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91.
A class of well behaved charged superdense star models of embedding class one is obtained by taking perfect fluid to be interior
matter. In the process we come across the models for white dwarf, quark and neutron stars. Maximum mass of the star of this
class is found to be 6.716998M
Θ with its radius is 18.92112 Km. In the absence of charge the models reduce to Schwarzchild’s interior model with constant
density. 相似文献
92.
In the present article a model of well behaved charged superdense star with surface density 2×1014 gm/cm3 is constructed by considering a static spherically symmetric metric with t=const hypersurfaces as hyperboloid. So far well behaved model described by such metric could not be obtained. Maximum mass
of the star is found to be 0.343457M
⊙ and the corresponding radius is 9.57459 km. The red shift at the centre and on the surface are given as 0.068887 and 0.031726
respectively. 相似文献
93.
Jayanta Roy Yashwant Gupta Ue-Li Pen Jeffrey B. Peterson Sanjay Kudale Jitendra Kodilkar 《Experimental Astronomy》2010,28(1):25-60
The new era of software signal processing has a large impact on radio astronomy instrumentation. Our design and implementation
of a 32 antennae, 33 MHz, dual polarization, fully real-time software backend for the GMRT, using only off-the-shelf components,
is an example of this. We have built a correlator and a beamformer, using PCI-based ADC cards and a Linux cluster of 48 nodes
with dual gigabit inter-node connectivity for real-time data transfer requirements. The highly optimized compute pipeline
uses cache efficient, multi-threaded parallel code, with the aid of vectorized processing. This backend allows flexibility
in final time and frequency resolutions, and the ability to implement algorithms for radio frequency interference rejection.
Our approach has allowed relatively rapid development of a fairly sophisticated and flexible backend receiver system for the
GMRT, which will greatly enhance the productivity of the telescope. In this paper we describe some of the first lights using
this software processing pipeline. We believe this is the first instance of such a real-time observatory backend for an intermediate
sized array like the GMRT. 相似文献
94.
Saibal Gupta Aditi Das Sudipta Goswami Ananda Modak Suman Mondal 《Journal of the Geological Society of India》2010,75(1):313-322
Inverted metamorphism in the Himalayas is closely associated with the Main Central Thrust (MCT). In the western Himalayas,
the Main Central Thrust conventionally separates high grade metamorphic rocks of the Higher Himalayan Crystalline Sequence
(HHCS) from unmetamorphosed rocks of the Inner sedimentary Belt. In the eastern Himalayas, the Inner sedimentary Belt is absent,
and the HHCS and meta-sedimentary Lesser Himalayan Sequence (LHS) apparently form a continuous Barrovian metamorphic sequence,
leading to confusion about the precise location of the MCT. In this study, it is demonstrated that migmatitic gneisses of
the sillimanite zone in the higher structural levels of the HHCS are multiply deformed, with two phases of penetrative fabric
formation (S1HHCS and S2HHCS) followed by third folding event associated with a spaced, NW-SE trending, north-east dipping foliation (S3HHCS). The underlying LHS schists (kyanite zone and lower) are also multiply deformed, with the bedding S0 being isoclinally folded (F1LHS), and subsequently refolded (F2LHS and F3LHS). The contact zone between the HHCS and LHS is characterized by ductile, top-to-the southwest shearing and stabilization
of a pervasive foliation that is consistently oriented NW-SE and dips northeast. This foliation is parallel to the S3HHCS foliation in the HHCS, and the S2LHS in the LHS. Early lineations in the HHCS and LHS also show different dispersions across the contact shear zone, implying
that pre-thrusting orientations of the two units were distinct. The contact shear zone is therefore interpreted to be a plane
of structural discordance, shows a shear sense consistent with thrust movement and is associated with mineral growth during
Barrovian metamorphism. It may well be considered to represent the MCT in this region. 相似文献
95.
Koushik Sen Ruchika Sharma B. R. Arora Vikram Gupta 《Journal of the Geological Society of India》2010,76(5):322-330
Anisotropy of Magnetic Susceptibility (AMS) and seismic wave velocity studies of some paramagnetic Himalayan granitoids show
good correlation between magnetic fabric anisotropy and P wave velocity (Vp). Vp shows strong positive correlation with magnetic
lineation (L) and degree of magnetic anisotropy (P′) having correlation coefficient (r) values of 0.93 and 0.89 respectively.
Both Vp and Vs show positive correlation with the SiO2 content of Proterozoic and Paleozoic granitoids. Velocity of S wave (Vs) shows negative correlation with mean magnetic susceptibility
(Km) having ‘r’ value of 0.86. The correlation between Vs-Km, Vp-P′, Vp-L also shows >95% probability in Spearman’s rank correlation. Based on the results from the present sample size it is suggested
that, in paramagnetic granites, Vp is proportional to intensity of deformation and preferred orientation of minerals as well as the mineralogy. On the other
hand, Vs is more dependent on the mineralogy alone. 相似文献
96.
Koushik Sen Ruchika Sharma B. R. Arora Vikram Gupta 《Journal of the Geological Society of India》2010,76(4):322-330
Anisotropy of Magnetic Susceptibility (AMS) and seismic wave velocity studies of some paramagnetic Himalayan granitoids show good correlation between magnetic fabric anisotropy and P wave velocity (Vp). Vp shows strong positive correlation with magnetic lineation (L) and degree of magnetic anisotropy (P′) having correlation coefficient (r) values of 0.93 and 0.89 respectively. Both Vp and Vs show positive correlation with the SiO2 content of Proterozoic and Paleozoic granitoids. Velocity of S wave (Vs) shows negative correlation with mean magnetic susceptibility (Km) having ‘r’ value of 0.86. The correlation between Vs-Km, Vp-P′, Vp-L also shows >95% probability in Spearman’s rank correlation. Based on the results from the present sample size it is suggested that, in paramagnetic granites, Vp is proportional to intensity of deformation and preferred orientation of minerals as well as the mineralogy. On the other hand, Vs is more dependent on the mineralogy alone. 相似文献
97.
