• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.713-718
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• 2003

Decubitus ulcer is a pressure-induced ulceration of the skin occurring in persons confined to bed for long periods of time. In order to prevent decubitus ulcer, the medical bed mechanism to minimize pressure, friction, and shear forces acting between bed and patient had been developed. Air mattress also can be effective for reducing pressure over bony prominence. In this study, motion analysis was performed to examine whether this bed mechanism functioned properly in case of using air mattress, which was much thicker than common hospital mattress. We found that the patient on the air mattress above the medical bed for preventing decubitus ulcer slipped upward and downward excessively as the general motored-bed. New bed mechanisms were synthesized kinematically using simple 4-bar and 6-bar linkages so as to reduce sliding between the bed and the patient on the air mattress for preventing decubitus ulcer.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2018년도 학술발표회
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• pp.149-149
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• 2018

Prediction on initial motion of sediment is crucial to evaluate sediment transport and channel stability. The condition of incipient movement of sediment is characterized by bed shear stress, which is generated from force of moving water against the bed of the channel, and by critical shear stress, which depends on force resisting motion of sediment due to the submerged weight of the grains. When the bed shear stress exceeds the critical shear stress, sediment particles begin rolling and sliding at isolated and random locations. In Mountain River, debris flow frequently occurs due to heavy rainfall and can lead some natural stones from mountain slope into the bed river. This phenomenon could add additional forces to sediment transport system in the bed of river and also affect or change direction and magnitude of sediment movement. In this paper, evaluations on incipient motion of uniform coarse gravel under falling spheres impacts using small scale flume channel were conducted. The drag force of falling spheres due to water flow and length movement of falling spheres were investigated. The experiments were carried out in flume channel made by glass wall and steel floor with 12 m long, 0.6 m wide, and 0.6 m deep. The bed slopes were selected with the range from 0.7% to 1.5%. The thickness of granular layer was at least 3 times of diameter of granular particle to meet grain placement condition. The sphere diameters were chosen to be 4cm, 6 cm, 8 cm, 10 cm. The spheres were fallen in to the bed channel for critical condition and under critical condition of motion particle. Based on the experimental results, the Shields curve of particles Reynold number and dimensionless critical shear stress were plotted. The relationship between with drag force and the length movement of spheres were plotted. The pathways of the bed material Under the impact of spheres falling were analyzed.

• 한국정밀공학회지
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• 제16권6호
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• pp.90-99
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• 1999

A vehicle driving simulator is a virtual reality device which a human being feels as if the one drives a vehicle actually. The driving simulator is used effectively for studying interaction of a driver-vehicle and developing vehicle system of a new concept. The driving simulator consists of a vehicle motion bed system, motion controller, visual and audio system, vehicle dynamic analysis system, cockpit system, and etc. In it is paper, the main procedures to develop the driving simulator are classified by five parts. First, a motion bed system and a motion controller, which can track a reference trajectory, are developed. Secondly, a performance evaluation of the motion bed system for the driving simulator is carried out using LVDTs and accelerometers. Thirdly, a washout algorithm to realize a motion of an actual vehicle in the driving simulator is developed. The algorithm changes the motion space of a vehicle into the workspace of the driving simulator. Fourthly, a visual and audio system for feeling higher realization is developed. Finally, an integration system to communicate and monitor between sub systems is developed.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1535-1538
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• 2004

In this paper, an Intelligent Bed Robot System (IBRS) is proposed, that is a special bed equipped with robot manipulator. To assist a patient using IBRS, pose and motion estimation process is fundamental. It is designed to help the elderly and the disabled for their independent life in bed without other assistants. For this purpose, we use the pressure sensor distributed mattress for detecting the change of motion on the bed. Using that data, we control the robot arm to move to the appropriate position and serve to the user. In addition, we can estimate the user's intention based on the change of pressure and use those data to control the robot arm guide.

