13,248 research outputs found
Exchange Field-Mediated Magnetoresistance in the Correlated Insulator Phase of Be Films
We present a study of the proximity effect between a ferromagnet and a
paramagnetic metal of varying disorder. Thin beryllium films are deposited onto
a 5 nm-thick layer of the ferromagnetic insulator EuS. This bilayer arrangement
induces an exchange field, , of a few tesla in low resistance Be films
with sheet resistance , where is the quantum resistance.
We show that survives in very high resistance films and, in fact,
appears to be relatively insensitive to the Be disorder. We exploit this fact
to produce a giant low-field magnetoresistance in the correlated insulator
phase of Be films with .Comment: To be published in Physical Review Letter
Natural language processing techniques for researching and improving peer feedback
Peer review has been viewed as a promising solution for improving studennts' writing, which still remains a great challenge for educators. However, one core problem with peer review of writing is that potentially useful feedbback from peers is not always presented in ways that lead to revision. Our prior investigations found that whether students implement feedback is significantly correlated with two feedback features: localization information and concrete solutions. But focusing on feedback features is time-intensive for researchers and instructors. We apply data mining and Natural Languagee Processing techniques to automatically code reviews for these feedback features. Our results show that it is feasible to provide intelligent suppport to peer review systems to automatically assess students' reviewing performance with respect to problem localization and solution. We also show that similar research conclusions about helpfulness perceptions of feedback across students and different expert types can be drawn from automatically coded data and from hand-coded data. © Earli
The position profiles of order cancellations in an emerging stock market
Order submission and cancellation are two constituent actions of stock
trading behaviors in order-driven markets. Order submission dynamics has been
extensively studied for different markets, while order cancellation dynamics is
less understood. There are two positions associated with a cancellation, that
is, the price level in the limit-order book (LOB) and the position in the queue
at each price level. We study the profiles of these two order cancellation
positions through rebuilding the limit-order book using the order flow data of
23 liquid stocks traded on the Shenzhen Stock Exchange in the year 2003. We
find that the profiles of relative price levels where cancellations occur obey
a log-normal distribution. After normalizing the relative price level by
removing the factor of order numbers stored at the price level, we find that
the profiles exhibit a power-law scaling behavior on the right tails for both
buy and sell orders. When focusing on the order cancellation positions in the
queue at each price level, we find that the profiles increase rapidly in the
front of the queue, and then fluctuate around a constant value till the end of
the queue. These profiles are similar for different stocks. In addition, the
profiles of cancellation positions can be fitted by an exponent function for
both buy and sell orders. These two kinds of cancellation profiles seem
universal for different stocks investigated and exhibit minor asymmetry between
buy and sell orders. Our empirical findings shed new light on the order
cancellation dynamics and pose constraints on the construction of order-driven
stock market models.Comment: 17 pages, 6 figures and 6 table
Quantized vortices in a rotating Bose-Einstein condensate with spatiotemporally modulated interaction
We present theoretical analysis and numerical studies of the quantized
vortices in a rotating Bose-Einstein condensate with spatiotemporally modulated
interaction in harmonic and anharmonic potentials, respectively. The exact
quantized vortex and giant vortex solutions are constructed explicitly by
similarity transformation. Their stability behavior has been examined by
numerical simulation, which shows that a new series of stable vortex states
(defined by radial and angular quantum numbers) can be supported by the
spatiotemporally modulated interaction in this system. We find that there exist
stable quantized vortices with large topological charges in repulsive
condensates with spatiotemporally modulated interaction. We also give an
experimental protocol to observe these vortex states in future experiments
Precision Measurement of the Spin-Dependent Asymmetry in the Threshold Region of ^3He(e, e')
We present the first precision measurement of the spin-dependent asymmetry in the threshold region of ^3He(e,e′) at Q^2 values of 0.1 and 0.2(GeV/c)^2. The agreement between the data and nonrelativistic Faddeev calculations which include both final-state interactions and meson-exchange current effects is very good at Q^2 = 0.1(GeV/c)^2, while a small discrepancy at Q^2 = 0.2(GeV/c)^2 is observed
Second harmonic generation in phase matched aluminum nitride waveguides
We demonstrate second order optical nonlinearity in aluminum nitride on
insulator substrates. Using sputter-deposited aluminum nitride thin films we
realize nanophotonic waveguides coupled to micro-ring resonators that
simultaneously support cavity resonant modes for both visible and IR light. By
using phase matched ring resonators, we achieve efficient second-harmonic
generation and are able to generate up to 0.5uW of visible light on the chip
with a conversion efficiency of -46dB. From the measured response we obtain a
second order non-linear susceptibility (\c{hi}2) of 4.7pm/V. Our platform
provides a viable route for realizing wideband linear and nonlinear optical
devices on a chip
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