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박순성,예윤해 경희대학교 레이저공학연구소 2004 레이저공학 Vol.15 No.-
A demodulator for a portable fiber Bragg grating sensor is implemented and tested. The demodulator that measures the reflection wavelength of fiber Bragg gratings was applied to a fiber Bragg temperature sensor. The test results show that it can measure the temperature with sensitivity of 0.1℃, error less than ±0.5℃, and long-time drift of 0.2℃.
대학생의 배경특성에 따른 여가활동 장애요인 분석 : 대구·경북 지역을 중심으로 Centered on Taegu-Kyungbuk Areas
이예선 한국교육학회 대구·경북지회 2000 교육학논총 Vol.21 No.2
This thesis is aimed at leading a sound society by means of healthy leisure activities in the Korean societies. For this purpose, first, I approached to understand students' leisure activities, and then tried to reduce the obstacles of their activities through analyzing their causes. This approach will be achieved by teaching college students healthy and desirable leisure activities in Korean societies; and as a long-term purpose, it will guide sound leisure activities on the level of permanent education. In this thesis, I approached the obstacles of college students' leisure activities through (one-way Anova). And I categorized the causes of their obstacles into eight units: lack of time, lack of money, lack of information, lack physical activity, lack of volition, obstacle caused by college study, lack of leisure facilities, and lack of the opportunities of leisure activities. And I focused on the students' sex, grade, average monthly pocket money, income of their families, and their fathers' schooling as the responding college students' background characteristics. The results of the analyses are as follows: 1. According to the results of sex analysis, female students showed fewer leisure activities than male students on account of their less physical strength. It was revealed that the female students have a significant difference by the level of p<.05. And the female students also had fewer opportunities of leisure activities than male students, which revealed the significant difference of p<.05. 2. According to the results of grade analysis, it was revealed that lower grade students(freshmen) have limitations of leisure activities on account of their less information, and the result was the significant difference p<.01. 3. According to students' leisure activities based on family income, in the case of the students who are from lower than 1 million won monthly family income, they showed the limitation of leisure activities on account of lack of money and there was a significant difference of p<.05. And the limitation of leisure activities on account of lack of information revealed a significant difference by the level of p<.05, 4. The obstacles of students' leisure activities based on fathers' schooling showed the results that in case that fathers' schooling was college drop out or junior college graduation, their lack of information was the cause of a significant difference by the level of p<.05. However, the difference of students' pocket money was not the cause of a significant difference. The research result of this thesis concluded that in order to solve the problem of obstacles of students' leisure activities, in case of female students, we need to intensify their physical strength; and in case of freshmen, it is required to provide them with more various kinds of information of leisure activities. However, in case of the students from lower income families, for their desirable leisure activities, colleges or societies should show the students more concern and give them various opportunities of free leisure activities instead of monetary aid. Despite fathers' lack of schooling, when colleges or societies provide more various kinds of information of leisure activities, students will enjoy more sound and desirable leisure activities. The insufficient advanced researches gave this thesis much difficulty. However, I expect that continuous researches and studies of this area will lead to great scholarly development in the aspect of the permanent education.
최선영,김도익,예윤해 경희대학교 레이저공학연구소 2001 레이저공학 Vol.12 No.-
We developed a high- speed signal processor for Fabry -Perot interferometric sensors using ramp modulation. The signal processor was implemented onto field programmable gate array(FPGA). This method has an advantage of simplifying the circuit of system as well as improving of the system performance. The signal processor was tested with FP interferometric temperature sensor with a cavity length of 1.52 cm. The random walk of the system was 1.1 □.
Electromagnetic Analysis of a Flat-Type Proportional Solenoid by the Reluctance Method
Yeh-Sun Hong,Yong-Cheol Kwon 한국정밀공학회 2006 International Journal of Precision Engineering and Vol.7 No.2
In this study, the electromagnetic characteristic of a flat-type two-dimensional proportional solenoid were analyzed by the magnetic reluctance method. The magnetic equivalent circuit equation for the solenoid was derived by modeling the reluctance of air gaps and magnetic structural components such as pole core, armature and yoke. It was solved iteratively because of the nonlinear magnetization properties of iron parts. The solutions showed good agreement with experimental data. Based on the magnetic equivalent circuit equation, the influence of design parameters on force-to-armature displacement curves was mathematically derived and experimentally verified. In this way, dominant design parameters could be analytically determined.
