• Title/Summary/Keyword: 유도 경화

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Properties of carbonated green construction materials by changes in processing conditions (공정조건 변화에 따른 탄산화 녹색건자재의 물성)

  • Kim, Yootaek
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.23 no.3
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    • pp.152-160
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    • 2013
  • The purpose of this study is to enhance the mechanical strength of specimens containing fly ash from fluidized bed type boiler, which the recycling rate will be eventually increased. Specimens containing fly ash in a certain portion were made and aged for 3, 14, and 28 days. Specimens were carbonated under the supercritical condition at 40C. The carbonation process under the supercritical condition was performed to enhance the mechanical property of specimens by filling the voids and cracks existing inside cement specimen with CaCO3 reactants. The additional aging effect after the supercritical carbonation process on mechanical strength of specimens was also investigated by comparing the compressive strength with and without 7 day extra aging. Under the supercritical condition and additional 7 day aging specimens were very effective for enhancement of mechanical strength and compressive strength increased by 44 %.

Prediction of Temperature and Degree of Cure of Carbon Fiber Composites Considering Thermal Chemical Reaction (화학 반응열을 고려한 탄소 섬유 복합재 온도와 경화도 예측)

  • Jae-Woo Yu;Wie-Dae Kim
    • Composites Research
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    • v.36 no.5
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    • pp.315-320
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    • 2023
  • In the manufacturing process of thermosetting carbon fiber composite materials using an autoclave, the internal temperature changes according to the set temperature cycle. This temperature change causes the resin in the composite material to cure. Heat is generated through the chemical reaction of the resin, which can result in a difference between the temperature inside the autoclave and the temperature of the composite material. Previous research assumed that the temperatures of the composite material and the autoclave were the same and analyzed to predict the residual stress and thermal deformation after manufacturing. However, these stresses and deformations depend on the temperature and degree of cure of the composite material. Therefore, this study verifies a thermal-chemical model analysis technique that takes into account the heat generated by the chemical reaction of the resin to accurately calculate the temperature and degree of cure. Additionally, case studies were conducted for different thicknesses to investigate whether this model exhibits similar trends across varying thicknesses.

Thermally-Expandable Molding Process for Thermoset and Thermoplastic Composite Materials (열팽창 고무치공구를 이용한 열경화성 및 열가소성 복합재료의 성형공정 연구)

  • 금성우;이준호;안영선;남재도;임인철;이창희;김이경
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2000.04a
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    • pp.116-119
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    • 2000
  • 본 연구에서는 온도의 상승에 의하여 부피가 팽창하는 열팽창 고무 치공구의 팽창 특성을 이용하여 열경화성 복합재료를 경화하고 압축하는 과정을 실험과 모델링을 통하여 해석하였으며, 열가소성 복합재료의 함침공정을 연구하였다. 열팽창 고무치공구가 사용되는 닫힌계와 열린계에서 예상되는 압력을 이론적으로 유도하였고, 경화가 수반되는 과정에 있어서는 실험을 통하여 열팽창치공구와 프리프레그가 나타내는 압력을 측정하였다. 온도가 상승하고 경화가 수반되는 경우에 등속도 압축실험에 의하여 얻어지는 응력-변형율 곡선은 비선형점탄성 특성을 보여주었는데, 본 연구에서는 Maxwell모델을 KWW(Kohlrausch-Williame-Watts)식으로 변형시킨 모델식을 이용하여 이를 매우 정확하게 표현할 수 있었다. 또한 고무치공구를 이용하여 열가소성 수지의 복합재료 성형공정을 실험하였고, 중성자 레디오그래피 촬영을 통하여 기공의 분포를 관찰하였다.

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An Analysis of High Speed Forming Using the Explicit Time Integration Finite Element Method(II) - Application to High Speed Rolling - (엑스플리시트 시간 적분 유한 요소법을 이용한 고속 성형 해석(II) - 고속 압연 해석)

