The visible and near infrared module of EChO     

A. Adriani  G. Bellucci  L. Gambicorti  M. Focardi  E. Oliva  M. Farina  A. M. Di Giorgio  F. Santoli  E. Pace  G. Piccioni  G. Filacchione  M. Pancrazzi  A. Tozzi  G. Micela 《Experimental Astronomy》2015,40(2-3):753-769

The Visible and Near Infrared (VNIR) is one of the modules of EChO, the Exoplanets Characterization Observatory proposed to ESA for an M-class mission. EChO is aimed to observe planets while transiting by their suns. Then the instrument had to be designed to assure a high efficiency over the whole spectral range. In fact, it has to be able to observe stars with an apparent magnitude M_v?=?9–12 and to see contrasts of the order of 10^?4–10^?5 necessary to reveal the characteristics of the atmospheres of the exoplanets under investigation. VNIR is a spectrometer in a cross-dispersed configuration, covering the 0.4–2.5 μm spectral range with a resolving power of about 330 and a field of view of 2 arcsec. It is functionally split into two channels respectively working in the 0.4–1.0 μm and 1.0–2.5 μm spectral ranges. Such a solution is imposed by the fact the light at short wavelengths has to be shared with the EChO Fine Guiding System (FGS) devoted to the pointing of the stars under observation. The spectrometer makes use of a HgCdTe detector of 512 by 512 pixels, 18 μm pitch and working at a temperature of 45 K as the entire VNIR optical bench. The instrument has been interfaced to the telescope optics by two optical fibers, one per channel, to assure an easier coupling and an easier colocation of the instrument inside the EChO optical bench.  相似文献   

Highly reproducible quasi-mosaic crystals as optical components for a Laue lens     

Riccardo Camattari  Alessandro Battelli  Valerio Bellucci  Vincenzo Guidi 《Experimental Astronomy》2014,37(1):1-10

The realization of a Laue lens for astronomical purposes involves the mass production of a series of crystalline tiles as optical components, allowing high-efficiency diffraction and high-resolution focusing of photons. Crystals with self-standing curved diffraction planes is a valid and promising solution. Exploiting the quasi-mosaic effect, it turns out to be possible to diffract radiation at higher resolution. In this paper we present the realization of 150 quasi-mosaic Ge samples, bent by grooving one of their largest surface. We show that grooving method is a viable technique to manufacture such crystals in a simple and very reproducible way, thus compatible with mass production. Realized samples present very homogenous curvature. Furthermore, with a specific chemical etch, it is possible to fine adjust one by one the radius of curvature of the grooved samples. Realized crystals was selected for the ASI’s Laue project, that involves the implementation of a prototype of a Laue lens for hard X- and soft γ-ray astronomy.  相似文献   

Groundwater flow in anisotropic aquifers reduced to the isotropic case     

Valerio Faraoni 《水文研究》2004,18(9):1735-1743

By applying the technique of conformal transformation of the metric, widely used in general relativity and cosmology, the analysis of groundwater flow in an anisotropic aquifer (in which the hydraulic conductivity is a tensor) is reduced to the case of an isotropic one. This reduction is achieved for a particular conformal factor of the transformation. Examples of application of this technique are given. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

NAO–ocean circulation interactions in a coupled general circulation model     

A. Bellucci  S. Gualdi  E. Scoccimarro  A. Navarra 《Climate Dynamics》2008,31(7-8):759-777

The interplay between the North Atlantic Oscillation (NAO) and the large scale ocean circulation is inspected in a twentieth century simulation conducted with a state-of-the-art coupled general circulation model. Significant lead–lag covariance between oceanic and tropospheric variables suggests that the system supports a damped oscillatory mode involving an active ocean–atmosphere coupling, with a typical NAO-like space structure and a 5 years timescale, qualitatively consistent with a mid-latitude delayed oscillator paradigm. The two essential processes governing the oscillation are (1) a negative feedback between ocean gyre circulation and the high latitude SST meridional gradient and (2) a positive feedback between SST and the NAO. The atmospheric NAO pattern appears to have a weaker projection on the ocean meridional overturning, compared to the gyre circulation, which leads to a secondary role for the thermohaline circulation in driving the meridional heat transport, and thus the oscillatory mode.  相似文献   

Correction to: Cultural heritage and earthquakes: bridging the gap between geophysics,archaeoseismology and engineering     

Pecchioli  Laura  Panzera  Francesco  Poggi  Valerio 《Journal of Seismology》2021,25(6):1557-1558

Journal of Seismology -  相似文献   

Adiabatic chaos in the spin–orbit problem     

Giancarlo Benettin  Massimiliano Guzzo  Valerio Marini 《Celestial Mechanics and Dynamical Astronomy》2008,101(1-2):203-224

We provide evidences that the angular momentum of a symmetric rigid body in a spin–orbit resonance can perform large scale chaotic motions on time scales which increase polynomially with the inverse of the oblateness of the body. This kind of irregular precession appears as soon as the orbit of the center of mass is non-circular and the angular momentum of the body is far from the principal directions with minimum (maximum) moment of inertia. We also provide a quantitative explanation of these facts by using the theory of adiabatic invariants, and we provide numerical applications to the cases of the 1:1 and 1:2 spin–orbit resonances.  相似文献   

Gully head modelling: A Mediterranean badland case study          下载免费PDF全文

Dino Torri  Jean Poesen  Mauro Rossi  Valerio Amici  Daniele Spennacchi  Cati Cremer 《地球表面变化过程与地形》2018,43(12):2547-2561

