Computer Simulations of the Chessboard-Like Microstructure Formation in Decomposing Alloys

1997 ◽  
Vol 481 ◽  
Author(s):  
Y. Le Bouar ◽  
A. G. Khachaturyan
Keyword(s):  
Computer Simulations ◽  
Temporal Evolution ◽  
Kinetic Equations ◽  
Coherency Strain ◽  
Precipitate Phase ◽  
Mechanism Of Formation ◽  
Microstructure Formation ◽  
Stochastic Field ◽  
Self Assembling ◽  
The Continuum

ABSTRACTThe mechanism of formation of a chessboard-like structure observed during coherent decomposition in alloys with several orientation variants of the precipitate phase is considered. It is based on the accommodation of coherency strain achieved by spatial rearrangement of orientation variants of the precipitate phase in an optimal pattern. The computational model of precipitation of the ordered tetragonal phase, based on the continuum stochastic field kinetic equations for the composition and lro parameters profiles, is formulated. Its numerical solution describes the spatial and temporal evolution of the microstructure, from nucleation to coarsening. It is shown that the chessboard-like microstructure is produced by strain-driven, self-assembling of orientation variants of the precipitate phase, faceted by the planes normal to the elastically soft directions. Coarsening of such microstructures occurs by consequent disappearance of entire rows of “tiles” in the pattern.

scholarly journals White-light continuum emission from a solar flare and plage

2015 ◽  
Vol 11 (S320) ◽  
pp. 268-277
Author(s):  
Arkadiusz Berlicki ◽  
Arun Kumar Awasthi ◽  
Petr Heinzel ◽  
Michal Sobotka
Keyword(s):  
Active Region ◽  
Solar Flare ◽  
White Light ◽  
Temporal Evolution ◽  
Continuum Emission ◽  
White Light Continuum ◽  
Multi Wavelength ◽  
Optical Continuum ◽  
The Continuum ◽  
Morphological Correlation

AbstractObservations of flare emissions in the optical continuum are very rare. Therefore, the analysis of such observations is useful and may contribute to our understanding of the flaring chromosphere and photosphere. We study the white light continuum emission observed during the X6.9 flare. This emission comes not only from the flare ribbons but also form the nearby plage area. The main aim of this work is to disentangle the flare and plage (facula) emission. We analyzed the spatial, spectral and temporal evolution of the flare and plage properties by analyzing multi-wavelength observations. We study the morphological correlation of the white-light continuum emission observed with different instruments. We found that some active region areas which produce the continuum emission correspond rather to plages than to the flare kernels. We showed that in some cases the continuum emission from the WL flare kernels is very similar to the continuum emission of faculae.

scholarly journals Multifrequency Variability of AGN's: Continuum Variations from the Near IR to the X-rays

1994 ◽  
Vol 159 ◽  
pp. 131-143
Author(s):  
J. Clavel
Keyword(s):  
Active Galactic Nuclei ◽  
Temporal Evolution ◽  
Line Emission ◽  
Galactic Nuclei ◽  
The Other ◽  
X Rays ◽  
Optical Telescope ◽  
Emission Process ◽  
Near Ir ◽  
The Continuum

Because they emit copiously over more than 10 decades in frequency, Active Galactic Nuclei (AGN) cannot be understood without the help of multiwavelength observations. On the other hand, variability monitoring has also proven to be invaluable in understanding the continuum and line emission process as well as the geometry of the innermost regions in these objects. Indeed, at the heart of AGN's lies an object which is so compact that the only way to probe its structure is the study of the temporal evolution of its spectrum. The equivalent resolution which can be achieved in this way is of the order of 10 microarcsecs, far beyond the capability of any UV or optical telescope.

Computer Simulations of Self-Assembling Comb Copolymers

Langmuir ◽  
1995 ◽  
Vol 11 (10) ◽  
pp. 3848-3855 ◽  
Author(s):  
Darrel J. Irvine ◽  
Dilip Gersappe ◽  
Anna C. Balazs
Keyword(s):  
Computer Simulations ◽  
Self Assembling

scholarly journals ON SPATIAL CONSENSUS FORMATION: IS THE SZNAJD MODEL DIFFERENT FROM A VOTER MODEL?

2003 ◽  
Vol 14 (10) ◽  
pp. 1331-1354 ◽  
Author(s):  
LAXMIDHAR BEHERA ◽  
FRANK SCHWEITZER
Keyword(s):  
Computer Simulations ◽  
Nearest Neighbor ◽  
Temporal Evolution ◽  
Relaxation Times ◽  
Nearest Neighbors ◽  
Voter Model ◽  
Consensus Formation ◽  
Spatio Temporal ◽  
Update Rules

In this paper, we investigate the so-called "Sznajd Model" (SM) in one dimension, which is a simple cellular automata approach to consensus formation among two opposite opinions (described by spin up or down). To elucidate the SM dynamics, we first provide results of computer simulations for the spatio-temporal evolution of the opinion distribution L(t), the evolution of magnetization m(t), the distribution of decision times P(τ) and relaxation times P(μ). In the main part of the paper, it is shown that the SM can be completely reformulated in terms of a linear voter model (VM), where the transition rates towards a given opinion are directly proportional to frequency of the respective opinion of the second-nearest neighbors (no matter what the nearest neighbors are). So, the SM dynamics can be reduced to one rule, "Just follow your second-nearest neighbor". The equivalence is demonstrated by extensive computer simulations that show the same behavior between SM and VM in terms of L(t), m(t), P(τ), P(μ), and the final attractor statistics. The reformulation of the SM in terms of a VM involves a new parameter σ, to bias between anti- and ferromagnetic decisions in the case of frustration. We show that σ plays a crucial role in explaining the phase transition observed in SM. We further explore the role of synchronous versus asynchronous update rules on the intermediate dynamics and the final attractors. As compared to the original SM, we find three additional attractors, two of them related to an asymmetric coexistence between the opposite opinions.

