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Rekha Dom,Pramod H. Borse,Kyong-Soo Hong,Seyong Choi,Byeong Seob Lee,Myoung Gyu Ha,Jong Pil Kim,Euh Duck Jeong,Hyun Gyu Kim 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.67 No.9
Magnesium ferrite (MgFe2O4) exhibiting a spinel phase was synthesized by using the polymerized complex and the solid-state reaction methods, and its physico-chemical properties were studied to explore the water-splitting under visible light photons. The study revealed the potential for using MgFe2O4 particles for photo-catalytic application. The structural study provided information on ferrite nano-crystallites fabricated by using the polymer complex method. The morphological studies demonstrated that, in contrast to the solid-state reaction method, a homogenous, monodispersed ferrite photocatalyst could be formed by using the polymerized complex method. The optical study revealed a larger visible-light absorption capability for the nanosized MgFe2O4 photocatalysts prepared by using the polymer complex methods, and indicated a red-shift of the bandgap by 0.06 eV as compared to the bandgap of the bulk. These nanocrystallites were highly photoactive with respect to the photodegradation and photocatalytic hydrogen evolution applications. The electrochemical analysis showed that they exhibited favorable bandedge positions suitable for photocatalytic H2 evolution. Thus, nanocrystalline MgFe2O4 is an active visible-light photocatalyst, that might be useful for the decomposition of water.
Performance of fly ash stabilized clay reinforced with human hair fiber
Rekha, L. Abi,Keerthana, B.,Ameerlal, H. Techno-Press 2016 Geomechanics & engineering Vol.10 No.5
Industrialization and urbanization are the two phenomena that are going relentless all over the world. The consequence of this economic success has been a massive increase in waste on one hand and increasing demand for suitable sites for construction on the other. Owing to the surplus raw materials and energy requirement needed for manufacturing synthetic fibers, applications of waste fibers for reinforcing soils evidenced to offer economic and environmental benefits. The main objective of the proposed work is to explore the possibilities of improving the strength of soil using fly ash waste as an admixture and Human Hair Fiber (HHF) as reinforcement such that they can be used for construction of embankments and land reclamation projects. The effect of fiber content on soil - fly ash mixture was observed through a series of laboratory tests such as compaction tests, CBR and unconfined compression tests. From the stress - strain curves, it was observed that the UCC strength for the optimised soil - flyash mixture reinforced with 0.75% human hair fibers is nearly 2.85 times higher than that of the untreated soil. Further, it has been noticed that there is about 7.73 times increase in CBR for the reinforced soil compared to untreated soil. This drastic increase in strength may be due to the fact that HHF offer more pull-out resistance which makes the fibers act like a bridge to prevent further cracking and thereby it improves the toughness which in turn prevent the brittle failure of soil-flyash specimen. Hence, the test results reveal that the inclusion of randomly distributed HHF in soil significantly improves the engineering properties of soil and can be effectively utilized in pavements. SEM analysis explained the change of microstructures and the formation of hydration products that offered increase in strength and it was found to be in accordance with strength tests.
Rekha Garg,Anita Kumari,S. C. Joshi,Nighat Fahmi 대한화학회 2013 Bulletin of the Korean Chemical Society Vol.34 No.8
A new series of Mn(II) and Mo(VI) complexes containing the Schiff bases hydrazinecarbothioamide and hydrazinecarboxamide of 5,6-dimethyl-1H-indol-2,3-dione have been synthesized.The nature of bonding and the stereochemistry of the complexes have been deduced from elemental analyses, molecular weight determinations and spectral studies viz. electronic IR, ESR, 1H NMR and 13C NMR and X-ray diffraction spectral studies. The magnetic moment values of the manganese(II) complexes are in the range of 5.80-6.15 B.M. suggesting a high spin state of manganese in these complexes. The spectral data are consistent with a tetrahedral geometry around Mn(II) and an octahedral geometry for Mo(VI), in which the ligands act as bidentate chelating agents, coordinated through the nitrogen and sulfur/oxygen atoms. The ligands and their metal complexes have been tested against a number of pathogenic fungi and bacteria at different concentrations and were found to possess sufficient fungicidal and bactericidal properties. Further, the complexes were also tested for their antifertility activity in male albino rats and the results were indeed positive.
Compression and Enhancement of Medical Images using Opposition Based Harmony Search Algorithm
Rekha Haridoss,Samundiswary Punniyakodi 한국정보처리학회 2019 Journal of information processing systems Vol.15 No.2
The growth of telemedicine-based wireless communication for images—magnetic resonance imaging (MRI)and computed tomography (CT)—leads to the necessity of learning the concept of image compression. Overthe years, the transform based and spatial based compression techniques have attracted many types ofresearches and achieve better results at the cost of high computational complexity. In order to overcome this,the optimization techniques are considered with the existing image compression techniques. However, it failsto preserve the original content of the diagnostic information and cause artifacts at high compression ratio. In this paper, the concept of histogram based multilevel thresholding (HMT) using entropy is appended withthe optimization algorithm to compress the medical images effectively. However, the method becomes timeconsuming during the measurement of the randomness from the image pixel group and not suitable formedical applications. Hence, an attempt has been made in this paper to develop an HMT based imagecompression by utilizing the opposition based improved harmony search algorithm (OIHSA) as anoptimization technique along with the entropy. Further, the enhancement of the significant informationpresent in the medical images are improved by the proper selection of entropy and the number of thresholdschosen to reconstruct the compressed image.
Leaching of rare earth metals (REMs) from Korean monazite concentrate
Rekha Panda,Manis Kumar Jha,이진영,Archana Kumari,Jhumki Hait,Vinay Kumar,J. Rajesh Kumar 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.4
Systematic scientific studies for dephosphorization and acid leaching of Korean monazite are reported here. 50% NaOH (w/v) solubilizes 99.99% phosphate, at 170 ℃, 100 g/L pulp density in 4 h. Kinetics of phosphate leaching fitted well with model ‘‘chemical reaction control,’’ i.e. 1 - (1 - X)1/2 = kct, Ea = 58.04 kJ/mol. Further, rare earth hydroxides (REHs) was leached using 6 N HCl at 90 ℃, 60 g/L pulp density for 2 h to recover ~95% REMs. Leach liquor generated can be further processed using solvent extraction/ion exchange techniques. From the pure solutions, metal/salts could be obtained using evaporation, precipitation, etc.