scholarly journals Characteristics of micro transfer paths and diffusion phenomena in the matrix of deep crystalline rock

2016 ◽  
Vol 23 (2) ◽  
pp. 121-130 ◽  
Author(s):  
Masayuki ISHIBASHI ◽  
Eiji SASAO ◽  
Katsuhiro HAMA
Keyword(s):  
Crystalline Rock ◽  
The Matrix ◽  
Diffusion Phenomena ◽  
And Diffusion

Nuclear Waste Repositories in Crystalline Rock- an Overview of Flow and Nuclide Transport Mechanisms

1994 ◽  
Vol 353 ◽  
Author(s):  
Ivars Neretnieks
Keyword(s):  
Nuclear Waste ◽  
Field Experiments ◽  
Fracture Network ◽  
Crystalline Rock ◽  
Transport Mechanisms ◽  
The Matrix ◽  
Nuclide Transport ◽  
Waste Repositories ◽  
And Diffusion ◽  
Diffusion Properties

AbstractNuclides eventually escaping from nuclear waste repositories in crystalline rock will move with the seeping water in the fracture network. Most important nuclides interact physically or chemically with the rock and are expected to be considerably retarded allowing them to decay to insignificant concentrations. Velocity variations may allow some portions of the nuclides to move faster. Matrix diffusion and sorption on the surfaces of the rock are by far the most powerful retardation mechanisms and depend, in addition to the sorption and diffusion properties, directly on the magnitude of the “flow wetted surface”which is the contact surface between the mobile water carrying the nuclides and the fracture surfaces over which the nuclides diffuse into the matrix.A number of field experiments have been performed over the last 15 years to help validate the concepts and models and to obtain data. A number of such experiments are described and discussed in relation to the above issues.

scholarly journals Ductile saline ice

1994 ◽  
Vol 40 (136) ◽  
pp. 566-568
Author(s):  
G. A. Kuehn ◽  
E. M. Schulson
Keyword(s):  
Fresh Water ◽  
Tensile Ductility ◽  
Compressive Deformation ◽  
Dislocation Creep ◽  
Diffusion Creep ◽  
Water Ice ◽  
The Matrix ◽  
And Diffusion

AbstractExperiments have shown that tensile ductility of about 5% or more can be imparted to columnar, saline ice by pre-compressing the material by about 3.5%. This effect is similar to that observed in granular, fresh-water ice and is attributed to the operation of both dislocation creep and diffusion creep within that part of the matrix which recrystallized during the pre-compressive deformation.

The geometry and motion of sharp fronts within geochemical transport problems

1995 ◽  
Vol 449 (1935) ◽  
pp. 123-138
Keyword(s):  
Front Propagation ◽  
Singular Perturbation Theory ◽  
Advective Transport ◽  
Natural Systems ◽  
Diffusion Phenomena ◽  
Sharp Fronts ◽  
Geochemical Transport ◽  
Transport Problems ◽  
Groundwater Flow Field ◽  
And Diffusion

We consider some reactive geochemical transport problems in groundwater sys­tems. When incoming fluid is in disequilibrium with the mineralogy, sharp tran­sition fronts may develop. We show that this is a generic property for a class of systems where the time scales associated with reaction and diffusion phenomena are much shorter than those associated with advective transport. Such multi­ple timescale problems are relevant to a variety of processes in natural systems: mathematically, methods of singular perturbation theory reduce the dimension of the problems to be solved locally. Furthermore, we consider how spatial heteroge­neous mineralogy can make an impact upon the propagation of sharp geochemical fronts. We develop an asymptotic approach in which we solve equations for the evolv­ing geometry of the front and indicate how the non-smooth perturbations, due to natural heterogeneity of the mineralogy on underlying groundwater flow field, are balanced against the smoothing effect of diffusion-dispersive processes. Fronts are curvature damped, and the results here indicate the generic nature of sepa­rate front propagation within both model (idealized) and natural (heterogeneous) geochemical systems.

Implementation of Finite Deformation Triphasic Modeling in the Finite Element Code FEBio

2012 ◽  
Author(s):  
Gerard A. Ateshian ◽  
Steve Maas ◽  
Jeffrey A. Weiss
Keyword(s):  
Soft Tissues ◽  
Mixture Theory ◽  
Solid Matrix ◽  
Osmotic Swelling ◽  
Solute Content ◽  
Counter Ions ◽  
The Matrix ◽  
Triphasic Theory ◽  
Ion Species ◽  
And Diffusion

Many biological soft tissues exhibit a charged solid matrix, most often due to the presence of proteoglycans enmeshed within the matrix. The predominant solute content of the interstitial fluid of these tissues consists of the monovalent counter-ions Na+ and Cl−. The electrical interactions between the mobile ion species and fixed charge density of the solid matrix produces an array of mechano-electrochemical effects, including Donnan osmotic swelling, and streaming and diffusion potentials and currents. These phenomena have been successfully modeled by the triphasic theory of Lai et al. [1], which is based on the framework of mixture theory [2]. Other similar frameworks have also been proposed [3, 4]. The equations of triphasic theory are nonlinear, even in the range of infinitesimal strains. Therefore, numerical schemes are generally needed to solve all but the simplest problems using this framework.

scholarly journals Methane Combustion Using Pd Deposited on CeOx-MnOx/La-Al2O3 Pellistors

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4888
Author(s):  
Ovidiu G. Florea ◽  
Adelina Stănoiu ◽  
Marin Gheorghe ◽  
Cornel Cobianu ◽  
Florentina Neaţu ◽  
...  
Keyword(s):  
Surface Reaction ◽  
Wheatstone Bridge ◽  
Methane Combustion ◽  
Sensitive Material ◽  
Voltage Signal ◽  
Coating Method ◽  
Diffusion Phenomena ◽  
Selective Sensitivity ◽  
And Diffusion ◽  
Operating Temperature Range

Pd deposited on CeOx-MnOx/La-Al2O3 has been prepared as a sensitive material for methane (CH4) detection. The effect of different amounts (1.25%, 2.5% and 5%) of Pd loading has been investigated. The as prepared materials were deposited on Pt microcoils using a drop-coating method, as a way of developing pellistors operated using a Wheatstone bridge configuration. By spanning the operating temperature range between 300 °C and 550 °C, we established the linearity region as well as the maximum sensitivity towards 4900 ppm of CH4. By making use of the sigmoid dependence of the output voltage signal from the Wheatstone bridge, the gas surface reaction and diffusion phenomena have been decoupled. The pellistor with 5% Pd deposited on CeOx-MnOx/La-Al2O3 exhibited the highest selective-sensitivity in the benefit of CH4 detection against threshold limits of carbon monoxide (CO), sulfur dioxide (SO2) and hydrogen sulfide (H2S). Accordingly, adjusting the percent of Pd makes the preparation strategies of pellistors good candidates towards CH4 detection.

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