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141.
Utpal Kumar Samanta Asit Saha Prasanta Chatterjee 《Astrophysics and Space Science》2013,347(2):293-298
Bifurcation behavior of nonlinear dust ion acoustic travelling waves in a magnetized quantum dusty plasma has been studied. Applying the reductive perturbation technique (RPT), we have derived a Kadomtsev-Petviashili (KP) equation for dust ion acoustic waves (DIAWs) in a magnetized quantum dusty plasma. By using the bifurcation theory of planar dynamical systems to the KP equation, we have proved that our model has solitary wave solutions and periodic travelling wave solutions. We have derived two exact explicit solutions of the above travelling waves depending on different parameters. 相似文献
142.
A. K. Saha M. K. Arora M. L. Virdi E. Csaplovics 《International journal of geographical information science》2013,27(10):1149-1175
Many parts of the world with young mountain chains, such as the Himalayas, are highly susceptible to landslides. Due to general ruggedness and steep slopes, roads provide the only way of transportation and connectivity in such terrains. Generally, landslide hazards are overlooked during route planning. In this study, in a test area in the Himalayas, various thematic layers, viz. landslide distribution, landslide hazard zonation, landuse/landcover, drainage order and lithology are generated and integrated using Remote Sensing–GIS techniques. The integrated data layer in raster form has been called a ‘thematic cost map’ and provides an estimate of the cost of route development and maintenance. The relative cost assignment is based on experts' knowledge. Route planning is based on neighbourhood analysis to find various movement possibilities from a pixel to its immediate neighbours. A number of patterns such as those analogous to movements in chess games have been considered. Two new neighbourhood patterns, named here Knight31 and Knight32, have been conceived in addition to commonly used Rook, Bishop and Knight patterns. The neighbourhood movement cost for moving from one pixel to a connected neighbour has been calculated for a 7×7 pixel window considering distance, gradient cost and thematic cost. Dijkstra's algorithm has been applied to compute the least‐cost route between source and destination points. A few examples are presented to show the utility of this approach for a landslide‐safe automatic route planning for a highly rugged hilly terrain. 相似文献
143.
G. Fiorentino G. Clementini M. Marconi I. Musella A. Saha M. Tosi R. Contreras?Ramos F. Annibali A. Aloisi R. van?der Marel 《Astrophysics and Space Science》2012,341(1):143-150
The cosmological distance ladder crucially depends on classical Cepheids (with P=3–80 days), which are primary distance indicators up to 33 Mpc. Within this volume, very few SNe Ia have been calibrated through classical Cepheids, with uncertainty related to the non-linearity and the metallicity dependence of their period–luminosity (PL) relation. Although a general consensus on these effects is still not achieved, classical Cepheids remain the most used primary distance indicators. A possible extension of these standard candles to further distances would be important. In this context, a very promising new tool is represented by the ultra-long period (ULP) Cepheids (P≳80 days), recently identified in star-forming galaxies. Only a small number of ULP Cepheids have been discovered so far. Here we present and analyse the properties of an updated sample of 37 ULP Cepheids observed in galaxies within a very large metallicity range of 12+log(O/H) from ∼7.2 to 9.2 dex. We find that their location in the colour-magnitude (V−I,V) diagram as well as their Wesenheit (V−I) index-period (WP) relation suggests that they are the counterparts at high luminosity of the shorter-period (P≲80 days) classical Cepheids. However, a complete pulsation and evolutionary theoretical scenario is needed to properly interpret the true nature of these objects. We do not confirm the flattening in the studied WP relation suggested by Bird et al. (Astrophys. J. 695:874, 2009). Using the whole sample, we find that ULP Cepheids lie around a WP relation similar to that of the LMC, although with a large spread (∼ 0.4 mag). 相似文献
144.
We study the effect of particle interaction models on the theoretical estimates of atmospheric antiproton flux by comparing the BESS observations of antiproton spectra with the spectra obtained by means of a full three dimensional Monte Carlo simulation program. For such a purpose, we use two popular microscopic interaction models, namely FLUKA and UrQMD, to simulate antiproton spectra at multiple observation levels. In this article, we further compare the atmospheric antiproton fluxes predicted by a few popular microscopic high energy particle interaction models with each other to get an idea about the influence of such models at energies beyond the BESS upper cutoff up to about 100 GeV. We find that the simulated antiproton flux has strong dependence on the choice of interaction models. The present analysis seems to further indicate that the theoretical prediction of galactic antiproton spectrum may be uncertain by an appreciable amount due to our limited knowledge of particle interaction characteristics. 相似文献
145.
