• Journal of radiological science and technology
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• v.43 no.5
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• pp.375-382
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• 2020

PET/CT is a medical equipment that detects 0.511 MeV of gamma rays. The radiation workers are inevitably exposed to ionizing radiation in the process of handling the isotope. Accordingly, PET/CT workers use syringe shields made of lead and tungsten to protect their hands. However, lead and tungsten are known to generate very high scattering particles by interacting with gamma rays. Therefore, in this study, we tried to find out the effect on the scattering particles emitted from the syringe shield. In the experiment, first, the exposure dose to the hand (Rod phantom) was evaluated according to the metal material (lead, tungsten, iron, stainless steel) using Monte Carlo simulation. The exposure dose was compared according to whether or not plastic is attached. Second, the exposure dose of scattering particles was measured using a dosimeter and lead. As a result of the experiment, the shielding rate of plastics using the Monte Carlo simulation showed the largest difference in dose of about 40 % in lead, and the lowest in iron, about 15 %. As a result of the dosimeter test, when the plastic tape was wound on lead, it was found that the reduction rate was about 15 %, 28 %, and 39 % depending on the thickness. Based on the above results, it was found that 0.511 MeV of gamma ray interacts with the shielding tool to emit scattered rays and has a very large effect on radiation exposure. However, it was considered that the scattering particles could be sufficiently removed with plastics with a low atomic number. From now on, when using high-energy radiation, the shielding tool and the skin should not be in direct contact, and should be covered with a material with a low atomic number.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.490-490
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• 2011

Graphene, hexagonal network of carbon atoms forming a one-atom thick planar sheet, has been emerged as a fascinating material for future nanoelectronics. Huge attention has been captured by its extraordinary electronic properties, such as bipolar conductance, half integer quantum Hall effect at room temperature, ballistic transport over ${\sim}0.4{\mu}m$ length and extremely high carrier mobility at room temperature. Several approaches have been developed to produce graphene, such as micromechanical cleavage of highly ordered pyrolytic graphite using adhesive tape, chemical reduction of exfoliated graphite oxide, epitaxial growth of graphene on SiC and single crystalline metal substrate, and chemical vapor deposition (CVD) synthesis. In particular, direct synthesis of graphene using metal catalytic substrate in CVD process provides a new way to large-scale production of graphene film for realization of graphene-based electronics. In this method, metal catalytic substrates including Ni and Cu have been used for CVD synthesis of graphene. There are two proposed mechanism of graphene synthesis: carbon diffusion and precipitation for graphene synthesized on Ni, and surface adsorption for graphene synthesized on Cu, namely, self-limiting growth mechanism, which can be divided by difference of carbon solubility of the metals. Here we present that large area, uniform, and layer controllable graphene synthesized on Cu catalytic substrate is achieved by acetylene-assisted CVD. The number of graphene layer can be simply controlled by adjusting acetylene injection time, verified by Raman spectroscopy. Structural features and full details of mechanism for the growth of layer controllable graphene on Cu were systematically explored by transmission electron microscopy, atomic force microscopy, and secondary ion mass spectroscopy.

• Fire Science and Engineering
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• v.33 no.4
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• pp.1-8
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• 2019

Reaction-to-fire performance of pipe insulation materials should be approved in accordance with KS standards prior to installing water-based suppression systems because several fire accidents are initiated from insulation materials around ceilings or concealed space. A small room test to evaluate the reaction-to-fire performance of the polyethylene foam and elastomeric pipe insulation materials was conducted according to ISO 20632. Different fire growth rate and heat release rate are observed depending on the materials and construction methods. In order to improve a fire safety, the reaction-to-fire performance of pipe insulation material needs to be subdivided with regard to the heat release rate and smoke generation. Furthermore, the characteristics of the applying space are also required to be considered. Subsidiary materials for installation process such as tape and adhesive are found to provide an adverse effect to maintain a fire safety.

