North Eastern Regional Institute of Science and Technology

About: North Eastern Regional Institute of Science and Technology is a education organization based out in Itanagar, India. It is known for research contribution in the topics: Population & Raman spectroscopy. The organization has 813 authors who have published 1429 publications receiving 16122 citations.

Microgrid System for A Rural Area - An Analysis of HOMER Optimised Model Using MATLAB

Abstract: There have been many methods of attaining a suitable combination of renewable energy sources. This work analyses the stability of one such system optimised by HOME-Rquickstart for a small community at Gurmia, India; on the occurrence of faults. The chosen location has a fair potential of solar and wind energy, trapping of these resources efficiently in the form of hybrid microgrid systems could solve major power issues and in the same time supersede the old grids. This work involves simulation of an optimised model obtained from HOMERquickstart package using Simulink. Various cases are considered in interlinking of the energy sources for the microgrid and their respective transient behaviour in the occurrence of faults are observed.

Structural and electrical studies of Ba5RTi3V7O30 (R=Ho, Gd, La) compounds

Abstract: The ferroelectric ceramics Ba5RTi3V7O30 (R=Ho, Gd, La) have been synthesized by solid-state reaction technique. Preliminary X-ray structural analysis confirmed a single-phase formation of the compound in orthorhombic structure. Surface morphology of the compounds was studied by scanning electron microscopy (SEM). Detailed studies of electrical properties (i.e., dielectric constant, loss tangent, ac conductivity) as a function of temperature (RT-773 K) and at four different frequencies (1 kHz, 10 kHz, 100 kHz and 1 MHz) show ferroelectric–paraelectric phase transition of the compounds of diffuse-type. The activation energy has been evaluated from ac conductivity following Arrhenius equation. The conductivity pattern shows that it is strongly frequency dependent and obeys Jonscher's power relation.

Materials Selection Approaches and Fabrication Methods in RF MEMS Switches

Abstract: A state of the art review on Radio Frequency Micro-Electromechanical Systems (RF MEMS) capacitive switches is reported by considering two key aspects: (1) materials selection approaches for improving performance, and (2) fabrication methods used in capacitive MEMS switches. The beam and dielectric materials used in capacitive MEMS switches and the performance achieved through them are reviewed and reported by a rigorous literature survey. Further, materials selection approaches for the beam membrane and the dielectric layer are discussed using Ashby’s methodology, and other associated methods based on it, which uses material indices to evaluate the performance of a switch. Performance indicators for the beam materials selection are the pull-in voltage, RF loss, thermal residual stress, contact resistance, thermal conductivity, and maximum displacement, whereas the hold-down voltage, dielectric charging, leakage current, heat dissipation, capacitance ratio, and stability are performance indicators in dielectric materials selection. MEMS switch fabrication can be achieved through bulk micromachining processes and surface micromachining processes, but the surface micromachining process has been preferred over the last few decades. The fabricated MEMS switch components can be integrated using a monolithic complementary metal oxide semiconductor–micro-electromechanical systems (CMOS-MEMS) process for the realization of applications in sensors, resonators, amplifiers, phase shifters, and MEMS satellite vehicles for space applications. CMOS-MEMS monolithic fabrication is discussed further with the help of fabrication process involved and the process technology. The TSMC-CMOS 0.35 $$\upmu \hbox {m}$$ technology is one of the leading technologies in CMOS-MEMS fabrication and is mainly used.

Improving Prediction Accuracy of Rainfall Time Series By Hybrid SARIMA–GARCH Modeling

Abstract: In this paper, a hybrid of seasonal autoregressive integrated moving average (SARIMA)-generalized autoregressive conditional heteroscedasticity (GARCH) was applied to eliminate conditional variance of the SARIMA model of rainfall time series in two different climatic environments (Agartala: humid, and Jodhpur: arid). In addition, the effectiveness of data normalization techniques (differencing and transformation) to stabilize conditional variance in the SARIMA residuals is additionally examined. The residuals from SARIMA models were tested for heteroscedasticity, utilizing the McLeod–Li test, and demonstrated some autocorrelation. Then, the rainfall time series was transformed (differencing and Box–Cox) so that the effect of heteroscedasticity is eliminated. The hybrid SARIMA–GARCH model based on transformed rainfall time series resulted in good statistics performance indices at both climatic environments. The findings of the study suggest that the performance of SARIMA models can be enhanced by using appropriate transformation (Box–Cox) along with GARCH model of residuals of highly skewed rainfall time series from both climatic environments. For Agartala station of monthly rainfall time series, the best model was SARIMA (0, 1, 1) (0, 1, 1)12–GARCH (1, 2) with coefficient of determination (R2) = 0.72 and root-mean-square error (RMSE) = 25.22, but after Box–Cox transformation of data, the best model was SARIMA (0, 1, 1) (0, 1, 1)12–GARCH (2, 4) with R2 = 0.87 and RMSE = 0.672. For the monthly rainfall series of Jodhpur station, the best model was SARIMA (0, 1, 1) (0, 1, 1)12–GARCH (1, 2) with R2 = 0.68 and RMSE = 16.75, but after Box–Cox transformation of data the best model was SARIMA (0, 1, 1) (0, 1, 1)12–GARCH (1, 2) with R2 = 0.79 and RMSE = 1.917. The performance indices indicate that hybrid (SARIMA–GARCH) models fitted to transformed time-series rainfall data performed best in the humid as well as the arid regions.