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MHD free convective flow past semi-infinite vertical permeable wall

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Applied Mathematics and Mechanics(English Edition) 2012年第9期33卷 1207-1222页

作者： R.k.SINGH A.k.SINGH Department of Mathematics Banaras Hindu University

In this paper, the basic equations governing the flow and heat transfer of an incompressible viscous and electrically conducting fluid past a semi-infinite vertical per- meable plate in the form of partial differential equations are reduced to a set of non-linear ordinary differential equations by applying a suitable similarity transformation. Approx- imate solutions of the transformed equations are obtained by employing the perturbation method for two cases, i.e., small and large values of the suction parameter. From the numerical evaluations of the solution, it can be seen that the velocity field at any point decreases as the values of the magnetic and suction parameters increase. The effect of the magnetic parameter is to increase the thermM boundary layer. It is also found that the velocity and temperature fields decrease with the increase in the sink parameter.

关键词： magnetohydrodynamics (MHD) suction source/sink Prandtl number permeability boundary layer

Spontaneous emission in the ellipsoidal nanocrystals

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Journal of Rare Earths 2009年第4期27卷 637-640页

作者： k.k.Pukhov General Physics Institute Russian Academy of Sciences 38 Vavilov Str.Bld.D Moscow 119991 Russia

The equation was presented for the spontaneous emission rate Anano of the two-level optical centers in the subwavelength eilipsoi- dal nanocrystals embedded in a dielectric medium. An important result was that the ratio Anano/Abulk could be estimated without recourse to a particular local-field model. On the ground of this equation the expression was derived for linestrength of electric-dipole transition in trivalent rare-earth ions. The applicability of the Judd-Ofelt equation for nanoparticles was discussed.

关键词： spontaneous emission lifetime nanocrystals Judd-Ofelt parameters rare earths

Preparation of Sm2O3 and Co3O4 from SmCo magnet swarf by hydrometallurgical processing in chloride media

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Journal of Rare Earths 2018年第7期36卷 725-732页

作者： k.Sahoo A.k.Nayak M.k.Ghosh k.Sarangi CSIR-Institute of Minerals and Materials Technology Bhubaneswar-751013OdishaIndia

The recycling of rare earth elements（REE） from end-of-life REE based products is an environment friendly proposition. Waste Sm-Co based permanent magnet generated during machining is a good source for both Sm and Co. In the present study a simpler process of acid leaching at 80 ℃ followed by solvent extraction, oxalate precipitation and calcination is described for producing pure Sm2 O3 and Co3 O4. With either 10 vol% H2SO4 or 15 vol% HCI at 80 ℃ more than 95% Sm and Co are leached in 1 *** of Sm from sulphate leach liquor with TBP or Aliquat 336 was poor. Although extraction with TOPS-99 is quantitative but Sm from sulphate leach liquor precipitated as Sm2（SO4）3·8 H2O. The chloride leach liquor at an initial pH of 2.5 and with 1.2 mol/L TOPS-99 shows requirement of 4-stages at A：O = 3：2. Stripping with oxalic acid precipitates Sm-oxalate which is calcined at 800 ℃ to produce Sm2 O3. Co3 O4 is recovered from the raffinate through oxalate precipitation followed by calcination at450℃.

关键词： SmCo magnet Samarium Cobalt TOPS-99 Solvent extraction Precipitation stripping

Tuning the Microstructural and Magnetic Properties of ZnO Nanopowders through the Simultaneous Doping of Mn and Ni for Biomedical Applications

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Journal of Materials Science & Technology 2015年第11期31卷 1111-1117页

作者： k.karthika k.Ravichandran Post Graduate & Research Department of Physics AVVM Sri Pushpam College(Autonomous)