• Korean Journal of Occupational Health Nursing
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• v.3
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• pp.5-20
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• 1993

This study was aimed to investigate the actual condition of the performance of the occupational health nursing services, and to analyze a main cause which affects on the execution of its duties for occupational health nurses in occupational group health service. It had been surveyed by responsed data from the 105 respondents out of 180 persons. The results were as follows : 1. In performance of occupational health nursing services by the number of assigned plant, participation rate of health examination tended to significantly increase with decreasing the number of assigned and it was observed that the visiting rate of every month was also significantly higher on touring inspection of work plant, recommendation of facility improvement for work environment, understanding the modification of manufacturing process, and inspection of welfare and sanitation facilities. 2. While they executed their nursing services according to duration of service, the more, their duration of service was, the higher, participation rate of health examination, health check in returning to work for injured workers, talk with other health managers on promoting welfare, service evaluation for a year plan, record of health statistic, and experience of first aid service were. And it was found out that the visiting rate of every month was also significantly higher on touring inspection of work plant. 3. In regard to occupational health nursing services by age, the participation rate of health examination and the experience of first aid service were significantly higher as the age increased. And also the visiting rate of every month was significantly higher on touring inspection of work plant, compared with young ones. 4. In performance of occupational health nursing services by the time required visiting plant, The shorter, the time required visiting plant was, the higher, the visiting rate of every month was, on time of health consultation for diseased workers, and inspection of welfare and sanitation facilities. 5. The subjects of health education were mostly liver disease and occupational hearing loss and video tape was used mostly in health education, monthly health education was the highest in 1-3 times(74.5%) and its duration was the highest in about 60 minutes(33.3%). 6. Vaccination of hepatitis among the specific health services was the highest accounting for 64.7%.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.12
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• pp.786-790
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• 2016

Hole explosion behaviors were observed during drilling fine holes with laser beam on the LTCC green bar of $320{\mu}m$ thick after lamination of green sheets prepared by tape casting of thick film process. The incidence of these hole explosions was inversely proportional to hole sizes. The incidence of hole explosion was 20 % number of hole with the size of $60{\mu}m$ exploded for the UV radiation, while the explosion did not appear for hole sizes over $100{\mu}m$. To prevent hole explosion behavior during laser-drilling of fine holes, carbon black powder was added as an additive in the LTCC composition, which has superior thermal durability. As a consequence, hole explosion rate was suppressed to 0.8 % for the hole size of $50{\mu}m$ green sheet with the carbon black amount of 10 weight % and the laser power of 3 watt. Added carbon is thought to reduce the heat-affected region during laser drilling.

• Progress in Superconductivity and Cryogenics
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• v.16 no.2
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• pp.1-6
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• 2014

The five-year national project in Japan for R&D of coated conductors and applications, named as the Materials and Power Applications of Coated Conductors (M-PACC) project, was finished at the end of FY2013. The project consists of four sub-themes as cable, transformer, SMES and coated conductors. In the theme of coated conductors, the fabrication process had been developed to satisfy the requirements from the applications such as in-field $I_c$ performance, low AC loss in the long tapes etc. Through the project, the remarkable progress was achieved as follows; a high in-field minimum $I_c$ value over 54A/cm-width under 3T at 77K was realized in a 200m long EuBCO tape with artificial pinning centers of $BaHfO_3$ by the pulsed laser deposition (PLD) technique on the IBAD template. On the other hand, the AC loss reduction was confirmed in the tapes fabricated by both PLD and the metal organic deposition (MOD) techniques by scribing 100m tapes into 10-filamments. Additionally, the mechanism of the delamination phenomenon was systematically investigated and the strength was improved by eliminating the origins of the weak points in the films. Through the development, all targeted goals were accomplished and the several results were appreciated as a world champion data.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.05a
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• pp.32-32
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• 2015

