National Institute of Technology, Silchar

About: National Institute of Technology, Silchar is a education organization based out in Silchar, Assam, India. It is known for research contribution in the topics: Computer science & Control theory. The organization has 1934 authors who have published 4219 publications receiving 41149 citations. The organization is also known as: NIT Silchar.

Study of optical parameters of two fluorinated isothiocyanato nematic liquid crystals exhibiting high birefringence

Abstract: Optical studies have been carried out on two fluorinated isothiocyanato nematic liquid crystal (LC) compounds 4′-butylcyclohexyl-3, 5-difluoro-4-isothiocyanatobiphenyl and 4′-pentylcyclohexyl-3, 5-difluoro-4-isothiocynatobiphenyl. Transition temperatures of the two samples were confirmed using a polarizing microscope. The two LC compounds were found to exhibit fairly high clearing temperatures. Measurements of refractive indices of the two compounds were done by using thin prism method with He-Ne laser beam of wavelength 630 nm. Birefringence of the two LC compounds was calculated from the measured refractive indices. Both the compounds are found to display fairly high values of birefringence. Validation of a modified four-parameter model, based on Vuks equation describing the temperature dependence of refractive indices of the two liquid crystals, is also presented in this paper. The model is validated by fitting the experimentally measured values of refractive indices, birefringence and average refractive indices of the two nematic LCs with the theoretical values. In this paper, the calculation of order parameters of the LCs is presented by using two methods: direct extrapolation method based solely on the birefringence data and by using modified Vuks method based on Haller’s extrapolation. As observed from the obtained results, this procedure of calculating order parameter gives very reasonable results.

Performance Measurement of a Three-Bladed Combined Darrieus-Savonius Rotor

Abstract: Combination of Savonius and Darrieus type Vertical Axis Wind Turbine (VAWT) rotors possess many advantages over their individual designs, like low starting torque, high power coefficient, low cut-in wind speed etc. However, there is still a need to do more research on such combination of rotors for their viability in the built environment where wind speed is low. In this paper, an attempt is made to measure the performance of a three-bladed combined Darrieus-Savonius rotor, with Darrieus mounted on top of Savonius rotor, for overlap variations from 10.8% to 25.8%. Power coefficients (C p ) and torque coefficients (C t ) were calculated in a low range of Tip Speed Ratio for each overlap condition. It is found that C p increases with the increase of overlap. However, there is an optimum value of overlap for which, C p is maximum, beyond this, C p starts decreasing. The similar trend is observed for C t as well. The maximum C p of 0.53 is obtained at 0.604 Tip Speed Ratio (TSR) for an optimum 16.8% overlap. The performance of the rotor is also compared with another version of this hybrid design with Savonius mounted on top of Darrieus rotor. The present Darrieus-Savonius rotor can be suitably placed in the built environment where it can harness more power from wind and, at the same time, would self-start in low wind condition prevalent in such environment.