Undoped and Mn＋Ni doped ZnO nanopowders were synthesized using a simple soft chemical route by varying the Ni doping level （1, 3, 5 and 7 at.%） and keeping the Mn doping level （10 at.%） constant, X-ray diffraction studies reveal that the incorporated Ni^2＋ ions form a secondary phase of cubic NiO beyond the Ni doping level of 3 at.%, which is also confirmed by Fourier transform infrared spectroscopy. The band gap of the nanopowders increases （from 3.32 to 3.44 eV） up to 3 at.% of Ni doping and decreases with further doping. ZnO：Mn：Ni nanopowders with 3 at.% of Ni concentration exhibit good antibacterial efficiency. The variation in the size of the nanoparticles, as observed from the TEM images and hydroxyl radicals as evidenced from the photoluminescence results, clearly substantiate the discussion on the antibacterial efficiency of the synthesized nanopowders. Magnetic properties of the synthesized nanopowders were studied using a vibrating sample magnetometer, and the results showed that the doping of Mn and Ni largely influences the magnetic properties of ZnO nanopowders.

关键词： ZnO Nanopowders Soft chemical route Magnetic properties Antibacterial activity

Investigation on the Reduction of Center of Mass Oscillations of Flexible Flapping Fins

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Journal of Bionic Engineering 2016年第4期13卷 544-557页

作者： Ashok k kancharala Michael k Philen Aerospace and Ocean Engineering Virginia Polytechnic Institute and State University Blacksburg VA 24061 USA

Nature has been a source of inspiration for developing advanced autonomous aerial and underwater vehicles. The bodies with flapping appendages produce Center of Mass （COM） oscillations as the flapping fins generate forces oscillatory in nature. The vehicles with larger COM oscillations pose the problems of control and maneuverability and this paper discusses the effect of flexibility and other operating parameters such as heaving, pitching amplitudes and operating frequency on COM oscillations. A detailed theoretical investigation has been carried out to predict the optimal operating parameters along with the fin stiffness to reduce the COM oscillations for a given Self-Propelled Speed （SPS）. Experiments have been performed to validate the theoretical results. It has been observed that the flexible fins operating at larger frequencies produce lower COM oscillations compared to stiffer fins operating at lower frequencies for a given mean thrust/SPS, and that the trailing edge amplitude along with the deformation pattern play a role in the generation of COM oscillations.

关键词： flapping fin fluid-structure interaction optimization digital image correlation

Preparation by chemical co-precipitation, spectral and electrical characteristics of neodymium orthophosphate nanoparticles

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Journal of Rare Earths 2015年第5期33卷 535-544页

作者： Seema Verma k.k.Bamzai Crystal Growth and Material Research Laboratory Department of Physics & Electronics University of Jammu

Nanoparticles of neodymium orthophosphate （NdPO4） were prepared through a facile wet co-precipitation technique. The X-ray diffraction （XRD） studies revealed the material belonging to monoclinic monazite phase with crystallite size of 30.8 nm. Scanning electron microscopic studies showed that the material was composed of a large number of agglomerated spherical particles having grain size of 92 nm. Thermogravimetric analysis suggested that the structural phase transition was seen above 800 °C. The spectroscopic investigations were carried out using Fourier transform infrared spectroscopy （FTIR）. UV-VIS-NIR ab-sorption spectrophotometer showed various transitions from the ground state 4I9/2 to various excited states within the 4f shell and the optical band gap came out to be 3.3 eV. The dielectric constant （ε′）, dielectric loss （tanδ） and ac conductivity ln（σac） were measured in the frequency range of 5 kHz to 1 MHz and in the temperature range of 40 to 500 °C. The dielectric measurement suggested that there was a shift in the value of transition temperature （Tc）, thereby indicating relaxor behaviour of the material. The activation energy value decreased with increase in frequency, thereby suggesting the role of mixed ionic-polaronic conduc-tivity.

