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441.
Narayan C. Ghosh Govinda C. Mishra Cornelius S. S. Sandhu Thomas Grischek Vikrant V. Singh 《Ground water》2015,53(5):794-805
The article presents semi‐analytical mathematical models to asses (1) enhancements of seepage from a canal and (2) induced flow from a partially penetrating river in an unconfined aquifer consequent to groundwater withdrawal in a well field in the vicinity of the river and canal. The nonlinear exponential relation between seepage from a canal reach and hydraulic head in the aquifer beneath the canal reach is used for quantifying seepage from the canal reach. Hantush's (1967) basic solution for water table rise due to recharge from a rectangular spreading basin in absence of pumping well is used for generating unit pulse response function coefficients for water table rise in the aquifer. Duhamel's convolution theory and method of superposition are applied to obtain water table position due to pumping and recharge from different canal reaches. Hunt's (1999) basic solution for river depletion due to constant pumping from a well in the vicinity of a partially penetrating river is used to generate unit pulse response function coefficients. Applying convolution technique and superposition, treating the recharge from canal reaches as recharge through conceptual injection wells, river depletion consequent to variable pumping and recharge is quantified. The integrated model is applied to a case study in Haridwar (India). The well field consists of 22 pumping wells located in the vicinity of a perennial river and a canal network. The river bank filtrate portion consequent to pumping is quantified. 相似文献
442.
443.
J. K. Ghosh J. Bhanja S. Purkayastha T. Samanta S. Sengupta 《Mathematical Geology》2002,34(5):505-528
A geological map is the representation, on a two-dimensional plane, of the disposition of three-dimensional rock bodies exposed on the earth's surface. The problem of mapping is essentially that of dividing an area into homogeneous subregions on the basis of the exposed rock types. Automatic Bayesian methods of model selection using default Bayes factors have been employed to solve the problem of choosing a set of boundaries between homogeneous subregions, assuming no complication excepting low-angle tilting affected rock bodies. The method is tested on two data sets. A sampling scheme for optimum allocation of observation points is also presented. 相似文献
444.
S. S. De B. K. Sarkar B. Ghosh Manasi Mal S. K. Adhikari 《Astrophysics and Space Science》1991,180(2):201-209
Magnetohydrodynamic formulation has been used to deduce the velocity distribution of the upper atmospheric movement caused by the auroral electric field at the thermospheric height. The expressions for Joule heating and viscous heating are obtained. Numerical analysis has been made to estimate their magnitudes as well as the rate of their variations with time. The results are presented graphically. 相似文献
445.
Arsenic (As) sorptivity and acetate (pH 4.8) and oxalate (pH 3.0) extractable iron levels were monitored for 180 d, during and after flooding of two As contaminated soils. The effects of three different organic matter supplements/amendments, for example farm yard manure (FYM), municipal solid waste compost (MSWC) and sewage-sludge (SS) on the above parameter were also examined. In nonflooded soils, As sorptivity was mainly influenced by clay content. On flooding, there were large increases in acetate, oxalate extractable iron and As sorptivity. Organic matter addition increased the same parameters. Among the organic matters, SS showed greater effect on As sorption followed by MSWC and FYM. During flooding, As sorption is mainly dependent upon poorly crystalline iron oxide. During oxidation of previously flooded soils, levels of As sorptivity, acetate and oxalate extractable iron decreased rapidly, but did not return to the levels occurring before reduction. SS and MSWC served as binding agents for native and irrigation water As, thereby moderating the rapid As mobilization to the crop rizosphere. 相似文献
446.
Amitabha Ghosh 《Journal of Astrophysics and Astronomy》1997,18(4):449-454
The paper shows that a phenomenological model of inertial induction based on a proposed extension of Mach’s Principle can
produce the observed cosmological red shift in a quasi-static infinite universe. Unlike all other theories (except the Doppler
effect) to explain the observed red shift this model can be verified from other local effects predicted by this mechanism.
A number of such phenomena have been investigated and these expected effects are not only found to be present but they also
explain a number of unexplained or ill explained observational results. It is suggested that attempts should be made to verify
the model through further tests and observations. 相似文献
447.
Many granitic bodies intrude the basement gneisses in Meghalaya Plateau, Northeast India. Rb-Sr whole-rock isotopic ages of the granitoids range from 881 to 479 Ma while the ages of the basement orthogneisses vary from 1714 to 1150 Ma. All the plutons are dominantly metaluminous and show geochemical variation. Oxygen isotopic compositions in the granitoids and gneisses are concordant (d18O: + 5.78% to + 8.70%). However, the gneisses from high-grade terrain have low d18O value of +2.52% to +5.31%. Initial 87Sr/86Sr (ISr) ratios of the plutons vary from 0.70459 to 0.71487 and tend to increase with progressive younging in age. The geochemical characters suggest derivation of the granites from lower crustal source. The fractionated rare earth patterns observed in the granitoids can be obtained by partial melting of gneisses or diorites. Some gneiss samples have experienced interaction with hydrothermal fluids resulting in lowering d18O. The isotopic ages of granite plutonism in Meghalaya are similar to the plutonic and tectonothermal events in other parts of India, southwestern Australia and document final amalgamation events of the Gondwana Supercontinent. 相似文献
448.
V. N. Sridhar R. P. Singh Anjum Mahtab Ranendu Ghosh 《Journal of the Indian Society of Remote Sensing》2005,33(2):339-344
This paper reports a study on multi-temporal polarized response of wheat crop from spaceborne ADEOS-POLDER sensor over a homogeneous
wheat region of Punjab, India. Both the polarized as well as total reflectance of wheat were observed at different scattering
angles for two spectral bands i.e. 670 nm and 865 nm during crop growth from November to April in rabi 1996-97 season. Results
show that sun-target-viewing geometry plays an important role in polarization property. The top of atmosphere (TOA) polarized
reflectance is found to decrease exponentially with increasing scattering angle. Polarized reflectance of crop was found to
be an order of magnitude smaller in comparison to the total reflectance. An attempt was also made to model the observed polarized
behavior over an agricultural area using a theoretical simplified crop reflectance model and accounting for atmospheric molecular
(Rayleigh) contribution in the single scattering approximation. It was found that there was a decrease in the polarized reflectance
at the grain filling (heading) stage of wheat crop. This is in accordance with ground- based observations and can be due to
the reduction in the specular component of the reflected light during post-heading stage of the crop. 相似文献
449.
Upper bound solutions of bearing capacity of strip footing by pseudo-dynamic approach 总被引:1,自引:0,他引:1
Priyanka Ghosh 《Acta Geotechnica》2008,3(2):115-123
This paper presents the pseudo-dynamic analysis of seismic bearing capacity of a strip footing using upper bound limit analysis.
However, in the literature, the pseudo-static approach was frequently used by several researchers to compute the seismic bearing
capacity factor theoretically, where the real dynamic nature of the earthquake accelerations cannot be considered. Under the
seismic conditions, the values of the unit weight component of bearing capacity factor N
γE are determined for different magnitudes of soil friction angle, soil amplification and seismic acceleration coefficients
both in the horizontal and vertical directions. The results obtained from the present study are shown both graphically as
well as in the tabular form. It is observed that the bearing capacity factor N
γE decreases significantly with the increase in seismic accelerations and amplification. The results are thoroughly compared
with the existing values in the literature and the significance of the present methodology for designing the shallow footing
is discussed. 相似文献
450.