  • 유요한;정동택
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.15 no.5
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    • pp.1551-1562
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    • 1991
  • 최근까지 발표된 유한 요소법을 이용한 압연 해석 관련 주요 논문들을 정리해 보면 다음과 같다. Li와 Kobayashil는 강소성 유한 요소법(rigidplastic finite element method)을 여러가지 마찰조건에 대하여 해석하였다. 이때 압연롤은 강체 (rigid body)로 시편은 가공경화(workhardening)를 동반한 강소성체로 모델링하였다. Hwang과 Kobayashi는 강소성 유한 요소법을 이용한 평면 변형 압연에서 재료 손실을 최소화하는 예비 성형체(preform)의 설계에 대한 연구를 수행하였다. 이 경우에도 역시 압연롤은 강체로 시편은 가공 경화를 동반한 강소성체와 완전 소성체로 모델링 되었으나, 고착(sticking) 마찰 조건에 대해서만 해석을 수행하였다. Mori와 Osak- ada 그리고 Oda는 약간 압축성이 있는 재료의 평면 변형 압연에 대하여 연구하였다. 이때 압연롤은 강체로 시편은 가공 경화를 동반한 강소성체로 모델링 되었으며 경계 면에서는 Coulomb 마찰을 고려하였다. 이밖에도 오일러(Eulerian) 수식화를 이용한 Dawson과 Thompson, Berman의 해석 결과가 있으며, 또 폭 방향의 변형까지를 고려한 Li와 Kobayashi, Mori와 Osakada의 3차원 해석 결과가 있다.

Functional Characteristics of Egg Oil Extracted from Duck's (청둥오리 압란유의 기능적 특성)

  • 김노준;류병호
    • The Korean Journal of Food And Nutrition
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    • v.11 no.1
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    • pp.41-46
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    • 1998
  • The aims of this study are conducted to investigate the effect of Duck's egg oil no new functional characteristics in the diabetics induced by streptozotocin(STZ) and inhibition of antitumor activity toward Sarcoma-180 bearing mice. Serum glucose content by administration of Duck's egg oil in diabetic group induced by STZ were maintained with normal state than that of control. Phospholipid and triglyceride contents were significant decrease in group of administration with Duck's egg oil than that of control group. Total cholesterol, LDL + VLDL cholesterol and atherosclerotic index were decreased in the group of treatment of Duck's egg oil when does level compared with that of control group. On the other hand, the growth inhibition of the Sarcoma-180 showed the highest level of 63.89% when 150㎎/㎏ Duck's egg oil administrated. The life prolongation effect showed 19.7% at dose of 150㎎/㎏.

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Antioxidative Effect of S-allylmercaptocysteine Derived from Aged Garlic on Oxidation of Human Low Density Lipoprotein (숙성 마늘 유래 S-allylmercaptocysteine의 human low density lipoprotein (LDL)에 대한 항산화 효과)

  • Yang, Seung Taek
    • Journal of Life Science
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    • v.22 no.12
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    • pp.1712-1717
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    • 2012
  • Oxidation of low density lipoprotein (LDL) plays an important role in the development and progression of atherosclerotic disease. In this study, human LDL was isolated and oxidized using CuSO4 in the presence or absence of S-allylmercaptocysteine. Oxidative modification of the LDL fraction was monitored by both the appearance of thiobarbituric acid substances (TBARS), an increase in electrophoretic mobility, and conjugated diene formation. The addition of S-allylmercaptocysteine reduced lipid peroxide formation, indicating it to be an effective antioxidant. The inhibition of LDL oxidation by 520μg/ml S-allylmercaptocysteine occurred in a dose-dependent manner, as assessed by the TBARS assay. S-allylmercaptocysteine at 20μg/ml almost completely inhibited the Cu2+ induced increases in electrophoretic mobility of LDL and almost completely inhibited conjugated diene formation. A more potent antioxidative activity was observed for S-allylmercaptocysteine than for either Vitamin C or dα-tocopherol. Thus, S-allylmercaptocysteine aid in preventing the development and progression of atherosclerotic disease.

Studies on the Chilling Injury of Rice Seedlings III. Possibility of Low-Temperature Hardening (수도의 유묘기 냉해에 관한 연구 III. 유묘의 저온경화 가능성 검토)

  • Kwon, Y.W.;Ahn, M.B.;Oh, Y.J.
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.24 no.3
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    • pp.21-25
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    • 1979
  • To evaluate the possibility of hardening of rice seedlings to chilling injury by low temperature conditioning for improvement of nursery temperature management a chilling sensitive new variety Tongil from Indica \times Japonica cross and a chilling tolerant Japonica variety Jinheung were reared by the 3rd leaf-stage in a day 30C/night20C growth chamber, and were subjected to temperature conditioning for hardening against chilling injury for 6 days. Then the seedlings conditioned and unconditioned were chilled in a day and night 8C chamber for 2, 4, 6, or 8 days long and returned to the day and night 30C/night20C condition for development of chilling injuries. Survival rate after chilling injury development of the variety Tongil showed distinct effect of hardening, i. e. the unhardened-25 % survival, the hardened by a gradual drop of temperature regime $(30^{\circ}C/20^{\circ}C\rightarrow24^{\circ}C/14^{\circ}C\rightarrow18^{\circ}C/12^{\circ}C\rightarrow8^{\circ}C)4 -59% survival and the hardened. by repeated brief exposure (4hrs. to 6hrs.) to 8C shock-89% survival against chilling of 8C for 4 days long. The variety Jinheung survived even against 8 days chilling at 8C C, but the discoloration rate of leaves due to chilling showed noticeably the hardening effect as repeated shock was much better than the gradually lowering temperatures.

