, Clayton Workman, Anup Thapa, Tom Jakobs Jan 1997

Preparation Of Powder Precursors And Evaporation Of Photoconductive Indium Sulfide Films, Chris Barber, Robert Engelken, Brandon Kemp, Wasim Aleem, Imran Khan, Chris Edrington, Michael Buck, Clayton Workman, Anup Thapa, Tom Jakobs

Journal of the Arkansas Academy of Science

We have demonstrated significant photoconductance in indium sulfide thin films prepared by thermal vacuum evaporation ofIn2$3 powders synthesized in-house by chemical precipitation ofInCl3 or In(CH3COO)3, and (NH4)2S or Na2S. The Delta G lambda/Gdark values have been as high as 0.1 in the initial unoptimized films. Excess sulfur (via a mixture of polysulfide and sulfide ions in the synthesis bath) appears to be important in achieving reproducible and large photoconductivities. In2S3 is particularly attractive as a lower toxicity alternative to CdS in optoelectronic applications such as photovoltaic and photoconductive cells.


Improved Methods For Electroplating Cadmium Sulfide Thin Films, Brandon Kemp, Robert Engelken, Arif Raza, Wasim Aleem, Imran Khan, Chris Barber Jan 1996

Improved Methods For Electroplating Cadmium Sulfide Thin Films, Brandon Kemp, Robert Engelken, Arif Raza, Wasim Aleem, Imran Khan, Chris Barber

Journal of the Arkansas Academy of Science

We report improved methods for electroplating cadmium sulfide (CMS) films. Aprevious problem was cracking/flaking of films deposited from organic solutions of elemental sulfur; attempts to improve adhesion via bath additives reduced grain size. Aqueous baths of thiosulfate ions yield cadmium-richness at low T temperatures (T), long deposition times, and/or poor bath stability. Developments in our work to be discussed include (1) plating ofuniform, adherent, and stoichiometric CdS from tetraethylene baths of CdCl 2 and elemental sulfur at T >70° C with minimal cracking/flaking, (2) improved uniformity/ adherence by use of CdL>, and (3) swept voltage methods in aqueous thiosulfate …