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1

The diffusion coefficients of gaseous and volatile species during the irradiation of uranium dioxide  

NASA Astrophysics Data System (ADS)

Measurements of release for rare gas fission products from single and polycrystalline uranium dioxide during irradiation are described. The fuel samples were enriched to 20% in 235U to avoid uncertainties in the fission rate due to plutonium production. The surface area of the single crystals was determined optically to provide a reference of known surface-to-volume ratio for the determination of diffusion coefficients for the rare gases and their halogen precursors. The initial part of the experiment was isothermal, during which the time dependence of release was observed and the polycrystalline material developed extensively interlinked grain-boundary porosity. Subsequently the temperature dependence of the release process was studied. It is concluded that the diffusion of rare gas atoms in UO 2 during irradiation is a complex process involving more than one rate-controlling mechanism and bears a close similarity to cation self-diffusion. In both cases, the low-temperature kinetics are radically affected by irradiation damage. The present results are well represented by a composite diffusion coefficient containing three terms — one representing high-temperature intrinsic behaviour whilst the other two represent the effect of irradiation enhancement. This equation should be modified to take account of intragranular bubbles at all temperatures for stable gas release, and at high temperatures in the case of unstable species.

Turnbull, J. A.; Friskney, C. A.; Findlay, J. R.; Johnson, F. A.; Walter, A. J.

1982-06-01

2

Virial Coefficients for Gaseous Hydrocarbons.  

National Technical Information Service (NTIS)

A compilation of second, third and, in some cases, fourth virial coefficients of the gaseous hydrocarbons is presented. Most of the values listed have been obtained from a re-analysis of the published experimental p-V-T data. However, where the publicatio...

A. Pompe T. H. Spurling

1974-01-01

3

Calculation of Viscosity and Diffusion Coefficients for Two Binary Gaseous Mixtures Using the Semi-empirical Inversion Method  

NASA Astrophysics Data System (ADS)

The accurate reduced potential energies for two binary gas mixtures including benzene-methanol and methane-tetrafluoromethane at low density have been obtained by direct inversion of the viscosity collision integral equations. The kinetic theory along with the extended principle of corresponding-states has been used to calculate the viscosity and diffusion coefficients over a wide range of temperature and composition. Good agreements between calculated and experimental data are obtained.

Rafiee, Hamid Reza; Rastgar, Mina; Heidari, Neda

2011-08-01

4

Predicting protein diffusion coefficients.  

PubMed Central

Diffusion coefficients for proteins in water are predicted. The numerical method developed is general enough to be applied to a wide range of protein surface shapes, from rodlike to globular. Results are presented for lysozyme and tobacco mosaic virus, and they are compared with actual data and with predictions made by less general methods. Images Fig. 2

Brune, D; Kim, S

1993-01-01

5

Feasibility of gas-phase decontamination of gaseous diffusion equipment  

Microsoft Academic Search

The five buildings at the K-25 Site formerly involved in the gaseous diffusion process contain 5000 gaseous diffusion stages as well as support facilities that are internally contaminated with uranium deposits. The gaseous diffusion facilities located at the Portsmouth Gaseous Diffusion Plant and the Paducah Gaseous Diffusion Plant also contain similar equipment and will eventually close. The decontamination of these

E. B. Munday; D. W. Simmons

1993-01-01

6

Studies of Gaseous Multiplication Coefficient in Isobutane  

SciTech Connect

This work presents the studies of gaseous multiplication coefficient behavior for isobutane, as function of the reduced electric field, by means of signal amplitude analysis. The experimental method used is based on the Pulsed Townsend technique, which follows from Townsend equation solution for a uniform electric field. In our configuration, the anode is made of a high resistivity (2.10{sup 12} OMEGA.cm) glass, while the cathode is of aluminium. In order to validate the technique and to analyze effects of non-uniformity, results for nitrogen, which has well-established data available in literature, are also presented.

Lima, Iara B.; Vivaldini, Tulio C. [Instituto de Pesquisas Energeticas e Nucleares, 05508-000, Cidade Universitaria, Sao Paulo (Brazil); Goncalves, Josemary A. C.; Botelho, Suzana; Bueno Tobias, Carmen C. [Instituto de Pesquisas Energeticas e Nucleares, 05508-000, Cidade Universitaria, Sao Paulo (Brazil); Departamento de Fisica, Pontificia Universidade Catolica de Sao Paulo, 01303-050, Sao Paulo (Brazil); Ridenti, Marco A.; Pascholati, Paulo R. [Instituto de Fisica, Universidade de Sao Paulo, 05508-090, Cidade Universitaria, Sao Paulo (Brazil); Fonte, Paulo; Mangiarotti, Alessio [Laboratorio de Instrumentacao e Fisica Experimental de Particulas, Departamento de Fisica da Universidade de Coimbra, 3004-516, Coimbra (Portugal)

2010-05-21

7

Feasibility of gas-phase decontamination of gaseous diffusion equipment.  

National Technical Information Service (NTIS)

The five buildings at the K-25 Site formerly involved in the gaseous diffusion process contain 5000 gaseous diffusion stages as well as support facilities that are internally contaminated with uranium deposits. The gaseous diffusion facilities located at ...

E. B. Munday D. W. Simmons

1993-01-01

8

Uranium enrichment export control guide: Gaseous diffusion  

SciTech Connect

This document was prepared to serve as a guide for export control officials in their interpretation, understanding, and implementation of export laws that relate to the Zangger International Trigger List for gaseous diffusion uranium enrichment process components, equipment, and materials. Particular emphasis is focused on items that are especially designed or prepared since export controls are required for these by States that are party to the International Nuclear Nonproliferation Treaty.

Not Available

1989-09-01

9

Portable vapor diffusion coefficient meter  

DOEpatents

An apparatus for measuring the effective vapor diffusion coefficient of a test vapor diffusing through a sample of porous media contained within a test chamber. A chemical sensor measures the time-varying concentration of vapor that has diffused a known distance through the porous media. A data processor contained within the apparatus compares the measured sensor data with analytical predictions of the response curve based on the transient diffusion equation using Fick's Law, iterating on the choice of an effective vapor diffusion coefficient until the difference between the predicted and measured curves is minimized. Optionally, a purge fluid can forced through the porous media, permitting the apparatus to also measure a gas-phase permeability. The apparatus can be made lightweight, self-powered, and portable for use in the field.

Ho, Clifford K. (Albuquerque, NM)

2007-06-12

10

Viscosity and Thermal Conductivity Coefficients of Gaseous and Liquid Oxygen.  

National Technical Information Service (NTIS)

Equations and tables are presented for the viscosity and thermal conductivity coefficients of gaseous and liquid oxygen at temperatures between 80 K and 400 K for pressures up to 200 atm. and at temperatures between 80 K and 2000 K for the dilute gas. A d...

H. J. M. Hanley R. D. Mccarty J. V. Sengers

1974-01-01

11

Radiant Extinction Of Gaseous Diffusion Flames  

NASA Technical Reports Server (NTRS)

The absence of buoyancy-induced flows in microgravity (mu:g) and the resulting increase in the reactant residence time significantly alters the fundamentals of many combustion processes. Substantial differences between normal gravity (ng) and :g flames have been reported in experiments on candle flames [1, 2], flame spread over solids [3, 4], droplet combustion [5,6], and others. These differences are more basic than just in the visible flame shape. Longer residence times and higher concentration of combustion products in the flame zone create a thermochemical environment that changes the flame chemistry and the heat and mass transfer processes. Processes such as flame radiation, that are often ignored in ng, become very important and sometimes even controlling. Furthermore, microgravity conditions considerably enhance flame radiation by: (i) the build-up of combustion products in the high-temperature reaction zone which increases the gas radiation, and (ii) longer residence times make conditions appropriate for substantial amounts of soot to form which is also responsible for radiative heat loss. Thus, it is anticipated that radiative heat loss may eventually extinguish the Aweak@ (low burning rate per unit flame area) :g diffusion flame. Yet, space shuttle experiments on candle flames show that in an infinite ambient atmosphere, the hemispherical candle flame in :g will burn indefinitely [1]. This may be because of the coupling between the fuel production rate and the flame via the heat-feedback mechanism for candle flames, flames over solids and fuel droplet flames. Thus, to focus only on the gas-phase phenomena leading to radiative extinction, aerodynamically stabilized gaseous diffusion flames are examined. This enables independent control of the fuel flow rate to help identify conditions under which radiative extinction occurs. Also, spherical geometry is chosen for the :g experiments and modeling because: (i) It reduces the complexity by making the problem one-dimensional. (ii) The spherical diffusion flame completely encloses the soot which is formed on the fuel rich side of the reaction zone. This increases the importance of flame radiation because now both soot and gaseous combustion products co-exist inside the high temperature spherical diffusion flame. (iii) For small fuel injection velocities, as is usually the case for a pyrolyzing solid, the diffusion flame in :g around the solid naturally develops spherical symmetry. Thus, spherical diffusion flames are of interest to fires in :g and identifying conditions that lead to radiation-induced extinction is important for spacecraft fire safety.

Berhan, S.; Chernovsky, M.; Atreya, A.; Baum, Howard R.; Sacksteder, Kurt R.

2003-01-01

12

Radiant Extinction of Gaseous Diffusion Flames  

NASA Technical Reports Server (NTRS)

The absence of buoyancy-induced flows in microgravity (mu-g) and the resulting increase in the reactant residence time significantly alters the fundamentals of many combustion processes. Substantial differences between normal gravity (ng) and mu-g flames have been reported in experiments on candle flames, flame spread over solids, droplet combustion, and others. These differences are more basic than just in the visible flame shape. Longer residence times and higher concentration of combustion products in the flame zone create a thermochemical environment that changes the flame chemistry and the heat and mass transfer processes. Processes such as flame radiation, that are often ignored in ng, become very important and sometimes even controlling. Furthermore, microgravity conditions considerably enhance flame radiation by: (1) the build-up of combustion products in the high-temperature reaction zone which increases the gas radiation; and (2) longer residence times make conditions appropriate for substantial amounts of soot to form which is also responsible for radiative heat loss. Thus, it is anticipated that radiative heat loss may eventually extinguish the "weak" (low burning rate per unit flame area) mu-g diffusion flame. Yet, space shuttle experiments on candle flames show that in an infinite ambient atmosphere, the hemispherical candle flame in mu-g will burn indefinitely. This may be because of the coupling between the fuel production rate and the flame via the heat-feedback mechanism for candle flames, flames over solids and fuel droplet flames. Thus, to focus only on the gas-phase phenomena leading to radiative extinction, aerodynamically stabilized gaseous diffusion flames are examined. This enables independent control of the fuel flow rate to help identify conditions under which radiative extinction occurs. Also, spherical geometry is chosen for the mu-g experiments and modeling because: (1) It reduces the complexity by making the problem one-dimensional; (2) The spherical diffusion flame completely encloses the soot which is formed on the fuel rich side of the reaction zone. This increases the importance of flame radiation because now both soot and gaseous combustion products co-exist inside the high temperature spherical diffusion flame; (3) For small fuel injection velocities, as is usually the case for a pyrolyzing solid, the diffusion flame in mu-g around the solid naturally develops spherical symmetry. Thus, spherical diffusion flames are of interest to fires in mu-g and identifying conditions that lead to radiation-induced extinction is important for spacecraft fire safety.

Berhan, Sean; Atreya, Arvind; Everest, David; Sacksteder, Kurt R.

1999-01-01

13

Paducah Gaseous Diffusion Plant Environmental report for 1990. Volume 3.  

National Technical Information Service (NTIS)

This two-part report, Paducah Gaseous Diffusion Plant Site Environmental Report for 1990, is published annually. It reflects the results of a comprehensive, year-round program to monitor the impact of operations at Paducah Gaseous Diffusion Plant (PGDP) o...

D. Counce-Brown

1991-01-01

14

Paducah Gaseous Diffusion Plant Environmental report for 1990  

Microsoft Academic Search

This two-part report, Paducah Gaseous Diffusion Plant Site Environmental Report for 1990, is published annually. It reflects the results of a comprehensive, year-round program to monitor the impact of operations at Paducah Gaseous Diffusion Plant (PGDP) on the area's groundwater and surface waters, soil, air quality, vegetation, and wildlife. In addition, an assessment of the effect of PGDP effluents on

Counce-Brown

1991-01-01

15

Paducah Gaseous Diffusion Plant environmental report for 1992  

Microsoft Academic Search

This two-part report, Paducah Gaseous Diffusion Plant Environmental Report for 1992, is published annually. It reflects the results of an environmental monitoring program designed to quantify potential increases in the concentration of contaminants and potential doses to the resident human population. The Paducah Gaseous Diffusion Plant (PGDP) overall goal for environmental management is to protect the environment and PGDP`s neighbors

1993-01-01

16

Favorite Demonstrations: Gaseous Diffusion: A Demonstration of Graham's Law.  

ERIC Educational Resources Information Center

Describes a demonstration in which gaseous ammonia and hydrochloric acid are used to illustrate rates of diffusion (Graham's Law). Simple equipment needed for the demonstration include a long tube, rubber stoppes, and cotton. Two related demonstrations are also explained. (DH)

Kauffman, George B.; Ebner, Ronald D.

1985-01-01

17

Feasibility of gas-phase decontamination of gaseous diffusion equipment  

SciTech Connect

The five buildings at the K-25 Site formerly involved in the gaseous diffusion process contain 5000 gaseous diffusion stages as well as support facilities that are internally contaminated with uranium deposits. The gaseous diffusion facilities located at the Portsmouth Gaseous Diffusion Plant and the Paducah Gaseous Diffusion Plant also contain similar equipment and will eventually close. The decontamination of these facilities will require the most cost-effective technology consistent with the criticality, health physics, industrial hygiene, and environmental concerns; the technology must keep exposures to hazardous substances to levels as low as reasonably achievable (ALARA). This report documents recent laboratory experiments that were conducted to determine the feasibility of gas-phase decontamination of the internal surfaces of the gaseous diffusion equipment that is contaminated with uranium deposits. A gaseous fluorinating agent is used to fluorinate the solid uranium deposits to gaseous uranium hexafluoride (UF{sub 6}), which can be recovered by chemical trapping or freezing. The lab results regarding the feasibility of the gas-phase process are encouraging. These results especially showed promise for a novel decontamination approach called the long-term, low-temperature (LTLT) process. In the LTLT process: The equipment is rendered leak tight, evacuated, leak tested, and pretreated, charged with chlorine trifluoride (ClF{sub 3}) to subatmospheric pressure, left for an extended period, possibly > 4 months, while processing other items. Then the UF{sub 6} and other gases are evacuated. The UF{sub 6} is recovered by chemical trapping. The lab results demonstrated that ClF{sub 3} gas at subatmospheric pressure and at {approx} 75{degree}F is capable of volatilizing heavy deposits of uranyl fluoride from copper metal surfaces sufficiently that the remaining radioactive emissions are below limits.

Munday, E.B.; Simmons, D.W.

1993-02-01

18

Diffusion coefficients of several aqueous alkanolamine solutions  

SciTech Connect

In absorption processes of acid gases (H[sub 2]S, CO[sub 2], COS) in alkanolamine solutions, diffusion coefficients are used for the calculation of the mass transfer rate. The Taylor dispersion technique was applied for the determination of diffusion coefficients of various systems. Experiments with the system KCl in water showed that the experimental setup provides accurate data. For the alkanolamines monoethanolamine (MEA), diethanolamine (DEA), methyldiethanolamine (MDEA), and di-2-propanolamine (DIPA), correlations for the diffusion coefficient as a function of temperature at different concentrations are given. A single relation for every amine has been derived which correlates the diffusion coefficients as a function of temperature and concentration. The temperature was varied between 298 and 348 K, and the concentration between 0 and 4000-5000 mol/m[sup 3]. Furthermore, a modified Stokes-Einstein relation is presented for the prediction of the diffusion coefficients in the alkanolamines in relation to the viscosity of the solvent and the diffusion coefficient at infinite dilution. The diffusion coefficients at low concentrations are compared with some available relations for the estimation of diffusion coefficients at infinite dilution, and it appears that the agreement is fairly good.

Snijder, E.D.; Riele, M.J.M. te; Versteeg, G.F.; Swaaij, W.P.M. van (Twente Univ. of Technology, Enschede (Netherlands). Dept. of Chemical Engineering)

1993-07-01

19

Radon diffusion coefficients for residential concretes  

SciTech Connect

Radon gas diffusion through concrete can be a significant mechanism for radon entry into dwellings. Measurements of radon diffusion coefficients in the pores of residential concretes ranged from 2.1 x 10{sup {minus}8} m{sup 2} s{sup {minus}1} to 5.2 x 10{sup {minus}7} m{sup 2} s{sup {minus}1}. The pore diffusion coefficients generally increased with the water-cement ratio of the concrete and decreased with its density. A least-squares regression of the diffusion coefficients on concrete density gave an r value of -0.73. 16 refs., 2 figs., 3 tabs.

Rogers, V.C.; Nielson, K.K.; Holt, R.B. [Rogers and Associates Engineering Corp., Salt Lake City, UT (United States); Snoddy, R. [Acurex Environmental Corp., Research Triangle Park, NC (United States)

1994-09-01

20

Radon diffusion coefficients for residential concretes  

Microsoft Academic Search

Radon gas diffusion through concrete can be a significant mechanism for radon entry into dwellings. Measurements of radon diffusion coefficients in the pores of residential concretes ranged from 2.1 x 10⁻⁸ m² s⁻¹ to 5.2 x 10⁻⁷ m² s⁻¹. The pore diffusion coefficients generally increased with the water-cement ratio of the concrete and decreased with its density. A least-squares regression

Vern C. Rogers; Kirk K. Nielson; Rodger B. Holt; Richard Snoddy

1994-01-01

21

Obtaining transport diffusion coefficients from self-diffusion coefficients in nanoporous adsorption systems  

NASA Astrophysics Data System (ADS)

In a continuation of the study of the adsorption and transport properties in a nanoporous adsorption system, transport diffusion coefficients are predicted from the self-diffusion coefficients using the Darken equation, modified for use in the adsorbed phase. We obtain self-diffusion coefficients using equilibrium molecular dynamics (MD) simulations. Adsorption equilibrium data are required in this modified form, which are obtained using grand canonical Monte Carlo (GCMC) simulations. We show that principal component regression provides an elegant and robust method to integrate the data available from the MD and GCMC simulations for the prediction of transport diffusivities. We investigate the effect of the adsorbed phase concentration, mole fraction and temperature on the transport diffusion coefficient thus predicted. We show that the self- and the transport diffusion coefficients decrease with increasing adsorbed phase concentration. We also show that the transport diffusion coefficients decrease with increasing methane mole fraction, in contrast to the behaviour of the self-diffusion coefficients.

Adhangale, Parag; Keffer, David J.

22

Molecular Diffusion Coefficients: Experimental Determination and Demonstration.  

ERIC Educational Resources Information Center

Presented are laboratory methods which allow the demonstration and determination of the diffusion coefficients of compounds ranging in size from water to small proteins. Included are the procedures involving the use of a spectrometer, UV cell, triterated agar, and oxygen diffusion. Results including quantification are described. (CW)

Fate, Gwendolyn; Lynn, David G.

1990-01-01

23

The effective diffusion coefficient for porous rubble  

Microsoft Academic Search

Each waste package in the proposed Yucca Mountain repository is to be separated from surrounded unsaturated rock by a 2-cm air gap annulus. However, if the annulus becomes filled with rock and rubble, there can exist pathways for diffusive release of radionuclides through pore liquid, even if the repository remains unsaturated. The effective diffusion coefficient for radionuclide release through pore

M. M. Sadeghi; W. W.-L. Lee; T. H. Pigford; P. L. Chambre

1990-01-01

24

Diffuse reflection coefficient of a stratified sea.  

PubMed

A differential equation of a Riccati type for the diffuse reflection coefficient of a stratified sea is proposed. For a homogeneous sea with arbitrary inherent optical properties this equation is solved analytically. For an inhomogeneous sea it is solved approximately for any arbitrary stratification. The resulting equation expresses the diffuse reflection coefficient of the sea through vertical profiles of absorption and backscattering coefficients, bottom albedo, and sea depth. The results of calculations with this equation are compared with Monte Carlo computations. It was found that the precision of this approach is in the range of 15%. PMID:18305694

Haltrin, V I

1999-02-20

25

State-Corporate Crime and the Paducah Gaseous Diffusion Plant  

Microsoft Academic Search

While criminologists have for some time examined state and corporate crime as separate entities, the concept of state-corporate crime highlighting joint government and private corporate action causing criminal harm is a recent area of study with relatively few published case studies (Matthews and Kauzlarich, 2000). This paper focuses on state-corporate crime at the Paducah Gaseous Diffusion Plant (PGDP) in Paducah,

Alan S. Bruce; Paul J. Becker

2007-01-01

26

Overview of seismic considerations at the Paducah Gaseous Diffusion Plant  

Microsoft Academic Search

This paper presents an overview of seismic considerations at the Paducah Gaseous Diffusion Plant (PGDP), which is managed by Martin Marietta Energy Systems, Inc., for the Department of Energy (DOE). The overview describes the original design, the seismic evaluations performed for the Safety Analysis Report (SAR) issued in 1985, and current evaluations and designs to address revised DOE requirements. Future

R. J. Hunt; W. C. Stoddart; W. A. Burnett; J. E. Beavers

1992-01-01

27

Paducah Gaseous Diffusion Plant environmental report for 1991  

Microsoft Academic Search

This two-part report is published annually. It reflects the results of an environmental monitoring program designed to quantify potential increases in the concentration of contaminants and potential doses to the resident human population from the Paducah Gaseous Diffusion Plant (PGDP). PGDP's overall goal for environmental management is to protect the environment and PGDP's neighbors and to maintain full compliance with

1992-01-01

28

Seismic issues at the Paducah Gaseous Diffusion Plant  

Microsoft Academic Search

A seismic expert workshop was held at the Paducah Gaseous Diffusion Plant (PGDP) on March 13--15, 1989. the PGDP is operated by Martin Marietta Energy Systems, Inc. for the United States Department of Energy (DOE). During the last twenty years the design criteria for natural phenomenon hazards has steadily become more demanding at all of the DOE Oak Ridge Operations

Fricke

1989-01-01

29

Radioactive effluents, Portsmouth Gaseous Diffusion Plant, calendar year 1982  

Microsoft Academic Search

Radioactive discharges from the Portsmouth Gaseous Diffusion Plant are discussed and tabulated. Tables indicate both the location of the discharge and the nuclides discharged. All discharges for 1982 are well below the Radioactive Concentration Guide limits specified in DOE Order 5480.1, Chapter XI. 1 figure.

T. A. Acox; L. F. Hary; L. S. Klein

1983-01-01

30

Paducah Gaseous Diffusion Plant environmental report for 1989  

Microsoft Academic Search

This two-part environmental report is published annually. It reflects the results of a comprehensive, year-round program to monitor the impact of operations at Paducah Gaseous Diffusion Plant (PGDP) on the area's groundwater and surface waters, soil, air quality, vegetation, and wildlife. In addition, an assessment of the effect of PGDP effluents on the resident human population is made. PGDP's overall

1990-01-01

31

Paducah Gaseous Diffusion Plant Northwest Plume interceptor system evaluation  

Microsoft Academic Search

The Paducah Gaseous Diffusion Plant (PGDP) recently installed an interceptor system consisting of four wells, evenly divided between two well fields, to contain the Northwest Plume. As stated in the Northwest Plume Record of Decision (ROD), groundwater will be pumped at a rate to reduce further contamination and initiate control of the northwest contaminant plume. The objective of this evaluation

A. D. Laase; J. L. Clausen

1998-01-01

32

An introduction to technetium in the gaseous diffusion cascades  

SciTech Connect

The radioisotope technetium-99 ({sup 99}Tc) was introduced into the gaseous diffusion plants (GDP) as a contaminant in uranium that had been reprocessed from spent nuclear reactor fuel. {sup 99}Tc is a product of the nuclear fission of uranium-235 ({sup 235}U). The significantly higher emitted radioactivity of {sup 99}Tc generates concern in the enrichment complex and warrants increased attention (1) to the control of all site emissions, (2) to worker exposures and contamination control when process equipment requires disassembly and decontamination, and (3) to product purity when the enriched uranium hexafluoride (UF{sub 6}) product is marketed to the private sector. A total of 101,268 metric tons of RU ({approximately}96% of the total) was fed at the Paducah Gaseous Diffusion Plant (PGDP) between FY1953 and FY1976. An additional 5600 metric tons of RU from the government reactors were fed at the Oak Ridge Gaseous Diffusion Plant (ORGDP), plus an approximate 500 tons of foreign reactor returns. Only a small amount of RU was fed directly at the Portsmouth Gaseous Diffusion Plant (PORTS). The slightly enriched PGDP product was then fed to either the ORGDP or PORTS cascades for final enrichment. Bailey estimated in 1988 that of the 606 kg of Tc received at PGDP from RU, 121 kg was subsequently re-fed to ORGDP and 85 kg re-fed to PORTS.

Simmons, D.W.

1996-09-01

33

Fluidized bed biodenitrification of gaseous diffusion plant aqueous wastes  

SciTech Connect

Decontamination and uranium recovery operations at the Portsmouth Gaseous Diffusion Plant generate nitrate containing raffinates. A biodenitrification process will be used to meet more stringent EPA nitrate emission constraints soon in effect. Fluidized bed reactor studies at ORNL provided data necessary to characterize bioreactor performance and generate design criteria. 11 refs., 4 figs., 5 tabs.

Kowalchuk, M.L.; Hancher, C.W.

1982-10-24

34

Plant air systems safety study: Portsmouth Gaseous Diffusion Plant  

SciTech Connect

The Portsmouth Gaseous Diffusion Plant Air System facilities and operations are reviewed for potential safety problems not covered by standard industrial safety procedures. Information is presented under the following section headings: facility and process description (general); air plant equipment; air distribution system; safety systems; accident analysis; plant air system safety overview; and conclusion. (JGB)

Not Available

1982-05-01

35

Radioactive effluents, Portsmouth Gaseous Diffusion Plant, calendar year 1982  

SciTech Connect

Radioactive discharges from the Portsmouth Gaseous Diffusion Plant are discussed and tabulated. Tables indicate both the location of the discharge and the nuclides discharged. All discharges for 1982 are well below the Radioactive Concentration Guide limits specified in DOE Order 5480.1, Chapter XI. 1 figure.

Acox, T.A.; Hary, L.F.; Klein, L.S.

1983-03-01

36

Measurement of the Portsmouth Gaseous Diffusion Plant criticality accident alarm.  

National Technical Information Service (NTIS)

Measurements of the Portsmouth Gaseous Diffusion Plant's nuclear criticality accident radiation alarm signal response time, sound wave frequency, and sound volume levels were made to demonstrate compliance with ANSI/ANS-8.3-1986. A steady-state alarm sign...

R. W. Tayloe B. McGinnis

1990-01-01

37

Radiant extinction of gaseous diffusion flames  

NASA Technical Reports Server (NTRS)

The absence of buoyancy-induced flows in microgravity significantly alters the fundamentals of many combustion processes. Substantial differences between normal-gravity and microgravity flames have been reported during droplet combustion, flame spread over solids, candle flames, and others. These differences are more basic than just in the visible flame shape. Longer residence time and higher concentration of combustion products create a thermochemical environment which changes the flame chemistry. Processes such as flame radiation, that are often ignored under normal gravity, become very important and sometimes even controlling. This is particularly true for conditions at extinction of a microgravity diffusion flame. Under normal-gravity, the buoyant flow, which may be characterized by the strain rate, assists the diffusion process to transport the fuel and oxidizer to the combustion zone and remove the hot combustion products from it. These are essential functions for the survival of the flame which needs fuel and oxidizer. Thus, as the strain rate is increased, the diffusion flame which is 'weak' (reduced burning rate per unit flame area) at low strain rates is initially 'strengthened' and eventually it may be 'blown-out'. Most of the previous research on diffusion flame extinction has been conducted at the high strain rate 'blow-off' limit. The literature substantially lacks information on low strain rate, radiation-induced, extinction of diffusion flames. At the low strain rates encountered in microgravity, flame radiation is enhanced due to: (1) build-up of combustion products in the flame zone which increases the gas radiation, and (2) low strain rates provide sufficient residence time for substantial amounts of soot to form which further increases the flame radiation. It is expected that this radiative heat loss will extinguish the already 'weak' diffusion flame under certain conditions. Identifying these conditions (ambient atmosphere, fuel flow rate, fuel type, etc.) is important for spacecraft fire safety. Thus, the objective is to experimentally and theoretically investigate the radiation-induced extinction of diffusion flames in microgravity and determine the effect of flame radiation on the 'weak' microgravity diffusion flame.

Atreya, Arvind; Agrawal, Sanjay; Shamim, Tariq; Pickett, Kent; Sacksteder, Kurt R.; Baum, Howard R.

1995-01-01

38

Self-diffusion coefficients of expanded rubidium  

NASA Astrophysics Data System (ADS)

The second-order and fourth-order frequency sum rules of the velocity autocorrelation function (VACF) of Rb have been evaluated for six thermodynamic states along the liquid - vapour coexistence curve by using the Ashcroft pseudopotential and corresponding pair distribution function obtained by molecular dynamics (MD) simulation. These sum rules and a model for the self-diffusion coefficient have been used to study the time evolution of the VACF and self-diffusion coefficients. The results obtained have been compared with MD simulation data. It is found that our model provides the first semiquantitative explanation for the density and temperature dependences of the VACF and self-diffusion coefficients of expanded Rb.

Sharma, Saroj K.; Tankeshwar, K.

1996-12-01

39

Radial diffusion coefficients in the outer heliosphere  

NASA Astrophysics Data System (ADS)

When cosmic ray streaming in the heliosphere is negligible, the basic onedimensional transport model gives a simple approximation for the diffusion coefficient of cosmic ray particles, ~Zrr=CVSW/gr, where C is the Compton-Gettiing factor, VSW is the solar wind velocity and gr is the radial intensity gradients. In a separate paper at this conference we made detailed measurement of radial intensity gradients in the outer heliosphere from the combined data set observed over the solar activity minima of 1977/1997(qA>0). Using these detailed gradients and onedimensional transport model we calculate the diffusion coefficients in the outerheliosphere. These diffusion coefficients are compared with those of 1987 to also search for drift effects as manifested over two successive solar minima periods

Fujii, Z.; McDonald, F. B.; Moraal, H.

2001-08-01

40

Radon diffusion coefficients for aged residential concretes  

Microsoft Academic Search

This note reports radon gas pore diffusion coefficient measurements for residential concretes from Florida, ranging in age from 12 y to 45 y. The coefficients ranged from 1.5 x 10⁻⁷ m² s⁻¹ to 5.5 x 10⁻⁷ m² s⁻¹. On the average, these values are about a factor of 1.6 higher than average values previously reported for new residential concretes in

Vern C. Rogers; Kirk K. Nielson; Rodger B. Holt

1995-01-01

41

Nuclear criticality safety guide for the Portsmouth Gaseous Diffusion Plant  

SciTech Connect

Safe geometrical, mass, and concentration limits are presented, together with the criticality control methods currently in use at the Portsmouth Gaseous Diffusion Plant. Basic information presented includes technical background, experimental data, and the best values inferred from experiments. Various tables and graphs are included. Design criteria include basic assumptions, fundamentals, concepts, applicable methods, and maintenance of safe geometry. Operating criteria include the operating philosophy at the Goodyear Atomic Corporation Gaseous Diffusion Plant and applied operating techniques. The appendices contain graphs, figures, a chart showing Goodyear organization for nuclear safety, a glossary, tables of critical values, methods for calculating solid angles, and the bases for safe handling of high-uranium-density compounds and uranium metal in various forms.

Feuerbacher, J.L. (comp.)

1981-03-15

42

Calculation of the Anisotropic Diffusion Coefficient  

Microsoft Academic Search

The one-group anisotropic diffusion coefficient is calculated for slab and square lattice cells with use made of Benoist's formula. In utilizing the integral transport theory, only several collisions suffered by a neutron have hitherto been considered. In this paper, we adopt the integral theory and take into consideration the effect of an infinite number of collisions suffered by a neutron,

Toshikazu TAKEDA; Tamotsu SEKIYA

1972-01-01

43

Paducah Gaseous Diffusion Plant environmental report for 1991. Volume 3  

Microsoft Academic Search

This two-part report is published annually. It reflects the results of an environmental monitoring program designed to quantify potential increases in the concentration of contaminants and potential doses to the resident human population from the Paducah Gaseous Diffusion Plant (PGDP). PGDP`s overall goal for environmental management is to protect the environment and PGDP`s neighbors and to maintain full compliance with

1992-01-01

44

Innovative Decontamination Technology for Use in Gaseous Diffusion Plant Decommissioning  

Microsoft Academic Search

The results of bench scale tests demonstrated that TechXtract{sup R} RadPro{sup TM} technology (hereinafter referred to as RadPro{sup R}) can provide 100% coverage of complex mockup gaseous diffusion plant (GDP) equipment and can decontaminate uranium (U) deposits with 98% to 99.99% efficiency. Deployment tests demonstrated RadPro{sup R} can be applied as foam, mist\\/fog, or steam, and fully cover the internal

M. J. Peters; C. J. Norton; G. B. Fraikor; G. L. Potter; K. C. Chang

2006-01-01

45

Environmental protection facilities safety study: Portsmouth Gaseous Diffusion Plant  

SciTech Connect

The purpose of this Safety Study is to examine the existing facilities at the Portsmouth Gaseous Diffusion Plant that are dedicated to environmental protection. Seven separate, numbered facilities and five unnumbered continuous air sampling stations are identified as the fixed facilities to protect the environment. Each is examined from the standpoint of hazardous materials, monitoring and protection systems, confinement systems, ventilation systems, criticality control systems, fire protection systems, waste disposal systems, and safety systems.

Not Available

1982-05-01

46

The electron diffusion coefficient in Jupiter's magnetosphere  

NASA Technical Reports Server (NTRS)

A steady-state model of Jupiter's electron radiation belt is developed. The model includes injection from the solar wind, radial diffusion, energy degradation by synchrotron radiation, and absorption at Jupiter's surface. A diffusion coefficient of the form D sub RR/R sub J squared = k times R to the m-th power is assumed, and then observed data on synchrotron radiation are used to fit the model. The free parameters determined from this fit are m = 1.95 plus or minus 0.5, k = 1.7 plus or minus 0.5 x 10 to the 9th power per sec, and the magnetic moment of injected particles equals 770 plus or minus 300 MeV/G. The value of m shows quite clearly that the diffusion is not caused by magnetic pumping by a variable solar wind or by a fluctuating convection electric field. The process might be field line exchange driven by atmospheric-ionospheric winds; our diffusion coefficient has roughly the same radial dependence but is considerably smaller in magnitude than the upper bound diffusion coefficients recently suggested for this process by Brice and McDonough (1973) and Jacques and Davis (1972).

Birmingham, T.; Northrop, T.; Baxter, R.; Hess, W.; Lojko, M.

1974-01-01

47

Simulation of gaseous diffusion in partially saturated porous media under variable gravity with lattice Boltzmann methods  

NASA Technical Reports Server (NTRS)

Liquid distributions in unsaturated porous media under different gravitational accelerations and corresponding macroscopic gaseous diffusion coefficients were investigated to enhance understanding of plant growth conditions in microgravity. We used a single-component, multiphase lattice Boltzmann code to simulate liquid configurations in two-dimensional porous media at varying water contents for different gravity conditions and measured gas diffusion through the media using a multicomponent lattice Boltzmann code. The relative diffusion coefficients (D rel) for simulations with and without gravity as functions of air-filled porosity were in good agreement with measured data and established models. We found significant differences in liquid configuration in porous media, leading to reductions in D rel of up to 25% under zero gravity. The study highlights potential applications of the lattice Boltzmann method for rapid and cost-effective evaluation of alternative plant growth media designs under variable gravity.

Chau, Jessica Furrer; Or, Dani; Sukop, Michael C.; Steinberg, S. L. (Principal Investigator)

2005-01-01

48

Simulation of gaseous diffusion in partially saturated porous media under variable gravity with lattice Boltzmann methods.  

PubMed

Liquid distributions in unsaturated porous media under different gravitational accelerations and corresponding macroscopic gaseous diffusion coefficients were investigated to enhance understanding of plant growth conditions in microgravity. We used a single-component, multiphase lattice Boltzmann code to simulate liquid configurations in two-dimensional porous media at varying water contents for different gravity conditions and measured gas diffusion through the media using a multicomponent lattice Boltzmann code. The relative diffusion coefficients (D rel) for simulations with and without gravity as functions of air-filled porosity were in good agreement with measured data and established models. We found significant differences in liquid configuration in porous media, leading to reductions in D rel of up to 25% under zero gravity. The study highlights potential applications of the lattice Boltzmann method for rapid and cost-effective evaluation of alternative plant growth media designs under variable gravity. PMID:16173154

Chau, Jessica Furrer; Or, Dani; Sukop, Michael C

2005-08-01

49

Micro-Fluidic Diffusion Coefficient Measurement  

SciTech Connect

A new method for diffusion coefficient measurement applicable to micro-fluidics is pre- sented. The method Iltilizes an analytical model describing laminar dispersion in rect- anglllar ~llicro_channe]s. The Illethod ~vas verified throllgh measllremen~ of fllloresceill diffusivity in water and aqueolls polymer solutions of differing concentration. The diffll- sivity of flllorescein was measlmed as 0.64 x 10-gm2/s in water, 0.49 x 10-gm2/s in the 4 gm/dl dextran solution and 0.38 x 10-9n12/s in the 8 gnl/dl dextran solution.

Forster, F.K.; Galambos, P.

1998-10-06

50

Gas phase decontamination of gaseous diffusion process equipment  

SciTech Connect

D&D of the process facilities at the gaseous diffusion plants (GDPs) will be an enormous task. The EBASCO estimate places the cost of D&D of the GDP at the K-25 Site at approximately $7.5 billion. Of this sum, nearly $4 billion is associated with the construction and operation of decontamination facilities and the dismantlement and transport of contaminated process equipment to these facilities. In situ long-term low-temperature (LTLT) gas phase decontamination is being developed and demonstrated at the K-25 site as a technology that has the potential to substantially lower these costs while reducing criticality and safeguards concerns and worker exposure to hazardous and radioactive materials. The objective of gas phase decontamination is to employ a gaseous reagent to fluorinate nonvolatile uranium deposits to form volatile LJF6, which can be recovered by chemical trapping or freezing. The LTLT process permits the decontamination of the inside of gas-tight GDP process equipment at room temperature by substituting a long exposure to subatmospheric C1F for higher reaction rates at higher temperatures. This paper outlines the concept for applying LTLT gas phase decontamination, reports encouraging laboratory experiments, and presents the status of the design of a prototype mobile system. Plans for demonstrating the LTLT process on full-size gaseous diffusion equipment are also outlined briefly.

Bundy, R.D.; Munday, E.B.; Simmons, D.W.; Neiswander, D.W.

1994-03-01

51

Trace-Element Diffusion Coefficients in Olivine  

NASA Astrophysics Data System (ADS)

We have undertaken chemical diffusion experiments at 1300°C to determine both crystal/melt partition coefficients and diffusion coefficients for a wide range of trace elements in forsteritic olivine. Experiments were conducted at 1 atm under controlled fO2 for up to 25 days using synthetic melts made to a composition in equilibrium with olivine for major elements, and doped with selected trace elements. The melt was put into a 5 mm diameter cylindrical hole in gem quality San Carlos olivine crystals drilled paralell to the a axis. Diffusion profiles were obtained both for trace elements that were added to the starting material and diffuse into the olivine, and also for several trace elements present at natural abundances in the olivine that diffuse out. The profiles were measured across sections perpendicular to crystal/melt boundary at a variety of crystallographic orientations (confirmed by EBSD) by laser-ablation ICP-MS. A thin laser slit oriented parallel to the crystal/melt interface was traversed from the melt through the crystal. Element concentrations were fitted to the diffusion equation to obtain both diffusion coefficients and concentrations at the crystal/melt interface, and hence partition coefficients. Calculated diffusivities for many trace elements (Ca, REE, Y, Sc, V, Cr, Ni, Co, Mn, Na, Li, Be, Ti) are relatively fast (D = 10-16 to 10^{-13 m2/s at 1300°C). The diffusion of Li in olivine (approx. D = 10^{-15} m2/s) is only slightly slower than REEs and similar to divalent cations, in good agreement with inferences from zoning profiles in natural olivine [1]. This rate is considerably slower than for plagioclase and clinopyroxene [2], a result which has important implications for interpreting Li isotopic data from mantle-derived rocks. The fastest diffusing trace element we observe is Be. Applying our diffusion and partition coefficients to the model of Qin et al. [3], we calculate that the REEs of olivine-hosted melt inclusions in the mantle will extensively re-equilibrate with external magma in weeks (heavy REEs) to a few years (light REEs). These timescales are significantly shorter than the times estimated for the production and extraction of magma from the mantle or magma residence in the lower crust, implying anomalous melt inclusions are probably not a direct result of melting of heterogeneities in the mantle. Instead, anomalous melt inclusions likely form by assimilation processes shortly before eruption [4] and so may be useful monitors of such processes. Refs: [1] Parkinson et al., Abstract, Goldschmidt Conference 2006; [2] Coogan et al., EPSL 240, 415-424 (2005); [3] Qin et al. Am. Min. 77, 565-576 (1992); [4] Danyushevsky et al., J. Petrol. 45, 2531-2553 (2004).

Spandler, C.; O'Neill, H. S.

2006-12-01

52

Laminar and Turbulent Gaseous Diffusion Flames. Appendix C  

NASA Technical Reports Server (NTRS)

Recent measurements and predictions of the properties of homogeneous (gaseous) laminar and turbulent non-premixed (diffusion) flames are discussed, emphasizing results from both ground- and space-based studies at microgravity conditions. Initial considerations show that effects of buoyancy not only complicate the interpretation of observations of diffusion flames but at times mislead when such results are applied to the non-buoyant diffusion flame conditions of greatest practical interest. This behavior motivates consideration of experiments where effects of buoyancy are minimized; therefore, methods of controlling the intrusion of buoyancy during observations of non-premixed flames are described, considering approaches suitable for both normal laboratory conditions as well as classical microgravity techniques. Studies of laminar flames at low-gravity and microgravity conditions are emphasized in view of the computational tractability of such flames for developing methods of predicting flame structure as well as the relevance of such flames to more practical turbulent flames by exploiting laminar flamelet concepts.

Faeth, G. M.; Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)

2001-01-01

53

Reliability study: maintenance facilities Portsmouth Gaseous Diffusion Plant  

SciTech Connect

A reliability study of the maintenance facilities at the Portsmouth Gaseous Diffusion Plant has been completed. The reliability study team analyzed test data and made visual inspections of each component contributing to the overall operation of the facilities. The impacts of facilities and equipment failures were given consideration with regard to personnel safety, protection of government property, health physics, and environmental control. This study revealed that the maintenance facilities are generally in good condition. After evaluating the physical condition and technology status of the major components, the study team made several basic recommendations. Implementation of the recommendations proposed in this report will help assure reliable maintenance of the plant through the year 2000.

Post, B.E.; Sikorski, P.A.; Fankell, R.; Johnson, O.; Ferryman, D.S.; Miller, R.L.; Gearhart, E.C.; Rafferty, M.J.

1981-08-01

54

Portsmouth Gaseous Diffusion Plant Environmental report for 1990  

SciTech Connect

This calendar year 1990 annual report on environmental surveillance of the US Department of Energy's (DOE's) Portsmouth Gaseous Diffusion Plant (PORTS) and its environs consists of two parts: the summary, discussion, and conclusions (Part 1) and the data presentation (Part 2). The objectives of this report are as follows: report 1990 monitoring data for the installation and its environs that may have been affected by operations on the plant site, provide reasonably detailed information about the plant site and plant operations, provide detailed information on input and assumptions used in all calculations, provide trend analyses (when appropriate) to indicate increases and decreases in environmental impact, and provide general information on plant quality assurance.

Counce-Brown, D. (ed.)

1991-09-01

55

Countercurrent Gaseous Diffusion Model of Oxidation Through a Porous Coating  

SciTech Connect

A countercurrent gaseous diffusion model was developed to describe oxidation through porous coatings and scales. The specific system modeled involved graphite oxidized through a porous alumina (Al{sub 2}O{sub 3}) overcoat between 570 C (1,058 F) and 975 C (1,787 F). The model separated the porous Al{sub 2}O{sub 3} coating into two gas diffusion regions separated by a flame front, where oxygen (O{sub 2}) and carbon monoxide (CO) react to form carbon dioxide (CO{sub 2}). In the outer region O{sub 2} and CO{sub 2} counterdiffused. In the inner region, CO{sub 2} and CO counterdiffused. Concentration gradients of each gaseous specie in the pores of the Al{sub 2}O{sub 3} were determined, and the oxidation rate was calculated. The model was verified by oxidation experiments using graphite through various porous Al{sub 2}O{sub 3} overcoats. The Al{sub 2}O{sub 3} overcoats ranged in fractional porosity and in average pore radius from 0.077 {micro}m (3.0 x 10{sup -6} in., Knudsen diffusion) to 10.0 {micro}m (3.9 x 10{sup -4} in., molecular diffusion). Predicted and measured oxidation rates were shown to have the same dependence upon porosity, pore radius, temperature, and oxygen partial pressure (P{sub O{sub 2}}). Use of the model was proposed for other oxidation systems and for chemical vapor infiltration (CVI). This work was part of the U.S. Bureau of Mines corrosion research program.

Holcomb, G.R.

1996-07-01

56

Control of technetium at the Portsmouth Gaseous Diffusion Plant  

SciTech Connect

Technetium-99 entered the gaseous diffusion complex as a volatile impurity in recycled uranium that was fed to the Paducah Gaseous Diffusion Plant. Subsequently, it entered the Oak Ridge and Portsmouth cascades as an impurity in Paducah product feed. Most of the technetium was adsorbed on cascade equipment in increasingly high concentrations as it moved up the cascade. Since the low energy beta radiation produced by technetium cannot penetrate cascade equipment, it presents no significant hazard to workers as long as it remains inside of equipment. However, when equipment that contains high concentrations of technetium is opened for maintenance or change-out, precautions are taken to ensure worker safety. Traps containing activated alumina are used at the plant vent streams to limit radioactive emissions as far as possible. Annual vent stream emissions have been well below DOE limits. To allow continued compliance, other potential trapping agents have been tested. Several that limit emissions more effectively than activated alumina have been found. Other traps containing magnesium fluoride are used in the upper cascade to reduce the technetium concentration. Waste solutions from decontamination can also contain technetium. These solutions must either be stored for controlled discharge or treated to remove the technetium. To allow the latter, an ion exchange facility is being installed for operation by the end of FY-1982. Liquid discharges at Portsmouth have usually been less than 5% of the DOE imposed limits.

Saraceno, A.J.

1981-11-23

57

Micro-Fluidic Diffusion Coefficient Measurement  

Microsoft Academic Search

A new method for diffusion coefficient measurement applicable to micro-fluidics is pre-;\\u000asented. The method Iltilizes an analytical model describing laminar dispersion in rect-;\\u000aanglllar ~llicro_channe]s. The Illethod ~vas verified throllgh measllremen~ of fllloresceill;\\u000adiffusivity in water and aqueolls polymer solutions of differing concentration. The diffll-;\\u000asivity of flllorescein was measlmed as 0.64 x 10-gm2\\/s in water, 0.49 x 10-gm2\\/s

F. K. Forster; P. Galambos

1998-01-01

58

Paducah Gaseous Diffusion Plant environmental report for 1991. Volume 3  

SciTech Connect

This two-part report is published annually. It reflects the results of an environmental monitoring program designed to quantify potential increases in the concentration of contaminants and potential doses to the resident human population from the Paducah Gaseous Diffusion Plant (PGDP). PGDP`s overall goal for environmental management is to protect the environment and PGDP`s neighbors and to maintain full compliance with all current regulations. The current environmental strategy is to identify any deficiencies and to develop a system to resolve them. The long-range goal of environmental management is to minimize the source of pollutants, to reduce the generation of waste, and to minimize hazardous waste by substitution of materials. Environmental-monitoring systems at PGDP include emission-monitoring networks for airborne and aqueous discharges, groundwater monitoring, solid waste characterization, and ambient-sampling networks for air, surface water, groundwater, vegetation, food crops, fish, wildlife, soil, and surface stream sediments.

Williams, M.F. [ed.] [Martin Marietta Energy Systems, Inc., Oak Ridge, TN (United States)

1992-10-01

59

Paducah Gaseous Diffusion Plant environmental report for 1991  

SciTech Connect

This two-part report is published annually. It reflects the results of an environmental monitoring program designed to quantify potential increases in the concentration of contaminants and potential doses to the resident human population from the Paducah Gaseous Diffusion Plant (PGDP). PGDP's overall goal for environmental management is to protect the environment and PGDP's neighbors and to maintain full compliance with all current regulations. The current environmental strategy is to identify any deficiencies and to develop a system to resolve them. The long-range goal of environmental management is to minimize the source of pollutants, to reduce the generation of waste, and to minimize hazardous waste by substitution of materials. Environmental-monitoring systems at PGDP include emission-monitoring networks for airborne and aqueous discharges, groundwater monitoring, solid waste characterization, and ambient-sampling networks for air, surface water, groundwater, vegetation, food crops, fish, wildlife, soil, and surface stream sediments.

Williams, M.F. (ed.) (Martin Marietta Energy Systems, Inc., Oak Ridge, TN (United States))

1992-10-01

60

Measurement of the Portsmouth Gaseous Diffusion Plant criticality accident alarm  

SciTech Connect

Measurements of the Portsmouth Gaseous Diffusion Plant's nuclear criticality accident radiation alarm signal response time, sound wave frequency, and sound volume levels were made to demonstrate compliance with ANSI/ANS-8.3-1986. A steady-state alarm signal is produced within one-half second of obtaining a two-out-of-three detector trip. The fundamental alarm sound wave frequency is 440 hertz. The sound volume levels are greater than 10 decibels above background and ranged from 100 to 125 A-weighted decibels. The requirements of the standard were met; however the recommended maximum sound volume level of 115 dBA was exceeded. Emergency procedures require immediate evacuation upon initiation of a facility's radiation alarm. Comparison with standards for allowable time of exposure at different noise levels indicate that the elevated noise level at this location does not represent an occupational injury hazard. 8 refs., 5 figs.

