scholarly journals Evaluation of Aerosol Fire Extinguishing Agent Using a Simple Diffusion Model

2012 ◽  
Vol 2012 ◽  
pp. 1-14 ◽  
Author(s):  
Chen-guang Zhu ◽  
Chun-xu Lü ◽  
Jun Wang
Keyword(s):  
Diffusion Coefficient ◽  
Effective Concentration ◽  
Diffusion Time ◽  
Simple Diffusion ◽  
Fire Extinguishing ◽  
Diffusion Source ◽  
Room Volume ◽  
Simple Diffusion Model ◽  
Kinetics Of ◽  
And Diffusion

Aerosol fire extinguishing agents have been recognized as an effective replacement of Halon. The uniform diffusion time and the effective concentration of the aerosol fire extinguishing agent are important parameters for putting out a fire. In this work, the effective concentration is derived based on the diffusion equation, and its variation with changing diffusion coefficient and diffusion time is analyzed. The uniform diffusion time could then be conveniently estimated using this equation. Based on experimental data, the concentration kinetics of the aerosol is drawn and the relation between the diffusion coefficient and the uniform diffusion time is analyzed. It was found that the uniform diffusion time is not dependent on the shape of the closed room but dependent on the total room volume and the position of its diffusion source. This model is demonstrated as a facile tool for the convenient evaluation and reasonable application of the aerosol fire extinguishing agent by predicting the uniform diffusion times of extinguishing aerosol in closed rooms.

Slow diffusion of Ca2+ in the rat's hippocampus

1981 ◽  
Vol 59 (9) ◽  
pp. 1022-1025 ◽  
Author(s):  
M. E. Morris ◽  
K. Krnjević
Keyword(s):  
Diffusion Coefficient ◽  
Apparent Diffusion Coefficient ◽  
Time Course ◽  
Transport Number ◽  
Dorsal Hippocampus ◽  
Simple Diffusion ◽  
Apparent Diffusion ◽  
Resultant Increase ◽  
Simple Diffusion Model

Ca2+-sensitive microelectrodes, attached to CaCl2-containing micropipettes, were inserted into the dorsal hippocampus of rats under urethane. When Ca2+ was released iontophoretically, the amplitude and time course of the resultant increase in extracellular Ca2+ concentration could be fitted to a simple diffusion model, but the apparent diffusion coefficient of Ca2+ was only about 1/100 of its value in water, possibly because of reversible Ca2+ binding to hippocampal tissue. A further anomaly was a very low transport number (<0.01) for the release of Ca2+ from microelectrodes in vivo.

A simple diffusion model for the growth kinetics of γ′ iron nitride on the pure iron substrate

2005 ◽  
Vol 242 (3-4) ◽  
pp. 369-374 ◽  
Author(s):  
M. Keddam ◽  
M.E. Djeghlal ◽  
L. Barrallier
Keyword(s):  
Diffusion Model ◽  
Growth Kinetics ◽  
Pure Iron ◽  
Iron Nitride ◽  
Simple Diffusion ◽  
Simple Diffusion Model ◽  
Kinetics Of

Energetic Landscapes and Diffusion Properties in FeCu Alloys

2007 ◽  
Vol 129 ◽  
pp. 31-39 ◽  
Author(s):  
Frédéric Soisson ◽  
Chu Chun Fu
Keyword(s):  
Binding Energies ◽  
Kinetic Properties ◽  
Simple Diffusion ◽  
Effective Interactions ◽  
Point Configurations ◽  
Migration Barriers ◽  
Copper Distribution ◽  
Simple Diffusion Model ◽  
And Diffusion ◽  
Diffusion Properties

The thermodynamic and kinetic properties of Fe-Cu alloys are studied by ab initio calculations, in the framework of a multiscale modeling of precipitation kinetics. The configuration energies at various compositions, the solute migration and binding energies, as well as the vacancy formation and binding energies are computed. The effects of the local copper distribution on the migration barriers are considered. We show that a simple diffusion model with effective interactions on a rigid lattice, which includes a description of the saddle-point configurations, captures the main features of the energetic landscapes explored by the vacancy during its diffusion in dilute and concentrated configurations.

