Role of Interstitial and Interstitial-Impurity Interaction on Irradiation-Induced Segregation in Austenitic Steels

1997 ◽  
Vol 481 ◽  
Author(s):  
M. Nastar ◽  
P. Bellon ◽  
G. Martin ◽  
J. Ruste
Keyword(s):  
Mean Field ◽  
Tracer Diffusion ◽  
Austenitic Steels ◽  
Rate Theory ◽  
Fitting Procedure ◽  
Surfaces And Interfaces ◽  
Total Inhibition ◽  
Impurity Interaction ◽  
Jump Frequencies

ABSTRACTSegregation under irradiation in austenitic steels is due to a permanent flux of vacancies and interstitials produced by irradiation towards sinks like surfaces and interfaces. A model based on a mean field lattice rate theory is proposed where kinetics and thermodynamics are treated in a mutually consistent way. For a Fe-Ni-Cr ternary alloy, the 15 parameters defining the jump frequencies of vacancies were fitted on equilibrium properties including ordering energies and tracer diffusion experiments with no use of segregation data. Measurements of RIS by Auger Electron Spectroscopy (AES) were used in the last step of the fitting procedure in order to choose the best set of the 27 interstitial jump frequencies. This fitting procedure strongly supports the idea that the interstitials are contributing to RIS in Fe-Cr-Ni alloys. We also simulate the trapping of interstitials by an impurity model and reproduce the total inhibition of RIS by this impurity as observed experimentally [1].

scholarly journals Filaments and the Solar Dynamo

1998 ◽  
Vol 167 ◽  
pp. 406-414
Author(s):  
N. Seehafer
Keyword(s):  
Mean Field ◽  
Decisive Role ◽  
Dynamo Theory ◽  
Simultaneous Generation ◽  
Alpha Effect ◽  
Generation Region ◽  
The Mean ◽  
Numerical Bifurcation ◽  
Dynamo Effect

AbstractFilaments are a global phenomenon and their formation, structure and dynamics are determined by magnetic fields. So they are an important signature of the solar magnetism. The central mechanism in traditional mean-field dynamo theory is the alpha effect and it is a major result of this theory that the presence of kinetic or magnetic helicities is at least favourable for the effect. Recent studies of the magnetohydrodynamic equations by means of numerical bifurcation-analysis techniques have confirmed the decisive role of helicity for a dynamo effect. The alpha effect corresponds to the simultaneous generation of magnetic helicities in the mean field and in the fluctuations, the generation rates being equal in magnitude and opposite in sign. In the case of statistically stationary and homogeneous fluctuations, in particular, the alpha effect can increase the energy in the mean magnetic field only under the condition that also magnetic helicity is accumulated there. Generally, the two helicities generated by the alpha effect, that in the mean field and that in the fluctuations, have either to be dissipated in the generation region or to be transported out of this region. The latter may lead to the appearance of helicity in the atmosphere, in particular in filaments, and thus provide valuable information on dynamo processes inaccessible to in situ measurements.

scholarly journals Paradox of integration — mean field approach

2017 ◽  
Vol 28 (11) ◽  
pp. 1750133 ◽  
Author(s):  
Krzysztof Kułakowski ◽  
Piotr Gronek ◽  
Alfio Borzì
Keyword(s):  
Social Status ◽  
Positive Emotions ◽  
Mean Field ◽  
Computational Approach ◽  
Transient Time ◽  
Field Approach ◽  
The Social ◽  
The Mean ◽  
High Social Status

Recently, a computational model has been proposed of the social integration, as described in sociological terms by Blau. In this model, actors praise or critique each other, and these actions influence their social status and raise negative or positive emotions. The role of a self-deprecating strategy of actors with high social status has also been discussed there. Here, we develop a mean field approach, where the active and passive roles (praising and being praised, etc.) are decoupled. The phase transition from friendly to hostile emotions has been reproduced, similarly to the previously applied purely computational approach. For both phases, we investigate the time dependence of the distribution of social status. There we observe a diffusive spread, which — after some transient time — appears to be limited from below or from above, depending on the phase. As a consequence, the mean status flows.

scholarly journals Combining experiments and in silico modeling to infer the role of adhesion and proliferation on the collective dynamics of cells

