• Title/Summary/Keyword: 유도 경화

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Development of High Strength Center-pillar by High Frequency Induction Heating (고주파유도가열에 의한 고강도 센터필라 개발)

  • Son, Jin-Hyug;Yum, Young-Jin;Kim, Won-Hyuck;Hwang, Jung-Bok;Kim, Sun-Ung;Yoo, Seung-Jo;Lee, Hyun-Woo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.32 no.6
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    • pp.533-539
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    • 2008
  • An high frequency induction hardening technology of vehicle body press-formed of thin sheet steel has been developed to increase the strength of vehicle body parts locally by high frequency induction heating, thereby eliminating the need for reinforcements. And this technique for increasing the tensile strength of sheet steel was practically applied to the front floor cross member and center pillar reinforcement of a passenger car. The side impact behavior has been investigated when induction hardening technology is applied to the conventional low-carbon steel and weight reduction of an automotive body is expected. In this paper, basic experiments were performed for the hat-shaped specimen under high frequency induction heating process. Martensitic transformation was found in the heating zone through microscopic observation which showed higher hardness. In addition, the hardness and strength of the center-pillar specimen made of boron steel increased remarkably by high frequency induction heating.

Micropropagation Using Shoot Tip Culture of Pyrus ussuriensis Maximowicz (정아배양에 의한 산돌배나무의 기내번식)

  • Moon, Heung-Kyu;Lee, Sung-Jae
    • Journal of Korean Society of Forest Science
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    • v.97 no.4
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    • pp.452-457
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    • 2008
  • In order to develop an efficient micropropagation technique effect of plant growth regulators (PGRs) affecting on shoot proliferation from shoot apex in Pyrus ussuriensis was tested. Generally, there was no conspicuous effect on shoot induction by the treatment of PGRs and one or two shoots/explant were induced when cultured on MS medium supplemented with BA and/or BA plus NAA. Both apical shoot necrosis and hyperhydric shoots were observed frequently in multiplied shoots, and callus was formed at the basal part of shoots. About 20% spontaneous rooting was achieved in growing shoots, however the proliferated shoots exhibited poor rooting rate in gelrite supported media. When we tried to ex vitro rooting of the shoot cutting, the shoot cuttings rooted up to 50% with 100 mg/L IBA application. The rooted plantlets grew normally after acclimatization in the greenhouse.

A Study on the Influence of Induction Coil Movement Speed and Frequency on Induction Hardening of SCM440 Steel (SCM440 강의 유도 경화에 미치는 유도코일 이동속도 및 주파수의 영향에 관한 연구)

  • Ki-Woo Nam;Ki-Hang Shin;Byoung-Chul Choi;Gum-Hwa Lee;Jong-Kyu Park
    • Journal of the Korean Society of Industry Convergence
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    • v.26 no.5
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    • pp.813-823
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    • 2023
  • In this study, microstructure, hardening layer hardness, and case depth were evaluated after induction hardening(IH) of base metal specimen(BM) treated with annealing and quenching-tempering specimen(QT) treated with quenching and tempering. The microstructure after IH was significantly influenced by the microstructure before IH and the induction coil heating movement speed, but the effect of the induction frequency was very small. The hardness of the hardened layer at an induction coil heating movement speed of 15 mm/s or less was more influenced by the microstructure before IH than the induction coil travel speed and induction frequency. The induction coil travel speed has the significantly effect on the case depth, the induction frequency has effect and the microstructure before IH has a small effect.

Antioxidative Role of Geraniin in Lipid Peroxidation of Human LDL (사람 LDL의 지질과산화에 의한 geraniin의 항산화 효과)

  • Ho, Ryu-Beung
    • Journal of Life Science
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    • v.14 no.1
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    • pp.180-187
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    • 2004
  • Crowing evidence indicates that oxidized low density lipoprotein (LDL) nay promote atherogenesis. Therefore, inhibition of LDL oxidation may impede this process. The effect of geraniin on the susceptibility of human low density lipoprotein (LDL) to macrophages-induced oxidation was investigated by monitoring a thiobarbiruric acid reactive substrance (TBARS). The antioxidative activity of geraniin was higher than that of αα-tocopherol on low density lipoprotein (LDL) oxidation by thiobarbituric acid reactive substance (TBARS). Geraniin inhibited the C u2+u2+ mediated oxidation of human LDL in a dose dependent manner at concentration of 50 and 100 μgμg/mL. Geraniin, almost completely inhibited the macrophages mediated LDL oxidation in electrophoretic mobility and conjugate diene of LDL oxidation. Also, geraniin almost completely inhibited 022[10][10] at concentration of 100 μgμg/mL. The physiological relevance of the antioxidative activity was validated at the cellular level where geraniin inhibited endothelial cell mediated LDL oxidation, When compound with several other antioxidants geraniin showed a high activity equal to natural antioxidants, αα-tocopherol and ascorbic acid, and the synthetic antioxidant, protocol. These results indicate that geraniin might play a protective antioxidant effects on LDL, probably affecting both the structural properties of macrophage and endothelial cell for the LDL oxidation..

