AR-2019-2020

activation and loss functions for different layers, op- timizer algorithm, regularization, etc. Thus, this work aims to cover different choices available un- der each of these major and minor decision criteria for building a neural network, and training it opti- mally to effectively serve the objectives, e.g., mal- ware detection, natural language processing, image recognition, etc. This work has been done in collab- oration with Mohit Sewak, and Hemant Rathore Secure and energy-efficient key-agreement protocol for multi-server architecture Authentication schemes are practiced globally to verify the legitimacy of users and servers for the exchange of data in different facilities. Generally, the server verifies a user to provide resources for dif- ferent purposes. But due to the large network sys- tem, the authentication process has become com- plex and therefore, time-to-time different authenti- cation protocols have been proposed for the multi- server architecture. However, most of the protocols are vulnerable to various security attacks and their performance is not efficient. In this work, we pro- pose a secure and energy-efficient remote user au- thentication protocol for multi-server systems. The results show that the proposed protocol is com- paratively ∼ 44 % more efficient and needs ∼ 38 % less communication cost. We also demonstrate that with only two-factor authentication, the proposed protocol is more secure from the earlier related au- thentication schemes. This work has been done in collaboration with Trupil Limbasiya Sandeep Sahijpal Evolution of the galaxy and the origin of the solar system We have developed galactic chemical evolution (GCE) models of the short-lived radio nuclides (SLRs), 26Al, 36Cl, 41Ca, 53Mn, and 60Fe, across the entire Milky Way galaxy. The objective was to understand the spatial and temporal distribution of the SLRs in the galaxy. Based on the formulation, we provide a novel method to amalgamate the ori- gin of the solar system with the gradual evolution of the galaxy along with a self-consistent origin of SLRs. We have explored the possibility of the birth of the solar system in an environment where one of the stellar clusters formed 25 Myr earlier. The de- caying 53Mn and 60Fe remnants from the evolved massive stars from the cluster probably contami- nated the local medium associated with the preso- lar molecular cloud. A Wolf-Rayet wind from a distant massive star, belonging to a distinct clus- ter, probably contributed, 26Al (and 41Ca) to the presolar cloud. This work has been done in collab- oration with Tejpreet Kaur. Thermodynamics of dust condensation in astro- physical environments We have performed comprehensive thermodynam- ical calculations of the condensation of dust grains around Wolf-Rayet (WR). A novel numerical code has been developed for dust condensation. It was found that mostly C (graphite), TiC, SiC, AlN, CaS and Fe-metal were condensed in WR winds. The results indicate that dust grains that are con- densed in the WC phase may make a substantial contribution of carbon-rich dust grains to the in- terstellar medium. We have also performed a com- prehensive correlated study of the thermodynam- ics condensation of dust grains in distinct stellar environments with the galactic chemical evolution of the Milky Way galaxy. Based on the elemen- tal composition of the evolving Galaxy, the rela- tive abundances of the major constituents of in- terstellar dust are assessed. The supernovae SN Ia are predicted as the most prominent sources of Fe-dust mass, the supernovae SN II + Ib/c pro- duces oxides and silicate dust mass, and the AGB stars contributes to carbonaceous dust mass. This is studied in collaboration with Anuj Gupta. Biplob Sarkar Effect of magnetic flux advection on the dynamics of shock in accretion flow around a rotating black hole We investigate the dynamical behaviour of a mag- netized, dissipative, accretion flow around a rapidly rotating black hole. We solve the magnetohydro- dynamic equations, and calculate the transonic ac- cretion solutions which may contain discontinuous shock transitions. We investigate the effect of ζ − parameter (parametrizing the radial variation of the toroidal magnetic flux advection rate) on the dynamical behaviour of shocks. For a rapidly rotat- ing black hole and for fixed injection parameters at the outer edge, we show that stationary shocks are sustained in the global magnetized accretion solu- tions for a wide range of ζ and accretion rate ( ˙ m ).