INDUCTION ANOMALY DUE TO AN ELONGATED COVERED ORE-ZONE EXCITED BY A LONG CURRENT CARRYING CABLE*     

J. G. NEGI  C. P. GUPTA  U. RAVAL 《Geophysical Prospecting》1972,20(1):193-211

A detailed analysis of the electromagnetic anomaly due to an elongated mineralized zone of low resistivity in presence of a fixed-transmitter (a long cable carrying an, alternating current Ie^Iωt) is presented where (i) the host rock is not highly resistive and might contain some disseminated mineralization, (ii) the ore-body has an inhomogeneous conductivity, (iii) there is a contrast in magnetic properties of the ore-body and the host rocks, and (iv) source is close to the conducting system i.e., anomalous zone is lying shallow. The numerical computation of the generalized analytical expressions have been made. The selective screening behaviour of the cover is delineated and suitable frequency ranges for maximum detectability of a covered conductor have been obtained. A paradoxical decrease of the in-phase component of the response function with the increase of the core conductivity has been found for large conductivities of the cover. For moderate values of response parameter the inhomogeneity in the conductivity is found to significantly affect the induced field. The present analysis of the various features of the secondary field will aid to the existing interpretation sensitivity of the induction prospecting data for porphyry conducting ore deposits with zonal wall-rock alteration and sulphide distributions.  相似文献   

Erratum to: Sand and clay mineralogy of sal forest soils of the Doon Siwalik Himalayas     

MUKESH  R K MANHAS  A K TRIPATHI  A K RAINA  M K GUPTA  S K KAMBOJ 《Journal of Earth System Science》2011,120(5):963-964

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The South India Precambrian crust and shallow lithospheric mantle: Initial results from the India Deep Earth Imaging Experiment (INDEX)     

S S RAI  KAJALJYOTI BORAH  RITIMA DAS  SANDEEP GUPTA  SHALIVAHAN SRIVASTAVA  K S PRAKASAM  K SIVARAM  SUDESH KUMAR  RISHIKESH MEENA 《Journal of Earth System Science》2013,122(6):1435-1453

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A mid to late Holocene record of palaeoclimatic changes from Nal Sarovar: a palaeodesert margin lake in western India     

SUSHMA PRASAD  SHEELA KUSUMGAR  S. K. GUPTA 《第四纪科学杂志》1997,12(2):153-159

With a view to obtain palaeoclimatic data from a climatically sensitive region we have studied core samples from Nal Sarovar, a large shallow lake lying within the palaeodesert margin of Thar in western India. A combination of C/N ratios and δ¹³C on a radiocarbon-dated core section have been used as climatic proxies. A high-resolution record extending back to ca. 6.6 ka BP has been reconstructed. The data indicate that, in the past, climate has varied from drier to wetter than present on time-scales of few hundreds to few thousands of years. There are, however, significant differences on the timing of these wet and dry periods, when compared with the available data from lakes farther north, in Rajasthan. Further, it looks unlikely that during the 6.6 ka the catchment areas of Nal Sarovar experienced such a significant increase in rainfall as has been suggested for the Rajasthan lakes. Interestingly, drier periods in Nal Sarovar data appear to correlate well with periods of glacier expansion in Eurasia indicating that the palaeoclimatic variations recorded in Nal Sarovar are a regional feature. © 1997 John Wiley & Sons, Ltd.  相似文献   

A NOTE ON DAMAGE-BASED INELASTIC SPECTRA     

B. BASU  V. K. GUPTA 《地震工程与结构动力学》1996,25(5):421-433

When a structure is subjected to moderate to severe ground motions, a few excursions of the response yield level may take place following the reductions usually enforced in the design forces. These excursions are associated with progressive damage in the structure. Thus, a choice of the design level has to be suitably based on the maximum damage to be allowed in the structure. In this paper, a stochastic technique of developing damage-based non-linear spectra has been proposed for the aseismic design of those structures which can be idealized through Single-Degree-Of-Freedom (SDOF) oscillators. The proposed technique has been illustrated by obtaining the non-linear spectra which can possibly be used for a damage-based design. Along with the spectra, allowable ductility demand which should be supplied through proper sizing and detailing of the members and is compatible with the damage has also been specified. The non-linear SDOF oscillators have been approximated for this purpose by equivalent linear oscillators using a new stochastic linearization technique. The proposed linearization technique has been validated through simulation results in the case of an idealized, non-hysteretic, Elasto-Plastic (EP) model.  相似文献   

A MARKOVIAN APPROACH TO ORDERED PEAK STATISTICS     

B. BASU  V. K. GUPTA  D. KUNDU 《地震工程与结构动力学》1996,25(12):1335-1351

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PROPAGATION OF TORSIONAL SURFACE WAVES IN VISCOELASTIC MEDIUM     

S. DEY  A. K. GUPTA  S. GUPTA 《国际地质力学数值与分析法杂志》1996,20(3):209-213

It is well known that an elastic homogeneous half-space does not allow torsional surface waves to propagate. The present paper attempts to find out the possibility of propagation of such waves in a viscoelastic half-space. The study reveals that although the homogeneous elastic half-space does not allow torsional surface waves to propagate, a viscoelastic half-space does so. The wave is damped due to the viscoelastic parameter. It has also been found that as the viscoelastic parameter decreases, the medium becomes elastic and the torsional surface waves ceases to propagate.  相似文献   

PERFORMANCE EVALUATION OF SUBMERGENCE RATIO OF A RECTANGULAR SUBMERGED VANE WITH A COLLAR     

Umesh P. GUPTA  Nayan SHARMA  C. S. P. OJHA 《国际泥沙研究》2006,21(1):42-49

1 INTRODUCTION Odgaard and Kennedy (1983) suggested that for values of angle of attack, α greater than or equal to approximately 20o, a persistent scour hole is produced near the upstream end of a vane. As α was reduced the number of vanes producing obj…  相似文献   

An isotopic investigation of a near-surface groundwater system     

S.K GUPTA 《水文科学杂志》2013,58(2):261-272

ABSTRACT

The distribution of environmental tritium, deuterium and oxygen-18 in the unsaturated zone and the underlying sandy phreatic aquifer was studied throughout 1981 in an area of high pine forests in the Rhine valley near Heidelberg. The observed vertical distribution of isotopes in the unsaturated zone can be satisfactorily explained by the combined use of a multi-cell model for moisture transport and an evapotranspiration model. The distribution in the underlying aquifer of the tracer input at the water table obtained using this method is found by replacing the total vertical diffusion coefficient in the diffusion equation with the dispersion coefficient. In this way observed tritium profiles are satisfactorily simulated for the period 1966–1981. The stable isotope profile in the unsaturated zone however remains largely unexplained due to inadequate data on the stable isotope content of precipitation over the investigated area.  相似文献   

OBSERVATIONS ON THE EFFECTS OF URBANIZATION ON RUNOFF AND SEDIMENT PRODUCTION IN SINGAPORE     

AVIJIT GUPTA 《Singapore journal of tropical geography》1982,3(2):137-146

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