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61.
S.S. De B.K. De B. Bandyopadhyay Suman Paul D.K. Haldar S. Barui 《Journal of Atmospheric and Solar》2010,72(11-12):829-836
The variation of the first Schumann resonance (SR) frequency spectra observed from the recorded data over Kolkata (22.56°N, 88.5°E) during a solar proton event (SPE) on July 14, 2000 has been presented. It shows increase in frequency during X-ray bursts and decrease during the period of occurrence of an SPE. The results from some other locations for the same event are also reported. The severe X-ray bursts recorded just before the proton event exhibit enhancement in frequency of the first mode due to enhancement of ionization in the D-region of the ionosphere. Some attempts are made to explain the observed variation during solar proton events in terms of the perturbations within the Earth–ionosphere waveguide on the basis of two-layer-model. 相似文献
62.
SCS-CN and GIS-based approach for identifying potential water harvesting sites in the Kali Watershed,Mahi River Basin,India 总被引:6,自引:0,他引:6
The Kali sub-watershed is situated in the semi-arid region of Gujarat, India and forms a part of the Mahi River Watershed.
This watershed receives an average annual rainfall of 900mm mainly between July and September. Due to high runoff potential,
evapo-transpiration and poor infiltration, drought like situation prevails in this area from December to June almost every
year. In this paper, augmentation of water resource is proposed by construction of runoff harvesting structures like check
dam, percolation pond, farm pond, well and subsurface dyke. The site suitability for different water harvesting structures
is determined by considering spatially varying parameters like runoff potential, slope, fracture pattern and micro-watershed
area. GIS is utilised as a tool to store, analyse and integrate spatial and attribute information pertaining to runoff, slope,
drainage and fracture. The runoff derived by SCS-CN method is a function of runoff potential which can be expressed in terms
of runoff coefficient (ratio between the runoff and rainfall) which can be classified into three classes, viz., high (>40%),
moderate (20–40%) and low (<20%). In addition to IMSD, FAO specifications for water harvesting/recharging structures, parameters
such as effective storage, rock mass permeability are herein considered to augment effective storage. Using the overlay and
decision tree concepts in GIS, potential water harvesting sites are identified. The derived sites are field investigated for
suitability and implementation. In all, the accuracy of the site selection at implementation level varies from 80–100%. 相似文献
63.
In Einstein gravity, for an inhomogeneous phantom energy distribution having linear equation of state (but anisotropic), there exists simple exact solution for spherically symmetric space time describing a wormhole. At infinity, the space time is not asymptotically flat and possesses a regular cosmological Killing horizon with an infinite area. In this work, we have shown that, this wormhole solution is also possible in brane world for various matter distribution, which are not necessarily phantom in nature. 相似文献
64.
Data obtained from the 30m high MONTBLEX tower installed at the Indian Institute of Technology, Kharagpur are described. Data
on wind speed and direction, temperature and humidity were recorded during the first week of July 1989 at six levels on the
tower. They indicate some of the atmospheric surface layer characteristics. Using two levels of tower data involving wind
speed and temperature a profile method was used for computing the surface fluxes of heat and momentum. A method for calculating
the surface roughness length using the data was also used to obtain the vertical windspeed profile. The computed wind profile
was compared with observations, while the surface roughness length was compared with values obtained by a least square fit.
The computed surface fluxes were compared with theoretical values obtained by an energy budget method which uses only wind
data at one level. The agreement was reasonably good. 相似文献
65.
Sudipta S. Bandyopadhyay 《国际地质力学数值与分析法杂志》1982,6(4):393-407
The dynamic behaviour of road structure has been analysed by idealizing the subgrade with different viscoelastic models having three and four elements. Complex Fourier transformation has been used to solve the resulting differential equations. The results are presented in non-dimensional form. A detailed study has been made to determine the effect of different parameters on the deflection and moment of the pavement. Also, the relative implications of idealizing the subgrade with different viscoelastic models have been studied. A numerical example has been solved. 相似文献
66.
67.
