Torsional vibration of a twisted composite cylindrical shell of cylindrically aeolotropic materials     

Jayasri Datta 《Pure and Applied Geophysics》1971,92(1):36-44

Summary The paper is concerned with the determination of torsional vibration of a twisted composite cylindrical shell assuming the elastic constants to be proportional to the square of the distance from the axis of the shell. The solution is obtained in the form of a series in terms of Bessel functions.  相似文献   

Torsional vibration of an orthotropic Cylindrical Shell     

Jayasri Datta 《Pure and Applied Geophysics》1972,98(1):102-105

Summary This paper is concerned with the determination of torsional vibration of an orthotropic Cylindrical Shell assuming the elastic constants to be proportional to thenth power of the distance from the axis of the shell. The solution is obtained in terms of Bessel functions.c/o Dr. A. K. Dutta, P. 7. A H. B. Town, Block A, P. O. Sodepur, Dt. 24-Paraganas, West Bengal, India.  相似文献   

An instrument for seismic velocity measurements     

Satyabrata Datta 《Pure and Applied Geophysics》1965,62(1):35-40

Summary The construction and performance of an instrument for the measurement of seismic velocity in rock specimens is described. In the instrument, the transducer which receives the seismic velocity after its travel through the specimen has been excited by a method from a stable quartz crystal pulser to generate synchronised time markers at intervals of 110 millimicrosecs. The method of measurement is accurate and needs no calibration. The instrument is specially suited for the study of seismic velocity variations with pressure. The accuracy of measurement is about 1% in a 10 cm long sample in which the velocity is 6.40 km/sec.This paper is published by the kind permission of the Director General, Geological Survey of India.  相似文献   

Characterization and evaluation of processes governing the groundwater quality in parts of the Sabarmati basin,Gujarat using hydrochemistry integrated with GIS   总被引：1，自引：0，他引：1  

Kumari Rina  P. S. Datta  Chander Kumar Singh  Saumitra Mukherjee 《水文研究》2012,26(10):1538-1551

Intense agricultural and industrial activities in any area are likely to make groundwater vulnerable with respect to its quality. In one such area which is a part of Sabarmati river basin of Gujarat, factors influencing the groundwater hydrochemistry in pre‐ and post‐monsoon season were evaluated. Groundwater samples were collected from 5 km × 5 km grids on the basis of spectral signature of vegetation and soil, observed on satellite image. Integration of Conventional graphical plots, Piper plot, saturation index values (estimated using PHREEQC) and GIS was helpful not only to create the database for analysis of spatial variation in respective water quality parameters but also to decipher the hydrogeochemical process occurring in such a large area. USSL diagram and % sodium were used to characterise the suitability of groundwater for irrigation. It was observed that leaching of wastes disposed from anthropogenic activities and agrichemicals is the major factor influencing the groundwater quality, in addition to the natural processes such as weathering, dissolution and ion exchange. Sea water relics are also impacting the groundwater quality. Control of indiscriminate and unplanned exploitation of groundwater, application of fertilizers and disposal of industrial wastes in the affected areas can possibly ensure groundwater protection from further pollution and depletion. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

The Effects of Solar Eclipse of August 1, 2008 on Earth’s Atmospheric Parameters     

Syam Sundar De  B. K. De  B. Bandyopadhyay  B. K. Sarkar  Suman Paul  D. K. Haldar  S. Barui  Asim Datta  Syam Sundar Paul  Nikhilesh Paul 《Pure and Applied Geophysics》2010,167(10):1273-1279

Several experiments were undertaken at Kolkata (latitude: 22°34′N, longitude: 88°30′E) on the solar eclipse day of August 1, 2008 to observe the effects of the solar eclipse on Fair Weather Field (FWF) and VLF amplitude and phase. The experimental results presented here show significant deviations of the observed parameters from their normal values, as they are determined by the average of the records obtained on 5 days adjacent to the day of the solar eclipse.  相似文献   

