• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.1
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• pp.33-40
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• 2021

The objective of this work is to prove a possibility of void f illing through a carbonation f or the purpose of improving the quality of recycled aggregate. Carbonation can permanently immobilize CO2, which is a greenhouse gas, and thus provides additional benefit on environment. In this work, recycled fine aggregate was reacted using gaseous CO2 and supercritical CO2(scCO2) in a closed chamber, and the changes in physical properties of the recycled f ine aggregate bef ore and af ter carbonation were analyzed using the apparent density, skeletal density, pH, and FE-SEM measurements. Thereafter, a mortar specimen was prepared and a compressive strength was measured. According to the experimental results, it was found that the increase in the apparent density and the true density was higher by the reaction with scCO2, which was conducted at high temperature and high pressure compared to the reaction with gaseous CO2. In addition, the pH of the eluted water was found to have a larger initial decrease than that observed with samples from reaction by gaseous CO2. The shape and amount of calcium carbonate crystals were also found to be larger than that from gaseous CO2. The increase in compressive strength was the largest when using recycled fine aggregate reacted with scCO2. It was clear that quality improvement of recycled fine aggregate was higher with scCO2 than with gaseous CO2.

• Journal of the Korea Institute of Building Construction
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• v.22 no.1
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• pp.11-21
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• 2022

Currently, in the domestic construction industry, the free web method has been emerging as a potential solution to the shortage of skilled workers due to the prolonged COVID-19 crisis, as it helps in securing economic feasibility through shortening the construction period and reducing labor costs. To consider one part of the construction method, in this study, the bending behavior according to the load was evaluated for the SY slope-type beam formwork, which was manufactured at a factory, assembled with rebar, brought into the site, and then poured into the site. For the SY Beam standard cross-sectional shape, a cross-sectional dimensional width of 400mm and depth 600mm determined through structural modeling using the MIDAS GEN program were applied. A total of 6 specimens were made with a member length of 5,000mm, 5 specimens and one RC specimen in the comparison group were manufactured in real-size format using the thickness of the steel plate(0.8, 1.0, 1.2mm) as a variable, and bending experiments were performed. In the bending test, the steel plate deck showed high initial stiffness and maximum strength as it yielded, which showed that it sufficiently contributed to the flexural strength. It is judged that additional analysis and experimental studies for 1.05, 1.1, and 1.15mm are needed to derive the appropriate steel plate thickness and the method for calculating the tensile force contribution of the steel plate to secure the manufacturing, construction and economic feasibility of SY Beam in the future.

• Journal of the Korean Geotechnical Society
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• v.24 no.2
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• pp.87-97
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• 2008

Behaviors of cemented engineered soils, composed of rigid sand particle and soft rubber particle, are investigated under $K_o$ condition. The uncemented and cemented specimens are prepared with various sand volume fractions to estimate the effect of the cementation in mixtures. The vertical deformation and elastic wave velocities with vertical stress are measured. The bender elements and PZT sensors are used to measure elastic wave velocities. After cementation, the slope of vertical strain shows bilinear and is similar to that of uncemented specimen after decementation. Normalized vertical strains can be divided into capillary force, cementation, and decementation region. The first deflection of the shear wave in near field matches the first arrival of the primary wave. The elastic wave velocities dramatically increase due to cementation hardening under the fixed vertical stress, and are almost identical with additional stress. After decementation, the elastic wave velocities increase with increase in the vertical stress. The effect of cementation hinders the typical rubber-like, sand-like, and transition behaviors observed in uncemented specimens. Different mechanism can be expected in decementation of the rigid-soft particle mixtures due to the sand fraction. a shape change of individual particles in low sand fraction specimens; a fabric change between particles in high sand fraction specimens. This study suggests that behaviors of cemented engineered soils, composed of rigid-soft particles, are distinguished due to the cementation and decementation from those of uncemented specimens.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.3
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• pp.47-58
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• 2024

