• 한국안전학회지
• /
• 제11권1호
• /
• pp.11-15
• /
• 1996

For the assessment of fracture behaviors of structural components, various fracture mechanics parameters have been applied to date. New approaches to analyze structural fracture performance under elastic-plastic condition have been proposed by the development of testing methods for characterization of material behavior which is defying to the analysis by conventional fracture parameters. In this study, on the assumption that, initiation of crack propagation of a piping materials occurs when the crack tip strain field reaches "the local fracture strain", following two major issues are discussed ; 1) The relationship between the critical value of J-integral($J_{IC}$) and the local fracture strain (${\varepsilon}_c$) in uniaxial tensile test in the region of maximum reduction area was described. 2) To proved the validity of above relations a series of tests were performed under various temperature and on the different piping materials.materials.

• 생약학회지
• /
• 제35권1호통권136호
• /
• pp.80-87
• /
• 2004

From the $CHCl_3$ and BuOH soluble fractions of the heartwood of Hemiptelea davidii, eleven compounds have been isolated. On the basis of spectral data, they were identified as ${\beta}-sitosterol$ (1), scopoletin (2), kaempferol (3), 4-hydroxybenzoic acid (4), 2-(4-hydroxyphenyl) ethanol (5), aromadendrin (6), scopolin (7), kaempferol 6-C-glucoside (8), aromadendrin 6-C-glucoside (9), taxifolin 6-C-glucoside (10) and quercetin 6-C-glucoside (11), respectively. Among these compounds, compounds 3, 8, 10, and 11 showed potent DPPH radical scavenging activity with $IC_{50}$ values of 11.9, 14.7, 10.3 and $6.2\;{\mu}g/ml$, respectively.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
• /
• pp.748-753
• /
• 2011

철도용 전자기기의 온도 환경시험을 함에 있어 일반적으로 내한성과 내열성에 관한 시험을 수행한다. KRS 규격의 온도환경시험에서 성능확인은 양부판단의 규정이 "이상이 없어야 한다"로 대부분 되어있다. 이 문구에 대하여 시험자들은 규격 내에서 제시하는 기능시험이나 성능시험을 온도쳄버 장치를 사용하여 시험절차 중에서 수행하기 용이한 몇 가지 시험으로 성능 확인시험을 한다. 이러한 방법으로는 저온 및 고온에서 정상 동작하는지 확인이 안 되는 부품이나 회로가 생길 수 밖에 없다. 이 문제는 성능시험이나 기능시험의 종류를 늘린다고 해서 문제가 해결될 수 있는 것이 아니라고 여겨진다. 본 논문에서는 철도용품에 대한 내한성 및 내열성에 대한 KS 및 KRS 규격 검토와 온도시험의 한계를 검토하여 그에 대한 대안으로 데이터쉬트(DataSheet)의 활용으로 장착된 부품의 사용온도가 기준에 적합한지 확인하는 방법을 제시하고 실제 현장적용 사례를 들어 국내의 주요 지방의 최저온도와 최고온도 데이터를 활용한 방법으로서 일반적인 IC 부품의 온도 규격과 비교하여 온도시험 범위를 산정하는 방안에 대한 의견을 제시하고자 한다.

• International journal of advanced smart convergence
• /
• 제4권1호
• /
• pp.54-63
• /
• 2015

Increasing air pollution levels and the global oil crisis has become a major hindrance in the growth of our automobile sector. Traditional Internal Combustion engines running on non-renewable fuels are proving to be the major culprit for the harmful effects on environment. With few modifications and also with assistance of few additional components current small SI engines can be modified into a pneumatic engine (commonly known as Compressed Air Engines) without much technical complications where the working fluid is compressed air. The working principle is very basic as adiabatic expansion of the compressed air takes place inside the cylinder pushing the piston downwards creating enough MEP to run the crank shaft at decent RPM. With the assistance of new research and development on pneumatic engines can explore the potential of pneumatic engines as a viable option over IC engines. The paper deals with analysis on RPM variation with corresponding compressed air injection at different crank angles from TDC keeping constant injection time period. Similarly RPM variation can also be observed at different injection pressures with similar injection angle variation. A setup employing a combination of magnetic switch (reed switch), magnets and solenoid valve is used in order to injection timing control. A conclusive data is obtained after detailed analysis of RPM variation that can be employed in newly modified pneumatic engines in order to enhance the running performance. With a number of benefits offered by pneumatic engine over IC engines such as no emissions, better efficiency, low running cost, light weight accompanied by optimized injection conditions can cause a significant development in pneumatic engines without any major alteration.

