National Institute of Technology, Meghalaya

About: National Institute of Technology, Meghalaya is a education organization based out in Shillong, India. It is known for research contribution in the topics: Control theory & Computer science. The organization has 503 authors who have published 1062 publications receiving 6818 citations. The organization is also known as: NIT Meghalaya & NITM.

Sensitivity Enhancement of Current Mirror Readout Circuit Based Piezoresistive Pressure Transducer Using Differential Amplifier

Abstract: This work describes an idea of implementing differential amplifier for enhancing the sensitivity of NMOS current mirror readout circuitry based piezoresistive pressure sensor. The complete pressure sensing structure along with differential amplifier consists of five n-channel MOSFETs which were designed and simulated using five micron CMOS technology parameters in T-Spice software for a drain current of 1 mA. The NMOS current mirror circuit has three n-channel MOSFET. MOSFET M1 of current mirror circuit acts as a reference transistor whereas MOSFET M2 and M3 act as the pressure sensing transistor. The pressure sensing MOSFETs M2 and M3 are embedded on a flexible square silicon diaphragm to sense both tensile and compressive stresses induced under an externally applied pressure. An n-channel MOSFET based differential amplifier consist of two MOSFETs M4 and M5 in common source configuration has been used to enhance the pressure sensitivity by amplifying the output voltage. The piezoresistivity in n-channel MOSFET has been studied for the calculation of carrier mobility variation in the channel region MOSFET under uniformly applied externally pressure. The pressure sensitivity of current mirror readout circuit based pressure sensor enhances from 783 mV/MPa to 1638 mV/MPa by using n-channel MOSFET based differential amplifier circuit.

Wavelet based Islanding Detection in a Three-Phase Grid Collaborative Inverter System using FPGA Platform

Abstract: Interconnection of the distributed generation (DG) system with utility provides significant benefits. However, it requires a suitable technique to identify the islanding situation and execute tripping signal for disconnection of the DG system from remaining network. Islanding detection techniques are mainly classified as remote, active, passive and signal processing techniques. The passive methods have significant advantages like lower power quality degradation, lower cost etc. over the active method, however, it has limitations due to large Non-Detection Zone (NDZ) and threshold setting. Various signal processing techniques are adopted to overcome these limitations of the passive islanding technique. This paper presents a Discrete Wavelet Transform (DWT) based signal processing island detection technique for utility-interactive DG system. The DWT based island detection method provides time-frequency localization of the islanding situation and executes a signal to disconnect the DG system from the rest of the power system. The experimental feasibility of the proposed method is verified using Xilinx System Generator (XSG) via MATLAB/Simulink platform for demonstrating the competency of db8 Wavelet Transform (WT) under various disruptions.

Effect of intake manifold design on the mixing of air and bio-CNG in a port-injected dual fuel diesel engine

Abstract: The awareness for an effective utilization of renewable energy and alternative fuels has been increasing. As alternative fuels, both liquid and gaseous biofuels have huge resources. A bio-CNG is a form of biogas with increased methane content. The present study comprises the development of intake manifold with the port fuel injector and investigate the mixing characteristics of air and bio-CNG. The aim of the study is to analyse the effect the R/D ratio on the flow behaviour and mixture formation of air and bio-CNG. The four configurations of intake manifold are investigated. The ratio of radius of curvature of manifold bend (R) to the diameter of manifold (D) is varied as 1, 1.5, 1.75 and 2. The port fuel injector for bio-CNG induction is placed at 200 mm from the manifold. The objective is to optimize the intake manifold to deliver the homogeneous mixture of air and bio-CNG inside the engine cylinder. As the bio-CNG is new age fuel, being produced to reduce the import of conventional CNG, the work for optimization of port injector and intake manifold are hardly available. The geometries are made in PTC-Creo 3.0, followed by CFD simulation in ANSYS Fluent. The different configurations are analysed for the comparison of the parameters such as, pressure, velocity, turbulence kinetic energy, helicity and mass fraction of CH4. The results show that the distribution of bio-CNG near the outlet of the manifold is uniform and homogeneous for the manifold with R/D ratio of 1.75 and 2.

Experimental and Numerical Flow Simulation over Weirs

Abstract: This paper reports a series of experimental studies done to simulate the flow behavior over crump and ogee type of weirs. The transition of subcritical to supercritical flow, as it moves over weir crest is experimentally simulated. The steady state centreline water surface elevations for several discharge values are measured and noted for both the weirs. Moreover, another numerical model is also developed for the same purpose. In this regard, the shallow water equations in a deviatoric version are solved with an efficient and simple finite difference method. The numerical results obtained are found to be almost exactly matching with the experimental results. The quality of the numerical results are further tested with the help of two indicators namely, Nash indicator and Index of Agreement. The excellent values for these two parameters establish the potential of the proposed model for this type of mixed flow scenarios.