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91.
92.
Summary Three sets of different formulae expressed as functions of dynamic elastic constants of rock and some design parameters involved in a buried explosion are derived explicitly for the prediction of peak particle velocity (PPV) and peak air pressure (PAP). Separate equations are derived to estimate PPV and PAP for inside, outside, and at the boundary of the crater zone. The equations incorporate the physical parameters including (i) longitudinal wave velocity, (ii) shear wave velocity, (iii) density of rock, (iv) characteristic impedance of air, (v) detonation pressure of explosive, (vi) depth of hole, (vii) radius of hole, (viii) distance of the measuring transducer. Suggested equations are tested for a few hard and medium-hard rocks. Characteristic features and important conclusions are described. 相似文献
93.
P. K. Pal B. M. Rao C. M. Kishtawal M. S. Narayanan G. Rajkumar 《Journal of Earth System Science》1989,98(4):353-364
INSAT visible and infrared imageries of three cyclones in the Bay of Bengal during the period 1984–1987 were analysed with
a view to improve the cyclone track prediction in this region. It was observed that the rotation in the major structural cloud
features (as seen from the cloud-top temperature maps) associated with these cyclones in the Bay of Bengal is followed with
a change in direction of their movement. This method is seen to be particularly effective when the cyclone is severe and when
the major cloud features persist for a reasonably longer time. In the present study, only the direction of movement is forecast
assuming a uniform speed of the cyclone. 相似文献
94.
C. Tuniz C.M. Smith R.K. Moniot T.H. Kruse W. Savin D.K. Pal G.F. Herzog R.C. Reedy 《Geochimica et cosmochimica acta》1984,48(9):1867-1872
Eleven samples taken from along the 35-cm core AIII of the LL-chondrite St. Severin have 10Be contents ranging from 20 to 28 dpm/kg and averaging 24.5 ± 0.9 dpm/kg. The 10Be contents increase with depth in the outermost 8 cm while at depths greater than 8 cm the 10Be contents change little. Calculations based on cross sections for proton-induced reactions that make 10Be disagree seriously with the measured values. Relatively large cross sections were constructed for neutron-induced reactions below 1 GeV. They give calculated 10Be production rates that agree with the measured values to within 10%. Cosmogenic 10Be in stony meteorites is better described as a medium-energy product than as a high-energy one. 相似文献
95.
Massive stars have significant influence on the evolution of the interstellar medium. Bright rims, cometary morphology of clouds, as well as their motion are some examples of the influence of massive stars on nearby molecular clouds. The cometary clouds in the Gum-Vela region are very good examples. In an attempt to understand the kinematics of the clouds in such regions we have carried out CO line observations towards bright-rimmed clouds near the OB Association Cep OB2. The radial velocities of the clouds are consistent with an expansion of the system at ≈ 4kms?1 away from the dominant O6.5V star in the association, HD206267. We find the rocket mechanism to be the most likely cause for expansion as found for both the Gum-Vela and the Rosette globules. We conclude that such expanding motions are quite common in regions near massive stars and make a brief comparison of the Cepheus system with the Gum-Vela system. 相似文献
96.
Randhir Singh B. G. Vasudevan P. K. Pal P. C. Joshi 《Journal of Earth System Science》2004,113(1):89-101
Microwave sensor MSMR (Multifrequency Scanning Microwave Radiometer) data onboard Oceansat-1 was used for retrieval of monthly
averages of near surface specific humidity (Q
a) and air temperature (T
a) by means of Artificial Neural Network (ANN). The MSMR measures the microwave radiances in 8 channels at frequencies of 6.6,
10.7, 18 and 21 GHz for both vertical and horizontal polarizations.
The artificial neural networks (ANN) technique is employed to find the transfer function relating the input MSMR observed
brightness temperatures and output (Q
a andT
a) parameters. Input data consist of nearly 28 months (June 1999 – September 2001) of monthly averages of MSMR observed brightness
temperature and surface marine observations ofQ
a
andT
a
from Comprehensive Ocean-Atmosphere Data Set (COADS).
The performance of the algorithm is assessed with independent surface marine observations. The results indicate that the combination
of MSMR observed brightness temperatures as input parameters provides reasonable estimates of monthly averaged surface parameters.
The global root mean square (rms) differences are 1.0‡C and 1.1 g kg−1 for air temperature and surface specific humidity respectively. 相似文献
97.
