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771.
Sensitivity of the radar scattering coefficient to the oceanic wind vector in the midangular range for frequencies from L-
to Ku- band is studied. This is based on computations of scattering coefficient via the two-scale scattering theory employing
a semi-empirical model for the ocean spectrum suggested by Fung and Lee and the slope distribution by Cox and Munk. Higher
frequency and incident angles of over 45 degrees seem to yield better wind sensitivity. 相似文献
772.
This paper points out certain discrepancies when the incoherent scatter radar observations at Jicamarca and the electron density models, (the Bent andiri) were compared. In all cases the bottomside semi-thickness of the observed profile was significantly greater than that of both Bent andiri models. The decay constants associated with the topside ionosphere for the observed profiles were generally greater than that of the two models, the difference being more pronounced in theiri model. The results call for a revision of the models so that they accurately represent the electron density distribution at the equator. 相似文献
773.
93 black & white panchromatic aerial photographs of 1972 on 1:20,000 scale were used for assessing the site quality of Sal forest of part of West Dehradun Forest Division, by both direct and indirect methods. The forests were stratified into 5 height and 5 density classes and according to species composition. For necessary data for the assessment of growing stock, field measurements were made on 54 sample plots of 0.1 hectare each. This provided direct indication of actual productive capacity of a particular site. According to indirect method, ground vegetation was sampled in 54 quadrats of 5m x 5m each and has been classified into statistically sound vegetation groupings by normal association analysis technique. These groups facilitated the standardisation of their photo perameters. The indicator value of the plants in a grouping was used to assess the suitability of the site. This was substantiated by super-imposing growing stock, present at that site. By combination of the direct and indirect methods, sites have been classified into 3 categories i.e., suitable, conditionally suitable and unsuitable. Suggestions have been made for management of conditionally suitable sites and the cause for unsuitability of sites are explored. Hence, interpretation of qualitative attributes of vegetation alongwith the measurements of quantitative parameters on aerial photographs have proved to be useful for site quality assessment. 相似文献
774.
Ashok Kumar Deepak Srivastava Sanjay Kumar Srivastava 《Journal of the Indian Society of Remote Sensing》1994,22(1):57-64
Remotely-sensed satellite data of Landsat 5 (TM) and IRS-1A (LISS II) covering parts of central portion of Chotanagapur plateau have been analysed visually to delineate some prominent lineaments in Ranchi district and its adjoining area. One of the most prominent lineament “Ranchi mega lineament? has been analysed in this paper. This lineament is a potential site for base metal mineralisation at some places, and it acts as good groundwater conduit in the region. No earlier attempt to map this entire structural unit as a separate entity is known. Geophysical bouguer gravity anomaly map, lithological and structural maps have some remarkable correlation with this lineament. In the present paper authors have tried to analyse the lineament with respect to its tectonic, mineralisation and groundwater prospects. Resistivity survey carried in close proximity of this lineament at selected sites, indicate that rocks are well fractured at depth. Available lithological and structural map support this lineament as a shear near Purulia (W.B.) and also having base-metal mineralisation potential in this area. Authors opine that existing gravity anomaly map may be further augmented in the light of present study. 相似文献
775.
There are several observations showing an enhancement of infrared emission and optical polarization at a distance of 4R
, (R
is the angular radius of the Sun) implying a ring of dust in near-ecliptic orbit about the Sun; but there is an almost equal number of observations, which do not show any such enhancement. We plotted the observational results for the detection and the non-detection of the circum-solar dust on a diagram for the variation of the sun-spot number with time, and found that its detection and non-detection occurred near the solar minimum and maximum phases, respectively. We present the possibility that this phenomena is caused by an additional process, i.e., the Lorentz force acting on a charged dust particle. Since, at the maximum phase a dust particle in a near-solar region acquires a higher positive potential, and the solar magnetic field is very strong, the Lorentz force becomes dominant and can affect the orbit of the dust particle. 相似文献
776.
