Bianchi II,VIII, and IX viscous fluid cosmology     

A. Banerjee  Abhik Kumar Sanyal  Subenoy Chakraborty 《Astrophysics and Space Science》1990,166(2):259-268

In this paper we study the exact solutions for a viscous fluid distribution in Bianchi II, VIII, and IX models. The metric is simplified by assuming a relationship between the coefficients of the metric tensor. Solutions are obtained in two special cases: in one an additional assumption is made where the matter density and the expansion scalar have a definite relation and in the other a barotropic equation of state of the formp= is assumed. While the Bianchi II solutions are already found in the literature the other two classes of solutions are apparently new.  相似文献   

Structure of the marine boundary layer over north western Indian Ocean during 1983 summer monsoon     

M. R. Ramesh Kumar  Y. Sadhuram  G. S. Michael  L. V. Gangadhara Rao 《Boundary-Layer Meteorology》1990,52(1-2):177-191

The spatial variability of the structure of the lower troposphere over the northwestern Indian Ocean for the period 12th July to 2nd September, 1983 has been studied using upper air data collected during the first scientific cruise of ORV Sagar Kanya.An analysis of thermodynamic structure and kinematics of the marine boundary layer for different zonal and meridional sections revealed the following features: (a) Temperature and humidity inversions were generally absent over the study area except over a few locations in the western region; (b) Large-scale subsidence was found over the central equatorial Indian Ocean; (c) The convective activity over the western Indian Ocean was found to be moderately suppressed as compared to the eastern region; (d) The zonal and meridional components of winds along the equator and 10° N zonal section exhibited a mirror-image-like distribution.  相似文献   

Rectangular tank surface aerators: scale up criteria and energy conservation     

A. R. Rao  B. Kumar 《International Journal of Environmental Science and Technology》2006,3(4):425-433

Surface aeration experiments were conducted in two types of rectangular tanks of aspect ratios i.e., length to width ratio (L/W) of 1.5 and 2 and developed simulation equations to correlate the oxygen transfer coefficient, k and power number, P₀ with a parameter governing theoretical power per unit volume X. The parameter X is defined as equal to F^4/3R^1/3, where F and R are impellers’ Froude and Reynolds numbers respectively). Results have shown that the P₀ can not be simulated singularly with either Reynolds number, R or Froude number, F, which results in scale-effects; there appears to be a need to incorporate the effects of both F and R. It was found that P⁰ is uniquely related to X for rectangular aeration tanks of both aspect ratios, however, such relationships are different depending upon the aspect ratios. It has been demonstrated that energy can be saved substantially if the aeration tanks are run at relatively higher input powers. It is also demonstrated that smaller sized tanks are more energy conservative and economical when compared to big sized tanks, while aerating the same volume of water, and at the same time by maintaining a constant input power in all the tanks irrespective of their size.  相似文献   

Charnockite genesis across the Archaean–Proterozoic terrane boundary in the South Indian Granulite Terrain: Constraints from major–trace element geochemistry and Sr–Nd isotopic systematics     

J.K. Tomson  Y.J. Bhaskar Rao  T. Vijaya Kumar  J. Mallikharjuna Rao 《Gondwana Research》2006,10(1-2):115

Major, trace element compositions and Sr–Nd isotopic characteristics of charnockitic gneisses from the Southern Granulite Terrain (SGT), South India are presented. The study region encompasses the central segment of the Cauvery Shear Zone system (CSZ) and regions within the Madurai Block (MB) immediately south of it (designated here as the CSZ/MB and MB domains). Differences in the compositions and source characteristics between charnockitic rocks of the CSZ vis-à-vis those of the CSZ/MB and MB regions are highlighted. Foremost, the charnockites and enderbites of the CSZ show highly fractionated REE patterns with positive Eu-anomalies, depleted HREE, Y and near chondritic εNd₀ and initial-⁸⁷Sr/⁸⁶Sr at ca. 2.5 Ga, consistent with hydrous partial melting of amphibolitic crust with residual garnet and hornblende for the parental melts. By contrast, modeled at ca. 1.8 Ga and 0.8 Ga, the CSZ/MB and MB charnockitic rocks, which show a wider range of Ti and P, relatively lower degree of HREE depletion, commonly negative Eu-anomalies and undepleted Y, present clear evidence for involvement of Archaean crustal components in sources of their magmatic protoliths. There is also evidence for significant intracrustal melting processes within a thickened crust at elevated temperatures between 800 and 1000 °C. Implications to the controversial Archaean–Neoproterozoic terrane boundary problem of the SGT are discussed.  相似文献   

