2,644 research outputs found
A robust design methodology suitable for application to one-off products
Robust design is an activity of fundamental importance when designing large, complex, one-off engineering products. Work is described which is concerned with the application of the theory of design of experiments and stochastic optimization methods to explore and optimize at the concept design stage. The discussion begins with a description of state-of-the-art stochastic techniques and their application to robust design. The content then focuses on a generic methodology which is capable of manipulating design algorithms that can be used to describe a design concept. An example is presented, demonstrating the use of the system for the robust design of a catamaran with respect to seakeeping
Mesoscopic Hall effect driven by chiral spin order
A Hall effect due to spin chirality in mesoscopic systems is predicted. We
consider a 4-terminal Hall system including local spins with geometry of a
vortex domain wall, where strong spin chirality appears near the center of
vortex. The Fermi energy of the conduction electrons is assumed to be
comparable to the exchange coupling energy where the adiabatic approximation
ceases to be valid. Our results show a Hall effect where a voltage drop and a
spin current arise in the transverse direction. The similarity between this
Hall effect and the conventional spin Hall effect in systems with spin-orbit
interaction is pointed out.Comment: 4 pages, 4 figure
Macroscopic thermodynamics of equilibrium characterized by power-law canonical distributions
Macroscopic thermodynamics of equilibrium is constructed for systems obeying
power-law canonical distributions. With this, the connection between
macroscopic thermodynamics and microscopic statistical thermodynamics is
generalized. This is complementary to the Gibbs theorem for the celebrated
exponential canonical distributions of systems in contact with a heat bath.
Thereby, a thermodynamic basis is provided for power-law phenomena ubiquitous
in nature.Comment: 12 page
Computed Tomography Appearance of Hem-O-Lok Clips in Patients Who Have Undergone Laparoscopic Nephrectomy or Nephroureterectomy
Hem-O-Lok clips are radiopaque on computed tomography in patients who have undergone laparoscopic nephrectomy and nephroureterectomy
Magneto-optics induced by the spin chirality in itinerant ferromagnet NdMoO
It is demonstrated both theoretically and experimentally that the spin
chirality associated with a noncoplanar spin configuration produces a
magneto-optical effect. Numerical study of the two-band Hubbard model on a
triangle cluster shows that the optical Hall conductivity
is proportional to the spin chirality. The detailed comparative experiments on
pyrochlore-type molybdates MoO with Nd (Ising-like moments)
and Gd (Heisenberg-like ones) clearly distinguishes the two mechanisms,
i.e., spin chirality and spin-orbit interactions. It is concluded that for
=Nd, is dominated by the spin chirality for the dc
() and the incoherent intraband optical transitions between
Mo atoms.Comment: 4 pages, 5 figures. submitted to Phys. Rev.
Velocity Statistics in the Two-Dimensional Granular Turbulence
We studied the macroscopic statistical properties on the freely evolving
quasi-elastic hard disk (granular) system by performing a large-scale (up to a
few million particles) event-driven molecular dynamics systematically and found
that remarkably analogous to an enstrophy cascade process in the decaying
two-dimensional fluid turbulence. There are four typical stages in the freely
evolving inelastic hard disk system, which are homogeneous, shearing (vortex),
clustering and final state. In the shearing stage, the self-organized
macroscopic coherent vortices become dominant. In the clustering stage, the
energy spectra are close to the expectation of Kraichnan-Batchelor theory and
the squared two-particle separation strictly obeys Richardson law.Comment: 4 pages, 4 figures, to be published in PR
Anomalous Hall effect in 2D Dirac band: link between Kubo-Streda formula and semiclassical Boltzmann equation approach
The anomalous Hall effect (AHE) is a consequence of spin-orbit coupling in a
ferromagnetic metal and is related primarily to density-matrix response to an
electric field that is off-diagonal in band index. For this reason disorder
contributions to the AHE are difficult to treat systematically using a
semi-classical Boltzmann equation approach, even when weak localization
corrections are disregarded. In this article we explicitly demonstrate the
equivalence of an appropriately modified semiclassical transport theory which
includes anomalous velocity and side jump contributions and microscopic
Kubo-Streda perturbation theory, with particular unconventional contributions
in the semiclassical theory identified with particular Feynman diagrams when
calculations are carried out in a band-eigenstate representation. The
equivalence we establish is verified by explcit calculations for the case of
the two-dimensional (2D) Dirac model Hamiltonian relevant to graphene.Comment: 17 pages, 13 figure
Two geometrically frustrated magnets studied by neutron diffraction
In the pyrochlore compounds, TbTiO and TbSnO, only
the Tb ions are magnetic. They exhibit quite abnormal -- and, in view of
their chemical similarity, strikingly different -- magnetic behaviour, as
probed by neutron diffraction at ambient and applied pressure.
TbTiO is a cooperative paramagnet (`spin liquid'), without long
range order at ambient pressure; however, it does become ordered under
pressure. By contrast, TbSnO enters an "ordered spin ice" state
already at ambient pressure. We analyse a simple model which already clearly
exhibits some of the qualitative features observed experimentally. Overall,
comparing these two compounds emphasizes the power of small perturbations in
selecting low-temperature states in geometrically frustrated systems.Comment: 6 pages, 4 figures, International Conference on Neutron Scattering
Sydney(2005
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