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University of Arkansas, Fayetteville

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Articles 1771 - 1800 of 2433

Full-Text Articles in Physical Sciences and Mathematics

Wayne E. Sabbe Arkansas Soil Fertility Studies 2002, Nathan A. Slaton Mar 2003

Wayne E. Sabbe Arkansas Soil Fertility Studies 2002, Nathan A. Slaton

Arkansas Agricultural Experiment Station Research Series

Rapid technological changes in crop management and production require that the research efforts also be presented in an expeditious manner. The contributions of soil fertility and fertilizers are major production factors in all Arkansas crops. The studies contained within will allow producers to compare their practices with the university’s research efforts. Additionally, soil test data and fertilizer sales are presented to allow comparisons among years, crops, and other areas within Arkansas.

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On The Existence And Stability Of Liquid Water On The Martian Surface, Justin Thompson Jan 2003

On The Existence And Stability Of Liquid Water On The Martian Surface, Justin Thompson

Inquiry: The University of Arkansas Undergraduate Research Journal

Present-day Mars is thought to be a frozen desert on which liquid water is not likely to be found. The prevailing assumption has been that due to average temperatures below 273 K and atmospheric pressures at or below water's triple-point vapor pressure of 6.1 mbar, the existence of liquid water as an equilibrium phase at or near the surface is impossible at the present epoch. However, there is substantial evidence that liquid water has existed in the past and may presently still exist on or directly below the Martian surface. I conducted simulation experiments in the Andromeda planetary environmental chamber …

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Fenske-Hall Approximate Molecular Orbital Analysis Of The Chelating Carbene Complex Eta5-Cp'(Co)Mn{C(Oet)Ch2pph2}, John P. Graham Jan 2003

Fenske-Hall Approximate Molecular Orbital Analysis Of The Chelating Carbene Complex Eta5-Cp'(Co)Mn{C(Oet)Ch2pph2}, John P. Graham

Journal of the Arkansas Academy of Science

The novel three legged piano stool chelating carbene complex, Cp'(CO)Mn{C(OEt)CH2PPh2}, 1, exhibits interesting structural, spectroscopic and electrochemical properties. It also readily undergoes reaction with CO to produce the three legged piano stool complex Cp'(CO)2{PPh2C(OEt)=CH2}, 2. This is in contrast to the analogous non-chelating complex Cp(CO)(PPh3)Mn{C(OMe)CH2CH3}, 3, which does not react with CO. This paper discusses the results of Fenske-Hall approximate molecular orbital calculations on model complexes for 1 and 3. The differences in spectroscopic and electrochemical properties are explained using molecular orbital analysis. Possible reasons for the enhanced reactivity of 1are also presented.

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Stabilization Of Polyvinyl Chloride By Some Conducting Polymers, Amit Shah, Brian C. Berry, Ali U. Shaikh Jan 2003

Stabilization Of Polyvinyl Chloride By Some Conducting Polymers, Amit Shah, Brian C. Berry, Ali U. Shaikh

Journal of the Arkansas Academy of Science

No abstract provided.

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Acoustic Mapping Of Aquatic Vegetation In Lakes: An Example From Northwest Arkansas, Angela M. Polly, Stephen K. Boss Jan 2003

Acoustic Mapping Of Aquatic Vegetation In Lakes: An Example From Northwest Arkansas, Angela M. Polly, Stephen K. Boss

Journal of the Arkansas Academy of Science

No abstract provided.

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Antiforce Wave Profile For Quasi-Neutral Region, Mostafa Hemmati, Pashupati Adhikari, Jeremy Eckart, Marcus Ilbara Jan 2003

Antiforce Wave Profile For Quasi-Neutral Region, Mostafa Hemmati, Pashupati Adhikari, Jeremy Eckart, Marcus Ilbara

Journal of the Arkansas Academy of Science

This article will present a fluid dynamical theory for breakdown waves in which the direction of electric field force on electrons is in the opposite direction of wave propagation. We will refer to such waves as antiforce waves. The set of equations describing the model will include the equation of particle mass balance, equation of conservation of momentum, and equation of conservation of energy, coupled with Poisson's equation. This model treats the potential wave front as an electron shock wave propagating forward mainly due to the electron impact ionization. The shock front is succeeded by a thin dynamical transition region …

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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 …

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Winter And Spring Water Quality Of The Big Creek Watershed, Craighead County, Arkansas: Nutrients, Habitat, And Macroinvertebrates, Alan D. Christian, Jennifer L. Bouldin, Nate A. Bickford, Samuel B. Mccord, Aboubakar Sako, Jerry L. Farris, Lynn Kanieski, Ashley Mcbride Jan 2003

