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.

Ambient and cryogenic tensile properties of AA2195T87 sheets with pre-aging cold work by a combination of cold rolling and stretching

Abstract: Al–Cu–Li–Mg–Ag–Zr alloy AA2195, in the form of 4 mm thick sheets, was heat treated to T87 temper with the pre-aging cold work provided by a combination of 5% cold rolling followed by 2% stretching. The tensile properties of the material were evaluated at ambient and cryogenic temperatures (i.e. −196 °C and −253 °C). Transmission electron microscopy of the heat treated (i.e. T87 treated) material revealed that the major strengthening precipitate is indeed the T 1 (Al 2 CuLi) phase nucleated on the {111} Al planes. In addition, θ′ [metastable Al 2 Cu (θ)] precipitates on {100} Al planes, and “plate like features” lying on {111} Al planes were further observed. The one atom layer thick “plate like features” have the same crystal structure as that of the matrix Al. The possibility of such “plate like features” being either the early stages of the Ω phase (i.e. a chemically modified coherent form of θ-Al 2 Cu phase) in the constituent Al–Cu–Mg–Ag system or the evolutionary stages of the T 1 phase itself is discussed.

Characteristics of the double intertropical convergence zone over the tropical Indian Ocean

Abstract: [1] Investigations on the double intertropical convergence zone (DITCZ) over the Indian Ocean using the monthly mean surface wind divergence data obtained from scatterometers on board the ERS-1/2 and QuikSCAT satellites (1991–2005) and the monthly mean cloud amount obtained from the International Satellite Cloud Climatology Project (1988–1989, 1998–2005) and the Advanced Very High Resolution Radiometer (AVHRR) data (1996–2003) reveal that its frequency of occurrence is considerably larger than that reported earlier, though the DITCZ feature in this region is rather diffused compared to Pacific. The 14-year analysis of monthly mean surface wind divergence shows that DITCZ structure is clearly discernible in April (frequency of occurrence, f = 64%), November (f = 73%) and December (f = 60%) in the 50–85°E longitude band over the tropical Indian Ocean. Though less frequent, DITCZ occur during other months also, except the Asian summer monsoon season. Most preferred latitudes of the north and south bands of DITCZ are ∼6°N and ∼7°S, respectively, during November and December. The DITCZ structure is well manifested in the cloud amount also during November and December, while it is less prominent in April. A weak but clearly identifiable hemispherical asymmetry is observed in latitude of occurrence and amplitude of the DITCZ bands. Since the sea surface temperature (SST) at the equatorial region over the Indian Ocean is nearly uniform, the DITCZ appears to be generated mainly by the atmospheric dynamics. This provides a unique opportunity to investigate the structure of ITCZ created by the atmospheric dynamics alone, which is one of the important problems in ITCZ dynamics.

Viscoelastic Behavior of NBR/EVA Polymer Blends: Application of Models

Abstract: The viscoelastic properties of blends based on nitrile rubber (NBR) and ethylene-vinyl acetate copolymer (EVA), a thermoplastic elastomer, are investigated in terms of storage modulus and loss tangent for different compositions. These small-strain dynamic mechanical properties have been evaluated using a Rheovibron Viscoelastometer covering a wide temperature range. Attempts have been made to fit the experimental results with computations based on mean field theories developed by Kerner. Predictions based on the discrete particle model (which assumes one of the components of the blend to be the matrix and the other dispersed as inclusions) are found to be satisfactory in the case of 30/70 NBR/EVA blend but not 70/30 and 50/50 blends. The packed grain model (which assumes neither of the components to be the matrix but approximates a co-continuous structure of the two) predictions do not agree with the experimental data on 50/50 blend for which a co-continuous morphology was revealed by SEM observa...