• Journal of the Korea Concrete Institute
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• v.14 no.6
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• pp.851-863
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• 2002

Corrosion products of reinforcement in concrete induce pressure to the adjacent concrete due to the expansion of steel. This expansion causes tensile stresses around the reinforcing bar and eventually induces cracking through the concrete cover The cracking of concrete cover will adversely affect the safety as well as the service life of concrete structures. The purpose of the this study is to examine the critical corrosion amount which causes the cracking of concrete cover. To this end, a comprehensive experimental and theoretical study has been conducted. Major test variables include concrete strength and cover thickness. The strains at the surface of concrete cover have been measured according to the amount of steel corrosion. The corrosion products which penetrate into the pores and cracks around the steel bar have been considered in the calculation of expansive pressure due to steel corrosion. The present study indicates that the critical amount of corrosion, which causes the initiation of cracking, increases with an increase of compressive strength. A realistic relation between the expansive pressure and average strain of corrosion product layer in the corrosion region has been derived and the representative stiffness of corrosion layer was determined. A concept of pressure-free strain of corrosion product layer was introduced to explain the relation between the expansive pressure and corrosion strain. The proposed theory agrees well with experimental data and may be a good base for the realistic durability design of concrete structures.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.1
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• pp.74-80
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• 2019

In this study, pyrolyzed oyster shells at a low temperature ($350^{\circ}C$) were applied for a mesocosm experiment to confirm resulting changes in the properties of sediment. After creating a covering of oyster shells, an increase in ORP and decrease in ammonia in the overlying water was observed in an experimental case. The decrease of TOC in this experiment was due to the dilution of organic matter due to the addition of inorganic matter (pyrolyzed oyster shells). The decrease in the concentration of AVS was observed due to the adsorption of AVS by the surface of the oyster shells. From the results obtained in this experiment, it has been concluded that pyrolyzed oyster shells at a low temperature can be used for remediation of polluted sediment.

• 한국해양학회지
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• v.29 no.1
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• pp.42-49
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• 1994

A series of radiocarbon dating from intertidal, subtidal, and inner continental shelf deposits investigated along the west coast of Korea as well as from its offshore sea floor (namely, the eastern Yellow Sea Basin) how (1) the Holocene sea level rise, i.e., the ecstatic sea-level history during the oxygen isotope stage 1, and (2) pre-Holocene sea-level fluctuations during the oxygen isotope stages 2 and 3. Marine geophysical investigations in the Yellow Sea reported a possible development of desert and loses deposits due to dieselization under the cold and dry climate during the Last Glacial Maximum. The Kanweoldo deposit overlain unconformably by the Holocene intertidal deposits, which is mainly exposed along the tidal channels and intertidal flats in the Cheonsu Bay, the west coast of Korea, shows the characteristic cryogenic structure (cryoturbation). Such cryoturbation structure of the Kanweoldo deposit appears to indicate the cold and dry climate under the ecstatic sea-level paleoshoreline standing before and after of the pre-Holocene interstitial period (about 30000 y BP is suggested and its shoreline curve is constructed.

• Journal of the Korean Ceramic Society
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• v.36 no.1
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• pp.21-29
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• 1999

The effects of density and pore size distribution of substrate in preparing SiC conversiton layer on graphite substrate were investigated. The chemical reaction for formation of SiC conversion layer was occurred at substrate surface or below surface through SiC gas infiltration. It was supposed that the pore size distribution required for the sufficient SiO gas infiltration and the continuous chemical reaction during conversion process was in the range of 1.0∼10.0$\mu\textrm{m}$. In the stress analysis of SiC layer with finite element method (FEM), the residual stress distribution due to thermal mismatch was shown. However, the compressive stress was measured in SiC layer by X-ray diffraction, it was presumed that the residual stress distribution of SiC layer was mainly influenced by the constraining effect of interlayer between SiC layer and graphite substrate, and the densification behaviro and the grain growth in SiC conversion layer.

• Journal of the Korean earth science society
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• v.43 no.5
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• pp.639-646
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• 2022

Occurrence of black opaque hydrocarbon (pyrobitumen) in some Cretaceous Jinju sandstones of the Sindong Group, Gyeongsang Basin in Korea is first reported in this study. The pyrobitumen is developed on chlorite pore-lining cement, or impregnated into the outer zone of chlorite cement. Therefore, it seems to have been formed after the precipitation of chlorite cement, indicating the former presence of crude oil. The liquid hydrocarbons migrated into sandstones during moderate burial and these sandstones seem to have acted as a liquid hydrocarbon reservoir. The presence of pyrobitumen in the Jinju Formation indicates that this formation underwent deep burial after liquid hydrocarbon migration. As reservoir temperatures increased further, hydrocarbons were cracked and a solid pyrobitumen residue remained in the reservoir.