Tayloe, R.W. Jr. (Battelle Columbus (USA)); McGinnis, B. (Martin Marietta Energy Systems, Inc., Piketon, OH (USA))

1990-08-31

61

Seismic issues at the Paducah Gaseous Diffusion Plant  

SciTech Connect

A seismic expert workshop was held at the Paducah Gaseous Diffusion Plant (PGDP) on March 13--15, 1989. the PGDP is operated by Martin Marietta Energy Systems, Inc. for the United States Department of Energy (DOE). During the last twenty years the design criteria for natural phenomenon hazards has steadily become more demanding at all of the DOE Oak Ridge Operations (ORO) sites. The purpose of the two-day workshop was to review the seismic vulnerability issues of the PGDP facilities. Participants to the workshop included recognized experts in the fields of seismic engineering, seismology and geosciences, and probabilistic analysis, along with engineers and other personnel from Energy Systems. A complete list of the workshop participants is included in the front of this report. 29 refs.

Fricke, K.E. (Martin Marietta Energy Systems, Inc., Oak Ridge, TN (USA))

1989-11-01

62

Natural phenomena hazards evaluation of equipment and piping of Gaseous Diffusion Plant Uranium Enrichment Facility  

Microsoft Academic Search

In support of the Gaseous Diffusion Plant Safety Analysis Report Upgrade program (GDP SARUP), a natural phenomena hazards evaluation was performed for the main process equipment and piping in the uranium enrichment buildings at Paducah and Portsmouth gaseous diffusion plants. In order to reduce the cost of rigorous analyses, the evaluation methodology utilized a graded approach based on an experience

M. K. Singhal; J. H. Kincaid; C. R. Hammond; B. I. Stockdale; J. C. Walls; W. R. Brock; D. R. Denton

1995-01-01

63

Results of the outdoor radiological survey at the Portsmouth Gaseous Diffusion Plant site, Piketon, Ohio  

Microsoft Academic Search

The Portsmouth Gaseous Diffusion Plant (PORTS) is owned by the US Department of Energy (DOE) and managed by Martin Marietta Energy Systems, Inc. As shown in Fig. 1, the plant is located in sparsely populated, rural Pike County, Ohio. PORTS began in 1952 as part of the Atomic Energy Commission`s (AEC) proposed expansion of the gaseous diffusion program in order

L. M. Rodriguez; L. M. Floyd; R. F. Carrier

1992-01-01

64

Results of the outdoor radiological survey at the Portsmouth Gaseous Diffusion Plant site, Piketon, Ohio  

Microsoft Academic Search

The Portsmouth Gaseous Diffusion Plant (PORTS) is owned by the US Department of Energy (DOE) and managed by Martin Marietta Energy Systems, Inc. As shown in Fig. 1, the plant is located in sparsely populated, rural Pike County, Ohio. PORTS began in 1952 as part of the Atomic Energy Commission's (AEC) proposed expansion of the gaseous diffusion program in order

L. M. Rodriguez; L. M. Floyd; R. F. Carrier

1992-01-01

65

Diffusion of gaseous and supercritical CO2 through polycarbonate  

NASA Astrophysics Data System (ADS)

The design of polymeric materials for applications such as separation membranes and nanostructured foams requires prediction of gas transport properties under a wide range of pressures. In the current study, transport of CO2 both in gaseous and supercritical state through samples of polycarbonate at 51 ^oC and pressures from 15 to 2000 psi was measured using an asymptotic time lag apparatus. Through volumetric calibration, the traditional analysis was extended to yield permeability (P) and solubility (S), in addition to the usual asymptotic diffusivity (Da). Nonlinear least squares fitting to a truncated series solution then provided an alternative measurement of the (transient) diffusivity (Dt), as well as the surface concentration (Co) of adsorbed gas. At 1 atm, Da and Dt were within a factor of 2 from selected handbook values; and with increasing pressure, both exhibited an overall downward trend, consistent with other studies, but an unexpected dropoff occurred between 1350 and 1500 psi. As expected, Co showed an overall increase with pressure, but as with P and S, displayed a peculiar drop between 1350 and 1500 psi. Measurement of Co in polycarbonate has never been done before and constitutes a novel feature of this study.

Goodman, Michael; Ozisik, Rahmi

2013-03-01

66

Diffusion coefficient of three-dimensional Yukawa liquids  

SciTech Connect

The purpose of this work is an investigation of the diffusion coefficient of the dust component in complex plasma. The computer simulation of the Yukawa liquids was made on the basis of the Langevin equation, which takes into account the influence of buffer plasma on the dust particles dynamics. The Green–Kubo relation was used to calculate the diffusion coefficient. Calculations of the diffusion coefficient for a wide range of the system parameters were performed. Using obtained numerical data, we constructed the interpolation formula for the diffusion coefficient. We also show that the interpolation formula correctly describes experimental data obtained under microgravity conditions.

Dzhumagulova, K. N.; Ramazanov, T. S.; Masheeva, R. U. [IETP, Al Farabi Kazakh National University, 71, al Farabi ave., Almaty 050040 (Kazakhstan)] [IETP, Al Farabi Kazakh National University, 71, al Farabi ave., Almaty 050040 (Kazakhstan)

2013-11-15

67

Comparison of field-measured radon diffusion coefficients with laboratory-measured coefficients  

Microsoft Academic Search

Experiments were conducted to compare radon diffusion coefficients determined for 0.1-m depths of soils by a steady-state method in the laboratory and diffusion coefficients evaluated from radon fluxes through several-fold greater depths of the same soils covering uranium-mill tailings. The coefficients referred to diffusion in the total pore volume of the soils and are equivalent to values for the quantity,

E. A. Lepel; W. B. Silker; V. W. Thomas; D. R. Kalkwarf

1983-01-01

68

Reliability study: process motors, Portsmouth Gaseous Diffusion Plant  

SciTech Connect

A study of the process motors was performed to determine their reliability through FY-2000. This study is part of an evaluation of the systems deemed critical to the operation of the Portsmouth Gaseous Diffusion Plant. The study of the process motors included the motor couplings and all sizes of process motors with the purpose of making recommendations for management's use in planning, budgeting and implementing corrective action. The study also covers the motors in the Inter-Building Booster Stations. It does not cover the motors in the Product Withdrawal Facilities or the Evacuation Booster Stations since they are the subjects of other studies. Each component of the process motors was studied to identify problem areas that exist. The study team felt it was not necessary to remove motors from service and disassemble them for inspection. Adequate information exists in this area from the information gained when failed motors are disassembled. Historical data on motor failures were used as a basis to predict future failure rates. The obsolescence of motors and the availability of spare parts were investigated. Maintenance methods, operating methods, and drawings for the process motors were examined for adequacy. Upon the completion of the Process Motors Reliability Study, recommendations were made to help assure that the equipment will operate reliably through the next twenty years. These recommendations are tabulated. The budget-type cost estimates for implementing the recommendations are presented in 1982 dollars.

Landrum, W.E.; Duffey, R.L.; Potts, N.B.; Stutzman, W.L.; Strickland, A.J. (comps.)

1982-06-01

69

Bioavailability study for the Paducah Gaseous Diffusion Plant  

SciTech Connect

The overall purpose of this plan is to assess the bioavailability of metals in the continuous and intermittent outfalls. The results may be used to determine alternative metal limits that more appropriately measure the portion of metal present necessary for toxicity to aquatic life. These limits must remain protective of in-stream aquatic life; thus, the highest concentration of metal in the water will be determined concurrently with an assessment of acute or chronic toxicity on laboratory tests. Using the method developed by the Kentucky Division of Water (KDOW), biomonitoring results and chemical data will be used to recommend alternative metal limits for the outfalls of concern. The data will be used to meet the objectives of the study: (1) evaluate the toxicity of continuous outfalls and intermittent outfalls at Paducah Gaseous Diffusion Plant; (2) determine the mean ratio of dissolved to Total Recoverable metal for Cd, Cr, Cu, Pb, Ni, and Zn in the continuous and intermittent outfalls; (3) determine whether the concentration of total recoverable metal discharged causes toxicity to fathead minnows and /or Ceriodaphnia; and (4) determine alternative metal limits for each metal of concern (Cd, Cr, Cu, Pb, Ni, and Zn).

Phipps, T.L.; Kszos, L.A.

1996-08-01

70

Surface diffusion coefficients for room acoustics: free-field measures.  

PubMed

A surface diffusion coefficient is needed in room acoustics to enable the quality of diffusing surfaces to be evaluated. It may also facilitate more accurate geometric room acoustic models. This paper concentrates on diffusion coefficients derived from free-field polar responses. An extensive set of two- and three-dimensional measurements and predictions was used to test the worth of different diffusion coefficient definitions. The merits and problems associated with these types of coefficients are discussed, and past parameters reviewed. Two new coefficients are described. The new measure based on the autocorrelation function is forwarded as the best free-field coefficient. The strengths and weaknesses of the coefficient are defined. PMID:11051498

Hargreaves, T J; Cox, T J; Lam, Y W; D'Antonio, P

2000-10-01

71

Temperature dependence of the diffusion coefficient of nanoparticles  

NASA Astrophysics Data System (ADS)

The temperature dependence of the diffusion coefficient of nanoparticles in gases has been experimentally studied. It is established that this dependence significantly differs from that predicted by various correlations, in particular, by the Cunningham-Millikan-Davies correlation that is used as an instrumental basis for virtually all methods of measurement of the diffusion coefficient in aerosols.

Rudyak, V. Ya.; Dubtsov, S. N.; Baklanov, A. M.

2008-06-01

72

IDENTIFICATION OF DIFFUSION COEFFICIENTS DURING POST-DISCHARGE NITRIDING  

Microsoft Academic Search

This work presents a model for computing the diffusion coefficients during post-discharge nitriding through an inverse problem of coefficient identification in a diffusion model, which considers several layers and Stefan type conditions. An approximate solution corresponding to a quasi-stationary state is obtained for the model, using qualitative and quantitative information from experimental results. To study the inverse problem we assume

J. A. GÓMEZ

73

Mixed waste storage facility CDR review, Paducah Gaseous Diffusion Plant; Solid waste landfill CDR review, Paducah Gaseous Diffusion Plant  

SciTech Connect

This report consists of two papers reviewing the waste storage facility and the landfill projects proposed for the Paducah Gaseous Diffusion Plant complex. The first paper is a review of DOE`s conceptual design report for a mixed waste storage facility. This evaluation is to review the necessity of constructing a separate mixed waste storage facility. The structure is to be capable of receiving, weighing, sampling and the interim storage of wastes for a five year period beginning in 1996. The estimated cost is assessed at approximately $18 million. The review is to help comprehend and decide whether a new storage building is a feasible approach to the PGDP mixed waste storage problem or should some alternate approach be considered. The second paper reviews DOE`s conceptual design report for a solid waste landfill. This solid waste landfill evaluation is to compare costs and the necessity to provide a new landfill that would meet State of Kentucky regulations. The assessment considered funding for a ten year storage facility, but includes a review of other facility needs such as a radiation detection building, compactor/baler machinery, material handling equipment, along with other personnel and equipment storage buildings at a cost of approximately $4.1 million. The review is to help discern whether a landfill only or the addition of compaction equipment is prudent.

NONE

1998-08-01

74

Comparison of radon diffusion coefficients measured by transient-diffusion and steady-state laboratory methods  

Microsoft Academic Search

A method was developed and used to determine radon diffusion coefficients in compacted soils by transient-diffusion measurements. A relative standard deviation of 12% was observed in repeated measurements with a dry soil by the transient-diffusion method, and a 40% uncertainty was determined for moistures exceeding 50% of saturation. Excellent agreement was also obtained between values of the diffusion coefficient for

D. R. Kalwarf; K. K. Nielson; D. C. Rich; V. C. Rogers

1982-01-01

75

Analysis of Fluorophore Diffusion by Continuous Distributions of Diffusion Coefficients: Application to Photobleaching Measurements of Multicomponent and Anomalous Diffusion  

Microsoft Academic Search

Fluorescence recovery after photobleaching (FRAP) is widely used to measure fluorophore diffusion in artificial solutions and cellular compartments. Two new strategies to analyze FRAP data were investigated theoretically and applied to complex systems with anomalous diffusion or multiple diffusing species: 1) continuous distributions of diffusion coefficients, ?(D), and 2) time-dependent diffusion coefficients, D(t). A regression procedure utilizing the maximum entropy

N. Periasamy; A. S. Verkman

1998-01-01

76

Comparison of Radon Diffusion Coefficients Measured by Transient-Diffusion and Steady-State Laboratory Methods.  

National Technical Information Service (NTIS)

A method was developed and used to determine radon diffusion coefficients in compacted soils by transient-diffusion measurements. A relative standard deviation of 12 percent was observed in repeated measurements with a dry soil by the transient-diffusion ...

D. R. Kalkwarf K. K. Nielson D. C. Rich V. C. Rogers

1982-01-01

77

Self-diffusion coefficient study of liquid lithium  

NASA Astrophysics Data System (ADS)

Little liquid lithium experimental self-diffusion coefficient were reported in the literature because of higher risk of radiation measurement method of diffusion coefficient. In the paper, the EAM potential is applied to calculate self-diffusion coefficient of liquid lithium with emphasis on a wide range of temperature, pressure, magnetic field, and gravity acceleration. The results show that the liquid lithium self-diffusion coefficient increases with temperature increasing and decreases with pressure increasing. Calculated self-diffusion coefficient is in good agreement with Murday's experiment results in atmosphere. We get the Arrhenius equation according to the simulation results. The increasing of pressure enlarges the liquid lithium activation energy and lowers the movement of atom in liquid lithium.

Wang, Z. H.; Ni, M. J.

2012-02-01

78

United States Department of Energy Paducah Gaseous Diffusion Plant. Environmental Monitoring Report, Calendar Year 1979.  

National Technical Information Service (NTIS)

Air, water, soil, and grass in the vicinity of the Paducah Gaseous Diffusion Plant were continuously or periodically sampled during 1979. Analyses for materials known to be in plant effluents were made to provide effluent control information and to determ...

1980-01-01

79

Diffusive expansion in kinetic theory and dynamics of gaseous stars  

NASA Astrophysics Data System (ADS)

This dissertation investigates the mathematical properties of nonlinear partial differential equations arising in kinetic theory, plasma physics, astrophysics, and fluid and gas dynamics. The first part of the thesis concerns the diffusive expansion to the Vlasov-Maxwell-Boltzmann system, the most fundamental model for an ensemble of charged particles. Such an expansion yields a set of dissipative new macroscopic PDEs, the incompressible Vlasov-Navier-Stokes-Fourier system and its higher order corrections for describing a charged fluid, where the self-consistent electromagnetic field is present. The uniform estimate on the remainders is established via a unified nonlinear energy method and it guarantees the global in time validity of such an expansion up to any order. The Euler-Poisson system for inviscid gases and the Navier-Stokes-Poisson system for viscous gases are the fundamental models for the dynamics of self-gravitating gaseous stars. The second part of the thesis contributes to the rigorous study of the nonlinear instability of the Euler-Poisson system with the adiabatic exponent g=65 . The instability is established by developing a bootstrap argument from the linear instability to the nonlinear model. A number of weighted energy norms are constructed to close the nonlinear energy estimates. The third part of the thesis is devoted to investigating the local in time well-posedness of strong solutions to the full Navier-Stokes-Poisson system with spherical symmetry as a vacuum free boundary problem. In particular, the result captures the behavior of the Lane-Emden steady star configurations for all ranges of g?65,2 . A weak solution is constructed via an iteration scheme defined in Lagrangian coordinates. A key idea in proving the uniform estimates as well as the regularity is to utilize both the Eulerian and Lagrangian formulations.

Jang, Juhi

80

Uranium deposit removal from the Oak Ridge Gaseous Diffusion Plant K-25 Building  

Microsoft Academic Search

The Oak Ridge Gaseous Diffusion Plant went into operation as the first plant to separate uranium by the gaseous diffusion process. It was built during World War II as part of the U.S. Army Corps of Engineers' Manhattan Project. Its war-time code name was K-25, which was also the name of the first uranium separation building constructed at the installation.

L. D. Ladd; E. C. Jr. Stinnett; J. R. Hale; M. J. Haire

1993-01-01

81

Depicting fire and other gaseous phenomena using diffusion processes  

Microsoft Academic Search

Developing a visually convincing model of fire, smoke, and othergaseousphenomenaisamongthemostdifficult andattractive problems in computer graphics. We have created new methods of animating a wide range of gaseous phenomena, including the particularlysubtleproblemofmodelling\\

Jos Stam; Eugene Fiume

1995-01-01

82

Improved diffusion coefficients generated from Monte Carlo codes  

SciTech Connect

Monte Carlo codes are becoming more widely used for reactor analysis. Some of these applications involve the generation of diffusion theory parameters including macroscopic cross sections and diffusion coefficients. Two approximations used to generate diffusion coefficients are assessed using the Monte Carlo code MC21. The first is the method of homogenization; whether to weight either fine-group transport cross sections or fine-group diffusion coefficients when collapsing to few-group diffusion coefficients. The second is a fundamental approximation made to the energy-dependent P1 equations to derive the energy-dependent diffusion equations. Standard Monte Carlo codes usually generate a flux-weighted transport cross section with no correction to the diffusion approximation. Results indicate that this causes noticeable tilting in reconstructed pin powers in simple test lattices with L2 norm error of 3.6%. This error is reduced significantly to 0.27% when weighting fine-group diffusion coefficients by the flux and applying a correction to the diffusion approximation. Noticeable tilting in reconstructed fluxes and pin powers was reduced when applying these corrections. (authors)

Herman, B. R.; Forget, B.; Smith, K. [Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States)] [Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Aviles, B. N. [Knolls Atomic Power Laboratory, Bechtel Marine Propulsion Corporation, P.O. Box 1072, Schenectady, NY 12301-1072 (United States)] [Knolls Atomic Power Laboratory, Bechtel Marine Propulsion Corporation, P.O. Box 1072, Schenectady, NY 12301-1072 (United States)

2013-07-01

83

Dispersion of UOâFâ aerosol and HF vapor in the operating floor during winter ventilation at the Paducah Gaseous Diffusion Plant  

Microsoft Academic Search

The gaseous diffusion process is currently employed at two plants in the US: the Paducah Gaseous Diffusion Plant and the Portsmouth Gaseous Diffusion Plant. As part of a facility-wide safety evaluation, a postulated design basis accident involving large line-rupture induced releases of uranium hexafluoride (UFâ) into the process building of a gaseous diffusion plant (GDP) is evaluated. When UFâ is

S. H. Kim; N. C. J. Chen; R. P. Taleyarkhan; K. D. Keith; R. W. Schmidt; J. C. Carter

1996-01-01

84

Local carbon diffusion coefficient measurement in the S-1 spheromak  

SciTech Connect

The local carbon diffusion coefficient was measured in the S - 1 spheromak by detecting the radial spread of injected carbon impurity. The radial impurity density profile is determined by the balance of ionization and diffusion. Using measured local electron temperature T/sub e/ and density n/sub e/, the ionization rate is determined from which the particle diffusion coefficient is inferred. The results found in this work are consistent with Bohm diffusion. The absolute magnitude of D/sub /perpendicular// was determined to be (4/approximately/6) /times/ D/sub Bohm/. 25 refs., 13 figs., 2 tabs.

Mayo, R.M.; Levinton, F.M.; Meyerhofer, D.D.; Chu, T.K.; Paul, S.F.; Yamada, M.

1988-10-01

85

Estimation of Effective Diffusion Coefficients in Porous Solids.  

National Technical Information Service (NTIS)

A major difficulty for reliable estimation of effective diffusion coefficients of gases in porous solids resides in the proper description of their highly complex internal structure. Within the concepts of percolation theory we make use of a network model...

S. Reyes K. F. Jensen

1984-01-01

86

Variable Eddington Factors and Flux-Limiting Diffusion Coefficients.  

National Technical Information Service (NTIS)

Variable Eddington factors and flux limiting diffusion coefficients arise in two common techniques of closing the moment equations of transport. The first two moment equations of the full transport equation are still frequently used to solve many problems...

P. P. Whalen

1982-01-01

87

Experimental Techniques for the Measurement of Diffusion Coefficients.  

National Technical Information Service (NTIS)

This paper describes techniques for the measurement of diffusion coefficients in solids. The focus is on depth profiling by various ion beam techniques, especially secondary ion mass spectrometry, Rutherford backscattering, and nuclear reaction analysis. ...

S. J. Rothman

1989-01-01

88

The temperature variation of hydrogen diffusion coefficients in metal alloys  

NASA Technical Reports Server (NTRS)

Hydrogen diffusion coefficients were measured as a function of temperature for a few metal alloys using an electrochemical evolution technique. Results from these measurements are compared to those obtained by the time-lag method. In all cases, diffusion coefficients obtained by the electrochemical method are larger than those by the time-lag method by an order of magnitude or more. These differences are attributed mainly to hydrogen trapping.

Danford, M. D.

1990-01-01

89

HOW DUAL-SCALE DIFFUSIVE PROPERTY HETEROGENEITY AFFECTS EFFECTIVE MATRIX DIFFUSION COEFFICIENT IN FRACTURED ROCK  

SciTech Connect

Matrix diffusion can significantly retard solute transport in fractured formations. Understanding matrix diffusion is crucial for predicting the arrival time, peak concentration, and tail of a contaminant breakthrough curve. Previous studies show that the effective matrix diffusion coefficient may be scale dependent. This study examines how heterogeneities of diffusion properties affect the effective matrix diffusion coefficient. Two types of heterogeneity in a channelized flow system are considered in the study: (1) interchannel heterogeneity, and (2) intrachannel heterogeneity. The objectives of this study are (1) to examine if it is appropriate to use a single, effective matrix diffusion coefficient in a standard solution model to predict breakthrough curves (BTC) in a fractured formation, (2) if so, how this effective value is related to the degree of the matrix diffusion coefficient variability; and (3) to examine if the observed scale dependence of the effective matrix-diffusion coefficient is caused by heterogeneity in diffusion properties. The results show that the use of a single effective matrix diffusion coefficient is appropriate only if the inter- and intrachannel variability of diffusion properties is small. The scale dependence of the effective matrix diffusion coefficient is not caused by either type of the studied heterogeneity.

Y. Zhang; H. Liu; Q. Zhou; S. Finsterle

2005-09-07

90

Calculation of self-diffusion coefficients in iron  

NASA Astrophysics Data System (ADS)

On the basis of available P-V-T equation of state of iron, the temperature and pressure dependence of self-diffusion coefficients in iron polymorphs (?, ?, ? and ? phases) have been successfully reproduced in terms of the bulk elastic and expansivity data by means of a thermodynamical model that interconnects point defects parameters with bulk properties. The calculated diffusion parameters, such as self-diffusion coefficient, activation energy and activation volume over a broad temperature range (500-2500 K) and pressure range (0-100 GPa), compare favorably well with experimental or theoretical ones when the uncertainties are considered.

Zhang, Baohua

2014-01-01

91

Anomalous behavior of the diffusion coefficient in thin active films  

NASA Astrophysics Data System (ADS)

Inspired by recent experiments in cell biology, we elucidate the visco-elastic properties of an active gel by studying the dynamics of a small tracer particle inside it. In a stochastic hydrodynamic approach for an active gel of finite thickness L, we calculate the mean square displacement of a particle. These particle displacements are governed by fluctuations in the velocity field. We characterize the short-time behavior when the gel is a solid as well as the limit of long times when the gel becomes a fluid and the particle shows simple diffusion. Active stresses together with local polar order give rise to velocity fluctuations that lead to characteristic behaviors of the diffusion coefficient that differ fundamentally from those found in a passive system: the diffusion coefficient can depend on system size and diverges as L approaches an instability threshold. Furthermore, the diffusion coefficient becomes independent of the particle size in this case.

Basu, Abhik; Joanny, Jean-Francois; Jülicher, Frank; Prost, Jacques

2012-11-01

92

Transient model of an intermediate surge system for the Paducah Gaseous Diffusion Plant  

SciTech Connect

Engineering design work (Reference 1) is underway for intermediate surge systems to be added to the Paducah Gaseous Diffusion Plant (PGDP) cascade as part of the Process Inventory Control System (PICS) project. These systems would be located between 000 buildings and lower half 00 buildings and would remove or add inventory during cascade transients in order to protect cascade compressors from overload and surge. Similar systems were operated in the Oak Ridge Gaseous Diffusion Plant cascade and are operated in the Portsmouth Gaseous Diffusion Plant cascade. A steady state flow analysis of the system to be installed at the PGDP has been made. The flow analysis did not address response of the surge system to the cascade transients, nor did it address automatic control of the system. The need to address these issues prompted development of the transient model described in this report. 2 refs., 8 figs., 2 tabs.

Beard, B.; Blankenship, J.G.; McGrady, P.W.

1989-09-01

93

Ion diffusion coefficient measurements in nanochannels at various concentrations.  

PubMed

Diffusion is one of the most fundamental properties of ionic transport in solutions. Here, we present experimental studies and theoretical analysis on the ion diffusion in nanochannels. Based on Fick's second law, we develop a current monitoring method to measure ion diffusion coefficient of high solution concentrations in nanochannels. This method is further extended to the cases at medium and low concentrations. Through monitoring ionic current during diffusion, we obtain diffusion coefficients of potassium chloride solution at different concentrations in nanochannels. These diffusion coefficients within the confined space are close to theirs bulk values. It is also found that the apparent ion diffusion equilibrium in the present experiments is very slow at low concentration, which we attribute to the slow equilibrium of the nanochannel surface charge. Finally, we get a primary acknowledge of the equilibrium rate between the nanochannel surface charge and electrolyte solution. The results in this work have improved the understanding of nanoscale diffusion and nanochannel surface charge and may be useful in nanofluidic applications such as ion-selective transport, energy conversion, and nanopore biosensors. PMID:24803967

Wang, Junrong; Zhang, Li; Xue, Jianming; Hu, Guoqing

2014-03-01

94

Lateral diffusion in an archipelago. Distance dependence of the diffusion coefficient.  

PubMed Central

An understanding of the distance dependence of the lateral diffusion coefficient is useful in comparing the results of diffusion measurements made over different length scales, and in analyzing the kinetics of mobile redox carriers in organelles. A distance-dependent, concentration-dependent diffusion coefficient is defined, and it is evaluated by Monte Carlo calculations of a random walk by mobile point tracers in the presence of immobile obstacles on a triangular lattice, representing the diffusion of a lipid or a small protein in the presence of immobile membrane proteins. This work confirms and extends the milling crowd model of Eisinger, J., J. Flores, and W. P. Petersen (1986. Biophys J. 49:987-1001). Similar calculations for diffusion of mobile particles interacting by a hard-core repulsion yield the distance dependence of the self-diffusion coefficient. An expression for the range of short-range diffusion is obtained, and the distance scales for various diffusion measurements are summarized.

Saxton, M J

1989-01-01

95

Photon diffusion coefficient in scattering and absorbing media.  

PubMed

We present a unified derivation of the photon diffusion coefficient for both steady-state and time-dependent transport in disordered absorbing media. The derivation is based on a modal analysis of the time-dependent radiative transfer equation. This approach confirms that the dynamic diffusion coefficient is given by the random-walk result D = cl(*)/3, where l(*) is the transport mean free path and c is the energy velocity, independent of the level of absorption. It also shows that the diffusion coefficient for steady-state transport, often used in biomedical optics, depends on absorption, in agreement with recent theoretical and experimental works. These two results resolve a recurrent controversy in light propagation and imaging in scattering media. PMID:16642188

Pierrat, Romain; Greffet, Jean-Jacques; Carminati, Rémi

2006-05-01

96

Gamma radiological surveys of the Oak Ridge Reservation, Paducah Gaseous Diffusion Plant, and Portsmouth Gaseous Diffusion Plant, 1990-1993, and overview of data processing and analysis by the Environmental Restoration Remote Sensing Program, Fiscal Year 1995  

Microsoft Academic Search

Three gamma radiological surveys have been conducted under auspices of the ER Remote Sensing Program: (1) Oak Ridge Reservation (ORR) (1992), (2) Clinch River (1992), and (3) Portsmouth Gaseous Diffusion Plant (PORTS) (1993). In addition, the Remote Sensing Program has acquired the results of earlier surveys at Paducah Gaseous Diffusion Plant (PGDP) (1990) and PORTS (1990). These radiological surveys provide

J. L. Smyre; B. W. Moll; A. L. King

1996-01-01

97

Predicting cation diffusion coefficients in clays and clay rocks  

NASA Astrophysics Data System (ADS)

Clay rocks are considered in several European countries as potential host rock formations for the underground disposal of radioactive waste. Because of their very low hydraulic conductivities, spreading of radionuclides through such formations may predominantly occur by molecular diffusion. Many experimental studies are thus being performed to investigate the diffusion of cations and other potential contaminants through various clay rocks as well as through pure swelling clays that may be used as additional buffer material. Whereas determining the diffusion properties of mobile tracers like tritiated water can be done within reasonable time, the measurements involving sorbing tracers are more complex and very time-consuming. It is thus tempting to determine diffusion coefficients of sorbing cations in an indirect way from more readily measurable quantities and based on cation diffusion coefficients measured for other materials. Various models exist that try to estimate cation diffusion coefficients from parameters like the bulk density, the porosity or the pore sizes of the rock, and the sorption distribution coefficient. In some models, an average mobility of cations that are sorbed on clay surfaces is in addition required, whereas other models rely on a constrictivity factor for transport in the interlayer space of the clays. In this contribution, we outline the differences and the commonalities of such models regarding some key parameters. We then compare model estimates with measured data from the literature, with a special emphasis on the associated uncertainties. Because some of the required parameters, notably the surface mobilities as well as the interlayer constrictivities, have typically large uncertainties, it is difficult to judge which model is best suited. However, it seems that several models can be used to set reasonable limits for cation diffusion coefficients in clay rocks that have not been investigated so far.

Gimmi, Thomas; Kosakowski, Georg; Glaus, Martin A.

2010-05-01

98

POTENTIAL SCALE DEPENDENCE OF EFFECTIVE MATRIX DIFFUSION COEFFICIENT  

SciTech Connect

It is well known that matrix diffusion (mass transfer between fractures and the rock matrix through molecular diffusion) can significantly retard solute transport processes in fractured rock, and therefore is important for analyzing a variety of problems, including geological disposal of nuclear waste. Matrix-diffusion-coefficient values measured from small rock samples in the laboratory are generally used for modeling field-scale solute transport in fractured rock. However, by compiling results from a number of field tracer tests corresponding to different geological settings, this study demonstrates that the effective matrix diffusion coefficient at field scale is generally larger than that at lab scale and tends to increase with testing scale. Preliminary interpretations of this observation are also investigated. We found that this interesting scale dependence may be related to the complexity of flow-path geometry in fractured rock.

H. Liu; Q. Zhou; Y. Zhang

2006-03-13

99

Apparatus for determining thermal-diffusion coefficients in gas mixtures  

Microsoft Academic Search

A description is given of the construction of, and the technique of measuring separation effects in a single-stage thermal-diffusion apparatus. For the separation analysis, use is made of the dependence of the viscosity of gas mixtures on composition. Results are presented of a determination of the coefficient of thermal diffusion of a He\\/N2 mixture in the pressure range 0. 0005–0.

L. S. Kotousov; A. V. Panyushkin

1965-01-01

100

On-line vibration and analysis system at the Paducah Gaseous Diffusion Plant  

SciTech Connect

The enrichment facility in Paducah, KY uses a unique hard-wired vibration monitoring and analysis system for gaseous diffusion equipment. The axial flow and centrifugal flow compressors used in uranium enrichment range in size from 6 feet in diameter to less than one foot in diameter. These compressors must operate smoothly and safely, without breech of containment, since the working fluid of gaseous diffusion is gaseous UF/sub 6/. The condition of 1925 compressors is monitored by use of the 2500 point vibration analysis system. Since the failure mechanisms of the compressors are well known and documented, only one accelerometer per machine is needed for most machines. The system is completely automated and can generate spectra or broadband levels in either acceleration or velocity units. Levels are stored for historical review. The analyst can, via a custom telecommunications link, view and analyze data from all monitored points with an office PC. 4 figs.

Herricks, D.M.; Strunk, W.D.

1988-02-01

101

Diffusion of gaseous products through a particle surface layer in a fluidized bed reactor  

Microsoft Academic Search

This paper examines a solid conversion process during hydrolysis and decomposition of cupric chloride in a thermochemical copper–chlorine (Cu–Cl) cycle of hydrogen production. Reaction rate constants and the time required for complete solid conversion are determined by a shrinking-core model. Diffusion of gaseous reactant occurs through a film surrounding the particle, after which the reactant penetrates and diffuses through a

V. N. Daggupati; G. F. Naterer; K. S. Gabriel

2010-01-01

102

Scaling Laws for Diffusion Coefficients in Mixtures of Alkanes  

NASA Astrophysics Data System (ADS)

Natural fluids, such as crude oils, are often mixtures of a broad range of different molecules, and in situ measurement of their composition is highly desirable. Furthermore, the relationship between their composition and their physical properties has always been a challenge for such mixtures. We have analyzed diffusion in alkane mixtures to find a power law for the self-diffusion coefficient in terms of molecular sizes. We demonstrate that this power law can be used to obtain the molecular size distribution of crude oils using noninvasive measurements of diffusion distributions.

Freed, Denise E.; Burcaw, Lauren; Song, Yi-Qiao

2005-02-01

103

MELCOR source term evaluation for UFâ release event in a gaseous diffusion plant feed facility  

Microsoft Academic Search

An assessment of UFâ release accidents was conducted for the feed facility of a gaseous diffusion plant. The MELCOR code was utilized for simulating the reactions of UFâ with moisture and the consequent transport of UOâFâ aerosols and HF vapor through the building and to the environment.

S. H. Kim; R. P. Taleyarkhan; D. Lombardi; R. Schmidt; K. Keith

1998-01-01

104

Report on the biological monitoring program at Paducah Gaseous Diffusion Plant, January--December 1997  

Microsoft Academic Search

On September 24, 1987, the Commonwealth of Kentucky Natural Resources and Environmental Protection Cabinet issued an Agreed Order that required the development of a Biological Monitoring Program (BMP) for the Paducah Gaseous Diffusion Plant (PGDP). A plan for the biological monitoring of the receiving streams was implemented in 1987 and consisted of ecological surveys, toxicity monitoring of effluents and receiving

L. A. Kszos; M. J. Peterson; M. G. Ryon; J. G. Smith; G. R. Southworth

1998-01-01

105

Report on the biological monitoring program at Paducah Gaseous Diffusion Plant, January--December 1996  

Microsoft Academic Search

On September 24, 1987, the Commonwealth of Kentucky Natural Resources and Environmental Protection Cabinet issued an Agreed Order that required the development of a Biological Monitoring Program (BMP) for the Paducah Gaseous diffusion Plant (PGDP). The PGDP BMP was conducted by the University of Kentucky Between 1987 and 1992 and by staff of the Environmental Sciences Division (ESD) at Oak

L. A. Kszos; B. K. Konetsky; M. J. Peterson; R. B. Petrie; M. G. Ryon; J. G. Smith; G. R. Southworth

1997-01-01

106

UF Sub 6 Release Experience and Prevention in United States Gaseous Diffusion Plants.  

National Technical Information Service (NTIS)

The three United States gaseous diffusion plants in operation at Oak Ridge, Tennessee, Paducah, Kentucky, and Portsmouth, Ohio have been in operation for a combined total of over 80 years, and in that period have produced or processed many thousands of to...

G. T. Hull

1978-01-01

107

Report on the biological monitoring program at Paducah Gaseous Diffusion Plant December 1990 to November 1992  

Microsoft Academic Search

On September 23, 1987, the Commonwealth of Kentucky Natural Resources and Environmental Protection Cabinet issued an Agreed Order that required the development of a Biological Monitoring Program (BMP) for the Paducah Gaseous Diffusion Plant (PGDP). Beginning in fall 1991, the Environmental Sciences Division (ESD) at Oak Ridge National Lab (ORNL) added data collection and report preparation to its responsibilities for

Kszos

1994-01-01

108

Regional flood hazard assessment of the Paducah and Portsmouth Gaseous Diffusion Plants  

Microsoft Academic Search

Regional flood-hazard assessments performed for the Paducah and Portsmouth Gaseous Diffusion Plants are reviewed, compared, and contrasted to determine the relationship of probable maximum flood methodology with respect to US Department of Energy design and evaluation guidelines. The Paducah assessment was carried out using probable maximum flood methodology, while the Portsmouth assessment utilized probabilistic techniques. Results indicated that regional flooding

R. O. Johnson; J. C. Wang; D. W. Lee

1991-01-01

109

Superfund Record of Decision (EPA Region 4): Paducah Gaseous Diffusion Plant Site, Paducah, KY., March 1994.  

National Technical Information Service (NTIS)

The decision document presents the selected interim action for the North-South Diversion Ditch (NSDD) at the Paducah Gaseous Diffusion Plant (PGDP) in Paducah, Kentucky. The primary objective of this interim remedial action is to initiate control of the s...

1994-01-01

110

Transient model of an intermediate surge system for the Paducah Gaseous Diffusion Plant  

Microsoft Academic Search

Engineering design work (Reference 1) is underway for intermediate surge systems to be added to the Paducah Gaseous Diffusion Plant (PGDP) cascade as part of the Process Inventory Control System (PICS) project. These systems would be located between 000 buildings and lower half 00 buildings and would remove or add inventory during cascade transients in order to protect cascade compressors

B. Beard; J. G. Blankenship; P. W. McGrady

1989-01-01

111

Assessment and interpretation of cross- and down-hole seismograms at the Paducah Gaseous Diffusion Plant  

Microsoft Academic Search

This paper is an assessment and interpretation of cross-and down-hole seismograms recorded at four sites in the vicinity of the Paducah Gaseous Diffusion Plant (PGDP). Arrival times of shear (S-) and compressional (P-) waves are recorded on these seismograms in milliseconds. Together with known distances between energy sources and seismometers lowered into boreholes, these arrival times are used to calculate

W. P. Staub; J. C. Wang; R. J. Selfridge

1991-01-01

112

Report on the Biological Monitoring Program at Paducah Gaseous Diffusion Plant December 1992December 1993  

Microsoft Academic Search

On September 24, 1987, the Commonwealth of Kentucky Natural Resources and Environmental Protection Cabinet issued an Agreed Order that required the development of a Biological Monitoring Program (BMP) for the Paducah Gaseous Diffusion Plant (PGDP). The goals of BMP are to demonstrate that the effluent limitations established for PGDP protect and maintain the use of Little Bayou and Big Bayou

L. A. Kszos; R. L. Hinzman; M. J. Peterson; M. G. Ryon; J. G. Smith; G. R. Southworth

1995-01-01

113

APPLICATION OF THE LASAGNA{trademark} SOIL REMEDIATION TECHNOLOGY AT THE DOE PADUCAH GASEOUS DIFFUSION PLANT  

Microsoft Academic Search

The Paducah Gaseous Diffusion Plant (PGDP), owned by the Department of Energy (DOE), has been enriching uranium since the early 1950s. The enrichment process involves electrical and mechanical components that require periodic cleaning. The primary cleaning agent was trichloroethene (TCE) until the late 1980s. Historical documentation indicates that a mixture of TCE and dry ice were used at PGDP for

Barry D. Swift; Tarantino; Joseph J

2003-01-01

114

Seismically-induced soil amplification at the DOE Paducah Gaseous Diffusion Plant site  

Microsoft Academic Search

A site-specific earthquake site response (soil amplification) study is being conducted for the Department of Energy (DOE), Paducah Gaseous Diffusion Plant (PGDP). This study is pursuant to an upgraded Final Safety Analysis Report in accordance with requirements specified by DOE. The seismic hazard at PGDP is dominated by the New Madrid Seismic Zone. Site-specific synthetic earthquake records developed by others

D. W. Sykora; M. E. Haynes; W. R. Brock; R. J. Hunt; K. E. Shaffer

1991-01-01

115

Environmental Restoration Site-Specific Plan for the Portsmouth Gaseous Diffusion Plant, FY 93  

SciTech Connect

The purpose of this Site-Specific Plan (SSP) is to describe past, present, and future activities undertaken to implement Environmental Restoration and Waste Management goals at the Portsmouth Gaseous Diffusion Plant (PORTS). The SSP is presented in sections emphasizing Environmental Restoration description of activities, resources, and milestones.

Not Available

1993-01-15

116

Impacts from PCB Accumulation on Amphibians Inhabiting Streams Flowing from the Paducah Gaseous Diffusion Plant  

Microsoft Academic Search

Contamination at the Paducah Gaseous Diffusion Plant (PGDP), Paducah, Kentucky, has been under evaluation for many years. We studied amphibians in selected outfalls (drainage ditches) flowing from the PGDP to determine if PCBs were accumulating in their tissues and how this might affect local populations. We determined relative amphibian species richness and abundance among seven outfalls and three reference streams

C. J. DeGarady; R. S. Halbrook

2003-01-01

117

Report on the biological monitoring program at Paducah Gaseous Diffusion Plant December 1993 to December 1994  

Microsoft Academic Search

On September 24, 1987, the Commonwealth of Kentucky Natural Resources and Environmental Protection Cabinet issued an Agreed Order that required the development of a Biological Monitoring Program (BMP) for the Paducah Gaseous Diffusion Plant (PGDP). The PGDP BMP was implemented in 1987 by the University of Kentucky. Research staff of the Environmental Sciences Division (ESD) at Oak Ridge National Laboratory

Kszos

1996-01-01

118

On-line vibration and analysis system at the Paducah Gaseous Diffusion Plant  

Microsoft Academic Search

The enrichment facility in Paducah, KY uses a unique hard-wired vibration monitoring and analysis system for gaseous diffusion equipment. The axial flow and centrifugal flow compressors used in uranium enrichment range in size from 6 feet in diameter to less than one foot in diameter. These compressors must operate smoothly and safely, without breech of containment, since the working fluid

D. M. Herricks; W. D. Strunk

2008-01-01

119

Superfund record of decision (EPA Region 4): Paducah Gaseous Diffusion Plant Site, Paducah, KY, March 1994  

SciTech Connect

The decision document presents the selected interim action for the North-South Diversion Ditch (NSDD) at the Paducah Gaseous Diffusion Plant (PGDP) in Paducah, Kentucky. The primary objective of this interim remedial action is to initiate control of the source of continued contaminant releases into the NSDD and mitigate the spread of contamination from the NSDD.

Not Available

1994-07-01

120

Handling and treatment of low-level radioactive wastes from United States gaseous diffusion plants  

Microsoft Academic Search

The US gaseous diffusion plants currently generate very small quantities of low-level radioactive wastes. These wastes consist primarily of airborne effluent solid trapping media and liquid scrubber solutions; liquid effluent treatment sludges; waste oils and solvents; scrap metals; and conventional combustible wastes such as floor sweepings, cleaning rags, and shoe covers. In addition to waste emanating from current operations, large

J. F. Wing; M. E. Mitchell; J. E. Behrend

1983-01-01

121

Oak Ridge Gaseous Diffusion Plant historical uranium and radionuclide release report  

Microsoft Academic Search

This report compiles all available historic data of the quantities of uranium and various radionuclides released from the Oak Ridge Gaseous Diffusion Plant (ORGDP) from 1946 through 1984. Concentrations in the environment and the probable health effects to the public due to those releases are also discussed. The historical release data are compiled into three major areas; airborne releases, liquid

A. C. Lay; J. G. Rogers

1986-01-01

122

Determination of operating limits for radionuclides for a proposed landfill at Paducah Gaseous Diffusion Plant  

Microsoft Academic Search

The operating limits for radionuclides in sanitary and industrial wastes were determined for a proposed landfill at the Paducah Gaseous Diffusion Plant (PGDP), Kentucky. These limits, which may be very small but nonzero, are not mandated by law or regulation but are needed for rational operation. The approach was based on analyses of the potential contamination of groundwater at the

J. C. Wang; D. W. Lee; R. H. Ketelle; R. R. Lee; D. C. Kocher

1994-01-01

123

Operating limit study for the proposed solid waste landfill at Paducah Gaseous Diffusion Plant  

Microsoft Academic Search

A proposed solid waste landfill at Paducah Gaseous Diffusion Plant (PGDP) would accept wastes generated during normal operations that are identified as non-radioactive. These wastes may include small amounts of radioactive material from incidental contamination during plant operations. A site-specific analysis of the new solid waste landfill is presented to determine a proposed operating limit that will allow for waste

D. W. Lee; J. C. Wang; D. C. Kocher

1995-01-01

124

Determination of operating limits for radionuclides for a proposed landfill at Paducah Gaseous Diffusion Plant  

Microsoft Academic Search

The operating limits for radionuclides in sanitary and industrial wastes were determined for a proposed landfill at the Paducah Gaseous Diffusion Plant (PGDP) in Paducah, Kentucky. These limits, which may be very small but nonzero, are not mandated by law or regulation but are needed for rational operation. The primary advantages of establishing such operating limits include (a) technically defensible

J. C. Wang; D. W. Lee; R. H. Ketelle; R. R. Lee; D. C. Kocher

1994-01-01

125

Results of the outdoor radiological survey at the Portsmouth Gaseous Diffusion Plant site, Piketon, Ohio.  

National Technical Information Service (NTIS)

The Portsmouth Gaseous Diffusion Plant (PORTS) is owned by the US Department of Energy (DOE) and managed by Martin Marietta Energy Systems, Inc. As shown in Fig. 1, the plant is located in sparsely populated, rural Pike County, Ohio. PORTS began in 1952 a...

L. M. Rodriguez L. M. Floyd R. F. Carrier

1992-01-01

126

Refrigerant114 Rankine cycle energy recovery technology from the gaseous diffusion industry  

Microsoft Academic Search

An unclassified accounting of energy recovery technology developed in the gaseous diffusion (uranium enrichment) industry during the past twenty years is presented. This spin-off knowledge may be of value to those in industry seeking to reduce operating costs while meeting the national objective of conserving energy. Four Rankine cycle energy recovery installations using Refrigerant-114 (R-114) as the working fluid are

C. O. Langerbbrake

1978-01-01

127

Experimental system to evaluate the effective diffusion coefficient of radon  

NASA Astrophysics Data System (ADS)

The effective diffusion coefficient of radon is a very important factor in estimating the rate of radon exhalation from the ground surface. In this study, we developed an experimental system that overcomes technical problems in previous studies to accurately evaluate the effective diffusion coefficient. The radon source used for this system was the National Institute of Radiological Sciences radon chamber. This chamber is a calibrated international standard facility that can produce stable radon concentrations for long periods of time. Our tests showed that leakage of radon from the system was negligible. After the leakage test, we evaluated the effective diffusion coefficient in free-space and in dry porous materials at porosities of 35% and 45%. To ensure that the porous material in the column was as homogeneous as possible, we filled the column with an artificial soil with controlled grain size and grain composition. The measured values and theoretical calculations agreed well, which indicate that the proposed system can be used to accurately and quickly evaluate the effective diffusion coefficient.

Hosoda, Masahiro; Tokonami, Shinji; Sorimachi, Atsuyuki; Janik, Miroslaw; Ishikawa, Tetsuo; Yatabe, Yoshinori; Yamada, Junya; Uchida, Shigeo

2009-01-01

128

Molecular dynamics calculations of point defect diffusion coefficients in vanadium  

NASA Astrophysics Data System (ADS)

Diffusion coefficients for vacancies and self-interstitial atoms (SIA) in vanadium at several temperatures have been calculated by the molecular dynamics method using EAM potential proposed by Foiles and Adams. Apart from the migration energy the preexponential factor was an object of interest. Simulation results show that the SIA in vanadium exists in a <111>-dumbbell configuration and migrates exceptionally along <111> directions.

Minashin, A. M.; Ryabov, V. A.

1996-10-01

129

Experimental system to evaluate the effective diffusion coefficient of radon.  

PubMed

The effective diffusion coefficient of radon is a very important factor in estimating the rate of radon exhalation from the ground surface. In this study, we developed an experimental system that overcomes technical problems in previous studies to accurately evaluate the effective diffusion coefficient. The radon source used for this system was the National Institute of Radiological Sciences radon chamber. This chamber is a calibrated international standard facility that can produce stable radon concentrations for long periods of time. Our tests showed that leakage of radon from the system was negligible. After the leakage test, we evaluated the effective diffusion coefficient in free-space and in dry porous materials at porosities of 35% and 45%. To ensure that the porous material in the column was as homogeneous as possible, we filled the column with an artificial soil with controlled grain size and grain composition. The measured values and theoretical calculations agreed well, which indicate that the proposed system can be used to accurately and quickly evaluate the effective diffusion coefficient. PMID:19191431

Hosoda, Masahiro; Tokonami, Shinji; Sorimachi, Atsuyuki; Janik, Miroslaw; Ishikawa, Tetsuo; Yatabe, Yoshinori; Yamada, Junya; Uchida, Shigeo

2009-01-01

130

Nitrogen-system safety study: Portsmouth Gaseous Diffusion Plant  

SciTech Connect

The Department of Energy has primary responsibility for the safety of operations at DOE-owned nuclear facilities. The guidelines for the analysis of credible accidents are outlined in DOE Order 5481.1. DOE has requested that existing plant facilities and operations be reviewed for potential safety problems not covered by standard industrial safety procedures. This review is being conducted by investigating individual facilities and documenting the results in Safety Study Reports which will be compiled to form the Existing Plant Final Safety Analysis Report which is scheduled for completion in September, 1984. This Safety Study documents the review of the Plant Nitrogen System facilities and operations and consists of Section 4.0, Facility and Process Description, and Section 5.0, Accident Analysis, of the Final Safety Analysis Report format. The existing nitrogen system consists of a Superior Air Products Company Type D Nitrogen Plant, nitrogen storage facilities, vaporization facilities and a distribution system. The system is designed to generate and distribute nitrogen gas used in the cascade for seal feed, buffer systems, and for servicing equipment when exceptionally low dew points are required. Gaseous nitrogen is also distributed to various process auxiliary buildings. The average usage is approximately 130,000 standard cubic feet per day.

