National Aerospace Laboratories

About: National Aerospace Laboratories is a facility organization based out in Bengaluru, India. It is known for research contribution in the topics: Coating & Corrosion. The organization has 1838 authors who have published 2349 publications receiving 36888 citations.

Dispersion, slip casting and reaction nitridation of silicon–silicon carbide mixtures

Abstract: The dispersing behaviour of silicon, silicon carbide and their mixtures in aqueous media were monitored by particle size, sedimentation, viscosity and zeta potential analyses as a function of pH of the slurry. The pH values for optimum dispersion were found to be 4 and 8 for silicon, 10 for SiC and 9 for Si +SiC mixtures. Optimum slips of Si + SiC mixtures were slip cast to obtain green compacts which were nitrided once at 1450xB0;C for 2 or 4h or successively and cumulatively for 8 (2 + 6) and 10 (4 + 6) h in a resistively heated graphite furnace. The binding13; phases in the nitrided products were found to be 13; fbrous/needle like a-Si 3N4 , faky grains of (3-Si3N413; and Si2ON2 . The products containing 19-47% of silicon nitride as bond/matrix possessed fexural strength (three ppoint bending) values of 50-85 MPa. 1999 Elsevier Science Limited. All rights reserved

Life Cycle of Deep Convective Systems over the Eastern Tropical Pacific Observed by TRMM and GOES-W

Abstract: The life cycle of deep convective systems over the eastern tropical Pacific (30°N to 30°S, 180 to 90°W) was studied in terms of cloud types, as classified by a split window (11 μm and 12 μm). Hourly split window image data of Geostationary Operational Environmental Satellite (GOES-W) from January 2001 to December 2002 was used in this study. Deep convective systems consist mostly of optically thick cumulus type clouds in the earlier stage and a cirrus type cloud area that increases with time in the later stage. During this analysis period and over the analysis area, the life stage of deep convective system, to a large extent, can be identified by computing the percentage of cirrus type clouds within the deep convective system from a single snap shot of the split window image. Coincident Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) observations were used to study the relationship between the percentage of cirrus type clouds within a deep convective system (i.e., its life stage) and the rainfall rate. It was found that the rainfall rate tends to be larger in the earlier stage of the life cycle when a smaller percentage of cirrus type cloud is present within the deep convection.

Novel Image Fusion Techniques using DCT

Abstract: Six different novel image fusion techniques using discrete Cosine transform were presented and studied. It is concluded from the study that DTMDCT (Dual tree multi-resolution discrete Cosine transform) provides better fusion results followed by Laplacian pyramid based image fusion technique. DTMDCT is simple and computationally efficient algorithm. Matlab code for these algorithms will be provided.