• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.671-674
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• 2002

Induction heating is a process with magnetic and thermal situation. Induction heating of flat metal products has an increasing importance in many applications, because it generates the heat within workpiece itself and provides high power densities and productivity. When the high frequency electric current flows in a coil, the process parameters which are air gap, power density, and heating time have a important roles on induction heating of steel plate. This study investigates an influence of the process parameters by means of experiments using Taguchi method.

• 한국재료학회지
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• 제14권12호
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• pp.851-856
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• 2004

The aim of this study is to investigate the optimum drawing parameter for BAS121 welded tubes. The BAS121 aluminium alloy tubes with 25 mm in external diameter and 1.3 mm in thickness for heat-exchangers were manufactured by high frequency induction welding with the V shaped convergence angle $6.5^{\circ}$ and power input 55 kW. With increasing the reduction of area ($13,\;21\%$) by drawing, tensile strength was increased and elongation was decreased. With increasing the reduction of area by drawing, hardness in weld metal increased rapidly, while that of base metal increased slowly. In the specimen with the outer diameter smaller than 22 mm, hardness of weld metal was higher than that of base metal. The optimum drawing parameter of area reduction in BAS121 alloys was estimated about $13\%$ because of the work hardening of welds.

• 열처리공학회지
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• 제6권1호
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• pp.1-8
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• 1993

In this paper, the surface roughness influenced by Sm45C hardness in high frequency induction hardening and mechanical characteristics for the changed Hv 598 part and the unchanged hardness Hv 223 part by use of cermet and ceramic cutting tools was experimentally examined. Finally, we could be had some important results by processing surface roughness on cutting conditions such as cutting speed, feed rate, depth of cut and changes of tool nose radius. The results are summarized as follows. 1. In case of the same cutting condition, the hardness of workpiece was high and acquired the best processing surface roughness when the radius of the tool nose had 0.8 mm and feed rate was 0.04 mm/rev. 2. In case of the hardness of workpiece, though the cutting speed didn't have an effect on processing surface roughness, the less feed rate and the more processing surface roughness improved. On the other hand, the low inside the hardness of workpiece, the more cutting speed and the more feed rate increase, the processing surface of roughness improved. 3. Regardless of the hardness of workpiece, the change of the cutting depth didn't have great effect on the surface roughness. 4. On cutting the high surface hardness part with cutting tools of cermet and ceramic, it can be acquired the higher processing surface roughness because it hadn't been taken effect on cutting speed, In case of the cutting process of the low inside hardness part the two cutting tools have acquired the similar processing surface roughness.

• 열처리공학회지
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• 제5권1호
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• pp.23-31
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• 1992

It is investigated that Fe-C-N compound layer, defusion layer, and induction hardened layer produced by nitrocarburizing blend heat treatment in austenitic temperature with high frequency induction heating of mild steel specimen sprayed sursulf salt-bath. As the temperature of blend-heat treatment got increased, the thickness and hardness of compound layer and diffusion layer were increased. Compound layer(max. $35{\mu}m$), diffusion layer (max. 2.5mm) and induction hardened layer were gained in the shortest time 10 sec and in the case of $1000^{\circ}C$ total hardness depth of those was about 3.5mm. When the blend-heat treated specimen was reheated, maximum hardness of compound layer was dropped more than that of the reheated compound layer after sursulf treated, whereas hardness of diffusion layer was increased.

• Journal of Plant Biotechnology
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• 제46권1호
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• pp.17-21
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• 2019

Ginger is an important monocotyledonous plant belonging to the family Zingiberaceae. The objective of this study was to investigate the regeneration potential of ginger using leaf base explants. Auxins such as 2, 4-D and NAA in combination with BA were used for initiation of callus. Different combinations of both ammonium ($NH^{4+}$) and nitrate ($NO^{3-}$) were also studied for efficient callus production. High frequency of white friable calli was observed on modified Murashige and Skoog (MS) medium supplemented with 2.0 mg/L 2, 4-D, 0.5 mg/L NAA and 0.5 mg/L BA. The highest shoot induction (92.33%), shootlets number ($7.33{\pm}0.33$) and length ($88.33{\pm}4.40$) mm were achieved on MS media containing 0.5 mg/L BA. Regenerated shoots were transferred to in vitro rooting media containing 1.0 mg/L IBA. Afterwards, plantlets with well-developed root and shoot system were subjected to a twostep hardening process. 71% of plantlets survived after secondary hardening without any abnormal morphology.

