Entity

Time filter

Source Type


Patent
Defence Research & Development Organization Drdo | Date: 2013-03-26

In the present disclosure!, there is disclosed an epoxy resin formulation for the manufacturing of large and thick composite structures, said formulation comprising i) at least one epoxy resin in a weight proportion varying between 50 parts to 70 parts; (ii) at least one hardening agent in a weight proportion varying between 21 phr to 29 phr; (iii) at least one diluent in a weight proportion varying between 10 phr to 40 phr; and (iv) N,Ndimethylaminopropylamine as an accelerator in a weight proportion varying between 0.5 phr to 3.0 phr. The formulation is used in the manufacturing of large and thick composite structures by employing Vacuum Assisted Resin Transfer Molding Process.


Singh M.,Shoolini University of Biotechnology and Management Sciences | Mishra V.D.,Defence Research Development Organization DRDO | Thakur N.K.,Defence Research Development Organization DRDO | Sharma J.D.,Shoolini University of Biotechnology and Management Sciences
Journal of the Indian Society of Remote Sensing | Year: 2015

Irregular shape of terrain causes variable illumination angles and diverse reflectance values within same land cover type in optical remote sensing image. It causes problems in image segmentation and misclassification (snow with other land cover). This perception leads to develop an empirical-statistical based topographic correction (ESbTC) algorithm for reflectance modeling after compared with existed topographic correction methods like Cosine correction, C-correction, Minnaert correction, sun–canopy–senor with c-correction (SCS + C) and slope matching, in the context of snow reflectance. An image based atmospheric correction has used in present study included dark-object subtraction (DOS) and effect of Rayleigh scattering on the transmissivity in different spectral bands of AWiFS and MODIS image data. The performance of different models is evaluated using (1) visual analysis, (2) change in snow reflectance on sunny and shady slopes after the corrections, (3) validation with in situ observations and (4) graphical analysis. Further snow cover area (SCA) has been estimated with normalized difference snow index (NDSI) and validated with support vector machine (SVM), a supervised classification technique. The result shows that the proposed algorithm (ESbTC) and slope-matching technique could eliminate most of the shadowing effects in Himalayan rugged terrain and correctly estimate snow reflectance from AWiFS and MODIS imagery as compared with in situ observations whereas other methods significantly underestimate reflectance values after the corrections. © 2015, Indian Society of Remote Sensing. Source


Singh M.,Shoolini University of Biotechnology and Management Sciences | Mishra V.D.,Defence Research Development Organization DRDO | Thakur N.K.,Defence Research Development Organization DRDO | Sharma J.D.,Shoolini University of Biotechnology and Management Sciences
Journal of the Indian Society of Remote Sensing | Year: 2015

Albedo is a critical snow physical parameter that affects the earth’s climate system directly by altering the energy balance at the ground surface and indirectly by controlling the ecosystem processes. Thus spatial variability of snow albedo has immense importance in the study of geomorphology, climate dynamics, seasonal snow melt and hydrology. This paper describes and examines the retrieval of snow albedo for the period October 2012 to May 2013 by using multispectral Advance Wide Field Sensor (AWiFS) on board IRS-P6 of RESOURCESAT-1. The analysis procedure to compute spectral reflectance is achieved by converting the digital numbers after an image based atmospheric and topographic correction that include dark object subtraction (DOS) and effect of Rayleigh scattering on the transmissivity in different spectral bands of AWiFS images. Snow spectral reflectance and satellite derived snow albedo has been validated with in-situ data at the time of satellite pass over the study area using spectroradiometer, pyronometer and Automated Weather Station (AWS) respectively. A fine agreement between satellite derived snow albedo and in-situ measurements shows the relative accuracy of model. Present study also reveal the temporal and spatial variability of snow albedo in a basin which is an evidently indication of the seasonal melt due to decreasing trend in snow depth, snow cover area (SCA) and increased degree day temperature. © 2015, Indian Society of Remote Sensing. Source


Singh M.K.,Defence Research Development Organization DRDO | Singh M.K.,Motilal Nehru National Institute of Technology | Gupta R.D.,Motilal Nehru National Institute of Technology | Bhardwaj A.,Defence Research Development Organization DRDO | And 2 more authors.
Geocarto International | Year: 2015

This work provides an overview of various methods for estimating snow cover and properties in high mountains using remote sensing techniques involving microwaves. Satellite-based remote sensing with its characteristics such as synoptic view, repetitive coverage and uniformity over large areas has great potential for identifying the temporal snow cover. Many sensors have been used in the past with various algorithms and accuracies for this purpose. These methods have been improving with the use of Synthetic Aperture Radar sensors, working in different microwave frequencies, polarisation and acquisition modes. The limitations, advantages and drawbacks are illustrated while error sources and strategies on how to ease their impacts are also reviewed. An extensive list of references, with an emphasis on studies since 1990s, allows the reader to delve into specific topics. © 2014, © 2014 Taylor & Francis. Source


Sudhendra C.,Defence Research Development Organization DRDO | Madhu A.R.,Defence Research Development Organization DRDO | Pillai A.C.R.,Defence Research Development Organization DRDO | Shekar G.,N.M.I.T. | Rukmini T.S.,N.M.I.T.
2014 1st International Conference on Computational Systems and Communications, ICCSC 2014 | Year: 2014

A novel rasorber based on frequency selective surfaces (FSS) for dual functions operating as stealthy FSS radome for an antenna operating at 3.7 GHz with RF transparency bandwidth of 400 MHz and also as a thin capacitive circuit radar absorber in X band with Radar Cross Section Reduction (RCSR) of 10 dB (minimum) is described. The conducting backplane of rasorber is modified by using a metallic Jerusalem cross slot FSS, which is designed to function as conducting ground plane in the radar absorber frequency range and also to function as radome with band pass spatial filtering properties in the antenna radiating band. © 2014 IEEE. Source

Discover hidden collaborations