• 열처리공학회지
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• 제17권6호
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• pp.336-341
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• 2004

The effect of shot peening conditions on the fatigue properties of heat-treated spring steel has been investigated by using residual stress measurement and metallography. The mechanical properties of material did not change so much by shot peening. However, the fatigue strength and fatigue life increased about 20% to 40% by 1-step and 2-step shot peening process. The fatigue strength and life were closely related to the value and position of maximum compressive residual stress by shot peening process. In the case of warm shot peening, compressive residual stress of specimens shot peening processed at $200^{\circ}C$ was higher than those of specimens shot peening processed at room temperature, $100^{\circ}C$ and $300^{\circ}C$.

• 한국재료학회지
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• 제24권10호
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• pp.538-542
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• 2014

Microstructural and mechanical characteristics of Al-6Si-2Cu alloy for lightweight automotive parts were investigated. The test specimens were prepared by gravity casting process. Solution heat treatments were applied to as-cast alloys to improve mechanical properties. The microstructure of the gravity casting specimen presents a typical dendrite structure, having a secondary dendrite arm spacing (SDAS) of $37{\mu}m$. In addition to the Al matrix, a large amount of coarsened eutectic Si, $Al_2Cu$ intermetallic phase, and Fe-rich phases were identified. After solution heat treatment, single-step solution heat treatments were found to considerably improve the spheroidization of the eutectic Si phase. Two-step solution treatments gave rise to a much improved spheroidization. The mechanical properties of the two-step solution heat treated alloy have been shown to lead to higher values of properties such as tensile strength and microhardness. Consequentially, the microstructural and mechanical characteristics of Al alloy have been successfully characterized and are available for use with other basic data for the development of lightweight automotive parts.

• 대한한의학원전학회지
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• 제31권2호
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• pp.155-172
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• 2018

Objectives : The first object is to reveal the mechanism of diarrhea based on exterior heat syndrome for Taeumin as explained in Donguisusebowon's Taeeumingansuyeoliyeolbyeonglon. The second objective is to review the treatment for Taeumin as explained in Leejema's Galgeunnabogjatang because the drug composition of Galgeunnabogjatang, the drug that treats this syndrome, is not written. Methods : As the first step, the paper will review the disease pathology for Taeumin written, and check the existence of disease path that can be viewed as exterior heat syndrome. As the second step, the paper will review the probability of exterior heat syndrome deriving from Taeumin disease path and morph into the exterior heat syndrome. Results : Using the first step to discover the direct correlation between exterior heat syndrome and the theory of disease for Taeumin led to a failure, but through the second step, the paper was able to confirm the probability that exterior heat syndrome could derive from Wiwansuhanpyohanbyeong's Wiwanhanjeung. Based on this, the paper was able to determine the Galgeunnabogjatang suitable for the treatment of exterior heat syndrome. Conclusions : Exterior heat syndrome is created when healthy qi is stimulated to quickly build up the pathogen of Taeumin exterior heat syndrome, but only exterior heat is generated and the cold remains. Its main symptoms are fever, excessive sweating, and difficult painful red-urination. Exterior heat syndrome diarrhea refers to the diarrhea which is generated from the Taeumin's disease pathology. The paper determined that Galgeunnabogjatang, which is listed in Donguisusebowon the seventh edition Boyubang.

• 소성∙가공
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• 제23권2호
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• pp.82-87
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• 2014

The plastic strain ratio is one of the factors that affect the deep drawability of Al alloy sheet. The deep drawability of Al alloy sheet is limited because of its low plastic strain ratio. Therefore an increase in the plastic strain ratio to improve the deep drawability of Al alloy sheet is needed. The current study investigated the increase of the plastic strain ratio and the change in texture of AA5083 Al alloy sheet after a 2 step asymmetric rolling with heat treatments. The average plastic strain ratio of initial AA5083 Al alloy sheets was 0.83. After the first asymmetric rolling step of 88% deformation and subsequent heat treatment at $320^{\circ}C$ for 10 minutes the value was still 0.83. After the second asymmetric rolling of 14% reduction and subsequent heat treatment at $330^{\circ}C$ for 10 minutes the plastic strain ratio rose to 1.01. The average plastic strain ratio after the 2 step asymmetric rolling and heat treatment is 1.2 times higher than that of initial AA5083 Al alloy sheet. This result is related to the development of ND/<111> texture component after the second asymmetric rolling and heat treatment.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 초전도 자성체 연구회
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• pp.73-76
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• 2003

