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Effect of dysprosium substitution on structural and dielectric properties of BiFeO_3-PbTiO_3 multiferroic composites

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Journal of Rare Earths 2015年第6期33卷 639-646页

作者： N.K.Mohanty A.K.behera S.K.Satpathy Banarji behera P.Nayak Materials Research Laboratory School of Physics Sambalpur University

0.5BiDyxFe1-xO3-0.5PbTiOa（0.5BDxF1-x-0.5PT）（x=0.00, 0.05, 0.10, 0.15, 0.20） multiferroic composites were pre- pared by conventional solid state reaction method. Structural characterization was performed by X-ray diffraction and the mate- rials showed tetragonal structure at room temperature. Surface morphology of the composites was studied by a scanning electron microscope （SEM）. Frequency and temperature dependence of dielectric constant （er） and dielectric loss （tan~） of 0.5BDxF1_x- 0.5PT were measured in a wide range of frequency （100 Hz to 1 MHz） and temperature （25 to 400 ~C）. The analysis of the study showed that the er and tang decreased with increasing frequency in the given range for all the samples which could be explained through the occurrence of dipole relaxation process. The effect of substitution of rare earth element dysprosium （Dy） showed increase in er in all the samples prepared for different concentrations from 0.00 to 0.20. An explanation for high value of er for Dy modified 0.5BiFeO3-0.5PbTiO3 （0.5BF-0.5PT） compared to Gd modified 0.5BF-0.5PT was provided. The variation of AC conductivity with inverse temperature found to obey the Arrhenius equation and the composites showed negative temperature coefficient of resistance （NTCR） behavior. The activation energy was found to be in the range from 0.25 to 0.40 eV for all the studied samples.

关键词： X-ray diffraction dielectric constant tangent loss activation energy rare earths

Cryogenic and conventional milling of AZ91 magnesium alloy

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Journal of Magnesium and Alloys 2024年第6期12卷 2503-2519页

作者： Vikas Marakini Srinivasa Pai P Gururaj Bolar bhaskara P Achar Department of Mechanical Engineering Nitte(Deemed to be University)NMAM Institute of Technology(NMAMIT)Nitte 574110India Department of Mechanical and Industrial Engineering Manipal Institute of TechnologyManipal Academy of Higher EducationManipal 576104India

Use of magnesium is the need of the hour due to its low density as well as its high strength-to-weight and stiffness-to-weight ratio *** study focuses on the effectiveness of liquid nitrogen(LN_(2))assisted cryogenic machining on the surface integrity(SI)characteristics of AZ91 magnesium *** milling using uncoated carbide inserts have been performed under liquid nitrogen(LN_(2))assisted cryogenic condition and compared with conventional(dry)*** are performed using machining parameters in terms of cutting speeds of 325,475,625 m/min,feed rates of 0.05,0.1,0.15 mm/teeth and depth of cuts of 0.5,1,1.5 mm *** significant surface integrity characteristics such as surface roughness,microhardness,microstructure,and residual stresses have been *** of SI characteristics with respect to milling parameters have been identified using statistical technique such as ANOVA and signal-to-noise(S/N)ratio ***,the multi criteria decision making(MCDM)techniques such as additive ratio assessment method(ARAS)and complex proportional assessment(COPRAS)have been utilized to identify the optimal conditions for milling AZ91 magnesium alloy under both dry and cryogenic *** of LN_(2)during machining,resulted in reduction in machining temperature by upto 29%with a temperature drop from 251.2℃under dry condition to 178.5℃in cryogenic *** showed the advantage of performing cryogenic milling in improving the surface integrity to a significant *** machining considerably minimized the roughness by upto 28%and maximised the microhardness by upto 23%,when compared to dry *** speed has caused significant impact on surface roughness(95.33%-dry,92.92%-cryogenic)and surface microhardness(80.33%-dry,82.15%-cryogenic).Due to the reduction in machining temperature,cryogenic condition resulted in compressive residual stresses(maximumσ║=-113 MPa)on the alloy *** indicate no

关键词： Magnesium alloy Cryogenic machining Roughness Microhardness Microstructure Residual stress Multi criteria decision making

Dynamic Response and Oscillating Behaviour of Fractionally Damped Beam

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Computer Modeling in Engineering & Sciences 2015年第3期104卷 211-225页

作者： Diptiranjan behera S.Chakraverty Corresponding Author.School of Mechatronics Engineering University of Electronic Science and Technology of ChinaNo.2006Xiyuan AvenueWest Hi-Tech ZoneChengduSichuan 611731P.R.China Department of Mathematics National Institute of Technology RourkelaOdisha-769008India

This paper presents the numerical solution of a viscoelastic continuous beam whose damping behaviours are defined in term of fractional derivatives of arbitrary *** Perturbation Method(HPM)is used to obtain the dynamic response with respect to unit impulse *** results are depicted in term of *** are made with the analytic solutions obtained by Zu-feng and Xiao-yan(2007)to show the effectiveness and validation of the present method.

