Birla Institute of Technology and Science

About: Birla Institute of Technology and Science is a education organization based out in Pilāni, Rajasthan, India. It is known for research contribution in the topics: Computer science & Population. The organization has 8897 authors who have published 13947 publications receiving 170008 citations.

New 'aggregation induced emission (AIE)' active cyclometalated iridium(III) based phosphorescent sensors: high sensitivity for mercury(II) ions.

Abstract: Design and syntheses of ‘aggregation induced emission (AIE)’ active blue-emitting bis-cyclometalated iridium(III) complexes with appended diphosphine ligands [Ir(F2ppy)2(L1/L2)2(Cl)] (F2ppy = 2-(2′,4′-difluoro) phenylpyridine; L1 = 1,2-bis(diphenylphosphino)ethane; L2 = bis(diphenylphosphino)propane) have been realized on a suitable route. The free phosphorous donor atom present on the appended diphosphine is shown to provide selective binding to the mercuric ion (Hg2+). The selective binding ability of the probe molecule towards mercuric ions results in a detectable signal due to complete quenching of their AIE properties. The quenching effect of the probe molecule has been explored and found to be the result of the degradation of the probe iridium(III) complex triggered by the presence of mercuric ions due to an interplay of a soft–soft interaction between the free phosphorous atom of the probe molecule and mercuric ions. These complexes were modelled to obtain deeper understanding of excited state properties and the results were tentatively correlated with the experimental data.

Optimal process design of two-stage multiple responses grinding processes using desirability functions and metaheuristic technique

Abstract: Two-stage grinding processes in mass-scale manufacturing unit are usually too complex to optimize, due to large number of interacting process variables, between and within the stages. Furthermore, statistical design of experiment techniques, such as factorial design, fractional factorial and response surface design by sequential experimentations, to determine the exact optimal process design for the overall interdependent two-stage system, are sometimes too difficult to implement, if not impossible. In this context, considering each stage in isolation and determining individual optimal conditions may not result in an optimal process design, when the entire two-stage system is considered. The aim of this study is to apply empirical modelling technique based on direct observations, for prediction of a two-stage grinding process behaviour having multiple response characteristics of continuous variables, and determine overall optimal process design to meet the specific customer requirements. In order to achieve the above goal, the study proposes an integrated approach using multivariate regression, desirability function, and metaheuristic search technique. Three different metaheuristic search techniques, viz. real-coded genetic algorithm, simulated annealing, and a modified Tabu search based on novel Mahalanobis multivariate distance approach to identify Tabu moves, are employed to determining near optimal path conditions for an industrial case study of two-stage CNC grinding (honing) optimization problem, having various process and variable constraints. Computational study results based on different metaheuristics, and applied on the same two-stage optimization problem, show that the modified Tabu search performs better and also offer opportunities to be extended for other multi-stage metal-cutting process optimization problems.

Cosmological bounds on dark matter-photon coupling

Abstract: We investigate an extension of the $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model where the dark matter (DM) is coupled to photons, inducing a nonconservation of the numbers of particles for both species, where the DM particles are allowed to dilute throughout the cosmic history with a small deviation from the standard evolution decaying into photons, while the associated scattering processes are assumed to be negligible. In addition, we consider the presence of massive neutrinos and the effective number of species ${N}_{\mathrm{eff}}$ as a free parameter. The effects of the DM-photon coupling on the cosmic microwave background (CMB) and matter power spectra are analyzed. We derive the observational constraints on the model parameters by using the data from Planck CMB, baryonic acoustic oscillation (BAO) measurements, the recently measured new local value of the Hubble constant from the Hubble Space Telescope, and large scale structure (LSS) information from the abundance of galaxy clusters. The DM-photon coupling parameter ${\mathrm{\ensuremath{\Gamma}}}_{\ensuremath{\gamma}}$ is constrained to ${\mathrm{\ensuremath{\Gamma}}}_{\ensuremath{\gamma}}\ensuremath{\le}1.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ (at 95% C.L.) from the joint analysis carried out by using all the mentioned data sets. The neutrino mass scale $\ensuremath{\sum}{m}_{\ensuremath{ u}}$ upper bounds at 95% C.L. are obtained as $\ensuremath{\sum}{m}_{\ensuremath{ u}}\ensuremath{\sim}0.9\text{ }\text{ }\mathrm{eV}$ and $\ensuremath{\sum}{m}_{\ensuremath{ u}}\ensuremath{\sim}0.4\text{ }\text{ }\mathrm{eV}$ with and without the LSS data, respectively. We observe that the DM-photon coupling can cause significant changes in the best fit value of ${N}_{\mathrm{eff}}$ but yields statistical ranges of ${N}_{\mathrm{eff}}$ compatible with the standard predictions, and we do not find any evidence of dark radiation. Due to nonconservation of photons in our model, we also evaluate and analyze the effects on the BAO acoustic scale at the drag epoch. The DM-photon coupling model yields high values of Hubble constant consistent with the local measurement, and thus alleviates the tension on ${H}_{0}$.