Analysis of gravity gradients over a thin infinite sheet     

N. Sundararajan  I. Arun Kumar  N. L. Mohan 《Journal of Earth System Science》1987,96(1):11-14

A simple method to interpret gravity gradients over a thin infinite dipping sheet is discussed. The Hilbert transform is used to compute the vertical gradient from the horizontal gradient of the gravity field. The method is illustrated with a theoretical example.  相似文献   

Unsteady free-convective flow and mass transfer in a rotating porous medium with Hall current,I     

T. P. Singh  A. K. Agrawal  H. L. Agrawal  A. Raptis 《Astrophysics and Space Science》1991,181(2):171-181

The Hall effect on the unsteady hydromagnetic free-convection resulting from the combined effects of thermal and mass diffusion of an electrical-conducting liquid through a porous medium past an infinite vertical porous plate in a rotating system have been analysed. The expressions for the mean velocity, mean skin friction, and mean rate of heat transfer on the plate are derived. The effects of magnetic parameterM, Hall parameterm, Ekman numberE, and permeability parameterK ^* on the flow field are discussed with the help of graphs and tables.Nomenclature C _p specific heat at constant pressure - C the species concentration inside the boundary layer - C _w the species concentration at porous plate - C the species concentration of the fluid at infinite - C dimensionless species concentration - D chemical molecular diffusivity - E Ekman number - Ec Eckert number - g acceleration due to gravity - Gr Grashof number - Gm modified Grashof number - H ₀ applied magnetic field - (J _x, J_y, J_z) components of current density - M magnetic parameter - m Hall parameter - P Prandtl number - q _m mean rate of heat transfer - Sc Schmidt number - t time - t dimensionless time - T temperature of fluid - T _w temperature of the plate - T temperature of fluid at infinite - T dimensionless temperature - (u, v, w) components of the velocityq - w ₀ suction velocity - (x, y, z) Cartesian coordinates - z dimensionless coordinate normal to the plate Greek symbols coefficient of volume expansion - * coefficient of thermal expansion with concentration - frequency - dimensionless frequency - k thermal conductivity - K ^* permeability parameter - dinematic viscosity - density of the fluid in the boundary layer - coefficient of viscosity - _e magnetic permeability - angular velocity - electrical conductivity of the fluid - _m mean skin friction - _mn mean skin friction in the direction ofx - _mv mean skin friction in the direction ofy  相似文献   

Certain vacuum Bianchi-type models in a new relativistic theory of gravitation     

T. Singh  Anil K. Agrawal 《Astrophysics and Space Science》1991,179(2):223-235

The vacuum Bianchi type-I, III, V, VI₀ and Kantowski-Sachs models have been obtained in a new scalar-tensor theory formulated by Lau and Prokhovnik (1986) under the assumption of a certain relationship between the cosmological term and the scalar field . The dynamical behaviour of these models have been studied.  相似文献   

Effect of alcohol and polyglycol ether frothers on foam stability,bubble size and coal flotation     

Ashiwani Kumar Gupta  P.K. Banerjee  Arun Mishra  P. Satish  Pradip 《International Journal of Mineral Processing》2007

The frothers of alcohol family (MIBC and Alpha-terpineol) were compared with polyglycol ethers (DF-1012) in terms of two phase characterization parameters like foamability, foam stability, surface activity and bubble size distribution. In this research, fundamental two phase frother characterization parameters were linked with three phase coal flotation behavior.  相似文献   

Numerical simulation by a stretched-coordinate Ocean General Circulation Model: A preliminary results     

Arun Chakraborty  H. C. Upadhyaya  O. P. Sharma  Divya Jaisawal  S. K. Deb 《Meteorology and Atmospheric Physics》2003,83(3-4):197-220

Summary ?A three-dimensional Ocean General Circulation Model has been developed in stretched coordinate from scratch. The same model has been used to perform some numerical experiments to simulate the basic circulation pattern and the model variability to atmospheric forcing. For numerical simulations 72 × 25 grid points in the horizontal directions and nine (10, 30, 75, 250, 500, 1000, 1500, 2000 and 3000 m) vertical levels are considered. The lateral boundaries are set at 60° N and 60° S. The basic focus of the paper is on the demonstration of the performance of the model and its assessment by employing appropriate forcing from the outputs of an atmospheric general circulation model. Hence, the model was forced with the forcing (wind and thermodynamic) derived from the ECMWF runs from the AMIP archives. The preliminary results show the realistic simulation of basic pattern of different fields. The model simulations show that the model is able to reproduce some of the general features of the ocean, such as surface currents, surface temperature and salinity, mass transport and meridional heat transport. It is also to be noted that the model is capable to capture the El-Ni?o and La-Ni?a type events. Received April 3, 2002; revised June 6, 2002; accepted July 24, 2002 Published online: February 20, 2003  相似文献   

