Abstract. The Soft X-ray focusing Telescope (SXT), India's first X-ray telescope based on the principle of grazing incidence, was launched aboard the AstroSat and made operational on October 26, 2015. X-rays in the energy band of 0.3-8.0 keV are focussed on to a cooled charge coupled device thus providing medium resolution X-ray spectroscopy of cosmic X-ray sources of various types. It is the most sensitive X-ray instrument aboard the AstroSat. In its first year of operation, SXT has been used to observe objects ranging from active stars, compact binaries, supernova remnants, active galactic nuclei and clusters of galaxies in order to study its performance and quantify its characteriztics. Here, we present an overview of its design, mechanical hardware, electronics, data modes, observational constraints, pipeline processing and its in-orbit performance based on preliminary results from its characterization during the performance verification phase.
In this work, an attempt has been made to understand the feasibility of using a ultrahigh frequency (UHF) technique for identification of any corona discharge/ arcing in insulating material due to water droplets. The sensors of broadband type are useful for the identification of such discharges. It is realized that corona discharges/arcing initiated by liquid droplet radiates UHF signals in the entire bandwidth up to 2 GHz. The frequency content of the UHF signal generated due to corona/arcing is not much varied in epoxy nanocomposites with different weight percentage of clay content. The exfoliated/intercalated properties were analysed through TEM studies. It is realized that corona initiated discharges are of intermittent process. It is observed that the permittivity and tan(δ) reduces with increase in percentage of clay in epoxy nanocomposite material up to 3 wt%. The hydrophobicity of the material is characterized through contact angle measurement. It is realized that low weight percentage of nanoclay content in epoxy resin reduces the surface carbonization due to arcing.
Flexible pressure sensors with self-healing abilities for wearable electronics are being developed, but generally either lack autonomous self-healing properties or require sophisticated material processing methods. To address this challenge, we...
Large light-weight deployable cable net reflectors are widely used in communication satellites. These are much larger than satellite and need stowing into a relatively small volume to fit into launch vehicle and are deployed in orbit. The cable net reflectors use deployable support structure along with pretensioned cable net. Due to its large dimensions, the deployed natural frequency will be quite low and may not be acceptable from controls point of view. In such cases, the deployed frequency needs to be enhanced to ensure that the same meets the minimum requirements. This article presents a study of the different parameters, which have been varied in order to assess the sensitivity of the same with respect to the deployed frequency. The effect of the flexibility of each sub-assembly has been assumed and this has helped to identify the sub-assembly, which has to be stiffened in order to enhance the overall frequency. Also, the results from this study have provided the design inputs for modifications to be carried out in order to realize a large cable net antenna.
Friction Stir Welding (FSW) and Friction Welding (FW) are the most popular emerging solid welding techniques in aircraft and shipbuilding industries. FSW is mainly used for the joining of metal plates and FW is mainly used for the joining of rods. Both techniques are suitable for high strength material having less weight. These techniques are environmentally friendly and easy to execute. Hence, study on these techniques can contribute much to the field of green technology. There is wide variety of tool pin profiles such as cylindrical, cone and frustum and these are available without and with threaded portion. Considering the work piece materials, the feasibility of this process depends mainly on the properties. Present work deals with welding the copper to copper and brass to brass specimens using cylindrical friction stir weld tool. The weld zones of the specimens were further tested to study tensile strength, hardness and impact strength. A comparative analysis was done to know the impact of friction stir welding on brass and copper material. Based on the comparative analysis prediction can be done for the feasibility of this process to the investigated materials.
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