Prototyping an artificial neural network for burned area mapping on a regional scale in Mediterranean areas using MODIS images     

Israel Gómez  M. Pilar Martín 《International Journal of Applied Earth Observation and Geoinformation》2011

Each year thousands of ha of forest land are affected by forest fires in Southern European countries such as Spain. Burned area maps are a valuable instrument for designing prevention and recovery policies. Remote sensing has increasingly become the most widely used tool for this purpose on regional and global scales, where a large variety of techniques and data has been applied. This paper proposes a semiautomatic method for burned area mapping on a regional scale in Mediterranean areas (the Iberian Peninsula has been used as a study case). A Multi-layer Perceptron Network (MLPN) has been designed and applied to MODIS/Terra Surface Reflectance Daily L2G Global 500m SIN Grid multitemporal composite monthly images. The compositing criterion was based on maximum surface temperature. The research covered a six year period (2001–2006) from June to September, when most of the forest fires occur. The resulting burned area maps have been validated using official fire perimeters and compared with MODIS Collection 5 Burned Area Product (MCD45A1). The MLPN shown as an effective method, with a commission error of 29.1%, in the classification of the burned areas, while the omission error was of 14.9%. The results were compared with the MCD45A1 product, which had a slightly higher commission error (30.2%) and a considerably higher omission error (26.2%), indicating a high underestimation of the burned area.  相似文献   

Search for radio pulsations in four Anomalous X-ray Pulsars and discovery of two new pulsars   总被引：1，自引：0，他引：1  

M. Burgay  N. Rea  G. L. Israel  A. Possenti  L. Burderi  T. Di Salvo  N. D'Amico  L. Stella 《Monthly notices of the Royal Astronomical Society》2006,372(1):410-416

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Long term spectral variability in the soft gamma-ray repeater SGR 1900+14     

Andrea Tiengo  Paolo Esposito  Sandro Mereghetti  Lara Sidoli  Diego Götz  Marco Feroci  Roberto Turolla  Silvia Zane  Gian Luca Israel  Luigi Stella  Peter Woods 《Astrophysics and Space Science》2007,308(1-4):33-37

We present a systematic analysis of all the BeppoSAX data of SGR1900+14. The observations spanning five years show that the source was brighter than usual on two occasions: ～20 days after the August 1998 giant flare and during the 10⁵?s long X-ray afterglow following the April 2001 intermediate flare. In the latter case, we explore the possibility of describing the observed short term spectral evolution only with a change of the temperature of the blackbody component. In the only BeppoSAX observation performed before the giant flare, the spectrum of the SGR1900+14 persistent emission was significantly harder and detected also above 10 keV with the PDS instrument. In the last BeppoSAX observation (April 2002) the flux was at least a factor 1.2 below the historical level, suggesting that the source was entering a quiescent period.  相似文献   

A Compton reflection dominated spectrum in a peculiar accreting neutron star     

N. Rea  L. Stella  G. L. Israel  G. Matt  S. Zane  A. Segreto  T. Oosterbroek  M. Orlandini 《Monthly notices of the Royal Astronomical Society》2005,364(4):1229-1238

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Studies of neutron stars at optical/IR wavelengths     

R. P. Mignani  S. Bagnulo  A. De Luca  G. L. Israel  G. Lo Curto  C. Motch  R. Perna  N. Rea  R. Turolla  S. Zane 《Astrophysics and Space Science》2007,308(1-4):203-210

In the last years, optical studies of Isolated Neutron Stars (INSs) have expanded from the more classical rotation-powered ones to other categories, like the Anomalous X-ray Pulsars (AXPs) and the Soft Gamma-ray Repeaters (SGRs), which make up the class of the magnetars, the radio-quiet INSs with X-ray thermal emission and, more recently, the enigmatic Compact Central Objects (CCOs) in supernova remnants. Apart from 10 rotation-powered pulsars, so far optical/IR counterparts have been found for 5 magnetars and for 4 INSs. In this work we present some of the latest observational results obtained from optical/IR observations of different types of INSs.  相似文献   

Discovery of the near-infrared counterpart of the X-ray transient XTE J1908+094     

S. Chaty  R. P. Mignani  G. L. Israel 《Monthly notices of the Royal Astronomical Society》2002,337(3):L23-L26

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MMIV: de SGR 1806–20 Anno Mirabili     

GianLuca Israel 《Astrophysics and Space Science》2007,308(1-4):25-31

On 27th December 2004 SGR 1806–20, one of the most active Soft γ-ray Repeaters (SGRs), displayed an extremely rare event, also known as giant flare, during which up to 10⁴⁷ ergs were released in the ∼1–1000 keV range in less than 1 s. Before and after the giant flare we carried out IR observations by using adaptive optics (NAOS-CONICA) mounted on VLT which provided images of unprecedented quality (FWHM better than 0.1″). We discovered the likely IR counterpart to SGR 1806–20 based on positional coincidence with the VLA uncertainty region and flux variability of a factor of about 2 correlated with that at higher energies. Moreover, by analysing the Rossi-XTE/PCA data we have discovered rapid Quasi-Periodic Oscillations (QPOs) in the pulsating tail of the 27th December 2004 giant flare of SGR 1806–20. QPOs at ∼92.5 Hz are detected in a 50 s interval starting 170 s after the onset of the giant flare. These QPOs appear to be associated with increased emission by a relatively hard unpulsed component and are seen only over phases of the 7.56 s spin period pulsations away from the main peak. QPOs at ∼18 and ∼30 Hz are also detected ∼200–300 s after the onset of the giant flare. This is the first time that QPOs are unambiguously detected in the flux of a Soft Gamma-ray Repeater, or any other isolated neutron star. We interpret the highest QPOs in terms of the coupling of toroidal seismic modes with Alfvén waves propagating along magnetospheric field lines. The lowest frequency QPO might instead provide indirect evidence on the strength of the internal magnetic field of the neutron star.   相似文献   

