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31.
Manjiri Bhat Sanjeev Dhurandhar Naresh Dadhich 《Journal of Astrophysics and Astronomy》1985,6(2):85-100
We have studied in detail the energetics of Kerr-Newman black hole by the Penrose process using charged particles. It turns out that the presence of electromagnetic field offers very favourable conditions for energy extraction by allowing for a region with enlarged negative energy states much beyondr = 2M, and higher negative values for energy. However, when uncharged particles are involved, the efficiency of the process (defined as the gain in energy/input energy) gets reduced by the presence of charge on the black hole in comparison with the maximum efficiency limit of 20.7 per cent for the Kerr black hole. This fact is overwhelmingly compensated when charged particles are involved as there exists virtually no upper bound on the efficiency. A specific example of over 100 per cent efficiency is given. 相似文献
32.
N. D. R. Bhat F. Camilo J. M. Cordes D. J. Nice D. R. Lorimer S. Chatterjee 《Journal of Astrophysics and Astronomy》2002,23(1-2):53-57
The on-going Parkes multibeam survey has been astoundingly successful (Manchesteret al. 2001), and its discovery of over 600 pulsars has opened up new avenues for probing the Galaxy’s electron content and magnetic
field. Here we report on recent observations made with the Arecibo 305-m telescope, where 80 distant, high dispersion measure
pulsars (of which 35 are from the multibeam survey) were studied at multiple frequency bands in the range 0.4–2.4 GHz, in
order to determine their scattering properties, rotation measures and spectral indices. The results will be used to meet a
variety of science goals; viz., creating an improved model of the electron density, mapping out the Galactic magnetic field,
and modeling the pulsar population. 相似文献
33.
M. L. Sapru A. K. Tickoo I. K. Kaul S. K. Kaul C. L. Bhat R. K. Kaul H. S. Rawat V. K. Senecha R. C. Rannot H. Razdan 《Journal of Astrophysics and Astronomy》1990,11(2):141-150
This paper presents a novel technique to derive the absolute time of occurrence of an event with an accuracy of < 200 μs by
adapting the HF time synchronization technique to correct for the aging rate and the frequency drift of a temperature-controlled
quartz frequency standard. The propagation delay suffered by the HF time signals has been estimated by monitoring the clock
error with respect to time signals from five broadcast stations located at distances in the range 500–3700 km from Gulmarg.
Using simulated data, we further show the viability of this technique in permitting periodicity searches on timescales of
≥5 milliseconds in cosmic gamma-ray data
An erratum to this article is available at . 相似文献
34.
Yudhbir?SinghEmail author G.?M.?Bhat Vinay?Sharma S.?K.?Pandita K.?K.?Thakur 《Journal of the Geological Society of India》2012,80(3):435-439
In February 2009, a huge landslide occurred at Assar in Doda district of Jammu and Kashmir state. The slide triggered after the reservoir level of the Baglihar dam increased from initial water level of 850 m to 870 m. The impounding of reservoir water created high angle scarps at number of fossil slide sites on either side of the river within the reservoir area. One such scarp (about 250 m long) at Assar caused a huge landslide washing out about 150 m road stretch. The sliding material is dominated by finer fraction (71.5 %) of micaceous silty sand and coarser fraction of gravel to boulder size. Over saturation of the slope forming material, weak rocks and high absorption and swelling nature of the soil, high slope angle and toe cutting by the water are the main reasons that triggered this slide. 相似文献
35.
Irfan Maqbool Bhat Talat Ahmad D.V. Subba Rao Srinivasan Balakrishnan N.V. Chalapathi Rao 《地学前缘(英文版)》2021,12(3):101118
Present study reports the PGE-geochemistry of mantle peridotites and Nd-isotope geochemistry of arc related mafic rocks from the Indus Suture Zone (ISZ), western Ladakh. The total PGE concentration of the Shergol and Suru Valley peridotites (∑PGE = 96–180 ppb) is much higher than that of the primitive mantle and global ophiolitic mantle peridotites. The studied peridotites show concave upward PGE-distribution patterns with higher palladium-group PGE/Iridium-group PGE ratios (i.e., 0.8–2.9) suggesting that the partial melting is not the sole factor responsible for the evolution of these peridotites. The observed PGE-distribution patterns are distinct from residual/refractory mantle peridotites, which have concave downward or flat PGE-distribution patterns. Relative enrichment of palladium-group PGE as well as other whole-rock incompatible elements (e.g., LILE and LREE) and higher Pd/Ir ratio (1.1–5.9) reflects that these peridotites have experienced fluid/melt interaction in a supra-subduction zone (SSZ) tectonic setting. Also, the Shergol mafic intrusives and Dras mafic volcanics, associated with the studied peridotites, have high 143Nd/144Nd ratios (i.e., 0.512908–0.513078 and 0.512901–0.512977, respectively) and positive εNd(t) (calculated for t = 140 Ma) values (i.e., +5.3 to +8.6 and + 5.1 to +6.6, respectively), indicating derivation from depleted mantle sources within an intra-oceanic arc setting, similar to Spongtang and Nidar ophiolites from other parts of Ladakh Himalaya. The transition from SSZ-type Shergol and Suru Valley peridotites to Early Cretaceous tholeiitic Shergol mafic intrusives followed by tholeiitic to calc-alkaline Dras mafic volcanics within the Neo-Tethys Ocean exhibit characteristics of subduction initiation mechanism analogous to the Izu-Bonin-Mariana arc system within western Pacific. 相似文献
36.
