| Multi-scale Modeling of Proton Transport, Water Distribution, and Methanol Permeability in Proton Exchange Membranes (PEMs) |
26-May-2008 |
9 pages |
| Authors:
Stephen J Paddison; Mark E Tuckerman; ALABAMA UNIV IN HUNTSVILLE
|
 | We have undertaken our multiscale modeling of proton exchange membranes through three simultaneous but distinct studies of perfluorosulfonic acid (PFSA) systems at different time and length scales: (1) hydrated morphology of PFSA membranes with dissipative particle dynamics (DPD) simulations; (2) classical MD simulations of the hydration and hydronium ion diffusion of the short-side chain (SSC) PFSA membrane; and (3) ab initio density functional theory Car-Parrinello MD simulations of model PFSA ... |
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| Simple Approximations of Quasi-Linear Diffusion Coefficients |
01 DEC 2007 |
10 pages |
| Authors:
J. M. Albert; AIR FORCE RESEARCH LAB HANSCOM AFB MA
|
| Quasi-linear diffusion by cyclotron-resonant plasma waves is likely a key ingredient of the behavior of electrons in the Earth's radiation belts. Multidimensional dynamical simulations are under development, which require the diffusion coefficients to be evaluated quickly as well as accurately. The recently developed parallel propagation approximation replaces the integration over wavenormal distribution to a closed form expression, and can be quite accurate. However, it can also perform badly, especially for ... |
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| Production of Dense Compact Billet From Ti-Alloy Powder Using Equal Channel Angular Extrusion |
06 APR 2007 |
50 pages |
| Authors:
Rimma Lapovok; Dacian Tomus; MONASH UNIV CLAYTON (AUSTRALIA) SCHOOL OF PHYSICS AND MATERIALS ENGINEERING
|
| The project was aimed at an investigation of the potential for cost-effective, efficient consolidation of pre-alloyed "PA" Ti-6Al-4V (HDH) powder at temperatures of 400?C and below using Equal Channel Angular Extrusion (ECAE), with applied back pressure. The limit on processing temperature was imposed to minimize the contamination of powder and compact with gaseous constituents known to be harmful to resultant properties. An analysis of existing published investigations of current processing ... |
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| Dual Control Cell Reaction Ensemble Molecular Dynamics: A Method for Simulations of Reactions and Adsorption in Porous Materials |
SEP 2006 |
18 pages |
| Authors:
Martin Lisal; John K. Brennan; William R. Smith; Flor R. Siperstein; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
|
| We present a simulation tool to study fluid mixtures that are simultaneously chemically reacting and adsorbing in a porous material. The method is a combination of the reaction ensemble Monte Carlo method and the dual control volume grand canonical molecular dynamics technique. The method, termed the dual control cell reaction ensemble molecular dynamics method, allows for the calculation of both equilibrium and nonequilibrium transport properties in porous materials such as ... |
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| Novel SICN Ceramics for Health Monitoring of High Temperature Systems |
14 AUG 2006 |
14 pages |
| Authors:
Rishi Raj; COLORADO UNIV AT BOULDER DEPT OF MECHANICAL ENGINEERING
|
| The objective of this MEANS program was to develop new methodologies for quantifying the variability in the performance of high temperature systems by coupling basic concepts from materials science with system design and engineering. The methodologies were validated by the fabrication and evaluation of new high temperature MEMS devices made from a novel polymer-derived ceramic material. The new results demonstrate two unique features: 1) how to hybridize computational approach with ... |
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| Interaction of Candidate Cleaning Solutions for Sensitive Equipment Decontamination With Polymeric Materials |
17 AUG 2005 |
8 pages |
| Authors:
Brian S. Ince; Wendel J. Shuely; SOLDIER AND BIOLOGICAL CHEMICAL COMMANDABERDEEN PROVING GROUND MD
|
| Chemical-polymer compatibility is an important criterion for the cleaning, decontamination, and extraction of hazardous chemicals from sensitive equipment (electronics, optics, and other advanced polymeric materials). Candidate cleaning fluids for sensitive equipment include fluorocarbons and supercritical fluids. The initial evaluation strategy involves the measurement of the sorption and desorption diffusion coefficients of the candidate cleaning fluid in a spectrum of polymer compositions. The objective was to characterize the complete desorption process ... |
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| Impurities in Inelastic Maxwell Models |
