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- PublicationMagnetic Field-Induced Polarization Rotation in Strain-Engineered 0.94(Na0.5Bi0.5TiO3)-0.06BaTiO3/CoFe2O4 Magnetoelectric Nanocomposites for Energy Harvesting(2023-01-01)The study focuses on the polarization dynamics of the ferroelectric phase under an external magnetic field in a trilayered magnetoelectric (ME) composite of 0.94(Na0.5Bi0.5TiO3)-0.06BaTiO3 (NBT-BT)/CoFe2O4(CFO)/NBT-BT. With the estimation of gradient size of the strain across the interface, the thin films with varying top layer (NBT-BT) thicknesses were fabricated. The piezoelectric displacement curves revealed the linear characteristics for the 30 nm NBT-BT ME composite due to the presence of dominant interfacial strain. Time-resolved polarization switching studies confirmed the role of interfacial strain on the time scale of polarization switching of the ferroelectric phase. Magnetic field-assisted piezoresponse force microscopy studies confirmed the presence of nonlinear contribution like polarization rotation in the 100 nm NBT-BT ME composite. The interfacial strain was found to operate in a way that imposes constraints on the polarization rotation in a spatial region of ∼20-30 nm away from the interface. However, at a spatial region >30 nm, the interfacial strain was found to supplement the field-induced strain and assisted the polarization rotation to happen. The spatial-dependent behavioral analysis of the interface strain on the polarization dynamics will help in using the ME composite for targeted device applications such as actuators or energy harvesters.
- PublicationInfluence of bed roughness parameter in storm surge modeling along the east coast of India(2024-01-01)The east coast of India is highly prone to devastating winds, torrential rainfall, and storm surges caused by tropical cyclones. The storm surge is affected by ocean basin characteristics involving the width and slope of the continental shelf. The bed roughness plays a major role in surge formation. The east coast of India is characterized by a broader shelf in the north and a narrow shelf in the south. This paper uses a hybrid Finite Volume Method–Finite Element Method based Shallow water equation (SWE) solver to predict the storm surges during different cyclone events, and the roughness parameter Manning’s n is used in bed friction calculations. The bottom friction coefficient parameterization involving bed roughness is used to calibrate the resistance to flow in the numerical model. The calibration exercises are carried out with different values of n for each surge simulations for different cyclones to predict the surface elevation. Different statistical parameters against the measured values are used to analyze the impact of varying n values on predicted surge levels, and the most suitable n value is carefully chosen. The relationship between n and the bed slope is established as an expression, to replace the formulations involving Manning’s n, thereby minimizing the usual computational efforts. The performance of the novel bed friction formulation involving the physical parameter in bed slope is demonstrated through statistical evaluations.
- PublicationNovel numerical methods based on graded, adaptive and uniform meshes for a time-fractional advection-diffusion equation subjected to weakly singular solution(2024-01-01)This paper presents adaptive, graded and uniform mesh schemes to approximate the solution of a fractional order advection-diffusion model, which generally shows a weak singularity at the initial time level. The temporal fractional derivative in the underlying problem is described in a Caputo form and is discretized by means of L1 scheme on a nonuniform mesh. The space derivative is discretized on a uniform mesh employing a fourth-order compact finite difference scheme. The adaptive grid is generated via equidistribution of a positive monitor function. Stability and convergence results for the proposed method on graded mesh are established. Numerical examples are provided to study the accuracy and efficiency of the proposed techniques and to support the theoretical results. A discussion about the advantages of the graded and adaptive meshes over the uniform one is also presented. The CPU times for the proposed numerical schemes are provided.
- PublicationAnalysis of induced dynamic biceps EMG signal complexity using Markov transition networks(2024-01-01)Purpose: Surface electromyography (sEMG) is a non-invasive technique to characterize muscle electrical activity. The analysis of sEMG signals under muscle fatigue play a crucial part in the branch of neurorehabilitation, sports medicine, biomechanics, and monitoring neuromuscular pathologies. In this work, a method to transform sEMG signals to complex networks under muscle fatigue conditions using Markov transition field (MTF) is proposed. The importance of normalization to a constant Maximum voluntary contraction (MVC) is also considered. Methods: For this, dynamic signals are recorded using two different experimental protocols one under constant load and another referenced to 50% MVC from Biceps brachii of 50 and 45 healthy subjects respectively. MTF is generated and network graph is constructed from preprocesses signals. Features such as average self-transition probability, average clustering coefficient and modularity are extracted. Results: All the extracted features showed statistical significance for the recorded signals. It is found that during the transition from non-fatigue to fatigue, average clustering coefficient decreases while average self-transition probability and modularity increases. Conclusion: The results indicate higher degree of signal complexity during non-fatigue condition. Thus, the MTF approach may be used to indicate the complexity of sEMG signals. Although both datasets showed same trend in results, sEMG signals under 50% MVC exhibited higher separability for the features. The inter individual variations of the MTF features is found to be more for the signals recorded using constant load. The proposed study can be adopted to study the complex nature of muscles under various neuromuscular conditions.
