142,708 research outputs found
Automatic large-scale classification of bird sounds is strongly improved by unsupervised feature learning
This is an Open Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY 4.0) license, which permits others to distribute, remix, adapt and build upon this work, for commercial use, provided the original work is properly cited. See: http://creativecommons.org/ licenses/by/4.0
Two-Dimensional Spectroscopy of Photospheric Shear Flows in a Small delta Spot
In recent high-resolution observations of complex active regions,
long-lasting and well-defined regions of strong flows were identified in major
flares and associated with bright kernels of visible, near-infrared, and X-ray
radiation. These flows, which occurred in the proximity of the magnetic neutral
line, significantly contributed to the generation of magnetic shear. Signatures
of these shear flows are strongly curved penumbral filaments, which are almost
tangential to sunspot umbrae rather than exhibiting the typical radial
filamentary structure. Solar active region NOAA 10756 was a moderately complex,
beta-delta sunspot group, which provided an opportunity to extend previous
studies of such shear flows to quieter settings. We conclude that shear flows
are a common phenomenon in complex active regions and delta spots. However,
they are not necessarily a prerequisite condition for flaring. Indeed, in the
present observations, the photospheric shear flows along the magnetic neutral
line are not related to any change of the local magnetic shear. We present
high-resolution observations of NOAA 10756 obtained with the 65-cm vacuum
reflector at Big Bear Solar Observatory (BBSO). Time series of
speckle-reconstructed white-light images and two-dimensional spectroscopic data
were combined to study the temporal evolution of the three-dimensional vector
flow field in the beta-delta sunspot group. An hour-long data set of consistent
high quality was obtained, which had a cadence of better than 30 seconds and
sub-arcsecond spatial resolution.Comment: 23 pages, 6 gray-scale figures, 4 color figures, 2 tables, submitted
to Solar Physic
Anomaly Detection in Multivariate Non-stationary Time Series for Automatic DBMS Diagnosis
Anomaly detection in database management systems (DBMSs) is difficult because
of increasing number of statistics (stat) and event metrics in big data system.
In this paper, I propose an automatic DBMS diagnosis system that detects
anomaly periods with abnormal DB stat metrics and finds causal events in the
periods. Reconstruction error from deep autoencoder and statistical process
control approach are applied to detect time period with anomalies. Related
events are found using time series similarity measures between events and
abnormal stat metrics. After training deep autoencoder with DBMS metric data,
efficacy of anomaly detection is investigated from other DBMSs containing
anomalies. Experiment results show effectiveness of proposed model, especially,
batch temporal normalization layer. Proposed model is used for publishing
automatic DBMS diagnosis reports in order to determine DBMS configuration and
SQL tuning.Comment: 8 page
iMapD: intrinsic Map Dynamics exploration for uncharted effective free energy landscapes
We describe and implement iMapD, a computer-assisted approach for
accelerating the exploration of uncharted effective Free Energy Surfaces (FES),
and more generally for the extraction of coarse-grained, macroscopic
information from atomistic or stochastic (here Molecular Dynamics, MD)
simulations. The approach functionally links the MD simulator with nonlinear
manifold learning techniques. The added value comes from biasing the simulator
towards new, unexplored phase space regions by exploiting the smoothness of the
(gradually, as the exploration progresses) revealed intrinsic low-dimensional
geometry of the FES
Non-local updates for quantum Monte Carlo simulations
We review the development of update schemes for quantum lattice models
simulated using world line quantum Monte Carlo algorithms. Starting from the
Suzuki-Trotter mapping we discuss limitations of local update algorithms and
highlight the main developments beyond Metropolis-style local updates: the
development of cluster algorithms, their generalization to continuous time, the
worm and directed-loop algorithms and finally a generalization of the flat
histogram method of Wang and Landau to quantum systems.Comment: 14 pages, article for the proceedings of the "The Monte Carlo Method
in the Physical Sciences: Celebrating the 50th Anniversary of the Metropolis
Algorithm", Los Alamos, June 9-11, 200
Learning Vine Copula Models For Synthetic Data Generation
A vine copula model is a flexible high-dimensional dependence model which
uses only bivariate building blocks. However, the number of possible
configurations of a vine copula grows exponentially as the number of variables
increases, making model selection a major challenge in development. In this
work, we formulate a vine structure learning problem with both vector and
reinforcement learning representation. We use neural network to find the
embeddings for the best possible vine model and generate a structure.
Throughout experiments on synthetic and real-world datasets, we show that our
proposed approach fits the data better in terms of log-likelihood. Moreover, we
demonstrate that the model is able to generate high-quality samples in a
variety of applications, making it a good candidate for synthetic data
generation
Invaded cluster algorithm for Potts models
The invaded cluster algorithm, a new method for simulating phase transitions,
is described in detail. Theoretical, albeit nonrigorous, justification of the
method is presented and the algorithm is applied to Potts models in two and
three dimensions. The algorithm is shown to be useful for both first-order and
continuous transitions and evidently provides an efficient way to distinguish
between these possibilities. The dynamic properties of the invaded cluster
algorithm are studied. Numerical evidence suggests that the algorithm has no
critical slowing for Ising models.Comment: 39 pages, revtex, 15 figures available on request from
[email protected], to appear in Phys. Rev.
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