Natural As-Sb alloys: texture types, thermal behaviour and mechanism of formation

1987 ◽  
Vol 51 (360) ◽  
pp. 295-304 ◽  
Author(s):  
G. P. Bernardini ◽  
C. Cipriani ◽  
F. Corsini ◽  
G. G. T. Guarini ◽  
G. Mazzetti ◽  
...  
Keyword(s):  
Solid Solution ◽  
Thermal Behaviour ◽  
Diffusion Mechanism ◽  
Kinetic Equations ◽  
State Theory ◽  
Mechanism Of Formation ◽  
Constant Composition ◽  
Rate Determining Step ◽  
Dta Studies ◽  
Annealing Experiments

AbstractThe thermal behaviour and mechanism of formation of different texture types of intergrown As-Sb alloys have been studied by DTA and annealing experiments performed on natural samples. The constant composition of the As-rich component and of the stibarsen in the intergrowths, and the large compositional range of the homogeneous solid solution obtained after heating in the DTA cycle, have been established using the linear relationship between cell volume and composition. The high-temperature features detected in the DTA studies of the natural samples confirm previously published phase relations for the synthetic As-Sb system. The low-temperature features can be correlated with the homogenization reaction which leads to the formation of a complete solid solution. Study of TTT plots based on the annealing experiments clearly shows that a diffusion mechanism is involved in the homogenization reaction. This has been further substantiated by fitting the experimental data to kinetic equations for diffusion-controlled processes. The kinetic parameters evaluated from the ending time for the 520, 480, and 420 °C annealing experiments, using both the Arrhenius and the transition state theory formalisms, suggests a rather rigid activated complex for the rate-determining step of the process.

Temporal evolution of concentration and microstructure of colloidal films during vertical drying: a lattice Boltzmann simulation study

Soft Matter ◽  
2020 ◽  
Vol 16 (2) ◽  
pp. 523-533 ◽  
Author(s):  
Byoungjin Chun ◽  
Taehyung Yoo ◽  
Hyun Wook Jung
Keyword(s):  
Computer Simulations ◽  
Simulation Study ◽  
Lattice Boltzmann ◽  
Temporal Evolution ◽  
Hydrodynamic Interactions ◽  
Colloidal Films ◽  
Lattice Boltzmann Simulation ◽  
Colloidal Film

Computer simulations of colloidal film drying including hydrodynamic interactions between the particles.

Theories and computer simulations of self-assembling surfactant solutions

1994 ◽  
Vol 6 (32) ◽  
pp. 6385-6408 ◽  
Author(s):  
T Kawakatsu ◽  
K Kawasaki ◽  
M Furusaka ◽  
O Okabayashi ◽  
T Kanaya
Keyword(s):  
Computer Simulations ◽  
Self Assembling ◽  
Surfactant Solutions

Continuum equations in the dynamics of rarefied gases

1959 ◽  
Vol 6 (4) ◽  
pp. 523-541 ◽  
Author(s):  
Max Krook
Keyword(s):  
Boundary Conditions ◽  
Half Space ◽  
Gas Dynamics ◽  
Kinetic Equations ◽  
Distribution Functions ◽  
State Variables ◽  
Moment Equations ◽  
Characteristic Temperatures ◽  
Equivalent Continuum ◽  
The Continuum

A procedure is given for translating boundary-value problems of gas dynamics from microscopic form into approximately equivalent continuum form. The continuum formulations involve state-variables that are either half-space moments, or complete moments of the molecular distribution functions. Moment equations derived from the kinetic equations are reduced to a determinate set by representing the distribution functions as sums of ‘modified Maxwellian functions based on various characteristic temperatures and velocities’. The particular choice of such a representation depends on the Knudsen number and on the nature of the microscopic boundary conditions.

The transient period for boundary layer disturbances

1999 ◽  
Vol 381 ◽  
pp. 89-119 ◽  
Author(s):  
D. G. LASSEIGNE ◽  
R. D. JOSLIN ◽  
T. L. JACKSON ◽  
W. O. CRIMINALE
Keyword(s):  
Boundary Layer ◽  
Stokes Equations ◽  
Temporal Evolution ◽  
Initial Conditions ◽  
Boundary Layer Transition ◽  
Navier Stokes ◽  
Spatial Evolution ◽  
Layer Transition ◽  
Transient Period ◽  
The Continuum

The onset of transition in a boundary layer is dependent on the initialization and interaction of disturbances in a laminar flow. Here, theory and full Navier–Stokes simulations focus on the transient period just after disturbances enter the boundary layer. The temporal evolution of disturbances within a boundary layer is investigated by examining a series of initial value problems. In each instance, the complete spectra (i.e. the discrete and the continuum) are included so that the solutions can be completely arbitrary. Both numerical and analytical solutions of the linearized Navier–Stokes equations subject to the arbitrary initial conditions are presented. The temporal evolution of disturbances during the transient period are compared with the spatial evolution of the same disturbances and a strong correlation between the two approaches is demonstrated indicating that the theory may be used for the transient period of disturbance evolution. The theory and simulations demonstrate that strong amplification of the disturbances can occur as a result of the inclusion of the continuum in the prediction of disturbance evolution. The results further show that any approach proposed for use in bypass boundary layer transition must include the transient growth that results from the continuum. Finally, although a connection between temporal and spatial evolution in the transient period has been demonstrated, a theoretical basis as an explanation for this connection remains the focus of additional study.

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