Sankt Petersburg State University

Saint Petersburg, Russia

Sankt Petersburg State University

Saint Petersburg, Russia
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Melchor-Aguilar D.,IPICYT | Kharitonov V.,Sankt Petersburg State University
International Journal of Robust and Nonlinear Control | Year: 2010

In this paper we consider a special class of integral delay systems arising in several stability problems of time-delay systems. For these integral systems we derive stability and robust stability conditions in terms of Lyapunov-Krasovskii functionals. More explicitly, after providing the stability conditions we compute quadratic functionals and apply them to derive exponential estimates for solutions, and robust stability conditions for perturbed integral delay systems. Copyright © 2008 John Wiley & Sons, Ltd.


Foulger G.R.,Durham University | Panza G.F.,University of Trieste | Panza G.F.,China Earthquake Administration | Artemieva I.M.,Copenhagen University | And 9 more authors.
Terra Nova | Year: 2013

Geological and geodynamic models of the mantle often rely on joint interpretations of published seismic tomography images and petrological/geochemical data. This approach tends to neglect the fundamental limitations of, and uncertainties in, seismic tomography results. These limitations and uncertainties involve theory, correcting for the crust, the lack of rays throughout much of the mantle, the difficulty in obtaining the true strength of anomalies, choice of what background model to subtract to reveal anomalies, and what cross-sections to select for publication. The aim of this review is to provide a relatively non-technical summary of the most important of these problems, collected together in a single paper, and presented in a form accessible to non-seismologists. Appreciation of these issues is essential if final geodynamic models are to be robust, and required by the scientific observations. © 2013 John Wiley & Sons Ltd.


Panin A.V.,Moscow State University | Adamiec G.,Silesian University of Technology | Arslanov K.A.,Sankt Petersburg State University | Bronnikova M.A.,Russian Academy of Sciences | And 4 more authors.
Geochronometria | Year: 2014

A set of 121 radiocarbon and OSL dates has been compiled from the Upper Dnieper River and tributary valleys, Western European Russia. Each date was attributed according to geo-morphic/sedimentological events and classes of fluvial activity. Summed probability density func-tions for each class were used to establish phases of increasing and reducing fluvial activity. The old-est detected reduction of fluvial activity was probably due to glacial damming at LGM. Within the Holocene three palaeohydrological epochs of millennial-scale were found: (1) high activity at 12,000-8,000 cal BP marked by large river palaeochannels; (2) low activity at 8,000-3,000 cal BP marked by formation of zonal-type soils on -floodplains; short episodes of high floods occurred be-tween 6,500-4,400 cal BP; (3) contrasting hydrological oscillations since 3,000 cal BP with periods of high floods between 3,000-2,300 (2,000) and 900-100 cal BP separated by long interval of low floods 2,300 (2,000)-900 cal BP when floodplains were not inundated-zonal-type soils were de-veloping and permanent settlements existed on floodplains. In the last millennium, four centennial-scale intervals were found: high flooding intervals are mid-11-mid-15th century and mid-17-mid-20th century. Intervals of flood activity similar to the present-day were: mid-15-mid-17th century and since mid-19th century till present. In the context of palaeohydrological changes, discussed are selected pal-aeogeographic issues such as: position of the glacial boundary at LGM, role of changing amounts of river runoff in the Black Sea level changes, floodplain occupation by Early Medieval population.A set of 121 radiocarbon and OSL dates has been compiled from the Upper Dnieper River and tributary valleys, Western European Russia. Each date was attributed according to geo-morphic/sedimentological events and classes of fluvial activity. Summed probability density func-tions for each class were used to establish phases of increasing and reducing fluvial activity. The old-est detected reduction of fluvial activity was probably due to glacial damming at LGM. Within the Holocene three palaeohydrological epochs of millennial-scale were found: (1) high activity at 12,000-8,000 cal BP marked by large river palaeochannels; (2) low activity at 8,000-3,000 cal BP marked by formation of zonal-type soils on -floodplains; short episodes of high floods occurred be-tween 6,500-4,400 cal BP; (3) contrasting hydrological oscillations since 3,000 cal BP with periods of high floods between 3,000-2,300 (2,000) and 900-100 cal BP separated by long interval of low floods 2,300 (2,000)-900 cal BP when floodplains were not inundated-zonal-type soils were de-veloping and permanent settlements existed on floodplains. In the last millennium, four centennial-scale intervals were found: high flooding intervals are mid-11-mid-15th century and mid-17-mid-20th century. Intervals of flood activity similar to the present-day were: mid-15-mid-17th century and since mid-19th century till present. In the context of palaeohydrological changes, discussed are selected pal-aeogeographic issues such as: position of the glacial boundary at LGM, role of changing amounts of river runoff in the Black Sea level changes, floodplain occupation by Early Medieval population. © 2013 Silesian University of Technology.


