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1.
Devendraa Siingh R. P. Singh Ashok K. Singh M. N. Kulkarni A. S. Gautam Abhay K. Singh 《Surveys in Geophysics》2011,32(6):659-703
The physics of solar forcing of the climate and long term climate change is summarized, and the role of energetic charged
particles (including cosmic rays) on cloud formation and their effect on climate is examined. It is considered that the cosmic
ray-cloud cover hypothesis is not supported by presently available data and further investigations (during Forbush decreases
and at other times) should be analyzed to further examine the hypothesis. Another player in climate is lightning through the
production of NOx; this greenhouse gas, water vapour in the troposphere (and stratosphere) and carbon dioxide influence the global temperature
through different processes. The enhancement of aerosol concentrations and their distribution in the troposphere also affect
the climate and may result in enhanced lightning activity. Finally, the roles of atmospheric conductivity on the electrical
activity of thunderstorms and lightning discharges in relation to climate are discussed. 相似文献
2.
Adaptive optimal control of an autonomous underwater vehicle in the dive plane using dorsal fins 总被引：1，自引：0，他引：1
In this paper, adaptive control of low speed bio-robotic autonomous underwater vehicles (BAUVs) in the dive plane using dorsal fins is considered. It is assumed that the model parameters are completely unknown and only the depth of the vehicle is measured for feedback. Two dorsal fins are mounted in the horizontal plane on either side of the BAUV. The normal force produced by the fins, when cambered, is used for the maneuvering. The BAUV model considered here is non-minimum phase. An indirect adaptive control system is designed for the depth control using the dorsal fins. The control system consists of a gradient based identifier for online parameter estimation, an observer for state estimation, and an optimal controller. Simulation results are presented which show that the adaptive control system accomplishes precise depth control of the BAUV using dorsal fins in spite of large uncertainties in the system parameters. 相似文献
3.
Md Maroof Azam Monika Kumari Chinmaya Maharana Abhay K. Singh Jayant K. Tripathi 《Environmental Earth Sciences》2018,77(8):313
The Ganga River plays a major role in the transfer of materials from the Indian sub-continent to the Bay of Bengal, both in dissolved and particulate forms. To understand the present elemental dynamics of the Ganga River system, it is important to assess the hydrogeochemical contribution of its tributaries. In this paper, we present an updated database on dissolved and particulate fluxes and denudation rates of the Himalayan tributaries of the Ganga River (Ramganga, Ghaghara, Gandak and Kosi). Dissolved trace element concentrations, their fluxes and suspended sediment-associated elemental fluxes of the Himalayan tributaries have been reported for the first time. Total dissolved flux of the Ramganga, Ghaghara, Gandak and Kosi was estimated as 4, 19.1, 10.3 and 8.8 million tons year?1 accounting for ~?5.7, ~?27.3, ~?14.7 and ~?12.6%, respectively, of the total annual dissolved load carried by the Ganga River. The total particulate flux of the Ramganga, Ghaghara, Gandak and Kosi was computed as 8.2, 81.6, 30.9 and 19.5 million tons year?1, respectively. Compared to earlier studies, we have found a significant increase in the total dissolved flux and chemical denudation rate of the studied tributaries. The estimated particulate fluxes were found to be low in comparison to the previous studies. We suggest that a significant increase in the dissolved fluxes and a decrease in the particulate fluxes are an indication of the increasing anthropogenic disturbances in the catchment of these tributaries. 相似文献
4.
