79,514 research outputs found
Highlights from galactic observations with MAGIC
MAGIC is one of the main instruments for exploring the galactic gamma-ray sky
from ground in the energy range of 50 GeV - 50 TeV. It consists of two 17 m
diameter imaging atmospheric Cherenkov telescopes located at the Roque de los
Muchachos Observatory, on the Canary island of La Palma. Thanks to its
excellent sensitivity, MAGIC has conducted relevant studies on galactic objects
of different types at Very High Energies. Among them, the Crab pulsar up to TeV
energies, the spectral cut-off of the supernova remnant Cassiopeia A, the
super-orbital variability of the binary system LSI +61 303, the search for
microqusars, multi-year observations of the Galactic Center and follow-up
studies of unidentified HAWC sources. In many cases, the results from these
observations challenge our understanding of the underlying emission mechanisms.
Here we review the latest results from the observation of these galactic
sources with MAGIC.Comment: Proceedings of the 35th International Cosmic Ray Conference (ICRC
2017), Bexco, Busan, Korea (arXiv:1708.05153
Business Cycle and Speculative Pressures in a Target Zone
In the past time, most economies have suffered cyclical fluctuations in their activity which may influence the optimal use of productive factors in long slow-growth phases or price stability in periods of fast growth. This paper focuses on the possible interrelationship between business cycles and exchange rate ‡uctuations. We have chosen the European Monetary System framework in the nineties, from June 1989 to December 1998, because the Peseta belonged to the EMS during that time. This sample is specially interesting because it includes the worst crisis of the System in 1992-93 and the following ones affecting emerging countries like Mexico, Brazil or Russia at the end of the decade. We use a Binary Dependent Variable Logit Model to estimate the readjustment probability inside a band for two currencies, the Peseta and the french Franc . We calculate the dependent variable values from a Markov-Switching Regime Model with constant transition probabilities. We prove that it is a suitable method and that it allows both real and monetary variables to be identified in order to explain speculative pressures.Readjustment Probability, Speculative Pressures, Economic Fluctuations.
Overview of methodologies for building ontologies
A few research groups are now proposing a series of steps and methodologies for developing ontologies. However, mainly due to the fact that Ontological Engineering is still a relatively immature discipline, each work group employs its own methodology. Our goal is to present the most representative methodologies used in ontology development and to perform an analysis of such methodologies against the same framework of reference. So, the goal of this paper is not to provide new insights about methodologies, but to put it all in one place and help people to select which methodology to use
The bulge luminosity functions in the MSX infrared bands
We use an inversion technique to derive the luminosity functions of the
Galactic bulge from point source counts extracted from the Midcourse Space
Experiment's Point Source Catalog (version 1.2).Comment: 5 pages, 2 figures, to be published in A&
f(R) brane cosmology
Despite the nice features of the Dvali, Gabadadze and Porrati (DGP) model to
explain the late-time acceleration of the universe, it suffers from some
theoretical problems like the ghost issue. We present a way to self-accelerate
the normal DGP branch, which is known to be free of the ghost problem, by means
of an f(R) term on the brane action. We obtain the de Sitter self-accelerating
solutions of the model and study their stability under homogeneous
perturbations.Comment: 4 pages, 2 figures. Contribution to the proceedings of Spanish
Relativity Meeting 2009, Bilbao, Spain, 7-11 September 200
Resource location based on precomputed partial random walks in dynamic networks
The problem of finding a resource residing in a network node (the
\emph{resource location problem}) is a challenge in complex networks due to
aspects as network size, unknown network topology, and network dynamics. The
problem is especially difficult if no requirements on the resource placement
strategy or the network structure are to be imposed, assuming of course that
keeping centralized resource information is not feasible or appropriate. Under
these conditions, random algorithms are useful to search the network. A
possible strategy for static networks, proposed in previous work, uses short
random walks precomputed at each network node as partial walks to construct
longer random walks with associated resource information. In this work, we
adapt the previous mechanisms to dynamic networks, where resource instances may
appear in, and disappear from, network nodes, and the nodes themselves may
leave and join the network, resembling realistic scenarios. We analyze the
resulting resource location mechanisms, providing expressions that accurately
predict average search lengths, which are validated using simulation
experiments. Reduction of average search lengths compared to simple random walk
searches are found to be very large, even in the face of high network
volatility. We also study the cost of the mechanisms, focusing on the overhead
implied by the periodic recomputation of partial walks to refresh the
information on resources, concluding that the proposed mechanisms behave
efficiently and robustly in dynamic networks.Comment: 39 pages, 25 figure
One-dimensional relativistic dissipative system with constant force and its quantization
For a relativistic particle under a constant force and a linear velocity
dissipation force, a constant of motion is found. Problems are shown for
getting the Hamiltoninan of this system. Thus, the quantization of this system
is carried out through the constant of motion and using the quantization of the
velocity variable. The dissipative relativistic quantum bouncer is outlined
within this quantization approach.Comment: 11 pages, no figure
- …