This study were conduced experimentally to analyze the heat-generating performance, flexural strength, and microstructure of conductive mortar mixed with micro steel fiber and multi-wall carbon nanotube (MWCNT). In the conductive mortar heat-generating performance and flexural strength tests, the mixing concentration of MWCNT was selected as 0.0wt%, 0.5wt%, and 1.0wt% relative to the weight of cement, and micro steel fibers were mixed at 2.0vol% relative to the volume. The performance experiments were conducted with various applied voltages (DC 10V, 30V, 60V) and different electrode spacings (40 mm, 120 mm) as parameters, and the flexural strength was measured at the curing age of 28 days and compared and analyzed with the normal mortar. Furthermore, the surface shape and microstructure of conductive mortar were analyzed using a field emission scanning electron microscope (FE-SEM). The results showed that the heat-generating performance improved as the mixing concentration of MWCNT and the applied voltage increased, and it further improved as the electrode spacing became narrower. However, even if the mixing concentration of MWCNT was added up to 1.0 wt%, the heat-generating performance was not significantly improved. As a result of the flexural strength test, the average flexural strength of all specimens except the PM specimen and the MWCNT mixed specimens was 4.5 MPa or more, showing high flexural strength due to the incorporation of micro steel fibers. Through FE-SEM image analysis, Through FE-SEM image analysis, it was confirmed that a conductive network was formed between micro steel fibers and MWCNT particles in the cement matrix.

• Journal of Korean Society of Water and Wastewater
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• v.37 no.4
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• pp.203-214
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• 2023

In this study, the physical properties and fracture characteristics according to the tensile load are evaluated on the materials of the polymeric filler and carbon fiber-based composite sleeve technique. The polymeric filler and the composite sleeve technique are applied to areas where the pipe body thickness is reduced due to corrosion in large-diameter water pipes. First, the tensile strength of the polymeric filler was 161.48~240.43 kg_f/cm², and the tensile strength of the polyurea polymeric filler was relatively higher than that of the epoxy. However, the tensile strength of the polymeric filler is relatively very low compared to ductile cast iron pipes(4,300 kg_f/cm²<) or steel pipes(4,100 kg_f/cm²). Second, the tensile strength of glass fiber, which is mainly used in composite sleeves, is 3,887.0 kg_f/cm², and that of carbon fiber is up to 5,922.5 kg_f/cm². The tensile strengths of glass and carbon fiber are higher than ductile cast iron pipe or steel pipe. Third, when reinforcing the hemispherical simulated corrosion shape of the ductile cast iron pipe and the steel pipe with a polymeric filler, there was an effect of increasing the ultimate tensile load by 1.04 to 1.06 times, but the ultimate load was 37.7 to 53.7% compared to the ductile cast iron or steel specimen without corrosion damage. It was found that the effect on the reinforcement of the corrosion damaged part was insignificant. Fourth, the composite sleeve using carbon fiber showed an ultimate load of 1.10(0.61T, 1,821.0 kg_f) and 1.02(0.60T, 2,290.7 kg_f) times higher than the ductile cast iron pipe(1,657.83 kg_f) and steel pipe(2,236.8 kg_f), respectively. When using a composite sleeve such as fiber, the corrosion damage part of large-diameter water pipes can be reinforced with same level as the original pipe, and the supply stability can be secured through accident prevention.

• The Korean Journal of Mycology
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• v.51 no.3
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• pp.205-217
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• 2023

