• Journal of radiological science and technology
• /
• v.40 no.4
• /
• pp.533-542
• /
• 2017

In diagnostic radiology, the imaging system has been changed from film/screen to digital system. However, the method for removing scatter radiation such as anti-scatter grid has not kept pace with this change. Therefore, authors have devised the indirect flat panel detector (FPD) system with net-like lead in substrate layer which can remove the scattered radiation. In clinical context, there are many radiographic examinations with angulated incident X-ray. However, our proposed FPD has net-like lead foil so the vertical lead foil to the angulate incident X-ray would have bad effect on its performance. In this study, we identified the effect of vertical/horizontal lead foil component on the novel system's performance and improved the structure of novel system for clinical usage with angulated incident X-ray. Grid exposure factor and image contrast were calculated to investigate various structure of novel system using Monte Carlo simulation software when the incident X-ray was tilted ($0^{\circ}$, $15^{\circ}$, and $30^{\circ}$ from the detector plane). More photons were needed to obtain same image quality in the novel system with vertical lead foil only then the system with horizontal lead foil only. An optimal structure of novel system having different heights of its vertical and horizontal lead foil component showed improved performance compared with the novel system in a previous study. Therefore, the novel system will be useful in a clinical context with the angulated incident X-ray if the height and direction of lead foil in the substrate layer are optimized as the condition of conventional radiography.

• Economic and Environmental Geology
• /
• v.55 no.3
• /
• pp.281-293
• /
• 2022

We examined degradation characteristics of lead based pigments(white lead, Red lead, Litharge) according to atmospheric environmet condition, for example atmospheric gas(CO₂, NO₂) and soluble salt. Painted samples not changed material compositions but were occured the color change(𝚫E 4~31) after exposed UV irradiation. All sample were not affected by CO₂ gas not only color but chemical composition. However, samples were remakably changed color exposed NO₂ gas and it was formed secondary product like as lead nitrate. Such as red lead and white lead samples' color difference were 𝚫E 2 and 𝚫 10 respectively and became dark, along with litharge became bright and color difference was 𝚫E 5 after react with NO₂ gas. It confirm that NO₂ was influential factor than CO₂ in the case of same concentration. Furthermore salt spray test was taken to figure out soluble salt influence in fine dust. The result showed noticeable color change and secondary product was formed on samples' surface. The glue film peeled off or hole, and color changed around the secondary products. After salt spray, XRD pattern showed decrease peak intensity and lower crystalinity. As a result of salt spray test, white lead was formed new product litharge and litharge was formed litharge and minium. According to the results, influential atmospheric factors for conservation of paint pigments were UV, NO₂, soluble salt, and litharge was most weakness throughout lead base pigments.

• Journal of Conservation Science
• /
• v.21
• /
• pp.41-48
• /
• 2007

The resistance for atmospheric corrosion of the conventional 5 epoxy resins (Araldite rapid, Araldite AW 106, Araldite SV 427, Devcon, and CDK), those were used to restoration of the iron relics, were investigated in this study. Temperature, UV light, and water were chosen for the factors of the atmospheric corrosion. The drastic voluminous changes of the epoxy resins were found at the temperature range between $40^{\circ}C$ and $70^{\circ}C$ After UV exposure, the colors of the epoxy resins were severely changed. In case of the indoor exposure the chroma value(${\Delta}E$) of the resins were less than 2, which showed a little changes of the colors. The result of the water contact angle test was Araldite rapid>AW 106>Devcon>SV 427>CDK. Although the contact angles of the resins were reduced by UV exposure, SV 427 was stable comparatively.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.22 no.4
• /
• pp.241-247
• /
• 2010

Corrosion of steel embedded in concrete is one of the foremost factors that affect the durability of concrete structures in marine environments. This paper presents an application technique of anode-ladder-system to evaluate corrosion behaviours of marine concrete structure. In order to investigate the behaviours quantitatively, the measurement of potential and current was performed on the concrete elements subjected to the penetration and diffusion of chloride ions. The main variable was the heights from seawater level; namely 3.7, 6.0 and 8.2 m. As a result of the monitoring, it was found that the corrosion characteristics differently behaved with the increasing height. Additionally, through migration test, the relationship between compressive strength of concrete and diffusivity of chloride ions was observed. It is suggested, ultimately, that in order to reduce or mitigate steel corrosion, both appropriate concrete cover depth and high-quality of concrete in early ages should be done.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.31 no.10
• /
• pp.21-26
• /
• 2003

In this research, the change of coefficient of thermal expansion (CTE) of graphite/epoxy composite laminate under space environment was measured using fiber optic sensors. Two fiber Bragg grating (FBG) sensors have been adopted for the simultaneous measurement of thermal strain and temperature. Low Earth Orbit (LEO) conditions with high vacuum, ultraviolet and thermal cycling environments were simulated in a thermal vacuum chamber. As a pre-test, a FBG temperature sensor was calibrated and a FBG strain sensor was verified through the comparison with the electric strain gauge (ESG) attached on an aluminun specimen at high and low temperature respectively. The change of the CTE in a composite laminate exposed to space environment was measured for intervals of aging cycles in real time. As a whole, there was no abrupt change of the CTE after 1000 aging cycles. After aging, however, the CTE decreased a Little all over the test temperature range. These changes are caused by outgassing, moisture desorption, matrix cracking etc.

