• 한국지반신소재학회논문집
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• 제9권2호
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• pp.33-40
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• 2010

본 연구에서는 강재스트립 보강재에 지지부재가 결속된 형태의 보강재에 대하여 인발시험을 수행하였으며, 인발시험결과와 기존에 제안된 지지저항 평가식에 의한 결과를 비교함으로서 인발변위 50mm일 때의 인발력과 최대 인발력에 의한 지지부재의 지지저항 특성을 평가하였다. 인발변위 50mm일 때의 인발력 적용에 의한 지지저항응력(${\sigma}^{\prime}_b$)은 수직응력 증가에 따라 전면전단파괴에서 펀칭전단파괴로 근접하였으며, 지지부재 개수의 증가에 따라서는 펀칭전단파괴에서 전면전단파괴로 근접하는 것으로 확인되었다. 최대 인발력을 적용한 지지저항응력(${\sigma}^{\prime}_b$) 은 수직응력 조건 및 지지부재 개수와 관계없이 전면전단파괴에 근접하였지만, 보강토옹벽의 허용변위를 고려한다면 설계 적용에는 무리가 있을 것으로 분석되었다. 그리고 Prandtl의 소성이론 및 원주공동확장이론에 의한 이론식을 이용한 지지저항 평가는 인발시험결과가 Prandtl의 소성이론을 이용한 예측결과에 보다 가까운 것으로 확인되었다. 또한 Prandtl의 소성이론 및 원주공동확장이론을 이용한 지지저항 평가모델은 전면전단파괴와 펀칭전단파괴모델 사이에 위치하는 것을 확인하였다.

• 한국해양공학회지
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• 제3권2호
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• pp.138-144
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• 1989

It has been very important in various industry fields to improve the fatigue strength characteristics of bearings such as bearing life, fatigue limit, etc., because such poor properties could result in shortening the machinery life as well as in decreasing the accuracy. However, no successful heat treatment criterion seems to be available at present. In this study, the effect of the $170^{\circ}C\times120min$ tempering cycles repeated after $380^{\circ}C\times80min$ oil quenching for $800^{\circ}C$ spheroidizing-annealed bearing steel (STB2) as base metal on the $120^{\circ}C$ high temperature rotary bending fatigue strength characteristics were investigated, including the effects on hardness, Charpy impact value and micro-structure, in order to seek for the best heat treatment condition finally. The important results obtained are as follows : 1) The optimal cycle of tempering so that the fatigue strength .sigma. could become the highest was the 4th cycle. And it is confirmed that this $\sigma_{F}$ is about 6 times more increased than that of base metal, and about 1.3 times more increased than the case of the 1 cycle tempered. 2) As a result of the investigation for the effects of tempering cycles on hardness, the hardness at the tempering number of 2 thru 5 cyles was not decreased severely ; only about 10% decrease from those of the quenched and 1 cycle tempered case. Such hardness is equivalent to $H_{R}$/C61-62 with no bad effect on anti-abrasion of bearing steel. 3) In the case of 2 thru 5 cycle tempering as well as 1 cycle tempering, the impact value was not so improved comparing with the case of quenching, but an increase of 5 to 10% could be expected at least. 4) It was experimentally confirmed that the control of the mechanical properties improvement such as fatigue strength and fatigue life for bearing steels could be possible by the number of tempering cycles.

• 한국해양공학회지
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• 제3권2호
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• pp.638-638
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• 1989

It has been very important in various industry fields to improve the fatigue strength characteristics of bearings such as bearing life, fatigue limit, etc., because such poor properties could result in shortening the machinery life as well as in decreasing the accuracy. However, no successful heat treatment criterion seems to be available at present. In this study, the effect of the $170^{\circ}C\times120min$ tempering cycles repeated after $380^{\circ}C\times80min$ oil quenching for $800^{\circ}C$ spheroidizing-annealed bearing steel (STB2) as base metal on the $120^{\circ}C$ high temperature rotary bending fatigue strength characteristics were investigated, including the effects on hardness, Charpy impact value and micro-structure, in order to seek for the best heat treatment condition finally. The important results obtained are as follows : 1) The optimal cycle of tempering so that the fatigue strength .sigma. could become the highest was the 4th cycle. And it is confirmed that this $\sigma_{F}$ is about 6 times more increased than that of base metal, and about 1.3 times more increased than the case of the 1 cycle tempered. 2) As a result of the investigation for the effects of tempering cycles on hardness, the hardness at the tempering number of 2 thru 5 cyles was not decreased severely ; only about 10% decrease from those of the quenched and 1 cycle tempered case. Such hardness is equivalent to $H_{R}$/C61-62 with no bad effect on anti-abrasion of bearing steel. 3) In the case of 2 thru 5 cycle tempering as well as 1 cycle tempering, the impact value was not so improved comparing with the case of quenching, but an increase of 5 to 10% could be expected at least. 4) It was experimentally confirmed that the control of the mechanical properties improvement such as fatigue strength and fatigue life for bearing steels could be possible by the number of tempering cycles.

