Showing papers by "Indian Institute of Science published in 2022"

Multi-UAV Collaborative Transportation of Payloads With Obstacle Avoidance

Abstract: Control barrier functions have been widely studied and applied to safety-critical systems, including multi-agent obstacle avoidance problems. In this work, we apply control barrier functions to a collaborative transportation problem involving two unmanned aerial vehicles (UAVs) moving a payload around obstacles as they deliver it to a target location. We develop a target-tracking controller for the UAVs, which is constrained to meet the requirements of payload dynamics and obstacle avoidance. We also present simulation results to demonstrate the benefits of the proposed problem formulation for a multi-obstacle environment.

Challenges and Future Prospects of Graphene Based Hybrids for Solar Fuel Generation: Moving Towards the Next Generation Photocatalysts

Abstract: Considering the current global energy crisis and the most alarming environmental pollution issues, moving towards renewable energy resources instead of fossil fuels, should be the ultimate goal of modern civilization. Alternative solar fuel generation by applying heterogenous photocatalysis is one of the major approaches in renewable energy research. After the discovery of the amazing material; graphene and its derivatives, it has become one of the most promising materials for efficient photocatalysis in terms of solar water splitting and CO2 photo-reduction. However, a lot of challenges are still there considering the efficiency, product selectivity, fabrication techniques, etc. Here in, we have discussed the deeper insight into the fundamental aspects of graphene/graphene oxide and their derivatives in terms of structural, electronic, and thermodynamic consideration for the fabrication of new generation photocatalysts. Finally, we have discussed the future directions and strategic insight to overcome the current challenges for sustainable production of solar fuels.

Safety-Critical Kinematic Control of Robotic Systems

Abstract: Over the decades, kinematic controllers have proven to be practically useful for applications like set-point and trajectory tracking in robotic systems. To this end, we formulate a novel safety-critical paradigm by extending the methodology of control barrier functions (CBFs) to kinematic equations governing robotic systems. We demonstrate a purely kinematic implementation of a velocity-based CBF, and subsequently introduce a formulation that guarantees safety at the level of dynamics. This is achieved through a new form of CBFs that incorporate kinetic energy with the classical forms, thereby minimizing model dependence and conservativeness. The approach is then extended to underactuated systems. This method and the purely kinematic implementation are demonstrated in simulation on two robotic platforms: a 6-DOF robotic manipulator, and a cart-pole system.

Robust and Reusable Laccase Mimetic Copper Oxide Nanozyme for Phenolic Oxidation and Biosensing

Abstract: The development of earth-abundant metal-oxide-based nanomaterials with an intrinsic enzyme-mimicking activity (nanozyme) is useful for both practical applications and fundamental research. The laccase enzyme is a multicopper oxidase that finds commercial utility in environmental remediation and biotechnology, but with significant limitations under harsh conditions. Herein, we present the laccase-like activity of Cu2O nanospheres, fabricated using a one-pot polyol-based microwave-assisted method. The as-synthesized Cu2O nanospheres possess great stability under harsh conditions and exhibit excellent laccase-like activity with a KM value of 0.2 mM, considerably smaller than those of previously reported nanozymes as well as native laccase. The utility of the nanozyme was demonstrated in the efficient oxidation of phenolic pollutants under real-life high-salinity conditions, as well as in the colorimetric detection of biomolecules such as epinephrine and dopamine with sensitivities of 10 and 6.5 μM, respectively. Notably, the Cu2O nanozyme enabled naked-eye detection of the acetylcholinesterase enzyme with a biorelevant sensitivity (2.5 pM). This robust and recyclable laccase-mimicking nanozyme introduces a simple and cost-effective metal oxide platform that would find multiple practical applications in environmental remediation, catalysis, and biosensing.

Next-generation Li-ion capacitor with high energy and high power by limiting alloying-intercalation process using SnO2@Graphite composite as battery type electrode

Abstract: Lithium-ion capacitors (LICs) with high energy density at high power capability are ideal for future energy storage applications. Group IV elements, mainly tin (Sn)-based derivatives, are considered as a viable option due to their high reversible capacity, lower redox potential, and moderately lower price. In the present work, we report the assembly of a new type of LIC with high energy and power with long-term stability by pairing SnO2@Graphite nanocomposites (SnO2@G ncs) as battery type electrodes and commercial activated carbon (AC) as capacitor type electrodes. SnO2@G ncs are synthesized by hydrothermal method followed by high-energy ball milling of SnO2 and commercial graphite. The testing potential window of the SnO2 @G ncs half–cells are limited to 1 V vs. Li+/Li to enable only the alloying process and avoid the conversion of Sn0 to SnOx. Among the compositions, the composite with 25% SnO2 and 75% graphite (C1)-based LIC, AC/C1 displayed stable performance with high energy and power. Furthermore, AC/C1-based LIC delivers an energy density of 172.33 Wh kg−1 and retains over 90% capacity after 9000 cycles. This study gives the idea of incorporating an alloying-intercalation-based battery-type electrode, which paves the way further to enhance the electrochemical performance of next-generation LICs.

How well are we able to close the water budget at the global scale?

Abstract: Abstract. The water budget equation describes the exchange of water between the land, ocean, and atmosphere. Being able to adequately close the water budget gives confidence in our ability to model and/or observe the spatio-temporal variations in the water cycle and its components. Due to advances in observation techniques, satellite sensors, and modelling, a number of data products are available that represent the components of water budget in both space and time. Despite these advances, closure of the water budget at the global scale has been elusive. In this study, we attempt to close the global water budget using precipitation, evapotranspiration, and runoff data at the catchment scale. The large number of recent state-of-the-art datasets provides a new evaluation of well-used datasets. These estimates are compared to terrestrial water storage (TWS) changes as measured by the Gravity Recovery And Climate Experiment (GRACE) satellite mission. We investigated 189 river basins covering more than 90 % of the continental land area. TWS changes derived from the water balance equation were compared against GRACE data using two metrics: the Nash–Sutcliffe efficiency (NSE) and the cyclostationary NSE. These metrics were used to assess the performance of more than 1600 combinations of the various datasets considered. We found a positive NSE and cyclostationary NSE in 99 % and 62 % of the basins examined respectively. This means that TWS changes reconstructed from the water balance equation were more accurate than the long-term (NSE) and monthly (cyclostationary NSE) mean of GRACE time series in the corresponding basins. By analysing different combinations of the datasets that make up the water balance, we identified data products that performed well in certain regions based on, for example, climatic zone. We identified that some of the good results were obtained due to the cancellation of errors in poor estimates of water budget components. Therefore, we used coefficients of variation to determine the relative quality of a data product, which helped us to identify bad combinations giving us good results. In general, water budget components from ERA5-Land and the Catchment Land Surface Model (CLSM) performed better than other products for most climatic zones. Conversely, the latest version of CLSM, v2.2, performed poorly for evapotranspiration in snow-dominated catchments compared, for example, with its predecessor and other datasets available. Thus, the nature of the catchment dynamics and balance between components affects the optimum combination of datasets. For regional studies, the combination of datasets that provides the most realistic TWS for a basin will depend on its climatic conditions and factors that cannot be determined a priori. We believe that the results of this study provide a road map for studying the water budget at catchment scale.