Pattern of sedimentation during the Late Paleozoic,Gondwanaland glaciation: An example from the Talchir Formation,Satpura Gondwana basin,central India   总被引：2，自引：0，他引：2  

Chandan Chakraborty  Sanjoy Kumar Ghosh 《Journal of Earth System Science》2008,117(4):499-519

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Dynamic Response of Machine Foundation on Layered Soil: Cone Model Versus Experiments   总被引：1，自引：0，他引：1  

P. K. Pradhan  A. Mandal  D. K. Baidya  D. P. Ghosh 《Geotechnical and Geological Engineering》2008,26(4):453-468

This paper presents the experimental validation of analytical solution based on cone model for machine foundation vibration analysis on layered soil. Impedance functions for a rigid massless circular foundation resting on a two layered soil system subjected to vertical harmonic excitation are found using cone model. Linear hysteretic material damping is introduced using correspondence principle. The frequency-amplitude response of a massive foundation is then computed using impedance functions. To verify the solution field experiments are conducted in two different layered soil systems such as gravel layer over in situ soil and gravel layer over concrete slab (rigid base). A total 72 numbers of vertical vibration tests on square model footing were conducted using Lazan type mechanical oscillator, varying the influencing parameters such as depth of top layer, static weight of foundation and dynamic force level. The frequency-amplitude response in general and in particular the resonant frequencies and resonant amplitudes predicted by cone model is compared with the results of experimental investigation, which shows a close agreement. Thus the cone model is reliable in its application to machine foundation vibration on layered soil.  相似文献   

Determination of true velocity dispersion and the dark matter problem in clusters of galaxies     

Amitabha Ghosh 《Astrophysics and Space Science》1995,227(1-2):41-52

According to the convention normally followed the redshifts of the galaxies in a cluster are assumed to be of purely dopplerian origin. The resulting velocity dispersion, when used in the virial theorem, leads to a very large proportion of dark matter to be present in the galaxy clusters. However, the recently proposed model of velocity dependent cosmic drag cause redshifts of photons and it is necessary to develop a procedure to determine the true velocity dispersion from the gross redshift data. A method for this has been presented in the paper. Coma and Perseus clusters have been investigated using this procedure and theM/L ratios for both were found to be approximately of the order of 30, i.e., approximately the order ofM/L ratios for individual galaxies. A study of them -z relation indicates that the galaxies with higher redshifts have fainter magnitudes. Distortion of the redshift plots and the typical elongation of the core regions along the line-of-sight is also explained.  相似文献   

Discovery of <Emphasis Type="Italic">Elephas</Emphasis> cf. <Emphasis Type="Italic">namadicus</Emphasis> from the late Pleistocene strata of Marginal Ganga Plain     

Rupa Ghosh  R. K. Sehgal  Pradeep Srivastava  U. K. Shukla  A. C. Nanda  D. S. Singh 《Journal of the Geological Society of India》2016,88(5):559-568

We describe an elephant skull recovered from a cliff section of Dhasan river of Marginal Ganga Plain. The dental morphology and cranial features of the skull have been compared with the known species of Elephas from the Indian subcontinent. Although it shows very near resemblance to Elephas namadicus, but being an isolated specimen its specific identity cannot be proclaimed with certainty. As such, the specimen is provisionally referred as E. cf. namadicus. The Optically Stimulated Luminescence ages place this find at ~56 ka BP. This is the first chronologically well constrained report of E. cf. namadicus from the Ganga Plain.  相似文献   

Characterizing the 2D shape complexity dynamics of the islands of Sundarbans,Bangladesh: a fractal dimension approach     

Sugata Hazra  Anirban Mukhopadhyay  Abhra Chanda  Parimal Mondal  Tuhin Ghosh  Sandip Mukherjee  Mashfiqus Salehin 《Environmental Earth Sciences》2016,75(20):1367

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Projected changes in area of the Sundarban mangrove forest in Bangladesh due to SLR by 2100     

Andres Payo  Anirban Mukhopadhyay  Sugata Hazra  Tuhin Ghosh  Subhajit Ghosh  Sally Brown  Robert J. Nicholls  Lucy Bricheno  Judith Wolf  Susan Kay  Attila N. Lázár  Anisul Haque 《Climatic change》2016,139(2):279-291

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Large phillipsite crystal as ferromanganese nodule nucleus   总被引：1，自引：0，他引：1  