Not Available

1982-07-01

131

Highly oblique shocks: Diffusion coefficients, acceleration rate and maximum energy  

NASA Astrophysics Data System (ADS)

We examine numerically using Monte Carlo simulations the effect of the diffusion coefficients and the obliquity of the magnetic field to the shock front on the energy gain and the acceleration rate of the accelerated particles in non-relativistic highly oblique shocks. Previous analytical work is justified showing that in highly oblique shocks the smaller the perpendicular diffusion gets compared to the parallel diffusion coefficient values, the greater the energy gain of the cosmic rays to be obtained and under specific conditions the acceleration rate of the particles allows for critical energies to be reached. Based on these circumstances and other striking findings, the cosmic ray spectrum in high energies between 1015eV and about 1018eV can be explained. We estimate the upper limit of energy that cosmic rays could gain in astrophysical sources following models of such as, Supernovae which explode into the interstellar medium, Red Supergiants, and Wolf-Rayet stars.

Meli, A.; Biermann, P. L.

2005-11-01

132

Physical modeling of 2,4-DNT gaseous diffusion through unsaturated soil  

NASA Astrophysics Data System (ADS)

Chemical detection of buried explosives devices (BEDs) through chemical sensing is influenced by factors affecting the transport of chemical components associated with the devices. Explosive-related chemicals, such as 2,4-dinitrotolune (DNT), are somewhat volatile and their overall transport is influenced by vapor-phase diffusion. Gaseous diffusion depends on environmental and soil conditions. The significance of this mechanism is greater for unsaturated soil, and increases as water content decreases. Other mechanisms, such as sorption and degradation, which affect the overall fate and transport, may be more significant under diffusion transport due to the higher residence time of ERCs in the soil system. Gaseous diffusion in soil was measured using a one-dimensional physical model (1-D column) to simulate the diffusion flux through soil under various environmental conditions. Samples are obtained from the column using solid phase microextraction (SPME) and analyzed with a gas chromatography. Results suggest that DNT overall diffusion is influenced by diffusive and retention processes, water content, source characteristics, and temperature. DNT effective gas phase diffusion in the soil decreases with increasing soil water content. Vapor transport retardation was more dominant at low water contents. Most of the retardation is associated to the partition of the vapor to the soil-water. DNT vapor flux is higher near the explosive source (mine) than at the soil surface. This flux also increases with higher soil water content and temperature. Results also suggest non-equilibrium transport attributed to mass transfer limitations and non-linear sorption.

Torres, Alexander; Padilla, Ingrid; Hwang, Sangchul

2007-05-01

133

Radiative Extinction of Gaseous Spherical Diffusion Flames in Microgravity  

NASA Technical Reports Server (NTRS)

Radiative extinction of spherical diffusion flames was investigated experimentally and numerically. The experiments involved microgravity spherical diffusion flames burning ethylene and propane at 0.98 bar. Both normal (fuel flowing into oxidizer) and inverse (oxidizer flowing into fuel) flames were studied, with nitrogen supplied to either the fuel or the oxygen. Flame conditions were chosen to ensure that the flames extinguished within the 2.2 s of available test time; thus extinction occurred during unsteady flame conditions. Diagnostics included color video and thin-filament pyrometry. The computations, which simulated flow from a porous sphere into a quiescent environment, included detailed chemistry, transport and radiation, and yielded transient results. Radiative extinction was observed experimentally and simulated numerically. Extinction time, peak temperature, and radiative loss fraction were found to be independent of flow rate except at very low flow rates. Radiative heat loss was dominated by the combustion products downstream of the flame and was found to scale with flame surface area, not volume. For large transient flames the heat release rate also scaled with surface area and thus the radiative loss fraction was largely independent of flow rate. Peak temperatures at extinction onset were about 1100 K, which is significantly lower than for kinetic extinction. One observation of this work is that while radiative heat losses can drive transient extinction, this is not because radiative losses are increasing with time (flame size) but rather because the heat release rate is falling off as the temperature drops.

Santa, K. J.; Chao, B. H.; Sunderland, P. B.; Urban, D. L.; Stocker, D. P.; Axelbaum, R. L.

2007-01-01

134

Diffusion coefficients of molecular iodine in aqueous solutions  

SciTech Connect

In the event of a severe accident on a light water nuclear reactor (LWR), resulting in overheating of the core, the fission products would be released into the containment building. Among the fission products, iodine represents a biological hazard for the environment by reason of the {sup 131}I radioactive isotope. As iodine is a highly reactive and volatile compound, it is involved in mass transfer from the liquid phase to the gas phase of the containment vessel. In order to determine the quantity of iodine present in the gas phase, it is necessary to know the diffusion coefficient of iodine in water at several temperatures. The diffusion coefficients of iodine in 0.075 mol/dm{sup 3} sulfuric acid have been determined between 298 K and 358 K, by measuring the limiting reduction currents at a platinum rotating disk electrode. A Stokes-Einstein relation is verified over the range of temperature studied. The experimental value obtained at 298 K is compared with some available relations for the estimation of diffusion coefficients at infinite dilution. The agreement is good.

Cantrel, L. [CEA Cadarache, Saint Paul lez Durance (France). Inst. de Protection et de Surete Nucleaire] [CEA Cadarache, Saint Paul lez Durance (France). Inst. de Protection et de Surete Nucleaire; Chaouche, R.; Chopin-Dumas, J. [Ecole Nationale Superieure de Syntheses, Marseille (France)] [Ecole Nationale Superieure de Syntheses, Marseille (France)

1997-01-01

135

An asixymmetric diffusion experiment for the determination of diffusion and sorption coefficients of rock samples  

SciTech Connect

Diffusion anisotropy is a critical property in predicting migration of substances in sedimentary formations with very low permeability. The diffusion anisotropy of sedimentary rocks has been evaluated mainly from laboratory diffusion experiments, in which the directional diffusivities are separately estimated by through-diffusion experiments using different rock samples, or concurrently by in-diffusion experiments in which only the tracer profile in a rock block is measured. To estimate the diffusion anisotropy from a single rock sample, this study proposes an axisymmetric diffusion test, in which tracer diffuses between a cylindrical rock sample and a surrounding solution reservoir. The tracer diffusion between the sample and reservoir can be monitored from the reservoir tracer concentrations, and the tracer profile could also be obtained after dismantling the sample. Semi-analytical solutions are derived for tracer concentrations in both the reservoir and sample, accounting for an anisotropic diffusion tensor of rank two as well as the dilution effects from sampling and replacement of reservoir solution. The transient and steady-state analyses were examined experimentally and numerically for different experimental configurations, but without the need for tracer profiling. These experimental configurations are tested for in- and out-diffusion experiments using Koetoi and Wakkanai mudstones and Shirahama sandstone, and are scrutinized by a numerical approach to identify favorable conditions for parameter estimation. The analysis reveals the difficulty in estimating diffusion anisotropy; test configurations are proposed for enhanced identifiability of diffusion anisotropy. Moreover, it is demonstrated that the axisymmetric diffusion test is efficient in obtaining the sorption parameter from both steady-state and transient data, and in determining the effective diffusion coefficient if isotropic diffusion is assumed. Moreover, measuring reservoir concentrations in an axisymmetric diffusion experiment coupled with tracer profiling may be a promising approach to estimate of diffusion anisotropy of sedimentary rocks.

Takeda, M.; Hiratsuka, T.; Ito, K.; Finsterle, S.

2011-02-01

136

Measurements of uranium holdup in an operating gaseous diffusion enrichment plant  

SciTech Connect

Holdup of nuclear material in process equipment is one of the major sources of uncertainty in materials balances, particularly for high-throughput facilities with large equipment and extensive piping, such as gaseous diffusion uranium-enrichment plants. Locating and measuring the holdup while the plant is operating is a challenging problem because of background from the process material and the neighboring equipment. This paper reports NDA measurements performed at the Goodyear Atomic Gaseous Diffusion Plant, Portsmouth, Ohio, on enrichment equipment at the higher enrichment and (>10% /sup 235/U isotopic abundance) of the cascade. Both neutron and gamma-ray measurements were made to locate anomalously large deposits in converters and compressors and, within the limitations of the techniques, to quantify the amount of the deposit.

Augustson, R.H.; Walton, R.B.; Harris, R.; Harbarger, W.; Hicks, J.; Timmons, G.; Shissler, D.; Tayloe, R.; Jones, S.; Fields, L.

1983-01-01

137

Natural phenomena hazards evaluation of equipment and piping of Gaseous Diffusion Plant Uranium Enrichment Facility  

SciTech Connect

In support of the Gaseous Diffusion Plant Safety Analysis Report Upgrade program (GDP SARUP), a natural phenomena hazards evaluation was performed for the main process equipment and piping in the uranium enrichment buildings at Paducah and Portsmouth gaseous diffusion plants. In order to reduce the cost of rigorous analyses, the evaluation methodology utilized a graded approach based on an experience data base collected by SQUG/EPRI that contains information on the performance of industrial equipment and piping during past earthquakes. This method consisted of a screening walkthrough of the facility in combination with the use of engineering judgment and simple calculations. By using these screenings combined with evaluations that contain decreasing conservatism, reductions in the time and cost of the analyses were significant. A team of experienced seismic engineers who were trained in the use of the DOE SQUG/EPRI Walkdown Screening Material was essential to the success of this natural phenomena hazards evaluation.

Singhal, M.K.; Kincaid, J.H.; Hammond, C.R.; Stockdale, B.I.; Walls, J.C. [Oak Ridge National Lab., TN (United States). Technical Programs and Services; Brock, W.R.; Denton, D.R. [Lockheed Martin Energy Systems, Inc., Oak Ridge, TN (United States)

1995-12-31

138

Measurement of diffusion coefficients important in modeling the absorption rate of carbon dioxide into aqueous N-methyldiethanolamine  

SciTech Connect

Natural gas processors use amine treating processes to remove the acid gases H{sub 2}S and CO{sub 2} from gas streams. Absorption rates of gaseous CO{sub 2} into aqueous N-methyldiethanolamine (MDEA) solutions were measured in a quiescent, inverted-tube diffusiometer by monitoring the rate of pressure drop. The absorption rate was found to be insensitive to the diffusion coefficient of CO{sub 2} in solution but very sensitive to the diffusion rate of bicarbonate and protonated MDEA ions. Evidence also suggested that chemical reaction equilibrium is rapid relative to diffusion. A numerical model was developed on the basis of these observations. The model was used to regress diffusion coefficients of bicarbonate and protonated amine, which must be equivalent by electroneutrality arguments, from measured absorption rates. Complete modeling of the absorption process also required data for the diffusion coefficient of MDEA in water. These were measured using a Taylor dispersion apparatus. CO{sub 2} absorption rates and diffusion coefficients of bicarbonate and protonated MDEA were obtained at 298.2 K and 318.2 K in solutions containing 20, 35, and 50 mass % MDEA in water.

Rowley, R.L.; Adams, M.E.; Marshall, T.L.; Oscarson, J.L.; Wilding, W.V.; Anderson, D.J. [Brigham Young Univ., Provo, UT (United States). Dept. of Chemical Engineering] [Brigham Young Univ., Provo, UT (United States). Dept. of Chemical Engineering

1997-03-01

139

Highly oblique shocks: Diffusion coefficients, acceleration rate and maximum energy  

NASA Astrophysics Data System (ADS)

We examine numerically using Monte Carlo simulations the effect of the diffusion coefficients and the obliquity of the magnetic field to the shock front, on the energy gain and the acceleration rate of the accelerated particles in non-relativistic highly oblique shocks. Previous analytical work (Jokipii 1987) is justified showing that in highly oblique shocks the smaller the perpendicular diffusion gets compared to the parallel diffusion coefficient values, the greater the energy gain of the cosmic rays to be obtained and under specific conditions the acceleration rate of the particles allows for critical energies to be reached. It is confirmed that the diffusive shock acceleration mechanism in non-relativistic highly oblique shocks is indeed efficient to accelerate particles up to energies just above the 'knee' and down close to the 'ankle'. The seed of particles which get accelerated in these shock fronts and in such energies, may come from the remnant winds of astrophysical sources with such magnetic field/plasma nearly perpendicular configurations.

Meli, A.; Biermann, P. L.

140

Diffusion coefficients of fluorescent organic molecules in inert gases  

NASA Astrophysics Data System (ADS)

We use arrested-flow pulse broadening to measure the diffusion coefficients of four archetype organic semiconductors in two carrier gases, N2 and Ar, with a precision of 5%. The measurements are realized by the injection and transport of pulses of organic molecules in an organic vapor phase deposition chamber, followed by their detection using laser induced fluorescence that dynamically measures the organic concentration in the gas phase. Measurements show that the diffusivity of tris(8-hydroxyquinoline) aluminum (Alq3) in N2 and Ar varies as the square of the temperature and inversely with pressure over a large range of gas conditions. We show that classical Chapman-Enskog theory can be used to approximate the diffusivity with an accuracy that depends on the physical dimensions of the organic molecular species, with the most accurate predictions for spherical and rigid molecules such as Alq3.

Rolin, Cedric; Forrest, Stephen R.

2013-07-01

141

Paducah Gaseous Diffusion Plant proposed pilot pump-and-treat project. Final report  

Microsoft Academic Search

On March 23, 1992, R.C. Sleeman of the Department of Energy, Oak Ridge Operations Office requested that a Groundwater Corrective Actions Team be assembled to evaluate the technical merit of and the need to implement a proposed groundwater pump-and-treat demonstration project for the Northwest contaminant plume at the Paducah Gaseous Diffusion Plant. In addition to other suggestions, the Team recommended

G. W. Bodenstein; R. R. Bonczek; T. O. Early; D. D. Huff; K. S. Jones; M. D. Nickelson; C. T. Rightmire

1994-01-01

142

Geologic characterization of the Paducah Gaseous Diffusion Plant and surrounding area determined from geophysical logs  

Microsoft Academic Search

The Paducah Gaseous Diffusion Plant (PGDP) discovered in August 1988 that several private wells, generally north of the plant, were contaminated with trichloroethylene and\\/or ⁹⁹Tc. Presumably, PGDP is the source of both contaminants, and the most likely pathway for contaminant transport is within a regional aquifer that underlies the site. However, it is not possible to characterize potential flow paths

R. B. Dreier; R. O. Kennard; R. J. Selfridge

1990-01-01

143

Fire protection review revisit No. 2, Paducah Gaseous Diffusion Plant, Paducah, Kentucky  

Microsoft Academic Search

A fire protection survey was conducted for the Department of Energy at the Paducah Gaseous Diffusion Plant, Paducah, Kentucky, from October 30--November 4, November 6--10, and December 4--8, 1989. The purpose of the survey was to review the facility fire protection program and to make recommendations. Surveys of other facilities resulted in a classification system for buildings which provide an

P. H. Dobson; D. R. Keller; S. D. Treece

1990-01-01

144

Inorganic soil and groundwater chemistry near Paducah Gaseous Diffusion Plant, Paducah, Kentucky  

Microsoft Academic Search

Near-surface soils, boreholes, and sediments near the Paducah Gaseous Diffusion Plant (PGDP) were sampled in 1989-91 as were monitoring wells, TVA wells, and privately-owned wells. Most wells were sampled two or three times. The resulting chemical analyses have been published in previous reports and have been previously described (CH2M HILL 1991, 1992; Clausen et al. 1992). The two reports by

1995-01-01

145

Infrared absorption strengths of potential gaseous diffusion plant coolants and related reaction products  

Microsoft Academic Search

The DOE gaseous diffusion plant complex makes extensive use of CFC-114 as a primary coolant. As this material is scheduled for production curtailment within the next few years, a search for substitutes is underway, and apparently workable alternatives have been found and are under testing. The presently favored substitutes, FC-c3l8 and FC-3110, satisfy ozone depletion and operational chemical compatibility concerns,

L. D. Trowbridge; E. C. Angel

1993-01-01

146

Relative risk of nuclear criticality occurring from LEU and HEU gaseous diffusion plant deposits  

Microsoft Academic Search

The Oak Ridge Gaseous Diffusion Plant was built during World War II and operated successfully until 1964 when shutdown was begun. The plant took natural (0.711% ²³⁵U) uranium as feed and processed it into both low-enriched uranium (LEU) and high-enriched uranium (HEU) with concentrations of â¼93% ²³⁵U. During operation, in-leakage of humid air into process piping and equipment caused reactions

M. J. Haire; W. C. Jordan; J. C. Ingram; T. L. Sr. Dahl

1996-01-01

147

On the global warming potentials of candidate gaseous diffusion plant coolants  

Microsoft Academic Search

CFC-114 has been used in large quantities as a coolant in gaseous diffusion plants for some time. International and national policy actions related to protection of the ozone layer now call for the elimination of the production of several chlorofluorocarbons, including CFâClCFâCl, termed CFC-114, by the end of this decade. Atmospheric researchers have played major roles in the research and

Wuebbles

1991-01-01

148

Gamma radiological surveys of the Oak Ridge Reservation, Paducah Gaseous Diffusion Plant, and Portsmouth Gaseous Diffusion Plant, 1990-1993, and overview of data processing and analysis by the Environmental Restoration Remote Sensing Program, Fiscal Year 1995.  

National Technical Information Service (NTIS)

Three gamma radiological surveys have been conducted under auspices of the ER Remote Sensing Program: (1) Oak Ridge Reservation (ORR) (1992), (2) Clinch River (1992), and (3) Portsmouth Gaseous Diffusion Plant (PORTS) (1993). In addition, the Remote Sensi...

J. L. Smyre B. W. Moll A. L. King

1996-01-01

149

Generalization and calculation of the thermal diffusion factor of binary hydrogen-containing gaseous mixtures  

NASA Astrophysics Data System (ADS)

The results of generalization of experimental data on the thermal diffusion factor ? T of hydrogen-containing gaseous mixtures within the framework of similarity theory have been given. The calculated relation which makes it possible to predict the thermal diffusion factor of hydrogen-containing mixtures of nonpolar gases with a limited body of data on the substance has been obtained. The ? T values of mixtures of hydrogen with inert gases, including radon Rn, and with N2, SiH4, and GeH4 in the temperature interval 100-1500 K have been calculated.

Shashkov, A. G.; Zolotukhina, A. F.; Fokin, L. R.

2011-01-01

150

Network modeling of diffusion coefficients for porous media: II. Simulations  

SciTech Connect

Gas diffusion often dominates constituent in porous media (PM) and it dependent on pore geometry, water content, and water distribution in PM. Network models of PM offer the ability to investigate the influence and interaction of pore-scale PM properties and fluid properties on macroscopic properties of the system. This study was conducted to investigate the macroscopic relative gas diffusion coefficient vs. air-filled porosity relationship or diffusion characteristic (DC) of PM using a network model. The network model was used to simulate DCs in wetting and drying PM containing air and water. A network size of nine by nine spheres was used; increasing the network size to 19 by 19 by 19 produced essentially no change in the DC. The DC was independent of Henry`s law gas-liquid partition coefficient (H) for H values of 0.1, 1.0, and 5.0. The product HR{sub W}, where R{sub W} is the ratio between the bulk gas- and liquid-phase diffusion coefficients, strongly influences the DC when H values of 1000 to 10 000 are considered; this indicates that certain organic compounds have DCs independent of air-filled porosity. Hysteresis in DCs was found in selected network cases, with the wetting DCs being greater than the drying DCs for most air-filled porosities, in accord with some experimental results reported in the literature. Spatial correlation of network pore space was shown to bring the simulated DCs into better agreement with some experimental DCs. 23 refs., 10 figs., 3 tabs.

Steele, D.D. [North Dakota State Univ., Fargo, ND (United States); Nieber, J.L. [Univ. of Minnesota, St. Paul, MN (United States)

1994-09-01

151

Effect of concentration dependence of the diffusion coefficient on homogenization kinetics in multiphase binary alloy systems  

NASA Technical Reports Server (NTRS)

Diffusion calculations were performed to establish the conditions under which concentration dependence of the diffusion coefficient was important in single, two, and three phase binary alloy systems. Finite-difference solutions were obtained for each type of system using diffusion coefficient variations typical of those observed in real alloy systems. Solutions were also obtained using average diffusion coefficients determined by taking a logarithmic average of each diffusion coefficient variation considered. The constant diffusion coefficient solutions were used as reference in assessing diffusion coefficient variation effects. Calculations were performed for planar, cylindrical, and spherical geometries in order to compare the effect of diffusion coefficient variations with the effect of interface geometries. In most of the cases considered, the diffusion coefficient of the major-alloy phase was the key parameter that controlled the kinetics of interdiffusion.

Tenney, D. R.; Unnam, J.

1978-01-01

152

Transient radon diffusion through radon-proof membranes: A new technique for more precise determination of the radon diffusion coefficient  

Microsoft Academic Search

The following paper is focused on the numerical modelling of the transient radon diffusion through radon-proof membranes during the measurement of their radon diffusion coefficient. The major aim of such numerical modelling is to increase the accuracy of radon diffusion coefficients derived from the measured data sets. The developed complex “transient” numerical model is able to calculate the radon diffusion

Martin Jiranek; Zbynek Svoboda

2009-01-01

153

Assessment of scale effects on effective diffusion coefficients  

NASA Astrophysics Data System (ADS)

Understanding contaminant movement in diffusion-dominated systems is important for the accurate prediction of long-term solute transport. At present, measurement of the effective diffusion coefficient (De) of clay-rich systems is determined using small-scale laboratory experiments. The application of these measurements to field studies assumes that De is not scale-dependent. Because of the empirical nature of equations describing the diffusion process, as well as the scale-dependent nature of other properties (e.g., hydraulic conductivity) controlling contaminant transport, this assumption warrants investigation. The objective of this study was to assess the scale dependence of De by comparing the De values obtained from three conservative tracers (?D, ?18O and chloride) at two scales of field-testing and laboratory-based double reservoir diffusion testing. Thein situ field-testing system consisted of purpose-built piezometers, pressure transducers, inflatable packers, and a circulation pump. All testing was conducted on an 80 m thick, clay-rich till sequence located in Saskatchewan, Canada. Results indicate the scale effects on conservative transport by diffusion are minimal. Using the same methodology, ongoing studies are being conducted in this system to determine effects of scaling on reactive transport.

Ingram, L.; Hendry, J.; Wassenaar, L.; Barbour, L.

2003-04-01

154

Determination of the response function for the Portsmouth Gaseous Diffusion Plant criticality accident alarm system neutron detectors.  

National Technical Information Service (NTIS)

Neutron-sensitive radiation detectors are used in the Portsmouth Gaseous Diffusion Plant's (PORTS) criticality accident alarm system (CAAS). The CAAS is composed of numerous detectors, electronics, and logic units. It uses a telemetry system to sound buil...

R. W. Tayloe A. S. Brown M. C. Dobelbower J. E. Woollard

1997-01-01

155

Demobilization of the World's Largest Decontamination and Decommissioning Project Project Closeout of three Gaseous Diffusion Plants for Re-industrialization  

SciTech Connect

This paper describes the challenges and lessons learned from the demobilization of the world' largest, and first, successfully decontaminated and decommissioned project. These gaseous diffusion plants are the first plants to be successfully decommissioned in the United States. (authors)

Stevens, J.L.; Miller, JA. [BNG America, ETTP Project, 705-3C, Aiken, SC 29808 (United States); 804 South Illinois Avenue, Oak Ridge, TN 37830 (United States)

2006-07-01

156

Comparison of radon diffusion coefficients measured by transient-diffusion and steady-state laboratory methods  

SciTech Connect

A method was developed and used to determine radon diffusion coefficients in compacted soils by transient-diffusion measurements. A relative standard deviation of 12% was observed in repeated measurements with a dry soil by the transient-diffusion method, and a 40% uncertainty was determined for moistures exceeding 50% of saturation. Excellent agreement was also obtained between values of the diffusion coefficient for radon in air, as measured by the transient-diffusion method, and those in the published literature. Good agreement was also obtained with diffusion coefficients measured by a steady-state method on the same soils. The agreement was best at low moistures, averaging less than ten percent difference, but differences of up to a factor of two were observed at high moistures. The comparison of the transient-diffusion and steady-state methods at low moistures provides an excellent verification of the theoretical validity and technical accuracy of these approaches, which are based on completely independent experimental conditions, measurement methods and mathematical interpretations.

Kalwarf, D.R.; Nielson, K.K.; Rich, D.C.; Rogers, V.C.

1982-11-01

157

Characterisation of gaseous and particulate atmospheric pollutants in the East Mediterranean by diffusion denuder sampling lines.  

PubMed

A field study aimed to characterize atmospheric pollutants in the gaseous and the particulate phases was conducted during the fall-winter of 2004 and the summer of 2005 in the Ashdod area, Israel. The site is influenced by both anthropogenic sources (power plants, refineries, chemical and metal industries, a cargo port, road traffic) and natural sources (sea-spray and desert dust). The use of diffusion lines--a series of annular diffusion denuders for sampling gaseous compounds followed by a cyclone and a filter pack for determining PM(2.5) composition--allowed a good daily characterization of the main inorganic compounds in both the gaseous (HCl, HNO(3), SO(2), NH(3)) and the particulate phase (Cl(-), NO(3)(-), SO(4)(=), NH(4)(+), and base cations). During the summer campaign two other activities were added: an intensive 3-h sampling period and the determination of PM(2.5) bulk composition. The results were interpreted on the basis of meteorological condition, especially the mixing properties of the lower atmosphere as determined by monitoring the natural radioactivity due to Radon progeny, a good proxy of the atmospheric ability to dilute pollutants. Several pollution episodes were identified and the predominance of different sources was highlighted (sea-spray, desert dust, secondary photochemical pollutants). During the summer period a considerable increase of nitric acid and particulate sulphate was observed. Secondary inorganic pollutants (nitrate, sulphate and ammonium) constituted, on the average, 57% of the fine particle fraction, organic compounds 20%, primary anthropogenic compounds 14%, natural components (sea-spray and crustal elements) 9%. The advantages of the diffusion lines in determining gaseous and particulate N- and S- inorganic compounds are discussed. PMID:18535917

Perrino, C; Catrambone, M; Esposito, G; Lahav, D; Mamane, Y

2009-05-01

158

Distributions of the diffusion coefficient for the quantum and classical diffusion in disordered media  

NASA Astrophysics Data System (ADS)

It is shown that the distribution functions of the diffusion coefficient are very similar in the standard model of quantum diffusion in a disordered metal and in a model of classical diffusion in a disordered medium: in both cases the distribution functions have lognormal tails, their part increasing with the increase of the disorder. The similarity is based on a similar behaviour of the high-gradient operators determining the high-order cumulants. The one-loop renormalization- group corrections make the anomalous dimension of the operator that governs the sth cumulant proportional to s( s-1) thus overtaking for large s the negative normal dimension. As behaviour of the ensemble-averaged diffusion coefficient is quite different in these models, it suggests that a possible universality in the distribution functions is independent of the behaviour of average quantities.

Lerner, Igor V.

1993-07-01

159

United States Department of Energy Paducah Gaseous Diffusion Plant. Environmental monitoring report, calendar year 1984  

SciTech Connect

Air, water, soil, sediments, grass, and groundwater in the vicinity of the Paducah Gaseous Diffusion Plant were continuously or periodically sampled during 1984. Analyses for materials known to be in plant effluents were made to provide effluent control information and to determine compliance with applicable environmental standards. Low sulfur coal is burned in the steam plant to meet Kentucky emission limits for sulfur dioxide. Air analyses for radioactivity indicated concentrations at each off-site sampling station averaged less than 1% of the DOE Radioactivity Concentration Guide (RCG). Offsite analyses for fluorides in grass met the Kentucky Air Quality Requirements. All onsite and offsite airborne fluoride samples met the Kentucky one-week and one-month standards for gaseous HF. Soil samples were analyzed for uranium and showed no significant deviation from normal background concentrations. There was no detectable change in chemical, physical, or radioactive characteristics of the Ohio River attributable to Paducah Gaseous Diffusion Plant operations. The results of water sample analyses of the Ohio River show the chromium and fluoride concentrations to be in compliance with the requirements of the applicable Kentucky regulations. 7 figs., 26 tabs.

Not Available

1985-07-01

160

Environmental monitoring report: United States Department of Energy, Paducah Gaseous Diffusion Plant, calendar year 1983  

SciTech Connect

Air, water, soil, sediments, grass, and groundwater in the vicinity of the Paducah Gaseous Diffusion Plant were continuously or periodically sampled during 1983. Analyses for materials known to be in plant effluents were made to provide effluent control information and to determine compliance with applicable environmental standards. Low sulfur coal is burned in the steam plant to meet Kentucky emission limits for sulfur dioxide. Air analyses for radioactivity indicated concentrations at each offsite sampling station averaged less than 1% of the applicable Radioactivity Concentration Guide. Offsite analyses for fluorides in grass met the Kentucky Air Quality Requirements. All onsite and offsite airborne fluoride samples met the Kentucky one-week and one-month standards for gaseous HF. Soil samples were analyzed for uranium and showed no significant deviation from normal background concentrations. There was no detectable change in chemical, physical, or radioactive characteristics of either the Ohio River or ground water attributable to Paducah Gaseous Diffusion Plant operations. The results of water sample analyses of the Ohio River show the chromium and fluoride concentrations to be in compliance with the requirements of the applicable Kentucky regulations. Algal activity resulted in an increase in pH violations during 1983. 7 references, 7 figures, 26 tables.

Not Available

1984-05-01

161

Environmental monitoring report: United States Deparment of Energy Paducah Gaseous Diffusion Plant  

SciTech Connect

Air, water, soil, and grass in the vicinity of the Padacuh Gaseous Diffusion Plant were continuously or periodically sampled during 1980. Analyses for materials known to be in plant effluents were made to provide effluent control information and to determine compliance with applicable air and water quality standards. Air analyses for radioactivity indicated concentrations at each offsite sampling station averaged less than 1% of the applicable Radioactivity Concentration Guide. Offsite analyses for fluorides in grass met the Kentucky Air Quality Requirements. All onsite and offsite airborne fluoride samples met the Kentucky one-week and one-month standards for gaseous HF. Soil samples were analyzed for uranium and showed no significant deviation from normal background concentrations. There was no detectable change in chemical, physical, or radioactive characteristics of either the Ohio River or ground water attributable to Paducah Gaseous Diffusion Plant operations. The results of water sample analyses of the Ohio River show the chromium and fluoride concentrations to be in compliance with the requirements of the applicable Kentucky regulations. The concentration of hexavalent chromium in Little Bayou Creek has occasionally been in excess of the Kentucky aquatic life standard of 0.05 mg/l due to cooling tower windage.

Not Available

1981-05-01

162

United States Department of Energy Paducah Gaseous Diffusion Plant. Environmental monitoring report, calendar year 1979  

SciTech Connect

Air, water, soil, and grass in the vicinity of the Paducah Gaseous Diffusion Plant were continuously or periodically sampled during 1979. Analyses for materials known to be in plant effluents were made to provide effluent control information and to determine compliance with applicable air and water quality standards. Stack emission tests determined that smelter operations were in compliance with Kentucky air pollution regulations. Low sulfur coal is burned in the steam plant to meet Kentucky emission limits for sulfur dioxide. Air analyses for radioactivity indicated concentrations at each offsite sampling station averaged less than 1% of the applicable Radioactivity Concentration Guide. Offsite analyses for fluorides in grass met the Kentucky Air Quality Requirements. All onsite and offsite airborne fluoride samples met the Kentucky one-week and one-month standards for gaseous HF. Soil samples were analyzed for uranium and showed no significant deviation from background. There was no detectable change in chemical, physical, or radioactive characteristics of either the Ohio river or ground water attributable to Paducah Gaseous Diffusion Plant operations.

Not Available

1980-06-02

163

Results of the outdoor radiological survey at the Portsmouth Gaseous Diffusion Plant site, Piketon, Ohio  

SciTech Connect

The Portsmouth Gaseous Diffusion Plant (PORTS) is owned by the US Department of Energy (DOE) and managed by Martin Marietta Energy Systems, Inc. As shown in Fig. 1, the plant is located in sparsely populated, rural Pike County, Ohio. PORTS began in 1952 as part of the Atomic Energy Commission`s (AEC) proposed expansion of the gaseous diffusion program in order to increase the production of enriched uranium. The 3,708-acre site is about a half mile east of US Interstate 23 (Fig. 2) and approximately 1 mile east of the Scioto River Valley (Fig. 3). The current layout of the plant is shown on Fig. 4. The principal site process is the separation of uranium isotopes {sup 235}U and {sup 238}U through gaseous diffusion. This uranium enrichment process involves the more rapid diffusion of lighter molecules of UF{sub 6} (uranium hexaflouride) through the barrier walls of a porous tube. The end result is a UF{sub 6} stream that is slightly enriched in the {sup 235}U isotope. The separation process is repeated in a cascade arrangement until the desired concentration is reached. At the request of the PORTS Environmental Safety and Health Division, the Health and Safety Research Division (HASRD), Oak Ridge National Laboratory (ORNL), conducted a radiological survey of the outdoor surface environment of the PORTS site. The surveyed area covered approximately 150 acres of fenced ground consisting of dirt, asphalt, and concrete. The survey was performed between July 1990 and April 1991, and the results reported to PORTS, Health Physics Department. The survey purpose was to determine the extent of radiological contamination and to locate and prioritize areas of concern from both a worker health/safety and an environmental standpoint. Specifically, the objectives of the survey were to assess the areal radioactive status of the site and to analyze surface soil samples for the presence of selected radionuclides. The principal radionuclide of concern is uranium.

Rodriguez, L.M.; Floyd, L.M.; Carrier, R.F.

1992-09-01

164

Results of the outdoor radiological survey at the Portsmouth Gaseous Diffusion Plant site, Piketon, Ohio  

SciTech Connect

The Portsmouth Gaseous Diffusion Plant (PORTS) is owned by the US Department of Energy (DOE) and managed by Martin Marietta Energy Systems, Inc. As shown in Fig. 1, the plant is located in sparsely populated, rural Pike County, Ohio. PORTS began in 1952 as part of the Atomic Energy Commission's (AEC) proposed expansion of the gaseous diffusion program in order to increase the production of enriched uranium. The 3,708-acre site is about a half mile east of US Interstate 23 (Fig. 2) and approximately 1 mile east of the Scioto River Valley (Fig. 3). The current layout of the plant is shown on Fig. 4. The principal site process is the separation of uranium isotopes [sup 235]U and [sup 238]U through gaseous diffusion. This uranium enrichment process involves the more rapid diffusion of lighter molecules of UF[sub 6] (uranium hexaflouride) through the barrier walls of a porous tube. The end result is a UF[sub 6] stream that is slightly enriched in the [sup 235]U isotope. The separation process is repeated in a cascade arrangement until the desired concentration is reached. At the request of the PORTS Environmental Safety and Health Division, the Health and Safety Research Division (HASRD), Oak Ridge National Laboratory (ORNL), conducted a radiological survey of the outdoor surface environment of the PORTS site. The surveyed area covered approximately 150 acres of fenced ground consisting of dirt, asphalt, and concrete. The survey was performed between July 1990 and April 1991, and the results reported to PORTS, Health Physics Department. The survey purpose was to determine the extent of radiological contamination and to locate and prioritize areas of concern from both a worker health/safety and an environmental standpoint. Specifically, the objectives of the survey were to assess the areal radioactive status of the site and to analyze surface soil samples for the presence of selected radionuclides. The principal radionuclide of concern is uranium.

Rodriguez, L.M.; Floyd, L.M.; Carrier, R.F.

1992-09-01

165

Relative risk of nuclear criticality occurring from LEU and HEU gaseous diffusion plant deposits  

SciTech Connect

The Oak Ridge Gaseous Diffusion Plant was built during World War II and operated successfully until 1964 when shutdown was begun. The plant took natural (0.711% {sup 235}U) uranium as feed and processed it into both low-enriched uranium (LEU) and high-enriched uranium (HEU) with concentrations of {approximately}93% {sup 235}U. During operation, in-leakage of humid air into process piping and equipment caused reactions with gaseous uranium hexafluoride (UF{sub 6}) that produced nonvolatile uranyl fluoride (UO{sub 2}F{sub 2}) deposits. After shutdown, the volatile UF{sub 6} was evacuated, but the UO{sub 2}F{sub 2} deposits remained. The U.S. Department of Energy has initiated a program to improve nuclear criticality safety by removing the larger deposits of enriched uranium.

Haire, M.J.; Jordan, W.C. [Oak Ridge National Laboratory, TN (United States); Ingram, J.C. III; Dahl, T.L. Sr. [Lockheed Martin Energy Systems, Inc., Oak Ridge, TN (United States)

1996-12-31

166

Characterization of process holdup material at the Portsmouth Gaseous Diffusion Plant  

SciTech Connect

The cascade material balance area at the Portsmouth Gaseous Diffusion Plant is characterized by continuous, large, in-process inventories of gaseous uranium hexafluoride (UF/sub 6/) and very large inputs and outputs of UF/sub 6/ over a complete range of /sup 235/U enrichments. monthly inventories are conducted to quantify the in-place material, but the inventory techniques are blind to material not in the gas phase. Material is removed from the gas phase by any one of four mechanisms: (1) freeze-outs which are the solidification of UF/sub 6/, (2) inleakage of wet air which produces solid uranium oxyfluorides, (3) consumption of uranium through UF/sub 6/ reaction with internal metal surfaces, and (4) adsorption of UF/sub 6/ on internal surfaces. This presentation describes efforts to better characterize and, where possible, to eliminate or reduce the effects of these mechanisms on material accountability.

Boyd, D.E.; Miller, R.R.

1986-01-01

167

Analytical solution of a spatially variable coefficient advection–diffusion equation in up to three dimensions  

Microsoft Academic Search

Analytical solutions are provided for the two- and three-dimensional advection–diffusion equation with spatially variable velocity and diffusion coefficients. We assume that the velocity component is proportional to the distance and that the diffusion coefficient is proportional to the square of the corresponding velocity component. There is a simple transformation which reduces the spatially variable equation to a constant coefficient problem

C. Zoppou; J. H. Knight

1999-01-01

168

Experimental study of advective-diffusive gaseous CO2 transport through porous media  

NASA Astrophysics Data System (ADS)

Leakage of gaseous CO2 into the shallow subsurface system is one of the main concerns associated with geologic storage resources. A better understanding of CO2 leakage in the shallow subsurface plays an important role for developing leakage monitoring programs. CO2 may reach the unsaturated zone by different leak mechanisms such as exsolution from CO2 supersaturated water and continuous bubbling or gas flow along a leakage path. In the unsaturated zone, the CO2 is heavier than air and may accumulate below the ground surface and move laterally. We developed a small-scale experiment setup to study the possible gaseous CO2 transport mechanisms with different controlled conditions. In this study, the experiment setup was applied to measure CO2 distributions in time and space through homogenous dry sand in which the CO2 concentrations through the domain were measured by sensitive gas sensors. The preliminary analysis of the result suggests that the transport and distribution of gaseous CO2 is spatially and temporally sensitive for the selected experimental conditions of gas flow rate and porous media. To better understand the advection and diffusion processes through the unsaturated zone, the experimental results are coupled with the dusty gas model (DGM) of Mason et al. (1967). The dusty gas model's constitutive relationships are integrated into a numerical model for multicomponent gas mixture flow and transport in porous media. The DGM considers interactions between all gaseous species and Knudsen diffusion which is important in fine grained soils. Results from the applied model were consistent with the experimental breakthrough curves obtained in this study.

Basirat, Farzad; Sharma, Prabhakar; Niemi, Auli; Fagerlund, Fritjof

2014-05-01

169

Turbulence coefficients and stability studies for the coaxial flow or dissimiliar fluids. [gaseous core nuclear reactors  

NASA Technical Reports Server (NTRS)

Analytical investigations of fluid dynamics problems of relevance to the gaseous core nuclear reactor program are presented. The vortex type flow which appears in the nuclear light bulb concept is analyzed along with the fluid flow in the fuel inlet region for the coaxial flow gaseous core nuclear reactor concept. The development of numerical methods for the solution of the Navier-Stokes equations for appropriate geometries is extended to the case of rotating flows and almost completes the gas core program requirements in this area. The investigations demonstrate that the conceptual design of the coaxial flow reactor needs further development.

Weinstein, H.; Lavan, Z.

1975-01-01

170

Occupational exposure to trichloroethylene and cancer risk for workers at the Paducah Gaseous Diffusion Plant  

Microsoft Academic Search

Objective  The Paducah Gaseous Diffusion Plant (PGDP) became operational in 1952; it is located in the western part of Kentucky. We conducted\\u000a a mortality study for adverse health effects that workers may have suffered while working at the plant, including exposures\\u000a to chemicals.\\u000a \\u000a \\u000a \\u000a \\u000a Materials and Methods  We studied a cohort of 6820 workers at the PGDP for the period 1953 to 2003;

Debra E. Bahr; Timothy E. Aldrich; Dazar Seidu; Gail M. Brion; David J. Tollerud; Susan Muldoon; Nancy Reinhart; Ahmed Youseefagha; Paul McKinney; Therese Hughes; Caroline Chan; Carol Rice; David E. Brewer; Ronald W. Freyberg; Adriane Moser Mohlenkamp; Kristen Hahn; Richard Hornung; Mona Ho; Aniruddha Dastidar; Samantha Freitas; Daniel Saman; Hege Ravdal; Douglas Scutchfield

2011-01-01

171

Construction and operation of an industrial solid waste landfill at Portsmouth Gaseous Diffusion Plant, Piketon, Ohio  

SciTech Connect

The US Department of Energy (DOE), Office of Waste Management, proposes to construct and operate a solid waste landfill within the boundary of the Portsmouth Gaseous Diffusion Plant (PORTS), Piketon, Ohio. The purpose of the proposed action is to provide PORTS with additional landfill capacity for non-hazardous and asbestos wastes. The proposed action is needed to support continued operation of PORTS, which generates non-hazardous wastes on a daily basis and asbestos wastes intermittently. Three alternatives are evaluated in this environmental assessment (EA): the proposed action (construction and operation of the X-737 landfill), no-action, and offsite shipment of industrial solid wastes for disposal.

NONE

1995-10-01

172

Messages Do Diffuse Faster than Messengers: Reconciling Disparate Estimates of the Morphogen Bicoid Diffusion Coefficient  

PubMed Central

The gradient of Bicoid (Bcd) is key for the establishment of the anterior-posterior axis in Drosophila embryos. The gradient properties are compatible with the SDD model in which Bcd is synthesized at the anterior pole and then diffuses into the embryo and is degraded with a characteristic time. Within this model, the Bcd diffusion coefficient is critical to set the timescale of gradient formation. This coefficient has been measured using two optical techniques, Fluorescence Recovery After Photobleaching (FRAP) and Fluorescence Correlation Spectroscopy (FCS), obtaining estimates in which the FCS value is an order of magnitude larger than the FRAP one. This discrepancy raises the following questions: which estimate is "correct''; what is the reason for the disparity; and can the SDD model explain Bcd gradient formation within the experimentally observed times? In this paper, we use a simple biophysical model in which Bcd diffuses and interacts with binding sites to show that both the FRAP and the FCS estimates may be correct and compatible with the observed timescale of gradient formation. The discrepancy arises from the fact that FCS and FRAP report on different effective (concentration dependent) diffusion coefficients, one of which describes the spreading rate of the individual Bcd molecules (the messengers) and the other one that of their concentration (the message). The latter is the one that is more relevant for the gradient establishment and is compatible with its formation within the experimentally observed times.

Sigaut, Lorena; Pearson, John E.; Colman-Lerner, Alejandro; Ponce Dawson, Silvina

2014-01-01

173

Messages do diffuse faster than messengers: reconciling disparate estimates of the morphogen bicoid diffusion coefficient.  

PubMed

The gradient of Bicoid (Bcd) is key for the establishment of the anterior-posterior axis in Drosophila embryos. The gradient properties are compatible with the SDD model in which Bcd is synthesized at the anterior pole and then diffuses into the embryo and is degraded with a characteristic time. Within this model, the Bcd diffusion coefficient is critical to set the timescale of gradient formation. This coefficient has been measured using two optical techniques, Fluorescence Recovery After Photobleaching (FRAP) and Fluorescence Correlation Spectroscopy (FCS), obtaining estimates in which the FCS value is an order of magnitude larger than the FRAP one. This discrepancy raises the following questions: which estimate is "correct''; what is the reason for the disparity; and can the SDD model explain Bcd gradient formation within the experimentally observed times? In this paper, we use a simple biophysical model in which Bcd diffuses and interacts with binding sites to show that both the FRAP and the FCS estimates may be correct and compatible with the observed timescale of gradient formation. The discrepancy arises from the fact that FCS and FRAP report on different effective (concentration dependent) diffusion coefficients, one of which describes the spreading rate of the individual Bcd molecules (the messengers) and the other one that of their concentration (the message). The latter is the one that is more relevant for the gradient establishment and is compatible with its formation within the experimentally observed times. PMID:24901638

Sigaut, Lorena; Pearson, John E; Colman-Lerner, Alejandro; Ponce Dawson, Silvina

2014-06-01

174

Direct estimation of diffuse gaseous emissions from coal fires: current methods and future directions  

USGS Publications Warehouse

Coal fires occur in nature spontaneously, contribute to increases in greenhouse gases, and emit atmospheric toxicants. Increasing interest in quantifying coal fire emissions has resulted in the adaptation and development of specialized approaches and adoption of numerical modeling techniques. Overview of these methods for direct estimation of diffuse gas emissions from coal fires is presented in this paper. Here we take advantage of stochastic Gaussian simulation to interpolate CO2 fluxes measured using a dynamic closed chamber at the Ruth Mullins coal fire in Perry County, Kentucky. This approach allows for preparing a map of diffuse gas emissions, one of the two primary ways that gases emanate from coal fires, and establishing the reliability of the study both locally and for the entire fire. Future research directions include continuous and automated sampling to improve quantification of gaseous coal fire emissions.

Engle, Mark A.; Olea, Ricardo A.; O'Keefe, Jennifer M. K.; Hower, James C.; Geboy, Nicholas J.

2013-01-01

175

On the structure of gaseous confined laminar diffusion flames: Numerical investigation  

NASA Technical Reports Server (NTRS)

The structure and characteristics of gaseous confined laminar diffusion flames are investigated by numerically solving the time-dependent two-dimensional axisymmetric conservation equations. The numerical model accounts for the important chemical and physical processes involved, including axial diffusion, viscous effects, radial convection, and finite-rate chemistry. The numerical results clearly show that the flame has a finite thickness and leakage of fuel vapor into the flame zone is possible. The effect of heat release is found to induce some radial flow. Predicted flame shape and dimensions are compared to the classical Burke-Schumann flame. The numerically calculated flame is observed to be about 15 percent taller and 5 percent narrower than that of the Burke-Schumann solution under the same conditions.

Mawid, M. A.; Bulzan, D. L.; Aggarwal, S. K.

1993-01-01

176

Portsmouth Gaseous Diffusion Plant environmental monitoring report for calendar year 1982  

SciTech Connect

At the Portsmouth Gaseous Diffusion Plant all effluent streams are sampled regularly and analyzed to assess compliance with applicable environmental standards. Radioactivity is measured in air, water, food, soil, and sediments; and radiation doses to the public are calculated. All public radiation doses from process effluents are well within Department of Energy and US EPA standards. Non-radioactive effluents either presently comply with federal standards or will comply upon completion of planned projects. CY-1982 was the second full year under a new National Pollutant Discharge Elimination System (NPDES) permit for liquid effluents; compliance with the permit's discharge limits, with the exception of the high suspended solids in effluent from the South Holding Pond, did not present any significant problems. Engineering is proceeding on projects to be constructed through 1985 to further reduce the impact of liquid effluents. Although neither the State of Ohio nor the federal government has established standards for fluoride in the atmosphere or in vegetation, fluorides are monitored because they are used extensively in the gaseous diffusion process.

Not Available

1983-04-27

177

Source term evaluation for postulated UFâ release accidents in gaseous diffusion plants -- Summer ventilation mode (non-seismic cases)  

Microsoft Academic Search

Computer models have been developed to simulate the transient behavior of aerosols and vapors as a result of a postulated accident involving the release of uranium hexafluoride (UFâ) into the process building of a gaseous diffusion plant. For the current study, gaseous UFâ is assumed to get released in the cell housing atmosphere through B-line break at 58.97 kg\\/s for

S. H. Kim; N. C. J. Chen; R. P. Taleyarkhan; M. W. Wendel; K. D. Keith; R. W. Schmidt; J. C. Carter; R. H. Dyer

1996-01-01

178

Biologistics--Diffusion coefficients for complete proteome of Escherichia coli  

PubMed Central

Motivation: Biologistics provides data for quantitative analysis of transport (diffusion) processes and their spatio-temporal correlations in cells. Mobility of proteins is one of the few parameters necessary to describe reaction rates for gene regulation. Although understanding of diffusion-limited biochemical reactions in vivo requires mobility data for the largest possible number of proteins in their native forms, currently, there is no database that would contain the complete information about the diffusion coefficients (DCs) of proteins in a given cell type. Results: We demonstrate a method for the determination of in vivo DCs for any molecule—regardless of its molecular weight, size and structure—in any type of cell. We exemplify the method with the database of in vivo DC for all proteins (4302 records) from the proteome of K12 strain of Escherichia coli, together with examples of DC of amino acids, sugars, RNA and DNA. The database follows from the scale-dependent viscosity reference curve (sdVRC). Construction of sdVRC for prokaryotic or eukaryotic cell requires ~20 in vivo measurements using techniques such as fluorescence correlation spectroscopy (FCS), fluorescence recovery after photobleaching (FRAP), nuclear magnetic resonance (NMR) or particle tracking. The shape of the sdVRC would be different for each organism, but the mathematical form of the curve remains the same. The presented method has a high predictive power, as the measurements of DCs of several inert, properly chosen probes in a single cell type allows to determine the DCs of thousands of proteins. Additionally, obtained mobility data allow quantitative study of biochemical interactions in vivo. Contact: rholyst@ichf.edu.pl Supplementary information: Supplementary data are available at Bioinformatics Online.

Kalwarczyk, Tomasz; Tabaka, Marcin; Holyst, Robert

2012-01-01

179

A theoretical framework for quantitatively characterizing sound field diffusion based on scattering coefficient and absorption coefficient of walls.  

