Variability of tropical error characteristics in the NCEP (MRF) lower tropospheric wind forecasts during two contrasting seasons     

S. De  D. R. Chakraborty 《Meteorology and Atmospheric Physics》2007,98(3-4):175-194

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Influence of fluvial‐tidal interactions on the nature of cross‐stratified packages in a deltaic setting: examples from the Barakar Coal Measure (Permian), Satpura Gondwana Basin,central India     

Sanjoy Kumar Ghosh  Chandan Chakraborty  Tapan Chakraborty 《Geological Journal》2005,40(1):65-81

Nine different types of cross‐stratified packages from the coal‐bearing, deltaic succession of the Barakar Formation (Permian) of the Satpura Gondwana Basin, central India, are described. The deposits are characterized by periodic mudstone drapes, reactivation surfaces including all other features suggestive of deposition from periodically unsteady, tidally‐influenced flows. The inferred flow patterns varied from purely bidirectional to pulsating unidirectional. The different types of cross‐stratified packages are interpreted to have resulted from superimposition of ebb‐oriented, steady, unidirectional fluvial currents of variable strength on the tidal flow in a deltaic setting. The study helps to distinguish cross‐strata that may develop in settings where fluvial and tidal currents interact. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Erratum to: Characterizing slope morphology using multifractal technique: a study from the western continental margin of India     

Chakraborty  Bishwajit  Karisiddaiah  S. M.  Menezes  A. A. A.  Haris  K.  Gokul  G. S.  Fernandes  W.  Kavitha  G. 《Natural Hazards》2015,77(1):127-127

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Askival: An altered feldspathic cumulate sample in Gale crater     

Donald Lewis Bowden  John C. Bridges  Agnes Cousin  William Rapin  Julia Semprich  Olivier Gasnault  Olivier Forni  Patrick Gasda  Debarati Das  Valerie Payré  Violaine Sautter  Candice C. Bedford  Roger C. Wiens  Patrick Pinet  Jens Frydenvang 《Meteoritics & planetary science》2023,58(1):41-62

Askival is a light-toned, coarsely crystalline float rock, which was identified near the base of Vera Rubin Ridge in Gale crater. We have studied Askival, principally with the ChemCam instrument but also using APXS compositional data and MAHLI images. Askival and an earlier identified sample, Bindi, represent two rare examples of feldspathic cumulate float rocks in Gale crater with >65% relict plagioclase. Bindi appears unaltered whereas Askival shows textural and compositional signatures of silicification, along with alkali remobilization and hydration. Askival likely experienced multiple stages of alteration, occurring first through acidic hydrolysis of metal cations, followed by deposition of silica and possible phyllosilicates at low T and neutral-alkaline pH. Through laser-induced breakdown spectroscopy compositional analyses and normative calculations, we suggest that an assemblage of Fe-Mg silicates including amphibole and pyroxene, Fe phases, and possibly Mg-rich phyllosilicate are present. Thermodynamic modeling of the more pristine Bindi composition predicts that amphibole and feldspar are stable within an upper crustal setting. This is consistent with the presence of amphibole in the parent igneous rocks of Askival and suggests that the paucity of amphiboles in other known Martian samples reflects the lack of representative samples of the Martian crust rather than their absence on Mars.  相似文献   

Discrimination between Babul plantations and Mustard crop using Polarimetric C- and L- band data     

R. L. Mehta  N. Parihar  A. Sinha  B. P. Shastri  M. Chakraborty 《Journal of the Indian Society of Remote Sensing》2014,42(2):439-444

