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Morphology control and optical properties of ZnO nanostructures grown by ultrasonic synthesis
Morales-Flores, N.,Galeazzi, R.,Rosendo, E.,Diaz1d, T.,Velumani, S.,Pal, U. Techno-Press 2013 Advances in nano research Vol.1 No.1
ZnO nanostructures of rod-like, faceted bar, cup-end bars, and spindle shaped morphologies could be grown by a low power ultrasonic synthesis process. pH of the reaction mixture seems to plays an important role for defining the final morphology of ZnO nanostructures. While the solution pH as low as 7 produces long, uniform rod-like nanostructures of mixed phase (ZnO and $Zn(OH)_2$), higher pH of the reaction mixture produces ZnO nanostructures of different morphologies in pure hexagonal wurtzite phase. pH of the reaction as high as 10 produces bar shaped uniform nanostructures with lower specific surface area and lower surface and lattice defects, reducing the defect emissions of ZnO in the visible region of their photoluminescence spectra.
Mo,Cu-doped CeO<sub>2</sub> as Anode Material of Solid Oxide Fuel Cells (SOFCs) using Syngas as Fuel
Diaz-Aburto, Isaac,Hidalgo, Jacqueline,Fuentes-Mendoza, Eliana,Gonzalez-Poggini, Sergio,Estay, Humberto,Colet-Lagrille, Melanie The Korean Electrochemical Society 2021 Journal of electrochemical science and technology Vol.12 No.2
Mo,Cu-doped CeO<sub>2</sub> (CMCuO) nanopowders were synthesized by the nitrate-fuel combustion method aiming to improve the electrical and electrochemical properties of its Mo-doped CeO<sub>2</sub> (CMO) parent by the addition of copper. An electrical conductivity of ca. 1.22·10<sup>-2</sup> S cm<sup>-1</sup> was measured in air at 800℃ for CMCuO, which is nearly 10 times higher than that reported for CMO. This increase was associated with the inclusion of copper into the crystal lattice of ceria and the presence of Cu and Cu<sub>2</sub>O as secondary phases in the CMCuO structure, which also could explain the increase in the charge transfer activities of the CMCuO based anode for the hydrogen and carbon monoxide electro-oxidation processes compared to the CMO based anode. A maximum power density of ca. 120 mW cm<sup>-2</sup> was measured using a CMCuO based anode in a solid oxide fuel cell (SOFC) with YSZ electrolyte and LSM-YSZ cathode operating at 800℃ with humidified syngas as fuel, which is comparable to the power output reported for other SOFCs with anodes containing copper. An increase in the area specific resistance of the SOFC was observed after ca. 10 hours of operation under cycling open circuit voltage and polarization conditions, which was attributed to the anode delamination caused by the reduction of the Cu<sub>2</sub>O secondary phase contained in its microstructure. Therefore, the addition of a more electroactive phase for hydrogen oxidation is suggested to confer long-term stability to the CMCuO based anode.
Diaz, Mark Angelo,Shin, Hyung Seop,Lee, Jae-Hun The Korean Society of Superconductivity and Cryoge 2018 한국초전도저온공학회논문지 Vol.20 No.4
When REBCO coated conductors (CCs) are applied to superconducting devices such as coils and magnets, they are subjected to deformation in various modes such as compression/tension bending, uniaxial/transverse tension and torsion. Despite outstanding performances by REBCO CC tapes, their electromechanical properties have been evaluated primarily under uniaxial tension, therefore data about the critical current ($I_c$) response in the compressive strain region are lacking. In this study, the characteristic responses of $I_c$ in REBCO CC tapes under bending strains in the range from tensile to compressive were evaluated. The springboard bending beam was used, wherein the CC tape sample was soldered onto the surface of the springboard. A Goldacker-type bending test rig, which lacks a support holding the sample during testing, was used as a comparator. Degradation in $I_c$ behaviors, including strain sensitivity, in differently processed REBCO CC tapes were examined based on the test rig used.
Invariant operators, orthogonal bases and correlators in general tensor models
Diaz, Pablo,Rey, Soo-Jong Elsevier 2018 Nuclear Physics, Section B Vol.932 No.-
<P><B>Abstract</B></P> <P>We study invariant operators in general tensor models. We show that representation theory provides an efficient framework to count and classify invariants in tensor models of (gauge) symmetry <SUB> G d </SUB> = U ( <SUB> N 1 </SUB> ) ⊗ ⋯ ⊗ U ( <SUB> N d </SUB> ) . As a continuation and completion of our earlier work, we present two natural ways of counting invariants, one for arbitrary <SUB> G d </SUB> and another valid for large rank of <SUB> G d </SUB> . We construct bases of invariant operators based on the counting, and compute correlators of their elements. The basis associated with finite rank of <SUB> G d </SUB> diagonalizes the two-point function of the free theory. It is analogous to the restricted Schur basis used in matrix models. We show that the constructions get almost identical as we swap the Littlewood–Richardson numbers in multi-matrix models with Kronecker coefficients in general tensor models. We explore the parallelism between matrix model and tensor model in depth from the perspective of representation theory and comment on several ideas for future investigation.</P>
Diaz, Melvin B.,Kim, Kwang Yeom,Kang, Tae-Ho,Shin, Hyu-Soung Elsevier 2018 Geothermics Vol.72 No.-
<P><B>Abstract</B></P> <P>Drilling parameters are analyzed here to improve forecasting of the rate of penetration (ROP) in enhanced geothermal systems (EGSs). Data recorded during drilling a 4.2-km-deep well at a pilot EGS project in South Korea were analyzed. The greatly fluctuating ROP values were smoothed using a fast Fourier transform filter. Two drilling optimization methods (multiple regression and artificial neural networks) then evaluated the effect of smoothing: it improved ROP prediction in both cases, with over 90% correlation at relatively low degrees of filtering. A methodology to optimize the degree of smoothness for a given drilling data set is suggested.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Analysis of drilling parameters recorded during drilling of a 4.2 km depth well. </LI> <LI> The drilling data comes from an Enhanced Geothermal System (EGS) project. </LI> <LI> The fluctuating ROP recorded values were smoothed using an FFT filter. </LI> <LI> Multiple regression and a neural network evaluated the filtering effect on ROP prediction. </LI> <LI> A methodology to optimize the degree of smoothness is suggested. </LI> </UL> </P>