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Magnetic ground state of the multiferroic hexagonal LuFeO3
Suresh, Pittala,Vijaya Laxmi, K.,Bera, A. K.,Yusuf, S. M.,Chittari, Bheema Lingam,Jung, Jeil,Anil Kumar, P. S. American Physical Society 2018 Physical Review B Vol.97 No.18
<P>The structural, electric, and magnetic properties of bulk hexagonal LuFeO3 are investigated. Single phase hexagonal LuFeO3 has been successfully stabilized in the bulk form without any doping by sol-gel method. The hexagonal crystal structure with P6(3)cm space group has been confirmed by x-ray-diffraction, neutron-diffraction, and Raman spectroscopy study at room temperature. Neutron diffraction confirms the hexagonal phase of LuFeO3 persists down to 6 K. Further, the x-ray photoelectron spectroscopy established the 3+ oxidation state of Fe ions. The temperature-dependent magnetic dc susceptibility, specific heat, and neutron-diffraction studies confirm an antiferromagnetic ordering below the Neel temperature (T-N) similar to 130 K. Analysis of magnetic neutron-diffraction patterns reveals an in-plane (ab-plane) 120 degrees antiferromagnetic structure, characterized by a propagation vector k = (0 0 0) with an ordered moment of 2.84 mu(B)/Fe3+ at 6 K. The 120 degrees antifferomagnetic ordering is further confirmed by spin-orbit coupling density functional theory calculations. The on-site coulomb interaction (U) and Hund's parameter (J(H)) on Fe atoms reproduced the neutron-diffraction Gamma(1) spin pattern among the Fe atoms. P-E loop measurements at room temperature confirm an intrinsic ferroelectricity of the sample with remnant polarization P-r similar to 0.18 mu(C) cm(2). A clear anomaly in the dielectric data is observed at similar to T-N revealing the presence of magnetoelectric coupling. A change in the lattice constants at T-N has also been found, indicating the presence of a strong magnetoelastic coupling. Thus a coupling between lattice, electric, and magnetic degrees of freedom is established in bulk hexagonal LuFeO3.</P>
Characterizations of plasma sprayed composite coatings over 1020 mild steel
P. Vijayanand,Amitesh Kumar,K. R. Vijaya Kumar,A. Vinod,P. Kumaran,S. Arungalai Vendan 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.10
The present work deals with the coating of mild steel using plasma spray coating technique to improve surface properties for various industrial applications. Three different composite coating powders namely Al 2 O 3 :TiO 2 , Al 2 O 3 :TiO 2 : CNT and Al 2 O 3 : CNT were coated on the surface of mild steel for a thickness of 0.25 mm. Subsequently, the coated samples were tested for their mechanical characteristics namely tensile, compression and hardness followed by tribological investigations primarily comprising of wear analysis. Further, metallurgical analysis engrossing the Scanning electron microscopy, X-Ray diffraction and Energy-dispersive X-ray spectroscopy analysis were carried out to assess the homogeneity, spread uniformity and bond integrity of the developed samples. The test results revealed that the performance measure of Al 2 O 3 :TiO 2 : CNT is way ahead than other two powder coatings while carbon nanotube majorly contributes to the strength and quality of the surface coating.
A Novel Boost PFC Converter Employing ZVS Based Compound Active Clamping Technique with EMI Filter
P. Ram Mohan,M. Vijaya Kumar,O.V. Raghava Reddy 대한전자공학회 2008 Journal of semiconductor technology and science Vol.8 No.1
A Boost Power Factor Correction (PFC) Converter employing Zero Voltage Switching (ZVS) based Compound Active Clamping (CAC) technique is presented in this paper. An Electro Magnetic Interference (EMI) Filer is connected at the line side of the proposed converter to suppress Electro Magnetic Interference. The proposed converter can effectively reduce the losses caused by diode reverse recovery. Both the main switch and the auxiliary switch can achieve soft switching i.e. ZVS under certain condition. The parasitic oscillation caused by the parasitic capacitance of the boost diode is eliminated. The voltage on the main switch, the auxiliary switch and the boost diode are clamped. The principle of operation, design and simulation results are presented here. A prototype of the proposed converter is built and tested for low input voltage i.e. 15V AC supply and the experimental results are obtained. The power factor at the line side of the converter and the converter efficiency are improved using the proposed technique.
A Novel Boost PFC Converter Employing ZVS Based Compound Active Clamping Technique with EMI Filter
Mohan, P. Ram,Kumar, M. Vijaya,Reddy, O.V. Raghava The Institute of Electronics and Information Engin 2008 Journal of semiconductor technology and science Vol.8 No.1
A Boost Power Factor Correction (PFC) Converter employing Zero Voltage Switching (ZVS) based Compound Active Clamping (CAC) technique is presented in this paper. An Electro Magnetic Interference (EMI) Filer is connected at the line side of the proposed converter to suppress Electro Magnetic Interference. The proposed converter can effectively reduce the losses caused by diode reverse recovery. Both the main switch and the auxiliary switch can achieve soft switching i.e. ZVS under certain condition. The parasitic oscillation caused by the parasitic capacitance of the boost diode is eliminated. The voltage on the main switch, the auxiliary switch and the boost diode are clamped. The principle of operation, design and simulation results are presented here. A prototype of the proposed converter is built and tested for low input voltage i.e. 15V AC supply and the experimental results are obtained. The power factor at the line side of the converter and the converter efficiency are improved using the proposed technique.