13 JUL 2005 |
7 pages |
| Authors:
Vicente Garzo; UNIVERSIDAD DE EXTREMADURA (SPAIN)
|
| Transport properties of impurities immersed in a granular gas undergoing homogenous cooling state are studied. The results are obtained from the Boltzmann-Lorentz kinetic equation for inelastic Maxwell models in 'd' dimensions. The kinetic equation is solved by means of the Chapman-Enskog method up to first order in the density gradient of impurities. The mass and heat fluxes associated with impurities are determined and the corresponding transport coefficients are identified. Both ... |
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| Numerical Simulation of Hydrogen Assisted Cracking in Supermartensitic Stainless Steel Welds |
27 JAN 2005 |
223 pages |
| Authors:
Ekkarut Viyanit; UNIVERSITAET DER BUNDESWEHR HAMBURG (GERMANY) FACHBEREICH MASCHINENBAU
|
| Replacement of expensive duplex stainless steel and conventional carbon steel by a new generation of supermartensitic stainless steel has been taken into account since the last decade in order to meet the technical-economical challenge for transportation flowlines of unprocessed oil and gas products in offshore technology. Supermartensitic stainless steels can provide appropriate material properties, such as: improved strength-to-weight ratio, enhanced useful corrosion resistance, as well as application at relatively low ... |
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| Low-Altitude Distribution of Radiation Belt Electrons |
10 NOV 2004 |
12 pages |
| Authors:
R. S. Selesnick; M. D. Looper; J. M. Albert; AEROSPACE CORP LOS ANGELES CA
|
| A numerical simulation of the low-altitude electron radiation belt is described. It includes dependences on the electron's bounce and drift phases, equatorial pitch angle, and kinetic energy in the range of 1 to several MeV at L = 3.5. Physical processes in addition to the adiabatic electron motion are pitch angle diffusion and backscattering from a realistic model atmosphere. Quasi-linear diffusion coefficients are calculated from a model of the whistler ... |
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| Using Quasi-Linear Diffusion to Model Acceleration and Loss from Wave- Particle Interactions |
28 SEP 2004 |
7 pages |
| Authors:
J. M. Albert; AIR FORCE RESEARCH LAB HANSCOM AFB MA SPACE VEHICLES DIRECTORATE
|
| Current research has reemphasized the importance of cyclotron resonant wave-particle interactions for radiation belt electrons. Whistler mode hiss, chorus, and EMIC waves can act in combination to cause acceleration and loss of radiation belt electrons at greater rates than previously appreciated. These processes can be described by quasi-linear theory, but calculating quasi- linear diffusion coefficients is computationally demanding. Recent advances have been made in computing bounce averaged quasi-linear pitch angle, ... |
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| Supercritical Carbon Dioxide Interaction with Polymeric Materials: Desorption Diffusion Coefficient Measurements |
JUL 2004 |
247 pages |
| Authors:
Wendel J. Shuely; Brian S. Ince; EDGEWOOD CHEMICAL BIOLOGICAL CENTER ABERDEEN PROVING GROUND MD RESEARCH AND TECHNOLOGY DIR
|
| Chemical-polymer compatibility is an important criterion in the development of solvent-based extraction and cleaning systems for removal of toxic contaminants from polymeric surfaces. The potential degradation of polymer properties and performance is especially critical for sensitive equipment cleaning, decontamination, and extraction. The candidate cleaning fluids for sensitive equipment include fluorinations and supercritical fluids. An overall material evaluation strategy has been developed for evaluating the degradation of polymer properties by exposure ... |
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| Therapeutic Vascular Targeting and Irradiation: Correlation of MRI and Tissue Changes at Cellular and Molecular Levels to Optimizing Outcomes |
JUN 2004 |
39 pages |
| Authors:
Dawen Zhao; TEXAS UNIV AT DALLAS SOUTHWESTERN MEDICAL CENTER
|
| Vascular targeting agents (VTA) are new types of anticancer drugs that act on existing tumor vasculature, causing vascular disruption, which ultimately leads to extensive ischemic tumor cell death. One major goal of this project is to precisely assess the dynamic changes in vascular perfusion and oxygenation at different time points following VTA in breast tumors. In vivo non-invasive MRI approaches observed significant decrease in signal intensity by DCE (dynamic contrast ... |
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| Increasing Oxygen Consumption During Shock |
04 MAY 2004 |
9 pages |
| Authors:
John L. Gainer; VIRGINIA UNIV CHARLOTTESVILLE DEPT OF CHEMICAL ENGINEERING
