• International Journal of Highway Engineering
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• v.10 no.4
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• pp.225-234
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• 2008

This study was carried out to select proper loading speed for deformation strength ($S_D$) of asphalt mixtures. Kim test using loading head of diameter(40mm) with radius(10mm) was conducted to measure $S_D$ in different loading speed (10mm/min, 30mm/min, 50mm/min, 70mm/min) and wheel tracking test was also conducted. The regression analyses between the So values and WT results were carried out by loading speeds. Higher $S_D$ was observed as increasing loading speed. This means that loading speed is a high influencing factor on $S_D$. The loading speed of 30mm/min was found as an optimum for better correlation with WT results than any other speeds from the regression analysis between $S_D$ and wheel tracking test results. $S_D$ value measured at other loading speed than 30mm/min has to apply the conversion coefficients.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2D
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• pp.243-248
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• 2008

Moisture damage of asphalt pavements can usually occur because of the loss of adhesion and cohesion between the asphalt binder and aggregate in the asphalt mixture due to presence of water. And this is one of the causes that is effect on the main distress of asphalt pavement. The objective of this study is to find out moisture damage characteristics of asphalt pavement. Effects of this study changes of the material properties and resistance characteristics of moisture damage on the asphalt mixtures under various temperatures and repeated immersion using indirect tensile test and modify Lottman test were evaluated during this study. The asphalt mixtures were produced using straight asphalt binder, SBS modified asphalt binder and aggregates. The material properties (resilient modulus, indirect tensile strength, failure energy and $DCSE_f$) of the asphalt mixtures were generally decreased with increasing to moisture damage caused by the number of repeated immersion. The decrease ratios of material properties by repeated immersion on SBS modified asphalt mixtures were lower than those of straight asphalt mixtures at all three test temperatures. As a conclusion, current criterion for evaluation moisture damage of asphalt mixtures is difficult for using distinction standard because of the limited evaluation criterion with one time immersion and single material property. Based on this research, to evaluate long term moisture damage on asphalt mixtures, material property tests of various kinds with repeated immersion test are considered.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.23 no.1
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• pp.51-54
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• 1978

3∼6m long plot with 3-4 replications will be practical for yield trials in the early hybrid generations. The C. V. values with 9m long plot was about 6.6％ in variety Yudal and 13.9％ in 12m plot. These results indicate that 9-12m plot with 3-4 replications could be employed in securate yield test in the advanced generations.

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.6
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• pp.824-831
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• 2011

This study was to investigate 90-day repeated-dose toxicities of 50 kGy irradiated methanol extract powder of red ginseng in ICR mice. The test materials (methanol extract powder of red ginseng with or without 50 kGy irradiation) were administered by gavage to male and female ICR mice at dose levels of 0, 125, 250 and 500 mg/kg/day for 90 days. In the results, no abnormality was observed in mortality, clinical findings, body weight changes, food consumptions, opthalmoscopic findings, necropsy findings and histopathological findings. Although the minor changes in blood and biochemical parameters were observed, they were not dose dependent and not affected by gamma irradiation. In conclusion, 90-day repeated oral dose of the methanol extract powder of red ginseng and 50 kGy irradiated methanol extract powder of red ginseng to ICR mice did not cause apparent toxicological change at the dose of 125, 250 and 500 mg/kg body weight.

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.5
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• pp.704-711
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• 2011

Traditionally, mistletoes have been used as immunostimulant for the management of certain diseases such as cancer with high profile immune depleting potentials. In order to examine the safety of the 20 kGy irradiated cold water extract powder of mistletoes, we performed a 90-day repeated-dose toxicity study with ICR mice. The mice were treated with daily doses of the 20 kGy irradiated cold water extract powder of mistletoes by gavage at 0, 20, 100, and 500 mg/kg/day for 90 consecutive days. We recorded clinical signs of toxicity, body weight, organ weights, histological changes in target organs, hematology, and clinical blood chemistry analysis data for all mice. There were no significant changes in body and organ weights during the experimental period. The hematological analysis and clinical blood chemistry data revealed no toxic effects from the 20 kGy irradiated cold water extract powder of mistletoes. Pathologically, neither gross abnormalities nor histopathological changes were observed between the control and treated mice of both sexes. Collectively, these data suggest that the 20 kGy irradiated cold water extract powder of mistletoes have a high margin of safety.

