• Journal of the Korean Electrochemical Society
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• v.1 no.1
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• pp.33-39
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• 1998

To AC impedance study was performed in this study on the interfacial reaction between organic electrolyte and amorphous tungsten oxides thin film, cathodically coloring oxide, prepared by e-beam evaporation method in the 1 M $LiClO_4/PC$ organic solution. The electrochemical reactions at the interface were analyzed by the transient method and the complex impedance spectroscopy. The impedance spectrums showed that the electro-chemical intercalation of lithium cations was consisted of the following three steps; the first step, the charge transfer reaction of lithium cation at the interface between amorphous tungsten oxides thin film and the organic electrolyte, the second step, the adsorption of lithium atom on the surface of amorphous tungsten oxides thin film, and then the third step, the absorption and the diffusion of lithium atom into amorphous tungsten oxides thin layer. The bleaching and the coloring characteristics of amorphous tungsten oxides thin film were explained in terms of thermodynamic and kinetic variables, the simulated $R_{ct},\;C_{dl},\;D$ and $\sigma_{Li}$ by CNLS fitting method. Especially it was found that the limiting values of electrochromic reaction were the molar ratio of lithium, y=0.167 and the electrode potential, E=2.245 V (vs. Li).

• Korean Journal of Heritage: History & Science
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• v.44 no.3
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• pp.44-61
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• 2011

This study consider the life and works of Hu ShunShen(胡舜申) who was the author of JiRiSinBub(地理新法) which the representative FengShui book in Choson dynasty. His adult name is RuJia(汝嘉). He was born in on September 6, 1091 at JiXi(績溪) in China as a son of Ho Xian(胡咸). He left his hometown with his family to avoid war and settled down in HuZhou(胡州). He took up an official post with his brother's YinPu(蔭補), and held several provincial official posts. After serving as vice governor(通判) of ShuZhou(舒州), he became supervisor of taoist temple(崇道觀) in TaiZhou(台州) and retired from office. After burying his father, he took an interest in fengShui(風水) and studied for a long time. People say that JiangXiDilixinfa(江西地理新法) is the well-known FengShui book written by him. When he was 74 years old, he suggested opening SheMen(蛇門) gate and XuMen(胥門) gate in SuZhou(蘇州) castle by "WoMenZhongGao(吳門忠告)". But it didn't come ture. He died March 9, 1177 at the age of 87 and was buried in HuZhou(胡州). His elder brother Hu Shunzhi(胡舜陟) and nephew HuZi(胡仔) is well-known. He had a son named Hu wei(胡偉) who served pacification commissioners of JiangXi(江西宣撫使). His Works were YiSiSiZhouLu(乙巳泗州錄), YiYouBiLuanLu(己酉避亂錄) as essay and YinYangBeiYong(陰陽備用), JiRiSinBub(地理新法), "WoMenZhongGao(吳門忠告)" as fengShui text.

• Therapeutic Science for Rehabilitation
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• v.11 no.3
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• pp.23-36
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• 2022

Objectives : This study aimed to provide basic data on intervention strategies that occupational therapists can access by systematically analyzing the intervention and effectiveness for youth with disabilities. Methods : The RISS, PubMed, and Web of Science databases were used to search for papers published between 2006 and 2021. The keywords were "Disability AND Adolescents OR Young adult AND Transition education OR Transition program". Seven papers were selected for analysis, and the full text was reviewed. The keywords and national relations were analyzed and visualized using the WoS (Web of Science) and VOSviewer programs. Results : The participants were classified into five types (ASD or ADHD, ID, DD, and physical disability). The areas used for the intervention were mixed into three categories: occupation (academic), self-management (time), and interaction (personal relations and communication). Sociality and adaptation, quality of life, and at least one of the three categories of daily life activities showed significant improvement. Conclusions : This study can be used as basic data to expand the area where only OTs can contribute while grasping the research trend of the conversion program and presenting the direction of exchange with various experts by organizing the application and its effects.