|
| Whole-body oxygen consumption is decreased after hemorrhage. Typical methods for increasing oxygen consumption have involved increasing the blood oxygen concentration using enriched oxygen gases, hemoglobins and fluorocarbon compounds; however, clinical trials involving these have not been totally successful. Increasing the oxygen concentration increases its diffusion rate through blood plasma; however, an alternative method would be to increase the diffusion coefficient of oxygen itself. This was shown to be possible using ... |
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| Unfolding of Proteins: Thermal and Mechanical Unfolding |
24 MAR 2004 |
14 pages |
| Authors:
Joe S. Hur; Eric Darve; STANFORD UNIV CA
|
| Over the past few decades, researchers have sequenced the human genome which is a blueprint for proteins. However, given only the information of the sequence we cannot yet accurately predict specific structural information such as the secondary and tertiary structure of a given protein, let alone its functionality in biological processes. Recent theoretical and experimental findings have shown that the topology or conformation of the native structure of small proteins ... |
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| Speed of Propagation for Some Models of Two-Phase Flow in Porous Media |
2004 |
13 pages |
| Authors:
C. E. Kees; NORTH CAROLINA STATE UNIV AT RALEIGH DEPT OF MATHEMATICS
|
| Flow of two immiscible, incompressible fluids in a porous medium is typically described by a nonlinear advection-diffusion equation for one of the fluid saturations. The diffusion coefficient, which represents the effect of capillary forces on the fluids, is zero when the medium is locally saturated by either fluid since in these limiting cases the effects of capillary forces tend to zero. This degeneracy in the second-order term usually gives rise ... |
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| Final Technical Report for Analytical Assessments Related to Microbubble Drag Reduction |
31 DEC 2003 |
23 pages |
| Authors:
M. A. Ebadian; P. V. Skudarnov; C. X. Lin; G. P. Philippidis; FLORIDA INTERNATIONAL UNIV MIAMI HEMISPHERIC CENTER FOR ENVIRONMENTAL TECHNOLOGY
|
| In this project, the Hemispheric Center for Environmental Technology (HCET) at Florida International University conducted computational studies of the microbubble drag reduction mechanism. The objective of the research was to assess the roles of mixture density variation and surface roughness in microbubble drag reduction. The research was carried out in collaboration with the Applied Research Laboratory (ARL) at Pennsylvania State University, where substantial experimental research and theoretical understanding and modeling ... |
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| Experimental and Detailed Numerical Studies of Fundamental Flame Properties of Gaseous and Liquid Fuels |
NOV 2003 |
14 pages |
| Authors:
Fokion N. Egolfopoulos; UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES DEPT OF AEROSPACE AND MECHANICAL ENGINEERING
|
| The dynamic behavior of laminar flames was studied for a wide range of conditions. The parameters considered included the fuel type, reactant composition, flame temperature, and combustion mode. The derived experimental data constitute a basis for partially validating the combustion chemistry for fuels ranging from hydrogen to gaseous and liquid hydrocarbons and alcohols. Emphasis was given to kinetics regimes that have not been systematically probed and/or in which current knowledge ... |
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| Monitoring Therapeutic Response of Metastatic Breast Lesions Using Magnetic Resonance Imaging of Water Self-Diffusion Coefficients |
OCT 2003 |
28 pages |
| Authors:
Douglas J. Ballon; SLOAN-KETTERING INST FOR CANCER RESEARCH NEW YORK
|
| A new magnetic resonance imaging technique has been developed that is designed to detect and monitor metastatic breast lesions in bone marrow and other organs. Specifically, a diffusion sensitive echo planar magnetic resonance pulse sequence has been developed for both 1.5 Tesla and 3.0 Tesla whole-body imaging systems along with image processing techniques to facilitate whole-body screening for breast metastases. The acquisition sequence allows for multi-shot, multi-excitation imaging at multiple ... |
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| Molecular Transport Mechanisms for Associating and Solvating Penetrant in Polymers |
30 JUN 2003 |
6 pages |
| Authors:
Timothy A. Barbari; MARYLAND UNIV COLLEGE PARK
|
