15,573 research outputs found
Improvements to context based self-supervised learning
We develop a set of methods to improve on the results of self-supervised
learning using context. We start with a baseline of patch based arrangement
context learning and go from there. Our methods address some overt problems
such as chromatic aberration as well as other potential problems such as
spatial skew and mid-level feature neglect. We prevent problems with testing
generalization on common self-supervised benchmark tests by using different
datasets during our development. The results of our methods combined yield top
scores on all standard self-supervised benchmarks, including classification and
detection on PASCAL VOC 2007, segmentation on PASCAL VOC 2012, and "linear
tests" on the ImageNet and CSAIL Places datasets. We obtain an improvement over
our baseline method of between 4.0 to 7.1 percentage points on transfer
learning classification tests. We also show results on different standard
network architectures to demonstrate generalization as well as portability. All
data, models and programs are available at:
https://gdo-datasci.llnl.gov/selfsupervised/.Comment: Accepted paper at CVPR 201
Exploration of the memory effect on the photon-assisted tunneling via a single quantum dot: A generalized Floquet theoretical approach
The generalized Floquet approach is developed to study memory effect on
electron transport phenomena through a periodically driven single quantum dot
in an electrode-multi-level dot-electrode nanoscale quantum device. The memory
effect is treated using a multi-function Lorentzian spectral density (LSD)
model that mimics the spectral density of each electrode in terms of multiple
Lorentzian functions. For the symmetric single-function LSD model involving a
single-level dot, the underlying single-particle propagator is shown to be
related to a 2 x 2 effective time-dependent Hamiltonian that includes both the
periodic external field and the electrode memory effect. By invoking the
generalized Van Vleck (GVV) nearly degenerate perturbation theory, an
analytical Tien-Gordon-like expression is derived for arbitrary order multi-
photon resonance d.c. tunneling current. Numerically converged simulations and
the GVV analytical results are in good agreement, revealing the origin of
multi- photon coherent destruction of tunneling and accounting for the
suppression of the staircase jumps of d.c. current due to the memory effect.
Specially, a novel blockade phenomenon is observed, showing distinctive
oscillations in the field-induced current in the large bias voltage limit
QCD Sum Rule Analysis of Heavy Quarkonium Hybrids
We have studied the charmonium and bottomonium hybrid states with various
quantum numbers in QCD sum rules. At leading order in , the
two-point correlation functions have been calculated up to dimension six
including the tri-gluon condensate and four-quark condensate. After performing
the QCD sum rule analysis, we have confirmed that the dimension six condensates
can stabilize the hybrid sum rules and allow the reliable mass predictions. We
have updated the mass spectra of the charmonium and bottomonium hybrid states
and identified that the negative-parity states with form the lightest hybrid supermultiplet while the positive-parity
states with belong to a heavier hybrid
supermultiplet.Comment: 7 pages, 1 figures. Some minor edits have been made. Presentation at
the DPF 2013 Meeting of the American Physical Society Division of Particles
and Fields, Santa Cruz, California, August 13-17, 201
Exploring the Spectrum of Heavy Quarkonium Hybrids with QCD Sum Rules
QCD Laplace sum rules are used to calculate heavy quarkonium (charmonium and
bottomonium) hybrid masses in several distinct channels. Previous
studies of heavy quarkonium hybrids did not include the effects of
dimension-six condensates, leading to unstable sum rules and unreliable mass
predictions in some channels. We have updated these sum rules to include
dimension-six condensates, providing new mass predictions for the spectra of
heavy quarkonium hybrids. We confirm the finding of other approaches that the
negative-parity states form the lightest hybrid
supermultiplet and the positive-parity
states are members of a heavier supermultiplet. Our results disfavor a pure
charmonium hybrid interpretation of the , in agreement with previous
work.Comment: Presented by RTK at the Theory Canada 9 Conference, held at Wilfrid
Laurier University in June 2014. Submitted for the conference proceedings to
be published in the Canadian Journal of Physics. 5 pages, 1 figure. Version
