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.

Sensitivity study on the role of Western Ghats in simulating the Asian summer monsoon characteristics

Abstract: The Advanced Research Weather Research and Forecasting (AR-WRF) model is used to study the influence of Western Ghats situated along the west cost of peninsular India in the mean characteristics of the Asian summer monsoon (ASM) through numerical simulations. A control simulation (CTRL) is carried out using 11-year (2000–2010) mean initial and lateral boundary conditions from the ERA-Interim reanalysis to simulate the mean atmospheric features of the ASM. The Modern-Era retrospective analysis for research and applications (MERRA) data along with the Tropical Rainfall Measuring Mission (TRMM, 3B42 daily rainfall) data are used to validate the CTRL simulation. The simulated dynamical features and precipitation characteristics during the ASM period agree well with the MERRA reanalysis and TRMM observations. In order to examine the role of Western Ghats on the mean characteristics of the ASM, a sensitivity simulation (NoWG) is carried out with orography reduced to surface over a domain bound between 5°–28°N and 72°–90°E, keeping all other conditions unchanged. This sensitivity analysis showed an enhancement in the low level monsoon flow over the Indian Ocean and peninsular India in the absence of Western Ghats. The prominent up-draft over the west coast of peninsular India observed in the CTRL simulation also decrease in the absence of Western Ghats. The simulated rainfall show a considerable decrease over the west coast and an enhancement over the east coast of peninsular India in the absence of Western Ghats. These simulations clearly depict the importance of Western Ghats in the circulation dynamics and rainfall features during the ASM period.

Functionalized Polysilsesquioxane-Based Hybrid Silica Solid Amine Sorbents for the Regenerative Removal of CO2 from Air

Abstract: Functionalized polysilsesquioxane-based hybrid silica materials are presented as solid amine sorbents for direct CO2 capture from air. The sorbent was synthesized from amine and vinyl functionalized alkoxysilanes by a simple, energy efficient, and cost-effective co-condensation method. The material, containing bound amine functionalities, was found to have a selective CO2 capturing capacity of 1.68 mmol/g from atmospheric air with an adsorption half time of 50 min. This material also showed a maximum adsorption capacity of 2.28 mmol/g in pure CO2 and 1.92 mmol/g in 10% CO2. Desorption started at a temperature as low as 60 °C, and complete desorption occurred at 80 °C. The sorbent exhibited high recycling ability, and 100 cycles of adsorption/desorption were demonstrated in pure CO2 and 50 cycles in ambient air without any loss in efficiency.

Forbidden oxygen lines at various nucleocentric distances in comets

Abstract: Aims. To study the formation of the [OI] lines - i.e., 5577.339 A (the green line), 6300.304 A and 6363.776 A (the two red lines) - in the coma of comets and to determine the parent species of the oxygen atoms using the green to red-doublet emission intensity ratio, I5577/(I6300+I6364), (hereafter the G/R ratio) and the lines velocity widths. Methods. We acquired at the ESO Very Large Telescope high-resolution spectroscopic observations of comets C/2002 T7 (LINEAR), 73P-C/Schwassmann-Wachmann 3, 8P/Tuttle, and, 103P/Hartley 2 when they were close to the Earth (< 0.6 au). Using the observed spectra, which have a high spatial resolution (<60 km/pixel), we determined the intensities and the widths of the t hree [OI] lines. We have spatially extracted the spectra in order to achieve the best possible resolution of about 1-2 ′′ , i.e., nucleocentric projected distances of 100 to 400 km depending on the geocentric distance of the comet. We have decontaminated the [OI] green line from C2 lines blends that we have identified. Results. It is found that the observed G/R ratio on all four comets varies as a function of nucleocentric projected distance (between ∼0.25 to∼0.05 within 1000 km). This is mainly due to the collisional quenching of O( 1 S) and O( 1 D) by water molecules in the inner coma. The observed green emission line width is about 2.5 km s −1 and decreases as the distance from the nucleus increases which can be explained by the varying contribution of CO2 to the O( 1 S) production in the innermost coma. The photodissociation of CO2 molecules seems to produce O( 1 S) closer to the nucleus while the water molecule forms all the O( 1 S) and O( 1 D) atoms beyond 10 3 km. Thus we conclude that the main parent species producing O( 1 S) and O( 1 D) in the inner coma is not always the same. The observations have been interpreted in the framework of the coupled-chemistry-emission model of Bhardwaj & Raghuram (2012) and the upper limits of CO2 relative abundances are derived from the observed G/R ratios. Measuring the [OI] lines could indeed provide a new way to determine the CO2 relative abundance in comets.

Large amplitude free vibrations of beams: an energy approach

Abstract: The conservation of energy principle, which says that the total energy of a vibrating system, at any given instant of time is constant, is used to evaluate the large amplitude free vibration behaviour of beams with immovable ends. With an assumed space mode, which satisfies the geometric boundary conditions, the final governing equation is obtained. This equation is solved by a numerical integration scheme to obtain the ratio of frequencies of nonlinear to linear systems. Comparison of the present results with those of other researchers on this topic and a Galerkin approximation is also included.