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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.
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, Mark A.,Shin, Hyung-Seop,Ha, Hongsoo,Oh, Sang-Soo The Korea Institute of Applied Superconductivity a 2019 한국초전도저온공학회논문지 Vol.21 No.4
Multilayered high-temperature superconductor coated conductor (CC) tapes are used in an extensive range of applications and are exposed to many stresses such as hoop stress, radial/transverse tensile stress under large Lorentz forces, and thermal stress while cooling if thermal expansion properties differ. Loads induced transversely at the tape surface inevitably create delamination phenomena in the multilayered CC tapes. Thus, delamination behaviors of CC tapes along the c-axis under transverse loading conditions, which can vary based on manufacturing process and constituent layers, must be characterized for applications. The anvil test method was used to mechanically investigate the delamination characteristics of various commercially available Ag-stabilized CC tapes at room temperature and 77 K, finding superior strength at the latter. The wide variations found depended on tape structure and fabrication technique. Fractographic morphologies of delaminated tapes supported the findings under transverse loading conditions.
Diaz Lantada, A.,Lafont Morgado, P.,Munoz-Guijosa, J.M.,Munoz Sanz, J.L.,Echavarri Otero, J.,Chacon Tanarro, E.,De la Guerra Ochoa, E. Techno-Press 2014 Smart Structures and Systems, An International Jou Vol.14 No.4
The combined use of smart materials, complementing each others' characteristics and resulting in devices with optimised features, is providing new solutions in many industries. The use of ingenious combinations of smart materials has led to improvements in actuation speed and force, signal-to-noise ratio, sensor precision and unique capabilities such as self-sensing self-healing systems and energy autonomy. This may all give rise to a revival for numerous families of smart materials, for which application proposals had already reached a stationary situation. It may also provide the boost needed for the definitive industrial success of many others. This study focuses on reviewing the proposals, preliminary studies and success cases related to combining smart materials to obtain multifunctional, improved systems. It also examines the most outstanding applications and fields for the combined use of these smart materials. We will also discuss related study areas which warrant further research for the development of novel approaches for demanding applications.
Diaz, Edgar A.,Chung, Yeonseung,Papapostolou, Vasileios,Lawrence, Joy,Long, Mark S.,Hatakeyama, Vivian,Gomes, Brenno,Calil, Yasser,Sato, Rodrigo,Koutrakis, Petros,Godleski, John J. Informa Healthcare 2012 Inhalation toxicology Vol.24 No.5
<P>The study presented here is a laboratory pilot study using diluted car exhaust from a single vehicle to assess differences in toxicological response between primary emissions and secondary products resulting from atmospheric photochemical reactions of gas phase compounds with O<SUB>3</SUB>, OH and other radicals. Sprague Dawley rats were exposed for 5 h to either filtered room air (sham) or one of two different atmospheres: (i) diluted car exhaust (P)+Mt. Saint Helens Ash (MSHA); (ii) P+MSHA+secondary organic aerosol (SOA, formed during simulated photochemical aging of diluted exhaust). Primary and secondary gases were removed using a nonselective diffusion denuder. Continuous respiratory data was collected during the exposure, and bronchoalveolar lavage (BAL) and complete blood counts (CBC) were performed 24 h after exposure. ANOVA models were used to assess the exposure effect and to compare those effects across different exposure types. Total average exposures were 363 ± 66 μg/m<SUP>3</SUP> P+MSHA and 212 ± 95 µg/m<SUP>3</SUP> P+MSHA+SOA. For both exposures, we observed decreases in breathing rate, tidal and minute volumes (TV, MV) and peak and median flows (PIF, PEF and EF50) along with increases in breathing cycle times (Ti, Te) compared to sham. These results indicate that the animals are changing their breathing pattern with these test atmospheres. Exposure to P+MSHA+SOA produced significant increases in total cells, macrophages and neutrophils in the BAL and <I>in vivo</I> chemiluminescence of the lung. There were no significant differences in CBC parameters. Our data suggest that simulated atmospheric photochemistry, producing SOA in the P+MSHA+SOA exposures, enhanced the toxicity of vehicular emissions.</P>
Diaz, Mark Angelo,Shin, Hyung-Seop The Korean Society of Superconductivity and Cryoge 2022 한국초전도저온공학회논문지 Vol.24 No.3
One of the major applications of REBCO coated conductor (CC) tapes is in superconducting magnets or coils that are designed for high magnet fields. For such applications, the CC tapes were exposed to a high level of stresses which includes uniaxial tensile or transverse compressive stresses resulting from a large magnetic field. Thus, CC tapes should endure such mechanical load or deformation that can influence their electromechanical performance during manufacturing, cool-down, and operation. It has been reported that the main cause of critical current (I<sub>c</sub>) degradation in CC tapes utilized in coil windings for superconducting magnets was the delamination due to transversely applied stresses. In most high-magnetic-field applications, the operating limits of the CC tapes will likely be imposed by the electromechanical properties together with its I<sub>c</sub> dependence on temperature and magnetic field. In this study, we examined the influence of the transverse compressive stress on the I<sub>c</sub> degradation behaviors in various commercially available CC tapes which is important for magnet design Four differently processed REBCO CC tapes were adopted to examine their I<sub>c</sub> degradation behaviors under transverse compression using an anvil test method and a newly developed instantaneous I<sub>c</sub> measurement system. As a result, all REBCO CC tapes adopted showed robustness against transverse compressive stresses for REBCO coils, notably at transverse compressive stresses until 250 MPa. When the applied stress further increased, different Ic degradation behaviors were observed depending on the sample. Among them, the one that was fabricated by the IBAD/MOCVD process showed the highest compressive stress tolerance.