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S. Sivasankaran,K. R. Ramkumar,Fahad A. Al‑Mufadi,Osama M. Irfan 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.6
Al 7075 alloy matrix reinforced with different weight percentage of titanium borides (TiB2, 0, 1.5, 3, 4.5 and 6 wt%) and1 wt% graphite (Gr) hybrid composites were synthesized by in-situ liquid metallurgy route, then the sliding wear characteristicswere performed and investigated in this research work. TiB2reinforced as 0, 1.5, 3, 4.5 and 6 wt% by the in situchemical reaction of KBF4and K2TiF6salts and 1 wt% Gr with the Al 7075 matrix were added constantly in the melt. Severalexperiments were carried out to examine the wear behavior of the fabricated composite specimens through a tribometer atambient temperature. The weight percentage of reinforcement (TiB2 particles), the applied load, the sliding velocity (SV),and the sliding distance (SD) were selected as process parameters at five different levels. The response surface methodology(RSM) was used to conduct the experiments as RSM is the feasible and accurate method employed for optimizing to set theparameters. To check the significance of the developed model by RSM, ANOVA and confirmatory tests were also accomplished. FESEM surface morphology was also carried out to illustrate the uniform dispersion of the TiB2–Gr particulatesin Al 7075 matrix. The predicted wear characteristics from the developed model were well agreed with the experimentalresults. The obtained results were explained that both the increase in the percentage of RF and SV have dropped the wearloss (WL) curve whereas the load at all SVs and the SDs were uplifted the WL. The worn surface morphology explainedthat the adhesive mechanisms were dominated during the sliding wear test. Further, severe and mild wear occurred duringhigher load and lower load respectively.
Retardation of Grain Growth in Al 3003 Nanocomposite Weldment Using ARB Filler Metal
K. R. Ramkumar,S. Natarajan 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.7
This research demonstrates the feasibility of fller rod fabrication to develop nanocomposite weldment to enhance the jointstrength via ARB technique. Al 3003 alloys were joined through GTAW by melting fabricated nanocomposite fller metal. TiO2 nanoparticles were chosen as reinforcement from 0 to 3 wt%. Roll bonding is desired owing to the proper distributionof TiO2 particles. SEM depicted the distribution of reinforcement particles in the grain boundaries. TEM disclosed theuniformity in particulates distribution, peening of dislocation and strain felds in 12 wt% TiO2 reinforced nanocompositeweldment. EBSD portrayed the grain refnement occurred in the weld zone due to reinforcement addition. The improvementin impact and bending strength were due to excellent bonding between the Al and reinforcement particles and excellent loadtransfer ability provided by reinforcement particles.
( K. Ramkumar ),( P. Calduwel Newton ) 한국인터넷정보학회 2018 KSII Transactions on Internet and Information Syst Vol.12 No.12
Adaptive Multi-Rate Codec is one of the codecs which is used for making voice calls. It helps to connect people who are scattered in various geographical areas. It adjusts its bit-rate according to the user’s channel conditions. It plays a vital role in providing an improved speech quality of voice connection in Long Term Evolution (LTE). There are some constraints which need to be addressed in providing this service profitably. Quality of Service (QoS) is the dominant mechanism which determines the quality of the speech in communication. On several occasions, number of users are trying to access the same channel simultaneously by standing in a particular region for a longer period of time. It refers to Multi-user channel sharing problem which leads to resource loss very often. The main aim of this paper is to develop a novel RSA - QoS scheduling algorithm for reducing the Resource Loss Ratio. Eventually, it increases the throughput.The simulation result shows that the RSA - QoS increases the number of users for accessing the resources better than the existing algorithms in terms of resource loss and throughput. Ultimately, it enhances the QoS in Mobile Networks.
K. RAMKUMAR,K. RAVIKUMAR,DIMPLEKUMAR CHALISHAJAR,A. ANGURAJ,MAMADOU ABDOUL DIOP The Korean Society for Computational and Applied M 2023 Journal of applied and pure mathematics Vol.5 No.1/2
This paper is concerned by the controllability results of impulsive neutral stochastic functional integrodifferential equations (INSFIDEs) driven by fractional Brownian motion with infinite delay in a real separable Hilbert space. The controllability results are obtained using stochastic analysis, Krasnoselkii fixed point method and the theory of resolvent operator in the sense of Grimmer. A practical example is provided to illustrate the viability of the abstract result of this work.
K. Ramkumar,K. Ravikumar,Dimplekumar Chalishajar,A. Anguraj,Mamadou Abdoul Diop 한국전산응용수학회 2023 Journal of Applied and Pure Mathematics Vol.5 No.1
This paper is concerned by the controllability results of impulsive neutral stochastic functional integrodifferential equations (INSFIDEs) driven by fractional Brownian motion with infinite delay in a real separable Hilbert space. The controllability results are obtained using stochastic analysis, Krasnoselkii fixed point method and the theory of resolvent operator in the sense of Grimmer. A practical example is provided to illustrate the viability of the abstract result of this work.