2: reference added, typo correcte
Lorentz Invariance in Chiral Kinetic Theory
We show that Lorentz invariance is realized nontrivially in the classical
action of a massless spin- particle with definite helicity. We find
that the ordinary Lorentz transformation is modified by a shift orthogonal to
the boost vector and the particle momentum. The shift ensures angular momentum
conservation in particle collisions and implies a nonlocality of the collision
term in the Lorentz-invariant kinetic theory due to side jumps. We show that
2/3 of the chiral-vortical effect for a uniformly rotating particle
distribution can be attributed to the magnetic moment coupling required by the
Lorentz invariance. We also show how the classical action can be obtained by
taking the classical limit of the path integral for a Weyl particle.Comment: 5 pages, 1 figur
Determinants and Impacts of the Relative Use of Depository Receipts and Euro Convertible Bonds by High-tech Corporations: An Empirical Study
This paper adopts Taiwan's high-tech companies as the sample to address and examine four new determinants of various foreign financing instruments and test their impacts on the issuing firms. Our empirical findings are consistent with the following notions. First, the firms with higher foreign holding and foreign investment will be likely to adopt foreign financing policy. Moreover, the firms with higher stock dividend payment in Taiwan will adopt both of ECB (Euro convertible bond) and DR (depository receipt). Firm managers with better education background will prefer DR. Second, the use of DR can effectively decrease the volatility of stock returns but also pronounce a negative influence on the mean of stock returns. In contrast, the use of ECB can effectively increase the mean but can not significantly decrease the volatility.
EFFECTS OF TAI-CHI CHUAN ON THE CONTROL OF BODY’S CENTRE OF MASS MOTION DRUING OBSTACLE-CROSSING IN THE ELDERLY
Tripping over obstacles is a common problem among the elderly, which often leads to physical injuries. Previous studies have shown the positive effects of Tai Chi Chuan (TCC) exercises on muscle power, flexibility, endurance, dexterity, physical fitness, and balance (Wolf et al., 1996; Li et al., 2004). These effects are beneficial for the control of the body stability and prevention of falls. The aim of this study was to investigate the effects of Tai-Chi Chun and obstacle heights on the inclination angles of the center of mass (COM) relative to the center of foot pressure (COP) during obstacle-crossing
Multilevel semantic analysis and problem-solving in the flight domain
A computer based cockpit system which is capable of assisting the pilot in such important tasks as monitoring, diagnosis, and trend analysis was developed. The system is properly organized and is endowed with a knowledge base so that it enhances the pilot's control over the aircraft while simultaneously reducing his workload
Fragmentation and OB Star Formation in High-Mass Molecular Hub-Filament System
Filamentary structures are ubiquitously seen in the interstellar medium. The
concentrated molecular mass in the filaments allows fragmentation to occur in a
shorter timescale than the timescale of the global collapse. Such hierarchical
fragmentation may further assist the dissipation of excessive angular momentum.
It is crucial to resolve the morphology and the internal velocity structures of
the molecular filaments observationally.
We perform 0".5-2".5 angular resolution interferometric observations toward
the nearly face-on OB cluster forming region G33.92+0.11. Observations of
various spectral lines as well as the millimeter dust continuum emission,
consistently trace several 1 pc scale, clumpy molecular arms. Some of the
molecular arms geometrically merge to an inner
3.0\,, 0.6
pc scale central molecular clump, and may directly channel the molecular gas to
the warm (50 K) molecular gas immediately surrounding the centrally
embedded OB stars. The NH spectra suggest a medium turbulence line width
of FWHM2\,km\,s in the central molecular clump, implying a
10 times larger molecular mass than the virial mass. Feedbacks from
shocks and the centrally embedded OB stars and localized (proto)stellar
clusters, likely play a key role in the heating of molecular gas and could lead
to the observed chemical stratification. Although (proto)stellar feedbacks are
already present, G33.92+0.11 chemically appears to be at an early evolutionary
stage given by the low abundance limit of SO observed in this region.Comment: 37 pages, 23 figure
- …