Dyeing Kinetics of Collagen Modified PAN Fiber

2014 ◽  
Vol 1048 ◽  
pp. 81-84
Author(s):  
Xue Min Hu
Keyword(s):  
Diffusion Coefficient ◽  
Polymer Chain ◽  
Rate Constant ◽  
Dye Uptake ◽  
Moisture Regain ◽  
Pan Fiber ◽  
Dyeing Rate ◽  
Kinetics Of ◽  
And Diffusion ◽  
Dyeing Kinetics

PAN fiber is one that contains at least 85% by mass of acrylonitrile co-monomer in the polymer chain. It has low moisture-absorbency and electrostatic tendency. The moisture regain of collagen modified PAN fiber is increased. Dyeing kinetics of collagen modified PAN fiber was studied using Cationic Red X-GRL dyes, including dyeing rate curve, equilibrium dyeing uptake, half dyeing time, dyeing rate constant and diffusion coefficient. The results show that: compared with PAN fiber, the equilibrium dye uptake decreased, half dyeing time, dyeing rate constant and diffusion coefficient reduced, and the dyeing behavior of collagen modified PAN fiber become worse than that of PAN fiber.

The Diffusion of Radionuclides through Waste Encapsulation Grouts

2006 ◽  
Vol 932 ◽  
Author(s):  
Adam V. Chambers ◽  
Andrew Green ◽  
Andrew W. Harris ◽  
Timothy G. Heath ◽  
Fiona M.I. Hunter ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Intrinsic Diffusion Coefficient ◽  
Intrinsic Diffusion ◽  
Simple Diffusion ◽  
Fuel Ash ◽  
Simple Diffusion Model ◽  
Environmentally Sound ◽  
One Year

ABSTRACTUnited Kingdom Nirex Limited develops and advises on safe, environmentally sound and publicly acceptable options for the long-term management of radioactive waste. One option Nirex has developed is a phased geological repository concept for intermediate level waste and some low level wastes that makes use of a combination of engineered and natural barriers. Physical containment of radionuclides would be achieved by immobilisation and packaging of wastes (mostly) in stainless steel containers.Existing models of the migration of dissolved radionuclides from packaged wastes suggest that radionuclide release is determined largely by the rate of diffusion through the encapsulation grout used to immobilise the waste. The use of such models requires diffusion coefficient data for radionuclides in waste encapsulation grouts. This paper describes a programme of through-diffusion experiments, and modelling interpretation, aimed at deriving diffusion coefficients for some radionuclides in two types of encapsulation grout.An intrinsic diffusion coefficient of HTO of around 1×10−13 to 2×10−13 m2s−1 was determined for a 3:1 mix of blast furnace slag to ordinary Portland cement, compared to around 4×10−13 to 5×10−13 m2s−1 for a 3:1 mix of pulverised fuel ash to ordinary Portland cement. These values are lower than that assumed for a non-sorbing radionuclide in an earlier modelling exercise. Porosity values around 0.3 were obtained in each case. For 36Cl as chloride, the experiments showed no significant breakthrough over the experimental timescale of about one year, suggesting an intrinsic diffusion coefficient below 5×10−13 m2s−1. One possibility is that chlorine-containing solids are precipitating in the cement. An intrinsic diffusion coefficient for 137Cs in the 3:1 mix of pulverised fuel ash to ordinary Portland cement of 4×10−15 m2s−1 was estimated, significantly lower than that determined for HTO.The results from three of the sixteen experiments could not be fitted with a simple diffusion model, and for a further five experiments there was some doubt as to whether simple diffusion behaviour had been observed. It is suggested that this may have been due to cracks in the grouts that were sufficiently large to affect the diffusion properties of the grouts, although none was visible to the naked eye. Cracking of the waste encapsulation grouts could provide a mechanism for enhanced migration of radionuclides from waste packages, compared with diffusion in a homogeneous porous medium alone.