• Journal of the Korean Society for information Management
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• v.39 no.3
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• pp.263-292
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• 2022

The purpose of this study is to identify the topics of research related to the concepts of literacy in the field of Library and Information Science which is related to user education in libraries. Data were collected from the WoS and KCI databases, and complementary keyword analysis and topic modeling analysis techniques were used to identify topics of literature-related research articles in the field of Library and Information Science. Findings presented that there was a difference in keywords and topics between the two databases. Literacy-related topics identified from the KCI database were classified into three groups through topic modeling. Also, it was analyzed that there is a difference between the overall literacy-related research trend, the timing of the surge in research volume, and key frequent keywords in the Library and Information Science field confirmed in the study. In particular, in the study of literacy in all fields, a number of words such as 'literacy', 'education', 'media', and 'digital' were derived. However, in literature research in the field of Library and Information Science, keywords such as 'information utilization ability' and 'school library' appeared. Based on this, it was concluded that research on the ability to develop an evaluative eye for information is needed in line with today's information environment, where information is rapidly increasing in Korea in the future.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.25 no.3
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• pp.294-300
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• 2015

Objectives: The aim of this study is to identify physicochemical properties such as chemical composition, size, shape and crystal structure of powder byproducts generated from a metallization process and its 1st scrubber in the semiconductor industry. Methods: Powder samples were collected from inner chambers during maintenance of the W-plug process equipment (using tungsten hexafluoride as a precursor material) and its 1st scrubber. The chemical composition, size and shape of the powder particles were determined by field emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM) equipped with an energy dispersive spectroscope (EDS). The crystal structure of the powders was analyzed by X-ray diffraction (XRD). Results: From the SEM-EDS and TEM-EDS analyses, O and W were mainly detected, which indicates the powder byproducts are tungsten trioxide ($WO_3$), whereas Al, F and Ti were detected as low peaks. The powder particles were spherical and nearly spherical, and the particle size collected from the process equipment and its 1st scrubber showed 10-20 nm (agglomerates: 55-90 nm) and 16-20 nm (agglomerates: 80-120 nm) as primary particles, respectively. The XRD patterns of the yellow powder byproducts exhibit five peaks at $23.8^{\circ}$ $33.9^{\circ}$ $41.74^{\circ}$ $48.86^{\circ}$ and $54.78^{\circ}$ which correspond to the (200), (220), (222), (400), and (420) planes of cubic $WO_3$. Conclusions: We elucidated the physicochemical characteristics of the powder byproducts collected from W-plug process equipment and its 1st scrubber. This study should provide useful information for the development of alternative strategies to improve the working environment and workers' health.

• Journal of Sensor Science and Technology
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• v.23 no.1
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• pp.15-18
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• 2014

We present gas sensing performance based on $2{\times}2$ sensor array with four different elements ($TiO_2$, $SnO_2$, $WO_3$ and $In_2O_3$ thin films) fabricated by rf sputter. Each thin film was deposited onto the selected $SiO_2$/Si substrate with Pt interdigitated electrodes (IDEs) of $5{\mu}m$ spacing which were fabricated on a $SiO_2$/Si substrate using photolithography and dry etching. For 5 ppm $NO_2$ and 50 ppm CO, each thin film sensor has a different response to offers the distinguishable response pattern for different gas molecules. Compared with the conventional micro-fabrication technology, $2{\times}2$ sensor array with such remarkable response pattern will be open a new foundation for monolithic integration of high-performance chemoresistive sensors with simplicity in fabrication, low cost, high reliablity, and multifunctional smart sensors for environmental monitoring.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.26 no.2
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• pp.119-138
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• 2016

Objectives: The purpose of this study is to review size, shape, and crystal structure-dependent toxicity of major metal oxide particles such as silicon dioxide, tungsten trioxide, aluminum oxide, and titanium dioxide as byproducts generated in semiconductor fabrication facility. Methods: To review the toxicity of major metal oxide particles, we used various reported research and review papers. The papers were searched by using websites such as Google Scholar and PubMed. Keyword search terms included '$SiO_2$(or $WO_3$ or $Al_2O_3$ or $TiO_2$) toxicity', 'health effects $SiO_2$(or $WO_3$ or $Al_2O_3$ or $TiO_2$). Additional papers were identified in references cited in the searched papers. Results: In various cell lines and organs of human and animals, cytotoxicity, genotoxicity, hepatoxicity, fetotoxicity, neurotoxicity, and histopathological changes were induced by silicon dioxide, tungsten trioxide, aluminium oxide, and titanium dioxide particles. Differences in toxicity were dependent on the cell lines, organs, doses, as well as the chemical composition, size, surface area, shape, and crystal structure of the particles. However, the doses used in the reported papers were higher than the possible exposure level in general work environment. Oxidative stress induced by the metal oxide particles plays a significant role in the expression of toxicity. Conclusions: The results cannot guarantee human toxicity of the metal oxide particles, because there is still a lack of available information about health effects on humans. In addition, toxicological studies under the exposure conditions in the actual work environment are needed.

