460 research outputs found
Universal router concept
Portable universal router can cut holes of large diameter and irregular shapes, machine recesses, and drill holes with certain edge-distance limitations. Rectangular and round holes may be cut without a template
Variable-speed, portable routing skate
Lightweight, portable, variable-speed routing skate is used on heavy metal subassemblies which are impractical to move to a stationary machine. The assembly, consisting of the housing with rollers, router, and driving mechanism with transmission, weighs about forty pounds. Both speed and depth of cut are adjustable
Weakly Nonlinear Theory of Pattern-Forming Systems with Spontaneously Broken Isotropy
Quasi two-dimensional pattern forming systems with spontaneously broken
isotropy represent a novel symmetry class, that is experimentally accessible in
electroconvection of homeotropically aligned liquid crystals. We present a
weakly nonlinear analysis leading to amplitude equations which couple the
short-wavelength patterning mode with the Goldstone mode resulting from the
broken isotropy. The new coefficients in these equations are calculated from
the hydrodynamics. Simulations exhibit a new type of spatio-temporal chaos at
onset. The results are compared with experiments.Comment: 4 pages, RevTeX, 4 PS-figures, to appear in PR
Miniature grinder for solid specimens
Machine grinds fines to appropriate micron sizes with the least biological trauma and greatest degree of reproducibility. Device controls destruction of material so that recovery of microorganisms is as great as possible and protects operation and grinding products from exogenous contamination
Numerical study of domain coarsening in anisotropic stripe patterns
We study the coarsening of two-dimensional smectic polycrystals characterized
by grains of oblique stripes with only two possible orientations. For this
purpose, an anisotropic Swift-Hohenberg equation is solved. For quenches close
enough to the onset of stripe formation, the average domain size increases with
time as . Further from onset, anisotropic pinning forces similar to
Peierls stresses in solid crystals slow down defects, and growth becomes
anisotropic. In a wide range of quench depths, dislocation arrays remain mobile
and dislocation density roughly decays as , while chevron boundaries
are totally pinned. We discuss some agreements and disagreements found with
recent experimental results on the coarsening of anisotropic electroconvection
patterns.Comment: 8 pages, 11 figures. Phys. Rev E, to appea
Hall Effect in the mixed state of moderately clean superconductors
The Hall conductivity in the mixed state of a clean () type-II
s-wave superconductor is determined from a microscopic calculation within a
quasiclassical approximation. We find that below the superconducting transition
the contribution to the transverse conductivity due to dynamical fluctuations
of the order parameter is compensated by the modification of the quasiparticle
contribution. In this regime the nonlinear behaviour of the Hall angle is
governed by the change in the effective quasiparticle scattering rate due to
the reduction in the density of states at the Fermi level. The connection with
experimental results is discussed
Whirling Hexagons and Defect Chaos in Hexagonal Non-Boussinesq Convection
We study hexagon patterns in non-Boussinesq convection of a thin rotating
layer of water. For realistic parameters and boundary conditions we identify
various linear instabilities of the pattern. We focus on the dynamics arising
from an oscillatory side-band instability that leads to a spatially disordered
chaotic state characterized by oscillating (whirling) hexagons. Using
triangulation we obtain the distribution functions for the number of pentagonal
and heptagonal convection cells. In contrast to the results found for defect
chaos in the complex Ginzburg-Landau equation and in inclined-layer convection,
the distribution functions can show deviations from a squared Poisson
distribution that suggest non-trivial correlations between the defects.Comment: 4 mpg-movies are available at
http://www.esam.northwestern.edu/~riecke/lit/lit.html submitted to New J.
Physic
Dynamics and Selection of Giant Spirals in Rayleigh-Benard Convection
For Rayleigh-Benard convection of a fluid with Prandtl number \sigma \approx
1, we report experimental and theoretical results on a pattern selection
mechanism for cell-filling, giant, rotating spirals. We show that the pattern
selection in a certain limit can be explained quantitatively by a
phase-diffusion mechanism. This mechanism for pattern selection is very
different from that for spirals in excitable media
Interfacial adsorption phenomena of the three-dimensional three-state Potts model
We study the interfacial adsorption phenomena of the three-state
ferromagnetic Potts model on the simple cubic lattice by the Monte Carlo
method. Finite-size scaling analyses of the net-adsorption yield the evidence
of the phase transition being of first-order and .Comment: 14 page
Quasiparticle Density of States of Clean and Dirty s-Wave Superconductors in the Vortex State
The quasiparticle density of states (DOS) in the vortex state has been probed
by specific heat measurements under magnetic fields (H) for clean and dirty
s-wave superconductors, Y(Ni1-xPtx)2B2C and Nb1-xTaxSe2. We find that the
quasiparticle DOS per vortex is appreciably H-dependent in the clean-limit
superconductors, while it is H-independent in the dirty superconductors as
expected from a conventional rigid normal electron core picture. We discuss
possible origins for our observations in terms of the shrinking of the vortex
core radius with increasing H.Comment: 5 pages, 4 figures, to appear in J. Phys. Soc. Jpn. Vol. 68 No.
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