Annama H chondrite—Mineralogy,physical properties,cosmic ray exposure,and parent body history          下载免费PDF全文

Tomáš Kohout  Jakub Haloda  Patricie Halodová  Matthias M. M. Meier  Colin Maden  Henner Busemann  Matthias Laubenstein  Marc. W. Caffee  Kees C. Welten  Jens Hopp  Mario Trieloff  Ramakant R. Mahajan  Sekhar Naik  Josep M. Trigo‐Rodriguez  Carles E. Moyano‐Cambero  Michael I. Oshtrakh  Alevtina A. Maksimova  Andrey V. Chukin  Vladimir A. Semionkin  Maksim S. Karabanalov  Israel Felner  Evgeniya V. Petrova  Evgeniia V. Brusnitsyna  Victor I. Grokhovsky  Grigoriy A. Yakovlev  Maria Gritsevich  Esko Lyytinen  Jarmo Moilanen  Nikolai A. Kruglikov  Aleksey V. Ishchenko 《Meteoritics & planetary science》2017,52(8):1525-1541

The fall of the Annama meteorite occurred early morning (local time) on April 19, 2014 on the Kola Peninsula (Russia). Based on mineralogy and physical properties, Annama is a typical H chondrite. It has a high Ar‐Ar age of 4.4 Ga. Its cosmic ray exposure history is atypical as it is not part of the large group of H chondrites with a prominent 7–8 Ma peak in the exposure age histograms. Instead, its exposure age is within uncertainty of a smaller peak at 30 ± 4 Ma. The results from short‐lived radionuclides are compatible with an atmospheric pre‐entry radius of 30–40 cm. However, based on noble gas and cosmogenic radionuclide data, Annama must have been part of a larger body (radius >65 cm) for a large part of its cosmic ray exposure history. The ¹⁰Be concentration indicates a recent (3–5 Ma) breakup which may be responsible for the Annama parent body size reduction to 30–35 cm pre‐entry radius.  相似文献   

On the Use of VLF Narrowband Measurements to Study the Lower Ionosphere and the Mesosphere–Lower Thermosphere     

Israel Silber  Colin Price 《Surveys in Geophysics》2017,38(2):407-441

The ionospheric D-region (~60 km up to ~95 km) and the corresponding neutral atmosphere, often referred to as the mesosphere–lower thermosphere (MLT), are challenging and costly to probe in situ. Therefore, remote sensing techniques have been developed over the years. One of these is based on very low frequency (VLF, 3–30 kHz) electromagnetic waves generated by various natural and man-made sources. VLF waves propagate within the Earth–ionosphere waveguide and are extremely sensitive to perturbations occurring in the D-region along their propagation path. Hence, measurements of these signals serve as an inexpensive remote sensing technique for probing the lower ionosphere and the MLT region. This paper reviews the use of VLF narrowband (NB) signals (generated by man-made transmitters) in the study of the D-region and the MLT for over 90 years. The fields of research span time scales from microseconds to decadal variability and incorporate lightning-induced short-term perturbations; extraterrestrial radiation bursts; energetic particle precipitation events; solar eclipses; lower atmospheric waves penetrating into the D-region; sudden stratospheric warming events; the annual oscillation; the solar cycle; and, finally, the potential use of VLF NB measurements as an anthropogenic climate change monitoring technique.  相似文献   

Can the pattern of juvenile recruitment and population structure of the speckled swimming crab Arenaeus cribrarius (Decapoda: Brachyura) be determined by geographical variations?          下载免费PDF全文

Luciana Segura de Andrade  Israel Fernandes Frameschi  Antônio Leão Castilho  Rogério Caetano da Costa  Adilson Fransozo 《Marine Ecology》2015,36(4):950-958

This study evaluated the effect of environmental stimuli and selective pressures in different geographical areas along a latitudinal gradient, on the juvenile recruitment, population structure, and sex ratio of the speckled swimming crab Arenaeus cribrarius. Samples were collected monthly during 1 year in three locations along the Brazilian coast: Macaé, state of Rio de Janeiro (MAC, 22°47′ S, 41°45′ W); Ubatuba, São Paulo (UBA, 23°27′ S, 44°58′ W); and São Francisco do Sul, Santa Catarina (SFS, 26°08′ S, 48°34′ W). The specimens of A. cribrarius were identified, counted, sexed, and measured for maximum carapace width (CW). The largest juvenile found was in UBA (47.7 ± 1.36 mm); and the largest adult females and males in MAC (74.26 ± 0.93 and 77.04 ± 0.79 mm, respectively). Recruitment in MAC was continuous, whereas in UBA and SFS, recruitment showed seasonal characteristics. The sex ratio was skewed toward females only in UBA; in MAC and SFS, males and females were present in equal proportions. These results indicate that geographical variations can cause differences in the recruitment and population structure of A. cribrarius. These regional differences call attention to the necessity for improved management plans and control of shrimp fishing, which can affect population patterns such as juvenile recruitment, population structure and life history of the target species and species that are caught in bycatch from shrimping, such as the swimming crab A. cribrarius.  相似文献