On reverberation and cross-correlation estimates of the size of the broad-line region in active galactic nuclei     

A. V. Melnikov  I. I. Shevchenko 《Monthly notices of the Royal Astronomical Society》2008,389(1):478-488

It is known that the dependence of the emission-line luminosity of a typical cloud in the active galactic nuclei (AGN) broad-line regions (BLRs) upon the incident flux of ionizing continuum can be non-linear. We study how this non-linearity can be taken into account in estimating the size of the BLR by means of the 'reverberation' methods. We show that the BLR size estimates obtained by cross-correlation of emission-line and continuum light curves can be much (up to an order of magnitude) less than the values obtained by reverberation modelling. This is demonstrated by means of numerical cross-correlation and reverberation experiments with model continuum flares and emission-line transfer functions and by means of practical reverberation modelling of the observed optical spectral variability of NGC 4151. The time behaviour of NGC 4151 in the Hα and Hβ lines is modelled on the basis of the observational data by Kaspi et al. and the theoretical BLR model by Shevchenko. The values of the BLR parameters are estimated that allow to judge on the size and physical characteristics of the BLR. The small size of the BLR, as determined by the cross-correlation method from the data of Kaspi et al., is shown to be an artefact of this method. So, the hypothesis that the BLR size varies in time is not necessitated by the observational data.  相似文献   

On the rotational dynamics of Prometheus and Pandora     

A. V. Melnikov  I. I. Shevchenko 《Celestial Mechanics and Dynamical Astronomy》2008,101(1-2):31-47

Possible rotation states of two satellites of Saturn, Prometheus (S16) and Pandora (S17), are studied by means of numerical experiments. The attitude stability of all possible modes of synchronous rotation and the motion close to these modes is analyzed by means of computation of the Lyapunov spectra of the motion. The stability analysis confirms that the rotation of Prometheus and Pandora might be chaotic, though the possibility of regular behaviour is not excluded. For the both satellites, the attitude instability zones form series of concentric belts enclosing the main synchronous resonance center in the phase space sections. A hypothesis is put forward that these belts might form “barriers” for capturing the satellites in synchronous rotation. The satellites in chaotic rotation can mimic ordinary regular synchronous behaviour: they preserve preferred orientation for long periods of time, the largest axis of satellite’s figure being directed approximately towards Saturn.  相似文献   

Co,Hf, Ce,Cr, Th,and REE Charateristics of Modern Bottom Sediments of the Barents Sea     

Maslov  A. V.  Politova  N. V.  Shevchenko  V. P.  Kozina  N. V.  Novigatsky  A. N.  Kravchishina  M. D. 《Doklady Earth Sciences》2019,485(1):298-302

Doklady Earth Sciences - The Co, Hf, Ce, Cr, Th, and REE characteristics are analyzed for modern sediments collected by a bottom grab during the 67th and 68th cruises of R/V Akademik Mstislav...  相似文献   

Experience of Studying the Turbulent Structure of the Atmospheric Boundary Layer Using an Unmanned Aerial Vehicle     

Chechin  D. G.  Artamonov  A. Yu.  Bodunkov  N. E.  Zhivoglotov  D. N.  Zaytseva  D. V.  Kalyagin  M. Yu.  Kouznetsov  D. D.  Kounashouk  A. A.  Shevchenko  A. M.  Shestakova  A. A. 《Izvestiya Atmospheric and Oceanic Physics》2021,57(5):526-532

Izvestiya, Atmospheric and Oceanic Physics - The growing relevance of the use of unmanned aerial vehicles (UAVs) for studying turbulence in the atmospheric boundary layer (ABL) is associated with...  相似文献   

Deep structure of the Amur lithospheric Plate border zone     

Yu. F. Malyshev  V. Ya. Podgornyi  B. F. Shevchenko  N. P. Romanovskii  V. B. Kaplun  P. Yu. Gornov 《Russian Journal of Pacific Geology》2007,1(2):107-119

Based on the study of the deep Amur Plate border structure, seismogravimetric (density) and geoelectric sections of the plate lithosphere crossing geologically and seismically defined plate boundaries are compiled to construct a three-dimensional model of its lithosphere. The model demonstrates the almost ring structure of the plate with its inner part dipping for 50 km and uplifted fringing. The plate boundary zone consists of orogenic belts (Mongol-Okhotsk, Selenga-Stanovoi, Transbaikal, and Sikhote-Alin) and margins of the Siberian and North China platforms. The plate boundaries are described by mantle diapirism models with a largely bilateral inclined dip of its bordering belts.  相似文献   

Peculiarity of the Relationship between the Seismicity and Tectonic Structure of the Pyrenees     

