The dust grains in the coma of Comet West     

K. S. Krishna Swamy  G. A. Shah 《Earth, Moon, and Planets》1987,38(3):273-283

The observed variation of reddening as function of the heliocentric distance and the spatial variation of reddening within the coma of Comet West in the visual wavelength range have been considered to infer the properties of the cometary dust grains. The relevant model incorporates the variation in the size distribution function as well as the composition of the spherical grains. The real part of the complex index of refraction (m = m – im) is chosen such thatm = 1.6. The imaginary part is required to vary from m = 0.2 to 0.05 over the wavelength range 0.4 to 0.7 m. This choice of refractive index corresponds to dirty silicate grains. As a by-product, the model also satisfies the observed polarization and albedo for the Comet West.  相似文献   

Detection of tsunami-induced changes using generalized improved fuzzy radial basis function neural network     

Akansha Mehrotra  Krishna Kant Singh  M. J. Nigam  Kirat Pal 《Natural Hazards》2015,77(1):367-381

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Investigation of different biogeochemical cover configurations for mitigation of landfill gas emissions: laboratory column experiments     

Chetri  Jyoti K.  Reddy  Krishna R.  Grubb  Dennis G. 《Acta Geotechnica》2022,17(12):5481-5498

Acta Geotechnica - Municipal solid waste (MSW) landfills are a major source of anthropogenic methane (CH4) and carbon dioxide (CO2) emissions, which are also major greenhouse gases. Apart from...  相似文献   

Production of Bauxite Certified Reference Material (BARC-B1201) for Nine Property Values (Al2O3, Fe2O3, SiO2, TiO2, V2O5, MnO,Cr2O3, MgO and LOI) Traceable to SI Units     

Ankam Durga Prasad  Lori Rastogi  Vinod Kumar Verma  Vasudevan Krishna Kumari  Sudhakar Yadlapalli  Kulamani Dash 《Geostandards and Geoanalytical Research》2023,47(3):629-636

The National Centre for Compositional Characterisation of Materials (NCCCM) / Bhabha Atomic Research Centre (BARC) and National Aluminium Company Limited (NALCO), India have produced an Indian origin bauxite certified reference material (CRM), referred to as BARC-B1201, certified for major (Al₂O₃, Fe₂O₃, SiO₂, TiO₂, loss on ignition - LOI) and trace contents (V₂O₅, MnO, Cr₂O₃, MgO). Characterisation was undertaken by strict adherence to ISO Guides. A method previously developed and validated in our laboratory, using single step bauxite dissolution and subsequent quantitation (of Al₂O₃, Fe₂O₃, SiO₂, TiO₂, V₂O_5, MnO, Cr₂O₃ and MgO) by ICP-AES (SSBD ICP-AES) was used for homogeneity studies and an inter-laboratory comparison exercise (ILCE) of the candidate CRM. LOI was determined by thermo-gravimetric analysis. Property values were assigned after an ILCE with participation from seventeen reputed government and private sector laboratories in India. The CRM was certified for nine property values: Al₂O₃, Fe₂O₃, SiO₂, TiO₂, V₂O_5, MnO, Cr₂O₃, MgO and LOI, which are traceable to SI units.  相似文献   

Influence of natural and anthropogenic activities on UV Index variations – a study over tropical urban region using ground based observations and satellite data     

K. V. S. Badarinath  Shailesh Kumar Kharol  V. Krishna Prasad  Anu Rani Sharma  E. U. B. Reddi  H. D. Kambezidis  D. G. Kaskaoutis 《Journal of Atmospheric Chemistry》2008,59(3):219-236

