Fuzzy parameters analysis of time‐dependent fracture of concrete dam models     

Fabrizio Barpi  Silvio Valente 《国际地质力学数值与分析法杂志》2002,26(10):1005-1027

In order to apply the mechanical properties (measured on material specimens or laboratory‐sized models) to large structures (such as concrete dams), a non‐linear theory able to predict the size‐scale effect has to be used. One of these theories was first proposed by Hillerborg and co‐workers (fictitious crack model) and is based on the earlier works by Barenblatt and Dugdale for metals (cohesive crack model). It is based on the existence of a fracture process zone (FPZ), where the material undergoes strain softening. The behaviour of the material outside the FPZ is linear elastic. A large number of short‐time laboratory tests were executed, by varying the load, under crack mouth opening displacement control. Since concrete exhibits a time‐dependent behaviour, an interaction between creep and micro‐crack growth occurs in the FPZ. Therefore, different testing conditions can be applied: rupture can be achieved by keeping the load constant before peak value (pre‐peak tests), or after peak value and after an unloading and reloading procedure (post‐peak tests). The crack propagation rate is shown to be small enough to neglect inertial forces and large enough to keep the time‐dependent behaviour of the process zone as dominant compared to the behaviour of the undamaged and viscoelastic zone. Due to the variability in material microstructure from one specimen to another, experimental data show large ranges of scatter. Well established methods in probability theory require sufficient experimental data in order to assume a probability density distribution. The objective of this study is to investigate the ranges of variation of the time response under constant load in simple structural elements associated with pre‐selected variation (fuzziness) in the main material parameters. For situations where the values of the material parameters are of a non‐stochastic nature, the fuzzy set approach to modelling variability has been proposed as a better and more natural approach. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Anomalous RR Lyrae stars(?): CM Leonis     

L. Di Fabrizio  G. Clementini  M. Marconi  E. Carretta  I. I. Ivans  A. Bragaglia  S. Di Tomaso  R. Merighi  H. A. Smith  C. Sneden  M. Tosi 《Monthly notices of the Royal Astronomical Society》2002,336(3):841-850

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Berkeley 29, the most distant old open cluster     

M. Tosi  L. Di Fabrizio  A. Bragaglia  P. A. Carusillo  G. Marconi 《Monthly notices of the Royal Astronomical Society》2004,354(1):225-234

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The Gaia spectrophotometric standard stars survey: II. Instrumental effects of six ground‐based observing campaigns     

G. Altavilla  S. Marinoni  E. Pancino  S. Galleti  S. Ragaini  M. Bellazzini  G. Cocozza  A. Bragaglia  J. M. Carrasco  A. Castro  L. Di Fabrizio  L. Federici  F. Figueras  M. Gebran  C. Jordi  E. Masana  W. Schuster  G. Valentini  H. Voss 《Astronomische Nachrichten》2015,336(6):515-529

The Gaia SpectroPhotometric Standard Stars (SPSS) survey started in 2006, was awarded almost 450 observing nights and accumulated almost 100000 raw data frames with both photometric and spectroscopic observations. Such large observational effort requires careful, homogeneous, and automatic data reduction and quality control procedures. In this paper, we quantitatively evaluate instrumental effects that might have a significant (i.e., ≥1 %) impact on the Gaia SPSS flux calibration. The measurements involve six different instruments, monitored over the eight years of observations dedicated to the Gaia flux standards campaigns: DOLORES@TNG in La Palma, EFOSC2@NTT and ROSS@REM in La Silla, CAFOS@2.2m in Calar Alto, BFOSC@Cassini in Loiano, and LaRuca@1.5m in San Pedro Mártir. We examine and quantitatively evaluate the following effects: CCD linearity and shutter times, calibration frames stability, lamp flexures, second order contamination, light polarization, and fringing. We present methods to correct for the relevant effects which can be applied to a wide range of observational projects at similar instruments. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

