• Journal of Drive and Control
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• v.9 no.2
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• pp.8-14
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• 2012

Electro-hydraulic spring return actuator(ESRA) is utilized for air conditioning facilities in a nuclear power plant. It features self-contained, hydraulic power that is integrally coupled to a single acting hydraulic cylinder and provides efficient and precise linear control of valves as well as return of the actuator to the de-energized position upon loss of power. In this paper, the algebraic equations of ESRA at steady-state have been developed for the analysis of static characteristics that includes control pressure and valve displacement of pressure reducing valve, flow force on flapper as well as its displacement over the entire operating range. Also, the effect of external load on piston deviation is investigated in terms of linear system analysis. The results of static characteristics show the unique feature of force balance mechanism and can be applied to the stable self-controlled mechanical system design of ESAR.

• Journal of Biomedical Engineering Research
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• v.34 no.4
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• pp.170-176
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• 2013

Lymphedema is a phenomenon in which fluid is accumulated inside tissues due to the damaged lymphatic systems. Lymphedema can cause complications such as lymphangitis, infection, changes in skin texture, fibrosis, and lymphangiosarcoma. In this study, a lymphedema screening system based on the elasticity of the skin is proposed to easily quantify lymphedema. The developed probe consists of touch sensors, a load cell and hall-effect sensors to measure the indentation force on the skin and the return time of the skin. The developed system can be used to estimate the change in the elasticity of the skin to quantify lymphedema. The system was tested with a thyroid phantom and gelatin phantoms of different concentrations and the resulting force and the time were recorded. It was found that the increase in the elasticity leads to a higher indentation force and shorter return time. This shows that the developed system can monitor the change in the skin elasticity by measuring the return time and the indentation force. The feasibility of the system in clinical applications will be evaluated in the future study.

• International Journal of Contents
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• v.18 no.3
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• pp.66-73
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• 2022

The purpose of this study is to evaluate the economic and social impact of the SEP in which the elderly participate by using the blended return on investment (BROI), economic return on investment (EROI), and social return on investment (SROI) research methods. And the sustainable conditions of SEP were confirmed. This study was conducted with one market-type SEP approved by the Korea Elderly Labor Force Development Institute (KLFDI), one preliminary social enterprise approved by Changwon City Hall, and one market-type SEP operated by a social welfare center for the elderly. As a result of the study, it was found that EROI, SROI, and BROI were the highest in the SEP of preliminary social enterprises operated by subsidies in Changwon.However, the difference between EROI and SROI was greatest in the market-type SEP operated by the elderly social welfare center. There was a big difference between economic and social impacts. The social influence of the elderly was evaluated to be higher than the income of the elderly.

• Proceedings of the ESK Conference
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• 1997.04a
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• pp.145-149
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• 1997

General joystick using spring only has a vibration when operaor drops the joystick. If it is used as input of motorized wheelchair, its system have a serious problem which operator fall into dangerous situation. Therefore, In this paper proposed non-vibration joustick which control a motorized wheelchair. Non-vibration joystick was designed which return to origin point when operator drops joystick by mistake. Reflected force of non- vibration joystick is defined as addition displacement and variation rate. And each parameter has elasticity of spring and viscosity of DC servo motor. Through simulation for virtual environment, we found two coefficient to return origin point smoothly when a disabled person drops the joystick. In case of larger elastic coefficient of spring than viscous coefficient, we confirmed the result has the equal vibration of general joystick (under-damping). In opposite case, joystick returned to origin point with excessive force. As a application of non-vibration joystick, we experimented wall-following controlling. In this trial, we corroborated that joystick follows smoothly around the corridors.

