Phases of the Fe–C–N system as hosts of mantle carbon and nitrogen: Experimental studies at 7.8 GPa and 1350°C     

A. G. Sokol  A. N. Kruk  Yu. N. Palyanov  N. V. Sobolev 《Doklady Earth Sciences》2017,475(1):780-783

Parts of the Fe–C–N system were studied in experiments at 7.8 GPa and 1350°C. It was shown that the admixture of nitrogen extends considerably the domain of melt stability in the system at temperatures close to the Fe–Fe₃C eutectic temperatures. Nitrogen solubility in cementite in equilibrium with the nitrogen- rich melt is below the detection limit of the EMPA technique applied. The metal melt is the only nitrogen concentrator (up to 4 wt % of N) in the range of compositions considered. The data obtained permit the conclusion that, in the case of complete dissolution of carbon and nitrogen, which might occur in the enriched mantle, native iron at ~250 km depth should either be completely molten or consist of a melt and carbide of iron.  相似文献   

Magnetostratigraphic correlation of the Oxfordian–Kimmeridgian boundary     

Piotr A. Przybylski  James G. Ogg  Andrzej Wierzbowski  Angela L. Coe  Mark W. Hounslow  John K. Wright  François Atrops  Erik Settles 《Earth and Planetary Science Letters》2010,289(1-2):256-272

A magnetic polarity pattern for Boreal and Sub-Boreal ammonite zones of the Upper Oxfordian to Lower Kimmeridgian was established and confirmed in four British sections, including the proposed Global Boundary Stratotype Section and Point (GSSP) on the Isle of Skye (Scotland) to define the base of the international Kimmeridgian Stage. A coeval pattern for Sub-Mediterranean ammonite zones was compiled from seven sections in Poland, one German section and multi-section composites from France and Spain. The mean paleopole for the European Craton (excluding Spain) at the Oxfordian–Kimmeridgian boundary is 74.2°N, 181.3°E (Α₉₅ = 3.8°). The common magnetic polarity scale enables inter-correlation of ammonite subzones among these three faunal provinces and to the marine magnetic-anomaly M-Sequence. The proposed GSSP at the base of the Pictonia baylei Zone is near the base of an extended interval dominated by reversed polarity, which is interpreted to be Chron M26r. This GSSP level projects to the lower to middle part of the Epipeltoceras bimammatum Subzone, which is the middle subzone of this E. bimammatum Zone in the Sub-Mediterranean standard zonation. In contrast, the traditional placement of the Oxfordian–Kimmeridgian boundary in that Sub-Mediterranean standard zonation (base of Sutneria platynota Zone) is at the base of Chron M25r, or nearly 1 million years younger.  相似文献   

Prospects for Scrutiny of Pulsars with Polish Part of LOFAR     

Leszek Błaszkiewicz  Wojciech Lewandowski  Andrzej Krankowski  Jarosław Kijak  Olga Koralewska  Bartosz P. Dąbrowski 《Acta Geophysica》2016,64(1):293-315

LOFAR (LOw Frequency ARray) is a new generation digitally controlled radio telescope consisting of phased array antenna stations with sensitivity, bandwidth, range of frequency, and digital processing power that makes it an excellent tool for observations of pulsars. This interferometric instrument is able to work in a single-station mode as well as in group-of-selected-stations mode. This article discusses the great opportunity for conducting unique and independent research of pulsar sources with the three LOFAR stations located in Poland and maintained by the POLFAR consortium.  相似文献   

Anisotropic visco-hypoplasticity   总被引：5，自引：5，他引：0  

Andrzej Niemunis  Carlos Eduardo Grandas-Tavera  Luis Felipe Prada-Sarmiento 《Acta Geotechnica》2009,4(4):293-314

Apart from time-driven creep or relaxation, most viscoplastic models (without plastic and viscous strain separation) generate no or a very limited accumulation of strain or stress due to cyclic loading. Such pseudo-relaxation (or pseudo-creep) is either absent or dwindles too fast with increasing OCR. For example, the accumulation of the pore water pressure and eventual liquefaction due to cyclic loading cannot be adequately reproduced. The proposed combination of a viscous model and a hypoplastic model can circumvent this problem. The novel visco-hypoplasticity model presented in the paper is based on an anisotropic preconsolidation surface. It can distinguish between the undrained strength upon triaxial vertical loading and horizontal loading. The strain-induced anisotropy is described using a second-order structure tensor. The implicit time integration with the consistent Jacobian matrix is presented. For the tensorial manipulation including numerous Fréchet derivatives, a special package has been developed within the algebra program MATHEMATICA (registered trade mark of Wolfram Research Inc.). The results can be conveniently coded using a special FORTRAN 90 module for tensorial operations. Simulations of element tests from biaxial apparatus and FE calculations are also shown.  相似文献   

Variation of the ionospheric scintillation index with elevation angle of the transmitter     