The Campo Imperatore Near Earth Object Survey (CINEOS)     

Andrea Boattini  Germano D’Abramo  Giovanni B. Valsecchi  Andrea Carusi  Andrea Di Paola  Fabrizio Bernardi  Robert Jedicke  Alan W. Harris  Elisabetta Dotto  Fiore De Luise  Davide Perna  Riccardo Leoni 《Earth, Moon, and Planets》2007,100(3-4):259-271

The Campo Imperatore Near Earth Object Survey (CINEOS) is an Italian survey dedicated to the search and follow-up of Near Earth Objects (NEOs). It is operated with the 90 cm f/3 Schmidt telescope at the Campo Imperatore of the Rome Astronomical Observatory (INAF-OAR) as a joint project with the Istituto di Astrofisica Spaziale and Fisica Cosmica (INAF-IASF) in Rome. Since the end of 2001 CINEOS has covered about 4,250 sq. deg to 20th magnitude in the course of about 160 nights. This effort led to the discovery of 7 Near Earth Asteroids (NEAs), 1 comet (167P/CINEOS; a member of the Centaur group) and a few other unusual objects including 2004 XH₅₀ with a unique comet-like orbit. CINEOS has also contributed almost 2,200 preliminary designations and over 30,000 detections to the Minor Planet Center. About 20% of the survey effort was carried out at low solar elongations (LSE), although no object with an orbit interior (Inner Earth Objects, IEO class) or nearly interior to the Earth (Aten class) was found. The work at LSE was, however, very important to test survey strategies implemented with larger telescopes. We also provide the results of a CINEOS simulation on a reliable NEO population model based on the results of two larger scale surveys, Spacewatch and LINEAR.  相似文献   

Large mafic eruptions at Alban Hills Volcanic District (Central Italy): Chronostratigraphy,petrography and eruptive behavior     

Fabrizio Marra  Daniel B. Karner  Carmela Freda  Mario Gaeta  Paul Renne 《Journal of Volcanology and Geothermal Research》2009,179(3-4):217-232

Despite its ultra-potassic, basic geochemistry (40 ≤ SiO₂ ≤ 50 wt.%), the Alban Hills Volcanic District was characterized by a highly explosive phase of activity, the Tuscolano–Artemisio phase, which emplaced very large volumes (several tens of km³ each cycle) of pyroclastic-flow deposits, mafic in composition (SiO₂ ≤ 45 wt.%) in the time span 600–350 ka. In contrast to the abundance of pyroclastic-flow deposits, very scarce basal Plinian deposits and, more in general, fallout deposits are associated to these products. While some of the pyroclastic-flow deposits have been described in previous literature, no specific work on the Tuscolano–Artemisio phase of activity has been published so far. In particular, very little is known on the products of the early stages, as well as of the final, post-caldera activity of each eruptive cycle. Here we present a comprehensive stratigraphic and geochronologic study of the Tuscolano–Artemisio phase of activity, along with new textural and petrographic data. We describe the detailed stratigraphy and petrography of five reference sections, where the most complete suites of products of the eruptive cycles, comprising the initial through the final stages, are exposed. We assess the geochronology of these sections by means of 18 new ⁴⁰Ar/³⁹Ar age determinations, integrating them with 16 previously performed, aimed to describe the eruptive behavior of the Alban Hills Volcanic District during this phase of activity, and to assess the recurrence time and the duration of the dormancies.The overall explosive activity appears to be strictly clustered in five eruptive cycles, fairly regularly spaced in time and separated by very long dormancies, in the order of several ten of kyr, during which no volumetrically appreciable eruption occurred, as the lack of deposits dated to this time-interval testify. We propose a volcano-tectonic model that explains this peculiar eruptive behavior, unparalleled in the other coeval volcanic districts of the Tyrrhenian margin of Italy, as related to the local transpressive tectonic regime.  相似文献   

The rivers are alive: on the potential for diatoms as a tracer of water source and hydrological connectivity     