Electrophoretic paint (E-paint) was investigated on four different magnesium substrates: as-extruded AZ61 (AZ61), heat-treated AZ61 (AZ61-H), as-extruded TZ61 (TZ61) and heat-treated TZ61 (TZ61-H), to elucidate the effect of heat treatment and alloying elements on the deposition and corrosion resistance of E-paint. It was found that, a rapid increase of voltage, indicating that the deposition of E-paint had started, was observed after an induction time of 0.39 min for AZ61-H, 0.43 min for AZ61, 0.51 min for TZ61-H and 0.58 min for TZ61. The amount of E-paint deposited on the four samples was approximately similar, but the electrical charge used for the deposition process on the heat-treated samples was smaller than that on the as-extruded samples. The current efficiencies of E-paint on AZ samples (AZ61 and AZ61-H) were higher than those of TZ samples (TZ61 and TZ61-H), and on the heat-treated samples were higher than on as-extruded samples. All E-paintings on the four magnesium substrates had an excellent adhesion without any paint detached by tape peel-test. However, many large blisters were formed on the surface of AZ samples, and none, or very small blisters were observed on TZ samples after immersion test in DI-water for 500 h at $40^{\circ}C$. Under salt spray test (SST) conditions, E-paint on AZ samples showed blistering adjacent to scribes, while blistering of E-paint occurred on intact areas of TZ samples. The E-paint on heat-treated samples showed much better corrosion resistance than that on as-extruded samples. The ranking of greater to lesser corrosion resistance of the E-paint on these four different magnesium substrates is indicated by the order: AZ61-H > AZ61 > TZ61-H > TZ61.

• Resources Recycling
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• v.7 no.4
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• pp.35-42
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• 1998

Surface mount technology is the biggest theme in the area of deιIronic component. To miniatunze an electronic component, s such as ferrite chip inductor, the cer뼈lic wet process for green-sheet lamination and/or screen printing method through a s solvent medium system is widely used. The preparation and characterization of NiCuZn Ferrite (NCZF) shurry and the green s sheet using the water mixed binder system has been studied. The 21 vol% of NCZF slurry was prepared by a ball milling. The p polyacrylic vinyl copolymer (Mw; 60,000) was used as a binder. Th$\xi$ mixture of distilled water, isopropyl alcohol (IPA) and 2l butoxy ethanol was used as a dispersion medium. The water content of medium varied from about 40% to 80%. As the results. Thc disp$\xi$rston stability of the NCZF slurry was attributed to the free polymer rather than the electrostatic force of the particle. T The viscosity of the NCZF slurry was greatly depended on the ratio of water content in the medium.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.267-267
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• 2006

전력에 큰 손실을 초래하는 고장전류를 차단하기 위한 한류기(FCL) 소재로서 고온 초전도체인 BSCCO 2212가 사용된다. 고온에서 용융된 BSCCO 2212 분말은 원심성형법에 의해 한류기용 튜브로 제조되었다. BSCCO 튜브의 기계적 특성을 높이고 용융온도를 낮추기 위해 $SrSO_4$(10wt-%)를 첨가하였다. 용탕은 $1200^{\circ}C$에서 완전히 용융되어 금속 몰드로 주입되었고 원심성형에 사용되는 금속 몰드는 $550^{\circ}C$ 온도로 2시간 예열 후 1020 ~ 2520 RPM으로 회전시켰다. 원심력에 의해 성형된 BSCCO 튜브는 약 48시간 동안 로에서 서냉 후 금속 몰드로부터 분리하였다. 튜브의 용이한 분리를 위해 이형제로서 BSCCO 2212 powder를 사용하였고 임계전류측정을 고려하여 Ag tape 단자를 튜브 끝단에 부착하였다. BSCCO 제조 공정에 있어서 몰드의 예열온도, 용융온도, 몰드 회전속도 등의 변수를 조절하여 최적의 조건을 확립하였다. 제조한 BSCCO 튜브의 임계전류($I_c$)와 임계전류밀도($J_c$)는 77K에서 536A와 $205A/cm^2$ 이었다. 본 연구에서는 BSCCO 2212 튜브를 제조하는 공정조건 변화와 각 조건에서 제조된 BSCCO 2212 튜브의 전기적 특성 및 그에 따른 분석에 대해 기술하였다.

• Conservation Science in Museum
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• v.18
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• pp.51-64
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• 2017

The Bracket clock in the collection of the Korean Christian Museum at Soongsil University underwent conservation treatment for a special exhibition. The compositional analysis showed that the body was made of brass plated with gold by fire-gilding(gold amalgam process), while the dial was identified as pure copper coated with enamel. The hands were made of steel. Remnants of adhesive tape on the dial were cleaned, followed by the addition of a protective coating. In order to restore it to a condition as similar to its original form as possible, replacements for missing parts were newly constructed out of brass and were connected to the hands and the dial. The dial was then fixed to the body using an acrylic support. The compositional analysis and conservation treatment have left the clock in stable condition and readily available for exhibitions and future studies.