• Magazine of the Korea Concrete Institute
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• v.10 no.3
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• pp.197-208
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• 1998

최근들어 손상된 실구조물의 보강공법들이 적용,발전되어왔다. 가장 보편적으로 사용된공법이 강판과 탄소섬유를 이용한 공법이지만, 이론적인 배경과 적용기술이 아직은 정립되어었지 않은 상태이다. 강판보강의 경우 단부에서의 응력집중이 보강 효과를 결정짓는 가장 중요한 변수이므로, 본 연구에서는 이러한 응력집중을 완화하기 위하여 단부에 보강판과확대판을 부착하여 실험을 하였고, 탄소섬유 보강 실험에서는 다층 시공시 보강량을 조절하여 실험하였다. 실험 결과는 하중-처짐, 항복하중, 최대하중, 보강재의 전단응력의 분포와 보강재의 파괴양상을 분류하여 정리하였다. 실험을 통하여 강판 보강의 경우 본 연구에서 제안된 단부에서의 보강방법이 보강효과가 향상된 것을 확인하였고 탄소섬유 보강시에는 탄소섬유의 보강량을 조절함으로써 경제적인 설계와 시공이 가능한 것으로 나타났다.

• Elastomers and Composites
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• v.36 no.4
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• pp.246-254
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• 2001

In this work, the stabilization of chlorosulfonated polyethylene (CSM) rubber emulsion with surfactants, i.e., nonionic (Span 60) or anionic (Sodium laurylsulfate, SLS) surfactants, was investigated. The phase inversion emulsification by interfacial chemical characteristics was used to emulsify the CSM rubber. As a result, the emulsion phase separation was observed in the case of any single surfactant. However, there was no phase separation in the mixture of Span 60 and SLS in the context of emulsion droplet size tests and rheological behaviors. The droplet size decreases by increasing the surfactant mixture, resulting in increasing the viscosity. The viscosity and shear stress determined from shear rate show a shear thinning and yield behaviors. It was then found that the emulsion stabilization can be improved using the phase inversion emulsification method and surfactant mixture.

• Korean Journal of Food Science and Technology
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• v.27 no.2
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• pp.246-250
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• 1995

Konjac(Amorphophallus konjac) glucomannan dispersions were prepared from konjac flour, pretreated konjac flour and purified glucomannan. Konjac glucomannan dispersions showed non-Newtonian fluid behavior without yield stress and higher shear stress at fixed shear rate than the dispersions of gum xanthan, gum carrageenan and sodium alginate. While temperature increased, shear stress at fixed shear rate of konjac glucomannan dispersion steadily decreased. The apparent viscosity of konjac glucomannan dispersion was in its maximum at pH 7, whereas decreased on the outskirts of pH 7. The change in apparent viscosity was not found up to 1% sodium chloride addition in case of konjac glucomannan dispersion. However, the apparent viscosity of konjac glucomannan dispersion decreased up to sugar addition of 10%, afterwards increased.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.451-456
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• 2002

This paper describes the properties of Temperature-Viscosity characteristics of hydrous and anhydrous ER fluids containing starch and titanium particle in silicone oil. ER effects arise from electrostatic forces between the starch particles and titanium particles dispersed in the electrically insulating silicone oil induced when electric field is applied. ER fluids under electric field have been found to provide resonable estimates of ER fluid viscosity variation characteristics. Yield shear stress of the ER fluids were measured on the couette cell type rheometer as a function of electric fields. The outer cup is connected to positive electrode(+) and bob becomes ground(-). The electric field is applied by high voltage DC power supply. In this experiment shear rates were increased from 0 to 200/equation omitted/ in 2 minutes.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.2 no.3
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• pp.48-55
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• 2003

This study investigates the effect of temperature and electric field strength on the Bingham characteristics of Electro-Rheological(ER) fluids which change their Yield shear stress and viscosity by temperature and electric field strength. It is found that under constant temperature the Yield sheal stress and viscosity of ER fluids proportionally increase with the applied electric field strength, and under constant applied electric field strength the Yield shear stress and viscosity of ER fluids decrease with the increasing temperature. These results are considered to be applied to the fluid and pneumatic power industry.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.3 no.1
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• pp.84-89
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• 2004

This study is a basic one for application of ER Fluid to fluid power systems. By mixing silicone oil with zeolite particles, four kinds of ER fluids were made, in which the weight ratio of zeolite particles are different. We examined how the Yield shear stress and Bingham characteristics of the ER fluids are effected by varying electric field intensity. We designed and constructed a disk type power transmission clutch in which ER fluid fills and this ER fluid transmits the power of drive shaft to the driven shaft. With this equipment, the revolution transmission ratio from the chive shaft to the driven shaft by varying electric field density of the ER fluid was examined.

