Juyoung Kim

Environmental asbestos exposure sources in Korea

Background: Because of the long asbestos-related disease latencies (10–50 years), detection, diagnosis, and epidemiologic studies require asbestos exposure history. However, environmental asbestos exposure source (EAES) data are lacking. Objectives: To survey the available data for past EAES and supplement these data with interviews. Methods: We constructed an EAES database using a literature review and interviews of experts, former traders, and workers. Exposure sources by time period and type were visualized using a geographic information system (ArcGIS), web-based mapping (Google Maps), and OpenWeatherMap. The data were mounted in the GIS to show the exposure source location and trend. Results: The majority of asbestos mines, factories, and consumption was located in Chungnam; Gyeonggi, Busan, and Gyeongnam; and Gyeonggi, Daejeon, and Busan, respectively. Shipbuilding and repair companies were mostly located in Busan and Gyeongnam. Conclusions: These tools might help evaluate past exposure from EAES and estimate the future asbestos burden in Korea.

Magnetoelectric Coupling of CuFe2O4/Pt/Pb(Zr0.52Ti0.48)O3 Multilayer Thin Films

CuFe2O4/Pt/Pb(Zr0.52Ti0.48)O3 (PZT) multilayer thin films were grown on (111)-oriented Pt/TiO2/SiO2/Si<100> substrate. PZT layer was fabricated by the sol-gel method. Afterwards, Pt layer was deposited by ion beam sputtering method. Finally, CuFe2O4 layer were deposited using pulsed laser deposition method (PLD). The film structure is tri-layered type, where the bottom PZT layer covered the whole substrate, while Pt and CuFe2O4 layers were deposited through circular shadow masks to measure ferroelectric and magnetoelectric properties. Film microstructure was observed using XRD and FE-SEM. Magnetoelectric coefficients were calculated by measured magnetoelectric voltages using magnetoelectric measurement system.

Influence of Annealing Temperature on Magnetoelectric Properties of CoFe2O4/Pt/Pb(Zr0.3Ti0.7)O3 Thin Films

CoFe2O4/Pt/Pb(Zr0.3Ti0.7)O3 thin films were grown on Pt/Ti/SiO2/Si substrate in order to investigate the magnetoelectric properties of ferromagnetic/ferroelectric multilayer thin films. Thin Pt layer was introduced to prevent inter-diffusion between CoFe2O4 and Pb(Zr0.3Ti0.7)O3 (PZT) layers. PZT thin film was grown directly on top of Pt substrate by utilizing sol-gel spin coating technique. In order to investigate the possible annealing effect on film microstructure and magnetoelectric properties, multilayer thin film stack was heat-treated at different temperatures ranging from 550°C to 650°C. The structural properties of the films were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Ferroelectric and ferromagnetic behaviors were analyzed by measuring polarization and magnetization – electric and magnetic field hysteresis. Magnetoelectric coefficients were calculated by measuring magnetoelectric voltages using magnetoelectric measurement system. Both the magnetoelectric properties and the coupling effect of CoFe2O4/Pt/PZT films on ferromagnetic and magnetoelectric properties are discussed as a function of heat-treatment temperature.

Spatial Analysis Methods for Asbestos Exposure Research

Objectives: Spatial analysis is useful for understanding complicated causal relationships. This paper focuses trends and appling methods for spatial analysis associated with environmental asbestos exposure. Methods: Literature review and reflection of experience of authors were conducted to know academic background of spatial analysis, appling methods on epidemiology and asbestos exposure. Results: Spatial analysis based on spatial autocorrelation provides a variety of methods through which to conduct mapping, cluster analysis, diffusion, interpolation, and identification. Cause of disease occurrence can be investigated through spatial analysis. Appropriate methods can be applied according to contagiousness and continuity. Spatial analysis for asbestos exposure source is needed to study asbestos related diseases. Although a great amount of research has used spatial analysis to study exposure assessment and distribution of disease occurrence, these studies tend to focus on the construction of a thematic map without different forms of analysis. Recently, spatial analysis has been advanced by merging with web tools, mobile computing, statistical packages, social network analysis, and big data. Conclusions: Because the trend in spatial analysis has evolved from simple marking into a variety of forms of analyses, environmental researchers including asbestos exposure study are required to be aware of recent trends.

Pyroelectric power generation with ferroelectrics (1-x)PMN-xPT

ABSTRACT A novel electrothermodynamic cycle based on temporal temperature variations (dT/dt); the pyroelectric effect was investigated for its potential role in the use of waste heat as renewable energy. Here, we present improved generating performance with relaxer ferroelectric ceramics ((1-x)Pb(Mg2/3Nb1/3)O3-xPbTiO3 (PMN-xPT)), which are well known for their strong dielectric and pyroelectric properties near the morphotropic phase boundary. The theoretical potential was evaluated using hysteresis loops, and the generating properties were analyzed in the laboratory using an engine dynamometer. The experiments yielded a value of 0.48 mW/cm3, which is 3 times larger than that obtained previously, because of the high polarization properties.

Degradation Behavior of BaTiO3Dielectrics for MLCCs by an Accelerated Life Test With Voltage and Temperature Stress Factors

An accelerated life test (ALT) was designed under voltage and temperature stresses using 1005 type multilayer ceramic capacitors (MLCCs) based Ni-BaTiO3, and failure analysis was also conducted to compare the individual stress. The inverse power and Arrhenius models were applied to the voltage and temperature accelerated tests, respectively, and times to failure (TTF) of MLCCs under individual stress were measured. The stress–life relation was plotted from obtained life data, and characteristic life (B63.5) was calculated at the same condition of 130°C and 3 times rated voltage. B63.5 under the voltage stress was 15.91 min and that of the temperature stress was 17.23 min. It was determined that the voltage stress had more influence on the degradation of insulation resistance for MLCCs. As a result of an analysis of the chemical bonding state from the dielectric ceramic and inner electrodes, according to increase in the stresses, the binding energy of Ti 2p3/2 and Ni 2p3/2 peak changed, which generated oxygen vacancies. These oxygen vacancies accelerated the degradation under the high-voltage stress, caused the reduction of the BaTiO3 ceramic and oxidation of the Ni electrode, and consequently decreased the insulation resistance.

ZrO₂-C계 침지노즐 제조시 상대습도에 따른 바인더용 페놀수지의 영향

The thermodynamic behavior of phenolic resin was investigated to verify the relation between the properties of porous ceramics with ZrO₂-C system for submerged entry nozzle and the characteristics of phenolic resin with various relative humidity. The green and the sintered density were decreased between 25% and 50% relative humidity, whereas they were gradually enhanced above 50% relative humidity. The highest value of apparent porosity was 20.1% and the minimum compressive strength was 69㎫ in the specimen using the powder exposed to 50% relative humidity. As a result of thermal analysis for phenolic resin, the shift of endothermic peak to low temperature and the reduction of exothermic peak were observed, and the peaks corresponded to melting and curing of phenolic resin, respectively. The melting and the curing of phenolic resin generate the change of green density, and it can affect the properties of submerged entry nozzle.