排序方式： 共有49条查询结果，搜索用时 906 毫秒
31.
32.
Jiří Borovička Juraj Tóth Antal Igaz Pavel Spurný Pavel Kalenda Jakub Haloda Ján Svoreň Leonard Kornoš Elizabeth Silber Peter Brown Marek Husárik 《Meteoritics & planetary science》2013,48(10):1757-1779
The Ko?ice meteorite fall occurred in eastern Slovakia on February 28, 2010, 22:25 UT. The very bright bolide was imaged by three security video cameras from Hungary. Detailed bolide light curves were obtained through clouds by radiometers on seven cameras of the European Fireball Network. Records of sonic waves were found on six seismic and four infrasonic stations. An atmospheric dust cloud was observed the next morning before sunrise. After careful calibration, the video records were used to compute the bolide trajectory and velocity. The meteoroid, of estimated mass of 3500 kg, entered the atmosphere with a velocity of 15 km s?1 on a trajectory with a slope of 60° to the horizontal. The largest fragment ceased to be visible at a height of 17 km, where it was decelerated to 4.5 km s?1. A maximum brightness of absolute stellar magnitude about ?18 was reached at a height of 36 km. We developed a detailed model of meteoroid atmospheric fragmentation to fit the observed light curve and deceleration. We found that Ko?ice was a weak meteoroid, which started to fragment under the dynamic pressure of only 0.1 MPa and fragmented heavily under 1 MPa. In total, 78 meteorites were recovered in the predicted fall area during official searches. Other meteorites were found by private collectors. Known meteorite masses ranged from 0.56 g to 2.37 kg. The meteorites were classified as ordinary chondrites of type H5 and shock stage S3. The heliocentric orbit had a relatively large semimajor axis of 2.7 AU and aphelion distance of 4.5 ± 0.5 AU. Backward numerical integration of the preimpact orbit indicates possible large variations of the orbital elements in the past due to resonances with Jupiter. 相似文献
33.
Hokkanen Jaro Kollet Stefan Kraus Jiri Herten Andreas Hrywniak Markus Pleiter Dirk 《Computational Geosciences》2021,25(5):1579-1590
Computational Geosciences - Rapidly changing heterogeneous supercomputer architectures pose a great challenge to many scientific communities trying to leverage the latest technology in... 相似文献
34.
We present a new hybrid method combining deterministic and stochastic features. The aim is to describe the crustal propagation better than deterministic or stochastic methods can do separately. We start from the deterministic hybrid method based on Discrete- Wavenumber and Finite-Difference techniques (DW–FD). First we modify the DW–FD procedure by introducing topographical variations and a spatially varying Q factor. Then, to take into account effects due to small-scale heterogeneities of the crust, we add a stochastic noise (perturbation) to the deterministic signal propagated through the crust. The stochastic noise is constructed using a kind of Markov-like process generator with two physical constraints: to have the Brune spectrum, and to reproduce the spatial decay of coherence reported in literature for real sites. We have chosen a Markov-like technique because it allows us to get stochastic noise, with the given coherence spatial decay, directly in time domain. This new hybrid method is applied in a numerical test, the parameters of which approximate the case of the 12 June, 1995 Rome earthquake. It is found that the coherence decay with distance at the alluvial valley surface is slower than the prescribed coherence decay inside the bedrock. 相似文献
35.
Rare late Neoproterozoic detritus in SW Scandinavia as a response to distant tectonic processes 
下载免费PDF全文
下载免费PDF全文 Jiri Slama 《地学学报》2016,28(6):394-401
Rare late Neoproterozoic (Cryogenian and Ediacaran) detrital zircons are detected in sedimentary sequences of Ediacaran to Carboniferous age in SW Scandinavia. New data on five samples of clastic metasediment corroborate their presence. Three distinct sources are proposed for late Neoproterozoic zircons based on new and literature data: (1) rift‐related magmatism along the W margin of Baltica connected with the opening of Iapetus in the Neoproterozoic, (2) the Neoproterozoic to Cambrian Timanian orogeny at the NE margin of Baltica and (3) Cadomian terranes incorporated into the Variscan orogen accreted from the south to Laurussia during the Devonian and Carboniferous. The appearance of late Neoproterozoic detritus, which is otherwise exotic to Baltica, is therefore bound to tectonic processes active at the margins of the palaeocontinent. In a broader perspective, rare detrital zircon populations, when confirmed as genuine, are extremely valuable provenance indicators. 相似文献
36.
Juraj Tóth Ján Svoreň Jiří Borovička Pavel Spurný Antal Igaz Leonard Kornoš Peter Vereš Marek Husárik Július Koza Aleš Kučera Pavel Zigo Štefan Gajdoš Jozef Világi David Čapek Zuzana Krišandová Dušan Tomko Jiří Šilha Eva Schunová Marcela Bodnárová Diana Búzová Tereza Krejčová 《Meteoritics & planetary science》2015,50(5):853-863
We provide the circumstances and details of the fireball observation, search expeditions, recovery, strewn field, and physical characteristics of the Ko?ice meteorite that fell in Slovakia on February 28, 2010. The meteorite was only the 15th case of an observed bolide with a recovered mass and subsequent orbit determination. Despite multiple eyewitness reports of the bolide, only three videos from security cameras in Hungary were used for the strewn field determination and orbit computation. Multiple expeditions of professionals and individual searchers found 218 fragments with total weight of 11.3 kg. The strewn field with the size of 5 × 3 km is characterized with respect to the space distribution of the fragments, their mass and size‐frequency distribution. This work describes a catalog of 78 fragments, mass, size, volume, fusion crust, names of discoverers, geographic location, and time of discovery, which represents the most complex study of a fresh meteorite fall. From the analytical results, we classified the Ko?ice meteorite as an ordinary H5 chondrite. 相似文献
37.
