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 & Electric power system. The organization has 503 authors who have published 1062 publications receiving 6818 citations. The organization is also known as: NIT Meghalaya & NITM.

Triazine based polyimide framework derived N-doped porous carbons: a study of their capacitive behaviour in aqueous acidic electrolyte

Abstract: Nitrogen-doped porous carbon materials have been synthesized from nitrogen and oxygen rich triazine based polyimide (TPI-P/TPI-N) frameworks using ZnCl2 as an activating agent at different temperatures (600 and 700 °C) for electrochemical energy storage applications. The morphology and structural features of the materials were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption/desorption isotherms, X-ray photoelectron spectroscopy (XPS) and Raman spectroscopic techniques. The resultant carbon materials possess large specific surface area and rich nitrogen contents. In particular, the material obtained at 700 °C (TPI-P-700) exhibits a surface area of up to 1650 m2 g−1 and a nitrogen content of up to 6.3%, and shows an excellent specific capacitance of 423 F g−1 in an aqueous acid electrolyte (1 M H2SO4) in a three electrode system. Moreover, the material also demonstrates nearly 100% capacitance retention up to 10 000 charge–discharge cycles. A symmetrical supercapacitor device assembled using TPI-P-700 as an active material delivered an energy density of 10.5 W h kg−1 at 0.5 A g−1.

Mathematical modeling of entropy generation in magnetized micropolar flow between co-rotating cylinders with internal heat generation

Abstract: The present study investigates analytically the entropy generation in magnetized micropolar fluid flow in between two vertical concentric rotating cylinders of infinite length. The surface of the inner cylinder is heated while the surface of the outer cylinder is cooled. Internal heat generation (which arises in energy systems) is incorporated. The Eringen thermo-micropolar fluid model is used to simulate the micro-structural rheological flow characteristics in the annulus region. The flow is subjected to a constant, static, axial magnetic field. The surface of the inner cylinder is prescribed to be isothermal (constant temperature wall condition), whereas the surface of the outer cylinder was exposed to convection cooling. The conservation equations are normalized and closed-form solutions are obtained for the velocity, microrotation and temperature. These are thereafter utilized to derive the expressions for entropy generation number, Bejan number and total entropy generation rate. The effects of relevant thermo-physical parameters on the flow, heat and entropy generation rate are displayed graphically and interpreted at length. It is observed that the external magnetic force enhances the entropy production rate is minimum at the center point of the channel and maximum in the proximity of the inner cylinder. This causes more wear and tear at the surface of the inner cylinder. Greater Hartmann number also elevates microrotation values in the entire annulus region. The study is relevant to optimization of chemical engineering processes, nuclear engineering cooling systems and propulsion systems utilizing non-Newtonian fluids and magnetohydrodynamics.

Performance parameters studies in machining of AISI D2 steel with dot-textured, groove-textured & non-textured cutting tool at the flank face

Abstract: Surface texturing is a method where there is a change in tribological properties due to change in surface characteristics. The present work is a comparison of the performance of dot-textured coated carbide tool with groove-textured and non-textured coated carbide tool in machining AISI D2 steel. Micro dot textures are made on the flank face using micro-electric discharge machining. Considering full factorial design, total 8 experiments are performed with cutting speed, feed and depth of cut as process parameters. For each parameter, two levels are considered. Flank wear and surface roughness are investigated to compare the function of dot-textured coated carbide tool with the groove-textured and non-textured coated carbide tool. In every condition, flank wear is less in machining with both types of textured tool in comparison to the non-textured coated carbide tool. In most of the cases, surface roughness is less for both types of textured tool than the non-textured tool. Comparing dot-textured tool over groove-textured tool, it is observed that dot-textured tool is better than the groove-textured tool in reducing flank wear and surface roughness. Analysis of white layer and micro hardness at the machined surfaces revealed that dot-texturing helps in minimizing the thickness of white layer and micro-hardness property in comparison to groove-textured and non-textured tool. Thus, dot texturing is found to be better in improving machinability than groove-textured and non-textured tool.