• Journal of Life Science
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• v.17 no.12
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• pp.1701-1708
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• 2007

Seed pelleting is generally conducted in order to save the labor for sowing and thinning by enabling the precision mechanical planting. In the present study, the influence of physical and chemical properties of pelleting solid materials was investigated on carrot seed germination. Among the pelleting solid materials evaluated, dialite, kaolin, and talc showed low bulk density and high porosity. Bentonite and dialite carried high water holding capacities of 184% and 173%, respectively, while calcium carbonate, calcium oxide, and fly ash showed relatively low water holding capacity. The pH of kaolin (6.8) and dialite (7.4) were close to neutral, while limestone (12.8), calcium oxide (13.0), and bentonite (10.0) were highly basic. High electro-conductivity was shown in limestone and calcium oxide. EDS analysis revealed that the main elemental compositions of talc were Si (71.0%) and Mg (29.0%), and those of calcium carbonate were Ca (66.6%), Si (22.9%), and Mg (10.5%). High granulation capacity was observed from talc and the mixture of talc and calcium carbonate. Seeds pelleted with bentonite showed the highest hardness. The dissolving type of the pellet layer after imbibition was split type in talc, limestone, zeolite, and fly ash, melt type in calcium carbonate and calcium oxide, and swell type in bentonite and vermiculite. The shortest dissolving time of pellet layer was observed from calcium carbonate and kaolin. The germination speed $(T_{50})$ was delayed as the size of pelleted seeds increased. The optimum size of pelleting was 19 ratio in carrot.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.13 no.2
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• pp.75-83
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• 2017

In severe accident conditions of light water reactors, the loss of coolant may cause problems in integrity of zirconium fuel cladding. Under the condition of the loss of coolant, the zirconium fuel cladding can be exposed to high temperature steam and reacted with them by producing of hydrogen, which is caused by the failure in oxidation resistance of zirconium cladding materials during the loss of coolant accident scenarios. In order to avoid these problems, we develop a multi-metallic layered composite (MMLC) fuel cladding which compromises between the neutronic advantages of zirconium-based alloys and the accident-tolerance of non-zirconium-based metallic materials. Cold pilgering process is a common tube manufacturing process, which is complex material forming operation in highly non-steady state, where the materials undergo a long series of deformation resulting in both diameter and thickness reduction. During the cold pilgering process, MMLC claddings need to reduce the outside diameter and wall thickness. However, multi-layers of the tube are expected to occur different deformation processes because each layer has different mechanical properties. To improve the utilization of the pilgering process, 3-dimensional computational analyses have been made using a finite element modeling technique. We also analyze the dimensional change, strain and stress distribution at MMLC tube by considering the behavior of rolls such as stroke rate and feed rate.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.25 no.1
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• pp.37-54
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• 1999

Planarized SiO$_2$ particles were prepared by two-step reduction method of making much smaller particles, micron-sized ones, to improve spreadability, adherence, and smoothness. Various pigments known as flaky extender usually have terrace layers on their surfaces, but SiO$_2$ Particles in this study exhibit a smooth surface structure. These single SiO$_2$ particles were used for core particles to prepare the composite particles coated with ultra fine TiO$_2$ particles by a homogeneous precipitation method. The thickness and the morphology of the deposited TiO$_2$ layer could be altered by adjusting the reactant concentrations, reaction time and temperature. The characteristics of SiO$_2$/TiO$_2$composite in the field of color cosmetics is to give a UV-cut effect and to enhance the chroma of human skin color, one of optical properties.

• Applied Chemistry for Engineering
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• v.3 no.3
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• pp.422-429
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• 1992

The morphology and adhesion properties of rubber compounds containing resorcinol formaldehyde(RF) resin and hexamethoxymethylmelamine(HMMM) used in adhesion of rubber to brass-plated steel cord was investigated. The resins were spherical particles about $2000{\AA}$ diameter and distributed in rubber compounds homogeneously, and the cured compound with steel cord showed migration of resin to steel cord. Also, modulus was increased with increasing HMMM contents. The loss of adhesion between rubber and steel cord was likely to be at initial stages by thermal aging. Considering the physical properties, suability of adhesion layer and thermal aging property, optimum ratio of RF resin and HMMM was 1 : 0.9.

• Journal of the Korean Geographical Society
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• v.47 no.3
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• pp.315-327
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• 2012

Red saprolites are appeared in granitic hills in Yeongam, Southern Korean Peninsula. These red saprolites were analyzed for their geochemistry, including CIA, A-CN-K and A-CNK-FM ternary plots, to understand the chemical weathering trend and rubefaction of the saprolites. These saprolites were compared with laterite profiles in Cameroon formed under humid tropical conditions. The red saprolites in Yeongam show commonly massive loss of CaO, $Na_2O$, but $K_2O$ is being slow. The red saprolites in Yeongam relative to laterite and kaolinite profiles of Cameroon and Spain show weak chemical alteration owing to slow removal of $K_2O$, but high mafic constituents, $Fe_2O_3$ and MgO, for most of the samples. In the saprolites of Yeongam, mafic oxides become enriched because of the fast and massive removal of alkali constituents, such as CaO, $Na_2O$ and $K_2O$, relative to other elements, resulting in rubefaction of the saprolites. It is found that the rubefaction of the saprolites is not necessarily proportional to chemical weathering intensity.