• Korean Chemical Engineering Research
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• v.54 no.6
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• pp.762-766
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• 2016

In this study, natural extract including Phellodendro namurense, Eucommia ulmides Oliv and Prunus padus were tested for antimicrobial activity and safety. Antimicrobial activity was measured by using opportunistic microbes such as Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Candida albicans. As safety test, cell viability test, single dose oral toxicity test, single dose inhalation toxicity test, repeat dose inhalation toxicity test and eye irritation test were done. From antimicrobial test, natural extract showed execellent antimicrobial activity against Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans, Escherichia coli. From 5 kinds of safety tests, toxicity was not observed. From experimental results, natural extract including Phellodendro namurense, Eucommia ulmides Oliv and Prunus padus showed superb safety and antimicrobial effect.

• Journal of Korean Society of Steel Construction
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• v.9 no.2 s.31
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• pp.193-204
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• 1997

In order to quantify the relationships of the important physical factors relating failure to strong earthquake loading, the plastic fatigue problems for structural components under repeated loading were reviewed first. A new concept of very low cycle fatigue failure for structural components under severe cyclic excitations as in strong earthquakes was represented. Also, an experimental study was made of the very low cycle fatigue failure of structural steel elements. It was attempted to realize the ultimate failure in the course of loading repetitions of the order of several to twenty. The test specimen had a form of rectangular plate, representing a thin-plated element in a steel member as wide-flange cross section. It was subjected to uniaxial loading repeatedly, until complete failure takes place after undergoing inelastic buckling, plastic elongation and/or their combination. It was seen as a result that the state of the ultimate failure is closely related to the maximum strain at the extreme fiber in the cross section.

• Journal of the Korean Geosynthetics Society
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• v.8 no.1
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• pp.25-32
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• 2009

In reclaimed loose sandy layer with dredged soil, liquefaction by the small scale earthquake coud be occurred easily. A study has been carried out to investigate the Liquefaction characteristic on Saemangeum dredged sandy soil, and compared with other results from the literature investigation. A series of undrained cyclic triaxial compression tests were performed on dredged sandy soil of Seamangeum area. The tests were performed at the three different initial relative densities(namely 30%, 50%, 70%), different cyclic stress ratio and different consolidation stress condition. The results of this study showed that cyclic stresses (${\sigma}_d$) increased linearly with increase of consolidation ratio, but the stress ratios (${\sigma}_d/2{\sigma}^{\prime}{_c}$) were almost same. The stress ratios were increased almost linearly with increase of relative density. Compared with other sandy soil, Saemangeum dredged sandy soil showed relatively weak liquifaction characteristics.

• Composites Research
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• v.19 no.1
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• pp.22-28
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• 2006

In manufacturing process of composite cylinders with metal liner, the autofrettage process which induces compressive residual stress on the liner to improve cycling life can be applied. In this study, a finite element analysis technique is presented, which can predict accurately the compressive residual stress on the liner induced by autofrettage and stress behavior after. Material and geometrical non-linearity is considered in the finite element analysis, and the Von-Mises stress of a liner is introduced as a key parameter that determines pressure cycling life of composite cylinders. Presented methodology is verified through fatigue test of liner material and pressure cycling test of composite cylinders.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1992.10a
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• pp.65-70
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• 1992

오래전부터 회전체 질량의 불균형에 의한 진동을 줄이기 위한 전용 밸런싱 장치와 프로그램이 개발되었다[1-5]. 그런데 밸런싱 장치는 센서로부터 측정 된 진동 신호를 이용하여 밸런싱을 함으로 밸런싱의 반복성과 정밀도 등에 따라 그 장치의 성능을 평가할 수 있으며, 국제 표준기구(ISO)에서도 장치의 성능을 평가하기 위한 각종 시험 규격들을 제시, 권장하고 있다[6]. 본 연구 에서는 강성 회전체의 밸런싱을 위해 연구실에서 제작한 탄성 베어링 밸런 싱 장치에 대해 ISO 규격에서 제시하는 성능 평가 시험들을 기초로 회전체 밸런싱과 여러가지 시험을 수행하고 장치의 특징과 성능을 알아보고자 한다.