Domain wall propagation in ferromagnetic semiconductors: Beyond the one-dimensional model

We consider the paper by Brugnot and Pochat (1981), which describes a one-dimensional model applied to a snow avalanche. The main advance made here is the introduction of the second dimension in the runout zone. Indeed, in the channelled course, we still use the one-dimensional model, but, when the avalanche spreads before stopping, we apply a (x, y) grid on the ground and six equations have to be solved: (1) for the avalanche body, one equation for continuity and two equations for momentum conservation, and (2) at the front, one equation for continuity and two equations for momentum conservation. We suppose the front to be a mobile jump, with longitudinal velocity varying more rapidly than transverse velocity.We solve these equations by a finite difference method. This involves many topological problems, due to the actual position of the front, which is defined by its intersection with the reference grid (SI, YJ). In the near future our two directions of research will be testing the code on actual avalanches and improving it by trying to make it cheaper without impairing its accuracy.

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A Stefan problem in a Bridgman crystal grower

European Journal of Applied Mathematics ◽

10.1017/s0956792500001790 ◽

1995 ◽

Vol 6 (3) ◽

pp. 191-199

Author(s):

P. den Decker ◽

R. van der Hout ◽

C. J. Van Duijn ◽

L. A. Peletier

Keyword(s):

Critical Speed ◽

Internal Heat ◽

Mushy Region ◽

Dimensional Model ◽

Real Situation ◽

One Dimensional ◽

Dimensional Approximation ◽

The One ◽

Strong Curvature ◽

Bridgman Crystal Grower

We discuss a one-dimensional model for a Bridgman crystal grower, where the removal of heat is described by an internal heat sink. A consequence is the apparent existence of mushy regions for relatively large velocities of the cooling machine; these mushy regions are an artefact of the one-dimensional approximation. We show that for some types of cooling profiles there exists a critical speed for the existence of mushy regions, whereas for different cooling profiles no such critical speed exists. The presence of a mushy region may indicate a strong curvature of the liquid/solid interface in the real situation.

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EXACT SOLUTION OF AN IRREVERSIBLE ONE-DIMENSIONAL MODEL WITH FULLY BIASED SPIN EXCHANGES

International Journal of Modern Physics B ◽

10.1142/s0217979296001847 ◽

1996 ◽

Vol 10 (25) ◽

pp. 3451-3459 ◽

Cited By ~ 2

Author(s):

ANTÓNIO M.R. CADILHE ◽

VLADIMIR PRIVMAN

Keyword(s):

Exact Solution ◽

Domain Wall ◽

Nearest Neighbor ◽

Spin Exchange ◽

Initial Conditions ◽

Strong Dependence ◽

Zero Temperature ◽

Dimensional Model ◽

One Dimensional ◽

Temperature Dynamics

We introduce a model with conserved dynamics, where nearest neighbor pairs of spins ↑↓ (↓↑) can exchange to assume the configuration ↓↑ (↑↓), with rate β(α), through energy decreasing moves only. We report exact solution for the case when one of the rates, α or β, is zero. The irreversibility of such zero-temperature dynamics results in strong dependence on the initial conditions. Domain wall arguments suggest that for more general, finite-temperature models with steady states the dynamical critical exponent for the anisotropic spin exchange is different from the isotropic value.

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On the numerical study of thermohydrodynamics and biochemistry of inland water bodies

10.5194/egusphere-egu21-13335 ◽

2021 ◽

Author(s):

Daria Gladskikh ◽

Evgeny Mortikov ◽

Victor Stepanenko

Keyword(s):

Mixed Layer ◽

Numerical Study ◽

Three Dimensional ◽

Water Bodies ◽

Dimensional Model ◽

Three Dimensional Model ◽

One Dimensional ◽

Lake Model ◽

Upper Mixed Layer ◽

The One

The study of thermodynamic and biochemical processes of inland water objects using one- and three-dimensional RANS numerical models was carried out both for idealized water bodies and using measurements data. The need to take into account seiche oscillations to correctly reproduce the deepening of the upper mixed layer in one-dimensional (vertical) models is demonstrated. We considered the one-dimensional LAKE model [1] and the three-dimensional model [2, 3, 4] developed at the Research Computing Center of Moscow State University on the basis of a hydrodynamic code combining DNS/LES/RANS approaches for calculating geophysical turbulent flows. The three-dimensional model was supplemented by the equations for calculating biochemical substances by analogy with the one-dimensional biochemistry equations used in the LAKE model. The effect of mixing processes on the distribution of concentration of greenhouse gases, in particular, methane and oxygen, was studied.The work was supported by grants of the RF President&#8217;s Grant for Young Scientists (MK-1867.2020.5, MD-1850.2020.5) and by the RFBR (19-05-00249, 20-05-00776).&#160;1. Stepanenko V., Mammarella I., Ojala A., Miettinen H., Lykosov V., Timo V. LAKE 2.0: a model for temperature, methane, carbon dioxide and oxygen dynamics in lakes // Geoscientific Model Development. 2016. V. 9(5). P. 1977&#8211;2006. 2. Mortikov E.V., Glazunov A.V., Lykosov V.N. Numerical study of plane Couette flow: turbulence statistics and the structure of pressure-strain correlations // Russian Journal of Numerical Analysis and Mathematical Modelling. 2019. 34(2). P. 119-132. 3. Mortikov, E.V. Numerical simulation of the motion of an ice keel in stratified flow // Izv. Atmos. Ocean. Phys. 2016. V. 52. P. 108-115. 4. Gladskikh D.S., Stepanenko V.M., Mortikov E.V. On the influence of the horizontal dimensions of inland waters on the thickness of the upper mixed layer // Water Resourses. 2021.V. 45, 9 pages. (in press)&#160;

