CLASS B 1359 + 154: Modelling lensing by a group of galaxies     

Sunita Nair 《Journal of Astrophysics and Astronomy》2002,23(1-2):115-118

The recently discovered gravitationally lensed system CLASS B1359 +154 appears to have six detectable images of a single background source at a redshift of 3.235. A group of galaxies acts as the lens, at a redshift of ∼ 1. The present work identifies two distinct, physically plausible image configurations, a 7-image one and a 9-image one. Mass models are constructed corresponding to realizations of these two configurations. Both models call for, in addition to non-singular galaxy-type lenses, a larger scale mass component that resembles the extended dark matter distributions seen in relatively low-redshift galaxy groups. It is presently observationally impossible to study the extended X-ray emission from a group at such a high redshift, hence lensing studies are of some interest. A lensed system with a high image multiplicity does not necessarily admit of a unique lensing interpretation; discrimination is possible with additional observable details (e.g., the image parities, which are uncommon among even the simpler systems).  相似文献   

Nonlinear electrodynamics in f(T) gravity and generalized second law of thermodynamics     

M. Sharif  Shamaila Rani 《Astrophysics and Space Science》2013,346(2):573-582

In this paper, we study the nonlinear electrodynamics in the framework of f(T) gravity for FRW universe along with dust matter, magnetic and torsion contributions. We evaluate the equation of state and deceleration parameters to explore the accelerated expansion of the universe. The validity of generalized second law of thermodynamics for Hubble and event horizons is also investigated in this scenario. For this purpose, we assume polelike and power-law forms of scale factor and construct f(T) models. The graphical behavior of the cosmological parameters versus smaller values of redshift z represent the accelerated expansion of the universe. It turns out that the generalized second law of thermodynamics holds for all values of z with Hubble and event horizons in polelike scale factor whereas for power-law form, it holds in a specific range of z for both horizons.  相似文献   

Intercomparison of Air–Sea Interface Fluxes over the Yellow Sea and Korea Strait: Impact of Tsushima Warm Current     

D. Bala Subrahamanyam  Radhika Ramachandran  S. Indira Rani  P. K. Kunhikrishnan  B. Prasad Kumar 《Boundary-Layer Meteorology》2008,127(2):333-344

Surface-layer meteorological observations obtained from oceanic buoys over the Korean Strait and the Yellow Sea are used to estimate surface-layer turbulent fluxes of heat, moisture and momentum over the East-Asian Marginal Seas. Special emphasis is paid towards explanation of the impact of the Tsushima warm current flowing through the Korean Strait on air–sea interface fluxes. During the active phase of the Tsushima warm current, when the difference in sea surface temperature and air temperature becomes as large as 8°C, the sensible heat flux increases to a value of about 135 W m⁻², while the latent heat flux is around 200 W m⁻². The study attempts to broaden our understanding on the air-sea interaction processes over the Yellow Sea and Korean Strait.  相似文献   

Quasi-static Planar Deformation in a Medium Composed of Elastic and Thermoelastic Solid Half Spaces Due to Seismic Sources in an Elastic Solid     

Anil K. Vashisth  Kavita Rani  Kuldip Singh 《Acta Geophysica》2015,63(3):605-633

A two-dimensional problem of quasi static deformation of a medium consisting of an elastic half space in welded contact with thermoelastic half space, caused due to seismic sources, is studied. Source is considered to be in the elastic half space. The basic equations, governed by the coupled theory of thermoelasticity, are used to model for thermoelastic half space. The analytical expressions for displacements, strain and stresses in the two half spaces are obtained first for line source and then for dip slip fault. The results for two particular cases, adiabatic conditions and isothermal conditions, are also obtained. Numerical results for displacements, stresses and temperature distribution have also been computed and are shown.  相似文献   

Feeder and post Deccan Trap dyke activities in the northern slope of the Satpura Mountain: Evidence from new 40Ar-39Ar ages     

J.P. Shrivastava  R. Kumar  N. Rani 《地学前缘(英文版)》2017,8(3):483-492

We present new 40Ar-39 Ar plagioclase crystallization ages from the dykes exposed at the northern slope of the Satpura Mountain range near Betul-Jabalpur-Pachmarhi area,~800 km NE of the Western Ghats escarpment.Among the two plateau ages,the first age of 66.56±0.42 Ma from a dyke near Mohpani village represents its crystallization age which is either slightly older or contemporaneous with the nearby Mandla lava flows(63-65 Ma).We suggest that the Mohpani dyke might be one of the feeders for the surrounding lava flows as these lavas are significantly younger than the majority of the main Deccan lavas of the Western Ghats(66.38-65.54 Ma).The second age of 56.95±1.08 Ma comes from a younger dyke near Olini village which cuts across the lava flows of the area.The age correlates well with the Mandla lavas which are chemically similar to the uppermost Poladpur,Ambenali and Mahabaleshwar Formation lavas of SW Deccan.Our study shows that the dyke activities occurred in two phases,with the second one representing the terminal stage.  相似文献   

Evaluation of atmospheric corrections on hyperspectral data with special reference to mineral mapping   总被引：1，自引：0，他引：1  

