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Ana Luisa Outa Mori Paulo Alves de Souza Juliana Charão Marques Ricardo da Cunha Lopes 《Gondwana Research》2012,21(2-3):654-669
Index species useful for correlations with the International Stratigraphical Column are rare or absent in the Pennsylvanian–Permian strata of the Paraná Basin in Brazil, preventing accuracy in geochronologic assignments. Besides, absolute datings are very scarce in comparison with other Gondwana basins. This paper presents palynological data from an outcrop on the surroundings of the Candiota coal mine, southmost Brazil, from several levels of the Rio Bonito and Palermo formations. The presence of certain index species of spore–pollen allowed the recognition of two Permian palynozones: the Vittatina costabilis and the Lueckisporites virkkiae zones. Furthermore, U–Pb in zircons from a volcaniclastic level interbedded in the coal strata of the former unit was analyzed through LA-MC-ICP-MS method, providing a new absolute age dating of 281.4 ± 3.4 Ma (Cisuralian, Early Permian). This dating is assumed as the oldest occurrence of the L. virkkiae Zone in Paraná Basin, which contains index species that are widespread in other Gondwana basins. A well distributed surface boundary occurs in this section also, allowing local and regional correlations. These new biostratigraphical and geochronological data are integrated, in order to offer a deep analysis on the stratigraphical significance for correlations across the Occidental Gondwana. 相似文献
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Channagiri V. Char 《Geotechnical and Geological Engineering》2011,29(1):37-47
Fernald site produced over 500 million pound of uranium metal products from 1952 to 1989 resulting in a huge quantity of hazardous
waste to be stored, treated and transported for final disposal. The structural integrity evaluation of specific types of waste
containers used in the Fernald Closure Project are briefly presented in this paper. Metal containers of various shapes and
sizes, concrete silos, gondola rail cars were successfully used for storage and disposal of low-level waste. Computer solutions
were obtained using finite element analyses techniques, destructive and non-destructive tests were used to get a realistic
response to complex loading conditions. Structural integrity is evaluated for concrete silos built in the fifties, unique
metal containers and fiberglass rail car lid. A failure modes and effects analysis was also made for the railcar lid to identify
the weak link for postulated failure mechanisms. Establishing the structural integrity was a key to the reliability of the
various containment systems for a successful storage, transportation and final disposal of the low-level radioactive wastes. 相似文献
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Vaduvescu O. Aznar Macias A. Wilson T. G. Zegmott T. Pérez Toledo F. M. Predatu M. Gherase R. Pinter V. Pozo Nunez F. Ulaczyk K. Soszyński I. Mróz P. Wrona M. Iwanek P. Szymanski M. Udalski A. Char F. Salas Olave H. Aravena-Rojas G. Vergara A. C. Saez C. Unda-Sanzana E. Alcalde B. de Burgos A. Nespral D. Galera-Rosillo R. Amos N. J. Hibbert J. López-Comazzi A. Oey J. Serra-Ricart M. Licandro J. Popescu M. 《Earth, Moon, and Planets》2022,126(2):1-26
Earth, Moon, and Planets - The Perseverance rover (Mars 2020) mission, the first step in NASA’s Mars Sample Return (MSR) program, will select samples for caching based on their potential to... 相似文献
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A. Collier Cameron F. M. Walter O. Vilhu T. Böhm C. Catala S. Char F. J. Clarke P. Felenbok B. H. Foing K. K. Ghosh J. Hao L. Huang D. A. Jackson E. Janot-Pacheco S. Jiang A.-M. Lagrange N. Suntzeff D. S. Zhai 《Monthly notices of the Royal Astronomical Society》1999,308(2):493-509
We present time-resolved optical spectroscopy and broad-band photometry of the rapidly rotating southern K0 dwarf star AB Doradus, obtained during 1994 November. The data were obtained as part of a collaboration dedicated to MUlti-SIte COntinuous Spectroscopy (MUSICOS), and entailed coordinated observations on three continents to obtain the fullest phase coverage possible subject to limitations of local weather conditions. The Doppler images from the three consecutive nights of the run show excellent mutual agreement, with a dark polar cap and numerous intermediate- and low-latitude features. Simultaneous optical photometry showed numerous short-duration U -band flares, and two longer duration optical flares