1. Journal Articles
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Item Highly steerable microwave beamforming system near Ku band based on the application of linearly CFBG(Institution of Engineering and Technology, 2020) Raghuwanshi, Sanjeev Kumar; Srivastava, Nimish Kumar; Singh, MandeepIn this study, the authors present theoretical and experimental results of wideband beamforming networks steered by a single linear chirped fibre Bragg grating (CFBG). The standard single-sideband modulation technique is followed to validate the wideband (at 18 GHz) operation of the proposed system. CFBG has been fabricated by phase mask technology for the desired specification to be compatible with the antenna array. To the authors knowledge, the effect of dispersion slope feature of fabricated FBG on the performance of beam-steering capability of the antenna is reported for the first time in this study. Theoretically preceded by experimental testing, it was found that the scanning angle increased with the rise in the number of antenna elements and the frequency of modulating microwave signal.Item Transient analysis of upstream wake inside turbine blade passage with purge flow(2020) Sushanlal, B.; Anish, S.Secondary air bled from the compressor which bypasses the combustion chamber is used to seal the turbine components from incoming hot gas. Interaction of this secondary air (also known as purge flow) with the mainstream flow can alter the flow characteristics of turbine blade passage. This paper presents numerical investigation of interaction between ejected purge flow and mainstream flow in the presence of upstream disturbances/wakes. Steady as well as unsteady simulations are carried out using Reynolds Averaged Navier Stokes equations and SST turbulence model. The numerical results are validated with experimental measurements obtained at the blade exit region using an L shaped 5 hole probe and Scanivalve. Upstream wakes are generated by a circular cylinder, kept upstream of blade leading edge at different pitch-wise positions. For transient analysis cylinders are kept at stagnation line (STW) and middle of the blade passage (MW). The analysis reveals the interaction effects of two more additional vortices, viz. the cylinder vortex (Vc) and the purge vortex (Vp). Steady state analysis shows an increase in the underturning at blade exit due to the squeezing of the pressure side leg (PSL) of horse shoe vortex towards the pressure surface by the cylinder vortices (Vp). The unsteady analysis reveals the formation of filament shaped wake structures which breaks into smaller vortical structures at the blade leading edge for STW configuration. These filaments lead to the formation of additional pressure surface vortices. On the contrary, in MW configuration, the obstruction created by the purge flow causes the upper portion of cylinder vortices bend forward, creating a shearing action along the spanwise direction. In MW configuration, the horse shoe vortices generated from the upstream cylinder are broken by the purge vortex whereas in the STW configuration it slides over the purge vortex and move towards the suction surface under the influence of the pitchwise pressure gradient. � 2019 Elsevier Masson SASItem Vanadium-Doped SrTiO3 Nanocubes: Insight into role of vanadium in improving the photocatalytic activity(2020) Bantawal, H.; Shenoy, U.S.; Bhat, D.K.SrTiO3 based materials have been gaining attention recently in the field of photocatalysis due to their tunable electronic structure. Herein, we employ a facile one pot solvothermal approach for the synthesis of V doped SrTiO3 nanocubes. First principles theoretical calculations reveal that the 3 'd' dopant level introduced by V reduces the band gap and extends the absorption to the visible region of spectrum. The occupancy of Ti site by V introduces dopant states overlapping with the conduction band, eliminating the formation of mid gap recombination centres. Photocatalytic experimental studies on degradation of methylene blue dye reveals the material to be an excellent photocatalyst with high photocorrosion resistance and cyclic stability. In addition, the material is also predicted to be a potential thermoelectric material. � 2020 Elsevier B.V.Item Thermodynamic irreversibility and conjugate effects of integrated microchannel cooling device using TiO2 nanofluid(2020) Narendran, G.; Gnanasekaran, N.; Perumal, D.A.Thermal management is highly essential for the latest electronic devices to effectively dissipate heat in a densely packed environment. Usually, these high power devices are cooled by integrating micro scale cooling systems. Most of the works reported in the literature majorly concentrate on microchannel heat sink in which the characteristics of friction factor and enhancement of heat transfer are analyzed in detail. However, due to the advent of compact electronic devices a crucial investigation is required to facilitate an amicable environment for the neighboring components so as to improve the reliability of the electronic devices. Henceforth, in the present study a combined experimental and numerical analysis is performed to provide an insight to determine the performance of a copper microchannel integrated with aluminium block using TiO2 nanofluid for different particle configurations. Needless to say, the present study, which also focuses on entropy generation usually attributed to the thermodynamic irreversibility, is very much significant to design an optimum operating condition for better reliability and performance of the cooling devices. 