Characterization of fully and partially penetrated Nd: YAG laser-weld dissimilar metal joints
A. P. Tadamalle,Y. P. Reddy,E. Ramjee,K. Vijaya Kumar Reddy 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.2
Welding dissimilar metals and alloys is essential to emerging new technologies in manufacturing industries. This process is difficult because of the formation of intermetallic layers and the variations in the chemical and mechanical properties in the weld region. This paper aimed to characterize fully and partially penetrated dissimilar metal weld joints. The welding experiments were conducted on 0.5 mm-thick dissimilar weld joints for the investigation of the effects of the process parameters on the weld joints. Variations in chemical composition, oxide formation, imperfections and mechanical properties were analyzed. Results revealed that the weld joint characteristics notably deviated from the base metal properties in terms of hardness, strength, chemical composition, oxide formation and other constituents of the weld pool region. This study offers insight into the effects of process parameters and the necessary changes in weld composition for the improvement of welds joints.
유창규,G. Vijaya Kumar,P. Ramalingam,Min Jung Kim,M. Dharmendira Kumar 한국화학공학회 2010 Korean Journal of Chemical Engineering Vol.27 No.5
Experimental studies and biosorption kinetics of an intraparticle diffusion model for acid dye removal using a musa spp. waste sorbent were carried out to find the removal effects and dynamics of various operating parameters,such as initial dye concentration, sorbent dosage, pH and temperature. Experimental data were modeled with kinetic models and two biosorption isotherms of intraparticle diffusion models as well as the physiochemical data of sorbents characterized by SEM and FT-IR. Kinetic studies showed that the sorption process follows second-order rate kinetics with an average rate constant of 0.0018675 (g/mg·min). Thermodynamic parameters such as entropy of biosorption (ΔS0), enthalpy of biosorption (ΔH0) and Gibbs free energy of biosorption (ΔG0) were obtained and analyzed. Sorbent,musa spp. waste (banana peel) was characterized by FTIR and SEM. The results showed that musa spp. waste can be considered as potential sorbent for the sorption of acid violet 54 from dilute aqueous solution.
Vijayanand Palani,Amitesh Kumar,K. R. Vijaya Kumar,P. Kumaran 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.2
The current study deals with the investigation on the performance characteristics of varying composition of coating mixture comprising carbon nano-tube, alumina and titanium dioxide on the thermal spray coating on mild steel. The performance properties, namely tensile and microhardness, were measured for the varying composition of coating mixture based thermal coating on mild steel. Response surface methodology was adopted to access the interdependencies prevailing between various dependent and independent parameters, namely composition of the mixture, tensile and microhardness. Scanning Electron Microscope coupled with elemental mapping were used to show the melting zones features and composition. The experimental results and response graphs indicated that increased weight percentages of carbon nano-tube and TiO2 with an optimal value of alumina at 87.5 percent of total weight showed better performance properties due to better dispersion leading to good bonding suitable for protective coatings. Scanning Electron Microscope images reveal partially melted zones that were restricted to smaller regions, and all particles tend to solidify beginning with a fully molten phase.
Chemical Investigations and Anti-inflammatory Activity of Fixed Oil of Butea monosperma Seeds
A. Gunakunru,K. Padmanaban,P. Thirumal,N. Vengatesan,N. Gnanasekar,S. Raja,A.T. Rajarajan,S.G. Vijaya Kumar,J. Britto Perianayagam 한국생약학회 2004 Natural Product Sciences Vol.10 No.2
The fruit and seeds of Butea monosperma (Lam) Kuntze (Fabaceae) are useful in piles, anthelmintic, eye diseases, and inflammation in the Indian system of medicine. Hence, we have evaluated the anti-inflammatory activity of the fixed oil, mixed fatty acids, and unsaponifiable matter of B. monosperma against carrageenan-induced paw oedema and cotton pellet-induced granuloma in rats. The fixed oil, mixed fatty acids, and unsaponifiable matter of the oil exhibited significant anti-inflammatory activity on the tested experimental animal models. The unsaponifiable matter of the oil produced higher protection compared to fixed oil and mixed fatty acids. Phytochemical analysis of the fixed oil revealed the presence of steroids and terpenoids while unsaponifiable matter of the oil showed the presence of β-sitosterol. Also, four fatty acids were identified in the fixed oil by gas liquid chromatography. The anti-inflammatory activity of the fixed oil may be due to unsaponifiable matter or combination of unsaponifiable matter and mixed fatty acids.
T. Anjaneyulu,A. T. Raghavender,K. Vijaya Kumar,P. Narayana Murthy,K. Narendra 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.8
Nanocrystalline Ni1−xZnxFe2O4 ( 0.0 ≤ x ≤ 0.8) ferrites have been synthesized by using an oxalic-acid-based precursor method. The X-ray diffraction (XRD) analysis revealed the formation of a single-phase spinel structure at very low annealing temperature. The particle size was observed to decrease with increasing Zn content x. The lattice constants was observed to increase with increasing Zn content x due to large ionic radii of the zinc ion when compared to that of the nickel ion. Magnetic measurements at room temperature revealed that the magnetization did not change monotonically with increasing Zn content x. The coercivity and the remanence were observed to decrease with increasing non-magnetic Zn content x. The observed magnetic properties may be due to a reduction in the number of exchange interactions and the nanocrystalline size with increasing Zn content x.