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41.
Dipak Ghosh Argha Deb Swarup Ranjan Sahoo Subrata Haldar Rosalima Sengupta 《Natural Hazards》2011,58(3):877-889
This paper reports the measurement of radon concentration in well water at the site of Jalpaiguri (26°32′N, 88°46′E) near
the active fault zone of West Bengal, India. Radon concentration has been measured in well water with the help of solid-state
nuclear track detectors (SSNTD). The study indicates a positive correlation between radon anomaly and earthquake. The data
of radon content in well water have been compared with that in soil gas at the same site. 相似文献
42.
Continental weathering plays a dominant role in regulating the global carbon cycle, soil chemistry and nutrient supply to oceans. The CO2-mediated silicate weathering acts as a major CO2 sink, whereas sulphuric acid-mediated carbonate dissolution releases CO2 to the atmosphere–ocean system. In this study, dissolved major ions and silica concentrations of two tropical (Damodar and Subarnarekha) river systems from India have been measured to constrain the type and rate of chemical weathering for these basins. The total dissolved solids (TDS) of these rivers, a measure of total solute supply from all possible sources, are about 2–3 times higher than that of the global average for rivers. Mass balance calculations involving inverse modelling estimate that 63 ± 11% of total cations are derived from rock weathering, of which 27 ± 7% of cations are supplied through silicate weathering. The sulphide-S concentrations are estimated by comparing the water chemistry of these two rivers with that of a nearby river (Brahmani) with similar lithology but no signatures of sulphide oxidation. The outflows of Damodar and Subarnarekha rivers receive 17% and 55% of SO4 through sulphide oxidation, respectively. The sulphide oxidation fluxes from the ore mining areas, such as upper Damodar (0.52 × 109 mol/yr) and lower Subarnarekha (0.66 × 109 mol/yr) basins, are disproportionally (~9 times) higher compared to their fractional areal coverage to the global drainage area. The corresponding CO2 release rate (2.84 × 104 mol/km2/yr) for the Damodar basin is lower by five times than its CO2 uptake rate (1.38 × 105 mol/km2/yr). The outcomes of this study underscore the dominance of sulphide oxidation in controlling the dissolved chemical (cationic and sulphur) fluxes. 相似文献
43.
Naveen Kumar Alagappan Ramanathan Aman Arora Mohd Soheb Arindan Mandal Parmanand Sharma Shyam Ranjan 《水文研究》2020,34(5):1285-1300
The impact of surface melt patterns and the Indian summer monsoon (ISM) is examined on the varying contributions of end member (snow, glacier ice, and rain) to proglacial streamflow during the ablation period (June–October) in the Chhota Shigri glaciated basin, Western Himalaya. Isotopic seasonality observed in the catchment precipitation was generally reflected in surface runoff (supraglacial melt and proglacial stream) and shows a shift in major water source during the melt season. Isotopically correlated (δ18O–δD) high deuterium intercept in the surface runoff suggests that westerly precipitation acts as the dominant source, augmenting the other snow- and ice-melt sources in the region. The endmember contributions to the proglacial stream were quantified using a three-component mixing. Overall, glacier ice melt is the major source of proglacial discharge. Snowmelt is the predominant source during the early ablation season (June) and the peak ISM period (August and September), whereas ice melt reaches a maximum in the peak melt period (July). The monthly contribution of rain is on the lower side and shows a steady rise and decline with onset and retreat of the monsoon. These results are persistent with the surface melt pattern observed in Chhota Shigri glacier, Upper Chandra basin. Moreover, the role of the ISM in Chhota Shigri glacier is unvarying to that observed in other glacierized catchments of Upper Ganga basin. Thus, this study augments the significant role of the ISM in glacier mass balance up to the boundary of the central-western Himalayan glaciated region. 相似文献
44.