Sea surface winds from the Oceansat-2 scatterometer (OSCAT) are important inputs to Numerical Weather Prediction (NWP) models. The Indian Space Research Organization (ISRO) recently updated the OSCAT retrieval algorithm in order to generate better products. An attempt has been made in this study to evaluate the updated OSCAT winds using buoy observations and the 6-hour short-term forecasts from the T574L64 model from the National Centre for Medium Range Weather Forecasting (NCMRWF) during the 2011 monsoon. The results of the OSCAT evaluation are also compared with those from the Advanced Scatterometer (ASCAT) on-board the Meteorological Operational Satellite-A (MetOp-A) which were evaluated in the same way. The root mean square differences (RMSDs) for wind speed and direction, are within 2?m?s?1 and 20° for both scatterometers. The RMSDs for OSCAT are slightly higher than those for ASCAT, and this difference may be attributed in part to the difference in frequency and resolution of the scatterometer payloads. The bias and standard deviation for ASCAT winds are also lower than those for OSCAT winds with respect to the model short-range forecast, and this can be attributed to the regular assimilation of ASCAT winds in the model. 相似文献
98.
In this study, we investigate a long-term modulation in the relationship between Indian summer monsoon rainfall with the subsequent Australian summer monsoon rainfall. The two monsoon rainfall time series are significantly correlated at 0.3 at the 99 % confidence level. However, the relationship weakens during the 1932–1966 period, with the inter-monsoon correlation for the period falling below statistical significance. We find that this modulation is consistent with a breakdown of the typical El Niño-Southern Oscillation (ENSO) influence on sea surface temperature in the northern region of Australia, during this period. In addition, a change in the relative influences of ENSO and Indian Ocean Basin-wide Warming sea surface temperature anomalies on the Australian summer monsoon rainfall is also apparent across different time periods. 相似文献
99.
Tourmaline occurs as a minor but important mineral in the alteration zc,ne of the Archean orogenic gold deposit of Guddadarangavanahalli (G.R.Halli) in the Chitradurga greenst~ne belt of the western Dharwar craton, southern India. It occurs in the distal alteration halo of the G.R.Halli golcl deposit as (a) clusters of very fine grained aggregates which form a minor constituent in the natrix of the altered metabasalt (AMB tourmaline) and (b) in quartz-carbonate veins (vein tourmaline). ~['he vein tourmaline, based upon the association of specific carbonate minerals, is further grouped as (i) albite-tourmaline-ankerite-quartz veins (vein-1 tourmaline) and (ii) albite-tourmaline-calcite-quartz veins (vein-2 tourmaline). Both the AMB tourmaline and the vein tourmalines (vein-I and vein-2) belong to the alkali group and are clas- sified under schorl-dravite series. Tourmalines occurring in the veins are zoned while the AMB tour- malines are unzoned. Mineral chemistry and discrimination diagrams 1eveal that cores and rims of the vein tourmalines are distinctly different. Core composition of the ve:n tourmalines is similar to the composition of the AMB tourmaline. The formation of the AMB tourmaline and cores of the vein tour- malines are proposed to be related to the regional D1 deformational event associated with the emplacement of the adjoining ca. 2.61 Ga Chitradurga granite whilst rims of the vein tourmalines vis-a- vis gold mineralization is spatially linked to the juvenile magmatic accretion (2.56-2.50 Ga) east of the studied area in the western part of the eastern Dharwar craton. 相似文献
100.
Appraisal of land use/land cover of mangrove forest ecosystem using support vector machine 总被引:2,自引:1,他引:1
Sudhir Kumar Singh Prashant K. Srivastava Manika Gupta Jay Krishna Thakur Saumitra Mukherjee 《Environmental Earth Sciences》2014,71(5):2245-2255
Human activities in many parts of the world have greatly changed the natural land cover. This study has been conducted on Pichavaram forest, south east coast of India, famous for its unique mangrove bio-diversity. The main objectives of this study were focused on monitoring land cover changes particularly for the mangrove forest in the Pichavaram area using multi-temporal Landsat images captured in the 1991, 2000, and 2009. The land use/land cover (LULC) estimation was done by a unique hybrid classification approach consisting of unsupervised and support vector machine (SVM)-based supervised classification. Once the vegetation and non-vegetation classes were separated, training site-based classification technology i.e., SVM-based supervised classification technique was used. The agricultural area, forest/plantation, degraded mangrove and mangrove forest layers were separated from the vegetation layer. Mud flat, sand/beach, swamp, sea water/sea, aquaculture pond, and fallow land were separated from non-vegetation layer. Water logged areas were delineated from the area initially considered under swamp and sea water-drowned areas. In this study, the object-based post-classification comparison method was employed for detecting changes. In order to evaluate the performance, an accuracy assessment was carried out using the randomly stratified sampling method, assuring distribution in a rational pattern so that a specific number of observations were assigned to each category on the classified image. The Kappa accuracy of SVM classified image was highest (94.53 %) for the 2000 image and about 94.14 and 89.45 % for the 2009 and 1991 images, respectively. The results indicated that the increased anthropogenic activities in Pichavaram have caused an irreversible loss of forest vegetation. These findings can be used both as a strategic planning tool to address the broad-scale mangrove ecosystem conservation projects and also as a tactical guide to help managers in designing effective restoration measures. 相似文献