• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.4
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• pp.373-380
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• 2023

This study investigated the carbonation of concrete brick cured in a CO₂ environment for the utilization of CO₂ captured in power plants. Concrete brick specimens were produced with electric arc furnace reducing slag (ERS) and electric arc furnace oxidizing slag (EOS), and cured for 3 days in a CO₂ chamber with a concentration of 20 % or in a constant temperature and humidity chamber. The weight change, compressive strength, flexural strength and carbonation depth of concrete bricks were measured. From the results, it was found that when subjected to CO₂ curing, CO₂ was absorbed at the level of 2.4 % of the weight of the specimen. The specimen incorporating ERS showed the highest carbonation depth, and satisfied KS F4004 standards for the concrete brick. Therefore, it is expected that the captured CO₂ can be utilized in the CO₂ curing process of concrete brick.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.4
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• pp.433-439
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• 2023

In this study, the bonding performance of repair materials was evaluated on concrete repair surface to develop concrete repair materials based on UHPC (Ultra High Performance Concrete) which has high mechanical and durability performance. The ten test variables were applied considering the roughness and wet condition of the concrete surface subject to repair, the addition of polymer, and the use PP and PVA fibers in repair materials. The addition of the polymer caused a significant decrease in strength, which was thought to be due to the effect of the additional super plasticizer used to adjust workability. Also, flow was reduced by up to 13.8 % with the use of plastic-based fibers. As a result of evaluating the bond strength of the repair material considering the condition of the surface subject to repair, it was thought that in the case of using UHPC-based repair material, high bonding performance could be secured without any additional surface treatment as long as the surface of the base material was sound. In addition, UHPC-based repair materials showed high bonding performance even when the attachment surface was wet. In the future, research will be conducted on shot-crete application and gradient pouring for the development of UHPC-based repair materials, and continuous improvement in the repair material mixing property will be carried out to ensure economic efficiency and performance as a concrete structural repair material.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.6_2
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• pp.1011-1017
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• 2023

In this study, the harmless crack size (a_hml) by double shot peening (DSP) using shot balls with different diameters was evaluated on carburized, quenched-tempered SCM822H steel. The minimum crack size (a_NDI) detectable by non-destructive inspection was also evaluated. The relationship between the crack size (a_25,50) that reduces the fatigue limit by 25% and 50% and a_hml was evaluated. The residual stress of DSP was greater in SP_(0.6+0.08) than SP_(0.8+0.08) and appeared deeper in the depth direction. In addition, the hardness below the surface appeared larger. The fatigue limit of DSP increased 2.07 times and 1.95 times compared to non-SP. All a_hml of the DSP specimen was determined at the depth (a). The compressive residual stress distribution affects a_hml, and the a_hml of SP_(0.6+0.08), which has a large compressive residual stress and a high fatigue limit, appeared large. a_hml of SP_(0.6+0.08) introduced deeper than the residual stress of SP_(0.8+0.08) is larger in the range of As=1.0-0.3. Since the residual stress in the thickness direction has a greater effect on a_hml than the residual stress at the surface, it is necessary to introduce it more deeply. The relation of a_hml, a_25,50, and a_NDI were evaluated in the point for safety and reliability.

• Journal of Korean Dental Hygiene Science
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• v.6 no.2
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• pp.1-12
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• 2023

Objectives: This study attempted to identify the eating habits and oral health behaviors of Korean teenagers, studying their relationship with oral health status. The findings serve as fundamental data to enhance proper eating habits and oral health-related projects, ultimately improving teenagers' oral health. Methods: It was analyzed through the original data of the 16th (2020) online survey of youth health behavior in Korea, Frequency analysis, complex sample cross-analysis, complex sample logistic regression analysis were conducted using the SPSSwin 21.0 program. Results: As a result of the study, was associated with the consumption of all sweet drinks, fast food intake, and the frequency of daily brushing over the past 7 days Teeth pain is noted with the consumption of soda, sweet drinks, fast food, and the frequency of daily brushing over the past 7 days. Gum bleeding is noted with the consumption of sweetened products, fast food intake, and the frequency of daily brushing over the past 7 days. Conclusions: Eating habits and oral health behaviors should be considered for the oral health management of middle and high school students. Specific measures should be sought to provide proper dietary education and systematic oral health education to improve the oral health of middle and high school students.