Abhay Kumar Singh G. C. Mondal T. B. Singh S. Singh B. K. Tewary A. Sinha 《Environmental Earth Sciences》2012,67(8):2175-2191
The hydrogeochemical study of groundwater in Dumka and Jamtara districts has been carried out to assess the major ion chemistry, hydrogeochemical processes and groundwater quality for domestic and irrigation uses. Thirty groundwater samples were collected and analyzed for pH, electrical conductivity, total dissolved solids (TDS), total hardness, anions (F?, Cl?, NO3 ?, HCO3 ?, SO4 2?) and cations (Ca2+, Mg2+, Na+, K+). The analytical results show the faintly alkaline nature of water and dominance of Mg2+ and Ca2+ in cationic and HCO3 ? and Cl? in anionic abundance. The concentrations of alkaline earth metals (Ca2+?+?Mg2+) exceed the alkali metals (Na+?+?K+) and HCO3 ? dominates over SO4 2??+?Cl? concentrations in the majority of the groundwater samples. Ca?CMg?CHCO3 is the dominant hydrogeochemical facies in 60?% of the groundwater samples, while 33?% samples occur as a mixed chemical character of Ca?CMg?CCl hydrogeochemical facies. The water chemistry is largely controlled by rock weathering and ion exchange processes with secondary contribution from anthropogenic sources. The inter-elemental correlations and factor and cluster analysis of hydro-geochemical database suggest combined influence of carbonate and silicate weathering on solute acquisition processes. For quality assessment, analyzed parameter values were compared with Indian and WHO water quality standards. In majority of the samples, the analyzed parameters are well within the desirable limits and water is potable for drinking purposes. Total hardness and concentrations of TDS, Cl?, NO3 ? , Ca2+ and Mg2+ exceed the desirable limits at a few sites, however, except NO3 ? all these values were below the highest permissible limits. The calculated parameters such as sodium adsorption ratio, percent sodium (%Na) and residual sodium carbonate revealed excellent to good quality of groundwater for agricultural purposes, except at few sites where salinity and magnesium hazard (MH) values exceeds the prescribed limits and demands special management. 相似文献
5.
Hydrogeochemical investigation and groundwater quality assessment of Pratapgarh district,Uttar Pradesh 总被引：3，自引：0，他引：3
Ashwani Kumar Tiwari Abhay Kumar Singh 《Journal of the Geological Society of India》2014,83(3):329-343
Hydogrochemical investigation of groundwater resources of Paragraph district has been carried out to assess the solute acquisition processes and water quality for domestic and irrigation uses. Fifty-five groundwater samples were collected and analyzed for pH, electrical conductivity, total dissolved solids, hardness, major anions (F?, Cl?, NO3, HCO3 ?, SO4 2?) and cations (Ca2+, Mg2+, Na+, K+). Study results reveal that groundwater of the area is alkaline in nature and HCO3 ?, Cl?, Mg2+, Na+ and Ca2+ are the major contributing ions to the dissolved solids. The hydrogeochemical data suggest that weathering of rock forming minerals along with secondary contributions from agricultural and anthropogenic sources are mainly controlling the groundwater composition of Pratapgarh district. Alkaline earth metals (Ca2++Mg2+) exceed alkalis (Na++K+) and weak acid (HCO3 ?) dominate over strong acids (Cl?+SO4 2?) in majority of the groundwater samples. Ca-Mg-HCO3 and Ca-Mg-Cl-HCO3 are the dominant hydrogeochemical facies in the groundwater of the area. The computed saturation indices demonstrate oversaturated condition with respect to dolomite and calcite and undersaturated with gypsum and fluorite. A comparison of groundwater quality parameters in relation to specified limits for drinking water shows that concentrations of TDS, F?, NO3 ? and total hardness exceed the desirable limits in many water samples. Quality assessment for irrigation uses reveal that the groundwater is good for irrigation. However, values of salinity, sodium adsorption ratio (SAR), residual sodium carbonate (RSC), %Na and Kelley index are exceeding the prescribed limit at some sites, demanding adequate drainage and water management plan for the area. 相似文献
6.