PubMed

This paper describes the development of a theoretical framework for quantitatively characterizing sound field diffusion based on scattering coefficient and absorption coefficient of walls. The concepts of equivalent scattering area, equivalent scatter reflection area, average scattering coefficient and average scatter reflection coefficient are introduced in order to express all walls' capability of scatter in a room. Using these concepts and the mean free path, scatter-to-absorption ratio, mean scatter time and diffusion time are defined in order to evaluate degree of diffusion of a space. Furthermore the effect of spatial scattering objects to sound field diffusion is formulated. In addition the time variation of specular and scattered components in a room impulse response is formulated. The verification of these characterization methods was performed with computer simulations based on the sound ray tracing method. The results supported that the ideas presented are basically valid. PMID:20815450

Hanyu, Toshiki

2010-09-01

180

Analysis of fluorophore diffusion by continuous distributions of diffusion coefficients: application to photobleaching measurements of multicomponent and anomalous diffusion.  

PubMed Central

Fluorescence recovery after photobleaching (FRAP) is widely used to measure fluorophore diffusion in artificial solutions and cellular compartments. Two new strategies to analyze FRAP data were investigated theoretically and applied to complex systems with anomalous diffusion or multiple diffusing species: 1) continuous distributions of diffusion coefficients, alpha(D), and 2) time-dependent diffusion coefficients, D(t). A regression procedure utilizing the maximum entropy method was developed to resolve alpha(D) from fluorescence recovery curves, F(t). The recovery of multi-component alpha(D) from simulated F(t) with random noise was demonstrated and limitations of the method were defined. Single narrow Gaussian alpha(D) were recovered for FRAP measurements of thin films of fluorescein and size-fractionated FITC-dextrans and Ficolls, and multi-component alpha(D) were recovered for defined fluorophore mixtures. Single Gaussian alpha(D) were also recovered for solute diffusion in viscous media containing high dextran concentrations. To identify anomalous diffusion from FRAP data, a theory was developed to compute F(t) and alpha(D) for anomalous diffusion models defined by arbitrary nonlinear mean-squared displacement versus time relations. Several characteristic alpha(D) profiles for anomalous diffusion were found, including broad alpha(D) for subdiffusion, and alpha(D) with negative amplitudes for superdiffusion. A method to deduce apparent D(t) from F(t) was also developed and shown to provide useful complementary information to alpha(D). alpha(D) and D(t) were determined from photobleaching measurements of systems with apparent anomalous subdiffusion (nonuniform solution layer) and superdiffusion (moving fluid layer). The results establish a practical strategy to characterize complex diffusive phenomena from photobleaching recovery measurements.

Periasamy, N; Verkman, A S

1998-01-01

181

Analysis of fluorophore diffusion by continuous distributions of diffusion coefficients: application to photobleaching measurements of multicomponent and anomalous diffusion.  

PubMed

Fluorescence recovery after photobleaching (FRAP) is widely used to measure fluorophore diffusion in artificial solutions and cellular compartments. Two new strategies to analyze FRAP data were investigated theoretically and applied to complex systems with anomalous diffusion or multiple diffusing species: 1) continuous distributions of diffusion coefficients, alpha(D), and 2) time-dependent diffusion coefficients, D(t). A regression procedure utilizing the maximum entropy method was developed to resolve alpha(D) from fluorescence recovery curves, F(t). The recovery of multi-component alpha(D) from simulated F(t) with random noise was demonstrated and limitations of the method were defined. Single narrow Gaussian alpha(D) were recovered for FRAP measurements of thin films of fluorescein and size-fractionated FITC-dextrans and Ficolls, and multi-component alpha(D) were recovered for defined fluorophore mixtures. Single Gaussian alpha(D) were also recovered for solute diffusion in viscous media containing high dextran concentrations. To identify anomalous diffusion from FRAP data, a theory was developed to compute F(t) and alpha(D) for anomalous diffusion models defined by arbitrary nonlinear mean-squared displacement versus time relations. Several characteristic alpha(D) profiles for anomalous diffusion were found, including broad alpha(D) for subdiffusion, and alpha(D) with negative amplitudes for superdiffusion. A method to deduce apparent D(t) from F(t) was also developed and shown to provide useful complementary information to alpha(D). alpha(D) and D(t) were determined from photobleaching measurements of systems with apparent anomalous subdiffusion (nonuniform solution layer) and superdiffusion (moving fluid layer). The results establish a practical strategy to characterize complex diffusive phenomena from photobleaching recovery measurements. PMID:9649418

Periasamy, N; Verkman, A S

1998-07-01

182

Determination of the concentration dependence of polyelectrolyte diffusion coefficients by application of the Boltzmann gradient method  

Microsoft Academic Search

The concentration dependence of a polyelectrolyte diffusion coefficient in aqueous low salt solution (KCl, 1 mM) is determined from a single dynamic gradient experiment. The Boltzmann method is applied to calculate the diffusion coefficient. A special diffusion cell is constructed that minimizes aberrations in the optical detection of the polyion concentration profile. Bovine serum albumin (BSA) is chosen as a

A. T. Wagner; H.-H. Kohler

2008-01-01

183

Anisotropic Diffusion Coefficient in a Cylindrical Cell by Integral Transport Theory  

Microsoft Academic Search

The anisotropic diffusion coefficient has been calculated in a cylindrical cell with use made of the integral transport theory. The previous method of calculating the diffusion coefficient requires much computer time to evaluate the generalized first-flight collision probabilities between two mesh points for a square cell. To circumvent this drawback, we introduce new calculation methods for determining the anisotropic diffusion

Toshikazu TAKEDA; Tamotsu SEKIYA

1973-01-01

184

Effect of detector exposure time on the apparent diffusion coefficient measured by single particle tracking  

Microsoft Academic Search

We present results from simulation of Brownian motion of nanoparticles where we also take into account the averaging imposed by the exposure period E of the detector. The diffusion coefficient is estimated from the measured displacements of the particles over a prescribed delay time deltat. Results from free diffusion simulations show a clear dependency of the estimated diffusion coefficient on

Shahram Pouya; Manoochehr Koochesfahani; Richard di Liu

2008-01-01

185

Experimental study on flow and gaseous diffusion behind an isolated building.  

PubMed

To assist validation of numerical models of urban pollution dispersion, the effect of obstacles building on the gaseous diffusion in the wake region have been investigated experimentally in the boundary layer wind tunnel under neutral atmospheric conditions using a tracer gas technique from a point source without buoyancy. The flow and diffusion fields in the boundary layer in an urban environment were investigated in the downwind distance of the obstacle building using an isolated high-rise building model. The scale of the model experiment was assumed to be at 1:500. In the experiment, gaseous pollutant was discharged in the simulated boundary layer over the flat terrain. The effluent velocity of the pollutant was set to be negligible. The velocity field and the turbulence characteristics were analyzed and measured using a hot wire anemometer with a split-fibre probe. The experimental technique was involved the continuous release of tracer gas from a ground level source which was located in the downwind distance of the obstacle model and measured using a fast flame ionization detector (FID). Diffusion characteristics were studied and included both the vertical and lateral mean concentrations and concentration fluctuation intensity at various downwind distances. The results of study were demonstrated that the vertical profiles of the longitudinal mean velocity are very thick around the obstacle wake region due to the turbulence mixing and the smoothing of concentration differences was increased with downwind distance from the obstacle model. Furthermore, the experimental results can help to improve the understanding of mechanisms of pollutant dispersion in an urban environment and also use to validate the corresponding computational fluid dynamics (CFD) prediction. PMID:18193336

Yassin, Mohamed F; Ohba, Masaake; Tanaka, Hideyuki

2008-12-01

186

Reassessment of liquefaction potential and estimation of earthquake- induced settlements at Paducah Gaseous Diffusion Plant, Paducah, Kentucky. Final report  

SciTech Connect

This report documents a reassessment of liquefaction potential and estimation of earthquake-induced settlements for the U.S. Department of Energy (DOE), Paducah Gaseous Diffusion Plant (PGDP), located southwest of Paducah, KY. The U.S. Army Engineer Waterways Experiment Station (WES) was authorized to conduct this study from FY91 to FY94 by the DOE, Oak Ridge Operations (ORO), Oak Ridge, TN, through Inter- Agency Agreement (IAG) No. DE-AI05-91OR21971. The study was conducted under the Gaseous Diffusion Plant Safety Analysis Report (GDP SAR) Program.

Sykora, D.W.; Yule, D.E.

1996-04-01

187

Coordinate-dependent diffusion coefficients: Decay rate in open quantum systems  

SciTech Connect

Based on a master equation for the reduced density matrix of an open quantum collective system, the influence of coordinate-dependent microscopical diffusion coefficients on the decay rate from a metastable state is treated. For various frictions and temperatures larger than a crossover temperature, the quasistationary decay rates obtained with the coordinate-dependent microscopical set of diffusion coefficients are compared with those obtained with the coordinate-independent microscopical set of diffusion coefficients and coordinate-independent and -dependent phenomenological sets of diffusion coefficients. Neglecting the coordinate dependence of diffusion coefficients, one can strongly overestimate or underestimate the decay rate at low temperature. The coordinate-dependent phenomenological diffusion coefficient in momentum are shown to be suitable for applications.

Sargsyan, V. V. [Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Institut fuer Theoretische Physik der Justus-Liebig-Universitaet, D-35392 Giessen (Germany); Palchikov, Yu. V.; Antonenko, N. V. [Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Kanokov, Z. [Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); National University, 700174 Tashkent (Uzbekistan); Adamian, G. G. [Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Institute of Nuclear Physics, 702132 Tashkent (Uzbekistan)

2007-06-15

188

Evaluation of the vertical diffusion coefficients from ERA-40 with 222Rn simulations  

NASA Astrophysics Data System (ADS)

Boundary layer turbulence has a profound influence on the distribution of tracers with sources or sinks at the surface. The 40-year ERA-40 meteorological data set of the European Centre for Medium-range Weather Forecasts contains archived vertical diffusion coefficients. We evaluated the use of these archived diffusion coefficients instead of off-line diagnosed coefficients based on other meteorological parameters archived during ERA-40 by investigation of the effect on the distribution of the radioactive tracer 222Rn in the chemistry transport model TM3. In total four different sets of vertical diffusion coefficients are compared: (i) 3-hourly vertical diffusion coefficients archived during the ERA-40 project, (ii) 3-hourly off-line diagnosed coefficients from a non-local scheme based on Holtslag and Boville (1993), Vogelezang and Holtslag (1996), and Beljaars and Viterbo (1999), (iii) 6-hourly coefficients archived during the ERA-40 project, and (iv) 6-hourly off-line diagnosed coefficients based on a local scheme described in Louis (1979) and Louis et al. (1982). The diffusion scheme to diagnose the coefficients off-line in (ii) is similar to the diffusion scheme used during the ERA-40 project (i and iii). The archived diffusion coefficients from the ERA-40 project which are time-averaged cause stronger mixing than the instantaneous off-line diagnosed diffusion coefficients. This can be partially attributed to the effect of instantaneous versus time-averaged coefficients, as well as to differences in the diffusion schemes. The 3-hourly off-line diagnosis of diffusion coefficients can reproduce quite well the 3-hourly archived diffusion coefficients. Boundary layer heights are also available for the sets (ii) and (iii). Both were found to be in reasonable agreement with observations of the boundary layer height from Cabauw in the Netherlands and from the FIFE-campaign in the United States. Simulations of 222Rn with the TM3 model using these four sets of vertical diffusion coefficients are compared to surface measurements of 222Rn in Freiburg, Schauinsland, Cincinnati and Socorro in order to evaluate the effect of these different sets of diffusion coefficients on the tracer transport. It is found that the daily cycle of the 222Rn concentration is well represented using 3-hourly diffusion coefficients. Comparison with observations of 222Rn data with the station in Schauinsland which is situated on a hill shows that all considered schemes underestimate the amplitude of the daily cycle of the 222Rn concentration in the upper part of the atmospheric boundary layer. We conclude that the 3-hourly archived diffusion coefficients from ERA-40 are well suited for use in chemistry transport models.

Olivié, D. J. L.; van Velthoven, P. F. J.; Beljaars, A. C. M.

2004-08-01

189

High silicon self-diffusion coefficient in dry forsterite  

NASA Astrophysics Data System (ADS)

Plastic deformation of mantle minerals is believed to be controlled by self-diffusion of the slowest species, which is silicon in silicate minerals. Olivine is the main constituent of upper mantle. Therefore, silicon self-diffusion coefficient (DSi) in olivine provides the basic information of upper mantle rheology. Dohmen et al. [1] and Jaoul et al. [2] measured the DSi at ambient pressure under dry conditions in natural olivine and iron-free forsterite, respectively. However, their results were ~2-3 orders of magnitude lower than that estimated from deformation experiments [3]. In this study, we revisited DSi in forsterite and resolved this discrepancy [4]. Forsterite single crystals were polished in colloidal silica solution, deposited with 300-500 nm of 29Si enriched Mg2SiO4 films, covered by 100 nm of ZrO2 films, and annealed at 1600-1800 K from ambient pressure up to 13 GPa using an ambient pressure furnace and multi-anvil apparatus. The surface roughness after diffusion were reduced to <50 nm by polishing again in colloidal silica solution. Diffusion profiles were obtained by SIMS. Water contents in the samples were <1 ?g/g by FT-IR [4]. logDSi were determined to be -19.7±0.4 and -18.1±0.3 log[m2/s] under ambient pressure at 1600 and 1800 K, respectively. These values were 2.4 orders of magnitude higher than that determined by Jaoul et al. [2] in forsterite, as well as that reprted by Dohmen et al. [1] in natural olivine. Their low DSi could be obtained due to the bad contact of the coated films with the substrate. Our results well explain the high dislocation climb rates in deformation experiments [4]. We also determined a small negative pressure dependence of DSi with an activation volume of 1.7±0.4 cm3/mol, and an activation energy of ~410 kJ/mol. Calibratied to the same temperature, the nearly linear relationship of DSi against pressure in dry forsterite in this study, iron and water bearing wadsleyite and ringwoodite by Shimojuku et al. [5] demostrates that effects of iron, water, and structural difference of (Mg,Fe)2SiO4 polymorphs on silicon diffusion are small. Viscosity in upper mantle should be almost constant with depth by assuming it inversely proportional to DSi [4]. [1] Dohmen et al. (2002), GRL 29 (21), 2030. [2] Jaoul et al. (1981), Anelasticity in the Earth, Geodyn. 4, 95-100. [3] Goetze and Kohlstedt (1973), JGR 78 (26), 5961-5971. [4] Fei et al. (2012), EPSL 345-348, 95-103. [5] Shimojuku et al. (2009), EPSL 284, 103-112.

Katsura, T.; Fei, H.; Hegoda, C.; Yamazaki, D.; Wiedenbeck, M.; Yurimoto, H.; Shcheka, S.

2012-12-01

190

Environmental monitoring report. United States Department of Energy, Paducah Gaseous Diffusion Plant. Calendar year 1985  

SciTech Connect

Air, water, soil, sediments, grass, and groundwater in the vicinity of the Paducah Gaseous Diffusion Plant were continuously or periodically sampled during 1985. Analyses for materials known to be in plant effluents were made to provide effluent control information and to determine compliance with applicable environmental standards. Low sulfur coal is burned in the steam plant to meet Kentucky emission limits for sulfur dioxide. Air analyses for radioactivity indicated concentrations at each offsite sampling station continue to remain at low levels as indicated by calculations of potential radiation dose to the public. Off-site analyses for fluorides in grass met the Kentucky Air Quality Requirements. All on-site and off-site airborne fluoride samples met the Kentucky one-week and one-month standards for gaseous HF. Soil samples were analyzed for uranium and showed no significant deviation from normal background concentrations. The results of water sample analyses of the Ohio River show the chromium and fluoride concentrations to be in compliance with the requirements of the applicable Kentucky regulations.

Not Available

1986-05-01

191

Characterization of process holdup material at the Portsmouth Gaseous Diffusion Plant  

SciTech Connect

The cascade material balance area at the Portsmouth Gaseous Diffusion Plant is characterized by continuous, large, in-process inventories of gaseous uranium hexafluoride (UF/sub 6/) and very large inputs and outputs of UF/sub 6/ over a complete range of /sup 235/U enrichments. Monthly inventories are conducted to quantify the in-place material, but the inventory techniques are blind to material not in the gas phase. Material is removed from the gas phase by any one of four mechanisms: (1) freeze-outs which are the solidification of UF/sub 6/, (2) inleakage of wet air which produces solid uranium oxyfluorides, (3) consumption of uranium through UF/sub 6/ reaction with internal metal surfaces, and (4) adsorption of UF/sub 6/ on internal surfaces. This presentation describes efforts to better characterize and, where possible, to eliminate or reduce the effects of these mechanisms on material accountability. Freeze-outs and wet air deposits occur under absormal operating conditions, and techniques are available to prevent, detect and reverse them. Consumption and adsorption occur under normal operating conditions and are more complex to manage, however, computer models have been developed to quantify monthly the net effects due to consumption and adsorption. These models have shown that consumption and adsorption effects on inventory differences are significant.

Boyd, D.E.; Miller, R.R.

1986-06-23

192

Report on the Biological Monitoring Program at Paducah Gaseous Diffusion Plant December 1992--December 1993  

SciTech Connect

On September 24, 1987, the Commonwealth of Kentucky Natural Resources and Environmental Protection Cabinet issued an Agreed Order that required the development of a Biological Monitoring Program (BMP) for the Paducah Gaseous Diffusion Plant (PGDP). The goals of BMP are to demonstrate that the effluent limitations established for PGDP protect and maintain the use of Little Bayou and Big Bayou creeks for growth and propagation of fish and other aquatic life, characterize potential health and environmental impacts, document the effects of pollution abatement facilities on stream biota, and recommend any program improvements that would increase effluent treatability. The BMP for PGDP consists of three major tasks: effluent and ambient toxicity monitoring, bioaccumulation studies, and ecological surveys of stream communities (i.e., benthic macroinvertebrates and fish). This report includes ESD activities occurring from December 1992 to December 1993, although activities conducted outside this time period are included as appropriate.

Kszos, L.A.; Hinzman, R.L.; Peterson, M.J.; Ryon, M.G.; Smith, J.G.; Southworth, G.R.

1995-06-01

193

Portsmouth Gaseous Diffusion Plant Annual Site Environmental Report summary for 1993  

SciTech Connect

This report contains summaries of the environmental programs at Paducah Gaseous Diffusion Plant, environmental monitoring and the results, and the impact of operations on the environment and the public for 1993. The environmental monitoring program at Paducah includes effluent monitoring and environmental surveillance. Effluent monitoring is measurement of releases as they occur. Contaminants are released through either airborne emissions or liquids discharged from the plant. These releases occur as part of normal site operations, such as cooling water discharged from the uranium enrichment cascade operations or airborne releases from ventilation systems. In the event of system failure, this monitoring provides timely warning so that corrective action can be taken before releases reach an unsafe level. Environmental surveillance tracks the dispersion of materials into the environment after they have been released. This involves the collection of samples from various media, such as water, soil, vegetation, and food crops, and the analysis of these samples for certain radionuclides, chemicals, and metals.

Not Available

1994-11-01

194

Gaseous Species Measurements of Alternative Jet Fuels in Sooting Laminar Coflow Diffusion Flames  

NASA Astrophysics Data System (ADS)

The gaseous species concentration of Jet A-1, GTL, CTL and a blend of 80 vol.% GTL and 20 vol.% hexanol jet fuels in laminar coflow diffusion flames have been measured and studied. These species are carbon monoxide, carbon dioxide, oxygen, methane, ethane, ethylene, propylene, and acetylene. Benzene and propyne concentrations were also detected in CTL flames. 1-Butene has been quantified for the blend of GTL and hexanol flame. The detailed experimental setup has been described and results from different flames are compared. The CO is produced in a same amount in all the flames. The CTL flame had the largest and GTL/hexanol flame had lowest CO2 concentrations. The results indicate that GTL and GTL hexanol blend flames produce similar concentrations for all the measured hydrocarbon species and have the highest concentration among all the jet fuels. The experimental results from Jet A-1 fuel are also compared with numerical studies by Saffaripour et al .

Zabeti, Parham

195

Study of technetium uptake in vegetation in the vicinity of the Portsmouth Gaseous Diffusion Plant  

SciTech Connect

Technetium-99 was measured in vegetation and soil collected on and near the Portsmouth Gaseous Diffusion Plant to obtain an estimate of the soil-to-vegetation concentration factors. The concentration factors appear to be lognormally distributed with a geometric mean of 3.4 (Bq/kg dry wt. tissue per Bq/kg dry wt. soil) and a geometric standard deviation of 4.7. A dose commitment was calculated using a hypothetical 3.7 x 10/sup 10/ Bq Tc-99/year release and the actual CY-1981 concentration release of Tc-99. The radiological significance of Tc-99 in the terrestial food chain is substantially less than previously believed.

Acox, T.A.

1982-01-01

196

Report on the biological monitoring program at Paducah Gaseous Diffusion Plant December 1990 to November 1992  

SciTech Connect

On September 23, 1987, the Commonwealth of Kentucky Natural Resources and Environmental Protection Cabinet issued an Agreed Order that required the development of a Biological Monitoring Program (BMP) for the Paducah Gaseous Diffusion Plant (PGDP). Beginning in fall 1991, the Environmental Sciences Division (ESD) at Oak Ridge National Lab (ORNL) added data collection and report preparation to its responsibilities for the PGDP BMP. The BMP has been continued because it has proven to be extremely valuable in identifying those effluents with the potential for adversely affecting instream fauna, assessing the ecological health of receiving streams, guiding plans for remediation, and protecting human health. In September 1992, a renewed permit was issued which requires toxicity monitoring of continuous and intermittent outfalls on a quarterly basis. The BMP for PGDP consists of three major tasks: (1) effluent and ambient toxicity monitoring, (2) bioaccumulation studies, and (3) ecological surveys of stream communities. This report includes ESD/ORNL activities occurring from December 1990 to November 1992.

Kszos, L.A. [ed.

1994-03-01

197

Spin Diffusion Coefficient of A1-PHASE of Superfluid 3He at Low Temperatures  

NASA Astrophysics Data System (ADS)

The spin diffusion coefficient tensor of the A1-phase of superfluid 3He at low temperatures and melting pressure is calculated using the Boltzmann equation approach and Pfitzner procedure. Then considering Bogoliubov-normal interaction, we show that the total spin diffusion is proportional to 1/T2, the spin diffusion coefficient of superfluid component D\\uparrowxzxz is proportional to T-2, and the spin diffusion coefficient of super-fluid component D\\uparrowxxxx (=D\\uarrowxyxy) is independent of temperature. Furthermore, it is seen that superfluid components play an important role in spin diffusion of the A1-phase.

Afzali, R.; Pashaee, F.

198

Diffusion (or conduction) along a slightly tapering tube, and its application to the determination of diffusion coefficients  

Microsoft Academic Search

The diffusion equation has been solved for the case of diffusion from a slightly tapering tube into an infinite medium of zero concentration. The theory provides a means of correcting results obtained for diffusion coefficients in the capillary tube method of Anderson and Saddington, when the tube is not of uniform bore throughout its length. This is frequently the case

A. Talbot; J. A. Kitchener

1956-01-01

199

Computational fluid dynamics tracking of UF{sub 6} reaction products release into a gaseous diffusion plant cell housing  

SciTech Connect

A three-dimensional (3-D) computational fluid dynamics (CFD) model has been developed using CFDS-FLOW3D Version 3.3 to model the transport of aerosol products formed during a release of uranium hexafluoride (UF{sub 6}) into a gaseous diffusion plant (GDP) process building. As part of a facility-wide safety evaluation, a one-dimensional (1-D) analysis of aerosol/vapor transport following such an hypothesized severe accident is being performed. The objective of this study is to supplement the 1-D analysis with more detailed 3-D results. Specifically, the goal is to quantify the distribution of aerosol passing out of the process building during the hypothetical accident. This work demonstrates a useful role for CFD in large 3-D problems, where some experimental data are available for calibrating key parameters and the desired results are global (total time-integrated aerosol flow rates across a few boundary surfaces) as opposed to local velocities, temperatures, or heat transfer coefficients.

Wendel, M.W.; Chen, N.C.J.; Kim, S.H.; Taleyarkhan, R.P.; Keith, K.D.; Schmidt, R.W.

1996-06-01

200

MELCOR source term evaluation for UF{sub 6} release event in a gaseous diffusion plant feed facility  

SciTech Connect

An assessment of UF{sub 6} release accidents was conducted for the feed facility of a gaseous diffusion plant. The MELCOR code was utilized for simulating the reactions of UF{sub 6} with moisture and the consequent transport of UO{sub 2}F{sub 2} aerosols and HF vapor through the building and to the environment.

Kim, S.H.; Taleyarkhan, R.P.; Lombardi, D. [Oak Ridge National Lab., TN (United States); Schmidt, R.; Keith, K. [Oak Ridge Y-12 Plant, TN (United States)

1998-09-01

201

LITHOLOGIC AND STRATIGRAPHIC COMPILATION OF NEAR-SURFACE SEDIMENTS FOR THE PADUCAH GASEOUS DIFFUSION PLANT, MCCRACKEN COUNTY, KY  

Microsoft Academic Search

The Jackson Purchase region of western Kentucky consists of Coastal Plain sediments near the northern margin of the Mississippi Embayment. Within this region is the Paducah Gaseous Diffusion Plant (PGDP), a uranium enrichment facility operated by the US Department of Energy. At PGDP, a Superfund site, soil and groundwater studies have provided subsurface lithologic data from hundreds of monitoring wells

Joshua L. Sexton

2006-01-01

202

Prediction of external corrosion for steel cylinders at the Paducah Gaseous Diffusion Plant: Application of an empirical method  

Microsoft Academic Search

During the summer of 1995, ultrasonic wall thickness data were collected for 100 steel cylinders containing depleted uranium (DU) hexafluoride located at Paducah Gaseous Diffusion Plant (PGDP) in Paducah, Kentucky. The cylinders were selected for measurement to assess the condition of the more vulnerable portion of the cylinder inventory at PGDP. The purpose of this report is to apply the

1996-01-01

203

COMBINED GEOPHYSICAL INVESTIGATION TECHNIQUES TO IDENTIFY BURIED WASTE IN AN UNCONTROLLED LANDFILL AT THE PADUCAH GASEOUS DIFFUSION PLANT, KENTUCKY  

Microsoft Academic Search

The primary objective of the investigation was to confirm the presence and determine the location of a cache of 30 to 60 buried 55-gallon drums that were allegedly dumped along the course of the pre-existing, northsouth diversion ditch (NSDD) adjacent to permitted landfills at the Paducah Gaseous Diffusion Plant, Kentucky. The ditch had been rerouted and was being filled and

Peter T. Miller; R. John Starmer

2003-01-01

204

An interim report to the manager of the Paducah Gaseous Diffusion Plant from the Paducah Environmental Advisory Committee  

Microsoft Academic Search

The Paducah Environmental Advisory Committee was formed as: (1) an outgrowth of other Environmental Advisory Committees already in existence at Oak Ridge and other Martin Marietta Energy Systems plants; (2) a result of public concern following significant nuclear incidents at Bhopal and Chernobyl; (3) a result of the new direction and commitment of the management of the Paducah Gaseous Diffusion

1987-01-01

205

PGDP (Paducah Gaseous Diffusion Plant)-UFâ handling, sampling, analysis and associated QC\\/QA and safety related procedures  

Microsoft Academic Search

This document is a compilation of Paducah Gaseous Diffusion Plant procedures on UFâ handling, sampling, and analysis, along with associated QC\\/QA and safety related procedures. It was assembled for transmission by the US Department of Energy to the Korean Advanced Energy Institute as a part of the US-Korea technical exchange program.

1987-01-01

206

Superfund Record of Decision (EPA Region 4): Paducah Gaseous Diffusion Plant (USDOE), Operable Unit 15, Paducah, KY., August 10, 1998.  

National Technical Information Service (NTIS)

This decision document presents the remedial action for the Solid Waste Management Unit (SWMU) 91 of the Waste Area Group (WAG) 27 at the Paducah Gaseous Diffusion Plant (PGDP) near Paducah, Kentucky. The primary objective of this remedial action is to re...

1998-01-01

207

Study of diffusion coefficients of glasses under zero-G  

NASA Technical Reports Server (NTRS)

Diffusion studies of the glass forming ion are examined in zero-g environments and diffusion data obtained from these experiments are unique because of earth based experimental problems. The choice of system for diffusion studies is discussed along with the lab processing. The space processing is described consisting of a heating cycle designed to maximize time exposed to the diffusion temperature without exposing the low viscosity melt to gravitational forces.

Kinser, D. L.

1975-01-01

208

Protein Diffusion Coefficients Determined by Macroscopic-Gradient Rayleigh Interferometry and Dynamic Light Scattering  

Microsoft Academic Search

Dynamic light scattering (DLS) is extensively used for measuring macromolecule diffusion coefficients. Contrary to classical techniques based on macroscopic concentration gradients, DLS probes microscopic fluctuations in concentration. DLS accuracy and its concordance with macroscopic-gradient techniques remains an outstanding important issue. We measured lysozyme diffusion coefficients in aqueous salt using both DLS and Rayleigh interferometry, a highly accurate macroscopic-gradient technique. The

Onofrio Annunziata; Daniela Buzatu; John G. Albright

2005-01-01

209

Fractal scaling of effective diffusion coefficient of solute in porous media.  

PubMed

Fractal approach is used to derive a power law relation between effective diffusion coefficient of solute in porous media and the geometry parameter characterizing the media. The results are consistent with the empirical equations analogous to Archie's law and are expected to be applied to prediction of effective diffusion coefficient. PMID:11590736

Liu, J G; Nie, Y F

2001-04-01

210

Effect of therapeutic ultrasound on partition and diffusion coefficients in human stratum corneum  

Microsoft Academic Search

Application of various enhancers including ultrasound and chemicals has been shown to enhance transdermal drug transport. Most of these enhancers increase transdermal transport by increasing either partition or diffusion coefficients in lipid bilayers. Although the effect of such enhancers on skin permeability has been measured in many cases, the effect of the same enhancers on solute partition and diffusion coefficients

Samir Mitragotri

2001-01-01

211

Radon diffusion coefficients of vapour barrier membranes used in Canadian building construction.  

PubMed

Vapour barrier membranes are often used as soil gas retarder in building construction. While vapour permeance characteristics of these membranes are well known and specified in Canadian standards, their radon diffusion coefficients are yet not available. This study provides test results of radon diffusion coefficients for 10 vapour barrier membranes commonly used in Canadian building construction. PMID:19214548

Chen, Jing; Ly, Jim; Schroth, Eveline; Hnatiuk, Stan; Frenette, Etienne; Blain, Marie-France

2009-04-01

212

Evaluation of Effective Diffusion Coefficient in Various Building Materials and Absorbents by Mercury Intrusion Porosimetry  

Microsoft Academic Search

An effective diffusion coefficient plays an important role in the numerical analysis model to predict the emission rate of VOCs from building materials. This research evaluates the effective diffusion coefficient of VOCs (toluene, formaldehyde, etc.) in building materials (gypsum boards, medium density fiberboard, etc.) and adsorbents (activated carbon, charcoal, etc.) using the mercury intrusion porosimetry (MIP) test. The MIP test

J Seo; S Kato; Y Ataka; Q Zhu

2005-01-01

213

MEASUREMENT OF EFFECTIVE AIR DIFFUSION COEFFICIENTS FOR TRICHLOROETHENE IN UNDISTURBED SOIL CORES. (R826162)  

EPA Science Inventory

Abstract In this study, we measure effective diffusion coefficients for trichloroethene in undisturbed soil samples taken from Picatinny Arsenal, New Jersey. The measured effective diffusion coefficients ranged from 0.0053 to 0.0609 cm2/s over a range of air...

214

Fricke gel diffusion coefficient measurements for applications in radiotherapy level dosimetry  

NASA Astrophysics Data System (ADS)

In gel dosimetry applied to radiotherapy, the space-time corrections are necessary due to the diffusion of ions in the oxidized solution dosimetry. Consequently, methodologies are applied in order to determine diffusion coefficients corrected in space and time. Therefore, in this study the dosimetric solution Fricke Xylenol Gel (FXG) was modified and applied to two Gaussian and ISQR methodologies for comparison of the diffusion coefficients obtained. The results show that the FXG system can be modified for new applications in radiotherapy, and it may be corrected in space-time to the appropriate methodologies in the determination of diffusion coefficients.

de Oliveira, Lucas Nonato; de Almeida, Adelaide; Caldas, Linda V. E.

2014-05-01

215

Intrinsic diffusion coefficients and the vacancy flow factor in dilute Cu-Zn alloys  

SciTech Connect

The interdiffusion coefficient and the intrinsic diffusion coefficient of Zn and Cu in dilute alloys at 1168 K have been determined with semi-infinite couples using Darken's relation. In addition, the Kirkendall effect in thin plate couples at 1168 K has been examined using Heumann's method to determine the ratio of the intrinsic diffusion coefficients in very dilute alloys. The correlation factor for impurity diffusion of zinc in copper has been estimated by combining the vacancy flow factor with the enhancement factor. This permits an estimate of the kinetic energy factor for impurity diffusion. 26 refs.

Hoshino, K.; Iijima, Y.; Hirano, K.

1982-07-01

216

Imaging cell size and permeability in biological tissue using the diffusion-time dependence of the apparent diffusion coefficient.  

PubMed

The purpose of this study was to analyze and evaluate a model of restricted water diffusion between equidistant permeable membranes for cell-size and permeability measurements in biological tissue. Based on the known probability distribution of diffusion distances after the diffusion time ? in a system of permeable membranes characterized by three parameters (membrane permeability P, membrane distance L, and free diffusivity D0), an equivalent dimensionless model was derived with a probability distribution characterized by only a single (dimensionless) tissue parameter [Formula: see text]. Evaluating this proposed model function, the dimensionless diffusion coefficient [Formula: see text] was numerically calculated for 60 values of the dimensionless diffusion time [Formula: see text] and 35 values of [Formula: see text]. Diffusion coefficients were measured in a carrot by diffusion-weighted magnetic resonance imaging (MRI) at 18 diffusion times between 9.9 and 1022.7 ms and fitted to the simulation results [Formula: see text] to determine L, P, and D0. The measured diffusivities followed the simulated dependence of [Formula: see text]. Determined cell sizes varied from 21 to 76 ?m, permeabilities from 0.007 to 0.039 ?m(-1), and the free diffusivities from 1354 to 1713 ?m(2)?s(-1). In conclusion, the proposed dimensionless tissue model can be used to determine tissue parameters (D0, L, P) based on diffusion MRI with multiple diffusion times. Measurements in a carrot showed a good agreement of the cell diameter, L, determined by diffusion MRI and by light microscopy. PMID:24839979

Dietrich, Olaf; Hubert, Alexander; Heiland, Sabine

2014-06-21

217

Temperature effects on diffusion coefficient for 6-gingerol and 6-shogaol in subcritical water extraction  

NASA Astrophysics Data System (ADS)

6-gingerol and 6-shogaol are the main constituents as anti-inflammatory or bioactive compounds from zingiber officinale Roscoe. These bioactive compounds have been proven for inflammatory disease, antioxidatives and anticancer. The effect of temperature on diffusion coefficient for 6-gingerol and 6-shogaol were studied in subcritical water extraction. The diffusion coefficient was determined by Fick's second law. By neglecting external mass transfer and solid particle in spherical form, a linear portion of Ln (1-(Ct/Co)) versus time was plotted in determining the diffusion coefficient. 6-gingerol obtained the higher yield at 130°C with diffusion coefficient of 8.582x10?11 m2/s whilst for 6-shogaol, the higher yield and diffusion coefficient at 170°C and 19.417 × 10?11 m2/s.

Ilia Anisa, Nor; Azian, Noor; Sharizan, Mohd; Iwai, Yoshio

2014-04-01

218

Study of diffusion coefficients of glasses under Zero-G  

NASA Technical Reports Server (NTRS)

A diffusion experiment for glasses was formulated, such theoretical and earth bound results as were available were outlined, and the preliminary earth based experimental work in preparation for a weightless experiment was done. The fundamental premise of the work was that diffusion studies of the glass forming ion can be conducted in zero-g environments, and diffusion data obtained from these experiments are unique and valuable because of earth based experimental difficulties.

Kinser, D. L.

1977-01-01

219

Diffusion in mixed solvents. III - The heat of mixing parameter and the Soret coefficient  

NASA Technical Reports Server (NTRS)

New evidence is presented that for aqueous glycerol solutions, the Soret coefficient of glycerol, sigma sub 1 = D sub 1 T/D sub 1 (where D sub 1 T and D sub 1 are the thermal and self-diffusion coefficients, respectively, of glycerol in aqueous solutions), is an integral part of the heat of mixing parameter. Expressions are presented indicating the importance of the Soret coefficients to correlations for diffusion processes in glycerol water solvents.

Carapellucci, P. A.

1976-01-01

220

Oxidation Rate and Phase Diagram of Mu-Zn Ferrite Determined from the Cation Diffusion Coefficient  

Microsoft Academic Search

Oxidation rate of Mn-Zn ferrite, which means the rate of change in oxygen content in spinel phase, was determined from the diffusion coefficient of 59Fe, by assuming that the diffusion coefficient was proportional to the cation vacancy density, i.e., the excess oxygen content. Volume oxidation rate and grain boundary oxidation rate are expressed by coefficients having the same dimension as

Seiya Ogawa

1967-01-01

221

Diffusion coefficients of vacancies and interstitials along tilt grain boundaries in molybdenum  

NASA Astrophysics Data System (ADS)

The diffusion coefficients of vacancies and interstitials along symmetrical tilt grain boundaries in molybdenum have been calculated using the molecular dynamics method. The migration energies of defects have been obtained. The activation energy and coefficients of grain boundary self-diffusion have been deter-mined. A comparison of the obtained results with the studies of other authors indicates that boundaries formed between particles in the powder in sintering experiments have a higher diffusion activity as compared to stable grain boundaries in polycrystals.

Novoselov, I. I.; Kuksin, A. Yu.; Yanilkin, A. V.

2014-05-01

222

The infinite dilution diffusion coefficient for A1(OH) 4- at 25°C  

NASA Astrophysics Data System (ADS)

The infinite dilution diffusion coefficient for Al(OH) 4- necessary to calculate fluxes of dissolved Al between sediments and overlying waters, was determined at 25°C. Measurements were made using the diaphragm-cell method by diffusing Al(OH) 4- spiked KBr solutions against KCL over a range of ionic strengths. The mean of 9 separate measurements gives 1.04 ± .02 × 10 -5cm 2/s as the infinite dilution diffusion coefficient for Al(OH) 4- at 25°C.

Mackin, James E.; Aller, Robert C.

1983-05-01

223

NMR measurements of solvent self-diffusion coefficients in polymer solutions  

NASA Astrophysics Data System (ADS)

The transport of solvents and other small molecules in polymer solutions is important in many areas such as reaction rates, drying of coatings, plasticizer loss, curing of resins, elimination of residual monomer, and controlled drug release. Some of the work done in our laboratory on the diffusion of small molecules in polymer solutions and dispersions is reviewed. The diffusion data was used to test the Vrentas and Duda's free-volume theory for self-diffusion coefficients; test the independence of the normalized solvent self-diffusion for several polymer-solvent systems; and predict the solvent loss curves for drying of coatings based on solvent self-diffusion coefficients.

Blum, Frank D.; Pickup, Stephen; Waggoner, R. Allen

1989-11-01

224

First-principles study of temperature-dependent diffusion coefficients: Hydrogen, deuterium, and tritium in ?-Ti  

NASA Astrophysics Data System (ADS)

We report the prediction of temperature-dependent diffusion coefficients of interstitial hydrogen, deuterium, and tritium atoms in ?-Ti using transition state theory. The microscopic parameters in the pre-factor and activation energy of the impurity diffusion coefficients are obtained from first-principles total energy and phonon calculations including the full coupling between the vibrational modes of the diffusing atom with the host lattice. The dual occupancy case of impurity atom in the hcp matrix is considered, and four diffusion paths are combined to obtain the final diffusion coefficients. The calculated diffusion parameters show good agreement with experiments. Our numerical results indicate that the diffusions of deuterium and tritium atoms are slower than that of the hydrogen atom at temperatures above 425 K and 390 K, respectively.

Lu, Yong; Zhang, Ping

2013-05-01

225

Measurement of the diffusion coefficient for salt in salt flat and mangrove soils  

Microsoft Academic Search

Excluded salt accumulated at mangrove roots must be transported away from the root zone by diffusive processes, due to the low permeability of most mangrove soils. The diffusion coefficient for salt in mangrove soils determines the rate of this diffusive transport but has not been determined experimentally before. In this work we used a 12-month long-time series of salt concentration

S. E. Hollins; P. V. Ridd; W. W. Read

2000-01-01

226

A comparison of ambipolar diffusion coefficients in meteor trains using VHF radar and UV lidar  

Microsoft Academic Search

In this paper we present the first comparative estimations of ionic diffusion rates for sporadic meteor trains near the mesopause made using VHF radar and UV Rayleigh lidar observations. In both cases we initially assumed that the meteor trains dissipate primarily through ambipolar diffusion. For the radar data, the diffusion coefficient within the meteor train was determined from the decay

Phillip B. Chilson; Peter Czechowsky; Gerhard Schmidt

1996-01-01

227

Impurity Diffusion Coefficients of Al and Zn in Mg Determined from Solid-to-Solid Diffusion Couples  

SciTech Connect

Increasing use and development of lightweight Mgalloys have led to the desire for more fundamental research in and understanding of Mg-based systems. As property enhancing components, Al and Zn are two of the most important and common alloying elements for Mg-alloys. We have investigated the concentration dependent interdiffusion of Al and Zn in Mg using diffusion couples of pure polycrystalline Mg mated to Mg solid solutions containing either <9 at.% Al or <3 at.% Zn. Concentration profiles were determined by electron micro-probe microanalysis of the diffusion zone. The interdiffusion coefficients were determined by the classical Boltzmann-Matano method within the Mg solid solution. As the concentration of Al or Zn approaches the dilute ends, we employ an analytical approach based on the Hall method to estimate the impurity diffusion coefficients. Results of Al and Zn impurity diffusion in Mg are reported and compared to published impurity diffusion coefficients typically determined by thin film techniques.

Kammerer, Catherine [University of Central Florida, Orlando; Kulkarni, Nagraj S [ORNL; Warmack, Robert J Bruce [ORNL; Perry, Kelly A [ORNL; Belova, Irina [University of Newcastle, NSW, Australia; Murch, Prof. Graeme [University of Newcastle, NSW, Australia; Sohn, Yong Ho [University of Central Florida

2013-08-01

228

Velocity-Space Diffusion Coefficients Due to Full-Wave ICRF Fields in Toroidal Geometry  

SciTech Connect

Jaeger et al. have calculated bounce-averaged QL diffusion coefficients from AORSA full-wave fields, based on non-Maxwellian distributions from CQL3D Fokker-Planck code. A zero banana-width approximation is employed. Complementing this calculation, a fully numerical calculation of ion velocity diffusion coefficients using the full-wave fields in numerical tokamak equilibria has been implemented to determine the finite orbit width effects. The un-approximated Lorentz equation of motion is integrated to obtain the change in velocity after one complete poloidal transit of the tokamak. Averaging velocity changes over initial starting gyro-phase and toroidal angle gives bounce-averaged diffusion coefficients. The coefficients from the full-wave and Lorentz orbit methods are compared for an ITER DT second harmonic tritium ICRF heating case: the diffusion coefficients are similar in magnitude but reveal substantial finite orbit effects.

Harvey, R.W. [CompX, P.O. Box 2672, Del Mar, CA 92014-5672 (United States); Jaeger, F.; Berry, L.A.; Batchelor, D.B.; D'Azevedo, E.; Carter, M.D. [ORNL, Oak Ridge, TN (United States); Ershov, N.M.; Smirnov, A.P. [Moscow State Univ. (Russian Federation); Bonoli, P.; Wright, J.C. [PSFC, MIT, Boston, MA (United States); Smithe, D.N. [ATK-Mission Research (United States)

2005-09-26

229

Nonlinearity Effects of Lateral Density Diffusion Coefficient on Gain-Guided VCSEL Performance  

NASA Technical Reports Server (NTRS)

Electron and hole diffusions in the plane of semiconductor quantum wells play an important part in the static and dynamic operations of semiconductor lasers. In this paper, we apply a hydrodynamic model developed from the semiconductor Bloch equations to numerically study the effects of nonlinearity in the diffusion coefficient on single mode operation and direct modulation of a gain-guided InGaAs/GaAs multiple quantum well laser, operating not too far from threshold. We found that a small diffusion coefficient is advantageous for lowering the threshold current and increasing the modulation bandwidth. Most importantly, the effects of nonlinearity in the coefficient can be approximately reproduced by replacing the coefficient with an effective constant diffusion coefficient, which corresponds roughly to the half height density of the density distribution.

Li, Jian-Zhong; Cheung, Samson H.; Ning, C. Z.; Biegel, Bryan (Technical Monitor)

2001-01-01

230

Evolution of Lesions in Susac Syndrome at Serial MR Imaging with Diffusion-Weighted Imaging and Apparent Diffusion Coefficient Values  

Microsoft Academic Search

BACKGROUND AND PURPOSE: Susac syndrome is a rare disorder consisting of encepha- lopathy, hearing loss, and retinal arteriolar occlusions. The purpose of this study was to evaluate the evolution of lesions in this disease by using serial MR imaging with diffusion- weighted imaging (DWI) and apparent diffusion coefficients (ADCs). Abnormalities in the nonlesional white matter (NLWM) were also analyzed. METHODS:

Matthew L. White; Yan Zhang; Wendy R. K. Smoker

231

Measurement of effective air diffusion coefficients for trichloroethene in undisturbed soil cores  

NASA Astrophysics Data System (ADS)

In this study, we measure effective diffusion coefficients for trichloroethene in undisturbed soil samples taken from Picatinny Arsenal, New Jersey. The measured effective diffusion coefficients ranged from 0.0053 to 0.0609 cm 2/s over a range of air-filled porosity of 0.23-0.49. The experimental data were compared to several previously published relations that predict diffusion coefficients as a function of air-filled porosity and porosity. A multiple linear regression analysis was developed to determine if a modification of the exponents in Millington's [Science 130 (1959) 100] relation would better fit the experimental data. The literature relations appeared to generally underpredict the effective diffusion coefficient for the soil cores studied in this work. Inclusion of a particle-size distribution parameter, d10, did not significantly improve the fit of the linear regression equation. The effective diffusion coefficient and porosity data were used to recalculate estimates of diffusive flux through the subsurface made in a previous study performed at the field site. It was determined that the method of calculation used in the previous study resulted in an underprediction of diffusive flux from the subsurface. We conclude that although Millington's [Science 130 (1959) 100] relation works well to predict effective diffusion coefficients in homogeneous soils with relatively uniform particle-size distributions, it may be inaccurate for many natural soils with heterogeneous structure and/or non-uniform particle-size distributions.

Bartelt-Hunt, Shannon L.; Smith, James A.

2002-06-01

232

Martin Marietta Paducah Gaseous Diffusion Plant comprehensive earthquake emergency management program  

SciTech Connect

Recognizing the value of a proactive, integrated approach to earthquake preparedness planning, Martin Marietta Energy Systems, Inc. initiated a contract in June 1989 with Murray State University, Murray, Kentucky, to develop a comprehensive earthquake management program for their Gaseous Diffusion Plant in Paducah, Kentucky (PGDP -- Subcontract No. 19P-JV649V). The overall purpose of the program is to mitigate the loss of life and property in the event of a major destructive earthquake. The program includes four distinct (yet integrated) components: an emergency management plan, with emphasis on the catastrophic earthquake; an Emergency Operations Center Duty Roster Manual; an Integrated Automated Emergency Management Information System (IAEMIS); and a series of five training program modules. The PLAN itself is comprised of four separate volumes: Volume I -- Chapters 1--3; Volume II -- Chapters 4--6, Volume III -- Chapter 7, and Volume IV -- 23 Appendices. The EOC Manual (which includes 15 mutual aid agreements) is designated as Chapter 7 in the PLAN and is a stand alone'' document numbered as Volume III. This document, Volume II, discusses methodology, engineering and environmental analyses, and operational procedures.

Not Available

1990-02-28

233

Report on the biological monitoring program at Paducah Gaseous Diffusion Plant, January--December 1997  

SciTech Connect

On September 24, 1987, the Commonwealth of Kentucky Natural Resources and Environmental Protection Cabinet issued an Agreed Order that required the development of a Biological Monitoring Program (BMP) for the Paducah Gaseous Diffusion Plant (PGDP). A plan for the biological monitoring of the receiving streams was implemented in 1987 and consisted of ecological surveys, toxicity monitoring of effluents and receiving streams, evaluation of bioaccumulation of trace contaminants in biota, and supplemental chemical characterization of effluents. Beginning in fall 1991, the Environmental Sciences Division (ESD) at Oak Ridge National Laboratory added data collection and report preparation to its responsibilities for the PGDP BMP. The BMP has been continued because it has proven to be extremely valuable in (1) identifying those effluents with the potential for adversely affecting instream fauna, (2) assessing the ecological health of receiving streams, and (3) guiding plans for remediation and protecting human health. The BMP for PGDP consists of three major tasks: (1) effluent toxicity monitoring, (2) bioaccumulation studies, and (3) ecological surveys of benthic macroinvertebrate communities and fish. With the exception of the benthic macroinvertebrate community surveys, this report focuses on activities from January to December 1997.

Kszos, L.A.; Peterson, M.J.; Ryon, M.G.; Smith, J.G.; Southworth, G.R.

