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.

Epoxy–imide resins based on bis (carboxyphthalimide)s

Abstract: Epoxy–imide resins have been obtained through the reaction of Araldite GY 250 (diglycidylether of bisphenol-A and epichlorohydrin; difunctional) and Araldite EPN 1138 (Novolac-epoxy resin; polyfunctional) with bis(carboxyphthalimide)s derived from 4,4′-diaminodiphenylsulfone, 3,3′-diaminodiphenylsulfone, 4,4′-diaminodiphenylmethane and 4,4′-diaminodiphenylmethane and trimellitic anhydride. For each epoxy-imide resin system, epoxy equivalent to carboxy equivalent ratio has been optimised to obtain the maximum tensile lap shear adhesive strength on stainless steel substrates at room temperature. The lap shear strength at 100, 150, and 175°C has been determined for the optimum ratio. Araldite EPN-1138-based systems give the lap shear strength of 141–182 kg/cm2 at room temperature for the optimum compositions and retain about 84–100% of the lap shear strength at 150°C. Araldite GY-250-based systems have lap shear strength of 183–193 kg/cm2 and retain 76–84% of the lap shear strength at 150°C except for the one cured with bis (carboxyphthalimide) prepared from 4,4′-diaminodiphenylmethane, which retains only 17% of the lap shear strength. Among the systems studied, Araldite GY 250 cured with bis (carboxyphalimide) synthesized from 3,3′-diaminodiphenylsulfone appears to be the best, retaining 75% (138 kg/cm2) of the lap shear strength at 175°C.

The formation and growth of ultrafine particles in two contrasting environments: a case study

Abstract: . Formation of ultrafine particles and their subsequent growth have been examined during new particle formation (NPF) events in two contrasting environments under varying ambient conditions, one for a tropical semi-urban coastal station, Trivandrum, and the other for a high-altitude free-tropospheric Himalayan location, Hanle. At Trivandrum, NPF bursts took place in the late evening/night hours, whereas at Hanle the burst was a daytime event. During the nucleation period, the total number concentration reached levels as high as ~ 15 900 cm−3 at Trivandrum, whereas at Hanle, the total number concentration was ~ 2700 cm−3, indicating the abundant availability of precursors at Trivandrum and the pristine nature of Hanle. A sharp decrease was associated with NPF for the geometric mean diameter of the size distribution, and a large increase in the concentration of the particles in the nucleation regime (Dp

Solvothermal synthesis of microporous superhydrophobic carbon with tunable morphology from natural cotton for carbon dioxide and organic solvent removal applications

Abstract: Microporous carbonaceous materials were developed by the solvothermal carbonization of natural cotton for the first time. The morphology and surface area of solvothermal char (STC) depends on the concentration of p-toluene sulfonic acid (PTSA) catalyst. STC showed a transformation from a fibrous to spherical morphology with an increase in the PTSA concentration. STC showed a maximum surface area of 477 m2 g−1, pore volume of 0.60 cm3 g−1 and CO2 sorption capacity (at 0 °C and 1 bar pressure) of 2.28 mmol g−1. The CO2 adsorption showed excellent recyclability and selectivity over nitrogen. STC-0.04 obtained at PTSA to cotton weight ratio of 0.04 showed superhydrophobic character due to the nano projections on the fiber surface produced by the heterogeneous nucleation of STC particles. STC-0.04 is an excellent sorbent for organic solvents from water–solvent mixtures.

Effect of oblateness and radiation pressure on angular frequencies at collinear points

Abstract: In the three-dimensional restricted three-body problem, by considering the more massive primary as an oblate spheroid with its equatorial plane coincident with the plane of motion as well as source of radiation, it is found that the collinear point L 1 comes nearer to the primaries with the increase in oblateness and radiation pressure, while L 2 and L 3 move away from the more massive primary with the increase in oblateness and come nearer to it with the increase in radiation pressure It is noted that the angular frequency s 1 at L 1 increases with oblateness as well as with radiation pressure s 2 increases with oblateness and decreases with radiation pressure and s 3 decreases with oblateness and increases with radiation pressure A study on the norms of the characteristic roots λ and s at L 1, L 2 and L 3 is carried out It is established that for certain oblateness and radiation pressure parameters there is a one-to-one commensurability at the collinear points L 2, L 3 between the planar angular frequencies (s 2,3) and the corresponding angular frequency (s z ) in the z-direction, and that at L 1 no such commensurability exists At L 2 and L 3, the value of oblateness parameter providing the commensurability decreases with the increase in the radiation pressure However, the commensurable angular frequencies and eccentricity of the periodic orbits decrease at L 2 and increase at L 3, with the increase in the radiation pressure