This study aimed to produce novel bioactive compounds from non-pathogenic pigmented wild yeasts. Culture supernatants and cell-free extracts of non-pathogenic pigmented yeast strains were prepared, and their physiological functionalities and enzyme activities were measured. Cell-free extracts from Rhodosporidium paludigenum HHGG35-1 and culture supernatants from Rhodosporidium diobovatum NMD18-1 demonstrated very high antioxidant activity (76.6%) and anti-gout xanthin oxidase inhibitory activity (86.2%), respectively. Maximal production of the antioxidants (76.9%) was obtained when Rh. Paludigenum HHGG35-1 was cultured in a yeasts extract-peptone-dextrose (YPD) medium (pH 6.5) at 30℃ for 24 h. The xanthin oxidase inhibitor was also maximally produced (91.6%) when Rh. Diobovatum NMD18-1 was cultured at 30℃ for 96h in a YPD medium (pH 6.5). Rh. Paludigenum HHGG35-1 was oval in shape and formed ascospre. The Rh.diobovatum NMD18-1 specimen displayed dimensions of 1.6 × 1.6 ㎛ and produced ascospores; however, it did not form pseudomycelium. Both of Rh. Paludigenum HHGG35-1 and Rh. Diobovatum NMD18-1 grew well in a 40%-glucose-containing YPD medium and 10%-NaCl-containing YPD medium.

• The Journal of Korean Academy of Prosthodontics
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• v.48 no.2
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• pp.151-157
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• 2010

Purpose: The purposes of this study was to evaluates shear bond strength between zirconia core and veneer-ceramic in order to examine the clinical practice of colored zirconia block fabricated by infiltration method into the metal chloride solution. Material and methods: CNU block and $Everest{(R)}$ ZS blank were used. VITA In-$Ceram{(R)}$2000 YZ Coloring liquid (LL1) and 3 aqueous metal chloride solutions containing chromium and molybdenum ingredients were used. 40 zirconia specimens were prepared into cuboid shape ($5{\times}5{\times}10 mm$). All specimens were divided into 5 groups by infiltrating into the coloring liquids. After that, porcelain was build up into the shape of $5{\times}5{\times}4mm^3$, followed by sintering. The maximum loading and shear bond strength was measured. Failure patterns and failure sites were examined. Results: 1. There were no statistical differences in shear bond strength between zirconia blocks (P > .05). 2. There were no statistically significant differences in shear bond strength between non-colored and colored zirconia blocks, while shear bond strength of non-colored zirconia blocks is higher than that of colored specimen (P > .05). 3. In the comparison with shear bond strength among colored zirconia blocks, there were no statistical differences according to kinds of coloring liquid (P > .05). 4. Mixed failure patterns were mainly observed in the failure between zirconia and veneering ceramic. The veneering ceramic failure of all specimens was observed in either interface of zirconia or veneering ceramic. Conclusion: Shear bond strength between colored zirconia and veneering ceramic shows lower tendency than non-colored zirconia, but there was clinically allowable value.

• The Korean Journal of Zoology
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• v.31 no.2
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• pp.111-121
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• 1988

This study was attempted to investigate the regional distribution and shapes of pancreatic endocrifle cells in the hedgehog, Erinaceus koneanus by the immunocytochemical PAP methods (Nalane, 1968; Stemberger, 1979). The tissue specimen taken from the splenic and duodenal regions of pancreas(proximai, middle and distal portions, respectively) were fixed with Bouin solution and the sections(5$\mu$ m) were followed by simple and double staining with 2 substrates, DAB and 4-CI-1-naphthol. The results were as following: Glucagon(A) cells, 13 $\mu$ m x 9.5 $\mu$ m in size, were found in the islets periphery and among the exocrine parenchyma. A cells were abundant in all the portions of splenic region and distal portion of duodenal region in contrast to a few in the proximal and middle portion of duodenal region. The shapes of the A cells were round, oval and pyramidal types. Insulin(B) cells, 11.6$\mu$m x 9.4$\mu$m in sise, were round or oval in shape and located throughout the islets. B cells were the most numerous cell types in all portions of splenic region and distal protion of duodenal region as compared with the other portions. Somatostatin(D) cells, 12.6$\mu$m x 9.1 $\mu$m in size, were round or oval in shape and found in the islets periphery and scattered in the exocrine parenchyma. These cells were rare in all the portions of splenic and duodenal region. Pancreatic polypeptide(PP) cells of various type, 12.8$\mu$ m x 8.5 $\mu$ m in size, were found in the islets periphery and among the exocrine parenchyma. PP cells were numerous in the proximal and middle portion of duodenal region, but rarely scattered in the other portions.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.34 no.2
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• pp.87-99
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• 2016