Sandip Kumar Saha Vasant A. Matsagar Arvind K. Jain 《Bulletin of Earthquake Engineering》2016,14(4):1153-1175
Seismic fragility curves for fixed-base and base-isolated liquid storage tanks are developed under non-stationary earthquakes, and their seismic performance are compared. The correlation between different earthquake intensity measure (IM) parameters and peak response quantities of the base-isolated liquid storage tanks are investigated. The failure criteria are chosen based on (1) the elastic buckling strength of the tank wall, which is defined in terms of critical base shear and critical overturning moment, and (2) in terms of the critical isolation displacement. The uncertainty involved is considered in the earthquake characteristics. Non-stationary earthquake ground motions are generated using Monte Carlo (MC) simulation. Influence of the isolator characteristic parameters and modeling approaches on the seismic fragility of the base-isolated liquid storage tanks is also investigated. Peak ground acceleration is found to be the well correlated IM parameter with the peak response quantities of the base-isolated liquid storage tanks. Substantial decrease in the seismic fragility of the base-isolated liquid storage tanks is observed as compared to the fixed-base tanks. Significant influence of the isolator characteristic parameters on the seismic fragility of the base-isolated liquid storage tanks are reported in the present study. 相似文献
146.
Auromeet Saha Marc Mallet Jean Claude Roger Philippe Dubuisson Jacques Piazzola Serge Despiau 《Atmospheric Research》2008,90(2-4):195-ICNAA07
We present results of direct aerosol radiative forcing over a French Mediterranean coastal zone based on one year of continuous observations of aerosol optical properties during 2005–2006. Monthly-mean aerosol optical depth at 440 nm ranged between 0.1 and 0.34, with high Angstrom coefficient (α > 1.2). The single scattering albedo (at 525 nm) estimated at the surface ranged between 0.7 and 0.8, indicating significant absorption. The presence of aerosols over the Mediterranean zone during summer decreases the shortwave radiation reaching the surface by as much as 26 ± 3.9 W m− 2, and increases the top of the atmosphere reflected radiation by as much as 5.2 ± 1.0 W m− 2. The shortwave atmospheric absorption translates to an atmospheric heating of 2.5 to 4.6 K day− 1. Concerted efforts are needed for investigating the possible impact of the increase in heating rate on the maintenance of heat-waves frequently occurring over this coastal region during summer time. 相似文献
147.
148.
Hetu C. Sheth Jyotiranjan S. Ray Ranjini Ray Loÿc Vanderkluysen John J. Mahoney Alok Kumar Anil D. Shukla Partha Das Subhrashis Adhikari Bikashkali Jana 《Contributions to Mineralogy and Petrology》2009,158(3):357-380
Many tholeiitic dyke-sill intrusions of the Late Cretaceous Deccan Traps continental flood basalt province are exposed in
the Satpura Gondwana Basin around Pachmarhi, central India. We present field, petrographic, major and trace element, and Sr–Nd–Pb
isotope data on these intrusions and identify individual dykes and sills that chemically closely match several stratigraphically
defined formations in the southwestern Deccan (Western Ghats). Some of these formations have also been identified more recently
in the northern and northeastern Deccan. However, the Pachmarhi intrusions are significantly more evolved (lower Mg numbers
and higher TiO2 contents) than many Deccan basalts, with isotopic signatures generally different from those of the chemically similar lava
formations, indicating that most are not feeders to previously characterized flows. They appear to be products of mixing between
Deccan basalt magmas and partial melts of Precambrian Indian amphibolites, as proposed previously for several Deccan basalt
lavas of the lower Western Ghats stratigraphy. Broad chemical and isotopic similarities of several Pachmarhi intrusions to
the northern and northeastern Deccan lavas indicate petrogenetic relationships. Distances these lava flows would have had
to cover, if they originated in the Pachmarhi area, range from 150 to 350 km. The Pachmarhi data enlarge the hitherto known
chemical and isotopic range of the Deccan flood basalt magmas. This study highlights the problems and ambiguities in dyke-sill-flow
correlations even with extensive geochemical fingerprinting. 相似文献
149.
D. Purushothaman J. P. Mohakul Asit Saha K. T. Vidyadharan N. Rajendran 《Journal of the Geological Society of India》2009,73(6):744-746
Geochemical mapping has been carried out in Goa using soil/laterite and stream sediment as media. The geochemical maps for
U, Th, Nb and Ta show a conspicuous pattern in the NW part of Goa. The anomaly axis shows a NE-SW trend which is across the
formational trend. The nickel and copper distribution around Usgaon area, east of Ponda, have indicated anomalous signature
in the northern continuation of the Usgaon ultramafic complex. 相似文献
150.
Natural radioactivity measurements in beach sand along southern coast of Orissa,eastern India 总被引:1,自引:1,他引:0
The beach placer deposits in the southern coastal Orissa, India may have significant levels of radiation due to the presence
of Th and U bearing minerals such as monazite and zircon. In this study, Gopalpur and Rushikulya beach regions were selected
to study the ambient radiation environment. The average activity concentrations of radioactive elements such as 232Th, 238U and 40K of beach sand samples were measured by γ-ray spectrometry using a HPGe detector, and found to be much higher than the internationally
accepted values. The cross plots of eTh/eU and eTh/K inferred that the sand samples of Gopalpur and Rushikulya beach placer
deposit were deposited in leached uranium and an oxidising environment. The absorbed γ dose rate levels of the study areas
are similar to other monazite sand-bearing HBRAs of southern and southwestern coastal regions of India and of world. Different
radiation hazard indices were estimated for the present study area and were found to be much higher than the internationally
accepted values. Hence, Gopalpur and Rushikulya beach placer region can be considered as a high background radiation area
and a potential zone for radiogenic heavy mineral exploration. 相似文献