Yeh-Sun Hong,Sang-Yul Lee,Sung-Hun Kim,Hyun-Sik Lim 대한기계학회 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.3
The hydraulic pump of an Electro-hydrostatic Actuator should be able to quickly feed large volume of oil into hydraulic cylinder in order to reduce the response time. On the other hand, it should be also able to precisely dispense small amount of oil through low-speed operation so that the steady state position control error of the actuator can be accurately compensated. Within the scope of axial piston type hydraulic pumps, this paper is focused on the investigation how the surface treatment of their cylinder barrel with TiN plasma coating can contribute to the reduction of the friction and were rate of valve plate in the low-speed range with mixed lubrication. The results showed that the friction torque of the valve plate mated with a TiN-coated cylinder barrel could reduced to 22% of that with an uncoated original one when load pressure was 300 var and rotational speed 100 rpm. It means that the torque efficiency of the test pump was expected to increase more than 1.3% under the same working condition. At the same time, the wear rate of the valve plate could be reduced to 40~50%.
Design of a Two-Dimensional Proportional Solenoid for Miniature Directional Control Pneumatic Valves
Yeh-Sun Hong,Dong-Hyun Ha,Myung-Ki Yeom 대한기계학회 2003 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.17 No.7
In this paper, a new proportional solenoid invented for pneumatic directional control valves is introduced. The new proportional solenoid has two-dimensional structure and a pivoting armature on which the friction force is inherently negligible. Another advantageous feature of this solenoid is that its mechanical parts can be easily manufactured and assembled. The working principle and design example of the now proportional solenoid. its application to the activation of a 4/3-way directional control valve, and the evaluation of its control performance in a position control loop are reported.
Analysis on the Friction Losses of a Bent-Axis Type Hydraulic Piston Pump
Yeh-Sun Hong,Yoon-Ho Doh 대한기계학회 2004 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.18 No.9
he design of an axial piston pump for electro-hydrostatic transmission systems requires accurate information where and how much the internal friction and flow losses are produced. This study is particularly focused on the friction losses of a bent-axis type hydraulic piston pump, aiming at finding out which design factors influence its torque efficiency most signiTo this end, the friction coefficients of the pump parts such as piston heads, spherical joints, shaft bearings, and valve plate were experimentally identified by a specially constructed tribometer. Applying the experimental data to the equations of motion for pistons as well as to the theoretical friction models for the pump parts, the friction torques produced by them were computed. The accuracy of the computed results was confirmed by the comparison with the practical input torque of the pump. In this paper, it is shown that the viscous friction forces on the valve plate and input shaft bearing are the primary source of the friction losses of the bent-axis type pump, while the friction forces and moments on the piston are of little significance.
Hybrid Constant Pressure Control of a Swash Plate Type Axial Piston Pump
Yeh-Sun Hong,Jong-Hyeok Kim 유공압건설기계학회 2015 유공압건설기계학회 학술대회논문집 Vol.2015 No.10
In this paper both the volumetric displacement and the shaft speed of a variable displacement swashplate type piston pump were varied in order to minimize power consumption in supplying constant-pressure oil to a valve-controlled hydraulic cylinder, particularly during idle modes. At operating modes which were triggered by position command inputs, the pump speed was varied by a pressure control algorithm to maintain a constant system pressure, with the swash plate angle fixed at the maximum. At idle, with no position controller input signal and the system pressure greater than or equal to the reference value, the swash plate angle and pump speed were lowered to their minimum limits. Computer simulation and experimental results showed that the idling power could be reduced by up to 83% by reducing the pump speed from 1800 rpm to 300 rpm and the swash plate angle to 3°, compared to a conventional system consisting of a pressure-compensated variable displacement type pump driven at a constant speed of 1800 rpm.
민항기 door damper용 칼날형 댐핑 오리피스의 설계
홍예선(Yeh-Sun Hong),권용철(Yong-Cheol Kwon),김종혁(Chong-Hyeok Kim),박설혜(Seol-Hye Park),박호열(Ho-Yeol Park),김상범(Sang-Beom Kim) 한국항공우주학회 2012 韓國航空宇宙學會誌 Vol.40 No.12
본 논문에서는 작동유의 최대 동점성 계수가 400cSt까지 변하는 조건에서 항공기 도어댐퍼용 칼날형 댐핑 오리피스를 설계하였다. 전산 유동 해석과 실험을 통하여 칼날 오리피스의 유량계수를 분석하였고, 오리피스의 크기와 칼날 각도, 유동방향, 레이놀즈수가 미치는 영향을 고려하였다. 이 결과를 바탕으로 오리피스의 크기에 따라 댐퍼의 성능 기준을 충족시키기 위해 제한해야 하는 댐퍼의 쿨롱 마찰력 범위를 유도하였다. In this paper a sharp-edged type damping orifice for an aircraft door damper were designed, where the dynamic viscosity of working fluid were assumed to change up to 400cSt. The discharge coefficient of the damping orifice were investigated by CFD analyses and experiments. In particular, the influences of orifice diameter, edge angle, flow direction and the Reynolds number were taken into consideration. Based on this, it has been deduced how high Coulomb friction forces of damper seals is to be allowed to meet the performance criterion with respect to the orifice size.