1998-03-01

234

Characteristics of Gaseous Diffusion Flames with High Temperature Combustion Air in Microgravity  

NASA Technical Reports Server (NTRS)

The characteristics of gaseous diffusion flames have been obtained using high temperature combustion air under microgravity conditions. The time resolved flame images under free fall microgravity conditions were obtained from the video images obtained. The tests results reported here were conducted using propane as the fuel and about 1000 C combustion air. The burner included a 0.686 mm diameter central fuel jet injected into the surrounding high temperature combustion air. The fuel jet exit Reynolds number was 63. Several measurements were taken at different air preheats and fuel jet exit Reynolds number. The resulting hybrid color flame was found to be blue at the base of the flame followed by a yellow color flame. The length and width of flame during the entire free fall conditions has been examined. Also the relative flame length and width for blue and yellow portion of the flame has been examined under microgravity conditions. The results show that the flame length decreases and width increases with high air preheats in microgravity condition. In microgravity conditions the flame length is larger with normal temperature combustion air than high temperature air.

Ghaderi, M.; Gupta, A. K.

2003-01-01

235

Assessment and interpretation of cross- and down-hole seismograms at the Paducah Gaseous Diffusion Plant  

SciTech Connect

This paper is an assessment and interpretation of cross-and down-hole seismograms recorded at four sites in the vicinity of the Paducah Gaseous Diffusion Plant (PGDP). Arrival times of shear (S-) and compressional (P-) waves are recorded on these seismograms in milliseconds. Together with known distances between energy sources and seismometers lowered into boreholes, these arrival times are used to calculate S- and P-wave velocities in unconsolidated soils and sediments that overlie bedrock approximately 320 ft beneath PGDP. The soil columns are modified after an earlier draft by ERC Environmental and Energy Services Company (ERCE), 1990. In addition to S- and P- wave velocity estimates from this paper, the soil columns contain ERCE's lithologic and other geotechnical data for unconsolidated soils and sediments from the surface to bedrock. Soil columns for Sites 1 through 4 and a site location map are in Plates 1 through 5 of Appendix 6. The velocities in the four columns are input parameters for the SHAKE computer program, a nationally recognized computer model that simulates ground response of unconsolidated materials to earthquake generated seismic waves. The results of the SHAKE simulation are combined with predicted ground responses on rock foundations (caused by a given design earthquake) to predict ground responses of facilities with foundations placed on unconsolidated materials. 3 refs.

Staub, W.P.; Wang, J.C. (Oak Ridge National Lab., TN (United States)); Selfridge, R.J. (Automated Sciences Group, (United States))

1991-09-01

236

Report on the biological monitoring program at Paducah Gaseous Diffusion Plant, January--December 1996  

SciTech Connect

On September 24, 1987, the Commonwealth of Kentucky Natural Resources and Environmental Protection Cabinet issued an Agreed Order that required the development of a Biological Monitoring Program (BMP) for the Paducah Gaseous diffusion Plant (PGDP). The PGDP BMP was conducted by the University of Kentucky Between 1987 and 1992 and by staff of the Environmental Sciences Division (ESD) at Oak Ridge National Laboratory (ORNL) from 1991 to present. The goals of BMP are to (1) demonstrate that the effluent limitations established for PGDP protect and maintain the use of Little Bayou and Big Bayou creeks for growth and propagation of fish and other aquatic life, (2) characterize potential environmental impacts, and (3) document the effects of pollution abatement facilities on stream. The BMP for PGDP consists of three major tasks: (1) effluent toxicity monitoring, (2) bioaccumulation studies, and (3) ecological surveys of stream communities (i.e., benthic macroinvertebrates and fish). This report focuses on ESD activities occurring from January 1996 to December 1996, although activities conducted outside this time period are included as appropriate.

Kszos, L.A. [ed.; Konetsky, B.K.; Peterson, M.J.; Petrie, R.B.; Ryon, M.G.; Smith, J.G.; Southworth, G.R.

1997-06-01

237

Paducah Gaseous Diffusion Plant proposed pilot pump-and-treat project. Final report  

SciTech Connect

On March 23, 1992, R.C. Sleeman of the Department of Energy, Oak Ridge Operations Office requested that a Groundwater Corrective Actions Team be assembled to evaluate the technical merit of and the need to implement a proposed groundwater pump-and-treat demonstration project for the Northwest contaminant plume at the Paducah Gaseous Diffusion Plant. In addition to other suggestions, the Team recommended that further characterization data be obtained for the plume. In the Fall of 1993 additional, temporary well points were installed so that groundwater samples from the shallow groundwater system and the Regional Gravel Aquifer (RGA) could be obtained to provide a three-dimensional view of groundwater contamination in the region of the plume. The results indicate that pure-phase DNAPL (trichloroethylene [TCE]) probably are present in the source area of the plume and extend in depth to the base of the RGA. Because the DNAPL likely will represent a source of a dissolved phase plume for decades it is essential that source containment take place. The Team recommends that although effective hydraulic containment can be achieved, other alternatives should be considered. For example, recent advances in emplacing low permeability barrier walls to depths of 100 to 150 ft make it possible to consider encirclement of the source of the Northwest plume.

Bodenstein, G.W.; Bonczek, R.R.; Early, T.O.; Huff, D.D.; Jones, K.S.; Nickelson, M.D.; Rightmire, C.T.

1994-01-01

238

Operating limit study for the proposed solid waste landfill at Paducah Gaseous Diffusion Plant  

SciTech Connect

A proposed solid waste landfill at Paducah Gaseous Diffusion Plant (PGDP) would accept wastes generated during normal operations that are identified as non-radioactive. These wastes may include small amounts of radioactive material from incidental contamination during plant operations. A site-specific analysis of the new solid waste landfill is presented to determine a proposed operating limit that will allow for waste disposal operations to occur such that protection of public health and the environment from the presence of incidentally contaminated waste materials can be assured. Performance objectives for disposal were defined from existing regulatory guidance to establish reasonable dose limits for protection of public health and the environment. Waste concentration limits were determined consistent with these performance objectives for the protection of off-site individuals and inadvertent intruders who might be directly exposed to disposed wastes. Exposures of off-site individuals were estimated using a conservative, site-specific model of the groundwater transport of contamination from the wastes. Direct intrusion was analyzed using an agricultural homesteader scenario. The most limiting concentrations from direct intrusion or groundwater transport were used to establish the concentration limits for radionuclides likely to be present in PGDP wastes.

Lee, D.W.; Wang, J.C.; Kocher, D.C.

1995-06-01

239

Report on the biological monitoring program at Paducah Gaseous Diffusion Plant December 1993 to December 1994  

SciTech Connect

On September 24, 1987, the Commonwealth of Kentucky Natural Resources and Environmental Protection Cabinet issued an Agreed Order that required the development of a Biological Monitoring Program (BMP) for the Paducah Gaseous Diffusion Plant (PGDP). The PGDP BMP was implemented in 1987 by the University of Kentucky. Research staff of the Environmental Sciences Division (ESD) at Oak Ridge National Laboratory (ORNL) served as reviewers and advisers to the University of Kentucky. Beginning in fall 1991, ESD added data collection and report preparation to its responsibilities for the PGDP BMP. The goals of BMP are to (1) demonstrate that the effluent limitations established for PGDP protect and maintain the use of Little Bayou and Big Bayou creeks for growth and propagation of fish and other aquatic life, (2) characterize potential environmental impacts, (3) document the effects of pollution abatement facilities on stream biota, and (4) recommend any program improvements that would increase effluent treatability. In September 1992, a renewed Kentucky Pollutant Discharge Elimination System (KPDES) permit was issued to PGDP. The BMP for PGDP consists of three major tasks: (1) effluent and ambient toxicity monitoring, (2) bioaccumulation studies, and (3) ecological surveys of stream communities (i.e., benthic macroinvertebrates and fish). This report includes ESD activities occurring from December 1993 to December 1994, although activities conducted outside this time period are included as appropriate.

Kszos, L.A. [ed.

1996-05-01

240

Seismic hazard evaluation for the Paducah Gaseous Diffusion Plant, Paducah, Kentucky  

SciTech Connect

The study presents the results of an investigation of seismic hazard at the site of the Paducah Gaseous Diffusion Plant. Paducah is located near the northern end of the Reelfoot Rift -- a large feature of the earth's crust that is believed to be associated with the New Madrid earthquakes of 1811 and 1812. Results from three separate seismic hazard analyses are presented here. The EPRI/SOG analysis uses the input data and methodology developed by the Electric Power Research Institute, under the sponsorship of several electric utilities, for the evaluation of seismic hazard in the central and eastern United States. Section 2 of this report documents the application of the EPRI/SOG methodology to the Paducah site (for both rock and soil conditions). The LLNL analysis uses the input data and methodology developed by the Lawrence Livermore National Laboratory for the Nuclear Regulatory Commission. This analysis was performed by LLNL and results were transmitted to us. Section 3 of this report contains a summary of LLNL inputs and results (for both rock and soil conditions, and considering 4 and 5 LLNL ground motion experts). 29 refs., 118 figs., 24 tabs.

Not Available

1991-07-01

241

Diffusion-weighted imaging with apparent diffusion coefficient mapping and spectroscopy in prostate cancer.  

PubMed

Prostate cancer is a major health problem, and the exploration of noninvasive imaging methods that have the potential to improve specificity while maintaining high sensitivity is still critically needed. Tissue changes induced by tumor growth can be visualized by magnetic resonance imaging (MRI) methods. Current MRI methods include conventional T2-weighted imaging, diffusion-weighted imaging (DWI) with apparent diffusion coefficient (ADC) mapping and magnetic resonance spectroscopy (MRS). Techniques such as DWI/ADC provide functional information about the behavior of water molecules in tissue; MRS can provide biochemical information about the presence or absence of certain metabolites, such as choline, creatine, and citrate. Finally, vascular parameters can be investigated using dynamic contrast-enhanced MRI. Moreover, with whole-body MRI and DWI, metastatic disease can be evaluated in 1 session and may provide a way to monitor treatment. Therefore, when combining these various methods, a multiparametric data set can be built to assist in the detection, localization, assessment of prostate cancer aggressiveness, and tumor staging. Such a comprehensive approach offers more power to evaluate prostate disease than any single measure alone. In this article, we focus on the role of DWI/ADC and MRS in the detection and characterization using both in vivo and ex vivo imaging of prostate pathology. PMID:19512848

Jacobs, Michael A; Ouwerkerk, Ronald; Petrowski, Kyle; Macura, Katarzyna J

2008-12-01

242

Cation Diffusion Coefficients and Vacancy Densities in Mn-Zn Ferrites  

Microsoft Academic Search

Cation diffusion in Mn-Zn ferrites having excess iron was investigated by means of the isotope tracer method using single and polycrystalline samples. In polycrystalline samples ``volume diffusion'' and ``grain boundary diffusion'' were observed and separated from each other. The results are: (1) The volume diffusion coefficient of 59Fe varied with the oxygen content, i.e., the density of cation vacancies in

Seiya Ogawa; Yasuaki Nakagawa

1967-01-01

243

Determination of the diffusion coefficient between corn syrup and distilled water using a digital camera  

NASA Astrophysics Data System (ADS)

A simple technique for determining the diffusion coefficient between two miscible liquids is presented based on observing concentration-dependent ultraviolet-excited fluorescence using a digital camera. The ultraviolet-excited visible fluorescence of corn syrup is proportional to the concentration of the syrup. The variation of fluorescence with distance from the transition zone between the fluids is fit by the Fick's law solution to the diffusion equation. By monitoring the concentration at successive times, the diffusion coefficient can be determined in otherwise transparent materials. The technique is quantitative and makes measurement of diffusion accessible in the advanced undergraduate physics laboratory.

Ray, E.; Bunton, P.; Pojman, J. A.

2007-10-01

244

Assessment of diffusion coefficient of glycerol into the skin ex vivo  

NASA Astrophysics Data System (ADS)

In present study we have considered diffusion of immersion agent into the skin through thermally pretreated stratum corneum solving the corresponding diffusion problem. Algorithm of refractive index of interstitial liquid and diffusion coefficient of immersion agent into biotissue estimations at a creation of lattice-like pattern of localized thermal damage islets in the stratum corneum, was develop. Theoretical model which sufficiently describes the influence of immersion agents on skin optical properties was presented. The diffusion coefficient of glycerol into pig skin ex vivo at creating a lattice of islets of damage in the stratum corneum is 0.84+/-0.08 ?m2/s.

Gavrilova, Anna A.; Pravdin, Alexander B.; Tuchin, Valery V.; Altshuler, Gregory B.; Yaroslavsky, Ilya V.

2007-05-01

245

Determination of the response function for the Portsmouth Gaseous Diffusion Plant criticality accident alarm system neutron detectors  

Microsoft Academic Search

Neutron-sensitive radiation detectors are used in the Portsmouth Gaseous Diffusion Plant`s (PORTS) criticality accident alarm system (CAAS). The CAAS is composed of numerous detectors, electronics, and logic units. It uses a telemetry system to sound building evacuation horns and to provide remote alarm status in a central control facility. The ANSI Standard for a CAAS uses a free-in-air dose rate

R. W. Jr. Tayloe; A. S. Brown; M. C. Dobelbower; J. E. Woollard

1997-01-01

246

Reassessment of liquefaction potential and estimation of earthquake induced settlements at Paducah Gaseous Diffusion Plant, Paducah, Kentucky. Final report  

Microsoft Academic Search

This report documents a reassessment of liquefaction potential and estimation of earthquake-induced settlements for the U.S. Department of Energy (DOE), Paducah Gaseous Diffusion Plant (PGDP), located southwest of Paducah, KY. The U.S. Army Engineer Waterways Experiment Station (WES) was authorized to conduct this study from FY91 to FY94 by the DOE, Oak Ridge Operations (ORO), Oak Ridge, TN, through Inter-

D. W. Sykora; D. E. Yule

1996-01-01

247

Summary of findings on evaluation of aqueous degreasers versus chlorinated solvents at the Paducah Gaseous Diffusion Plant  

Microsoft Academic Search

Spent trichloroethylene (TCE), 1,1,1-trichloroethane (TC-ane), and sludge are generated mainly as a result of vapor degreasing operations at the Paducah Gaseous Diffusion Plant (PGDP). Additionally, small quantities of spent chlorinated solvents are generated as a result of small parts cleanup. Additionally, some of the solvents become contaminated with uranium which classifies them as mixed waste for which no disposal method

Gunn

1988-01-01

248

Utilization of 4Dimensional Data Visualization Modeling to Evaluate Burial Ground Contaminants at the Paducah Gaseous Diffusion Plant, Paducah, Kentucky  

Microsoft Academic Search

This paper describes how 4-Dimensional (4D) Data Visualization Modeling was used to evaluate historical data and to help guide the decisions for the sampling necessary to complete a Remedial Investigation\\/Feasibility Study (RI\\/FS) for the burial ground sites at the Department of Energy (DOE) Paducah Gaseous Diffusion Plant (PGDP). DOE at the Paducah Site is primarily involved in environmental cleanup and

T. L. Brindley; J. J. Tarantino; A. L. Locke; D. W. Dollins

2006-01-01

249

Diffusion coefficients of water and leachables in methacrylate-based crosslinked polymers using absorption experiments.  

PubMed

The diffusion of water into dentin adhesive polymers and leaching of unpolymerized monomer from the adhesive are linked to their mechanical softening and hydrolytic degradation. Therefore, diffusion coefficient data are critical for the mechanical design of these polymeric adhesives. In this study, diffusion coefficients of water and leachables were obtained for sixteen methacrylate-based crosslinked polymers using absorption experiments. The experimental mass change data was interpreted using numerical solution of the two-dimensional diffusion equations. The calculated diffusion coefficients varied from 1.05 × 10(-8) cm(2)/sec (co-monomer TMTMA) to 3.15 × 10(-8) cm(2)/sec (co-monomer T4EGDMA). Correlation of the diffusion coefficients with crosslink density and hydrophilicity showed an inverse trend (R(2) = 0.41). The correlation of diffusion coefficient with crosslink density and hydrophilicity are closer for molecules differing by simple repeat units (R(2) = 0.95). These differences in the trends reveal mechanisms of interaction of the diffusing water with the polymer structure. PMID:22430592

Parthasarathy, Ranganathan; Misra, Anil; Park, Jonggu; Ye, Qiang; Spencer, Paulette

2012-05-01

250

On the determinatino of high-pressure mass-diffusion coefficients for binary mixtures  

NASA Technical Reports Server (NTRS)

A model for high-pressure binary diffusion coefficient calculation is proposed based on considerations originating from recasting both the low pressure kinetic theory and the Stokes-Einstein infinite dilution expressions into forms consistent with corresponding states theory.

Bellan, J.; Harstad, K.

2003-01-01

251

Nitric oxide diffusion coefficients in solutions, proteins and membranes determined by phosphorescence.  

PubMed

The reactivity of nitric oxide under a given condition is a complex function of its diffusivity and the concentration of reacting partners. Quenching by NO of luminescence from Ru and Pd chelates of mesoporphyrin IX, two molecules which exhibit phosphorescence at room temperature, was utilized to evaluate the gas concentration and apparent diffusion coefficients. The properties of Ru-mesoporphyrin, a dye not previously employed as a probe for O2 or NO, were determined and the assay was verified and used to quantify NO produced by decomposition of nitrosocysteine. The pseudo-second order quenching constants were obtained from Stern-Volmer plots measured under various conditions and used to calculate diffusion coefficients for nitric oxide in solutions, proteins and membranes. The diffusion coefficients were greater at 37 than at 25 degrees C and, at a given temperature, smaller in proteins and membranes than in water. The conclusion is that NO and O2 closely resemble each other in diffusivity but that NO is slightly less lipophilic, resulting in somewhat faster apparent diffusion in protein and slower diffusivity in lipid, relative to O2. Taking a mean diffusion coefficient for NO of 10(-7) cm2s-1, then within 10 s the mean path is 10(-3) cm, or less than the diameter of a single cell. However, at low NO and O2 concentrations, the halflife of NO will be considerably longer than 10 s, and consequently the path of NO diffusion much greater. PMID:8075157

Vanderkooi, J M; Wright, W W; Erecinska, M

1994-08-17

252

Determination of the zincate diffusion coefficient and its application to alkaline battery problems  

NASA Technical Reports Server (NTRS)

The diffusion coefficient for the zincate ion at 24 C was found to be 9.9 X 10 to the minus 7th power squared cm per sec + or - 30 percent in 45 percent potassium hydroxide and 1.4 x 10 to the minus 7 squared cm per sec + or - 25 percent in 40 percent sodium hydroxide. Comparison of these values with literature values at different potassium hydroxide concentrations show that the Stokes-Einstein equation is obeyed. The diffusion coefficient is characteristic of the zincate ion (not the cation) and independent of its concentration. Calculations with the measured value of the diffusion coefficient show that the zinc concentration in an alkaline zincate half cell becomes uniform throughout in tens of hours by diffusion alone. Diffusion equations are derived which are applicable to finite size chambers. Details and discussion of the experimental method are also given.

May, C. E.; Kautz, Harold E.

1978-01-01

253

The size of the unstirred layer as a function of the solute diffusion coefficient.  

PubMed Central

By monitoring the concentration distribution of several solutes that are diffusing at the same time under given mixing conditions, it was established that the unstirred layer (USL) has no clearly defined boundary. For the cases of solute permeation and water movement across planar bilayer lipid membranes, respectively, experiments carried out with double-barreled microelectrodes have shown that the thickness of the USL depends on which species is diffusing. Small molecules with a larger diffusion coefficient encounter an apparently thicker USL than larger molecules with a smaller diffusion coefficient. The ratio of the USL thicknesses of two different substances is equal to the third root of the ratio of the respective diffusion coefficients. This experimental finding is in good agreement with theoretical predictions from the theory of physicochemical hydrodynamics.

Pohl, P; Saparov, S M; Antonenko, Y N

1998-01-01

254

Imaging cell size and permeability in biological tissue using the diffusion-time dependence of the apparent diffusion coefficient  

NASA Astrophysics Data System (ADS)

The purpose of this study was to analyze and evaluate a model of restricted water diffusion between equidistant permeable membranes for cell-size and permeability measurements in biological tissue. Based on the known probability distribution of diffusion distances after the diffusion time ? in a system of permeable membranes characterized by three parameters (membrane permeability P, membrane distance L, and free diffusivity D0), an equivalent dimensionless model was derived with a probability distribution characterized by only a single (dimensionless) tissue parameter \\tilde{P}. Evaluating this proposed model function, the dimensionless diffusion coefficient \\tilde{D}_{eff}(\\tilde{\\tau };\\,\\tilde{P}) was numerically calculated for 60 values of the dimensionless diffusion time \\tilde{\\tau } and 35 values of \\tilde{P}. Diffusion coefficients were measured in a carrot by diffusion-weighted magnetic resonance imaging (MRI) at 18 diffusion times between 9.9 and 1022.7 ms and fitted to the simulation results \\tilde{D}_{eff}(\\tilde{\\tau };\\,\\tilde{P}) to determine L, P, and D0. The measured diffusivities followed the simulated dependence of \\tilde{D}_{eff}(\\tilde{\\tau };\\tilde{P}). Determined cell sizes varied from 21 to 76 ?m, permeabilities from 0.007 to 0.039 ?m?1, and the free diffusivities from 1354 to 1713 ?m2?s?1. In conclusion, the proposed dimensionless tissue model can be used to determine tissue parameters (D0, L, P) based on diffusion MRI with multiple diffusion times. Measurements in a carrot showed a good agreement of the cell diameter, L, determined by diffusion MRI and by light microscopy.

Dietrich, Olaf; Hubert, Alexander; Heiland, Sabine

2014-06-01

255

Note on coefficient matrices from stochastic Galerkin methods for random diffusion equations  

SciTech Connect

In a recent work by Xiu and Shen [D. Xiu, J. Shen, Efficient stochastic Galerkin methods for random diffusion equations, J. Comput. Phys. 228 (2009) 266-281], the Galerkin methods are used to solve stochastic diffusion equations in random media, where some properties for the coefficient matrix of the resulting system are provided. They also posed an open question on the properties of the coefficient matrix. In this work, we will provide some results related to the open question.

Zhou Tao, E-mail: tzhou@lsec.cc.ac.c [Institute of Computational Mathematics, The Chinese Academy of Sciences, Beijing 100190 (China); Tang Tao, E-mail: ttang@hkbu.edu.h [Department of Mathematics, Hong Kong Baptist University, Kowloon Tong (Hong Kong)

2010-11-01

256

Optical determination of ionophore diffusion coefficients in plasticized poly(vinyl chloride) sensing films  

Microsoft Academic Search

The knowledge of accurate diffusion coefficients of electrically neutral ionophores in solvent polymeric membranes is important in view of understanding and optimizing important sensor characteristics of ion-selective electrodes (ISEs) and their corresponding optical sensors. A spectroscopic imaging technique is introduced here to determine the diffusion coefficient of the chromoionophore (N,N-diethyl-5-(octadecanoylimino)-5H-benzo[a]phenoxazine-9-amine, ETH 5294) in solvent polymeric membranes with different types of

Robert Long; Eric Bakker

2004-01-01

257

Chemical diffusion coefficient measurements in pure and lithium doped cobaltous oxide  

Microsoft Academic Search

The chemical diffusion coefficient in pure and lithium doped cobaltous oxide has been deduced from electrical conductivity measurements performed during the equilibration of the gas-oxide system, in the temperature range 1000-1400° and for oxygen partial pressures higher than 10 atm.The results obtained for the pure Co1-?O single crystals show a small decrease of the values of the chemical diffusion coefficient

G. Petot-ervas; O. Radji; B. Sossa; P. Ochin

1983-01-01

258

Correlations for predicting air permeabilities and 222Rn diffusion coefficients of soils  

Microsoft Academic Search

The rate of 222Rn gas transport through earthen materials controls 222Rn releases to the atmosphere and to indoor environments. The key soil-related parameters characterizing 222Rn transport in earthen materials are the 222Rn diffusion coefficient and the soil air permeability. Simple correlations have been developed for predicting the 222Rn diffusion coefficient and the air permeability of soils based on fraction of

V. C. Rogers; K. K. Nielson

1991-01-01

259

Radon diffusion coefficients of vapour barrier membranes used in Canadian building construction  

Microsoft Academic Search

Vapour barrier membranes are often used as soil gas retarder in building construction. While vapour permeance characteristics\\u000a of these membranes are well known and specified in Canadian standards, their radon diffusion coefficients are yet not available.\\u000a This study provides test results of radon diffusion coefficients for 10 vapour barrier membranes commonly used in Canadian\\u000a building construction.

Jing Chen; Jim Ly; Eveline Schroth; Stan Hnatiuk; Etienne Frenette; Marie-France Blain

2009-01-01

260

Influence of binder composition and concrete pore structure on chloride diffusion coefficient in concrete  

Microsoft Academic Search

The influence of binder composition and pore structure of concrete on chloride diffusion coefficient in concrete were investigated\\u000a by the natural immersion test, MIP test, SEM and EDS test, respectively. The experimental results showed that the effect of\\u000a binder composition on chloride diffusion coefficient was the comprehensive result of concrete pore structure and binder hydration\\u000a products, and the porosity and

Pengping Li; Dagen Su; Shengnian Wang; Zhihong Fan

2011-01-01

261

Intrinsic diffusion coefficients and the vacancy flow factor in Dilute Cu-Zn Alloys  

Microsoft Academic Search

Interdiffusion coefficients in copper-rich copper-zinc solid solutions containing up to 8 at. pct of Zn at 1168 K have been\\u000a determined by Matano's analysis using semi-infinite diffusion couples consisting of pure copper and Cu-Zn alloys with Kirkendall\\u000a markers. From the marker shift and Darken's relation, intrinsic diffusion coefficients, DZn and DCu, in the alloys containing 3.2 and 4.7 at. pct

Kazutomo Hoshino; Yoshiaki Iijima; Ken-Ichi Hirano

1982-01-01

262

Effect of gamma irradiation on the structural properties and diffusion coefficient in Co–Zn ferrite  

Microsoft Academic Search

A series of samples of Co1?xZnxFe2O4 were prepared by the usual ceramic technique where x=0.3,0.5,0.6, and 0.8. The samples were irradiated by Co60 gamma source with a high dose equal to 106rad\\/h. The diffusion coefficient of oxygen vacancies was estimated from DC conductivity measurements. It was noticed that the diffusion coefficient increased after gamma irradiation for all Zn2+ concentrations. This

O. M. Hemeda; M. El-Saadawy

2003-01-01

263

Evaluation of aqueous degreasers versus chlorinated solvents at the Paducah Gaseous Diffusion Plant  

SciTech Connect

Spent chlorinated solvents are produced mainly as a result of degreasing operations at several Paducah Gaseous Diffusion Plant (PGDP) locations. This waste is a listed hazardous waste under Resource Conservation and Recovery Act (RCRA) regulations (40 CFR 261). In addition, some of the solvents become contaminated with uranium which classifies the waste as a mixed waste for which no disposal method is currently available. Due to health and environmental concerns and the desire to minimize mixed and hazardous waste generation, degreasing operations in the plant were delineated and alternate nonhazardous solvents were evaluated for their suitability for replacing the chlorinated solvents. Metal cleanliness testing of eight aqueous degreasers using ultrasonic cleaning and immersion with agitation, and vapor degreasing with trichloroethylene (TCE) and 1,1,1-trichloroethane (TC-ane) was performed. Soils such as dust, fingerprints, lube oil, water-soluble oil, silicone grease, and petroleum-based grease were removed from Monel, copper, mild steel, aluminum, and phosphor bronze. Cleanliness was determined by estimating the surface energy of metal coupons before and after cleaning. A Kepner-Tregoe (KT) decision analysis was utilized to determine the three best multipurpose degreasers for the plant. Additional testing was performed on the top three selected degreasers to evaluate corrosive effects of the cleaning solutions (general surface corrosion and pitting), and to determine the compatability of any residual contamination with process gases. Corrosion testing was performed in an electrochemical corrosion tester. Cleaned coupons were exposed to uranium hexafluoride, fluorine, and chlorine trifluoride. In addition, metal cleanliness testing was conducted to evaluate the cleaning efficiency of parts cleaned in the field.

Gunn, D.

1988-10-31

264

Modeling and analyses of postulated UF{sub 6} release accidents in gaseous diffusion plant  

SciTech Connect

Computer models have been developed to simulate the transient behavior of aerosols and vapors as a result of a postulated accident involving the release of uranium hexafluoride (UF{sub 6}) into the process building of a gaseous diffusion plant. UF{sub 6} undergoes an exothermic chemical reaction with moisture (H{sub 2}O) in the air to form hydrogen fluoride (HF) and radioactive uranyl fluoride (UO{sub 2}F{sub 2}). As part of a facility-wide safety evaluation, this study evaluated source terms consisting of UO{sub 2}F{sub 2} as well as HF during a postulated UF{sub 6} release accident in a process building. In the postulated accident scenario, {approximately}7900 kg (17,500 lb) of hot UF{sub 6} vapor is released over a 5 min period from the process piping into the atmosphere of a large process building. UO{sub 2}F{sub 2} mainly remains as airborne-solid particles (aerosols), and HF is in a vapor form. Some UO{sub 2}F{sub 2} aerosols are removed from the air flow due to gravitational settling. The HF and the remaining UO{sub 2}F{sub 2} are mixed with air and exhausted through the building ventilation system. The MELCOR computer code was selected for simulating aerosols and vapor transport in the process building. MELCOR model was first used to develop a single volume representation of a process building and its results were compared with those from past lumped parameter models specifically developed for studying UF{sub 6} release accidents. Preliminary results indicate that MELCOR predicted results (using a lumped formulation) are comparable with those from previously developed models.

Kim, S.H.; Taleyarkhan, R.P.; Keith, K.D.; Schmidt, R.W. [Oak Ridge National Lab., TN (United States); Carter, J.C. [J.C. Carter Associates, Inc., Oak Ridge, TN (United States); Dyer, R.H. [Dyer Enterprises, Oak Ridge, TN (United States)

1995-10-01

265

Ground penetrating radar surveys over an alluvial DNAPL site, Paducah Gaseous Diffusion Plant, Kentucky  

SciTech Connect

Ground penetrating radar (GPR) surveys were used to map shallow sands and gravels which are DNAPL migration pathways at the Paducah Gaseous Diffusion Plant in western Kentucky. The sands and gravels occur as paleochannel deposits, at depths of 17-25 ft, embedded in Pleistocene lacustrine clays. More than 30 GPR profiles were completed over the Drop Test Area (DTA) to map the top and base of the paleochannel deposits, and to assess their lateral continuity. A bistatic radar system was used with antenna frequencies of 25 and 50 MHz. An average velocity of 0.25 ft/ns for silty and clayey materials above the paleochannel deposits was established from radar walkaway tests, profiles over culverts of known depth, and comparison of radar sections with borings. In the south portion of the DTA, strong reflections corresponded to the water table at approximately 9-10 ft, the top of the paleochannel deposits at approximately 18 ft, and to gravel horizons within these deposits. The base of these deposits was not visible on the radar sections. Depth estimates for the top of the paleochannel deposits (from 50 records) were accurate to within 2 ft across the southern portion of the DTA. Continuity of these sands and gravels could not be assessed due to interference from air-wave reflections and lateral changes in signal penetration depth. However, the sands and gravels appear to extend across the entire southern portion of the DTA, at depths as shallow as 17 ft. Ringing, air-wave reflections and diffractions from powerlines, vehicles, well casings, and metal equipment severly degraded GPR profiles in the northern portion of the DTA; depths computed from reflection times (where visible) were accurate to within 4 ft in this area. The paleochannel deposits are deeper to the north and northeast where DNAPL has apparently pooled (DNAPL was not directly imaged by the GPR, however). Existing hydrogeological models of the DTA will be revised.

Carpenter, P.J. [Northern Illinois Univ., DeKalb, IL (United States). Dept. of Geology]|[Oak Ridge National Lab., TN (United States); Doll, W.E. [Oak Ridge National Lab., TN (United States); Phillips, B.E. [Paducah Gaseous Diffusion Plant, KY (United States)

1994-09-01

266

The measurement of precise solute diffusion coefficients in molten metals and semiconductors  

NASA Astrophysics Data System (ADS)

The measurement of precise solute diffusion coefficients in molten metals and semiconductors is of fundamental importance when studying and modeling metallurgical and crystal growth processes. Unfortunately, buoyancy-driven convection influences terrestrial experimentation so precise solute diffusion data cannot be generated without the use of a microgravity environment. In order to perform diffusion experiments in space, existing experimental techniques must be modified. The long capillary and the shear cell techniques have been adopted for our planned liquid diffusion experiments in microgravity conditions. Experimental parameters, such as the sample dimensions and diffusion time have been determined and are fully discussed in this report. The cast-coating technique for long capillary diffusion couple preparation has been refined. A modified shear cell has been developed, which can be used to measure the diffusion coefficient of the liquids with high vapor pressure and also provide for safe operation in a manned space vehicle. Comparative experiments have shown that buoyancy-driven convection exists in the liquid during ground-based diffusion experiments even when used in a vertical orientation in a small temperature gradient to reduce convection. It was found that the diffusion coefficients of antimony in lead obtained terrestrially are remarkably similar to the values obtained in space. This suggests that radial temperature gradients in the diffusion samples cause buoyancy-driven convection, which enhances solute transport and increases the measured diffusion coefficient value. However, if the density of the solute is significantly less than that of the solvent, then the radial-temperature-gradient-induced flow will be minimized. The significance of this effect may be gauged from the fact that, while the solute antimony gave 1 g results close to the microgravity values, it was present only in a small section of 1% alloy at the upper end of the diffusion couple at the start of the diffusion period.

Huang, Weidong

267

Comparison of ICRF-Induced Ion Diffusion Coefficients Calculated with the DC and AORSA Codes  

SciTech Connect

The DC (Diffusion Coefficient) code obtains RF diffusion coefficients by direct numerical integration of the Lorentz force equation for ion motion in the combined equilibrium fields and the RF full wave EM fields from the AORSA full-wave code. Suitable averaging over initial gyro- and toroidal-angle of coordinate 'kicks' after a bounce-period, gives noise-free bounce-averaged diffusion coefficients. For direct comparison with zero-banana-width coefficients from AORSA, perpendicular-drift terms in the Lorentz equation are subtracted off the integration. The DC code has been coupled to the CQL3D Fokker-Planck code. For a C-Mod minority ion ICRF heating test case, the total power absorption using the diffusion coefficients agree well, and the profiles are similarly close. This supports the DC calculation and the Kennel-Engelmann-based, no-correlations, coefficient calculation in AORSA. However, resonance correlations cause large differences in the pitch angle variations of the diffusion coefficients, and in the resulting evolution of the ion distribution functions.

Harvey, R. W.; Petrov, Yu. [CompX, P.O. Box 2672, Del Mar, CA 92014-5672 (United States); Jaeger, E. F.; Berry, L. A.; Batchelor, D. B. [Oak Ridge National Laboratory, Oak Ridge (United States); Bonoli, P. T.; Wright, J. C. [MIT Plasma Science and Fusion Center, Cambridge (United States)

2009-11-26

268

Diffusion Coefficients of SO2 in Water and Partition Coefficients of SO2 in Water-Air Interface at Different Temperature and pH Values  

Microsoft Academic Search

Reversed flow gas chromatography was applied to measure the diffusion coefficient of SO2 in water, the partition coefficient of SO2 in air–water interface, and the rate constant, kR, for chemical reaction between SO2 and water at various temperature and pH values. A linear increment of the diffusion coefficients of SO2 in water with temperature is drawn while the partition coefficients

A. Koliadima; J. Kapolos; L. Farmakis

2009-01-01

269

Strong solutions of SDES with singular drift and Sobolev diffusion coefficients  

Microsoft Academic Search

In this paper we prove the existence of a unique strong solution up to the explosion time for an SDE with a uniformly non-degenerate Sobolev diffusion coefficient (non-Lipschtiz) and locally integrable drift coefficient. Moreover, two non-explosion conditions are given.

Xicheng Zhang

2005-01-01

270

Measurement of diffusion coefficients of francium and rubidium in yttrium based on laser spectroscopy  

Microsoft Academic Search

We report the measurement of the diffusion coefficients of francium and rubidium ions implanted in a yttrium foil. We developed a methodology, based on laser spectroscopy, which can be applied to radioactive and stable species, and allows us to directly take record of the diffusion time. Francium isotopes are produced via fusion-evaporation nuclear reaction of a O18 beam on a

C. de Mauro; R. Calabrese; L. Corradi; A. Dainelli; A. Khanbekyan; E. Mariotti; P. Minguzzi; L. Moi; S. Sanguinetti; G. Stancari; L. Tomassetti; S. Veronesi

2008-01-01

271

Comparison of diffusion coefficients obtained from ternary polymer solutions using dynamic light scattering and ultra centrifugation  

Microsoft Academic Search

Dynamic light scattering has been used to measure the interpenetration diffusion coeffient of ternary polymer solutions formed with 233 000 dalton polystyrene and a trace amount of 330 000 dalton PMMA dissolved in thiophenol. These measurements have been compared with the diffusion coefficients obtained from ultracentrifuge studies of the same solutions by observing the change in shape of the sedimentation

D. N. Pinder; T. Ueleni; J. A. Lewis

1996-01-01

272

Inverse Problem for a Class of Two-Dimensional Diffusion Equations with Piecewise Constant Coefficients  

Microsoft Academic Search

In this paper, we consider an inverse problem for a class of two-dimensional diffusion equations with piecewise constant coefficients. This problem is studied using an explicit formula for the relevant spectral measures and an asymptotic expansion of the solution of the diffusion equations. A numerical method that reduces the inverse problem to a sequence of nonlinear least-square problems is proposed

M. Mochi; G. Pacelli; M. C. Recchioni; F. Zirilli

1999-01-01

273

Solute diffusion coefficient in the internal medium of a new gel based controlled release fertilizer  

Microsoft Academic Search

The diffusion of solutes in a new controlled release device was investigated and in situ measurements of constant and variable diffusion coefficients were obtained. The new controlled release device consists of a dry mixture of fertilizer and gel forming thickener contained in a nonpermeable coating having at least one opening. Water penetrates into the device through the opening, forms a

Uri Shavit; Avi Shaviv; Dan Zaslavsky

1995-01-01

274

An alternative model for estimating liquid diffusion coefficients requiring no viscosity data  

NASA Technical Reports Server (NTRS)

An equation, based on the free volume of a liquid solvent, was derived via dimensional analysis, to predict binary diffusion coefficients. The equation assumed that interaction between the solute and liquid solvent molecules followed a Lennard-Jones potential. The equation was compared to other diffusivity equations and was found to give good results over the temperature range examined.

Morales, Wilfredo

1993-01-01

275

Association of Early CT Abnormalities, Infarct Size, and Apparent Diffusion Coefficient Reduction in Acute Ischemic Stroke  

Microsoft Academic Search

BACKGROUND AND PURPOSE: Diffusion-weighted (DW) imaging is more sensitive for early ischemia than CT, and apparent diffusion coefficient (ADC) mapping permits quantification of the severity of cytotoxic edema. We examined the relationship between early CT findings, ischemic lesion volume on DW images, and edema subtype. METHODS: Patients in whom early signs of ischemia were detected on baseline CT scans were

Diederik M. Somford; Michael P. Marks; Vincent N. Thijs; David C. Tong

276

A theoretical approach to the measurement of radon diffusion and adsorption coefficients in radonproof membranes  

Microsoft Academic Search

Theoretical expressions for the determination of radon diffusion and adsorption coefficients in radonproof membranes using the standard method for testing the radon insulation effectiveness of a membrane tightly placed between two compartments are derived from the steady-state solution of the differential equation for radon diffusion. These expressions are applied to an experimental set-up designed specifically to carry out such a

Pedro L. Fernández; Luis S. Quindós; Carlos Sainz; José Gómez

2004-01-01

277

Measuring Oxygen, Carbon Monoxide and Hydrogen Sulfide Diffusion Coefficient and Solubility in Nafion Membranes  

Microsoft Academic Search

A Devanathan-Stachurski type diffusion cell made from a fuel cell assembly is designed to evaluate the gas transport properties of a proton exchange membrane as a function of cell temperature and gas pressure. Data obtained on this cell using the electrochemical monitoring technique (EMT) is used to estimate solubility and diffusion coefficient of oxygen (O2), carbon monoxide (CO) and hydrogen

Vijay A. Sethuraman; Saahir Khan; Jesse S. Jur; Andrew T. Haug; John W. Weidner

2011-01-01

278

Measuring oxygen, carbon monoxide and hydrogen sulfide diffusion coefficient and solubility in Nafion membranes  

Microsoft Academic Search

A Devanathan–Stachurski type diffusion cell made from a fuel cell assembly is designed to evaluate the gas transport properties of a proton exchange membrane as a function of cell temperature and gas pressure. Data obtained on this cell using the electrochemical monitoring technique (EMT) is used to estimate solubility and diffusion coefficient of oxygen (O2), carbon monoxide (CO) and hydrogen

Vijay A. Sethuraman; Saahir Khan; Jesse S. Jur; Andrew T. Haug; John W. Weidner

2009-01-01

279

Determination of Effective Diffusion Coefficients of Nitrogen in Extruded Polystyrene Foam by Gravimetric Sorption  

Microsoft Academic Search

A macrogravimctric sorption technique has been employed to obtain time-dependent weight gain data for thin-sliced closed-cell extruded polystyrene foam samples Effective diffusion thickness and diffusion time were used to compute a scaled age parameter The weighing apparatus operated in an isolated chamber filled with pure nitrogen gas The effective diffusion coefficient of the gas in the foam structure was computed

J. R. Booth; T. J. Holstein

1993-01-01

280

A first-principles methodology for diffusion coefficients in metals and dilute alloys  

Microsoft Academic Search

This work is a study exploring the extent of suitability of static first-principles calculations for studying diffusion in metallic systems. Specifically, vacancy-mediated volume diffusion in pure elements and alloys with dilute concentration of impurities is studied. A novel procedure is discovered for predicting diffusion coefficients that overcomes the shortcomings of the well-known transition state theory, by Vineyard. The procedure that

Manjeera Mantina

2008-01-01

281

Determination of methanol diffusion and electroosmotic drag coefficients in proton-exchange-membranes for DMFC  

NASA Astrophysics Data System (ADS)

Methanol diffusion and electroosmotic drag coefficients for different polymer-electrolyte-membranes have been investigated. It is essential to understand the transport phenomena of water and methanol transport in perfluoro sulfonic acid (PSA) membranes under different methanol concentrations and current densities in order to optimize cell performance and operation. The dependence of the methanol diffusion coefficient as well as the electroosmotic drag coefficient on methanol concentration and current density were observed. The results are discussed in comparison to measured values obtained by other scientific groups.

Schaffer, Thomas; Tschinder, Thomas; Hacker, Viktor; Besenhard, Jürgen O.

282

Temperature-Dependent Diffusion Coefficients from ab initio Computations: Hydrogen in Nickel  

SciTech Connect

The temperature-dependent mass diffusion coefficient is computed using transition state theory. Ab initio supercell phonon calculations of the entire system provide the attempt frequency, the activation enthalpy, and the activation entropy as a function of temperature. Effects due to thermal lattice expansion are included and found to be significant. Numerical results for the case of hydrogen in nickel demonstrate a strong temperature dependence of the migration enthalpy and entropy. Trapping in local minima along the diffusion path has a pronounced effect especially at low temperatures. The computed diffusion coefficients with and without trapping bracket the available experimental values over the entire temperature range between 0 and 1400 K.

E Wimmer; W Wolf; J Sticht; P Saxe; C Geller; R Najafabadi; G Young

2006-03-16

283

Temperature dependence of diffusion coefficient of nitrogen gas in water: A molecular dynamics study  

NASA Astrophysics Data System (ADS)

We have carried out the molecular dynamics (MD) simulation to study the structural properties and to estimate the diffusivity of molecular nitrogen (N2) gas (solute) in extended simple point charge model (SPC/E) water (solvent) with N2 mole fraction of 0.018 at different temperatures. For the structural properties of the system, we have determined radial distribution function (RDF). The solute-solute, solute-solvent and solvent-solvent RDF have been evaluated. Self-diffusion coefficient of N2 was estimated by evaluating mean-squared displacement (MSD) and velocity autocorrelation function (VACF) separately. The diffusion coefficients obtained from the two methods agree within 3%. The results are in agreement with the experimentally determined values within 10%. The self-diffusion coefficient of water (H2O) was also estimated by evaluating MSD. Mutual diffusion coefficient of the system have also been estimated invoking Darken's relation. The temperature dependance of the diffusion coefficients were found to follow Arrhenius relation.

Sharma, Keshav; Adhikari, Narayan P.

2014-04-01

284

Deconvolution of Compartmental Water Diffusion Coefficients in Yeast-Cell Suspensions Using Combined T1 and Diffusion Measurements  

Microsoft Academic Search

An NMR method is presented for measuring compartment-specific water diffusion coefficient (D) values. It uses relaxography, employing an extracellular contrast reagent (CR) to distinguish intracellular (IC) and extracellular (EC) 1H2O signals by differences in their respective longitudinal (T1) relaxation times. A diffusion-weighted inversion-recovery spin-echo (DW-IRSE) pulse sequence was used to acquire IR data sets with systematically and independently varying inversion

Matthew D. Silva; Karl G. Helmer; Jing-Huei Lee; Sam S. Han; Charles S. Springer; Christopher H. Sotak

2002-01-01

285

Deconvolution of Compartmental Water Diffusion Coefficients in Yeast-Cell Suspensions Using Combined T 1 and Diffusion Measurements  

Microsoft Academic Search

An NMR method is presented for measuring compartment-specific water diffusion coefficient (D) values. It uses relaxography, employing an extracellular contrast reagent (CR) to distinguish intracellular (IC) and extracellular (EC) 1H2O signals by differences in their respective longitudinal (T1) relaxation times. A diffusion-weighted inversion-recovery spin-echo (DW-IRSE) pulse sequence was used to acquire IR data sets with systematically and independently varying inversion

Matthew D. Silva; Karl G. Helmer; Jing-Huei Lee; Sam S. Han; Charles S. Springer; Christopher H. Sotak

2002-01-01

286

Effect of pore wall model on prediction of diffusion coefficients for graphitic slit pores.  

PubMed

The effect of the pore wall model on the self-diffusion coefficient and transport diffusivity predicted for methane in graphitic slit pores by equilibrium molecular dynamics (EMD) and non-equilibrium MD (NEMD) is investigated. Three pore wall models are compared--a structured wall and a smooth (specular) wall, both with a thermostat applied to the fluid to maintain the desired temperature, and a structured wall combined with the diffuse thermalizing scattering algorithm of MacElroy and Boyle (Chem. Eng. J., 1999, 74, 85). Pore sizes ranging between 7 and 35 angstroms and five pressures in the range of 1-40 bar are considered. The diffuse thermalizing wall yields incorrect self-diffusion coefficients and transport diffusivities for the graphitic slit pore model and should not be used. Surprisingly, the smooth specular wall gives self-diffusion coefficients inline with those obtained using the structured wall, indicating that this computationally much faster wall can be used for studying this phenomenon provided the fluid-wall interactions are somewhat weaker than the fluid-fluid interactions. The structured wall is required, however, if the transport diffusivity is of interest. PMID:18446252

Cai, Qiong; Biggs, Mark J; Seaton, Nigel A

2008-05-14

287

Development of phase-shifting interferometry for measurement of isothermal diffusion coefficients in binary solutions  

NASA Astrophysics Data System (ADS)

In this study, a phase-shifting interferometer to conduct real-time high-resolution measurements of concentration profiles in binary diffusion fields was developed. The phase-shifting interferometer comprises a Mach-Zehnder interferometer, a rotating polarizer, a CCD camera, and an image-processing unit. A phase-shifting technique was used to determine the phase difference between a test beam and a reference beam by using three images taken at intervals of 1/30 s. The phase difference is obtained for a spatial resolution of 640×240. This data is further processed in real-time to visualize the concentration profile inside a diffusion cell. The diffusion coefficient is determined by performing an inverse analysis of the experimental concentration profile. The objective function makes use of a numerical calculation, based on Fick's law, for which the initial experimental concentration profile is taken as initial condition. The diffusion field was formed inside a thermally controlled diffusion cell with optical paths as large as 20 mm. This large optical path allows measurements of diffusion fields with concentration differences as narrow as 1 mg/ml. In order to validate the measurement method, the concentration dependence of the isothermal diffusion coefficient of NaCl and Sucrose was determined in the dilute region at 25 °C, such values being extensively reported in the literature. It was found that our optical system is much faster and accurate than similar optical systems to determine the diffusion coefficients in binary systems.

Torres, Juan F.; Komiya, Atsuki; Shoji, Eita; Okajima, Junnosuke; Maruyama, Shigenao

2012-09-01

288

Measurement of Diffusion Coefficient of Liquids by Using an Asymmetric Liquid-Core Cylindrical Lens: Observing the Diffusion Process Directly  

NASA Astrophysics Data System (ADS)

We report a method for measuring diffusion coefficient D of liquids by using an aplanatic and asymmetric cylinder lens with a liquid core, which is designed as both a diffusion pool and the main imaging element. The precision is better than 10?4 RIU in measuring refractive index. The D values of ethylene glycol (EG) in water are measured for various EG concentrations at 25°C, and Dinf = 1.043 × 10?5 cm2/s under the condition of infinite dilution is obtained. The method is characterized by observing the diffusion process directly, faster measurement and obtaining the D value under the condition of infinite dilution.

Li, Qiang; Pu, Xiao-Yun; Yang, Rui-Fen; Zhai, Ying

2014-05-01

289

Experimental method development for estimating solid-phase diffusion coefficients and material/air partition coefficients of SVOCs  

NASA Astrophysics Data System (ADS)

The solid-phase diffusion coefficient (Dm) and material/air partition coefficient (Kma) are key parameters for characterizing the sources and transport of semivolatile organic compounds (SVOCs) in the indoor environment. In this work, a new experimental method was developed to estimate parameters Dm and Kma. The SVOCs chosen for study were polychlorinated biphenyl (PCB) congeners, including PCB-52, PCB-66, PCB-101, PCB-110, and PCB-118. The test materials included polypropylene, high density polyethylene, low density polyethylene, polytetrafluoroethylene, polyether ether ketone, glass, stainless steel and concrete. Two 53-L environmental chambers were connected in series, with the relatively stable SVOCs source in the source chamber and the test materials, made as small “buttons”, in the test chamber. Prior to loading the test chamber with the test materials, the test chamber had been dosed with SVOCs for 12 days to “coat” the chamber walls. During the tests, the material buttons were removed from the test chamber at different exposure times to determine the amount of SVOC absorbed by the buttons. SVOC concentrations at the inlet and outlet of the test chamber were also monitored. The data were used to estimate the partition and diffusion coefficients by fitting a sink model to the experimental data. The parameters obtained were employed to predict the accumulation of SVOCs in the sink materials using an existing mass transfer model. The model prediction agreed reasonably well with the experimental data.

