1,824 research outputs found
The Lagrangian description of aperiodic flows: a case study of the Kuroshio Current
This article reviews several recently developed Lagrangian tools and shows
how their combined use succeeds in obtaining a detailed description of purely
advective transport events in general aperiodic flows. In particular, because
of the climate impact of ocean transport processes, we illustrate a 2D
application on altimeter data sets over the area of the Kuroshio Current,
although the proposed techniques are general and applicable to arbitrary time
dependent aperiodic flows. The first challenge for describing transport in
aperiodical time dependent flows is obtaining a representation of the phase
portrait where the most relevant dynamical features may be identified. This
representation is accomplished by using global Lagrangian descriptors that when
applied for instance to the altimeter data sets retrieve over the ocean surface
a phase portrait where the geometry of interconnected dynamical systems is
visible. The phase portrait picture is essential because it evinces which
transport routes are acting on the whole flow. Once these routes are roughly
recognised it is possible to complete a detailed description by the direct
computation of the finite time stable and unstable manifolds of special
hyperbolic trajectories that act as organising centres of the flow.Comment: 40 pages, 24 figure
Identifying Near Earth Object Families
The study of asteroid families has provided tremendous insight into the
forces that sculpted the main belt and continue to drive the collisional and
dynamical evolution of asteroids. The identification of asteroid families
within the NEO population could provide a similar boon to studies of their
formation and interiors. In this study we examine the purported identification
of NEO families by Drummond (2000) and conclude that it is unlikely that they
are anything more than random fluctuations in the distribution of NEO
osculating orbital elements. We arrive at this conclusion after examining the
expected formation rate of NEO families, the identification of NEO groups in
synthetic populations that contain no genetically related NEOs, the orbital
evolution of the largest association identified by Drummond (2000), and the
decoherence of synthetic NEO families intended to reproduce the observed
members of the same association. These studies allowed us to identify a new
criterion that can be used to select real NEO families for further study in
future analyses, based on the ratio of the number of pairs and the size of
strings to the number of objects in an identified association.Comment: Accepted for publication in Icarus. 19 pages including 11 figure
Identification of earthquake precursors in the hydrogeochemical and geoacoustic data for the Kamchatka peninsula by flicker-noise spectroscopy
A phenomenological systems approach for identifying potential precursors in
multiple signals of different types for the same local seismically active
region is proposed based on the assumption that a large earthquake may be
preceded by a system reconfiguration (preparation) at different time and space
scales. A nonstationarity factor introduced within the framework of
flicker-noise spectroscopy, a statistical physics approach to the analysis of
time series, is used as the dimensionless criterion for detecting qualitative
(precursory) changes within relatively short time intervals in arbitrary
signals. Nonstationarity factors for chlorine-ion concentration variations in
the underground water of two boreholes on the Kamchatka peninsula and
geacoustic emissions in a deep borehole within the same seismic zone are
studied together in the time frame around a large earthquake on October 8,
2001. It is shown that nonstationarity factor spikes (potential precursors)
take place in the interval from 70 to 50 days before the earthquake for the
hydrogeochemical data and at 29 and 6 days in advance for the geoacoustic data.Comment: 8 pages, 4 figures; to be published in Nat. Hazards Earth Syst. Sc
Scientific research trends about metaheuristics in process optimization and case study using the desirability function
This study aimed to identify the research gaps in Metaheuristics, taking into account the publications entered in a database in 2015 and to present a case study of a company in the Sul Fluminense region using the Desirability function. To achieve this goal, applied research of exploratory nature and qualitative approach was carried out, as well as another of quantitative nature. As method and technical procedures were the bibliographical research, some literature review, and an adopted case study respectively. As a contribution of this research, the holistic view of opportunities to carry out new investigations on the theme in question is pointed out. It is noteworthy that the identified study gaps after the research were prioritized and discriminated, highlighting the importance of the viability of metaheuristic algorithms, as well as their benefits for process optimization
Nonextensive statistics: Theoretical, experimental and computational evidences and connections
The domain of validity of standard thermodynamics and Boltzmann-Gibbs
statistical mechanics is discussed and then formally enlarged in order to
hopefully cover a variety of anomalous systems. The generalization concerns
{\it nonextensive} systems, where nonextensivity is understood in the
thermodynamical sense. This generalization was first proposed in 1988 inspired
by the probabilistic description of multifractal geometries, and has been
intensively studied during this decade. In the present effort, after
introducing some historical background, we briefly describe the formalism, and
then exhibit the present status in what concerns theoretical, experimental and
computational evidences and connections, as well as some perspectives for the
future. In addition to these, here and there we point out various (possibly)
relevant questions, whose answer would certainly clarify our current
understanding of the foundations of statistical mechanics and its
thermodynamical implicationsComment: 15 figure
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