Showing papers by "National Institute of Technology, Meghalaya published in 2020"

An investigation into the identification of potential inhibitors of SARS-CoV-2 main protease using molecular docking study.

Abstract: A new strain of a novel infectious disease affecting millions of people, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has recently been declared as a pandemic by the World...

A Switched-Capacitor Self-Balanced High-Gain Multilevel Inverter Employing a Single DC Source

Abstract: Multilevel inverters (MLIs) with self-balanced switched-capacitors (SC) have received wide recognition for increasing power capacity and power quality of the renewable energy and high-frequency power distribution systems. This brief presents a new SC MLI structure using a reduced number of switches and a single dc source. By suitable charging-discharging patterns, the SCs are self-balanced and high voltage boosting is achieved. Comparative analysis with state-of-art MLIs in terms of the number of components, standing voltage, boosting factor, and cost factor demonstrate the merit of presented topology. Further, experimental results confirm the workability of the proposed MLI under linear, non-linear loading and dynamic test conditions using both the 50 Hz and 2.5 kHz modulation.

Exploring the interaction of bioactive kaempferol with serum albumin, lysozyme and hemoglobin: A biophysical investigation using multi-spectroscopic, docking and molecular dynamics simulation studies.

Abstract: In recent years research based on kaempferol (KMP) has shown its potential therapeutic applications in medicinal chemistry and clinical biology. Therefore, to understand its molecular recognition mechanism, we studied its interactions with the carrier proteins, namely, human serum albumin (HSA), bovine hemoglobin (BHb) and hen egg white lysozyme (HEWL). The ligand, KMP was able to quench the intrinsic fluorescence of these three proteins efficiently through static quenching mode. The binding constant (Kb) for the interactions of KMP with these three proteins were found in the following order: HSA-KMP > BHb-KMP > HEWL-KMP. Different non-covalent forces such as hydrogen bonding and hydrophobic forces played a major role in the binding of KMP with HSA and HEWL, whereas hydrogen bonding and van der Waals forces contribute to the complexation of BHb with KMP. KMP was able to alter the micro-environment near the Trp fluorophore of the proteins. KMP altered the secondary structural component of all three proteins. The putative binding sites and the residues surrounding the KMP molecule within the respective protein matrix were determined through molecular docking and molecular dynamics (MD) simulation studies. The conformational flexibility of the ligand KMP and the three individual proteins were also evident from the MD simulation studies.

Power Quality Performance Evaluation of Multilevel Inverter With Reduced Switching Devices and Minimum Standing Voltage

Abstract: Multilevel inverters (MLIs) have been extensively employed to improve the power quality of the photovoltaic (PV) systems. However, the need for large number of components, higher standing voltage, and high harmonic content in the output of a conventional MLI greatly affects the system efficiency. Asymmetrical MLIs have been therefore developed as a suitable alternative to address these issues. This article aims at developing such a hybrid asymmetrical structure suitable for PV application that has a high level per component ratio and minimum standing voltage. The proposed MLI is assembled using a reduced switch H-bridge-based (RSHB) MLI structure with n asymmetrical repeating units and different level doubling circuit (LDC) combinations. The two dc sources used in the repeating units are in the ratio of 1: n voltage ratio, and using n such units, the proposed MLI structures, i.e., PS1 and PS2 can synthesize 4 n + 5 and 4 n + 7 levels, respectively, at the output instead of 2 n + 3 levels with only RSHB MLI. Comparative analysis reveals that both PS1 and PS2 have fewer switches, low standing voltage, less power loss, and lower cost. A 3.9-kW standalone solar PV system is considered for performance evaluation of the PS1 structure applying both the selective harmonic elimination and carrier-based pulsewidth modulation control schemes. In light of this, dc-link voltage balancing and self-voltage balancing mechanism of the LDC are warranted. Extensive simulation of the proposed MLI is performed in MATLAB/Simulink platform under a change in modulation index, sudden load change, frequency change, and step change in solar insolation. Furthermore, theoretical and simulation findings are validated experimentally by performing similar tests on a prototype of the proposed 17-level MLI.