Rainwater plays an important role in scavenging of aerosols and gases from atmosphere, and its chemistry helps to understand the relative contributions of atmospheric pollution sources. The present work is aimed to understand and explain the sources, seasonal patterns and the processes thereof affecting rainwater chemistry in an urban environment of Delhi, India. Rainwater samples (n = 111) collected throughout the year in New Delhi showed alkalinity in general. Eight rainwater samples, collected in late monsoon and winter season, had pH less than 5.6 indicating that Delhi continues to face the prospects of acid rain despite the introduction of compressed natural gas as the clean fuel in city transport. Organic acids could be the possible contributors of acidity in rainwater samples having the fractional acidity (FA) value of 0.174, which is greater than the annual average FA (0.011) and the (Ca2+ + Mg2+ + NH4 +)/(SO4 2? + NO3 ?) ration of more than one. Average acid neutralization factors of cations decrease in the order Ca2+ (1.01) > NH4 + (0.77) > Mg2+ (0.10). However, neutralization by Ca2+ dominates only in summer season as cation-rich dust is transported from the Great Indian Thar Desert to this region by strong summer S–SW winds, while NH4 + dominates in rainwater of other three sampling seasons. Identified dominant sources for soluble ions in rainwater are (1) non-silicate crustal source for carbonates and sulfates of Ca and Mg, (2) emissions from catalytic convertor-fitted vehicles and agriculture fields for NH3 and (3) mixed anthropogenic sources for SO4 2?, NO3 ? and Cl?. Rainwater chemistry showed significant seasonal variations. This could be due to the changes in relative proportions of natural and anthropogenic sources of soluble ions to rainwater. Dominance of anthropogenic sources over crustal sources can result in acidic rains, which can adversely affect the environment and human health in this region. 相似文献
7.
The coal seams of Sawang Colliery, East Bokaro Coalfields are bituminous to sub-bituminous in nature and categorized as high
gaseous seams (degree II to degree III level). These seams have the potential for coal bed methane (CBM) and their maturity
increases with increasing depth, as a result of enhanced pressure-temperature conditions in the underground. The vitrinite
maceral group composition of the investigated coal seams ranges from 62.50–83.15%, whereas the inertinite content varies from
14.93–36.81%. The liptinite content varies from 0.66% to 3.09%. The maximum micro-pores are confined within the vitrinite
group of macerals. The coal seams exhibit vitrinite reflectance values (Ro% calculated) from 0.94% (sample CG-97) to 1.21%
(sample CG-119).
Proximate analyses of the investigated coal samples reveal that the moisture content (M%) ranges from 1.28% to 2.98%, whereas, volatile matter (VM%) content is placed in the range of 27.01% to 33.86%. The ash
content (A%) ranges from 10.92% to 30.01%. Fixed carbon (FC%) content varies from 41.53% to 55.93%. Fuel ratio variation shows a restricted
range from 1.53 to 1.97. All the coal samples were found to be strongly caking and forming coke buttons.
The present study is based on the adsorption isotherm experiments carried out under controlled P-T conditions for determination of actual gas adsorption capacity of the coal seams. This analysis shows that the maximum methane
gas adsorbed in the coal sample CG-81 is 17 m3/t (Std. daf), at maximum pressure of 5.92 MPa and experimental temperature of 30°C. The calculated Langmuir regression parameters
PL and VL range from 2.49 to 3.75 MPa and 22.94 to 26.88 m3/t (Std. daf), respectively. 相似文献
8.