2019, Springer-Verlag GmbH Germany, part of Springer Nature.Item Study of devolatilization during chemical looping combustion of large coal and biomass particles(2020) Pragadeesh, K.S.; Regupathi, I.; Sudhakar, D.R.Chemical Looping Combustion (CLC) is one of the emerging technologies for carbon capture, with less energy penalty. The present way of using pulverized coals in a fluidized bed (FB)-CLC have limitations like loss of unconverted char and gaseous combustibles, which could be mitigated by use of coarser fuel particles. Devolatilization time is a critical input for the effective design of FB-CLC systems, primarily when large fuel particles are used. The present study investigates the devolatilization time and the char yield of three coals of two shapes, namely, two high ash Indian coals and a low ash Indonesian coal and a wood (Casuarina equisetifolia) in the size range of +8 25 mm, at different fuel reactor temperatures (800 950 C) of a hematite based CLC unit. The devolatilization times of single fuel particles during CLC are determined using a visual method called Color Indistinction Method . Indonesian coal has the longest devolatilization time among the fuels, and biomass has the least. Increasing the bed temperature enhances the rate of volatile release, whereas this effect is less pronounced in larger particles. Devolatilization of Indonesian coal is found to be strongly influenced by the changes in operating conditions. With the decrease in sphericity, a maximum of 56% reduction in devolatilization time is observed for the +20 25 mm slender particles of Indonesian coals when compared to the near-round particles. The maximum average char yields at the end of the devolatilization phase for coal and biomass are about 55 76% and 16% respectively. Char yield in coal particles increases with an increase in particle size, whereas biomass particles show relatively consistent yield across all experimental conditions. Increase in bed temperature reduces the char yields of coal up to 12% and in biomass up to 30%. High volatile Indian coal is the most influenced fuel by the changes in fuels shape. A correlation for determining devolatilization time under CLC environment is presented, and it successfully fits most of the experimental values within 20% deviation for coals (R2 = 0.95) and within 15% deviation for biomass (R2 = 0.97). 2020 Energy InstituteItem Structural and Thermophysical Anomalies of Liquid Water: A Tale of Molecules in the Instantaneous Low- and High-Density Regions(2020) Priyadarshini, A.; Biswas, A.; Chakraborty, D.; Mallik, B.S.Water is believed to be a heterogeneous liquid comprising multiple density regions that arise because of the presence of interstitial molecules and can be differentiated by their structure as well as the existence of hydrogen-bonded pairs with varying strengths. First-principles molecular dynamics studies were performed at six different temperatures to investigate the effect of temperature on the thermophysical, structure, dynamics, and vibrational spectral properties of the water molecules using dispersion-corrected density functional theory. The variation of properties like density, cohesive energy, and compressibility with a change in temperature produces a trend that matches with the experiments and resembles the experimentally observed anomalous behavior. We explore the possibility of explaining the trends in calculated properties by analyzing the structure and dynamics of the water molecules in terms of instantaneous low- and instantaneous high-density regions that are found during the simulation time. The dynamics of these two types of water molecules were studied by calculating the lifetime from the proposed autocorrelation functions. The lifetime of formation of instantaneous low-density water is found to decrease with an increase in temperature, whereas the lifetime of instantaneous high-density water is found to be maximum at 298 K among all the considered temperatures. The presence of more interstitial water molecules is observed at this temperature. The signature of these water molecules is found in the radial distribution function, spatial distribution function, void distribution, configurational space, orientational dynamics, and spectral diffusion calculations. It is also found that around 298 K, these water molecules are present distinctively that mix up with the first and second solvation shells with the rise of the temperature. The outlook of the reported results can be extended to other thermodynamic conditions to explain some of the anomalous properties, which can be related to the presence of the interstitial molecules in water.Item Performance of cascode Class-EF?1 PA with built-in techniques for UWB radar toward monitoring of patient actions(2020) Kumar, R.; Dwari, S.; Kanaujia, B.K.; Kumar, S.; Song, H.This work proposes a performance of the cascode Class-EF?1 power amplifier (PA) for UWB radar transmitter. The