Quiescent times in gamma-ray bursts – I. An observed correlation between the durations of subsequent emission episodes     

Enrico Ramirez-Ruiz  Andrea Merloni 《Monthly notices of the Royal Astronomical Society》2001,320(3):L25-L29

Although more than 2000 astronomical gamma-ray bursts (GRBs) have been detected, the precise progenitor responsible for these events is unknown. The temporal phenomenology observed in GRBs can significantly constrain the different models. Here we analyse the time histories of a sample of bright, long GRBs, searching for the ones exhibiting relatively long (more than 5 per cent of the total burst duration) 'quiescent times', defined as the intervals between adjacent episodes of emission during which the gamma-ray count rate drops to the background level. We find a quantitative relation between the duration of an emission episode and the quiescent time elapsed since the previous episode. We suggest here that the mechanism responsible for the extraction and the dissipation of energy has to take place in a metastable configuration, such that the longer the accumulation period, the higher the stored energy available for the next emission episode.  相似文献   

Polynomial chaos expansion for global sensitivity analysis applied to a model of radionuclide migration in a randomly heterogeneous aquifer     

Valentina Ciriello  Vittorio Di Federico  Monica Riva  Francesco Cadini  Jacopo De Sanctis  Enrico Zio  Alberto Guadagnini 《Stochastic Environmental Research and Risk Assessment (SERRA)》2013,27(4):945-954

We perform global sensitivity analysis (GSA) through polynomial chaos expansion (PCE) on a contaminant transport model for the assessment of radionuclide concentration at a given control location in a heterogeneous aquifer, following a release from a near surface repository of radioactive waste. The aquifer hydraulic conductivity is modeled as a stationary stochastic process in space. We examine the uncertainty in the first two (ensemble) moments of the peak concentration, as a consequence of incomplete knowledge of (a) the parameters characterizing the variogram of hydraulic conductivity, (b) the partition coefficient associated with the migrating radionuclide, and (c) dispersivity parameters at the scale of interest. These quantities are treated as random variables and a variance-based GSA is performed in a numerical Monte Carlo framework. This entails solving groundwater flow and transport processes within an ensemble of hydraulic conductivity realizations generated upon sampling the space of the considered random variables. The Sobol indices are adopted as sensitivity measures to provide an estimate of the role of uncertain parameters on the (ensemble) target moments. Calculation of the indices is performed by employing PCE as a surrogate model of the migration process to reduce the computational burden. We show that the proposed methodology (a) allows identifying the influence of uncertain parameters on key statistical moments of the peak concentration (b) enables extending the number of Monte Carlo iterations to attain convergence of the (ensemble) target moments, and (c) leads to considerable saving of computational time while keeping acceptable accuracy.  相似文献   

Supernovae and Gaia     

Giuseppe Altavilla  Maria Teresa Botticella  Enrico Cappellaro  Massimo Turatto 《Astrophysics and Space Science》2012,341(1):163-178

Despite decades of dedicated efforts there are still basic questions to answer with regard to Supernova progenitor systems and explosion mechanisms. In particular, in the last years a number of exceptionally bright objects and extremely faint events have demonstrated an unexpected large Supernova variety.  相似文献   

Descent into the Abyss     

Enrico Bonatti 《地学学报》1995,7(6):578-579

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A Lagrangian Decorrelation Time Scale in the Convective Boundary Layer   总被引：1，自引：1，他引：0  

Gervasio Degrazia  Domenico Anfossi  Haroldo Fraga De Campos Velho  Enrico Ferrero 《Boundary-Layer Meteorology》1998,86(3):525-534

A new method for deriving the Lagrangian decorrelation time scales for inhomogeneous turbulence is described. The expression for the time scales here derived for the convective boundary layer is compared to those estimated by Hanna during the Phoenix experiment. Then the values of C₀, the Lagrangian velocity structure function constant, and of B_i, the Lagrangian velocity spectrum constant, were evaluated from the Eulerian velocity spectra and from the Lagrangian time scales derived, under unstable conditions, from Taylor's statistical diffusion theory. The numerical coefficient of the lateral and vertical Lagrangian spectra in the inertial subrange was found equal to 0.21, in good agreement with previous experimental estimates.  相似文献   

Variability of Mediterranean coralligenous assemblages subject to local variation in sediment deposition     

Balata D  Piazzi L  Cecchi E  Cinelli F 《Marine environmental research》2005,60(4):403-421

This study tested whether the development of coralligenous assemblages on horizontal and vertical surfaces differed between localities of high and low sediment deposition. The development and structure of these assemblages varied in predictable ways according to the level of sediment deposition. These differences were largely independent of the orientation of substratum. Turfs were more extensive in areas of high sediment deposition while erect and encrusting algae were most extensive in areas of low sediment deposition. Encrusting invertebrates characterised vertical surfaces and were most extensive in areas of high sediment deposition. These results are consistent with studies from other temperate regions of the globe, suggesting that effects of sedimentation on temperate coasts are substantial and widespread.  相似文献   

Vertical tectonism in oceanic fracture zones     

Enrico Bonatti 《Earth and Planetary Science Letters》1978,37(3):369-379

Anomalous topographic highs are found along many large oceanic fracture zones, frequently in the form of transverse ridges elongated parallel to the fractures both within and outside of the transform zone. These crustal highs are one or more kilometers shallower than the adjacent “normal” crust of equivalent age. Their elevation is frequently higher than the axial zone of lithospheric accretion. Geophysical and petrological data from the Vema, St. Paul, Romanche (Atlantic Ocean), Owen (Indian Ocean), Alula (Gulf of Aden), and other fracture zones suggest that the anomalous transverse ridges are not the result of excess volcanism, but rather of tectonic uplift of upper mantle and crustal blocks.Factors which may determine vertical tectonism along fracture zones include: (1) horizontal thermal conduction across a fracture zone from a lithospheric accreting segment; (2) viscodynamic forces operating in a fracture zone close to its intersection with an accreting segment; and (3) compressional and tensional horizontal stresses operating along a fracture zone, and created by several causes, the major one being small changes in the direction of spreading. Among these various factors, compressional and tensional horizontal stresses are probably the main cause of vertical tectonism in fracture zones. During the vertical motion of upper mantle/crustal blocks, ultramafic rocks, due to their physical properties, are uplifted preferentially.One of the implications of fracture zone vertical tectonism is that the age/depth of the crust relationship may not apply in regions with large fracture zones. In one well-documented case, a transverse crustal block at the Romanche fracture zone subsided during the last 5 m.y. at an average rate more than one order of magnitude faster than crust of equivalent age.  相似文献   

Preliminary tests on large-scale suppression of warm fog by means of giant monodisperse particulates. Part II. An extensive systematic experiment in the Ghedi-Monte Orfano area     

Alberto C. Montefinale  Gianna L. Petriconi  Enrico G. Gori  Henry M. Papee 《Pure and Applied Geophysics》1970,83(1):173-181

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Project ‘climatite’     

Enrico G. Gori  Gianna L. Petriconi  Alberto C. Montefinale  Tito Montefinale  Henry M. Papee 《Pure and Applied Geophysics》1972,99(1):230-250

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Is the Travertine on the Eastern Margin of the Qinghai-Xizang (Tibet) Plateau as a Surface Rock Record of the Lower Crustal Channel Flow?   总被引：1，自引：0，他引：1  

WANG Fudong  DONG Faqin  ENRICO Capezzuoli  ZHAO Xueqin 《《地质学报》英文版》2019,93(Z2):141-142

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