Winter And Spring Water Quality Of The Big Creek Watershed, Craighead County, Arkansas: Nutrients, Habitat, And Macroinvertebrates, Alan D. Christian, Jennifer L. Bouldin, Nate A. Bickford, Samuel B. Mccord, Aboubakar Sako, Jerry L. Farris, Lynn Kanieski, Ashley Mcbride

Journal of the Arkansas Academy of Science

The objective of this study was to assess the water quality of the Big Creek watershed during the winter and spring of 2002 by analyzing water physical, chemical variables, aquatic macro-invertebrates, and habitat. The Big Creek watershed, arising on Crowley's Ridge in northeast Arkansas, is a small deltaic watershed and is an area of intense cultivation. Four stations, Big Creek Upper (BCU), Mud Creek (MC),Lost Creek (LC), and Big Creek Lower (BCL) were established for this study from Big Creek, Mud Creek and Lost Creek. Water samples were collected on a weekly basis for 10 weeks from January 2002 through …

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Thesis Digest: Mathematical Interpretation Of Political Power And The Arkansas State Government, Andrew King Jan 2003

Thesis Digest: Mathematical Interpretation Of Political Power And The Arkansas State Government, Andrew King

Inquiry: The University of Arkansas Undergraduate Research Journal

On the whole, political power can he very difficult to quantify. A person may be powerful due to his or her personal charm, wealth, fame, credibility, or influential connections. Political bodies do not account for these qualities when creating voting procedures; they only assign voting rules to specific positions. For example, most would say that in the United States government that a Senator is more powerful than a Representative, but less powerful than the President, without knowing any way to quantify or verify those differences. Since the 1950's, mathematicians and political scientists have attempted to create mathematical models that partially …

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Multiphoton Interaction In A System Of Two Quantum Dots, Brian Sawyer Jan 2003

Multiphoton Interaction In A System Of Two Quantum Dots, Brian Sawyer

Inquiry: The University of Arkansas Undergraduate Research Journal

As the size and proximity of components on modern computer chips approaches quantum mechanical limits, various novel solutions have been proposed to ensure further increases in processing speed and reliability. Of these, small semiconductor devices called quantum dots may constitute the logic gates of future quantum computers - processors taking advantage of phenomena such as entanglement and quantum teleportation to enable ultra-fast computation speeds. Quantum dots behave much like designer atoms in that their absorption/emission energies can be adjusted lo desired values. A quantum mechanical model of semiconductor quantum dots having equal size and interacting with a single-mode electric field …

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Evaluation Of Sampling Strategies On Load Estimation For Illinois River At Highway 59, T. S. Soerens, M. A. Nelson Jan 2003

Evaluation Of Sampling Strategies On Load Estimation For Illinois River At Highway 59, T. S. Soerens, M. A. Nelson

Technical Reports

This study investigated the precision and accuracy of the two load calculation techniques. The study compared total phosphorus loads calculated by integration of Arkansas Water Resources Center (AWRC) intensive sampling data to loads calculated by a regression technique (rating curve) using fewer data. The 1998 AWRC dataset from the Illinois River at Arkansas Highway 59 was sub-sampled in a manner to simulate fixed period monitoring schemes supplemented with storm sampling. The ESTIMATOR software program was used to calculate loads. These loads were compared to the integrated load. The error of the integrated load when the variation in concentration between samples …

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Watershed-Scale Agricultural Land-Use Impact On Instream Physicochemical Parameters, William Dillahunty, Indrajeet Chaubey, Marty Matlock Jan 2003

Watershed-Scale Agricultural Land-Use Impact On Instream Physicochemical Parameters, William Dillahunty, Indrajeet Chaubey, Marty Matlock

Discovery, The Student Journal of Dale Bumpers College of Agricultural, Food and Life Sciences

Nonpoint source (NPS) pollution is often the result of runoff losses from agricultural or urban areas. Even though the watershed approach to controlling NPS pollution is identified as the most efficient approach, data linking watershed scale land use and specific water quality implications are very limited. The objective of this study was to quantify the impact of agricultural land use on stream physico-chemical properties. The upper reach of Flint Creek was monitored at two sampling points draining an agricultural land. At each of these points, continuous measurement of stream characteristics such as temperature, dissolved oxygen (DO) concentration, depth, pH, and …