J. Borovička P. Spurný D. Šegon Ž. Andreić J. Kac K. Korlević J. Atanackov G. Kladnik H. Mucke D. Vida F. Novoselnik 《Meteoritics & planetary science》2015,50(7):1244-1259
The Kri?evci H6 meteorite was recovered on the basis of fireball data obtained by the cameras of the Croatian Meteor Network. The fireball, which occurred on February 4, 2011, 23:20:40 UT, was also observed by meteor cameras in Slovenia and by the Autonomous Fireball Observatory in Martinsberg, Austria, which belongs to the European Fireball Network. Here, we present detailed data on fireball trajectory, velocity, deceleration, light curve, and orbit. We also modeled the atmospheric fragmentation of the meteoroid on the basis of the light curve and deceleration. The initial mass of the meteoroid was between 25–100 kg, most probably about 50 kg. Severe fragmentation occurred at heights of approximately 60 and 31 km, under dynamic pressures of 0.1 and 3 MPa, respectively. The peak absolute magnitude of ?13.7 was reached during the second severe fragmentation event. The recovered 291 g meteorite was probably the only fragment with a terminal mass exceeding 100 g. The orbit had a low inclination of 0.6 degrees, perihelion distance 0.74 AU, and semimajor axis 1.54 AU. Kri?evci can be ranked among the 10 best documented meteorite falls. 相似文献
38.
We present detailed data on 8 bright meteors recorded simultaneously by different observational techniques. All meteors were
recorded by all-sky cameras at the Czech stations of the European Fireball Network and by image intensified TV cameras placed
at Ondrejov and Kunzak observatories. As well as direct photographic and LLLTV recordings, most of meteors were recorded also
by the spectral TV camera and some also by photographic spectral cameras. For 6 cases, lightcurves from radiometers with very
high time resolution (1200 s−1) are also available. From all these detections we found a significant difference between TV and photographic beginning heights.
TV beginnings are in average about 40 km higher than the photographic ones. We found that meteor brightness is up to 2 magnitudes
higher in the photographic system than in the TV system. This difference for high velocity meteors is mainly caused by the
presence of strong Ca+ lines in the blue part of the spectrum, where the image intensifier is only marginally sensitive. At heights above 110 km,
the Na line is usually brighter than the Mg line, while at lower heights both lines have comparable brightness. In one of
two captured spectra of short duration luminous trains, a small initial brightening of the Mg and Na lines caused by recombination
processes was observed. 相似文献
39.
Jiří Borovička 《Earth, Moon, and Planets》2005,97(3-4):279-293
High resolution photographic spectra of two fireballs have been analyzed. The fireballs were produced by meteoroids of asteroidal origin of the mass of the order of 1 kg. Temperature, size, and mass of the vapor cloud around the meteoroid was derived at selected points along the trajectory. Abundances of 11 elements, including lithium, were determined. The abundances of refractory elements in the vapors of the first meteoroid indicate that only 90–95% of the ablated material was vaporized. The meteoroid was likely a chondritic body. Relative stability of the vapor cloud was disturbed for 0.1 s after a major fragmentation of the meteoroid at the height of 42 km. Size and mass of the cloud decreased after the fragmentation and this enabled more intensive heat transfer from the incoming airflow. Both the vapor temperature and the vaporization temperature of the ablated melt increased. A brief millisecond flare of the fireball was produced under these conditions by a violent vaporization of small amount of material. The composition of the vapors of the second meteoroid can be explained either by an anomalous meteoroid composition with severely depleted Al, Ca, and Mg or by highly incomplete evaporation of the ablated material reaching only about 50%. 相似文献
40.
Christian Anibas Abebe Debele Tolche Gert Ghysels Jiri Nossent Uwe Schneidewind Marijke Huysmans Okke Batelaan 《Hydrogeology Journal》2018,26(3):819-835
Among the advances made in analytical and numerical analysis methods to quantify groundwater/surface-water interaction, one methodology that stands out is the use of heat as an environmental tracer. A large data set of river and riverbed temperature profiles from the Aa River in Belgium has been used to examine the spatial-temporal variations of groundwater/surface-water interaction. Exchange fluxes were calculated with the numerical heat-transport code STRIVE. The code was applied in transient mode to overcome previous limitations of steady-state analysis, and allowed for the calculation of model quality. In autumn and winter the mean exchange fluxes reached ?90 mm d?1, while in spring and early summer fluxes were ?42 mm d?1. Predominantly gaining conditions occurred along the river reach; however, in a few areas the direction of flow changed in time. The river banks showed elevated fluxes up to a factor of 3 compared to the center of the river. Higher fluxes were detected in the upstream section of the reach. Due to the influence of exchange fluxes along the river banks, larger temporal variations were found in the downstream section. The exchange fluxes at the river banks seemed more driven by variable local exchange flows, while the center of the river was dominated by deep and steady regional groundwater flows. These spatial and temporal differences in groundwater/surface-water exchange show the importance of long-term investigations on the driving forces of hyporheic processes across different scales. 相似文献