• Journal of Sensor Science and Technology
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• v.28 no.6
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• pp.371-376
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• 2019

We have developed an acoustic resonance inspection system to inspect the welding defects in the mechanical parts fabricated using friction stir welding method. The inspection system was consisted of a DAQ board, a microphone sensor, an impact hammer, and controlled by a PC software. The system was developed to collect and analyze the sound signal generated by hitting the sample with an impact hammer to determine whether it is defective. In this study, 100% welded good samples were compared with 95%, 90%, and 85% welded samples, respectively. The variation of the completeness in welding did not affect the visual appearance in the samples. As a result of analyzing the natural frequencies of the good samples, the five natural frequency peaks were identified. In the case of the defective samples, the frequency change was observed. The welding failure detection time was fast enough to be only 0.7 seconds. Employing our welding defect inspection system to the actual industrial field will maximize the efficiency of quality inspection and thus improve the productivity.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.10
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• pp.15-20
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• 2013

In this paper, wireless power transfer system using the magnetic resonance was designed and applied to LED lighting for implementation of wireless lighting. This lighting was made by the converted DC driving type and the direct AC driving type. In the former, transferred AC power was rectified into DC and regulated to the specified voltage value, which leads to produce the loss at the rectifying and regulating circuit. In the latter, wireless-transferred AC power was directly applied to LED, which get rid of the loss derived from the additional circuit. For the efficiency-comparison between the former and the latter, the power at each stage was measured when the same optical output radiated from LED lighting part. The result revealed that the direct AC driving type had 18% higher efficiency than the DC driving type and confirmed that LED lighting using magnetic resonance wireless power transfer system can be efficient by direct AC power supply. And the direct AC driving type had the simple circuit structure and the simple LED lighting formation, so this can leads to various application.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.4
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• pp.413-421
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• 2018

The pyroshocks can cause failure of electronics devices and structures. Metal-metal impact methods are utilized to simulate mechanical pyroshock, and to adjust the knee frquency of the SRS(Shock Response Spectrum) through resonant structures. In this paper, the major parameters of pyroshock simulation device which affect the SRS were examined. Through the Hertzian contact law and the modal characteristics of the resonant bar, it was found that the SRS is affected by the length and mass of a bar and various impact conditions such as velocity and mass of impactor. The characteristics due to the geometric parameters of a resonant bar was analyzed by performing FEA and also the resonant bar was designed and fabricated. Through the pyroshock simulation test, the characteristics of SRS due to the variation of impact parameters were examined.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.2
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• pp.216-222
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• 2013

A solar power generator is usually installed outdoors and it is exposed to extreme environments such as heavy fall of snow and high speed wind. Therefore, the solar tracker structure should be designed to have sufficient static and dynamic stiffness against such environmental conditions. In this paper, eigenvalue analysis of the solar tracker is carried out by varying the pose of the solar panel and unsteady flow analysis around a single tracker or multi-trackers arranged in a line is performed by varying the parameters such as wind directions, wind speeds and the pose of the solar panel to evaluate whether there exists an instability of resonance due to vortex shedding. Finite element eigenvalue analysis shows that natural frequencies and modes are almost not influenced by the pose of the solar panel and the finite element flow analysis shows that there does not exist periodic vortex shedding due to the flow around single tracker or multiple solar trackers in a line.

• The Journal of the Acoustical Society of Korea
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• v.13 no.5
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• pp.15-23
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• 1994

We developed an electronic lens for acoustic imaging systems, which is linear array with 31 microphones equally spaced with distance 34mm. Resonant frequency fo receiver circuit coupled to microphone is 20 kHz. We arranged 16 microphones horizontally and 15 microphones vertically, so that the array allows us to obtain a 2 dimensional angle of source, and to track the motion of source in real time. Due to the problem of aliasing in discrete Fourier Transfrom, the maximum observable angle of the lens is limited to 15${\circ}$. We also employed quadrature phase detection scheme to adjust the focus. We have tested the acoustic lens with a personal computer in an anechoic room and obtained the results agreed with the acoustic imaging theory.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.7
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• pp.45-51
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• 2012