| The long-term objective of this research is to develop structure- property relationships for the diffusion of associating and solvating penetrants in polymers, which can be used to guide the selection or synthesis of polymers for use as protective barriers or separation membranes. The immediate objective of this project was to understand, using FTIR-ATR spectroscopy, how penetrant- penetrant and penetrant-polymer interactions, particularly hydrogen bonding, dictate transport rates through polymers using model ... |
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| Assessment of Perchlorate Releases in Launch Operations II |
01 DEC 2002 |
35 pages |
| Authors:
V. I. Lang; K. R. Bohman; J. T. Tooley; S. A. Frolik; E. W. Fournier; AEROSPACE CORP EL SEGUNDO CA SYSTEMS PLANNING DIV
|
| Laboratory studies were conducted to determine the rates at which perchlorate is released from perchlorate-containing solid propellants and the influence of temperature and salinity on the rates. Perchlorate release rates from carboxyl-terminated polybutadiene (CTPB), hydroxyl-terminated polybutadiene (HTPB), polybutadiene-acrylic acid-acrylo-nitrile terpolymer (PBAN), and polyurethane (PU) solid propellants were determined and are reported as diffusion coefficients. The diffusion coefficients for all propellant types and conditions tested were in the range of 3.6 ... |
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| Computational Issues in Analysis and Design of Chemical-Laser Flow- Fields |
30 SEP 2002 |
62 pages |
| Authors:
W. M. Eppard; Eugene M. Cliff; AEROSOFT INC BLACKSBURG VA
|
| In support of the Air Force's airborne laser (ABL) development program. state-of-the-art CFD analysis and design methods have been extended to include the physical models important in chemical oxygen-iodine laser (COIL) systems. The three-dimensional COIL simulation model is based on the CFD flow solver GASP v4 which solves the conservative, finite-volume formulation of the Navier-Stokes equations with general thermo-chemistry. The COIL design software is based on the continuous sensitivity equation ... |
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| Two-Temperature Equilibration Rate for a Two-Component (e.g., Antihydrogen) Plasma in a Penning Trap |
24 JUN 2002 |
6 pages |
| Authors:
Yongbin Chang; C. A. Ordonez; UNIVERSITY OF NORTH TEXAS DENTON DEPT OF PHYSICS
|
| An expression for an equilibration time scale is developed that characterizes the rate for a group of (test particles with a Maxwellian velocity distribution but different temperature from that of Maxwellian field particles to relax to the same temperature of the field particles. The expression, which can be used for any value of the Coulomb logarithm, is based on onefold integral expressions for Fokker-Planck velocity-space friction and diffusion coefficients presented ... |
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| Aerospace Composite Materials Delivery Order 0003: Nanocomposite Polymeric Resin Enhancements for Improved Composite Performance |
MAR 2002 |
38 pages |
| Authors:
Chenggang Chen; DAYTON UNIV OH RESEARCH INST
|
| Epoxy nanocomposites were successfully prepared using different montmorillonite-based organoclays with an epoxy resin system including several added to fiber preforms. The cation exchange capacity of the clays was the most important factor affecting the clay exfoliation. The addition of clays does not significantly alter the viscosity or cure kinetics so that the modified resin will still be suitable for liquid composite molding techniques such as resin transfer molding. The cure ... |
|
| Maritime Frontogenesis |
DEC 2001 |
62 pages |
| Authors:
Catherine M. McDougall; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Numerical experiments are conducted with a hydrostatic primitive equation model initialized in a baroclinically unstable slate to simulate the passage of cold fronts over the ocean. The model includes K-theory planetary boundary layer (PBL) parameterization with implicitly defined diffusion coefficients. An adiabatic and inviscid simulation provided the control for these experiments. The PBL simulations are integrated: (1) with Z(sub o) held constant at 0.4 m and no heat flux; (2) ... |
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| Measurement of Ferric Ion Diffusion Coefficient in Fricke-Infused Agarose Gel From MR Image Intensity Changes |
25 OCT 2001 |
|
| Authors:
Yin-Jiun Tseng; Woei-Chyn Chu; Sung-Cheng Huang; NATIONAL YANG-MING UNIV TAIPEI (TAIWAN)
|
 | A mathematical modeling was adopted to calculate the ferric ion diffusion coefficient based on the radiation induced magnetic resonance (MR) image intensity change in Fricke-agarose gels. A fast magnetic resonance imaging acquisition technique was employed to avoid the smearing of acquired data due to diffusion over an extended period of time. Our results showed that for a Fricke- agarose gel contained 1mM ammonium ferrous sulfate, 1% agarose, 1mM sodium chloride ... |
