4,732 research outputs found
Fractal Dimension of Backbone of Eden Trees
We relate the fractal dimension of the backbone, and the spectral dimension
of Eden trees to the dynamical exponent z. In two dimensions, it gives fractal
dimension of backbone equal to 4/3 and spectral dimension of trees equal to
5/4. In three dimensions, it provides us a new way to estimate z numerically.
We get z=1.617 +/- 0.004.Comment: 6 pages, Latex, and 4 postscript figures, uuencoded. Minor
typographical errors, and problems with postscript files fixe
Internal Avalanches in a Granular Medium
Avalanches of grain displacements can be generated by creating local voids
within the interior of a granular material at rest in a bin. Modeling such a
two-dimensional granular system by a collection of mono-disperse discs, the
system on repeated perturbations, shows all signatures of Self-Organized
Criticality. During the propagation of avalanches the competition among grains
creates arches and in the critical state a distribution of arches of different
sizes is obtained. Using a cellular automata model we demonstrate that the
existence of arches determines the universal behaviour of the model system.Comment: 4 pages (Revtex), Four ps figures (included
Critical States in a Dissipative Sandpile Model
A directed dissipative sandpile model is studied in the two-dimension.
Numerical results indicate that the long time steady states of this model are
critical when grains are dropped only at the top or, everywhere. The critical
behaviour is mean-field like. We discuss the role of infinite avalanches of
dissipative models in periodic systems in determining the critical behaviour of
same models in open systems.Comment: 4 pages (Revtex), 5 ps figures (included
Mechanical and electrochemical properties of multiple-layer diode laser cladding of 316L stainless steel
In the present investigation, a detailed mechanical and electrochemical properties of multiple-layer laser clad 316L stainless steel (from the powders produced by gas atomized route) has been carried out. Multiple-layer laser cladding of 316L stainless steel has been conducted using a diode laser. The mechanical property (rmcrohardness) of the fabricated product has been evaluated using a microhardness testing machine and correlated with the process parameters. The electrochemical property, mainly pitting corrosion resistance of the fabricated layer corresponding to maximum microhardness (in a 3.56% NaCl solution) has been evaluated using standard potentiodynamic polarization testing. The microhardness of the laser assisted fabricated layers was found to vary from 170 to 278 VHN, increased with decrease in applied power density and increase in scan speed and was higher than that of conventionally processed 316L (155 VHN). The superior microhardness value is attributed to grain refinement associated with laser melting and rapid solidification. The critical potential to pit formation (E-PP1) was measured to be 550 mV saturated calomel electrode (SCE) and superior to the conventionally processed 316L stainless steel (445 mV (SCE)). (c) 2005 Elsevier B.V. All rights reserved
Chaos in Sandpile Models
We have investigated the "weak chaos" exponent to see if it can be considered
as a classification parameter of different sandpile models. Simulation results
show that "weak chaos" exponent may be one of the characteristic exponents of
the attractor of \textit{deterministic} models. We have shown that the
(abelian) BTW sandpile model and the (non abelian) Zhang model posses different
"weak chaos" exponents, so they may belong to different universality classes.
We have also shown that \textit{stochasticity} destroys "weak chaos" exponents'
effectiveness so it slows down the divergence of nearby configurations. Finally
we show that getting off the critical point destroys this behavior of
deterministic models.Comment: 5 pages, 6 figure
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