Studies on flow characteristics of coal–oil–water slurry system     

Subrata Kumar Majumder  Kamal ChandnaDhiren Sankar De  Gautam Kundu 《International Journal of Mineral Processing》2006

Experiments were carried out to investigate the rheological properties of coal–oil–water suspension containing solids of different sizes. Two different coal samples with mean particle sizes of 120 mesh, 175 mesh and 220 mesh were used. The coal concentration was varied from 5% to 25% by weight. Sodium silicate has been used as an additive to study the behavior of the variation of average viscosity of the suspension. A generalized correlation has been developed to predict the average viscosity of suspension in terms of particle diameter of the coal, concentration of coal, viscosity of the suspending medium and the concentration of water. Experimental investigations revealed that coal–oil–water suspensions show an increase in the viscosity with decrease in coal size but with the addition of an additive, the average viscosity tends to decrease initially up to a certain optimum dosages and thereafter it increases with further addition of additives. Two empirical correlations are proposed for average viscosity of the coal–oil–water suspension, μ_sL in terms of physical properties of the solid and viscosity of the suspending medium with and without additives.  相似文献   

Geotechnical Properties of Low Calcium and High Calcium Fly Ash   总被引：1，自引：0，他引：1  

Sarat Kumar Das  Yudhbir 《Geotechnical and Geological Engineering》2006,24(2):249-263

In this paper, a comparative study has been made for physical and engineering properties of low calcium and high calcium Indian fly ash. The grain size distribution of fly ash is independent of lime content. Fly ash particles of size >75 μm are mostly irregular in shape whereas finer fractions are spherical for low calcium fly ash. For high calcium fly ash, chemical and mineralogical differences have been observed for different size fractions. Compared to low calcium fly ash, optimum moisture content is low and maximum dry density is high for high calcium fly ash. Optimum moisture content is directly proportional and maximum dry density is inversely proportional to the carbon content. The mode and duration of curing have significant effect on strength and stress–strain behavior of compacted fly ash. The gain in strength with time for high calcium fly ash is very high compared to that of low calcium fly ash due to presence of reactive minerals and glassy phase.  相似文献   

Identification and evaluation of hydrogeochemical processes in the groundwater environment of Delhi, India   总被引：10，自引：0，他引：10  

Manish Kumar  AL. Ramanathan  M. S. Rao  Bhishm Kumar 《Environmental Geology》2006,50(7):1025-1039

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Eddies and planetary waves in the Central Arabian Sea     