• 융합신호처리학회논문지
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• 제19권2호
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• pp.61-67
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• 2018

용접예열은 본 용접 전에 금속이 융착되는 모재면을 일정한 온도로 가열하는 것을 의미한다. 냉각속도 조절에 따른 재료 경화 정도 감소, 불순물 편석억제, 열적 변형방지, 그리고 수분제거 등 인접 영향부의 균열을 방지할 수 있다. 이러한 이유에서 고품질의 용접을 위하여 반드시 필요한 작업이다. 유도가열은 전자기유도 현상을 응용하여 전기에너지를 열에너지로 변환시키는 효율적인 가열방식이다. 기체 및 액체를 이용한 연소발열과 비교하여 신속한 가열뿐만 아니라 청결하고, 안정적이며, 경제적이다. 단순한 구조로 주파수와 코일의 형태를 변형하여 가열체의 형상, 깊이, 재질에 관계없이 가열할 수 있다. 본 논문에서는 유도가열 기법을 이용하여 저주파 용접예열 시스템을 구현하였으며, 3종의 자동차 변속기 부품을 대상으로 권선코일 내에서 각 변속기 높이에 따라 권선코일 저항, 인덕턴스 및 자동차 변속기 부품의 온도변화를 관찰한 결과 전류의 변화는 저주파 가열에 있어 매우 중요한 요인으로 작용함을 확인하였다.

• Journal of Plant Biotechnology
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• 제34권3호
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• pp.189-195
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• 2007

Helicteres isora is medicinally important plant effective against asthma, diabetes, hypolipidemia, HIV, besides a good source of diosgenin. Seed dormancy and low rate of natural fruit production make this plant a perfect candidate for developing an in vitro method useful for its clonal propagation and further biotechnological developments. This is the first report on in vitro production of this plant. Nodal explants obtained from aseptically germinated seedlings were cultured on MS medium (Murashige and Skoog 1962) fortified with indole-3-acetic acid (IAA) ($0.57-22.83\;{\mu}M$), indole-3-butyric acid (IBA) ($0.41-16.58\;{\mu}M$), 6-benzylaminopurine (BA) ($0.44-17.75\;{\mu}M$) and kinetin (Kin) ($0.46-13.94\;{\mu}M$) either singly or in combinations of IAA + BA, IAA + Kin and BA + Kin. Combinations of cytokinins (BA and Kin) were most suitable for multiple shoot induction and $13.94\;{\mu}M\;Kin\;+\;13.31\;{\mu}M\;BA$ was optimum (79% frequency) associated with high number of microshoots (7.1 shoots per explant) after 20 days of culture. Maximum shoot elongation and proliferation (10 shoots per explant with 4.8 cm average height) was achieved on MS media containing $2.32\;{\mu}M\;Kin\;+\;2.22\;{\mu}M\;BA\;+\;2.85\;{\mu}M\;IAA$. High rooting frequency (70%) was achieved on MS medium (1/2 basal strength) fortified with $4.14\;{\mu}M$ IBA, while activated charcoal showed inhibitory effects on rooting. Hardening was done with 76% survival rate and these plants were growing without any visual defects and morphologically mimicking the naturally growing plants.

• 한국재료학회지
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• 제10권6호
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• pp.409-414
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• 2000

