• Natural Product Sciences
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• 제21권4호
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• pp.255-260
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• 2015

Two new thiodiketopiperazines (TDKPs), designated graphiumins I (1) and J (2), were isolated from the culture broth of the marine-derived fungus Graphium sp. OPMF00224 by solvent extraction, silica gel column chromatography, and HPLC. Their absolute structures were elucidated by spectroscopic analyses (1D and 2D NMR data, ROESY correlations, and CD data) and chemical methods. They were found to be structurally rare TDKPs with a phenylalanine-derived indolin substructure. Compounds 1 and 2 inhibited yellow pigment production by methicillin-resistant Staphylococcus aureus (MRSA) with $IC_{50}$ values of 63.5 and $76.5{\mu}g/ml$, respectively, without inhibiting its growth, even at $250{\mu}g/ml$.

• 한국안전학회지
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• 제11권1호
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• pp.11-15
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• 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.

• 전자통신동향분석
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• 제36권6호
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• pp.78-87
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• 2021

Information technology (IT) has been applied to various fields, and currently, IT devices and systems are used in very important areas, such as aviation, industry, and national defense. Such devices and systems are subject to various types of malicious attacks, which can be software or hardware based. Compared to software-based attacks, hardware-based attacks are known to be much more difficult to detect. A hardware Trojan horse is a representative example of hardware-based attacks. A hardware Trojan horse attack inserts a circuit into an IC chip. The inserted circuit performs malicious actions, such as causing a system malfunction or leaking important information. This has increased the potential for attack in the current supply chain environment, which is jointly developed by various companies. In this paper, we discuss the future direction of research by introducing attack cases, the characteristics of hardware Trojan horses, and countermeasure trends.

• Natural Product Sciences
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• 제29권1호
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• pp.17-23
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• 2023

A phytochemical investigation of the fruits extract of Melia toosendan afforded the isolation of two new nor-neolignans, meliasendanins E (1) and F (2), as well as twelve known compounds (3 - 14) using various separation technique such as Diaion HP20, silica, RP-18 gel column chromatography and semi-preparative HPLC. Their chemical structures were elucidated by extensive NMR spectroscopic data including 2D-NMR, and HR-ESI-MS as well as ECD data. Among the twelve known compounds, the absolute structures of 3 - 6 were determined first, and given the trivial names as meliasendanins G-J (3 - 6). Based on the evaluation of anti-inflammatory activity, compounds 7 - 8 exhibited inhibitory effects on LPS-induced nitric oxide production in RAW 264.7 macrophages with IC₅₀ values of 34.6 and 39.5 µM, respectively.

• 대한미생물학회지
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• 제20권1호
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• pp.115-125
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• 1985

Hemorrhagic fever with renal syndrome (HFRS) is a debilitating disease of humans caused by Hantaan virus (HV), the prototype member of a newly proposed genus of Bunyaviridae. Studies of HV pathogenesis have been limited by the absence of a well defined model for a virus-induced disease state. In an attempt to devise a model for HV pathogenesis in laboratory rodents, newborn outbred suckling ICR mice were shown to be uniformly susceptible to lethal infection with non- mouse adapted HV by intracerebral (IC), intraperitoneal (IP), intramuscular (IM), and subcutaneous (SC) inoculation routes. Clinical coures, mean time to death, and fatal outcome were age-dependent. With an inoculum of 10 $LD_{50}$, mortality was 100% in mice infected within 72h of birth, but declined to 50% by 7 days. By 2-2.5 weeks, animals developed complete resistance to clinical disease. Virus was consistently detected in serum by day 6 post-infection in IC- and IP- inoculated animals, and reached peak levels of $10^5\;PFU/ml$ by day 8 Mice infected IM and SC showed delays in onset of viremia, but achieved similar titers. Immunofluorescent antibody appeared by 17-18 days, and neutralizing antibody by 15 days, in all experimental groups. Two of 8 inbred mouse strains were identified as resistant to clinical disease : SJL/J and A/J. Manipulation of this model will allow investigation of natural rodent pathogenesis with HV, as well as offer insight into disease mechanisms and therapy of HFRS.

