• Journal of the Korean Chemical Society
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• v.54 no.1
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• pp.105-109
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• 2010

HEMA (2-hydroxyethyl methacrylate), EGDMA (ethylene glycol dimethacrylate) and propylene glycol was copolymerized in the presence of AIBN (azobisisobutyronitrile) initiator in a mould. The physical properties of the contact lens were measured. The water content of 37.06~38.71%, refractive index of 1.492~1.432, visible transmittance of 89.4~91.5%, tensile strength of 0.1416~0.2302 kgf, and contact angle of $38.60{\sim}53.53^{\circ}$ were obtained. Therefore, the contact lens material produced using propylene glycol as an additive satisfied the basic physical properties required for contact lenses application. It is interesting to note that an increase in wettability and tensile strength while having no significant changes in water content.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.3
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• pp.39-43
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• 2010

The main objective of this research is to develop a mechanistic performance predictive model for fatigue cracking of asphalt-aggregate mixtures. Controlled-stress diametral fatigue tests were performed to characterize fatigue cracking of asphalt-aggregate mixtures. Performance prediction model for fatigue cracking was developed using the internal damage ratio (IDR) growth method. In the IDR growth method, the general concepts of the dissipated energy, the reference tensile strain, the threshold tensile strain, and the strain shift factor were introduced. The source of the dissipated energy in the fatigue test is from the intrinsic viscoelastic material property of an asphalt concrete mixture and the damage growth within the asphalt concrete specimen. In controlled-stress mode test, the dissipated energy is gradually increased with an increasing number of load applications.

• Korean Journal of Materials Research
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• v.8 no.2
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• pp.99-104
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• 1998

사용중인 중화학 설비의 재료물성의 경년열화적 특성을 평가하기 위하여 기존 실험법의 인장시험편이나 충격시험편을 채취하기는 실제적으로 불가능하다. 인장강도등 인장특성과 비교한 결과 인장강도, 연신율, 항복강도, 종탄성계수와 소형펀치실험의 각 특성과 선형적 관계를 얻을 수 있었다. 또한 경년열화도를 평가하는 두구인 파면천이온도(FATT)와 비교하기 위하여 저온 소형펀치실험을 실시한 결과 충격실험을 통하여 구한 FATT온도와 소형펀치실험의 천이온도 ( $T_{sp}$ )와 일정한 관계가 있음이 밝혀져 사용재의 열화도를 평가할 수 있다.

• Journal of the Korean Magnetics Society
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• v.25 no.4
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• pp.123-128
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• 2015

The iron is an element having a high yield strength, mechanical hardness, good electrical conductivity, and also it has been used in various fields because of ease machining. In bridges have been used tendon made of a steel wire for large loads and light weight. Tension measurement of tendon employed in PreStressed Concrete (PSC) bridge is very important for the bridge safety check. NDT (Non-Destructive Testing) is essential for the safety check, however, magnetic NDT is difficult to apply due to the non-linear magnetization curve and hysteresis loop in the magnetic properties. In this work, for basic study of magnetic NDT application, we have constructed a B-H loop measuring system for 7-strand tendon of which diameter is 15.5 mm, and which can apply tensile stress up to 2.0 GPa. We have measured hysteresis loops of two kinds of tendons under different tensile stress. Amplitude permeability and maximum magnetic induction near knee show the most sensitive and high linearity depends on tensile stress. Relative amplitude permeability was decreased from 500 to 200 and maximum magnetic flux density changed 0.6 T.

• Journal of Korea Foundry Society
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• v.41 no.5
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• pp.434-444
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• 2021

This study investigated the overall dependence of the tensile properties of Al-Si alloys on the distribution aspect of a eutectic Si particle in terms of defect susceptibility to the effective void area fraction, referring to the sum of pre-existing microvoids and the damage evolution of the Si particle. The network morphology of as-cast Al-xSi (x=2,5,8,11) alloys was modified to a granular type via a T4 treatment, after which a computational topography (CT) analysis and scanning electron microscope (SEM) observations were utilized to evaluate the size and distribution of the microvoids. The CT and SEM analyses indicated that the main cracks grow along local regions that possess the highest porosity level. The local plastic deformation around the microvoids and the distribution aspect of the microvoids induced a practical difference between the iso-volumetric CT measurement and the SEM fractography outcomes. The results demonstrated that the overall dependence of the ultimate tensile strength (UTS) and elongation on the effective void area fraction is more sensitive to the variation of the area fraction of the Si particle in the network morphology than in the granular type; this is due to the sequential damage evolution of the neighboring Si particles in the eutectic Si colony.