cascode Class-E PA with built-in techniques overcomes the traditional mismatch and provides good performance of PA. Incurs the resonance and switching effect is observed in cascode Class-E PA that compensates for the parasitic effects and provides a wide-impedance range. While design-II includes negative capacitance and inverse Class-F, which achieves a redundant performance of wide bandwidth and power-added efficiency (PAE). Design-II achieves the redundant performance compared with design-I. Both design-I and design-II are implemented and analysed through simulation and experimental results using RF 65 nm Samsung Magnachip Hynix CMOS process. Design-I achieves a wide-impedance bandwidth ranging from 3 to 11.7 GHz with drain efficiency (DE) and maximum PAE of 80 and 73% at the output power of 26.4 dBm. The global efficiency (GE) and error vector magnitude (EVM) of 70 and 5.2% are also achieving for design-I. The redundant performance in design-II achieves wide bandwidth with operating frequency range of 2-13 GHz with maximum DE and PAE of 85 and 76%. For design-II, GE and EVM are investigated as 68 and 4.9% that could validate the accuracy and robustness of the UWB radar. The Institution of Engineering and Technology 2019Item Simulation of coastal aquifer using mSim toolbox and COMSOL multiphysics(2020) Kumar, S.S.; Deb, Barma, S.; Amai, M.Fluctuations in groundwater levels along the coast have a significant impact on the extent of saltwater intrusion into freshwater aquifers. This study aims to simulate the groundwater flow and solute transport in the region by using the mSim toolbox in the MATLAB and COMSOL Multiphysics. The investigation is focussed on a micro-basin of Pavanje river located along the west coast of India. The model results are calibrated and validated against the field observations. The results show that the variation of the water table over the year is significant and range from about 3 14 m. There exists a reasonable correlation between the simulated and observed values of groundwater level and salinity. The wells that are most vulnerable to seawater intrusion in the region are identified. The COMSOL model estimated a salinity range of 0 20 mol/m3. Additionally, the model is used to understand the response of coastal aquifer to various stress scenarios. The study reveals that reduced recharge rate with increased pumping has a serious impact on aquifer system. 2020, Indian Academy of Sciences.Item Predicting ICD-9 code groups with fuzzy similarity based supervised multi-label classification of unstructured clinical nursing notes(2020) Gangavarapu, T.; Jayasimha, A.; Krishnan, G.S.; Sowmya, Kamath S.In hospitals, caregivers are trained to chronicle the subtle changes in the clinical conditions of a patient at regular intervals, for enabling decision-making. Caregivers text-based clinical notes are a significant source of rich patient-specific data, that can facilitate effective clinical decision support, despite which, this treasure-trove of data remains largely unexplored for supporting the prediction of clinical outcomes. The application of sophisticated data modeling and prediction algorithms with greater computational capacity have made disease prediction from raw clinical notes a relevant problem. In this paper, we propose an approach based on vector space and topic modeling, to structure the raw clinical data by capturing the semantic information in the nursing notes. Fuzzy similarity based data cleansing approach was used to merge anomalous and redundant patient data. Furthermore, we utilize eight supervised multi-label classification models to facilitate disease (ICD-9 code group) prediction. We present an exhaustive comparative study to evaluate the performance of the proposed approaches using standard evaluation metrics. Experimental validation on MIMIC-III, an open database, underscored the superior performance of the proposed Term weighting of unstructured notes AGgregated using fuzzy Similarity (TAGS) model, which consistently outperformed the state-of-the-art structured data based approach by 7.79% in AUPRC and 1.24% in AUROC. 2019 Elsevier B.V.Item Pixelwise improvised blend of predictors in HEVC lossless mode(2020) Shilpa, Kamath, S.; Aparna, P.; Antony, A.The commendable work by the two video coding pioneers ISO/IEC and ITU-T, to handle the next-generation of multimedia services has led to the evolution of High Efficiency Video Coding (HEVC) standard. The lossless mode of HEVC is essential when no loss in fidelity is desired to aide most of the real-world applications like video analytics, web collaboration, remote desktop sharing, etc. The proposed work intends to improvise the HEVC intra prediction scheme through the application of the heuristic history-based blend of predefined sub-predictors, while in lossless mode. The prime element of the locally adaptive mechanism is the derivation of the penalizing factors that are imposed on the sub-predictors, based on the neighborhood residuals. The experimental analysis highlights that the proposed method outperforms the lossless mode of HEVC anchor and the prevalent state-of-the-art prediction techniques in terms of savings in bit-rate which is achieved without any increase in run-time. 2019 Elsevier GmbH