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81.
Anil Kumar Yadav Anirudh Pradhan Ajay Kumar Singh 《Astrophysics and Space Science》2012,337(1):379-385
The present study deals with spatially homogeneous and totally anisotropic locally rotationally symmetric (LRS) Bianchi type
I cosmological model with variable G and Λ in presence of imperfect fluid. To get the deterministic model of Universe, we assume that the expansion (θ) in the model is proportional to shear (σ). This condition leads to A=ℓB
n
, where A, B are metric potential. The cosmological constant Λ is found to be decreasing function of time and it approaches a small positive
value at late time which is supported by recent Supernovae Ia (SN Ia) observations. Also it is evident that the distance modulus
curve of derived model matches with observations perfectly. 相似文献
82.
The present study deals with spatial homogeneous and anisotropic locally rotationally symmetric (LRS) Bianchi-II dark energy model in general relativity. The Einstein’s field equations have been solved exactly by taking into account the proportionality relation between one of the components of shear scalar $(\sigma^{1}_{1})$ and expansion scalar (?), which, for some suitable choices of problem parameters, yields time dependent equation of state (EoS) and deceleration parameter (DP), representing a model which generates a transition of universe from early decelerating phase to present accelerating phase. The physical and geometrical behavior of universe have been discussed in detail. 相似文献
83.
The morphometric analysis of river basin helps to explore the interrelationship between hydraulic parameters and geomorphologic characteristics. The study has been conducted in the Upper Tons basin of Northern Foreland of Peninsular India. The river basin has been characterized using the topographical maps, CARTOSAT satellite image integrated using the GIS techniques. The drainage density analysis indicates lower values in the north-eastern regions and thus these regions can be categorized as better ground water potential zone. There are in total 10 sub-watersheds which have been delineated; SW-4 has maximum drainage density (4.75), stream frequency (5.61) and drainage texture (26.64) followed by SW-6–10. The prioritized sub-watershed numbers SW-4 and SW-6–10 need conservation practices because of their high erodibility and run-off. SW-1–3 and SW-5 regions have better permeable bed rocks and hence good for water harvesting. The areal parameter indicates elongated shape of basin and moderate to steeper ground slope. The results are supported by extensive field survey. This study can be applied for soil and water management, as well as disaster prevention from similar type of drainage basins. 相似文献
84.
R. R. Yadav Dilip Kumar Jaiswal Hareesh Kumar Yadav Gulrana 《Environmental Earth Sciences》2012,65(3):849-859
A three-dimensional model for non-reactive solute transport in physically homogeneous subsurface porous media is presented.
The model involves solution of the advection-dispersion equation, which additionally considered temporally dependent dispersion.
The model also account for a uniform flow field, first-order decay which is inversely proportional to the dispersion coefficient
and retardation factor. Porous media with semi-infinite domain is considered. Initially, the space domain is not solute free.
Analytical solutions are obtained for uniform and varying pulse-type input source conditions. The governing solute transport
equation is solved analytically by employing Laplace transformation technique (LTT). The solutions are illustrated and the
behavior of solute transport may be observed for different values of retardation factor, for which simpler models that account
for solute adsorption through a retardation factor may yield a misleading assessment of solute transport in ‘‘hydrologically
sensitive’’ subsurface environments. 相似文献
85.
Amrita Yadav D. Shashidhar K. Mallika N. Purnachandra Rao Sunil Rohilla H. V. S. Satyanarayana D. Srinagesh Harsh Gupta 《Natural Hazards》2013,69(1):965-979
New empirical relations are derived for source parameters of the Koyna–Warna reservoir-triggered seismic zone in Western India using spectral analysis of 38 local earthquakes in the magnitude range M L 3.5–5.2. The data come from a seismic network operated by the CSIR-National Geophysical Research Institute, India, during March 2005 to April 2012 in this region. The source parameters viz. seismic moment, source radius, corner frequency and stress drop for the various events lie in the range of 1013–1016 Nm, 0.1–0.4 km, 2.9–9.4 Hz and 3–26 MPa, respectively. Linear relationships are obtained among the seismic moment (M 0), local magnitude (M L), moment magnitude (M w), corner frequency (fc) and stress drop (?σ). The stress drops in the Koyna–Warna region are found to increase with magnitude as well as focal depths of earthquakes. Interestingly, accurate depths derived from moment tensor inversion of earthquake waveforms show a strong correlation with the stress drops, seemingly characteristic of the Koyna–Warna region. 相似文献
86.
