1,857 research outputs found
Weak formulation for singular diffusion equation with dynamic boundary condition
In this paper, we propose a weak formulation of the singular diffusion
equation subject to the dynamic boundary condition. The weak formulation is
based on a reformulation method by an evolution equation including the
subdifferential of a governing convex energy. Under suitable assumptions, the
principal results of this study are stated in forms of Main Theorems A and B,
which are respectively to verify: the adequacy of the weak formulation; the
common property between the weak solutions and those in regular problems of
standard PDEs.Comment: 23 page
Universal computation with limited resources: Belousov-Zhabotinsky and Physarum computers
Using the examples of an excitable chemical system (Belousov-Zhabotinsky
medium) and plasmodium of Physarum polycephalum we show that universal
computation in a geometrically unconstrained medium is only possible when
resources (excitability or concentration of nutrients) are limited. In
situations of limited resources the systems studied develop travelling
localizations. The localizations are elementary units of dynamical logical
circuits in collision-based computing architectures.Comment: Int. J. Bifurcation and Chaos (2008), accepte
Coherent addition of two dimensional array of fiber lasers
Configurations for efficient free space coherent addition of four separate
fiber lasers arranged in two dimensional array are presented. They include
compact and robust interferometric combiners that can be inserted either inside
or outside the cavity of the combined lasers system. The results reveal that
over 85% combining efficiency can be obtained.Comment: To be published in Optics Communicatio
Physarum boats: If plasmodium sailed it would never leave a port
Plasmodium of \emph{Physarum polycephalum} is a single huge (visible by naked
eye) cell with myriad of nuclei. The plasmodium is a promising substrate for
non-classical, nature-inspired, computing devices. It is capable for
approximation of shortest path, computation of planar proximity graphs and
plane tessellations, primitive memory and decision-making. The unique
properties of the plasmodium make it an ideal candidate for a role of amorphous
biological robots with massive parallel information processing and distributed
inputs and outputs. We show that when adhered to light-weight object resting on
a water surface the plasmodium can propel the object by oscillating its
protoplasmic pseudopodia. In experimental laboratory conditions and
computational experiments we study phenomenology of the plasmodium-floater
system, and possible mechanisms of controlling motion of objects propelled by
on board plasmodium
Spin and density excitations in the triangular-lattice - model with multiple-spin exchange interactions: He on graphite
Using an exact diagonalization technique on small clusters, we study spin and
density excitations of the triangular-lattice - model with multiple-spin
exchange interactions, whereby we consider anomalous properties observed in the
doped Mott region of the two-dimensional liquid He adsorbed on a graphite
surface. We find that the double-peak structure consistent with experiment
appears in the calculated temperature dependence of the specific heat; the
low-temperature sharp peak comes from the spin excitations reflecting the
frustrated nature of the spin degrees of freedom and high-temperature broad
peak comes from the density excitations extending over the entire band width.
The clear separation in their energy scales is evident in the calculated spin
and density excitation spectra. The calculated single-particle excitation
spectra suggest the presence of fermionic quasiparticles dressed by the spin
excitations, with an enhanced effective mass consistent with experiment.Comment: 9 pages, 9 figure
Uniaxial-Pressure induced Ferromagnetism of Enhanced Paramagnetic Sr3Ru2O7
We report a uniaxial pressure-dependence of magnetism in layered perovskite
strontium ruthenate Sr3Ru2O7. By applying a relatively small uniaxial pressure,
greater than 0.1 GPa normal to the RuO2 layer, ferromagnetic ordering manifests
below 80 K from the enhanced-paramagnet. Magnetization at 1 kOe and 2 K becomes
100 times larger than that under ambient condition. Uniaxial pressure
dependence of Curie temperature T_C suggests the first order magnetic
transition. Origin of this uniaxial-pressure induced ferromagnetism is
discussed in terms of the rotation of RuO6 octahedra within the RuO2 plane.Comment: 8 pages, 3 figures. to be published in Journal of the Physical
Society of Japan, vol.73, No.5 (2004
Composite Yb : YAG/Cr4+: YAG ceramics picosecond microchip lasers
Efficient laser-diode pumped picosecond self-Q-switched all-ceramic composite Yb: YAG/ Cr4+: YAG microchip lasers with 0.72 MW peak power has been developed. Lasers with nearly diffraction-limited beam quality (M-2 < 1.09), oscillate at stable single- and multi- longitudinal-modes due to the combined etalon effects in the Yb:YAG and Cr4(+:) YAG parts of its binary structure. (C) 2007 Optical Society of America
Linear Field Dependence of the Normal-State In-Plane Magnetoresistance of Sr2RuO4
The transverse and longitudinal in-plane magnetoresistances in the normal
state of superconducting Sr2RuO4 single crystals have been measured. At low
temperatures, both of them were found to be positive with a linear
magnetic-field dependence above a threshold field, a result not expected from
electronic band theory. We argue that such behavior is a manifestation of a
novel coherent state characterized by a spin pseudo gap in the quasi-particle
excitation spectrum in Sr2RuO4.Comment: 4 pages + 5 figure
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