Recent star formation history of the Large and Small Magellanic Clouds

We traced the age of the last star formation event (LSFE) in the inner Large & Small Magellanic Cloud (L&SMC) using the photometric data from the Optical Gravitational Lensing Experiment (OGLE-III) and the Magellanic Cloud Photometric Survey (MCPS). The LSFE is estimated from the main-sequence turn off point in the color-magnitude diagram (CMD) of a region. Extinction corrected turn off magnitude is converted to age, which represents the LSFE in a region. The spatial map of the LSFE age shows that the star formation has shrunk to the central regions in the last 100Myr in both the galaxies. The location and age of LSFE is found to correlate well with those of the star cluster in both the Clouds. The SMC map shows two separate concentrations of young star formation. We detect peaks of star formation at 0-10, 90-100Myr in the LMC, and 0-10, 50- 60Myr in the SMC. The quenching of star formation in the LMC is found to be asymmetric with respect to the optical center such that most of the young star forming regions are located to the north and east. On deprojecting the data on the LMC plane, the recent star formation appears to be stretched in the north-east direction and the HI gas is found to be distributed preferentially in the North. The centroid is found to shift to north in 200-40Myr, and to north-east in the last 40Myr. In the SMC, we detect a shift in centroid of population of 500-40Myr in the direction of the LMC. We propose that the HI gas in the LMC is pulled to the north of the LMC in the last 200Myr due to the gravitational attraction of our Galaxy at the time of perigalactic passage. The shifted HI gas is preferentially compressed in the north during 200-40Myr and in the north-east in the last 40Myr, due to the motion of the LMC in the Galactic halo. The recent star formation in the SMC is due to the combined gravitational effect of the LMC and the perigalactic passage.Comment: Accepted to A&A on August 31, 201

Enhancing piezocatalysis for chemical transformations using cocatalysed ferroelectrics

This thesis presents a comprehensive investigation into the piezocatalytic capabilities of barium titanate (BTO), both as a bare material and in combination with metal and metal oxide cocatalysts, for renewable energy production and environmental remediation. The research emphasises the degradation of organic dye pollutants and the enhancement of water splitting for hydrogen production. The degradation of Rhodamine B (RhB) using BTO nanoparticles is explored with the efficiency of the process depending on variables such as calcination temperature, structural properties, and the influence of atmosphere and agitation. The findings reveal the crucial role of oxygen in the degradation process and identify optimal conditions for catalyst loading and stirring parameters, positioning BTO as a viable candidate for environmental remediation. The application of BTO is extended to hydrogen production by mixing it with metallic Pt nanoparticles through a simple solid-state synthesis method. The interaction between BTO and Pt highlights a significant enhancement in hydrogen evolution rate, marking a substantial increase compared to pristine BTO. The research highlights the importance of BTO's ferroelectric properties and their contribution to improved catalytic activity. The formation of hydrogen peroxide as a byproduct presents both a challenge and an opportunity for future research aimed at optimising the selectivity and efficiency of piezocatalytic reactions. Furthermore, the investigation delves into BTO-metal oxide composites and their piezocatalytic application for dye degradation. The structural properties of various BTOmetal oxide heterostructures are analysed, with BTO-CuO and BTO-NiO heterojunctions leading to an enhanced piezocatalytic activity compared to the other composites examined. The potential for generating reactive oxygen species (ROS) is discussed in relation to energy band theory, which is useful for understanding the mechanisms occurring at heterojunction interfaces. Collectively, the thesis demonstrates the comprehensive understanding of BTO as a piezocatalyst, and it confirms the role of cocatalysts in increasing BTO's piezocatalytic activity for dye degradation and hydrogen production, whether for environmental or in renewable energy applications. Overall, the insights and methodologies offered in this work have significant implications for designing and optimising materials for environmental and energy applications in pollution reduction, and the harnessing of renewable energy. This detailed abstract encapsulates the core advancements of the thesis, bridging multiple investigations that showcases both the challenges and breakthroughs encountered throughout the research journey. It offers a comprehensive view of the scholarly contributions made in the domain of piezocatalysis, paving the way for future innovations in the emerging field

Ultra-fast escape maneuver of an octopus-inspired robot

We design and test an octopus-inspired flexible hull robot that demonstrates outstanding fast-starting performance. The robot is hyper-inflated with water, and then rapidly deflates to expel the fluid so as to power the escape maneuver. Using this robot we verify for the first time in laboratory testing that rapid size-change can substantially reduce separation in bluff bodies traveling several body lengths, and recover fluid energy which can be employed to improve the propulsive performance. The robot is found to experience speeds over ten body lengths per second, exceeding that of a similarly propelled optimally streamlined rigid rocket. The peak net thrust force on the robot is more than 2.6 times that on an optimal rigid body performing the same maneuver, experimentally demonstrating large energy recovery and enabling acceleration greater than 14 body lengths per second squared. Finally, over 53% of the available energy is converted into payload kinetic energy, a performance that exceeds the estimated energy conversion efficiency of fast-starting fish. The Reynolds number based on final speed and robot length is $Re \approx 700,000$. We use the experimental data to establish a fundamental deflation scaling parameter $\sigma^*$ which characterizes the mechanisms of flow control via shape change. Based on this scaling parameter, we find that the fast-starting performance improves with increasing size.Comment: Submitted July 10th to Bioinspiration & Biomimetic

Business Intelligence And Its Impact Towards The Performance Of The Local Manufacturing Enterprises.

