scholarly journals Computer simulations on three-dimensional plasmoid dynamics by the spontaneous fast reconnection model

1998 ◽  
Vol 103 (A3) ◽  
pp. 4573-4585 ◽  
Author(s):  
M. Ugai ◽  
W. B. Wang
Keyword(s):  
Computer Simulations ◽  
Three Dimensional ◽  
Reconnection Model ◽  
Fast Reconnection

scholarly journals Three-dimensional earthward fast flow in the near-Earth plasma sheet in a sheared field: comparisons between simulations and observations

2009 ◽  
Vol 27 (6) ◽  
pp. 2297-2302 ◽  
Author(s):  
K. Kondoh ◽  
M. Ugai
Keyword(s):  
Magnetic Field ◽  
Plasma Sheet ◽  
Three Dimensional ◽  
The Real ◽  
Mhd Simulations ◽  
Simulation Domain ◽  
Three Dimensional Configuration ◽  
Fast Flow ◽  
Reconnection Model ◽  
Fast Reconnection

Abstract. Three-dimensional configuration of earthward fast flow in the near-Earth plasma sheet is studied using three-dimensional magnetohydrodynamics (MHD) simulations on the basis of the spontaneous fast reconnection model. In this study, the sheared magnetic field in the plasma sheet is newly considered in order to investigate the effects of it to the earthward fast flow, and the results are discussed in comparison with no-shear simulations. The virtual probes located at different positions in our simulation domain in shear/no-shear cases could explain different behavior of fast flows in the real observations.

scholarly journals Geometric auxetics

2015 ◽  
Vol 471 (2184) ◽  
pp. 20150033 ◽  
Author(s):  
Ciprian Borcea ◽  
Ileana Streinu
Keyword(s):  
Computer Simulations ◽  
Mathematical Theory ◽  
Three Dimensional ◽  
Numerical Approximations ◽  
Periodic Frameworks ◽  
Infinite Supply

We formulate a mathematical theory of auxetic behaviour based on one-parameter deformations of periodic frameworks. Our approach is purely geome- tric, relies on the evolution of the periodicity lattice and works in any dimension. We demonstrate its usefulness by predicting or recognizing, without experiment, computer simulations or numerical approximations, the auxetic capabilities of several well-known structures available in the literature. We propose new principles of auxetic design and rely on the stronger notion of expansive behaviour to provide an infinite supply of planar auxetic mechanisms and several new three-dimensional structures.

Mechanical evaluation of theories of neurulation using computer simulations

Development ◽  
1993 ◽  
Vol 118 (3) ◽  
pp. 1013-1023 ◽  
Author(s):  
D. A. Clausi ◽  
G. W. Brodland
Keyword(s):  
Computer Simulations ◽  
Driving Forces ◽  
Shape Change ◽  
Three Dimensional ◽  
Dorsal Surface ◽  
Neural Plate ◽  
Neural Tube Closure ◽  
Amphibian Embryo ◽  
Axial Elongation ◽  
Shape Changes

Current theories about the forces that drive neurulation shape changes are evaluated using computer simulations. Custom, three-dimensional, finite element-based computer software is used. The software draws on current engineering concepts and makes it possible to construct a ‘virtual’ embryo with any user-specified mechanical properties. To test a specific hypothesis about the forces that drive neurulation, the whole virtual embryo or any selected part of it is ascribed with the force generators specified in the hypothesis. The shape changes that are produced by these forces are then observed and compared with experimental data. The simulations demonstrate that, when uniform, isotropic circumferential microfilament bundle (CMB) constriction and cephalocaudal (axial) elongation act together on a circular virtual neural plate, it becomes keyhole shaped. When these forces act on a spherical (amphibian) embryo, dorsal surface flattening occurs. Simulations of transverse sections further show that CMB constriction, acting with or without axial elongation, can produce numerous salient transverse features of neurulation. These features include the sequential formation of distinct neural ridges, narrowing and thickening of the neural plate, skewing just medial to the ridges, ‘hinge’ formation and neural tube closure. No region-specific ‘programs’ or non-mechanical cell-cell communications are used. The increase in complexity results entirely from mechanical interactions. The transverse simulations show how changes to the driving forces would affect the patterns of shape change produced. Hypotheses regarding force generation by microtubules, intercellular adhesions and forces extrinsic to the neural plate are also evaluated. The simulations show that these force-generating mechanisms do not, by themselves, produce shape changes that are consistent with normal development. The simulations support the concept of cooperation of forces and suggest that neurulation is robust because redundant force generating mechanisms exist.

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