Browsing by Author "Sarkar, A."

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Comparative study of ocean wave spectrum using ENVISAT SAR data and wave rider buoy data
(2006) Pai, B, J.; Kumar, R.; Sarkar, A.; Hegde, A.V.; Dwarakish, G.S.
A comparative study of ENVISAT ASAR data and corresponding wave rider buoy data has been attempted. An algorithm has been developed to retrieve Ocean Wave Spectrum from SAR data. The resulting spectrum is compared with the wave rider buoy measured wave spectrum. To compute the 2-D image spectrum from multi-look SAR data, various corrections to the original SAR data has been applied. Thereafter, Modulation Transfer Function has been computed and utilized to convert image spectrum to the Ocean Wave Spectrum. This final ocean wave height spectrum is used to estimate the ocean wave spectral parameters and has been compared with the in-situ measurements and model derived wave spectrum. An attempt has also been made to process the Single Look Complex (SLC) data to reduce the speckle noise in the SAR data using Fast Fourier Transform (FFT).
Comparative study of ocean wave spectrum using ENVISAT SAR data and wave rider buoy data
(2006) Pai, J.; Kumar, R.; Sarkar, A.; Hegde, A.V.; Dwarakish, G.S.
A comparative study of ENVISAT ASAR data and corresponding wave rider buoy data has been attempted. An algorithm has been developed to retrieve Ocean Wave Spectrum from SAR data. The resulting spectrum is compared with the wave rider buoy measured wave spectrum. To compute the 2-D image spectrum from multi-look SAR data, various corrections to the original SAR data has been applied. Thereafter, Modulation Transfer Function has been computed and utilized to convert image spectrum to the Ocean Wave Spectrum. This final ocean wave height spectrum is used to estimate the ocean wave spectral parameters and has been compared with the in-situ measurements and model derived wave spectrum. An attempt has also been made to process the Single Look Complex (SLC) data to reduce the speckle noise in the SAR data using Fast Fourier Transform (FFT).
Determination of mixed layer depth from C-Band Synthetic Aperture Radar (SAR)
(2010) Pai, J.; Kumar, R.; Sarkar, A.; Hegde, A.V.; Dwarakish, G.S.
Oceanic internal waves are frequently observed on the continental shelf during the summer season, when the ocean is stratified. The appearance of internal wave phenomena in remote sensing images has been increasing the curiosity to observe internal wave at specific area in the world. Studies reveal that Synthetic Aperture Radar has a capability to detect internal waves. In the present study, ENVISAT Advanced Synthetic Aperture Radar (ASAR) image acquired on October 4, 2003, was used to determine Mixed Layer Depth (MLD) off Bay of Bengal of Indian Ocean region. The image showed several prominent trains of internal waves, with several wave packets in each train. The ocean was assumed to be a two layer system, and that the local semidiurnal tide is the generating force for the internal waves. By assuming that the local semidiurnal tide period is the generating source for these waves, and by measuring the distance between the wave packets, it is possible to derive the group velocity of the internal waves from Synthetic Aperture Radar (SAR) images directly. The mixed -layer depth is then derived by assuming the ocean as a two-layer finite depth model. The group velocity measured from the SAR image and the simulated group velocity by the two layer finite depth model was matched to get the mixed layer depth. The estimated mixed layer depth was 21m. This value show reasonably good agreement with the actual depth of 19.5m of in-situ ARGO buoy. © 2010 by IJI (CESER Publications).
High temperature gradient cobalt based clad developed using microwave hybrid heating
(2018) Prasad, C.D.; Joladarashi, S.; Ramesh, M.R.; Sarkar, A.
The development of cobalt based cladding on a titanium substrate using microwave cladding technique is benchmark in coating area. The developed cladding would serve the function of a corrosion resistant coating under high temperatures. Clads of thickness 500 ?m have been developed by microwave hybrid heating. A microwave furnace of 2.45GHz frequency was used at a 900W power level for processing. Impact of processing time on melting and adhesion of clad has been discussed. The study also extended to static thermal analysis of simple parts with cladding using commercial Finite Element analysis (FEA) software. A comparative study is explored between four variants of the clad being developed. The analysis has been conducted using a square sample. Similar temperature gradient is also shown for a proposed multi-layer coating, which includes a thermal barrier coating yttria stabilized zirconia (YSZ) on top of the corrosion resistant clad. The YSZ coating would protect the corrosion resistant cladding and substrate from high temperatures. � 2018 Author(s).
High temperature gradient cobalt based clad developed using microwave hybrid heating
(American Institute of Physics Inc. subs@aip.org, 2018) Prasad, C.D.; Joladarashi, S.; Ramesh, M.R.; Sarkar, A.
The development of cobalt based cladding on a titanium substrate using microwave cladding technique is benchmark in coating area. The developed cladding would serve the function of a corrosion resistant coating under high temperatures. Clads of thickness 500 Î¼m have been developed by microwave hybrid heating. A microwave furnace of 2.45GHz frequency was used at a 900W power level for processing. Impact of processing time on melting and adhesion of clad has been discussed. The study also extended to static thermal analysis of simple parts with cladding using commercial Finite Element analysis (FEA) software. A comparative study is explored between four variants of the clad being developed. The analysis has been conducted using a square sample. Similar temperature gradient is also shown for a proposed multi-layer coating, which includes a thermal barrier coating yttria stabilized zirconia (YSZ) on top of the corrosion resistant clad. The YSZ coating would protect the corrosion resistant cladding and substrate from high temperatures. Â© 2018 Author(s).