Salah satu cabaran terbesar yang dialami oleh dunia korporat masa kini ialah mengurus informasi. One of the biggest challenges presently characterizing today’s corporate context is the management of information due to scarcity of information

Star Clusters in the Magellanic Clouds-1: Parameterisation and Classification of 1072 Clusters in the LMC

We have introduced a semi-automated quantitative method to estimate the age and reddening of 1072 star clusters in the Large Magellanic Cloud (LMC) using the Optical Gravitational Lensing Experiment (OGLE) III survey data. This study brings out 308 newly parameterised clusters. In a first of its kind, the LMC clusters are classified into groups based on richness/mass as very poor, poor, moderate and rich clusters, similar to the classification scheme of open clusters in the Galaxy. A major cluster formation episode is found to happen at 125 +- 25 Myr in the inner LMC. The bar region of the LMC appears prominently in the age range 60 - 250 Myr and is found to have a relatively higher concentration of poor and moderate clusters. The eastern and the western ends of the bar are found to form clusters initially, which later propagates to the central part. We demonstrate that there is a significant difference in the distribution of clusters as a function of mass, using a movie based on the propagation (in space and time) of cluster formation in various groups. The importance of including the low mass clusters in the cluster formation history is demonstrated. The catalog with parameters, classification, and cleaned and isochrone fitted CMDs of 1072 clusters, which are available as online material, can be further used to understand the hierarchical formation of clusters in selected regions of the LMC.Comment: 19 pages, 19figures, published in MNRAS on August 16, 2016 Supplementary material is available in the MNRAS websit

A multiscale model for dilute turbulent gas-particle flows based on the equilibration of energy concept

The objective of this study is to improve Eulerian-Eulerian models of particle-laden turbulent flow. We begin by understanding the behavior of two existing models—one proposed by Simonin [von Kármán Institute of Fluid Dynamics Lecture Series, 1996], and the other by Ahmadi [Int. J. Multiphase Flow16, 323 (1990)]—in the limiting case of statistically homogeneous particle-laden turbulent flow. The decay of particle-phase and fluid-phase turbulent kinetic energy (TKE) is compared with direct numerical simulation results. Even this simple flow poses a significant challenge to current models, which have difficulty reproducing important physical phenomena such as the variation of turbulent kinetic energy decay with increasing particle Stokes number. The model for the interphase TKE transfer time scale is identified as one source of this difficulty. A new model for the interphase transfer time scale is proposed that accounts for the interaction of particles with a range of fluid turbulence scales. A new multiphase turbulence model—the equilibration of energy model (EEM)—is proposed, which incorporates this multiscale interphase transfer time scale. The model for Reynolds stress in both fluid and particle phases is derived in this work. The new EEM model is validated in decaying homogeneous particle-laden turbulence, and in particle-laden homogeneous shear flow. The particle and fluid TKE evolution predicted by the EEM model correctly reproduce the trends with important nondimensional parameters, such as particle Stokes number

H I Kinematics of the Large Magellanic Cloud revisited : Evidence of possible infall and outflow

The neutral atomic Hydrogen (H I) kinematics of the Large Magellanic Cloud (LMC) is revisited in light of two new proper motion estimates. We analysed the intensity weighted H I velocity maps of the ATCA/Parkes and GASS data sets. We corrected the line of sight velocity field for the systemic, transverse, precession, and nutation motions of the disk using two recent proper motion estimates, and estimated the kinematic parameters of the H I disk. The value of position angle (PA) of kinematic major axis estimated using ATCA/Parkes data is found to be similar to the recent estimate of the PA using stellar tracers. The effect of precession and nutation in the estimation of PA is found to be significant. Using ATCA/Parkes data, most of the H I gas in the LMC is found to be located in the disk. We detected 12.1% of the data points as kinematic outliers. We identified the well-known Arm E, Arm S, Arm W, Arm B and a new stream, Outer Arm, as part of outlier components. The GASS data analysis brings out the velocity details of the Magellanic Bridge (MB) and its connection to the LMC disk. We find that the Arm B and the Outer Arm are connected to the MB. We detect high velocity gas in the western disk of the LMC and the south-west and southern parts of the MB. We proposed two models (in plane and out of plane) to explain the outlier gas. We suggest that the Arm B could be an infall feature, originating from the inner MB. The Arm E could be an outflow feature. We suggest possible outflows from the western LMC disk and south and south western MB, which could be due to ram pressure. The velocity pattern observed in the MB suggests that it is being sheared. We suggest that the various outliers identified in this study may be caused by a combination of tidal effects and hydrodynamical effect due to the motion of the LMC in the Milky Way (MW) halo.Comment: Accepted in A&A for publication. 15 pages, 14 figure