• Membrane Journal
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• v.19 no.4
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• pp.333-340
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• 2009

This paper is designed with the purpose of improving the efficiency of the sulfonic acid ion exchange membranes by radiation induced graft polymerization. It has been shown that the porous hollow fiber membranes could cause permeability blocking between pores and ion exchanged graft chains. Addition of crosslinker such as N-ethylene glycol dimethacrylate will permit to increase the permeation flux. In this research, the ethylene glycol dimethacrylate (EDMA) and diethylene glycol dimethacrylate (DDMA) with different length are used as crosslinkers. The ion exchanged cross-linked membrane (EDMA, DDMA) containing sulfonic acid group by radiation induced grafted polymerization are sn died for adsorb metal ions (Pb). It has been shown that adsorbed metal ions ($Pb^{2+}$) for the EDMA and DDMA membranes with the density of sulfonic acid groups, 1.40 mmol/g and 2.14 mmol/g, respectively are 13.82 mg/g, 17.37 mg/g, accordingly.

• Journal of Radiation Protection and Research
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• v.24 no.2
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• pp.55-63
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• 1999

For understanding the radiation environment in the land of Korea and acquiring baseline data to be referred to at the time of a nuclear accident, cultivated soils in the $0{\sim}15cm$ layer were sampled at 33 sites scattered all over the country and $^{137}Cs$ concentrations were measured by $\gamma$-spectrometry. The soil $^{137}Cs$ concentrations were in the range of $0.7{\sim}17.7$ Bq/kg-dry in the paddy field and $1.2{\sim}27.8$ Bq/kg-dry in the upland field, The means were 6.9 Bq/kg-dry and 9.9 Bq/kg-dry, respectively. In the paddy field, the soil $^{137}Cs$ concentration was positively correlated to the organic matter content and negatively correlated to the clay content. In the upland field, it was positively correlated to the cation exchange capacity. It was revealed that soil organic matter play an important role in the change of soil $^{137}Cs$ concentration.

• Membrane Journal
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• v.17 no.1
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• pp.54-60
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• 2007

In this research, the cation-exchange membrane (SS membrane) containing sulfonic acid group was prepared by radiation induced grafted polymerization onto a porous hollow fiber membrane to effectively remove ammonia which was produced by urea decomposition for peritoneum dialysis system. And the metal ionic cross-linking cation-exchange membrane (SS-M membrane) was prepared by the adsorption of metallic ions (Cu, Ni, Zn) to the SS membranes. The pure water flux and adsorption capacities of ammonia to SS and SS-M membranes were examined. The pure water flux of SS membrane decreased rapidly with the density of $SO_3H$ group increasing. As the metallic ions were adsorbed to the SS membrane, the pure water flux was increased. The adsorption capacities of ammonia at the SS membrane increased with increasing of density of $SO_3H$ group. The ion-exchange capacity of ammonia of the SS membrane was approximately proportional 1 : 1 to the density of $SO_3H$ group. The SS membrane had higher adsorption capacities than the SS-M membrane. The highest adsorption capacities of SS and SS-M membrane appeared the highest pH 9.

• Journal of Preventive Medicine and Public Health
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• v.31 no.4 s.63
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• pp.616-627
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• 1998

In order to evaluate the cytogenetic hazard among hospital workers potentially exposed to low dose of radiation, the analysis of chromosome aberrations(CA) and sister chromatid exchanges(SCE) in lymphocytes were performed in 79 hospital workers and 79 non-exposed workers. The mean frequency of chromosomal exchange and deletion(respectively, $0.20\times10^{-2}/cell\;and\;0.39\times10^{-2}/cell$) in the exposed group were significantly higher than those$(0.07\times10^{-2}/cell\;and\;0.23\times10^{-2}/cell)$ in control group. The frequency of sister chromatid exchanges was 5.04/cell in the control vs. 6.57/cell in the exposed group. There were also significant differences in the mean frequencies of CA and SCE adjusted for age, sex, smoking, drinking between two groups. There were no evidence of significant increase of CA and SCE according to the department or duration of employment. But the frequency of cells having chromosome aberration was significantly higher in the exposed group than in the control group related to duration of employment. There was no dose-effect relationship between the cumulative doses and the frequency of CA and SCE. But in the case of last 1 yr cumulative dose, there were evidence of significant dose-dependant increase of chromosome type CA and percentage of cells with aberration. The result suggest that there is cytogenetic hazard in risk group like hospital workers handling low dose radiation. And the analysis CA and SCE are useful biological indicators for the exposure of low dose level of radiation.