Liu, Xiaoyu; Guo, Zhishi; Roache, Nancy F.

2014-06-01

290

Sublimation kinetics and diffusion coefficients of TNT, PETN, and RDX in air by thermogravimetry.  

PubMed

The diffusion coefficients of explosives are crucial in their trace detection and lifetime estimation. We report on the experimental values of diffusion coefficients of three of the most important explosives in both military and industry: TNT, PETN, and RDX. Thermogravimetric analysis (TGA) was used to determine the sublimation rates of TNT, PETN, and RDX powders in the form of cylindrical billets. The TGA was calibrated using ferrocene as a standard material of well-characterized sublimation rates and vapor pressures to determine the vapor pressures of TNT, PETN, and RDX. The determined sublimation rates and vapor pressures were used to indirectly determine the diffusion coefficients of TNT, PETN, and RDX for the first time. A linear log-log dependence of the diffusion coefficients on temperature is observed for the three materials. The diffusion coefficients of TNT, PETN, and RDX at 273 K were determined to be 5.76×10(-6)m(2)/sec, 4.94×10(-6)m(2)/s, and 5.89×10(-6)m(2)/s, respectively. Values are in excellent agreement with the theoretical values in literature. PMID:24840410

Hikal, Walid M; Weeks, Brandon L

2014-07-01

291

Theoretical evaluation of diffusion coefficients of (Al2O3)n clusters in different bath gases  

NASA Astrophysics Data System (ADS)

The binary diffusion coefficients of two low lying isomers of (Al2O3) n , n = 1...4, clusters in different bath gases, that most frequently met in the nature and in the technical applications: H2, N2, O2, CO, H2O as well as their self-diffusion coefficients have been calculated on the basis of kinetic theory and dipole reduced formalism. The parameters of interaction potential have been determined taking into account the contributions of a dispersion, dipole-dipole and dipole-induced dipole interactions between alumina clusters and bath molecules. The dipole moments, polarizabilities and collision diameters of clusters have been obtained by using quantum chemical calculations of cluster structure. The approximations for temperature dependencies of diffusion coefficients for two low-lying isomers of each considered alumina clusters are reported. It is demonstrated that an account for the contributions of the second for each type of clusters does not affect substantially the value of net diffusion coefficient. The diffusion coefficients of the isomers of small (Al2O3) n clusters can differ notably in the case when their dipole moments are distinct and they interact with strongly dipole molecules.

Sharipov, Alexander S.; Loukhovitski, Boris I.; Tsai, Chuen-Jinn; Starik, Alexander M.

2014-04-01

292

Mutual diffusion coefficients of heptane isomers in nitrogen: A molecular dynamics study  

NASA Astrophysics Data System (ADS)

The accurate knowledge of transport properties of pure and mixture fluids is essential for the design of various chemical and mechanical systems that include fluxes of mass, momentum, and energy. In this study we determine the mutual diffusion coefficients of mixtures composed of heptane isomers and nitrogen using molecular dynamics (MD) simulations with fully atomistic intermolecular potential parameters, in conjunction with the Green-Kubo formula. The computed results were compared with the values obtained using the Chapman-Enskog (C-E) equation with Lennard-Jones (LJ) potential parameters derived from the correlations of state values: MD simulations predict a maximum difference of 6% among isomers while the C-E equation presents that of 3% in the mutual diffusion coefficients in the temperature range 500-1000 K. The comparison of two approaches implies that the corresponding state principle can be applied to the models, which are only weakly affected by the anisotropy of the interaction potentials and the large uncertainty will be included in its application for complex polyatomic molecules.The MD simulations successfully address the pure effects of molecular structure among isomers on mutual diffusion coefficients by revealing that the differences of the total mutual diffusion coefficients for the six mixtures are caused mainly by heptane isomers. The cross interaction potential parameters, collision diameter ?12, and potential energy well depth ?12 of heptane isomers and nitrogen mixtures were also computed from the mutual diffusion coefficients.

Chae, Kyungchan; Violi, Angela

2011-01-01

293

Estimation of diffusion coefficients from voltammetric signals by support vector and gaussian process regression  

PubMed Central

Background Support vector regression (SVR) and Gaussian process regression (GPR) were used for the analysis of electroanalytical experimental data to estimate diffusion coefficients. Results For simulated cyclic voltammograms based on the EC, Eqr, and EqrC mechanisms these regression algorithms in combination with nonlinear kernel/covariance functions yielded diffusion coefficients with higher accuracy as compared to the standard approach of calculating diffusion coefficients relying on the Nicholson-Shain equation. The level of accuracy achieved by SVR and GPR is virtually independent of the rate constants governing the respective reaction steps. Further, the reduction of high-dimensional voltammetric signals by manual selection of typical voltammetric peak features decreased the performance of both regression algorithms compared to a reduction by downsampling or principal component analysis. After training on simulated data sets, diffusion coefficients were estimated by the regression algorithms for experimental data comprising voltammetric signals for three organometallic complexes. Conclusions Estimated diffusion coefficients closely matched the values determined by the parameter fitting method, but reduced the required computational time considerably for one of the reaction mechanisms. The automated processing of voltammograms according to the regression algorithms yields better results than the conventional analysis of peak-related data.

2014-01-01

294

Radon diffusion coefficients in 360 waterproof materials of different chemical composition.  

PubMed

This paper summarises the results of radon diffusion coefficient measurements in 360 common waterproof materials available throughout Europe. The materials were grouped into 26 categories according to their chemical composition. It was found that the diffusion coefficients of materials used for protecting houses against radon vary within eight orders from 10(-15) to 10(-8) m(2) s(-1). The lowest values were obtained for bitumen membranes with an Al carrier film and for ethylene vinyl acetate membranes. The highest radon diffusion coefficient values were discovered for sodium bentonite membranes, rubber membranes made of ethylene propylene diene monomer and polymer cement coatings. The radon diffusion coefficients for waterproofings widely used for protecting houses, i.e. flexible polyvinyl chloride, high-, low-density polyethylene, polypropylene and bitumen membranes, vary in the range from 3 × 10(-12) to 3 × 10(-11) m(2) s(-1). Tests were performed which confirmed that the radon diffusion coefficient is also an effective tool for verifying the air-tightness of joints. PMID:21450700

Jiránek, M; Kotrbatá, M

2011-05-01

295

A first-principles methodology for diffusion coefficients in metals and dilute alloys  

NASA Astrophysics Data System (ADS)

This work is a study exploring the extent of suitability of static first-principles calculations for studying diffusion in metallic systems. Specifically, vacancy-mediated volume diffusion in pure elements and alloys with dilute concentration of impurities is studied. A novel procedure is discovered for predicting diffusion coefficients that overcomes the shortcomings of the well-known transition state theory, by Vineyard. The procedure that evolves from Eyring's reaction rate theory yields accurate diffusivity results that include anharmonic effects within the quasi-harmonic approximation. Alongside, the procedure is straightforward in its application within the conventional harmonic approximation, from the results of static first-principles calculations. To prove the extensibility of the procedure, diffusivities have been computed for a variety of systems. Over a wide temperature range, the calculated self-diffusion and impurity diffusion coefficients using local density approximation (LDA) of density functional theory (DFT) are seen to be in excellent match with experimental data. Self-diffusion coefficients have been calculated for: (i) fcc Al, Cu, Ni and Ag (ii) bcc W and Mo (v) hcp Mg, Ti and Zn. Impurity diffusion coefficients have been computed for: (i) Mg, Si, Cu, Li, Ag, Mo and 3d transition elements in fcc Al (ii) Mo, Ta in bcc W and Nb, Ta and W in bcc Mo (iii) Sn and Cd in hcp Mg and Al in hcp Ti. It is also an observation from this work, that LDA does not require surface correction for yielding energetics of vacancy-containing system in good comparison with experiments, unlike generalized gradient approximation (GGA). It is known that first-principles' energy minimization procedures based on electronic interactions are suited for metallic systems wherein the valence electrons are freely moving. In this thesis, research has been extended to study suitability of first-principles calculations within LDA/GGA including the localization parameter U, for Al system with transition metal solutes, in which charges are known to localize around the transition metal element. U parameter is determined from matching the diffusivities of 3d transition metal impurity in aluminum with reliable experimental data. The effort yielded activation energies in systematic agreement with experiments and has proved useful in obtaining insights into the complex interactions in these systems. Besides the prediction of diffusion coefficients, this research has been helpful in understanding the physics underlying diffusion. Within the scope of observations from the systems studied, certain diffusion related aspects that have been clarified are: (i) cause for non-Arrnenius' nature of diffusion plots (ii) definitions of atom migration properties (iii) magnitude and sign of diffusion parameters enthalpy and entropy of formation and migration and characteristic vibrational frequency (iv) trends in diffusivities based on activation energy and diffusion prefactor (vi) cause for anomalous diffusion behavior of 3d transition metals in Al, and their magnetic nature (vii) contributions from electronic contributions to curvature at very high temperatures of bcc refractory elements (viii) temperature dependence of impurity diffusion correlation factors. Finally, the double-well potential of diffusion by vacancy mechanism has been calculated from first-principles. This aided calculation of entropy of migration and thus free energy of migration along with characteristic vibrational frequency. Also for the first time, temperature dependence of enthalpy of migration and thus atom jump frequency has been accurately predicted. From the broad perspective of predicting diffusion coefficients from computational methodologies, it can be stated as a result of this work that: static first-principles extend an irreplaceable contribution to the future of diffusion modeling. The procedure obviated the use of (i) redundant approximations that limit its accuracy and (ii) support from other computational techniques that restrict its extensibility due to insufficient i

Mantina, Manjeera

296

Estimation of radon diffusion coefficients in soil using an updated experimental system.  

PubMed

Radon diffusion through soil is strongly affected by the degree of water saturation of the soil pores. Methods have been developed by many researchers to measure radon diffusion coefficient. We developed an updated experimental system to estimate radon diffusion coefficients for typical types of soil in Japan and applied it to a typical loam with different water saturation levels (0-0.82). The system consists of a passive-type scintillation cell, soil column, accumulation tank, and radon source. The radon concentration in the accumulation tank is kept stable, and radon diffused through the soil column is continuously measured with the passive-type scintillation cell. We found the radon diffusion coefficients vary from 9.60 × 10(-6) m(2) s(-1) to 1.27 × 10(-7) m(2) s(-1) for the loam samples. Generally, the diffusion coefficients are almost constant for a water saturation range of 0-0.4 and decrease with increasing water saturation from 0.4 to 0.82. PMID:23020372

Prasad, Ganesh; Ishikawa, Tetsuo; Hosoda, Masahiro; Sorimachi, Atsuyuki; Janik, Miroslaw; Sahoo, Sarata Kumar; Tokonami, Shinji; Uchida, Shigeo

2012-09-01

297

Superfund record of decision (EPA Region 4): Paducah Gaseous Diffusion Plant, Northwest Plume, Paducah, KY, July 1993  

SciTech Connect

This decision document presents the selected remedial action for the Northwest Plume at the Paducah Gaseous Diffusion Plant (PGDP) in Paducah, Kentucky. The primary objective of this interim remedial action is to initiate a first phase remedial action, as an interim action to initiate control of the source and mitigate the spread of contamination in the Northwest plume. This operable unit addresses a portion of the contaminated ground water. Additional interim actions associated with this integrator operable unit are being considered, as well as for other areas of contaminated ground water.

Not Available

1993-07-01

298

Health risk from earthquake caused releases of UF{sub 6} at the Paducah Gaseous Diffusion Plant  

SciTech Connect

The health risk to the public and workers from potential exposure to the toxic materials from earthquake caused releases of uranium hexafluoride from the Paducah gaseous Diffusion Plant are evaluated. The results of the study show that the health risk from earthquake caused releases is small, and probably less than risks associated with the transportation of hydrogen fluoride and other similar chemicals used by industry. The probability of more than 30 people experiencing health consequences (injuries) from earthquake damage is less than 4xlO{sup 4}/yr.

Brown, N.W; Lu, S.; Chen, J.C.; Roehnelt, R.; Lombardi, D.

1998-05-01

299

Relationships between Atomic Diffusion Mechanisms and Ensemble Transport Coefficients in Crystalline Polymorphs.  

PubMed

Ionic transport in conventional ionic solids is generally considered to proceed via independent diffusion events or "hops." This assumption leads to well-known Arrhenius expressions for transport coefficients, and is equivalent to assuming diffusion is a Poisson process. Using molecular dynamics simulations of the low-temperature B1, B3, and B4 AgI polymorphs, we have compared rates of ion hopping with corresponding Poisson distributions to test the assumption of independent hopping in these common structure types. In all cases diffusion is a non-Poisson process, and hopping is strongly correlated in time. In B1 the diffusion coefficient can be approximated by an Arrhenius expression, though the physical significance of the parameters differs from that commonly assumed. In low temperature B3 and B4, diffusion is characterized by concerted motion of multiple ions in short closed loops. Diffusion coefficients cannot be expressed in a simple Arrhenius form dependent on single-ion free energies, and intrinsic diffusion must be considered a many-body process. PMID:24765989

Morgan, Benjamin J; Madden, Paul A

2014-04-11

300

Combined measurement of surface, grain boundary and lattice diffusion coefficients on olivine bi-crystals  

NASA Astrophysics Data System (ADS)

Diffusion along interface and grain boundaries provides an efficient pathway and may control chemical transport in rocks as well as their mechanical strength. Besides the significant relevance of these diffusion processes for various geologic processes, experimental data are still very limited (e.g., Dohmen & Milke, 2010). Most of these data were measured using polycrystalline materials and the formalism of LeClaire (1951) to fit integrated concentration depth profiles. To correctly apply this formalism, certain boundary conditions of the diffusion problem need to be fulfilled, e.g., surface diffusion is ignored, and furthermore the lattice diffusion coefficient has to be known from other studies or is an additional fitting parameter, which produces some ambiguity in the derived grain boundary diffusion coefficients. We developed an experimental setup where we can measure the lattice and grain boundary diffusion coefficients simultaneously but independent and demonstrate the relevance of surface diffusion for typical grain boundary diffusion experiments. We performed Mg2SiO4 bicrystal diffusion experiments, where a single grain boundary is covered by a thin-film of pure Ni2SiO4 acting as diffusant source, produced by pulsed laser deposition. The investigated grain boundary is a 60° (011)/[100]. This specific grain boundary configuration was modeled using molecular dynamics for comparison with the experimental observations in the transmission electron microscope (TEM). Both, experiment and model are in good agreement regarding the misorientation, whereas there are still some disagreements regarding the strain fields along the grain boundary that are of outmost importance for the strengths of the material. The subsequent diffusion experiments were carried out in the temperature range between 800° and 1450° C. The inter diffusion profiles were measured using the TEMs energy dispersive x-ray spectrometer standardized using the Cliff-Lorimer equation and EMPA measurements. To evaluate the obtained diffusion profiles we adapted the isolated grain boundary model, first proposed by Fisher (1951) to match several observations: (i) Anisotropic diffusion in forsterite, (ii) fast diffusion along the grain boundary, (iii) fast diffusion on the surface of the sample. The latter process is needed to explain an additional flux of material from the surface into the grain boundary. Surface and grain boundary diffusion coefficients are on the order of 10000 times faster than diffusion in the lattice. Another observation was that in some regions the diffusion profiles in the lattice were greatly extended. TEM observations suggest here that surface defects (nano-cracks, ect.) have been present, which apparently enhanced the diffusion through the bulk lattice. Dohmen, R., & Milke, R. (2010). Diffusion in Polycrystalline Materials: Grain Boundaries, Mathematical Models, and Experimental Data. Reviews in Mineralogy and Geochemistry, 72(1), 921-970. Fisher, J. C. (1951). Calculations of Diffusion Penetration Curves for Surface and Grain Boundary Diffusion. Journal of Applied Physics, 22(1), 74-77. Le Claire, A. D. (1951). Grain boundary diffusion in metals. Philosophical Magazine A, 42(328), 468-474.

Marquardt, Katharina; Dohmen, Ralf; Wagner, Johannes

2014-05-01

301

Moisture loss from wood products during drying. Part 1: Moisture diffusivities and moisture transfer coefficients  

SciTech Connect

This study deals with the development of an analytical technique for determining the moisture diffusivities and moisture transfer coefficients for wood products subjected to drying. The wood products are idealized in the modeling as either infinite plates or long cylinders. The analysis of transient moisture diffusion is carried out on the basis of two important practical criteria: 0.1 < Bi < 100 and Bi> 100 where Bi = Biot number. The drying coefficients and lag factors were incorporated into the models. The developed analytical models are then verified by experimental measurements taken from the literature. Results show that the method presented here is capable of accurately determining the moisture diffusivities and moisture transfer coefficients for such objects. The models can be used for a variety of wood-drying applications.

Dincer, I. [Tubitak-Marmara Research Center, Gebze (Turkey)

1998-01-01

302

Crack diffusion coefficient - A candidate fracture toughness parameter for short fiber composites  

NASA Technical Reports Server (NTRS)

In brittle matrix composites, crack propagation occurs along random trajectories reflecting the heterogeneous nature of the strength field. Considering the crack trajectory as a diffusive process, the 'crack diffusion coefficient' is introduced. From fatigue crack propagation experiments on a set of identical SEN polyester composite specimens, the variance of the crack tip position along the loading axis is found to be a linear function of the effective 'time'. The latter is taken as the effective crack length. The coefficient of proportionality between variance of the crack trajectory and the effective crack length defines the crack diffusion coefficient D which is found in the present study to be 0.165 mm. This parameter reflects the ability of the composite to deviate the crack from the energetically most efficient path and thus links fracture toughness to the microstructure.

Mull, M. A.; Chudnovsky, A.; Moet, A.

1987-01-01

303

Diffusion coefficient of CO(2) molecules as determined by (13)C NMR in various carbonated beverages.  

PubMed

In this paper, the NMR technique was used, for the first time, to accurately determine the diffusion coefficient D of CO(2)-dissolved molecules in various carbonated beverages, including champagne and sparkling wines. This parameter plays an important role concerning the bubble growth during its rise through the liquid (see ref 3). The diffusion coefficient of CO(2)-dissolved molecules D was compared with that deduced from the well-known Stokes-Einstein equation and found to significantly deviate from the general trend expected from Stokes-Einstein theory, i.e, D(SE) proportional, variant 1/eta, where D(SE) is the Stokes-Einstein diffusion coefficient and eta the viscosity of the liquid medium. PMID:14664507

Liger-Belair, Gerard; Prost, Elise; Parmentier, Maryline; Jeandet, Philippe; Nuzillard, Jean-Marc

2003-12-17

304

Approximating high angular resolution apparent diffusion coefficient profiles using spherical harmonics under BiGaussian assumption  

NASA Astrophysics Data System (ADS)

Magnetic Resonance Imaging (MRI) techniques have achieved much importance in providing visual and quantitative information of human body. Diffusion MRI is the only non-invasive tool to obtain information of the neural fiber networks of the human brain. The traditional Diffusion Tensor Imaging (DTI) is only capable of characterizing Gaussian diffusion. High Angular Resolution Diffusion Imaging (HARDI) extends its ability to model more complex diffusion processes. Spherical harmonic series truncated to a certain degree is used in recent studies to describe the measured non-Gaussian Apparent Diffusion Coefficient (ADC) profile. In this study, we use the sampling theorem on band-limited spherical harmonics to choose a suitable degree to truncate the spherical harmonic series in the sense of Signal-to-Noise Ratio (SNR), and use Monte Carlo integration to compute the spherical harmonic transform of human brain data obtained from icosahedral schema.

Cao, Ning; Liang, Xuwei; Zhuang, Qi; Zhang, Jun

2009-02-01

305

Comparison between different spectral models of the diffuse attenuation and absorption coefficients of seawater  

NASA Astrophysics Data System (ADS)

The goal of this work is to verify different spectral models of the diffuse attenuation and absorption coefficients of sea water and to work out a recommendation for their use. It is shown that the spectral models of the diffuse attenuation coefficient Kd((lambda) ) developed by Austin, Petzold, 1984 and by Volynsky, Sud'bin, 1992 correspond with each other, as well the models of Ivanov, Shemshura, 1973 and of Kopelevich, Shemshura, 1988 for calculation of the spectral absorption coefficient a((lambda) ) on the values of Kd((lambda) ). Theoretical foundation of the relation between a((lambda) ) and Kd((lambda) ) is given. The up-to-date physical model of the sea water light absorption is considered and checked by means of comparison with measured values of the attenuation coefficient at the ultraviolet and visible spectral ranges.

Kopelevich, Oleg V.; Filippov, Yuri V.

1994-10-01

306

Effective concentration difference model to study the effect of various factors on the effective diffusion coefficient in the dialysis membrane  

Microsoft Academic Search

Cellulose acetate dialysis membrane (CDM) has been used in the diffusive gradients in thin films (DGT) technique, where accurate diffusion coefficients are essential for the assessment of the concentrations of labile metal in solution. Effective concentration difference model (ECDM), based on the assumption that the effective diffusion coefficient of metal ion in the dialysis membrane is determined by the effective

Hong Chen; Ting Sun; Dianpeng Sui; Jia Dong

2011-01-01

307

Third-order transport properties of ion-swarms from mobility and diffusion coefficients  

NASA Astrophysics Data System (ADS)

A method is presented for the calculation of third order transport properties of ions drifting in gases under the action of an electrostatic field with the use of mobility and ion-diffusion coefficients. The approach is based on a three-temperature treatment of the Boltzmann equation for the ion transport and follows the development of generalized Einstein relations (GER), between diffusion coefficients and mobility. The whole procedure is tested by comparison with numerical and molecular dynamics simulation results for three available alkali ion-noble gas systems. Extension to systems involving internal degrees of freedom and inelastic collisions is shown to follow the development of molecular GER.

Koutselos, Andreas D.

2005-08-01

308

Flow injection analysis simulations and diffusion coefficient determination by stochastic and deterministic optimization methods.  

PubMed

Stochastic and deterministic simulations of dispersion in cylindrical channels on the Poiseuille flow have been presented. The random walk (stochastic) and the uniform dispersion (deterministic) models have been used for computations of flow injection analysis responses. These methods coupled with the genetic algorithm and the Levenberg-Marquardt optimization methods, respectively, have been applied for determination of diffusion coefficients. The diffusion coefficients of fluorescein sodium, potassium hexacyanoferrate and potassium dichromate have been determined by means of the presented methods and FIA responses that are available in literature. The best-fit results agree with each other and with experimental data thus validating both presented approaches. PMID:23845484

Kucza, Witold

2013-07-25

309

LETTER TO THE EDITOR: Fractal diffusion coefficient from dynamical zeta functions  

NASA Astrophysics Data System (ADS)

Dynamical zeta functions provide a powerful method to analyse low-dimensional dynamical systems when the underlying symbolic dynamics is under control. On the other hand, even simple one-dimensional maps can show an intricate structure of the grammar rules that may lead to a non-smooth dependence of global observables on parameters changes. A paradigmatic example is the fractal diffusion coefficient arising in a simple piecewise linear one-dimensional map of the real line. Using the Baladi-Ruelle generalization of the Milnor-Thurnston kneading determinant, we provide the exact dynamical zeta function for such a map and compute the diffusion coefficient from its smallest zero.

Cristadoro, Giampaolo

2006-03-01

310

Density scaling of the diffusion coefficient at various pressures in viscous liquids.  

PubMed

Fundamental thermodynamics and an earlier elastic solid-state point defect model [P. Varotsos and K. Alexopoulos, Phys. Rev. B 15, 4111 (1977); Phys. Rev. B 18, 2683 (1978)] are employed to formulate an analytical second-order polynomial function describing the density scaling of the diffusion coefficient in viscous liquids. The function parameters are merely determined by the scaling exponent, which is directly connected with the Grüneisen constant. Density scaling diffusion coefficient isotherms obtained at different pressures collapse on a unique master curve, in agreement with recent computer simulation results of Lennard-Jones viscous liquids [D. Coslovich and C. M. Roland, J. Phys. Chem. 112, 1329 (2008)]. PMID:19391997

Papathanassiou, A N

2009-03-01

311

1st International comparison measurement on assessing the diffusion coefficient of radon.  

PubMed

Radon diffusion coefficient is a material parameter which is usually used in the radon mitigation measures design. There are different approaches used for radon diffusion coefficient measurement and assessment. The International comparison measurement which was jointly organised by National Radiation Protection Institute and Faculty of Civil Engineering CTU Prague in 2009 and 2010 has registered 11 laboratories from all over the world. Three sets of samples of polyethylene damp-proof membranes were sent to these laboratories for measurement. Till today, the organisers received only five sets of results. The results showed a great variability among laboratories involved. PMID:21471130

Rovenska, Katerina; Jiránek, Martin

2011-05-01

312

Density scaling of the diffusion coefficient at various pressures in viscous liquids  

NASA Astrophysics Data System (ADS)

Fundamental thermodynamics and an earlier elastic solid-state point defect model [P. Varotsos and K. Alexopoulos, Phys. Rev. B 15, 4111 (1977); Phys. Rev. B 18, 2683 (1978)] are employed to formulate an analytical second-order polynomial function describing the density scaling of the diffusion coefficient in viscous liquids. The function parameters are merely determined by the scaling exponent, which is directly connected with the Grüneisen constant. Density scaling diffusion coefficient isotherms obtained at different pressures collapse on a unique master curve, in agreement with recent computer simulation results of Lennard-Jones viscous liquids [D. Coslovich and C. M. Roland, J. Phys. Chem. 112, 1329 (2008)].

Papathanassiou, A. N.

2009-03-01

313

Determination of diffusion coefficients in polypyrrole thin films using a current pulse relaxation method  

NASA Technical Reports Server (NTRS)

The current pulse E sub oc relaxation method and its application to the determination of diffusion coefficients in electrochemically synthesized polypyrrole thin films is described. Diffusion coefficients for such films in Et4NBF4 and MeCN are determined for a series of submicron film thicknesses. Measurement of the double-layer capacitance, C sub dl, and the resistance, R sub u, of polypyrrole thin films as a function of potential obtained with the galvanostatic pulse method is reported. Measurements of the electrolyte concentration in reduced polypyrrole films are also presented to aid in the interpretation of the data.

Penner, Reginald M.; Vandyke, Leon S.; Martin, Charles R.

1987-01-01

314

Minority carrier diffusion lengths and absorption coefficients in silicon sheet material  

SciTech Connect

One of the indicators which determine a material's potential for use as a solar cell is the minority carrier diffusion length (L/sub D/) of the material. To determine L/sub D/ a surface photovoltage (SPV) technique is used. This method is dependent upon an accurate knowledge of the optical absorption coefficient as function of wavelength. The results for the absorption coefficients for various types of silicon sheet material are compared to those previously used in the two models. The resultant effect upon the diffusion length is also discussed in detail. 7 refs.

Dumas, K.A.; Swimm, R.T.

1980-01-01

315

Effect of particle-hole symmetry on the behavior of tracer and jump diffusion coefficients.  

PubMed

This paper analyzes the effect of particle-hole symmetry on the behavior of the tracer diffusion coefficient as well as the jump diffusion coefficient. The coefficients are obtained by performing a random walk of individual atoms in a two-dimensional square lattice at monolayer, using the n-fold way Monte Carlo simulation. Different hopping mechanisms have been introduced to study the effect of particle-hole symmetry. For hopping kinetics where the initial-state interactions are involved, the diffusion coefficient at high coverage falls several orders of magnitude due to the effect of particle-hole symmetry. For hopping kinetics where the final-state interactions are present, the effect is the opposite. For those involving both initial- and final-state interactions, like the so-called interaction kinetics, the effect of particle-hole symmetry is also discussed. This effect seems to be critical for repulsive lateral interactions, for which the behavior of the diffusion coefficients is modified by introducing the particle-hole symmetry condition. PMID:23767481

Torrez Herrera, J J; Ranzuglia, G A; Manzi, S J; Pereyra, V D

2013-05-01

316

Prediction of Diffusion Coefficients in Porous Media using Tortuosity Factors Based on Interfacial Areas  

SciTech Connect

Determination of aqueous phase diffusion coefficients of solutes through porous media is essential for understanding and modeling contaminant transport. Prediction of diffusion coefficients in both saturated and unsaturated zones requires knowledge of tortuosity and constrictivity factors. No methods are available for the direct measurement of these factors, which are empirical in their definition. In this paper, a new definition for the tortuosity factor is proposed, as the real to ideal interfacial area ratio. We define the tortuosity factor for saturated porous media (ts) as the ratio S/So (specific surface of real porous medium to that of an idealized capillary bundle). For unsaturated media, tortuosity factor (ta) is defined as aaw/aaw,o (ratio of the specific air-water interfacial area of real and the corresponding idealized porous medium). This tortuosity factor is suitably measured using sorptive tracers (e.g., nitrogen adsorption method) for saturated media and interfacial tracers for unsaturated media. A model based on this new definition of tortuosity factors, termed the Interfacial Area Ratio (IAR) model, is presented for the prediction of diffusion coefficients as a function of the degree of water saturation. Diffusion coefficients and diffusive resistances measured in a number of saturated and unsaturated granular porous media, for solutes in dilute aqueous solutions, agree well with the predictions of the IAR model. A comparison of permeability of saturated sands estimated based on ts and the same based on the Kozeny-Carman equation confirm the usefulness of the ts parameter as a measure of tortuosity.

Saripalli, Kanaka P.; Serne, R. Jeffrey; Meyer, Philip D.; McGrail, B. Peter

2002-08-01

317

Determining diffusion coefficients of ionic liquids by means of field cycling nuclear magnetic resonance relaxometry.  

PubMed

Field Cycling Nuclear Magnetic Resonance (FC NMR) relaxation studies are reported for three ionic liquids: 1-ethyl-3- methylimidazolium thiocyanate (EMIM-SCN, 220-258 K), 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM-BF4, 243-318 K), and 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6, 258-323 K). The dispersion of (1)H spin-lattice relaxation rate R1(?) is measured in the frequency range of 10 kHz-20 MHz, and the studies are complemented by (19)F spin-lattice relaxation measurements on BMIM-PF6 in the corresponding frequency range. From the (1)H relaxation results self-diffusion coefficients for the cation in EMIM-SCN, BMIM-BF4, and BMIM-PF6 are determined. This is done by performing an analysis considering all relevant intra- and intermolecular relaxation contributions to the (1)H spin-lattice relaxation as well as by benefiting from the universal low-frequency dispersion law characteristic of Fickian diffusion which yields, at low frequencies, a linear dependence of R1 on square root of frequency. From the (19)F relaxation both anion and cation diffusion coefficients are determined for BMIM-PF6. The diffusion coefficients obtained from FC NMR relaxometry are in good agreement with results reported from pulsed- field-gradient NMR. This shows that NMR relaxometry can be considered as an alternative route of determining diffusion coefficients of both cations and anions in ionic liquids. PMID:24985656

Kruk, D; Meier, R; Rachocki, A; Korpa?a, A; Singh, R K; Rössler, E A

2014-06-28

318

Estimation of cell membrane permeability and intracellular diffusion coefficient of human gray matter.  

PubMed

The signal intensity of diffusion-weighted imaging (DWI) is sensitive to the intra- and extracellular diffusion coefficient of water and cell membrane permeability. We applied a method we proposed in previous papers to estimate noninvasively the membrane permeability and intracellular diffusion coefficient of normal human brain (gray matter) in 3 normal volunteers. We theoretically compared predicted signals and experiment results using a 1.5-tesla magnetic resonance (MR) imaging system. We acquired images using an echo planar imaging (EPI) sequence, applying motion-probing gradient (MPG) pulses in 3 directions. We periodically performed numerical simulations for various combinations of membrane permeability and intracellular diffusion coefficients using the finite-difference method. By minimizing the difference between signals obtained experimentally and those from numerical simulation, we could estimate membrane permeability (76+/-9 mm2/s mum) and intracellular diffusion coefficient (1.0+/-0.0 mm2/s) for the human brain. The estimated membrane permeability was the criterion value for diagnosing disease in gray matter. PMID:19336983

Imae, Toshikazu; Shinohara, Hiroyuki; Sekino, Masaki; Ueno, Shoogo; Ohsaki, Hiroyuki; Mima, Kazuo; Ohtomo, Kuni

2009-01-01

319

A numerical method for determination of moisture transfer coefficient according to the diffusion moisture profiles  

Microsoft Academic Search

For a set of the measured diffusion moisture profiles, a numerical method for determination of moisture transfer coefficient\\u000a D(w, t) is suggested. The transfer coefficient is found as a sum of the degree $$\\u000ap_0 w^{p(t)} \\u000a$$ and exponential $$\\u000aAe^{\\\\mu (w - v_0 )} \\u000a$$ functions of the moisture concentration w, as opposite to the previous works. The exponent

E. Pavlusová; M. Pavlus; I. Sarhadov; I. V. Amirkhanov; T. P. Puzynina; I. V. Puzynin

2008-01-01

320

Non-Fermi liquid behavior of the drag and diffusion coefficients in QED plasma  

SciTech Connect

We calculate the drag and diffusion coefficients in low temperature QED plasma and go beyond the leading order approximation. The non-Fermi-liquid behavior of these coefficients are clearly revealed. We observe that the subleading contributions due to the exchange of soft transverse photon in both cases are larger than the leading order terms coming from the longitudinal sector. The results are presented in closed form at zero and low temperature.

Sarkar, Sreemoyee; Dutt-Mazumder, Abhee K. [High Energy Nuclear and Particle Physics Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata-700 064 (India)

2011-11-01

321

In-reactor experiment and the tritium diffusion coefficient in molten lithium–tin alloy  

Microsoft Academic Search

The measurement of the tritium diffusion coefficient in molten Li20Sn80 alloy was carried out using an in-reactor tritium release experiment. The analysis of the measurements is based on a diffusion-controlled steady state model. When the hydrogen partial pressure was higher than 1100 Pa in the purge gas, and the temperature was 873 K or higher, it satisfied the requirements of

Y. Kang; Takayuki Terai

2004-01-01

322

Characterisation of the gas transport properties of porous materials by determining the radon diffusion coefficient  

Microsoft Academic Search

A method for the determination of the diffusion coefficient of materials by using the radioactive gas radon is presented.\\u000a This gas is inert and extremely low concentrations can be detected because of the radioactive decay. The method was applied\\u000a to mortars and concretes in order to optimise their composition with respect to a low radon diffusion rate. These optimised\\u000a materials

T. Klink; K. Gaber; E. Schlattner; M. J. Setzer

1999-01-01

323

Self-Diffusion Coefficient of fcc Mg: First-Principles Calculations and SemiEmpirical Predictions  

Microsoft Academic Search

First-principles calculations and semi-empirical equations are employed to determine the self-diffusion mobility of fcc Mg.\\u000a All factors entering the vacancy-mediated self-diffusion coefficient, which include the equilibrium lattice parameter, the\\u000a enthalpy of vacancy formation and atom migration, and the vibrational entropy of vacancy formation as well as the effective\\u000a frequency, are evaluated with the local density approximation (LDA) and generalized gradient

Dongdong Zhao; Yi Kong; Aijun Wang; Liangcai Zhou; Senlin Cui; Xiaoming Yuan; Lijun Zhang; Yong Du

2011-01-01

324

Pc 5 Spectral Density at ULTIMA stataions and its Radial Diffusion Coefficients for REE  

NASA Astrophysics Data System (ADS)

Pc 5 magnetic pulsations with frequencies between 1.67 and 6.67 mHz, are believed to contribute to the Relativistic Electron Enhancement (REE) in the outer radiation belt during magnetic storms. Ground-based observations suggested that high-speed solar wind and large-amplitude Pc 5 waves with a long duration during the storm recovery phase are closely associated with the production of relativistic electrons [Baker et al., 1998; Rostoker et al., 1998; Mathie and Mann, 2000; O’Brien et al., 2001, 2003]. On the other hand, many relativistic electron acceleration mechanisms have been proposed theoretically. They are separated roughly into two themes: in situ acceleration at L lower than 6.6 by wave particle interactions (as internal source acceleration mechanisms) [Liu et al., 1999; Summers et al., 1999; Summers and Ma, 2000] and acceleration by radial diffusion to transport and accelerate a source population of electrons from the outer to the inner magnetosphere (as external source acceleration mechanisms) [Elkington et al., 1999, 2003; Hudson et al., 2000; Kim et al., 2001]. One possible external source acceleration mechanism is the resonant interaction with ULF toroidal and poloidal waves. In order to verify which of the two mechanisms is more effective for the REE, we have to examine the time variation of electron phase space density. Electron phase space density is not directly measured, but we can estimate radial diffusion coefficients using observational electric and magnetic data. The goal of this paper is to get more reliable radial diffusion coefficient from ground-based observational magnetic field and to show reasonability of it for radial diffusion model. We use the global magnetometer data obtained from ULTIMA (Ultra Large Terrestrial International Magnetic Array, see http://www.serc.kyushu-u.ac.jp/ultima/ultima.html) stations, to precisely define the radial diffusion timescales. The ULTIMA includes McMAC, CARISAM, 210MM and MAGDAS/CPMN magnetometer arrays. The radial diffusion coefficient can be given from the magnetic field power spectral density as a function of L, frequency (f) and m-number (m) in the Pc 5 frequency range during the REE related magnetic storms [see Brautigam et al., 2005]. We can fit Pc 5 power spectral density (L, f, m) using the ULTIMA data. The m-number of global Pc 5 pulsation on the ground is found to be almost less than 5. This is consistent with m-number required in the radial diffusion theory by Elkington et al. [1999, 2003]. We will compare the observationally estimated diffusion coefficient with theoretical diffusion coefficient [e.g. Elkington et al., 2006], and discuss adequacy of our diffusion coefficient.

Fujimoto, A.; Tokunaga, T.; Abe, S.; Uozumi, T.; Yoshikawa, A.; Mann, I. R.; Chi, P. J.; Engebretson, M. J.; Yumoto, K.

2009-12-01

325

Diffusion coefficient, correlation function, and power spectral density of velocity fluctuations in monolayer graphene  

NASA Astrophysics Data System (ADS)

In this paper, the diffusivity in suspended monolayer graphene at low and high electric fields is investigated. The knowledge of this quantity and its dependence on the electric field is of primary importance not only for the investigation of the electronic transport properties of this material but also for the development of accurate drift-diffusion models. The results have been obtained by means of an ensemble Monte Carlo simulation. For the calculation of the diffusion coefficient, two different methods are considered, one based on the second central moment and the other one based on the Fourier analysis of velocity fluctuations, which are directly related to the noise behaviour at high frequencies. The diffusion coefficient is analyzed considering both parallel and transversal directions with regard to the applied field. Taking into account the importance of degeneracy in this material, the calculations are properly performed by considering an excess electron population obeying a linearized Boltzmann transport equation, which allows studying in an adequate fashion the diffusivity phenomena. The results show the importance of degeneracy effects at very low fields in which transport is mainly dominated by acoustic phonon scattering. Values of the diffusion coefficient larger than 40 000 cm2/Vs are obtained for a carrier concentration equal to 1012 cm-2. The correlation function of instantaneous velocity fluctuation is explained in terms of the wavevector distribution, and their power spectral density is evaluated in the THz range, showing an important dependence on the applied field and being strongly related to microscopic transport processes.

Rengel, R.; Martín, M. J.

2013-10-01

326

The effect of recombination and attachment on meteor radar diffusion coefficient profiles  

NASA Astrophysics Data System (ADS)

Estimates of the ambipolar diffusion coefficient producedusing meteor radar echo decay times display an increasing trend below 80-85 km, which is inconsistent with a diffusion-only theory of the evolution of meteor trails. Data from the 33 MHz meteor radar at King Sejong Station, Antarctica, have been compared with observations from the Aura Earth Observing System Microwave Limb Sounder satellite instrument. It has been found that the height at which the diffusion coefficient gradient reverses follows the height of a constant neutral atmospheric density surface. Numerical simulations of meteor trail diffusion including dissociative recombination with atmospheric ions and three-body attachment of free electrons to neutral molecules indicate that three-body attachment is responsible for the distortion of meteor radar diffusion coefficient profiles at heights below 90 km, including the gradient reversal below 80-85 km. Further investigation has revealed that meteor trails with low initial electron line density produce decay times more consistent with a diffusion-only model of meteor trail evolution.

Lee, C. S.; Younger, J. P.; Reid, I. M.; Kim, Y. H.; Kim, J.-H.

2013-04-01

327

Molecular dynamics simulation of imidazolium-based ionic liquids. I. Dynamics and diffusion coefficient  

NASA Astrophysics Data System (ADS)

Molecular dynamics simulations are used to study the dynamics and transport properties of 12 room-temperature ionic liquids of the 1-alkyl-3-methylimidazolium [amim]+ (alkyl=methyl, ethyl, propyl, and butyl) family with PF6-, NO3-, and Cl- counterions. The explicit atom transferable force field of Canongia Lopes et al. [J. Phys. Chem. B 108, 2038 (2004)] is used in the simulations. In this first part, the dynamics of the ionic liquids are characterized by studying the mean-square displacement (MSD) and the velocity autocorrelation function (VACF) for the centers of mass of the ions at 400 K. Trajectory averaging was employed to evaluate the diffusion coefficients at two temperatures from the linear slope of MSD(t) functions in the range of 150-300 ps and from the integration of the VACF(t) functions at 400 K. Detailed comparisons are made between the diffusion results from the MSD and VACF methods. The diffusion coefficients from the integration of the VACFs are closer to experimental values than the diffusion coefficients calculated from the slope of MSDs. Both methods can show good agreement with experiment in predicting relative trends in the diffusion coefficients and determining the role of the cation and anion structures on the dynamical behavior of this family of ionic liquids. The MSD and self-diffusion of relatively heavier imidazolium cations are larger than those of the lighter anions from the Einstein results, except for the case of [bmim][Cl]. The cationic transference number generally decreases with temperature, in good agreement with experiments. For the same anion, the cationic transference numbers decrease with increasing length of the alkyl chain, and for the same cation, the trends in the cationic transference numbers are [NO3]-<[Cl]-<[PF6]-. The trends in the diffusion coefficient in the series of cations with identical anions are [emim]+>[pmim]+>[bmim]+ and those for anions with identical cations are [NO3]->[PF6]->[Cl]-. The [dmim]+ has a relatively low diffusion coefficient due to its symmetric structure and good packing in the liquid phase. The major factor for determining the magnitude of the self-diffusion is the geometric shape of the anion of the ionic liquid. Other important factors are the ion size and the charge delocalization in the anion.

Kowsari, M. H.; Alavi, Saman; Ashrafizaadeh, Mahmud; Najafi, Bijan

2008-12-01

328

Molecular dynamics simulation of imidazolium-based ionic liquids. I. Dynamics and diffusion coefficient.  

PubMed

Molecular dynamics simulations are used to study the dynamics and transport properties of 12 room-temperature ionic liquids of the 1-alkyl-3-methylimidazolium [amim](+) (alkyl = methyl, ethyl, propyl, and butyl) family with PF(6)(-), NO(3)(-), and Cl(-) counterions. The explicit atom transferable force field of Canongia Lopes et al. [J. Phys. Chem. B 108, 2038 (2004)] is used in the simulations. In this first part, the dynamics of the ionic liquids are characterized by studying the mean-square displacement (MSD) and the velocity autocorrelation function (VACF) for the centers of mass of the ions at 400 K. Trajectory averaging was employed to evaluate the diffusion coefficients at two temperatures from the linear slope of MSD(t) functions in the range of 150-300 ps and from the integration of the VACF(t) functions at 400 K. Detailed comparisons are made between the diffusion results from the MSD and VACF methods. The diffusion coefficients from the integration of the VACFs are closer to experimental values than the diffusion coefficients calculated from the slope of MSDs. Both methods can show good agreement with experiment in predicting relative trends in the diffusion coefficients and determining the role of the cation and anion structures on the dynamical behavior of this family of ionic liquids. The MSD and self-diffusion of relatively heavier imidazolium cations are larger than those of the lighter anions from the Einstein results, except for the case of [bmim][Cl]. The cationic transference number generally decreases with temperature, in good agreement with experiments. For the same anion, the cationic transference numbers decrease with increasing length of the alkyl chain, and for the same cation, the trends in the cationic transference numbers are [NO(3)](-) < [Cl](-) < [PF(6)](-). The trends in the diffusion coefficient in the series of cations with identical anions are [emim](+) > [pmim](+) > [bmim](+) and those for anions with identical cations are [NO(3)](-) > [PF(6)](-) > [Cl](-). The [dmim](+) has a relatively low diffusion coefficient due to its symmetric structure and good packing in the liquid phase. The major factor for determining the magnitude of the self-diffusion is the geometric shape of the anion of the ionic liquid. Other important factors are the ion size and the charge delocalization in the anion. PMID:19071929

Kowsari, M H; Alavi, Saman; Ashrafizaadeh, Mahmud; Najafi, Bijan

2008-12-14

329

Diffusion-weighted imaging in the prostate: an apparent diffusion coefficient comparison of half-Fourier acquisition single-shot turbo spin-echo and echo planar imaging  

Microsoft Academic Search

Prostate cancer detection using diffusion-weighted imaging is highly affected by the accuracy of the apparent diffusion coefficient (ADC) values in an image. Echo planar imaging (EPI) is a fast sequence commonly used for diffusion imaging but has inherent magnetic susceptibility and chemical shift artefacts associated. A diffusion sequence that is less affected by these artefacts is therefore advantageous. The half-Fourier

Ben Babourina-Brooks; Gary J. Cowin; Deming Wang

330

Diffusion Coefficients from Molecular Dynamics Simulations in Binary and Ternary Mixtures  

NASA Astrophysics Data System (ADS)

Multicomponent diffusion in liquids is ubiquitous in (bio)chemical processes. It has gained considerable and increasing interest as it is often the rate limiting step in a process. In this paper, we review methods for calculating diffusion coefficients from molecular simulation and predictive engineering models. The main achievements of our research during the past years can be summarized as follows: (1) we introduced a consistent method for computing Fick diffusion coefficients using equilibrium molecular dynamics simulations; (2) we developed a multicomponent Darken equation for the description of the concentration dependence of Maxwell-Stefan diffusivities. In the case of infinite dilution, the multicomponent Darken equation provides an expression for [InlineEquation not available: see fulltext.] which can be used to parametrize the generalized Vignes equation; and (3) a predictive model for self-diffusivities was proposed for the parametrization of the multicomponent Darken equation. This equation accurately describes the concentration dependence of self-diffusivities in weakly associating systems. With these methods, a sound framework for the prediction of mutual diffusion in liquids is achieved.

Liu, Xin; Schnell, Sondre K.; Simon, Jean-Marc; Krüger, Peter; Bedeaux, Dick; Kjelstrup, Signe; Bardow, André; Vlugt, Thijs J. H.

2013-07-01

331

Measurement and modeling of CO2 diffusion coefficient in Saline Aquifer at reservoir conditions  

NASA Astrophysics Data System (ADS)

Storage of CO2 in deep saline aquifers is a promising techniques to mitigate global warming and reduce greenhouse gases (GHG). Correct measurement of diffusivity is essential for predicting rate of transfer and cumulative amount of trapped gas. Little information is available on diffusion of GHG in saline aquifers. In this study, diffusivity of CO2 into a saline aquifer taken from oil field was measured and modeled. Equilibrium concentration of CO2 at gas-liquid interface was determined using Henry's law. Experimental measurements were reported at temperature and pressure ranges of 32-50°C and 5900-6900 kPa, respectively. Results show that diffusivity of CO2 varies between 3.52-5.98×10-9 m2/s for 5900 kPa and 5.33-6.16×10-9 m2/s for 6900 kPa initial pressure. Also, it was found that both pressure and temperature have a positive impact on the measures of diffusion coefficient. Liquid swelling due to gas dissolution and variations in gas compressibility factor as a result of pressure decay was found negligible. Measured diffusivities were used model the physical model and develop concentration profile of dissolved gas in the liquid phase. Results of this study provide unique measures of CO2 diffusion coefficient in saline aquifer at high pressure and temperature conditions, which can be applied in full-field studies of carbon capture and sequestration projects.

Azin, Reza; Mahmoudy, Mohamad; Raad, Seyed Mostafa Jafari; Osfouri, Shahriar

2013-12-01

332

Self-diffusion coefficients of methane or ethane mixtures with hydrocarbons at high pressure by NMR  

SciTech Connect

Self-diffusion coefficients have been measured in homogeneous mixtures of methane + hexane, ethane + hexane, methane + octane, ethane + octan, methane + decane, ethane + decane, and methane + hexane + benzene over the whole concentration range, at 303.2 K and 333.2 K and 30 MPa, 40 MPa, and 50 MPa. The experiments were performed in a glass cell by application of the NMR-PGSE technique. The estimated accuracy of the measurements is {+-}5%. Experimental self-diffusion coefficients were compared to the Sigmund correlation, which was found not to fit the experimental data. The main motivation for this work was the need for diffusion data in reservoir studies. Gas injection in heterogeneous or fractured reservoirs and gas diffusion through cap rock are processes where diffusion may play a significant role. Although these processes occur in porous oil- and water-saturated rock, diffusion data pertaining to bulk liquids are useful because the effect of the tortuosity of the rock can be represented by formation resistivity data. Moreover, a diffusion model at the molecular level can include rock-fluid interactions.