Detection and Mitigation of Cyber-Attacks on AGC Systems of Low Inertia Power Grid

Abstract: Automatic generation control (AGC) plays a salient role in modern power systems by maintaining grid frequency within acceptable limits. Since AGC is the only automatic feedback loop between cyber and physical infrastructures, it is greatly vulnerable to malicious attacks and hence, required urgent investigations. Attackers can falsify the sensor measurements employed for AGC operation causing service outage and infrastructural damage. In this article, a method is developed to detect and mitigate possible cyber-attack schemes such as false data injection and denial-of-service attacks targeting the AGC systems. The proposed method is termed as cyber-attack detection and mitigation platform (CDMP) and utilizes the forecasted data of area control error for identification and mitigation of attacks. The CDMP strategy involves three stages for optimal operation and identifies any arbitrary false data injected to the grid. For the investigation, three area system with multiple generations and distribution companies under bilateral trading is considered. The test model is also equipped with inertia emulation technique supported by battery management system. It is because the modern power system is advancing toward inverter-dominated system from synchronous-based system due to high penetration of renewables. The effectiveness of the proposed strategy is verified using rigorous simulation results.

Unsteady electro-osmotic flow of couple stress fluid in a rotating microchannel: An analytical solution

Abstract: In this work, we present the theoretical investigation of the transient rotating electro-osmotic flow of a couple stress fluid in a microchannel, through the Laplace transform technique. The analysis is dependent on the Debye–Huckel linear approximation for electrical potentials. The governing equations of the couple stress fluid are taken to address the flow field in a rotating environment. The mathematical formulation of these governing equations provides a system of ordinary differential equations, which are then solved to achieve analytical solutions for electrostatic potential, axial and transverse velocity distribution, and volumetric flow rate. A comparison was made for the present analytical solution with data available in the literature. There was excellent matching. The characteristics of different influential parameters on axial and transverse velocity distributions, volume, and angle flow rates are pictorially deliberated. The study reveals that the rise in the couple stress parameter accelerates the axial electro-osmotic flow velocity inside the electrical double layer.

Improved Power Quality in a Solar PV Plant Integrated Utility Grid by Employing a Novel Adaptive Current Regulator

Abstract: Integration of solar photovoltaic plants into the distribution systems using various power processing units produces the harmonics that may cause malfunctioning of sensitive equipment connected to the point of common coupling. To overcome this drawback, a novel adaptive current regulator is employed for the grid interfacing voltage source inverter. In addition, a high-gain dc–dc converter with a Kalman-based maximum power point tracking algorithm is designed to achieve the high voltage level at the common dc bus. To determine three-phase reference currents, the proposed adaptive current regulator is designed by using a recurrent neural network trained with the Hebbian least mean square weight updating algorithm. They are used to generate the three-phase compensating currents for suppressing the harmonics present in the system. The proposed method has several merits, such as better harmonic mitigation ability, adaptive behavior, improved stability, and lesser settling time, as compared with the conventional PI controller. The system performance with the proposed current control regulator is analyzed via MATLAB/Simulink. Comparative analysis via simulation platform assures the improved performance in terms of power quality, settling time, and stability of the proposed controller. Also, the effectiveness of the proposed controller is validated under several transient conditions by developing a laboratory scale prototype model with the dSPACE control desk.

Targeting the heme protein hemoglobin by (-)-epigallocatechin gallate and the study of polyphenol-protein association using multi-spectroscopic and computational methods.

Abstract: In this work, the interaction of a bioactive tea polyphenol (-)-epigallocatechin gallate (EGCG) with bovine hemoglobin (BHb) along with its anti-oxidative behavior and the anti-glycation property have been explored using multi-spectroscopic and computational techniques. The binding affinity for EGCG towards BHb was observed to be moderate in nature with an order of 104 M-1, and the fluorescence quenching mechanism was characterized by an unusual static quenching mechanism. The binding constant (Kb) showed a continuous enhancement with temperature from 3.468 ± 0.380 × 104 M-1 at 288 K to 6.017 ± 0.601 × 104 M-1 at 310 K. The fluorescence emission measurements along with molecular docking studies indicated that EGCG binds near the most dominant fluorophore of BHb (β2-Trp37, at the interface of α1 and β2 chains) within the pocket formed by the α1, α2 and β2 chains. The sign and magnitude of the thermodynamic parameters, changes in enthalpy (ΔH = +17.004 ± 1.007 kJ mol-1) and in entropy (ΔS = +146.213 ± 2.390 J K-1 mol-1), indicate that hydrophobic forces play a major role in stabilizing the BHb-EGCG complex. The micro-environment around the EGCG binding site showed an increase in hydrophobicity upon ligand binding. The binding of EGCG with BHb leads to a decrease in the α-helical content, whereas that of the β-sheet increased. FTIR studies also indicated that the secondary structure of BHb changed upon binding with EGCG, along with providing further support for the presence of hydrophobic forces in the complexation process. Molecular docking studies indicated that EGCG binds within the cavity of α1, α2, and β2 chains surrounded by residues such as α1- Lys99, α1-Thr134, α1-Thr137, α1-Tyr140, α2-Lys127 and β2-Trp37. Molecular dynamics simulation studies indicated that EGCG conferred additional stability to BHb. Furthermore, moving away from the binding studies, EGCG was found to prevent the glyoxal (GO)-mediated glycation process of BHb, and it was also found to act as a potent antioxidant against the photo-oxidative damage of BHb.

