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Anirban Mukhopadhyay Arun Mondal Sandip Mukherjee Dipam Khatua Subhajit Ghosh Debasish Mitra Tuhin Ghosh 《Journal of Earth System Science》2014,123(6):1349-1360
In the Himalayan states of India, with increasing population and activities, large areas of forested land are being converted into other land-use features. There is a definite cause and effect relationship between changing practice for development and changes in land use. So, an estimation of land use dynamics and a futuristic trend pattern is essential. A combination of geospatial and statistical techniques were applied to assess the present and future land use/land cover scenario of Gangtok, the subHimalayan capital of Sikkim. Multi-temporal satellite imageries of the Landsat series were used to map the changes in land use of Gangtok from 1990 to 2010. Only three major land use classes (built-up area and bare land, step cultivated area, and forest) were considered as the most dynamic land use practices of Gangtok. The conventional supervised classification, and spectral indices-based thresholding using NDVI (Normalized Difference Vegetation Index) and SAVI (Soil Adjusted Vegetation Index) were applied along with the accuracy assessments. Markov modelling was applied for prediction of land use/land cover change and was validated. SAVI provides the most accurate estimate, i.e., the difference between predicted and actual data is minimal. Finally, a combination of Markov modelling and SAVI was used to predict the probable land-use scenario in Gangtok in 2020 AD, which indicted that more forest areas will be converted for step cultivation by the year 2020. 相似文献
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Ankur Sarkar Debasish Sarkar Madhurima Gupta Chiranjib Bhattacharjee 《洁净——土壤、空气、水》2012,40(8):830-837
Polyvinyl alcohol (PVA), the major constituent of desizing water constituting 45% of the total BOD load has a significant environmental impact owing to its poor biodegradability. In order to prevent PVA from being discharged by the effluent stream, modern textile industries opt for membrane based separation techniques using ultrafiltration so that the recovery and recycle of PVA in tandem could be achieved. However, the process of ultrafiltration is still not widely accepted as expected due to the well‐known non‐idealities of concentration polarization and pore blockage. In this article, design and performance characterization of a lab‐scale novel shear enhanced ultrafiltration unit, named as spinning basket membrane (SBM) module are discussed. The proposed module is unique in terms of its inbuilt cleaning facility eliminating the effects of polarization and subsequent periodic fouling leading to its uninterrupted production operation. The test fluid, necessarily a solution of PVA was treated in the proposed module under different parametric conditions with polyvinylidene fluoride (PVDF) membranes of two different molecular weight cut‐off (50 and 100 kDa). After 2 h of continuous operation the permeate flux was observed to be within 95–97% of the respective initial fluxes. Such performance is rarely been attained in practice. Hence, the novelty of the present research is achieved. Considering the performance of the present module in terms of flux regeneration and product recovery, it may be regarded as an efficient device and can be potentially deployed for cleaning of other industrial wastewater. 相似文献
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Climate Dynamics - The suitability of dynamical downscaling in producing high-resolution climate scenarios for impact assessments is limited by the quality of the driving data and regional climate... 相似文献
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The Palaeo–Mesoproterozoic Tadapatri formation of the Cuddapah basin is comprised of clastic sedimentary rocks with minor carbonates and mafic–ultramafic sill bodies. Geochemistry of the shale is used to study the provenance, paleoweathering and paleoredox conditions of this Tadpatri formation in order to better understand the development of the Cuddapah basin during Palaeo–Mesoproterozoic time. The higher CIA (average 74.39), PIA (average 85.94) and CIW (average 87.59) values of the Tadpatri shales suggest intensely weathered sources. Higher Al2O3/TiO2 (average 30.78) and LREE/HREE ratio (average 8.80) with negative europium anomaly indicate derivation of the clastic sediments from a felsic source rock. The geochemical parameters like U, U/Th, Cu/Zn, Ni/Co, V/Cr ratios reveal that the Tadpatri shales are mainly deposited in an oxic condition. 相似文献
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Prashanth Reddy Hanmaiahgari Nooka Raju Gompa Debasish Pal Jaan Hui Pu 《Natural Hazards》2018,91(3):1075-1096
The present study attempts to predict the reservoir sedimentation in 32 km region of the Tenryu River between the Hiraoka and Sakuma Dams in Japan. For numerical simulations of the reservoir sedimentation, the one-dimensional model of the Hydrologic Engineering Centre-River Analysis System (HEC-RAS) is used together with the inclusion of channel geometry, bed gradation curve, Exner-5 bed sorting mechanisms, fall velocity of the particle, and flow and sediment boundary conditions pertaining to modeling region. The modeling region of the Tenryu River is divided into 48 river stations with 47 reaches in the numerical simulations. The numerical model is calibrated using the available data for 48 years from 1957 to 2004. The formulae of sediment transport function, Manning’s roughness coefficient, computational increment and fall velocity have been identified for getting the best estimation of the Sakuma Dam reservoir sedimentation. Combination of obtained sensitive parameters and erodible limits of 2 m gave the best comparison with the measured bed profile. The computed results follow the trend of measured data with a small underestimation. Although Manning’s roughness coefficient has an effect on the sedimentation, no direct relation is found between the Manning’s roughness coefficient and reservoir sedimentation. It is found that the temperature of water has no effect on the reservoir sedimentation. 相似文献
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Debasish Chakraborty Vinay Kumar Sehgal Rajkumar Dhakar Deb Kumar Das Rabi Narayan Sahoo 《Journal of the Indian Society of Remote Sensing》2018,46(1):59-68
The virtual certainty of the anticipated climate change will continue to raise many questions about its aggregated impact of environmental changes on our regional food security in imminent future. Crop responses to these changes are certain, but its exact characteristics are hardly understood at regional scale due to complex overlapping effects of climate change and anthropogenic manipulation of agro-ecosystem. This study derived phenology of wheat in north India from satellite data and analyzed trends of phenology parameters over last three decades. The most striking change-point period in phenology trends were also derived. The phenology was derived from two sources: (1) STAR-Global vegetation Health Products-NDVI, and (2) GIMMS-NDVI. The results revealed significant earliness in start of growing season (SOS) in Punjab and Haryana while delay was found in Uttar Pradesh (UP). End of the wheat season almost always occurred early, to even those place where SOS was delayed. Length of growing season increased in most of Punjab and northern Haryana whereas its decrease dominated in UP. The early sowing practice of the farmers of the Punjab and Haryana may be one of the adaptation strategies to manage the terminal heat stress in reproductive stage of the crop in the region. The change-point occurred in late 1990s (1998–2000) in Punjab and Haryana, while in eastern UP it was in early 1990s (1990–1995). Despite the difference in temporal aggregation and spatial resolution, both the datasets yielded similar trends, confirming both the robustness of the results and applicability of the datasets over the region. The results demands further research for proper attribution of the effects into its causes and may help devising crop adaption practices to climatic stresses. 相似文献