• Steel and Composite Structures
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• 제37권1호
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• pp.75-90
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• 2020

This paper introduces a new composite joint, which is the composite CFST beam- concrete column joint, and it is more convenient for transportation and erection than conventionally welded joints. The main components of this joint include steel H-beams welded with CFST beams, reinforced concrete columns, and reinforced concrete slabs. The steel H-beams and CFST beams are connected with a concrete slab using shear connectors to ensure composite action between them. An experimental investigation was conducted to evaluate the proposed composite joint performance. A three-dimensional (3D) finite element (FE) model was developed and analyzed for this joint using the ABAQUS/explicit. The FE model accuracy was validated by comparing its results with the relevant test results. Additionally, the parameters that consisted of the steel box beam thickness, concrete compressive strength, steel yield strength, and reinforcement ratio in the concrete slab were considered to investigate their influence on the proposed joint performance.

• Steel and Composite Structures
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• 제16권1호
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• pp.97-114
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• 2014

This paper deals with a study on ultimate strength behaviour of eccentrically loaded CFT columns with and without shear connectors. Thirty specimens are subjected to experimental investigation under eccentric loading condition. P-M curves are generated for all the test specimens and critical eccentricities are evaluated. Three different D/t ratios such as 21, 25 and 29 and L/D ratios varying from 5 to 20 are considered as experimental parameters. Six specimens of bare steel tubes as reference specimens, twelve specimens of CFT columns without shear connectors and twelve specimens of CFT columns with shear connectors, in total thirty specimens are tested. The P-M values at the ultimate failure load of experimental study are found to be well agreed with the results of the proposed P-M interaction model. The load-deflection and load-strain behaviour of the experimental column specimens are presented. The behaviour of the CFT columns with and without shear connectors is compared. Experimental results indicate that the percentage increase in load carrying capacity of CFT columns with shear connectors compared to the ordinary CFT columns is found to be insignificant with a value ranging from 6% to 13%. However, the ductility factor of columns with shear connectors exhibit higher values than that of the CFT columns without shear connectors. This paper presents the proposed P-M interaction model and experimental results under varying parameters such as D/t and L/D ratios.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 토목섬유 특별세미나
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• pp.9-16
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• 2000

Applicability of the cross shaped drain in a soft clay ground is examined using the laboratory discharge capacity test, column consolidation test and 3-D numerical flow analysis. The equivalent diameter of the tested drains is back-calculated from the laboratory experiment and compared with those calculated from the formula suggested in the literature. The effective range of the cross shaped drain about the discharge capacity and coefficient of permeability is analyzed. The results of numerical analysis show that the cross shaped drain which has a cross-sectional area twice of the band shaped drain can reduce the consolidation time by 30% from that for the band shaped drain in a soft clay ground that K is over 1${\times}$10$\^$-7/cm/sec

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.1-5
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• 2008

An experimental study was performed to develop the rotational fuel injection system of the micro turbojet engine. In this system, fuel is sprayed by centrifugal forces of engine shaft. The test rig was designed and manufactured to get droplet information on combustion space. This experimental apparatus consist of a high speed rotational device(Air-Spindle), fuel feeder, rotational fuel injector and acrylic case. To understand spray characteristics, spray droplet size, velocity and distribution were measured by PDPA (Phase Doppler Particle Analyzer) and spray was visualized by using Nd-Yag laser-based flash photography. From the test results, the length of liquid column from injection orifice is controlled by the rotational speeds and Sauter Mean Diameter(SMD) is decreased with rotational speed. Also, Sauter Mean Diameter is increased as increasing mass flow rate at same rotational speeds.

