• Journal of the Korea Concrete Institute
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• v.21 no.4
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• pp.441-447
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• 2009

This paper presents a detailed experimental study on the sulfate resistance of specimens made with portland cement exposed to sulfate attack. The mortar specimens were immersed in a 5% sodium sulfate solution for 360 days and regularly monitored for visual damage, compressive strength loss and expansion. In addition, at the end of 360 days, the products of sulfate attack and the mechanism of attack were investigated through X-ray diffraction, TG&DSC and scanning electron microscopy. The test results indicated that the sulfate deterioration data was ordinary portland cement > sulfate resistance portland cement > low heat portland cement. The microstructural studies indicated that the main reaction product of deterioration of the mortar specimens was the formation of ettringite, gypsum and thaumasite due to sulfate attack. For portland cement matrices, a low heat cement matrix containing the lowest C3A and silicate ratio (C/S) was beneficient against the sulfate attack.

• The Journal of Korean Medical History
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• v.31 no.1
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• pp.71-87
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• 2018

This study investigated Hua Tuo's Shang-han theory, which precedes the period of Zhang Zhong Jing's Shang-han theory, and considers the relationship between the two approaches. Researchers compared terminology and language of Hua Tuo's Shang-han theory as published in Theory in Qian Jin Yao Fang and Wai Tai Mi Yao, with Zhang Zhong Jing's Shang-han theory. In Hua Tuo's theory, Shang-han involves pathogenic invasion of the body surface, where the pathogen transforms to 6 different stages, Pi (皮), Fu (膚), Ji (肌), Xiong (胸), Fu (腹), Wei (胃). Among these, the stage sof Pi (皮), Fu (膚), Ji (肌) can be considered as exterior syndrome (表證). Those that invade the lower chest can be considered as lower chest disease, and those that violate the abdomen or stomach can be considered as Interior heat excess syndrome (裏熱實證). Stomach heat excess syndrome (胃中實熱證) is the most severe and is similar to septicaemia or bubonic plague. Hua Tuo's treatment used three methods which are 汗 (perspiration), 吐 (emesis), 下 (purgation). In the case of Phlegm syndrome (痰?證), HuoTuo's theory was similar to Zhang Zhong Jing's Shang-han exterior syndrome (傷寒表證) and therefore used Zhuling-powder (猪?散). In the case of deficiency hot flush Syndrome (虛煩證) in Shang-han disease, HuoTuo uses ZhuYe-decoction (竹葉湯), of which the drug contents is the same as Zhang Zhong Jing's ZhuYeShiGao-decoction (竹葉石膏湯), which was used for the same condition.

• Journal of Physiology & Pathology in Korean Medicine
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• v.17 no.3
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• pp.791-797
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• 2003

This study investigated the effect of Yanggyuksanhwa-tang on cerebral ischemia of the rats. Considering age-related impact on cerebral ischemia, aged rats (18 months old) were used for this study. Ischemic damage was induced by the transient occlusion of bilateral common carotid arteries (BCAO) under the hypotension. Yanggyuksanhwa-tang was administered twice orally. Then changes of pyramidal neurons and heat shock protein 72 (HSP72) expressions in ischemic damaged hippocampus were of observed. The BCAO in aged rats led significant decrease of pyramidal neurons in CA1 hippocampus. While the treatment of Yanggyuksanhwa-tang significantly attenuated the reduction of pyramidal neurons in CA1 hippocampus following BCAO ischemia. The BCAO in aged rats led significant increase of HSP72 expression in CA1 and mild in CA3 hippocampus. While the treatment of Yanggyuksanhwa-tang significantly attenuated the increase of HSP72 expression in CA1 hippocampus following BCAO ischemia. The extent of HSP72 expression in CA2 and DG of hippocampus was not different between the sham operated group, the BCAO ischemia control group, and the group of Yanggyuksanhwa-tang administration after BCAO ischemia. The treatment of Yanggyuksanhwa-tang significantly attenuated the increase of normalized optical density depending on HSP72 expression in CA1 hippocampus following BCAO ischemia.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.7
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• pp.1026-1033
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• 2009

Fine ceramics have high strength, excellent wear resistance, chemical stability and high strength at high temperature and are receiving attention in various fields such as construction, engineering, aerospace and marine science. Finish machining process is required to obtain precise ceramics components because sintering process necessary for obtaining high strength and high quality ceramics reduces the dimensions of components and precision of shape. But high strength and brittleness of ceramics materials cause difficulty in processing. So a process for obtaining wanted dimensions is studying using high temperature which makes ceramics softened and thermal affected recently. Laser beam is a very useful optical device for these kinds of processes. Laser process such as laser cutting, laser machining, laser heat treatment and laser-assisted machining(LAM) is researching to manufacture practical ceramics components using intense laser source which can cause local softening and damage of workpiece. In this paper, microstructural and mechanical properties of silicon nitride heated are studied as a basic study for researching of ceramics process by laser beam. The surface variation of HIP and SSN-silicon nitride was analyzed with SEM and EDS. A processing at $1,300^{\circ}C$ or above causes N element to combine into $N_2$ gas and the gas busts from surface. These phenomena make bloat, craters and heat defects on the surface of silicon nitride. Also, oxygen content is largely increased to oxidize the surface and it causes changing of phases and reducing of hardness of surface.

