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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>
Suresh Kumar, A.,Sri Gowri, K.,Vijaya Kumar, M. The Korean Institute of Power Electronics 2020 JOURNAL OF POWER ELECTRONICS Vol.20 No.1
The space vector (SV) pulse-width modulation (PWM) approach is extensively preferred in the control of multilevel inverters (MLI). In this paper, the implementation of various advanced discontinuous pulse-width modulation (ADPWM) strategies using a generalized space vector algorithm is presented. The ADPWM MIN, ADPWM MAX, and ADPWM 0~ADPWM 3, strategies are developed using a combination of advanced switching sequences 1012-2721 and 0121-7212. The output performance in terms of voltage THD, current THD, and reduction of common mode voltage (CMV) of a three-level inverter-fed induction motor for different ADPWM strategies is investigated initially through MATLAB simulation and comparison of the obtained results is presented. It can be observed that the ADPWM 1 strategy with the 0121-7212 switching sequence offered the best performance in terms of the voltage and current THD at the modulation range of 47.5 Hz to 50 Hz. In addition, it is validated experimentally. Experimental work is done on a V/f-controlled three-level inverter-fed induction motor with the help of dSPACE. To validate the study, experimental results of the line voltage, stator current, and CMV waveforms for the ADPWM 1 (optimal performance PWM strategy) are presented in comparison with the 0127 sequence at fundamental frequencies of 49 Hz and 30 Hz.
Vinod Kumar Sharma,Vijaya Banu,K. Chandrasekar,Bimal K. Bhattacharya,M. V. R. Sesha Sai,V. Bhanumurthy 대한공간정보학회 2017 Spatial Information Research Vol.25 No.1
Heavy rains causing a flood like situation affect the grains stored in godowns. To save the grains from floods, they have to be transferred to safer places. Historical flood layers derived using the remote sensing data can be helpful in determining the safe place for transferring the grains from the flood affected godowns. Analyzing of satellite data for determining the safer locations needs specialized skills and GIS software’s. To overcome this, a web based information system, capable of organizing, hosting, and sharing of the flood layers and other spatial datasets as open geospatial consortium compatible web processing services is needed. For transferring the grains, the management must have the existing stock information of the flood affected godown as well as stock information of the godown where the grains are planned to be shifted. Mobile application, capable of reporting the stock information along with the godown location and ground photographs can be an efficient solution to do so. This paper presents work on web processing services integrated with mobile application using open source technologies to identify suitable grain godowns location.
R. Prabu,K. M. Kumar,R. Selvam,K. R. Vijaya Kumar 한국고분자학회 2021 폴리머 Vol.45 No.3
The main objective of this work is to investigate the effect of shape memory alloy reinforcement in Kevlar polymer composites on mechanical and low-velocity impact properties. The sheet and wire forms of shape memory alloy (SMA-nickel-titanium alloy) are used as potential reinforcements in Kevlar-reinforced polymer composite. The developed composites were analyzed for tensile and flexural behavior. The effective bonding area, referred to as core density, contributes to incremental flexural strength in the SMA sheet reinforced composites. The developed composites exhibited better impact resistance during low-velocity impact tests at different velocities, 2.80, 3.96, and 4.85 m/sec, and simulated using a CEAST drop hammer testing machine. The impact surface of the specimen was studied on a micro-level using SEM analysis and macro-level using Image J software. The impact force, the energy absorbed, and the deformation of the specimen during impact were recorded and analyzed. The experimental results reveal that the SMA sheet reinforced Kevlar composites exhibited appreciable impact resistance with maximum energy absorbing capacity comparatively with plain Kevlar and SMA wire reinforced composites.
Efficacy of Selenium on Silkworm (Bombyx mori L.) Cocoon Characters
( S. Smitha ),( K. Anil Kumar ),( A. Vijaya Bhaskara Rao ) 한국잠사학회 2006 International Journal of Industrial Entomology Vol.13 No.2
As the Selenium is known to be growth promoter in sheep and cattle, the efficacy of selenium has been tested in silkworm Bombyx mori L. The V ins tar larvae were fed with lethal and sub-lethal doses of selenium treated leaves. The larvae fed with lethal dose showed a significant decrease in growth and Cocoon commercial characters. The treatment with sub lethal dose exhibited a significant increase in the growth of the silkworm. Correspondingly, the cocoon commercial characters on exposure to the lethal dose showed significant decrease and sub lethal dose showed a significant increase. In the light of similar findings reported earlier in other cocoon crops and vertebrates, it can be inferred that selenium at lower doses acts as a growth stimulator, resulting in the higher yield of cocoon crop.
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.
Electrical Properties of Copper Substituted Nickel Ferrites
G. Ravi Kumar,Y. C. Venudhar,A. T. Raghavender,K. Vijaya Kumar 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.7
The Ni-Cu ferrites, Ni1−xCuxFe2O4 (0.0 ≤ x ≤ 1.0) were prepared by using the sol-gel method. The X-ray diffraction patterns of all the samples showed the formation of a single-phase spinel structure. The lattice parameter was found to increase with increasing copper concentration. The electrical properties, such as the d. c. conductivity as a function of the temperature, and the dielectric constant, the dielectric loss factor and the dielectric loss tangent as function of the frequency were investigated. The d. c. conductivity was found to increase with increasing temperature in accordance with the Verwey hopping mechanism. The dielectric constant, the dielectric loss factor and the dielectric loss tangent were found to decrease with increasing frequency. The dielectric constant followed the Maxwell-Wagner interfacial polarization. A suitable explanation was given for the frequency and the composition dependences of the dielectric properties.