On the relative performance of spectrum superposition methods considering modal interaction effects     

R.G. Joshi  I.D. Gupta 《Soil Dynamics and Earthquake Engineering》1998,17(6):357-369

The contribution of modal interaction in the various available spectrum superposition methods is accounted via the modal cross-correlation coefficient, which has been defined in several different approximate ways. Further, in these methods, to define the final expressions directly in terms of the response spectrum amplitudes, the peak factors for all the modal responses are approximated to be equal to the peak factor for the total structural response. However, these assumptions have been found to be violated significantly in many cases and do not hold good in general. Therefore, some recent studies have attempted to improve upon these assumptions. In this paper, detailed investigations are made to study the relative performance of the various available methods considering the modal interaction effects. To find out which of the available methods, in general, gives the better results, the response of a five-storey asymmetric hypothetical building, characterized by significant interaction effects, has been computed from different methods for several widely differing input excitations and the results have been compared with the exact time-history solution.  相似文献   

Evaluation of multisensor data for delineating salt affected soils in arid rajasthan     

N K Kalra°  D C Joshi 《Journal of the Indian Society of Remote Sensing》1997,25(2):79-91

The Landsat (MSS and TM), SPOT (PLA and MLA) and IRS (LISS-I and LISS-II) images of crop free period (April, May), rainfed crop (October) and rabi irrigated crop (January, February) have been evaluated for their capabilities of mapping (1) primary salt affected soils: (slightly, moderately and severely) (2) saline water irrigated saline soils, (3) sodic water irrigated sodic soils and (4) salt affected soils due to tank seepage in the arid region of Rajasthan. The moderately and severe salt affected soils could be mapped with Landsat, (IRS LISS-I) and SPOT, images of any season. However, the summer season imagery provided maximum extent of salt affected soils. The LISS-II imagery also provided delineation of slightly salt affected soils in addition to the moderate and severely salt affected soils. The delineation of saline and sodic water irrigated areas was possible by using Landsat False Colour Composite for the January month by their characteristic reflectance, existing cropping pattern and the quality of irrigation water being used in the area. The IRS (LISS-II) and SPOT PLA images for the May month were also used for mapping of saline and sodic water irrigated soils.  相似文献   

Determination of Lead-210, Radium-226, Thorium-228 and Uranium-238 in Five CCRMP Reference Samples by Gamma-Ray Spectrometry     

S.R. Joshi 《Geostandards and Geoanalytical Research》1987,11(2):199-201

Lead-210, radium-226, thorium-228 and uranium-238 concentrations have been determined in five CCRMP reference samples using direct gamma-ray spectrometry. Literature data are available for only lead-210 and radium-226 levels in these samples.  相似文献   

An evaluation of the CIC model of210Pb dating of sediments     

B. S. Shukla  S. R. Joshi 《Environmental Geology》1989,14(1):73-76

Both linear and polynomial regression analysis techniques are used to assess the CIC (constant initial concentration) model of²¹⁰Pb dating. Results obtained using published²¹⁰Pb and porosity profiles in 12 freshwater sediment cores show that linear regression affords more reliable results. The polynomial regression, while capable of predicting the values of the constant or derived from porosity data, gives reasonable results only when all the coefficients of the polynomial are of appropriate sign. Lower values for all the parameters are obtained in all cases if the effect of compaction is not considered.  相似文献   

Artificial neural network approach for estimation of surface specific humidity and air temperature using multifrequency scanning microwave radiometer     

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   

A comparison of climate response to different radiative forcings in three general circulation models: towards an improved metric of climate change   总被引：3，自引：0，他引：3  

M. Joshi  K. Shine  M. Ponater  N. Stuber  R. Sausen  L. Li 《Climate Dynamics》2003,20(7-8):843-854

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Predicting strong motion parameters for the Chamoli earthquake of 28th March, 1999, Garhwal Himalaya, India, from simplified finite fault model     

