• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.487-490
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• 2005

In this study, for the establishment of the performance evaluation methods and the quality control standards of durability recovery method, the data of indoor durability test and the data of the long term exposure test under the coast are accumulated and analyzed. As a result of the indoor test, durability of repair material was more superior to that of plain concrete, but as a result of investigating and evaluating exposure test at 30 month of exposure age under the coastal environment, the difference in electric potential and the reinforcement corrosion at place replaced with repair material are found.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.333-336
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• 2006

In general, polymer materials undergo degradation when exposed to ultraviolet radiation, which can cause dissociation of chemical bonds. FRP composites which are used in strengthening existing structure are usually adhered on the concrete surface, its mechanical properties as well as appearance such as color, surface conditions are affected by sunlight and expecially ultraviolet light. In this study, variations of tensile strength after exposure for certain period of time through accelerated exposure by Xe arc methods specified in KS F 2274 are measured in order to examine strength degradation characteristics of FRP composite. As a result of ultraviolet light test for FRP composite after accelerated exposure for 0, 500, 1000, 1500 hour, discoloration of FRP composite occurs according to the passage of time. But, few strength degradations of FRP composite are observed due to exposure of ultraviolet ray with an small variation of tensile strength.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.05a
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• pp.73-77
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• 2008

In this study, we would like to study on the application of roof exposure waterproofing method of joint stability through shiplap rubberized asphalt color sheet to complement problem of fracture, exfoliation and water leakage by existing roof exposure sheet waterproofing material joint weakness. Accordingly, examined basis performance and stability for joint that shiplap rubberized asphalt color sheet through test of that tensile strength, bonding strength, water permeability after bonding, peel resistance after bonding, lengthen resistance after bonding and hang resistance after bonding. The results of this study, waterproofing method to using shiplap rubberized asphalt color sheet is judged to solved fracture, exfoliation and water leakage problems happened in joint by problem was joint of exposure sheet by minimizing gap of joint being integration by shiplap.

• Nuclear Engineering and Technology
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• v.53 no.8
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• pp.2652-2660
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• 2021

The gamma-ray exposure doses in decontamination operation after a nuclear accident were evaluated with a consideration of various geometrical conditions and specific gamma-ray energies. The calculation domain is organized with three residence types and each form is divided into two kinds of geometrical arrangements. The position-wise air KERMA values were calculated with an assumption of evenly distributed gamma-ray source based on Monte Carlo radiation transport analysis using the MCNP code. The radioactivity is initially set to be unity to be multiplied by the deposition value measured in the actual accident condition. The workforce data set depending on the target object was determined by modifying the Fukushima report. The external exposure doses for decontamination workers were derived from the calculated KERMA values and the workforce analysis. These results can be used to efficiently determine the workforce required by the characteristics of the area and the structure to be decontaminated within the dose limits.

• Korean Journal of Environmental Biology
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• v.39 no.3
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• pp.344-353
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• 2021

Juvenile olive flounder, Paralichthys olivaceus (mean weight 66.7±7.1 g; mean length 19.2±0.9 cm) in a bio-floc environment were exposed to microplastic (PE: polyethylene, size 40-48 ㎛) at 0, 4, 20, 100, 500 and 2,500 mg L^-1 for 96 hours. No P. olivaceus deaths were observed following microplastic exposure. In the plasma components, calcium was significantly decreased whereas there was no significant change with magnesium following microplastic exposure. Glucose was significantly decreased with over 100mg L^-1 at 48 hours and 20mg L^-1 at 96 hours. Cholesterol was significantly decreased with over 20mg L^-1 after 48 hours, whereas there was no significant change in the total protein content. In enzymatic plasma components, the AST(Aspartate aminotransferase) was significant decreased by microplastic exposure. The results of this study indicate that acute exposure to microplastic induces blood physiological changes in P. olivaceus.

