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41.
R. S. Dwivedi K. Sreenivas K. V. Ramana 《International journal of remote sensing》2013,34(8):1589-1599
Waterlogging and subsequent salinization and/or alkalization are the major land degradation processes in irrigated agricultural lands of arid and semiarid regions. The use of spaceborne multispectral data has been shown to have potential for deriving information on the nature, extent, spatial distribution and magnitude of various degraded lands. Indian Remote Sensing Satellite (IRS-1B) Linear Imaging Self-scanning Sensor (LISS-I) and Landsat Thematic Mapper (TM) data in the form of standard false colour composite (FCC) prints at 1 100000 scale covering Nagarjunsagar Left Bank canal command area in Andhra Pradesh, southern India, have been used to delineate waterlogged areas and salt-affected soils through a systematic visual interpretation approach. Waterlogged areas are estimated at 1380ha whereas salt-affected soils of mostly saline-sodic nature cover 6830ha of the command area. The methodology used and results are described in detail. 相似文献
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Satyam Naidu V. Aghalayam Preeti Jayanti Sreenivas 《Clean Technologies and Environmental Policy》2018,20(6):1207-1218
Clean Technologies and Environmental Policy - CO2 capture from coal-fired power plants is necessary for continued use of coal as a fuel. Proven CO2 capture techniques such as amine absorption and... 相似文献
44.
P. Mahesh G. Sreenivas P.V.N. Rao V.K. Dadhwal S.V.S. Sai Krishna K. Mallikarjun 《International journal of remote sensing》2013,34(22):5754-5765
An enhanced performance model of the greenhouse gas analyser (GGA) instrument from Los Gatos Research (LGR), which uses off-axis integrated cavity output spectroscopy (OA-ICOS) technology to obtain highly precise and accurate measurements, has been installed at the National Remote Sensing Center (NRSC), Shadnagar with the objective of generating a long-term record of measurements conforming to standards set by the World Meteorological Organisation (WMO). A calibration procedure to ensure the precision and accuracy of measurements was formulated using National Oceanic and Atmospheric Administration-Earth System Research Laboratory (NOAA-ESRL) calibration gases bearing WMO certification. The 10 s (1 σ) average precision of carbon dioxide (CO2) and (methane (CH4)) measurements by the GGA was 101 parts per billion volume (0.30 ppbv) and accuracy 78 ppbv (0.24 ppbv), respectively. The 5 s average of 1 Hz measurements was used to compute precision, which varied from 92.52 to 116.36 ppbv (1σ, 1 Hz = 0.66 parts per million volume (ppmv), WMO-2009)) for CO2 and CH4 0.45 ppbv to 0.55 ppbv (1 σ, 1 Hz = 2.48 ppbv, WMO-2009) respectively. Diurnal variation of greenhouse gas concentrations, temperature, and pressure, showed high fluctuations when cavity pressure and temperature varied from the standard values. The residuals of dry mixing ratios with respect to (w.r.t.) the NOAA span gases varied from +30 to ?60 ppbv for CO2 and ±0.35 ppbv for CH4. A case study using the corrected observations over 1 year revealed the role of wind velocity and anthropogenic emissions, as well as the seasonal variations in the ambient concentrations of CO2 and CH4 gases near the surface. 相似文献
45.
Optical waveguiding characteristics of amorphous TeO2−x films deposited by reactive sputtering under different O2:Ar gas mixtures are investigated on fused quartz and Corning glass substrates. Infra-red absorption band in the range 641-658 cm−1 confirmed the formation of a TeO bond, and a 20:80 O2:Ar gas mixture ratio is found to be optimum for achieving highly uniform and transparent films at a high deposition rate. As grown amorphous films exhibited a large band gap (3.76 eV); a high refractive index value (2.042-2.052) with low dispersion over a wide wavelength range of 500-2000 nm. Optical waveguiding with low propagation loss of 0.26 dB/cm at 633 nm is observed on films subjected to a post-deposition annealing treatment at 200 °C. Packing density and etch rates have been determined and correlated with the lowering of optical propagation loss in the annealed films. 相似文献
46.