• Journal of the Korea Concrete Institute
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• v.14 no.4
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• pp.608-614
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• 2002

The effects of slag content and polymer-binder ratio on the strength properties of autoclaved SBR-modified concretes using ground granulated blast-furnace slag(slag) and a styrene-butadiene rubber (SBR) latex are examined. As a result, the compressive and tensile strengths of the autoclaved SBR-modified concretes using slag increase with increasing slag content, and reach a maximum at a slag content 40％, and increase with increasing polymer-binder ratio. In particular, the autoclaved SBR-modified concretes with a slag content of 40％ provide about three times higher tensile strength than unmodified concretes. Such high strength development is attributed to the high tensile strength of SBR polymer and the improved bond between cement hydrates and aggregates because of the addition of SBR latex.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.3
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• pp.29-34
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• 2008

Purpose: In this study, we compared the physical properties of the compositions that were mixed with basic materials of HEMA (2-Hydroxyethyl methacrylate)/Silicone and BMA (Butyl methacrylate), MMA (Methyl methacrylate) by making the silicone contact lens. Method: Each sample of contact lenses was fabricated by cast mould method. We analyzed results by using average values of physical property of each sample. Results: In the composition of HEMA/Silicone/BMA, water contents of samples showed the value from 24.69% to 29.26%. Ultimate strength of samples showed the value from 0.109 kgf to 0.263 kgf. In the composition of HEMA/Silicone/MMA, swelling ratio of samples showed the value from 13.56% to 14.83%. Water contents of samples showed the value from 25.61% to 29.33%. Ultimate strength of samples showed the value from 0.107 kgf to 0.286 kgf. Conclusions: The compositions of percents of silicone were ranged from 0.20% to 11.50% and the composition percent of BMA and MMA was 5.15% in total. Swelling ratio and water contents increased with decreasing of BMA (Butyl methacrylate) and MMA (Methyl methacrylate) percent. In the composition of HEMA/Silicone/MMA, the values of ultimate strength increased with increasing of silicone percent to 4-MMA sample. In the composition of HEMA/Silicone/BMA, the values of ultimate strength decreased with increasing of silicone percent.

• Journal of the Korean Institute of Gas
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• v.9 no.4 s.29
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• pp.11-16
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• 2005

In this paper, the hydrogen osmosis test and the mechanical tensile test were carried out to examine hydrogen cracking behavior of STS444 with welding conditions. In $0.5MH_2SO_4+0.001M \;As_2O_3$ solution, the hydrogen embrittlement characteristics of weld zone of STS444 added to load of $1,400 kg/cm^2$ together with hydrogen osmosis by current of $30mA/cm^2$ for 60 min. was considered. As a result of study on the hydrogen embrittlement and mechanical characteristics of STS444외와 with welding conditions the tensile stress and elongation of STS444 get lower by the absorption of oil or water before welding. Also, the reduction rate of tensile stress and elongation of STS444 is larger because of hydrogen embrittlement by the absorption of oil or water. STS444 by the absorption of water before welding is more sensitive to hydrogen embrittlement than oil.

• Korean Journal of Food Science and Technology
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• v.34 no.6
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• pp.1023-1029
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• 2002

Relationship between RVA properties and physical properties of film made from native corn starch and hydroxypropylated corn starch at various levels of plasticizers was examinel. Tensile strength of the film decreased, but its elongation and water vapor permeability increased with increasing plasticizer concentration. The film with glycerol showed greater changes in physical properties than that with sorbitol. Hydroxypropylated starch film showed lower tensile strength, higher elongation, and higher water vapor permeability than the native starch film. Sorbitol resulted in films with relatively high tensile strength, whereas glycerol produced films with increased elongation. The most reliable parameters for the relationship between RVA properties and film properties were RVA peak viscosity, tensile strength, and water vapor permeability. Water vapor permeability and tensile strength had linear relationship with RVA properties. The tensile strength and water vapor permeability of film could be predicted using the RVA peak viscosity.

• Korean Journal of Materials Research
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• v.2 no.2
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• pp.133-142
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• 1992

The slow strain-rate test($1{\times}10^{-4}~1{\times}10^{-7}sec^{-1}$) was performed to understand the tensile properties of chopped strand glass mat/polyester composite in air and synthetic sea water. (pH 6.0, 8.2, 10.0) For the tested composite subjected to tensile loading in air and synthetic sea water (ph 6.0, 8.2, 10.0), the tensile properties are a little decreased as strain rate decrease and a little decrease in stiffness is observed in $1{\times}10^{-7}sec^{-1}$. The tensile properties were some changed in case the pH value in synthetic sea water is varied.