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   

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   

From Mantle Transition Zone with Microstructures:A New Paradigm in Ophiolite Studies     

Souvik DAS 《《地质学报》英文版》2020,94(Z1):53-54

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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   

The Plagioclase-Magma Density Paradox Re-examined and the Crystallization of Proterozoic Anorthosites: a Discussion     

MUKHERJEE  AMALBIKASH; DAS  SUBHASISH 《Journal of Petrology》2002,43(10):1975-1978

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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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Tidal variations in the Sundarbans Estuarine System, India   总被引：1，自引：0，他引：1  

MEENAKSHI CHATTERJEE  D SHANKAR  G K SEN  P SANYAL  D SUNDAR  G S MICHAEL  ABHISEK CHATTERJEE  P AMOL  DEBABRATA MUKHERJEE  K SUPRIT  A MUKHERJEE  V VIJITH  SIDDHARTHA CHATTERJEE  ANWESHA BASU  MADHUMITA DAS  SARANYA CHAKRABORTI  ARAVIND KALLA  SURJA KANTA MISRA  SOUMYA MUKHOPADHYAY  GOPAL MANDAL  KANKAN SARKAR 《Journal of Earth System Science》2013,122(4):899-933

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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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