• 한국지반환경공학회 논문집
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• 제9권6호
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• pp.5-12
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• 2008

본 연구에서는 타이어셀로 보강된 모래지반에 대한 평판재하시험을 유한요소법에 의해 모델링하였다. 타이어셀의 기능과 외양은 지오셀과 비슷하며 지오셀과 마찬가지로 토목구조물에서 지반보강 목적으로 사용할 수 있다. 해석결과는 모델링의 적절성을 평가하기 위해 현장 재하시험결과와 비교하였다. 두 결과의 비교로부터 유한요소해석에 의한 침하량은 극한지지력에서 실험결과와 유사한 값을 나타내었다. 모델링을 검증한 후 타이어셀의 보강깊이와 보강층 수의 변화에 대한 해석을 수행하였다. 보강효과는 보강깊이가 증가함에 따라 감소하였으며 이러한 경향은 기존의 시험결과와 유사하였다. 보강층수가 증가함에 따라 보강효과는 증가하였다. 그러나 2층 이상의 보강은 효과가 무시할 정도였다. 결론적으로 본 연구에서의 모델링 방법은 타이어셀을 사용한 지반구조물의 해석에 사용할 수 있을 것으로 생각된다.

• 대한화학회지
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• 제34권2호
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• pp.189-196
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• 1990

아세트아닐리드와 부타노일, 헥사노일, 옥타노일기를 가진 n-acyl chloride류로부터 6-acylbenzofuroxan류를 합성하고, 이들과 히드로퀴논 및 4-아미노페놀을 반응시켜 8-Acyl-2-hydroxyphenazine-5,10-dioxide류와 8-acyl-2-aminophenazine-5,10-dioxide류를 합성하였다. 이들 phenazine dioxide 유도체의 향균성을 희석법에 의하여 최소 발육저지 농도로서 조사하였는데, 그람양성균에서 옥타노일기를 가진 phenazine dioxide 유도체들이 부타노일기나 헥사노일기를 가진 유도체를 보다 항균성이 더 강하였으나, 그람음성균에서는 항균성과 아실기의 탄소수와는 관계가 없다는 것은 알았다. 활성산소($O_2^-$) 생성의 주효소인 xanthine oxidase의 활성을 phenazine dioxide류의 효소활성 저해작용은 아실기의 탄소수가 증가함에 따라 증가하였다.

• Tribology and Lubricants
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• 제38권6호
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• pp.267-273
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• 2022

Surface texturing is the latest technology for processing grooves or dimples on the friction surface of a machine. When appropriately applied, it can reduce friction and significantly increase durability. Despite many studies over the past 20 years, most are isothermal (ISO) analyses in which the viscosity of the lubricant is constant. In practice, the viscosity changes significantly owing to the heat generated by the viscous shear of the lubricant and film-temperature boundary condition (FTBC). Although many thermohydrodynamic (THD) analyses have been performed on various sliding bearings, only few results for surface-textured bearings have been reported. This study investigates the effects of the FTBC and groove number on the THD lubrication characteristics of a surface-textured parallel thrust bearing with multiple rectangular grooves. The continuity, Navier-Stokes, and energy equations with temperature-viscosity-density relations are numerically analyzed using a commercial computational fluid dynamics code, FLUENT. The results show the pressure and temperature distributions, variations of load-carrying capacity (LCC), and friction force with four FTBCs. The FTBCs greatly influence the lubrication characteristics of surface-textured parallel thrust bearings. A groove number that maximizes the LCC exists, which depends on the FTBC. ISO analysis overestimates the LCC but underestimates friction reduction. Additional analysis of various temperature boundary conditions is required for practical applications.

• Tribology and Lubricants
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• 제38권5호
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• pp.191-198
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• 2022

With the world's fast expanding energy usage comes a slew of new issues. Because one-third of energy is lost in overcoming friction, tremendous effort is being directed into minimizing friction. Surface texturing is the latest surface treatment technology that uses grooves and dimples on the friction surface of the machine to significantly reduce friction and improve wear resistance. Despite the fact that many studies on this issue have been conducted, most of them focused on parallel surfaces, with relatively few cases of converging films, as in most sliding bearings. This study investigated the lubrication performance of surface-textured inclined slider bearings. We analyzed the continuity and Navier-Stokes equations using a commercial computational fluid dynamics code, FLUENT. The results show the pressure and velocity distributions and the lubrication performance according to the number and orientation of rectangular dimples. Partial texturing somewhat improves the lubrication performance of inclined slider bearings. The number of dimples with the maximum load-carrying capacity (LCC) and minimum friction is determined. When the major axis of the dimple is arranged in the sliding direction, the LCC and friction reduction are maximized. However, full texturing significantly reduces the LCC of the slider bearing and increases the flow rate. The results have the potential to improve the lubrication performance of various sliding bearings, but further research is required.

