• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.12
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• pp.956-963
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• 2002

In a recent construction industry, cable supported structures such as a cable-stayed bridge or space stadium have been increasingly constructed according to rapidly upgrade their related technologies. Generally stay cables as a critical member need to be rearranged for being satisfied with design tension forces. In this purpose, a vibration method has been applied to estimate the tension forces exerted on existing stay cables. In this study, cable vibration tests were tarried out to evaluate the cable tension forces comparing with theoretical and practical formulas. Using the measured frequencies obtained from free vibration and Impulsive tests, an accuracy of the estimated tension forces is confirmed according to use the first single mode only or higher multiple modes.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.2
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• pp.200-206
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• 2013

The paper was investigated on the mooring forces(or tension) and motion response characteristics for a 8-point mooring floating dock in regular waves using a commercial code(AQWA). To achieve the aim of the research, a numerical simulation was adapted on an inner port environment condition, which the water depth is 10 meters, significant wave amplitude(1.05 m). wave period(3.85 sec), wind speed(20.21 m/s), wind and current direction ($90^{\circ}$), incident waves(${\chi}=180^{\circ}$, $135^{\circ}$ and $90^{\circ}$). The dimension of the numerical model is length(140 m), breadth(32 m), depth(14.6 m). The maximum length of a mooring line is 120m. We can expected that roll and pitch motions appeared in beam seas better than head sea. the mooring forces also indicated higher in bean seas than in head seas including wind forces.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1996.11a
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• pp.102-105
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• 1996

난지도 매립지는 매립충의 불균질성과 고온의 침출수 및 가스의 흐름이 동시에 복합적으로 일어나는 현상 때문에 수리지질학적으로 매우 복잡한 지역이다. 난지도의 수문층서단위 조사와 디스크-장력 침투계(Disc tension Infiltrometer)로 불포화대 수리 특성을 추정하였으며 가스 거동 현상을 이해하기 위해 지온을 측정하였다. 매립지 주변의 지하수위 변화를 조사하기 위해 양수정과 다중-수위관측정(Multi-Level Monitoring Well)에서 수위변화를 관측하였다. 불포화대 수리특성과 기상자료를 바탕으로 매립지로의 순침투량을 추정하였다. 이것을 근거로 총 침출수 발생량을 추정하였으며, 기저 지하수면 상부에 분포하는 포화 침출수대, 즉 부유침출수의 생성 메카니즘에 대한 연구도 수행하였다.

• Korean Journal of Soil Science and Fertilizer
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• v.13 no.4
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• pp.115-118
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• 1981

Effect of water potential of culture solution on photosynthesis, transpiration and water uptake was investigated using polyethylene glycol 6000. 1. Even at -0.5 bar of culture solution phothosynthesis was decreased by 20% within 1 hour. Plant in control showed 3.26% loss of initial water for 13 hours suggesting very sensitive in water uptake. 2. Relation between water potential of culture solution (${\psi}$) and water uptake amount (W) 2-year root was ${\psi}=-2.890/e^{2.796W}$ indicating that permanent wilting point will be greater than -2.89 bar. 3. Transpiration considerably decreased with the decrease of water potential and thus by 23.9% at -0.5 bar after 4 hours. 4. From the above results ginseng plant appears to have high root water potential at permanent wilting point and thus very week to water stress due to drought or high salt content in soils.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.1A
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• pp.1-10
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• 2012

Along with the development of coasts, islands and mountains, the demand of long-span bridges increases which, in turn, brings forth the construction of cable-supported bridges like suspension and cable-stayed bridges. There are various types of statically indeterminate structures widely applied that supported the main girder with stay cables, main cables, hanger cables with aesthetic structural appearance. As to the cable-supported bridges, the health monitoring of a bridge can be identified by measuring tension force on cable repeatedly. The tension force on cable is measured either by direct measurement of stress of cable using load cell or hydraulic jack, or by vibration method estimating tension force using cable shape and measured dynamic characteristics. In this study, a method to estimate dynamic characteristics of hanger cables by using a digital image processing is suggested. Digital images are acquired by a portable digital camcorder, which is the sensor to remotely measure dynamic responses considering convenient and economical aspects for use. A digital image correlation(DIC) technique is applied for digital image processing, and an image transform function(ITF) to correct the geometric distortion induced from the deformed images is used to estimate subpixel. And, the correction of motion of vision-based measurement system using a fixed object in an image without installing additional sensor can be enhanced the resolution of dynamic responses and modal frequencies of hanger cables.

