• Journal of Radiation Protection and Research
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• v.48 no.1
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• pp.15-19
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• 2023

Background: Cone beam computed tomography (CBCT) is a specialized medical equipment and plays a significant role in the diagnosis of oral and maxillofacial diseases and abnormalities; however, it is attributed to risk of exposure of ionizing radiation. The aim of the study was to estimate and determine the amount of scattered radiation dose to the thyroid gland in dental CBCT during maxilla and mandible scan. Materials and Methods: The average scattered radiation dose for i-CAT 17-19 Platinum CBCT (Imaging Sciences International) was measured using a Multi-O-Meter (Unfors Instruments), placed at the patient's neck on the skin surface of the thyroid cartilage, with an exposure parameter of 120 kVp and 37.07 mAs. The surface entrance dose was noted using the Multi-O-Meter, which was placed at the time of the scan at the level of the thyroid gland on the anterior surface of the neck. Results and Discussion: The surface entrance dose to the thyroid from both jaws scans was 191.491±78.486 µGy for 0.25 mm voxel and 26.9 seconds, and 153.670±74.041 µGy from the mandible scan, whereas from the maxilla scan the surface entrance dose was 5.259±10.691 µGy. Conclusion: The surface entrance doses to the thyroid gland from imaging of both the jaws, and also from imaging of the maxilla and mandible alone were within the threshold limit. The surface entrance dose and effective dose in CBCT were dependent on the exposure parameters (kVp and mAs), scan length, and field of view. To further reduce the radiation dose, care should be taken in selecting an appropriate protocol as well as the provision of providing shielding to the thyroid gland.

• Journal of the Korean Society of Safety
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• v.19 no.3 s.67
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• pp.14-19
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• 2004

The objective of the present work is to examine evaporation cooling of droplet due to surface roughness under radiative heat input condition. The surface temperatures varied from $80\~160^{\circ}C$ on aluminum alloy (AL 2024) and surface roughness was $0.18{\mu}m,\;1.36{\mu}m$. The results are as follows; Regardless of surface roughness under radiative heat input condition, as droplet diameter is larger, the in-depth temperature of solid decreases and evaporation time increases. In the case of $0.18{\mu}m\;and\;1.36{\mu}m$ of surface roughness, the larger the surface roughness is, the less the evaporation time is and the larger the temperature within the solid is. In the case of $Ra=0.18{\mu}m$ evaporation time and time averaged heat flux for radiative heat input case is shorter than for the conductive case.

• Journal of the Korea Concrete Institute
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• v.11 no.6
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• pp.79-88
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• 1999

In this paper, the electro-deposition method for the rehabilitation of cracked concrete, based on the electro-chemical technique, is presented. The main purpose of this paper is to apply this technique to reinforced concrete members on land. After cracking with a specified load(crack width 0.5mm), 10$\times$10$\times$20cm concrete specimens with embedded steel bars were immersed in several solutions, then a constant current density between the embedded steel in concrete and an electrode in the solution was applied for 4~20 weeks. The results indicate that electro-deposits formed in this process are able to close concrete cracks and to coat the concrete surface and that formation of these electro-deposits is confirmed to have an effect of protection against detrimental materials. Therefore, it is demonstrated that the electro-deposition method can be usefully applied for the rehabilitation technique of concrete.

• Journal of Radiation Protection and Research
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• v.28 no.3
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• pp.239-245
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• 2003

Every nuclear power plant measured concentrations of tritium in groundwater and surface water around the plants periodically. It was not easy to predict the tritium concentration only with these measurement data in case of various release scenarios. KAERI developed a new approach to find the relationship between the tritium release rate and tritium concentration in the environment. The approach was based upon a dynamic compartment model. In this paper the dynamic compartment model was modified to predict the tritium behavior more accurately. The mechanisms considered for the transfer of tritium between the compartments were evaporation, groundwater flow, infiltration, runoff, and hydrodynamic dispersion. Time dependent source terms of the compartment model were introduced to refine the release scenarios. Also, transfer coefficients between the compartments were obtained using realistic geographical data. In order to illustrate the model various release scenarios were developed, and the change of tritium concentration in groundwater and surface water around the nuclear power plants was estimated.

• Tribology and Lubricants
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• v.2 no.1
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• pp.53-60
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• 1986

The methods to prevent or suppress the initial failure of the sliding surfaces by the formation of the protection film during the manufacturing process were studied. Now it has been known that the surface protection film which was formed during the running-in process is mainly $Fe_3O_4$ and its film was formed only at the limited oxygen ability during the lubricated sliding. So it was tried to form the same oxide film before the sliding by heat treatment at 300$\circ$C with the wetted specimen by oil. The results show that a thin oxide film ($Fe_3O_4$) was formed on the surface beneath the solid oil film and the specimen with this film has much better friction properties than those prepared with heat treatment at 500$\circ$C and 700$\circ$C or the original one.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.354-354
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• 2006

Alginic acid-silica hydrogel films was prepared for testing as protective coating materials for PTFE OD membranes. Unprotected hydrophobic membranes are subject to wet-out when contacted by surface-active agents. Films were characterised using SEM, XRD, DSC, mechanical strength measurements, and water-swelling measurements. In OD trials using coated membranes, no wet-out occurred over the 15 h duration of three consecutive 5 h OD trials using orange oil-water mixtures. In the case of detergent solutions, the coating afforded protection to the membrane for 4-5 h. In a separate trial, no wet-out occurred when the coated side of the membrane was placed in contact with 1.2 wt % orange oil for 72 hours.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.173-176
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• 2006

Concrete has been considered as a semi-permanent structural material, because its excellent durability. But concrete durability is affected by carbon dioxide, chloride, water, etc. This study is about surface protection materials-one materials is silane type and the other silicate type for the promoting of concrete durability. As a results, Silane type could protect affection of chloride(Cl-), water(H2O), carbon dioxide(CO2). Also silicate type could improve the abrasion of concrete.

• Journal of Power System Engineering
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• v.8 no.4
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• pp.38-43
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• 2004

Thermal spraying onto the metal substrate has been widely used as a technique of the surface treatment in the various industrial field. A wide range of thermal spray technologies exist and all rely on the fundamental process of fusing a metal feedstock, atomizing it and transporting it to the surface of a substrate. Specially, these methods have been taken into account as the protection method against the corrosion. In this study, the polarization characteristics were carried out on the thermal sprayed coating layer immersed in various pH of diluted aqueous solutions at $25^{\circ}C$. Aluminum, Zinc, Ni-base alloy, alumina and polyethylene powder were used with sprayed coating materials. From the polarization curves, the electrochemical corrosion potential($E_{corr}$) and the corrosion current density($I_{corr}$) were investigated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.256-259
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• 2002

The critical currents of sintered $YBa_{2}Cu_{3}O_{6.5+\delta}$ were measured as the variables with the corrosive time in the humid air. The corrosive process was studied by means of the current changes. Ag coating on the textured YBCO and polytetrafluoroethylene (PTFE) coating on the sintered YBCO were prepared. The critical current densities of different YBCO samples with and without coatings were compared. Both Ag coating and PTFE coating can well protect YBCO from moisture and $CO_{2}$.

• Journal of the Korea Safety Management & Science
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• v.11 no.1
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• pp.59-65
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• 2009

The aim of these studies is to confirm the red and blue painting damages during the fire suppression of wooden cultural assets by using the loaded stream charge extinguishant. As a results of these experiments, the ingredients of extinguishant existing on the surface of wooden cultural assets were perfectly eliminated by the water washing only. Any changes on the surface of wooden cultural assets couldn't be detected. Moreover, any color changes of the red and blue painting didn't occur.