Feasibility of vermicomposting for the management of terrestrial weed Ageratum conyzoides using earthworm species Eisenia fetida

Abstract: This study illustrates the feasibility of vermicomposting of an invasive terrestrial weed Ageratum conyzoides for environment and economic benefits. This study presents the different mix proportion of substrate and cow dung as blending material in the vermicomposting process. It also advocates the potential of earthworm species Eisenia fetida for the bioconversion of A. conyzoides into a valuable end product. The work is based on biochemical characterization along with earthworm growth and cocoon production to evaluate the properties of the final product. The vermicompost obtained from all the reactors attained stabilization with increase in nutrients and decrease in total organic carbon (TOC), CO2 evolution rate after the end of the process. The pH was obtained in the range of 6.7–7.4 during vermicomposting. The final C/N ratio falls within 12–17 in all the reactors. The highest Total Kjeldahl Nitrogen (TKN) value observed in the final vermicompost was 2.67% which was higher than the initial value 1.83%. TOC decreased up to 30.05% at the end of the process. The earthworm biomass increased in a similar trend in all the reactors with highest biomass change of 25.75%. The results indicate that the biomass of A. conyzoides can be efficiently utilized to produce a mature vermicompost with the potential of further applications. It may be inferred from the findings that vermicomposting can be an alternative environment friendly option for the management of A. conyzoides and recommendable for on site management of the weed in an economical way.

Evolution of wireless sensor network design from technology centric to user centric: An architectural perspective:

Abstract: Wireless sensor networks form the crux of a wide range of automated applications that are gaining popularity with every passing day. The journey of wireless sensor networks has seen simple sensory ...

Enhanced Sparse Vector Coding for Ultra-Reliable and Low Latency Communications

Abstract: An important observation in the ultra-reliable and low latency communications is that the size of transmit information is tiny. To support the effective short packet transmission, a sparse vector coding (SVC) scheme where an information is encoded into the positions of the sparse vector was proposed. In this paper, we propose a novel SVC technique further improving the reliability of the short packet transmission. Key idea of the proposed technique is to encode information both in the position as well as symbols. From the performance analysis and numerical evaluations on realistic channel models, we demonstrate that the proposed scheme outperforms the conventional SVC scheme in terms of the block error rate (BLER) and transmission latency.

Performance analysis of internally helically v-grooved absorber tubes using nanofluid

Abstract: With the depletion of fossil fuel effective utilization and efficient collection of solar energy has gained popularity in the recent days. In the present study an attempt is made for the performance improvement of parabolic trough collector (PTC) by modifying absorber tube with internally helically groove. Further, base working fluid of water is replaced with Aluminium oxide (Al2O3) nanofluid (3–8% by volume) for better thermal performance. Tests are performed considering 600, 800, and 1000 W/m2 heat flux at the tube outer surface. ANSYS Fluent 14.0 is used to simulate the problem considering two distinct Reynolds number (Re) of 4000 and 6000. Results indicate that with the increase in concentration of Al2O3 from 3% to 8%, pressure drop is increased by 14.5%. Heat transfer coefficient is enhanced by as high as 13.8% with the nanofluid compared to base fluid working at heat flux of 1000 W/m2 and Re = 4000. Further, increase in the value of Re from 4000 to 6000 heat transfer coefficient with nanofluid is increased by as high as 41.3%.