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Fishes Of The Red River In Arkansas, Thomas M. Buchanan, Drew Wilson, L. G. Claybrook, William G. Layher Jan 2003

Fishes Of The Red River In Arkansas, Thomas M. Buchanan, Drew Wilson, L. G. Claybrook, William G. Layher

Journal of the Arkansas Academy of Science

Fishes were collected from Red River mainstem habitats in Arkansas with seines, rotenone, hoop nets, gill nets, and trotlines from 1995 through 2001. Seventy-two species were identified distributed among 17 families, and 15 species were new records for the Red River in Arkansas. Eighty-three species are now historically known from the Arkansas segment of the Red River. Approximately 67% of the fishes known from the entire Red River have been found in the Arkansas segment, which is only 11% of the entire river length. Baseline data on the fish fauna of the Red River is critical for the analysis of …

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Pid Stabilization Of A Position-Controlled Robot Manipulator Acting Independently Of In Collaboration With Human Arm, Anindo Roy, Kamran Iqbal Jan 2003

Pid Stabilization Of A Position-Controlled Robot Manipulator Acting Independently Of In Collaboration With Human Arm, Anindo Roy, Kamran Iqbal

Journal of the Arkansas Academy of Science

In this paper we develop framework for PID stabilization of a robot manipulator when using an object independently or in collaboration with a human arm. In both applications, the manipulator is equipped with a wrist sensor represented by an impedance. A second order manipulator transfer function along each coordinate direction is assumed. The aim of the paper is to design a PID controller when measurement of contact force, available via wrist sensor, is used to command the position controlled manipulator to a desired position and/or force profile. Necessary and sufficient conditions for stability of the closed loop system are developed …

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Identifying Minimum G Aberration Designs For Hadamard Matrices Of Order 28, Steffany Belcher-Novosad, Debra Ingram Jan 2003

Identifying Minimum G Aberration Designs For Hadamard Matrices Of Order 28, Steffany Belcher-Novosad, Debra Ingram

Journal of the Arkansas Academy of Science

No abstract provided.

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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 …

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Study Of Nanoidentation And Tip Geometry In Gaas (100) At Ultra-Low-Loads For The Patterning Of Quantum Dots, Robin Prince Jan 2003

Study Of Nanoidentation And Tip Geometry In Gaas (100) At Ultra-Low-Loads For The Patterning Of Quantum Dots, Robin Prince

Inquiry: The University of Arkansas Undergraduate Research Journal

In this study, nanoindentations were produced and characterized for the future patterning of quantum dots. Nanoindentation was performed on a Si-doped (n-type) Vertical Gradient Freeze (VGF) GaAs (100) wafer with a 700 nm GaAs (100) layer grown by molecular beam epitaxy (MBE). Nanoindentation was performed with a Berkovich diamond tip, a cube corner diamond tip, and a 600 conical diamond tip. Nanoindentation of GaAs has been studied in the past, but not at extremely low loads. Previous research has been done on high load (50-200 mN) and low load (200-8000 mN) nanoindentation. The applied load in this study ranges from …

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Soil Particle-Size Analysis: A Comparison Of Two Methods, Lauren Williams-Caudle, Kristofor Brye, E. Moye Rutledge Jan 2003

Soil Particle-Size Analysis: A Comparison Of Two Methods, Lauren Williams-Caudle, Kristofor Brye, E. Moye Rutledge

Discovery, The Student Journal of Dale Bumpers College of Agricultural, Food and Life Sciences

Knowing the proportion of particle sizes in soil is important to soil scientists and agronomists. The mixture of sand, silt, and clay influences water movement, solute transport, nutrient retention, and many other properties and processes in soil. The standard method for particle size determination is a somewhat time-consuming process. An equally accurate but shorter method would be appealing for many reasons. The objective of this study was to compare a standard method of particle-size analysis using a hydrometer to an abbreviated hydrometer method, which, instead of 12 h for the standard method, requires about 3 h to complete. Twenty-four soil …

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Soils Of Mississippi County, Arkansas, J. M. Mckimmey, B. Dixon, H. D. Scott, C. M. Scarlat Nov 2002

Soils Of Mississippi County, Arkansas, J. M. Mckimmey, B. Dixon, H. D. Scott, C. M. Scarlat

Research Reports and Research Bulletins

Along with air and water, soil contributes essential processes to the natural order of global cycles. With the exception of edibles from the sea, virtually everything we, and most other land-based animals, eat is derived from soil. Soil is a storage medium of essential minerals and nutrients for fulfilling our agricultural and nutritional needs. Humans work the soil to provide the basics of food, clothing, and shelter. We also use the soil as a medium to store and discard our waste. Virtually everything we do is in some way connected to soil