2021 ◽  
Author(s):  
Hygor P. M. Melo ◽  
F. Raquel Maia ◽  
André S. Nunes ◽  
Rui L. Reis ◽  
Joaquim M. Oliveira ◽  
...  
Keyword(s):  
Tissue Engineering ◽  
Cell Adhesion ◽  
Glioblastoma Multiforme ◽  
In Silico ◽  
Relative Importance ◽  
Collective Dynamics ◽  
Surfaces And Interfaces ◽  
In Silico Modeling ◽  
Cell Cell

ABSTRACTThe collective dynamics of cells on surfaces and interfaces poses technological and theoretical challenges in the study of morphogenesis, tissue engineering, and cancer. Different mechanisms are at play, including, cell-cell adhesion, cell motility, and proliferation. However, the relative importance of each one is elusive. Here, experiments with a culture of glioblastoma multiforme cells on a substrate are combined with in silico modeling to infer the rate of each mechanism. By parametrizing these rates, the time-dependence of the spatial correlation observed experimentally is reproduced. The obtained results suggest a reduction in cell-cell adhesion with the density of cells. The reason for such reduction and possible implications for the collective dynamics of cancer cells are discussed.

scholarly journals Role of Deformation-Induced Martensite in TRIP Effect of Metastable Austenitic Steels

2021 ◽  
Vol 61 (2) ◽  
pp. 556-563
Author(s):  
Noriyuki Tsuchida ◽  
Eiichiro Ishimaru ◽  
Masatomo Kawa
Keyword(s):  
Austenitic Steels ◽  
Trip Effect

INVESTIGATIONS ON THE NUCLEAR HALO STRUCTURES

2008 ◽  
Vol 17 (09) ◽  
pp. 1729-1738
Author(s):  
YU-JIE LIANG ◽  
ZU-HUA LIU ◽  
HONG-YU ZHOU
Keyword(s):  
Mean Field ◽  
Light Nuclei ◽  
Halo Nuclei ◽  
Asymptotic Normalization ◽  
Relativistic Mean Field ◽  
Asymptotic Normalization Coefficient ◽  
Nuclear Halo ◽  
Coulomb Effects ◽  
Qualitative Analyses

The halo structures in some light nuclei are investigated systemically with the nuclear asymptotic normalization coefficient (ANC) method and the relativistic mean-field (RMF) theory. Some important results about the halo structures in mirror nuclei are obtained, and some qualitative analyses are made to explore the role of Coulomb effects on the formation of proton halo nuclei.

scholarly journals Improvements to the Sink Strength Theory Used in Multi-Scale Rate Equation Simulations of Defects in Solids

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2621
Author(s):  
Tommy Ahlgren ◽  
Kalle Heinola
Keyword(s):  
Interaction Parameter ◽  
Rate Equation ◽  
Mean Field ◽  
Interaction Parameters ◽  
Rate Theory ◽  
Sink Strength ◽  
Strength Theory ◽  
Dissociation Process ◽  
Multi Scale ◽  
Defect Interaction

The application of mean-field rate theory equations have proven to be a versatile method in simulating defect dynamics and temporal changes in the microstructure of materials. The reliability and usefulness of the method, however, depends critically on the defect interaction parameters used. In this study, we show that the main interaction parameter, the sink strength, intrinsically depends on the detrapping, or the dissociation process itself. We present a theory on how to determine the appropriate sink strengths. The correct sink strength required for a detrapping defect, is considerably larger than the values commonly used, and thus should not be neglected.

scholarly journals Effect of weak disorder on the BCS–BEC crossover in a two-dimensional Fermi gas

2017 ◽  
Vol 31 (09) ◽  
pp. 1750066
Author(s):  
Ayan Khan ◽  
B. Tanatar
Keyword(s):  
Field Theory ◽  
Mean Field Theory ◽  
Mean Field ◽  
Fermi Gas ◽  
Ultracold Fermi Gas ◽  
Condensate Fraction ◽  
Two Dimensional ◽  
Weak Disorder ◽  
Unique Nature

In this paper, we study the two-dimensional (2D) ultracold Fermi gas with weak impurity in the framework of mean-field theory where the impurity is introduced through Gaussian fluctuations. We have investigated the role of the impurity by studying the experimentally accessible quantities such as condensate fraction and equation of state of the ultracold systems. Our analysis reveals that at the crossover, the disorder enhances superfluidity, which we attribute to the unique nature of the unitary region and to the dimensional effect.

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