17,397 research outputs found

    Fireside corrosion degradation of ferritic alloys at 600°C in oxy-fired conditions

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    This paper reports the results of a study carried out to investigate the effects of simulated coal/biomass combustion conditions on the fireside corrosion. The 1000 h deposit recoat exposure (5 × 200 h cycles) was carried out at 600 °C. In these tests ferritic alloys were used 15Mo3, T22, T23 and T91. Kinetics data were generated for the alloys exposed using both traditional weight change methods and metal loss measurements. The highest rate of corrosion based on EDX results occurred under D1 deposit where provoke mainly by the formation of alkali iron tri-sulphate phase

    Synthesis and characterization of silver nanoarticles from extract of Eucalyptus citriodora

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    The primary motivation for the study to develop simple eco-friendly green synthesis of silver nanoparticles using leaf extract of Eucalyptus citriodora as reducing and capping agent. The green synthesis process was quite fast and silver nanoparticles were formed within 0.5 h. The synthesis of the particles was observed by UV-visible spectroscopy by noting increase in absorbance. Characterization of the particles was carried out by X-ray diffraction, FTIR and electron microscopy. The developed nanoparticles demonstrated that E. citriodora is good source of reducing agents. UV-visible absorption spectra of the reaction medium containing silver nanoparticles showed maximum absorbance at 460 nm. FTIR analysis confirmed reduction of Ag+ to Ag0 atom in silver nanoparticles. The XRD pattern revealed the crystalline structure of silver nanoparticles. The SEM analysis showed the size and shape of the nanoparticles. The method being green, fast, easy and cost effective can be recommended for large scale production of AgNPs for their use in food, medicine and materials

    Influence of heterogeneous-homogeneous reactions in thermally stratified stagnation point flow of an Oldroyd-B fluid

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    AbstractThis communication explores the effects of homogeneous-heterogeneous reactions in thermally stratified mixed convection flow of an Oldroyd-B fluid. Flow situation is addressed when the diffusion coefficients of the reactant and auto catalyst are equal. The stagnation point flow towards a stretching surface is discussed. Mathematical equations are developed for velocity, temperature and concentration functions through boundary layer theory. Resulting differential systems are computed for the convergent series solutions. Influences of various pertinent variables on the velocity, temperature and concentration are discussed. Comparison of present study is shown with the previous results. The outcomes are found in very good agreement

    Underlying Fermi surface of Sr14x_{14-x}Cax_xCu24_{24}O41_{41} in two-dimensional momentum space observed by angle-resolved photoemission spectroscopy

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    We have performed an angle-resolved photoemission study of the two-leg ladder system Sr14x_{14-x}Cax_xCu24_{24}O41_{41} with xx= 0 and 11. "Underlying Fermi surfaces" determined from low energy spectral weight mapping indicates the quasi-one dimensional nature of the electronic structure. Energy gap caused by the charge density wave has been observed for xx=0 and the gap tends to close with Ca substitution. The absence of a quasi-particle peak even in xx=11 is in contrast to the two-dimensional high-TcT_c cuprates, implying strong carrier localization related to the hole crystalization.Comment: 5 pages, 3 figure

    Nodal metallic behavior of lightly-doped La2x_{2-x}Srx_xCuO4_4

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    Lightly-doped La2x_{2-x}Srx_xCuO4_4 in the so-called "insulating" spin-glass/diagonal-stripe phase has been studied by angle-resolved photoemission spectroscopy. A quasi-particle (QP) peak crossing the Fermi level has been observed in the node direction of the d-wave superconducting gap, forming an "arc" of Fermi surface consistent with the recently observed metallic transport behavior at high temperatures of lightly-doped materials. The spectral weight of the nodal QP smoothly increases with hole doping, corresponding to the nxn \sim x behavior of the carrier number in the underdoped and lightly-doped regions.Comment: 5 pages, 4 figure

    Polaronic behavior of undoped high-Tc cuprates

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    We present angle-resolved photoemission spectroscopy (ARPES) data on undoped La2CuO4, indicating polaronic coupling between bosons and charge carriers. Using a shell model, we calculate the electron-phonon coupling and find that it is strong enough to give polarons. We develop an efficient method for calculating ARPES spectra in undoped systems. Using the calculated couplings, we find the width of the phonon side band in good agreement with experiment. We analyze reasons for the observed dependence of the width on the binding energy.Comment: 4 pages, RevTeX, 5 eps figures, more material available at http://www.fkf.mpg.de/andersen/phonons

    The Coronal Structure of AB Doradus

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    We perform a numerical simulation of the corona of the young, rapidly rotating K0 dwarf AB Doradus using a global MHD model. The model is driven by a surface map of the radial magnetic field constructed using Zeeman-Doppler Imaging. We find that the global structure of the stellar corona is dominated by strong azimuthal tangling of the magnetic field due to the rapid rotation. The MHD solution enables us to calculate realistic Alfv\'en surfaces and we can therefore estimate the stellar mass loss rate and angular momentum loss rate without making undue theoretical simplifications. We consider three cases, parametrized by the base density of the corona, that span the range of possible solutions for the system. We find that overall, the mass and angular-momentum loss rates are higher than in the solar case; the mass loss rates are 10 to 500 times higher, and the angular momentum loss rate can be up to 3×1043\times{10}^4 higher than present day solar values. Our simulations show that this model can be use to constrain the wide parameter space of stellar systems. It also shows that an MHD approach can provide more information about the physical system over the commonly used potential field extrapolation.Comment: 13 pages, 7 figure
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