산화아연 나노막대/PDMS 제작기술과 광학적 특성 연구

  • Go, Yeong-Hwan;Lee, Su-Hyeon;Yu, Jae-Su
    • Proceedings of the Korean Vacuum Society Conference
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    • 2013.02a
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    • pp.474-474
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    • 2013
  • PDMS는 미세패턴을 위해 소프트 리소그래피 널리 활용되어질 뿐만 아니라, 재질이 투명하고 탄성과 강한 내구성을 갖고 있어 유연한 광학 및 전자소자에 이용될 수 있다. 최근에는, 이러한 PDMS를 서브파장구조(subwavelength grating structure)를 형성하거나 텍스쳐(texture)표면구조를 이용한 효과적인 반사방지막(antireflection coating)기판을 제작하여 태양전지 및 디스플레이 소자의 성능을 발전시키는 연구가 활발히 진행되고 있다. 한편, 수열합성법(hydrothermal method)이나 전기화학증착법(electrodeposition method)으로 비교적 간단한 공정을 통해서 다양한 기판위에 산화아연(ZnO) 나노막대(nanorod)를 수직정렬로 성장시킬 수 있는데, 이러한 구조는 반사방지특성의 유효 굴절률 분포(effective refractive index profile)를 갖고 있기 때문에 LED나 태양전지에 성능을 개선할 수 있다. 이에 본 연구에서는 수열합성법을 통해 성장된 수직 정렬된 산화아연 나노막대를 이용한 PDMS 표면의 미세패턴 형성하여 광학적 특성을 분석하였다. 실험을 위해, 스퍼터링을 통해서 산화아연 시드층을 형성한 후, 질산아연헥사수화물과 헥사메틸렌테트라민을 수용액에 담가두어 산화아연 나노막대를 성장시켰으며, PDMS의 베이스와 경화제의 질량비를 10:1으로 용액을 준비하여 수직 정렬된 산화아연 나노막대 표면을 casting method으로 코팅하여 열경화 처리하였다. 제작된 샘플의 형태, 구조 광특성을 관찰하기 위해서 전계방출형전자현미경, X선 회절 분석기, 분광 광도계를 이용하였다.

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Localized Plastic Deformation in Plastic Strain Gradient Incorporated Combined Two-Back Stress Hardening Model (변형량 기울기 이론이 조합된 이중후방응력 경화모델에서의 국부적 소성변형)

  • Yun, Su-Jin;Lee, Sang-Youn;Park, Dong-Chang
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2011.11a
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    • pp.528-535
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    • 2011
  • In the present, the formation of shear band under a simple shear deformation is investigated using a rate-independent elastic-plastic constitutive relations. Moreover, the strain gradient terms are incorporated to obtain a non-local plastic constitutive relation, which in turn represented using combined two-back stress hardening model. Then, the continuum damage model is also included to the proposed model. The post-localization behavior are studied by introducing a small imperfection in a work piece. The strain gradient affects the shear localization significantly such that the intensity of shear band decreases as the strain gradient coefficient increases when the J2 flow theory is employed.

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Preventive Effect of Lamprey Oil and Corn Oil on the Experimental Atherosclerosis in Rats (랫트의 실험적 동맥경화증에 대한 칠성장어유 및 옥수수유의 예방적 효과)