• Journal of Korea Water Resources Association
• /
• v.48 no.12
• /
• pp.1037-1049
• /
• 2015

The most of natural disasters that occur in North Korea are flood, typhoon and damage from heavy rain. The damage caused by those disasters since the mid-1990s is aggravating North Korea's economic difficulties every year. By recognizing the seriousness of the damages from the floods, the North Korean government has carried out the river maintenance, farmland restoration, land readjustment and afforestation projects since the last-1990s, but it has failed preventing the damages. In order to estimate the degree of flood risk regarding damage from chronic floods that occur inveterately in North Korea, this research conducted an additional simulation for rainfall-runoff analysis to reflect the characteristics of the ungauged area that make foreign countries hard to obtain the hydrological data and do not open the topographical data to public. In addition, this research estimates the degree of flood risk by selecting the factors of the hazard, exposure and vulnerability by following the standards of the Intergovernmental Panel on Climate Change (IPCC).

• Journal of the Korea Concrete Institute
• /
• v.17 no.6 s.90
• /
• pp.893-902
• /
• 2005

Reasonable prediction of residual capacity of fire-damaged reinforced columns is important for both the safety measurement and the rehabilitation of the reinforced concrete structures suffered from exposure to extensive fire. In order to predict the residual behavior of fire-damaged reinforced concrete columns, its predictive model must be able to take into account the amount of heat transferred into the column, the level of deterioration of constituent materials and various column geometries. The numerical model presented in this research includes all these factors. The model has been shown to reasonably predict the residual behavior of fire-damaged columns. Parametric studies were performed using this model for the effects of cover thickness, exposure time to fire and column geometries on the residual behavior of reinforced concrete columns. It was found that serious damage on the residual capacity of column resulted from a longer exposure time to fire but only marginal differences from other factors.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.7 no.4
• /
• pp.316-322
• /
• 2019

A probabilistic approach considering uncertainties was employed to investigate the effects on the material characteristics and strength of nuclear bio-logical shield concrete walls, when exposed to long-term radiation during the entire service life. Time-dependent compressive and tensile strengths were estimated by conducting the neutron fluence analysis. For the contaminated concrete, individual compressive and tensile failure probabilities can be possibly evaluated by not only establishing limit-state function withthe predefined critical values but also performing Monte Carlo Simulation. Nuclear power plant types similar to the Kori Unit 1, which was shut off permanently in 2017 after the 40-year operation, were herein selected for an illustrative purpose. Consequently, the probability-based performance assessment and prediction of contaminated concrete walls were well demonstrated.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.28 no.4
• /
• pp.393-405
• /
• 2018

Objective: This study examines the types of hazardous factors in the working environment and the time-trend for their exposure levels over 10 years (2007 to 2016). Study Design and Method: The types of hazardous factors and exposure levels were drawn from the 19 measurement reports on the working environment over 10 years at a shock absorber manufacturing facility. Risk assessment of the types of factors and time-trend of exposure levels were evaluated using the factors and exposure levels. Results: A total of 34 hazardous factors were evaluated. The types were noise, 15 organic compounds, seven kinds of acid sand alkalis, eight kinds of heavy metals, and three other compounds. Special management materials used were nickel, hexavalent chrome, and sulfuric acid. Human carcinogens (1A) used were trichloroethylene, nickel, and sulfuric acid. There were six types of substances belonging to the IARC's 2B (body carcinogens) classification or higher, including, methyl isobutyl ketone, ethyl benzene, and trichloroethylene. No detection was found for 627 out of the 2065 total measurements in 19 exposure survey reports, representing 30.4%. Organic solvents, acid and alkali products, and heavy metals showed continuous low exposure concentrations. Noise, welding fumes, and the evaluation of mixed solvents show a gradual decrease in geometric mean and maximum over the time-trend of 10 years. Conclusions: In the case of a shock absorber manufacturing facility, the hazardous factors of noise and the evaluation of mixed solvents still indicate high concentrations exceeding the exposure limits and necessitate reduction studies. These two factors and welding fumes showed a continuous decrease in their ten-year tendency. Organic compounds, acids/alkalis, and heavy metals were managed smoothly in a work environment of continuous low concentrations.

• Journal of odor and indoor environment
• /
• v.17 no.4
• /
• pp.315-321
• /
• 2018

Phthalate is an endocrine disruptor that interferes with homeostasis and developmental regulation. It is highly toxic to the environment and is associated with various diseases of the human body. Using biological samples from 140 adult subjects, to evaluate the influencing factors which are related to contaminant concentration levels, we used correlation analysis and multiple regression analysis. Lastly, in order to analyze the health effects related to exposure to phthalates, we conducted a risk assessment by estimating acceptable daily intake exposure according to the influential factors. When we compared the concentration level according to influential factors, in general, the subjects who had engaged in home remodeling work had higher urinary phthalate metabolite concentrations levels than the subjects who had not engaged in home remodeling work. We can confirm statistically significant differences in DBP metabolites. In addition, we can confirm the concentration appeared higher in the categories such as using air freshener, sofa and foods. Through conducting a risk assessment of DEHP, BBzP, DiBP, and DnBP by using data on phthalate metabolite concentration in urine, it was found that the average concentration of all metabolites did not exceed TDI.