• Nuclear Engineering and Technology
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• v.52 no.2
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• pp.373-380
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• 2020

This study was carried out to convert the hydrophobic characteristics of PVDF to hydrophilic. Poly(-vinylidene fluorine) (PVDF) was grafted by electron beam irradiation and sulfonated. The grafting degree of modified PVDF increased with the monomer concentration, but not the conversion degree. From the results of FTIR and XPS, it was shown that the amount of converted sulfur increased with the grafting degree. The radiation-induced graft polymerization led to decrease fluorine from 35.7% to 21.3%. Meanwhile, the oxygen and sulfur content increased up to 8.1% and 3.2%. The pore size of modified membranes was shrunken and the roughness sharply decreased after irradiation. The ion exchange capacity and contact angle were investigated to show the characteristics of PVDF. The enhanced ion exchange capacity and lower contact angle of modified PVDF showed that the hydrophilicity played a role in determining membrane fouling. Electron beam irradiation successfully modified the hydrophobic characteristics of PVDF to hydrophilic.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.3
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• pp.409-424
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• 1987

Simulation on the hot water ONDOL heating system was made in order to investigate the variation of room temperature and specific fuel consumption of boiler. Heat balance equation was derived by response factors and solved implicitly. Variation of room temperature and specific fuel consumption of boiler were calculated with respect to the thickness of room floor, the absorptivity of wall for solar radiation, on-off temperature range of boiler and air exchange. The results show that specific fuel consumption of boiler is independent of the thickness of room floor and decreases with increasing the absorptivity of wall and on-off temperature range of boiler. However, it increases with increasing the air exchange. They also show that, when the absorptivity and on-off temperature range of boiler are increased, the amplitudes of room temperature variation increase.

• Journal of computational fluids engineering
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• v.19 no.1
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• pp.1-6
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• 2014

Since experiments on the actual operational status are said to be very impractical because of their economic and repeatability problems, it is difficult to understand the thermal profiles of aerospace or military equipments. Thus, the CFD codes with considering the radiation heat transfer are used to compensate the defect. In case, analyzing the radiation exchanges between the object surfaces are very important. Because the temperature and the IR signal distributions of the object surface are significantly affected by the radiative heat transfer. To achieve accurate thermal radiation exchange between surfaces, it is important to calculate the radiation view factor precisely. Finer subdivision of meshes can be used to increase the accuracy of radiation view factor, but if the mesh is subdivided infinitely, the time required for calculation increases significantly and thus decreasing the efficiency. If the subdivision is not sufficient, assurance of accuracy is not guaranteed. In this paper, optimal mesh subdivision method using the solid angle has been successfully tested and found to be useful in increasing the efficiency of calculating the shape factors.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.278-283
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• 2003

Analysis has been carried out to investigate the temperature variation and the uniformity of the temperature distribution of the glass panel by infrared radiant heating. Halogen lamps are used to heat the panel and located near the top and bottom of the rectangular chamber. The thermal energy is transfered only by radiation and the radiation exchange occurs only on the solid surfaces and is considered by using the view factor. The results show that the uniformity of the temperature distribution of the panel is improved but the time for heating increases as the wall reflectivity is large. The temperature difference reaches a maximum in the early stage of the heating process and then decreases until it reaches the uniform steady-state value.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.38 no.7
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• pp.549-556
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• 1989

Radiation induced current of the insulating oil used for X-ray tube housing was investigated in this paper. The X-ray induced current increased in proportion to the X-ray intensity and X-ray wave length and was greatly affected by the temperature of the insulating oil and the gap length` however, the current was not varied by the amount of the X-ray absorbed. The results suggest that one must consider the following problems as important factors for X-ray machine design and normal operation: cooling system of the X-ray tube housing, X-ray intensity, increasing temperature due to continuous operation, years used, and oil exchange and management.

• Journal of Environmental Science International
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• v.11 no.10
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• pp.1117-1123
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• 2002

Coating ceramic balls activate water molecular in water as radiate far-infrared radiation of high efficiency, and then prevent formation of scale and corrosion of pipe. Therefore, but only keep away drop of heat exchange efficiency of boiler, not also remove formed scale. As a result, pipe of boiler has clean and has form thin protection film in inner of pipe. Also, the water treated by rust preventing system using the ceramic balls, that is harmless, tasteless, odorless, and non-toxicity in the human body, and it can use drinking water. This rust preventing system can save energy and protect environment.