• 한국지반공학회논문집
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• 제35권7호
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• pp.41-50
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• 2019

국내 고준위폐기물처분장 공학적방벽(EBS)의 일부가 되는 완충재로 경주 벤토나이트가 우선적으로 고려되고 있다. 압축벤토나이트는 지하수침투로 인한 팽윤압과 처분용기에서 발산되는 열응력을 경험한다. 따라서 EBS의 성능평가를 위해서 역학적 물성의 산정이 중요하다. 본 논문은 탄성파를 이용하여 경주 압축벤토나이트의 변형특성 측정을 목표로 하였다. 두 개의 $1.59g/cm^3$와 $1.75g/cm^3$의 건조밀도를 가지는 압축벤토나이트 시편을 제작하였고, 자유단-자유단 공진주시험을 수행하여 구속압축파속도와 비구속압축파속도를 측정하였다. 측정된 압축파속도를 이용하여 미소변형에서의 탄성계수($E_{max}$), 구속탄성계수($M_{max}$), 감쇠비($D_{min}$), 포아송비를 측정하였다. 그 결과로 경주 압축벤토나이트의 변형특성을 산정 제시하여 선행연구 결과들과 비교 분석하였다.

• 생약학회지
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• 제41권4호
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• pp.313-318
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• 2010

Guibi-tang, a traditional herbal medicine, is used for anti-oxidant, anti-osteoporosis, hemostasis and gastroprotection. To develop an analysis method of simultaneous determination of six compounds, swertisin, decursinol, glycyrrhizin, 6-gingerol, costunolide and decursin in Guibi-tang, a high performance liquid chromatography was used with diode array detector. Six bioactive components were separated on a SHISEIDO $C_{18}$ column ($5\;{\mu}m$, 4.6 mm I.D.${\times}$250 mm) with column temperature $30^{\circ}C$. The gradient elution was composed of water with 0.1% trifluoroacetic acid (TFA) and acetonitrile. UV wavelength was set at 230 nm, 254 nm and 330 nm, respectively. Calibration curve showed good linear regression ($R^2$ > 0.9999). The limits of detection (LOD) and the limits of quantification (LOQ) ranged in 0.03 - 0.23 ${\mu}g/ml$ and 0.08 - $0.70\;{\mu}g/ml$, respectively. The RSD values of intra- and inter-day test were in the range of 0.03 ~ 0.96% and 0.01 ~ 1.46%, respectively. The evaluated results of accuracy test were varied from 92.28% ~ 105.14% with RSD < 1.60%. In conclusion, this developed simultaneous determination method was accuracy and sensitive to the quality evaluation of Guibi-tang.

• Architectural research
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• 제17권1호
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• pp.41-48
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• 2015

Early investigations focused mainly on manipulating the confinement effect to develop a reinforced concrete column with lateral hoops. Based on this legacy model, Li's model incorporated the additional confinement effect of a steel jacket. However, recent experiments on plain concrete cylinders with steel jackets revealed relatively large discrepancies in the estimates of strength enhancement and the post-peak behavior. Here, we describe a modified constitutive law for confined concrete with an unbonded external steel jacket in terms of three regions for the loading stage. We used a two-phase heterogeneous concrete model to simulate the uniaxial compression test of a $150mm{\times}300mm$ concrete cylinder with three thicknesses of steel jackets: 1.0 mm, 1.5 mm, and 2.0 mm. The proposed constitutive model was verified by a series of finite element analyses using a finite element program. The damaged plasticity model and extended Drucker-Prager model were applied and compared in terms of the level of pressure sensitivity for confinement in 3D. The proposed model yielded results that were in close agreement with the experimental results.

• 생명과학회지
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• 제19권6호
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• pp.698-704
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• 2009

