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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.
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.
Synthesis of SrFe12O19 and Sr7Fe10O22 systems for visible light photocatalytic studies
Rekha Dom 한양대학교 세라믹연구소 2012 Journal of Ceramic Processing Research Vol.13 No.4
Solid state synthesis of two Sr-Fe-O systems viz. Sr7Fe10O22 and SrFe12O19 was attempted and they were investigated for their photocatalytic properties. Although, both the systems exhibited good cystallinity and optical properties, only Sr7Fe10O22 was found to be active for the photocatalytic decomposition of iso-propanol under visible light. It also yielded a significant quantum yield (~1.7%) for photo-reduction of water under visible light irradiation, much better than titanium oxy-nitride samples. The inactiveness of SrFe12O19 was due to its unsuitable band energetics. The Sr7Fe10O22 acted more efficiently than TiO2-xNx due to its suitable band positions and high visible light photon absorptivity.
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.
Study on NOx reduction capacity of catalytic coated cordierite monolith
Rekha Durairaj,Neelakrishnan Subramanyan,Divakar Duraiswamy 한양대학교 세라믹연구소 2019 Journal of Ceramic Processing Research Vol.20 No.6
Legislation world-wide imposes stringent emission norms, particularly EURO V and beyond. In this regard, extensive research is being conducted for improving the existing filter design, material properties and developing alternative design, materials, testing procedures for more sensitive to reduce NOX values. Cordierite ceramics are having good chemical and electrical properties like high thermal resistance, low dielectric constant, low thermal expansion coefficient, and high chemical and mechanical stability, which makes it for many industrial applications like manufacturing of the thermal insulation materials, optoelectronic devices, plasma display panels, solar panels, catalytic convertors etc. In this work, a pair of cordierite monolith with catalyst coating to NOx storage and reduction was developed. The effectiveness of the catalysis was verified with engine exhaust gas analyser. The testing was carried out with diesel as fuel in a Kirloskar engine with Non-filter, NSR, and combined NSR-SCR system. The investigation was done for five trials with different emission parameters and analysed.