• 생명과학회지
• /
• 제18권2호
• /
• pp.273-278
• /
• 2008

콜레스테롤 생합성 과정에 있어서 속도조절 단계 효소의 하나인 squalene synthase에 대한 저해물질의 탐색을 목적으로, 30종의 다양한 천연물을 대상으로 squalene synthase에 대해 저해효과를 검토한 결과 녹차추출물에서 비교적 저해활성이 높고 재현성이 있게 저해효과를 나타내는 것으로 확인되었다. 녹차에 함유되어 있는 squalene synaase에 대한 저해물질의 용매추출성을 검토한 결과 ethyl acetate와 n-butanol 층에 저해물질이 많이 함유되어 있는 것으로 확인되었으며 저해물질은 녹차의 polyphenol 화합물인 catechin에 의한 것으로 추정되었다. Catechin 표준용액의 각 농도에 따른 squalene synthase 저해작용을 살펴 본 결과, (-)-epigallocatechin gallate, (-)-epicatechin gallate, (-)-epigauocatechin, (-)-epicatechin, (+)-catechin의 순으로 저해활성이 강한 것으로 나타났으며 가장 강한 저해활성을 나타내는 (-)-epigallocatechin gallate의 $IC_{50}$값은 $90{\mu}M$이었다.

• 한국버섯학회지
• /
• 제14권4호
• /
• pp.232-236
• /
• 2016

본 연구는 국내산과 중국산 복령의 원산지를 판별하기 위한 방법을 모색하고자 진행되었다. 분석 결과 일반 성분은 산소 45.32-48.07%, 탄소 38.90-40.12%, 수소 6.05-6.78% 및 질소 0.16-0.23%로 국내산과 중국산 복령에서 유사한 값을 가짐을 확인하였으며, DPPH 자유라디칼 소거능 확인을 통한 항산화 활성 또한 유의적인 차이는 없었으나, ED-XRF (X-선 형광 분석기)를 이용한 무기원소 분석에서 국내산과 중국산 복령간에 차이점을 확인하였다. 중국산 복령의 경우 칼륨(K), 철(Fe)이 각각 $47.60{\pm}8.78%$와 $14.5{\pm}3.86%$로 확인되었으며 이는 국내산 복령($33.14{\pm}17.27%$, $9.13{\pm}4.83%$)보다 높은 수치를 보였다. 전반적인 실험 결과 ED-XRF 분석을 통한 무기원소의 차이를 확인할 수 있었으므로 향후 복령의 원산지 판별에 이를 이용할 수 있을 것이라 생각된다.

• 한국미생물·생명공학회지
• /
• 제45권4호
• /
• pp.311-315
• /
• 2017

화살나무 가지로부터 activity based fractionation에 의해 ${\alpha}$-glucosidase 저해 활성 물질 compound 1-4을 분리하였고, $^1H$ NMR, $^{13}C$ NMR, $^1H-^1H$ COSY와 HMBC 등의 spectral data에 의해 구조를 결정하였다. Compound 1-4는 모두 flavonol 물질로 ${\alpha}$-glucosidase에 대해 $IC_{50}$ 값이 각각 25.3, 17.1, 47.3과 $35.1{\mu}M$로 positive control로 사용한 acarbose 보다 강한 활성을 나타내었다. 화살나무의 혈당 저하 기능의 유효성분으로 처음 동정된 Compound 1-4는 ${\alpha}$-glucosidase에만 특이적 활성을 갖는 물질로 당뇨병 치료제로의 개발 가능성이 높은 물질로 사료된다.