Radar sensors can be used for large-scale vegetation mapping and monitoring using backscattering coefficients in different polarizations and wavelength bands. C-band space borne SAR is widely used for the classification of agricultural crops, but can only perform a limited discrimination of various tree species. This paper presents the results of discrimination between mustard crop and babul plantation (Prosopis sp.) using quad polarisation Radarsat 2 and ALOS PALSAR data. Study area is comprised of dense babul plantation along the canal, mustard crop on one side of the canal and Fallow land near to Ramgarh village of Jaisalmer district. Three bands of Radarsat (HH, HV and VV) acquired during peak mustard crop growth stage were integrated with four polarizations (HH, HV, VH and VV) of ALOS PALSAR acquired when crop cover was absent. Using only Radarsat data Jefferies-Matusita (JM) separability between mustard crop and babul plantation was found to be poor (710). Where as in the seven band combination the separability was observed to be high (1374). Among the different polarizations three layer combination, highest separability was observed using cross polarizations (HV and VH) of L-band with any one of the Radarsat Polarisation (HH/HV/VV). This combination of C- and L-band resulted in easy separation of mustard and babul plantation which was otherwise difficult using only Radarsat data.  相似文献   

Inflationary Solutions for Higher Dimensional Anisotropic Cosmological Model in Scalar-Tensor Theory II     

Subenoy Chakraborty  Tapan Kumar Ghosh 《Astrophysics and Space Science》1997,257(2):175-182

This is the second paper of the series where we have considered Brans-Dicke (B-D) theory as well as general scalar tensor theory of gravitation in higher dimensional space-time model in the false vacuum state. We have examined whether inflationary solutions are possible both for constant or variable coupling parameter ω. Also the nature of the scalar field and the coupling parameter are discussed in the asymptotic limit. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Nonlinear shift of wave parameters of whistlers in the ionosphere     

S. N. Paul  G. C. Das  A. K. Sur  B. Chakraborty 《Astrophysics and Space Science》1987,129(1):123-129

The expression for nonlinear shift of a wave number of a whistler wave propagating through the ionosphere has been derived and the results have been discussed. It is seen that nonlinear shift of a wave number of a whistler is significant in some physical situations. From numerical estimations it is observed that wave number shifts of a whistler for both the LCP and RCP waves become significant when the frequency of the waves are nearly equal to the ion-cyclotron frequency.  相似文献   

Propagation of plane relativistic shock waves in a slowly moving medium     

T. K. Chakraborty 《Astrophysics and Space Science》1980,68(2):469-474

Similarity solutions for the propagation of plane relativistic shock waves in a slowly moving medium, where the nucleon number density obeys an exponential law ofx/t, is obtained in this paper. The shock surface moves with constant velocity and the total energy of the disturbance is dependent on time. The solutions are applicable only to an isothermal medium.  相似文献   

Tectonothermal modelling for Sikkim Himalaya: Implications for channel flow to thrust tectonics in collision zones     

Dilip K. Mukhopadhyay  Sumit Chakraborty  Somnath Dasgupta 《《地质学报》英文版》2018,92(Z1):37-37

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Record of Leaf and Pollen cf. <Emphasis Type="Italic">Sloanea</Emphasis> (Elaeocarpaceae) from the Middle Siwalik of Darjeeling sub-Himalaya,India and its Palaeobiogeographic Implications     

Sandip More  Rajarshi Rit  Mahasin Ali Khan  Dipak Kumar Paruya  Suchana Taral  Tapan Chakraborty  Subir Bera 《Journal of the Geological Society of India》2018,91(3):301-306

Fossil leaf impressions and pollen grains comparable to modern Sloanea sp. of Elaeocarpaceae collected from the middle part of the Siwalik sediments (Geabdat Sandstone Formation; Pliocene) in Darjeeling foothills of eastern Himalaya are reported in the present communication. On the basis of macro morphological features, leaf remains are described as a new species Sloanea siwalika sp. nov. This is the first authentic record of the occurrence of leaf and pollen grains comparable to the genus Sloanea L. from the Cenozoic sediments of India and Asia as well. The recovery of this species and other earlier-described evergreen taxa from the same formation, suggests the existence of a tropical, warm and humid climatic conditions during the depositional period. The present study further suggests that after Pliocene the taxon might have shifted from Darjeeling Himalayan region to the adjoining southeast Asian land masses, due to possible climate change caused by post-Pliocene orogenic movement of the Himalaya.  相似文献