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Protection Effects of Allylmercaptan, Metabolite of Garlic on Endothelial Cell Injury Induced by Oxidized Low Density Lipoprotein (산화된 low density lipoprotein (LDL)에 의해 유도된 내피세포의 손상에 대한 마늘 대사산물인 allylmercaptan의 보호 효과)

  • Yang, Seung-Taek
    • Journal of Life Science
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    • v.20 no.11
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    • pp.1595-1602
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    • 2010
  • Oxidation of low density lipoprotein (LDL) has been recognized as an important role in the initiation and progression of atherosclerosis. In this study, effects of allylmercaptan, a major metabolite compound of garlic, was studied on endothelial cell injury induced by oxidized low density lipoprotein (ox-LDL). The antioxidative activity of allylmercaptan was investigated by monitoring a thiobarbituric acid substance (TBARS). Allylmercaptan inhibited LDL oxidation induced by Cu2+ at concentrations of 0.1, 1 and 10 mM in a dose dependent manner. Lactate dehydrogenase (LDH) release, as an index of cell injury, and intracellular glutathione levels were determined. Pulmonary artery endothelial cells were preincubated with allylmercaptan at 37C and 5% CO2 for 24 hr, washed, and then exposed to 0.1 mg/ml oxidized LDL for 24 hr. Preincubation of endothelial cells with allylmercaptan significantly prevented the LDH release and depletion of GSH. Peroxides were measured directly in 24 well plates using a fluorometric assay. Allylmercaptan inhibited release of peroxides induced by ox-LDL in pulmonary artery endothelial cells. In a free system, allylmercaptan was shown to scavenge hydrogen peroxide. The data indicate that allylmercaptan can protect pulmonary artery endothelial cells from injury caused by oxidized LDL, and suggest that allylmercaptan may be useful for the prevention of atherosclerosis.

Numerical Analysis of ECC Uniaxial Tension Behavior (ECC의 1축 인장 거동 해석)

  • Kim, Yun-Yong;Lee, Bang-Yeon;Kwon, Seung-Hee;Kim, Jeong-Su
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.04a
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    • pp.917-920
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    • 2008
  • ECC is a special kind of high performance cementititous composite which exhibits typically more than 2% tensile strain capacity by bridging microcracks at a crack section. Therefore, micromechanics should be adopted to obtain multiple cracking and strain hardening behavior. This paper propose a linear elastic analysis method to simulate the multiple cracking and strain hardening behavior of ECC. In an analysis, the stress-crack opening relation modified considering the orientation of fibers and the number of effective fibers is adopted. Furthermore, to account for uncertainty of materials and interface between materials, the randomness is assigned to the tensile strength(σfci), elastic modulus(Eci), peak bridging stress(σBi) and crack opening at peak bridging stress(δBi), initial stress at a crack section due to chemical bonding, (σ0i), and crack spacing(αcXd). Test results shows the number of cracking and stiffness of cracked section are important parameters and strain hardening behavior and maximum strain capacity can be simulated using the proposed method.

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A Constitutive Model for Soil Using Mohr-Coulomb Criteria (Mohr-Coulomb식(式)을 사용한 흙의 구성(構成)모델)

  • Lee, Hyung Soo;Lee, Byung Dae
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.14 no.6
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    • pp.1405-1415
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    • 1994
  • The soil on the behavior of the nonlinear elastic work-hardening plasticity has a variety of stress paths due to the state of soil and the test conditions. The soil with a specific volume υ in principal stress space (σ1, σ2, σ3, and υv) displays the shape of an irregular hexagonal pyramid with an end cap. With variations of υ the size of the cap is changed but its shape remains unchanged and the movement of the cap is controlled by the increase or decrease of the plastic volumetric strain. By reflecting such a property of soil various cap models have been developed by researchers. In this thesis, a constitutive model of soil with a combination of the nonlinear elastic work-hardening plastic cap and the failure surfaces of Mohr-Coulomb (M-C cap model) has been developed. According to the the results of analyses using the work-hardening plastic cap model, the normally consolidated soil under shearing has experienced the work-hardening and plastic flow (movement of the cap). But in the shearing of the overconsolidated soil the elastic behavior is shown until the stress path has reached the failure surface and the cap does not move.

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