In this paper, the wireless power transfer system using the magnetic resonance was designed and the effect of resonant coil radius and load resistance to this system was analyzed by the circuit analysis method. As a result, the calculated transmitted-power is similar to measured one, and the coil size has a small effect to the coupling coefficients in the resonant frequency band. In addition, the fact that the calculated transmitted-power according to the source frequency is similar to measured one confirms that the circuit analysis methode in this paper is valid. The input side transmission efficiency ${\eta}_i$ including only the loss in the power transfer circuit is almost 90[%] with the large coil in the 10[cm] transfer distance, and 65[%] with the small coil in 1[cm]. The source side transmission efficiency ${\eta}_s$ is 30~40[%] at both coil when load resistance below 4.7[${\Omega}$] has been connected. Considering that the maximum ${\eta}_s$ is 50[%], this is valid in the practical applications.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.233-236
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• 2002

The solution for PFC(Power Factor Correction), as a regulation in energy Policy, is becoming a hot Issue in every country because of the shortage of electrical energy. Therefore, a new improved idea for PFC problem has been introduced in this study. A lot of merits, effective cost by simple circuit, reduced PCB size, lighter than reactor in the view of weight, lower level of screen noise by leakage inductance in CTV applications, have been stated by comparing to the earlier method of using a Reactor. All test results in this statement were done by using a power device of STR-G9600 series based on the real load condition of color television. furthermore, the study shows that the test results also meets the IEC-1000-3-2 class D, which regulates the PFC when input power of a set is more than 75watts. More improved PFC in other applications hopes to be implemented by using the proposed method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.189-190
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• 2005

본 논문에서는 카메라폰용 광학줌(Optical zooming)과 자동초점조절장치(Auto Focusing,AF)에 쓰일 초음파모터를 제작하였다. 초음파모터의 제작 및 시뮬레이션은 유한요소해석 프로그램인 ATILA 5.2 1(Magsoft co.)를 사용하여 디자인설계에 따른 구동특성을 고찰하였고 제작된 초음파모터는 한쪽 면이 없는 사작형의 탄성체를 제작하였으며 탄성체의 양쪽 다리에 각각 압전체를 부착하였다 또한 압전세라익의 조성은 0.9Pb$(Zr_{0.51}Ti_{0.49})O_3$ - 0.1Pb$(Mn_{1/3}Nb_{1/3}Sb_{1/3})O_3$ 의 조성으로 설계하였고 시편의 제조는 7-layer로 적층하였다. 제작된 압전세라믹의 치수는 6*2*0.35mm$^3$(길이*폭*두께)로 제작하였다. 또한 탄성체의 외형치수는 8*4*2mm$^3$로 제작하였으며 회전축의 지름은 2mm로 제작하였다. 인가전압과 공진주파수가 각각 20Vpp, 64kHz일 때 소비전력은 0.3[W]이며 회전속도는 500rpm 으로 측정되었다.

• Proceedings of the KIEE Conference
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• 2002.11d
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• pp.263-266
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• 2002

In this paper, It is indicating that an issues of the conventional boost converter for high frequency induction heating. To improve those issues, it is proposed, simulated and analyzed that the current resonant circuit, simulated. As the result, we knew that the proposed circuit has a good point to improve the waveform of input current and to make high efficiency. On the other side, in the inverter for the high current power supply, it is proposed that the high frequency inverter of the half bridge topology, be done the circuit analysis to extract the optimal circuit parameter. It is making sure of the soft switching operating by the inductor to reverse parallel connected on the inverter main switch, decreasing the surge voltage when the switch is turn-off by compulsion, and repressing the switch current and bringing the high current amplitude operation by the multi resonance.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.1054-1056
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• 1999

It is necessary to install the arc generation facility to obtain the important technology for the design of breakers and switches, and the improvement of their performance and reliability. With this facility it is possible to study the characteristics of Arc in air/gas/vacuum insulation environment. The arc generation facility briefly consists of capacitor bank which can charge enormous energy, an air-core reactor, and several measurement equipments. This facility can simulates the arc phenomena in breakers and switches by means of generating high currents. In order to the protect electrode damage during the arcing time in arc extinguishing chamber, we installed auxiliary current source in addition to main capacitor bank, This auxiliary current source produces relatively small arc between electrodes before high current generation by main capacitor bank. Therefore it is possible to observe and measure the arcing phenomenon without damage of electrodes.