关键词： Viscoelastic beam Fractional derivative Impulse response function Homotopy Perturbation Method(HPM)

Electrical conductivity of Gd doped BiFeO3-PbZrO3 composite

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Frontiers of Materials Science 2013年第3期7卷 295-301页

作者： Santosh Kumar SATPATHY Nilaya Kumar MOHANTY Ajay Kumar behera Banarji behera Pratibindhya NAYAK Materials Research Laboratory School of Physics Sambalpur University Jyoti Vihar Burla-768019 Odisha India

The composite, 0.5（BiGd0.15Fe0.85O3）-0.5（PbZrO3）, was synthesized using the solid-state reaction technique. The formation of the compound was confirmed by XRD with an orthorhombic structure at room temperature. The impedance parameters were studied using an impedance analyzer in a wide range of frequency （10z-106Hz） at different temperatures. The Nyquist plot suggests the contribution of bulk effect and a slight indication of grain boundary effect and the bulk resistance decreases with a rise in temperature. The presence of temperature-dependent relaxation process occurs in the material. Electrical modulus reveals the presence of the hopping mechanism in the materials. The value of exponent n, pre-factor A and adc were obtained by fitting ac conductivity data with Jonscher＇s universal power law. The activation energies calculated from the ac conductivity were found to be 0.50, 0.46, 0.44, 0.43, 0.42 and 0.38 eV at 1, 10, 50, 100, 500 kHz and I MHz respectively in the temperature region of 110℃-350℃. The dc conductivity was found to increase with the rise in temperature. The activation energy calculated from complex impedance plot and from the fitted Jonscher＇s power law are very close, which results similar type of charge carrier exist in conduction mechanism of the material.

关键词： solid state reaction XRD impedance electrical conductivity

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

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Acta Metallurgica Sinica(English Letters) 2015年第7期28卷 847-857页

作者： Ajay Kumar behera N.K.Mohanty S.K.Satpathy Banarji behera P.Nayak Materials Research Laboratory School of PhysicsSambalpur University

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5（Bi LaxFe1-xO3）–0.5（Pb Ti O3）（x = 0.05,0.10,0.15,0.20）（BLxF1-x-PT） were prepared by mixed oxide *** characterization was performed by X-ray diffraction and shows a tetragonal structure at room *** lattice parameter c/a ratio decreases with increasing of La（x = 0.05–0.20） concentration of the *** effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range（102–106Hz） at different *** nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the *** electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the *** ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures（200–300 ℃）.

关键词： X-ray diffraction Composite materials Impedance spectroscopy Modulus studies Activation energy Relaxation phenomena

Fundamental buckling of circular plates with elastically restrained edges and resting on concentric rigid ring support

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Frontiers of Mechanical Engineering 2013年第3期8卷 291-297页

作者： Lokavarapu bhaskara Rao Chellapilla Kameswara Rao School of Mechanical and Building Sciences VIT UniversityVandalur-Kelambakkam RoadChennai 600127Tamil NaduIndia Department of Mechanical Engineering Guru Nanak Institutions Technical CampusIbrahimpatnamHyderabad 501506A.PIndia

This work presents the existence of buckling mode switching with respect to the radius of concentric rigid ring *** buckling mode may not be axisymmetric as previously *** general,the plate may buckle in an axisymmetric mode but when the radius of the ring support becomes small,the plate may buckle in an asymmetric *** optimum radius of the concentric rigid ring support for maximum buckling load is also *** internal rigid ring support,when placed at an optimal position increases the elastic buckling load capacity by 149.39 *** numerical results obtained are in good agreement with the previously published data.

