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1.
A. K. Pathak M. Sridhar Y. Harsha A. Markandeyulu B. V. S. N. Raju A. K. Chaturvedi 《Journal of the Geological Society of India》2017,89(6):675-678
Aravalli fold belt has witnessed major tectonism resulting in intense deformation and associated mafic magmatism. Recently acquired high resolution aeromagnetic data over central Aravalli fold belt brought out a conspicuous E-W trending magnetic anomaly extending for more than 35 km in length cutting across the whole succession of Aravalli Supergroup. This anomaly on ground is manifested as undeformed basic dyke intruding into metasediments of Aravalli Supergroup. The E-W trend and undeformed nature of these dykes suggest that they represent post Aravalli mafic magmatism which are emplaced sympathetic to the axial plane of F3 folding. 相似文献
2.
The process of drilling, in general, always produces sound. Though sound is used as a diagnostic tool in mechanical industry, its application in predicting rock property is not much explored. In this study, an attempt has been made to estimate rock properties such as uniaxial compressive strength, Schmidt rebound number and Young's modulus using sound level produced during rotary drilling. For this purpose, a computer numerical controlled vertical milling centre was used for drilling holes with drill bit diameters ranging from 6 to 20 mm with a shank length of 40 mm. Fourteen different rock types were tested. The study was carried out to develop the empirical relations using multiple regression analysis between sound level produced during drilling and rock properties considering the effects of drill bit diameter, drill bit speed and drill bit penetration rate. The F-test was used to check the validity of the developed models. The measured rock property values and the values calculated from the developed regression model are fairly close, indicating that the developed models could be efficiently used with acceptable accuracy in prediction of rock properties. 相似文献
3.
Chetana Jain Biswajit Paul Kaustubh Joshi Anjan Dutta Harsha Raichur 《Journal of Astrophysics and Astronomy》2007,28(4):175-184
We report here results from a new search for orbital motion of the accretion powered X-ray pulsar 4U 1626–67 using two different
analysis techniques. X-ray light curve obtained with the Proportional Counter Array of the Rossi X-ray Timing Explorer during
a long observation carried out in February 1996, was used in this work. The spin period and the local period derivative were
first determined from the broad 2–60 keV energy band light curve and these were used for all subsequent timing analysis. In
the first technique, the orbital phase dependent pulse arrival times were determined for different trial orbital periods in
the range of 500 to 10,000 s. We have determined a 3σ upper limit of 13 lt-ms on the projected semimajor axis of the orbit of the neutron star for most of the orbital period range,
while in some narrow orbital period ranges, covering about 10% of the total orbital period range, it is 20lt-ms. In the second
method, we have measured the pulse arrival times at intervals of 100 s over the entire duration of the observation. The pulse
arrival time data were used to put an upper limit on any periodic arrival time delay using the Lomb-Scargle periodogram. We
have obtained a similar upper limit of 10 lt-ms using the second method over the orbital period range of 500–10,000 s. This
puts very stringent upper limits for the mass of the compact object except for the unlikely case of a complete face-on orientation
of the binary system with respect to our line-of-sight. In the light of this measurement and the earlier reports, we discuss
the possibility of this system being a neutron star with a supernovae fall-back accretion disk. 相似文献
4.
U. Mukherjee H. Raichur B. Paul S. Naik N. Bhatt 《Journal of Astrophysics and Astronomy》2006,27(4):411-423
We report here results from detailed timing and spectral studies of the high mass X-ray binary pulsar 4U 1538-52 over several
binary periods using observations made with the Rossi X-ray Timing Explorer (RXTE) and BeppoSAX satellites. Pulse timing analysis
with the 2003 RXTE data over two binary orbits confirms an eccentric orbit of the system. Combining the orbitial parameters
determined from this observation with the earlier measurements we did not find any evidence of orbital decay in this X-ray
binary. We have carried out orbital phase resolved spectroscopy to measure changes in the spectral parameters with orbital
phase, particularly the absorption column density and the iron line flux. The RXTE-PCA spectra in the 3–20 keV energy range
were fitted ∼6.4 keV, whereas the BeppoSAX spectra needed only a power law and Gaussian emission line at ∼6.4 keV in the restricted
energy range of 0.3–10.0 keV. An absorption along the line of sight was included for both the RXTE and BeppoSAX data. The
variation of the free spectral parameters over the binary orbit was investigated and we found that the variation of the column
density of absorbing material in the line of sight with orbital phase is in reasonable agreement with a simple model of a
spherically symmetric stellar wind from the companion star. 相似文献
5.
