6,792 research outputs found

    FARC Terrorism in Colombia: A Clustering Analysis

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    This paper applies clustering analysis to the Colombian armed conflict. Indeed, when applied to a FARC terrorist act database, this statistical procedure finds a natural clustering of the diferent FARC units according to the diferent types of terrorist acts they commit and identities the military hard core of the FARC. The facts revealed in this paper should be useful not only for future military strategies, but also to determine a better priorization and geographical allocation of the scarce military resources.Clustering Analysis,

    Flux-cutting and flux-transport effects in type-II superconductor slabs in a parallel rotating magnetic field

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    The magnetic response of irreversible type-II superconductor slabs subjected to in-plane rotating magnetic field is investigated by applying the circular, elliptic, extended-elliptic, and rectangular flux-line-cutting critical-state models. Specifically, the models have been applied to explain experiments on a PbBi rotating disk in a fixed magnetic field Ha{\bm H}_a, parallel to the flat surfaces. Here, we have exploited the equivalency of the experimental situation with that of a fixed disk under the action of a parallel magnetic field, rotating in the opposite sense. The effect of both the magnitude HaH_a of the applied magnetic field and its angle of rotation αs\alpha_s upon the magnetization of the superconductor sample is analyzed. When HaH_a is smaller than the penetration field HPH_P, the magnetization components, parallel and perpendicular to Ha{\bm H_a}, oscillate with increasing the rotation angle. On the other hand, if the magnitude of the applied field, HaH_a, is larger than HPH_P, both magnetization components become constant functions of αs\alpha_s at large rotation angles. The evolution of the magnetic induction profiles inside the superconductor is also studied.Comment: 12 pages, 29 figure

    Infrared excesses in stars with and without planets using revised WISE{\it WISE} photometry

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    We present an analysis on the potential prevalence of mid infrared excesses in stars with and without planetary companions. Based on an extended database of stars detected with the WISE{\it WISE} satellite, we studied two stellar samples: one with 236 planet hosts and another with 986 objects for which planets have been searched but not found. We determined the presence of an excess over the photosphere by comparing the observed flux ratio at 22 μ\mum and 12 μ\mum (f22/f12f_{22}/f_{12}) with the corresponding synthetic value, derived from results of classical model photospheres. We found a detection rate of 0.85%\% at 22 μ\mum (2 excesses) in the sample of stars with planets and 0.1%\% (1 detection) for the stars without planets. The difference of the detection rate between the two samples is not statistically significant, a result that is independent of the different approaches found in the literature to define an excess in the wavelength range covered by WISE{\it WISE} observations. As an additional result, we found that the WISE{\it WISE} fluxes required a normalisation procedure to make them compatible with synthetic data, probably pointing out a revision of the WISE{\it WISE} data calibration.Comment: 10 pages, 6 figures, 3 tables. Accepted for publication in MNRA
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