K. Vinod Kumar Arup SPaltt A. K. Chakrabortt S. K. Bhan B. Chowdhury T. Sanyal 《Journal of the Indian Society of Remote Sensing》1994,22(1):1-7
River estuarine environment constitutes a highly dynamic fluvio-morphological setting where processes of accretion and deposition are active. Hooghly estuary, being one of the largest of estuaries in the east coast of India, needs constant monitoring. Multidate satellite images of IRS-1A L1SS-I and Landsat MSS for 1975–1991 period are studied to detect long term morphological changes in this estuary. The study reveals that the estuarine islands like Sagar, Ghorarmara and Suparbhanga are eroding whereas Lohachara islands has completely eroded off Nayachara island near Haldia due to its shape and size bifurcates the river into two channels. The island as revealed from Satellite images is in accretional phase where the total surface area has increased. The study, therefore, indicates that constant monitoring of spatial and temporal changes in this type of environment would help to understand physical processes. 相似文献
777.
O. S. R. U. Bhanu Kumar C. V. Naidu S. R. L. Rao 《Journal of Earth System Science》2004,113(3):313-319
An analysis of the mean monthly data of 124 years reveals that the relationship between the Southern Oscillation Index in
September and the winter monsoon rainfall (WMR) over Coastal Andhra Pradesh (CAP) is variable and non-stationary. In the recent
four decades, however, SOI (Sept) is negatively and significantly correlated with CAP WMR. A similar analysis is performed
using 50 years of mean monthly SSTs over Nino-3.4 region in August and September and CAP WMR to detect a possible relationship
and there is a striking positive relation between them. In both of the above cases, the September signal is more significant
in the recent four decades than for the other months and seasons for probable prediction of CAP WMR. Finally, to examine the
influence of SO on the winter monsoon rainfall, a non-parametric test “Mann-Whitney Rank Statistics” test has been applied
to the rainfall associated with extreme positive and negative SOI events 相似文献
778.
Fluorescence efficiencies of electrons in a large number of bands of the N2 First Positive and O2+ First Negative groups lying in the 4900–10,500 Å wavelength range have been investigated theoretically. The variation of transition moment with internuclear distance is taken into consideration. For the First Positive group of N2 the calculations are carried out at very low pressure as well as at 600 Torr. In general the present values are higher than the experimental values but in most of the cases fair agreement has been obtained. For the O2+ First Negative group no direct experimental data is available. However, the present ratio of the total efficiency in the O2+ First Negative group to the N2+ First Negative group is found to be in good agreement with the experimental intensity ratio. 相似文献
779.
Ajoy Kumar Dasgupta 《Astrophysics and Space Science》1979,60(2):455-464
Charged dust grains of radiia3×10–63×10–5 cm may be driven out of the galaxy due to radiation pressure of starlight. Once clear of the main gas-dust layer, dust grains may then escape into intergalactic space. Such grains are virtually indestructible-being evaporated only during galaxy formation. The dust grains, once injected into the intergalactic medium, may acquire suprathermal energy, thus suprathermal grains in collision with magnetized cloud by the Fermi process. In order to attain relativistic energy, suprathermal grains have to move in and out (scattering) of the magnetic field of the medium. It is now well established that high energy cosmic rays are of the order 1020 eV or more. We have speculated that these high energy (>-1018 eV) cosmic ray particles are charged dust grains, of intergalactic origin. This is possible only if there exists a magnetic field in the intergalactic medium. 相似文献
780.
Bearing capacity of rectangular footing on reinforced soil 总被引:2,自引:4,他引:2
In the present paper, a method of analysis for calculating the pressure intensity corresponding to a given settlement for
a rectangular footing resting on reinforced soil foundation has been presented. The process has been simplified by presenting
non-dimensional charts for the various terms used in the analysis, which can be directly used by practicing engineers. An
empirical method has been suggested to find out the ultimate bearing capacity of footing on reinforced soil. The results have
been validated with large-scale model tests also. The procedure has been made clear by giving an illustrative example.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献