• Coupled systems mechanics
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• v.2 no.1
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• pp.111-126
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• 2013

The structural design requirements of an offshore platform subjected to wave induced forces and moments in the jacket can play a major role in the design of the offshore structures. For an economic and reliable design; good estimation of wave loadings are essential. A nonlinear response analysis of a fixed offshore platform under structural and wave loading is presented, the structure is discretized using the finite element method, wave plus current kinematics (velocity and acceleration fields) are generated using 5th order Stokes wave theory, the wave force acting on the member is calculated using Morison's equation. Hydrodynamic loading on horizontal and vertical tubular members and the dynamic response of fixed offshore structure together with the distribution of displacement, axial force and bending moment along the leg are investigated for regular and extreme conditions, where the structure should keep production capability in conditions of the 1-yr return period wave and must be able to survive the 100-yr return period storm conditions. The result of the study shows that the nonlinear response investigation is quite crucial for safe design and operation of offshore platform.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.548-551
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• 2004

Magnetostrictive actuators have seen increasing use in fine positioning system because it has many advantages such as friction free, resolution of ${\mu}{\textrm}{m}$ or nm scale, and powerful output force. Usually, the magnetic circuit of magnetostrictive actuator has components which are flux return path, coil, and magnetostrictive material. It is classified in two types according to existence of the permanent magnet. The magnetic circuit having optimal performances transfer magnetic field which is obtained by providing input current at coil without energy loss. This paper described mathematical model of magnetic circuit for getting design variables. The modeling equation is obtained from the relations between flux and reluctance of the magnetic equivalent circuit. Also, finite element analysis has been used to study the performance of magnetic circuit according to change of design variables such as existence and shape of the permanent magnet, flux return path etc. The modification of dimensions enables us to optimize magnetic circuit.

• International Journal of High-Rise Buildings
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• v.10 no.2
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• pp.99-107
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• 2021

This research investigates the potential of Adaptive TMDs for tall building damping. The Adaptive TMD under consideration is based on real-time controlled hydraulic dampers generating purely dissipative control forces. The control approach is designed to enhance the Adaptive TMD efficiency for moderate wind loads with return periods below 50 years. The resulting enhanced TMD efficiency is used to reduce the pendulum mass by 15% compared to the passive TMD while still guaranteeing the acceleration limits of the one and ten year return period winds. Furthermore, the adaptive control approach is designed to disproportionally increase the controlled damping force at wind loads with return periods of 50 years and more in order to reduce the maximum relative motion of the Adaptive TMD with only 85% pendulum mass. Compared to the passive TMD with 100% pendulum mass the maximum relative motion is reduced by 20%. Both the pendulum mass reduction and the maximum relative motion reduction significantly reduce the foot print of the Adaptive TMD which is highly desirable from the economic point of view.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.2
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• pp.150-158
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• 2002

Through experimental works, the damping force vibration problem was investigated, which results from valve and surge pressure in the oil return line of the hydraulic circuit of an active suspension system in a passenger cu. Experiments were carried out under passive system, where an orifice valve was closed and non-active system, where an orifice valve was opened, using a pressure control valve controlled by solenoid. The effects of parameters of the valve overlap and accumulator on smoothing surge pressure was elucidated. It was proved that the apparent variation of damping force due to the overlap amount of pressure control valve is the most important factor to control the damping force variation. The procedure of the experimental works shows the development process of a proportional pressure control valve in the hydraulics system of an active suspension system of passenger car.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.7
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• pp.709-716
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• 2013

Rehabilitation of finger patients requires that the patients exercise their hands and fingers for proper functioning to return. A thumb rehabilitation robot, equipped with a two-axis force sensor, can prevent injury to the thumb by monitoring the applied pulling force. In this paper, we describe a link-type thumb rehabilitation robot designed for patients' thumb rehabilitation exercise. Tests of the manufactured link-type thumb rehabilitation robot were performed on normal male patients. Our results show that the robot can be used for flexibility and muscle-strength rehabilitation exercises for a patient's thumb.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.6
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• pp.18-27
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• 2001

In this paper, the MSA to load a capacitor without limitation of the electric force on the transformed MSA is proposed. Bandwidth of the proposed antenna is 7.76% at the resonant frequency of 1.9 GHz, is observed the resonant frequency and bandwidth versus change of any arbitrary feed point. It was found that the bandwidth of this MSA to load a capacitor is broader than that of the transformed MSA. Antenna,s equivalent circuit with transmission line model is designed to find more accurate resonant frequency and is calculated return loss value. The calculated value is agreed resonably with experimental value.