• Journal of Powder Materials
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• v.28 no.3
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• pp.216-220
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• 2021

The effect of tert-butyl alcohol (TBA) as a freezing solvent on the pore structure of a porous tungsten body prepared by freeze-drying is analyzed. TBA slurries with a WO3 content of 10 vol% are prepared by mixing with a small amount of dispersant and binder at 30℃. The slurries are frozen at -25℃, and pores are formed in the frozen specimens by the sublimation of TBA during drying in air. After hydrogen reduction at 800℃ and sintering at 1000℃, the green body of WO₃ is completely converted to porous W with various pore structures. Directional pores from the center of the specimen to the outside are observed in the sintered bodies because of the columnar growth of TBA. A decrease in pore directionality and porosity is observed in the specimens prepared by long-duration drying and sintering. The change in pore structure is explained by the growth of the freezing solvent and densification.

• Structural Engineering and Mechanics
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• v.85 no.1
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• pp.29-53
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• 2023

High-strength shielding concrete against gamma radiation is a priority for many medical and industrial facilities. This paper aimed to investigate the gamma-ray shielding properties of high-strength hematite concrete mixed with silica fume (SF) with nanoparticles of lead dioxide (PbO₂), tungsten oxide (WO₃), and bismuth oxide (Bi₂O₃). The effect of mixing steel fibres with the aforementioned binders was also investigated. The reference mixture was prepared for high-strength concrete (HSCC) containing 100% hematite coarse and fine aggregate. Thirteen mixtures containing 5% SF and nanoparticles of PbO₂, WO₃, and Bi₂O₃ (2%, 5%, and 7% of the cement mass, respectively) were prepared. Steel fibres were added at a volume ratio of 0.28% of the volume of concrete with 5% of nanoparticles. The slump test was conducted to workability of fresh concrete Unit weight water permeability, compressive strength, splitting tensile strength, flexural strength, and modulus of elasticity tests were conducted to assess concrete's engineering properties at 28 days. Gamma-ray radiation of 137Cs emits photons with an energy of 662 keV, and that of 60Co emits two photons with energies of 1173 and 1332 keV were applied on concrete specimens to assess radiation shielding properties. Nanoparticles partially replacing cement reduced slump in workability of fresh concrete. The compressive strength of mixtures, including nanoparticles was shown to be greater, achieving 94.5 MPa for the mixture consisting of 7.5 PbO2. In contrast, the mixture (5PbO₂-F) containing steel fibres achieved the highest values for splitting tensile, flexural strength, and modulus of elasticity (11.71, 15.97, and 42,840 MPa, respectively). High-strength shielded concrete (7.5PbO2) showed the best radiation protection. It also showed the minimum concrete thickness required to prevent the transmission of radiation.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.34 no.1
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• pp.16-21
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• 2024

Using electrochromic devices (ECD), smart window films that can change the colors from tinted state into transparent state by applying an external voltage were manufactured. Polyethylene terephthalate (PET) film was used as a substrate instead of conventional glass, and ECD modules having a total thickness of about 50 ㎛ were manufactured by sequentially introducing an ITO/Ag/ITO electrode layer, a WO3/TIC2 organic discoloration layer, and a Nafion fluorine electrolyte layer. Through a series of sputtering, bar coating, and thermal compression processes, a large scale smart window with a horizontal and vertical length of more than 80 mm was manufactured. When DC 3.5 V was applied, the transmittance decreased from 54 % to 24 % and moreover the color change could be confirmed even with the naked eye. Reversible color change capability at low external voltage implies that external sunlight can be selectively blocked which is effective in terms of energy saving.