K. V. Sanil Kumar  P. V. Hareesh Kumar 《Journal of the Indian Society of Remote Sensing》2005,33(1):137-146

Eddies and planetary waves are identified as one of the important factors that control the dynamics of the Arabian Sea. During 10–14 January 1990, Ignat, Paulyuchenkov (USSR ship) conducted an experiment in the central Arabian Sea and of late TOPEX/POSEIDON satellites collected data on sea surface height (SSH) anomalies of the Arabian Sea. These data sets give an opportunity to understand the characteristic of eddies and planetary waves in this region during winter. The geostrophic flow revealed three anticyclonic and two cyclonic eddies of diameters ranging from 75 to more than 150 km from surface to subsurface levels. Current speeds around different eddies were maximum at surface and varied from 9 cm/s to 25 cm/s (at the middle point between the center and periphery). The occurrence of eddies were further investigated with the TOPEX/POSEIDON altimetry for the years 1993–97. The analysis revealed multiple eddies of diameter 100 to 550 km occur every year with maximum number of eddies during 1997 and minimum during 1995. The calculated speed varied between 8–30 cm/s around various eddies. Longitude-Time plots showed annual Rossby waves generating at the eastern Arabian Sea and propagating westwards with a phase speed of ~ 10 cm/s along 16° N. Further, it was observed that these waves arrived in the study area by January. In addition, another positive anomaly of SSH was found generating at the western Arabian Sea simultaneously and extended up to the study region by April–June. Time series of SSH at selected locations along 16°N revealed many small-scale oscillations and their spatial variability. These oscillations were delineated using the FFT analysis. Other than the Rossby wave, the major components at the study region were 40–60 and 26–32 day oscillations. The implications of these long period waves associated with eddies are discussed.  相似文献   

Chlorophyll modulation of mixed layer thermodynamics in a mixed-layer isopycnal General Circulation Model — An example from Arabian Sea and equatorial Pacific     

S. Nakamoto  S. Prasanna Kumar  J. M. Oberhuber  H. Saito  K. Muneyama  R. Frouin 《Journal of Earth System Science》2002,111(3):339-349

Western tropical Indian Ocean, Arabian Sea, and the equatorial Pacific are known as regions of intense bio-chemical-physical interactions: the Arabian Sea has the largest phytoplankton bloom with seasonal signal, while the equatorial Pacific bloom is perennial with quasi-permanent upwelling. Here, we studied three dimensional ocean thermodynamics comparing recent ocean observation with ocean general circulation model (OPYC) experiment combined with remotely sensed chlorophyll pigment concentrations from the Coastal Zone Color Scanner (CZCS). Using solar radiation parameterization representing observations that a higher abundance of chlorophyll increases absorption of solar irradiance and heating rate in the upper ocean, we showed that the mixed layer thickness decreases more than they would be under clear water conditions. These changes in the model mixed layer were consistent with Joint Global Ocean Flux Study (JGOFS) observations during the 1994-1995 Arabian Sea experiment and epi-fluorescence microscopy (EFM) on samples collected during Equatorial Pacific Ocean Climate Study (EPOCS) in November, 1988. In the Arabian Sea, as the chlorophyll concentrations peak in October (3 mg/m³) after the summer plankton bloom induced by coastal upwelling, the chlorophyll induced biological heating enhanced the sea surface temperature (SST) by as much as 0.6‡C and sub-layer temperature decreases and sub-layer thickness increases. In the equatorial Pacific, modest concentrations of chlorophyll less than 0.3 mg/m³ is enough to introduce a meridional differential heating, which results in reducing the equatorial mixed layer thickness to more than 20 m. The anomalous meridional tilting of the mixed layer bottom enhances off equatorial westward geostrophic currents. Consequently, the equatorial undercurrent transports more water from west to east. We proposed that these numerical model experiments with use of satellite andin situ ocean observations are consistent under three dimensional ocean circulation theory combined with solar radiation transfer process.  相似文献   

Static deformation of two welded monoclinic elastic half-spaces due to a long inclined strike-slip fault     

Anil Kumar  Sarvajit Singh  Jagdish Singh 《Journal of Earth System Science》2002,111(2):125-131

Static deformation of two monoclinic elastic half-spaces in welded contact due to a long inclined strike-slip fault situated in one of the half-spaces is studied analytically and numerically. Closed-form algebraic expressions for the displacement at any point of the medium are obtained. The variation of the displacement at the interface with the horizontal distance from the fault is studied. The effect of anisotropy on the displacement field is examined. It is found that while the anisotropy of the source half-space has a significant effect on the displacement at the interface, the anisotropy of the other half-space has only a marginal effect.  相似文献