14,764 research outputs found
Analysis of flight data from a High-Incidence Research Model by system identification methods
Data partitioning and modified stepwise regression were applied to recorded flight data from a Royal Aerospace Establishment high incidence research model. An aerodynamic model structure and corresponding stability and control derivatives were determined for angles of attack between 18 and 30 deg. Several nonlinearities in angles of attack and sideslip as well as a unique roll-dominated set of lateral modes were found. All flight estimated values were compared to available wind tunnel measurements
Efficient current-induced domain-wall displacement SrRuO3
We demonstrate current-induced displacement of ferromagnetic domain walls in
sub-micrometer fabricated patterns of SrRuO3 films. The displacement, monitored
by measuring the extraordinary Hall effect, is induced at zero applied magnetic
field and its direction is reversed when the current is reversed. We find that
current density in the range of 10^9 - 10^10 A/m^2 is sufficient for
domain-wall displacement when the depinning field varies between 50 to 500 Oe.
These results indicate relatively high efficiency of the current in displacing
domain walls which we believe is related to the narrow width ~3 nm of domain
walls in this compound
An optimistic CoGeNT analysis
Inspired by a recently proposed model of millicharged atomic dark matter
(MADM), we analyze several classes of light dark matter models with respect to
CoGeNT modulated and unmodulated data, and constraints from CDMS, XENON10 and
XENON100. After removing the surface contaminated events from the original
CoGeNT data set, we find an acceptable fit to all these data (but with the
modulating part of the signal making a statistically small contribution), using
somewhat relaxed assumptions about the response of the null experiments at low
recoil energies, and postulating an unknown modulating background in the CoGeNT
data at recoil energies above 1.5 keVee. We compare the fits of MADM---an
example of inelastic magnetic dark matter---to those of standard elastically
and inelastically scattering light WIMPs (eDM and iDM). The iDM model gives the
best fit, with MADM close behind. The dark matter interpretation of the DAMA
annual modulation cannot be made compatible with these results however. We find
that the inclusion of a tidal debris component in the dark matter phase space
distribution improves the fits or helps to relieve tension with XENON
constraints.Comment: 16 pages, 11 figures; v2: added discussion of dipole-dipole
scattering and details of matrix elements; also implications of XENON100 2012
limits. Qualitative conclusions unchanged. Published versio
Field induced resistivity anisotropy in SrRuO3 films
SrRuO3 is an itinerant ferromagnet with orthorhombic structure and uniaxial
magnetocrystalline anisotropy - features expected to yield resistivity
anisotropy. Here we explore changes in the resistivity anisotropy of epitaxial
SrRuO3 films due to induced magnetization in the paramagnetic state by using
the planar Hall effect. We find that the effect of the induced magnetization on
the in-plane anisotropy is strongly angular dependent, and we provide a full
description of this behavior at 160 K for induced magnetization in the (001)
plane.Comment: 6 pages, 4 figure
Embedding, compression and fiberwise homotopy theory
Given Poincare spaces M and X, we study the possibility of compressing
embeddings of M x I in X x I down to embeddings of M in X. This results in a
new approach to embedding in the metastable range both in the smooth and
Poincare duality categories.Comment: Published by Algebraic and Geometric Topology at
http://www.maths.warwick.ac.uk/agt/AGTVol2/agt-2-15.abs.htm
Paramagnetic anisotropic magnetoresistance in thin films of SrRuO3
SrRuO3 is an itinerant ferromagnet and in its thin film form when grown on
miscut SrTiO3 it has Tc of ~ 150 K and strong uniaxial anisotropy. We measured
both the Hall effect and the magnetoresistance (MR) of the films as a function
of the angle between the applied field and the normal to the films at
temperatures above Tc. We extracted the extraordinary Hall effect that is
proportional to the perpendicular component of the magnetization and thus the
MR for each angle of the applied field could be correlated with the magnitude
and orientation of the induced magnetization. We successfully fit the MR data
with a second order magnetization expansion, which indicates large anisotropic
MR in the paramagnetic state. The extremum values of resistivity are not
obtained for currents parallel or perpendicular to the magnetization, probably
due to the crystal symmetry.Comment: 3 pages, 3 figure
Looking Backward, Looking Forward: Where is Pension Policy Headed?
Since the passage of the Employee Retirement Income Security Act of 1974, public policy has continuously shaped the trajectory of the US retirement system. It is clear that the policy process will continue to be key in the future reinvention of the retirement paradigm. Our study sets forth four perspectives on strengths and weaknesses of the current retirement system, with the goal of helping shape an environment more conducive to a vibrant, effective, and easily administered retirement system
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