A. Joshi 《Journal of Seismology》2003,7(1):1-17

State of Uttaranchal in the northern part of India in the Garhwal Himalaya was hit by the Chamoli earthquake on 28th March, 1999 (GMT). This earthquake was recorded on a strong motion array installed in this region. The maximum peak ground acceleration of 353 cm/sec² was recorded at an accelerograph located at the Gopeshwar station at an approximate epicentral distance of 14 km. The simplified method of Midorikawa (1993) has been used to model finite fault responsible for causing the Chamoli earthquake. This method is based on the Empirical Green's Function (EGF) technique of Irikura (1986).Modifications in this method have been made to include layered earth model and transmission effects at each boundary by Joshi (2001). Rupture causing the Chamoli earthquake is placed in two structural models of the earth in this work: one is a homogeneous half space and other is the multi layered earth model. Comparison in terms of root mean square error (RMSE) is made between the simulated and actual strong motion parameters like peak acceleration and duration. It is seen that the introduction of multi layered earth system in this simplified technique is capable of significantly reducing the RMSE in observed and predicted strong motion parameters and defining the attenuation rate for peak ground acceleration of this earthquake.  相似文献   

Landscape dynamics in Hokersar Wetland, Jammu & Kashmir—An application of geospatial approach     

P K Joshi  Humayun Rashid  P S Roy 《Journal of the Indian Society of Remote Sensing》2002,30(1-2):1-5

Geospatial presentation of habitat has become a key issue for planning conservation and management of any ecosystem. Hokersar wetland, one of the best resorts of migratory waterfowl in Kashmir, is under anthropogenic pressure and siltation due to floods. This has resulted in the degradation and change in the habitat quality of varied aquatic flora and fauna. Moreover, the seasonal changes affect the water level and land cover characteristics of the landscape. In the present study temporal mapping of the wetland has been carried out using the data sets for the autumn and spring seasons to assess the land cove/land use dynamics. The temporal change analysis, in the urban sprawl and the wetland, has been carried out to assess the rate of changes in the wetland and its environs. The wetland initially comprised of patch of marshy waterfowl habitat with some open water bodies. It has been fragmented into a large number of land uses because of anthropogenic activities. The increase in the settlement has been observed proportionate to the rate of fragmentation in the wetland. This study has created an information base, which will help to design conservation schemes for long term maintenance of the wetland.  相似文献   

Visual discrimination of surface features of salt affected soils using satellite images in arid region of Rajasthan (India)     

D C Joshi  Tibor Tóth  Diana Sári 《Journal of the Indian Society of Remote Sensing》2002,30(1-2):33-38

The study has been carried for visual discrimination of natural salt affected soils on FCC images of IRS 1 B in Pali district of Rajasthan. The salt affected soils show wide variations in salinity (EC_2.53.7 to 28 dSm^-1), alkalinity (pH 8.5-9.8), cover ofP. juliflora (10-90%), salt tolerant grasses (10–55%) and gravelly surface (20–35%). ThoughP. juliflora and grasses were present at most of the observation points their cover decreased with soil EC_2.5 values more than 10 and 13 dSm^-1, respectively. Five darkness categories derived as the result of visual interpretation of FCCs; and ground and laboratory studies revealed that the darkness category 1 represented fewer plant community with high salinity (EC 28.7 dSm^-1) and gravelly surface, categories 2 and 3 were characterised by grass cover and moderate salt affected soils (EC 3-10 dSm^-1) whereas category 4 was dominated by thicket ofP. juliflora. The derived numerical darkness categories of the FCC images were slightly low for February images. The darkness values of observation pixel on February images correlated positively withP. juliflora cover and negatively with grass cover and soil pH indicating that surface features on FCC were related with the immediate observation pixels.  相似文献   

Scattering coefficient for S wave incident in a random medium characterized by exponential correlation function     

Jayant N. Tripathi 《Geophysical Journal International》2002,150(2):415-421

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