• 대한기계학회논문집A
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• 제25권5호
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• pp.765-771
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• 2001

Elastic-plastic fracture toughness JIC can be used a s an effective design criterion in elastic-plastic fracture mechanics. Among the JIC test methods approved by ASTM, unloading compliance method was used in this study. In order to examine the relationship between fracture behavior of JIC test and AE signals, the post processing of AE signals has been carried out by Short Time Fourier Transform(STFT), one of the time-frequency analysis methods. The objective of this study is to evaluate the application of characterization of AE signals for unloading compliance method of JIC test. As a result of time-frequency analysis, we could extract the AE from the raw signal and analyze the frequencies in AE signal at the same time. AE signal generated by elastic-plastic fracture of material has some different aspects at elastic and plastic ranges, or the first portion of crack growth by fracture. First of all, increased energy recorded and detected by using AE count method increase rapidly from the start of ductile fracture. The variation of main frequency range with time-frequency analysis method could be confirmed. We could know fracture behavior of interior material by examination AE characteristics generated in real-time when elastic-plastic fracture occurred in material under loading.

• 대한전자공학회논문지SD
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• 제49권5호
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• pp.16-21
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• 2012

본 논문에서는 CMOS 기반의 BJT 제작에 있어서 일반적인 BJT 구조에 비해 정합특성이 우수한 새로운 BJT 구조를 제안하고, 특성을 비교 분석하였다. 새로운 정합 구조가 기존의 정합 구조에 비해 콜렉터 전류 밀도 $J_C$는 0.361% 감소하였고, 전류이득 ${\beta}$는 0.166% 증가하여 큰 차이가 보이지 않았지만, 소자 면적이 10% 감소했으며, 콜렉터 전류($A_{Ic}$)와 전류이득($A_{\beta}$)의 정합 특성이 각각 45.74%, 38.73% 향상되었다. 이와 같이 정합특성이 개선된 주 이유는 쌍으로 형성된 BJT 소자들의 에미터 간의 거리가 감소한 것이라고 생각되며, deep n-well 저항의 표준편차 값이 다른 저항들에 비해 큰 것으로부터 간접적으로 증명이 된다고 여겨진다.

• 대한기계학회논문집A
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• 제22권3호
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• pp.611-623
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• 1998

The delamination fracture of multidirectional carbon-fiber/epoxy laminates under the Mode I condition has been studied using the modified beam analysis for a fracture mechanics approach. It was found that the variation of fracture energy $G_IC$ with increasing length of the propagating crack exhibited a minimum for the pure interlaminar fracture and a maximum for the intraply fracture,i.e. a rising "R-curve", which was strongly affected by the degree of fiber bridging and crack-tip splitting arising in the global delamination. The maximum $G_IC$ value was significantly dependent on such types of delamination as no crack jumping, crack jumping into the adjacent ply and edge-delamination. It was shown also that the value of "effective flexural modulus" estimated from the modified beam analysis increased much with the development of fiber bridging behind the crack tip.ehind the crack tip.

• Natural Product Sciences
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• 제20권1호
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• pp.7-12
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• 2014

Twelve triterpenoids (1 - 12) were isolated from $CHCl_3$-soluble fraction of fruiting bodies of Ganoderma lucidum. Extensive spectroscopic and chemical studies established the structures of these compounds as butyl lucidenate P (1), butyl lucidenate $E_2$ (2), butyl lucidenate $D_2$ (3), butyl lucidenate Q (4), ganoderiol F (5), methyl ganoderate H (6), methyl ganoderate J (7), lucidumol B (8), ganodermanondiol (9), methyl lucidenate N (10), methyl lucidenate A (11) and butyl lucidenate N (12). All of the compounds were examined for their cytotoxic activity against HL-60, HeLa, and MCF-7 cancer cell lines. Among them, compounds 4 and 8 showed cytotoxic activity with $IC_{50}$ values of 6.6 and 1.6 ${\mu}M$ against HL-60, respectively. In addition, compound 8 also showed cytotoxic activity with $IC_{50}$ values of 2.0 ${\mu}M$ against HeLa cancer cell line, other compounds were moderate or inactive.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(1)
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• pp.33-37
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• 2004

Slotless Permanent magnet Brushless DC Motor(PM BLDC) with the characteristics of high speed and high power density has been more widely used in industrial and automatic machine. Generally, PM BLDC meter is necessary that the three Hall-ICs evenly be distributed around the stator circumference in case of the 3 phase motor. The Hall-ICs are set up in this motor to detect the main flux from the rotor. therefore the output signal from Hall-ICs is used to drive a power transistor to control the stator winding current. However, instead of using three Hall-ICs, if only we used one Hall-IC, we estimate information of the others phase in sequence through a revolving rotor. This paper identified the characteristics and performance by using one Hall-IC for the 3 phase PM BLDC whose six stator and two rotor designed.