Basin-Scale 3D Sedimentary Modelling: An Approach to Subdivide Baltic Sea Onshore Sediments for Land use and Construction     

Ojala  Antti E. K.  Virtasalo  Joonas J.  Lindsberg  Elina  Markovaara-Koivisto  Mira 《Geotechnical and Geological Engineering》2021,39(7):4855-4876

Geotechnical and Geological Engineering - Understanding the local stratigraphy and geometry of sediment units is necessary for successful 3D modelling and the prediction of ground behaviour and...  相似文献   

Reverse currents in fast magnetic reconnection     

Mira Jardine  Eric R Priest 《地球物理与天体物理流体动力学》2013,107(1-2):163-168

Abstract

It is suggested that reverse currents seen in recent numerical reconnection experiments (Biskamp, 1986; Forbes and Priest, 1983) are caused by the choice of outflow boundary conditions. The specification of the normal velocity at the outflow boundary may result in a mismatch in velocity at the diffusion region which is manifested as a spike of reverse current.  相似文献   

Structural pattern in the Precambrian rocks of Sonua-Lotapahar region,North Singhbhum,eastern India     

Dhruba Mukhopadhyay  Tapas Bhattacharya  Tapan Chakraborty  Arun Kanti Dey 《Journal of Earth System Science》1990,99(2):249-268

In the western part of the North Singhbhum fold belt near Lotapahar and Sonua the remobilized basement block of Chakradharpur Gneiss is overlain by a metasedimentary assemblage consisting of quartz arenite, conglomerate, slate-phyllite, greywacke with volcanogenic material, volcaniclastic rocks and chert. The rock assemblage suggests an association of volcanism, turbidite deposition and debris flow in the basin. The grade of metamorphism is very low, the common metamorphic minerals being muscovite, chlorite, biotite and stilpnomelane. Three phases of deformation have affected the rocks. The principal D1 structure is a penetrative planar fabric, parallel to or at low angle to bedding. No D1 major fold is observed and the regional importance of this deformation is uncertain. The D2 deformation has given rise to a number of northerly plunging major folds on E-W axial planes. These have nearly reclined geometry and theL ₂lineation is mostly downdip on theS ₂surface, though some variation in pitch is observed. The morphology of D2 planar fabric varies from slaty cleavage/schistosity to crenulation cleavage and solution cleavage. D3 deformation is weak and has given rise to puckers and broad warps on schistosity and bedding. The D2 major folds south of Lotapahar are second order folds in the core of the Ongarbira syncline whose easterly closure is exposed east of the mapped area. Photogeological study suggests that the easterly and westerly closing folds together form a large synclinal sheath fold. There is a continuity of structures from north to south and no mylonite belt is present, though there is attenuation and disruption along the fold limbs. Therefore, the Singhbhum shear zone cannot be extended westwards in the present area. There is no evidence that in this area a discontinuity surface separates two orogenic belts of Archaean and Proterozoic age.  相似文献   

Wave propagation in two layered medium under initial stresses     

Sukhendu Dey 《Pure and Applied Geophysics》1971,90(1):38-52

Summary In this paper, the frequency equation for phase velocity of waves propagated in a laminated medium consisting of two eleastic layers of finite thickness under initial stresses, has been obtained. It has been shown that when wave length becomes very small compared to the thickness of each layer, the wave approaches two Rayleigh waves at the two outer surfaces with the possibility of Stoneley waves at the interface. The propagation ofSH-waves in the composite medium under initial stresses has also been discussed. A particular case has been taken to find the velocity of Love wave in the homogeneous half space under initial compressive stresses.Biot's incremental deformation theory has been used.  相似文献   

Erratum to: Comparative Analysis of Phytoplankton Composition and Abundance over a Two-Decade Period at the Land<Emphasis Type="Italic">–</Emphasis>Ocean Boundary of a Tropical Mangrove Ecosystem     

Haimanti Biswas  Mitali Dey  Dipnarayan Ganguly  Tarun K. De  Sandip Ghosh  Tapan K. Jana 《Estuaries and Coasts》2010,33(2):395-398

Inter-annual variations of phytoplankton abundance and community organization were observed over a two-decade period along with the ancillary parameters at the land–ocean boundary associated with the Sundarban mangrove forest (21°32′ and 22°40′ N and 88°05′ and 89° E), along the NE Coast of the Bay of Bengal. The number of definable Bacillariophyceae species exceeded Dinophyceae taxa, and the total number of bloom-forming species declined from a maximum of ten in 2000 and a minimum of two in 2007. Blooms of the diatom Coscinodiscus radiatus were common in 2000 and 2007. Tide cycles and the onset of the monsoon season played important roles in diurnal and seasonal variability of phytoplankton. Phytoplankton biovolume showed seasonality, with the highest levels during post-monsoon periods and lowest levels during the monsoon period. Phytoplankton abundance was correlated to rainfall patterns, which may be altered by long-term changes in climate.  相似文献   

