• 농촌의학ㆍ지역보건
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• 제24권1호
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• pp.1-11
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• 1999

본 연구는 농약에 직업적으로 폭로되고 있는 농부들의 말초신경 기능을 평가하고자 농약살포 남성 농민 34명을 대상으로, 1998년 5월부터 1999년 2월에 걸쳐 실시하였다. 연구내용으로는 말초신경병변을 평가하기 위한 방법으로 현재 가장 많이 사용되고 있는 신경전도 검사를 우세 상하지의 청중신경, 척골신경, 비골신경, 후경골신경, 비복신경 대해 각 구간별로 나누어 실시하였다. 조사결과 조사대상자들은 평균 60세로서 농약살포 경력은 평균 33년이었다. 농사 유형은 주로 논, 밭, 고추 농사를 경작하고 있었으며 년간 평균 약 35일간 농약을 살포하였고 1일 살포시간은 약 9시간이었다. 또한 농약 중독 관련 증상을 경험한 적이 약 82%이상에서 보고되었다. 신경전도 검사상 조사원 모든 신정에서의 값이 정상범위에는 포함되었지만, 일부구간(척골감각 신경의 wrist-elbow, 후경골신경의 terminal latency)을 제외하고는 모두 참고치의 평균값보다 유의하게 낮은 것으로 나타났다. 또한 상대적 고폭로군과 저폭로군 간의 신경전도 검사치 비교에 의하면 정중감각 및 운동, 비골신경의 일부 구간 값이 고폭로군에서 높은 것을 제외하고는 유의한 차이를 발견할 수 없었다. 이것은 고폭로군의 연령이 저폭로군보다 유의하게 낮기 때문으로 판단되며, 조사 대상자들의 값이 참고치 평균보다 떨어진 것도 연령이 높음으로 인한 것임을 연령군별 비교에 의해 확인할 수 있었다. 따라서 향후 농약 폭로로 인한 미세한 말초신경 기의 이상여부를 조기에 파악하기 위해서는 감각역치 검사등 다론 신경학적 검사들을 함께 실시하는 것이 바람직하다고 판단되었다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1239-1244
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• 2004

Precise positioning is an important problem facing motion control systems which usually use electric motor. A motor possesses a nonlinear property which degrades the positioning accuracy. Therefore, a compensator which linearizes the relationship between the angular velocity and input signal of the motor is required to enable precise positioning. In this paper, the design of a Model Reference Adaptive Control System (MRACS) for realizing the precise positioning for a system using a motor including the nonlinear property is described. The designed MRACS is applied to the attitude control problem on a satellite using a DC servomotor to drive its reaction wheel. Experimental results demonstrate the validity of a proposed control method for a positioning control system with an electric motor.

• International Journal of Control, Automation, and Systems
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• 제1권1호
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• pp.35-42
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• 2003

This paper proposes a simple, robust, nonlinear controller based on Lyapunov stability for tracking the reference welding path and velocity of a two-wheeled welding mobile robot (WMR). The system has three degrees of freedom including two wheels and one torch slider. Torch slider motion is used for faster tracking because the welding speed is very slow. Control law is obtained from the Lyapunov control function to ensure the asymptotical stability of the system. The controller has three free parameters for adjusting the performance of the controlled system. A simple way of measuring the errors using two potentiometers is introduced. The effectiveness of the proposed controller is shown through simulation results.

• 한국정밀공학회지
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• 제17권4호
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• pp.121-128
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• 2000

In this paper, the control algorithm fur an autonomous vehicle is studied and applied to an actual 2 wheel-driven vehicle system. In order to control a nonholonomic system, the kinematic model for an autonomous vehicle is constructed by relative velocity relationship about the virtual point at distance from the vehicle's frame. And the optimal controller that based on the kinematic model is operated on purpose to track a reference vehicle's path. The actual system is designed with named 'HYAVI' and the system controller is applied. Because all the results of simulation don't satisfy the driving conditions of HYAVI, a reformed control algorithm that satisfies an actual autonomous vehicle is applied at HYAVI. At the results of actual experiments, the path tracking works very well by the reformed control algorithm. An autonomous vehicle that applied this control algorithm can be easily used for a path generation algorithm.