I. Sadhu Khan D. Lohar D. K. Pal 《Journal of the Indian Society of Remote Sensing》2003,31(4):261-269
Changes in land surface characteristics have become a matter of great concern in the recent years. It is particularly important
when the mesoscale phenomena control the climatic variables of a region. Gangetic West Bengal with its neighbourhood is such
a region where during premonsoon season, mesoscale phenomena, i.e., sea breeze circulation and severe convective development,
control the local climate of the season. It is also reported that a drastic changes in land use pattern has taken place in
recent period over the region, which might affect the local climate, resulting in severe water crisis over the semi-arid part
of the region. A detailed study has been undertaken to investigate the changes in land use pattern through satellite data
over the area and its possible impact on the local climate through numerical modeling. Satellite (IRS-IC and Landsat 4 and
5) data shows a sharp change in dynamic vegetation during this period, which is due to, increased agricultural practices in
the recent years. Mesoscale model indicates that agricultural practices hinder the development of sea breezes over the coastal
and inland places, causing less incursion of moisture towards inland. This may be associated with less number of convective
developments over the coastal and neighbouring places. 相似文献
98.
The atmospheric correction bands 7 and 8 (765nm and 865nm respectively) of the Indian Remote Sensing Satellite IRS P4-0CM
(Ocean Colour Monitor) can be used for deriving aerosol optical depth (AOD) over the oceans. A retrieval algorithm has been
developed which computes the AOD using band 7 data by treating the ocean surface as a dark background after removing the Rayleigh
path radiance in the sensor-detected radiances. This algorithm has been used to detect marine aerosol distributions at different
coastal and offshore locations around India.
A comparison between OCM derived AOD and the NOAA operational AOD shows a correlation ∼0.92 while that between OCM derived
AOD and the ground-based sun photometer measurements near the coast of Trivandrum shows a correlation of ∼0.90. 相似文献
99.
First Order Seismic Microzonation of Delhi,India Using Geographic Information System (GIS) 总被引:2,自引:4,他引:2
William K. Mohanty M. Yanger Walling Sankar Kumar Nath Indrajit Pal 《Natural Hazards》2007,40(2):245-260
A first order seismic microzonation map of Delhi is prepared using five thematic layers viz., Peak Ground Acceleration (PGA)
contour, different soil types at 6 m depth, geology, groundwater fluctuation and bedrock depth, integrated on GIS platform.
The integration is performed following a pair-wise comparison of Analytical Hierarchy Process (AHP), wherein each thematic
map is assigned weight in the 5-1 scale: depending on its contribution towards the seismic hazard. Following the AHP, the
weightage assigned to each theme are: PGA (0.333), soil (0.266), geology (0.20), groundwater (0.133) and bedrock depth (0.066).
The thematic vector layers are overlaid and integrated using GIS. On the microzonation theme, the Delhi region has been classified
into four broad zones of vulnerability to the seismic hazard. They are very high (> 52%), high (38–52%), moderate (23–38%)
and less ( < 23%) zones of seismic hazard. The “very high” seismic hazard zone is observed where the maximum PGA varies from
140 to 210 gal for a finite source model of Mw 8.5 in the central seismic gap. A site amplification study from local and regional earthquakes for Delhi region using Delhi
Telemetry Network data shows a steeper site response gradient in the eastern side of the Yamuna fluvial deposits at 1.5 Hz.
The ‘high’ seismic hazard zone occupies most of the study area where the PGA value ranges from 90 to 140 gal. The ‘moderate’
seismic hazard zone occurs on either side of the Delhi ridge with PGA value varying from 60 to 90 gal. The ‘less’ seismic
hazard zone occurs in small patches distributed along the study area with the PGA value less than 60 gal. Site response studies,
PGA distribution and destruction pattern of the Chamoli earthquake greatly corroborate the seismic hazard zones estimated
through microzonation on GIS platform and also establishes the methodology incorporated in this study. 相似文献
100.
The paper presents the seasonal variation of 6300 Å line intensity at Calcutta with relative sunspot number, solar flare number and variable component of 10.7 cm solar flux. A study has been made and important results have been obtained which are as follows. (i) Intensity of 6300 Å line shows periodic variation with relative sunspot number, solar flare number and variable component of 10.7 cm solar flux during the period 1984–1986 which is the secondary peak of the descending phase of 21st solar cycle. (ii) 6300 Å line intensity at Cachoeira Paulista station, taken by Sahai et al. (1988), also shows periodic variation with solar parameters during the period 1978–1980 which is the peak phase of the solar cycle. (iii) A possible explanation of such a type of variation is also presented. 相似文献