136,249 research outputs found
A stroboscopic averaging algorithm for highly oscillatory delay problems
We propose and analyze a heterogenous multiscale method for the efficient
integration of constant-delay differential equations subject to fast periodic
forcing. The stroboscopic averaging method (SAM) suggested here may provide
approximations with \(\mathcal{O}(H^2+1/\Omega^2)\) errors with a
computational effort that grows like \(H^{-1}\) (the inverse of the
stepsize), uniformly in the forcing frequency Omega
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Learning distance to subspace for the nearest subspace methods in high-dimensional data classification
The nearest subspace methods (NSM) are a category of classification methods widely applied to classify high-dimensional data. In this paper, we propose to improve the classification performance of NSM through learning tailored distance metrics from samples to class subspaces. The learned distance metric is termed as ‘learned distance to subspace’ (LD2S). Using LD2S in the classification rule of NSM can make the samples closer to their correct class subspaces while farther away from their wrong class subspaces. In this way, the classification task becomes easier and the classification performance of NSM can be improved. The superior classification performance of using LD2S for NSM is demonstrated on three real-world high-dimensional spectral datasets
Octet Baryon Charge Radii, Chiral Symmetry and Decuplet Intermediate States
We compute the octet baryon charge radii to O(1/Heavy^3) in heavy baryon
chiral perturbation theory. We examine the effect of including the decuplet of
spin-3/2 baryons explicitly. We find that it does no t improve the level of
agreement between the HBchiPT and experimental values for the Sigma^- charge
radius.Comment: 9 pages, 2 figures. Uses axodraw.sty, include
Phonon-phason coupling in icosahedral quasicrystals
From relaxation simulations of decoration-based quasicrystal structure models
using microscopically based interatomic pair potentials, we have calculated the
(usually neglected) phonon-phason coupling constant. Its sign is opposite for
the two alloys studied, i-AlMn and i-(Al,Cu)Li; a dimensionless measure of its
magnitude relative to the phonon and phason elastic constants is of order 1/10,
suggesting its effects are small but detectable. We also give a criterion for
when phonon-phason effects are noticeable in diffuse tails of Bragg peaks.Comment: 7 pages, LaTeX, uses Europhys Lett macros (included
Nonlinear Schr\"odinger Equation for Superconductors
Using the Hartree-Fock-Bogoliubov factorization of the density matrix and the
Born-Oppenheimer approximation we show that the motion of the condensate
satisfies a nonlinear Schr\"odinger equation in the zero temperature limit. The
Galilean invariance of the equation is explicitly manifested. {}From this
equation some general properties of a superconductor, such as Josephson
effects, the Magnus force, and the Bogoliubov-Anderson mode can be obtained
readily.Comment: Latex, 12 page
Mechanism for current saturation and energy dissipation in graphene transistors
From a combination of careful and detailed theoretical and experimental
studies, we demonstrate that the Boltzmann theory including all scattering
mechanisms gives an excellent account, with no adjustable parameters, of high
electric field transport in single as well as double-oxide graphene
transistors. We further show unambiguously that scattering from the substrate
and superstrate surface optical (SO) phonons governs the high field transport
and heat dissipation over a wide range of experimentally relevant parameters.
Models that neglect SO phonons altogether or treat them in a simple
phenomenological manner are inadequate. We outline possible strategies for
achieving higher current and complete saturation in graphene devices.Comment: revtex, 5 pages, 3 figures, to appear in Phys. Rev. Lett
Is Explicit Congestion Notification usable with UDP?
We present initial measurements to determine if ECN is usable with
UDP traffic in the public Internet. This is interesting because ECN
is part of current IETF proposals for congestion control of UDPbased
interactive multimedia, and due to the increasing use of UDP
as a substrate on which new transport protocols can be deployed.
Using measurements from the author’s homes, their workplace,
and cloud servers in each of the nine EC2 regions worldwide, we
test reachability of 2500 servers from the public NTP server pool,
using ECT(0) and not-ECT marked UDP packets. We show that
an average of 98.97% of the NTP servers that are reachable using
not-ECT marked packets are also reachable using ECT(0) marked
UDP packets, and that ~98% of network hops pass ECT(0) marked
packets without clearing the ECT bits. We compare reachability of
the same hosts using ECN with TCP, finding that 82.0% of those
reachable with TCP can successfully negotiate and use ECN. Our
findings suggest that ECN is broadly usable with UDP traffic, and
that support for use of ECN with TCP has increased
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