Orography profoundly influences seasonal rainfall amount in several places in south Asia by affecting rain intensity and duration. One of the fundamental questions concerning orographic rainfall is nature of the associated precipitating clouds in the absence of synoptic forcing. It is believed that these clouds are not very deep, however, there is not much information in the literature on their vertical structure. The present study explores the vertical structure of precipitating clouds associated with orographic features in south Asia using data collected with the precipitation radar on board the Tropical Rainfall Measuring Mission satellite. Two types of precipitating clouds have been defined based on cloud echo top height, namely, shallow echo-top cloud and medium echo-top cloud. In both, radar reflectivity factor is at least 30 dBZ at 1.5 km altitude, and tops of shallow and medium echo-top clouds lie below 4.5 km and between 4.5 and 8 km, respectively. The Western Ghats contains the highest fraction of the shallow echo-top clouds followed by the adjacent eastern Arabian Sea, while the Khasi Hills in Meghalaya and Cardamom Mountains in Cambodia contain the least fraction of them. Average vertical profiles of shallow echo-top clouds are similar in different mountainous areas while regional differences are observed in the medium echo-top clouds. Below 3 km, precipitation liquid water content in medium echo-top clouds is the highest over the Western Ghats and the eastern Arabian Sea. The average precipitation liquid water content increases by \(0.16\,\hbox { gm m}^{-3}\) for shallow echo-top clouds between 3 and 1.5 km altitude, while the corresponding increase for medium echo-top clouds is in 0.05–0.08 \(\hbox { gm m}^{-3}\) range. 相似文献
37.
Mushtaq A. Wani J. A. Wani M. A. Bhat N. A. Kirmani Zahid M. Wani Shaista Nazir Bhat 《Journal of the Indian Society of Remote Sensing》2013,41(2):319-329
Soil nutrient maps based on intensive soil sampling are useful to adopt site-specific management practices. Geostatistical methods have been widely used to determine the spatial correlation and the range of spatial dependence at different sampling scales. If spatial dependence is detected, the modeled semivariograms can then be used to map the interested variable by kriging, an interpolation method that produces unbiased estimates with minimal estimation variance. The objectives of this paper were to examine and map the spatial distribution of the soil micronutrients Cu, Zn, Fe and Mn on an agricultural area in Kupwara, J&K, under temperate climatic conditions. The ordinary kriging was first used to determine the values for the non-sampled locations, and then the indicator approach was used to transform the micronutrient content values into binary values having the mean values of each nutrient as the threshold content. All four elements analyzed showed spatial dependence using the indicator semivariograms. The strength of spatial dependence was assessed using the values of nugget effect and range from the semivariogram, the fitted range values decreased in the order Zn > Cu > Mn > Fe. The spatial dependence of the combination of two or more of the studied micronutrients was also examined using indicator semivariograms. In opposition to spatial analysis of individual microelements, indicator semivariograms obtained for the binary coding of the variables showed a great nugget effect value or a low proportion of sill. The maps for each nutrient obtained using indicator kriging showed some similarity in the spatial distribution, suggesting the delimitation of uniform management areas. 相似文献
38.
39.
Denny P. Alappattu D. Bala Subrahamanyam P. K. Kunhikrishnan K. M. Somayaji G. S. Bhat R. Venkatesan C. B. S. Dutt A. Bagavath Singh V. K. Soni A. S. Tripathi 《Journal of Earth System Science》2008,117(1):281-291
Detailed measurements were carried out in the Marine Atmospheric Boundary Layer (MABL) during the Integrated Campaign for Aerosols, gases and Radiation Budget (ICARB) which covered both Arabian Sea and Bay of Bengal during March to May 2006. In this paper, we present the meteorological observations made during this campaign. The latitudinal variation of the surface layer turbulent fluxes is also described in detail. 相似文献
40.
Environmental isotopes including \({\updelta }^{18}\)O, \({\updelta }^{2}\)H and \(^{3}\)H of precipitation, streams and springs were determined in the mountainous Bringi catchment of Kashmir Himalaya, dominated by carbonate lithology. The isotopic signature of winter precipitation is reflected in stream and spring water in late spring and is, therefore, representative of snow melting. The spring waters in September bear the enriched isotopic signatures of summer rainfall. The strong correlation (\(r^{2} = 0.97\)) between the isotopic composition of streams and springs indicates the streams and springs either share similar catchments or the springs are recharged by the streams. Chloride mass balance and isotopic mass balance studies suggest that the surface recharge component averages 337.35 m\(^{3}\)/s, which is about 75% of total stream discharge during the high flow period. Similarly, the contribution of surface water to groundwater recharge during the low flow period averages 7.5 m\(^{3}\)/s, which is about 18.6% of total stream flow. Furthermore, the mean residence time of the springs calculated from the tritium decay equation is very short (<1 year). The residence time is longer for Kongamnag and short for Achabalnag, which is further supported by dye testing. 相似文献