排序方式： 共有41条查询结果，搜索用时 31 毫秒
21.
Two storey bilinear hysteretic structures have been studied with a view to exploring the possibility of using the dynamic vibration absorber concept in earthquake-resistant design. The response of the lower storey has been optimized for the Taft 1952, S69°E accelerogram with reference to parameters such as frequency ratio, yield strength ratio and mass ratio. The influence of viscous damping has also been examined. 相似文献
22.
Summary Indian monsoon rainfall data is shown to be decomposable into six empirical time series, called intrinsic mode functions. This helps one to identify the first empirical mode as a nonlinear part and the remaining as the linear part of the data. The nonlinear part is handled by artificial neural network (ANN) techniques, whereas the linear part is amenable for modeling through simple regression concepts. It is found that the proposed model explains between 75 to 80% of the interannual variability (IAV) of eight regional rainfall series considered here. The model is efficient in statistical forecasting of rainfall as verified on an independent subset of the data series. It is demonstrated that the model is capable of foreshadowing the drought of 2002, with the help of only antecedent data. The statistical forecast of All India rainfall for the year of 2004 is 80.34 cms with a standard deviation of 3.3 cms. This expected value is 94.25% of the longterm climatic average. 相似文献
23.
Estimation of seismic spectral acceleration in Peninsular India 总被引：6，自引：0，他引：6
Peninsular India (PI), which lies south of 24°N latitude, has experienced several devastating earthquakes in the past. However,
very few strong motion records are available for developing attenuation relations for ground acceleration, required by engineers
to arrive at rational design response spectra for construction sites and cities in PI. Based on a well-known seismological
model, the present paper statistically simulates ground motion in PI to arrive at an empirical relation for estimating 5%
damped response spectra, as a function of magnitude and source to site distance, covering bedrock and soil conditions. The
standard error in the proposed relationship is reported as a function of the frequency, for further use of the results in
probabilistic seismic hazard analysis. 相似文献
24.
The timely prediction of thunderstorms (TS) is always a challenging task for operational and research community. The present study is aimed to address the credibility of the high grid-spacing and downscaling approach for improved simulation of TS. Fourteen TS are simulated with different domain configurations using weather research and forecasting (WRF) model. Two nested domains with 9–3 km (known as DD3), and 6–2 km (DD2), and 3 km single domain (SD3) are considered for simulations. Results indicate that the high-resolution DD2 has improved 2-m temperature (T2), 2-m relative humidity (RH2), and 10-m wind speed (WS10) at different stages of TS. The average mean error of T2 and RH2 in the DD2 experiment is 0.7 °C, ??6% during the mature stage, and 0.2 °C, ??4% at dissipating stage. The error in SD3 and DD3 is relatively higher (9–17% for T2 and 20–60% for RH2). Better horizontal and vertical representation of thermodynamic variables in DD2 run reinforces the atmosphere to initiate and intensify the convection in the right place. The DD2 could show slightly higher instability (convective available potential energy, CAPE, 3188 J kg?1) as compared with DD3 (3164 J kg?1) and SD3 (3020 J kg?1). The model is biased to simulate early TS activity. DD2 run could simulate the formation, mature and dissipation stages with fewer timing errors (??1.35 h, ??1.5 h, and ??2.6 h, respectively) than other experiments. The critical success index of the DD2 run is higher for all the rainfall thresholds; however, it is more than 0.2 up to 2.5 mm h?1. The results highlight that high resolution nested configuration yields better simulation skills than the single domain configuration.
相似文献25.
Sagar S. Salunkhe S. S. Rao I. Prabu V. Raghu Venkataraman Y. V. N. Krishna Murthy Chintamani Sadolikar Supriya Deshpande 《Journal of the Indian Society of Remote Sensing》2018,46(6):915-925
In many flood prone river basins, water inundates vast areas of land causing loss of life and heavy damage to the dwellings in flood plains. It also impacts agricultural productivity and cause severe economic losses. One of the reasons for flooding in plains of Brahmaputra valley in north east India is embankment breaching. In this study, an attempt was made for probabilistic flood hazard modelling of July 2008 embankment breaching scenario of Brahmaputra river at Matmara village, Lakhimpur district in Assam, based on various numerical simulations with the help of Center for Computational Hydro science and Engineering hydro-dynamic model. The methodology was applied over 2146 km2 flood prone area. Data inputs in the study include: Advanced Spaceborne Thermal Emission and Reflection Radiometer Digital Elevation Model, Pre-flood and Post flood satellite images of Landsat Enhanced Thematic Mapper Plus (ETM+) and other ancillary data. The simulation was carried out for various discharge levels based on flood frequency analysis. The result of the model includes spatial variations of inundated water depth and water velocity. The results were validated by comparing it with the post-flood ETM+ data and flood situation status report of National Informatics Centre. Flood hazard maps were prepared by carrying out a spatial analysis of simulated inundation depth and velocity. It was seen that the majority of flooded area fell into the very high and high categories. This information can be used to plan appropriate cost effective flood mitigation schemes. 相似文献
26.
