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$Bi_2O_3{\cdot}3TiO_2$의 첨가량에 따른 $(SrPb)(CaMg)TiO_3$ 세라믹의 전기적 특성
김충혁,Kim, Chung-Hyeok 한국전기전자재료학회 1998 전기전자재료학회논문지 Vol.11 No.2
In this paper, the $(SrPb)(CaMg)TiO_3$ ceramics with paraelectric properties were fabricated by the mixed oxide method. It was investigated that which the variation of contents of $Bi_2O_3{\cdot}3TiO_2$ effects on structural, dielectrical and electrical properties of specimens. As a result, the grain size were grown with increasing the contents of $Bi_2O_3{\cdot}3TiO_2$. The relative dielectric constants were increased up to 4[mol%] of $Bi_2O_3{\cdot}3TiO_2$, and decreased more or less at a low temperature in the specimens which had more than. But the temperature coefficient. of capacitance were showed ${\pm}25$[%]. The dielectric loss were less than 0.05 in all specimens which had more than 4[mol%] of $Bi_2O_3{\cdot}3TiO_2$. In order to investigate the behavior of charged particles, the characteristics of electrical conduction were measured. As a result, the conduction current was divided into the three steps as a function of DC electric field. The first step was Ohmic region due to ionic conduction, below 15[kV/cm]. The second step was showed a saturation which seems to be related to a depolarizing field occuring in field-enforced ferroelectric phase, between 15[kV/cm] and 40[kV/cm]. The third step was attributed to Child's law related to space charge which injected from electrode, above 40[kV/cm].
Ag의 두께에 따른 비정질 As-Ge-Se-S의 홀로그래픽 특성연구
김충혁,Kim, Chung-Hyeok 한국전기전자재료학회 2012 전기전자재료학회논문지 Vol.25 No.3
In this study, we have investigated the holographic grating formation on Ag-doped amorphous As-Ge-Se-S thin films. The dependence of diffraction efficiency as afunction of Ag layer thickness has been investigated in this amorphous chalcogenide films. Holographic gratings was formed using [P:P] polarized Diode Pumped Solid State laser (DPSS, 532.0 nm). The diffraction efficiency was obtained by +1st order intensity. The results were shown that the diffraction efficiency of Ag/AsGeSeS double layer thin films for the Ag thickness, the maximum grating diffraction efficiency using 60 nm Ag layer is 0.96%.
As<sub>2</sub>Se<sub>3</sub> 기반 Resistive Random Access Memory의 채널 직선화를 통한 신뢰성 향상
남기현,김충혁,Nam, Ki-Hyun,Kim, Chung-Hyeok 한국전기전자재료학회 2016 전기전자재료학회논문지 Vol.29 No.6
Resistive random access memory (ReRAM) of metallic conduction channel mechanism is based on the electrochemical control of metal in solid electrolyte thin film. Amorphous chalcogenide materials have the solid electrolyte characteristic and optical reactivity at the same time. The optical reactivity has been used to improve the memory switching characteristics of the amorphous $As_2Se_3$-based ReRAM. This study focuses on the formation of holographic lattices patterns in the amorphous $As_2Se_3$ thin film for straight conductive channel. The optical parameters of amorphous $As_2Se_3$ thin film which is a refractive index and extinction coefficient was taken by n&k thin film analyzer. He-Cd laser (wavelength: 325 nm) was selected based on these basic optical parameters. The straighten conduction channel was formed by holographic lithography method using He-Cd laser.$ Ag^+$ ions that photo-diffused periodically by holographic lithography method will be the role of straight channel patterns. The fabricated ReRAM operated more less voltage and indicated better reliability.
시스템 LED 조명의 전기적·열적 안전성 확보 방안에 대한 연구
김영우,김충혁,최운식,Kim, Yeong Woo,Kim, Chung Hyeok,Choi, Woon Shik 한국전기전자재료학회 2020 전기전자재료학회논문지 Vol.33 No.5
This study tested the electrical, structural, and thermal safety of LED lighting products, available on the market. Five recessed LED systems, 20 W each, and five fixed LED systems, 25 W each, were selected. Dielectric strength tests, live part electric shock protection tests, and thermal tests were conducted on the LEDs. These were key tests for user safety, according to the specification of the safety criteria for electric products, KC 60598-1, South Korea. In addition, the wiring temperature of UL1007, 60227 IEC 08, and UTP cables, was measured. The results of the study gave an in-depth examination of the safety of LED lighting systems for users.