• Journal of Korean Society of Steel Construction
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• v.20 no.5
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• pp.609-616
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• 2008

Recently, many ocean bridges that connect land to island or island to island have been constructed along with the improvement of the nation's economy. Long-span bridges can be categorized as suspension bridge, cable-stayed bridge, arch bridge and truss bridge. In this study, correction with respect to construction error can be presented on site through the monitoring of the cable tension change of real structure for four major construction stages so that construction accuracy, including the management of profiles, can be improved. A vibration method, the so-called indirect method that uses the cable's natural frequency changes from the acceleration sensor installed on the cable, is applied in measuring cable tension. In this study, the estimation formula for the effective length of cable with damper is presented by comparing and analyzing between actual measurement and analysis result for the change of the cable's effective length. By the way, it is known that the reliability of estimating cable tension by applying the former method that uses the net distance from damper to anchorage is low. Therefore, for future reference of the maintenance stage, the presented formula for estimating the effective length of cable can be used as a reference for the rational decision-making, such as the re-tensioning and replacement of cable.

• Applied Chemistry for Engineering
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• v.7 no.2
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• pp.215-220
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• 1996

Nine kinds of amphoteric surfactants were derived from 1-(2-hydroxyethyl)-2-undecyl-2-imidazoline. Their surface activities including surface tension and isoelectric points were measured in aqueous solution and critical micelle concentration(cmc) was also evaluated by the measurement of surface tension. From the measurement of surface tension, carboxylated amides revealed to be 26~40dyne/cm at $4.0{\times}10^{-4}{\sim}1.0{\times}10^{-3}mol/{\ell}$, sulfonated or sulfated imidazolines, 30~35 dyne/cm at $1.5{\times}10^{-3}{\sim}2.5{\times}10^{-3}mol/{\ell}$ and sulfonated amides, 25~33 dyne/cm at $5.8{\times}10^{-4}{\sim}8.0{\times}10^{-4}mol/{\ell}$ concentration range. It was found that isoelectric points of carboxylated amides were pH 7.2~7.9 and those of sulfonated or sulfated imidazolines and sulfonated amides were pH 4.5~5.5.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.33 no.1 s.60
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• pp.7-10
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• 2007

The interaction between polymers and surfactants was investigated by means of rheological and surface tension measurements. The polymers used in this study were acrylates/$C_{10-30}$ alkyl acrylate crosspolymer (AC) and ammonium acryloyldimethyltaurate/VP copolymer (AV). And the surfactants were PEG-40 hydrogenated castor oil (HC) and polysorbate 60 (P60). HC and P60 made the micelles intervening between AC polymers, resulting in the increase of viscosity. However, HC showed a similar behavior over the wider range of surfactant concentration than P60. Regarding of surface tensions in the same range of surfactant concentration, AC/HC solution showed the area of increasing surface tension with surfactant concentration in contrast to the AC/P60 solution showing no increasing area. It is assumed that the micelles between AC/HC were formed so cooperatively and strongly that the surfactants located at the surface originally moved to the micelles.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.10
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• pp.869-877
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• 2013

Tension force of hanger ropes has been recognized and utilized as an important parameter for health monitoring of suspension bridges. Conventional vibration method based on string theory has been utilized to estimate tension forces of relatively long hanger ropes without any problem, however it is convinced that the vibration method is not applicable for shorter hanger ropes in which the influence of flexural stiffness is not ignorable. Therefore, as an alternative of vibration method, a number of feasibility studies of system identification(SI) technique considering flexural stiffness of the hanger ropes are recently performed. In this study, the influence of support condition of the finite element model utilized for the SI method is investigated with numerical examples. The numerical examples are prepared with the specification of the Kwang-Ahn bridge hanger ropes, and it is revealed that the estimation result of the tension force can be varied from -21.6 % to +35.3 % of the exact value according to the consideration of the support condition of FE model. Therefore, it is concluded that the rotational stiffness of the support spring should be included to the list of the identification parameters of the FE model to improve the result of tension estimation.

• Journal of Drive and Control
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• v.15 no.3
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• pp.21-28
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• 2018

We propose a tension controller based on a time-delay estimation (TDE) technique for a winding machine. Firstly, we perform the necessary calculations to derive a mathematical model of the winding machine. In this sense, it is revealed that the roll radius of the winding machine is characteristically seen to be increasing or decreasing during the winding process. That being said, it is noted that the parameters of the winding machine are coupled and constantly changing during this process. Understandably then, it is noted that the model is shown to be nonlinear and time-varying. Secondly, we propose the way to apply the TDE based controller which is the so-called Time-delay Control (TDC). The TDC utilizes the time-delayed information intentionally to compensate the nonlinear and time-varying characteristics. As we have seen, the proposed controller consists of two parts: one is a TDE component, and the other is an error dynamics component which is defined by a user. In a computer simulation based on the Matlab/Simulink program, the proposed controller is compared with a conventional PID controller, which is widely used in the tension control of the winding machine. The proposed controller reduces the incidence of overshoot and steady-state error in the tension control, as compared to the conventional PID controller.