Measurements of total ozone column and solar UV radiation under different atmospheric conditions are needed to define variations of both UV and ozone and to study the impact of ozone depletion at the Earth’s surface. In this study, spectral and broadband measurements of UV-B irradiance were obtained along with total ozone observations and aerosol optical depth measurements in the tropical urban region of Hyderabad, south India. We specifically used an Ultra-Violet Multifilter Rotating Shadow band Radiometer (UVMFR-SR), to measure UV irradiance in time and space. To assess the aerosol and O₃ effects on ground-reaching UV irradiance, we used measurements from a Microtops II sun photometer in addition to the Tropospheric Ultraviolet Visible radiation (TUV) model. We also assessed the Defense Meteorological Satellite Program – Operational Line Scanner (DMSP-OLS) night time satellite data for inferring biomass burning fires during the study period. Results clearly suggested a negative correlation between the DMSP-OLS satellite derived fire count data and UVMFR-SR data suggesting that aerosols from biomass burning are directly attenuating UV irradiance in the study region. Also, correlation analysis between UV index and ozone measurements from sun photometer and TOMS-Ozone Mapping Instrument (OMI) indicated a clear decrease in ground reaching UV-B irradiance during higher ozone conditions. The higher levels are attributed to photochemical production of O₃ during the oxidation of trace gases emitted from biomass burning. Results also suggested a relatively high attenuation in UV irradiance (~6% higher) from smoke particles than dust. We also found a relatively good agreement between the modeled (TUV) and measured UV irradiance spectra for different atmospheric conditions. Our results highlight the factors affecting UV irradiance in a tropical urban environment, south India.  相似文献   

Variations in CO,O<Subscript>3</Subscript> and black carbon aerosol mass concentrations associated with planetary boundary layer (PBL) over tropical urban environment in India     

K. V. S. Badarinath  Anu Rani Sharma  Shailesh Kumar Kharol  V. Krishna Prasad 《Journal of Atmospheric Chemistry》2009,62(1):73-86

Carbon monoxide (CO), Ozone (O₃) and Black Carbon (BC) aerosol mass concentrations in relation to planetary boundary layer (PBL) height measurements were analyzed from January–December, 2008 over tropical urban environment of Hyderabad, India. DMSP-OLS night-time satellite data were analyzed for fire occurrence over the region and its correlation with pollution concentrations over the urban region. Results of the study suggested considerable increase in CO and BC concentrations during early morning hours. Higher concentration of BC, CO and ozone was observed during pre-monsoon, post-monsoon and winter and lowest concentrations exhibited during monsoon season. NCEP/NCAR reanalysis winds suggested long range transport of aerosols and trace gases from forest fires are enhancing the pollutant concentrations over the study area.  相似文献   

Technical Challenges to In-situ Remediation of Polluted Sites     

Krishna R. Reddy 《Geotechnical and Geological Engineering》2010,28(3):211-221

Throughout the world, subsurface contamination has become a widespread and pervasive problem. Toxic chemicals such as heavy metals and organic compounds are commonly used in a myriad of industries. However, largely through inadvertent or accidental release, these chemicals are presently polluting sites across the United States. In order to protect public health and the environment, further pollution must be prevented and sites with existing contamination urgently need remediation. Unfortunately, remediating subsurface contamination has proved to be a daunting task. Heavy metals and organic compounds often coexist and their distribution within the subsurface is highly dependent on particle and macro-scale heterogeneities. Vast resources have been invested to develop efficient remediation technologies, yet very few of these technologies have been successful. In-situ remediation is often preferred due to minimal site disturbance, safety, simplicity, and cost-effectiveness. The effectiveness of in-situ remediation technologies depends largely on the contaminant chemistry and subsurface heterogeneities (including particle-scale heterogeneities such as fine-grained soils, soils with reactive minerals, and/or soils rich in organic matter as well as macro-scale heterogeneities such as irregular soil layers and/or lenses). Under such heterogeneous conditions, integrated electrokinetic remediation technology has great potential. As a safe and economical remedial option for so many contaminated sites, the application of integrated electrokinetic remediation offers enormous public health, environmental, and financial benefits.  相似文献   

Long-Term Variability of Nutrients and Chlorophyll in the Chesapeake Bay: A Retrospective Analysis, 1985–2008     

