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T. J. Sudhavani,N. Sivagangi Reddy,K. Madhusudana Rao,K. S. V. Krishna Rao,Jayshree Ramkumar,A. V. R. Reddy 대한화학회 2013 Bulletin of the Korean Chemical Society Vol.34 No.5
Novel chitosan (CS) based membrane networks were developed by solution casting and followed by crosslinking with different crosslinkers such as glutaraldehyde, urea-formaldehyde, and thiourea-formaldehyde. The developed membrane networks were designated as CS-GA, CS-UF and CS-TF. Crosslinking reaction of CS membranes was confirmed by Fourier transform infrared spectroscopy. Membrane rigidity and compactness were studied by the differential scanning calorimetry. The surface morphology of CS membranes was characterized by scanning electron microscopy. The sorption behaviour with respect to contact time, initial pH and initial metal ion concentration were investigated. The maximum adsorption capacity of CS-GA, CS-UF and CS-TF sorbents was found to be 1.03, 1.2 and 1.18 mM/g for Cu2+ and 1.48, 1.55 and 2.18 mM/g for Ni2+ respectively. Swelling experiments have been performed on the membrane networks at 30 oC. Desorption studies were performed in acid media and EDTA and it was found that the membranes are reusable for the metal ion removal for three cycles. The developed membranes could be successfully used for the separation of Cu2+ and Ni2+ metal ions from aqueous solutions.
Sudhavani, T.J.,Reddy, N. Sivagangi,Rao, K. Madhusudana,Rao, K.S.V. Krishna,Ramkumar, Jayshree,Reddy, A.V.R. Korean Chemical Society 2013 Bulletin of the Korean Chemical Society Vol.34 No.5
Novel chitosan (CS) based membrane networks were developed by solution casting and followed by crosslinking with different crosslinkers such as glutaraldehyde, urea-formaldehyde, and thiourea-formaldehyde. The developed membrane networks were designated as CS-GA, CS-UF and CS-TF. Crosslinking reaction of CS membranes was confirmed by Fourier transform infrared spectroscopy. Membrane rigidity and compactness were studied by the differential scanning calorimetry. The surface morphology of CS membranes was characterized by scanning electron microscopy. The sorption behaviour with respect to contact time, initial pH and initial metal ion concentration were investigated. The maximum adsorption capacity of CS-GA, CS-UF and CS-TF sorbents was found to be 1.03, 1.2 and 1.18 mM/g for $Cu^{2+}$ and 1.48, 1.55 and 2.18 mM/g for $Ni^{2+}$ respectively. Swelling experiments have been performed on the membrane networks at $30^{\circ}C$. Desorption studies were performed in acid media and EDTA and it was found that the membranes are reusable for the metal ion removal for three cycles. The developed membranes could be successfully used for the separation of $Cu^{2+}$ and $Ni^{2+}$ metal ions from aqueous solutions.
A New Cascaded Multilevel Inverter Topology with Voltage Sources Arranged in Matrix Structure
Thamizharasan. S,Baskaran. J,Ramkumar. S 대한전기학회 2015 Journal of Electrical Engineering & Technology Vol.10 No.4
The paper unleashes a new idea to arrive at reduced switch count topological structures configured in the form of a matrix for a cascaded Multi level inverter (CMLI). The theory encircles to minimize the number of switches involved in the conduction path and there from acclaim reduced input current distortion, lower switching losses and electromagnetic interference. The focus extends to standardize the number of power devices required for reaching different levels of output voltage from the same architecture. It includes appropriate pulse width modulation (PWM) strategy to generate firing pulses and ensure the desired operation of the power modules. The investigative study carries with it MATLAB based simulation and experimental results obtained using suitable prototypes to illustrate the viability of the proposed concept. The promising nature of the performance projects a new dimension in the use of single phase MLIs for renewable energy related applications.