방출 수 에너지 하베스팅을 위한 수차 설계에 관한 연구
정한석,김충혁,Cheong, Han Seok,Kim, Chung Hyeok 한국전기전자재료학회 2021 전기전자재료학회논문지 Vol.34 No.1
We modeled the helical turbine and three modified helical turbines for the structure of the hydraulic turbine for discharge water energy harvesting. A structure that can reduce the load applied to the blade by placing a center plate is our basic concept. The shape was reduced to 1/5, fixed to a size of 240 mm in height and 247 mm in diameter, and modeled by changing the width and the angle of the hydraulic turbine blade. The pipe inner diameter of the simulation pipeline equipment is 309.5 mm, and the simulation section was 4 m in the entire section. The flow velocity was measured for two cases, 1.82 m/s and 2.51 m/s, with the parameters being the amount of power generation, hydraulic turbine's torque, and hydraulic turbine's rotation speed. The measurement results confirmed that the flow velocity at the center, which has no pipe surface resistance, has a great influence on the amount of power generation; therefore, the friction area of the turbine blade should be increased in the center area. In addition, if the center plate is placed on the helical turbine, durability can be improved as it reduces the stress on the blade.
RF 스퍼터링법에 의한 SBN 박막의 표면형상 및 유전특성
김진사,김충혁,Kim, Jin-Sa,Kim, Chung-Hyeok 한국전기전자재료학회 2009 전기전자재료학회논문지 Vol.22 No.8
The $Sr_{0.7}Bi_{2.3}Nb_2O_9$(SBN) thin films are deposited on Pt-coated electrode(Pt/Ti/$SiO_2$/Si) using RF sputtering method at various deposition conditions. We investigated the effect of deposition condition on the surface morphology and dielectric properties of SBN thin films. The optimum of the rougness showed about 4.33 nm in 70/30 of Ar/$O_2$ ratio. The crystallinity and rougness of SBN thin films were increased with the increase of rf power. Also, Deposition rate of SBN thin films was about 4.17 nm/min in 70 W of rf power. The capacitance of SBN thin films were increased with the increase of Ar/$O_2$ ratio, rf power and deposition temperature respectively.
악천후 시 낮은 도로조명을 이용한 도로 시인성 향상에 대한 연구
남기호,김충혁,최운식,Nam, Ki Ho,Kim, Chung Hyeok,Nam, Ki Ho 한국전기전자재료학회 2020 전기전자재료학회논문지 Vol.33 No.3
We investigate a fog-detection CCT control system using low deck lighting as a solution to the forward visibility of pole-type street lamps employed on existing roads. The lighting standards were met with a light source that has less compared with those of pole-type street lamps. The results show that the transmission rate was increased by changing the color temperature by automatically recognizing fog in bad weather and minimizing the phenomenon of lighting. In addition, it was allowed to create a safer and more comfortable driving environment for drivers owing to flicker or light pollution of existing pole-type street lamps. As a result, if lighting is used at a lower level than pole-type street lamps, the accident rate caused by securing the driver's forward visibility can be reduced sharply and existing problems can be resolved.
허민,고재준,김충혁,Heo, Min,Ko, Jae-jun,Kim, Chung-hyeok 한국전기전자재료학회 2016 전기전자재료학회논문지 Vol.29 No.11
It is highly important issue to use an energy efficiently for sustainable prosperity of mankind. From this point of view, using LED lighting can be a good alternative because it has a lot of advantages such as high efficiency, long life time and eco-friendly manufacturing process. That is the reason why using LED lighting has been encouraged worldwide. However, in situations that LED lighting is replacing traditional lighting quickly, the problem of the flicker of LED lighting has emerged as an important issue. Therefore, in foreign countries like US or Japan in order to ensure the reliability of LED lighting, study for flickering effects of the human body and test methods are have been actively conducted. But related research in domestic situation is an insufficient condition. In this study, a flicker characteristic was measured conventional lamps such as incandescent lamps or fluorescent lamp and 81 items of LED lightings which are distributed in domestic markets.