Laurent Pfister  Jeffrey J. McDonnell  Sebastian Wrede  Daša Hlúbiková  Patrick Matgen  Fabrizio Fenicia  Luc Ector  Lucien Hoffmann 《水文研究》2009,23(19):2841-2845

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F-phlogopites in the Alban Hills Volcanic District (Central Italy): indications regarding the role of volatiles in magmatic crystallisation     

M. Gaeta  G. Fabrizio  G. Cavarretta 《Journal of Volcanology and Geothermal Research》2000,99(1-4)

A systematic analysis of micas contained in effusive, pyroclastic and hypabyssal rocks of the Alban Hills Volcanic District (AHVD) (Central Italy) was made in order to characterise minerals of pyroclastic units for tephrostratigraphy and to obtain as much information as possible on the activity of volatiles in this magmatic system. The phlogopite shows a large range of F contents (between 0.50 and 7.50 wt%) that make it possible to discriminate different AHVD lithologies; in particular, micas of lava groundmass are characterised by extremely high F (up to 7.50 wt%) and Ba (up to 9.70 wt%) contents, seldom or never found in other magmatic ultrapotassic rocks. Moreover, the micas of pyroclastics, ultramafic cumulates and holocrystalline inclusions made up of leucite, clinopyroxene and phlogopite (hereafter italites) show Mg/(Mg+Fe) values between 0.65 and 0.90 that are not correlated with F contents. The variations in F contents observed in the AHVD micas do not appear to be due to a “temperature” effect or pressure changes, but they may be due to variations in the H₂O and CO₂ activities in the magma chamber. They make it possible to differentiate three crystallisation environments in the AHVD magmatic system. The first one had elevated CO₂ activity and formed the italites near the carbonate contact; these rocks represent, at least those enriched in clinopyroxene without skarn-minerals, the hypabyssal crystallisation of the AHVD magmas at the periphery of magma chamber. The second one, characterised by a higher water activity, is represented by the micas of the ultramafic cumulates and pyroclastic scorias, and is located in the inner part of magma chamber. The third environment, the groundmass of the lavas, it is not related with the previous ones and is characterised by the absence of water and by a high F activity. In general, our results suggest that the compositional variations observed in the micas (Al, Si, Ti, Ba) reflect different H₂O activities (inversely correlated with F activity) in the magma chamber.  相似文献   

Seismic heterogeneity of Mt Etna: structure and activity   总被引：3，自引：0，他引：3  

Alfred Hirn  Alexandre Nercessian  Martine Sapin  Fabrizio Ferrucci  Gérard Wittlinger 《Geophysical Journal International》1991,105(1):139-153

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Hydrothermal dolomitization of the carbonate Jurassic succession in the Provençal and Subbriançonnais Domains (Maritime Alps,North-Western Italy)     

Luca Barale  Carlo Bertok  Anna d’Atri  Gabriele Domini  Luca Martire  Fabrizio Piana 《Comptes Rendus Geoscience》2013,345(1):47-53

The present article illustrates a straightforward case of hydrothermal dolomitization, affecting Jurassic platform limestones of the Provençal and Subbriançonnais Domains (Maritime Alps, North-Western Italy). Dolomitized bodies are randomly distributed within the host limestone, and are commonly associated with dolomite vein networks and tabular bodies of dolomite-cemented breccias discordant with respect to bedding. Main dolomite types are a finely to medium-crystalline replacive dolomite and a coarsely-crystalline saddle dolomite occurring both as replacive and as cement. Stratigraphic constraints indicate that dolomitization occurred during the Cretaceous, in a shallow burial context, and was due to the circulation of hot fluids (temperature about 200 °C, as indicated by fluid inclusion microthermometry) through faults and related fracture networks. Hydrothermal dolomitization therefore indirectly documents a Cretaceous fault activity in the Maritime Alps segment of the European Tethyan passive margin.  相似文献