Microstructural Evolution of Transparent PLZT Ceramics Sintered in Air and Oxygen Atmospheres

Transparent lanthanum-doped lead zirconate titanate (PLZT) ceramics were fabricated by air-pressure sintering. When the PLZT (9/65/35) specimens were sintered in air, the microstructure was not uniform throughout the body; the outer region near the surface was completely dense, while the inner region of the body was porous. The thickness of the outer dense layer increased parabolically with sintering time. When the specimen was sintered in air at 1200°C for 8 h, the thickness of the dense layer was ∼0.25 mm. Therefore, when the specimen had a thickness of <0.5 mm, it was dense and transparent. This difference in microstructure was attributed to the formation of lattice vacancies as a result of PbO evaporation from the surface. The sintering atmosphere also was important in determining the thickness of the dense layer. The thickness was strongly dependent on the oxygen partial pressure of the atmosphere. The oxygen-gas trapped in pores was deemed to migrate easily through the lattice vacancies. By sintering in an oxygen-gas atmosphere at 1200°C for 8 h, a transparent PLZT with thickness up to 2 mm was fabricated.     

Oxidation and reduction characteristics of oxygen carrier particles and reaction kinetics by unreacted core model

The reaction kinetics of the oxygen carrier particles, which are used as bed material for a fluidized bed chemical looping combustor (CLC), has been studied experimentally by a conventional thermal gravimetrical analysis technique. The weight percent of nickel and nickel oxide in oxygen carrier particles and reaction temperature were considered as experimental variables. After oxidation reaction, the pure nickel particle was sintered and unsuitable to use as fluidizing particles. The oxidation reaction rate increased with increasing weight percent of nickel in oxygen carrier particles and reaction temperature. The rate of reduction shows maximum point with weight percent of nickel oxide (57.8%) and reaction temperature (750 or 800 °C) increased. In this work, the reaction between air and Ni/ bentonite particle was described by a special case of unreacted core model in which the global reaction rate is controlled by product layer diffusion resistance. However, the reaction between CH₄ and NiO/bentonite particle was described by unreacted core model in which the global reaction rate is controlled by chemical reaction resistance. The temperature dependence of the effective diffusivity of oxidation reaction and reaction rate constant of reduction reaction could be calculated from experimental data and fitted to the Arrhenius equation. Presented at the Int’l Symp. on Chem. Eng. (Cheju, Feb. 8-10, 2001), dedicated to Prof. H. S. Chun on the occasion of his retirement from Korea University.     

A numerical approach to determine creep constants for Time-Temperature Parametric methods

This study dealt with how to mathematically obtain creep constants of C, Q/2.3R, T _a and t _a used in Time-Temperature Parametric (TTP) methods. A number of creep rupture data from 550 °C to 800 °C for Type 316LN stainless steel were collected through a worldwide literature survey and experimental data produced at KAERI. It was found that the creep rupture data revealed a linear relationship when the data were plotted by the semilogarithmic coordinates of log (t _r ) versus stress. On the basis of this linear relationship, the creep constants of C, Q/2.3R, T _a and t _a used in the Larson-Miller (LM), the Orr-Sherby-Dorn (OSD), and the Manson-Haferd (MH) methods were obtained by a new numerical method. This approach can be utilized as a useful method to predict the long-term creep life of Type 316 stainless steel.     

Reinforcement of styrene‐butadiene/polybutadiene rubber compounds by modified silicas with different surface and networked states

In this study, the reinforcement performance of the modified silicas prepared through the incorporation of 3‐aminopropyltriethoxy silane (AP) and further reaction of bisphenol A diglycidyl ether (BG) to styrene‐butadiene/butadiene rubber (SBR/BR) compounds was investigated to discuss the effect of surface and networked states on the properties of silica‐filled rubber compounds. The adjustment of the ratio of BG to AP varied the surface and networked states of silica. The amino and glycidyl groups dispersed on the silica and the networks formed on/between silica particles considerably influenced the properties of SBR/BR compounds reinforced with the modified silicas. The presence of amino group increased viscosity of the rubber compounds due to the attrition between rubber chains and silica particles, while the entanglement of rubber chains with the networks successfully improve both wet traction and rolling resistance, without sacrificing the fundamental properties of the rubber compounds, even though no coupling agents were applied. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44893.     

Preparation and properties of emulsifier‐/solvent‐free polyurethane‐acrylic hybrid emulsions for binder materials: Effect of the glycidyl methacrylate/acrylonitrile content

To obtain binder materials, emulsions of emulsifier‐/solvent‐free waterborne polyurethane‐acrylic hybrids with a fixed acrylic monomer content (30 wt %) were prepared in this study. This study focused on the effect of glycidyl methacrylate (GMA)/acrylonitrile (AN) wt % on the shelf stability, mean particle size and viscosity of hybrid emulsion samples, water swelling %/dynamic mechanical thermal properties/mechanical properties of hybrid film samples, and the failure mode and adhesive strength of binder materials prepared in this study. Characterization of the chemical structures of prepolymers, hybrid materials (binder materials), and atmospheric pressure plasma‐treated polyethylene (PE) has been performed by means of Fourier transformed infrared spectroscopy to determine the presence/disappearance/peak intensity change of functional groups. Various properties such as mean particle size, viscosity, T_g, water swelling %, hardness and mechanical properties, and failure mode and adhesive strength for leather/leather, control PE/leather, and plasma‐treated PE/leather were found to be significantly dependent on the weight ratio of GMA/AN. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44497.     