The peculiar cluster MACS J0417.5-1154 in the C and X-bands     

Pritpal Sandhu  Siddharth Malu  Ramij Raja  Abhirup Datta 《Astrophysics and Space Science》2018,363(6):133

We present 5.5 and 9.0 GHz Australia Telescope Compact Array (ATCA) observations of the cluster MACSJ0417.5-1154, one of the most massive galaxy clusters and one of the brightest in X-ray in the Massive Cluster Survey (MACS). We estimate diffuse emission at 5.5 and 9.0 GHz from our ATCA observations, and compare the results with the 235 MHz and 610 MHz GMRT observations and 1575 MHz VLA observations. We also estimate the diffuse emission at low frequencies from existing GLEAM survey data (using the MWA telescope (http://www.mwatelescope.org)), and find that the steepening reported in earlier studies may have been an artefact of underestimates of diffuse emission at low frequencies. High-frequency radio observations of galaxy cluster mergers therefore provide an important complement to low-frequency observations, not only for a probing the ‘on’ and ‘off’ state of radio halos in these mergers, but also to constrain energetics of cluster mergers. We comment on the future directions that further studies of this cluster can take.  相似文献   

Assessing Li and other leachable geochemical proxies for paleo-salinity in lake sediments from the Mono Basin, CA (USA)     

Rahul Sahajpal  Saugata Datta  Sidney R. Hemming 《Geochimica et cosmochimica acta》2011,75(24):7855-7863

Regional climate-driven hydrological changes are accompanied by salinity changes in closed basin lakes. We have investigated acid leachable Li, along with other leachable ions including Mg, Ca and Sr, as geochemical proxies of salinity in lake sediments in the Mono Basin, California. All the elements in the acid leachable suite show a strong correlation with paleo-lake level estimates based on physical and stratigraphic evidence. The CaCO₃ content of lake sediments, which has been shown to be a reliable proxy for lake level changes in the Mono basin and the adjoining Owens Lake basin, corresponds well with our acid-leachable proxy data.  相似文献   

Spectral analysis of systems with non-classical damping using classical mode superposition technique     

R. S. Jangid  T. K. Datta 《地震工程与结构动力学》1993,22(8):723-735

A spectral method for random vibration analysis of a structural system with non-proportional damping is presented using classical (undamped) mode superposition technique. The method obtains the frequency response function of the system by solving the dynamic equilibrium equations in generalized co-ordinates through an iterative process. The iterative solution is written in closed form and the proof for convergence of the iterative process is given. Numerical examples show the convergence characteristics of the process and an excellent accuracy of the obtained results. The method turns out to be computationally more efficient than the conventional methods of spectral analysis using damped mode shapes and frequencies.  相似文献   

Evaluating sustainability of community endeavours in an Indian floodplain wetland using multi‐criteria decision analysis          下载免费PDF全文

Debajit Datta  Proshanta Kumar Ghosh 《Singapore journal of tropical geography》2015,36(1):38-56

The floodplain wetlands of Ganga‐Ichamati interfluves in India have become severely degraded due to incessant, unsustainable utilization practices and lack of community awareness. In spite of the wetlands being the prime source of livelihood for millions, no comprehensive management strategy to accommodate the diverse aspirations and priorities of different users has been implemented for the wetlands to date. In this paper, the authors applied a framework of criteria and indicators to evaluate the status of sustainability achieved by community endeavours in one such wetland. The priorities, consumption patterns and contributions towards wetland conservation of major user groups functioning in that area were assessed by the framework developed through participatory multi‐criteria decision analysis. Results show the deteriorating status of the wetland at present regarding biodiversity conservation and livelihood generation. Fishing activities were identified as the dominant utilization option here followed by agriculture. The paper further explored the preferred alternative utilization strategies for achieving sustainability. Effectiveness of the developed framework in evaluating the extent of sustainability achieved in community endeavours was also highlighted in this context.  相似文献   

Book Review     

Sujit S. Datta 《Pure and Applied Geophysics》2010,167(11):1457-1458

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