Influence of plate tectonics on the locations of geothermal fields     

Hemendra Acharya 《Pure and Applied Geophysics》1983,121(5-6):853-867

A number of geothermal fields explored so far in the circum-Pacific area occur along spreading ridges and subduction zones in areas of young tectonism and volcanism. A preliminary analysis, however, suggests that these geothermal fields are not situated along entire segments of plate boundaries but only at certain locations. In convergent zones these locations are (i) near the ends of plate boundary segments or (ii) in transverse zones that divide plates into several blocks 100–1000 km long. The locations of geothermal fields therefore appear to be influenced by plate geometry and correspond to lateral breaks in the continuity of the underthrusting plate.  相似文献   

Some studies in the resistivity of Indian sandstones     

Jagdeo Singh  B. P. Jha  U. B. Acharya 《Pure and Applied Geophysics》1972,98(1):153-162

Summary In this paper some measurements of the resistivity of Talchir and Barakar sandstones of the Jharia Coal field under dry and saturated conditions have been made and the results are discussed in the light of known theories. Techniques of measurement have been briefly described.  相似文献   

Silver losses from ammoniacal solutions on complex sulphide and chalcopyrite ammonia leach residues     

S. Acharya  S. Anand  R.P. Das 《International Journal of Mineral Processing》1987,20(3-4)

Extraction and subsequent loss of silver from leach liquor during oxidative ammonia leaching of complex sulphide and chalcopyrite concentrates have been observed. The lost silver value from the leach liquor was unrecoverable when the residues were treated with ammonia-ammonium sulphate buffer (pH=9.5) solutions at 27°C. However, when the same slurry was heated to 75°C in an autoclave under an atmosphere of oxygen, almost all the silver value could be redissolved. The leach residues lost their silver absorbance property from ammoniacal solutions on repeatedly heating and cooling the leached slurries in the presence of oxygen. In this work, silver losses from ammoniacal solutions on various leach residues, synthetic iron oxides, and freshly precipitated Fe(II) and Fe(III) hydroxides are reported. None of the major constituents present in the leach residues were responsible for the silver losses but small amounts of Fe(II) associated with the residues could take up silver from the leach solutions.  相似文献   

The ALICE instrument and the measured cosmic ray elemental abundances     

J.A. Esposito  E.R. Christian  V.K. Balasubrahmanyan  L.M. Barbier  J.F. Ormes  R.E. Streitmatter  B. Acharya  B. Luzietti  A. Hesse  U. Heinbach  W. Heinrich  M. Henkel  C. Pfeifer  M. Simon 《Astroparticle Physics》1992,1(1)

A Large Isotopic Composition Experiment (ALICE) is a balloon-borne spectrometer which can determine the elemental and isotopic composition of galactic cosmic rays with energies near 1 GeV/nucleon. ALICE was flown from Prince Albert, Canada in August 1987, and remained at float altitude (120000 feet) for 14.7 hours. In this paper, we describe the experimental methods and analysis which will be used for subsequent isotopic analysis. We obtained very precise charge resolution over the entire designed range: 0.10 and 0.16 charge units at neon and iron, respectively. Results on the galactic cosmic ray abundances and absolute fluxes of the elements from neon through nickel are reported.  相似文献   

Differential evolution of Lyman alpha lines     

M. Acharya  Pushpa Khare 《Journal of Astrophysics and Astronomy》1993,14(2):97-102

We have analysed a large, homogeneous sample of Lyman alpha lines, observed at intermediate resolution, using the maximum likelihood method. The analysis shows that the evolutionary index γ, is a function of rest equivalent width with stronger lines evolving faster. The mean equivalent width increases with redshift. This behaviour is similar to that exhibited by the heavy element absorption lines in the quasar spectra.  相似文献   

Gamma Ray and Hadron generated Čerenkov Photon Spectra at Various Observation Altitudes     

M. A. Rahman  P. N. Bhat  B. S. Acharya  V. R. Chitnis  P. Majumdar  P. R. Vishwanath 《Experimental Astronomy》2001,11(2):113-131

We study the propagation of erenkov photons generated by Very HighEnergy -rays and hadrons in the atmosphere. The photon productionheight distributions are estimated from semi-empirical methods andcompared with those derived by standard simulation techniques. Incidentspectra at various observation altitudes are then derived after applyingwavelength dependent corrections due to photon attenuation in theatmosphere during the propagation of photons from the height of productionto the height of observation. These are generated both for -ray and hadron primaries of various energies. The derivedproduction height distributions agree very well with those generated bythe simulation package `CORSIKA' at all energies and for both -ray and proton primaries. The incident photon spectra are found to beboth altitude and primary energy dependent. The peak ofthe incident spectrum shifts towards the shorter wavelength withincreasing altitude of observation for a given primary. Also the peak ofthe photon spectrum shifts towards the shorter wavelength withincreasing energy of the primary at a given altitude. The fraction of the UVcomponent in the incident erenkov spectrum is estimated both for-ray and hadronic primaries at various observation altitudes andenergies. Hadron generated erenkov spectra are marginally richer in UVlight and the difference increases slightly at higher altitudes. The fraction of the UV to the visible light in the erenkov spectrum could be a usefulparameter to separate -rays from cosmic ray background only if onecan measure this fraction very accurately.  相似文献   