K. Navaneetha Pandiyaraj,A. Arun Kumar,M.C. RamKumar,K. Thirupugalmani,Avi Bendavid,Pi-Guey Su,S. Uday Kumar,P. Gopinath 한국물리학회 2016 Current Applied Physics Vol.16 No.7
In the present investigation, we have studied the influence of oxygen (O2) flow rate in the atmospheric pressure argon (Ar) plasma zone for improvement of the surface and cell compatible properties of LDPE film. Various characterization techniques such as contact angle (CA), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), etc were used to investigate the hydrophilicity, surface chemistry and morphology of LDPE films respectively. Fowke's approximation method was used to evaluate the polar and dispersion components of the total surface energy of LDPE films using contact angle values of three testing liquids. Moreover T-peel and lap shear tests were used to analyze the adhesive strength of the surface modified LDPE films. Finally cyto-compatibility of the surface modified LDPE film was analyzed by in vitro cell compatibility analysis which includes the cell viability and adhesion using NIH-3T3 fibroblast cells. The results obtained from various characterization techniques evidently revealed that cold atmospheric pressure (CAP) plasma treatment enhanced the surface properties (hydrophilicity, surface morphology and surface chemistry) of LDPE film. Owing to tailored physico-chemical changes induced by the CAP plasma treatment facilitates improvement in adhesive strength as well as adhesion and proliferation of cells on the surface of LDPE films.
K. Gokul Kumar,K. Devendranath Ramkumar,N. Arivazhagan 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.3
This article investigated the weldability, metallurgical and mechanical properties of Inconel 625 and AISI 316L stainless steel weldmentsobtained by continuous current (CC) and pulsed current (PC) gas tungsten arc welding (GTAW) processes employing ERNiCr-3and ER2209 fillers. Microstructure studies showed the migrated grain boundaries at the weld zone of ERNiCr-3 weldments and multidirectionalgrain growth for ER2209 weldments. It was inferred from the tension tests that the fracture occurred at the parent metal ofAISI 316L in all the cases. Charpy V-notch impact tests accentuated that the CCGTA weldments employing ERNiCr-3 filler offeredbetter impact toughness of 77 J at room temperature. Further a detailed study has been carried out to analyze the structure - property relationshipsof these weldments using the combined techniques of scanning electron microscopy (SEM) and energy dispersive spectroscopy(EDS) analysis.
Jaspreet K. Sembi,Himani,Thakku R. Ramkumar,Shivi Tyagi,Himanshu Sharma,Santosh K. Upadhyay 한국식물생명공학회 2019 JOURNAL OF PLANT BIOTECHNOLOGY Vol.46 No.4
Orchids are indispensable to the floriculture industry due to their unique floral organization. The flowers have two outer whorls of tepals including a lip (labellum), and two inner whorls, pollinia and gynostemiun (column). The floral organization and development is controlled at the molecular level, mainly by the MADS-box gene family, comprising homeotic genes divided into type I and type II groups. The type I group has four sub-groups, Mα, Mβ, Mγ, and Mδ, playing roles in seed, embryo, and female repro-ductive organ development; the type II group genes form classes A, B, C, D, and E, which are a part of the MIKCC subgroup with specific roles in florigenesis and organization. The coordinated functioning of these classes regulates the development of various floral whorls. The availability of genome and transcriptome sequence data for Phalaenopsis equestris offers an opportunity to validate the ABCDE model of flower development. Hence, this study sought to characterize the MADS-box gene family and elucidate of the ABCDE model. A total of 48 identified MADS-box proteins, including 20 type I [Mα (12), Mγ (8)] and 28 type II [MIKCC (27), MIKC* (1)] members, were characterized for physico-chemical features and domains and motifs organization. The exon-intron distribution and the upstream cis-regulatory elements in the promoter regions of MADS-box genes were also analysed. The discrete pace of duplication events in type I and type II genes suggested differential evolutionary constraints between groups. The correlation of spatio-temporal expression pattern with the presence of specific cis-regulatory elements and putative protein–protein interaction within the different classes of MADS-box gene family endorse the ABCDE model of floral development.
Flow Stress Modeling for Copper under Changing Process Conditions
Oruganti, Ramkumar K .,Rao, K . P . 대한금속재료학회(대한금속학회) 1998 METALS AND MATERIALS International Vol.4 No.3
Realistic simulation of metal forming processes requires constitutive equations that describe the behavior of a material under varying process conditions. The equations that have hitherto been developed to address this problem are generally too involved and require the determination of many constants. In this paper, a simple approach based on the representative nature of the work hardening rate, which enables the use of an elementary rate equation in such modelling, is introduced. A prediction methodology based on the concept of fading memory is developed and is found to give good predictions in the case of copper. A mechanistic interpretation of the approach is proposed.