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.

Analysis of Chaos and Bifurcation Due to Slotting Effect and Commutation in a Current Discontinuous Permanent Magnet Brushed DC Motor Drive

Abstract: The aim of this paper is to study the dynamics of a permanent magnet direct current (PMDC) brushed motor while two crucial space-domain effects, namely, slotting effect and commutation phenomenon are taken into account. Semi-analytical dynamic time-domain PMDC brushed motor model inclusive of these space-domain effects is used to analyze and investigate the dynamics. Pulse width modulation operated discontinuous current PMDC brushed motor drive with steady duty cycle is employed to acquire the bifurcation patterns. The chaotic nature due to slotting effect and commutation is identified from the bifurcation patterns and reported. It also has to be admired that such nonlinear dynamical behavior with the same set of parameters at similar operating condition has not been observed when a conventional PMDC brushed motor dynamic model is considered. These space-domain effects, namely, slotting effect and commutation also have a prominent impact to make some time-domain states of a PMDC brushed motor drive chaotic. The role of slotting effect and commutation phenomenon to analyze the chaos over time-domain state variables of the PMDC brushed motor drive is investigated and validated experimentally in this paper.

Two parameter exponentiated Gumbel distribution: properties and estimation with flood data example

Abstract: This article addresses various properties and different methods of estimation of the parameters of exponentiated Gumbel distribution from the frequentist point of view. Various mathematical and statistical properties of the exponentiated Gumbel distribution, such as quantiles, moments, conditional moments, hazard rate function, mean residual lifetime, mean deviation about mean and median, entropies and order statistics, are derived. We briefly describe different frequentist approaches, namely, maximum likelihood estimation, method of moments, percentile-based estimation method, least squares estimation, method of maximum product of spacings, method of Cramer-von-Mises and methods based on Anderson-Darling statistic. Monte Carlo simulations are performed to compare the performance of the estimation methods for small and large samples. The application of the model is studied using a flood data example. Bootstrap method was used to obtain bias and standard error of the estimates as well as the percen...

Reliability Modeling of Microgrid System Using Hybrid Methods in Hot Standby Mode

Abstract: The purpose of this paper is to accomplish the reliability assessment of hot standby microgrid system by using few hybrid methods. This paper has shown relative analysis on failure probability and reliability of microgrid system by means of Markov model, fault tree analysis (FTA) using reduced binary decision diagram (RBDD), and reduced sequential binary decision diagram (RSBDD) approaches. Hot standby mode is usually employed for the enrichment of reliability to prolong the system availability during any catastrophic situation. By analysis, microgrid which falls under the hot standby mode indicates that both the redundant as well as active components have similar failure rates. An inverter dominated photovoltaic system integrated to an IEEE 5-bus microgrid system is designed for which comparative overall system availability is calculated and analyzed in terms of failure probability and reliability by using hybrid approaches. Markov-based models mostly suffer from state-space explosion problems and it needs exponential probability distribution function only. Again, FTA-RBDD and FTA-RSBDD approaches have neither any constraint on time-to-failure distributions nor any computational burden issue. Moreover, FTA-RSBDD-based reliability assessment dealings are reusable with different time-to-failure rates.

Biological conservation through marine protected areas in the presence of alternative stable states

Abstract: This article addresses how depleted stock can be restored by creation of marine reserve and species mobility when alternative stable states persist in a marine ecosystem. To understand the role of a marine protected area, we develop a two-patch version of an originally single-patch model. In the two-patch model, we prove that some of the locally stable equilibria are not stable equilibria from an ecological viewpoint. Similarly, some unstable equilibria determined classically from the mathematical model are no longer equilibria. It is shown that increasing reserve size may produce three alternative stable states in the presence of harvesting. Dynamic solutions have a tendency to reach an upper stable state from a lower stable state when reserve size is increased, but the opposite phenomenon (i.e., shifting to a lower stable state from an upper one) never occurs. This suggests that MPAs always have a positive effect in stock conservation even when alternative stable states inherently persist in marine ecosystems.