Diffuse reflection and transmission in accordance with the phase function 3/4(1+cos2Θ)     

Rabindra Nath Das 《Astrophysics and Space Science》1979,60(2):321-327

We have considered the transport equation for the problem of diffuse reflection and transmission on Rayleigh's phase function and obtained the exact solution of this equation for angular distributions of the intensities diffusely reflected from the surfacet=0 and diffusely transmitted below the surfacet=t ₀ of a finite atmosphere of optical deptht=t ₀ using the Laplace transform and the theory of singular operators. This is an exact method.  相似文献   

A new method for exact solution of transfer equations in finite media     

Rabindra Nath Das 《Astrophysics and Space Science》1981,76(2):441-463

In this paper we develop a new exact method combined with finite Laplace transform and theory of linear singular operators to obtain a solution of transport equation in finite plane-parallel steady-state scattering atmosphere both for angular distribution of radiation from the bounding faces of the atmosphere and for intensity of radiation at any depth of the atmosphere. The emergent intensity of radiation from the bounding faces are determined from simultaneous linear integral equations of the emergent intensity of radiation in terms ofX andY equations of Chandrasekhar. The intensity of radiation at any optical depth for a positive and negative direction parameter is derived by inversion of the Laplace transform in terms of intergrals of the emergent intensity of radiation. A new expression of theX andY equation is also derived for easy numerical computation. This is a new and exact method applicable to all problems in finite plane parallel steady scattering atmosphere.  相似文献   

Monitoring the Impact of Simulated Deep-sea Mining in Central Indian Basin     

R. Sharma  B. Nagender Nath  S. Jai Sankar 《Marine Georesources & Geotechnology》2013,31(4):339-356

Monitoring of deep-sea disturbances, naturai or man-made, has gained significance due to the associated sediment transport and for the ensuing alterations in environmental conditions. During the Indian Deep-sea Environment Experiment (INDEX), resuspension of deep-sea sediment in the Central Indian Basin (CIB) resulted in an increase and lateral movement of suspended particles, vertical mixing of sediments, changes in sedimentological, biochemical, and geochemical conditions and an overall reduction in benthic biomass. Monitoring the conditions 44 months after the experiment has shown a partial recovery of the benthic ecosystem, with indications of restoration and recolonization.  相似文献   

Radioactive quartz-pebble conglomerates from western margin of Bonai granite pluton,Sundargarh district,Orissa — A new find     

Ajay Kumar  S. N. S. Birua  Dheeraj Pande  A. R. Nath  P. V. Ramesh Babu  S. A. Pandit 《Journal of the Geological Society of India》2009,73(4):537-542

Several radioactive quartz-pebble conglomerate (QPC) occurrences at the western margin of Archaean Bonai granite and overlying Iron Ore Group (IOG) rocks have recently been located over a total strike length of 8–10 km intermittently in a NE-SW to E-W trend with steep dips due north-west to north in parts of Sundargarh district of Orissa. The QPC samples have analysed up to 0.039% U₃O₈ and 0.035% ThO₂ with high concentration of Y (74 to 518 ppm), La(<100 to 880 ppm), Cr ( 126 to 633 ppm), Zr (137 to 1250 ppm) and Pb (31 to 581 ppm). Cellulose Nitrate (CN) film studies of few QPC samples indicated adsorbed uranium over goethite and infiltrated ferruginous material (limonite), secondary uranium as encrustation and fracture filling and discrete sub-rounded grains of monazite, zircon, allanite and rare xenotime in the matrix of QPC as radioactive phases. Higher content of Th over U, elevated concentration of Y and La in QPC eliminates the possibility of its low temperature product by epigenetic processes. Poor correlation of U with elements like Pb, Y, Zr, La and Cr can be explained due to surficial leaching of uranium from QPC after its deposition as reflected by adsorbed U over iron-oxides and low U/Th ratio in QPC in the area.  相似文献   

Geochemical characteristics of the fluids and muds from two southern Taiwan mud volcanoes: Implications for water–sediment interaction and groundwater arsenic enrichment     

Chia-Chuan Liu  Jiin-Shuh Jean  Bibhash Nath  Ming-Kuo Lee  Lien-I Hor  Kao-Hung Lin  Jyoti Prakash Maity 《Applied Geochemistry》2009,24(9):1793-1802

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Solution of a Riemann–Hilbert problem for a new expression of Chandrasekhar’s H-function in radiative transfer     

Rabindra Nath Das 《Astrophysics and Space Science》2008,317(1-2):119-126

The linear singular integral equation derived from the nonlinear integral equation of Chandrasekhar’s H-function in radiative transfer is considered here to develop a new form of H-function as a solution of a Riemann–Hilbert problem using Plemelj and Cauchy integral formulae for complex domain. This new form of H-function is a simple integral of known functions. Forms of H-function both for conservative and nonconservative cases are obtained. Their numerical evaluations are made by Simpson’s one-third rule to arrive at an accuracy to ninth places of decimals.  相似文献   

