• Journal of Magnetics
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• 제20권2호
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• pp.103-109
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• 2015

In this study, the authors attempted to produce a medical radiation shielding fiber that can be produced at a nanosize scale and that is, unlike lead, harmless to the human body. The performance of the proposed medical radiation shielding fiber was then evaluated. First, diamagnetic bismuth oxide, an element which, among elements that have a high atomic number and density, is harmless to the human body, was selected as the shielding material. Next, 10-100 nm sized nanoparticles in powder form were prepared by ball milling the bismuth oxide ($Bi_2O_3$), the average particle size of which is $1-500{\mu}m$, for approximately 10 minutes. The manufactured bismuth oxide was formed into a colloidal solution, and the radiation shielding fabric was fabricated by curing after coating the solution on one side or both sides of the fabric. The thicknesses of the shielding sheets prepared with bismuth oxide were 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, and 1.0 mm. An experimental method was used to measure the absorbed dose and irradiation dose by using the lead equivalent test method of X-ray protection goods presented by Korean Industrial Standards; the resultant shielding rate was then calculated. From the results of this study, the X-ray shielding effect of the shielding sheet with 0.1 mm thickness was about 55.37% against 50 keV X-ray, and the X-ray shielding effect in the case of 1.0 mm thickness showed shielding characteristics of about 99.36% against 50 keV X-ray. In conclusion, it is considered that nanosized-bismuth radiation shielding fiber developed in this research will contribute to reducing the effects of primary X-ray and secondary X-ray such as when using a scattering beam at a low level exposure.

• Structural Engineering and Mechanics
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• 제85권1호
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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.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 1999년도 춘계학술발표회 초록집
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• pp.130-130
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• 1999

• Nuclear Engineering and Technology
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• 제52권7호
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• pp.1565-1570
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• 2020

Photons with the energy of 60 keV are regularly used for some kinds of bone density examination devices, like the single photon absorptiometry (SPA). This article reports a flexible and lightweight rare earth/polymer composite for enhancing shielding efficiency against photon radiation with the energy of 60 keV. Lead oxide (PbO) and several rare earth element oxides (La₂O₃, Ce₂O₃, Nd₂O₃) were dispersed into natural rubber (NR) and the photon radiation shielding performance of the composites were assessed using monte carlo simulation method. For 60 keV photons, the shielding efficiency of rare earthbased composites were found to be much higher than that of the traditional lead-based composite, which has bad absorbing ability for photons with energies between 40 keV and 88 keV. In comparison with the lead oxide based composite, Nd₂O₃-NR composite with the same protection standard (the lead equivalent is 0.25 mmPb, 0.35 mmPb and 0.5 mmPb, respectively), can reduce the thickness by 35.29%, 37.5% and 38.24%, and reduce the weight by 38.91%, 40.99% and 41.69%, respectively. Thus, a flexible, lightweight and lead-free rare earth/NR composite could be designed, offering efficient photon radiation protection for the users of the single photon absorptiometry (SPA) with certain energy of 60 keV.

• 대한한의학회지
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• 제20권1호
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• pp.151-160
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• 1999

