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.

Studies on frequency dependent electrical and dielectric properties of sintered zinc oxide pellets: effects of Al-doping

Abstract: Sintered pellets of zinc oxide (ZnO), both undoped and Al-doped are prepared through a chemical process. Dopant concentration of Aluminium in ZnO [Al/Zn in weight percentage (wt%)] is varied from 0 to 3 wt%. After synthesis structural characterisation of the samples are performed with XRD and SEM-EDAX which confirm that all the samples are of ZnO having polycrystalline nature with particle size from 108.6 to 116 nm. Frequency dependent properties like a.c. conductivity, capacitance, impedance and phase angle are measured in the frequency range 10 Hz to 100 kHz as a function of temperature (in the range 25–150 °C). Nature of a.c. conductivity in these samples indicates hopping type of conduction arising from localised defect states. The frequency and temperature dependent properties under study are found to be as per correlated barrier hoping model. Dielectric and impedance properties studied in the samples indicate distributed relaxation, showing decrease of relaxation time with temperature.

Effects of Multiple Semiconducting Screens on Line Parameters and Wave Properties of Underground Cable

Abstract: Along with the geometric and electromagnetic properties, incorporation of multiple semiconducting screens in an underground (UG) power cable influences the primary line parameters as well as wave properties of the cable. The impacts of multiple semiconducting screens in UG cable structure compared to the cable with single and without semiconducting screen have been reported in this paper. The effective impedance of conductor-semiconductor assembly in cable structure is determined based on the electromagnetic theory of tubular conductor. Further, the complete impedance matrix of the UG cable with multiple semiconducting screens is determined in both mesh and phase domain and reported in this paper. The expressions of the impedances of UG cable with multiple semiconducting screens as obtained using the electromagnetic approach also have been reproduced using the conventional loop current method to justify the robustness and accuracy of the adopted approach. Comparative analyses of various line parameters and wave properties between UG cables with multiple, single and without semiconducting screens have been carried out by varying the frequency as well as semiconducting screen properties. Such analyses indicate that the inclusion of multiple semiconducting screens can lead to the improvement in wave properties of UG cable in high frequency zone.

Large-area two-dimensional bismuth selenide crystals synthesized by solution-based control of the nucleation environment

Abstract: Two-dimensional (2D) Bi2Se3 is one of the most studied nanomaterials in recent years because of its fascinating electronic properties. However, previous synthesis methods, especially solution-based methods, were not capable of growing laterally large 2D Bi2Se3 crystals (mostly up to a few micrometers), and thus its real application and in-depth study was practically impossible. In this communication, we report a simple, reliable two-step method to synthesize large (20–50 μm in the lateral diameter and 10–15 nm in the thickness) disks of Bi2Se3 in the presence of ethylenediamine-tetraacetic acid (EDTA) and chloride ion, where EDTA acts as a complexing agent with bismuth(III). Depending on the growth conditions, we obtained 2D Bi2Se3 crystals having either a flat or spiral surface. We have thoroughly characterized the morphology, crystal structures, and electrical properties of these new disks, and we also discussed a possible growth mechanism based on the control over the surface chemistry and the nucleation stage.

Sensing of 0.1 ppm of methanol, ethanol, and propanol vapors at 130°C by SnO2 thin film

Abstract: SnO2 thin film was synthesized by spray pyrolysis. The sensing properties of the same for detecting volatile organic compounds (VOCs) were investigated. It was observed that the sensing was maximum for methanol vapor (96.82%) in case of both experimental and theoretical results. The gas was detected for as low as 0.08 ppm, which has not been reported till date. The Levenberg–Marquardt (LM) algorithm was used for the theoretical analysis using the Electrochemical Impedance Spectroscopy (EIS) Spectrum analyzer. Theoretical calculation revealed that the resistance due to the grain boundary reduces when gases were introduced into the chamber.

CFD Analysis of The Hydraulic Turbine Draft Tube to Improve System Efficiency

Abstract: Demand of the power is increasing day by day with the development of the science and technology. Development of the renewable energy sector has become essential issue at the present situation due to the limited source of the non-renewable energy. Hydro energy power generation sector is superior over the other renewable sector due to the high efficiency, ability to continuous generation and low generation cost. In India a great amount of the power generation is taken care by the hydro power system but still some more potential have unexplored. The efficiency improvement of the hydro turbine system can be done for the new installation or installed system by the improvement in component level. The system can be installed by the state of the art equipment, like modern inlet guide vane (IGV) control system, improved design of the runner, IGV system, draft tube, penstock to reduce the loss, hence improve the efficiency. The energy recovery in the draft tube depends on the design of draft tube. In the present work the optimized design of the draft tube shape through computational fluid dynamics (CFD) simulation has been carried out in ANSYS FLUENT platform. The design objective of the draft tube is to reduce the flow loss and improve the energy recovery, hence to improve the efficiency.