• Journal of the Korean Geotechnical Society
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• v.19 no.5
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• pp.223-232
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• 2003

In this study, a constitutive model called the disturbed state concept (DSC) was modified to be applied to the interface shear stress-displacement relationship between geosynthetics. The DSC model is comprised of two reference states, namely the relative intact (RI) and the fully adjusted (FA) state, and one function, namely the disturbance function. This model is a unified approach and can allow for various models as an RI state such as elastic-perfectly plastic model, hierarchical model, and so on. In addition, by using this model, the elastic and plastic displacements can be considered simultaneously. Comparisons between the measured data and predicted results through the parameters determined from four sets of large direct shear tests showed good agreements with each other, especially for the smooth geomembrane-involved interface. Although there are slight differences at peak shear strength for textured geomembrane-involved interface, this model can still be useful to predict the position of displacement at peak strength and the large displacement (or residual) shear strength.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.6
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• pp.26-37
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• 2019

This paper aims to investigate the seismic characteristics of strip-type damping devices possessing optimized shapes for the moment-resisting mechanism throughout analytical and experimental studies. Predicting equations for initial stiffness and yielding strength were introduced and compared with analytical results obtained from finite element analyses (FEAs) using commercial FEA program ABAQUS. In order for establishing predicting equations, two idealized processes were considered and both predicting equations showed that they could provide enough approximations for seismic applications in building structures. Throughout experimental studies, it was noted that structural uncertainties on mild steels, connection details and structural types linking damping devices with building structures could interrupt predicting structural behavior of the devices. Also, it was observed that shear stress concentrations should be considered if shear yielding type devices are applied into building structures. Nevertheless, it was shown that structural conservatism can be established using the predicting equations and seismic applications of the damping devices can enhance the seismic performance of building structures efficiently in the viewpoint that they have high resistance to low-cycle fatigue failures.

• Journal of the Korean Geotechnical Society
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• v.27 no.10
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• pp.81-92
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• 2011

The rheological properties of Wyoming bentonites are strongly influenced by the size of particles, cation exchangeable capacity, arrangement and morphology of clay mineral. This paper presents the results of rheological investigations on the Wyoming bentonites aqueous dispersions: two types of particle flocculation were considered. For the Wyoming bentonite, 0g/L and 30g/L NaCl equivalent salinity were added in fresh and salt water to examine the rheological behavior. This paper examined the general rheological characteristics, compatibility of rheological models and correlation between soil structure and change in rheological properties of Wyoming bentonite caused by increasing salinity. From flow curves of bentonites hydrated with fresh water and salt water, the observed general flow behavior is very close to shear thinning with yield stress (or ideal Bingham fluid with yield stress and plastic viscosity). However, the change of shear stress at the same shear rate is clear, particularly for lower shear rate. Well-known rheological models are used to fit the data. There is a good agreement between rheological model and data: Carreau, Herschel-Bulkley and power-law for S=0g/L and bilinear, Herschel-Bulkley and power-law for S=30g/L. It may be due to the fact that the internal structural bonding (strong modification of particle-particle interactions from edge-to-edge and/or edge-to-face to face-to-face) in soil matrix is affected from the evolution of rheological properties with different salinities.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.1
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• pp.43-52
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• 2003

The present study is to investigate the ultimate behavior and limit state design of 2-I) R/C structures, with the changing of crack direction, and the yielding of the reinforcing steel bars, and Is to introduce an algorithm for the limit state design and analysis of 2-D R/C structures, directly from the finite element model. For the design of reinforcement in concrete the limit state design equation is incorporated into finite element algorithm to be based on the pointwise elemental ultimate behavior. It is also introduced a simplified nonlinear analysis algorithm for stress-strain relationship of R/C plane stress problem considering the cracking and its rotation in concrete and the yielding of the reinforcing steel bar. The algorithm is incorporated into the nonlinear finite element analysis. The analysis model is compared with the experimental model of R/C shear wall. In a simple design example for a shear wall, the required reinforcement ratios in each finite element is obtained from the limit state design equations.