with durations of the order of hours. The latter produced broad-band continuum enhancements throughout the optical spectrum. Where simultaneous spectroscopy was available, both types of flare were seen to have counterparts in H and the Ca ii H line. Simultaneous time-resolved ultraviolet spectroscopy from the Goddard High Resolution Spectrograph (GHRS) aboard the Hubble Space Telescope , reported elsewhere, shows that at least one of the short-duration U -band flares was also observed in C iv with the GHRS. Time-series H spectra showed significant evolution of the circumstellar prominence system over five consecutive stellar rotations. One prominence underwent a dramatic increase in distance from the stellar rotation axis. We speculate that this event may have been associated with one of the long-duration flares. 相似文献
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O. Vaduvescu M. Popescu I. Comsa A. Paraschiv D. Lacatus A. Sonka A. Tudorica M. Birlan O. Suciu F. Char M. Constantinescu T. Badescu M. Badea D. Vidican C. Opriseanu 《Astronomische Nachrichten》2013,334(7):718-728
The ESO/MPG WFI and the INT WFC wide field archives comprising 330 000 images were mined to search for serendip‐itous encounters of known Near Earth Asteroids (NEAs) and Potentially Hazardous Asteroids (PHAs). A total of 152 as‐teroids (44 PHAs and 108 other NEAs) were identified using the PRECOVERY software, their astrometry being measured on 761 images and sent to the Minor Planet Centre. Both recoveries and precoveries were reported, including prolonged orbital arcs for 18 precovered objects and 10 recoveries. We analyze all new opposition data by comparing the orbits fitted before and after including our contributions. We conclude the paper presenting “Mega‐Precovery”, a new online service focused on data mining of many instrument archives simultaneously for one or a few given asteroids. A total of 28 instrument archives have been made available for mining using this tool, adding together about 2.5 million images forming the “Mega‐Archive” 相似文献
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O. Vaduvescu A. Aznar Macias V. Tudor M. Predatu A. Galád Š. Gajdoš J. Világi H. F. Stevance R. Errmann E. Unda-Sanzana F. Char N. Peixinho M. Popescu A. Sonka R. Cornea O. Suciu R. Toma P. Santos-Sanz A. Sota J. Licandro M. Serra-Ricart D. Morate T. Mocnik M. Diaz Alfaro F. Lopez-Martinez J. McCormac N. Humphries 《Earth, Moon, and Planets》2017,120(2):41-100
This data paper presents lightcurves of 101 near Earth asteroids (NEAs) observed mostly between 2014 and 2017 as part of the EURONEAR photometric survey using 11 telescopes with diameters between 0.4 and 4.2 m located in Spain, Chile, Slovakia and Romania. Most targets had no published data at the time of observing, but some objects were observed in the same period mainly by B. Warner, allowing us to confirm or improve the existing results. To plan the runs and select the targets, we developed the public Long Planning tool in PHP. For preliminary data reduction and rapid follow-up planning we developed the LiDAS pipeline in Python and IRAF. For final data reduction, flux calibration, night linkage and Fourier fitting, we used mainly MPO Canopus. Periods of 18 targets are presented for the first time, and we could solve or constrain rotation for 16 of them. We secured periods for 45 targets (\(U\sim 3\)), found candidate periods for other 16 targets (\(U\sim 2\)), and we propose tentative periods for other 32 targets (\(U\sim 1\)). We observed 7 known or candidate binary NEAs, fiting 3 of them (2102 Tantalus, 5143 Heracles and 68348). We observed 8 known or candidate tumbling NEAs, deriving primary periods for 3 objects (9400, 242708 and 470510). We evidenced rapid oscillations (few minutes) and could fit fast tentative periods TP2 for 5 large newly suggested tumbling or binary candidates (27346, 112985, 285625, 377732, 408980), probably discovering at least one new binary NEA (2011 WO41). We resolved periods of 4 special objects which include two proposed space mission targets (163249 and 101955 Bennu), one very fast rotator NEA discovered by EURONEAR (2014 NL52) and the “Halloween asteroid” (2015 TB145). Using Mercator in simultaneous 3 band MAIA imaging, we could evidence for the first time clear variation in the color lightcurves of 10 NEAs. The periods derived from the g–r color lightcurves are found to match individual band period fits for 4 NEAs (27346, 86067, 112985 and 275976). 相似文献
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