A kinematic study of orion nebula in the emission line [S II] 6731 Å     

K. P. Raju  C. Debi Prasad  J. N. Desai  L. Mishra 《Astrophysics and Space Science》1993,204(2):205-212

Fabry-Perot Interferometric observations were made on Orion Nebula in the forbidden emission line [S II] 6731 Å line. The observed field is about 6 × 6 on the face of the nebula and it covers the Orion Trapezium stars and the nearby regions. The relative line of sight velocities which denote the average deviations from the systematic velocities were derived at a large number of points in the nebula. Velocities were found to show a gradient towards the north of Trapezium stars. Large blue shifted velocities were found at the nebular boundaries, probably associated with the ionization fronts. The observed velocities, in general, show agreement with the flow model of Balick, Gull and Smith (1980).  相似文献   

Early prediction of onset of south west monsoon from ERS-1 scatterometer winds     

U. R. Rao  P. S. Desai  P. C. Joshi  P. C. Pandey  B. S. Gohil  B. Simon 《Journal of Earth System Science》1998,107(1):33-43

Detailed analysis of the surface winds over the Indian Ocean derived from ERS-1 scatterometer data during the years 1993 and 1994 has been used to understand and unambiguously identify the onset phase of south-west monsoon. Five day (pentad) averaged wind vectors for the period April to June during both years have been examined to study the exact reversal of wind direction as well as the increase in wind speed over the Arabian Sea in relation to the onset of monsoon over the Indian west coast (Kerala). The related upper level humidity available from other satellites has also been analysed. The results of our analysis clearly show a consistent dramatic reversal in wind direction over the western Arabian Sea three weeks in advance of the onset of monsoon. The wind speed shows a large increase coinciding with the onset of monsoon. These findings together show the dominant role of sea surface winds in establishing the monsoon circulation. The study confirms that the cross equatorial current phenomenon becomes more important after the onset of monsoon.  相似文献   

Fabry-Pérot line profiles in the λ5303 å and λ6374 å coronal lines obtained during the 1983 Indonesian eclipse     

T. Chandrasekhar  J. N. Desai  N. M. Ashok  Jay M. Pasachoff 《Solar physics》1991,131(1):25-39

During the total solar eclipse of 11 June, 1983, an imaging dual-channel Fabry-Pérot interferometer was used to obtain line profiles simultaneously in the green 5303 Å [Fe xiv] and the red 6374 Å [Fe x] coronal lines at various positions in the corona. Extensive microdensitometry followed by multi-Gaussian curve-fitting analysis has resulted in the determination of coronal temperatures and velocity separations between different pockets of coronal gas in the line of sight over a large extent of the corona. Fewer high temperature zones are to be found in the corona of 1983 compared with our similar green-line measurements of the solar maximum corona of 1980. The data are consistent with a temperature maximum occurring at 1.2 R , as found at the 1980 eclipse, but our new data are insufficient to observe farther out than this radius and so determine the position of a maximum. The velocity field in the corona at the 1983 eclipse is less structured compared with that at the 1980 eclipse and is mainly confined to the zone 20–30km s^–1.  相似文献   

Statistical Evaluation of the Jason-1 Operational Sensor Data Record     

Shailen D. Desai  Patrick Vincent 《Marine Geodesy》2003,26(3):187-199

The Jason-1 satellite altimeter mission represents a first step towards operational oceanography from satellite altimeter missions. An operational data product, the Operational Sensor Data Record (OSDR), provides measurements from the on-board altimeter and radiometer within 3-5 h of real time. This data product is a wind and wave product that is aimed towards near-real-time meteorological applications. A higher accuracy and more detailed data product, the Interim Geophysical Data Record (IGDR), that is better suited to detailed scientific studies of ocean topography, is available no sooner than 2-3 days from real time. The measurements reported on the OSDR primarily differ from those on the IGDR in that the OSDR reports measurements derived from on-board processing of the altimeter waveforms, while ground retracking of the waveforms is performed for the IGDR. The altimeter-derived measurements on the OSDR are validated through a statistical evaluation of the differences between data on the OSDR and IGDR. In doing so, the impact of ground retracking of the altimeter waveforms is also illustrated.  相似文献   

