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61.
CHANDRA K. SHARMA 《水文科学杂志》2013,58(3):327-333
Abstract In a mountainous country like Nepal, where precipitation from the monsoon (July) and the westerlies (January) occurs yearly, it is surprising to find partial drought conditions in space and time. This paper deals with the partial drought conditions and also the measures to combat them. 相似文献
62.
In this paper we present a new class of nonsingular solutions representing time dependent balls of perfect fluid with matter-radiation
in general relativity. The solution of the class is suitable for interior modeling of a quasar i.e. a massive radiating star.
The interior solution is matched with a zero pressure Vaidya metric. From this solution we constructed a quasar model by assuming
the life time of the quasar of ≈107 year. We obtained a mass of the quasar of ≈109 M
θ
, linear dimension ≈1017 km and a rate of emission L
∞≈1047 erg/s. 相似文献
63.
64.
P. Pant 《Journal of Astrophysics and Astronomy》2006,27(2-3):293-297
The solar observational facilities at ARIES (erstwhile U.P. State Observatory, UPSO), Nainital, began in the sixties with
the acquisition of two moderate sized (25 cm, f/66 off-axis Skew Cassegrain and 15 cm, f/15 refractor) telescopes. Both these
systems receive sunlight through a 45 cm and 25 cm coelostat respectively. The backend instruments to these systems comprised
of a single pass grating spectrograph for spectroscopic study of the Sun and a Bernhard-HalleHα filter, coupled with a Robot recorder camera for solar patrolling inHα respectively. With the advancement in solar observing techniques with high temporal and spatial resolution inHα and other wavelengths, it became inevitable to acquire sophisticated instrumentation for data acquisition. In view of that,
the above facilities were upgraded, owing to which the conventional photographic techniques were replaced by the CCD camera
systems attached with two 15 cm, f/15 Coude refractor telescopes. These CCD systems include the Peltier cooled CCD camera
and photometrics PXL high speed modular CCD camera which provide high temporal and spatial resolution of ∼ 25 ms and ∼ 1.3
arcsec respectively. 相似文献
65.
Neeraj Pant 《Astrophysics and Space Science》2011,334(2):267-271
The paper presents a class of interior solutions of Einstein-Maxwell field equations of general relativity for a static, spherically
symmetric distribution of the charged fluid. This class of solutions describes well behaved charged fluid balls. The class
of solutions gives us wide range of parameter K (0.3277≤K≤0.49), for which the solution is well behaved hence, suitable for modeling of super dense star. For this solution the mass
of a star is maximized with all degree of suitability and by assuming the surface density ρ
b
=2×1014 g/cm3. Corresponding to K=0.3277 with X=−0.15, the maximum mass of the star comes out to be M=0.92M
Θ with radius r
b
≈17.15 km and the surface red shift Z
b
≈0.087187. It has been observed that under well behaved conditions this class of solutions gives us the mass of super dense
object within the range of white-dwarf. 相似文献
66.
Ritesh Patel Amareswari K Vaibhav Pant Dipankar Banerjee Sankarasubramanian K. Amit Kumar 《Solar physics》2018,293(7):103
ADITYA-L1 is India’s first space mission to study the Sun from the Lagrange 1 position. The Visible Emission Line Coronagraph (VELC) is one of seven payloads on the ADITYA-L1 mission, which is scheduled to be launched around 2020. One of the primary objectives of the VELC is to study the dynamics of coronal mass ejections (CMEs) in the inner corona. This will be accomplished by taking high-resolution (\({\approx}\,2.51~\mbox{arcsec}\,\mbox{pixel}^{-1}\)) images of the corona from \(1.05~\mbox{R}_{\odot}\,\mbox{--}\,3~\mbox{R}_{\odot}\) at a high cadence of 1 s in the 10 Å passband centered at 5000 Å. Because telemetry at the Lagrangian 1 position is limited, we plan to implement an onboard automated CME detection algorithm. The detection algorithm is based on intensity thresholding followed by area thresholding in successive difference images that are spatially rebinned to improve the signal-to-noise ratio. We present the results of the application of this algorithm on the data from existing coronagraphs such as STEREO/SECCHI COR-1, which is a space-based coronagraph, and K-Cor, a ground-based coronagraph, because they have a field of view (FOV) that is most similar to that of VELC. Since no existing space-based coronagraph has a FOV similar to VELC, we have created synthetic coronal images for the VELC FOV after including photon noise and injected CMEs of different types. The performance of the CME detection algorithm was tested on these images. We found that for VELC images, the telemetry can be reduced by a factor of 85% or more while maintaining a CME detection rate of 70% or higher at the same time. Finally, we discuss the advantages and disadvantages of this algorithm. The application of such an onboard algorithm in future will enable us to take higher resolution images with an improved cadence from space and simultaneously reduce the load on limited telemetry. This will help understanding CMEs better by studying their characteristics with improved spatial and temporal resolution. 相似文献
67.