• Journal of Mechanical Science and Technology
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• 제19권4호
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• pp.976-984
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• 2005

This paper presents the analysis results of dynamics in the billiards game within the frame­work of rigid-body mechanics and a numerical simulation program. The friction exists between the ball and the table bed as well as between the ball and the rail. There are three parts in the dynamic behavior of the ball on the table bed; motion of the ball on the table bed, collision between balls, and collision between the ball and the cushion. During the development of the simulation program, the dynamics problems such as rolling motion and three-dimensional frictional impact motion have been analyzed in detail. The theoretical issues are implemented into a viable graphic simulation program and its efficacy is demonstrated through the experi­mental validation of the billiards game. The resulting analysis results are verified quantitatively and qualitatively using high-speed video camera. Through the experimental tests, it was found that the physical parameters such as coefficients of restitution and friction vary according to the motion variables and corresponding empirical formulations were developed. The simulation and experimental results agree well.

• 한국전산유체공학회지
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• 제15권1호
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• pp.9-16
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• 2010

The characteristics of flow and heat transfer in a bubbling fluidized bed are investigated by means of computational fluid dynamics (CFD). To simulate two-phase flow for the gas and solid flows, Eulerian-Eulerian approach is applied. Attention is paid for a heat transfer from the wall to fluidized bed by bubbling motion of the flow. From the result, it is confirmed that heat transfer is promoted by chaotic bubbling motion of the flow by enhancement of mixing among solid particles. In particular, the vortical flow motion around gas bubble plays an important role for the mixing and consequent heat transfer. Discussion is made for the time and space averaged Nusselt number which shows peculiar characteristics corresponding to different flow regimes.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2005년도 학술발표회(1)
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• pp.499-500
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• 2005

• 공업화학
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• 제22권6호
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• pp.642-647
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• 2011

회전형 휘발성 산화장치(voloxidizer)와 200 g $U_3O_8$ 분말을 사용하여 초기 미세 입자층의 운동형태, 열처리 온도 및 시간, voloxidizer의 회전속도에 따른 다공성 그래뉼의 회수율과 특성을 분석하였다. 초기 미세 입자층의 운동형태에 따른 1 mm 이상의 그래뉼의 회수율은 rolling 운동 때보다 slumping 운동일 경우에 보다 높았다. 초기 미세 입자층이 rolling 운동형태인 경우에는 미세입자로부터 그래뉼이 생성됨에 따라서 slumping 운동형태로 변하며 slumping 빈도가 매우 높았다. 열처리 온도의 증가 및 10 h까지는 시간의 증가에 따라서 그래뉼의 회수율이 매우 크게 증가하였다. Slumping 운동형태를 보이는 초기 미세 입자층의 경우에 voloxidizer의 회전속도가 증가함에 따라서 그래뉼의 회수율 은 81.5에서 88.7%로 증가하였으나, 그래뉼 특성 측면에서 보면 회전속도가 2 rpm인 경우에 밀도, 파쇄강도, 구형도가 가장 높았다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.755-760
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• 2006

The exhaust gas with solid particle goes through the riser in both particle circulating type and circulating fluidized bed type heat exchanger to recover the heat. During heat transfer, gas velocity in vertical riser decreases as viscosity of exhaust gas decreases. In this case, when the particle size is fixed, sometimes the exhaust gas happens to have lower velocity which prohibit them to go out of the riser. In this paper the particle motion in vertical Rayleigh flow was studied. The behavior of heat transfer was investigated by means of velocity and temperature distribution. The result from numerical analysis was validated by the experimental results. Fortran code was used to analyze the particle motion in vertical Rayleigh flow.

• 한국멀티미디어학회논문지
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• 제25권8호
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• pp.1109-1121
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• 2022

As the demand for quality sleep increases in modern society, the importance of sleep technology has increased. Recently, development of sleep environment improvement products and research on the user's sleep improvement have been activated. Representatively, user sleep pattern analysis research is being conducted through the existing polysomnography, but it is difficult to use it in the sleep environment of daily life. Therefore, in this paper, we propose a system design that can provide a customized deep sleep service to users by detecting sleep disturbance factors in a motion bed environment. In order to improve the user's sleep satisfaction, a logistic regression-based sleep pattern analysis model is proposed and accuracy and significance are verified through experiments. And to improve user's sleep satisfaction, we propose a logistic regression-based sleep pattern analysis model and verify accuracy and significance through experiments. The proposed system is expected to improve the user's sleep quality and effectively prevent and manage sleep disorders.