Nitric oxide(NO) is synthesized via the oxidation of L-arginine by a family of nitric oxide synthases(NOS), which are either constitutive(cNOS) or inducible(iNOS). The induction of iNOS in tissues can lead to the sustained production of high concentrations of NO which may exert pro-inflammatory effects including vasodilation. edema, cyototoxicity, and its activity can be mediated by various pro-inflammatory cytokine, including interferon ${\gamma}(INF-{\gamma})$. tumor necrosis factor, IL- 1 and IL-6. The enzyme, iNOS, became a new target for pharmacologcal research with the aim to find new substances for the treatment of chronic inflammatory disorders. Murine macrophages produce large amounts of NO when activated with $TFN-{\gamma}$ plus LPS. The murine macrophage-like cell line, RAW 264.7, is a suitable cell model on which to perform vitro studies regarding the iNOS system. Semen jugrandis is a fatty walnut seed found in Korea. The walnut have been used in foik medicine to improve virility, to relieved asthma, and to relieve constipation. Sesquiterpenelactones were isolated from this plant. In the course of screening for NO inhibitory activity from medicnial plants, the aqueous extract of this plant was found to have a significant activity. The result are summarized as followings. 1. The viability of cells incubated in the presence of semen jugrandis increased mare than non incubated cells. 2. Semen jugrandis suppressed the production of NO in tissues dependent on density. 3. Semen jugrandis suppressed the induction of iNOS in tissues dependent on density can lead to reduced production of NO. 4. Semen jugrandis suppressed the production of superoxide in tissue depend on density. According to the above mentioned results, semen jugrandis could be applied production of NO and superoxide can lead to reduction of chronic inflammatary. And as a depence matter come into a virus of microbe and tumor cells.

• Nuclear Engineering and Technology
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• 제54권6호
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• pp.1972-1981
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• 2022

A typical ferritic/martensitic (F/M) steel sheet was subjected to pulsed laser surface remelting (LSR) and corrosion test in lead-bismuth eutectic (LBE) at 550 ℃. There present two modification zones with distinct microstructures in the LSRed specimen: (1) remelted zone (RZ) consisting of both bulk δ-ferrite grains and martensitic plates and (2) heat-affected zone (HAZ) below the RZ, mainly composed of martensitic plates and high-density precipitates. Martensitic transformation occurs in both the RZ and the HAZ with the Kurdjumov-Sachs and Nishiyama-Wassermann orientation relationships followed concurrently, resulting in scattered orientations and specific misorientation characteristics. Hardnesses of the RZ and the HAZ are 364 ± 7 HV and 451 ± 15 HV, respectively, considerably higher than that of the matrix (267 ± 3 HV). In oxygen-saturated and oxygen-depleted LBE, thicknesses of oxide layers developed on both the as-received and the LSRed specimens increase with prolonging corrosion time (oxide layers always thinner under the oxygen-depleted condition). The corrosion resistance of the LSRed F/M steel in oxygen-saturated LBE is improved, which can be attributed to the grain-refinement accelerated formation of dense Fe-Cr spinel. In oxygen-depleted LBE, the growth of oxide layers is very low with both types of specimens showing similar corrosion resistance.

• 한국진공학회지
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• 제1권3호
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• pp.376-381
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• 1992

Tungsten silicide films were deposited on the highly phosphorus-doped poly Si/SiO2/Si substrates by Low Pressure Chemical Vapor Deposition. They were heat treated in different conditions. XTEM, SIMS and high frequency C-V analysis were conducted for characterization. It can be concluded that outdiffusion of phosphours impurity throught the silicide films lead to its depletion in the poly-Si gate region near the gate oxide, resulting in loss of capacitance and increase of effective gate oxide thickness.

• 한국환경성돌연변이발암원학회:학술대회논문집
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• 한국환경성돌연변이발암원학회 2002년도 Molecular and Cellular Response to Toxic Substances
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• pp.188-189
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• 2002

• 한국독성학회:학술대회논문집
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• 한국독성학회 2002년도 Molecular and Cellular Response to Toxic Substances
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• pp.188-189
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• 2002

This work aimed to identify neuronal cell toxicity induced by decrease of physiological NO production by differential phosphorylation of constitutive neuronal NO synthase (nNOS), which can be mediated by Ca2+-dependent PKC and/or CaM-KII activities activated by metals.(omitted)

• 대한약학회:학술대회논문집
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• 대한약학회 2003년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.2-2
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• pp.177.1-177.1
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• 2003

Styrylheterocycles were synthesized as a novel calss of inhibitors on nitric oxide(NO) production. Their inhibitory activities were evaluated using lipopolysaccharid-stimulated RAW264.7 macrophage cells. This series of inhibitors are suggested as lead comounds for the development of potent and selective inhibitors