An Adaptive Differentiation Frequency Based Advanced Reference Current Generator in Grid-Tied PV Applications

Abstract: In this article, an advanced reference current generator employing a combination of novel dual multi-layer fifth-order generalized integrator and adaptive differentiation frequency locked loop scheme (DMFOGI-dFLL) is proposed for mitigation of harmonics present in a grid-tied photovoltaic (PV) system. The proposed DMFOGI reference current generator is utilized to separate the fundamental constituents from grid voltage distortions, sag, swell, unbalance, frequency variation, and dc offset conditions. In addition, a dFLL is implemented to estimate the system frequency adaptively at grid transient conditions, which is fed as feedback to the pre-filtering unit. Similarly, a fuzzy tuned proportional integral derivative (FPID) voltage controller is incorporated in the proposed controller to maintain the power balance between dc and ac sides by controlling the dc-link voltage. An incremental conductance (IC) control technique is additionally utilized to generate maximum power from the PV source through a boost converter. The proposed system is simulated on MATLAB/SIMULINK under various transient conditions, such as steady state, voltage sag, swell, distorted, unbalance, dynamic load, and load shedding conditions. Moreover, the overall system is developed on a laboratory prototype experimental setup. The simulation outcomes are validated through an experimental platform under above said conditions in respect of total harmonic distortion (THD) of grid current and voltages. Results of the system are found well and also maintained within the standard limits of IEEE-519.

FPGA-Based Real-Time Implementation of Quadral-Duty Digital-PWM-Controlled Permanent Magnet BLDC Drive

Abstract: Brushless dc (BLDC) motors are sparsely employed for domestic applications due to the mandatory cost inflation related to BLDC drive besides their numerous constructional advantages. Controllers involving lesser computational complexity, which ultimately leads to reduced-size application-specific integrated circuits (ASICs) for the drive, are highly advantageous in addressing the issue. Recent state-of-the-art dual-duty digital pulsewidth modulation (DDDPWM) techniques are among such. However, the DDDPWM-based controller restricts the motor speed within a narrow range, and the motor suffers from inevitable speed and torque ripples. In this article, an advanced quadral-duty digital pulsewidth modulation (QDDPWM) technique has been proposed to drive the BLDC motor. The QDDPWM-technique-based BLDC motor drive can be controlled in a wider range of speed with reduced steady-state speed ripples, audible noise, and vibrations. The controller has been implemented in real-time using field-programmable gate array, which can also be fabricated in a reduced-size ASIC. Various dynamic and steady-state speeds, vibration responses, time response, and speed tracking ability have been examined and reported in this article. The effectiveness of the proposed technique is justified by the comparison of the real-time responses with the DDDPWM-algorithm-based BLDC motor drive.

A Novel Hybrid Neural Network-Based Multirobot Path Planning With Motion Coordination

Abstract: Multi-robot navigation is a challenging task, especially for many robots, since individual gains may more often than not adversely affect the global gain. This paper investigates the problem of multiple robots moving towards individual goals within a common workspace whereas the motion of every individual robot is deduced by a novel Particle Swarm Optimization (PSO) tuned Feed Forward Neural Network (FFNN). Motion coordination among the robots is implemented using a cooperative coordination algorithm that identifies critical robots and maintains cooperation count while actuating deviation in select robots. The contribution of this paper is twofold; firstly in hybridizing the Artificial Neural Network(ANN) by employing PSO, an evolutionary algorithm, to find optimal values of deviation for every critical robot using velocity and acceleration constraints, secondly ensuing the convergence of the PSO by carrying first and second order stability analysis. Experiments have been carried out to evaluate and validate the efficacy of the proposed coordination schemes by changing the number of robots under hundred different scenarios each, and the founded results demonstrate the efficacy of the proposed schemes.

Unsteady MHD free convective flow past a permeable vertical plate with periodic movement and slippage in the presence of Hall current and rotation

Abstract: The present investigation aims to analyze unsteady magnetohydrodynamic free convective flow of an electrically conducting and incompressible fluid past a permeable and periodically moving infinite flat plate with slippage at the surface in the presence of Hall current, rotation, thermal radiation and internal heat generation/absorption. The model equations are converted into non-dimensional form using suitable dimensionless variables and parameters. Exact analytical solutions, in closed form, for the velocity and temperature fields have been obtained upon solving these non-dimensional equations with the help of Laplace transform technique. The impact of various physical parameters on the velocity and temperature fields are illustrated and depicted in graphical form. Moreover, numerical values of coefficient of skin friction measuring the shear stress at the surface and Nusselt number measuring the rate of heat transfer at the surface are analyzed and shown in the form of tables.