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61.
Singh Jagdev Cowsik R. Raveendran A. V. Bagare S. P. Saxena A. K. Sundararaman K. Krishan Vinod Naidu Nagaraja Samson J. P. A. Gabriel F. 《Solar physics》1997,170(2):235-252
An experiment to search for short-period oscillations in the solar corona was conducted during the total solar eclipse of 1995 October 24 at Kalpi, India. The intensity in the continuum, centred around 5500 Å and with a passband having a half-width of 240 Å, was recorded at a counting rate of 20 Hz using a thermoelectric-liquid cooled photomultiplier. The power-spectrum analysis of the data reveals that most of the power is contained in 6 frequencies below 0.2 Hz. A least-square analysis gives the periods of the 6 frequency components to be 56.5, 19.5, 13.5, 8.0, 6.1, and 5.3 s. These oscillations are found to be sinusoidal, and their amplitudes are found to lie in the rangeinebreak 0.2–1.3% of the coronal brightness. Assuming these oscillations to be fast magnetosonic modes, the calculations indicate the availability of enough flux for the heating of the active regions in the solar corona. 相似文献
62.
Improvement of groundwater quality due to fresh water ingress in Potharlanka Island, Krishna delta, India 总被引:1,自引:0,他引:1
Hydrochemical study had been carried out on the groundwater resources of Potharlanka Island, Krishna delta, India. Groundwater
samples were collected and analyzed at 42 sites in December 2001 and October 2006. A comparative study of hydrochemical data
indicates: groundwater is mildly alkaline with a pH of 7.0–8.2; electrical conductivity (EC) varies from 605 to 5,770 μS/cm
in December 2001, and 652–5,310 μS/cm in October 2006. More than 62% of the groundwater samples in 2006 have TDS value <2,000 mg/l,
which is within permissible limit of potable water, but 57% of the samples in 2001, are higher than the maximum permissible
limit. Extremely low HCO3/Cl and variable high Mg/Ca (molar ratios) had been indicated the transformation of the fresh groundwater aquifer systems
to saline in 2001. Groundwater of this Island is mainly classified as Na–Cl and mixed types. A high percentage of Na–Cl type
of these waters indicates the possibility of seawater ingression/intrusion process during 2001 and comparatively mixed water
type indicates the dilution activities of groundwater. Excessive withdrawal of groundwater has caused the increase of saline
water intrusion. Improvement of groundwater quality in this Island due to artificial recharge structures made by NGRI under
RGNDWM project and affects of the flood due to heavy rainfall of the months of September–October 2005 are discussed in this
paper. 相似文献
63.
S. K. Sharma T. K. Mandal A. K. De N. C. Deb Srishti Jain Mohit Saxena S. Pal A. K. Choudhuri Saraswati 《Journal of Atmospheric Chemistry》2018,75(2):219-233
Ambient concentrations of organic carbon (OC), elemental carbon (EC) and water soluble inorganic ionic components (WSIC) of PM10 were studied at Giridih, Jharkhand, a sub-urban site near the Indo Gangatic Plain (IGP) of India during two consecutive winter seasons (November 2011–February 2012 and November 2012–February 2013). The abundance of carbonaceous and water soluble inorganic species of PM10 was recorded at the study site of Giridih. During winter 2011–12, the average concentrations of PM10, OC, EC and WSIC were 180.2?±?46.4; 37.2?±?6.2; 15.2?±?5.4 and 18.0?±?5.1 μg m?3, respectively. Similar concentrations of PM10, OC, EC and WSIC were also recorded during winter 2012–13. In the present case, a positive linear trend is observed between OC and EC at sampling site of Giridih indicates the coal burning, as well as dispersed coal powder and vehicular emissions may be the source of carbonaceous aerosols. The principal components analysis (PCA) also identifies the contribution of coal burning? +?soil dust, vehicular emissions?+?biomass burning and seconday aerosol to PM10 mass concentration at the study site. Backward trajectoy and potential source contributing function (PSCF) analysis indicated that the aerosols being transported to Giridih from upwind IGP (Punjab, Haryana, Uttar Pradesh and Bihar) and surrounding region. 相似文献
64.