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| Diffusion of Molecular Probes in Thermoresponsive Poly(N- isopropylacrylamide) Hydrogels: Electroanalytical Studies |
15 JUL 2001 |
24 pages |
| Authors:
W. Zhang; I. Gaberman; M. Ciszkowska; BROOKLYN COLL NY DEPT OF CHEMISTRY
|
| Poly(N-isopropylacrylamide), NIPA, thermoresponsive hydrogels with well defined concentrations of an electroactive probe, 1,1'-ferrocenedimethanol, Fc(MeOH)2, were prepared. The discontinuous reversible volume phase transition of such gels occurs at 32 +/- deg C, and results in a release of approximately 93% of the solvent from the polymeric network. Transport of Fc(MeOH)2 in both swollen and collapsed gels was studied using steady state voltammetry and chronoamperometry at platinum microelectrodes. The diffusion coefficient of ... |
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| Ionic and Electronic Transport in Gels and Aerogels |
15 JUL 2001 |
38 pages |
| Authors:
M. Ciszkowska; M. Tomkiewicz; BROOKLYN COLL NY DEPT OF CHEMISTRY
|
| Organic and inorganic gels, and gel-derivatives such as aerogels and xerogels, find numerous applications in areas such as batteries, fuel cells, photoelectrochemical solar cells, photocatalytic devices, supercapacitors, control-release drug delivery systems, separation techniques, and others. Modern microscopic and electrochemical techniques offer the possibility of understanding structural properties of these systems down to almost atomic level. Most of the applications involve solid-liquid interfaces that occupy a significant fraction of the volume ... |
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| Transport of Ions and Electrostatic Interactions in Thermoresponsive Poly (N-Isopropylacrylamide-co-Acrylic Acid) Hydrogels: Electroanalytical Studies |
15 JUL 2001 |
33 pages |
| Authors:
C. Ma; W. Zhang; M. Ciszkowska; BROOKLYN COLL NY DEPT OF CHEMISTRY
|
| To study transport phenomena and electrostatic interactions in negatively charged poly(N-isopropylacrylacrylamide-co-acrylic acid) hydrogels, NIPA-AA, electroanalytical experiments with two positively charged probes, ferrocenylmethyltrimethylammonium, FcTMA(+), and hexaammineruthenium(III), Ru(NH3)6(3+), cations were performed, and the results compared with those for an uncharged electroactive probe, 1,1'-ferrocenedimethanol, Fc(MeOH)2. Steady-state voltammetry and chronoamperometry at platinum disk microelectrodes were used to determine diffusion coefficients of those probes. For temperatures below the volume phase transition of a gel, there ... |
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| Molecular and Ionic Transport in Polymeric Systems: Electroanalytical Studies |
15 JUL 2001 |
26 pages |
| Authors:
M. Ciszkowska; BROOKLYN COLL NY DEPT OF CHEMISTRY
|
| Transport of simple ions and molecules in polymeric systems such as solutions, colloidal suspensions and polymeric gels is of interest for the description of many biological and synthetic systems, such as cellular membranes, biological matrices, ion-exchangers, new materials for power sources, and gel-based sensors. The transport of ions in ionic polymeric media is suppressed due to long range electrostatic interactions between polyions and counterions or coions. This paper presents an ... |
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| Lithium Insertion in Nanoporous Carbon Materials Produced from Carbides |
APR 2001 |
6 pages |
| Authors:
J. M. Kotina; V. M. Lebedev; A. G. Ilves; G. V. Patsekina; L. M. Tuhkonen; NUCLEAR PHYSICS INST SAINT PETERSBURG (RUSSIA)
|
| In this work, the results of a study of the lithium insertion process in nanoporous carbons (NPC) obtained from carbides (SiC, TiC, Mo(2)C) by chlorination are presented. Lithium insertion was produced in the temperature range of 30-200 degrees C via the vacuum deposition and diffusion. The major analytical tools for study included nuclear reaction method and X-ray diffraction. Diffusion coefficients of lithium at this temperature interval were estimated. Possible mechanism ... |
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| Transitioning Model Potentials to Real Systems |
FEB 2001 |
40 pages |
| Authors:
Scott D. Bembenek; Betsy M. Rice; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
|
| The parameters of two pairs of potentials that describe argon over its entire liquid phase at a fixed pressure were optimized through a novel application of constant temperature and pressure molecular dynamics (NPT-MD) and Monte Carlo (NPT-MC) computer simulations. The forms of these potentials were those of a modified Lennard-Jones potential and a Lennard-Jones potential (Lennard-Jones, J. E. Physica, Vol. 4. p. 941, 1937). The optimized potential determined using NPT-MD ... |