Helbaek, M. [Nord-Troendelag Coll., Levanger (Norway). Dept. of Engineering] [Nord-Troendelag Coll., Levanger (Norway). Dept. of Engineering; Hafskjold, B.; Dysthe, D.K.; Soerland, G.H. [Norwegian Univ. of Science and Technology, Trondheim (Norway). Dept. of Physical Chemistry] [Norwegian Univ. of Science and Technology, Trondheim (Norway). Dept. of Physical Chemistry

1996-05-01

333

VARYING COEFFICIENT MODEL FOR MODELING DIFFUSION TENSORS ALONG WHITE MATTER TRACTS  

PubMed Central

Diffusion tensor imaging provides important information on tissue structure and orientation of fiber tracts in brain white matter in vivo. It results in diffusion tensors, which are 3×3 symmetric positive definite (SPD) matrices, along fiber bundles. This paper develops a functional data analysis framework to model diffusion tensors along fiber tracts as functional data in a Riemannian manifold with a set of covariates of interest, such as age and gender. We propose a statistical model with varying coefficient functions to characterize the dynamic association between functional SPD matrix-valued responses and covariates. We calculate weighted least squares estimators of the varying coefficient functions for the Log-Euclidean metric in the space of SPD matrices. We also develop a global test statistic to test specific hypotheses about these coefficient functions and construct their simultaneous confidence bands. Simulated data are further used to examine the finite sample performance of the estimated varying co-efficient functions. We apply our model to study potential gender differences and find a statistically significant aspect of the development of diffusion tensors along the right internal capsule tract in a clinical study of neurodevelopment.

Yuan, Ying; Zhu, Hongtu; Styner, Martin; Gilmore, John H.; Marron, J. S.

2012-01-01

334

Diffusion Coefficients and Heats of Mixing in Aqueous Alkanolamines. Annual Report, January-December 1992.  

National Technical Information Service (NTIS)

The objective of the work is to provide accurate data on diffusion coefficients and heats of absorption of acid gases in aqueous amine solutions to assist in the design of economical new amine treating systems and to improve the efficiency of existing pla...

R. L. Rowley J. L. Oscarson

1993-01-01

335

Modeling ion exchange in glass with concentration-dependent diffusion coefficients and mobilities  

Microsoft Academic Search

Multimode buried waveguides made in silicate glass by field-assisted ion exchange present very asymmetric profiles. We show how this phenomenon originates in the large dependence of the kinetics on the local ion concentrations. For this purpose, we derive an interdiffusion equation that includes the effects of concentration-dependent diffusion coefficients and mobilities. We show how to deduce this dependence from measurements

Alexandru I. Lupascu; Antoine P. Kevorkian; Thierry Boudet; Francoise Saint-Andre; Dominique Persegol; Michel Levy

1996-01-01

336

Longitudinal and Transverse Diffusion Coefficients of Mass-Identified n(+) And N2(+) Ions in Nitrogen.  

National Technical Information Service (NTIS)

Longitudinal and transverse diffusion coefficients for mass-identified N(+) and N2(+) ions in nitrogen in an applied electric field have been measured at room temperature on the E/N range. For E/N below about 30 x 10 to the minus 17th power V cm2 the long...

J. T. Moseley R. M. Snuggs D. W. Martin E. W. McDaniel

1968-01-01

337

Backscattering coefficient and drift-diffusion mobility extraction in short channel MOS devices  

Microsoft Academic Search

A new method for the extraction of the backscattering coefficient in nanoMOS devices has been demonstrated. The method, which relies on mobility measurements in linear operation, proves very simple and reliable for the determination of the ballistic rate of transport. Moreover, it allows to obtain the drift-diffusion mobility corrected from ballistic effects and therefore to make a diagnostic of the

I. Pappas; G. Ghibaudo; C. A. Dimitriadis; C. Fenouilletberanger

2009-01-01

338

On Determining Magnetospheric Diffusion Coefficients from the Observed Effects of Jupiter’s Satellite Io  

Microsoft Academic Search

Several previously proposed techniques for determining the radial diffusion coefficient from the observed effects of the inner Jovian satellites on the energetic particle fluxes are discussed, and important shortcomings are pointed out. A new method is proposed which avoids the most important shortcoming by dealing with data from regions somewhat removed from the actual sweeping region. The new technique is

M. F. Thomsen; C. K. Goertz; J. A. Van Allen

1977-01-01

339

Measurement of Diffusion Coefficients for the Reduction of Copper(I) and (II) in Acetonitrile.  

National Technical Information Service (NTIS)

Values of the diffusion coefficients in the reductions Cu(II) to Cu(I), Cu(II) to Cu(0), and Cu(I) to Cu(0) have been determined. Owing to the fast exchange of coordinated and uncoordinated acetonitrile molecules, the greater probability of ion-pair forma...

R. R. Bessette, J. W. Olver

1968-01-01

340

Experimental determination of the theophylline diffusion coefficient in swollen sodium-alginate membranes  

Microsoft Academic Search

In this paper attention is focused on the determination of the drug diffusion coefficient in a swollen polymeric membrane referring to a recent mathematical model (linear model). The main advantage deriving from its use is that, despite its analytical nature and its ability to account for the most important aspects characterising a permeation experiment, it can also be applied in

M. Grassi; I. Colombo; R. Lapasin

2001-01-01

341

A method for measuring effective radon diffusion coefficients in radon barriers by using modified Lucas cells  

Microsoft Academic Search

Radon proof barriers are used for lowering of radon transport from the soil into the house and the determination of the radon diffusion coefficient is an important parameter to be determined in order to design the minimal thickness of the radon proof insulation. A method has been developed in our laboratory by using modified Lucas cells connected to a radon

L. S. Quindos Poncela; P. L. Fernandez; J. Gomez Arozamena; C. Sainz Fernandez

2005-01-01

342

The Value of Apparent Diffusion Coefficient Maps in Early Cerebral Ischemia  

Microsoft Academic Search

BACKGROUND AND PURPOSE: Prediction of the regions of the ischemic penumbra that are likely to progress to infarction is of great clinical interest. Whether lowered apparent diffusion coefficient (ADC) values were present in the ischemic penumbra of patients presenting with acute ischemic stroke and were specific to regions of the penumbra that proceeded to infarction was investigated. METHODS: Nineteen patients

Patricia M. Desmond; Amanda C. Lovell; Andrew A. Rawlinson; Mark W. Parsons; P. Alan Barber; Qing Yang; Ting Li; David G. Darby; Richard P. Gerraty; Steven M. Davis; Brian M. Tress

2001-01-01

343

Correlation Between the Field Line and Particle Diffusion Coefficients in the Stochastic Fields of a Tokamak  

Microsoft Academic Search

We use the method of quasi-magnetic surfaces to calculate the correlation between the field line and particle diffusion coefficients. The magnetic topology of a tokamak is perturbed by a spectrum of neighboring resonant resistive modes. The Hamiltonian equations of motion for the field line are integrated numerically. Poincare plots of the quasi-magnetic surfaces are generated initially and after the field

Mark Calvin; Alkesh Punjabi

1996-01-01

344

Determination of the Zincate Diffusion Coefficient and Its Application to Alkaline Battery Problems.  

National Technical Information Service (NTIS)

The diffusion coefficient for the zincate ion at 24 C was found to be 9.9 X 10 to the minus 7th power squared cm per sec + or - 30 percent in 45 percent potassium hydroxide and 1.4 x 10 to the minus 7 squared cm per sec + or - 25 percent in 40 percent sod...

C. E. May

1978-01-01

345

Determination of the zincate diffusion coefficient and its application to alkaline battery problems  

Microsoft Academic Search

The diffusion coefficient for the zincate ion at 24 C was found to be 9.9 X 10 to the minus 7th power squared cm per sec + or - 30 percent in 45 percent potassium hydroxide and 1.4 x 10 to the minus 7 squared cm per sec + or - 25 percent in 40 percent sodium hydroxide. Comparison of

C. E. May; Harold E. Kautz

1978-01-01

346

DIFFUSION COEFFICIENTS OF CRITICAL RADIONUCLIDES FROM RADIOACTIVE WASTE IN GEOLOGICAL MEDIUM  

Microsoft Academic Search

Diffusion (Ds) and distribution coefficients (K d) are needed to assess the migration of radionuclides through the geological medium proposed to locate the low and intermediate level radioactive waste disposal (an intermediate level radioactive waste is considered that waste who have an activity less than 10 4 Ci\\/m 3 ).

C. Bucur; A. Popa; C. Arsene; M. Olteanu

2000-01-01

347

Applicability of Simplified Models for the Estimation of Ion Exchange Diffusion Coefficients in Zeolites  

Microsoft Academic Search

The applicability of simplified models for the determination of ion exchange diffusion coefficients in zeolites is examined. The simplified models examined are Vermeulen's, Paterson's, and Nernst–Plank's approximations for isotopic and ion exchange processes, used in ion exchange systems analysis. Parameter analysis indicates the limits for fractional attainment of equilibrium U(t), the ratio of exchangeable ions in liquid to solid phase

Vassilis J. Inglezakis; Helen P. Grigoropoulou

2001-01-01

348

Normed Bellman Equation with Degenerate Diffusion Coefficients and Its Application to Differential Equations.  

National Technical Information Service (NTIS)

The purpose of this paper is to prove the existence and uniqueness of generalized solution of the normed bellman equation with degenerate diffusion coefficients and also to prove that this unique solution is the cost function of a stochastic control probl...

M. Fujisaki

1987-01-01

349

The Diffusion Coefficient of Ferricyanide in Aqueous Potassium Chloride Solutions with and without Polyethylene Oxide.  

National Technical Information Service (NTIS)

The diffusion coefficient of the ferricyanide ion was determined in the temperature range 20-35C in equimolar solutions of ferri- and ferro-cyanide (.005M) with potassium chloride (0,5; 1,0; 2,0 M) as a carrier electrolyte and with and without polyethylen...

J. J. Graaf

1975-01-01

350

Single-relaxation-time lattice Boltzmann scheme for advection-diffusion problems with large diffusion-coefficient heterogeneities and high-advection transport  

NASA Astrophysics Data System (ADS)

The paper presents an approach that extends the flexibility of the standard lattice Boltzmann single relaxation time scheme in terms of spatial variation of dissipative terms (e.g., diffusion coefficient) and stability for high Péclet mass transfer problems. Spatial variability of diffusion coefficient in SRT is typically accommodated through the variation of relaxation time during the collision step. This method is effective but cannot deal with large diffusion coefficient variations, which can span over several orders of magnitude in some natural systems. The approach explores an alternative way of dealing with large diffusion coefficient variations in advection-diffusion transport systems by introducing so-called diffusion velocity. The diffusion velocity is essentially an additional convective term that replaces variations in diffusion coefficients vis-à-vis a chosen reference diffusion coefficient which defines the simulation time step. Special attention is paid to the main idea behind the diffusion velocity formulation and its implementation into the lattice Boltzmann framework. Finally, the performance, stability, and accuracy of the diffusion velocity formulation are discussed via several advection-diffusion transport benchmark examples. These examples demonstrate improved stability and flexibility of the proposed scheme with marginal consequences on the numerical performance.

Perko, Janez; Patel, Ravi A.

2014-05-01

351

Expression of optical diffusion coefficient in high-absorption turbid media  

NASA Astrophysics Data System (ADS)

The optical diffusion coefficient in a homogeneous turbid medium with high absorption was determined by steady-state measurements of the light transmission under the infinite-boundary condition. The intensity of the transmission was well described by the solution of the optical diffusion equation. Moreover, the optical diffusion coefficient D was given by a constant, , where is the reduced scattering coefficient, up to the absorption coefficient of about . These results mean that attenuation by absorption only contributes to exponential attenuation along the optical path defined by the scattering coefficient and geometry of the system even in high-absorption turbid media such as the pathological living tissues of bleeding or haematoma.

Nakai, T.; Nishimura, G.; Yamamoto, K.; Tamura, M.

1997-12-01

352

Thaumatin Crystallization Aboard the International Space Station Using Liquid-Liquid Diffusion in the Enhanced Gaseous Nitrogen Dewar (EGN)  

NASA Technical Reports Server (NTRS)

This paper reports results from the first biological crystal growth experiment on the International Space Station (ISS). Crystals of thaumatin were grown using liquid-liquid diffusion in Tygon tubing transported in the Enhanced Gaseous Nitrogen Dewar (EGN). Different Volume ratios and concentrations of protein and precipitant were used to test different adaptations of the vapor diffusion crystallization recipe to the liquid-liquid diffusion method. The EGN warmed up from -196 C to 0 C in about four days, about the same time it took to warm from 0 C to 20 C. The temperature within the EGN was 20 - 24 C for the majority of the experiment. Air gaps that blocked liquid-liquid diffusion formed in the tubes. Nonetheless, crystals were grown. Synchrotron diffraction data collected from the best space grown crystal extended to 1.28 Angstroms, comparable to previous studies of space-grown thaumatin crystals. The resolution of the best ground control crystal was only 1.47 Angstroms. It is not clear if the difference in diffraction limit is due to factors other than crystal size. Improvements in temperature control and the elimination of air gaps are needed, but the results show that EGN on the ISS can be used to produce space grown crystals that diffract to high resolution.

Kundrot, Craig; Barnes, Cindy L.; Snell, Edward H.; Stinson, Thomas N. (Technical Monitor)

2002-01-01

353

Theoretical prediction of thermal diffusion coefficients for ternary hydrocarbon mixtures based on the irreversible thermodynamics theory  

NASA Astrophysics Data System (ADS)

An accurate thermodiffusion model is of paramount importance to the petroleum industry for the prediction of the compositional variation in hydrocarbon reservoirs. Several theoretical models have been developed. Kempers and Firoozabadi models are the latest two models, which are not only applicable for binary mixtures but also for multi-component mixtures. In this paper, we applied the Firoozabadi model to a ternary hydrocarbon mixture of n-Dodecane, n-Butane and Methane with different mass fraction. It reveals that the accuracy of the thermal diffusion coefficients for a specific mixture of interest relies on the accuracy of the thermodynamic properties from equations of state, corresponding Fick's diffusion coefficients, and the thermal diffusion modeling.

Jaber, T. J.; Yan, Y.; Pan, S.; Saghir, M. Z.

2009-10-01

354

Effect of computed horizontal diffusion coefficients on two-dimensional N2O model distributions  

NASA Technical Reports Server (NTRS)

The effects of horizontal diffusion coefficients K(yy) and K(yz), computed directly from the residual circulation, on the N2O distribution in a photochemical model were investigated, using a modified version of the two-dimensional model of Guthrie et al. (1984). The residual circulation was computed using the NMC's temperature data and the heating rates reported by Rosenfield et al. (1987). As compared with the effect of the residual circulation alone, the use of horizontal diffusion coefficients produced substantial changes in the N2O distribution and increased the N2O's lifetime values by a few percent. It is suggested that trace gases, such as CH4, CFCl3, CF2Cl2, CH3Cl, and CCl4, which impact the NO(x), HO(x), and Cl(x) radical distributions and therefore ozone, will be influenced in a similar manner by the addition of more realistic diffusion fields.

Jackman, Charles H.; Guthrie, Paul D.; Schoeberl, Mark R.; Newman, Paul A.

1988-01-01

355

Calculation of diffusion coefficients for aqueous organic species at temperatures from 0 to 350 °C  

NASA Astrophysics Data System (ADS)

Evaluation of hydrocarbon transport through the pore spaces of saturated rock in the subsurface as a function of time and distance requires accurate values of diffusion coefficients for aqueous organic species. Analysis of aqueous tracer diffusion coefficients ( D0) for normal alkanes, alcohols, amides, carboxylic acids, alkylbenzenes, and alkylnaphthalenes reported in the literature indicates that diffusional activation energies decrease with increasing temperature, reaching a constant limiting value of ~3300 cal mol -1 at temperatures a: 1?00°C. This observation is consistent with the modified Arrhenius expression reported by OELKERS and HELGESON (1988). The Kirkwood-Riseman equation is used to predict D0 values as a function of the polymer chain length of hydrocarbons. Regression of experimental D0 data with a combined expression of the Kirkwood-Riseman and modified Arrhenius equations yields parameters which permit calculation of tracer diffusion coefficients for over 50 aqueous organic species at temperatures from 0° to 350°C and Psat. ( psat refers to pressures corresponding to the liquid-vapor equilibrium curve for H 2O at temperatures greater than 100°C and 1 bar at lower temperatures.) Resulting values of D0 permit evaluation of the extent of diffusional mass transfer in both contaminated near-surface environments and in the porewater adjoining oil field reservoirs. The computed tracer diffusion coefficients, which are qualitatively similar to D0 values previously calculated for aqueous ions, increase substantially with increasing temperature. For example, the tracer diffusion coefficient of aqueous toluene increases from 0.36 to 27.1 × 10 -5 cm 2sec-1 in response to increasing temperature from 0 to 350°C.

Oelkers, Eric H.

1991-12-01

356

Compilation and evaluation of gas-phase diffusion coefficients of inorganic reactive trace gases in the atmosphere  

NASA Astrophysics Data System (ADS)

Diffusion of gas molecules to the surface is the first step for all gas-surface reactions. Gas phase diffusion can influence and sometimes even limit the overall rates of these reactions; however, there is no database of the gas phase diffusion coefficients of atmospheric reactive trace gases. Here we compile and evaluate, for the first time, the diffusivities (pressure-independent diffusion coefficients) of atmospheric inorganic reactive trace gases reported in the literature. The measured diffusivities are then compared with estimated values using a semi-empirical method developed by Fuller et al. (1966). The diffusivities estimated using Fuller's method are typically found to be in good agreement with the measured values within ±30%, and therefore Fuller's method can be used to estimate the diffusivities of trace gases for which experimental data are not available. The two experimental methods used in the atmospheric chemistry community to measure the gas phase diffusion coefficients are also discussed.

Tang, M. J.; Cox, R. A.; Kalberer, M.

2014-06-01

357

Network modeling of diffusion coefficients for porous media: I. Theory and model development  

SciTech Connect

Gas diffusion often dominates constituent transport in porous media and is dependent on pore geometry, water content, and water distribution in a porous medium. Network models of porous media offer the ability to investigate the influence and interaction of pore-scale porous media properties and fluid properties on macroscopic properties of the medium. This study was conducted to investigate the macroscopic relative gas diffusion coefficient vs. air-filled porosity relationship (diffusion characteristic) of porous media using a network modeling approach. A cubic sphere-and-tube network model of porous media was adapted from petroleum engineering using Fick`s law and the principle of conservation of mass to simulate one-dimensional, steady-state, isothermal, isobaric, molecular diffusion of a dilute binary gas in a nonadsorbing porous medium containing a single nonwetting fluid (air) and a single wetting fluid (water). The network model simulates hysteresis in air and water distribution in porous media for boundary drying and wetting curves of the soil water characteristic and demonstrates the effect of air-filled porosity, Henry`s law liquid-gas partitioning coefficient, the ratio between gas- and liquid-phase diffusion rates, and pore geometry on the diffusion characteristic. 41 refs., 8 figs.

Steele, D.D. [North Dakota State Univ., Fargo, ND (United States); Neiber, J.L. [Univ. of Minnesota, St. Paul, MN (United States)

1994-09-01

358

Estimating diffusion coefficients in low-permeability porous media using a macropore column  

SciTech Connect

Diffusion coefficients in an aquitard material were measured by conducting miscible solute transport experiments through a specially constructed macropore column. Stainless steel HPLC columns were prepared in a manner that created an annular region of repacked aquitard material and a central core of medium-grained quartz sand. The column transport approach minimizes volatilization and sorption losses that can be problematic when measuring hydrophobic organic chemical diffusion with diffusion-cell methods or column-sectioning techniques. In the transport experiments, solutes (triated water, 1,2,4-trichlorobenzene, and tetrachloroethene) were transported through the central core by convection and hydrodynamic dispersion and through the low-permeability annulus by radial diffusion. All transport parameters were independently measured except for the effective diffusion coefficient in the aquitard material, which was obtained by model fitting. Batch-determined retardation factors agreed very closely with moment-derived retardation factors determined from the column experiments, and no evidence of pore exclusion was found. A model with retarded diffusion was found to apply, and the effective tortuosity factor of the aquitard material was estimated at an average value of 5.1.

Young, D.F.; Ball, W.P. [Johns Hopkins Univ., Baltimore, MD (United States). Dept. of Geography and Environmental Engineering] [Johns Hopkins Univ., Baltimore, MD (United States). Dept. of Geography and Environmental Engineering

1998-09-01

359

Self-diffusion coefficients and shear viscosity of model nanocolloidal dispersions by molecular dynamics simulation  

NASA Astrophysics Data System (ADS)

The self-diffusion coefficients D of both species in model nanocolloidal dispersions have been computed using molecular dynamics (MD) simulation, in which three-dimensional model spherical colloidal particles were in a molecularly discrete solvent. The effects of the relative density, size, and concentration of the two species were explored. Simulations were carried out at infinite dilution (a single colloidal particle) and at finite packing fractions (many colloidal particles) in the simulation cell using single interaction centers between the model colloidal particles and solvent molecules. The calculations used the Weeks-Chandler-Andersen (WCA) or Lennard-Jones (LJ), interaction potentials between all species. Nanocolloid particles with diameters up to ~6 times the solvent molecule were modeled. At liquidlike densities the self-diffusion coefficients of the colloidal particles, Dc, for all sizes and packing fractions, statistically exhibited no mass dependence but a significant colloid particle size dependence. This can be interpreted in a systematic manner using a Mori series expansion. The first Mori coefficient (which is inversely proportional to particle mass) dominates the value of the self-diffusion coefficient for both species, and which also leads to a formal cancellation of the mass dependence at the order of the first Mori coefficient KB1 (the self-diffusion coefficient is therefore determined by a ``static'' property to this order). The values of Dc at each packing fraction are found to be approximately inversely proportional to the colloidal particle diameter, quantitatively following the same trend as the Stokes-Einstein equation, even for the small colloidal particle sizes and finite colloidal particle concentrations studied here. Another consequence of the dominance of the first Mori coefficient is that the normalized velocity autocorrelation function of the colloidal particle at a short time can be represented well at all state points and packing fractions by the analytic form ~=cos(?0t), where ?0=KB1, which is the so-called Einstein frequency. LJ and WCA systems with otherwise the same system parameters manifest the same oscillation frequency, but the LJ oscillation amplitudes are larger and the values of Dc are smaller. The self-diffusion coefficients and shear viscosities obey a volume fraction dependence similar to that found for much larger colloidal particles.

Nuevo, María J.; Morales, Juan J.; Heyes, David M.

1998-11-01

360

Gamma radiological surveys of the Oak Ridge Reservation, Paducah Gaseous Diffusion Plant, and Portsmouth Gaseous Diffusion Plant, 1990-1993, and overview of data processing and analysis by the Environmental Restoration Remote Sensing Program, Fiscal Year 1995  

SciTech Connect

Three gamma radiological surveys have been conducted under auspices of the ER Remote Sensing Program: (1) Oak Ridge Reservation (ORR) (1992), (2) Clinch River (1992), and (3) Portsmouth Gaseous Diffusion Plant (PORTS) (1993). In addition, the Remote Sensing Program has acquired the results of earlier surveys at Paducah Gaseous Diffusion Plant (PGDP) (1990) and PORTS (1990). These radiological surveys provide data for characterization and long-term monitoring of U.S. Department of Energy (DOE) contamination areas since many of the radioactive materials processed or handled on the ORR, PGDP, and PORTS are direct gamma radiation emitters or have gamma emitting daughter radionuclides. High resolution airborne gamma radiation surveys require a helicopter outfitted with one or two detector pods, a computer-based data acquisition system, and an accurate navigational positioning system for relating collected data to ground location. Sensors measure the ground-level gamma energy spectrum in the 38 to 3,026 KeV range. Analysis can provide gamma emission strength in counts per second for either gross or total man-made gamma emissions. Gross count gamma radiation includes natural background radiation from terrestrial sources (radionuclides present in small amounts in the earth`s soil and bedrock), from radon gas, and from cosmic rays from outer space as well as radiation from man-made radionuclides. Man-made count gamma data include only the portion of the gross count that can be directly attributed to gamma rays from man-made radionuclides. Interpretation of the gamma energy spectra can make possible the determination of which specific radioisotopes contribute to the observed man-made gamma radiation, either as direct or as indirect (i.e., daughter) gamma energy from specific radionuclides (e.g., cesium-137, cobalt-60, uranium-238).

Smyre, J.L.; Moll, B.W.; King, A.L.

1996-06-01

361

Diffusion coefficients from resonant interactions with electrostatic electron cyclotron harmonic waves  

SciTech Connect

Pitch-angle diffusion coefficients have been calculated for resonant interaction with electrostatic electron cyclotron harmonic (ECH) waves using quasilinear diffusion theory. Unlike previous calculations, the parallel group velocity has been included in this study. Further, ECH wave intensity is expressed as a function of wave frequency and wave normal angle with respect to ambient magnetic field. It is found that observed wave electric field amplitudes in Earth's magnetosphere are sufficient to set electrons on strong diffusion in the energy ranges of a few hundred eV. However, the required amplitudes are larger than the observed values for keV electrons and higher by about a factor of 3 compared to past calculations. Required electric field amplitudes are smaller at larger radial distances. It is concluded that ECH waves are responsible for diffuse auroral precipitation of electrons with energies less than about 500 eV.

Tripathi, A. K.; Singhal, R. P. [Department of Applied Physics, Institute of Technology, Banaras Hindu University, Varanasi U.P. 221005 (India)

2009-11-15

362

Measurements of the Fe(3+) diffusion coefficient in Fricke Xylenol gel using optical density measurements.  

PubMed

In Fricke dosimetry, optical density measurements are performed some time after dosimeter irradiation. Values of the diffusion coefficient of Fe(3+) in Fricke Xylenol gel (FXG) are necessary for determining the spatial distribution of the absorbed dose from measurements of the optical density. Five sets of FXG dosimeters, kept at different constant temperatures, were exposed to collimated 6MV photons. The optical density profile, proportional to the Fe(3+) concentration, at the boundary between irradiated and non-irradiated parts of each dosimeter was measured periodically over a period of 60h. By comparing the experimental data with a function that accounts for the unobserved initial concentration profile of Fe(3+) in the FXG, we obtained diffusion coefficients 0.30±0.05, 0.40±0.05, 0.50±0.05, 0.60±0.05 and 0.80±0.05mm(2)/h for the temperatures 283.0±0.5, 286.0±0.5, 289.0±0.5, 292.0±0.5, and 296.0±0.5K, respectively. The activation energy of Fe(3+) diffusion in the gel, 0.54±0.06eV, was determined from the temperature dependence of the diffusion coefficients. PMID:24836903

de Oliveira, Lucas Nonato; Sampaio, Francisco Glaildo Almeida; Moreira, Marcos Vasques; de Almeida, Adelaide

2014-08-01

363

An interpretation of potential scale dependence of the effectivematrix diffusion coefficient  

SciTech Connect

Matrix diffusion is an important process for solutetransport in fractured rock, and the matrix diffusion coefficient is akey parameter for describing this process. Previous studies indicatedthat the effective matrix diffusion coefficient values, obtained from alarge number of field tracer tests, are enhanced in comparison with localvalues and may increase with test scale. In this study, we have performednumerical experiments to investigate potential mechanisms behind possiblescale-dependent behavior. The focus of the experiments is on solutetransport in flow paths having geometries consistent with percolationtheories and characterized by local flow loops formed mainly bysmall-scale fractures. The water velocity distribution through a flowpath was determined using discrete fracture network flow simulations, andsolute transport was calculated using a previously derivedimpulse-response function and a particle-tracking scheme. Values foreffective (or up-scaled) transport parameters were obtained by matchingbreakthrough curves from numerical experiments with an analyticalsolution for solute transport along a single fracture. Results indicatethat a combination of local flow loops and the associated matrixdiffusion process, together with scaling properties in flow pathgeometry, seems to be the dominant mechanism causing the observed scaledependence of theeffective matrix diffusion coefficient (at a range ofscales).

Liu, H.H.; Zhang, Y.Q.; Zhou, Q.; Molz, F.J.

2005-11-30

364

Measurement and correlation of diffusion coefficients for CO/sub 2/ and rich-gas applications  

SciTech Connect

A novel in-situ method for measuring molecular diffusion coefficients of CO/sub 2/ and other solvent gases in consolidated porous media at high pressure has been developed and is described. This technique is unique because visual observations and measurements of composition are not required. Experimental diffusion coefficients are reported for CO/sub 2/ in decane up to 850 psia (5.86 MPa), for CO/sub 2/ in 0.25 N NaCl brine up to 850 psia (5.86 MPa), and for ethane in decane up to 600 psia (4.14 MPa). All tests were conducted in Berea cores saturated with liquid phase at 100/sup 0/F (311 K). Cores were oriented both vertically and horizontally to assess the effects of gravity-induced convection on the observed mass transfer. The experimental diffusion coefficients obtained from this study have also been correlated, together with literature data for methane, ethane, and propane, as a function of liquid viscosity and thermophysical properties of the diffusing gases.

Renner, T.A.

1988-05-01

365

A new model of thermal diffusion coefficients in binary hydrocarbon mixtures  

SciTech Connect

Thermal diffusion is important for the study of composition variations in hydrocarbon reservoirs, and it can either enhance or weaken the separation in mixtures. The authors present a new model for the prediction of thermal diffusion coefficients in binary mixtures of reservoir fluids using the thermodynamics of irreversible processes. the model needs equilibrium properties of mixtures and energy of viscous flow. Equilibrium properties are obtained from the volume translated Peng-Robinson equation of state, and the energy of viscous flow is estimated from viscosity. The model has been applied to predict thermal diffusion coefficients of several mixtures consisting of nonhydrocarbon and hydrocarbon fluids. Comparisons of theoretical results with experimental data show a good performance of the model except in the near-critical region where all existing models are deficient. In particular, the predicted sign of thermal diffusion coefficients is consistent with experimental observations in systems investigated here, namely, C{sub 1}/C{sub 3}, C{sub 1}/C{sub 4}, C{sub 7}/C{sub 12}, C{sub 7}/C{sub 16}, Ar/CO{sub 2}, N{sub 2}/CO{sub 2}, H{sub 2}/N{sub 2}, H{sub 2}/CO{sub 2}, and C{sub 1}/CO{sub 2}, except in C{sub 1}/N{sub 2}, in which the values of thermal diffusion coefficients are extremely low. The authors have also modified some of the earlier models, such as the Kempers, Haase, and Rutherford models, which are based on phenomenological and kinetic approaches. In general, the model has been found to be most reliable and represents a significant improvement over the earlier models.

Shukla, K.; Firoozabadi, A. [Reservoir Engineering Research Inst., Palo Alto, CA (United States)] [Reservoir Engineering Research Inst., Palo Alto, CA (United States)

1998-08-01

366

Calculation of radon diffusion coefficient and diffusion length for different building construction materials  

Microsoft Academic Search

The diffusion of radon in dwellings is a process determined by the radon concentration gradient across the building material\\u000a structure between the radon source and the surrounding air, and can be a significant contributor to indoor radon inflow. Radon\\u000a can originate from the deeply buried deposit beneath homes and can migrate to the surface of earth. Radon emanates to the

A. K. Narula; S. K. Goyal; Savita Saini; R. P. Chauhan; S. K. Chakarvarti

2009-01-01

367

New Consistent Definition of the Homogenized Diffusion Coefficient of a Lattice, Limitations of the Homogenization Concept, and Discussion of Previously Defined Coefficients.  

National Technical Information Service (NTIS)

The problem concerned with the correct definition of the homogenized diffusion coefficient of a lattice, and the concurrent problem of whether or not a homogenized diffusion equation can be formally set up, is studied by a space-energy angle dependent tre...

V. C. Deniz

1978-01-01

368

An interim report to the manager of the Paducah Gaseous Diffusion Plant from the Paducah Environmental Advisory Committee  

SciTech Connect

The Paducah Environmental Advisory Committee was formed as: (1) an outgrowth of other Environmental Advisory Committees already in existence at Oak Ridge and other Martin Marietta Energy Systems plants; (2) a result of public concern following significant nuclear incidents at Bhopal and Chernobyl; (3) a result of the new direction and commitment of the management of the Paducah Gaseous Diffusion Plant following contract acquisition by Martin Marietta Energy Systems; and (4) a means of reducing and/or preventing local and/or public concern regarding the activities of and potential risks created by PGDP. This report discusses the following issues and concerns of the Committee arrived at through a series of meetings: (1) groundwater monitoring; (2) long-range tails storage; C-404, scrap yrads, and PCB and TCE cleanup; nuclear criticality plan and alarm systems; documentation of historical data regarding hazardous waste burial grounds; dosimeter badges; and asbestos handling and removal.

Jackson, G.D.

1987-10-01

369

The Mailbox Computer System for the IAEA verification experiment on HEU downlending at the Portsmouth Gaseous Diffusion Plant  

SciTech Connect

IN APRIL 1996, THE UNITED STATES (US) ADDED THE PORTSMOUTH GASEOUS DIFFUSION PLANT TO THE LIST OF FACILITIES ELIGIBLE FOR THE APPLICATION OF INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA) SAFEGUARDS. AT THAT TIME, THE US PROPOSED THAT THE IAEA CARRY OUT A ''VERIFICATION EXPERIMENT'' AT THE PLANT WITH RESPECT TO DOOWNBLENDING OF ABOUT 13 METRIC TONS OF HIGHLY ENRICHED URANIUM (HEU) IN THE FORM OF URANIUM HEXAFLUROIDE (UF6). DURING THE PERIOD DECEMBER 1997 THROUGH JULY 1998, THE IAEA CARRIED OUT THE REQUESTED VERIFICATION EXPERIMENT. THE VERIFICATION APPROACH USED FOR THIS EXPERIMENT INCLUDED, AMONG OTHER MEASURES, THE ENTRY OF PROCESS-OPERATIONAL DATA BY THE FACILITY OPERATOR ON A NEAR-REAL-TIME BASIS INTO A ''MAILBOX'' COMPUTER LOCATED WITHIN A TAMPER-INDICATING ENCLOSURE SEALED BY THE IAEA.

Aronson, A.L.; Gordon, D.M.

2000-07-31

370

Determination of time-dependent partition coefficients for several pesticides using diffusion theory.  

PubMed

Diffusion-retarded partitioning of pesticides with aggregated soils results in a time-dependent partition coefficient (Kd') which is different at equilibrium from the partition coefficient derived from conventional 24-h batch studies (Kd) measured on dispersed soil. An experiment was undertaken to determine the importance of Kd' for the prediction of pesticide concentrations in solutions bathing artificial soil aggregates and to determine whether diffusion theory could accurately predict the concentrations. Two clay soils were mixed with polyacrylamide to create artificial aggregates of 0.8, 1.4 and 1.7 cm diameter when dry. After saturation, the aggregates were immersed in solutions containing isoproturon or a mixture of isoproturon, chlorotoluron and triasulfuron. The decline with time of the pesticide concentrations in the bathing solution was monitored and the results were compared with predictions from a diffusion-based model. The effective diffusion coefficients of the compounds were obtained by either fitting the non-linear diffusion model to the data (D(ef)) or by independent calculations based on the properties of the compounds and of the aggregates (D(ec)). The diffusion model was able to predict the temporal variation in pesticide concentrations in the bathing solution reasonably well whether D(ef) or D(ec) values were used. However, equilibrium concentrations in solution were sometimes overestimated due to increased sorption with time at the particle scale. Overall, the ratio between D(ef) and D(ec) ranged from 0.23 to 0.95 which was a reasonable variation when compared to the range of aggregate sizes used in the experiments and of the Kd values of the compounds. PMID:15519397

Renaud, Fabrice G; Leeds-Harrison, Peter B; Brown, Colin D; van Beinum, Wendy

2004-12-01

371

Use of a clear plastic dome to measure gaseous diffusion rates in natural waters  

Microsoft Academic Search

ABS'I'RACT Experiments were conducted in both standing and moving water communities to evaluate the use of a plastic dome for correcting diurnal oxygen curves for diffusion of oxygen between the air-water intcrfacc. Diurnal oxygen curves in systems where diffusion of oxy- gen through the air-water boundary occurs were corrected by means of data from the plastic dome expcrimcnts to obtain

B. J. COPELAND; W. R. DUFFER

1964-01-01

372

Measurement of the absorption coefficient of sound absorbing materials under a synthesized diffuse acoustic field.  

PubMed

This letter proposes an experimental method to estimate the absorption coefficient of sound absorbing materials under a synthesized diffuse acoustic field in free-field conditions. Comparisons are made between experiments conducted with this approach, the standard reverberant room method, and numerical simulations using the transfer matrix method. With a simple experimental setup and smaller samples than those required by standards, the results obtained with the proposed approach do not exhibit non-physical trends of the reverberant room method and provide absorption coefficients in good agreement with those obtained by simulations for a laterally infinite material. PMID:24993232

Robin, Olivier; Berry, Alain; Doutres, Olivier; Atalla, Noureddine

2014-07-01

373

Thermal Expansion and Diffusion Coefficients of Carbon Nanotube-Polymer Composites  

NASA Technical Reports Server (NTRS)

Classical molecular dynamics (MD) simulations employing Brenner potential for intra-nanotube interactions and van der Waals forces for polymer-nanotube interface have been used to investigate thermal expansion and diffusion characteristics of carbon nanotube-polyethylene composites. Addition of carbon nanotubes to polymer matrix is found to significantly increase the glass transition temperature Tg, and thermal expansion and diffusion coefficients in the composite above Tg. The increase has been attributed to the temperature dependent increase of the excluded volume for the polymer chains, and the findings could have implications in the composite processing, coating and painting applications.

Wei, Chengyu; Srivastava, Deepak; Cho, Kyeongjae; Biegel, Bryan (Technical Monitor)

2001-01-01

374

The role of apparent diffusion coefficient values in differentiation between adrenal masses.  

PubMed

The aim of this study was to evaluate the utility of apparent diffusion coefficient (ADC) values in differentiation between solid adrenal masses. The ADC values of 73 adrenal lesions (54 benign, 19 malignant) in 69 patients were measured at b 100, 600 and 1000 gradients on diffusion-weighted magnetic resonance imaging (DW-MRI). No statistically significant difference was found between ADC values of benign and malignant adrenal masses, nonadenomatous benign adrenal masses and malignant adrenal masses, adrenal adenomas and nonadenomatous lesions, adenomas and metastases, adenomas and pheochromocytomas, metastases and pheochromocytomas. ADC values are not helpful in the differentiation between solid adrenal masses. PMID:24332557

Ciçekçi, Mehtap; Onur, Mehmet Ruhi; Aydin, Ayse Murat; Gül, Yeliz; Ozkan, Yusuf; Akpolat, Nusret; Kocakoç, Ercan

2014-01-01

375

Environmental monitoring report: United States Department of Energy Paducah Gaseous Diffusion Plant, calendar year 1982  

SciTech Connect

Air, water, soil, and grass were analyzed for materials known to be in plant effluents to provide effluent control information and to determine compliance with applicable air and water quality standards. Offsite air radioactivity averaged less than 1% of the applicable Radioactivity Concentration Guide. Offsite analyses for fluorides in grass met the Kentucky Air Quality Requirements. All onsite and offsite airborne fluoride samples met the Kentucky standards for gaseous HF. Soil samples were analyzed for uranium and showed no significant deviation from normal background concentrations. There was no detectable change in characteristics of either the Ohio River or ground water attributable to plant operations. The chromium and fluoride concentrations in the Ohio River were in compliance with applicable Kentucky regulations. The concentration of hexavalent chromium in Little Bayou Creek has occasionally been in excess of the Kentucky aquatic life standard of 0.05 mg/1 due to cooling tower windage.

Not Available

1983-05-01

376

A MATLAB program to calculate translational and rotational diffusion coefficients of a single particle  

NASA Astrophysics Data System (ADS)

We developed a graphical user interface, MATLAB based program to calculate the translational diffusion coefficients in three dimensions for a single diffusing particle, suspended inside a fluid. When the particles are not spherical, in addition to their translational motion also a rotational freedom is considered for them and in addition to the previous translational diffusion coefficients a planar rotational diffusion coefficient can be calculated in this program. Time averaging and ensemble averaging over the particle displacements are taken to calculate the mean square displacement variations in time and so the diffusion coefficients. To monitor the random motion of non-spherical particles a reference frame is used that the particle just have translational motion in it. We call it the body frame that is just like the particle rotates about the z-axis of the lab frame. Some statistical analysis, such as velocity autocorrelation function and histogram of displacements for the particle either in the lab or body frames, are available in the program. Program also calculates theoretical values of the diffusion coefficients for particles of some basic geometrical shapes; sphere, spheroid and cylinder, when other diffusion parameters like temperature and fluid viscosity coefficient can be adjusted. Program summaryProgram title: KOJA Catalogue identifier: AEHK_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEHK_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 48 021 No. of bytes in distributed program, including test data, etc.: 1 310 320 Distribution format: tar.gz Programming language: MatLab (MathWorks Inc.) version 7.6 or higher. Statistics Toolbox and Curve Fitting Toolbox required. Computer: Tested on windows and linux, but generally it would work on any computer running MatLab (MathWorks Inc.). There is a bug in windows 7, if the user is not the administrator sometimes the program was not able to overwrite some internal files. Operating system: Any supporting MatLab (MathWorks Inc.) v7.6 or higher. RAM: About eight times that of loaded data Classification: 12 Nature of problem: In many areas of physics, knowing diffusion coefficients is vital and gives useful information about the physical properties of diffusive particles and the environment. In many cases a diffusive particle is not a sphere and has rotation during its movements. In these cases information about a particle's trajectory both in lab and body frame would be useful. Also some statistical analysis is needed to obtain more information about a particle's motion. Solution method: This program tries to gather all required tools to analyse raw data from the Brownian motion of a diffusing particle. Ability to switch between different methods of calculation of mean square displacement to find diffusion coefficients depends on the correlations between data points. There are three methods in the program: time average, ensemble average and their combinations. A linear fit is done to measure Diffusion Coefficient (D), the weight and fraction of data points is controllable. Given physical properties of the system, the program can calculates D theoretically for some basic geometrical shapes; sphere, spheroid and cylinder. In the case of non-spherical particles if data of rotation is available, the code can calculate trajectory and diffusion also in body frame. There are more statistical tools available in the program, such as histogram and autocorrelation function to obtain more information e.g. relaxation time to ideal diffusion motion. Code uses log-log diagram of mean square displacement (MSD) to calculate the amount of deviation from normal diffusion to sub- or super-diffusion. Running time: It is dependent on the input data, but for typical data in the order of mega bytes, it would take tens of minutes.

Charsooghi, Mohammad A.; Akhlaghi, Ehsan A.; Tavaddod, Sharareh; Khalesifard, H. R.

2011-02-01

377

Oxygen and chloride diffusion in cement pastes as a validation of chloride diffusion coefficients obtained by steady-state migration tests  

Microsoft Academic Search

When chloride ions diffuse through concrete, it has been found that they interact with the surface charge and electrical double layer developed at the cementitious matrix\\/pore solution interface. As a consequence of this interaction, the diffusion of chloride ions is retarded in comparison with that of dissolved oxygen molecules, although the two species have very similar diffusion coefficients in infinitely

M Castellote; C Alonso; C Andrade; G. A Chadbourn; C. L Page

2001-01-01

378

Quantitative photoacoustic microscopy of optical absorption coefficients from acoustic spectra in the optical diffusive regime  

NASA Astrophysics Data System (ADS)

Photoacoustic (PA) microscopy (PAM) can image optical absorption contrast with ultrasonic spatial resolution in the optical diffusive regime. Conventionally, accurate quantification in PAM requires knowledge of the optical fluence attenuation, acoustic pressure attenuation, and detection bandwidth. We circumvent this requirement by quantifying the optical absorption coefficients from the acoustic spectra of PA signals acquired at multiple optical wavelengths. With the acoustic spectral method, the absorption coefficients of an oxygenated bovine blood phantom at 560, 565, 570, and 575 nm were quantified with errors of <3%. We also quantified the total hemoglobin concentration and hemoglobin oxygen saturation in a live mouse. Compared with the conventional amplitude method, the acoustic spectral method provides greater quantification accuracy in the optical diffusive regime. The limitations of the acoustic spectral method was also discussed.

Guo, Zijian; Favazza, Christopher; Garcia-Uribe, Alejandro; Wang, Lihong V.

2012-06-01

379

Diffusion coefficients and heats of mixing in aqueous alkanolamines. Annual report, January-December 1992  

SciTech Connect

The objective of the work is to provide accurate data on diffusion coefficients and heats of absorption of acid gases in aqueous amine solutions to assist in the design of economical new amine treating systems and to improve the efficiency of existing plants. Specifically covered in the report are measurements of the mutual diffusion coefficient of methyldiethanolamine(MDEA) and diethanolamine in water. Measurements have been made at 25, 50 and 75C and at 0, 20, 35 and 50 wt% amine. Heats of absorption of CO2 into aqueous mixtures of MDEA have also been measured calorimetrically. Results are reported at temperatures of 120 and 260F and pressures of 500 and 1000 psia at total MDEA concentrations of 20, 35 and 50%.

Rowley, R.L.; Oscarson, J.L.

1993-01-01

380

Diffusion coefficients of energetic water group ions near Comet Giacobini-Zinner  

NASA Astrophysics Data System (ADS)

Data from the ultralow-energy charge analyzer and energetic particle anisotropy spectrometer sensors, acquired when the ICE spacecraft flew past Comet Giacobini-Zinner on September 11, 1985, are combined, and a single, self-consistent analysis technique is applied to derive a single-particle spectrum from about 200 to 1600 km/s. This information, together with the deduced bulk flow speed of the ions, is used to calculate a parallel diffusion coefficient in the transition region downstream of the bow wave (2.3 +/- 0.5) x 10 exp 17 sq cm/s; the corresponding scattering mean free path is (6 +/- 1) x 10 exp 4 km. The parallel diffusion coefficient is found to depend on the collision frequency of water group ions with Alfven waves, which are assumed to be propagating parallel (antiparallel) to the magnetic field.

Tan, L. C.; Mason, G. M.; Richardson, I. G.; Ipavich, F. M.

1993-03-01

381

Molecular dynamics simulation of self-diffusion coefficients for liquid metals  

NASA Astrophysics Data System (ADS)

The temperature-dependent coefficients of self-diffusion for liquid metals are simulated by molecular dynamics methods based on the embedded-atom-method (EAM) potential function. The simulated results show that a good inverse linear relation exists between the natural logarithm of self-diffusion coefficients and temperature, though the results in the literature vary somewhat, due to the employment of different potential functions. The estimated activation energy of liquid metals obtained by fitting the Arrhenius formula is close to the experimental data. The temperature-dependent shear-viscosities obtained from the Stokes—Einstein relation in conjunction with the results of molecular dynamics simulation are generally consistent with other values in the literature.

Ju, Yuan-Yuan; Zhang, Qing-Ming; Gong, Zi-Zheng; Ji, Guang-Fu

2013-08-01

382

Determination of the diffusion coefficient and solubility of radon in plastics.  

PubMed

This paper describes a method for determination of the diffusion coefficient and the solubility of radon in plastics. The method is based on the absorption and desorption of radon in plastics. Firstly, plastic specimens are exposed for controlled time to referent (222)Rn concentrations. After exposure, the activity of the specimens is followed by HPGe gamma spectrometry. Using the mathematical algorithm described in this report and the decrease of activity as a function of time, the diffusion coefficient can be determined. In addition, if the referent (222)Rn concentration during the exposure is known, the solubility of radon can be determined. The algorithm has been experimentally applied for different plastics. The results show that this approach allows the specified quantities to be determined with a rather high accuracy-depending on the quality of the counting equipment, it can be better than 10 %. PMID:21467078

Pressyanov, D; Georgiev, S; Dimitrova, I; Mitev, K; Boshkova, T

2011-05-01

383

New technique for the determination of radon diffusion coefficient in radon-proof membranes.  

PubMed

This paper describes a new device and a method to determine the radon diffusion coefficient in damp-proof membranes developed in the Czech Republic. The main advantage of the device is that it enables tests to be carried out in all the known measuring modes used throughout Europe. Two recently developed computer programs are presented for the numerical modelling of the time-dependent radon transport through damp-proof membranes. According to this method, the radon diffusion coefficient is derived from the process of fitting the numerical solution to the measured curve of radon concentration in a receiver container. Numerical simulation and measured data are also compared. Reasons for disagreements between different methods and specific configurations of the measuring device are also discussed. PMID:18397928

Jiránek, M; Fronka, A

2008-01-01

384

A Monte Carlo model for determination of binary diffusion coefficients in gases  

SciTech Connect

A Monte Carlo method has been developed for the calculation of binary diffusion coefficients in gas mixtures. The method is based on the stochastic solution of the linear Boltzmann equation obtained for the transport of one component in a thermal bath of the second one. Anisotropic scattering is included by calculating the classical deflection angle in binary collisions under isotropic potential. Model results are compared to accurate solutions of the Chapman-Enskog equation in the first and higher orders. We have selected two different cases, H{sub 2} in H{sub 2} and O in O{sub 2}, assuming rigid spheres or using a model phenomenological potential. Diffusion coefficients, calculated in the proposed approach, are found in close agreement with Chapman-Enskog results in all the cases considered, the deviations being reduced using higher order approximations.

Panarese, A. [Department Physics, University of Bari, Bari (Italy); Bruno, D.; Colonna, G. [CNR IMIP Bari (Italy); Diomede, P. [Department Chemistry, University of Bari, Bari (Italy); Laricchiuta, A. [CNR IMIP Bari (Italy); Longo, S., E-mail: savino.longo@ba.imip.cnr.i [Department Chemistry, University of Bari, Bari (Italy); CNR IMIP Bari (Italy); Capitelli, M. [Department Chemistry, University of Bari, Bari (Italy); CNR IMIP Bari (Italy)

2011-06-20

385

Determination of the diffusion coefficient of protons in Nafion thin films by ac-electrogravimetry.  

PubMed

This letter deals with an adaptation of the ac-electrogravimetry technique to extract separately the dynamic properties of H(+) and water in Nafion nanometric thin films (average thickness of 400 nm). An original theoretical approach was developed to extract the representative parameters from ac-electrogravimetry data. The concentration change of the exchanged species and the diffusion coefficient of the protons in a Nafion nanometric thin film (D = 0.5 × 10(-6) cm(2) s(-1) at 0.3 V vs SCE) were estimated for the first time according to the applied potential. The conductivity value of Nafion thin films was calculated from the Nernst-Einstein equation using diffusion coefficients and concentration values extracted from ac-electrogravimetry data. The calculated conductivity results agree well with the experimental proton conductivity values of Nafion thin films. PMID:24131383

Sel, Ozlem; To Thi Kim, L; Debiemme-Chouvy, Catherine; Gabrielli, Claude; Laberty-Robert, Christel; Perrot, Hubert

2013-11-12

386

Radial Diffusion Coefficients of Galactic and Anomalous Cosmic Rays in the Heliosphere  

NASA Astrophysics Data System (ADS)

When cosmic ray streaming in the heliosphere is negligible, the basic transport equation gives a simple approximation for the diffusion coefficient of cosmic ray particles, ?=CVSW/gr, where C is the Compton-Getting factor, VSW is the solar wind velocity and gr is the radial intensity gradients. In a separate paper at this conference, Fujii and McDonald (1999) have shown that the measured radial intensity gradients are well described with a functional form of dJ/Jdr= G0r, and have determined G0 and for selected galactic and anomalous cosmic rays. Using these values of gr, we obtained first order estimates of the particle diffusion coefficient over period from 1974 to 1997 out to heliocentric distance of 60 AU.