Estimates of fishery potentials of the EEZ of India     

B. N. Desai  R. M. S. Bhargava  J. S. Sarupria 《Estuarine, Coastal and Shelf Science》1990,30(6)

An attempt has been made to estimate the fishery potentials of the EEZ of India on the basis of data on primary and secondary production. The total column primary production and zooplankton production have been calculated to be 265·9 and 9 million tonnes of carbon per year, respectively. From these values the fishery potential has been estimated as 2·5 million tonnes per year. To this, if we add the estimated demersal fish catch, being 1·2 million tonnes per year, the total potential yield comes to 3·7 million tonnes per year. Since the present average total catch is about 1·6 million tonnes in a year, the fish catch could be doubled.  相似文献   

An analytic study on the horizontal motion of monsoon depressions     

S. K. Mishra  D. R. Chakraborty  S. S. Desai 《Meteorology and Atmospheric Physics》1983,32(1-2):35-53

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An exact numerical time integration of scalar equations for undamped structural systems     

Jerzy Kujawski  Chandrakant S. Desai 《地震工程与结构动力学》1984,12(1):137-142

An exact numerical time integration of scalar equations for undamped structural systems is presented. Typical numerical examples are included to illustrate the use of the proposed procedure.  相似文献   

Morphological study of the time histories of gamma-ray bursts   总被引：4，自引：0，他引：4  

U. D. Desai 《Astrophysics and Space Science》1981,75(1):15-20

Time histories of -ray bursts have revealed a great diversity, both in total duration and in the details of fine time structure. Results of the -ray experiment on the Helios-2 spacecraft have suggested some similarities in time profiles of events. The possibility of some characteristic separation times in events may also be indicated.Paper presented at the Symposium on Cosmic gamma-Ray Bursts, held at Toulouse, France, 26–29 November, 1979.  相似文献   

Large area soil moisture estimation and mapping using space-borne multi-frequency passive microwave data     

S. R. Oza  R. P. Singh  V. K. Dadhwal  P. S. Desai 《Journal of the Indian Society of Remote Sensing》2006,34(4):343-350

The paper reports the estimation of surface soil moisture (SM) using surface wetness Index (SWI) retrieved from multi-frequency passive microwave radiometer. A change detection algorithm was followed which transforms SWI variations in to SM variations using per pixel soil property of field capacity and air-dry status. Estimated soil moisture was compared with the point measurements made at the Monmouth and De Kalb sites of Illinois (USA) for the validation. Sensitivity of the SWI to the variations of rainfall at various vegetation fractions is analyzed. RMS error of volumetric soil moisture is found to be in the range of 6.35 to 8.85 %. The method works well up to the vegetation fraction of 40 %. Applications of the technique are demonstrated by the spatio-temporal analysis of estimated soil moisture maps for India. Characteristic increase in soil moisture was observed with the progress of monsoon from 25 to 32 week in northern India and 46 to 52 week in the costal parts of Tamil Nadu in south.  相似文献   

Performance of small group of geosynthetic-reinforced granular piles     

Yogendra Tandel  Mohsin Jamal  Chandresh Solanki  Atul Desai  Jignesh Patel 《Marine Georesources & Geotechnology》2017,35(4):504-511

Granular piles are frequently used as a method of improving soft grounds as they provide increased bearing capacity and reduce foundation settlements. However, in very soft clayey soils, they may not derive their load-carrying capacity by low confining pressure provided by the surrounding soil. In such circumstances, granular piles may be reinforced with suitable geosynthetic to increase its load-carrying capacity and to reduce excessive bulging. In this study, the performance of small group of geosynthetic-reinforced granular piles (GRGPs) is examined in terms of load-carrying capacity, settlement, and modulus by laboratory model tests. The parameters investigated include modulus of reinforcement material, area replacement ratio (ARR) based on the column diameter and reinforcement length. The results indicated that increasing the modulus of the reinforcement and the ARR based on the column diameter enhances the overall performance of the GRGP group. It was also observed that reinforcement on top portion of the granular pile is sufficient to substantially increase the load-carrying capacity of granular pile group.  相似文献