On the anomalous precipitation enhancement over the Himalayan foothills during monsoon breaks     

Ramesh K. Vellore  R. Krishnan  Jayant Pendharkar  Ayantika Dey Choudhury  T. P. Sabin 《Climate Dynamics》2014,43(7-8):2009-2031

An intriguing feature associated with ‘breaks’ in the Indian summer monsoon is the occurrence of intense/flood-producing precipitation confined to central-eastern parts of the Himalayan (CEH) foothills and north-eastern parts of India. Past studies have documented various large-scale circulation aspects associated with monsoon-breaks, however the dynamical mechanisms responsible for anomalous precipitation enhancement over CEH foothills remain unclear. This problem is investigated using diagnostic analyses of observed and reanalysis products and high-resolution model simulations. The present findings show that the anomalous precipitation enhancement over the CEH foothills during monsoon-breaks emerges as a consequence of interactions between southward intruding mid-latitude westerly troughs and the South Asian monsoon circulation in its weak phase. These interactions facilitate intensification of mid-tropospheric cyclonic vorticity and strong ascending motion over the CEH foothills, so as to promote deep convection and concentrated rainfall activity over the region during monsoon-breaks. Mesoscale orographic effects additionally tend to amplify the vertical motions and precipitation over the CEH foothills as evidenced from the high-resolution model simulations. It is further noted from the model simulations that the coupling between precipitation and circulation during monsoon-breaks can produce nearly a threefold increase of total precipitation over the CEH foothills and neighborhood as opposed to active-monsoon conditions.  相似文献   

From the Seam to the Stove: greenhouse gas assessment and the coal seam gas industry in Australia     

Mischa Vickas  Christopher Dey 《The Australian geographer》2015,46(1):73-90

In Australia, Coal Seam Gas (CSG) is a relatively new source of natural gas commonly advocated as a lower greenhouse gas (GHG) emissions alternative to coal. This study investigates how GHG emissions have been, and potentially could be, assessed within the Australian CSG industry. The research involved a document analysis of several Environmental Impact Statements (EISs) and consultant reports prepared as part of the Environmental Impact Assessment (EIA) process for major CSG projects in New South Wales (NSW) and Queensland (Qld). There were found to be inconsistencies in the conduct of greenhouse assessment by the CSG industry, including how complete and transparent assessments were, as well as how effectively they addressed project emission intensity and cumulative impacts. There were also found to be large inconsistencies between assessments carried out for Qld projects and those for NSW projects, likely because of differences in how assessment requirements are applied by planning bodies. This study also highlights how alternative assessment approaches, such as Cumulative Impact Assessment (CIA) and Strategic Environmental Assessment (SEA), have potential to enable a broader and more consistent understanding of emission sources that cross a range of geographical and project boundaries.  相似文献   

Copepod communities in the estuary and coastal plume of the Hudson River     

Jeanne C. Stepien  Thomas C. Malone  Mira B. Chervin 《Estuarine, Coastal and Shelf Science》1981,13(2):185-195

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Intercomparison and Evaluation of MM5 and Meso-NH mesoscale models in the stable boundary layer     

M. Bravo  T. Mira  M. R. Soler  J. Cuxart 《Boundary-Layer Meteorology》2008,128(1):77-101

Atmospheric numerical models depend critically on realistic treatment of the lower boundary conditions. In strongly thermally-stratified conditions, turbulence may be very weak and the models may find it difficult to produce a good forecast near the surface. Under clear skies and for weak synoptic winds the determining factors are the turbulent kinetic energy and surface-layer parameterizations, which can be very different between models. Here, two state-of-the-art mesoscale models (MM5 and Meso-NH) are operated under exactly the same conditions for two different nights over the Duero basin in the Iberian Peninsula: one night with a well-defined synoptic wind and a second with practically no horizontal pressure gradient. The models are inter-compared and checked against available information, and their performances are evaluated.  相似文献   

Members of the double pulsar system PSR J0737-3039: Neutron stars or strange stars?     

Manjari Bagchi  Jishnu Dey  Sushan Konar  Gour Bhattacharya  Mira Dey 《New Astronomy》2009,14(1):37-39

One interesting method of constraining the dense matter Equations of State is to measure the advancement of the periastron of the orbit of a binary radio pulsar (when it belongs to a double neutron star system). There is a great deal of interest on applicability of this procedure to the double pulsar system PSR J0737-3039 (A/B). Although the above method can be applied to PSR A in future within some limitations, for PSR B this method cannot be applied. On the other hand, the study of genesis of PSR B might be useful in this connection and its low mass might be an indication that it could be a strange star.  相似文献