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To understand the transport processes in a repository silo for radioactive waste, the diffusion behavior of tritium (THO), strontium (Sr), cesium (Cs), and americium (Am) through concrete was investigated using a through-diffusion setup. The concrete and groundwater used in this study were sampled from the waste repository site. The diffusivity of the nuclides was obtained by a linear curve fitting of the diffused concentration data against time. After 18 months, the concrete coupons and solutions were recovered from the experimental setups. A sequential chemical extraction was carried out with the recovered coupons to determine the types of sorption involved in the nuclides diffusion processes. The THO transported freely through the concrete pores without sorption. The sorption of Sr and Cs was reversible, whereas that of Am was highly irreversible with a very low diffusivity. After a year in the diffusion test, some precipitate and suspended matter were observed. The precipitates were analyzed with SEM, EDS, and XRD. Identified as calcium carbonates and magnesium compound, they are likely formed by the chemical degradation of the concrete. [ABSTRACT FROM AUTHOR]

The second leading cause of death among Korean adolescents was suicide in 2014. We assessed the relationship between sleep duration and suicidal behavior (ideation, planning and attempt) using data from the Korea Youth Risk Behavior Web-based Survey (KYRBS). KYRBS is an anonymous online survey in self-reporting format that investigates the health status of middle and high school students. Weekly sleep duration was divided into six groups (more than 8, 7-8, 6-7, 5-6, 4-5 h, less than 4 h). We compared the more-than-8-h group with others for sleep duration-associated suicidal behavior. Results showed that even though the confidence interval for the odds ratio for some sleep duration groups was not significant, there was a statistically significant inverse positive trend of suicidal behavior (ideation, planning and attempt) with the sleep duration groups ( P value for trend ≤0.001). In conclusion, this study found that short average weekday sleep duration among Korean adolescents was associated with suicidal behavior independent of various confounding factors, which includes depressed mood. [ABSTRACT FROM AUTHOR]

In this study, the status of natural analogue studies in Korea is briefly summarized and applicability of existing natural analogue information to the Korean safety case has been evaluated. To enable effective application of natural analogue information to the overall evaluation of long-term safety (the 'safety case') for the geological disposal of radioactive wastes, a natural analogue database has been developed by collecting, classifying, and evaluating relevant data. The natural analogue data collected were classified into categories based on site information, components/processes of the disposal system, properties/phenomena, reference, safety case application, application method, and suitability to a safety case. Suitability of the natural analogue data to a specific safety case was evaluated based upon the importance and the applicability to the Korean safety case. As a result, 75 natural analogue datasets were selected as important for the Korean safety case. The database developed can now be utilized in the RD&D (Research, Development, and Demonstration) program development for natural analogue studies. In addition, the methodology developed and the database compiled in this study may assist in the development of safety case including safety assessment for high-level radioactive waste disposal in Korea as well as in other countries. [ABSTRACT FROM AUTHOR]

High power densities have been obtained from MFC reactors having a purple color characteristic of Rhodopseudomonas. We investigated the microbial community structure and population in developed purple MFC medium (DPMM) and MFC effluent (DPME) using 16S rRNA pyrosequencing. In DPMM, dominant bacteria were Comamonas (44.6%), Rhodopseudomonas (19.5%) and Pseudomonas (17.2%). The bacterial community of DPME mainly consisted of bacteria related to Rhodopseudomonas (72.2%). Hydrogen oxidizing bacteria were identified in both purple-colored samples: Hydrogenophaga and Sphaerochaeta in the DPMM, and Arcobacter, unclassified Ignavibacteriaceae, Acinetobacter, Desulfovibrio and Wolinella in the DPME. The methanogenic community of both purple-colored samples was dominated by hydrogenotrophic methanogens including Methanobacterium, Methanobrevibacter and Methanocorpusculum with significantly lower numbers of Methanosarcina. These results suggeste that hydrogen is actively produced by Rhodopseudomonas that leads to the dominance of hydrogen consuming microorganisms in both purple-colored samples. The syntrophic relationship between Rhodopseudomonas and hydrogenotrophic microbes might be important for producing high power density in the acetate-fed MFC under light conditions. [ABSTRACT FROM AUTHOR]

