529 research outputs found
Global Continuous Optimization with Error Bound and Fast Convergence
This paper considers global optimization with a black-box unknown objective
function that can be non-convex and non-differentiable. Such a difficult
optimization problem arises in many real-world applications, such as parameter
tuning in machine learning, engineering design problem, and planning with a
complex physics simulator. This paper proposes a new global optimization
algorithm, called Locally Oriented Global Optimization (LOGO), to aim for both
fast convergence in practice and finite-time error bound in theory. The
advantage and usage of the new algorithm are illustrated via theoretical
analysis and an experiment conducted with 11 benchmark test functions. Further,
we modify the LOGO algorithm to specifically solve a planning problem via
policy search with continuous state/action space and long time horizon while
maintaining its finite-time error bound. We apply the proposed planning method
to accident management of a nuclear power plant. The result of the application
study demonstrates the practical utility of our method
Increase of Q-Factor of RF Magnetic Thin Film Inductor by Introducing Slit-Patterned Magnetic Thin Film and Multiline-Conductor Spiral Coil
In order to increase Q-factor of radio-frequency (RF) magnetic thin film inductor integrated in chip-size-package RF-ICs, two schemes have been investigated experimentally. For suppressing the in-plane eddy current of the magnetic thin film, a slit-patterned structure was introduced, and it was found that the slit-patterned magnetic thin film is very effective for increasing Q-factor. On the other hand, for suppressing alternating current (ac) copper loss, a multiline-conductor spiral coil was introduced, and it was found that the multiline coil is effective for improving decrease of inductance at high frequencies. By introducing the two schemes, a maximum Q-factor of 18 at 1.5 GHz was obtained in a spiral inductor with a bottom slit-patterned CoFeSiO/SiO granular multilayer film and triple-line-conductor spiral coil.ArticleIEEE TRANSACTIONS ON MAGNETICS. 47(10):3196-3199 (2011)journal articl
Simulation of Transitions between "Pasta" Phases in Dense Matter
Calculations of equilibrium properties of dense matter predict that at
subnuclear densities nuclei can be rodlike or slablike. To investigate whether
transitions between phases with non-spherical nuclei can occur during the
collapse of a star, we perform quantum molecular dynamic simulations of the
compression of dense matter. We have succeeded in simulating the transitions
between rodlike and slablike nuclei and between slablike nuclei and cylindrical
bubbles. Our results strongly suggest that non-spherical nuclei can be formed
in the inner cores of collapsing stars.Comment: 4 pages, 4 figures, final version published in Phys. Rev. Lett.,
high-res figures can be seen at http://www.nordita.dk/~gentaro/research/fig
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