Soma Mukherjee Ujjwal Bhattacharya S. K. Parui Ranjan Gupta Ravi K. Gulati 《Astrophysics and Space Science》1996,239(2):361-373
In this paper we present an application of an artificial neural network model based on a multi-layered backpropagation algorithm for spectral classification of UV data from the International Ultraviolet Explorer (IUE) low dispersion spectra reference atlas. The model used is similar to that of von Hippel et al. (1994), and is found to reduce the classification error as compared to the recently reported results on the same data set (Gulati et al. 1994b). The improved version of the network is much simpler in structure and the training time is reduced by a factor of almost 20. Such networks will prove very useful in efficient classification of large databases
Subject headings: neural networks, stellar spectra, classification 相似文献
45.
46.
So Kazama Hirokazu Izumi Priyantha Ranjan Sarukkalige Takayuki Nasu Masaki Sawamoto 《水文研究》2008,22(13):2315-2324
The spatial and temporal distribution of the snow water equivalent (SWE), snow density and snow depth were estimated by a method combining remote sensing technology and degree‐day techniques over a study area of 370 000 km2. The advantages of this simulation model are its simplicity and the availability of degree‐day parameters, which can be successively evaluated by referring to snow area maps created from satellite images. This simulation worked very well for estimating SWE and helped to separate the areas of thin snow cover from heavier snowfall. However, shallow snow in warm regions led to some misjudgments in the snow area maps because of the time lag between when the satellite image was acquired and the simulation itself. Vulnerable areas, where a large variation in the amount of snow affects people's life, could be identified from the differences between heavy and light snow years. This vulnerability stems from a predicted lack of irrigation water for rice production caused by future climate change. The model developed in this study has the potential to contribute to water management activities and decision‐making processes when considering necessary adaptations to future climate change. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
47.
The headwaters of the Ganga (the Alaknanda, Bhagirathi and the Ganga) were analysed for their dissolved major ions, Sr and 87Sr/86Sr on a biweekly to monthly basis over a period of one year to determine their temporal variations and the factors contributing to them. The concentrations of major ions and Sr show significant seasonal variation with lower values during monsoon period in all the three rivers. A similar trend is also observed for 87Sr/86Sr and Na*/Ca (Na* = Nar? Clr) suggesting relatively lower contribution of Sr and Na from silicates (which are more radiogenic in Sr) during monsoon. Budget calculations show that silicate derived dissolved Sr (Srs) in the river Ganga, Alaknanda and the Bhagirathi varied from 10 ± 4 to 27 ± 11, 7 ± 3 to 30 ± 12, 16 ± 6 to 57 ± 23% of measured Sr respectively with lower values during monsoon. The relative decrease in silicate erosion compared to carbonate during monsoon can result from several factors, these include higher dissolution kinetics of the carbonates, lower water–rock interaction time and availability of larger area for weathering. The annual discharge weighted Sr flux derived from the time series data is higher by ~20% from that based on peak flow Sr, and lower by ~40% compared to that derived from lean flow Sr concentration. The area‐normalized annual flux of dissolved Sr from the Ganga at Rishikesh is about five times its flux at Rajshahi (Bangladesh) and a few other major global rivers, such as the Amazon, indicating higher erosion rate over the Himalaya. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
48.
Naveen Kumar Tirumalesh Keesari S. Chidambaram Shyam Ranjan Mohd Soheb 《水文科学杂志》2013,58(11):1717-1732
ABSTRACTThe temporal variations in electrical conductivity and the stable isotopes of water, δD and δ18O, were examined at Chhota Shigri Glacier, India, to understand water sources and flow paths to discharge. Discharge is highly influenced by supraglacially derived meltwater during peak ablation, and subglacial meltwaters are more prominent at the end of the melt season. The slope of the best fit linear regression line for δD versus δ18O, for both supraglacial and runoff water, is lower than that for precipitation (snow and rain) and surface ice, indicating strong isotopic fractionation associated with the melting processes. The slope of the local meteoric water line (LMWL) is close to that of the global meteoric water line (GMWL), reflecting that the moisture source is predominantly oceanic. The d-excess variation in rainwater confirms that the southwest monsoon is the main contributor during summer while the remainder including winter is mostly influenced by westerlies. 相似文献
49.
