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R. S. Sidhu 《Pure and Applied Geophysics》1970,80(1):48-70
Summary The frequency equation of Rayleigh waves propagating over the free surface of an isotropic, perfectly elastic, heterogeneous semi-infinite medium with material properties varying as =
0
e
az
, =
0
e
az
, =
0
e
az
(a>0) has been obtained. Solution of the frequency equation in closed form is obtained in two cases (i) =0, (ii) =, and the Rayleigh wave dispersion curves for phase and group velocities drawn. In both the cases the medium yields single Rayleigh modes which cannot propagate below certain cut-off frequencies. It is found that in case (i), <c<c
0 and 0.87500 <c
g
<c
0, and in case (ii), 1.03082 <c<c
1 and 0.90850 <c
g
<c
1, wherec andc
g
denote phase nad group velocities respectively, is the constant shear wave velocity of the mediumc
0 andc
1 are the corresponding Rayleigh wave velocities of the homogeneous medium of the same Poisson's ratio. The motion of the surface particles is found to be retrograde elliptical as in the homogeneous case, but the ratic of the major and minor axes now becomes frequency dependent and is plotted against frequency. In both the cases (i) and (ii), the ratio starts at a lower value at the cut-off frequency and approaches the corresponding value of the homogeneous medium at high frequencies. 相似文献
2.
R. S. Sidhu 《Pure and Applied Geophysics》1971,91(1):76-94
Summary This paper studies the propagation of Love waves in the following two-layered models: (i) a heterogeneous layer overlying a heterogeneous halfspace, (ii) a heterogeneous layer overlying homogeneous halfspace, (iii) a homogeneous layer overlying a homogeneous halfspace. The heterogeneities of the layer and halfspace are specified by different exponential functions of the depth. The dispersion curves have been drawn taking account of the actual variation of elastic parameters with depth in the Earth. The effects of the heterogeneities of the layer (crust) and halfspace (mantle) on dispersion curves have been discussed. 相似文献
3.
M D Shamim Ansari R. K. Mahey S. S. Sidhu 《Journal of the Indian Society of Remote Sensing》1999,27(4):185-192
To predict the crop yield from spectral parameters, a field experiment was conducted on cotton crop during 1997-98 Kharif season on a sandy loam soil at the Punjab Agricultural Unjversity, Ludhiana. India. Spectral reflectance and agronomic measurements were made for cotton species (American and Desi cotton), sown on two dates (May 1 and May 29) under five nitrogen levels (0, 40, 80, 120 and 160 kg/ha). Regression analysis showed that growth variables had poor correlation with seed cotton yield for all three models, however, yield attributes were significantly and highly correlated for second degree model with seed cotton yield. The integrated Radiance Ratio (RR) and Normalized Difference Vegetation Index (NDVI) measured over time were significantly correlated quadratically with seed cotton yield on three time segment periods viz., 81–110, 111–140 and 141–200 DAS, but highest correlation values were obtained during 81–110 DAS, In American cotton, the highest correlation coefficient for RR and NDVI were 0.91 and 0.81, respectively; whereas for Desi cotton these values were 0.88 and 0.84, respectively. 相似文献
4.
Parvesh Chandna J.K. LadhaU.P. Singh Milap PuniaRaj Gupta B.S. Sidhu 《Applied geography (Sevenoaks, England)》2012,32(2):757-765
Satisfying the food demands of an ever-increasing population, preserving the natural resource base, and improving livelihoods are major challenges for South Asia. A large area of land in the Middle and Lower Gangetic Plains of South Asia remains either uncultivated or underused following the rice harvest in the kharif (wet) season. The area includes “rice-fallow,” estimated at 6.7 million ha, flood-prone riversides (“diara lands,” 2.4 million ha), waterlogged areas (4.9 million ha), and salt-affected soils (2.3 million ha). Bringing these lands under production could substantially improve the food supply and enhance livelihoods in the region. This paper describes a methodological case study that targeted resource-conserving technologies in underused lands of the Ballia District of eastern Uttar Pradesh (India) using multispectral remote-sensing images. Classification of temporal satellite data IRS-P6 in combination with Spot VGT 2 permitted the identification of all major categories of underused land during the post-rainy rabi/winter season, with an average accuracy of 89%. Based on three-year averages of field demonstrations, farmers gained an additional income of $63 ha−1 by introducing raised beds in salt-affected soils; $140 and $800 ha−1 by introducing deepwater rice varieties (monsoon) and boro rice (winter) in waterlogged areas; and $581 ha−1 by introducing zero-till lentil (winter) in rain-fed fallow lowland. Timely wheat planting through zero-tillage implies an additional income of $147 ha−1 and could increase wheat production by 35,000-65,000 tons in the district. The methodologies and technologies suggested in the study are applicable to more than 15 million ha of underutilized lands of the Indo-Gangetic Plains of South Asia. If the technologies are precisely applied, they can result in more than 3000 million US $ of additional income every year to these poverty prone areas. 相似文献
5.