Shishir Priyadarshi  Andrzej W. Wernik 《Acta Geophysica》2013,61(5):1279-1288

We have analyzed GPS data from 2007–2011 to determine the nature of variation of scintillation index with elevation of the direction of propagation at an observing point Warsaw, Poland, and Hornsund, Svalbard. To compare with the theory, the intensity scintillation index is simulated as a function of elevation angle, azimuth, magnetic field inclination, and shape of irregularities, using the phase screen model of scintillation as formulated by Rino (1979). Data analysis has been done for the seasonal as well as geomagnetic activity dependence of ionospheric scintillation. Scintillation index is a power-law function of the cosecant of the elevation angle. Results show that the power law strongly depends on the form of irregularities, being larger than in isotropic case for irregularities with dimension along the magnetic field direction smaller than those across the magnetic field. The present work also shows the need to use experimentally derived dependence on elevation.  相似文献   

Petrology of the tin-bearing granite-leucogranites of the Piaoak Massif, Northern Vietnam     

A. G. Vladimirov  Phan Luu Anh  N. N. Kruk  C. Z. Smirnov  I. Yu. Annikova  G. G. Pavlova  M. L. Kuibida  E. N. Moroz  E. N. Sokolova  E. I. Astrelina 《Petrology》2012,20(6):545-566

The Piaoak tin-bearing granite-leucogranites located in the Caobang Province of Northern Vietnam compose a stock-like hypabyssal body. Host rocks are represented by Early Devonian carbonate sequences and Early Triassic ??black?? shales. The geochronological age of the Piaoak granite-leucogranites corresponds to the Late Cretaceous: T = 83.5 ± 6.2 Ma, ⁸⁷Rb/⁸⁶Sr method; T = 89.7 ± 1.0 Ma, ³⁹Ar/⁴⁰Ar method. The massif has a simple basic to acid order: two-mica and muscovite granite-leucogranite ?? raremetal aplites, pegmatites ?? tin-bearing greisens and hydrothermal veins. The petrographic and microstructural studies revealed a sharp change in crystallization conditions of the granite-leucogranite magma at the late magmatic stage and formation of muscovite via incongruent melting of protolithionite. The study of melt and coexisting fluid inclusions showed that solidus crystallization occurred under fluid-saturated conditions at 635?C600°C. In composition, the granite-leucogranites of the Piaoak Massif correspond to the raremetal-plumasite geochemical type (according to L.V. Tauson), and reach Li-F facies in terms of their rare-element composition. The composition of aplites and pegmatites demonstrates that granite-leucogranite magma did not accumulate lithophile and volatile components in the residual melt during differentiation, but was initially enriched in rare-metals. It is most probable that the melt was generated from Proterozoic lithotectonic complexes and overlaying Lower Triassic ??black?? shales.  相似文献   

Book Review
Advanced Ocean Modelling: Using Open-Source Software, by J. K?mpf, Springer, 2010; ISBN: 978-3-642-10609-5     

Andrzej Icha 《Pure and Applied Geophysics》2011,168(10):1893-1894

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Modeling atmospheric circulations with sound-proof equations     

Szymon P. Malinowski  Andrzej A. Wyszogrodzki  Michał Z. Ziemiański 《Acta Geophysica》2011,59(6):1073-1075

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Activation of cloud droplets in bin-microphysics simulation of shallow convection     

Andrzej A. Wyszogrodzki  Wojciech W. Grabowski  Lian-Ping Wang 《Acta Geophysica》2011,59(6):1168-1183

This paper describes implementation of the warm-rain bin microphysics in a LES model based on the EULAG fluid flow solver. The binmicrophysics EULAG is applied to the case of shallow nonprecipitating tropical convection to investigate the impact of the secondary activation of cloud droplets above the cloud base. In a previous study applying the EULAG model with the double-moment bulk warm-rain microphysics scheme, the in-cloud activation was shown to have significant implications for the mean microphysical and optical characteristics of the cloud field. By contrasting the simulations with and without in-cloud activation as in the previous study, we show that the in-cloud activation has qualitatively similar but quantitatively smaller effect. In particular, the concentration of cloud droplets in the bin simulation without in-cloud activation decreases with height not as strongly as in corresponding simulations applying the double-moment bulk scheme.  相似文献   

Seismic risk ranking for large dams in South Africa     

Mayshree Singh  Andrzej Kijko  Leo van den Berg 《Acta Geophysica》2011,59(1):72-90

Earthquake motion is one of the extreme loads acting on large dams. Dam owners and regulators must therefore ensure that dams are safely operated and present minimal risk to the public in case of extreme loads such as floods and earthquakes. Owners of many dams or officials in charge of dam safety programs may consider comparative assessment of the seismic risk associated with their dams and establish priorities for detailed evaluation. South Africa has in excess of 100 large state-owned dams and the characteristics of these dams have been used to perform a basic seismic hazard assessment and rank the vulnerability of these dams from the lowest to highest. One of the most decisive factors that contributes to the risk of a dam is the wall type; with gravity and earthfill dams being the most vulnerable to earthquake motion. Another aspect that needs further investigation is the downstream hazard potential which, if known to a better degree of accuracy, can provide more reasonable estimates of the risk factors.  相似文献