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11.
N. P. Honkanadavar Nripendra Kumar Murari Ratnam 《Geotechnical and Geological Engineering》2014,32(4):1001-1015
Two types of modeled rockfill materials were collected from Renuka dam site, Himachal Pradesh, India and Salma dam site, Afghanistan. The rockfill material collected from Renuka dam site is rounded to sub-rounded in shape and the rockfill material collected from Salma dam site is angular to sub-angular in shape. The prototype gradation rockfill material consists maximum particle size larger than 1,000 mm. Therefore, for carrying out laboratory testing and modeling the bahaviour, the prototype rockfill material is scaled down to the maximum particle size (dmax) of 25, 50 and 80 mm for both projects material using parallel gradation technique. Triaxial compression and Index properties tests were conducted on both project rockfill materials and are presented. From the triaxial behaviour, it is observed that the stress–strain behaviour is non-linear, inelastic and stress dependent for both the materials. The material compresses during the initial shearing and shows dilation effect with further shearing. It is observed that the ?-value for alluvial rockfill material increases with increase in dmax and reverse trend is observed for blasted quarried rockfill material which shows the importance of the type of material. The stress–strain-volume change behaviour of both projects modeled rockfill material was predicted by using hierarchical single surface (HISS) model based on elasto plasticity and compared with the laboratory test results. From the comparison, it is observed that both results match closely. It is, therefore, suggested that the behaviour of both types of rockfill materials can be characterized successfully using HISS model. 相似文献
12.
J. V. Ratnam S. K. Behera Y. Masumoto K. Takahashi T. Yamagata 《Climate Dynamics》2012,39(1-2):227-238
The winter months from December 2009 to February 2010 witnessed extreme conditions affecting lives of millions of people around the globe. During this winter, the El Ni?o Modoki in the tropical Pacific was a dominant climatic mode. In this study, exclusive impacts of the El Ni?o Modoki are evaluated with an Atmospheric General Circulation Model. Sensitivity experiments are conducted by selectively specifying anomalies of the observed sea surface temperature in the tropical Pacific. Observed data are also used in the diagnostics to trace the source of forced Rossby waves. Both the observational results and the model simulated results show that the heating associated with the El Ni?o Modoki in the central tropical Pacific accounted for most of the anomalous conditions observed over southern parts of North America, Europe and over most countries in the Southern Hemisphere viz. Uruguay. Unlike those, the model-simulated results suggest that the anomalously high precipitation observed over Australia and Florida might be associated with the narrow eastern Pacific heating observed during the season. 相似文献
13.
K Charan Kumar T Rajendra Prasad M Venkat Ratnam Kamsali Nagaraja 《Journal of Earth System Science》2016,125(7):1391-1397
Analysis of one year measurements of in situ radon (222Rn) and its progenies along with surface air temperature, relative humidity and pressure near to the Earth’s surface has been carried out for the first time at the National Atmospheric Research Laboratory (NARL, 13.5°N and 79.2°E) located in a rural site in Gadanki, south India. The dataset was analysed to understand the behaviour of radon in relation to the surface air temperature and relative humidity at a rural site. It was observed that over a period of the 24 hours in a day, the activity of radon and its progenies reaches a peak in the morning hours followed by a remarkable decrease in the afternoon hours. Relatively, a higher concentration of radon was observed at NARL during fair weather days, and this can be attributed to the presence of rocky hills and dense vegetation surrounding the site. The high negative correlation between surface air temperature and activity of radon (R = – 0.70, on an annual scale) suggests that dynamical removal of radon due to increased vertical mixing is one of the most important controlling processes of the radon accumulation in the atmospheric surface layer. The annual averaged activity of radon was found to be 12.01±0.66 Bq m?3 and 4.25±0.18 Bq m?3 for its progenies, in the study period. 相似文献
14.
15.
Charishma Ratnam 《Urban geography》2013,34(8):1198-1209
Australia publicly espouses its multiculturalism as a key component of its national identity. In this paper, I argue that despite the importance of multiculturalism to Australia’s identity, political decisions and discourse has muddied its remit with respect to humanitarian migrant intake programs and outcomes. Australia’s history of selective migrant intake and restrictive refugee policy continues the Othering of past policies into contemporary settings. Refugee policy has become a political football. During the most recent national election campaign (May 2019), the plight of sick and ill refugees, currently housed offshore in detention centers, was used as a political pawn. Lost amid this political rhetoric were the traumatic narratives of forced migrants resettling in Australia’s cities. Without possibility for a loud voice in public discourse, there is little opportunity for more Australians to understand how refugees experience detention centers, struggle to attain residency visas, and make “home” in multicultural Australia. I draw on research with Sri Lankan refugees in Sydney to give voice to these micro-level, place-based experiences of vulnerable arrivals. These stories, I think, can (re)shape and enrich Australia’s multicultural identity because they challenge us to not only accept difference but recognize the circumstances through which Australia’s diversity seeds its narrative. 相似文献
16.