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| The Morphological Evolution of TiO2 Scale Formed on Various 1-D and 2-D Geometries of Titanium |
23 SEP 2000 |
106 pages |
| Authors:
David H. Allen; TEXAS A AND M UNIV COLLEGE STATION DEPT OF AEROSPACE ENGINEERING
|
| The purpose of this study is to experimentally quantify the multi- dimensional growth characteristics of the oxide scale formed on commercially pure titanium at 700 deg C in a flowing air environment. The geometries considered herein had characteristic dimensions that were appropriately sized to match the thickness of the oxide scale and were fabricated into shapes of solid and hollow cylinders and external and internal wedges. Scanning electron microscopy (SEM) ... |
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| Transparent Barrier Urethanes Based on Polyethylene Soft Segments |
AUG 2000 |
33 pages |
| Authors:
Nora C. Beck Tan; Eugene Napadensky; James M. Sloan; Sharon Ma; Stuart L. Cooper; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
|
| A series of polyurethane elastomers has been synthesized through co- polymerization of polyethylene soft segments and methylene bis(4- phenylisocyanate) (MDI) and hydrogenated MDI (H(12)MDI). Polyethylene soft segments were prepared by the hydrogenation of polybutadiene polyols, either before or after copolymer synthesis. Polyols from three different suppliers were used as precursors and ranged in branch content from 15% to ^90%. Flexible, transparent materials were produced. ... |
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| Complex Impedance Studies of S-SEBS Block Polymer Proton-Conducting Membranes |
01 JUL 2000 |
23 pages |
| Authors:
C. A. Edmondson; J. J. Fontanella; S. H. Chung; S. G. Greenbaum; G. E. Wnek; NAVAL ACADEMY ANNAPOLIS MD DEPT OF PHYSICS
|
| Water uptake, swelling, H pulsed gradient spin-echo nuclear magnetic resonance (NMR) and variable temperature and pressure complex impedance/ electrical conductivity studies have been carried out on the sulfonated styrene/ ethylene-butylene/styrene (S-SEBS) triblock polymer proton conducting membrane. All of the data show different characteristics above and below about 10 wt-% water. For example, the diffusion coefficients, D from NMR and D, calculated from conductivity data (which ... |
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| Modeling the Environmental Effects on Carbon Fibers in a Ceramic Matrix at Oxidizing Conditions |
JUL 2000 |
12 pages |
| Authors:
Michael C. Halbig; James D. Cawley; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH GLENN RESEARCH CENTER
|
| Carbon fiber/silicon carbide matrix composites (C/SiC) are promising materials for space applications such as nozzles, thrusters, and bladed disks. However the as-fabricated, cracked nature of the material makes it susceptible to environmental degradation due to fiber oxidation. Theoretical models can be used to gain a better understanding of how certain variables (i.e. temperature, environment, diffusion coefficient and reaction rate constant) are related to a ... |
|
| Computational Issues in Analysis and Design of Chemical-Laser Flow-Fields (CD-ROM) |
08 MAY 2000 |
|
| Authors:
W. M. Eppard; Eugene M. Cliff; AEROSOFT INC BLACKSBURG VA
|
| ELECTRONIC FILE CHARACTERISTICS: 1 file; Adobe Acrobat v.3.0 PDF; col. ill. PHYSICAL DESCRIPTION: 1 computer laser optical disc (CD-ROM); 4 3/4 in.; 818KB. SYSTEMS DETAIL NOTE: IBM-clone PC-compatible; requires CD-ROM drive. ABSTRACT: The Phase-I COIL effort has focused on extending AeroSoft's GASP and SENSE software for COIL-laser analysis and design. Important improvements include: modifications to the species diffusion model to account for effective diffusion coefficients and pressure-driven diffusion effects, modifications ... |
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| Modeling the Oxidation Kinetics of Continuous Carbon Fibers in a CeramicMatrix |
JAN 2000 |
11 pages |
| Authors:
Michael C. Halbig; James D. Cawley; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH GLENN RESEARCH CENTER
|
| A finite difference model has been developed and was used to study the oxidation kinetics of carbon fibers exposed by the presence of a through- thickness matrix crack in a ceramic matrix composite. Air was the environment of interest so that the model could be compared to experimental testing. The limiting steps of diffusion controlled and reaction controlled kinetics were investigated by changing the value of ... |
|
| Computational Issues in Analysis and Design of Chemical-Laser FLow- Fields |
31 DEC 1999 |
32 pages |
| Authors:
W. M. Eppard; Eugene Cliff; AEROSOFT INC BLACKSBURG VA
|
| The Phase-I COIL effort has focused on extending AeroSoft's GASP and SENSE software for COIL-laser analysis and design. Important improvements include: modifications to the species diffusion model to account for effective diffusion coefficients and pressure-driven diffusion effects, modifications to account for laser power extraction, the addition of a COIL chemistry model, and the development of a strategy for implementing a coupled flow-solver/power- extraction sensitivity ... |
|
| New Microlayer and Nanolayer Polymer Composites |
DEC 1999 |
12 pages |
| Authors:
Eric Baer; Anne Hiltner; CASE WESTERN RESERVE UNIV CLEVELAND OH
|
| The highlights of this period are centered around the development of polymer nanolayer systems by a novel continuous coextrusion method. Nanolayers ranging in thickness between 5 rim to 500 nm have been manufactured using inexpensive polymeric materials such as polystyrene, polystryene acrylonitrile copolymers, polypropylene, polyethylene, polycarbonate and polymethylmethacrylate. Two and three component systems have been made from various combinations of these polymers. In particular, the morphology of polypropylene has been ... |
|
| Microscopic Modeling Of Nanotribology, Elastohydrodynamics, Lubrication and Interfacial Structures |
28 OCT 1999 |
20 pages |
| Authors:
Uzi Landman; GEORGIA INST OF TECH ATLANTA SCHOOL OFPHYSICS
|
| The research program focused on formulation, development, implementation and application of novel modeling and large-scale atomistic classical and quantum molecular dynamics simulations, for investigations of critical issues in areas of basic and technological importance. These studies include: atomic-scale processes and mechanisms underlying tribological phenomena and thin-film lubrication; mechanical, electronic and transport properties of nanoscale interfacial junctions; structure and thermodynamics of noncrystalline systems and surface ... |
|
| Transport of Ions and Molecules in Biopolymeric Gels: Electroanalytical Studies |
15 JUL 1999 |
9 pages |
| Authors:
Richard T. Carlin; M. Ciszkowska; M. D. Guillaume; BROOKLYN COLL NY DEPT OF CHEMISTRY
|
| Transport of ions and molecules was studied in hydrogels of uncharged and anionic biopolymers, agarose and iota-carrageenan. Diffusion coefficients of neutral and ionic electroactive probes, the uncharged radical 2,2,6,6- tetramethyl-1-pipperidinyloxy, TEMPO, and Tl(I), were determined rapidly and precisely from steady-state transport-limited currents at platinum and mercury microelectrodes. Transport properties of both probes were studied in gels as effected by temperature, ionic strength and concentration of the biopolymer, and they were ... |
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| Electroanalytical Studies of Transport Phenomena and Electrostatic Interactions in Polyacrylate Gels |
15 JUL 1999 |
11 pages |
| Authors:
Wojciech Hyk; Malgorzata Ciszkowska; BROOKLYN COLL NY DEPT OF CHEMISTRY
|
| The transport of uncharged electroactive probes, 1,1'- ferrocenedimethanol and 4-hydroxy-TEMPO, and electroactive cations, Tl(+), was studied in polyacrylate hydrogels using steady-state voltammetry at platinum and mercury film microelectrodes, and conductance measurements. It was found that for concentrations of polymer less than 1.5%, the diffusion coefficient of uncharged probes does not differ significantly from that observed in aqueous solutions without a polymeric network. For the probe cation, strong electrostatic interactions were ... |
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| Atomic Resolution Observation of GaAs Doped with Sn by Scanning Tunneling Microscopy |
JUN 1998 |
4 pages |
| Authors:
S. Y. Shapoval; V. L. Gurtovoi; U. Hakansson; L. Samuelson; L. Montelius; LUND UNIV (SWEDEN) DEPT OF SOLID STATEPHYSICS
|
| Substitutional donor Sn(sub Ga) atoms in the near surface region below the GaAs (110) cleaved surface were observed by ultrahigh vacuum STM. Surface Sn atoms were observed as localized features, whereas subsurface Sn atoms have delocalized nature wfth the mean width of 2.5 nm. For an atom, elementary act of surface diffusion was observed and surface diffusion coefficient at room temperature was evaluated. |
|
| Investigating Sorbent Geometry Response Surfaces from Sorption Rate Data |
MAR 1998 |
91 pages |
| Authors:
H. M. Harrison; AIR FORCE INST OF TECH WRIGHT-PATTERSONAFB OH DEPT OF OPERATIONAL SCIENCE
|
| Sorption and desorption of hydrophobic organic compounds (HOCs) into soil particles occurs at Air Force contamination sites. Long-term desorption extends clean up time, costing billions. Accurately modeling desorption will reduce costs and improve clean up designs. State of the art models depict soil as uniform spherical particles which lose the effect of longer sorption path lengths. An alternate approach, the multiple sites in series (MSS) ... |