A. K. Ghosh  Ranadhir Mukhopadhyay 《Geo-Marine Letters》1995,15(1):59-62

We report here the occurrence of, to date, the largest (21 × 10 × 8 mm) phillipsite crystal forming the nucleus of a diagenetically formed ferromanganese nodule from the Central Indian Ocean Basin (CIOB). Assuming an average rate of ferromanganese nodule accretion as ~ 2 mm/Ma and that of phillipsite growth as ~ 0.65 mm/Ka, the nucleus material appears to have been growing for ~4.5–5 Ma. Originally surfaced as a rock fragment from late Miocene volcanism, this nucleus was later altered to phillipsite under alkaline, silica-undersaturated, low-temperature conditions through the length of the Neogene sedimentary hiatus.  相似文献   

Geospatially based distributed rainfall‐runoff modelling for simulation of internal and outlet responses in a semi‐forested lower Himalayan watershed     

RAAJ Ramsankaran  U. C. Kothyari  S. K. Ghosh  A. Malcherek  K. Murugesan 《水文研究》2012,26(9):1405-1426

This study presents a Geographic Information System (GIS)‐based distributed rainfall‐runoff model for simulating surface flows in small to large watersheds during isolated storm events. The model takes into account the amount of interception storage to be filled using a modified Merriam ( 1960 ) approach before estimating infiltration by the Smith and Parlange ( 1978 ) method. The mechanics of overland and channel flow are modelled by the kinematic wave approximation of the Saint Venant equations which are then numerically solved by the weighted four‐point implicit finite difference method. In this modelling the watershed was discretized into overland planes and channels using the algorithms proposed by Garbrecht and Martz ( 1999 ). The model code was first validated by comparing the model output with an analytical solution for a hypothetical plane. Then the model was tested in a medium‐sized semi‐forested watershed of Pathri Rao located in the Shivalik ranges of the Garhwal Himalayas, India. Initially, a local sensitivity analysis was performed to identify the parameters to which the model outputs like runoff volume, peak flow and time to peak flow are sensitive. Before going for model validation, calibration was performed using the Ordered‐Physics‐based Parameter Adjustment (OPPA) method. The proposed Physically Based Distributed (PBD) model was then evaluated both at the watershed outlet as well as at the internal gauging station, making this study a first of its kind in Indian watersheds. The results of performance evaluation indicate that the model has simulated the runoff hydrographs reasonably well within the watershed as well as at the watershed outlet with the same set of calibrated parameters. The model also simulates, realistically, the temporal variation of the spatial distribution of runoff over the watershed and the same has been illustrated graphically. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Characterizing acidic fly ash with and without biomass combustion residue for adsorptive removal of crystal violet with optimization of mixed adsorbent by response surface modeling     

Sandip K. Ghosh  Amitava Bandyopadhyay 《Environmental Earth Sciences》2016,75(9):820

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Can an annual flood induce changes in channel geomorphology?     

Islam  Aznarul  Sarkar  Biplab  Saha  Ujwal Deep  Islam  Mainul  Ghosh  Susmita 《Natural Hazards》2022,111(1):1019-1046

The present study has been a pioneering effort examining the role of an annual flood as a potent stimulus inducing changes in channel geomorphology of the Mayurakshi River, India. Twenty cross sections have been considered for the measurement of various hydro-geomorphic attributes of the river in both the pre- and post-flood conditions in 2018. The study sensed an escalating trend for channel width, width/depth ratio, and wetted perimeter while the reverse was also detected for average depth, maximum depth, cross-sectional area, and hydraulic radius. For example, the width/depth ratio recorded an increase of?~?11%, and the hydraulic radius depicted a decrease of?~?8%. Furthermore, channel asymmetry, bed asymmetry and bed relief index experienced a decrease after the flood. The sudden hydraulic impulse during monsoon flood as manifested in velocity, discharge, specific stream power, Reynolds number, Froude number increases the erosivity of the fluid. Besides the hydraulic factors, bank material (massive sandbank susceptible to hydraulic action and mixed bank constituted by alternate bands of sand and silt, and vulnerable to failure by piping action) brings substantial changes in channel morphology. Moreover, anthropogenic interventions such as sand mining are found to play a significant role in channel behaviour. The role of the multiple factors driving the morphological changes of the cross sections has been unpacked using canonical component analysis.

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