Indian Institute of Technology Hyderabad
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Integration of deep eutectic solvent in biorefining process of lignocellulosic biomass valorization
Full text linkPretreatment is the crucial step in the biorefinery process for the bioconversion of lignocellulosic biomass to value-added products. Among various chemical pretreatment methods, deep eutectic solvents (DESs) are novel green solvents to effectively reduce the recalcitrant nature of the biomass that result in an increase in the sugar and product yields after the enzymatic saccharification and fermentation process. This review summarizes the properties, mechanisms, applications and parameters of various types of DESs to improve the delignification from the lignocellulosic biomass and fractionation process. In addition, different integrated methods related to DES pretreatment used in recent studies are also discussed in this paper. Even though this strategy is in the infant stage, further research is required to meet the challenges and increase the efficiency of the process. Moreover, such an approach is desirable to ensure the extensive utilization of biomass for developing sustainable products by mitigating global energy crises
Effect of quenching rate on the structural and hard magnetic properties of Nd-Fe-B melt-spun ribbons
Full text linkThe phase structure, microstructure, magnetic and thermomagnetic properties of nanostructured Nd-Fe-B melt-spun ribbons were investigated. The melt-spun ribbons have been prepared at different wheel speeds varying from 17 to 25 m/s. The hard magnetic Nd2Fe14B phase with (00l) texture, indicating preferred crystallographic orientation, was observed in all the ribbons with some α-Fe(Co) as the minor phase. Nd2Fe14B grains are uniformly distributed with grain sizes ranging from 50 to 150 nm. A decrease in the average grain size of Nd2Fe14B and fading away of texture formation in the ribbons were found with the increase in the wheel speeds. The best combination of magnetic properties with a coercivity of 14.5 kOe, the saturation magnetization of 132 emu/g, and the energy product of 16 MGOe was achieved at 23 m/s and these ribbons are suitable for the fabrication of hot deformation Nd-Fe-B magnets
State Separate Modular Modeling Methodology of Multioutput DC-DC Converters
Full text linkConventional modeling and simulation of n -output dc-dc converters requires (n+1) × (n+1) matrix computations. This approach increases the modeling approach's complexity and increases the design and simulation time required for the modeling process. A state separate modeling methodology is proposed where each state of the dc-dc converter is considered separately and combined with the help of a multiplexer. The proposed modeling approach is modular and thus improves the scalability to multiple outputs. The proposed methodology aids the designer in designing and modeling multioutput dc-dc converters faster, enabling fast prototyping. The proposed model outperforms the existing mathematical models in terms of computation time. The output voltage variation to duty cycles has a root mean square error in between 0.08 and 0.22 V
Bulk and monolayer thermoelectric and optical properties of anisotropic NbS2Cl2
Full text linkRecently, the chalcogenide-based materials are attracting the scientific community due to their promising thermoelectric properties. Monoclinic compounds of the chalcogenide class of materials are the least explored for thermoelectric and optoelectronic device applications. In our present study, we have taken NbS2Cl2 to analyse its electronic properties of bulk and monolayer to understand its electronic and thermal transport properties along with its optical properties, using the density functional theory framework. The investigated compound has direct bandgap values of 1.41 eV and 1.67 eV in its bulk and monolayer phases, respectively, making it a semiconductor. The lattice thermal conductivity(κl), being a crucial parameter for a thermoelectric material, is observed to be ultra-low along ‘c’ direction for the bulk (0.44 Wm/K) and the same along ‘b’ direction for monolayer (0.36 Wm/K). We also predict a great potential for nanostructuring with 72% reduction in the thermal conductivity for the crystal grain size of 10 nm. Further, carrier lifetimes for various concentrations and temperatures are estimated by incorporating different scattering mechanisms in the calculations, such as acoustic deformation scattering (ADP), ionized impurity scattering (IMP) and polar optical scattering (POP). Based on thermoelectric performance, we predict n-type doping would be more favourable. At 700 K, n-type bulk has a maximum thermoelectric performance (ZT) of 0.4, higher than the well-known monoclinic GaTe (0.24) TE material. In addition, the calculated absorption coefficient reveals the optical anisotropy. The predicted absorption coefficients for bulk and monolayer in the visible range are 7.5×105/cm and 3×105/cm, respectively. The current work highlights its extremely low thermal conductivity and significant absorption coefficients, which could lead to future applications in thermoelectric and optical devices
TOPress: a MATLAB implementation for topology optimization of structures subjected to design-dependent pressure loads
No full textIn a topology optimization (TO) setting, design-dependent fluidic pressure loads pose several challenges as their direction, magnitude, and location alter with topology evolution. This paper offers a compact 100-line MATLAB code, TOPress, for TO of structures subjected to fluidic pressure loads using the method of moving asymptotes. The code is intended for pedagogical purposes and aims to ease the beginners’ and students’ learning toward the TO with design-dependent fluidic pressure loads. TOPress is developed per the approach first reported in Kumar et al. (Struct Multidisc Optim 61(4):1637–1655, 2020). The Darcy law, in conjunction with the drainage term, is used to model the applied pressure load. The consistent nodal loads are determined from the obtained pressure field. The employed approach facilitates inexpensive computation of the load sensitivities using the adjoint-variable method. Compliance minimization subject to volume constraint optimization problems is solved. The success and efficacy of the code are demonstrated by solving benchmark numerical examples involving pressure loads, wherein the importance of load sensitivities is also demonstrated. TOPress contains six main parts, is described in detail, and is extended to solve different problems. Steps to include a projection filter are provided to achieve loadbearing designs close to 0-1