• 한국자원식물학회지
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• 제35권6호
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• pp.825-830
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• 2022

"Doha" is a new strawberry (Fragaria x ananassa Duch.) variety, which was released by the Highland Agriculture Research Institute in 2021. The "Doha" variety originates from a 2014 cross between "Saebong No. 3" and "Yeolha," both of which exhibited excellent ever-bearing characteristics, including continuous flowering and large fruits under long-day and high temperature conditions. This new cultivar was initially named "Saebong No. 13" after examining its characteristics and productivity during summer cultivation between 2015 and 2018. After regional adaptability tests, "Doha" was selected from "Saebong No. 13" as an elite cultivar. The general characteristics of "Doha" include spreading, elliptic leaves, and strong growth. The fruits are long and conical and of a red color. The plant height of "Doha" was similar to that of "Goha," but the number of leaves was lower. The number of flower clusters of "Doha" was 8.6, which was 2.8 fewer than that of the control variety, "Goha," with 11.4. The average fruit weight of "Doha" was 13.9 g, which was 4.9 g heavier than that of "Goha." The fruit hardness of "Doha" was 35.5 g·mm^-2, which was 9.4 g·mm^-2 harder than that of "Goha." The marketable yield of "Doha" was 26,971 kg·ha^-1, 125% more than that of "Goha" with 21,479 kg·ha^-1. The findings of this study suggest that "Doha" is a hard fruit and high-yielding variety of ever-bearing strawberries that could increase farming income when distributing to farmers.

• 약학회지
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• 제46권1호
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• pp.11-17
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• 2002

$\beta$-Immunan, a proteoglycan, was isolated from the mycelium of Canoderma lucidum which belongs to a medicinal mushroom. The effects of $\beta$-Immunan on cell-cell and cell-matrix interactions mediated by carbohydrate-recognition and the mechanism responsible for the inhibition of experimental metastasis of Bl6-F10 and B16/BL6 murine melanoma were studied. The results showed that $\beta$-Immunan inhibited Bl6-Fl melanoma cell's adhesion to laminin and asialofetuin-induced homotypic aggregation and reduced invasion against Bl6-F10 murine melanoma cells through matrigel in vivo assay. When $\beta$-Immunan was intraperitoneally administrated to C57B/6 mice bearing B16/BL6 murine melanoma cells, it was decreased the number of pulmonary metastatic colony by the dose dependent manner ranging from 20 to 100 mg/kg/day. The results indirectly indicate that clinical treatment with $\beta$-Immunan might be expected to exhibit anti-metastatic effect. In the pulmonary metastasis, the number of pulmonary metastatic colony of melanoma when $\beta$-Immunan was intraperitoneally administrated to C57BL/6 mice bearing B16/BL6 murine melanoma cells by intravenous injection were decreased by the dose dependent manner ranging from 20 to 100 mg/kg/day.

• Biomolecules & Therapeutics
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• 제1권1호
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• pp.71-76
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• 1993

It has been reported that d-limonene inhibits chemical-induced rat mammary cancer by the mechanism of increases in detoxification enzymes such as glutathione S-transferases and that cineole fails to exhibit significant suppressive effect on chemical-induced carcinogenesis. The present study was designed to compare the effects of d-limonene and cineole on the benzo(a)pyrene (BP)-induced mutagenicity, BP metabolism and lipid peroxidation. Modified Ames assay was employed to evaluate the inhibitory effect of d-limonene and cineole on the BP-induced mutagenicity. The number of revertant-bearing wells was decreased by 44~77% in the presence of both BP and d-limonene compared with that of BP alone whereas cineole decreased the number of revertant-bearing wells by 28~45% at the concentrations between $2{\mu}m$m.TEX> and 2 mM. d-Limonene suppressed BP metabolism by 16, 54 and 67% at 1, 10 and 100 mM, respectively while cineole inhibited the metabolism by 16, 26 and 55% at the same concentrations. The $EC_{50}$ values for d-limonene and cineole in inhibiting lipid peroxidation were 2.0 mM and 16 mM respectively, as assayed by thiobarbituric acid method. The present study showed that d-limonene and cineole have common antimutagenic effects although d-limonone appeared to be more effective than cineole in suppressing mutation and lipid peroxidation. The results suggest that the antimutagenic effects of d-limonene and cineole may be associated with alternation in enzyme activities and with inhibition of lipid peroxidation.