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.

Characteristics of a persistent "pool of inhibited cloudiness" and its genesis over the Bay of Bengal associated with the Asian summer monsoon

Abstract: . Using spatial and vertical distributions of clouds derived from multi-year spaceborne observations, this paper presents the characteristics of a significant "pool of inhibited cloudiness" covering an area of >106 km2 between 3–13° N and 77–90° E over the Bay of Bengal (BoB), persisting throughout the Asian summer monsoon season (ASM). Seasonal mean precipitation rate over the "pool" is

Developmental Studies on Metallised UDMH and Kerosene Gels

Abstract: The influence of particulate and hydrocolloid gellants and different surfactants on gellation of metallised stable gels of unsymmetrical dimethyl hydrazine (UDMH) and kerosene containing 30 per cent 15 micron Aluminium was studied. Metallised UDMH and kerosene gels were characterised with respect to pseudoplasticity, thixotropy, consistency and yield stress using Contrave's rheometer. The effect of shear rate and temperature on the viscosity of these gels was determined. Thermal stability, hypergolicity tests and flow rate studies were also conducted. Metallised UDMH and kerosene gels are found to be stable, thixotropic and pseudoplastic and easily flowing like a liquid under shear force.

Marine boundary-layer variability over the Indian Ocean during INDOEX (1998)

Abstract: The variability in boundary-layer structure over the Indian Ocean during a north-east monsoon and the factors influencing it are investigated. This study was made possible as a component of the Indian Ocean Experiment (INDOEX), conducted from February 19 to March 30, 1998. The data used are, surface-layer mean and turbulence measurements of temperature, humidity and wind, and vertical soundings of temperature and humidity. Significant spatio-temporal variability was observed in the boundary-layer structure throughout the cruise. The ITCZ was characterized as the region with strongest winds and maximum surface turbulent fluxes of momentum and heat. One of the important findings from this study was a strong influence of continental air masses on the boundary-layer structure in the Northern Hemisphere, even at a distance of 600 km off the Indian coast. This was generally evident in the form of an elevated plume of dry continental air between altitudes of 1500 m and 2700 m. Advection of continental aerosols in this layer presents potential for significant entrainment into shallow clouds in this region, which eventually feed deeper clouds at the ITCZ. This finding provides an explanation for anomalous higher aerosol concentrations found during previous studies. The structure of the marine boundary layer was influenced by various factors such as proximity to land, an anomalous warm pool in the ocean and the ITCZ. In the southern hemisphere, the boundary-layer height was primarily governed by surface-layer sensible heat flux and was found to be highest in the vicinity of the ITCZ. North of the equator it was strongly influenced by land-air-sea interactions. In addition to this synoptic modulation, there was also a significant diurnal variability in the boundary-layer height

Synthesis, characterization and thermal properties of boron and silicon containing preceramic oligomers

Abstract: In recent years, considerable interest has been shown towards developing boron and silicon containing polymers as they possess certain technological advantages when compared to polymers containing only boron or silicon [1, 2]. These polymers on pyrolysis in inert atmosphere give mixed non-oxide ceramics such as B4CSiC, B4C-Si3N4 and BN-SiC. These mixed non-oxide ceramics are reported to possess superior high temperature properties, oxidation resistance and thermal shock resistance when compared to boron and silicon based simple non-oxide ceramics [1, 3, 4]. Boron and silicon containing polymers have also gained importance as protective coatings for materials which are constantly exposed to oxidizing environment [5–8]. When these coatings are exposed to oxidizing environment at elevated temperatures, a protective passive borosilicate glassy layer is formed on the surface which prevents further oxidation of the protective coating and the substrate. Boric acid is considered to be the cheapest source of boron for making boron and silicon containing polymers. Yajima and coworkers [9] synthesized poly (borodiphenylsiloxane) through the reaction of boric acid with diphenyldichlorosilane in n-butylether at 300 ◦C. Hoshii et al. [10–12] prepared borodiphenylsiloxane oligomer by reacting boric acid and diphenylsilanediol. However, these polymers give relatively low ceramic residue on pyrolysis (<50%) and also require high temperature (∼300◦) for their synthesis. In this communication, we report the synthesis of boron and silicon containing oligomers, capable of giving a high ceramic yield, through the condensation of boric acid with phenyltrimethoxysilane and vinyltriethoxysilane at a relatively low temperature (150–160 ◦C). A mixture containing 57 g (0.3 mol) of vinyltriethoxy-silane, 9.27 g (0.15 mol) of boric acid, 50 ml of diglyme and 1 ml of concentrated hydrochloric acid was taken in a three necked round bottom flask equipped with a mechanical stirrer, an inlet and outlet for nitrogen. The contents of the flask were heated under the flow of nitrogen in an oil bath maintained at 150–160 ◦C. The reaction mixture was stirred for 3 h at this temperature, after which it was allowed to cool to room temperature. Ethanol which was formed as a by product was distilled off. Diglyme was distilled off