Viewers watching Interactive TV can click on video objects on the screen, connecting them to an advertisement or more detailed content. But this requires an interactive authoring process to attach triggers to clickable objects, which is time-consuming because these objects can appear intermittently, move, and change shape. We facilitate authoring by combining a sketching interface with shot-based object tracking and trigger verification. Experiments involving professional video authors and non-specialist viewers suggest that this approach is an improvement on previous methods. [ABSTRACT FROM AUTHOR]

Strontium titanium silicates are possible oxide forms for immobilization of short lived fission products in radioactive waste. Through beta decay, strontium decays to yttrium, and then to zirconium. Therefore, not only the stability of Sr-loaded waste forms, but also that of a potential decay product series with charge-balance in a naturally occurring mineral or a ceramic is of fundamental importance. Strontium titanosilicate (SrTiSiO5) is the Sr-analogue of titanite (CaTiSiO5). To incorporate the reaction 3Sr2+ = 2Y3+ + vacancy in the titanite composition, Y-substituted Sr-analogues of titanite, (Sr1–xY2/3x)TiSiO5 (x = 0, 0.25, 0.5, 0.75) were prepared by high temperature synthesis and were found to form glass upon cooling. The Y-end-member (Y2/3TiSiO5, x = 1) crystallized to a mixture of Y2TiSiO7, TiO2, and SiO2 upon quenching in air. The enthalpies of formation of Y-substituted Sr-titanite glasses were obtained from drop solution calorimetry in a molten lead borate (2PbO·B2O3) solvent at 702 °C. The enthalpies of formation from constituent oxides are exothermic but become less so with increasing Y content. The thermodynamic stability of the Y-substituted Sr-analogue of crystalline titanite may become marginal with increasing yttrium content. [ABSTRACT FROM AUTHOR]

The electrorheological (ER) and dielectric behaviors of the polypyrrole(PPy)-coated poly(ethyl methacrylate)(PEMA) suspensions in mineral oil were investigated. PPy was coated on PEMA particles to enhance the particle polarization, which would lead to the enhanced ER response. Various PPy-coated PEMA particles were synthesized by controlling the oxidant amount during the pyrrole polymerization, and the ER responses of their suspensions were investigated. The ER response initially increases with the oxidant amount, passes through a maximum, and then decreases with the oxidant amount. The initial increase in the ER response with oxidant amounts is due to the enhanced particle polarization with the increased particle surface conductivity. The dielectric properties of the corresponding suspensions support that the ER enhancement arises from the enhanced particle polarization. The decrease in the ER response at large oxidant amounts seems to arise from the increased conduction between the PPy-coated PEMA particles. [ABSTRACT FROM AUTHOR]

Aerogels of titania, zirconia, niobia, and silica were prepared by CO2 supercritical drying of the corresponding alcogels. Their porous texture could be modified by further aging of the alcogels. This kind of textural modification was found to be different according to the nature of the metal precursor and sol-gel conditions. [ABSTRACT FROM AUTHOR]

For the preparation of HFC-134a, the isomerization of CFC-114 and the hydrogenation of CFC-114a were investigated. Both reactions were catalyzed by AlC and supported Pd catalysts, respectively. For the comparison purpose, the isomerization of CFC-113 was carried out also. With virgin AICI catalyst, both isomerization reactions proceeded after a certain induction period probably because the catalyst needed the activation by the halogen exchange. The catalyst deactivated gradually with the time on stream. However, the deactivation rate could be reduced by removing impurities from the reactants. Isomerization rate of CFC-114 was much slower than that of CFC-113. Palladium supported on carbon catalyzed the hydrogenation reaction quite selectively while the selectivity declined when the support was replaced with different supports. The catalytic activity and selectivity to desired products increased in the following order. Pd/kieselguhr Pd/silica-alumina ≅Pd/silica gel Pd/TiOPd/AlOPd/C [ABSTRACT FROM AUTHOR]

Abstracts are not published in this journal [ABSTRACT FROM AUTHOR]