Ram Ranjan 《Stochastic Environmental Research and Risk Assessment (SERRA)》2006,20(5):353-362
This paper estimates the expected annual impacts of the Pink Hibiscus Mealybug infestation on the economies of Florida and the rest of the United States. The approach involves a Markov chain analysis wherein both short run and long run expected damages from infestation are calculated. Use is made of the CLIMEX model that predicts the potential pest-establishment regions in the US. While predictions based upon the CLIMEX model extend the scope of damages beyond Florida, the damages are significantly dependent upon the rate of arrival and detection of species in those regions. Damages are significantly higher when a longer time horizon is considered. When nursery owners bear the full cost of quarantines in the form of loss of sales and treatment costs of infected plants, the cost-effectiveness of quarantines as a regulatory tool is diminished. The long run propensity of the system, in terms of the fraction of time spent in the possible ‘states’ of infestation and control, determines the extent of damages, and not the annual value of crops that could be potential hosts to the pest.
相似文献
Ram RanjanEmail: Phone: +1-352-3921881Fax: +1-352-3929898 |
50.
K. Naha A. Rai Choudhuri V. Ranjan R. Srinivasan 《Journal of Earth System Science》1995,104(3):327-347
The supracrustal enclave within the Peninsular Gneiss in the Honakere arm of the Chitradurga-Karighatta belt comprises tremolite-chlorite
schists within which occur two bands of quartzite coalescing east of Jakkanahalli(12°39′N; 76°41′E), with an amphibolite band
in the core. Very tight to isoclinal mesoscopic folds on compositional bands cut across in the hinge zones by an axial planar
schistosity, and the nearly orthogonal relation between compositional bands and this schistosity at the termination of the
tremolite-chlorite schist band near Javanahalli, points to the presence of a hinge of a large-scale, isoclinal early fold
(F1). That the map pattern, with an NNE-plunging upright antiform and a complementary synform of macroscopic scale, traces folds
'er generation (F
2),is proved by the varying attitude of both compositional bands (S0) and axial pranar schistosity (S
1), which are effectively parallel in a major part of the area. A crenulation cleavage (S
2) has developed parallel to the axial planes of theF
2 folds at places. TheF
2 folds range usually from open to rarely isoclinal style, with theF
1 andF
2 axes nearly parallel. Evidence of type 3 fold interference is also provided by the map pattern of a quartzite band in the
Borikoppalu area to the north, coupled with younging directions from current bedding andS
0
-S
1 inter-relation.
Although statistically theF
1 andF
2 linear structures have the same orientation, detailed studies of outcrops and hand specimens indicate that the two may make
as high an angle as 90°. Usually, in these instances, theF
1 lineations are unreliable around theF
2 axes, implying that theF
2 folding was by flexural slip. In zones with very tight to almost isoclinalF
2 folding, however, buckling attendant with flattening has caused a spread of theF
1 lineations almost in a plane. Initial divergence in orientation of theF
1 lineations due to extreme flattening duringF
1 folding has also resulted in a variation in the angle between theF
1 andF
2lineations in some instances. Upright later folding (F3) with nearly E-W strike of axial planes has led to warps on schistosity, plunge reversals of theF
1 andF
2 axes, and increase in the angle between theF
1 andF
2 lineations at some places. Large-scale mapping in the Borikoppalu sector, where the supposed Sargur rocks with ENE ‘trend’
abut against the N-‘trending’ rocks of the Dharwar Supergroup, shows a continuity of rock formations and structures across
the hinge of a large-scaleF
2 fold. This observation renders the notion, that there is an angular unconformity here between the rocks of the Sargur Group
and the Dharwar Supergroup, untenable. 相似文献