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41.
Olga Podvigina 《地球物理与天体物理流体动力学》2013,107(3):299-326
We investigate instability of convective flows of simple structure (rolls, standing and travelling waves) in a rotating layer with stress-free horizontal boundaries near the onset of convection. We show that the flows are always unstable to perturbations, which are linear combinations of large-scale modes and short-scale modes, whose wave numbers are close to those of the perturbed flows. Depending on asymptotic relations of small parameters α (the difference between the wave number of perturbed flows and the critical wave number for the onset of convection) and ε (ε2 being the overcriticality and the perturbed flow amplitude being O(ε)), either small-angle or Eckhaus instability is prevailing. In the case of small-angle instability for rolls the largest growth rate scales as ε8/5, in agreement with results of Cox and Matthews (Cox, S.M. and Matthews, P.C., Instability of rotating convection. J. Fluid. Mech., 2000, 403, 153–172) obtained for rolls with k = k c . For waves, the largest growth rate is of the order ε4/3. In the case of Eckhaus instability the growth rate is of the order of α2. 相似文献
42.
Numerical Modeling of Hydraulic Fractures Interaction in Complex Naturally Fractured Formations 总被引:1,自引:0,他引:1
Olga Kresse Xiaowei Weng Hongren Gu Ruiting Wu 《Rock Mechanics and Rock Engineering》2013,46(3):555-568
A recently developed unconventional fracture model (UFM) is able to simulate complex fracture network propagation in a formation with pre-existing natural fractures. A method for computing the stress shadow from fracture branches in a complex hydraulic fracture network (HFN) based on an enhanced 2D displacement discontinuity method with correction for finite fracture height is implemented in UFM and is presented in detail including approach validation and examples. The influence of stress shadow effect from the HFN generated at previous treatment stage on the HFN propagation and shape at new stage is also discussed. 相似文献
43.
The Hydrograph model (a distributed process-based model) was applied to the simulation of soil freeze-thaw and runoff processes, to assess the viability of the model approach and the influence of specific environmental factors in a permafrost environment. Three mountainous permafrost watersheds were studied, at the Kolyma Water Balance Station in north-eastern Russia. The watersheds include rocky talus, mountainous tundra and moist larch-forest landscape regimes, and they were modelled at daily time-steps for the period 1971–1984. Simulated results of soil freeze-thaw depth and runoff showed reasonable agreement with observed values. This study reveals and mathematically describes the dependence of surface and subsurface flow on thawing depth and landscape characteristics. Process analysis and modelling in permafrost regions, including ungauged basins, is suggested, with observable properties of landscapes being used as model parameters, combined with an appropriate level of physically based conceptualization. 相似文献
44.
Cd, Cu, Fe, Mn, Ni, Pb, Zn concentration in the organs (muscle, gonads, mantle, gills, digestive gland, kidney) of mussel Modiolus modiolus was studied. Mussels were collected from shelf upwelling sites of Kuril Is. Sea of Okhotsk (104 and 85 m) and, for comparison, coastal high contaminated and clean sites (Peter the Great Bay, Sea of Japan). It was found that mussels from shelf upwelling regions accumulated unusually high Cd concentration in studied organs, excepting digestive gland. Shelf mussels have evolved passive adaptation to elevated level of ambient heavy metals (distribution of heavy metal load between all organs, especially, muscle). In contrast, mussels from high contaminated sites have evolved active adaptation (strong regulation of metal concentration in the organs at the maximal permissible concentration due to increased kidney function). We supported that under natural condition, passive adaptation of aquatic organisms to increased ambient metal level have been evolved only under constant low-water temperature. 相似文献
45.
Nino MATESHVILI Giuli MATESHVILI Iuri MATESHVILI Lev GHEONDJIAN Olga AVSAJANISHVILI 《Meteoritics & planetary science》1999,34(6):969-973
Abstract— Photometric observations of the twilight sky were carried out during Leonids 1998. The obtained vertical distributions of aerosol between 20 and 140 km demonstrate the processes of the intrusion of fine meteor dust and its subsequent intra-atmospheric dynamics. The characteristic radii of two fractions of the meteor dust particles were estimated by their sedimentation velocities. They varied within rp = 0.006–0.06 μm and rp = 19–81 μm limits depending on an assumed particle density within ρp = 0.4–4.0 g cm?3. The assumption of ρp = 2.0 g cm?3 gave radii of the two fractions to be 0.01 and 30 μm, respectively. 相似文献
46.
We have investigated the frustule ultrastructure of Baikalian Aulacoseira: A.baicalensis (K.Meyer) Sim. and of thin-wall, spore-producing Aulacoseira which has long been designated as A. islandica (O.Muller) Sim. or A.islandica ssp. helvetica (O.Muller) Sim. (now A.skvortzowii Edlund, Stoermer,Taylor). It was found that the disagreement on the name of spore-forming Aulacoseira is due to the destruction of its vegetative frustules in the process of breaking free of the organic content, while ultrastructure data on A.islandica from different Russia''s regions can reflect signatures of different species.A. baicalensis is characterized by great polymorphism. A. baicalensis starts its development from the initial cell (auxospore). The morphological characteristics of the frustule undergo the drastic changes in the course of the life cycle. It sequentially changes the morphology and structure of its valves. Its cells evolve through several stages of development:from cyclotella-like cells to narrow and short reproducing cells. In the influence zone of the Baikalsky Pulp-and-Paper Plant (BPPP), waste waters, disturbances in the frustule structure both in vegetative and generative cells have been detected. 相似文献
47.
Upper Cambrian to Middle Ordovician radiolarian chert successions from Kazakhstan were studied to clarify the history of the emergence of benthic animals in ocean floor sediments. Radiolarian tests and clay were deposited for a period of 30 Myr without experiencing an influx of continent-derived coarse clastic materials. Red, grey and black cherts of the Upper Cambrian to the upper mid-Darriwilian are thinly laminated, and no trace of benthic animal activity is recognized in that time interval. Bioturbation structures and burrow traces in mid-Darriwilian stage red chert in Kazakhstan suggest that benthic animals colonized the location where radiolarian chert formed, but that there was a significant delay in colonization when compared with similar reported occurrences in Australia and Canada. 相似文献
48.
49.
Olga V. Babanazarova 《International Journal of Salt Lake Research》1997,6(3):217-231
Phytoplankton and its production in water-bodies of the lower Amu Dar'ya were investigated in 1984–1989. The structure and
functional nature of the phytoplankton in the water-bodies studied were analogous to those of the littoral zone of eutrophic
lakes, considering hydrological and hydrochemical conditions. The very high average annual P/B ratios (453–582) are considered
as regional features, namely high light intensity and prolonged light period, the salinity usual for saline waters under anthropogenic
influence, the frequent and discrete income of nutrients in drainage water and from sediments. 相似文献
50.
Olga I. Vendina 《GeoJournal》1997,42(4):349-363
Major trends of social restructuring of Moscow population and processes of intra-urban segregation are discussed. The article comprises two main parts. The first part deals with differences between the population of Moscow and that of Russia based on the main socio-economic indicators. In the second part, emphasis is placed on the urban processes of social stratification of the population on the basis of analysis of the demographic and employment patterns of the population and peculiarities of the functioning housing market. The merging of top government officials and new business elites is stressed. A conclusion is drawn about the variation of the character of urban population differentiation and its transition to a stage of property-based spatial segregation. 相似文献