A. K. Srivastava Anju Saxena Deepa Agnihotri 《Journal of the Geological Society of India》2012,80(5):676-684
Plant fossils from the coal bearing Barakar Formation exposed in Gottitoria open cast mine of Mohpani Coalfield, Satpura Gondwana Basin are described for the first time. The assemblage is represented by Glossopteris communis, G. indica, G. stenoneura, Gangamopteris angustifolia, G. cyclopteroides, G. karharbariensis, G. major, seeds of Cordaicarpus zeilleri and equisetaceous stems. The dominance of the species of Gangamopteris over the species of Glossopteris and absence of Noeggerathiopsis indicate the floral affinity with the flora of Lower Barakar Formation of Lower Gondwana. 相似文献
65.
Suryendu Dutta Monalisa Mallick Runcie Paul Mathews Ulrich Mann Paul F. Greenwood Rakesh Saxena 《Journal of Earth System Science》2010,119(5):711-716
The terpenoid composition of resins from the Miocene lignite horizons from the Kerala-Konkan Coast, western India was analyzed
by Curie-point pyrolysis-gas chromatography-mass spectrometry (Cupy-GC-MS). The major pyrolysates were cadalene-based bicyclic
sesquiterpenoids including some C30-C31 bicadinenes and bicadinanes typical of dammar resin from angiosperm plants of Dipterocarpaceae family. These plants are typically
supported by tropical climates which the western Indian region was known to have experienced during early Tertiary period.
The present study suggests that these palaeoclimatic conditions persisted until at least the Miocene epoch. These sesquiterpenoids
which are commonly detected in many SE Asian crude oils may be utilised as useful biomarkers for petroleum exploration in
the western Indian region. 相似文献
66.
Sanjay Kumar Jain Sharad K. Jain V. Hariprasad Anju Choudhry 《Journal of the Indian Society of Remote Sensing》2011,39(2):259-270
Water balance of a basin involves estimation of input precipitation, runoff, infiltration and evapotranspiration (ET). Although
ET may have large variations over a big basin, it is commonly estimated using a few point measurements and this makes the
estimation error prone. Satellite based remote sensing data provides few parameters for estimation of energy fluxes, at the
land surface and atmosphere interaction in a distributed manner using the meteorological parameters. These parameters through
surface energy balance equation have been used for the estimation of ET in this study. Various spatially distributed variables
required for ET estimation; viz. NDVI, surface albedo, surface temperature etc. have been derived using remote sensing and
ancillary data for Tapi basin located in western India. Beside this field data such as rainfall, air temperature, relative
humidity, sunshine hours etc. have been used. For computation of runoff, Soil Conservation Services (SCS) approach has been
considered. Tapi basin up to Ukai dam has been selected as the study area. Satellite data from National Oceanic and Atmospheric
Administration (NOAA), Polar Orbiting Environmental Satellite, which carries the Advanced Very High Resolution Radiometer
(AVHRR), have been used for preparation of various maps required for runoff and ET analysis. The results of runoff and ET
have been compared with observed data for 2 years, 2002–2003 and the results have been found in good agreement with observed
data. 相似文献
67.
Aruna Srivastava Corresponding author B. N. Nagpal Rekha Saxena Vas Dev S. K. Subbarao 《International journal of geographical information science》2013,27(1):91-98
This paper reports research to predict the distribution of An. minimus, a malaria vector in forest fringe areas using GIS to support precision surveys for malaria control. Because An. minimus is a forest‐associated species, generalized thematic maps (1:6?000?000) of forest cover, soil type, altitude, rainfall and temperature were used. Digitization, overlaying, integration and analysis of thematic maps were done using Arc/Info 8.1 NT and Arc/View 3.2 (GIS, ESRI) software. GIS delineated favourable areas for An. minimus where the species is likely to be found, and precision surveys can be conducted. Precision field surveys in selected locations of favourable/non‐favourable areas were carried out. The species could be found in all locations designated as a favourable area and was absent in non‐favourable areas. In two districts, one where the species is reported to have disappeared in the early 1950s and the other where it was not reported in earlier surveys, GIS helped in precision surveys, and An. minimus was found. The technique can quickly cover vast and inaccessible areas and is easy to duplicate in other parts of the world to assist cost‐effective control of malaria. It can also delineate areas favourable for any species of flora and fauna to help precision surveys. 相似文献
68.