Muhlberg M.,Ludwig Maximilians University of Munich | Hegner E.,Ludwig Maximilians University of Munich | Klemd R.,Friedrich - Alexander - University, Erlangen - Nuremberg | Pfander J.A.,TU Bergakademie Freiberg | And 2 more authors.
Lithos | Year: 2016

High-pressure (HP) metamorphism of the Kassan Metamorphic Complex (KMC) in the western Kyrgyz Tianshan has been related to either late Ordovician or late Carboniferous-Permian subduction processes. We report Sm-Nd ages for retrogressed eclogite samples and 40Ar/39Ar cooling ages for enclosing garnet-muscovite samples from the KMC as new age constraints on HP metamorphism and rock exhumation. These data will be used for an upgraded paleogeographic model for late Paleozoic crustal consolidation in the southwestern Central Asian Orogenic Belt. The retrogressed eclogite samples have transitional alkaline to tholeiitic affinity and trace-element patterns consistent with protoliths derived from garnet-bearing mantle sources at rifting plate margins. Geothermobarometric data for a retrogressed eclogite sample indicate peak-metamorphic conditions of 540 ± 30 °C at 1.6 ± 0.1 GPa. Samples from different lithotectonic units of the KMC provide coherent Sm-Nd garnet-whole rock ages of 317 ± 4 Ma and 316 ± 3 Ma (2σ). The prograde major-element zoning in the mm-sized garnets in combination with the moderate peak-metamorphic temperature, support our interpretation of the Sm-Nd garnet ages as unambiguous evidence for late Carboniferous HP metamorphism. The Sm-Nd garnet growth ages overlap within-error with the 40Ar/39Ar mica cooling ages of 314 ± 2 Ma and 313 ± 2 Ma (2σ) indicating rapid uplift of the subduction complex after peak metamorphism. The ca. 317-313 Ma HP-exhumation event of the KMC is contemporaneous with those of the Atbashi and Akeyazi (ca. 500 km east in NW China) HP complexes and implies similar collision histories at the South Tianshan Suture to the east and west of the Talas-Fergana Fault (TFF). The exhumation of the KMC and Atbashi HP complexes overlaps with the initiation of the TFF (Rolland et al., 2013) suggesting incipient separation of the Chatkal and Atbashi complexes during rock exhumation and early plate collision. © 2016 Elsevier B.V.


Kulish P.P.,Russian Academy of Sciences | Lyakhovsky V.D.,Sankt Petersburg State University | Postnova O.V.,Sankt Petersburg State University
Journal of Physics: Conference Series | Year: 2012

For classical Lie algebras g = A r the tensor power (L ω1) ⊗p| pεZ+ of the first fundamental module L ω1 is considered. We study the behavior of fusion coefficients in the decomposition (L ω1) ⊗p = Σ ν m (p, ν) L ν. Using symmetry properties of singular elements corresponding to tensor powers we find the coefficients m(p, ν). The multiplicity function M (p; ν) is constructed that shows explicitly how multiplicities of irreducible submodules L ν depend on power p and coordinates V i of their highest weight. This function provides an effective tool to study different properties of fusion.


Kulish P.P.,Russian Academy of Sciences | Lyakhovsky V.D.,Sankt Petersburg State University | Postnova O.V.,Sankt Petersburg State University
Journal of Physics: Conference Series | Year: 2012

Recurrent properties of fusion coefficients in a tensor power decomposition (L ω1) ⊗p = Σ ν m (ν, p)L ν are studied for classical Lie algebras B n and the spinor fundamental B n-module L ω1. We find the set of recurrent relations for fusion coefficients m(ν,p). The general structure of a solution for these recurrent relations is formulated using Weyl symmetry properties for singular elements of (L ω1) ⊗p. We prove that such a solution is unique and defines explicitly coefficients m(ν,p) as functions of coordinates ν i and the tensor power p.


