• Tribology and Lubricants
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• v.14 no.1
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• pp.70-78
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• 1998

Two different friction materials (organic and low-metallic pads) for automotive brakes were studied to investigate the anti-fading phenomena during stop. The anti-fading phenomena were pronounced more in the case of using low metallic friction materials than organic friction materials. The main cause of the anti-fading phenomena was the high dependence of friction coefficient on a sliding speed. The anti-fading was prominent when the initial brake temperature was high in the case of low-metallic friction materials due to the strong stick-slip event at high temperature. On the other hand, the anti-fading was not severe in organic friction materials and the effect was reduced at high braking temperature due to the thermal decomposition of organic friction materials. The strong stickslip phenomena of low metallic friction materials at high temperature induced high torque oscillations during drag test. During this experiment two different braking control modes (pressure controlled and torque controlled modes) were compared. The type of the control mode used for brake test significantly affected the friction characteristics.

• Journal of the Korean Chemical Society
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• v.48 no.1
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• pp.77-84
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• 2004

The purpose of this study was to analyze the controversial points in the concepts of materials in the science textbook of middle school and to provide alternatives of teaching method. For this study, units in connected textbooks were analyzed and the teaching method using ball-and-stick models was developed. The subjects were 130 second graders from a middle school in Seoul, Korea. It aimed to compare the effectiveness of using ball-and-stick models for lesson with the one of traditional lessons, in learning concepts concerning materials by cognitive levels and to investigate the difference of scientific concept formation about concepts concerning materials by their cognitive levels between experimental group and control group by using concept formation questionnaires. Before the instructions, a short-version GALT was administered. After instructions, the posttest of concepts and attitude test connected with science subject were administered, and 10 months later, the posttest of concepts was administered to analyze the long-term memory effects. According to the results, the experimental group using the ball-and-stick models had significantly higher scores at conceptual understanding and long-term memory effects than the control group and improved the attitude relevant to science subject, and also had affirmative effects in attitude for science and science work. When analyzing the results according to the cognitive level, the long-term memory effects was high in the concrete operational stage students. From the results of this study, middle school students that are more concrete operational stage and transitional stage than formal operational stage elevates interesting in studying by using ball-and-stick models and making material form concretely. It would be effective in helping the students develope the correct concepts by connecting real world as materials and the particle world as atom.

• Journal of the Korea Society for Simulation
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• v.13 no.2
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• pp.45-52
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• 2004

This paper presents a prototype visualization system of mixed reality for a VR flight simulator. The chroma key technique is used to build the mixed reality model for a VR flight simulator. The Daedeok science town can be visualized in real time according to the rider control. He can also see his own hand/foot operating the control stick/rudder as well as virtual environment projected to the blue-screen using a video-see-through HMD.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.2 no.2
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• pp.146-152
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• 2002

Mold level control has been a major control task for continuous casting plants. The system involves nonlinearities such as stick-slip friction in the sliding gate, time-delay, friction force variations between molten steel and the inner wall of mold, and nozzle logging/unclogging. These complex problems should be solved to control mold level for steel cast. In this paper, we propose a neural fuzzy mold level control technique for solving these complex problems and give experiment studies to show the mold level control in continuous casting process.

• Journal of Korean society of Dental Hygiene
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• v.2 no.2
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• pp.215-225
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• 2002

Objectives: Dental personnels have high chances of exposure to various infections during many dental procedures. This study was performed to investigate the state of infection control in the private dental clinics and prevention state of hepatitis B virus infection among the dental hygiene students in Kwanju city, Korea. Methods: Questionnaires were obtained from 94 dental hygiene students who participated in dental practice in private dental clinics for more than five weeks. Results: 83.9% of dentists and 17.2% of dental hygienists routinely used the mask for treating all patients, 32.3% of dentists and 6.5% of dental hygienists routinely used the rubber gloves. The use of protective eyeware was much lower in each group. Disinfectant was used in 52.7% for sanitization of dental instruments before cleansing. The prevalence of HBsAg and anti-HBs were 3.8% and 67.1% respectively, 52.7% of dental hygiene students had history of accidental needle stick. Conclusion: Routine use of personal barrier techniques by dental personnels should be emphasized. Dental hygiene students were not properly immunized against hepatitis B virus and had high incidence of accidental needle stick. It is necessary to establish specific regulations or recommendations for cross infection control in dental practice and to performed scheduled vaccination program for hepatitis B virus for dental hygiene students.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.405-408
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• 1998

