Vikram Sarabhai Space Centre

About: Vikram Sarabhai Space Centre is a facility organization based out in Thiruvananthapuram, India. It is known for research contribution in the topics: Aerosol & Ultimate tensile strength. The organization has 2092 authors who have published 3058 publications receiving 47975 citations. The organization is also known as: VSSC.

Aerosol characteristics in the marine atmospheric boundary layer over the Bay of Bengal and Arabian Sea during ICARB: Spatial distribution and latitudinal and longitudinal gradients

Abstract: [1] Characteristics of aerosols in the marine atmospheric boundary layer (MABL) over the Bay of Bengal (BoB), northern Indian Ocean (NIO), and Arabian Sea (AS) have been investigated using extensive measurements of the mass concentrations and mass size distributions of composite aerosols and mass concentrations of black carbon (BC) aerosols on board an oceanographic research vessel during its 2-month-long cruise of March–May 2006 as a part of Integrated Campaign for Aerosols, Gases, and Radiation Budget (ICARB). The data have been examined for the spatial distribution of aerosols over the oceans around India, for the north-south (latitudinal) and east-west (longitudinal) gradients, and to delineate the distinctiveness of these two oceanic regions with regard to aerosol properties. The results show that in general, aerosol concentrations (total and BC) are significantly higher over the BoB, compared to the AS. Over the BoB, there exists a strong latitudinal gradient with the aerosol concentrations (of total and BC) decreasing rapidly from north to south. On the other hand, over the AS the north-south gradient was very weak and showed an opposite trend; with the concentrations, particularly of BC, increasing from north to south. In the northern BoB, due north of 13°N, BC showed strong longitudinal gradient, with the concentrations increasing from west to east; whereas due south, the longitudinal gradients were weak or insignificant. Over the southern AS, BC tended to decrease westward from the western coast of India, reached a minimum at 60°E, and increased thereafter. No longitudinal gradients were noticed in northern AS. Despite these, the BC mass fraction (FBC) was nearly constant spatially over the entire BoB, implying an almost uniformly mixed nature of BC with the composite aerosols over the BoB. In contrast, over the AS, FBC showed an increase southward along the latitude and decrease westward along the longitude. In general, the BC mass fraction was nearly 3 times higher over the BoB compared to the AS implying thereby that the aerosols over the BoB are significantly more absorbing in nature than those over the AS.

Equatorial counter electrojets and polar stratospheric sudden warmings - a classical example of high latitude-low latitude coupling?

Abstract: . Favored occurrences of Equatorial Counter Electrojets (CEJs) with a quasi 16-day periodicity over Trivandrum (8.5° N, 76.5° E, 0.5° N diplat.) in association with the polar Stratospheric Sudden Warming (SSW) events are presented. It is observed that, the stratospheric temperature at ~30 km over Trivandrum shows a sudden cooling prior to the SSWs and the CEJs of maximum intensity which occurs around this time. In general stronger CEJs are associated with more intense SSW events. The stratospheric zonal mean zonal wind over Trivandrum also exhibits a distinctly different pattern during the SSW period. These circulation changes are proposed to be conducive for the upward propagation of the lower atmospheric waves over the equatorial latitudes. The interaction of such waves with the tidal components at the upper mesosphere and its subsequent modification are suggested to be responsible for the occurrence of CEJs having planetary wave periods.

Processing of copper-carbon nanotube composites by vacuum hot pressing technique

Abstract: Copper (Cu) matrix composites reinforced with 0.2, 5 and 10 vol% single wall carbon nanotubes (SWCNT) and 5 and 10 vol% multi-wall carbon nanotubes (MWCNT) were processed by high energy milling of pure copper powder with carbon nanotubes (CNTs) and subsequent consolidation by vacuum hot pressing. Microstructural observations of the sintered composites revealed equiaxed twinned microstructure for 0.2 vol% SWCNT composite and elongated grain structure, with CNT layers in between, in composites having higher CNTs content. The porosity in the composites was associated with CNT layers. The distribution of CNTs was found to be different in axial and transverse directions. Significant improvement in hardness of Cu–SWCNT composite was observed with increase in CNTs content. Whereas, in case of MWCNT composite, hardness reduced for 10 vol% CNT composites. Compression strength of the SWCNT samples was found to be higher than the MWCNT reinforced samples.