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21.
The vacuum Friedmann models are investigated in self-creation theory of gravitation proposed by Barber. New solutions are obtained forK=±1, and some properties of the solutions are discussed. Only theK=0 solution in self-creation cosmology was previously shown. 相似文献
22.
S. K. Roy Bhowmik Soma Sen Roy Kuldeep Srivastava B. Mukhopadhay S. B. Thampi Y. K. Reddy Hari Singh S. Venkateswarlu Sourav Adhikary 《Meteorology and Atmospheric Physics》2011,111(3-4):133-147
This paper demonstrates the usefulness of Indian Doppler Weather Radar (DWR) data for nowcasting applications, and assimilation into a mesoscale Numerical Weather Prediction (NWP) model. Warning Decision Support System Integrated Information (WDSS-II) developed by National Severe Storm Laboratory (NSSL) and Advanced Regional Prediction System (ARPS) developed at the Centre for Analysis and Prediction, University of Oklahoma are used for this purpose. The study reveals that the WDSS-II software is capable of detecting and removing anomalous propagation echoes from the Indian DWR data. The software can be used to track storm cells and mesocyclones through successive scans. Radar reflectivity mosaics are created for a land-falling tropical cyclone??Khaimuk of 14 November 2008 over the Bay of Bengal using observations from three DWR stations, namely, Visakhapatnam, Machilipatnam and Chennai. Assimilation of the quality-controlled radar data (DWR, Chennai) of the WDSS-II software in a very high-resolution NWP model (ARPS) has a positive impact for improving mesoscale prediction. This has been demonstrated for a land-falling tropical cyclone Nisha of 27 November 2008 of Tamil Nadu coast. This paper also discusses the optimum scan strategy and networking considerations. This work illustrates an important step of transforming research to operation. 相似文献
23.
D. S. V. V. D. Prasad P. V. S. Rama Rao G. Uma S. Gopi Krishna K. Venkateswarlu 《Journal of Earth System Science》2005,114(4):437-441
Using the data of amplitude scintillations recorded at 244 MHz from the geostationary satellite, FLEETSAT (73‡E) at a low
latitude station, Waltair (17.7‡N, 83.3‡E, 20‡N dip), during the increasing sunspot activity period of 1997–2000, the effect
of the geomagnetic storms on the occurrence of ionospheric scintillations has been studied. A total of 60 SC storms studied
during this period, following the Aarons’ criterion, reveals that the local time of onset of the recovery phase of the geomagnetic
storms play an important role in the generation or inhibition of the ionospheric irregularities. Out of the 60 storms studied,
nearly 60 to 70% satisfied the categories I, II and III of Aarons’ criteria. However, in the remaining 30 to 40% of the cases,
no consistent results were observed. Thus, there is a necessity for further investigation of the effect of geomagnetic storms
on ionospheric irregularities, particularly with reference to the altitude variations of the F-layer (h’F) relating to the
changes in the local electric fields. 相似文献
24.
The present investigation evaluates the adsorption effectiveness of Cd(II) ions on Ficus religiosa leaf powder (FRL). The experimental parameters chosen included time, pH, particle size, temperature, adsorbate, anion, and Pb(II) concentrations. The time data followed pseudo‐second‐order kinetics. Cd(II) adsorption increased from 1.38 to 75.17% with the increase in pH from 2 to 4 and further increase in pH to 5.5 resulted in its marginal increase to 77.52%. Based on regression coefficient values, the isothermic data fitted the various models in the order Langmuir > Redlich–Peterson > Temkin > Freundlich model. The maximum loading capacity of FRL was estimated to be 27.14 mg g?1. The presence of Cl?, , or Pb2+ exhibited adverse effect on Cd(II) uptake. The thermodynamic parameters of enthalpy (ΔH0) and entropy (ΔS0) were estimated to be 8.31 kJ mol?1 and 38.22 J mol?1 K?1, respectively. SEM‐EPMA of the loaded FRL showed Cd(II) distribution at specific sites. The XRD patterns of Cd(II) loaded FRL sample showed disappearance of some peaks corresponding to β‐Ca(PO3)2; shifting of peaks and decrease in %RI corresponding to γ‐CaSO4 phase. Positive shift of IR bands for the Cd(II) loaded sample was observed. 相似文献
25.
Ch. Srinivasarao S. Rama Gayatri B. Venkateswarlu V. S. Jakkula S. P. Wani S. Kundu K. L. Sahrawat B. K. Rajasekhara Rao S. Marimuthu G. Gopala Krishna 《International Journal of Environmental Science and Technology》2014,11(7):1959-1972
Heavy metals are governed by parent material of soils and influenced by the soil physicochemical properties and soil and crop management practices. This paper evaluates total heavy metal concentrations in rainfed soils under diverse management practices of tropical India. Vertisols (clayey soils with high shrink/swell capacity) had the highest concentrations of heavy metals. However, chromium (Cr) content was above the threshold value in Aridisol [calcium carbonate (CaCO3)]-containing soils of the arid environments with subsurface horizon development. Concentration increased at lower depths (>30 cm). Basaltic soils showed higher concentrations of nickel (Ni), copper (Cu) and manganese (Mn). Cadmium (Cd), cobalt (Co), Cu and Mn concentrations were higher in soils cultivated to cotton, whereas Cr concentration was above the threshold level of 110 mg kg?1 in food crop cultivated soils. As the specific soil surface is closely related to clay content and clay type, soil’s ability to retain heavy metals is more closely tied to the specific surface than to the soil cation exchange capacity. Higher positive correlations were found between heavy metal concentrations and clay content [Cd(r = 0.85; p ≤ 0.01); Co (r = 0.88; p ≤ 0.05); Ni (r = 0.87; p ≤ 0.01); Co (r = 0.81; p ≤ 0.05); Zn (r = 0.49; p ≤ 0.01); Cr (r = 0.80; p ≤ 0.05); Mn (r = 0.79; p ≤ 0.01)]. The amounts of nitrogen–phosphorus–potassium applied showed a positive correlation with Co and Ni (r = 0.62; p ≤ 0.05). As several soils used for growing food crops are high in Ni, Cr and Mn, the flow of these metals in soil–plant–livestock/human chain needs further attention. 相似文献
26.
Field equations in the presence of a perfect fluid distributionc for Einstein-Rosen cylindrically symmetric metric are obtained in the scale-covariant theory of gravitation proposed by Canuto et al. (1977a). A static vacuum model and a non-static cosmological model corresponding to perfect fluid are presented. Physical and Kinematical properties of the models are also discussed. 相似文献
27.
A spatially-homogeneous and anisotropic magnetized cosmological model in Lyra's manifold is obtained when the source of the gravitational field is a perfect fluid distribution. The magnetic field is due to an electric current produced along thex-axis. The physical behaviour of the model is discussed. 相似文献
28.
It is shown that an analog of Birkhoff's theorem of general relativity exists in the scale-covariant theory of gravitation when the gauge function which occurs in the theory is independent of time. 相似文献
29.
Vacuum field equations for the static and non-static plane-symmetric metric are obtained in self-creation theory of gravitation proposed by Barber (1982). It is shown that, in both static and non-static cases, the only plane-symmetric solution in vacuum is the empty flat space-time of Einstein's theory. It is observed that this result is quite different from that of the Brans-Dicke and other scalar-tensor theories of gravitation. 相似文献
30.
An exact Bianchi type-VI0 cosmological model in the presence of zero-mass scalar fields is obtained when the source of the gravitational field is a perfect fluid with pressure equal to energy density. Some physical properties of the model are discussed. 相似文献