Primordial magnetic fields and formation of molecular hydrogen     

Shiv K. Sethi  Biman B. Nath  Kandaswamy Subramanian 《Monthly notices of the Royal Astronomical Society》2008,387(4):1589-1596

We study the implications of primordial magnetic fields for the thermal and ionization history of the post-recombination era. In particular, we compute the effects of dissipation of primordial magnetic fields owing to ambipolar diffusion and decaying turbulence in the intergalactic medium (IGM) and the collapsing haloes, and compute the effects of the altered thermal and ionization history on the formation of molecular hydrogen. We show that, for magnetic field strengths in the range  2 × 10⁻¹⁰≲ B ₀≲ 2 × 10⁻⁹ G  , the molecular hydrogen fraction in IGM and collapsing halo can increase by a factor of 5 to 1000 over the case with no magnetic fields. We discuss the implication of the increased molecular hydrogen fraction on the radiative transfer of ultraviolet photons and the formation of first structures in the universe.  相似文献   

International Conference on Natural Resources,Environment and Health (ICNREH-2017)     

Rabindra Nath Tiwari 《Journal of the Geological Society of India》2017,90(4):504-505

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Groundwater arsenic contamination and its health effects in India   总被引：2，自引：0，他引：2  

Dipankar Chakraborti  Mohammad Mahmudur Rahman  Bhaskar Das  Amit Chatterjee  Dipankar Das  Biswajit Nayak  Arup Pal  Uttam Kumar Chowdhury  Sad Ahmed  Bhajan Kumar Biswas  Mrinal Kumar Sengupta  Md. Amir Hossain  Gautam Samanta  M. M. Roy  Rathindra Nath Dutta  Khitish Chandra Saha  Subhas Chandra Mukherjee  Shyamapada Pati  Probir Bijoy Kar  Adreesh Mukherjee  Manoj Kumar 《Hydrogeology Journal》2017,25(4):1165-1181

During a 28-year field survey in India (1988–2016), groundwater arsenic contamination and its health effects were registered in the states of West Bengal, Jharkhand, Bihar and Uttar Pradesh in the Ganga River flood plain, and the states of Assam and Manipur in the flood plain of Brahamaputra and Imphal rivers. Groundwater of Rajnandgaon village in Chhattisgarh state, which is not in a flood plain, is also arsenic contaminated. More than 170,000 tubewell water samples from the affected states were analyzed and half of the samples had arsenic >10 μg/L (maximum concentration 3,700 μg/L). Chronic exposure to arsenic through drinking water causes various health problems, like dermal, neurological, reproductive and pregnancy effects, cardiovascular effects, diabetes mellitus, diseases of the respiratory and gastrointestinal systems, and cancers, typically involving the skin, lungs, liver, bladder, etc. About 4.5% of the 8,000 children from arsenic-affected villages of affected states were registered with mild to moderate arsenical skin lesions. In the preliminary survey, more than 10,000 patients were registered with different types of arsenic-related signs and symptoms, out of more than 100,000 people screened from affected states. Elevated levels of arsenic were also found in biological samples (urine, hair, nails) of the people living in affected states. The study reveals that the population who had severe arsenical skin lesions may suffer from multiple Bowens/cancers in the long term. Some unusual symptoms, such as burning sensation, skin itching and watering of eyes in the presence of sun light, were also noticed in arsenicosis patients.  相似文献   

Alongshore Sediment Transport Near Tidal Inlets of Chilika Lagoon; East Coast of India     

Subhasis Pradhan  Sujit Kumar Mishra  Rakesh Baral  Rabindro Nath Samal  Pratap Kumar Mohanty 《Marine Geodesy》2017,40(2-3):187-203

ABSTRACT

Chilika, a lagoon along the east coast of India, is undergoing transformation due to frequent shoreline change near inlet(s). Shoreline change near inlet includes change in position and shape of inlet, inlet channel length, and spit growth/erosion. These variable features of lagoon inlet(s) critically depend on alongshore sediment transport (LST) and discharge (water and sediment) from the lagoon to the sea. The LST and the processes responsible for sand spit growth/erosion, considered as important attributes of inlet stability, are the subject matter of the present investigation and hence the study assumes importance. The study includes integration of observational and modeling framework. Observations include nearshore wave, bathymetry, beach profile, shoreline and sediment grain size of spits while numerical modeling includes simulation of the wave using MIKE 21 Spectral Wave model and LST simulation using LITtoral DRIFT. The results indicate that the predominant wave directions as S and SSE, which induces round the year south to north alongshore transport with significant seasonal variation in magnitude. The estimated LST closely matches with previous studies near Chilika inlet and for other locations along the Odisha coast. Besides temporal variability, the study reveals spatial variability in alongshore transport near Chilika inlet and considers it as one of the important attributes along with northward spit growth for inlet migration/closure/opening.  相似文献