Predicting the location of gully heads in various environments is an important step towards predicting gully erosion rates. So far, field data collection and modelling of topographic thresholds for gully head development has mainly focused on gullies that formed in forested areas, rangelands, pastures and cropland. Such information for gullies in badlands however is very scarce. Therefore, this paper aims to extend the database on gully head topographical thresholds through data collection in a badland area and to improve the prediction of gully heads forming at sites with a very low erosion resistance value. For this, we chose a badland site located in central Italy that is characterized by biancana forms and both active and dormant gullies. The definition of the conditions under which present‐day gully heads developed allowed a better modelling of the gully head threshold equation, with modification of a previous model and the exemplification of how to use the updated model. The model shows that the resistance to gully head retreat depends on slope gradient and drainage area at gully heads, land use at the moment of gully development (as numerically expressed using parameters derived from the Runoff Curve Number method), surface rock fragment cover, presence of joints, pipes, and factors/processes affecting detachment rate. This study attempted to better understand environmental conditions that control the development of gully heads in badlands through a combination of field data collection of gully heads, an analysis of land use changes over 10 centuries, focusing on the period 1820–2005, and land use management through repeat photography and a critical examination of historical documents. © 2018 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.  相似文献   

Solving the Vialov Equation of Glaciology in Terms of Elementary Functions     

Valerio Faraoni 《Mathematical Geosciences》2017,49(8):1057-1067

Very few exact solutions are known for the non-linear Vialov ordinary differential equation describing the longitudinal profiles of alpine glaciers and ice caps under the assumption that the ice deforms according to Glen’s constitutive relationship. Using a simple, yet wide, class of models for the accumulation rate of ice and Chebysev’s theorem on the integration of binomial differentials, many new exact solutions of the Vialov equations are obtained in terms of elementary functions.  相似文献   

Exploiting historical rainfall and landslide data in a spatial database for the derivation of critical rainfall thresholds     

Domenico Caracciolo  Elisa Arnone  Francesco Lo Conti  Leonardo Valerio Noto 《Environmental Earth Sciences》2017,76(5):222

Critical rainfall thresholds for landslides are powerful tools for preventing landslide hazard. The thresholds are commonly estimated empirically starting from rainfall events that triggered landslides in the past. The creation of the appropriate rainfall–landslide database is one of the main efforts in this approach. In fact, an accurate agreement between the landslide and rainfall information, in terms of location and timing, is essential in order to correctly estimate the rainfall–landslide relationships. A further issue is taking into account the average moisture conditions prior the triggering event, which reasonably may be crucial in determining the sufficient amount of precipitation. In this context, the aim of this paper is exploiting historical landslide and rainfall data in a spatial database for the derivation of critical rainfall thresholds for landslide occurrence in Sicily, southern Italy. The hourly rainfall events that caused landslides occurred in the twentieth century were specifically identified and reconstructed. A procedure was proposed to automatically convert rain guages charts recorded on paper tape into digital format and then to provide the cumulative rainfall hyetograph in digital format. This procedure is based on a segmentation followed by signal recognition techniques which allow to digitalize and to recognize the hyetograph automatically. The role of rainfall prior to the landslide events was taken into account by including in the analysis the rainfall occurred 5, 15 and 30 days before each landslide. Finally, cumulated rainfall duration thresholds for different exceedance probability levels were determined. The obtained thresholds resulted in agreement with the regional curves proposed by other authors for the same area; antecedent rainfall turned out to be particularly important in triggering landslides.  相似文献   

Long-Term RST Analysis of Anomalous TIR Sequences in Relation with Earthquakes Occurred in Greece in the Period 2004–2013     

Alexander Eleftheriou  Carolina Filizzola  Nicola Genzano  Teodosio Lacava  Mariano Lisi  Rossana Paciello  Nicola Pergola  Filippos Vallianatos  Valerio Tramutoli 《Pure and Applied Geophysics》2016,173(1):285-303

Real-time integration of multi-parametric observations is expected to accelerate the process toward improved, and operationally more effective, systems for time-Dependent Assessment of Seismic Hazard (t-DASH) and earthquake short-term (from days to weeks) forecast. However, a very preliminary step in this direction is the identification of those parameters (chemical, physical, biological, etc.) whose anomalous variations can be, to some extent, associated with the complex process of preparation for major earthquakes. In this paper one of these parameters (the Earth’s emitted radiation in the Thermal InfraRed spectral region) is considered for its possible correlation with M ≥ 4 earthquakes occurred in Greece in between 2004 and 2013. The Robust Satellite Technique (RST) data analysis approach and Robust Estimator of TIR Anomalies (RETIRA) index were used to preliminarily define, and then to identify, significant sequences of TIR anomalies (SSTAs) in 10 years (2004–2013) of daily TIR images acquired by the Spinning Enhanced Visible and Infrared Imager on board the Meteosat Second Generation satellite. Taking into account the physical models proposed for justifying the existence of a correlation among TIR anomalies and earthquake occurrences, specific validation rules (in line with the ones used by the Collaboratory for the Study of Earthquake Predictability—CSEP—Project) have been defined to drive a retrospective correlation analysis process. The analysis shows that more than 93 % of all identified SSTAs occur in the prefixed space–time window around (M ≥ 4) earthquake's time and location of occurrence with a false positive rate smaller than 7 %. Molchan error diagram analysis shows that such a correlation is far to be achievable by chance notwithstanding the huge amount of missed events due to frequent space/time data gaps produced by the presence of clouds over the scene. Achieved results, and particularly the very low rate of false positives registered on a so long testing period, seems already sufficient (at least) to qualify TIR anomalies (identified by RST approach and RETIRA index) among the parameters to be considered in the framework of a multi-parametric approach to t-DASH.  相似文献