341 research outputs found
Observation of Spin Wave Soliton Fractals in Magnetic Film Active Feedback Rings
The manifestation of fractals in soliton dynamics has been observed for the
first time. The experiment utilized self-generated spin wave envelope solitons
in a magnetic film based active feedback ring. At high ring gain, the soliton
that circulates in the ring breathes in a fractal pattern. The corresponding
power frequency spectrum shows a comb structure, with each peak in the comb
having its own comb, and so on, to finer and finer scales.Comment: 4 pages, 4 figure
Synthesis of a Galile oand Wi-Max Three-Band Fractal-Eroded Patch Antenna
In this letter, the synthesis of a three-band patch antenna working in E5-L1 Galileo and Wi − Max frequency bands is described. The geometry of the antenna is defined by performing a Koch-like erosion in a classical rectangular patch structure according to a Particle Swarm strategy to optimize the values of the electrical parameters within given specifications. In order to assess the effectiveness of the antenna design, some results from the numerical synthesis procedure are described and a comparison between simulations and experimental measurements is reported. (c) 2007 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works
Eikonal equations on the Sierpinski gasket
We study the eikonal equation on the Sierpinski gasket in the spirit of the
construction of the Laplacian in Kigami [8]: we consider graph eikonal
equations on the prefractals and we show that the solutions of these problems
converge to a function defined on the fractal set. We characterize this limit
function as the unique metric viscosity solution to the eikonal equation on the
Sierpinski gasket according to the definition introduced in [3]
On the Permeability of Fractal Tube Bundles
The permeability of a porous medium is strongly affected by its local geometry and connectivity, the size distribution of the solid inclusions, and the pores available for flow. Since direct measurements of the permeability are time consuming and require experiments that are not always possible, the reliable theoretical assessment of the permeability based on the medium structural characteristics alone is of importance. When the porosity approaches unity, the permeability-porosity relationships represented by the Kozeny-Carman equations and Archie's law predict that permeability tends to infinity and thus they yield unrealistic results if specific area of the porous media does not tend to zero. The aim of this article is the evaluation of the relationships between porosity and permeability for a set of fractal models with porosity approaching unity and a finite permeability. It is shown that the tube bundles generated by finite iterations of the corresponding geometric fractals can be used to model porous media where the permeability-porosity relationships are derived analytically. Several examples of the tube bundles are constructed, and the relevance of the derived permeability-porosity relationships is discussed in connection with the permeability measurements of highly porous metal foams reported in the literatur
- …