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Jan Svoren Marek Husarik Jaroslav Ambroz Jiri Drbohlav Jaroslav Medek 《Earth, Moon, and Planets》2009,105(2-4):361-365
A semi-automated photometric telescope built at the Skalnate Pleso Observatory is described. In December 2000, the 0.3-m f/5 Zeiss astrograph was replaced by a 0.61-m f/4.3 mirror telescope equipped with a CCD camera. The observing programme is created to conform to the photometry of asteroids which are suspected to be of binary nature; photometry of NEAs and MBAs; a long-term photometry for theoretical modelling of the shape of asteroids; and photometry and astrometry of active comets and asteroids. Some results concerning the binary character of the asteroids are described in the paper. 相似文献
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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
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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
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Rare late Neoproterozoic detritus in SW Scandinavia as a response to distant tectonic processes 
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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
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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
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In biological wastewater treatment, bacteria tend to aggregate by forming flocs, biofilms and even granules. A large part of the floc structure in activated sludge is composed of extracellular polymers. The extracellular polymeric substances (EPS) are mainly responsible for the structural and functional integrity of biofilms/flocs and they are considered to be important for the physico‐chemical properties of activated sludge. This review considers the composition of EPS and proportion between the constituents. Moreover it includes the relationship between the EPS constituents and sludge properties such as sludge retention time, hydrophobicity and surface charge. 相似文献
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Two seismic agencies reported a very low double-couple percentage (DC%) of the Amfilochia earthquake, of about 30% and 60%,
by Schweizerischer Erdbebendienst and Mediterranean Very Broadband Seismographic Network, respectively. Near-regional waveforms,
carefully analyzed in this paper for the DC%, suggested a higher DC%, ranging from 75 to 100, dependent on the uncertainty
of the source position (optimum value DC% = 93). Using a statistical F test, forward modeling of the near-regional data with a single-event low-DC% source yields a significantly worse waveform
match. The fit of near-regional data can be further improved (although at the 90% significance level only) when considering
a speculative two-event model. The same model, when viewed at the very-low frequency range, reaches the very low DC% values.
However, two features make the two-event model unlikely: The two subevents strongly differ in their focal mechanism, and their
mutual separation (3.5 s) is larger than the expected duration of this earthquake. Therefore, the two-source model appears
to be nothing but an interesting equivalent representation of the non-DC model, providing some insight into the possible origin
of the apparently low DC%. Preference is given to the simple interpretation, most clearly supported by the near-regional data,
that the Amfilochia earthquake was an almost pure-shear event. 相似文献
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Lucie Novakova Milan Broz Jiri Zaruba Karel Sosna Jan Najser Lenka Rukavickova Jan Franek Vladimir Rudajev 《应用地球物理》2016,13(2):315-325
Underground storage systems are currently being used worldwide for the geological storage of natural gas (CH4), the geological disposal of CO2, in geothermal energy, or radioactive waste disposal. We introduce a complex approach to the risks posed by induced bedrock instabilities in deep geological underground storage sites. Bedrock instability owing to underground openings has been studied and discussed for many years. The Bohemian Massif in the Czech Republic (Central Europe) is geologically and tectonically complex. However, this setting is ideal for learning about the instability state of rock masses. Longterm geological and mining studies, natural and induced seismicity, radon emanations, and granite properties as potential storage sites for disposal of radioactive waste in the Czech Republic have provided useful information. In addition, the Czech Republic, with an average concentration radon of 140 Bq m?3, has the highest average radon concentrations in the world. Bedrock instabilities might emerge from microscale features, such as grain size and mineral orientation, and microfracturing. Any underground storage facility construction has to consider the stored substance and the geological settings. In the Czech Republic, granites and granitoids are the best underground storage sites. Microcrack networks and migration properties are rock specific and vary considerably. Moreover, the matrix porosity also affects the mechanical properties of the rocks. Any underground storage site has to be selected carefully. The authors suggest to study the complex set of parameters from micro to macroscale for a particular place and type of rock to ensure that the storage remains safe and stable during construction, operation, and after closure. 相似文献
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Glaciers around the world retreated as the climate warmed substantially. For the majority of alpine and arctic areas, however, the lack of meteorological data over a long period makes it difficult to build long-term climate and glacial fluctuation relationships, emphasizing the importance of natural proxy archives. Here we use the 230-year record of stem radial growth of birch trees (Betula ermanii) from the treeline forests above the receding glaciers in eastern maritime Kamchatka to analyse temporal variations of climate as well as glacial advance and retreat. Glaciers in Kamchatka Peninsula represent the southern limit of glaciation in far eastern Eurasia, which makes them prone to global warming. Using instrumental climate data (1930–1996) from local meteorological stations, we find that the July temperature had most prominent positive impact on birch growth. On the contrary, smaller ring increments are associated with the positive summer and net annual ice mass balance of Koryto Glacier. The prevailing trend of higher summer temperatures and lower snowfall over the past 70 years has enhanced tree growth while causing the glacier’s surface to lower by about 35 m and its front to retreat by about 490 m. Assuming these same relationships between climate, tree growth, and glacier mass balance also existed in the past, we use tree rings as a proxy record of climatically induced temporary halts in the glacier’s retreat over the past two centuries, which in total was over 1,000 m. Both direct observations and tree ring proxies indicate several prolonged warm periods (1990s, 1960s, 1930–1940s, 1880–1900s) interspersed with cooler periods (1984–1985, 1970–1976, 1953–1957, 1912–1926, 1855–1875, 1830–1845, 1805–1820 and 1770–1780) when the glacier re-advanced, creating several consecutive terminal moraine ridges. We conclude that birch tree-rings are suitable for assessing tree growth/climate/glacial relationships over a longer timescale in maritime Kamchatka. 相似文献