排序方式: 共有48条查询结果,搜索用时 15 毫秒
31.
Farook Rahaman 《Astrophysics and Space Science》2002,282(4):625-633
Thick domain walls with time dependent displacement vector based on Lyra's geometry are considered. Their exact solutions are obtained in the background of a five-dimensional space time. The field theoretic energy-momentum tensor is considered assuming with $$T_t^t = T_x^x = T_y^y = T_\psi ^\psi .$$ Acceleration due to the domain wall has been evaluated by studyinggeodesic equation. 相似文献
32.
Mahmud Sultan Sumana Ferdausi Mahojabin Mohsin Md Khan Md. Hasinur Rahaman 《Natural Hazards》2022,111(2):1863-1884
Natural Hazards - The knowledge of the climate pattern for a particular region is important for taking appropriate actions to alleviate the impact of climate change. It is also equally important... 相似文献
33.
S J Prasad T M Balakrishnan Nair Hasibur Rahaman S S C Shenoi T Vijayalakshmi 《Journal of Earth System Science》2018,127(8):111
A Liquefied Petroleum Gas (LPG) tanker and a chemical tanker collided two nautical miles off Ennore port on 28 January, 2017. Around 196.4 metric tons (MT) of Heavy Furnace Oil (HFO) was spilled and drifted towards the shore. Oil spill drift advisory and prediction was made by Indian National Centre for Ocean Information Services (INCOIS) using General National Oceanic and Atmospheric Administration (NOAA) Operational Modeling Environment (GNOME), an oil spill trajectory model. The trajectory model was forced with analysed and forecasted ocean currents from Global Ocean Data Assimilation System (GODAS) based on Modular Ocean Model 4p1 (GM4p1). It was found that spread of HFO obtained from oil spill trajectory model GNOME, has matched well with the observed spread from Sentinel-1A satellite dataset. However, the spread of the HFO was underestimated by the trajectory model, when forced with forecasted GM4p1 currents. Additional ground truth observation from Indian Coast Guard also corroborates this finding. 相似文献
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35.
Mohammad Nuruzzama Waliur Rahaman Gyana R. Tripathy Rahul Mohan Shramik Patil 《水文研究》2020,34(11):2351-2364
Dissolved major ions, Sr concentrations and 87Sr/86Sr ratios of 10 coastal lakes from the Larsemann Hills, East Antarctica have been studied to constrain their solute sources, transport and glacial weathering patterns in their catchments. In absence of perennial river/streams, lakes serve as only reliable archive to study land surface processes in these low-temperature regions. The lake water chemistry is mostly Na-Cl type and it does not show any significant depth variations. Sr isotope compositions of these lakes vary from 0.7110 to 0.7211 with an average value of 0.7145, which is higher than modern seawater value. In addition to oceanic sources, major ions and Sr isotopic data show appreciable amount of solute supply from chemical weathering of silicate rocks in lake catchments and dissolution of Ca-Mg rich salts produced during the freezing of seawaters. The role of sulphide oxidation and carbonate weathering are found to be minimal on lake hydro-chemistry in this part of Antarctica. Inverse model calculations using this chemical dataset provide first-order estimates of dissolved cations and Sr; they are mostly derived from oceanic (seawater + snow) sources (cations approximately 76%) and (Sr approximately 92%) with minimal supplies from weathering of silicates (cations approximately 15%); (Sr approximately 2%) and Ca-rich minerals (cations approximately 9%); (Sr approximately 7%). The silicate weathering rate and its corresponding atmospheric CO2 consumption rate estimates for Scandrett lake catchment (3.6 ± 0.3 tons/km2/year and 0.5 × 105 moles/km2/year), are lower than that of reported values for the average global river basins (5.4 tons/km2/year and 0.9 × 105 tons/km2/year) respectively. The present study provides a comprehensive report of chemical weathering intensity and its role in atmospheric CO2 consumption in low-temperature pristine environment of Antarctica. These estimates underscore the importance of Antarctica weathering on atmospheric CO2 budget, particularly during the past warmer periods when the large area was exposed and available for intense chemical weathering. 相似文献
36.
Few years ago, Cho and Vilenkin have proposed that topological defects can arise in symmetry breaking models without having degenerate vacua. These types of defects are known as vacuumless defects. In the present work, the gravitational field of a vacuumless global string and global monopole have been investigated in the context of Lyra geometry. We find the metric of the vacuumless global string and global monopole in the weak field approximations. It has been shown that the vacuumless global string can have repulsive whereas global monopole exerts attractive gravitational effects on a test particle. It is dissimilar to the case studied in general relativity. 相似文献
37.
It is known that for a thin domain wall the pressure in the perpendicular direction to the wall is negligible. In this paper,
we have evaluated solutions for thin domain walls with spherical symmetry following two different approaches. The exact solutions
are obtained using functional separability of the metric coefficients.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
38.
The problem of semiclassical gravitational effects of globalmonopole in Kalb-Ramond backgroundinvestigated. It is shown that the monopoleexerts repulsive gravitational force on nonrelativistic matter and space around it hasa deficit solid angle. 相似文献
39.
Farook Rahaman 《Astrophysics and Space Science》2003,283(2):155-159
W.A. Hiscock (1990, Class. Quantum Gravitation
7, L235) obtained the vacuum expectation value of the stress-energy tensor of an arbitrary collection of conformal massless
free quantum fields (scalar, spinor and vectors) in the space-time of a static global monopole. With this stress-energy tensor,
the semi-classical Einstein equations are solved retaining terms up to first order in ħ in Lyra geometry.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
40.
Exact analytical solutions are obtained for a higher dimensional spherically symmetric inhomogeneous metric in presence of
a mass-less scalar field with a flat potential within the framework of Lyra geometry. Assuming a homogeneous scalar field,
we have shown that the metric can be reduced to a generalized FRW type. 相似文献