Using the global positioning system (GPS) measurements, the total electron content (TEC) at station Bangalore (13.02°N, 77.57°E geographic; 04.44°N, 150.84°E geomagnetic), lying at the equatorial region, and station Lucknow (26.91°N, 80.95°E geographic; 17.96°N, 155.24°E geomagnetic), lying at equatorial ionospheric anomaly (EIA) crest region, have been estimated for the year 2012–2013. In order to evaluate the International Reference Ionosphere (IRI) model regarding simulation/modeling of ionospheric studies specially at equatorial and EIA crest regions, we have compared the TEC derived from the recent version of the IRI-2012 model and the older IRI-2007 with its three topside options, namely IRI-NeQuick (IRI-NeQ), IRI-2001, and IRI01-corr, with that of GPS-TEC over Bangalore and Lucknow. For the EIA station Lucknow, the IRI-2012 model with IRI-NeQ and IRI01-corr topside is found in good agreement with GPS-TEC during summer and equinox season, while the IRI-2012 model for all three topside options significantly overestimates the GPS-TEC during winter season. The IRI-2001 topside overestimates the GPS-TEC over both the stations during all seasons. The anomalous difference between the IRI-2012 model prediction and ground-based GPS-TEC in daytime hours during the winter season observed at Lucknow could be attributed to discrepancies in the slab thickness predicted by the model, which is more during the winter season as compared to summer and equinox. These large discrepancies in the slab thickness predicted by the IRI-2012 as well as the IRI-2007 model during the winter season have been supported by using the foF2 data from Constellation Observing System for Meteorology, Ionosphere, and Climate radio occultation-based measurements. We also observed that the discrepancies in the recent IRI-2012 model with respect to GPS-TEC are found to be slightly larger than those with the older IRI-2007 model over the EIA region Lucknow. However, over the equatorial region Bangalore, the discrepancy with the older model IRI-2007 was found to be larger than with the recent IRI-2012 model. This suggests that the performance of the IRI-2012 model is poorer than the IRI-2007 model at the EIA region while better at equatorial region, and that further improvements in the IRI-2012 models are required particularly in the low-latitude and EIA regions. The GPS-TEC showed disappearance of the winter anomaly during 2012–2013, while the IRI model failed to predict the disappearance of winter anomaly. 相似文献
9.
Babita Neogi Abhay Kumar Singh D. D. Pathak Aaditya Chaturvedi 《Environmental Earth Sciences》2017,76(14):489
Mine water samples collected from different mines of the North Karanpura coalfields were analysed for pH, electrical conductivity, total dissolved solids (TDS), total hardness (TH), major anions, cations and trace metals to evaluate mine water geochemistry and assess solute acquisition processes, dissolved fluxes and its suitability for domestic, industrial and irrigation uses. Mine water samples are mildly acidic to alkaline in nature. The TDS ranged from 185 to 1343 mg L?1 with an average of 601 mg L?1. Ca2+ and Mg2+ are the dominant cations, while SO4 2? and HCO3 ? are the dominant anions. A high concentration of SO4 2? and a low HCO3 ?/(HCO3 ? + SO4 2?) ratio (<0.50) in the majority of the water samples suggest that either sulphide oxidation or reactions involving both carbonic acid weathering and sulphide oxidation control solute acquisition processes. The mine water is undersaturated with respect to gypsum, halite, anhydrite, fluorite, aluminium hydroxide, alunite, amorphous silica and oversaturated with respect to goethite, ferrihydrite, quartz. About 40% of the mine water samples are oversaturated with respect to calcite, dolomite and jarosite. The water quality assessment shows that the coal mine water is not suitable for direct use for drinking and domestic purposes and needs treatment before such utilization. TDS, TH, F?, SO4 2?, Fe, Mn, Ni and Al are identified as the major objectionable parameters in these waters for drinking. The coal mine water is of good to suitable category for irrigation use. The mines of North Karanpura coalfield annually discharge 22.35 × 106 m3 of water and 18.50 × 103 tonnes of solute loads into nearby waterways. 相似文献
10.
Abhay M. Varade Y. D. Khare N. C. Mondal Sarang Muley Pawan Wankawar Priti Raut 《Journal of the Indian Society of Remote Sensing》2013,41(3):619-630
The paper deals with the application of Remote Sensing and Geographical Information System (GIS) technique for a watershed development program. For this study, the WRJ-2 watershed falling under Narkhed and Katol Tahsils of Nagpur district, Maharashtra, India is investigated. Various thematic maps (i.e. drainage, geology, soil, geomorphology and land use/ land cover) have been prepared using the remote sensing and GIS techniques. Initially, differential weightage values are assigned to all the thematic maps as per their runoff characteristics. Subsequently, the maps are integrated in GIS environment to identify potential sites for water conservation measures like gully plugs, earthen check dams, continuous contour trenches, percolation tanks, cement bandhara, afforestration and farm ponds, etc. The study depicts that the GIS technique facilitates integration of thematic maps and thereby helps in an identification of micro-zones each with unique characters in-terms of hydrogeology, thus amenable to specific water conservation techniques. It is therefore concluded that, the GIS technique is suitable for an identification of water conservation structures. 相似文献