• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
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• pp.1034-1037
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• 2003

Microcrystalline silicon(c-Si:H) thin-film solar cells are prepared with intrinsic Si-layer by hot wire CVD. The operating parameters of solar cells are strongly affected by the filament temperature ($T_f$) during intrinsic layer. Jsc and efficiency abruptly decreases with elevated $T_f$ to $1400^{\circ}C$. This deterioration of solar cell parameters are resulted from increase of crystalline volume fraction and corresponding defect density at high $T_f$. The heater temperature ($T_h$) are also critical parameter that controls device operations. Solar cells prepared at low $T_h$ ($<200^{\circ}C$) shows a similar operating properties with devices prepared at high $T_f$, i.e. low Jsc, Voc and efficiency. The origins for this result, however, are different with that of inferior device performances at high $T_f$. In addition the phase transition of the silicon films occurs at different silane concentration (SC) by varying filament temperature, by which highest efficiency with SC varies with $T_f$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.2
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• pp.969-972
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• 2004

Al doped Zinc Oxide(ZnO:Al) films, which is widely used as a transparent conductor in optoelectronic devices such as solar cell, liquid crystal display, plasma display panel, thermal heater, and other sensors, were prepared by using the capacitively coupled DC magnetron sputtering method. In this paper the effect of doping amounts of $Al_2O_3$ on the electrical, optical and morphological properties were investigated experimentally, The results show that the structural and electrical properties of the film are highly affected by the doping. The optimum growth conditions were obtained for films doped with 2 wt% of Al203 which exhibit a resistivity of $8.5{\times}10^{-4}{\Omega}-cm$ associated with a transmittance of 91.7 % for 840 nm in film thickness in the wavelength range of the visible spectrum.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.143-146
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• 2003

Al doped Zinc Oxide(ZnO:Al) films, which is widely used as a transparent conductor in optoelectronic devices such as solar cell, liquid crystal display, plasma display panel, thermal heater, and other sensors, were prepared by using the capacitively coupled DC magnetron sputtering method. The influence of the substrate temperature, working gas pressure and discharge power on the electrical, optical and morphological properties were investigated experimentally. The consideration on the effect of doping amounts of Al on the electrical and optical properties of ZnO thin film were also carried out. ZnO:Al films with the optimum growth conditions showed resistivity of $9.42{\times}10^{-4}\;{\Omeg}-cm$ and transmittance of 90.88% for 840nm in film thickness in the wavelength range of the visible spectrum.

• 한국건설순환자원학회논문집
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• 제7권3호
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• pp.85-90
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• 2012

In this study, temperature profile of the fly ash concrete were studied in accordance with the change of heating curing method combination for the slab concrete in order to develop efficient protection method of the concrete subjected to $-20^{\circ}C$. The slab concretes with the size of $1200mm{\times}600mm{\times}200mm$ were fabricated with W/B of 50% and exposed to $-20^{\circ}C$ for 7 days. Five different combinations of heat curing methods were applied to the slab concrete specimen; two combinations of heat supplying by electrical heater and surface heat insulation material such as polyethylene film and quadrupled layer bubble sheet based on heat enclosure installment; three combinations of heating coil embedment and surface heat insulation materials such as polyethylene film, sawdust and quadrupled layer bubble sheet based on heat enclosure installment. Test results showed that by applying both heating coil and bubble sheet and heat enclosure, the concrete exposed to $-20^{\circ}C$ can be effectively protected from early-age frost damage.

• 한국광학회지
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• 제25권5호
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• pp.279-285
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• 2014

본 논문에서는 온도 변화에 따라 절연체-금속 상전이 특성을 보이는 이산화바나듐($VO_2$)과 메타물질을 이용하여 전기적으로 제어 가능한 테라헤르츠 변조기를 제시하였다. 변조기 기능을 하는 메타물질 구조가 $VO_2$의 도전율 변화에 영향을 주는 열을 전기적으로 조절할 수 있는 히터의 역할도 동시에 할 수 있는 정사각고리 구조의 메타물질을 설계하였다. 설계한 $VO_2$기반 메타물질 변조기의 전파 투과량은 정사각고리 메타물질에 직접 연결된 전압 인가용 도선을 통한 인가 전압 변화로 조절이 가능하다. $VO_2$의 도전율 변화에 따라 전파 투과계수는 470 GHz 에서 0.27에서 0.80으로 안정적으로 조절되었고, 13% 주파수 대역폭에서 투과계수 변화폭이 일정하게 유지되었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 C
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• pp.1598-1600
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• 2003