关键词： nanoparticles spectroscopic dielectric properties rare earths

Enhancement of Photocatalytic and Antibacterial Activities of ZnO：Ag Nanopowders Through the Addition of Bamboo Charcoal： An Efficient Natural Adsorbent

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Acta Metallurgica Sinica(English Letters) 2017年第12期30卷 1249-1256页

作者： k. Nithiyadevi k. Ravichandran PG Research and Department of Physics AVVM Sri Pushpam College (Autonomous) Poondi Thanjavur Tamil Nadu 613 503 India Department of Physics Bharathidasan University Constituent College (Women) Orathanadu Tamil Nadu 614 625 India

This research article explains the removal of methylene blue （MB） and malachite green （MG） from aqueous solution using adsorption/photodegradation activity of ZnO：Ag/bamboo charcoal （BC） nanocomposite. In addition, the antibacterial studies of the prepared samples were tested against Staphylococcus aureus （S. aureus） Gram-positive and Escherichia coli （E. coli） Gram-negative bacteria by the well diffusion method. The ZnO：Ag/BC nanocomposite exhibits superior photocatalytic activity compared with ZnO：Ag. Remarkable degradation efficiencies of 93.95% （MB） and 95.75% （MG） were recorded for ZnO：Ag/BC nanocomposite after 45 min. The degradation process follows a pseudo-first-order kinetics. The rate constant of ZnO：Ag/BC nanocomposite is two times greater than that of pristine ZnO nanopowder for the degradation of MB dye, while for MG dye degradation, it is three times. It is found that the ZnO：Ag/BC nanocomposite shows a higher rate of dye removal due to excellent adsorbing properties of bamboo charcoal （BC）. The ZnO：Ag/BC nanocomposite showed better antibacterial properties compared to ZnO：Ag. In this study, the samples were prepared using a simple and low-cost soft chemical route and they were characterized by optical, structural, surface morphological, antibacterial and photocatalytic properties. These characterization studies substantiate the discussions on the photocatalytic and antibacterial activities of the synthesized samples.

关键词： Bamboo charcoal Adsorbent ZnO Photocatalysis Antibacterial

Synthesis, evaluation of kinetic characteristics and investigation of apoptosis of Cu^(2+)-modified ceria nano discs

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Journal of Rare Earths 2018年第10期36卷 1050-1059页

作者： k.Nusrath k.Muraleedharan Department of Chemistry University of Calicut

Ceria nano discs were synthesized by the stepwise thermal decomposition strategy of the oxalate precursor. A series of Ce（1-x）CuxO2（x = 0, 0.02, 0.1, 0.2 and 0.3） nano sized oxide systems were prepared through thermal decomposition route. kinetic characterization of formation of solid solution was made by isoconversional strategy under non-isothermal condition. Introduction of various reactant molar ratios of Cu2＋：Ce4＋ has a pivotal role in the creation of new oxygen vacancies, decomposition strategy,particle size and shape. Cu2＋ doping（x = 0.02 and 0.1） damages the disc shaped morphology of *** distribution of Cu2＋ on the oxalate precursor has a significant role in the catalyzing activity for the destruction of oxalate bond to oxide. 2 mol% doped Cu2＋ promotes breaking of oxalate bonds in nitrogen atmosphere. In vitro cell viability assay illustrates enhanced toxicity to cancer cells with 10 mol% Cu2＋ doped ceria.

关键词： Nano disc Isoconversional Oxygen vacancies Decomposition strategy Cell viability Rare earths

Type Inversion and Certain Physical Properties of Spray Pyrolysed SnO_2:Al Films for Novel Transparent Electronics Applications

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Journal of Materials Science & Technology 2014年第2期30卷 97-102页

作者： k.Ravichandran k.Thirumurugan Post Graduate and Research Department of Physics AVVM Sri Pushpam College(Autonomous)

Aluminium doped tin oxide films have been deposited onto glass substrates by using a simplified and low cost spray pyrolysis technique. The AI doping level varies between 0 and 30 at.% in the step of 5 at.%. The resistivity （p） is the minimum （0.38 Ω cm） for 20 at.% of AI doping. The possible mechanism behind the phenomenal zig-zag variation in resistivity with respect to AI doping is discussed in detail. The nature of conductivity changes from n-type to p-type when the AI doping level is 10 at.%. The results show that 20 at.% is the optimum doping level for good quality p-type SnO2：AI films suitable for transparent electronic devices.

关键词： Tin oxide films P-type transparent conducting oxide (TCO) Spray pyrolysis Transparent electronics Electrical properties Optical properties