두충 (Eucommia ulmoides Oliver)으로부터 항고혈압 활성을 가진 유효물질을 분리하였으며, 두충의 잎, 껍질 및 줄기를 건조한 것과, 건조한 후 붉은 것에 대하여 ACE (angiotensin converting enzyme) 저해활성을 실험하였다. 두충으로부터 분리 한 유효물질은 pinoresinol-4,4'-di-O-${\beta}$-D-glucoside (PG)와 dehydrodiconiferyl alcohol 4,${\gamma}$'-di-O-${\beta}$-D-glucoside (DAG)였으며, 이들은 각각 껍질과 잎에 많이 함유되 어 있었다. 즉 pinoresinol-4,4'-di-O-${\beta}$-D-glucoside (PG)는 자연 건조한 껍질에 135.12 mg%, 붉은 껍질에 163.94 mg%로 가장 많이 함유되어 있었으며, dehydrodiconiferyl alcohol 4,${\gamma}$'-di-O-${\beta}$-D-glucoside (DAG)는 자연 건조한 잎에 117.43 mg%, 붉은 잎에 133.93 mg%로 비교적 많이 함유되어 있었다. ACE 억제활성은 볶은 잎, 말린 껍질 및 볶은 껍질을 10 mg/ml씩 처리하였을 때, 각각 77.49, 75.52 및 75.36%의 억제효과를 나타내었으며, 두충으로부터 분리한 화합물인 pinoresinol-4,4'-di-O-${\beta}$ -D-glucoside (PG)와 dehydrodiconiferyl alcohol 4,${\gamma}$'-di-O-${\beta}$-D-glucoside (DAC)를 1${\sim}$10 mg/ml 처리하였을 때에 는 67.1${\sim}$85.25% 의 억제활성을 나타내었으며, $IC_{50}$값은 각각 0.6${\pm}$0.2, 0.5${\pm}$0.2 mg/ml 였다. 이것은 PG와 DAG가 두충에서 분리한 천연물임을 감안하면 매우 높은 활성을 가지고 있다고 할 수 있다.

• Archives of Pharmacal Research
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• 제26권4호
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• pp.279-285
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• 2003

In our ongoing study to identity antioxidants from natural sources, the antioxidant activity of Nelumbo nucifera stamens was evaluated for their potential to scavenge stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radicals, inhibit total reactive oxygen species (ROS) generation, in kidney homogenates using 2 ,7 -dichlorodihydrofluorescein diacetate (DCHF-DA), and scavenge authentic peroxynitrites ($ONOO^-$). A methanol (MeOH) extract of the stamens of N. nucifera showed strong antioxidant activity in the $ONOO^-$system, and marginal activity in the DPPH and total ROS systems, so were therefore fractionated with several organic solvents, such as dichloromethane ($CH_2 Cl_2$), ethyl acetate (EtOAc) and n-butanol (n-BuOH). The EtOAc soluble fraction, which exhibited strong antioxidant activity in all the model systems tested, was further purified by repeated silica gel and Sephadex LH-20 column chromatographies. Seven known flavonoids [kaempferol (1), kaempferol 3-Ο-$\beta$-D-glucuronopyranosyl methylester (2), kaempferol 3-Ο-$\beta$-D-glucopyranoside (3), kaempferol 3-Ο-$\beta$-D-galactopyranoside (4), myricetin 3 ,5 -dimethylether 3-Ο-$\beta$-D-glucopyranoside (5), kaempferol 3-Ο-$\alpha$-L-rhamnopyranosyl-(1$\rightarrow$6)-$\beta$-D-glucopyranoside (6) and kaempferol 3-Ο-$\beta$-D-glucuronopyranoside (7)], along with $\beta$-sitosterol glucopyranoside (8), were isolated. Compound 1 possessed good activities in all the model systems tested. Compounds 2 and 7 showed scavenging activities in the DPPH and $ONOO^-$ tests, while compounds 3 and 4 were only active in the $ONOO^-$ test. Conversely, compound 8 showed no activities in any of the model systems tested.

• Journal of the Korean Wood Science and Technology
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• 제33권5호통권133호
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• pp.86-91
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• 2005

Six compounds were isolated from the EtOAc and $Et_2O$ fractions of the bark of Rhus chinensis by repeated column chromatography with $SiO_2$ and Sephadex LH-20. The structures were determined by instrumental analysis using MS and NMR spectrophotometer as: gallic acid (1), methyl gallate (2), 6, 7-dimethoxycoumarin (3), orcinol-${\beta}$-D-glucoside (4), scopoletin (5), semialactone (6). Among these compounds, 6,7-dimethoxycoumarin (3) was isolated from this plant for the first time. To measure the antioxidant activity, the DPPH radical scavenging activity test was performed. Gallic acid (1) showed the strongest activity, while orcinol-${\beta}$-D-glucoside (4), semialactone (5) and scopoletin (6) had the low activities.