Garnet metagabbro-ultramafic complexes in the Pekulney Range, northeast Russia     

Akira  Ishiwatari  Galina V.  Ledneva  Boris A.  Bazylev  Yasutaka  Hayasaka  Suren A.  Palandzhyan  Odin L.  Morozov  Kazuto  Koizumi  Vasily D.  Stcherbakov  Sergey D.  Sokolov 《Island Arc》2007,16(1):1-3

  相似文献   

Application of the wavelet transform to automatic seismic signal detection     

S. V. Baranov 《Izvestiya Physics of the Solid Earth》2007,43(2):177-188

The paper is devoted to such a priority direction of digital seismology as the detection of seismic signals in a noisy medium. Various formulations of the problem of seismic event detection are analyzed. The reasons for the ineffectiveness of the classical formulation of the detection problem are revealed, and an adequate general formulation of the problem in the frequency-time space is proposed. A criterion for the automatic determination of the length of a seismic signal is proposed. The time-scale STA/LTA (Short Time Average to Long Time Average) detector, utilizing the expansion of a seismogram in a packet of wavelets, is proposed. The method eliminates the shortcomings of the standard scheme and enables the detection of seismic events with a low signal-to-noise ratio. The problems of the choice of the mother wavelet and the decomposition level of seismograms are discussed from the standpoint of physical properties of seismic wave fields.  相似文献   

Response of alpine chironomid communities (Lake Chuna, Kola Peninsula, northwestern Russia) to atmospheric contamination   总被引：1，自引：0，他引：1  

Boris Ilyashuk  Elena Ilyashuk 《Journal of Paleolimnology》2001,25(4):467-475

A short sediment core from the deepest part of an alpine lake (Lake Chuna, Kola Peninsula, northwestern Russia), covering about the past 200 yrs of sediment accumulation, was analysed for chironomid head capsule remains. The lake has been receiving acidic precipitation and heavy metals loading from the atmosphere since the 1940's. A total of 22 chironomid taxa were recorded. The most important taxa were typical elements of oligotrophic lakes, i.e.Micropsectra insignilobus, Paratanytarsus penicillatus, Stictochironomus spp. and Heterotrissocladius marcidus. Based on the cluster analyses results for the reconstructed environmental variables and chironomid communities, three developmental stages were distinguished from the lake history: (1) Natural ontogeny stage (before ~1945); (2) Initial stage of anthropogenic ontogeny (~1945-~1982); and (3) Anthropogenic ontogeny stage (~1982-~1996). During the first period, the changes in the chironomid fauna were characterized as an anthropogenically undisturbed community, with M. insignilobus dominating (46-66%). The changes during the second period reflected the initial phase of anthropogenic succession associated with the beginning of acidification and heavy metal pollution. The main species showed opposite distributional patterns in this period; the abundance of the group M. insignilobus/Stictochironomus spp. decreased, whereas the abundance of P. penicillatus/H. marcidus increased. The third period was characterized by a major shift in the faunal assemblages, from M. insignilobus to other dominant species including P. penicillatus (19-30%). The increases of Orthocladiinae relative abundance and total organic content in the uppermost sediment layers may be explained by a decrease in lake productivity. The decreases of cold-stenothermal taxa Stictochironomus spp. and M. insignilobus in the uppermost sediment layers can be explained by the global warming during the 20th century. The lake ecosystem is likely to be affected by both inputs of airborne contaminants and climate changes.  相似文献   

Modelling of global ocean tides with allowance for island effects     

Prof. Dr. Boris A. Kagan  Dr. Gennady A. Kivman 《Ocean Dynamics》1993,45(1):1-13

Summary Parameterization schemes for single islands, island chains and archipelagos are described. It is shown that their utilization within the framework of a global tidal model leads not only to local peculiarities in the spatial structure of tidal characteristics, but also to cardinal restructuring of the tidal pattern far beyond the islands and an appreciable increase (about 0.5·10¹²W) of the global tidal energy dissipation. The latter is commensurable by the order of magnitude with the imbalance between estimates of tidal energy dissipation in the World Ocean as a whole and on the continental shelf.

---

Modellierung der Gezeiten der weltmeere unter Berücksichtigung von Inseleffekten

Zusammenfassung Es werden parametrisierte Darstellungen von einzelnen Inseln, Inselketten und Inselgruppen beschrieben. Es wird gezeigt, daß ihre Anwendung bei einem globalen Gezeitenmodell nicht nur zu lokalen Besonderheiten in der geographischen Struktur der Gezeiten führt, sondern auch zur grundsätzlichen Restrukturierung des Gezeitenmusters weit über die Inseln hinaus und zu einer deutlichen Zunahme (etwa 0,5·10¹² W) des globalen Gezeiten-Energieverlusts für die M₂-Tide. Dieser hat etwa die Größenordnung des Unterschiedes zwischen dem Gezeiten-Energieverlust des gesamten Weltmeeres und dem auf dem Kontinentalschelf.