Cage Dynamics-Mediated High Ionic Transport in Li-O2 Batteries with a Hybrid Aprotic Electrolyte: LiTFSI, Sulfolane, and N,N-Dimethylacetamide
Full text linkMixed electrolytes perform better than single solvent electrolytes in aprotic lithium-O2 batteries in terms of stability and transportation. According to an experimental study, a mixed electrolyte consisting of dimethylacetamide (DMA)/sulfolane (TMS) with lithium bisfluorosulfonimide (LiTFSI) showed high ionic conductivity, oxygen solubility, remarkable stability, and better cycle life than only DMA-based or TMS-based electrolytes. In this work, we used classical molecular dynamics simulations to explore the structure and ionic dynamics of the DMA/TMS hybrid electrolytes at two compositions. We calculated radial, combined, and spatial distribution functions for the structural examination. These properties depict a minimal change in the electrolyte structure by increasing the DMA content in the electrolyte from 20 to 50% by volume. We used the diffusive regimes from mean square displacements for diffusion coefficient calculations. Ionic conductivities calculated using the Green-Kubo equation have an acceptable agreement with the experimental values, whereas the Nernst-Einstein relation is found insufficient to explain the ionic transport. The relatively lower value of the ion-cage lifetime of electrolyte components with 50% DMA shows their faster dynamics. Moreover, we present the new physical insight by focusing on ion-pair and ion-cage formation and their correlation with ionic conductivity. The atomic-level understanding through this work may assist in designing electrolytes for aprotic Li-O2 cells
Characterization of Spatial–Temporal Distribution of Forest Fire in Chhattisgarh, India, Using MODIS-Based Active Fire Data
Full text linkForest fires are one of the most common natural and anthropogenic events that have long-term impacts on the environment. In this study, we analyzed 17 years of data on forest fires in Chhattisgarh, India, using active fire and burned area data from the Moderate Resolution Imaging Spectroradiometer. Chhattisgarh was selected as the study area due to its high incidences of forest fires, significant forest cover, and scarce studies on forest fires. Our findings showed that the number of forest fires in the region increased over time, from 1487 forest fires in 2005 to 3074 forest fires in 2021, with the highest number of fires occurring in 2017 and 2009. Most of the fires occurred in deciduous broadleaf forests and savannas, following a consistent seasonal pattern, with the highest percentage of fires (88.88%) occurring in March, April, and May. The fire hotspot was located in the southwest region, dominated by deciduous broadleaf forests which are particularly prone to fires. These results emphasize the significance of effective fire management strategies that consider the seasonal and annual variability of forest fires, particularly in high-risk areas. Immediate attention to controlling forest fires is also critical to minimize its impact on the environment and local communities
A review on battery technology for space application
Full text linkThis review article comprehensively discusses the energy requirements and currently used energy storage systems for various space applications. We have explained the development of different battery technologies used in space missions, from conventional batteries (Ag–Zn, Ni–Cd, Ni–H2), to lithium-ion batteries and beyond. Further, this article provides a detailed overview of the current development of lithium batteries concerning their different electrode and electrolyte system, which needs special consideration for enabling their use for space application. This review also provides an outlook on the battery technology development for interplanetary space missions enlisting the research emphasis to be directed to meet the special energy requirements during various stages of such missions. This review is an attempt to provide a one-step comprehensive overview for any researchers, scientists, batteries manufacturers, and space agencies to first understand the current requirements critically and, accordingly, the solutions to prepare a future roadmap to develop highly efficient, next-generation advanced energy storage systems to mitigate the technical challenges and at the same time, minimizing the cost associated
Effect of Co- and Counterswirl Air on Swirl Airblast Atomization
No full textFor swirl-stabilized gas turbine combustor, liquid fuel distribution in the near field dictates local equivalence ratio, volumetric heat release, and heat transfer to the chamber wall, and hence its understanding is essential. The effect of inlet air aerodynamics on spray characteristics in a primary zone of a simulated gas turbine burner is studied using a phase Doppler particle analyzer, high-speed Mie scatter imaging, and an orthogonal decomposition method. By employing intense coswirl air, the luminous spray region shifts upstream to the burner exit, where lower mass flux can be observed in the central region and higher mass flux in the outer region of the spray due to the recirculation zone formation. Based on the size velocity joint probability distribution functions (JPDFs) and the individual droplet transport with acquisition time, we conclude that the recirculation zone entraps the smaller droplets and transports them from the downstream to the upstream spray region. Compared to coswirl, counterswirl air exhibits torsion instability, intensifies the concentration of drops in the central region, and improves secondary atomization. Finally, five distribution functions are curve-fitted to the experimental data to capture the atomization process accurately