Phase transformation of Bi-2223 tape during the final heat treatment has been investigated through the various duration time of heat treatment in a specially designed 3-step heat treatment. It was found that the phase assemblage in the sintering was determined by the sintering time and temperature. In this study, sintering time was changed to optimize the Bi-2223 phase assemblage, and acquire high critical current density. High critical current samples with Ic = 85 A and Je = 8.9 kA/$cm^2$ have been measured at 77K and self-field for 55-filament tapes sintered by optimum condition.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2002년도 High Temperature Superconductivity Vol.XII
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• pp.76-76
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• 2002

• 한국수소및신에너지학회논문집
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• 제17권1호
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• pp.109-116
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• 2006

The heat treatment characteristics of natural talc sample was investigated in diverse analytical view point. The mass decrease comes to heat treatment was resulted by the continuous and the discontinuous process and the obtained result show very similar two step profiles with 8.9 % mass decrease. The dehydroxylation of -OH groups contained talc crystal was analyzed by spectroscopic method and the crystallographic variations was also observed after heat treatment. According to XPS result, the magnesium hydroxide($Mg(OH)_2$) of untreated talc powder changed to magnesium oxides(MgO) after heat treatment.

• 한국주조공학회지
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• 제10권4호
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• pp.299-308
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• 1990

Ductile cast iron has a good ductility and ductility and toughness than those of gray cast iron, because the shape of graphite is spheroidal. It has been reported that the strengthening and toughening of the ductile cast iron was resulted from the good modification of various matrix structures obtained by the heat treatment or addition of alloying elements. This study aims to investigate the effect of various special heat treatment(Cyclic Heat Treatment, Intermediate Heat Treatment, Step Quenching), austempering and alloying element(Ni) on the strength and toughness of ductile cast iron. The results obtained from this study are summarized as follows. 1) With addition of Ni, the amount of pearlite or bainite were increased and the morphologies of pearlite or bainite became finer by special heat treatments. 2) As the Ni added and not added ductile cast iron were treated by austenitizing at $900^{\circ}C$ and $840^{\circ}C$, in the latter the austenite was mostly formed in the vicinity of eutectic cell boundary, but in the former on the whole matrix. 3) In cyclic heat treatment, the volume fraction of pearlite was increased and the shape of pearlite was fined with increase of the number of cycle. 4) The shape of pearlite was mostly bar type in the intermediate heat treatment, but spheroidal type in step quenching. 5) The mechanical properties of ductile cast iron containing 1.5%Ni austempered at $400^{\circ}C$ for 25min. after austenitizing at $900^{\circ}C$ for 15min. were a good value of hardness 105(HRB), impact energy 12.5(kg.m), tensile strength 112($kg/mm^2$) and elongation 6.8(%).

• 열처리공학회지
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• 제10권2호
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• pp.150-156
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• 1997

The effect of variation of pack activators, compositions, temperature and time on the thickness and structure of aluminide coatings formed on the TiAl alloy was studied in one-step packs and two-step packs containing aluminum for the purpose of improvement of oxidation resistance. The thickness of coating layer was increased with increasing $NH_4Cl$ content up to 3wt% and then it was saturated. Oxidation resistance of coating layers carried out at one step pack was superior to that of ones through of two step pack. The improvement of high temperature oxidation resistance was due to the formation of a protective $Al_2O_3$ surface layers and coating the alloys with $TiAl_3$ phase.

• 공업화학
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• 제23권1호
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• pp.77-85
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• 2012

팽창진주암(expanded perlite)과 섬유상 해포석(sepiolite)과의 복합화를 통해 유연성을 지닌 세라믹 발포체의 제조가능성을 조사하였다. 무기광물 섬유 해포석의 해섬처리는 팽창진주암과 해포석으로 이루어진 세라믹발포체의 제조를 위해 가장 중요한 전 처리공정이다. 해섬된 해포석과 팽창진주암은 혼합 교반되어 슬러리 상태로 이루어지며, 이 슬러리상의 복합물은 $300^{\circ}C$ 이하의 저온 열처리과정을 통해 형상화 및 발포화되어 괴상의 발포체로 제조된다. 슬러리상 복합물의 열처리공정은 슬러리 복합물 중에 잔존하는 수분의 증발단계, 일정발포온도에서 발포화제가 분해되어 진행되는 발포화단계 및 발포 후 잔류되는 유기물질의 분해제거단계를 포함하는 것으로 설계되어야 한다. 열처리 공정조건과 발포제는 상관성이 있으며 팽창진주암과 해포석섬유로 이루어진 슬러리상 혼합물의 발포에 적절한 발포제는 유기계 발포제가 적절하며 DSS (dioctyl sodium sulfosuccinte)가 효과적이었다.