• Archives of Pharmacal Research
• /
• 제24권1호
• /
• pp.44-50
• /
• 2001

To search for cytotoxic components from Allium victoriallis , MTT assays on each extract and an isolated component, gitogenin 3-O-lycotetroside, were performed against cancer cell lines. Cytotoxicities of most extract were shown to be comparatively weak, though $IC_50$ values of $CHCl_3$fraction was found to be <31.3-368.4 $\mu\textrm{g}/ml$. From the incubated methanol extract at $36^{\circ}C, eleven kinds of organosulfuric flavours were predictable by CG-MS performance. The most abundant peak was revealed to be 2-vinyl-4H-1,3-dithiin(1) by its mass spectrum. Further, this extract showed significant cytotoxicities toward cancer cell lies. Silica gel column chromatography of the n-butanol fraction led to the isolation of gitogenin 3-O-lycotetroside (3) along with astragalin (4) and kaempferol 3, 4'-di-O-$\beta$-D-glycoside (5). This steroidal saponin exhibited significant cytotoxic activities ($IC_50$, 6.51-36.5 $\mu\textrm{g}/ml$) over several cancer cell lines. When compound 3 was incubated for 24 h with human intestinal bacteria, a major metabolite was produced and then isolated by silica gel column chromatography. By examining parent and prominent ion peak in FAB-MS spectrum of the metabolite, the structure was speculated not to be any of prosapogenins of 3, suggesting that spiroketal ring were labile to the bacterial reaction. These suggest that disulfides produced secondarily are the antitumor principles.

• 생약학회지
• /
• 제44권1호
• /
• pp.10-15
• /
• 2013

This study was carried to establish a simple isolation and purification method of ginsenoside $F_1$ from leaves of Panax ginseng and was to evaluate the inhibitory effect of purified ginsenoside $F_1$ on the activities of elastase and tyrosinase. The content of ginsenoside $F_1$ was 90-fold higher in leaves than in root of ginseng. Ginsenoside $F_1$ was isolated from EtOAc fraction between EtOAc and alkalized water of 80% EtOH extract after remove of hydrophobic components. The 50% inhibitory concentration ($IC_{50}$) of ginsenoside $F_1$ on elastase activity and tyrosinase activity was 1.07 mM and 1.81 mM, respectively. Especially, inhibitory effect of ginsenoside $F_1$ on tyrosinase activity was higher than that of arbutin ($IC_{50}$; 2.20 mM). These results indicate that ginsenoside $F_1$ have a potential for industrial cosmetic materials.

• Parasites, Hosts and Diseases
• /
• 제53권1호
• /
• pp.21-27
• /
• 2015

Plants used for traditional medicine contain a wide range of substances that can be used to treat various diseases such as infectious diseases. The present study was designed to evaluate the antileishmanial effects of the essential oil and methanolic extract of Myrtus communis against Leishmania tropica on an in vitro model. Antileishmanial effects of essential oil and methanolic extract of M. communis on promastigote forms and their cytotoxic activities against J774 cells were evaluated using MTT assay for 72 hr. In addition, their leishmanicidal activity against amastigote forms was determined in a macrophage model, for 72 hr. Findings showed that the main components of essential oil were ${\alpha}$-pinene (24.7%), 1,8-cineole (19.6%), and linalool (12.6%). Findings demonstrated that M. communis, particularly its essential oil, significantly (P<0.05) inhibited the growth rate of promastigote and amastigote forms of L. tropica based on a dose-dependent response. The $IC_{50}$ values for essential oil and methanolic extract was 8.4 and $28.9{\mu}g/ml$ against promastigotes, respectively. These values were 11.6 and $40.8{\mu}g/ml$ against amastigote forms, respectively. Glucantime as control drug also revealed $IC_{50}$ values of 88.3 and $44.6{\mu}g/ml$ for promastigotes and amastigotes of L. tropica, respectively. The in vitro assay demonstrated no significant cytotoxicity in J774 cells. However, essential oil indicated a more cytotoxic effect as compared with the methanolic extract of M. communis. The findings of the present study demonstrated that M. communis might be a natural source for production of a new leishmanicidal agent.