Geospatial network analysis for path optimisation in solid waste management - a case study of Haridwar (India)     

P. K. Joshi  M. Kumar  D. Agrawal 《Journal of the Indian Society of Remote Sensing》2004,32(4):387-392

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The ambient environment of the Gangetic sediments of chalcolithic period     

D P Agrawal  M N Deshpande  S N Rajaguru  Bhaskar Roy 《Journal of Earth System Science》1978,87(3):23-28

There is considerable controversy regarding the mode of deposition of the OCP culture-associated sediments in the Gangetic valley and their ecological implications. SEM and sedimentologic studies show a fluvial mode of deposition of sediments originally derived from a glacial environment.  相似文献   

A short-spread configuration for mapping dipping horizons in reflection seismic surveys     

D. N. Avasthi  M. C. Agrawal 《Pure and Applied Geophysics》1974,112(5):845-854

Summary In areas of steeply dipping seismic horizons, the conventional split-spread seismic reflection method may yield poor seismograms. In order to develop a suitable field technique to improve the record quality in such areas, an analysis of the effect of spherical divergence, reflection coefficient, and absorption on the amplitude of the signal reflected from a dipping interface has been carried out. It has been found that for a dipping interface the reflected signal amplitude in many cases may be higher for the larger angles of incidence at the reflecting bed than for the normal incidence. Thus, a suitable inline-offset spread in the updip direction is likely to increase the recorded reflected signal amplidute and improve the signal-to-noisre ratio in areas of dipping reflectors. The design of such a shot-spread configuration has been developed in this paper, and a field method using this configuration is suggested for continuous mapping of subsurface horizons.  相似文献   

Unsteady flow of a viscoelastic Maxwell fluid in a channel bounded by two concentric circular arcs under a radial magnetic field     

Arun Kumar Ghosh 《Pure and Applied Geophysics》1974,112(1):162-171

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Arcellaceans (thecamoebians) as indicators of land-use change: settlement history of the Swan Lake area, Ontario as a case study   总被引：1，自引：0，他引：1  

R. Timothy Patterson  Andrew Dalby  Arun Kumar  Lori A. Henderson  Robert E.A. Boudreau 《Journal of Paleolimnology》2002,28(3):297-316

Arcellaceans have been used as indicators of a variety of paleolimnological conditions including pH, eutrophication, oxygen level, and heavy metal contamination, but there has only been limited application of the group to climate and land-use change research. The limnological evolution of Swan Lake in southwestern Ontario was documented using arcellaceans as proxies, and compared to the results of a palynological analysis, with which it closely correlated. The palynological record documents the rapid disappearance of forest by around 1850 as the area was cleared for agriculture and settlements. The change was characterized by a shift in the palynological record from the Woodland to High Diversity assemblages. Similarly the arcellacean fauna changed from the Pre-European Settlement Assemblage to the distinctive low diversity, stressed environment European Deforestation Assemblage. The introduction of high-yield chemical fertilizers in the post World War II era, and the resultant eutrophication of the lake, was clearly recognizable in the palynological record as indicated by the dramatic increase in the algae Pediastrum (High Nutrient Assemblage). This change in farming practice was also identifiable with arcellacean proxies, as indicated by the appearance of the algalphilic Eutrophication Assemblage. The arcellacean Ecologically Destabilized Assemblage dominated the lake for short intervals during the transition between the Pre-European Settlement and European Deforestation assemblages and again at the transition between the European Deforestation and Eutrophication Assemblages, indicative of periods of ecological destabilization as the lake adjusted to new trophic inputs. A stressed environment arcellacean Ecologically Destabilized Assemblage found in a portion of the core estimated to have been deposited between AD 1350 and AD 1700 may provide evidence of an earlier phase of deforestation associated with Huron Indian agricultural practices. The close correlation between the palynological and arcellacean proxy data clearly demonstrates the potential of arcellaceans as land-use change proxies, and indicates that changes in land-use had an almost immediate impact on the Swan Lake ecosystem. This observation raises concerns about the impact that rapid urbanization is having on the environmentally sensitive Oak Ridges Moraine watershed, of which Swan Lake is a part.  相似文献