• Journal of the Korean Ceramic Society
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• v.40 no.12
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• pp.1235-1240
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• 2003

The mixtures which are in the chemical composition of Portland cement were prepared from oyster shell, casting dust and BOF slag. The clinkerbility and the behaviour of formation of clinker minora]s were studied using the mixtures mainly by the mineral and microstructural observation. By virtue of the characteristics of starting raw materials, the clinkering temperature was lower as much as 100$^{\circ}C$ than that of a mixture prepared from normal raw materials. Uncombined calcium oxide was vanished entirely below 1350$^{\circ}C$. and the formation of major cement minerals such as alite and belite could be nearly accomplished without too much liquid phase within 1400$^{\circ}C$.

• Journal of the Korean Society for Heat Treatment
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• v.19 no.2
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• pp.96-102
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• 2006

Development of Rotation-Cylinder Method(RCM) is given for Mg-Al-Zn-X(X=Sr) alloys, identifying some of the key factors that need to be controlled and indicating subsequent casting processes. Effects of Sr addition on the microstructure and mechanical properties of as-cast and T6 heat-treated Mg-Al-Zn-X alloys fabricated by the RCM were investigated. The microstructural and mechanical characterizations were performed by utilizing optical microscope, scanning electron microscope, transmission electron microscope, hardness test and ultimate tensile test. The solution and aging treatment time was varied to optimize the T6 heat treatment conditions, and experimental results were discussed. The grain size of Sr containing alloys was refined by increasing Sr content, but the tensile and yield strengths were increased by addition up to 1wt% Sr.

• Computers and Concrete
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• v.3 no.4
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• pp.249-260
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• 2006

Self-consolidating concrete (SCC) in the fresh state is known for its excellent deformability, high resistance to segregation, and use, without applying vibration, in congested reinforced concrete structures characterized by difficult casting conditions. Such a concrete can be obtained by incorporating either mineral or chemical admixtures. This paper presents the results of an investigation to asses the applicability of Abram's law in predicting the compressive strength of SCC to any given age. Abram's law is based on the assumption that the strength of concrete with a specific type of aggregate at given age cured at a prescribed temperature depends primarily on the water-to-cement ratio (W/C). It is doubtful that such W/C law is applicable to concrete mixes with mineral or chemical admixtures as is the case for SCC where water to binder ratio (W/B) is used instead of W/C as the basis for mix design. Strength data of various types of SCC mixtures is collected from different sources to check the performance of Abram's law. An attempt has been made to generalize Abram's law by using various optimization methodologies on collected strength data of various SCC mixtures. A set of generalized equations is developed for the prediction of SCC strength at various ages. The performance of generalized equations is found better than original Abram's equations.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.629-632
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• 2008

As concrete is a material which is subject to wide quality fluctuations by temperature, grip of seasonal feature and maintenance of ambient temperature and humidity to secure the quality required after casting concrete are able to keep away from harmful effects. In case of summer, a high temperature has caused rapid hydration reaction of cement in early age, which has caused to decrease strength by autogenous shrinkage. Therefore we need to consider a countermeasure for decrease in the hydration heat of hot-weather concrete, according to minimize water and cement content and use mineral admixtures In this experimental research, the compressive strength development for replacement ratio of mineral admixtures, curing temperature and methods of concrete was investigated to confirm the effects of mixture design and curing condition on compressive strength of concrete.

• Food Science and Biotechnology
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• v.14 no.1
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• pp.112-116
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• 2005

Composite films were prepared with soy protein isolate (SPI) and various clay minerals by casting from polymer and clay water suspension. Effects of clay minerals on film thickness, moisture content (MC), tensile strength (TS), elongation at break (E), water vapor permeability (WVP), and water solubility (WS) were tested. Properties including thickness, surface smoothness, and homogeneity of films prepared with organically modified montmorillonite (O-MMT), Wamok clay (W-clay), bentonite, talc powder, and zeolite were comparable to those of control SPI films. TS increased significantly (p<0.05) in films prepared with O-MMT and bentonite, while WVP decreased significantly (p<0.05) in bentonite-added films. WS of most nanocomposite films decreased significantly (p<0.05).

• Journal of the Korean Ceramic Society
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• v.56 no.4
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• pp.365-373
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• 2019

Pond ash is a mixture of mostly coarser fly ash and bottom ash. The recycling rate of pond ash is low because pond ash is mixed with seawater and deposited in ponds. The pond ash is also subjected to natural weathering over a period of time. In this study, we investigated whether pond ash can be used as a raw material of geopolymers, without any purification process or through a minimal purification process. In addition, we investigated whether synthetic basalt made by adding foaming agent to geopolymer or casting it into a mold can show the surface of the natural basalt as it is. The highest 7-day compressive strength in geopolymers from pond ash without purification process was 26 MPa. The highest 7-day compressive strength in geopolymers from pond ash with impurities removed through dry sieve analysis was found to improve to 80 MPa. On the other hand, synthetic basalt made with geopolymer was shown to be more advantageous aesthetically when produced by casting it in a silicone mold rather than by adding a foaming agent. Non-purified pond ash can be made into geopolymers having low strength. Pond ash purified by sieving can, without use of an aggregate, be made into geopolymer having high-strength. Also, it is possible to produce synthetic basalt with the same appearance as natural basalt and sufficient strength for commercialization. This process will contribute to the mass consumption and recycling of pond ash.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.1057-1060
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• 2008

