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261.
Northwest Africa 6232: Visible–near infrared reflectance spectra variability of an olivine diogenite
Cristian Carli Giovanni Pratesi Vanni Moggi-Cecchi Francesca Zambon Fabrizio Capaccioni Simone Santoro 《Meteoritics & planetary science》2018,53(10):2228-2242
Visible and near-infrared (VNIR) reflectance is an important spectroscopic technique to identify minerals, and their associations, on planetary body surfaces. Howardites, eucrites, and diogenites (HED) are a class of igneous-like meteorites whose genetic connection with asteroid 4 Vesta has since long been inferred and recently confirmed by Dawn mission results. Pyroxene and olivine are the two major mafic minerals present in HED which can be identified with VNIR reflectance measurements. Thus, studying the compositional variability of those phases and their mixtures by means of laboratory spectroscopic measurements on different diogenitic or eucritic samples is one of the prime methods to better understand the evolution of 4 Vesta's crust. Here, we report the VNIR reflectance spectral analysis of a harzburgitic olivine diogenite, Northwest Africa 6232 (probably paired with Northwest Africa 5480), containing variable amounts of olivine as small grains or aggregates. We found that the olivine diogenite spectral parameters (e.g., band position) of powdered samples and polished slabs are in agreement. Moreover, the olivine diogenite band position shifts from synthetic orthopyroxene in accordance with the presence of olivine and chromite. In particular, the presence of a large olivine clast permits us to determine a linear variation of the band position from synthetic orthopyroxene and olivine, but underestimates the presence of olivine in the olivine diogenite spot. 相似文献
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Luca Pellegrino Francesco Dela Pierre Richard W. Jordan Kenta Abe Yuta Mikami Marcello Natalicchio Rocco Gennari Francesca Lozar Giorgio Carnevale 《Sedimentology》2020,67(7):3389-3421
During the late Miocene the Mediterranean experienced a dramatic intensification of opaline accumulation, recorded by the deposition of diatomaceous sediments. The fine lamination of these deposits potentially records annual to sub-annual palaeoceanographic processes that occurred during a critical phase of the geodynamic evolution of the Mediterranean basin, which eventually led to the Messinian salinity crisis. The diatomaceous facies has been interpreted by previous researchers as the product of intensified upwelling currents and of bottom anoxia formation in the Mediterranean basin. However, until now, no efforts have been made to unravel the sedimentological and micropalaeontological content of these deposits at the lamina-scale. This paper presents the first case study of a systematic scanning electron microscope-based morphological investigation of the diatomaceous sediments deposited during the late Miocene at the northernmost offshoot of the Mediterranean basin (Piedmont Basin, north-west Italy). Using a non-invasive analytical approach, six faciological components (laminae, laminated packets, non-laminated intervals, burrows, opal-rich aggregates and mixed pelletal structures) and their relationships are described and interpreted herein. Following the lamina-scale study of these sediments, an annual sedimentary cycle could be identified and an accumulation rate (ca 50 cm kyr−1) inferred that is atypical for a setting actively influenced by upwelling. The role played by the entanglement of diatom valves in creating a physical barrier to the bioturbation is here emphasized as the main process responsible for the preservation of the laminated fabric of diatomaceous sediments, challenging the supposed role of deep anoxia. These results suggest that the late Miocene diatomaceous deposition in the Piedmont Basin cannot be univocally considered as a by-product of upwelling intensification and seafloor oxygen depletion. 相似文献
264.
Experimental characterization,design and modelling of the RBRL seismic‐isolation system for lightweight structures
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The Rolling‐Ball Rubber‐Layer (RBRL) system was developed to enable seismic isolation of lightweight structures, such as special equipment or works of art, and is very versatile, a great range of equivalent natural frequencies and coefficients of damping being achievable through choice of the system parameters. The necessity to have a simple and effective design procedure has led to a new parametric experimentation at Tun Abdul Razak Research Centre (TARRC) on the rolling behaviour of the RBRL system and load–deflection behaviour of the recentering springs. The experimental results, together with theories for the rolling resistance of a loaded steel ball on a thin rubber layer and the lateral load–deflection behaviour of cylindrical rubber springs, are used to develop a general design method for the RBRL system, which allows the system to be tailored to the specific application. Sinusoidal test results are presented for the small‐deflection behaviour of the system, influenced by the presence of a viscoelastic depression on the rubber tracks beneath each ball, and an amplitude‐dependent time‐domain model is proposed, based on these results and on the steady‐state behaviour of the system. The model is validated through comparison with previously performed shaking‐table tests. Attention is here restricted to uniaxial behaviour. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
265.