Generally, the principle function of simulator control loading system is to provide the pilot or student with the "feel" of the actual aircraft flight control systems during flight, taxing, and in malfunction. Flight control "feel" is the resistance felt by the pilot when moving a control stick or pedal, coupled with the amount of control surface deflection, and hence aircraft response, resulting from the input. Therefore, the control loading servo must be capable of performing to some general list of requirements derived from real aircraft control forces. In this paper, we deal with a $\mu-controller$ design for a control loading system of the flight simulator. For this, we derive a frequency response of the hydraulic system from the identification data and then design a controller using a $\mu-synthesis$ method. Under the same condition of simulation, $\mu-controller$ provides the superior performance than PID controller.than PID controller.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.11
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• pp.1061-1064
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• 2006

In this study, the performance of the tracking control of a pneumatic servo motor driven position control system using sliding mode is investigated. It is usually quite difficult to obtain precise tracking control of a pneumatic servo motor driven position control system because of the nonlinear deadband and stick-slip friction of the proportional valve. Therefore, a continuous sliding mode controller with velocity feedforward gain is proposed. Experimental results show that the tracking accurracy can be remarkably improved by adding a proper velocity feedforward term to continuous sliding mode controller.

• Transactions on Control, Automation and Systems Engineering
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• v.3 no.2
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• pp.111-116
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• 2001

A neural network compensator for stick-slip friction phenomena in meashartonics servo systems is practically proposed to supplement the traditionally available position and velocity control loops for precise motion control. The neural network compensa-tor plays the role of canceling the effect of nonlinear slipping friction force. It works robustly and effectively in a real control system. This enables the mechatronics servo systems to provide more precise control in the digital computer. It was confirmed that the con-trol accuracy is improved near zero velocity and points of changing the moving direction through numerical simulation. However, asymptotic property on the steady state error of the normal operation points is guaranteed by the integral term of traditional velocity loop controller.

• Proceedings of the IEEK Conference
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• 2002.06e
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• pp.261-264
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• 2002

In this study, we used a 16-bit microprocessor, 80C196KC for a control part in order to develop a multi-functional wheel-chair system, and implemented a joy-stick to control this system. For the complete system, we used a commercial electromotive wheelchair as a basic plant, and applied an encoder to get the rotating number of the motor to transfer data to the MCU to control the motor. We used PWM (Pulse Width Modulation) method to control the wheel-chair motor where a H-bridge circuit was configured. We used the fuzzy control algorithm for the operation of DC motor, which was attached to the electromotive wheelchair and manipulated following the change of the joystick position while a user was controlling the joystick. He also could control the speed and direction of DC motor as well as control position information.

• Clinical and Experimental Pediatrics
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• v.51 no.5
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• pp.481-486
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• 2008

Purpose : The aims of this study were to test the efficacy of vapocoolant spray to decrease the symptoms associated with pain in newborns undergoing heel stick and intramuscular injection and compare the pain relief effect of oral glucose. Methods : Randomized, controlled study including sixty newborns undergoing heel stick and intramuscular injection. Group 1 was heelsticked, Group 2 was intramuscular injected, Group A did not recieve any treatment, Group B recieved 30% glucose solution orally, Group C was applied vapocoolant spray symptoms and signs associated with pain at heel stick and intramuscular injection were measured with the premature Infant Pain Profile (PIPP) scale. Results : There was no significant difference in the PIPP score between intramuscular injected group control and heel stick group control (P=0.07). The mean PIPP score of Group 1A (control) $10.6{\pm}2.4$, Group 1B $5.5{\pm}2.0$, Group 1C $5.2{\pm}1.8$. The mean PIPP score 1B and 1C were significantly lower than control (1B P<0.001, 1C P<0.001). The mean PIPP score of Group 2A (control) $12.5{\pm}1.4$, Group 2B $7.0{\pm}1.7$, Group 2C $6.4{\pm}1.6$. The mean PIPP score 2B and 2C were significantly lower than control (2B P<0.001, 2C P<0.001). Conclusion : The antinociceptive effect of vapocoolant sparay is as effective as 30% oral glucose solution for pain control. So this study support the use of vapocoolant spray for reducing pain during painful procedure in the neonatal intensive care units.