• Imaging Science in Dentistry
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• v.54 no.2
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• pp.129-137
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• 2024

Purpose: Patients with head and neck cancer (HNC) who undergo dental procedures during radiotherapy (RT) face an increased risk of developing osteoradionecrosis (ORN). Accordingly, new tools must be developed to extract critical information regarding the dose delivered to the teeth and mandible. This article proposes a novel approach for visualizing 3-dimensional planned dose distributions on panoramic reconstruction computed tomography (pCT) images. Materials and Methods: Four patients with HNC who underwent volumetric modulated arc therapy were included. One patient experienced ORN and required the extraction of teeth after RT. In the study approach, the dental arch curve (DAC) was defined using an open-source platform. Subsequently, pCT images and dose distributions were generated based on the new coordinate system. All teeth and mandibles were delineated on both the original CT and pCT images. To evaluate the consistency of dose metrics, the Mann-Whitney U test and Student t-test were employed. Results: A total of 61 teeth and 4 mandibles were evaluated. The correlation coefficient between the 2 methods was 0.999, and no statistically significant difference was observed (P>0.05). This method facilitated a straightforward and intuitive understanding of the delivered dose. In 1 patient, ORN corresponded to the region of the root and the gum receiving a high dosage (approximately 70 Gy). Conclusion: The proposed method particularly benefits dentists involved in the management of patients with HNC. It enables the visualization of a 3-dimensional dose distribution in the teeth and mandible on pCT, enhancing the understanding of the dose delivered during RT.

• Korean Journal of Soil Science and Fertilizer
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• v.29 no.2
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• pp.113-123
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• 1996

This experiment was carried out to compare with the physico-chemical properties of granular fused magnesium phosphates which were two domestic products(Pungnong Biryo Industrial Co., LTD and Kyunggi Chemical Industrial Co., LTD) and a imported Chinese product. The changes of pH, distribution of particle size, disintegration in water and in soil, hardness in soil, chemical composition, and dissolution rates in water, in soil and in 2% citric acid solution were investigated. The changes in pH were bigger in Jungmun series(black volcanic soil), in the imported chinese product, and in Jungmun series with the larger quantities applied. The domestic products were lower in pH, calcium, alkalinity and 1/2N-HCl soluble silicate than the Chinese product but total(Aqua regia) soluble phosphate, 2% citric acid soluble phosphate, 1/2N-HCl soluble and 2% citric acid soluble magnesium, and 2% citric acid soluble manganese concentration were similar among the domestic products and the imported product. In particle sizes, Chinese product was the biggest, Kyunggi product was the next, and Pungnong product was the smallest. The changes of disintegration rate in water and in soil were smaller in Pungnong and Kyunggi products at the early days of dissolution, and there were decreased with the order of Kyunggi product> Chinese product> Pungnong product at the latter days. The hardness of the products in soil was the strongest in Kyunggi product, the next was Pungnong product and Chinese product was the weakest so as to hardly measurable. The changing dissolution rates of 2% citric acid soluble phosphate concentration of granular fused magnesium phosphate products were the highest in Kyunggi product and the lowest in Pungnong product at the early days, the three products were dissolved over 90% within 50 days, and there were no clear difference among the products after 70 days of dissolution. The dissolution rates of 2% citric acid soluble phosphate concentration of granular fused magnesium phosphate products in soil were the highest in Pungnong product and Chinese product was the lowest, but they were less than 60% in 100 days of dissolution.

• Korean Journal of Soil Science and Fertilizer
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• v.29 no.2
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• pp.165-172
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• 1996

Symbiotic effectiveness and significance of Bradyrhizobium japonicum strains in five serogroups which were consisted of three corresponding serotype strains, respectively, indigenous to Korean soils were evaluated in terms of utility of strain serogroup for symbiotic improvement on soybean plant. The nodulation by rhizobia of each serogroup on four soybean cultivars(Danweonkong, Kwangkyo, Pangsakong, and Eunhakong) was good in order of USDA 123 > YCK 150 > YCK 117 > YCK 141 > USDA 110 serogroup members. Shoot dry weight of soybean was relatively high with USDA 110 serogroup members as well as with YCK 141 serogroup members, whereas the effectiveness of USDA 123 serogroup members was the lowest among the serogroups examined. In particular, Pangsakong among soybeans inoculated with five-serogroup members was positively outstanding on nodulation and shoot dry weight of the plant. Overall, symbiotic parameters of serogroup members associated with soybean plant such as nodule number, nodule mass, $N_2$ase activity, and shoot dry weight showed significantly different responses at level of 1% probability among both rhizobial serogroups and soybean cultivars, respectively. The rate in symbiotic similarity of the members of each serogroup from F-test ($$P{\leq_-}0.05$$) was 100% for nodule No., 90% for $N_2$ase activity. and 80% for soybean shoot dry weight. Taken together, the results indicated that the serological grouping of B. japonicum could be strongly useful for improving the symbiotic effectiveness hetween soybean and Rhizobium.