• Journal of Ginseng Research
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• v.42 no.1
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• pp.21-26
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• 2018

Background: Furosine (${\varepsilon}$-N-2-furoylmethyl-L-lysine, FML) is an amino acid derivative, which is considered to be an important indicator of the extent of damage (deteriorating the quality of amino acid and proteins due to a blockage of lysine and a decrease in the digestibility of proteins) during the early stages of the Maillard reaction. In addition, FML has been proven to be harmful because it is closely related to a variety of diseases such as diabetes. The qualitative analysis of FML in fresh and processed ginsengs was confirmed using HPLC-MS. Methods: An ion-pair reversed-phase LC method was used for the quantitative analysis of FML in various ginseng samples. Results: The contents of FML in the ginseng samples were 3.35-42.28 g/kg protein. The lowest value was observed in the freshly collected ginseng samples, and the highest value was found in the black ginseng concentrate. Heat treatment and honey addition significantly increased the FML content from 3.35 g/kg protein to 42.28 g/kg protein. Conclusion: These results indicate that FML is a promising indicator to estimate the heat treatment degree and honey addition level during the manufacture of ginseng products. The FML content is also an important parameter to identity the quality of ginseng products. In addition, the generation and regulation of potentially harmful Maillard reaction products-FML in ginseng processing was also investigated, providing a solid theoretical foundation and valuable reference for safe ginseng processing.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.1
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• pp.60-70
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• 2007

Statement of problem: The cement-type abutment would be needed for the reduction of its body in order to correct the axis and to assure occlusal clearance. In the case of intraoral preparation, there is a potential risk that generated heat could be transmitted into the bone-implant interface, where it can cause deterioration of tissues around the implant and failed osseointegration. Purpose: The purpose of this study was to assess the difference of the heat transmitting effect on external and internal connection implant types under various conditions. Material and method: For evaluating the effects of alternating temperature, the thermocoupling wires were attached on 3 areas of the implant fixture surface corresponding to the cervical, middle, and apex. The abutments were removed 1mm in depth horizontally with diamond burs and were polished for 30 seconds at low speed with silicone points using pressure as applied in routine clinical practice. Obtained data were analyzed using Mann-Whitney rank-sum test and Wilcoxon / Kruskal-Wallis Tests. Result: Increased temperature on bone-implant interface was evident without air-water spray coolant both at high speed reduction and low speed polishing (p<.05). But, the difference between connection types was not shown. Conclusion: The reduction procedure of abutment without using proper coolant leads to serious damage of oral tissues around the implant irrespective of external and internal connection type.

• Aerospace Engineering and Technology
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• v.6 no.2
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• pp.111-118
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• 2007

KSLV-I which is being developed in KARI is composed with two stages, and adaptor ring is used for coupling stage. Cables for interconnecting between stage is exposed on the outside. Also 8 pyro bolts which are installed in adaptor ring are used for separation of stage. In general, cowl is used for protecting exposed parts or structure which are anxious about damage from outer environment. In KSLV-I, two kind of cowls are designed. The one is umbilical cowl, and the other is pyro bolt cowl. Because cowl is exposed on the outside, heat and pressure load developed from air have effect on cowls. Therefore verification of structural strength through static analysis is required. In this study, static analysis in load condition except heat load is accomplished. In result of analysis, structural strength of pyro bolt cowl is verified. But breakage of umbilical cowl is confirmed in pressure load condition. So design of umbilical cowl is modified for satisfying required structural strength. And structural strength of umbilical cowl through analysis is verified.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.11
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• pp.1979-1985
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• 2003

Fretting is a kind of surface degradation mechanism observed in mechanical components and structures. The fretting damage decreases in 50-70% of the plain fatigue strength. This may be observed in the fossil power plant and the nuclear power plant used in special environments and various loading conditions. The thermal degradation of material is observed when the heat resisting steel is exposed for long period time at the high temperature. In the present study, the degraded 1Cr-0.5Mo steel used for long period time at high temperature (about 515$^{\circ}C$) and artificially reheat-treated materials are prepared. These materials are used for evaluating an effect of thermal aging on the fretting fatigue behavior. Through the experiment, it is found that the fretting fatigue endurance limit of the reheat-treated 1Cr-0.5Mo steel decreased about 46% from the non-fretting fatigue endurance limit, while the fretting fatigue endurance limit of the degraded 1Cr-0.5Mo steel decreased about 53% from the non-fretting fatigue endurance limit. The maximum value of fatigue endurance limit difference is observed as 57%(244 MPa) between the fretting fatigue of degraded material and non-fretting fatigue of reheat-treated material. These results can be a basic data to a structural integrity evaluation of heat resisting steel considered to thermal degradation effect.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.8
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• pp.831-836
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• 2014

In this study, high temperature integrity evaluation on a pressure vessel of the expansion tank operating at elevated temperature of $510^{\circ}C$ in the sodium test facility of the SEFLA(Sodium Thermal-hydraulic Experiment Loop for Finned-tube Sodium-to-Air heat exchanger) to be constructed at KAERI has been performed. Evaluations of creep-fatigue damage based on a full 3D finite element analyses were conducted for the expansion tank according to the recent elevated temperature design codes of ASME Section III Subsection NH and French RCC-MRx. It was shown that the expansion tank maintains its integrity under the intended creep-fatigue loads. Quantitative code comparisons were conducted for the pressure vessel of austenitic stainless steel 316L.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.12
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• pp.15-21
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• 2019

The worm reducer is capable of quadrature power transmission when the shafts are disposed at right angles to each other. Since a large reduction ratio can be obtained of up to approximately 1/100 and a sliding movement is performed during operation compared with other gears, the noise and vibration are small, and there is the advantage that reverse rotation can be prevented. On the other hand, severe wear and damage are displayed on the gear and worm tooth surface, and many defects, such as intense heat generation of the reducer, occur. In the reducer case, the four-piece casing method was selected to solve the problems of heat generation, transmission efficiency, and assemblability. In this paper, we analyzed the problems of the worm and worm wheel (the core parts of a 5-Ton worm reducer) and casing through these methods and researched how to solve them.