Abstract The tsunami travel‐time charts that are presently in use by the Tsunami Warning Center were constructed originally in 1948 based on the hydrographic data available in the mid 1940s. Even the revised charts of 1971 made use of essentially the same data. It is shown here that the travel times deduced by these charts could be in error by as much as two hours in some cases. Even worse, the compiled travel times as deduced from these charts are generally greater than the observed travel times, which is a dangerous situation from a tsunami warning point of view. 相似文献
69.
The origin of anorthosite and associated igneous gabbronorite and ferrodiorite was investigated through detailed study of
a typical massif-type anorthosite complex from Gruber, Central Dronning Maud Land, East Antarctica. Field observations showed
that the Gruber Complex is made up of gabbronorite-anorthosite pluton which was intruded by ferrodiorite dykes. Systematic
samples collected from the Gruber Complex revealed significant geochemical variations within the region. Four rock types have
been identified, based on modal proportions of mineral phases and their geochemistry data. Clinopyroxene-gabbronorite and
plagioclase-gabbronorite are the two types of gabbronorite with the dominance of clinopyroxene and plagioclase, respectively.
Anorthosite is represented by rocks having predominance of plagioclase with minor clinopyroxene. Ferrodiorite is characterized
by modal abundance of orthopyroxene and Fe-Ti oxide. Major and trace element systematics showed that all the four rock types
are co-magmatic and are related through fractional crystallization. Based on this study, it is reported that clinopyroxene
was the first phase to crystallize followed by plagioclase and then Fe-Ti oxides. Furthermore, trace element composition of
the parental melt was calculated using LA-ICPMS analysis of the most primitive, pure clinopyroxene found in the clinopyroxene
gabbronorite. Our analyses suggested that the parental melt was similar to that of continental arc basalt and showed signatures
of subduction-related metasomatism. Based on mineral chemical and geochemical data, it is interpreted that the parent melt
went through changing sequence of crystallization which led to the formation of massive anorthosite. 相似文献
70.
Kamal Jeet Singh Srikanta Murthy Anju Saxena Husain Shabbar 《Journal of Earth System Science》2017,126(2):25
The coal-bearing sequences of Barakar and Raniganj formations exposed in Bina and Jhingurdah open-cast collieries, respectively, are analysed for their macro- and miofloral content. The sediment successions primarily comprise of sandstones, shales, claystones and coal seams. In addition to the diverse glossopterid assemblage, four palynoassemblage zones, namely Zones I and II in Bina Colliery and Zones III and IV in Jhingurdah Colliery, have also been recorded in the present study. The megafossil assemblage from the Barakar strata of Bina Colliery comprises of three genera, namely Gangamopteris, Glossopteris and cf. Noeggerathiopsis. Palynoassemblage-I is characterised by the dominance of non-striate bisaccate pollen genus Scheuringipollenites and subdominance of striate bisaccate Faunipollenites and infers these strata to be of Early Permian (Artinskian) age (Lower Barakar Formation). The palynoassemblage has also yielded a large number of naked fossil spore tetrads, which is the first record of spore tetrads from any Artinskian strata in the world and has a significant bearing on the climatic conditions. The palynoassemblage-II is characterised with the dominance of Faunipollenites over Scheuringipollenites and is indicative of Kungurian age (Upper Barakar Formation). The megafossil assemblage from the Raniganj Formation of Jhingurdah Colliery comprises of five genera with 26 species representing four orders, viz., Equisetales, Cordaitales, Cycadales and Glossopteridales. The order Glossopteridales is highly diversified with 23 taxa and the genus Glossopteris, with 22 species, dominates the flora. The mioflora of this colliery is represented by two distinct palynoassemblages. The palynoassemblage-III is correlatable with the palynoflora of Early Permian (Artinskian) Lower Barakar Formation. The assemblage suggests the continuity of older biozones into the younger ones. The palynoassemblage-IV equates the beds with composition V: Striatopodocarpites–Faunipollenites–Gondisporites assemblage zone of Tiwari and Tripathi (1992) of Late Permian (Lopingian) Raniganj Formation in Damodar Basin. The FAD’s of Alisporites, Klausipollenites, Falcisporites, Arcuatipollenites pellucidus and Playfordiaspora cancellosa palynotaxa in this assemblage enhance the end Permian level of the Jhingurdah Top seam, as these elements are the key species to mark the transition of Permian into the Lower Triassic. 相似文献