3%C-10%Cr-5%Mo-5%W, 3%C-10%V-5%Mo-5%W 및 3%C-17%Cr-3%V의 3종류 고합금백주철에 있어서 열처리후의 기지조직의 변태거동을 연구하였다. 15kg 용량의 고주파 유도용해로에 선철, 고철, Fe-Cr, Fe-V, Fe-Mo 및 Fe-W 등을 장입시켜 용해시킨 후 슬래그를 제거시키고 $1550^{\circ}C$에서 Y-block의 펩 주형에 주입시켰다. 적당한 크기로 절단한 시편을 진공분위기하에$950^{\circ}C$에서 5시간동안 우선 균질화처리를 실시하였다. 그 후 다시 이 시편을 $1050^{\circ}C$에서 2시간동안 오스테나이징시킨 후 강제공냉을 행하였다. 강제공냉된 시편을 $300^{\circ}C$에서 3시간 유지시킨 후 템퍼링을 실시하였다. 주방상태에서의 기지조직은 3합금 공히 퍼얼라이트이었으며 강제공냉후에는 마르텐사이트 및 오스테나이트로 변태하였다. 또한 기지조직내에 무수히 많은 이차탄화물 입자들의 석출되었다. 템프링 후 일부 오스테나이트 및 마르텐사이트는 템퍼드마르텐사이트로 변태하였다. 변태하였다.

• 한국주조공학회지
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• 제20권2호
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• pp.104-109
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• 2000

Three different white cast irons alloyed with Cr, V, Mo and W were prepared in order to study their abrasion wear behavior in as-cast and heat-treated conditions. The specimens were produced using a 15㎏-capacity high frequency induction furnace. Melts were super-heated to $1600^{\circ}C$, and poured at $1550^{\circ}C$ into Y-block pepset molds. Three combinations of the alloying elements were selected so as to obtain the different types of carbides : 3%C-10%Cr-5%Mo-5%W(alloy No. 1: $M_7C_3$ and $M_6C$), 3%C -10%V-5%Mo-5%W(alloy No. 2: MC and $M_2C$) and 3%C-17%Cr-3%V(alloy No. 3: $M_7C_3$ only). A scratching type abrasion test was carried out in the states of as-cast(AS), homogenizing(AH), air-hardening(AHF) and tempering(AHFT). First of all, the as-cast specimens were homogenized at $950^{\circ}C$ for 5h under the vacuum atmosphere. Then, they were austenitized at $1050^{\circ}C$ for 2h and followed by air-hardening in air. The air-hardened specimens were tempered at $300^{\circ}C$ for 3h. 1 ㎏ load was applied in order to contact the specimen with abrading wheel which was wound by 120 mesh SiC paper. The wear loss of the test piece(dimension: $50{\times}50{\times}5$ mm) was measured after one cycle of wear test and this procedure was repeated up to 8 cycles. In all the specimens, the abrasion wear loss was found to decrease in the order of AH, AS, AHFT and AHF states. Abrasion wear loss was lowest in the alloy No.2 and highest in the alloy No.1 except for the as-cast and homogenized condition in which the alloy No.3 showed the highest abrasion wear loss. The lowest abrasion wear loss of the alloy No.2 could be attributed to the fact that it contained primary and eutectic MC carbides, and eutectic $M_2C$ carbide with extremely high hardness. The matrix of each specimen was fully pearlitic in the as-cast state but it was transformed to martensite, tempered martensite and austenite depending upon the type of heat-treatment. From these results, it becomes clear that MC carbide is a significant phase to improve the abrasion wear resistance.

• 한국자원식물학회지
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• 제24권2호
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• pp.168-173
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• 2011

본 연구는 수수의 성숙 종자로부터 캘러스유기 및 재분화 효율 조사하기위하여 수행되었다. 배발생 캘러스 형성을 살펴보기 위해 생장조절제 효과를 조사하였다. 수수 성숙종자로부터 캘러스 유기에 적합한 생장조절제 종류와 농도는 2 mg/L 2,4-D인 것으로 나타났다. 배발생 캘러스의 고효율 빈도는 B5 배지에 2 mg/L 2,4-D을 첨가하였을 때 가장 양호한 것으로 나타났다. 배발생 캘러스로부터 식물체 재분화는 BAP와 IBA를 넣은 MS 배지가 가장 적절한 것으로 나타났다. BAP 농도가 높을수록 신초재분화가 활발하였다. 따라서, 본 연구 결과로부터 수수 기내배양시 신초와 발근 형성에 효과적인 생장조절제 조합은 0.5 $mg\;l^{-1}$ BAP와 0.25 $mg\;l^{-1}$ IBA인 것으로 나타났다.