• Journal of Mechanical Science and Technology
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• 제17권11호
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• pp.1682-1692
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• 2003

This paper proposes an adaptive controller for partially known system and applies to a two-wheeled Welding Mobile Robot (WMR) to track a reference welding path at a constant velocity of the welding point. To design the tracking controller, the errors from WMR to steel wall is defined, and the controller is designed to drive the errors to zero as fast as desired. Additionally, a scheme of error measurement is implemented on the WMR to meet the need of the controller. In this paper, the system moments of inertia are considered to be partially unknown parameters which are estimated using update laws in adaptive control scheme. The simulations and experiments on a welding mobile robot show the effectiveness of the proposed controller.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.57.2-57.2
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• 2011

In this study, the effects of shear flows around a 2-dimensional airfoil, S809 on its aerodynamic characteristics were analyzed by CFD simulations. Various parameters including reference inflow velocity, shear rate, angle of attack, and cord length of the airfoil were examined. From the simulation results, several important characteristics were found. Shear rate in a flow makes some changes in the lift coefficient depending on its sign and magnitude but angle of attack does not have a distinguishable influence. Cord length and reference inflow also cause proportional and inversely proportional changes in lift coefficient, respectively. We adopted an analytic expression for the lift coefficient from the thin airfoil theory and proposed a modified form applicable to the traditional load analysis procedure based on the blade element momentum theory. Some preliminary results applied to an well known load simulation software, FAST, are presented.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2001년도 유체기계 연구개발 발표회 논문집
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• pp.63-68
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• 2001

A numerical analysis to predict the flow characteristics in turbo fan for vacuum cleaner has been performed by using CFD. The rotating reference frame method is applied to compute the impeller-diffuser interaction and the characteristics of two models, 460 and 380, are calculated for various rotating speeds and flow rates. The flow in impeller, diffuser and return channel is assumed as steady and compressible. STAR-CD with k- $\epsilon$ turbulence model is used to solve the Navier-Stokes equations. Computed relative velocity, absolute pressure and flow angles are shown and compared with measurement results. The good agreement between the predictions and measurement results confirms the validity of this study.

• 한국분무공학회지
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• 제2권4호
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• pp.22-28
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• 1997

In this paper an experimental study of a spray created by two impinging jets is presented utilizing a novel two-reference-beam double-pulse holographic technique. Visualization of the overall spray pattern as well as measurements on the size and velocity of the droplets were performed with the special emphasis on the effect of physical properties of liquids. The overall spray pattern clearly revealed the inherent wave nature In the disintegration process of this type of atomization. The structure of liquid elements near the impingement point is indicative of the mechanisms of the disintegration process. Surface tension plays an important role in the droplet size without any noticeable effect on the spray pattern, whereas viscosity affects the structure without any significant effect on the droplet sire. The droplet velocities were not affected by liquid properties.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.387-392
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• 1992

This paper presents a local trajectory generation method which is based on a sequence of reference posture-velocities and the efficient low level control algorithm which constructs the complete smooth curve from the trajectory specification. The reference trajectory generator(RTG) which is in between the local path planner(LPP) and the robot motion controller(RMC) generates a sequence of set-points for each path segments from the LPP and pass it to the RMC. The RMC controls the motions of vehicle which should follow the sequence. In the feedback controller of VMC, the method which compensates robot posture-velocity error correctly is used. These methods are implemented on indoor autonomous vehicle, 'ALIVE' mobile robot. The ALIVE mobile robot system is implemented on the 32bit VME bus system: the two VME CPU's are used for RTG and RMC, while the 80C196KC-based VME board is used for motor controller.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 추계종합학술대회 논문집
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• pp.464-467
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• 1999

Usually, more reference signatures result in better performance in signature verification. However, registering .many signatures may be a tedious work for users, so algorithms that use less signatures for the registration without increasing error rate is needed. In this paper, we find the features such as pen-down duration, the number of locally minimum velocity points, and the number of locally maximum curvature points. Then we find the relationship between these features and the optimal decision boundary. We apply this relationship in deciding threshold for signature verification. Experimental results show that the method using three reference signatures has almost same error rate as algorithms with many references.