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Illinois River 2001 Pollutant Loads At Arkansas Highway 59 Bridge, Marc A. Nelson, Thomas S. Soerens Sep 2002

Illinois River 2001 Pollutant Loads At Arkansas Highway 59 Bridge, Marc A. Nelson, Thomas S. Soerens

Technical Reports

Automatic water samplers and a U. S. Geological Survey gauging station were established in 1995 on the main stem of the Illinois River at the Arkansas Highway 59 Bridge. Since that time, continuous stage and discharge measurements and water quality sampling have been used to determine pollutant concentrations and loads in the Arkansas portion of the Illinois River. This report represents the results from the measurement and sampling for January 1, 2001 to December 31, 2001.

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Illinois River Bmp Implementation & Phosphorus Management, Marc A. Nelson, Keith Trost Jun 2002

Illinois River Bmp Implementation & Phosphorus Management, Marc A. Nelson, Keith Trost

Technical Reports

No abstract provided.

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Pesticide Ground Water Monitoring Project Phase Viii, K. F. Steele, M. A. Nelson, T. Nichols, R. Polite, H. D. Scott, Charles Armstrong May 2002

Pesticide Ground Water Monitoring Project Phase Viii, K. F. Steele, M. A. Nelson, T. Nichols, R. Polite, H. D. Scott, Charles Armstrong

Technical Reports

During Phase VIII monitoring (March 24, 2000 to June 30, 2001 ), 86 samples were collected from 77 new wells and 9 samples were collected from wells with previous detectable herbicide.

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Solid Phase Extraction Of Pesticides With Determination By Gas Chromatography, Anwar A. Bhuiyan, Harry O. Brotherton Jan 2002

Solid Phase Extraction Of Pesticides With Determination By Gas Chromatography, Anwar A. Bhuiyan, Harry O. Brotherton

Journal of the Arkansas Academy of Science

A simple, rapid, and effective method for the extraction of fifteen organochlorine and organophosphorus pesticides based on the use of solid phase Bond Elut C-18 cartridges was studied as an alternative method to those based on extraction with organic solvents. Solid phase extraction is an attractive chromatographic sample preparation technology that reduces analysis time, costs, labor, and solvent consumption relative to traditional liquid/liquid extraction methods. The sample recoveries with the use of solid phase extractions were excellent for most pesticides. Analyte concentration by a factor as great as 1000-fold was achieved readily. The adsorbed pesticides were eluted from the solid …

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Stimulation And Modeling Of Pond Formations On The Asteroid 433 Eros, Justin Thompson Jan 2002

Stimulation And Modeling Of Pond Formations On The Asteroid 433 Eros, Justin Thompson

Inquiry: The University of Arkansas Undergraduate Research Journal

"Ponds" are surface features that appear to be the result of the deposition of finer material on the asteroid's regolith, the layer of loose sediment that blankets the entire asteroid. Ponds were discovered by the NEAR Shoemaker spacecraft in January, 2001, on the asteroid 433 Eros. The objective of experimentation is to simulate the development of these ponds in the Andromeda planetary sciences environmental chamber. The Andromeda Chamber offers a unique ability to simulate surface environments that occur on Eros. The chamber was used to simulate the processes that occur as Eros emits gas through its outer surface, including the …

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Revised Bedrock Geology Of War Eagle Quadrangle, Benton County, Arkansas, Robert A. Sullivan, Stephen K. Boss Jan 2002

Revised Bedrock Geology Of War Eagle Quadrangle, Benton County, Arkansas, Robert A. Sullivan, Stephen K. Boss

Journal of the Arkansas Academy of Science

A digital geologic map of War Eagle quadrangle (WEQ) was produced at the 1:24000 scale using the geographic information system (GIS) software ArcView® by digitizing geological contacts onto the United States Geological Survey (USGS) digital raster graphic (DRG). The geology of WEQ consists of sedimentary rocks of Ordovician (Cotter, Powell, and Everton Formations), Devonian (Clifty Formation and Chattanooga Shale), and Mississippian (St. Joe-Boone, Batesville, and Fayetteville Formations) systems. Impoundment of Beaver Lake in 1966 inundated most Ordovician rocks cropping out in WEQ, but all three formations were present in isolated outcrops along the present shoreline of the lake. The St. …