Bhal Chandra Joshi Prakash Arumugasamy Manjari Bagchi Debades Bandyopadhyay Avishek Basu Neelam Dhanda Batra Suryarao Bethapudi Arpita Choudhary Kishalay De L. Dey A. Gopakumar Y. Gupta M. A. Krishnakumar Yogesh Maan P. K. Manoharan Arun Naidu Rana Nandi Dhruv Pathak Mayuresh Surnis Abhimanyu Susobhanan 《Journal of Astrophysics and Astronomy》2018,39(4):51
Radio pulsars show remarkable clock-like stability, which make them useful astronomy tools in experiments to test equation of state of neutron stars and detecting gravitational waves using pulsar timing techniques. A brief review of relevant astrophysical experiments is provided in this paper highlighting the current state-of-the-art of these experiments. A program to monitor frequently glitching pulsars with Indian radio telescopes using high cadence observations is presented, with illustrations of glitches detected in this program, including the largest ever glitch in PSR B0531+21. An Indian initiative to discover sub-\(\mu \)Hz gravitational waves, called Indian Pulsar Timing Array (InPTA), is also described briefly, where time-of-arrival uncertainties and post-fit residuals of the order of \(\mu \)s are already achievable, comparable to other international pulsar timing array experiments. While timing the glitches and their recoveries are likely to provide constraints on the structure of neutron stars, InPTA will provide upper limits on sub-\(\mu \)Hz gravitational waves apart from auxiliary pulsar science. Future directions for these experiments are outlined. 相似文献
68.
Andrew J. Gosling Reba M. Bandyopadhyay Katherine M. Blundell 《Monthly notices of the Royal Astronomical Society》2009,394(4):2247-2254
Using deep J -, H - and K S -band observations, we have studied the near-infrared extinction of the Nuclear Bulge, and find significant, complex variations on small physical scales. We have applied a new variable near-infrared colour excess (V-NICE) method to measure the extinction; this method allows for variation in both the extinction law parameter α and the degree of absolute extinction on very small physical scales. We see significant variation in both these parameters on scales of 5 arcsec. In our observed fields, representing a random sample of sight lines to the Nuclear Bulge, we measure α to be 2.64 ± 0.52 , compared to the canonical 'universal' value of 2. Our measured levels of are similar to previously measured results ; however, the steeper extinction law results in higher values for AJ (4.5 ≤ AJ ≤ 10 ) and AH (1.5 ≤ AH ≤ 6.5 ). Only when the extinction law is allowed to vary on the smallest scales can we recover self-consistent measures of the absolute extinction at each wavelength, allowing accurate reddening corrections for field star photometry in the Nuclear Bulge. The steeper extinction law slope also suggests that previous conversions of near-infrared extinction to AV may need to be reconsidered. Finally, we find that the measured values of extinction are significantly dependent on the filter transmission functions of the instrument used to obtain the data. This effect must be taken into account when combining or comparing data from different instruments. 相似文献
69.
In this work, we have discussed the Maxwell’s electrodynamics in non-linear forms in FRW universe. The energy density and pressure for non-linear electrodynamics have been written in the electro-magnetic universe. The Einstein’s field equations for flat FRW model in loop quantum cosmology have been considered if the universe is filled with the matter and electro-magnetic field. We separately assumed the magnetic universe and electric universe. The interaction between matter and magnetic field have been considered in one section and for some particular form of interaction term, we have found the solutions of magnetic field and the energy density of matter. We have also considered the interaction between the matter and electric field and another form of interaction term has been chosen to solve the field equations. The validity of generalized second law of thermodynamics has been investigated on apparent and event horizons using Gibb’s law and the first law of thermodynamics for magnetic and electric universe separately. 相似文献
70.
We investigate the effect of exotic matter in particular, hyperon matter on neutron star properties such as equation of state
(EoS), mass-radius relationship and bulk viscosity. Here we construct equations of state within the framework of a relativistic
field theoretical model. As hyperons are produced abundantly in dense matter, hyperon–hyperon interaction becomes important
and is included in this model. Hyperon–hyperon interaction gives rise to a softer EoS which results in a smaller maximum mass
neutron star compared with the case without the interaction. Next we compute the coefficient of bulk viscosity and the corresponding
damping time scale due to the non-leptonic weak process including Λ hyperons. Further, we investigate the role of the bulk
viscosity on gravitational radiation driven r-mode instability in a neutron star of given mass and temperature and find that
the instability is effectively suppressed.
相似文献