A. A. Lukk  V. I. Shevchenko 《Izvestiya Physics of the Solid Earth》2018,54(3):415-429

The geotectonic position of the Pyrenees mountain massif in the Alpine–Indonesian mobile belt is considered. The geological data testify to the formation of the structure of the Pyrenees in the setting of a subhorizontal compression perpendicular to the ridge. The commonly accepted interpretation considers this compression in the context of plate tectonic notions related to the collision between the Iberian and Eurasian lithospheric plates resulting from the convergence of the Eurasian and African plates. However, this interpretation is challenged by the the geodetic and seismological measurements. The GPS measurements suggest a certain cross-strike spreading rather than shortening of the Earth’s crust; the focal mechanisms of the earthquakes indicate the predominance of a subhorizontal extension perpendicular to the strike of the Pyrenees mountain range. The processes of the gravitational collapse of the mountain chain during the isostatic upwelling of the orogenic crust are considered as the most probable cause of this spreading by a number of the authors.  相似文献   

Factors governing strontium-90 export with surface runoff in the Chernobyl NPP restricted zone     

A. L. Shevchenko  D. V. Charnyi  G. A. Akinfiev  S. I. Kireev 《Water Resources》2016,43(3):522-532

Statistical analysis of collected data revealed priority factors affecting radionuclide migration in water. Considerable changes in the coefficients of correlations between the many-year values of those factors and the water export of ⁹⁰Sr make it possible to identify the stages associated with a mass passage of primary ⁹⁰Sr inputs into water-soluble forms. The landscape characteristics of drainage basins were used to construct regression forecast models of the export of pollutants from watersheds.  相似文献   

Peculiarities of the rare-earth element distribution in the modern bottom sediments of the White Sea and the lower reaches of the Severnaya Dvina River     

A. V. Maslov  V. P. Shevchenko  Yu. L. Ronkin  O. P. Lepikhina  A. N. Novigatsky  A. S. Filippov  N. V. Shevchenko 《Oceanology》2013,53(6):702-714

The study of the rare-earth element (REE) systematics in the modern bottom sediments of the White Sea and the lower reaches of the Severnaya Dvina River showed that they were derived by the simple mixing of the detrital material from two geochemically contrasting provenances: the Kola-Karelian geoblock almost completely consisting of Archean rocks and the northwestern Mezen syneclise made up of the Upper Vendian, Paleozoic, and Mesozoic rocks. This is best manifested by the changes in ?_Nd(0). In terms of the Gd_N/Yb_N and Eu/Eu*, most of the studied samples are comparable with the Post-Archean craton complexes, some of which resemble the average composition of the Archean mudstone. Based on the ΣREE and La_N/Yb_N, the modern bottom sediments are subdivided into two groups: (1) those close to basalts and granites and (2) those approximating common sedimentary rocks. From the lower reaches of the Pinega River to the Tersky coast, the maximal average (La/Yb)_RPSC, (Gd/Yb)_RPSC, La_N/Yb_N, and Gd_N/Yb_N ratios were determined in the samples taken at the boundary of Dvina Bay with the Basin, i.e., in the sediments with the highest content of the pelitic component. In general, the geochemical composition of the modern bottom sediments of almost the entire White Sea area was defined by input of the eroded products of the mature continental crust with the Severnaya Dvina River, the main river of the region. Such a setting, when the formation of the sediments in a peri- or intracontinental marine basin is controlled by one large river system, presumably may be propagated to the sedimentation in the Laptev Sea, the eastern Kara Sea, the Bay of Bengal, and other basins.  相似文献   

Dynamics of the main components of fluxes of sedimentary matter in the White Sea     

Lisitzin  A. P.  Novigatsky  A. N.  Shevchenko  V. P.  Klyuvitkin  A. A.  Kravchishina  M. D.  Politova  N. V. 《Doklady Earth Sciences》2017,472(2):252-255

Doklady Earth Sciences - The results of long-term investigations in a small sea of the Arctic Ocean served as a basis for revealing new regularities characteristic of the sedimentary process in the...  相似文献   

REE systematics in modern bottom sediments of the Caspian Sea and river deltas worldwide: Experience of comparison     

A. V. Maslov  N. V. Kozina  V. P. Shevchenko  A. A. Klyuvitkin  Ph. V. Sapozhnikov  P. O. Zavialov 《Doklady Earth Sciences》2017,475(1):797-802

The results of comparison of a number of main parameters of the chondrite-normalized REE distribution spectra in modern bottom, mainly pelitic, sediments of various sedimentary subsystems of the Caspian Sea and marginal filters of the Volga and Ural rivers with those characteristic of the pelitic fraction of modern bottom sediments of different river deltas worldwide are discussed. According to the features of the REE distribution spectra, as well as the ε_Nd(0) values, it has been established that most samples of the Caspian bottom sediments are similar to those of large rivers and rivers, draining watersheds composed of sedimentary formations.  相似文献