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Anirban Bhattacharya,Ajay Batish,Naveen Kumar 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.1
The present study reports the results of an experimental work carried out to evaluate the improvement in machined surface properties of die steels machined using powder mixed electric discharge machining (PMEDM) process. Two surface responses, surface finish and microhardness were analyzed for changes when machined with Si, W and graphite powders mixed in dielectric fluid. The machined surfaces were subsequently analyzed using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) to study the element migration from powder, dielectric and the tool. The powder mixed with dielectric and its concentration, current and pulse on time were identified as the significant factors affecting surface finish. Brass electrode and tungsten powder resulted in good surface finish. Amongst the dielectrics used, kerosene provided a better cooling effect whereas EDM oil resulted in better surface finish. The microhardness of the machined surface was also affected by powder and its concentration, current, pulse on time and electrode material. W-Cu electrode and W powder resulted in a higher microhardness. The SEM and EDS analysis showed significant migration of material from the suspended powder, electrode and dielectric to the machined surface.
Design of a cost-effective electrochlorination system for point-of-use water treatment
Mainak Bhattacharya,Koyel Bandyopadhyay,Anirban Gupta 대한환경공학회 2021 Environmental Engineering Research Vol.26 No.5
Bacteriological contamination in drinking water is known to be responsible for the spread of various waterborne diseases. Although chlorine is frequently used as disinfectant in water treatment, low-cost disinfecting technologies in the villages of developing and under-developed countries are not yet successfully implemented. This study contributed in designing a simple and inexpensive water disinfection unit to produce chlorine from the naturally available dissolved chloride of groundwater by electrochlorination, using inert and cheap graphite electrodes. Laboratory-based experiments were performed in both batch and continuous flow reactors to study the effect of time, current, electro charge loading (ECL), and surface area of electrodes in chlorine generation and bacterial inactivation. Controlled experiments in continuous mode in the absence of chlorine further indicated the possibility of partial inactivation of bacteria under the influence of the electric field. Finally, a treatment unit with drilled anodes, and undrilled cathode electrodes, in continuous flow set-up was installed in four schools of four different villages in West Bengal, India. An average residual chlorine concentration and removal efficiency of total coliform in the designed systems were determined as 0.3 ± 0.07 ㎎/L, and 98.4% ± 1.6%, respectively.
Ajay Batish,Anirban Bhattacharya,Manwinder Kaur,Manjot Singh Cheema 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.5
The present study reports the effect of different process parameters on machining forces, surface roughness, dimensional deviation and material removal rate during hard turning of EN31, SAE8620 and EN9 tool steels. Feed rate followed by hardness, cutting speed and nose radius-depth of cut significantly affected machining forces whereas feed rate had the largest effect on surface roughness. The four responses were subsequently optimized for both rough and finish machining using genetic algorithm to determine the optimum combination of input parameters. Machined surfaces were subsequently analyzed using XRD followed by analysis of grain size and crystallite size of the machined samples and SEM analysis. Higher chromium content was observed at the machined surface as manganese dissolves in cementite and may replace iron atoms in the cementite lattice after machining. High heat is generated when machining at higher cutting speeds causing severe strain. The depth of the white layer decreases with increasing tool nose radius and increases at larger feeds because of greater heat generation. The SEM observations showed a smooth pattern with very low undulations with almost no crack damage.
Min, Sun-Hong,Kwon, Ohjoon,Sattorov, Matlabjon,Jung, Hoechun,Baek, In-Keun,Kim, Seontae,Bera, Anirban,Barik, Ranjan Kumar,Bhattacharya, Ranajoy,Park, Gun-Sik IEEE 2017 IEEE transactions on plasma science Vol.45 No.4
<P>Researchers have investigated plasma-related phenomena and internal breakdowns in the gigawatt-terahertz relativistic backward wave oscillator (RBWO) caused by field emissions from the surfaces of the waveguide circuits in these oscillators. In order to increase the power-handling capability of relativistic electron beam devices, an RBWO is proposed in the form of an oversized structure in which the diameter (D) of the electrodynamic structure is increased to several times the free-space wavelength (lambda). An optimal periodic rectangular corrugation structure of which the axial mode is matched to the pi mode is designed in order to determine only the TM01 mode without mode competition in a slow-wave structure (SWS). The oversized RBWO has a fairly large diameter and uses a resonant reflector to achieve optimum efficiency while also preventing mode competition in the SWS. Absorption of a decelerated electron beam is achieved by the collector, which protects against breakdown and damage. The results of 0.5-0.1 THz from 500 kV-5 kA in the relativistic region are observed by means of a particle-in-cell simulation, and the dispersion relationship is determined by a finite-difference time-domain simulation. The outcomes show that a high-power oversized RBWO can control the selection of the mode and the interaction efficiency.</P>
Efficient terahertz oscillation using a half-period staggered grating resonator
Kwon, Ohjoon,Sattorov, Matlabjon Abdurahimovich,Min, Sun-Hong,Baek, In-Keun,Kim, Seontae,Bera, Anirban,Barik, Ranjan Kumar,Bhattacharya, Ranajoy,Jeong, Jin-Young,Won, Jong-Hyo,Park, Gun-Sik IOP Publishing 2014 Japanese journal of applied physics Vol.53 No.6
A highly efficient terahertz (THz) radiation mechanism is studied with the use of strong interaction between convection electrons and a half-period phase-shifted grating resonator. The large fraction of the fundamental TE mode is longitudinally polarized, and it excites the intense plasma-terahertz wave coupling at the shallow grating, which enables highly efficient RF generation at a relatively low operating voltage. A particle-in-cell (PIC) simulation predicts that the half-period phase-staggered grating resonator generates 0.22 THz wave with output power exceeding 100 W and interaction efficiency of more than 15% at a low beam acceleration voltage of 5.2 kV. (C) 2014 The Japan Society of Applied Physics