Effects of oxygen concentration on the electrical properties of ZnO films

In this paper, electrical characteristics by various oxygen content in ZnO films were studied. To control the oxygen content of ZnO films, post-thermal annealing was performed in N₂ and air ambient, led to improve crystallinity and optical properties of ZnO films. The oxygen concentration was measured by Auger electron spectroscopy. The ZnO films having the deficiency of oxygen showed the electron concentrations between 10²¹ and mid 6 × 10¹⁷ cm⁻³ and resistivity at 10⁻³–10⁻¹ Ω cm. On the other hand, when the oxygen concentration of the ZnO films was up to the stoichiometry with Zn, the ZnO films showed low electron concentration at −10¹⁷ cm⁻³ and resistivity at 10 Ω cm.     

p53 Enhances Artemisia annua L. Polyphenols-Induced Cell Death Through Upregulation of p53-Dependent Targets and Cleavage of PARP1 and Lamin A/C in HCT116 Colorectal Cancer Cells

Plant-derived natural polyphenols exhibit anticancer activity without showing any noticeable toxicities to normal cells. The aim of this study was to investigate the role of p53 on the anticancer effect of polyphenols isolated from Korean Artemisia annua L. (pKAL) in HCT116 human colorectal cancer cells. We confirmed that pKAL induced reactive oxygen species (ROS) production, propidium iodide (PI) uptake, nuclear structure change, and acidic vesicles in a p53-independent manner in p53-null HCT116 cells through fluorescence microscopy analysis of DCF/PI-, DAPI-, and AO-stained cells. The pKAL-induced anticancer effects were found to be significantly higher in p53-wild HCT116 cells than in p53-null by hematoxylin staining, CCK-8 assay, Western blot, and flow cytometric analysis of annexin V/PI-stained cells. In addition, expression of ectopic p53 in p53-null cells was upregulated by pKAL in both the nucleus and cytoplasm, increasing pKAL-induced cell death. Moreover, Western bot analysis revealed that pKAL-induced cell death was associated with upregulation of p53-dependent targets such as p21, Bax and DR5 and cleavage of PARP1 and lamin A/C in p53-wild HCT116 cells, but not in p53-null. Taken together, these results indicate that p53 plays an important role in enhancing the anticancer effects of pKAL by upregulating p53 downstream targets and inducing intracellular cell death processes.     

A system for supporting paper-based augmented reality

In this paper, we aim to implement augmented reality (AR) on distant text documents or books. For this purpose, we propose a new paper-based AR system that can detect text documents in real scenes, markerize and identify them, estimate their relative 3D poses to the camera, and augment them with virtual contents. Unlike the previous paper-based AR systems (applicable to only close documents), the proposed system not only requires no detection of words or characters, but allows partial occlusions like the previous systems. In our experiments, the proposed system worked at 24 fps and could consistently achieve high identification rates for both occluded and unoccluded pages.     

Potential role of chlorination pathways in PCDD/F formation in a municipal waste incinerator

The role of chlorination reactions in the formation of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) in a municipal waste incinerator was assessed by comparing predicted chlorination isomer patterns with incinerator flue gas measurements. Complete distributions of PCDD and PCDF congeners were obtained from a stoker-type municipal waste incinerator operated under 13 test conditions. Samples were collected from the flue gas prior to the gas cleaning system. While total PCDD/F yields varied by a factor of 5 to 6, the distributions of congeners were similar. A conditional probability model, dependent only on the observed distribution of monochlorinated isomers, was developed to predictthe distributions of polychlorinated isomers formed by chlorination of dibenzo-p-dioxin (DD) and dibenzofuran (DF). Agreement between predicted and measured PCDF isomer distributions was high for all homologues, supporting the hypothesis that DF chlorination can play an important role in the formation of PCDF byproducts. The PCDD isomer distributions, on the other hand, did not agree well with model predictions, suggesting that DD chlorination was not a dominant PCDD formation mechanism at this incinerator. This work demonstrates the use of PCDD/F isomer patterns for testing formation mechanism hypotheses, and the findings are consistent with those from other municipal waste combustion studies.     

Development of oscillation method for reducing foodborne pathogens on lettuce and spinach

In this study, the efficacy of an oscillator for reducing the numbers of foodborne pathogens on lettuce and spinach was tested. A cocktail of three strains each of Salmonella typhimurium, Escherichia coli O157:H7 and Listeria monocytogenes cells and of Bacillus cereus spores was inoculated onto lettuce and spinach leaves and followed by oscillation at 10 Hz and 20 Hz for up to 30 s. After treatment of inoculated lettuce leaf with an oscillator at 20 Hz for 30 s, 2.58, 2.82, 2.21 and 2.22 Log₁₀ CFU/g reductions were obtained with the cells of S. typhimurium, E. coli O157:H7 and L. monocytogenes and the spores of B. cereus, respectively. In the case of the oscillation treatment of spinach leaf, 2.89, 3.73, 2.46 and 2.25 Log₁₀ CFU/g reductions of those pathogens were achieved under the same condition. Statistically significant reductions were observed after oscillation treatment at 20 Hz for 5-10 s. The oscillation treatment at 10 Hz led to slightly less reductions of the pathogens tested as compared to the treatment at 20 Hz. In conclusion, the oscillation method developed shows to be highly efficacious in reducing foodborne pathogens on lettuce and spinach leaves.