  相似文献   

Comparison of the classical and the global solutions of the Ideal Resonance Problem     

Boris Garfinkel 《Celestial Mechanics and Dynamical Astronomy》1972,5(4):451-469

The Ideal Resonance Problem is defined by the Hamiltonian $$F = B(y) + 2\varepsilon A(y) \sin ^2 x,\varepsilon \ll 1.$$ The classical solution of the Problem, expanded in powers of ε, carries the derivativeB′ as a divisor and is, therefore, singular at the zero ofB′, associated with resonance. With α denoting theresonance parameter, defined by $$\alpha \equiv - B'/|4AB''|^{1/2} \mu ,\mu = \varepsilon ^{1/2} ,$$ it is shown here that the classical solution is valid only for $$\alpha ^2 \geqslant 0(1/\mu ).$$ In contrast, the global solution (Garfinkelet al., 1971), expanded in powers ofμ=ε^1/2, removes the classical singularity atB′=0, and is valid for all α. It is also shown here that the classical solution is an asymptotic approximation, for largeα ², of the global solution expanded in powers ofα ^?2. This result leads to simplified expressions for resonancewidth and resonantamplification. The two solutions are compared with regard to their general behavior and their accuracy. It is noted that the global solution represents a perturbed simple pendulum, while the classical solution is the limiting case of a pendulum in a state offast circulation.  相似文献   

A potentiometric study of Eu complexation with acetate ligand from 25 to 170°C at P_sat     

Alexander V Zotov  Boris R Tagirov  Igor I Diakonov  K.Vala Ragnarsdottir 《Geochimica et cosmochimica acta》2002,66(20):3599-3613

  相似文献   

Rapid biotic molecular transformation of fulvic acids in a karst aquifer   总被引：2，自引：0，他引：2  

Florian Einsiedl  Norbert Hertkorn  Moritz Frommberger  Boris P. Koch 《Geochimica et cosmochimica acta》2007,71(22):5474-5482

The study of molecular transformation processes of dissolved organic carbon (DOC) in the environment significantly contributes to a better understanding of the global biogeochemical organic matter cycle. In an oxic karst groundwater system, in which the most powerful abiotic DOC degradative reactions, photodegradation and metal-mediated redox chemistry, are at best marginal contributors, a near complete turnover of fulvic acids (FAs) has been observed within decades (∼60 years). Depletion of oxygen for a very extensive range of aliphatic and aromatic carbon chemical environments has been confirmed as well as the formation of novel classes of compounds, suggesting a major contribution from biotic processes. From these results we infer that FAs must be perceived as a rather active participant in the global carbon cycle. Molecular-level alterations of such magnitude and rapidity on such short-time scales ought to be considered as widespread in the processing of “refractory” DOC in the environment.  相似文献   

Probabilistic elasto-plasticity: solution and verification in 1D     

Kallol Sett  Boris Jeremić  M. Levent Kavvas 《Acta Geotechnica》2007,2(3):211-220

In this paper, a solution is presented for evolution of probability density function (PDF) of elastic–plastic stress–strain relationship for material models with uncertain parameters. Developments in this paper are based on already derived general formulation presented in the companion paper. The solution presented is then specialized to a specific Drucker–Prager elastic–plastic material model. Three numerical problems are used to illustrate the developed solution. The stress–strain response (1D) is given as a PDF of stress as a function of strain. The presentation of the stress–strain response through the PDF differs significantly from the traditional presentation of such results, which are represented by a single, unique curve in stress–strain space. In addition to that the numerical solutions are verified against closed form solutions where available (elastic). In cases where the closed form solution does not exist (elastic–plastic), Monte Carlo simulations are used for verification.  相似文献   

Three-dimensional sedimentary architecture of Quaternary sand and gravel resources: a case study of economic sedimentology (SW Germany)     

Boris Kostic  M. Peter Süss  Thomas Aigner 《International Journal of Earth Sciences》2007,96(4):743-767

Quaternary sands and gravels form important, yet often highly heterogeneous economic deposits. Detailed 3-D analysis of the sedimentary structure and stratigraphy of these deposits allows for an accurate estimation of exploitable material. This paper presents a case study in SW Germany reconstructing the 3-D distribution of glacial sediments based on a high-resolution, process-orientated sedimentary facies classification and lithostratigraphy integrated within the geo-modelling package gOcad. Situated along the maximal ice-extent of the Rhine glacier during the last glaciation, the study area is characterised by a morphologically prominent terminal moraine and its associated sandur, which form the stratigraphically youngest sediments of a glacial basin, partially exposed in two gravel pits. These outcrops helped to reconstruct the complex sedimentary architecture of the northern part of the glacial basin. The regional analysis is based on core data, as well as geoelectric and geomagnetic surveys. All data were integrated into km-scale, high-resolution geological 3-D models, depicting the large-scale dynamics of multiple glacier advances and retreats during the Early to Late Pleistocene. These models allow quantifying the thickness and volume distribution of exploitable sandy gravel and help to evaluate the occurrence of non-exploitable interbedded diamicton horizons. The high quality and quantity of gravels particularly north of the terminal moraine classifies the investigated area as very prospective for raw materials exploitation in the future.  相似文献   

Quasi-isotropic approximation of ray theory for anisotropic media     

Matthias Zillmer  Boris Kashtan  & Dirk Gajewski 《Geophysical Journal International》1998,132(3):643-653

Wave propagation in weakly anisotropic inhomogeneous media is studied by the quasi-isotropic approximation of ray theory. The approach is based on the ray-tracing and dynamic ray-tracing differential equations for an isotropic background medium. In addition, it requires the integration of a system of two complex coupled differential equations along the isotropic ray.
The interference of the qS waves is described by traveltime and polarization corrections of interacting isotropic S waves. For qP waves the approach leads to a correction of the traveltime of the P wave in the isotropic background medium.
Seismograms and particle-motion diagrams obtained from numerical computations are presented for models with different strengths of anisotropy.
The equivalence of the quasi-isotropic approximation and the quasi-shear-wave coupling theory is demonstrated. The quasi-isotropic approximation allows for a consideration of the limit from weak anisotropy to isotropy, especially in the case of qS waves, where the usual ray theory for anisotropic media fails.  相似文献