• Natural Product Sciences
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• v.8 no.1
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• pp.30-33
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• 2002

From the bioassay-directed fractionation and isolation of dichloromethane fraction of Aquilaria agallocha, four compounds having MAO inhibitory effect were isolated by repeated silica gel column chromatography. Their chemical structures were established as psoralen (1), bergapten (2), ${\alpha}-amyrin\;acetate$ (3) and 5-hydroxymethylfurfural (4) on the basis of their physicochemical and spectral data. Among these compounds, psoralen and bergapten showed high inhibitory activities in vitro against mouse brain MAO with $IC_{50}$ values $21.3\;{\mu}M\;and\;13.8\;{\mu}M$, respectively.

• Korean Journal of Pharmacognosy
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• v.47 no.2
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• pp.110-116
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• 2016

As a part of an ongoing search for natural plants with antioxidant compounds by measuring the radical scavenging effect on 1,1-diphenyl-2-picrylhydrazyl (DPPH), a total extract of the aerial parts of Bidens frondosa L. (Compositae) was found to show potent antioxidant activity. Subsequent activity-guided fractionation of the methanolic extract led to the isolation of five compounds, quercetin-3-O-${\beta}$-D-glucopyranoside (1), luteolin-7-O-${\beta}$-D-glucopyranoside (2), 7,8,3',4'-tertrahydroxy-flavanone (3), okanin-4-O-${\beta}$-D-glucopyranoside (4), and okanin (5). Their structures were elucidated by spectroscopic studies. Compounds 3-5 were isolated for the first time from this plant. Among them, compounds 3 and 5 showed the significant radical scavenging effects on DPPH, and compounds 3 and 5 also showed the potent riboflavin and xanthine originated superoxide quenching activities.

• Tunnel and Underground Space
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• v.10 no.3
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• pp.481-485
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• 2000

Vibration screening trench is very effective to reduce the ground vibration, but to construct the trench in the rock mass is not easy. Various line drilling methods have been tried to replace the trenching. In this study, UDEC was applied to simulate the screening effect of drilling holes in 2 dimensional ground model. Field measurement was conducted and compared to numerical analysis.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2000.09a
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• pp.235-239
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• 2000

Vibration screening trench is very effective to reduce the ground vibration, but to construct the trench in the rock mass is not easy. Various line drilling methods have been tried to replace the trenching. In this study, UDEC was applied to simulate the screening effect of drilling hopes in 2 dimensional ground model. Field measurement was conducted and compared to numerical analysis.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.296-299
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• 2004

단열 완충재의 하부단면에서 양각 형태가 전체 면적에서 .차지하는 비율에 따라 진동 충격음 저감량을 실험하였다. 양각 형태가 차지하는 비율이 높더라도 진동 충격음 저감량에는 큰 성능을 나타내지 않았다. 바닥 구조에서 슬래브와 상판 사이에 단열완충재를 설치할 경우 중량 충격음이 오히려 증가하는 경향을 보이고 있다. 이것은 뜬 바닥 구조에서 완충재의 설치로 인하여 슬래브와 상판간의 거동이 다르게 발생하기 때문이다.

• Journal of KSNVE
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• v.9 no.3
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• pp.472-476
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• 1999

The effect of static preload on the dynamic properties of rubber materials is rather important, especially when good isolation characteristics are required at high frequencies. However, there are still few papers for dynamic characteristics of compressed rubber components. It was demonstrated in reference (4) that for bonded rubber material of a cylindrical shape, a simplified theory equation between linear dynamic and nonlinear static behavior of rubber material was useful to predict their combined effects. This paper presents the second part of the study. It is confirmed that for the compressed rubber material, the stress can be factored into a function of frequency and a function of strain(stretch). The finite element methodis applied to analyze non-linear large deformation of rubber material and its results are compared with those of a simplified theory equation. The predicted dynamic material properties based on non-linear static finite element analyses have a good agreement of experimental results and those based on simplified theory equation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.940-948
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• 2000

Noise and vibration generated at construction sites become serious issues because of bigger construction projects and growing use of heavy equipment. Especially in downtown construction, noise and vibration easily exceed the legal standards that can suffer the most of surrounding residents. The number of complaints by the residents who are exposed to the noise increases as their consciousness grows. However, the Korean regulations for the construction noise and vibration only present the overall limits for target areas and times zones, and this make it difficult to take effective measures. Also in rural area, disputes between construction sites and residents arise, but the dispute resolution or taking measures are difficult because clear standards concerning cause-and-effect, estimation of effective levels, calculation of damages, and future precautions and examples lack. This paper describes legal standards regarding the noise and vibration and presents judging standards for the physical damages. This paper also introduces example public complaints that happened at Daewoo construction sites to describe the problems in the existing law and further to enable smooth construction progresses by emphasizing the seriousness of public complaints.

• Biomolecules & Therapeutics
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• v.6 no.4
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• pp.364-370
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• 1998

Glycosidase inhibitors from urine of Bombyx mori were isolated and their inhibitory activities on glycosidases were evaluated. Six compounds were isolated by using several ion exchange columns, and their chemical structures were identified by the physicochemical and spectral data. Compound IV, V and Ⅵ were identified as 1-deoxynojirimycin, fagomine and 1,4-dideoxy-1,4-imino-D-arabinitol, respectively. Among six compounds isolated,1-deoxynojirimycin(IV) was the most potent inhibitor on $\alpha$-glucosidase and $\beta$-galactosidase of rat intestine, and its inhibitory activities for trehalase and almond $\beta$-glucosidase were relatively weak. Compound V and Ⅵl retained a little inhibitory potency toward $\alpha$-glucosidase and $\beta$-galactosidase. Compound II and III, however, have been found to have no effect on all glycosidases tested in this study.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.09a
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• pp.191-194
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• 2002

Humic acid, fulvic acid and humin present in volcanic ash soil were isolated by IHSS standard procedure and their characteristics were analyzed as a basic study to evaluate the effect of humic substances on the behaviour of pollutants in contaminated surface soil. The volcanic ash soil contained 42.1 % of total organic matter based on the oven-dried soil, and humin, humic and fulvic acids corresponded to 67.5 %, 15.2 %, 7.6 % of TOM respectively. Structural informations of the humic fractions were obtained from their elemental analysis and IR, CPMAS C-13 NMR spectral analysis and the differences among them are discussed with their C/H, O/C ratios and distributions of carbon types in the molecules.

• Transactions on Control, Automation and Systems Engineering
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• v.4 no.4
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• pp.270-276
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• 2002

An integrated robust fault diagnosis and fault accommodation strategy for a class of linear stochastic systems subjected to unknown disturbances is presented under the assumption that only a single fault may occur at a given time. The strategy is based on the fault isolation and estimation using a bank of robust two-stage Kalman filters and introduction of the additive compensation input for cancelling out the fault's effect on the system. Each filter is set up such that the residual is decoupled from unknown disturbances and fault with the influence vector designed in the filter. Simulation results for the simplified longitudinal flight control system with parameter uncertainties, process and sensor noises demonstrate the effectiveness of the present approach.