We present a variety of well behaved classes of Charge Analogues of Tolman’s iv (1939). These solutions describe charged fluid
balls with positively finite central pressure, positively finite central density; their ratio is less than one and causality
condition is obeyed at the centre. The outmarch of pressure, density, pressure-density ratio and the adiabatic speed of sound
is monotonically decreasing, however, the electric intensity is monotonically increasing in nature. These solutions give us
wide range of parameter for every positive value of n for which the solution is well behaved hence, suitable for modeling
of super dense stars. keeping in view of well behaved nature of these solutions, one new class of solutions is being studied
extensively. Moreover, this class of solutions gives us wide range of constant K (0.3≤K≤0.91) for which the solution is well behaved hence, suitable for modeling of super dense stars like Strange Quark stars,
Neutron stars and Pulsars. For this class of solutions the mass of a star is maximized with all degree of suitability, compatible
with Quark stars, Neutron stars and Pulsars. By assuming the surface density ρ
b
=2×1014 g/cm3 (like, Brecher and Caporaso in Nature 259:377, 1976), corresponding to K=0.30 with X=0.39, the resulting well behaved model has the mass M=2.12M
Θ, radius r
b
≈15.27 km and moment of inertia I=4.482×1045 g cm2; for K=0.4 with X=0.31, the resulting well behaved model has the mass M=1.80M
Θ, radius r
b
≈14.65 km and moment of inertia I=3.454×1045 g cm2; and corresponding to K=0.91 with X=0.135, the resulting well behaved model has the mass M=0.83M
Θ, radius r
b
≈11.84 km and moment of inertia I=0.991×1045 g cm2. For n=0 we rediscovered Pant et al. (in Astrophys. Space Sci. 333:161, 2011b) well behaved solution. These values of masses and moment of inertia are found to be consistent with other models of Neutron
stars and Pulsars available in the literature and are applicable for the Crab and the Vela Pulsars. 相似文献
68.
We present a new spherically symmetric solution of the general relativistic field equations in isotropic coordinates. The
solution is having positive finite central pressure and positive finite central density. The ratio of pressure and density
is less than one and casualty condition is obeyed at the centre. Further, the outmarch of pressure, density and pressure-density
ratio, and the ratio of sound speed to light is monotonically decreasing. The solution is well behaved for all the values
of u lying in the range 0<u≤.186. The central red shift and surface red shift are positive and monotonically decreasing. Further, we have constructed
a neutron star model with all degree of suitability and by assuming the surface density ρ
b
=2×1014 g/cm3. The maximum mass of the Neutron star comes out to be M=1.591 M
Θ with radius R
b
≈12.685 km. The most striking feature of the solution is that the solution not only well behaved but also having one of the
simplest expressions so far known well behaved solutions. Moreover, the good matching of our results for Vela pulsars show
the robustness of our model. 相似文献
69.
The spectral AOD measurements have been made for the first time over Patiala during multi-platform field campaign ICARB—2006 using a Multi-Wavelength Radiometer (MWR) along with the suspended particulate matter measurements with a high volume sampler. Spectral AOD has higher values in May in comparison to March and April. The monthly mean AOD values at 500 nm are 0.26 ± 0.08, 0.36 ± 0.19 and 0.58 ± 0.20 for the months of March, April and May respectively. The mean AOD is more during afternoon in comparison to forenoon at all wavelengths. The atmospheric turbidity is higher in May and is attributed to dust transported by southerly winds prevailing during this month. The Ångström parameter α varies between zero and 0.68 while β ranges from 0.1 to 0.9. The columnar water vapour content ranges from 0.12 to 2.92 cm, having a mean value of 1.06 ± 0.648 cm. The mean total suspended particulate matter is 334.41 ± 97.56 μgm/m3, an indication of high aerosol loading over Patiala during the campaign period. 相似文献
70.
40Ar/39Ar Geochronology of the Rajmahal Basalts, India, and their Relationship to the Kerguelen Plateau 总被引:3,自引:0,他引:3
KENT RAY W.; PRINGLE MALCOLM S.; MULLER R. DIETMAR; SAUNDERS ANDREW D.; GHOSE NARESH C. 《Journal of Petrology》2002,43(7):1141-1153
During the mid-Cretaceous, extensive magmatism occurred in theIndian Ocean to form volcanic portions of the southern and centralKerguelen Plateau, Elan Bank and Broken Ridge. Basalt was eruptedalso along the rifted margin of eastern India (Rajmahal). Weinvestigated the ages of these Indian basalts using 40Ar/39Arincremental-heating experiments on whole rocks. Our resultsare consistent with the hypothesis that the lava pile of 相似文献