Nisha Rani  Venkata Ravibabu Mandla  Tejpal Singh 《地学前缘(英文版)》2017,8(4):797-808

Hyperspectral images have wide applications in the fields of geology, mineral exploration, agriculture, forestry and environmental studies etc. due to their narrow band width with numerous channels. However, these images commonly suffer from atmospheric effects, thereby limiting their use. In such a situation, atmospheric correction becomes a necessary pre-requisite for any further processing and accurate interpretation of spectra of different surface materials/objects. In the present study, two very advance atmospheric approaches i.e. QUAC and FLAASH have been applied on the hyperspectral remote sensing imagery. The spectra of vegetation, man-made structure and different minerals from the Gadag area of Karnataka, were extracted from the raw image and also from the QUAC and FLAASH corrected images. These spectra were compared among themselves and also with the existing USGS and JHU spectral library. FLAASH is rigorous atmospheric algorithm and requires various parameters to perform but it has capability to compensate the effects of atmospheric absorption. These absorption curves in any spectra play an important role in identification of the compositions. Therefore, the presence of unwanted absorption features can lead to wrong interpretation and identification of mineral composition. FLAASH also has an advantage of spectral polishing which provides smooth spectral curves which helps in accurate identification of composition of minerals. Therefore, this study recommends that FLAASH is better than QUAC for atmospheric correction and correct interpretation and identification of composition of any object or minerals.  相似文献   

Static deformation of a uniform half-space due to a long dip-slip fault     

Sunita Rani  Sarva Jit Singh 《Geophysical Journal International》1992,109(2):469-476

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Evaluation of the Comparative Toxicity of Thiotox,Dichlorvos and Carbofuran to Two Fresh Water Teleosts Ophiocephalus punctatus and Mystus Vittatus     

S. R. Verma  Sarita Rani  S. K. Bansal  R. C. Dalela 《洁净——土壤、空气、水》1981,9(2):119-129

The present study was undertaken to evaluate the comparative toxicity of Thiotox (Endosulfan) (an organochlorine), Dichlorvos (DDVP) (an organophosphorus) and Carbofuran (a carbamate) so as to determine the TL 50 values, acute toxicity ranges, relative toxicities, relative susceptibility, safe concentrations, regression equations, heterogeneity factor and 95% confidence limits for the period of 24, 48, 72 and 96 h, taking two fresh water teleosts, Mystus vittatus and Ophiocephalus punctatus as test animals. From the relative toxicity of these pesticides it is evident that thiotox was the most toxic and dichlorvos the least toxic one, while the toxicity of carbofuran was in between these two extremes for both the fishes. On the basis of relative susceptibility, Mystus vittatus was found to be more susceptible than Ophiocephalus punctatus for thiotox, dichlorvos and carbofuran, respectively. The safe concentrations were computed for all the three pesticides taking different application factors, so as to avoid the long term water pollution by these pesticides.  相似文献   

Quasi-static deformation of a poroelastic half-space with anisotropic permeability by two-dimensional surface loads     

Sarva Jit Singh  Sunita Rani  Raman Kumar 《Geophysical Journal International》2007,170(3):1311-1327

An analytical solution is obtained of the fully coupled diffusion–deformation system of equations governing the quasi-static plane strain deformation of a poroelastic half-space with anisotropic permeability and compressible constituents. The stresses and the pore pressure are taken as the basic state variables. Displacements are obtained by integrating the coupled constitutive relations. The problem of surface loads is discussed in detail. Explicit analytical solutions are derived for normal line loading, shear line loading and normal strip loading. The permeability anisotropy is found to have a significant effect on the quasi-static deformation of the half-space. However, in the drained and undrained limits, the anisotropy has no effect. The stresses in the drained and undrained states are independent of the poroelastic parameters. Numerical computation of the pore pressure indicates that ignoring permeability anisotropy may lead to an overestimation of the pore pressure at points vertically below the point of normal loading. Further, anisotropy in permeability may lead to a dilution in the theoretical prediction of the Mandel–Cryer Effect.  相似文献   

Assessing coastal landscape vulnerability using geospatial techniques along Vizianagaram–Srikakulam coast of Andhra Pradesh,India     

Meenu Rani  Sufia Rehman  Haroon Sajjad  B. S. Chaudhary  Jyoti Sharma  Sandeep Bhardwaj  Pavan Kumar 《Natural Hazards》2018,94(2):711-725

Vizianagaram–Srikakulam coastal shoreline consisting of beaches, mangrove swamps, tidal channel and mudflats is one of the vulnerable coasts in Andhra Pradesh, India. Five site-specific parameters, namely rate of geomorphology, coastal elevation, coastal slope, shoreline change and mean significant wave height, were chosen for constructing coastal vulnerability index and assessing coastal landscape vulnerability. The findings revealed a shift of 2.5 km in shoreline towards the land surface because of constant erosion and that of 1.82 km towards the sea due to accretion during 1997–2017. The rate of high erosion was found in zones IV and V, and high accretion was found in zones II and III. Coastal vulnerability index analysis revealed constant erosion along shoreline and sea level rise in the study area. Most of the coast in zone V has recorded very high vulnerability due to erosion, high slope, significant wave height and sea level rise. Erosion and accretion, significant wave height, sea level rise and slope are attributed to high vulnerability in zones III and IV. Zone II recorded moderate vulnerability. Relatively lower slope, mean sea wave height and sea level rise have made this zone moderately vulnerable. Very low vulnerability was found in zone I, and low vulnerability was recorded in zone II. Accretion, low slope and low sea level rise were found to be causative factors of lower vulnerability. Thus, zones III, IV and V should be accorded higher priorities for coastal management. The findings can be helpful in coastal land planning and management and preparing emergency plans of the coastal ecosystems.  相似文献