Arun Kumar Singh Chauhan Vinay Gupta K. Sreenivas 《Materials Science and Engineering: B》2006,130(1-3):81-88
Synthesis of Ca doped PbTiO3 powder by a chemically derived sol–gel process is described. Crystallization characteristics of different compositions Pb1−xCaxTiO3 (PCT) with varying calcium (Ca) content in the range x = 0–0.45 has been investigated by DTA/TGA, X-ray diffraction and scanning electron microscopy. The crystallization temperature is found to decrease with increasing calcium content. X-ray diffraction reveals a tetragonal structure for PCT compositions with x ≤ 0.35, and a cubic structure for x = 0.45. Dielectric properties on sintered ceramics prepared with fine sol–gel derived powders have been measured. The dielectric constant is found to increase with increasing Ca content, and the dielectric loss decreases continuously. Sol–gel derived Pb1−xCaxTiO3 ceramics with x = 0.45 after poling exhibit infinite electromechanical anisotropy (kt/kp) with a high d33 = 80 pC/N, ′ = 298 and low dielectric loss (tan δ = 0.0041). 相似文献
47.
S. Arunkumar K.V. Sreenivas Rao T.S. Prasanna Kumar 《International Journal of Heat and Mass Transfer》2008,51(11-12):2676-2685
Most of the research work pertaining to metal–mold heat transfer in casting solidification either assumes no spatial variation in the air gap formation or limits the study to only those experimental systems in which air gap formation is uniform. However, in gravity die-casting, filling effects induce variation in thermal field in the mold and casting regions. In this paper, we show that this thermal field variation greatly influences the time of air gap initiation along a vertical mold wall, which subsequently leads to the spatial variation of air gap and in turn, the heat flux at the metal–mold interface.In order to study the spatial variation of heat flux at the metal–mold interface, an experimental setup that involved mold filling was devised. A Serial-IHCP (inverse heat conduction problem) algorithm was used to estimate the multiple heat flux transients along the metal–mold interface. The analysis indicates that the fluxes at different mold segments (bottom, middle, and top) of the metal–mold interface reaches the peak value at different time steps, which shows that the initiation of air gap differs along the mold wall. The experimental and numerical results show that the heat transfer in the mold is two-dimensional during the entire period of phase change, which is initially caused by the filling effects and further enhanced by the spatial variation of the air gap at the metal–mold interface. 相似文献
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49.
Vinod M. Janardhanan Srinivas Appari Sreenivas Jayanti Olaf Deutschmann 《Chemical engineering science》2011,(3):490
A pseudo-transient numerical model is used for the simulation of a multi-functional catalytic plate reactor (CPR). The work mainly addresses the problems associated with on-board reforming for solid-oxide fuel cells. Heat management is achieved by indirectly coupling partial oxidation with reforming. Water management is achieved by partially recycling the anode stream from a solid-oxide fuel cell. The model uses detailed heterogeneous chemistry for reforming and oxidation reactions occurring on the catalyst beds. 相似文献
50.
Nitu Kumari Shagun Monga Mohd. Arif Neeraj Sharma Arun Singh Vinay Gupta Paula M. Vilarinho K. Sreenivas R.S. Katiyar 《Ceramics International》2019,45(4):4398-4407
The paper reports highest obtained dielectric constant for Ni-doped Lead Zirconate Titanate [PZT, Pb(Zr0.52Ti0.48)O3] ceramics. The Ni-doped PZT ceramic pellets were prepared via conventional solid-state reaction method with Ni content chosen in the range 0–20?at%. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were employed to investigate the crystal structure of the prepared ceramics. The X-ray diffraction analysis indicated that the ceramic pellets had crystallized into tetragonal perovskite structure. A minute displacement of XRD peaks was detected in the diffraction spectra of Ni-doped PZT ceramic samples which when examined by size-strain plot (SSP) method revealed presence of homogenous strain that decreased with increase in concentration of Ni. In FTIR the maximum absorption at 597?cm?1, 608?cm?1, 611?cm?1, 605 and 613?cm?1 for Ni?=?0, 5, 10, 15 and 20?at%, respectively, confirmed the formation of perovskite structure in all the compositions and the slight shift suggests decrease in cell size on doping. The values of dielectric constant (ε′) & tanδ as a function of frequency and temperature were measured for the prepared ceramics and it revealed highest ever reported dielectric constant for Ni - doped PZT with Ni?=?5?at%. The dielectric variation with temperature exhibited a diffused type ferroelectric–paraelectric phase transition for the doped samples. Also, the maximum dielectric constant value (ε′max) decreased while the phase transition temperature increased with increase in doping concentration of Ni. The estimated activation energy of different compositions was found to increase from 0.057 to 0.068?eV for x?=?0.00 to x?=?0.20 in ferroelectric phase. The piezoelectric, ferroelectric and magnetic properties were also investigated. 相似文献