• Korean Journal of Soil Science and Fertilizer
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• v.42 no.6
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• pp.500-512
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• 2009

This study was carried out to evaluate the effect of temperature on soil microbial biomass, enzyme activities, and PLFA content in the volcanic(VAS) and the non-volcanic ash soil(NVAS). The soils were treated with organic materials such as organic fertilizer pelleted(OFPL), organic fertilizer powdered(OFPD), pig manure compost(PMC), and food waste compost(FWC). Two grams of organic materials were well mixed with 30g of dried volcanic and non-volcanic ash soil(< 2 mm) with 50% of soil moisture content. And the soils were incubated at 10, 20, $30^{\circ}C$ in incubator. Soils were analysed on the incubation times as followed; soil pH, total nitrogen, organic matter(at 75, 150, 270 days), microbial biomass C and PLFA (at 75, 270 days), microbial biomass N and soil enzyme(at 150, 270 days). pH values of soils treated with PMC and FWC had no changes on soil type, and incubation temperature. However, the pH was increased with temperature in the soils treated with OFPL. The changes in NVAS was higher than in VAS. Soil microbial biomass C content were high in the condition of high temperature and organic fertilizers treatment in VAS. But the contents were gradually decreased with incubation period in both NVAS and VAS. Soil microbial biomass N was high in NVAS treated with organic fertilizers and in VBS treated with PMC and FWC. PLFA content was higher in NVBS than in VBS at 75 days but showed high in VBS at 270 days. Urease activity of NVBS treated with OFPL showed $10^{\circ}C$ (75.0)> $20^{\circ}C$ (16.3)>$30^{\circ}C$ ($4.6ug\;NH{_4-}N\;g^{-1}\;2h^{-1}$) at 150 days. It were decreased gradually high temperature and time passes. And it showed high at $10^{\circ}C$ in VBS. Glucosidase activity was higher in NVBS than in VBS. Correlation coefficient of between soil microbial biomass C and microbial activity indicators showed that PLFA was high significantly at $r^2=0.91$ in NVBS and ${\beta}-glucosidase$ was $r^2=0.83$ in VBS. Soil microbial activities showed differences in the relative sensitivities of soil type and soil temperature.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.2
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• pp.192-197
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• 2012

The competition between green manure and forage crops frequently occurred at agricultural field because of soil fertility and livestock feeding selection. These experiments were carried out to evaluate the effects shoot and residue for green manure and forage production by leguminous crops and barley mixtures at paddy. Field experiments were conducted at paddy soil from 2008 to 2009. Treatments consisted of mixture and inter-seeding of barley and leguminous crops (hairy vetch and crimson clover). These treatments were divided into cutting height of 8 and 25 cm for using of green manure and forage at once. The residue biomass of 25 cm cutting height was higher than 8 cm and were no significantly between mixture and inter-seeding. However, residues of legume crop were significantly higher at inter-seeding than mixture. The shoot biomass of 8 cm cutting height was higher than 25 cm for forage using. The production of legume crop was high at the barley and hairy vetch seeding plot. The mixture of hairy vetch and barley showed the best biomass of shoot and residue for green manure and forage using at 25 cm of cutting height. Also this treatment could be possible to rice cultivation by no fertilization. Therefore, we suggested that 25 cm cutting of hairy vetch and barley mixture could be used for green manure and forage at the same time under rice-based cropping system.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.2
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• pp.198-203
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• 2012

Leguminous cover crops fix nitrogen from the atmosphere. The objective of this research was carried out to decrease fertilizer amount by cover crops-wheat mixtures cultivation. Field experiment was conducted at upland soil 2008 to 2009. Cover crops were used crimson clover and hairy vetch. Treatments consisted of three wheat-crimson clover (wheat 10 kg + crimson clover 1, 3, $5kg\;10a^{-1}$), wheat-hairy vetch mixture (wheat 10 kg + hairy vetch $2kg\;10a^{-1}$), and wheat - hairy vetch mixture - crimson clover (wheat 10 kg + hairy vetch 2 kg + crimson clover $3kg\;10a^{-1}$). These treatments were divided into no fertilizer and top dressing. The yield of wheat and crimson clover mixtures had no significantly differences compared to wheat only at top dressing plots. Also soil chemical and physical properties were a little bit improved such as OM, $NO_3$-N, and bulk density etc by wheat-crimson clover mixtures. Therefore, we suggested that crimson clover and wheat mixture could be used to reduction of fertilizers amount for environmental friendly wheat production.