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- PublicationOptimization of power quality problem for a windturbine fixed speed induction generatorunder asymmetric faultsusing UPFC fed vector control-PI, hysteresis and fuzzy logic(16-06-2015)Most of the pollution issues created in power system is due to the power quality problems like faults, harmonics etc. In this paper a grid connected fixed speed wind turbine induction generator subjected to asymmetric fault gets attenuated by unified power flow controller (UPFC) as it compensates the positive and negative sequence voltages thereby reducing the torque oscillations and improving the life time of the drain. It is the combination of static compensator (STATCOM) and static synchronous series compensator (SSSC). The control theory is based on vector control- dq(direct quadrature axis) reference frame fed PI, hysteresis control and fuzzy logic control using DSOGI-PLL(Dual second order generalized integrator- Phase locked loop). The proposed system is implemented using MATLAB / SIMULINK platform with and without Unified power flow controller. The effect of UPFC for fixed speed windturbine under faults is analysed using the above three controllers and its performance is evaluated.
- PublicationSpectroscopic studies for the changes of a Cr(II) compound in solution triggered by the deprotonation of an aqua ligand(18-06-2015)Recently, we reported dioxygen binding and its activation by the Cr(II) compound [Cr(H2O)(LISQ)2] (1) [(LISQ)1- is o-iminothionebenzosemiquinonate(1-) π-radical]. In this work, we report the existence of ferromagnetism in its solid form. The plot of (χm)-1 versus T from 250 to 20 K reveals a Curie-Weiss constant of θ ~26 K suggesting a ferromagnetic coupling. A theoretical simulation on the susceptibility curve and the fitting of the χm versus T yielded g = 1.83 ± 0.002, J = 33.4 ± 0.001 cm-1, and θ = 25.2 ± 0.02 K with J D. Increase in EPR line width on cooling helped us calculate the Cr(II)-Cr(II) distance in the proposed dimer. Also we find that deprotonation of the aqua ligand in 1 is essential for dioxygen binding and its activation. Reaction with dioxygen is completely inhibited when there is no deprotonation. Reaction of 1 with dioxygen in pyridine (py) resulted in isolation of the O=Cr(IV) compound [O=Cr(LAP)2(py)] (2) [(LAP)1- is o-aminothiophenolate anion] and no monomeric O=Cr(V) has been detected by EPR. 1H NMR study of 1 in d6-DMSO with time shows increase in intensity of the -NH2 peak at 5.46 ppm, suggesting gradual reduction of the -NH groups in (LISQ)1- ligands.
- PublicationBiosorption Potential of Coco-Peat in the Removal of Methylene Blue from Aqueous Solutions(13-06-2015)An agro-waste, coco-peat was investigated as a biosorbent for methylene blue from aqueous solutions. The practicability of biosorption process was examined by varying the experimental parameters such as pH (2-9), initial concentration (50-200 mg/L), contact time (2-240 min), and temperature (298-318 K). Maximum uptake of 212.8 mg/g was observed at pH 8 based on the Langmuir model. Among different isotherm models examined (Langmuir, Freundlich, Redlich-Peterson, and Sips), the Redlich-Peterson model described the experimental isotherms well. Coco-peat was characterized using the Fourier Transform Infrared Spectroscopy and their morphology was analyzed using scanning electron microscopy.
- PublicationRecommendations for screening and early detection of common cancers in India(01-07-2015)Cancers of the breast, uterine cervix, and lip or oral cavity are three of the most common malignancies in India. Together, they account for about 34% of more than 1 million individuals diagnosed with cancer in India each year. At each of these cancer sites, tumours are detectable at early stages when they are most likely to be cured with standard treatment protocols. Recognising the key role that effective early detection and screening programmes could have in reducing the cancer burden, the Indian Institute for Cytology and Preventive Oncology, in collaboration with the US National Cancer Institute Center for Global Health, held a workshop to summarise feasible options and relevant evidence for screening and early detection of common cancers in India. The evidence-based recommendations provided in this Review are intended to act as a guide for policy makers, clinicians, and public health practitioners who are developing and implementing strategies in cancer control for the three most common cancers in India.
- PublicationElectrochemical reduction of carbon dioxide on zinc-modified copper electrodes(01-01-2017)Electrochemical reduction of carbon dioxide (CO2) was performed on zinc-deposited copper (Cu/Zn) electrodes, and the faradaic efficiency of this system toward methane, ethane, and hydrogen was evaluated. Hierarchically structured Zn was electrodeposited on a Cu substrate under constant voltage in a varying bath concentration of Zn to yield low-and high-concentration deposits, represented as Cu/Zn-A and Cu/Zn-B, respectively. The prepared materials were characterized by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. The reduction of CO2 was performed with the Cu/Zn electrodes in an H-type cell, and the results obtained were compared with those from bare Cu and Zn electrodes, revealing that a high deposit of Zn on Cu (Cu/Zn-B) shows greater conversion efficiency than does a low Zn deposit (Cu/Zn-A) and the maximum faradaic efficiency of methane follows the order Cu/Zn-B (52%) > Cu (23%) > Zn (7%). Moreover, the efficiency of hydrogen formation is suppressed on Cu/Zn-B (8%) compared to bare Cu (68%) in the potential range studied. The results suggest that depositing Zn on Cu favors a protonation reaction, which results in higher C1 product formation on a Cu/Zn-B electrode.