U. Mukherjee S. Bapna H. Raichur B. Paul S. N. A. Jaaffrey 《Journal of Astrophysics and Astronomy》2006,27(1):25-35
We have investigated the Quasi Periodic Oscillation (QPO) properties of the transient accreting X-ray pulsar XTE J1858 + 034
during the second outburst of this source in April–May 2004. We have used observations made with the Proportional Counter
Array (PCA) of the Rossi X-ray Timing Explorer (RXTE) during May 14–18, 2004, in the declining phase of the outburst. We detected
the presence of low frequency QPOs in the frequency range of 140–185 mHz in all the RXTE-PCA observations. We report evolution
of the QPO parameters with the time, X-ray flux, and X-ray photon energy. Though a correlation between the QPO centroid frequency
and the instantaneous X-ray flux is not very clear from the data, we point out that the QPO frequency and the one day averaged
X-ray flux decreased with time during these observations. We have obtained a clear energy dependence of the RMS variation
in the QPOs, increasing from about 3% at 3 keV to 6% at 25 keV. The X-ray pulse profile is a single peaked sinusoidal, with
pulse fraction increasing from 20% at 3 keV to 45% at 30keV. We found that, similar to the previous outburst, the energy spectrum
is well fitted with a model consisting of a cut-off power law along with an iron emission line. 相似文献
6.
We have investigated the long-term flux variation in Cen X-3 using orbital modulation and pulsed fraction in different flux states using observations made with the All-Sky Monitor and the Proportional Counter Array on board the Rossi X-ray Timing Explorer . In the high state, the eclipse ingress and egress are found to be sharp whereas in the intermediate state the transitions are more gradual. In the low state, instead of eclipse ingress and egress, the light curve shows a smooth flux variation with orbital phase. The orbital modulation of the X-ray light curve in the low state shows that the X-ray emission observed in this state is from an extended object. The flux-dependent orbital modulations indicate that the different flux states of Cen X-3 are primarily due to varying degree of obscuration. Measurement of the pulsed fraction in different flux states is consistent with the X-ray emission of Cen X-3 having one highly varying component with a constant pulsed fraction and an unpulsed component and in the low state, the unpulsed component becomes dominant. The observed X-ray emission in the low state is likely to be due to scattering of X-rays from the stellar wind of the companion star. Though we cannot ascertain the origin and nature of the obscuring material that causes the aperiodic long-term flux variation, we point out that a precessing accretion disc driven by radiative forces is a distinct possibility. 相似文献
7.
Ocean Dynamics - Wave energy assessment at a regional scale is required for planning installation of wave energy converters. Based on continuously measured wave data at 14-m water depth in the... 相似文献
8.
Yuvraj Harsha Sreedhar Karl Rakos Gerhard Hensler 《Journal of Astrophysics and Astronomy》2014,35(1):55-68
Evolutionary models form a vital part of stellar population research in understanding their evolution, but despite their long history of development, they are often misrepresented and the properties of stellar population observed through broadband and spectroscopic measurements are also misinterpreted. With growing numbers of these synthesis models, model comparison becomes an important analysis to choose a suitable model for understanding stellar populations and model up-gradation. Along with model comparison, we reinvestigate the technique of modified Strömgren photometry to measure reliable parameter-sensitive colours and estimate precise model ages and metallicities. The assessment of Rakos/Schulz models with GALEV and Worthey’s Lick/IDS model find smaller colour variation: Δ(uz ? vz) ≤ 0.056, Δ(bz ? yz) ≤ ?0.05 and Δ(vz ? yz) ≤ 0.061. The study conveys a good agreement of GALEV models with modified Strömgren colours but with poor UV model predictions and observed globular cluster data, while the spectroscopic models perform badly because of outdated isochrone and stellar spectral libraries with inaccurate/insufficient knowledge of various stellar phases and their treatment. Overall, the assessment finds modified Strömgren photometry well suited to study different types stellar populations by mitigating the effects of age-metallicity degeneracy. 相似文献
9.
A. K. Pathak Harsha Yalla R. P. Singh A. K. Chaturvedi 《Journal of the Geological Society of India》2018,91(6):687-694
The Callovian-Oxfordian Kuldhar Member of Middle-Upper Jurassic Jaisalmer Formation, Rajasthan is characterized by a rich cephalopod (ammonites and belemnites) fauna along with other invertebrates. They are embedded in oolitic limestone, at places in nodular limestone, grey shale and occasional red mud. The belemnite rostra bear bioerosions in the form of borings of circular or elliptical type. The present study identified those as Trypanites isp. and Rogerella isp. and characterized the hitherto unnoticed bioerosions of these belemnite rostra to be post-mortal. Different dispositions of major diameter of belemnite rostra has been interpreted to represent churning effect of ichnofossil producing organisms which put evidences of several generations of omission surfaces. Vertical and horizontal orientations of stephanoceratid ammonites side by side have been critically analysed in the light of lithology and prevailing environmental condition and inferred to be an artifact of gravity and thixotropic property of clay. Ammonites like Stephanoceratids and Macrocephalitids inhabit within 110m depth which is also permissible depth of belemnites as well as probable depth of formation of oolites, carbonate mud and aluminosilicate mud. Considering the lithology of the rocks like oolites, carbonate mud, aluminosilicate, the habitat of stephanoceratid and habitat of acrothoracid barnacles (organisms responsible for Rogerella isp.), the environment has been delineated to be sublittoral which was previously designated as shoreface zone to offshore transition zone. 相似文献
10.