This study was carried out to characterize 127 recently developed cultivars of Rose of Sharon (Hibiscus spp.) in Korea and foreign Countries for landscape uses. The examined factors were growth characteristics such as tree height of a 1-year grafted plant(cm), plant type, growth habit, leaf characteristics such as shape and size, flower characteristics such as color, shape, size, and red eye during 2014 and 2015 for landscape uses. The results are obtained as follows; Hibiscus hybrid 'Daewangchun', 'Daeil', 'Lohengrin', 'Yeonam', 'Joomong', 'Jina', and H. syriacus 'Honggarosu' had vigorous shoot growth and tall tree size of 100cm. New Hibiscus cultivars, Hibiscus hybrid 'Daewangchun' and 'Daeil', having vigorous growth, uniform plant habit, upright, and compact branches were developed through interspecific crosses between H. syriacus 'Samchully' (♀) and H. sinosyriacus 'Seobong' (♂). This newly developed cultivar 'Daewangchun', 'Daeil', 'Lohengrin', 'Yeonam', 'Joomong', 'Jina', and H. syriacus 'Honggarosu' having tall vigorous growth d unique flower with long red eye can be used as street tree or specimen plant in landscape. Otherwise, H. syriacus 'Tamla', 'Melrose', 'Bidan', 'Hi Lea', 'Byeollee', 'Byunghwa', 'Mibak', 'Hanyang', 'Chungam', 'Lil Kim Violet', 'Jongmoo', 'Eunhasu', Hibiscus hybrid 'Saehanseo', and Hibiscus hybrid 'Yousoon' were selected as small tree of 30~39cm. They had dwarf form in tree seemed to be suitable for pot or flower bed planting on both indoor and outdoor conditions. H. syriacus 'Antong', 'Chungjo', and 'Lil Kim' were less than 30 cm of tree size. H. syriacus 'Antong', 'Chungjo', and 'Lil Kim', characterized by its compact, upright and outwardly spreading plant habit; freely branching habit; dark green-colored leaves; good garden performance. Therefore, the new cultivars with tall and small tree size were a promising cultivar as a ground covers or pot planting as woody landscape plant.

• Journal of the Korean Wood Science and Technology
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• v.10 no.3
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• pp.4-12
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• 1982

1. Under the request of the Dept. of Navy, U.S.A. this investigation has been done as a part work of the Navy Research Project of Tropical Woods at the Wood Technology Laboratory, School of Forestry, Yale University, New Haven, Conn., U.S.A. 2. In order to determine the equilibrium moisture content and hysteresis loop of three tropical woods (Ocotea, Tablebuia, and Hymenaea) which have not been tested the physical properties, this investigation has made with small thin specimens (1.5"${\times}$1.0${\times}$0.4) under four different controlled relative humidity conditions (that is, 21%, 53%, 60%, and 83%). 3. As the result, the equilibrium moisture content and hysteresis loop of three tropical woods have been shown in the Table and Figures 2, 3 and 4. 4. According to the results, it is concluded that there are the considerable differences in the equilibrium moisture content under the same relative humidity condition and the type of hysteresis loop between different species which have been tested. 5. Desorption of lumber with slightly oscillating humidity of each species tested, has shown on the Table 9 and it has almost the same tendency of results showing the difference between species as the small specimen. 6. Although it is hard to compare the difference of results, E.M.C., and hysteresis between tropical wood and woods from temperate zone, there are, however, still some difference between species. 7. The author wishes to acknowledge my indebtedness to Prof. Wangaard, and Prof. Dickinson for the competent guidance and good advice on this study, and also to Mr. Clanchs for the help in getting materials for the experiment.