• Analytical Science and Technology
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• v.27 no.5
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• pp.261-268
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• 2014

In advanced countries, a variety of consumer exposure assessment models including CONSEXPO, are developed to manage risks of consumer products containing hazardous materials. The models are used to assess the risks of exposure to hazardous chemicals in consumer products, which serves as a foundation for regulation standards. In this study, exposure assessment models applicable for various scenarios were reviewed and a proper model was applied for the selected products and risk assessment was conducted at each stage to establish a risk assessment procedure for different types of products. Based on the exposure scenario, exposure factor was selected and according to the algorithm produced based on CONSEXPO exposure model, some level of phthalates were detected from some types of PVC flooring. However, a correlation between phthalate content and migration rate showed r-square 0.0065, little correlation, which is inadequate for estimating standard value. For this reason, it seems valid that the current standard be in place. Additionally, any new standard was not suggested as VOCs were not found harmful to human health, allowing the existing standard to be continuously applied. No migration rate was found for heavy metals and risk assessment was not performed accordingly. In this aspect, it is presumed that hazards to health through dermal exposure would be very little.

• Journal of Radiation Protection and Research
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• v.42 no.4
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• pp.189-196
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• 2017

Background: The effects of radiation on tissues vary depending on the radiation type. In this study, a minipig model was used to compare the effects of ${\beta}$-rays from $^{166}Ho$ and ${\gamma}$-rays from $^{60}Co$ on the skin. Materials and Methods: In this study, the detrimental effects of ${\beta}$- and ${\gamma}$-irradiation on the skin were assessed in minipigs. The histopathological changes in the skin from 1 to 12 weeks after exposure to 50 Gy of either ${\beta}$- (using $^{166}Ho$ patches) or ${\gamma}$- (using $^{60}Co$) irradiation were assessed. Results and Discussion: The skin irradiated by ${\beta}$-rays was shown to exhibit more severe skin injury than that irradiated by ${\gamma}$-rays at 1-3 weeks post-exposure; however, while the skin lesions caused by ${\beta}$-rays recovered after 8 weeks, the ${\gamma}$-irradiated skin lesions were not repaired after this time. The observed histopathological changes corresponded with gross appearance scores. Seven days post-irradiation, apoptotic cells in the basal layer were detected more frequently in ${\beta}$-irradiated skin than in ${\gamma}$-irradiated skin. The basal cell density and skin thickness gradually decreased until 4 weeks after ${\gamma}$- and ${\beta}$- irradiation. In ${\beta}$-irradiated skin lesions, and the density and thickness increased sharply back to control levels by 6-9 weeks. However, this was not the case in ${\gamma}$-irradiated skin lesions. In ${\gamma}$-irradiated skin, cyclooxygenase-2 (COX-2) was shown to be expressed in the epidermis, endothelial cells of vessels, and fibroblasts, while ${\beta}$-irradiated lesions exhibited COX-2 expression that was mostly limited to the epidermis. Conclusion: In this study, ${\beta}$-rays were shown to induce more severe skin injury than ${\gamma}$-rays; however, the ${\beta}$-rays-induced injury was largely repaired over time, while the ${\gamma}$-rays-induced injury was not repaired and instead progressed to necrosis. These findings reveal the differential effects of ${\gamma}$- and ${\beta}$-irradiation on skin and demonstrate the use of minipigs as a beneficial experimental model for studying irradiation-induced skin damage.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.22 no.2
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• pp.293-303
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• 1992