M. Bala Krishna Prasad Wen Long Xinsheng Zhang Robert J. Wood Raghu Murtugudde 《Aquatic Sciences - Research Across Boundaries》2011,73(3):437-451
Eutrophic depletion of dissolved oxygen (DO) and its consequences for ecosystem dynamics have been a central theme of research,
assessment and management policies for several decades in the Chesapeake Bay. Ongoing forecast efforts predict the extent
of the summer hypoxic/anoxic area due to nutrient loads from the watershed. However, these models neither predict DO levels
nor address the intricate interactions among various ecological processes. The prediction of spatially explicit DO levels
in the Chesapeake Bay can eventually lead to a reliable depiction of the comprehensive ecological structure and functioning,
and can also allow the quantification of the role of nutrient reduction strategies in water quality management. In this paper,
we describe a three dimensional empirical model to predict DO levels in the Chesapeake Bay as a function of water temperature,
salinity and dissolved nutrient concentrations (TDN and TDP). The residual analysis shows that predicted DO values compare
well with observations. Nash–Sutcliffe efficiency (NSE) and root mean square error-observations standard deviation ratio (RSR)
are used to evaluate the performance of the empirical model; the scores demonstrate the usability of model predictions (NSE,
surface layer = 0.82–0.86; middle layer = 0.65–0.82; bottom layer = 0.70–0.82; RSR surface layer = 0.37–0.44; middle layer = 0.43–0.58
and bottom layer = 0.43–0.54). The predicted DO values and other physical outputs from downscaling of regional weather and
climate predictions, or forecasts from hydrodynamic models, can be used to forecast various ecological components. Such forecasts
would be useful for both recreational and commercial users of the Chesapeake Bay. 相似文献
27.
Bidyut B. Goswami Medha Deshpande P. Mukhopadhyay Subodh K. Saha Suryachandra A. Rao Raghu Murthugudde B. N. Goswami 《Climate Dynamics》2014,43(9-10):2725-2745
We have evaluated the simulation of Indian summer monsoon and its intraseasonal oscillations in the National Centers for Environmental Prediction climate forecast system model version 2 (CFSv2). The dry bias over the Indian landmass in the mean monsoon rainfall is one of the major concerns. In spite of this dry bias, CFSv2 shows a reasonable northward propagation of convection at intraseasonal (30–60 day) time scale. In order to document and understand this dry bias over the Indian landmass in CFSv2 simulations, a two pronged investigation is carried out on the two major facets of Indian summer monsoon: one, the air–sea interactions and two, the large scale vertical heating structure in the model. Our analysis shows a possible bias in the co-evolution of convection and sea surface temperature in CFSv2 over the equatorial Indian Ocean. It is also found that the simulated large scale vertical heat source (Q1) and moisture sink (Q2) over the Indian region are biased relative to observational estimates. Finally, this study provides a possible explanation for the dry precipitation bias over the Indian landmass in the simulated mean monsoon on the basis of the biases associated with the simulated ocean–atmospheric processes and the vertical heating structure. This study also throws some light on the puzzle of CFSv2 exhibiting a reasonable northward propagation at the intraseasonal time scale (30–60 day) despite a drier monsoon over the Indian land mass. 相似文献
28.
Evaluation of liquefaction potential of Guwahati: Gateway city to Northeastern India 总被引：1，自引：0，他引：1
Guwahati city is a major city in the northeastern region of India, which is growing rapidly in every aspect, particularly the major infrastructures like sports complex, educational institutions, flyovers, multiplex halls, etc. Two great earthquakes struck this region in 1897 and 1950, and large-scale liquefaction was reported in and around the Guwahati city. However, a detailed microzonation study for liquefaction is not available so far and is taken up accordingly. The liquefaction potential of the Guwahati city is estimated using hundred boreholes data located at different places of city with a design peak ground acceleration of 0.36?g. The results are presented in the form of factor of safety contours at several depths below the ground surface. These contour maps indicate that most of the sites in Guwahati city area are susceptible to liquefaction and hence this aspect has to be considered in earthquake-resistant design of foundations/structures in Guwahati city. 相似文献
29.
A. Raghu Kumar M. Purnachandra Rao J. Sree Rama Murthy 《Boundary-Layer Meteorology》1986,35(3):303-308
Acoustic sounder data obtained for a period of three years have been analysed to estimate the monthly mean percentage time of occurrences of sea breezes, thermal plumes, and nocturnal radiative inversion layers. The intrusion of marine air has been found to suppress daytime convection and also to inhibit the development of nocturnal inversions. 相似文献
30.
Raghu K. Chunduru Mrinal K. Sen Paul L. Stoffa R. Nagendra 《Geophysical Prospecting》1995,43(8):979-1003
The inversion of resistivity profiling data involves estimation of the spatial distribution of resistivities and thicknesses of rock layers from the apparent resistivity data values measured in the field as a function of electrode separation. The drawbacks of using traditional curve-matching techniques to solve this inverse problem have been overcome by iterative linear techniques but these require good starting models even if the shape of the causative body is asssumed known. In spite of the recent developments in inversion techniques, no robust method exists for the inversion of resistivity profiling data for the simple model of dikes and spheres which are the classical models of geophysical prospecting. We apply three different non-linear inversion schemes to invert synthetic resistivity profiling data for the classical models embedded in a uniform matrix of contrasting resistivity. The three non-linear algorithms used are called the Metropolis simulated annealing (SA), very fast simulated annealing (VFSA) and a genetic algorithm (GA). We compare the performance of the three algorithms using synthetic data for an outcropping vertical dike model. Although all three methods were successful in obtaining optimal solutions for arbitrary starting models, VFSA proved to be computationally the most efficient. 相似文献