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| Analysis of Linear and Monoclinal River Wave Solutions |
JAN 1998 |
32 pages |
| Authors:
Michael G. Ferrick; Nicholas J. Goodman; COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER NH
|
| Linear dynamic wave and diffusion wave analytical solutions are obtained for a small, abrupt flow increase from an initial to a higher steady flow. Equations for the celerities of points along the wave profiles are developed from the solutions and related to the kinematic wave and dynamic wave celerities. The linear solutions are compared systematically in a series of case studies to evaluate the differences caused by inertia. These comparisons ... |
|
| Vapor Transport in Unsaturated Soil |
30 JUN 97 |
38 pages |
| Authors:
Leonard W. Lion; Brent Alspach; Jason Gilbert; Sean Lorden; CORNELL UNIV ITHACA NY DEPT OF CIVIL AND ENVIRONMENTAL ENGINEERING
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| Experiments were performed to determine the desorption kinetics, diffusion, and advection of two common subsurface VOC contaminants: trichloroethylene (TCE), and chloroform (CF) both individually and as a gas mixtures. Effective diffusion coefficients of TCE were determined in the absence and presence of CF. At high relative pressure the 'effective' distribution coefficient for these vapors decreased and consequently their diffusive transport was enhanced. This result is attributed to the presence of ... |
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| Numerical Modeling Study of the Gulf of Mexico Basin: Skill Assessment |
APR 1997 |
107 pages |
| Authors:
A. D. Kirwan; OLD DOMINION UNIV NORFOLK VA DEPT OF OCEANOGRAPHY
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| This report contains the results of an assessment of a three dimensional primitive equation model simulation of the Gulf of Mexico, using surface drifter observations collected as part of the Sculp program. The assessment focuses mainly on the surface circulation of the Louisiana-Texas shelf. The model is fully thermodynamic, and it assimilates both TOPEX and ERS-1 altimetric data. The drifter observations were used to asses the model's ability to accurately ... |
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| Crystal Chemistry of Ceramic/Metal Systems |
16 JAN 97 |
9 pages |
| Authors:
Robert R. Reeber; NORTH CAROLINA UNIV AT CHAPEL HILL DEPT OF GEOLOGY
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| Robust models for predicting high temperature/pressure thermal expansion for a range of solids have been developed. The inter-relationships between several thermophysical properties including thermal expansion, specific heat, elastic properties, and self-diffusion of materials has been investigated. The role of defects on thermal expansion at high temperature and pressure has also been explored. During the course of the project several models for thermal expansion were developed extending earlier work of Reeber. ... |
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| Investigations of Shock Wave Synthesis of Metastable Compounds |
JAN 1997 |
14 pages |
| Authors:
Oleg N. Breusov; Anatoly N. Dremin; AKADEMIYA NAUK SSSR MOSCOW INST KHIMICHESKOI FIZIKI
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| In accordance with the contract requirements the investigation of phase formation in GeO2-SiO2 system under the effect of shock waves has been undertaken with the aim of revealing of possibilities of explosion as a preparative method in the chemistry of metastable compounds as well as of investigating of the mechanism of chemical reactions in shock wave. The system has been taken as a model since no compounds were obtained in ... |
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| Boundary Layer Effect on the Frontal Interaction with Mountain |
1997 |
8 pages |
| Authors:
Melinda S. Peng; John Powell; R. T. Williams; NAVAL RESEARCH LAB MONTEREY CA MARINE METEOROLOGY DIV
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| A hydrostatic, primitive equation model with frontogenetical deformation forcing is used to simulate the passage of cold fronts over a two dimensional ridge. The model includes a K-theory boundary layer (PBL) parameterization with implicitly defined diffusion coefficients. Relative to the inviscid results, the PBL simulations produced reduced frontolysis on the upwind slope and reduced frontogenesis on the lee slope, resulting in significantly smaller frontogenetic variations over the mountain. This is ... |
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