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Simulation Video Electric Single Particle Aerodynamic Relaxation Time Analyzers, Steve Farmer, Robert A. Sims Jan 2002

Simulation Video Electric Single Particle Aerodynamic Relaxation Time Analyzers, Steve Farmer, Robert A. Sims

Journal of the Arkansas Academy of Science

The simulation of physical parameters provides a virtual environment for the design and optimization of instrumentation. applying physical laws and theorems to natural phenomena defines the behavior of analytical processes. Simulation provides means for the adjustment of specific operating parameters while maintaining the repeatability of constant parameters. The video Electric Single Particle Aerodynamic Relaxation Time Analyzer (VESPART) is an instrument that provides the diameter and charge-to-mass (q/m) ratio of particles. The simulation of the VESPART requires the modeling of the physical environment and application of modeling to simulations. Simulation includes characterization of the various natural forces that "feet particle motion …

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Synthesis And Chemistry Of Naphthalene Annulated Trienyl Iron Complexes: Potential Anticancer Dna Alkylation Reagents, Traci Means Jan 2002

Synthesis And Chemistry Of Naphthalene Annulated Trienyl Iron Complexes: Potential Anticancer Dna Alkylation Reagents, Traci Means

Inquiry: The University of Arkansas Undergraduate Research Journal

Iron complex chemistry that opens a new door to the medicinal and pharmaceutical worlds is the aim of this research. Specifically, ortho-quinone methide moieties are intermediates in several antitumor drugs and have been identified as bioreductive alkylators of DNA. In our research, a class of iron compounds has been targeted to resemble these quinone methides. It is hoped that these new compounds could be modified to provide a window of opportunity toward the discovery of a selective mode of drug delivery. We have focused our efforts on generating a reactive transition metal complexed 5-membered ring analog of o-quinone methide based …

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Modification Of Surface Properties Of Polymeric Materials, Rajesh Sharma, Robert A. Sims, Malay K. Mazumder Jan 2002

Modification Of Surface Properties Of Polymeric Materials, Rajesh Sharma, Robert A. Sims, Malay K. Mazumder

Journal of the Arkansas Academy of Science

Polymeric materials are successfully used in virtually all industries ranging from semiconductors, and coatings, to household appliances, automotive, and biomedical implants. Polymers generally have excellent bulk physical and chemical properties. However, certain properties of polymers such as low surface energy, low wettability, and high electrical resistivity sometimes limit their applications. Changing the bulk formulation of the polymers can alter some of these properties, but in general this is not acceptable as it can affect "desirable" bulk properties. Surface modification techniques have been used to alter polymer surfaces without affecting the bulk properties of the material. Most polymers have very high …

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Illinois River Phosphorus Sampling Results And Mass Balance Computation, Marc Nelson, K.L. White, T.S. Soerens Jan 2002

Illinois River Phosphorus Sampling Results And Mass Balance Computation, Marc Nelson, K.L. White, T.S. Soerens

Technical Reports

Phosphorus levels in the Illinois River are of great interest to the people of the States of Arkansas and Oklahoma. A great deal of effort has been expended to ascertain and modify the phosphorus impacts on the river. An automatic water sampling station was installed on the Illinois River just upstream from the State line in 1996 to accurately quantify the phosphorus in the Arkansas portion of the watershed. This paper summarizes five years worth of phosphorus sampling results at that site. In addition, a simple mass balance for phosphorus in the Illinois River Watershed above the sampling station was …

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Reduction Of Dendrite Formations To Improve The Appearance Of The Powder Cured Films For Automotive Industry, Alexandru S. Biris, C. U. Yurteri, Malay K. Mazumder, Robert A. Sims, P. H. Williams Jan 2002

Reduction Of Dendrite Formations To Improve The Appearance Of The Powder Cured Films For Automotive Industry, Alexandru S. Biris, C. U. Yurteri, Malay K. Mazumder, Robert A. Sims, P. H. Williams

Journal of the Arkansas Academy of Science

The appearance of powder-coated films is dependent upon powder chemistry and spraying parameters. One of the most important physical factors controlling the powder film appearance is the microdeposition of the powder particles on the grounded substrate. During the electrostatic deposition of powder, the formation of dendrites and agglomerates was observed; these formations have an adverse effect on the final film appearance and their elimination may result in smoother and glossier films. Dendrites are generated due to bipolar charging and inter-particulate electrostatic attractive forces. The corona charging technique is mostly used in industrial powder coating applications. At low corona voltages (- …

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