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.

Meteor radar observations of short-term variability of quasi 2 day waves and their interaction with tides and planetary waves in the mesosphere–lower thermosphere region over Thumba (8.5°N, 77°E)

Abstract: [1] Meteor radar measurements of zonal and meridional winds over a low-latitude station, Thumba (8.5°N, 77°E), during March 2006 to March 2009 are used to study the quasi 2 day wave structure in the mesosphere–lower thermosphere (MLT) region. Emphasis is placed on the study of the day-to-day variations of quasi 2 day waves and their interaction with diurnal tides and planetary waves. The seasonal variation of quasi 2 day waves showed two maxima, one during summer and the other during winter, coinciding with the strong eastward winds in the MLT region along with a distinct peak during the month of October. Subsequent analysis of TIMED/SABER observations during October revealed the presence of a westward propagating quasi 2 day wave with zonal wave number 3 over the present latitude. The seasonal variation of quasi 2 day wave is also discussed with respect to the Stratospheric Semiannual Oscillation (SSAO), and we found that the quasi 2 day wave activity peaks in the MLT region during the phase transition of SSAO as well as during the eastward phase. Wavelet and subsequent bispectral analysis confirmed the wave-wave interactions of quasi 2 day wave and planetary waves with periods of 5–10 and 15–20 days. The 16 h oscillation, which is believed to be generated by interaction of quasi 2 day wave and diurnal tide, showed an excellent correlation with quasi 2 day wave activity. Apart from reporting day-to-day variation of quasi 2 day wave for the first time over this latitude, there are two new results from the present study: (1) a consistent peak in quasi 2 day activity during October, which has never been reported and has been observed for the first time over low latitudes, and (2) the relation between SSAO and quasi 2 day wave activity.

Thermoplastic toughened layered silicate epoxy ternary nanocomposites—Preparation, morphology, and thermomechanical properties

Abstract: Epoxy–clay ternary nanocomposites were processed by melt blending of hydroxyl terminated poly (ether ether ketone) oligomer with pendant methyl groups (PEEKMOH) with diglycidyl ether of bisphenol A (DGEBA) epoxy resin along with organically modified montmorillonite (OMC-OH) followed by curing with 4,4′-diamino diphenyl sulfone. Small angle X-ray diffraction and transmission electron microscopy revealed an intercalated morphology. Tensile, flexural, storage, and loss moduli were increased whereas the tensile, flexural, and impact strength and glass transition temperature were decreased with increase in clay content for the PEEKMOH toughened epoxy system. Fracture toughness and percentage strain were increased by 66% and 45% respectively whereas the coefficient of the thermal expansion was decreased by 27% with the incorporation of 1 phr OMC-OH to the PEEKMOH toughened epoxy system compared with neat epoxy. The scanning electron microscope pictures of fracture and tensile failed surfaces revealed crack path deflection and ductile fracture with the incorporation of OMC-OH confirming the improvement in toughness. The domain size and the distance between the domains of thermoplastic phase were decreased with the addition of nanoclay into the epoxy matrix indicating the restriction of the growth mechanism by nucleation during phase separation. A marginal increase in thermal stability was observed with increase in clay content. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

Possible climatic implications of high-altitude black carbon emissions

Abstract: . On account of its strong absorption of solar and terrestrial radiation, black carbon (BC) aerosol is known to impact large-scale systems, such as the Asian monsoon and the Himalayan glaciers, in addition to affecting the thermal structure of the lower atmosphere. While most studies focus on the near-surface abundance and impacts of BC, our study examines the implications of sharp and confined layers of high BC concentration (called elevated BC layers) at altitudes more than 4 km over the Indian region using the online regional chemistry transport model (WRF-Chem) simulations. These elevated BC layers were revealed in the recent in situ measurements using high-altitude balloons carried out on 17 March 2010, 8 January 2011 and 25 April 2011. Our study demonstrates that high-flying aircraft (with emissions from the regionally fine-tuned MACCity inventory) are the most likely cause of these elevated BC layers. Furthermore, we show that such aircraft-emitted BC can be transported to upper tropospheric or lower stratospheric heights ( ∼ 17 km) aided by the strong monsoonal convection occurring over the region, which is known to overshoot the tropical tropopause, leading to the injection of tropospheric air mass (along with its constituent aerosols) into the stratosphere. We show observational evidence for such an intrusion of tropospheric BC into the stratosphere over the Indian region using extinction coefficient and particle depolarisation ratio data from CALIOP Lidar on-board the CALIPSO satellite. We hypothesise that such intrusions of BC into the lower stratosphere and its consequent longer residence time in the stratosphere have significant implications for stratospheric ozone, especially considering the already reported ozone-depleting potential of BC.