10,164 research outputs found
155-day Periodicity in Solar Cycles 3 and 4
The near 155 days solar periodicity, so called Rieger periodicity, was first
detected in solar flares data and later confirmed with other important solar
indices. Unfortunately, a comprehensive analysis on the occurrence of this
periodicity during previous centuries can be further complicated due to the
poor quality of the sunspot number time-series. We try to detect the Rieger
periodicity during the solar cycles 3 and 4 using information on aurorae
observed at mid and low latitudes. We use two recently discovered aurora
datasets, observed in the last quarter of the 18th century from UK and Spain.
Besides simple histograms of time between consecutive events we analyse monthly
series of number of aurorae observed using different spectral analysis (MTM and
Wavelets). The histograms show the probable presence of Rieger periodicity
during cycles 3 and 4. However different spectral analysis applied has only
confirmed undoubtedly this hypothesis for solar cycle 3.Comment: 13 pages, 6 figures, to appear in New Astronom
Study of angulations of visceral abdominals arteries in their abdominal aorta emergency
Postprint (author's final draft
Auto-tuning Distributed Stream Processing Systems using Reinforcement Learning
Fine tuning distributed systems is considered to be a craftsmanship, relying
on intuition and experience. This becomes even more challenging when the
systems need to react in near real time, as streaming engines have to do to
maintain pre-agreed service quality metrics. In this article, we present an
automated approach that builds on a combination of supervised and reinforcement
learning methods to recommend the most appropriate lever configurations based
on previous load. With this, streaming engines can be automatically tuned
without requiring a human to determine the right way and proper time to deploy
them. This opens the door to new configurations that are not being applied
today since the complexity of managing these systems has surpassed the
abilities of human experts. We show how reinforcement learning systems can find
substantially better configurations in less time than their human counterparts
and adapt to changing workloads
Towards a Protocol for Benchmark Selection in IPC
The planning competition has traditionally played an
important role in motivating research and advances in
Planning & Scheduling techniques. Despite its pivotal
role in the planning community, some aspects of the
competition have not been engineered yet. This is the
case for the protocol for selecting benchmark instances.
Benchmarks are of critical importance, since they can
significantly affect competition results.
In this paper we describe desirable properties of a selection
protocol, discuss methods exploited in past SAT
and planning competitions, and identify challenges that
organisers of future competitions have to address in order
to improve reliability and usefulness of the insights
gained by looking at competitions’ results
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