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Hydraulic modeling of combined sewers overflow integrating the results of the SWMM and CFX models.

Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería ◽

10.23967/j.rimni.2021.01.006 ◽

2021 ◽

Vol 37 (1) ◽

Author(s):

D. Pulgarín ◽

J. Plaza ◽

J. Ruge ◽

J. Rojas

Keyword(s):

Three Dimensional ◽

Hydraulic Modeling ◽

Dimensional Model ◽

Three Dimensional Model ◽

One Dimensional ◽

Ansys Cfx ◽

Combined Sewer ◽

The One ◽

Swmm Model

This study proposes a methodology for the calibration of combined sewer overflow (CSO), incorporating the results of the three-dimensional ANSYS CFX model in the SWMM one-dimensional model. The procedure consists of constructing calibration curves in ANSYS CFX that relate the input flow to the CSO with the overflow, to then incorporate them into the SWMM model. The results obtained show that the behavior of the flow over the crest of the overflow weir varies in space and time. Therefore, the flow of entry to the CSO and the flow of excesses maintain a non-linear relationship, contrary to the results obtained in the one-dimensional model. However, the uncertainty associated with the idealization of flow methodologies in one dimension is reduced under the SWMM model with kinematic wave conditions and simulating CSO from curves obtained in ANSYS CFX. The result obtained facilitates the calibration of combined sewer networks for permanent or non-permanent flow conditions, by means of the construction of curves in a three-dimensional model, especially when the information collected in situ is limited.

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Quantum entanglement in some topological insulator models

International Journal of Modern Physics B ◽

10.1142/s0217979219502849 ◽

2019 ◽

Vol 33 (24) ◽

pp. 1950284 ◽

Cited By ~ 1

Author(s):

L. S. Lima

Keyword(s):

Quantum Entanglement ◽

Topological Insulator ◽

Topological Charge ◽

Two Dimensional ◽

Dimensional Model ◽

Model Case ◽

Topological Transition ◽

One Dimensional ◽

Zhang Model ◽

The One

Quantum entanglement is studied in the neighborhood of a topological transition in some topological insulator models such as the two-dimensional Qi–Wu–Zhang model or Chern insulator. The system describes electrons hopping in two-dimensional chains. For the one-dimensional model case, there exist staggered hopping amplitudes. Our results show a strong effect of sudden variation of the topological charge Q in the neighborhood of phase transition on quantum entanglement for all the cases analyzed.

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Quantitative Spectroscopy of Wolf-Rayet Stars

International Astronomical Union Colloquium ◽

10.1017/s0252921100093611 ◽

1988 ◽

Vol 108 ◽

pp. 133-140

Author(s):

W. Schmutz

Keyword(s):

Representative Point ◽

Dimensional Model ◽

Model Calculations ◽

One Dimensional ◽

The Past ◽

First Results ◽

The One ◽

Expanding Atmospheres ◽

New Generation ◽

The Continuum

Advances in theoretical modeling of rapidly expanding atmospheres in the past few years made it possible to determine the stellar parameters of the Wolf-Rayet stars. This progress is mainly due to the improvement of the models with respect to their spatial extension: The new generation of models treat spherically-symmetric expanding atmospheres, i.e. the models are one-dimensional. Older models describe the wind by only one representative point. The older models are in fact ‘core-halo’ approximations. They have been introduced by Castor and van Blerkom (1970), and were extensively employed in the past (cf. e.g. Willis and Wilson, 1978; Smith and Willis, 1982). First results from new one-dimensional model calculations are published by Hillier (1984), Schmutz (1984), Hamann (1985), Hillier (1986), and Schmutz et al. (1987a); more detailed results are presented by Schmutz and Hamann (1986), Hamann and Schmutz (1987), Hillier (1987a,b), Wessolowski et al. (1987), Hillier (1987c) and Hamann et al. (1987). These results demonstrate that the step from zero- to one-dimensional calculations is essential. The important point is that the complicated interrelation between NLTE-level populations and radiation field is treated adequately (Schmutz and Hamann, 1986; Hillier, 1987). For this interrelation it is crucial to model consistently not only the line-formation region, but also the layers where the continuum is emitted. In fact, it is the core-halo approximation that causes the one-point models to fail in certain aspects.