Generally the patient's absorb dose and readability of radiograms are affected by the exposure time and kVp of which are related with the radiographic density and contrast The investigator carried studies to know the adequate level of exposure time and kVp to obtain the better readability of radiograms. In these studies dried human mandible with selfcuring acrylic resins attached with aluminum step wedge was used and readability of radiograms were compared with each other by videodensitometry among various combination sets of the exposure time, such as 5, 6, 8, 12, 15, 19, 24, 30, 38, 48 and 60, and varing level of kVp, such as 60, 65, 70, 80 and 90 respectively. The obtained results were as follows: 1. As exposure time and kVp were increased, radiographic density of radiograms was increased. 2. The subject contrast was increased where aluminum step wedge was thin and reduced in the reversed condition. At the thin aluminum step wedge, subject contrast was increased at the condition of lower kilovoltage than that of higher kilovoltage. 3. In the case of non-constant radiographic density, the radiographic contrast was reduced with the increment kilovoltage. The radiographic contrast was increased in the lower kilovoltage with the longer exposure time and the higher kilovoltage with the shorter exposure time. 4. At the condition of short exposure time, better readability of each reading item was obtained with the increment of the kilovoltage but at the opposite condition increasing exposure time worsened readability of radiograms. Since X-ray machine in the current dental clinics is fixed between the range of 60-70kVp and 10mA, good radiograms can be obtained by varied exposure time. But according to the conclusion of these studies, better radiograms can be obtained by using filtered high kVp and then the absorb dose to patient and exposure time can be reduced.

• Environmental Analysis Health and Toxicology
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• v.27
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• pp.5.1-5.10
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• 2012

Objectives: The purpose of this study was to assess the risk of ingestion exposure of lead by particle sizes of crumb rubber in artificial turf filling material with consideration of bioavailability. Methods: This study estimated the ingestion exposure by particle sizes (more than 250 um or less than 250 um) focusing on recyclable ethylene propylene diene monomer crumb rubber being used as artificial turf filling. Analysis on crumb rubber was conducted using body ingestion exposure estimate method in which total content test method, acid extraction method and digestion extraction method are reflected. Bioavailability which is a calibrating factor was reflected in ingestion exposure estimate method and applied in exposure assessment and risk assessment. Two methods using acid extraction and digestion extraction concentration were compared and evaluated. Results: As a result of the ingestion exposure of crumb rubber material, the average lead exposure amount to the digestion extraction result among crumb rubber was calculated to be $1.56{\times}10^{-4}$ mg/kg-day for low grade elementary school students and $4.87{\times}10^{-5}$ mg/kg-day for middle and high school students in 250 um or less particle size, and that to the acid extraction result was higher than the digestion extraction result. Results of digestion extraction and acid extraction showed that the hazard quotient was estimated by about over 2 times more in particle size of lower than 250 um than in higher than 250 um. There was a case of an elementary school student in which the hazard quotient exceeded 0.1. Conclusions: Results of this study confirm that the exposure of lead ingestion and risk level increases as the particle size of crumb rubber gets smaller.

• Asian Journal of Atmospheric Environment
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• v.6 no.3
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• pp.206-221
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• 2012

Hazardous chemicals can be released from artificial turf used in some school playgrounds. To distinguish between Health risk assessment (HRA) exposure scenarios for this study, the ratio of elementary, middle and high schools was considered before final selection. Considering exposure pathways (inhalational, oral and dermal), media and materials were examined, targeting hazardous chemicals released from artificial turf playground-related products. Upon evaluation, the quantity of infill chips was shown to exceed the domestic product content standard (90 mg/kg) at eight (16%) out of 50 schools. PAHs were shown to exceed standards (10 mg/kg) at two (4%) out of the 50 schools. The excess cancer risk (ECR) of carcinogens was shown to be $1{\times}10^{-6}$ in most users for the worst exposure scenario. In children with pica, who represented the most extreme exposure group, the ECR was expected to be as high as $1{\times}10^{-4}$, showing the low risk level of carcinogens. The hazard index (HI) for individual chemicals was shown to be low, at around 0.1 or less, except for children with pica, according to the mean exposure scenario of artificial turf playground exposure. However, the HI was shown to exceed 1.0 in children with pica. Therefore, no direct health risk was found in using artificial turf playgrounds and urethane flooring tracks for the mean exposure scenario, except in children with pica.