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Kim, G.,Jin, H.J.,Jo, W.,Nam, D.H.,Cheong, H.,Kim, H.S.,Oh, S.S.,Ko, R.K.,Jo, Y.S.,Ha, D.W. North-Holland 2015 Physica. C, Superconductivity Vol.513 No.-
Structural and transport properties of high performance SmBa<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>7-x</SUB> coated conductors produced by a dual-chamber co-evaporation are presented. The 5μm-thick SmBCO coated conductors grown on IBAD-MgO based Hastelloy metal templates show critical currents larger than 1020-1560A/cm at 77K and self-field. The current transport characteristics of the conductors are investigated by room-temperature thermoelectric microscopy and low-temperature bolometric microscopy. The local thermoelectric images show the tilted grains, grain boundaries, and microstructural defects on the surface of the coated conductors. The bias current-dependent bolometric response at low temperature displays the current of the local flux flow dissipation as an increasing bias. Furthermore, we measured micro-Raman scattering microscopic imaging on oxygen-related peaks of the conductors. Comparing the Raman signal images with the low temperature optical scanning maps, it is remarkable that the structural disorders represented by oxygen-related Raman peaks are closely related to the low temperature bolometric abnormalities. From this result, a nature of the dissipative current distribution in coated conductors is revealed. The scanning optical microscopic study will provide a promising method for quality assurance of coated conductors.
Viability estimation of pepper seeds using time-resolved photothermal signal characterization
Kim, G.,Kim, G.H.,Lohumi, S.,Kang, J.S.,Cho, B.K. Pergamon 2014 Infrared physics & technology Vol.67 No.-
We used infrared thermal signal measurement system and photothermal signal and image reconstruction techniques for viability estimation of pepper seeds. Photothermal signals from healthy and aged seeds were measured for seven periods (24, 48, 72, 96, 120, 144, and 168h) using an infrared camera and analyzed by a regression method. The photothermal signals were regressed using a two-term exponential decay curve with two amplitudes and two time variables (lifetime) as regression coefficients. The regression coefficients of the fitted curve showed significant differences for each seed groups, depending on the aging times. In addition, the viability of a single seed was estimated by imaging of its regression coefficient, which was reconstructed from the measured photothermal signals. The time-resolved photothermal characteristics, along with the regression coefficient images, can be used to discriminate the aged or dead pepper seeds from the healthy seeds.
Kim, G.,Lee, N.,Kim, K.B.,Kim, B.K.,Chang, H.,Song, S.J.,Park, J.Y. Pergamon Press ; Elsevier Science Ltd 2013 INTERNATIONAL JOURNAL OF HYDROGEN ENERGY - Vol.38 No.3
This article investigates the relationship between ionic conductivity and various processing methods for aliovalent-doped, ceria solid solution particles, as an intermediate temperature-solid oxide electrolyte to explain the wide range of conductivity values that have been reported. The effects of doping material and content on the ionic conductivity are investigated comprehensively in the intermediate temperature range. The chemical routes such as coprecipitation, combustion, and hydrothermal methods are chosen for the synthesis of ceria-based nanopowders, including the conventional solid-state method. The ionic conductivity for the ceria-based electrolytes depends strongly on the lattice parameter (by dopant type and content), processing parameters (particle size, sintering temperature and microstructure), and operating temperature (defect formation and transport). Among other doped-ceria systems, the Nd<SUB>0.2</SUB>Ce<SUB>0.8</SUB>O<SUB>2-d</SUB> electrolyte synthesized by the combustion method exhibits the highest ionic conductivity at 600 <SUP>o</SUP>C. Further, a novel composite Nd<SUB>0.2</SUB>Ce<SUB>0.8</SUB>O<SUB>2-d</SUB> electrolyte consisting of a combination of powders (50:50) synthesized by coprecipitation and combustion is designed. This electrolyte demonstrates an ionic conductivity two to four times higher than that of any singly processed electrolytes.
Kim, G.,Jeong, A.R.,Jo, W.,Park, D.Y.,Cheong, H.,Tsukada, A.,Hammond, R.H.,Beasley, M.R. The Korean Superconductivity Society 2010 Progress in superconductivity Vol.11 No.2
Phase stability diagram and boundary of a- and c-axis orientation of $SmBa_2Cu_3O_{7-y}$ (SmBCO) thin films grown by pulsed laser deposition (PLD) were reported with studies based on x-ray diffraction [1]. Four different samples are systematically analyzed: normal c-axis oriented orthorhombic $SmBa_2Cu_3O_{7-y}$, a-axis oriented $SmBa_2Cu_3O_{7-y}$, c-axis oriented orthorhombic $SmBa_2Cu_3O_{7-y}$ with $Sm_2BaCuO_5$ phase, and a mixture with c-axis oriented orthorhombic $SmBa_2Cu_3O_{7-y}$ and anomalously long-c tetragonal $SmBa_2Cu_3O_x$. Raman scattering spectroscopy equipped with polarization analysis elucidates the crystal orientation and the origin of the growth of the materials. It indicates that the technique can be used for quality control of conductor manufacturing processes as well as for enhancement of the materials properties.