  • 이범준;이영순;미끼도꾸타로
    • Journal of Food Hygiene and Safety
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    • v.4 no.2
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    • pp.133-153
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    • 1989
  • The present study was carried out to investigate the preventive effects of lamprey oil and corn oil on atherosclerotic rats induced by oral administration of cholesterol and vitamin D2D2. The obtaind results were summarized as fellows; 1. The group, fed only the mixture of cholesterol and vitamin D2D2 showed the significant increase of total lipid, total cholesterol phospholipid, LDL&HDL-cholesterol in the serum, triglyceride and cholesterol in the heart and the aorta, but the significant decrease of triglyceride in the liver, as comparing with normal control group (p<0.05). The aorta showed the severe damage of disorganization, calcification, necrosis and lipid deposition in the aortic wall. 2. The group, adminstered the mixture of cholesterol and vitamin D2D2 and fed 15% lamprey oil diet, showed the significant decrease of total lipid, triglyceride, total cholesterol, phospholipid and LDL&VLDL-cholesterol in the serum, triglyceride and cholesterol in the heart and the aorta, but the significant increase of cholesterol in the liver, as comparing with atherogenic control group (p<0.05). The aorta showed slight calcification and no lipid deposition in the aortic wall as comparing with atherogenic control group. 3. The group, administerd the mixture of cholesterol and vitamin D2D2 and fed 15% corn oil diet, showed the decrease of total lipid, triglyceride and VLDL-cholesterol in the serum, and triglyceride in the heart and the aorta, as comparing with atherogenic control group (p<0.05). The aorta showed calcification and no lipid deposition in the aortic wall. In reviewing above results it was concluded that lamprey oil and corn oil in polyunsaturated fatty acids had the preventive effect on atherosclerotic rats induced by cholesterol and vitamin D2D2. And the effect of lamprey oil in n-3 polyunsaturated fatty acids was higher than that of corn oil rich in n-6 polyunsturated fatty acids.

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Thermal Insulation Property of UV Cure Coatings Using Hollow Micro-Spheres (마이크로 중공구를 이용한 자외선 경화 코팅 박막의 단열 특성)

  • Kim, Nam Yi;Chang, Young-Wook;Kim, Seong Woo
    • Korean Chemical Engineering Research
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    • v.50 no.4
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    • pp.621-626
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    • 2012
  • In this study, the composite coating materials with improved thermal insulation property were prepared by incorporating the hollow micro-spheres with high heat transfer resistance. The UV curable resin system consisting of hexa aliphatic urethane acrylate (UP118), trimethylolpropane triacrylate (TMPTA), 1,6-hexanediol diacrylate (HDDA), and photoinitiator (Irgacure184) was employed as an organic binder. The glass substrates were coated by the prepared composites via bar coating method and cured under UV radiation. The optical transparency, thermal insulation property, adhesion, and surface hardness of the glass coated with composites containing different type of micro-spheres were investigated. The incorporation of micro-spheres with only 20 vol% of content resulted in remarkable improvement in the thermal insulation property of the coated glass. In addition, the transparent coated glass with light transmittance of about 80% could be obtained when silica micro-sphere (SP) was used as a thermal barrier.

Effect of Rare Earth Metal on Catalyst for Hydrogenation Reaction (희토류가 수소화 촉매에 미치는 영향)

  • An, Jae Young;Jeon, Jong-Ki
    • Journal of the Korean Applied Science and Technology
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    • v.35 no.1
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    • pp.151-156
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    • 2018
  • As industry and medicine developed, many people became interested in the quality of life. As the concern for health became higher, vegetarian or vegetable oils became more popular than meat. With the development of processes primarily using nickel catalysts today, the shelf life of vegetable oils has increased and mobility has become more convenient. Currently nickel catalysts for the curing of oil are dominated by foreign companies in the world market. On the other hand, the mass production technology of domestic nickel catalyst is backward, and the entire amount is imported from foreign countries. Therefore, there is a need for active research and development of a catalyst that can be commercialized in korea. In this study, nickel as a main active catalyst was used as a base for hydrogen curing reaction, and the effect of rare earth on catalytic activity was investigated. A certain amount of rare earths could induce the dispersion of nickel to increase efficiency and use as co-catalyst.

Preparation and Thermal Insulation Property of UV Curable Hybrid Coating Materials Based on Silica Aerogel (실리카 에어로겔을 이용한 자외선 경화형 복합 코팅 물질의 제조 및 단열 특성)

  • Kim, Nam-Yi;Kim, Seong-Woo
    • Journal of the Korean Applied Science and Technology
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    • v.29 no.1
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    • pp.141-148
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    • 2012
  • In this study, the composite coating materials with improved thermal insulation property were prepared by incorporating the hydrophobic silica aerogel. The surface modification of silica aerogel was performed to obtain UV curable urethane acrylate hybrid coating sols with good compatibility by using surfactant(Brij 56). The polycarbonate substrates were coated by the prepared composites and cured under UV radiation. The incorporation of aerogel with only 10 vol% of content resulted in remarkable improvement by about 28% in the thermal insulation property of the coated film, as compared with substrate. In addition, increasing aerogel content was found to give minor effect on the variation of optical transparency, adhesion, and surface hardness of the coated film.