Microcrystalline silicon(c-Si:H) thin-film solar cells are prepared with intrinsic Si-layer by hot wire CVD. The operating parameters of solar cells are strongly affected by the filament temperature ($T_f$) during intrinsic layer. Jsc and efficiency abruptly decreases with elevated $T_f$ to $1400^{\circ}C$. This deterioration of solar cell parameters are resulted from increase of crystalline volume fraction and corresponding defect density at high $T_f$ The heater temperature ($T_h$) are also critical parameter that controls device operations. Solar cells prepared at low $T_h$ (<$200^{\circ}C$) shows a similar operating properties with devices prepared at high $T_f$, i.e. low Jsc, Voc and efficiency. The origins for this result, however, are different with that of inferior device performances at high $T_f$. In addition the phase transition of the silicon films occurs at different silane concentration (SC) by varying filament temperature, by which highest efficiency with SC vanes with $T_f$.

• 센서학회지
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• 제17권5호
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• pp.329-337
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• 2008

Simple, small and portable oxygen sensors were fabricated by tape casting technique. Yttria stabilized zirconia containing cordierite ceramics (YSZC) were used as a porous diffused layer of oxygen in pumping cell. Yttria stabilized zirconia (YSZ) solid electrolyte, YSZC porous diffusion layer and heater-patterned ceramic sheets were prepared by co- firing method. Limit current characteristics and the linear relationship of current to oxygen concentration were observed. Viscosity variation of the slurries both YSZ and YSZC showed a similar behavior, but micro pores in the fired sheet were increased with increasing of the cordierite amount. Molecular diffusion was dominated due to the formation of large pores in porous diffusion layer. The plateau range of limit current in porous-type oxygen sensor was narrow than the one of aperture-type oxygen sensor. However limit current curve was appeared in porous-type oxygen sensor even at the lower applied voltage. The plateau range of limit-current was widen as increasing the thickness of porous diffusion layer of the YSZ containing cordierite. Measuring temperature of $600{\sim}650^{\circ}C$ was recommended for limit-current oxygen sensor. Porous diffusion layer-type oxygen sensor showed faster response than the aperture-type one and was stable up to 30 days running without any crack at interface between the layers.

• 한국가시화정보학회지
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• 제22권1호
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• pp.6-17
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• 2024

This study examined the natural convection heat flow characteristics of the melting process of PCM (palm oil) inside a liquid flexitank(bag) for a cargo container. A film heating element was installed on the bottom of the container, and numerical analysis was performed under heat flux conditions of 1,000 to 4,000 W/m². As a result, the melt interface of the PCM rises to a nearly horizontal state over time. In the initial stage, conduction heat transfer dominates, but gradually waves at the cell flow and melt interfaces are formed due to natural convection heat transfer. As melting progresses, the Ra number increases parabolically, and the Nu number increases linearly and has a constant value. The Nu number rises slowly under low heat flux conditions, whereas under high heat flux conditions, the Nu number rises rapidly. As the heat flux increases, the internal temperature oscillation of the liquid phase after melting increases. However, under high heat flux conditions, excess heat exceeding the latent heat is generated, and the temperature of the molten liquid is raised, so the increase in melting rate decreases. Therefore, the appropriate heating element specification applied to a 20-ton palm oil container is 2,000 W/m².

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2194-2199
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• 2007

An experimental study is performed to investigate the thermal and flow characteristics of subcooled liquid nitrogen in a natural circulation loop. Experimental apparatus is designed and constructed such that a closed loop is cooled at the top by a cryocooler and heated nearly at the bottom by cartridge heaters. Steady state is obtained by controlling the heating power to the cartridge heaters and a thin-film heater to reduce the cooling power of the cryocooler. Temperature is measured at several locations of the loop and the mass flow rate through the loop is estimated from the energy balance in terms of the measured temperatures. Experiment is repeated for various values of the vertical height between the cooling and heating parts. The results show that the heat transfer capability of the loop has a maximum at a certain value of height. The optimal height to maximize the heat transfer is in a good agreement with analytical prediction to take into account the buoyancy and viscous forces in the loop.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -1
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• pp.22-25
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• 2002

The Mass production of ceramic heater has encountered with the estimation for the proper parameters of the printing conditions. This paper presents a method to estimate the squeegee pressure. It uses resistance distribution from the trial run with approximate squeegee pressure which comes from statistical process control (SPC). Then, the resistance distribution and its total resistance are input to the backpropagation neural networks that can recognize resistance's distribution patterns. The value of output network derived from the input value can identify to the appropriate squeegee pressure. The experimental results are demonstrated In ensure the efficiency and the reliability of this method with the accuracy 96.75 percent. Indeed, embedded on this method will aid us to reduce the loss from the normal mass production.