M. Venkat Ratnam M. Shravan Kumar Ghouse Basha V.K. Anandan A. Jayaraman 《Journal of Atmospheric and Solar》2010,72(18):1393-1400
This paper documents the effect of the annular solar eclipse of 15 January 2010 on the lower atmospheric boundary layer dynamics over a complex terrain environment at Gadanki (13.5°N, 79.2°E,) using a suite of instruments namely automatic weather station, mini boundary layer mast (15 m), Doppler SODAR, GPS radiosonde and ozonesonde observations. The net heating rates are estimated using radiative transfer algorithm before, during and after the eclipse. Effect on soil temperature is seen clearly up to 20 cm depth and at all the levels up to 15 m. Decrease in the thermal plume level, a dip in the surface layer and a strong vertical downdrafts (subsidence) are noticed during the peak eclipse. Upper layer winds did not show any variation during the eclipse. It is also found to have pronounced effect on all the surface meteorological parameters for a two-day period. 相似文献
17.
The paper presents an analytical study of the consolidation of a semi-infinite clay layer subjected to a shear load distributed over a rectangular area. Biot's theory is made use of, along with the three displacement functions suggested by Verruijt. A complex Fourier and Laplace transformation technique enables the solution to be obtained in terms of non-dimensional parameters. Settlements and pore pressures under the loaded area are evaluated for two types of surface drainage conditions. Extension of the solutions to point loads is also suggested. The Mandel–Cryer effect is seen in the behaviour of the pore pressure. 相似文献
18.
J. Venkata Ratnam Filippo Giorgi Akshara Kaginalkar Stefano Cozzini 《Climate Dynamics》2009,33(1):119-139
A regional coupled atmosphere–ocean model was developed to study the role of air–sea interactions in the simulation of the
Indian summer monsoon. The coupled model includes the regional climate model (RegCM3) as atmospheric component and the regional
ocean modeling system (ROMS) as oceanic component. The two-way coupled model system exchanges sea surface temperature (SST)
from the ocean to the atmospheric model and surface wind stress and energy fluxes from the atmosphere to the ocean model.
The coupled model is run for four years 1997, 1998, 2002 and 2003 and the results are compared with observations and atmosphere-only
model runs employing Reynolds SSTs as lower boundary condition. It is found that the coupled model captures the main features
of the Indian monsoon and simulates a substantially more realistic spatial and temporal distribution of monsoon rainfall compared
to the uncoupled atmosphere-only model. The intraseasonal oscillations are also better simulated in the coupled model compared
to the atmosphere-only model. These improvements are due to a better representation of the feedbacks between the SST and convection
and highlight the importance of air–sea coupling in the simulation of the Indian monsoon. 相似文献
19.
Sanjay Kumar Mehta M. Venkat Ratnam B.V. Krishna Murthy 《Journal of Atmospheric and Solar》2011,73(17-18):2462-2473
The characteristics of the cold point tropopause (CPT), convective tropopause (COT) and tropical tropopause layer (TTL) in the tropical region at different longitudes are studied using radiosonde data at 5 stations in the tropical belt (±15°) and high resolution GPS radiosonde data from April 2006 to December 2008 at Gadanki (13.5°N, 79.2°E) also a tropical station. The CPT over Gadanki is found to be higher than over the rest of the stations. This aspect is further confirmed using COSMIC GPS RO observations. In the Northern Hemisphere (NH) winter, the CPT is coldest over stations in the Pacific region compared to the other stations while in the NH summer, it is coldest at Gadanki, a station in the Indian monsoon region. The range of seasonal variation of the CPT temperature is found to be quite small over Gadanki compared to the other stations whereas that of the CPT altitude is nearly the same. 相似文献
20.
M. Venkat Ratnam M. Roja Raman Sanjay Kumar Mehta Debashis Nath B.V. Krishnamurthy M. Rajeevan S. Vijaya Bhaskara Rao D. Narayana Rao 《Journal of Atmospheric and Solar》2011,73(7-8):731-740
To investigate the sub-daily variation in Tropical Easterly Jet (TEJ), a few special experiments have been conducted with mesosphere–stratosphere–troposphere (MST) radar located at Gadanki(13.5°N, 79.2°E) under Study on Atmospheric Forcing and Responses (SAFAR) campaign during 2008–2009. Large sub-daily changes in the TEJ characteristics are observed within a day in addition to day-to-day changes. Based on this observational study, three possible mechanisms for the sub-daily variations are proposed i.e., (1) motion of TEJ core, (2) large updrafts and downdrafts, and (3) strong wave activity. Interestingly, TEJ peak altitude is seen above the Cold Point Tropopause altitude for about 42% of the days. 相似文献