关键词： buckling circular plate elastically restrained edge rigid ring support mode switching

Numerical solution of the imprecisely defined inverse heat conduction problem

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Chinese Physics B 2015年第5期24卷 153-162页

作者： Smita Tapaswini S.Chakraverty Diptiranjan behera Department of Mathematics National Institute of Technology Rourkela

This paper investigates the numerical solution of the uncertain inverse heat conduction problem. Uncertainties present in the system parameters are modelled through triangular convex normalized fuzzy sets. In the solution process, double parametric forms of fuzzy numbers are used with the variational iteration method （VIM）. This problem first computes the uncertain temperature distribution in the domain. Next, when the uncertain temperature measurements in the domain are known, the functions describing the uncertain temperature and heat flux on the boundary are reconstructed. Related example problems are solved using the present procedure. We have also compared the present results with those in [Inf. Sci. （2008） 178 1917] along with homotopy perturbation method （HPM） and [Int. Commun. Heat Mass Transfer （2012） 39 30] in the special cases to demonstrate the validity and applicability.

关键词： triangular fuzzy number double parametric form of fuzzy numbers uncertain inverse heat con-duction variational iteration method (VIM)

Antioxidant activity of newly discovered lineage of marine actinobacteria

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Asian Pacific Journal of Tropical Medicine 2013年第4期6卷 325-332页

作者： Loganathan Karthik Gaurav Kumar Kokati Venkata bhaskara Rao Environmental Biotechnology Division School of Bio Sciences and TechnologyVIT UniversityVelloreTamil NaduIndia

Objective:To investigate the antioxidant activity of marine ***:The content of total phenolics,the level of antioxidant potential by DPPH radical scavenging activity,metal chelating activity,FRAP method,βcarotene assay and NO scavenging activity in extract were ***:In all the methods the extract exhibited good scavenging activity except NO scavenging *** IC50 values of marine actinobacteria extract on DPPH radical were found to be 41.09μg/*** zone of color retention was 12 mm inβ-carotene bleaching assay. DNA protective efficiency of the extracts was also studied using UV- photolysed H2O2-driven oxidative damage to *** analysis identified some of the major phenolic compounds in extracts,which might he responsible for the antioxidant potential and *** showed a 100%cytotoxic effect in brine shrimp lethality assay within 10 *** novel actinobacteria was identified as Streptomyces LK-3（JF710608） through I6S rDNA ***:The results obtained suggest that the extracts bear anti-cancer metabolites and could be considered as a potential source for anti-cancer drug development.

关键词： Streptomyces LK-3 Antioxidant DPPH radical scavenging assay Cytotoxicity

Phytochemical composition and in vitro antioxidant activity of aqueous extract of Aerva lanata(L.) *** ***(Amaranthaceae)

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Asian Pacific Journal of Tropical Medicine 2013年第3期6卷 180-187页

作者： Gaurav Kumar Loganathan Karthik Kokati Vankata bhaskara Rao Molecular and Microbiology Research Laboratory Environmental Biotechnology DivisionSchool of Bio Sciences and TechnologyVIT UniversityVelloreTamil Nadu-632 014India

Objective:To analyze the phytochemical composition and in vitro antioxidant properties of aqueous extract of Aerva Lanata（***） ***:During the preliminary phytochemical analysis,the aqueous extract of *** was screened for the presence of carbohydrates,proteins,phenolic compounds,oil and fats,saponins,flavonoids,alkaloids. tannins and *** activity of the extract was determined by 2.2-dipbenyl- 1-picrylhydrazyl radical scavenging activity,metal chelating activity,reducing power activity and DNA damage inhibition *** of phenolic compounds was performed by FolinCiocaiteau reagent method and gradient high performance liquid chromatography technique. Results:Preliminary phytochemical analysis exhibited the presence of phenolic compounds, *** and phytosterols as major phytochemical *** extract exhibited high 2.2—diphenyl-1-picrylhydrazyl radical scavenging activity(IC50= 110.74μg/ mL).metal chelating activity(IC50= 758.17μg/mL).reducing power activity and DIA damage inhibition *** extract was reported to possess a high amount of total phenolic content and some of them were identified as gallic acid（3,4,3-OH）,apigenin-7—O-glucoside tapigetrin), quercetin-3—O-rutinoside（rutin） and myricetin（3,5,7,3,4,5-OH）by high performance liquid chromatography *** extract was found non toxic towards human erythrocytes in the hemolytic assay(IC50= 24.89 mg/mL).Conclusions:These results conclud that *** stem possesses high antioxidant activity and can he used for the development of natural and sale antioxidant compounds.

关键词： Aerva lanata Antioxidant DPPH radical scavenging assay Phenolic compounds Hemolytic activity