Electro-discharge machining performance of TiCN-based cermets
Manoj Kumar, B.V.,Ramkumar, J.,Basu, B.,Kang, S. MPR Pub. Services 2007 INTERNATIONAL JOURNAL OF REFRACTORY METALS AND HAR Vol.25 No.4
The present investigation aims at evaluating the die sinking electro-discharge machining (EDM) performance of TiCN-20wt.% Ni cermets containing 10wt.% of different secondary carbides: WC, NbC and TaC. Such performance is assessed in terms of making cavity of 1mm depth on a commercial high speed tool steel (HSS). The material removal rate (MRR) is found to be higher for TiCN-20wt.% Ni cermet; however tool wear ratio (TWR) is lower for TiCN-20Ni-10TaC cermet. The quality of cermet tool surface has been quantitatively assessed using surface roughness tester and it was observed that the roughness (R<SUB>a</SUB> or R<SUB>z</SUB>) of TiCN-20Ni-10TaC cermet tool surface is lower, when compared with that of other investigated cermets. SEM-EDAX analysis of EDM surfaces reveal melting and evaporation of the binder as well as pull-out and spalling of brittle carbonitride/carbide grains as the dominant wear mechanisms. The layer formation due to solidification of molten layer and/or transfer of material from workpiece is commonly observed for all the cermet tool surfaces.
Vijay Mandal,Shashank Sharma,Sudhanshu S. Singh,J. Ramkumar 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.1
Laser surface texturing can improve the surface properties of the metallic components. In this work, surface texturing hasbeen carried in a powder bed fusion of Inconel 718 (IN718) rather than material removal process. A 2D fnite element method(FEM) has been built to simulate the thermo-fuidic dynamics of surface texturing, incorporating the phase-feld method inthe preplaced IN718 powder. The temperature and induced velocity felds have been predicted using transient heat transferand fuid fow based on the conservation of mass, momentum, and energy in the melt pool. Furthermore, the roles of drivingforces such as Marangoni force, recoil pressure, and thermal buoyancy force on the melt pool behavior have been evaluated. Micro-textures were developed using laser on the powder bed by using diferent scanning patterns, such as line, circle, hatchand convex dimple. The efect of process parameters (pitch distance, number of pulses and number of layers) on the surfacehydrophobicity were evaluated by measuring the contact angle, where the convex dimple texture exhibited the maximumcontact angle. The hydrophobicity was afected by the ripples (2nd level of roughness) on the surface, which increased withan increase in number of pulses.
Performance assessment of microwave treated WC insert while turning AISI 1040 steel
Durwesh Jhodkar,M. Amarnath,H. Chelladurai,J. Ramkumar 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.6
This study attributed to post treatment of tungsten carbide (WC) inserts using microwave irradiation. Tungsten carbide inserts were subjected to microwave radiation (2.45 GHz) to enhance its performance in terms of reduction in tool wear rate, cutting force surface roughness and improvement in tool life. Performance of tungsten carbide insert is very much affected by machine operating parameters i.e. speed, feed and depth of cut. An attempt has been made to investigate the effects of machining parameters on microwave treated tool inserts. This paper describes the comparative study of machining performance of untreated and microwave treated WC tool inserts used for turning of AISI 1040 steel. Machining performance has been evaluated in terms of flank wear, cutting force, surface roughness, tool wear mechanisms. Critical examinations of tool wear mechanisms and improvements in metallurgical properties such as microstructural change, phase activation of WC grains were identified using scanning electron microscope (SEM). Results obtained from the turning using the microwave treated tool inserts showed a significant reduction tool wear thereby enhancing the surface quality of workpiece.
Rajesh Kumar Porwal,Vinod Yadava,J. Ramkumar 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.2
Thin sheets of titanium alloys are widely used in aerospace and automotive industries for specific applications. The creation of microholes with requisite hole quality in thin sheets of these alloys using energy of electric discharge is a challenging task for manufacturingengineers. Hole sinking electrical discharge micromachining (HS-EDMM) is one of the most promising micromachining processes tocreate symmetrical and non-symmetrical micro holes. The present paper is related to selection of optimum parameter settings for obtainingmaximum material removal, minimum tool wear and minimum hole taper in HS-EDMM. In this paper an attempt has been made todevelop an integrated model (ANN-GRA-PCA) of single hidden layer back propagation neural network (BPNN) for prediction and greyrelational analysis (GRA) coupled with principal component analysis (PCA) hybrid optimization strategy with multiple responses of HSEDMMof Ti-6Al-4V. Experiments have been conducted to generate dataset for training and testing of the network where input parametersconsist of gap voltage, capacitance of capacitor and the resulting performance parameters are represented by material removal rate(MRR), tool wear rate (TWR), and hole taper (Ta). The results indicate that the integrated model is capable to predict and optimize processperformance with reasonable accuracy under varied operating conditions of HS-EDMM. The proposed approach would be extendableto other configurations of EDMM processes for different materials.