scholarly journals Evaluation of Phenol Transport Using Polymer Inclusion Membrane (PIM) with Polyeugenol as a Carrier

2016 ◽  
Vol 11 (2) ◽  
pp. 99
Author(s):  
Arifina Febriasari ◽  
Dwi Siswanta ◽  
Agung Abadi Kiswandono ◽  
Nurul Hidayat Aprilita
Keyword(s):  
Diffusion Coefficient ◽  
Optimum Condition ◽  
Evaluation Studies ◽  
Transport Kinetics ◽  
Membrane Selectivity ◽  
Study Results ◽  
Transport Kinetic ◽  
Recovery Study ◽  
Kinetics Of ◽  
And Diffusion

A recovery study of phenol with Polymer Inclusion Membranes (PIMs) needs to be evaluated to determine values of transport kinetic parameter, level of stability, and selectivity of the membrane. This paper describes results of the evaluation of phenol transport using PIMs with polyeugenol as a carrier. PIMs were made by mixing polyeugenol, dibenzylether, and polyvinylchloride in a solvent (tetrahydrofuran) then printed in a container with diameter 4.5 cm and allowed to vaporize for 72 hours. Further evaluation studies are conducted at pH 4.5 with various parameters, among of them are various times that were taken to identify parameters of the transport kinetics of phenol, membrane stability, characterization, and testing of membrane selectivity by comparing transport of phenol with another compound, in this study chromium is used. This study results in calculation of values of transport kinetics of membrane permeability obtained at 8.8 x 10-5 m/s, flux value of 9.512 x 10-4 g/m2s, and diffusion coefficient of 3.826 x 10-11 m2/s. Repeating use over three times, 48 hours, indicates reduction in power of phenol transport by 70.81%. While selectivity test indicates that membrane is used more selectively against phenol than chromium metal. Based on study results, phenol transport effectiveness using PIM with polyeugenol as carrier is 91.4% in optimum condition.

Meridional Circulation, Turbulence, and Diffusion Processes in Stars

1976 ◽  
Vol 32 ◽  
pp. 109-116 ◽  
Author(s):  
S. Vauclair
Keyword(s):  
Convection Zone ◽  
Diffusion Processes ◽  
Meridional Circulation ◽  
Diffusion Time ◽  
Work In Progress ◽  
First Results ◽  
Stellar Envelopes ◽  
And Diffusion ◽  
Turbulence And Diffusion ◽  
Hr Diagram

This paper gives the first results of a work in progress, in collaboration with G. Michaud and G. Vauclair. It is a first attempt to compute the effects of meridional circulation and turbulence on diffusion processes in stellar envelopes. Computations have been made for a 2 Mʘstar, which lies in the Am - δ Scuti region of the HR diagram.Let us recall that in Am stars diffusion cannot occur between the two outer convection zones, contrary to what was assumed by Watson (1970, 1971) and Smith (1971), since they are linked by overshooting (Latour, 1972; Toomre et al., 1975). But diffusion may occur at the bottom of the second convection zone. According to Vauclair et al. (1974), the second convection zone, due to He II ionization, disappears after a time equal to the helium diffusion time, and then diffusion may happen at the bottom of the first convection zone, so that the arguments by Watson and Smith are preserved.

Velocity and diffusion coefficient of a random asymmetric one-dimensional hopping model

1989 ◽  
Vol 50 (8) ◽  
pp. 899-921 ◽  
Author(s):  
C. Aslangul ◽  
N. Pottier ◽  
D. Saint-James
Keyword(s):  
Diffusion Coefficient ◽  
One Dimensional ◽  
And Diffusion ◽  
Hopping Model
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