M. Bala Krishna Prasad  Mathew R. P. Sapiano  Clarissa R. Anderson  Wen Long  Raghu Murtugudde 《Estuaries and Coasts》2010,33(5):1128-1143

A retrospective analysis of freshwater discharge, riverine dissolved nutrient loads, dissolved nutrients, and chlorophyll in the Chesapeake Bay from 1985 to 2008 is presented. It is evident that each field displays an interannual variability averaged over the Bay. The N and P loads peaked in 1997 and have fluctuated with a decreasing trend since early 2004. Dissolved nutrient concentrations in the Bay appear to be largely controlled by riverine nutrient loads. The temporal variability of chlorophyll is positively correlated with nutrient loads and concentrations. Over the study period, N:P (DIN:DIP) molar ratios were consistently higher than the Redfield ratio (N:P?=?16:1) and strongly correlated with river discharge (R ²?=?0.68, p??16:1), and N is the limiting nutrient in summer and early autumn (N:P?4 from anoxic sediments. Long-term climate indices, such as El Niño Southern Oscillation (ENSO) and North Atlantic Oscillation (NAO), appear to exert only a moderate control over the riverine discharge to the Bay or over the ecosystem response in terms of chlorophyll in the Bay. While not all related mechanisms can be inferred from available data, this analysis should help in determining future data needs for monitoring water quality and human and climate influence on the health of the Bay.  相似文献   

Simulation of heavy rainfall events over Indian monsoon region using WRF-3DVAR data assimilation system     

A. Routray  U. C. Mohanty  Dev Niyogi  S. R. H. Rizvi  Krishna K. Osuri 《Meteorology and Atmospheric Physics》2010,106(1-2):107-125

We present the results of the impact of the 3D variational data assimilation (3DVAR) system within the Weather Research and Forecasting (WRF) model to simulate three heavy rainfall events (25–28 June 2005, 29–31 July 2004, and 7–9 August 2002) over the Indian monsoon region. For each event, two numerical experiments were performed. In the first experiment, namely the control simulation (CNTL), the low-resolution global analyses are used as the initial and boundary conditions of the model. In the second experiment (3DV-ANA), the model integration was carried out by inserting additional observations in the model’s initial conditions using the 3DVAR scheme. The 3DVAR used surface weather stations, buoy, ship, radiosonde/rawinsonde, and satellite (oceanic surface wind, cloud motion wind, and cloud top temperature) observations obtained from the India Meteorological Department (IMD). After the successful inclusion of additional observational data using the 3DVAR data assimilation technique, the resulting reanalysis was able to successfully reproduce the structure of convective organization as well as prominent synoptic features associated with the mid-tropospheric cyclones (MTC). The location and intensity of the MTC were better simulated in the 3DV-ANA as compared to the CNTL. The results demonstrate that the improved initial conditions of the mesoscale model using 3DVAR enhanced the location and amount of rainfall over the Indian monsoon region. Model verification and statistical skill were assessed with the help of available upper-air sounding data. The objective verification further highlighted the efficiency of the data assimilation system. The improvements in the 3DVAR run are uniformly better as compared to the CNTL run for all the three cases. The mesoscale 3DVAR data assimilation system is not operational in the weather forecasting centers in India and a significant finding in this study is that the assimilation of Indian conventional and non-conventional observation datasets into numerical weather forecast models can help improve the simulation accuracy of meso-convective activities over the Indian monsoon region. Results from the control experiments also highlight that weather and regional climate model simulations with coarse analysis have high uncertainty in simulating heavy rain events over the Indian monsoon region and assimilation approaches, such as the 3DVAR can help reduce this uncertainty.  相似文献   

Selection of Suitable Window Size for Speckle Reduction and Deblurring using SOFM in Polarimetric SAR Images     

Sanjay Shitole  Shaunak De  Y. S. Rao  B. Krishna Mohan  Anup Das 《Journal of the Indian Society of Remote Sensing》2015,43(4):739-750

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