Fujii, Zenjiro

387

In situ effective diffusion coefficient profiles in live biofilms using pulsed-field gradient nuclear magnetic resonance  

PubMed Central

Diffusive mass transfer in biofilms is characterized by the effective diffusion coefficient. It is well-documented that the effective diffusion coefficient can vary by location in a biofilm. The current literature is dominated by effective diffusion coefficient measurements for distinct cell clusters and stratified biofilms showing this spatial variation. Regardless of whether distinct cell clusters or surface-averaging methods are used, position-dependent measurements of the effective diffusion coefficient are currently: 1) invasive to the biofilm, 2) performed under unnatural conditions, 3) lethal to cells, and/or 4) spatially restricted to only certain regions of the biofilm. Invasive measurements can lead to inaccurate results and prohibit further (time-dependent) measurements which are important for the mathematical modeling of biofilms. In this study our goals were to: 1) measure the effective diffusion coefficient for water in live biofilms, 2) monitor how the effective diffusion coefficient changes over time under growth conditions, and 3) correlate the effective diffusion coefficient with depth in the biofilm. We measured in situ two-dimensional effective diffusion coefficient maps within Shewanella oneidensis MR-1 biofilms using pulsed-field gradient nuclear magnetic resonance methods, and used them to calculate surface-averaged relative effective diffusion coefficient (Drs) profiles. We found that 1) Drs decreased from the top of the biofilm to the bottom, 2) Drs profiles differed for biofilms of different ages, 3) Drs profiles changed over time and generally decreased with time, 4) all the biofilms showed very similar Drs profiles near the top of the biofilm, and 5) the Drs profile near the bottom of the biofilm was different for each biofilm. Practically, our results demonstrate that advanced biofilm models should use a variable effective diffusivity which changes with time and location in the biofilm.

Renslow, Ryan S.; Majors, Paul D.; McLean, Jeffrey S.; Fredrickson, Jim K.; Ahmed, Bulbul; Beyenal, Haluk

2010-01-01

388

Determination of the lithium diffusion coefficient in irradiated boron carbide pellets  

Microsoft Academic Search

During neutron irradiation, 10B atoms in B4C are destroyed, producing lithium and helium atoms according to the well-known 10B(n,?)7Li reaction. The aim of this work is to measure the lithium diffusion coefficient of high density boron carbide material. The nuclear microprobe technique is used to determine lithium concentration profiles in irradiated B4C pellets. The analysis of the measured lithium concentration

X. Deschanels; D. Simeone; J. P. Bonal

1999-01-01

389

Scaling Limits of a Tagged Particle in the Exclusion Process with Variable Diffusion Coefficient  

NASA Astrophysics Data System (ADS)

We prove a law of large numbers and a central limit theorem for a tagged particle in a symmetric simple exclusion process in ? with variable diffusion coefficient. The scaling limits are obtained from a similar result for the current through -1/2 for a zero-range process with bond disorder. For the CLT, we prove convergence to a fractional Brownian motion of Hurst exponent 1/4.

Gonçalves, Patrícia; Jara, Milton

2008-09-01

390

Apparent Diffusion Coefficient Thresholds Do Not Predict the Response to Acute Stroke Thrombolysis  

Microsoft Academic Search

Background and Purpose—Apparent diffusion coefficient (ADC) thresholds for tissue infarction have been identified in acute stroke. IV tissue plasminogen activator (tPA) is associated with tissue salvage. We hypothesized that tPA would lower the ADC threshold for infarction. Methods—ADC and mean transit time (MTT) maps were generated for 26 patients imaged within 6 hours of stroke onset (12 tPA and 14

Poh-Sien Loh; Ken S. Butcher; Mark W. Parsons; Lachlan MacGregor; Patricia M. Desmond; Brian M. Tress; Stephen M. Davis

2010-01-01

391

Effective Diffusion Coefficients of CO2 and HCFC22 in Polyurethane and Polyisocyanurate Foams  

Microsoft Academic Search

Thin-slice accelerated desorption of gases using a gravimetric methodology has been used to determine effective diffusion coefficients of both carbon dioxide and HCFC-22 in thermoset foam structures. Foam samples consisting of a polyurethane appliance foam and a polyisocyanurate boardstock foam both blown with CFC-11, and polyurethane foams blown with HCFC-22 and carbondioxide have been employed as polymer substrates for the

D. Bhattacharjee; J. R. Booth

1995-01-01

392

Synoptic water clarity assessment in the Florida Keys using diffuse attenuation coefficient estimated from Landsat imagery  

Microsoft Academic Search

The diffuse attenuation coefficient, K (m–1), is a measure of the effective attenuation of light in the water column. It characterizes water clarity and is used as a\\u000a proxy for water quality. Mapping of shallow water benthic habitats using optical means, including daytime visible satellite\\u000a imagery, requires knowledge of K to correct for water column effects such as light absorption

D. Palandro; C. Hu; S. Andréfouët; F. E. Muller-Karger

393

Synoptic water clarity assessment in the Florida Keys using diffuse attenuation coefficient estimated from Landsat imagery  

Microsoft Academic Search

The diffuse attenuation coefficient, K (m? 1), is a measure of the effective attenuation of light in the water column. It characterizes water clarity and is used as a\\u000a proxy for water quality. Mapping of shallow water benthic habitats using optical means, including daytime visible satellite\\u000a imagery, requires knowledge of K to correct for water column effects such as light

D. Palandro; C. Hu; S. Andréfouët; F. E. Muller-Karger

2004-01-01

394

An absorbance-based micro-fluidic sensor for diffusion coefficient and molar mass determinations  

Microsoft Academic Search

The H-Sensor reported herein is a micro-fluidic device compatible with flow injection analysis (FIA) and high performance liquid chromatography (HPLC). The device detects analytes at two separate off-chip absorbance flow cells, providing two simultaneous absorbance measurements. The ratio of these two absorbance signals contains analyte diffusion coefficient information. A theoretical model for the sensing mechanism is presented. The model relates

Adam D. McBrady; Rattikan Chantiwas; Ana Kristine Torgerson; Kate Grudpan; Robert E. Synovec

2006-01-01

395

Electrical conductivity and chemical diffusion coefficient of Sr-doped lanthanum chromites  

Microsoft Academic Search

The electrical conductivity and chemical diffusion coefficient of Sr-doped lanthanum chromites were measured as a function of oxygen partial pressure (Po2) and temperature, and the results were discussed in light of defect chemistry. The electrical conductivity was independent of Po2 and in proportion to the Sr-content at high Po2, while at low Po2, the conductivity decreased exponentially with decrease of

I. Yasuda; M. Hishinuma

1995-01-01

396

Diffusion coefficients significant in modeling the absorption rate of carbon dioxide into aqueous blends of N-methyldiethanolamine and diethanolamine and of hydrogen sulfide into aqueous N-methyldiethanolamine  

SciTech Connect

Absorption rates of gaseous CO{sub 2} into aqueous blends of N-methyldiethanolamine (MDEA) and diethanolamine (DEA) and of gaseous H{sub 2}S into aqueous MDEA were measured in a quiescent, inverted-tube diffusiometer by monitoring the rate of pressure drop. A numerical model for absorption, diffusion, and reaction of CO{sub 2} and H{sub 2}S in blends of MDEA, DEA, and water was developed. The model was used to regress diffusion coefficients of bicarbonate, carbamate, and MDEAH{sub 2}CO{sub 3} for the case of CO{sub 2} absorption and of bisulfide ion for the case of H{sub 2}S absorption from measured absorption rates. CO{sub 2} absorption rates and diffusion coefficients of bicarbonate, carbamate, and MDEAH{sub 2}CO{sub 3} were obtained at 298.2 K and 318.2 K in aqueous solutions containing 50 mass % total amine at DEA:MDEA mole ratios of 1:20, 1:4, 1L3, and 2:3. H{sub 2}S absorption rates and diffusion coefficients of bisulfide ion were obtained at 298.2 K and 318.2 K in aqueous solutions containing 20, 35, and 50 mass % MDEA.

Adams, M.E.; Marshall, T.L.; Rowley, R.L. [Brigham Young Univ., Provo, UT (United States). Dept. of Chemical Engineering] [Brigham Young Univ., Provo, UT (United States). Dept. of Chemical Engineering

1998-07-01

397

Sorption kinetics of polycyclic aromatic hydrocarbons removal using granular activated carbon: intraparticle diffusion coefficients.  

PubMed

Granular activated carbon (GAC) was evaluated as a suitable sorbent for polycyclic aromatic hydrocarbons (PAHs) removal from aqueous solutions. For this purpose, kinetic measurements on the extraction of a family of six PAHs were taken. A morphology study was performed by means of a scanning electron microscopy (SEM) analysis of GAC samples. Analyses of the batch rate data for each PAH were carried out using two kinetic models: the homogenous particle diffusion model (HPDM) and the shell progressive model (SPM). The process was controlled by diffusion rate the solutes (PAHs) that penetrated the reacted layer at PAH concentrations in the range of 0.2-10 mg L(-1). The effective particle diffusion coefficients (D(eff)) derived from the two models were determined from the batch rate data. The Weber and Morris intraparticle diffusion model made a double contribution to the surface and pore diffusivities in the sorption process. The D(eff) values derived from both the HPMD and SPM equations varied from 1.1 x 10(-13) to 6.0 x 10(-14) m(2) s(-1). The simplest model, the pore diffusion model, was applied first for data analysis. The model of the next level of complexity, the surface diffusion model, was applied in order to gain a deeper understanding of the diffusion process. This model is able to explain the data, and the apparent surface diffusivities are in the same order of magnitude as the values for the sorption of functionalized aromatic hydrocarbons (phenols and sulphonates) that are described in the literature. PMID:18308468

Valderrama, C; Gamisans, X; de las Heras, X; Farrán, A; Cortina, J L

2008-09-15

398

US Department of Energy Waste Heat Utilization Project for the Paducah, Kentucky Uranium Enrichment Gaseous Diffusion Plant. Final Report, 29 September 1978, Volume I.  

National Technical Information Service (NTIS)

Concepts which would make optimum use of the process heat currently being wasted at the Paducah Gaseous Diffusion Plant (GDP) were studied. The results show that a waste heat complex could be developed which would take the 150 exp 0 F GDP cooling water an...

1978-01-01

399

Dual wall reverse circulation drilling with multi-level groundwater sampling for groundwater contaminant plume delineation at Paducah Gaseous Diffusion Plant, Paducah, Kentucky  

Microsoft Academic Search

Dual wall reverse circulation (DWRC) drilling was used to drill 48 borings during a groundwater contaminant investigation at the Paducah Gaseous Diffusion Plant, Paducah, Kentucky. This method was selected as an alternative to conventional hollow stem auger drilling for a number of reasons, including the expectation of minimizing waste, increasing the drilling rate, and reducing the potential for cross contamination

D. R. Smuin; E. E. Morti; J. L. Zutman; D. A. Pickering

1995-01-01

400

Assessment of the influences of groundwater colloids on the migration of technetium-99 at the Paducah Gaseous Diffusion Plant Site in Paducah, Kentucky  

Microsoft Academic Search

This short report summarizes the influences of groundwater colloids on the migration\\/transport of Tc at the Paducah Gaseous Diffusion Plant (PGDP) site in Paducah, Kentucky. Limited data suggest that inorganic colloidal materials (e.g., aluminosilicate clay minerals) may not play a significant role in the retention and transport of Tc. Studies by size fractionation reveal that both Tc and natural organic

B. Gu; J. A. McDonald; J. F. McCarthy; J. L. Clausen

1994-01-01

401

Thermal discharges from Paducah Gaseous Diffusion Plant outfalls: Impacts on stream temperatures and fauna of Little Bayou and Big Bayou Creeks  

Microsoft Academic Search

The development of a biological monitoring plan for the receiving streams of the Paducah Gaseous Diffusion Plant (PGDP) began in the late 1980s, because of an Agreed Order (AO) issued in September 1987 by the Kentucky Division of Water (KDOW). Five years later, in September 1992, more stringent effluent limitations were imposed upon the PGDP operations when the KDOW reissued

W. K. Roy; M. G. Ryon; R. L. Hinzman

1996-01-01

402

Thermal Discharges from Paducah Gaseous Diffusion Plant Outfalls: Impacts on Stream Temperatures and Fauna of Little Bayou and Big Bayou Creeks  

Microsoft Academic Search

The development of a biological monitoring plan for the receiving streams of the Paducah Gaseous Diffusion Plant (PGDP) began in the late 1980s, because of an Agreed Order (AO) issued in September 1987 by the Kentucky Division of Water (KDOW). Five years later, in September 1992, more stringent effluent limitations were imposed upon the PGDP operations when the KDOW reissued

Roy

1999-01-01

403

ENZYME ACTIVITY PROBE AND GEOCHEMICAL ASSESSMENT FOR POTENTIAL AEROBIC COMETABOLISM OF TRICHLOROETHENE IN GROUNDWATER OF THE NORTHWEST PLUME, PADUCAH GASEOUS DIFFUSION PLANT, KENTUCKY  

Microsoft Academic Search

The overarching objective of the Paducah Gaseous Diffusion Plant (PGDP) enzyme activity probe (EAP) effort is to determine if aerobic cometabolism is contributing to the attenuation of trichloroethene (TCE) and other chlorinated solvents in the contaminated groundwater beneath PGDP. The site-specific objective for the EAP assessment is to identify if key metabolic pathways are present and expressed in the microbial

B Looney; M M. Hope Lee; S S. K. Hampson

2008-01-01

404

Aerial radiological survey of the Paducah Gaseous Diffusion Plant, Paducah, Kentucky. Date of aerial survey: August 1976. Date of ground survey: May 1977  

Microsoft Academic Search

An airborne radiological survey of a 57 km² area surrounding the Paducah Gaseous Diffusion Plant (PGDP) site was made during August 1976. Detected radioisotopes, and their associated gamma ray exposure rates, were consistent with those expected from normal background emitters, except at certain locations. Average exposure rates 1 m above the ground, as calculated from the aerial data, are presented

Hilton

1978-01-01

405

Fissible Deposit Characterization at the Former Oak Ridge K-25 Gaseous Diffusion Plant by ²⁵²CF-Source-Driven Measurements  

Microsoft Academic Search

The Deposit Removal Project was undertaken with the support of the U. S. Department of Energy at the East Tennessee Technology Park (ETTP) formerly the Oak Ridge K-25 Site. The project team performed the safe removal of the hydrated uranyl fluoride (UOâFâ) deposits from the K-29 Building of the former Oak Ridge Gaseous Diffusion Plant. The deposits had developed as

T. F. Hannon; J. T. Mihalczo; J. A. Mullens; T. Uckan; T. E. Valentine; M. S. Wyatt

1998-01-01

406

DIFFUSIVE EXCHANGE OF GASEOUS POLYCYCLIC AROMATIC HYDROCARBONS AND POLYCHLORINATED BIPHENYLS ACROSS THE AIR-WATER INTERFACE OF THE CHESAPEAKE BAY. (R825245)  

EPA Science Inventory

Dissolved and gas-phase concentrations of nine polycyclic aromatic hydrocarbons and 46 polychlorinated biphenyl congeners were measured at eight sites on the Chesapeake Bay at four different times of the year to estimate net diffusive air-water gas exchange rates. Gaseous PAHs ar...

407

Experimental determination of the diffusion coefficient in two-dimensions in ferrous sulphate gels using the finite element method  

Microsoft Academic Search

A novel two-dimensional finite element method for modelling the diffusion which occurs in Fricke or ferrous sulphate type\\u000a radiation dosimetry gels is presented. In most of the previous work, the diffusion coefficient has been estimated using simple\\u000a one-dimensional models. This work presents a two-dimensional model which enables the diffusion coefficient to be determined\\u000a in a much wider range of experimental

C. Baldock; P. J. Harris; A. R. Piercy; B. Healy

2001-01-01

408

A new method for determining the initial mobile formaldehyde concentrations, partition coefficients, and diffusion coefficients of dry building materials.  

PubMed

The initial mobile formaldehyde concentration, C(m,0); the partition coefficient, K; and the diffusion coefficient, D, of a dry building material are key parameters to characterize formaldehyde emissions from the building material. The solvent extraction method and direct thermal desorption method can overestimate C(m,0) because of high temperature. A new method has been developed to determine C(m,0) under similar conditions to common indoor environment, together with K and D. In the proposed method, the tested materials are placed in an airtight environmental chamber for which the temperature can be controlled by a water bath, then the materials undergo a multisorption/emission process and the instantaneous formaldehyde concentration in the chamber is recorded. The K and C(m,0) are determined from the equilibrium concentrations after every sorption by means of the linear least-square regression, and D is obtained by fitting the concentration at the emission stage into a mass-transfer-based model in the literature. Four kinds of wooden medium-density boards are tested. The C(m,0) measured using this method is the mobile formaldehyde concentration in the material, which differs significantly from the total formaldehyde concentration in the material measured by using the traditional method recommended by the Chinese standard (GB/T 17657-1999) extraction method. This means that the mobile formaldehyde takes only a small portion of the total quantity in the tested material. The K, D, and C(m,0) values measured using this new method are used to predict formaldehyde concentrations for sorption processes. The results agree well with experimental data. In addition, some factors influencing the accuracy are analyzed. PMID:19645266

Wang, Xinke; Zhang, Yinping

2009-07-01

409

Partial structure factors and diffusion coefficients of liquid potassium-cesium alloys  

NASA Astrophysics Data System (ADS)

With use of the square-well potential as a perturbation on the hard-sphere potential, the partial structure factors defined by Ascroft and Langreth [Phys. Rev. 159, 500 (1967)] and also the number-number, number-concentration, and concentration-concentration structure factors of Bhatia and Thornton [Phys. Rev. 32, 3004 (1970)] are calculated for liquid potassium-cesium alloys at various concentrations at 100 °C. From the partial structure factors, the total structure factors are also calculated and compared with experimental values. The hard-sphere values are also computed for the same concentrations. The difference plots of the total structure factors of the square well and those of the hard spheres are also presented. The total structure factors obtained from these partial structure factors in the long-wavelength limit are used to calculate the isothermal compressibilities. With the partial structure factors and using Helfand's prescription extended by Davies and Polyvos, we calculate the self-diffusion coefficients. From the self-diffusion coefficients, an estimate of the mutual diffusion coefficients has been made to a good approximation.

Gopala Rao, R. V.; Das Gupta, B.

1985-11-01

410

The Diffusion Coefficient of Scandium in Dilute Aluminum-Scandium Alloys  

NASA Astrophysics Data System (ADS)

The diffusion coefficient of Sc in dilute Al-Sc alloys has been determined at 748 K, 823 K, and 898 K (475 °C, 550 °C, and 625 °C, respectively) using semi-infinite diffusion couples. Good agreement was found between the results of the present study and both the higher temperature, direct measurements and lower temperature, indirect measurements of these coefficients reported previously in the literature. The temperature-dependent diffusion coefficient equation derived from the data obtained in the present investigation was found to be D left( {{text{m}}2 /{text{s}}} right) = left( {2.34 ± 2.16} right) × 10^{ - 4} left( {{text{m}}2 /{text{s}}} right) { exp }left( {{ - left( {167 ± 6} right) left( {{text{kJ}}/{text{mol}}} right)}/RT} right). Combining these results with data from the literature and fitting all data simultaneously to an Arrhenius relationship yielded the expression D left( {{text{m}}2 /{text{s}}} right) = left( {2.65 ± 0.84} right) × 10^{ - 4} left( {{text{m}}2 /{text{s}}} right) { exp }left( {{ - left( {168 ± 2} right) left( {{text{kJ}}/{text{mol}}} right)}/RT} right). In each equation given above, R is 0.0083144 kJ/mol K, T is in Kelvin, and the uncertainties are ±1 standard error.

Kerkove, Marcel A.; Wood, Thomas D.; Sanders, Paul G.; Kampe, Stephen L.; Swenson, Douglas

2014-06-01

411

Computing quasi-linear diffusion coefficients using the delta-f particle-in-cell method  

SciTech Connect

Linear wave codes AORSA and TORIC couple to the bounce-averaged nonlinear Fokker-Planck code CQL3D through quasi-linear diffusion coefficients. Both linear wave codes rely on the quasi-local approximation that includes only first-order parallel and perpendicular gradient variations of cyclotron frequency and ignores field line curvature along with temperature and density gradient effects. The delta-f particle-in-cell (DFPIC) method has been successfully used for simulating ion-cyclotron fast wave behavior. This method also permits particle behavior such as multiple pass resonance, banana orbits, and superadiabaticity. We present new work on generating quasi-linear diffusion coefficients using the DFPIC method that will permit the electromagnetic particle-in-cell (EMPIC) code, VORPAL, to couple to CQL3D and to compare to AORSA and TORIC. A new multiple weight delta-f approach will be presented that converts velocity derivatives to action derivatives and yields a full tensor quasi-linear diffusion coefficient.

Austin, T. M.; Smithe, D. N.; Ranjbar, V. [Tech-X Corporation, 5621 Arapahoe Ave., Suite A, Boulder, CO 80303 (United States)

2009-11-26

412

Computing quasi-linear diffusion coefficients using the delta-f particle-in-cell method  

NASA Astrophysics Data System (ADS)

Linear wave codes AORSA and TORIC couple to the bounce-averaged nonlinear Fokker-Planck code CQL3D through quasi-linear diffusion coefficients. Both linear wave codes rely on the quasi-local approximation that includes only first-order parallel and perpendicular gradient variations of cyclotron frequency and ignores field line curvature along with temperature and density gradient effects. The delta-f particle-in-cell (DFPIC) method has been successfully used for simulating ion-cyclotron fast wave behavior. This method also permits particle behavior such as multiple pass resonance, banana orbits, and superadiabaticity. We present new work on generating quasi-linear diffusion coefficients using the DFPIC method that will permit the electromagnetic particle-in-cell (EMPIC) code, VORPAL, to couple to CQL3D and to compare to AORSA and TORIC. A new multiple weight delta-f approach will be presented that converts velocity derivatives to action derivatives and yields a full tensor quasi-linear diffusion coefficient.

Austin, T. M.; Smithe, D. N.; Ranjbar, V.

2009-11-01

413

Radial diffusion coefficients and the distance to the modulation boundary for galactic and anomalous cosmic rays  

NASA Astrophysics Data System (ADS)

When cosmic ray streaming in the heliosphere is negligible, the basic transport equation gives a simple approximation for the diffusion coefficient of cosmic ray particles, Krr = CVSW/ gr, where C is the Compton-Getting factor, VSW is the solar wind velocity and gr is the radial intensity gradients. Using this equation we calculated the particle diffusion coefficients from 1974 to 1995 out to heliocentric distances of ˜70 AU, using the measured gr for galactic 180-450 MeV/n He, 130-220 MeV H and anomalous 30-57 MeV/n He and 10-20 MeV/n He. Further we made first order estimates of the distance to the modulation boundary, using these diffusion coefficients and the modulation function for galactic 180-450 MeV/n He. It was shown that the distance is from about 65 AU to 110 AU varying inversely proportional to the solar activity for the period from 1978 to 1990. After 1990 these estimation were not significant because of the very small gradients in the outer heliosphere.

Fujii, Z.; McDonald, F. B.

414

a New Method for Measuring Diffusion Coefficient of Gases in Liquids by Plif  

NASA Astrophysics Data System (ADS)

Gas-liquid mass transfer is a major issue in engineering processes such as wastewater treatment or biogas production since this phenomenon is directly linked to their design and efficiency. In recent years, much research has been done in this area but some gaps still remain in our knowledge of gas-liquid transfer, in particular concerning molecular diffusivity. The determination of molecular diffusivity is commonly based on empirical correlations, such as the widely used Wilke and Chang13 expression, valid under specific conditions and with relatively high uncertainties. In the present work, an innovative and promising technique is proposed to determine diffusion coefficients of gases in liquids. This technique is based on visualizing and quantifying oxygen diffusion across a flat gas-liquid interface, in a Newtonian medium, using planar laser induced fluorescence (PLIF) with inhibition. Particle image velocimetry (PIV) experiments were conducted to confirm the hydrodynamic flow field in the liquid phase. Results included the visualization of oxygen diffusion over time, and the quantification of this visualization. The oxygen diffusivity thus determined is in agreement with values found in the literature.

Jimenez, Mélanie; Dietrich, Nicolas; Hebrard, Gilles

415

Evaluation of archived and off-line diagnosed vertical diffusion coefficients from ERA-40 with 222Rn simulations  

NASA Astrophysics Data System (ADS)

Boundary layer turbulence has a profound influence on the distribution of tracers with sources or sinks at the surface. The 40-year ERA-40 meteorological data set of the European Centre for Medium-range Weather Forecasts contains archived vertical diffusion coefficients. We evaluated the use of these archived diffusion coefficients versus off-line diagnosed coefficients based on other meteorological parameters archived during ERA-40 by examining the influence on the distribution of the radionuclide 222Rn in the chemistry transport model TM3. In total four different sets of vertical diffusion coefficients are compared: (i) 3-hourly vertical diffusion coefficients archived during the ERA-40 project, (ii) 3-hourly off-line diagnosed coefficients from a non-local scheme based on Holtslag and Boville (1993), Vogelezang and Holtslag (1996), and Beljaars and Viterbo (1999), (iii) 6-hourly coefficients archived during the ERA-40 project, and (iv) 6-hourly off-line diagnosed coefficients based on a local scheme described in Louis (1979) and Louis et al. (1982). The diffusion scheme to diagnose the coefficients off-line in (ii) is similar to the diffusion scheme used during the ERA-40 project (i and iii).

Olivié, D. J. L.; van Velthoven, P. F. J.; Beljaars, A. C. M.

2004-11-01

416

Minority carrier diffusion lengths and absorption coefficients in silicon sheet material  

NASA Technical Reports Server (NTRS)

Most of the methods which have been developed for the measurement of the minority carrier diffusion length of silicon wafers require that the material have either a Schottky or an ohmic contact. The surface photovoltage (SPV) technique is an exception. The SPV technique could, therefore, become a valuable diagnostic tool in connection with current efforts to develop low-cost processes for the production of solar cells. The technique depends on a knowledge of the optical absorption coefficient. The considered investigation is concerned with a reevaluation of the absorption coefficient as a function of silicon processing. A comparison of absorption coefficient values showed these values to be relatively consistent from sample to sample, and independent of the sample growth method.

Dumas, K. A.; Swimm, R. T.

1980-01-01

417

Quasi-linear diffusion coefficients for field-aligned electromagnetic waves with applications to the magnetosphere  

NASA Astrophysics Data System (ADS)

Much current research in magnetospheric physics is directed toward understanding the dramatic variations in relativistic (>1 MeV) electron fluxes that can take place in the Earth's outer zone during magnetic storms. The behavior of outer-zone energetic electrons is partly controlled by the competing mechanisms of acceleration and loss that result from wave-particle interactions, in particular electron gyroresonance with ELF, VLF, and electromagnetic ion cyclotron (EMIC) waves. Powerful techniques for treating gyroresonant wave-particle interactions are provided by quasi-linear diffusion theory. In this paper, we derive formulae for the quasi-linear (momentum, mixed, and pitch-angle) diffusion coefficients for cyclotron resonance with field-aligned electromagnetic waves of any mode and general spectral density. The formulae are fully exact, expressed in closed analytical form, and easily computable. Our results can therefore be readily used to determine accurate diffusion rates for many forms of wave-particle interaction in the magnetosphere and other space plasmas. We find that momentum diffusion rates for MeV electrons in gyroresonance with VLF chorus can be less than a day in the lower-density regions outside the plasmasphere. The mechanism of stochastic acceleration by VLF chorus could therefore be instrumental in generating relativistic electrons during the recovery phase of a magnetic storm. Pitch-angle diffusion rates of MeV electrons scattered by EMIC waves along the plasmapause can approach the limit of strong diffusion. EMIC wave scattering could hence contribute significantly to electron precipitation loss over the course of a storm. Codes designed to model electron dynamics in the radiation belts need to incorporate, in addition to radial (cross-L) diffusion, resonant diffusion due to electron gyroresonance with ELF, VLF, and EMIC waves. In order to determine the quasi-linear diffusion coefficients for such codes, observational data are required on the power spectral density, spatial distribution, and temporal variation of these wave modes. Currently, only limited wave data sets are available. In addition, problems of numerical instability associated with diffusion codes need to be solved. The development of fully comprehensive models of radiation belt electron dynamics remains a considerable scientific challenge.

Summers, Danny

2005-08-01

418

Colloid diffusion coefficients in compacted and consolidated clay barriers: Compaction density and colloid size effects  

NASA Astrophysics Data System (ADS)

An experimental methodology applying the nuclear ion beam technique Rutherford Backscattering Spectrometry (RBS) is used to measure colloid diffusion profiles within three different types of clay: consolidated Opalinus clay (Switzerland), Callovo-Oxfordian clay (France) and FEBEX bentonite (Spain) compacted at different densities. The RBS technique is widely applied in materials science and it was selected because it allows the measurement of concentration profiles at short range distances (?m). The effects of colloid size, clay type and clay density were analyzed with negatively charged Au colloids of 2, 20 and 40 nm. Apparent diffusion coefficients ( Da) for gold colloids could be measured and Da values ranged from (10 -18 to 10 -19 m 2/s). The larger diffusion coefficient was measured for 2 nm colloids in the Opalinus clay with Da(Au 2 nm) = (2.1 ± 0.5) × 10 -18 m 2/s. The accessible porosity for colloids is even lower than that measured for anions, since not only anion exclusion but also size exclusion hinders diffusion. For example, 40 nm colloids did not accede at all to bentonite compacted at higher densities.

Alonso, Ursula; Missana, Tiziana; Garcia-Gutierrez, Miguel; Patelli, Alessandro; Albarran, Nairoby; Rigato, Valentino

419

Single master curve for self-diffusion coefficients in distinctly different glass-forming liquids  

NASA Astrophysics Data System (ADS)

An existence of a single master curve for the long-time self-diffusion coefficients DSL(T) in diversely different glass-forming liquids is predicted over wide temperature T ranges above the glass transition point Tg by analyzing various experimental and simulation data consistently from a unified point of view based on the mean-field theory recently developed. In order to scale those data appropriately, the power-law dependence of the ? - and the ? -relaxation times on DSL is used. Then, it is shown that any equilibrium data for self-diffusion of atom in different systems are all collapsed onto a singular function f(Tf(?)/T) , where Tf(?) is a fictive singular temperature of atom ? . Thus, we emphasize that any equilibrium self-diffusion data can be described by a single master curve f(x) above Tg(>Tf) , while the data out of equilibrium start to deviate from f(x) around Tg .

Tokuyama, Michio

2010-10-01

420

Fluoride levels in vegetation in the vicinity of the Portsmouth Gaseous Diffusion Plant. Final report  

SciTech Connect

Battelle initiated a survey of vegetation samples at new and established sites in the vicinity of the Portsmouth Gaseous Diffision Plant. Forty-nine vegetation samples were collected and analyzed for fluoride. Three samples from inside the plant boundaries contained fluoride in concentrations great enough to be of concern to grazing livestock (>40 ppm). All other samples were below the action level. Fluoride concentrations in vegetation reported by Battelle were somewhat greater than identical samples analyzed by GAT. This differences may be accounted for by the fact that GAT rinsed their samples prior to the analysis for fluoride while Battelle did not. Battelles' samples were not washed because fluoride containing particulates on the surface of vegetation can be readily ingested by livestock and may contribute to the total amount of fluoride absorbed by the livestock. Results of the vegetational survey were not correlated with the deposition pattern modeled by Battelle. Apparently, levels of fluoride in vegetation near the plant are not greatly influenced by plant emissions. Extraneous sources such as dust and other forms of atmospheric fluoride appear to be the predominant influence governing fluoride in vegetation. Results from the fluoride deposition model indicate that a deficiency of sampling points may exist in the northwest sector immediately adjacent to the plant perimeter. The addition of new sampling stations in this area would create closer surveillance of potential fluoride emissions from the plant.

Jackson, D.R.

1986-04-01

421

Diffusion-based process for carbon dioxide uptake and isoprene emission in gaseous/aqueous two-phase photobioreactors by photosynthetic microorganisms.  

PubMed

Photosynthesis for the generation of fuels and chemicals from cyanobacteria and microalgae offers the promise of a single host organism acting both as photocatalyst and processor, performing sunlight absorption and utilization, as well as CO(2) assimilation and conversion into product. However, there is a need to develop methods for generating, sequestering, and trapping such bio-products in an efficient and cost-effective manner that is suitable for industrial scale-up and exploitation. A sealed gaseous/aqueous two-phase photobioreactor was designed and applied for the photosynthetic generation of volatile isoprene (C(5)H(8)) hydrocarbons, which operates on the principle of spontaneous diffusion of CO(2) from the gaseous headspace into the microalgal or cyanobacterial-containing aqueous phase, followed by photosynthetic CO(2) assimilation and isoprene production by the transgenic microorganisms. Volatile isoprene hydrocarbons were emitted from the aqueous phase and were sequestered into the gaseous headspace. Periodic replacement (flushing) of the isoprene (C(5)H(8)) and oxygen (O(2)) content of the gaseous headspace with CO(2) allowed for the simultaneous harvesting of the photoproducts and replenishment of the CO(2) supply in the gaseous headspace. Reduction in practice of the gaseous/aqueous two-phase photobioreactor is offered in this work with a fed-batch and a semi-continuous culturing system using Synechocystis sp. PCC 6803 heterologously expressing the Pueraria montana (kudzu) isoprene synthase (IspS) gene. Constitutive isoprene production was observed over 192 h of experimentation, coupled with cyanobacterial biomass accumulation. The diffusion-based process in gaseous/aqueous two-phase photobioreactors has the potential to be applied to other high-value photosynthetically derived volatile molecules, emanating from a variety of photosynthetic microorganisms. PMID:21830206

Bentley, Fiona K; Melis, Anastasios

2012-01-01

422

Electrochemical methods for the determination of the diffusion coefficient of ionophores and ionophore-ion complexes in plasticized PVC membranes.  

PubMed

The diffusion coefficients of active components in ion-selective membranes have a decisive influence on the life-time and detection limit of the respective ion-selective electrodes, as well as influencing the rate of polarization and relaxation processes of electrically perturbed ion sensors. Therefore, the rational design of mass transport controlled ion-selective electrodes with sub-nanomolar detection limits requires reliable data on the diffusion coefficients. We have implemented electrochemical methods for the quantitative assessment of both the diffusion coefficients of free ionophores and ion-ionophore complexes. The diffusion coefficients of the pH-sensitive chromoionophore ETH 5294 and the calcium-selective ionophore ETH 5234 were determined in plasticized PVC membranes with different PVC to plasticizer ratios. The diffusion coefficient of the free chromoionophore determined by a chronoamperometric method was validated with optical methods for a variety of membrane compositions. The calcium-selective ionophore ETH 5234 was used as a model compound to assess the diffusion coefficient of the ion-ionophore complex calculated from the time required for the complexes to cross a freshly prepared membrane during potentiometric ion-breakthrough experiments. The difference between the diffusion coefficients of the free ionophore ETH 5234 and the ion-ionophore complex was found to be significant and correlated well with the geometry of the respective species. PMID:18427685

Bodor, Sándor; Zook, Justin M; Lindner, Erno; Tóth, Klára; Gyurcsányi, Róbert E

2008-05-01

423

Universal model for accurate calculation of tracer diffusion coefficients in gas, liquid and supercritical systems.  

PubMed

In this work it is presented a new model for accurate calculation of binary diffusivities (D12) of solutes infinitely diluted in gas, liquid and supercritical solvents. It is based on a Lennard-Jones (LJ) model, and contains two parameters: the molecular diameter of the solvent and a diffusion activation energy. The model is universal since it is applicable to polar, weakly polar, and non-polar solutes and/or solvents, over wide ranges of temperature and density. Its validation was accomplished with the largest database ever compiled, namely 487 systems with 8293 points totally, covering polar (180 systems/2335 points) and non-polar or weakly polar (307 systems/5958 points) mixtures, for which the average errors were 2.65% and 2.97%, respectively. With regard to the physical states of the systems, the average deviations achieved were 1.56% for gaseous (73 systems/1036 points), 2.90% for supercritical (173 systems/4398 points), and 2.92% for liquid (241 systems/2859 points). Furthermore, the model exhibited excellent prediction ability. Ten expressions from the literature were adopted for comparison, but provided worse results or were not applicable to polar systems. A spreadsheet for D12 calculation is provided online for users in Supplementary Data. PMID:23601290

Lito, Patrícia F; Magalhães, Ana L; Gomes, José R B; Silva, Carlos M

2013-05-17

424

Evaluation of apparent diffusion coefficient thresholds for diagnosis of medulloblastoma using diffusion-weighted imaging.  

PubMed

We assess a diffusion-weighted imaging (DWI) analysis technique as a potential basis for computer-aided diagnosis (CAD) of pediatric posterior fossa tumors. A retrospective medical record search identified 103 children (mean age: 87 months) with posterior fossa tumors having a total of 126 preoperative MR scans with DWI. The minimum ADC (ADCmin) and normalized ADC (nADC) values [ratio of ADCmin values in tumor compared to normal tissue] were measured by a single observer blinded to diagnosis. Receiver operating characteristic (ROC) curves were generated to determine the optimal threshold for which the nADC and ADCmin values would predict tumor histology. Inter-rater reliability for predicting tumor type was evaluated using values measured by two additional observers. At histology, ten tumor types were identified, with astrocytoma (n=50), medulloblastoma (n=33), and ependymoma (n=9) accounting for 89%. Mean ADCmin (0.54 × 10(-3) mm(2)/s) and nADC (0.70) were lowest for medulloblastoma. Mean ADCmin (1.28 × 10(-3) mm(2)/s) and nADC (1.64) were highest for astrocytoma. For the ROC analysis, the area under the curve when discriminating medulloblastoma from other tumors using nADC was 0.939 and 0.965 when using ADCmin. The optimal ADCmin threshold was 0.66 × 10(-3) mm(2)/s, which yielded an 86% positive predictive value, 97% negative predictive value, and 93% accuracy. Inter-observer variability was very low, with near perfect agreement among all observers in predicting medulloblastoma. Our data indicate that both ADCmin and nADC could serve as the basis for a CAD program to distinguish medulloblastoma from other posterior fossa tumors with a high degree of accuracy. PMID:24571835

Pierce, Theodore Thomas; Provenzale, James M

2014-02-01

425

Theory and simulation of the time-dependent rate coefficients of diffusion-influenced reactions.  

PubMed Central

A general formalism is developed for calculating the time-dependent rate coefficient k(t) of an irreversible diffusion-influenced reaction. This formalism allows one to treat most factors that affect k(t), including rotational Brownian motion and conformational gating of reactant molecules and orientation constraint for product formation. At long times k(t) is shown to have the asymptotic expansion k(infinity)[1 + k(infinity) (pie Dt)-1/2 /4 pie D + ...], where D is the relative translational diffusion constant. An approximate analytical method for calculating k(t) is presented. This is based on the approximation that the probability density of the reactant pair in the reactive region keeps the equilibrium distribution but with a decreasing amplitude. The rate coefficient then is determined by the Green function in the absence of chemical reaction. Within the framework of this approximation, two general relations are obtained. The first relation allows the rate coefficient for an arbitrary amplitude of the reactivity to be found if the rate coefficient for one amplitude of the reactivity is known. The second relation allows the rate coefficient in the presence of conformational gating to be found from that in the absence of conformational gating. The ratio k(t)/k(0) is shown to be the survival probability of the reactant pair at time t starting from an initial distribution that is localized in the reactive region. This relation forms the basis of the calculation of k(t) through Brownian dynamics simulations. Two simulation procedures involving the propagation of nonreactive trajectories initiated only from the reactive region are described and illustrated on a model system. Both analytical and simulation results demonstrate the accuracy of the equilibrium-distribution approximation method.

Zhou, H X; Szabo, A

1996-01-01

426

On the thickness-dependent diffusion coefficient of perfluoropolyether lubricants on a thin diamond-like film  

NASA Astrophysics Data System (ADS)

Diffusion of perfluoropolyethers (PFPEs) lubricants on a hard disk surface is an important self healing characteristic to replenish PFPEs lubricants on their uncovered surface. In the present paper, we study the diffusion coefficients of non-functional PFPE Z and PFPE Zdol with functional end groups as a function of lubricant film thickness on a thin DLC (diamond-like) film. Diffusion coefficients of PFPE Z and PFPE Zdol molecules on a DLC film are calculated using the equation of Einstein's law of diffusion (Guo et al. J. Appl. Phys 93:8707, 2003; Guo Ph.D. thesis, 2006; Chung et al. IEEE Trans. Magn. 45:3644, 2009) considering the movement of their center of mass to reach their equilibrium positions from their original configurations. And it is averaged with the film thickness to show the thickness dependence on the diffusion of PFPEs lubricants on a DLC substrate. Firstly diffusion coefficients of sub-monolayer of partially coverage PFPE Z and PFPE Zdol on a DLC substrate are studied briefly and secondly the diffusion coefficient of monolayer PFPE Zdol on a DLC substrate is also studied elaborately. To support our results, we compare our thickness-dependent diffusion coefficients of PFPE Z and PFPE Zdol with those of published theoretical (Guo Ph.D. thesis, 2006; Chung et al. IEEE Trans. Magn. 45:3644, 2009) and experimental results (Chung et al. Tribol. Lett. 32:35, 2008; Ma et al. Tribol. Lett. 10:203, 2001). Here we study how lubricant film thickness plays an important role on its diffusion. Effects of polar end bead functionality, lubricant film thickness enhance the anisotropic behavior of diffusion coefficients of PFPE Zdol on the DLC substrate. But in the present analysis we consider hard disk carbon overcoat as a thin DLC film and we include all of their atoms within the force cut-off distance with PFPEs lubricant molecules for the interactions to study the thickness dependence on their diffusion coefficients.

Deb Nath, S. K.

2014-05-01

427

Physics-based ULF Wave Radial Diffusion Coefficients in the Van Allen Belts  

NASA Astrophysics Data System (ADS)

Power in the Pc5 ULF wave band is believed to have strong impact on the acceleration and transport of MeV energy electrons in the outer radiation belt. Typically, radial belt diffusion coefficients are defined from empirical approaches, based on observed flux variations and param-eterised by geomagnetic indices. We report the results of new ULF wave diffusion coefficients derived from statistical analyses of ULF wave power from ground-based magnetometers from the CARISMA chain, as well as from in-situ data from GOES and THEMIS. These results are compared to previous empirical results, and the dependence of the wave-driven coefficients on energy and solar wind speed presented. The ULF wave physics model illustrates the importance of global measurements for identifying dominant or active acceleration mechanisms. Future in-situ radiation belt missions such as the Canadian Space Agency Outer Radiation Belt Injec-tion, Transport, Acceleration and Loss Satellite (ORBITALS) will enable these physics-based models to be tested and the relative importance of various ULF and VLF wave acceleration and loss processes established. In combination with the approved NASA LWS RBSP mission, and the proposed Japanese ERG satellite, the ORBITALS-RBSP-ERG three petal constella-tion together with supporting ground-based and geosynchronous measurements will resolve the spatio-temporal ambiguities and global dynamics and morphology of the Earths radiation belts.

Mann, Ian; Rae, Jonathan; Murphy, Kyle; Ozeke, Louis; Milling, David; Chan, Anthony; Elkington, Scot; Angelopoulos, Vassilis

428

Lateral Diffusion Coefficients of an Eicosanyl-Based Bisglycerophosphocholine Determined by PFG-NMR and FRAP  

PubMed Central

We report the lateral diffusion properties of 2,2?-di-O-decyl-3,3?-di-O-(eicosanyl)-bis-(rac-glycero)-1,1?-diphosphocholine (C20BAS) using pulsed-field gradient NMR (PFG-NMR) and fluorescence recovery after photobleaching (FRAP). C20BAS membranes display a melting transition at Tm = 15.7 °C as determined by differential scanning calorimetry and 31P NMR chemical shift anisotropy. The lateral diffusion coefficient of C20BAS, as determined by PFG-NMR and FRAP, at 25 °C, were DPFG-NMR = 1.9 ± 0.6 × 10?8 cm2/s and DFRAP C20BAS = 1.2 ± 0.1 × 10?8 cm2/s, respectively. In comparison, the lateral diffusion coefficient of the monopolar phospholipid, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), was 1.8 ± 0.9 × 10?8 and 2.5 ± 0.9 × 10?8 cm2/s using PFG-NMR and FRAP, respectively.

Febo-Ayala, Wilma; Holland, David P.; Bradley, Scott A.; Thompson, David H.

2008-01-01

429

Bounce-averaged diffusion coefficients in the Tsyganenko field model for oblique chorus waves  

NASA Astrophysics Data System (ADS)

We present the results of computations of bounce-averaged quasi-linear momentum Dpp, pitch-angle D?? and mixed D?p diffusion coefficients in the Tsyganenko magnetic field model. We assume that electrons are scattered by oblique whistler mode chorus waves of Gaussian spread of wave power spectral density and wave normal angle outside the plasmasphere. The scat-tering rates are computed using the full electromagnetic dispersion relation and up to 5-order resonance condition including Landau resonance. The diffusion coefficients are calculated for quiet conditions and storm-time conditions for the day and night sides. We compare scattering rates bounce-averaged in the Tsyganenko field model with those in the dipole field and discuss the differences. The results are followed by a physical explanation of how the magnetic field model can change the bounce-averaged scattering rates. The calculations show that, during active conditions, the pitch-angle scattering by chorus waves in the realistic magnetic field can diffuse relativistic electrons to the loss cone not only on the day side, but also on the night side. Our study shows that while there are still a number of unknown parameters that determine scattering rates, inclusion of bounce-averaging in the realistic field will be crucially important for future radiation belt modeling.

Orlova, Ksenia; Shprits, Yuri

430

System size dependence of the diffusion coefficient in a simple liquid  

NASA Astrophysics Data System (ADS)

An equation to estimate the system size dependence of the self-diffusion coefficient of a tagged particle moving in a simple fluid is given using linear-response theory and linearized hydrodynamics. Estimates made by the equation are compared with the results of the molecular dynamics simulation for a hard-sphere fluid at two densities, ??3?0.88 and 0.47, where ? is the hard-sphere diameter. Good agreement between theory and simulation is obtained at the higher density. At the lower density, the agreement becomes poorer, but it is improved by taking into account the diffusion effect of the tagged particle. The equation gives the same diffusion coefficient for the infinite system as that obtained by taking into account the long-time tail contribution of the velocity autocorrelation function [B. J. Alder, D. M. Gass, and T. E. Wainwright, J. Chem. Phys. 53, 3813 (1970)]. When the tagged particle has a larger mass than the fluid particles, the equation presented here gives the better estimates. It is confirmed by the molecular dynamics calculation.

Fushiki, M.

2003-08-01

431

Optimal estimation of the diffusion coefficient from non-averaged and averaged noisy magnitude data  

NASA Astrophysics Data System (ADS)

The magnitude operation changes the signal distribution in MRI images from Gaussian to Rician. This introduces a bias that must be taken into account when estimating the apparent diffusion coefficient. Several estimators are known in the literature. In the present paper, two novel schemes are proposed. Both are based on simple least squares fitting of the measured signal, either to the median (MD) or to the maximum probability (MP) value of the Probability Density Function (PDF). Fitting to the mean (MN) or a high signal-to-noise ratio approximation to the mean (HS) is also possible. Special attention is paid to the case of averaged magnitude images. The PDF, which cannot be expressed in closed form, is analyzed numerically. A scheme for performing maximum likelihood (ML) estimation from averaged magnitude images is proposed. The performance of several estimators is evaluated by Monte Carlo (MC) simulations. We focus on typical clinical situations, where the number of acquisitions is limited. For non-averaged data the optimal choice is found to be MP or HS, whereas uncorrected schemes and the power image (PI) method should be avoided. For averaged data MD and ML perform equally well, whereas uncorrected schemes and HS are inadequate. MD provides easier implementation and higher computational efficiency than ML. Unbiased estimation of the diffusion coefficient allows high resolution diffusion tensor imaging (DTI) and may therefore help solving the problem of crossing fibers encountered in white matter tractography.

Kristoffersen, Anders

2007-08-01

432

Influence of the scattering and absorption coefficients on homogeneous room simulations that use a diffusion equation model.  

PubMed

The diffusion equation model was used for room acoustic simulations to predict the sound pressure level and the reverberation time. The technical literature states that the diffusion equation method accurately models the late portion of the room impulse response if the energy is sufficiently scattered. This work provides conclusions on the validity of the diffusion equation model for rooms with homogeneous dimensions in relation to the scattering coefficients of the boundaries. A systematic evaluation was conducted out to determine the ranges of the absorption and scattering coefficient values that result in low noticeable differences between the predictions from a geometrical acoustic model and those from the diffusion equation model. PMID:23463993

Navarro, Juan M; Escolano, José; Cobos, Maximo; López, José J

2013-03-01

433

Cathodic reduction of sulfur dioxide in nonaqueous electrolytes. The effect of solution composition on the diffusion coefficient of sulfur dioxide  

SciTech Connect

The authors measured the diffusion coefficients of SO/sub 2/ in electrolytes based on propylene carbonate, acetonitrile, dimethylformamide and dimethylsulfoxide in order to estimate possible diffusion limitations with respect to SO/sub 2/ and to establish the influence exerted by the solvent type on the process. The diffusion coefficients were calculated from the limiting diffusion currents of steady-state polarization curves for sulfur dioxide reduction recorded at a gold micro