The extent of salt-affected soils in Punjab based on the 1984 Landsat-MSS data (FCC) has been investigated. The area of salt-affected soils has decreased from 0.699 million ha in 1972 to 0.488 million ha in 1984. The 1972 extent of salt-affected soils is based on the available maps and interpretation of ERTS pictures. The morphological, physical, chemical and minerological characteristics of salt-affected soils in Punjab are described. These soils are charaterised by high pH, ESP and EC but lack columnar or prismatic structure. The highest salt accumulation is observed at the surface and decreases with depth. The only sodium containing silicate mineral identified in these soils is albite. The development of salt-affected soils in Punjab is intimately connected with fluctuation of ground water. These soils have been formed by a combination of topographic, climatic, hydrological and geochemical conditions conducive for the accumulation of brackish waters at or near soil surface. 相似文献
6.
R. S. Sidhu 《Pure and Applied Geophysics》1971,85(1):125-139
Summary The wave equations of elasticity in the presence of body forces for a semi-infinite, isotropic, heterogeneous medium with exponentially varying material properties have been solved. Using double Fourier transform the equations are first transformed to linear second order differential equations. From the solution of these equations the displacements are obtained by the use of inversion theorem for double Fourier transform. The method followed resolves the disturbance into its constitutive parts—incident and reflectedP, SV andSH type waves. Surface displacements due to a single couple, double couple and various other sources have been calculated. 相似文献
7.
R. S. Sidhu 《Pure and Applied Geophysics》1971,87(1):55-65
Summary The theory of Hankel transforms is used to obtain the displacement field forSH waves generated by time harmonic, buried, torsional sources in semi-infinite heterogenous media in which material properties are functions of the depth coordinate. An application to a heterogeneous medium with exponentially varying properties has been discussed. Surface displacements from a surface source have been evaluated at large distances from the source. The results have been compared with those for the homogeneous medium. 相似文献
8.
Natural Hazards - Cyclone tracks over the Great Lakes of North America shift, both East–West as well as North–South. The reasons for the shifts are various small-scale as well as... 相似文献
9.
S. Bazgeer R. K. Mahey P. K. Sharma A. Sood S. S. Sidhu 《Journal of the Indian Society of Remote Sensing》2006,34(3):269-277
Wheat yield prediction using different agrometeorological indices, spectral index (NDVI, Normalized Difference Vegetation
Index) and trend predicted yield (TPY) were developed in Hoshiarpur and Rupnagar districts of Punjab. On the basis of examination
of Correlation Coefficients (R), Standard Error of Estimate (SEOE) and Relative Deviation (RD) values resulted from different
agromet models, the best agromet subset were selected as Minimum Temperature (Tmin), Maximum Temperature (Tmax) and accumulated Heliothermal Units (HTU) in case of Hoshiarpur district and Minimum Temperature (T--min), accumulated Temperature Difference (TD) and accumulated Pan Evaporation (E) for Rupnagar district at reproductive stage
(2nd week of March) of wheat. It was found that Agromet-Spectral-Trend-Yield model could explain 96 % (SEOE = 87 kg/ha) and 91
% (SEOE = 146 kg/ha) of wheat yield variations for Hoshiarpur and Rupnagar districts, respectively. 相似文献
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