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31.
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
32.
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 F4/3R1/3, 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
33.
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, μsL in terms of physical properties of the solid and viscosity of the suspending medium with and without additives. 相似文献
34.
35.
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
36.
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
37.
Pradeep Srivastava Indra Bir Singh Shikha Sharma Uma Kant Shukla Ashok Kumar Singhvi 《Geomorphology》2003,54(3-4):279-292
Abandoned channel belts, ponds and point bar deposits of palaeochannels in the interfluve regions of the central Ganga Plain suggest changes in the morphohydrologic conditions during the Latest Pleistocene–Holocene. Stratigraphy of these ponds comprises channel sand at the base overlain by shell-bearing clayey silt. The contact of the two facies marks the phase when channels converted into standing water bodies. Point bar deposits of some palaeochannels are overlain by oxidised aeolian sand, indicating that the channel abandonment possibly occurred due to the desiccation and aridity in the region.Optically stimulated luminescence (OSL) chronometry of the pond sediments suggests that the deposition of the basal channel sand started before 13 ka and continued up to 8 ka. The ponds formed around 8–6 ka when the channel activity ceased. Evidence from the point bar deposits also indicates that the fluvial activity in the region ended sometime during 7–5 ka. This was followed by aeolian aggradation. The present study thus suggests that the hydrologic conditions in the Gangetic plains, i.e. initiation of channels and their abandonment, formation of microgeomorphologic features such as ponds and their eventual siltation, were controlled largely by climatic changes (i.e. monsoon changes) supported by tectonic activity. For the past 2 ka, increasing human and related agricultural activity has substantially accentuated the natural siltation rate of ponds. 相似文献
38.
Ashwani Kumar S. C. Gupta A. K. Jindal Sanjay Jain Vandana 《Journal of Earth System Science》2003,112(3):391-395
Following a large-sized Bhuj earthquake (M
s = 7.6) of January 26th, 2001, a small aperture 4-station temporary local network was deployed, in the epicentral area, for
a period of about three weeks and resulted in the recording of more than 1800 aftershocks (-0.07 ≤M
L <5.0). Preliminary locations of epicenters of 297 aftershocks (2.0 ≤M
L <5.0) have brought out a dense cluster of aftershock activity, the center of which falls 20 km NW of Bhachau. Epicentral
locations of after-shocks encompass a surface area of about 50 × 40 km2 that seems to indicate the surface projection of the rupture area associated with the earthquake. The distribution of aftershock
activity above magnitude 3, shows that aftershocks are nonuniformly distributed and are aligned in the north, northwest and
northeast directions. The epicenter of the mainshock falls on the southern edge of the delineated zone of aftershock activity
and the maximum clustering of activity occurs in close proximity of the mainshock. Well-constrained focal depths of 122 aftershocks
show that 89% of the aftershocks occurred at depths ranging between 6 and 25 km and only 7% and 4% aftershocks occur at depths
less than 5 and more than 25 km respectively. The Gutenberg-Richter (GR) relationship, logN = 4.52 - 0.89ML, is fitted to the aftershock data (1.0<-M
L<5.0) and theb-value of 0.89 has been estimated for the aftershock activity. 相似文献
39.
The Gondwana successions (1–4 km thick) of peninsular India accumulated in a number of discrete basins during Permo-Triassic period. The basins are typically bounded by faults that developed along Precambrian lineaments during deposition, as well as affected by intrabasinal faults indicating fault-controlled synsedimentary subsidence. The patterns of the intrabasinal faults and their relationships with the respective basin-bounding faults represent both extensional and strike-slip regimes. Field evidence suggests that preferential subsidence in locales of differently oriented discontinuities in the Precambrian basement led to development of Gondwana basins with varying, but mutually compatible, kinematics during a bulk motion, grossly along the present-day E–W direction. The kinematic disparity of the individual basins resulted due to different relative orientations of the basement discontinuities and is illustrated with the help of a simple sandbox model. The regional E–W motion was accommodated by strike-slip motion on the transcontinental fault in the north. 相似文献
40.
Sarbari Ghosh Utpal Kumar De Atmospheric Science Research Department of Physics Jadavpur University Calcutta India Received April revised July 《大气科学进展》1997,(1)
AComparativeStudyoftheAtmosphericLayersbelowFirstLiftingCondensationLevelforInstantaneousPre-MonsoonThunderstormOcurenceatAga... 相似文献