Francesca Barbagallo Melina Bosco Edoardo M. Marino Pier Paolo Rossi Paola R. Stramondo 《地震工程与结构动力学》2017,46(7):1099-1119
In the world, many existing buildings with RC framed structure were designed according to old seismic standards and present structural deficiencies. Buckling Restrained Braces (BRBs) can be effective for seismic upgrading of these structures, as pointed out by many studies. Nevertheless, Eurocode 8 (EC8) does not provide any rules for design of BRBs. This lack represents a big obstacle for application of this seismic upgrading technique in Europe. For this reason, a method for the design of seismic upgrading interventions by BRBs is proposed in this paper. The method is obtained as the best between two variants developed, investigated and compared in this paper. Based on a numerical investigation, the parameters that control the design method are calibrated to ensure the fulfillment of the Near Collapse performance objective stipulated in EC8. Finally, the capability of the proposed design method in fulfilling also performance objectives not explicitly considered in design is investigated. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
266.
Filippo?Domma Francesca?CondinoEmail authorView authors OrcID profile 《Stochastic Environmental Research and Risk Assessment (SERRA)》2017,31(3):799-813
Starting from a recent paper by Murshed (Stoch Environ Res Risk Assess 25:897–911, 2011) in which a good performance of the Beta-k distribution in analyzing extreme hydrologic events is shown, in this paper, we propose the use of two new four-parameters distribution functions strongly related to the Beta-k distribution, namely the Beta-Dagum and the Beta-Singh-Maddala distributions. More in detail, the new distributions are a generalization of a reparametrization of Beta-k and Beta-p distributions, respectively. For these distributions some particular interpretations in terms of maximum and minimum of sequences of random variables can be derived and the maximal and minimal domain of attraction can be obtained. Moreover, the method of maximum likelihood, the method of moments and the method of L-moments are examined to estimate the parameters. Finally, two different applications on real data regarding maxima and minima of river flows are reported, in order to show the potentiality of these two models in the extreme events analysis. 相似文献
267.
Mauro Celussi Alessandro Paoli Erica Crevatin Andrea Bergamasco Francesca Margiotta Vincenzo Saggiomo Serena Fonda Umani Paola Del Negro 《Estuarine, Coastal and Shelf Science》2009,81(4):491-500
During the 2006 Italian Antarctic expedition a diel sampling was performed close to Cape Hallett (Ross Sea) during the Austral summer. Under-ice seawater samples (4 m) were collected every 2 h for 28 h in order to estimate prokaryotic processes' variability and community structure dynamics. Prokaryotic and viral abundances, exoenzymatic activities (β-glucosidase, chitinase, lipase, alkaline phosphatase and leucine aminopeptidase), prokaryotic carbon production (3H-leucine incorporation) and community structure (Denaturing Gradient Gel Electrophoresis – DGGE fingerprints) were analysed. Results showed that the diel variability of the prokaryotic activity followed a variation in salinity, probably as a consequence of the periodical thawing of sea ice (driven by solar radiation and air temperature cycles), while negligible variation in viral and prokaryotic abundances occurred. The Bacterial and Archaeal community structures underwent an Operational Taxonomic Units (OTUs) temporal shift from the beginning to the end of the sampling, while Flavobacteria-specific primers highlighted high variations in this group possibly related to sea ice melting and substrate release. 相似文献
268.
Llanes Francesca V. Eco Rodrigo Herrero Tatum Miko Briones Jo Brianne Louise Escape Carmille Marie Sulapas Jolly Joyce Galang Jan Albert Macario Ortiz Iris Jill Sabado Jasmine May Lagmay Alfredo Mahar Francisco Rodolfo Kelvin 《Natural Hazards》2022,114(1):665-690
Natural Hazards - In October 2015, heavy rains brought by Typhoon Koppu generated landslides and debris flows in the municipalities of Bongabon, Laur, and Gabaldon in Nueva Ecija province.... 相似文献
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270.
Dino Bindi Lucia Luzi Francesca Pacor Roberto Paolucci 《Bulletin of Earthquake Engineering》2011,9(6):1921-1939
In this work, we analyze the records of the Italian strong motion database (ITACA,
) with the aim of identifying stations affected by site effects that are not captured by standard seismic classification schemes.
In particular, we consider four different site classifications, two of them based on geological/geophysical characteristics
and two driven by data. For each classification we develop a ground motion prediction equation using a random effect approach
to isolate the between-station and within-station distribution of errors. The site coefficients obtained for the different
classes confirm that site amplification effects are significant for both the horizontal and vertical components. The between-station
error normalized to the standard deviation of the between-station error distribution is then used to identify stations characterized
by large errors, attributable to site effects not accounted for by the classification schemes. The results show that large
errors can affect the predictions when the site effects are not uniquely related to the reduction of the seismic impedance
in the uppermost layers. For example, amplifications of ground motion over the long period range are observed for stations
installed within alluvial closed-shape basins, as consequence of locally generated surface waves. For these stations, classifications
based on the horizontal to vertical response spectra ratio are not reliable, since amplifications are also affecting the vertical
component. Another interesting feature which emerges from the analysis is the significant de-amplification of short period
spectral ordinates that seems to be related to stations typically set in at the foundation level of massive structures. To
increase the usefulness of the data set, the most important distinctive features of the strong motion stations are documented
in the ITACA database reports containing the instrument information and the available geological-geotechnical data. 相似文献