For high performance concrete, due to its low water cement ratio (water binder ratio) and addition of mineral admixtures, pretty high autogenous shrinkage and thermal deformation occur at very early age of casting (especially before hardening). This may lead to early age cracking of HPC structures, and then may influence the durability of HPC. This paper has monitored the early age properties of HPC successfully by embedded FBG strain sensor. The results showed that the deformation increased rapidly within the first day after HPC casting. And its value is up to $85{\mu}{\varepsilon}$, which is the 30% of two-month deformation ($280{\mu}{\varepsilon}$). Considering the durability and permeability of HPC, the first-day deformation is pretty high and can not be neglected. Also the superior capability of FBG sensors such as continuity, stability and multiplexed technique etc, has been demonstrated.

• Resources Recycling
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• v.31 no.3
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• pp.61-72
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• 2022

We investigated the electrochemical behavior of Sn (93.0 %)-Ag (4.06 %)-Cu (0.89 %) during electrolysis of Pb-free solder waste to recover tin and silver. A thin strip of the solder waste produced by high-temperature melting and casting was used as a working electrode to perform electrochemical analysis. During anodic polarization, the current peak of an active region decreased with an increase in the concentration of sulfuric acid used as an electrolyte. This resulted in the electro-dissolution of the working electrode in the electrolyte (1.0 molL^-1 sulfuric acid) for a constant current study. The study revealed that the thickening of an anode slime layer at the working surface continuously increased the electrode potential of the working electrode. At 10 mAcm^-2, the dissolution reaction continued for 25 h. By contrast, at 50 mAcm^-2, a sharp increase in the electrode potential stopped the dissolution in 2.5 h. During dissolution, silver enrichment in the anode slime reached 94.3% in the 1 molL^-1 sulfuric acid electrolyte containing a 0.3 molL^-1 chlorine ion, which was 12.7% higher than that without chlorine addition. Moreover, the chlorine enhanced the stability of the dissolved tin ions in the electrolyte as well as the current efficiency of tin electro-deposition at the counter electrode.

• Korean Journal of Exercise Nutrition
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• v.23 no.3
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• pp.45-49
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• 2019

[Purpose] Recent studies suggest that ursolic acid (UA) is a potential candidate for a resistance exercise mimetic that can increase muscle mass and alleviate the deleterious effect of skeletal muscle atrophy on bone health. However, these studies evaluated the effects of UA on skeletal muscle and bone tissues, and they have not verified whether such effect could occur concurrently on muscle and bone, as is the case with resistance exercise. Thus, the aim of this study was to analyze the effect of UA injection on muscle mass and bone microstructure using an animal model of atrophy to demonstrate the potential of UA as a resistance exercise mimetic. [Methods] The immobilization (IM) method was used on the left hindlimb of Sprague Dawley (SD) rats for 10 days to induce muscle atrophy, whereas the right hindlimb was used as an internal control (IC). The animal models were divided into two groups, SED (sedentary, n=6) and UA (n=6) to demonstrate the effect of UA on atrophic skeletal muscles. The UA group received a daily intraperitoneal injection of UA (5 mg/kg/day) for 8 weeks. After 10 days of IM, the data collected for the IC were compared with that of IM to determine whether muscle atrophy might occur. [Results] Muscle atrophy was induced and bone mineral density (BMD) decreased significantly. The 8-week UA treatment significantly increased the gastrocnemius muscle mass compared to the SED group. In regard to the effect of UA on bones, negative results such as a decrease in BMD, trabecular bone volume fraction, and trabecular number, and an increase in trabecular separation, were observed in the SED group, but no such difference was observed in the UA group. No significant difference was observed in atrophic hindlimbs between SED and UA groups. [Conclusion] These results alone are insufficient to suggest that UA is a potential resistance exercise mimetic for atrophic skeletal muscle and weakened bone. However, this study will help determine the potential of UA as a resistance exercise mimetic.

• Journal of Pharmaceutical Investigation
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• v.29 no.4
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• pp.343-348
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• 1999

The purpose of this study is to prepare the controlled release adhesive patch containing naproxen. Pressuresensitive adhesive (PSA)-type patch was fabricated by casting of polyisobutylene (PIE.) and mineral oil in toluene. Membrane-controlled release (MCR)-type patch was prepared by the attachment of the controlled release membrane on the PSAtype patch. The membrane was mainly composed of Eudragit, polyethylene glycol(PEG) and glycerin. The drug release profile and skin permeation test with various patches were evaluated in vitro. The release of naproxen from PIE-based PSAtype patch with various loading doses fitted Higuchi's diffusion equation. However, the permeation of naproxen through hairless mouse skin from PSA-type patch followed zero-order kinetics. In MCR-type patch, thickness of controlled release membrane affected on the drug release rate highly. In the composition of membrane, the release rate was decreased as the ratio of Eudragit increased. The drug release from the MCR-type patch followed zero order kinetics. The permeation of naproxen through hairless mouse skin from MCR-type patch showed lag time for the intial release period and didn't fit the zero-order kinetics