Kulish P.P.,Russian Academy of Sciences | Lyakhovsky V.D.,Sankt Petersburg State University | Postnova O.V.,Sankt Petersburg State University
Journal of Physics: Conference Series | Year: 2012

We study the decomposition problem for tensor powers of B 2-fundamental modules. To solve this problem singular weight technique and injection fan algorithms are applied. Properties of multiplicity coefficients are formulated in terms of multiplicity functions. These functions are constructed showing explicitly the dependence of multiplicity coefficients on the highest weight coordinates and the tensor power parameter. It is thus possible to study general properties of multiplicity coefficients for powers of the fundamental B 2-modules.


Lyakhovsky V.D.,Sankt Petersburg State University | Uvarov Ph.V.,Sankt Petersburg State University
Journal of Physics A: Mathematical and Theoretical | Year: 2013

We study multivariate Chebyshev polynomials associated with root systems. Using properties of specialized singular elements φg a corresponding to.© 2013 IOP Publishing Ltd.


Tikhomirov V.,Sankt Petersburg State University
Marine and Petroleum Geology | Year: 2015

To unravel the mystery of the relationship between evaporates, Ca-Cl brines and accumulations of oil and N2 in the basins of ancient cratons, their N2, CH4 and He concentration ratios, as well as the isotopic composition (δ15N, δ13C and 3He/4He) were compared within the Volga-Ural basin. The study allowed subsalt fluids from Volga-Ural Basin to divide into two genetic groups. The first one is found within the basin's platform area. It includes Ca-Cl brines, high-viscosity heavy oil, bitumen and N2, which has concentrations higher than that of CH4 and positive values of δ15N. The second one is tied to the edge of the platform, the Ural Foredeep and Peri-Caspian Depression. In this group, only the oil and gas reservoirs, which have more CH4 than N2, and possibly negative values of δ15N, were discovered. Interaction of gas components in compared fluids indicates great role of degassing in the formation of their composition. It is suggested that the fluids of the first group (N2CH4) is what remains, and the second group (N24) is what is disappears from the rocks during their metamorphism and degassing. •This study allows to divide the subsalt fluids for nitrogen and methane group.•The nitrogen group includes Ca-Cl brines, heavy oils, bitumens and N2 gases.•The methane group includes methane gases and possibly volatile crudes.•Gas exchange of the groups is accompanied by degassing and mass transfer between them.•It may be that the groups are products of metamorphism of different times and places. © 2015 Elsevier Ltd.


Yanovskaya T.B.,Sankt Petersburg State University | Koroleva T.Y.,Sankt Petersburg State University
Izvestiya, Physics of the Solid Earth | Year: 2011

Surface wave tomography method based on analysis of ambient noise is widely used during the last decade. It is assumed that correlated component of noise is composed of surface waves generated by sources distributed over the Earth's surface more or less uniformly. In such a case the cross-correlation function (CCF) at two stations may be considered as the Green's function of surface wave. This function should be symmetric relatively to zero time. However analysis of CCF at the stations located at the East-European Platform shows that as a rule CCF is characterized with a strong asymmetry. Since "pure" noise cannot be extracted from seismic records due to superposition of earthquake signals, the method for calculation of CCF includes amplitude normalization for suppression of earthquakes that reduces signals from earthquakes to a noise level. The parts of records containing waves from earthquakes are neglected because of their short duration. Present study shows that this contribution turns out to be dominant at periods larger than 20-40 s. In other words, what is assumed as a "noise" in reality is a superposition of signals from earthquakes. This fact results in distortion of the Green's function and of surface wave dispersion curve used in surface wave tomography if in the time interval used for calculation of CCF many earthquakes occur within a small area apart of an extension of the interstation path (clustering). Numerical modeling shows how clusters of sources affect CCF and dispersion curve correspondingly. Means for reducing this effect are outlined. © 2011 Pleiades Publishing, Ltd.

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