Natural Hazards - Investigations of micro- and low-magnitude earthquakes in the Kangra-Chamba region of the NW Himalaya were performed to evaluate the relationship between earthquake source,... 相似文献
87.
Annual Cyclic Variations (ACV) in the Total Ozone Column (TOC) were estimated in latitudinally averaged Multi Sensor Reanalysis (MSR) monthly mean TOC time-series data-set from Jan 1979 to Dec 2008 for Indian region. The TOC contents over any latitude is controlled by the photochemistry and dynamics present in different regions of the stratosphere and troposphere, correlation between ACV in TOC, and ACV in other climatic and dynamical factors—(i) Solar Insolation on a horizontal surface at the top of the atmosphere (ETSI); (ii) Zonal Wind at 30 hPa pressure level (ZW); (iii) Meridional Wind at 30 hPa pressure level (MW); and (iv) Air Temperature at 30 hPa pressure level (AT)—were taken into account to understand their role in the annual cyclic variability present in the TOC over Indian region. Contributions of ACV present in these climatic and dynamical factors to the ACV in TOC were ascertained by performing a multiple linear regression analysis by taking ACV in ETSI, ACV in ZW and ACV in AT as independent variables (co-variates) for ACV in TOC. It is concluded that in the tropical part of Indian region ACV in TOC is largely controlled by the photochemistry; whereas in the subtropical part of the region, the dynamics present in the stratosphere mainly decides ACV in TOC. 相似文献
88.
Divya Prakash Dhananjay Kumar Patel Suparna Tewari Manoj Kumar Yadav Roopali Yadav 《Journal of the Geological Society of India》2017,89(2):139-144
The pelitic schists of the area around Kandra, Singhbhum district, Jharkhand belong to the Chaibasa Formation of the Singhbhum Group, which constitute a part of the youngest Precambrian orogenic cycle of the Singhbhum region. Structurally, the area represents the Singhbhum anticlinorium and is overlain by Dalma traps which form the synclinorium towards the north of the area around Kandra. This area mainly consists of medium to high grade rocks belonging to greenschist and amphibolite facies. These rocks are folded in the E-W trending doubly plunging folds (F1) overturned towards the south with low plunges and superposed by cross-folds (F2). The spatial distribution of the index minerals in the pelitic schists of the area shows Barrovian type of metamorphism. Four isograds, viz. biotite, garnet, staurolite and sillimanite have been delineated by the first appearance of the index minerals and also by isograd reactions. The textural relation suggests that sillimanite is formed from staurolite consumption reaction instead of kyanite consumption. 相似文献
89.
Ram Bichar Singh Yadav Jayant Nath Tripathi Bal Krishna Rastogi Mridul Chandra Das Sumer Chopra 《Pure and Applied Geophysics》2010,167(11):1331-1342
Northeast India and adjoining regions (20°–32° N and 87°–100° E) are highly vulnerable to earthquake hazard in the Indian
sub-continent, which fall under seismic zones V, IV and III in the seismic zoning map of India with magnitudes M exceeding 8, 7 and 6, respectively. It has experienced two devastating earthquakes, namely, the Shillong Plateau earthquake
of June 12, 1897 (M
w
8.1) and the Assam earthquake of August 15, 1950 (M
w
8.5) that caused huge loss of lives and property in the Indian sub-continent. In the present study, the probabilities of
the occurrences of earthquakes with magnitude M ≥ 7.0 during a specified interval of time has been estimated on the basis of three probabilistic models, namely, Weibull,
Gamma and Lognormal, with the help of the earthquake catalogue spanning the period 1846 to 1995. The method of maximum likelihood
has been used to estimate the earthquake hazard parameters. The logarithmic probability of likelihood function (ln L) is estimated
and used to compare the suitability of models and it was found that the Gamma model fits best with the actual data. The sample
mean interval of occurrence of such earthquakes is estimated as 7.82 years in the northeast India region and the expected
mean values for Weibull, Gamma and Lognormal distributions are estimated as 7.837, 7.820 and 8.269 years, respectively. The
estimated cumulative probability for an earthquake M ≥ 7.0 reaches 0.8 after about 15–16 (2010–2011) years and 0.9 after about 18–20 (2013–2015) years from the occurrence of
the last earthquake (1995) in the region. The estimated conditional probability also reaches 0.8 to 0.9 after about 13–17
(2008–2012) years in the considered region for an earthquake M ≥ 7.0 when the elapsed time is zero years. However, the conditional probability reaches 0.8 to 0.9 after about 9–13 (2018–2022)
years for earthquake M ≥ 7.0 when the elapsed time is 14 years (i.e. 2009). 相似文献
90.