Performance of GCMs for seasonal prediction over India��a case study for 2009 monsoon     

Nachiketa Acharya  Sarat C. Kar  U. C. Mohanty  Makarand A. Kulkarni  S. K. Dash 《Theoretical and Applied Climatology》2011,105(3-4):505-520

The 2009 drought in India was one of the major droughts that the country faced in the last 100?years. This study describes the anomalous features of 2009 summer monsoon and examines real-time seasonal predictions made using six general circulation models (GCMs). El Ni?o conditions evolved in the Pacific Ocean, and sea surface temperatures (SSTs) over the Indian Ocean were warmer than normal during monsoon 2009. The observed circulation patterns indicate a weaker monsoon in that year over India with weaker than normal convection over the Bay of Bengal and Indian landmass. Skill of the GCMs during hindcast period shows that neither these models simulate the observed interannual variability nor their multi-model ensemble (MME) significantly improves the skill of monsoon rainfall predictions. Except for one model used in this study, the real-time predictions with longer lead (2- and 1-month lead) made for the 2009 monsoon season did not provide any indication of a highly anomalous monsoon. However, with less lead time (zero lead), most of the models as well as the MME had provided predictions of below normal rainfall for that monsoon season. This study indicates that the models could not predict the 2009 drought over India due to the use of less warm SST anomalies over the Pacific in the longer lead runs. Hence, it is proposed that the uncertainties in SST predictions (the lower boundary condition) have to be represented in the model predictions of summer monsoon rainfall over India.  相似文献   

Concealed thrusts in the Middle Gangetic plain,India – A ground penetrating radar study proves the truth against the geomorphic features supporting normal faulting     

Pitambar Pati  B. Parkash  A.K. Awasthi  Vivekanand Acharya  Satvindar Singh 《Journal of Asian Earth Sciences》2011,40(1):315-325

As no evidence for thrusting has yet been reported from the Indo-Gangetic plain so, the Himalayan Frontal Thrust (HFT) has been considered to be the southern most limit of the Siwaliks to the Indo-Gangetic plain. The present study highlights the thrusting activities between the Gandak and Kosi megafan area in the Middle Gangetic plain. As these thrust sheets are concealed beneath thick sediment cover, direct surficial studies of the discontinuity planes are not possible. Further, the topographic breaks formed by the backward erosion of the uplifted thrust faces resemble normal faults with hanging walls to south. Due to gradual decreasing upliftment and/or erosion from north to south, the area shows a step like topographic appearance. Ground penetrating radar (GPR) studies reveal the concealed thrust planes beneath the sediments and the topographic breaks looking like normal faults are interpreted to be the relief created by backward erosion of the thrust sheets along with the overlying sediments. Out of four GPR profiles taken using 100 MHz antennae, three are across the topographic breaks along which most of the terminal fans are formed and one across the basement fault to study its subsurface nature. Initially GPR failed to strike any subsurface discontinuities at the topographic breaks. However, at certain distance to the south of the topographic breaks, GPR was able to strike the northerly dipping subsurface discontinuity planes. By combining the seismological signatures (distribution of earthquake epicenters) with geomorphology, these discontinuities are identified as thrusts. The GPR profiles show a gradual decrease of dip of the thrust planes from north to south across the area. Hence, by the geomorphology, seismological behavior, topography, orientation and continuity, other topographic breaks can be compared with the proven thrusts. GPR study on the basement fault revealed that the NE–SW trending basement faults are not active in the area. The compression between the South Muzaffarpur fault and the peninsular shield led to the generation of the N–S trending extensional Hathauri–Simariaghat fault with downthrown block towards east. Due to depth penetration limit, the GPR study was confined within 15 m depth. The presence of the discontinuity planes up to the base of the GPR profiles indicate their continuity at least up to the base of Holocene sediments. Although this study brought out the presence of concealed thrusts to the south of the HFT, more detailed work is needed further to study their depth extension, relation to the basement and their implication in Himalayan tectonics in a broad manner. At present, we consider these thrusts to be the splays of the HFT. For confirmation, we propose to carryout detail seismic surveys in future research work.  相似文献   

Interaction of accretion shocks with winds     

Kinsuk Acharya  Sandip K. Chakrabarti  D. Molteni 《Journal of Astrophysics and Astronomy》2002,23(1-2):155-164

Accretion shocks are known to oscillate in presence of cooling processes in the disk. This oscillation may also cause quasi-periodic oscillations of black holes. In the presence of strong winds, these shocks have oscillations in vertical direction as well. We show examples of shock oscillations under the influence of both the effects. When the shocks are absent and the flow is cooler, the wind becomes weaker and the vertical oscillation becomes negligible.  相似文献   

Training Programme on Hyperspectral Remote Sensing and Applications in Water Resources (HYPERWATER-2013)     

Sujay Bandyopadhyay  Tapas Acharya 《Journal of the Geological Society of India》2013,82(2):200-201

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