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Rare temperature histories and cirrus ice number density in a parcel and a one-dimensional model

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-13013-2014 ◽

2014 ◽

Vol 14 (23) ◽

pp. 13013-13022 ◽

Cited By ~ 22

Author(s):

D. M. Murphy

Keyword(s):

Temperature Dependence ◽

Low Temperatures ◽

Ice Crystals ◽

Strong Increase ◽

Number Density ◽

Dimensional Model ◽

One Dimensional ◽

Slow Growth Rate ◽

Wide Range ◽

The One

Abstract. A parcel and a one-dimensional model are used to investigate the temperature dependence of ice crystal number density. The number of ice crystals initially formed in a cold cirrus cloud is very sensitive to the nucleation mechanism and the detailed history of cooling rates during nucleation. A possible small spread in the homogeneous freezing threshold due to varying particle composition is identified as a sensitive nucleation parameter. In a parcel model, the slow growth rate of ice crystals at low temperatures inherently leads to a strong increase in ice number density at low temperatures. This temperature dependence is not observed. The model temperature dependence occurs for a wide range of assumptions and for either homogeneous or, less strongly, heterogeneous freezing. However, the parcel model also shows that random temperature fluctuations result in an extremely wide range of ice number densities. A one-dimensional model is used to show that the rare temperature trajectories resulting in the lowest number densities are disproportionately important. Low number density ice crystals sediment and influence a large volume of air. When such fall streaks are included, the ice number becomes less sensitive to the details of nucleation than it is in a parcel model. The one-dimensional simulations have a more realistic temperature dependence than the parcel mode. The one-dimensional model also produces layers with vertical dimensions of meters even if the temperature forcing has a much broader vertical wavelength. Unlike warm clouds, cirrus clouds are frequently surrounded by supersaturated air. Sedimentation through supersaturated air increases the importance of any process that produces small numbers of ice crystals. This paper emphasizes the relatively rare temperature trajectories that produce the fewest crystals. Other processes are heterogeneous nucleation, sedimentation from the very bottom of clouds, annealing of disordered to hexagonal ice, and entrainment.

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The Influence of Wood Specimen Surface Coating on Moisture Movement during Drying

Holzforschung ◽

10.1515/hf.2002.083 ◽

2002 ◽

Vol 56 (5) ◽

pp. 541-546 ◽

Cited By ~ 4

Author(s):

R. Baronas ◽

F. Ivanauskas

Keyword(s):

Surface Coating ◽

Transverse Section ◽

Wood Specimen ◽

Two Dimensional ◽

Drying Process ◽

Dimensional Model ◽

Wood Drying ◽

Moisture Movement ◽

One Dimensional ◽

The One

Summary A model of wood drying under isothermal conditions taking into consideration coating of the surface of a specimen is presented in this paper in a two-dimensional formulation. The influence of the surface coating degree as well as geometrical shape of a wood specimen on the dynamics of drying is investigated. Exponentials, describing the dependence of the halfdrying time on the degree of coating of the edges, as well as on the ratio of the width to the thickness of the transverse section of specimens from the northern red oak (Quercus rubra), are presented for drying from above the fiber saturation point. This paper describes the conditions of usage of the two-dimensional moisture transfer model in contrast to the one-dimensional model for accurate prediction of the drying process taking into consideration the coating of edges of specimens having a rectangular transverse section. A measure of reliability of the one-dimensional model to predict the wood drying process of sawn boards is introduced in this paper.

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The Formation of Stratified Combustible Mixtures in Closed Tubes by Molecular and Convective Diffusions

Journal of Fluids Engineering ◽

10.1115/1.3242490 ◽

1985 ◽

Vol 107 (3) ◽

pp. 348-353 ◽

Cited By ~ 1

Author(s):

O. Badr

Keyword(s):

Theoretical Study ◽

Concentration Profiles ◽

Dimensional Model ◽

One Dimensional ◽

Test Conditions ◽

Experimental Justification ◽

The One ◽

Combustible Mixtures

This paper describes a theoretical study on the formation of stratified combustible mixtures in closed long vertical flame tubes. The concentration profiles of the fuel (methane) in air, just before ignition took place, were predicted using a one-dimensional model involving molecular and convective diffusional processes. Phenomenological and experimental justification of the one-dimensional assumption was given and some of the predicted data were compared with experiment for different test conditions. The model appears to have successfully predicted the concentration profiles in some situations where other models failed.

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