• Fire Science and Engineering
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• v.16 no.2
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• pp.8-13
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• 2002

Induction heating is widely used in today's industry, in operations such as metal hardening, pre-heating for forging operations, melting or cooking. In this paper, the magneto-thermal analysis of an induction heating jar(IH-JAR) was presented as an efficient design. The magnetic field intensity inside the axisymmetric shaped cooker was analyzed using three-dimensional axisymmetric finite element method(FLUX2D) and the effectual heat source was obtained by ohmic losses from eddy currents induced in the jar. The heat was calculated using the heat source and heating equation. Also, it was presented the temperature characteristics of the IH-JAR according to time and relative permeability in stainless parts and in aluminum parts.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.7
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• pp.610-614
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• 2008

In this work, the electrical and optical properties of the two different p-type GaN electrode schemes, ZnNi/ITO and ZnNi/Au, were compared each other, and applied to the top-emitting GaN/InGaN light-emitting diodes (LEDs). The ZnNi/ITO electrode showed much higher transmittance (90%) and slightly lower contact resistance $(1.27{\times}10^{-4}{\Omega}cm^2)$ than those (77%, $(2.26{\times}10^{-4}{\Omega}cm^2)$) of the ZnNi/Au at a wavelength of 460 nm. In addition, GaN LEDs having ZnNi/ITO showed accordingly higher light output power and luminous intensity than those having ZnNI/Au did at the current levels up to 1 A.

• Transactions on Electrical and Electronic Materials
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• v.14 no.4
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• pp.165-171
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• 2013

Nanostructured pure a-C and nitrogen doped a-C: N thin films with small particle size of, ~50 nm were obtained by Aerosol-assisted CVD method from the natural precursor camphor oil. Five samples were prepared for the a-C and a-C: N respectively, with the deposition temperatures ranging from $400^{\circ}C$ to $600^{\circ}C$. At high temperature, the AFM clarifies an even smoother image, due to the increase of the energetic carbon ion bombardment at the surface of the thin film. An ohmic contact was acquired from the current-voltage solar simulator characterization. The higher conductivity of a-C: N, of ${\sim}{\times}10^{-2}Scm^{-1}$ is due to the decrease in defects since the spin density gap decrease with the nitrogen addition. Pure a-C exhibit absorption coefficient, ${\alpha}$ of $10^4cm^{-1}$, whereas for a-C:N, ${\alpha}$ is of $10^5cm^{-1}$. The high ${\sigma}$ value of a-C:N is due to the presence of more graphitic component ($sp^2$ carbon bonding) in the carbon films.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.2
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• pp.152-155
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• 2011

Even though nano-scale materials were very advantageous for various applications, there are still problems to be solved such as the stabilization of surface state and realization of low contact resistances between a semiconducting nanowire and electrodes in nano-electronics. It is well known that the effects of contacts barrier between nano-channel and metal electrodes were dominant in carrier transportation in individual nano-electronics. In this report, it was investigated the electrical properties of GaN nanorod devices after chemical etching and rapid thermal annealing for making good contacts. After KOH wet-etching of the contact area the devices showed better electrical performance compared with non-treated GaN individual devices but still didn't have linear voltage-current characteristics. The shape of voltage-current properties of GaN devices were improved remarkably after rapid thermal annealing as showing Ohmic behaviors with further bigger conductivities. Even though chemical etching of the nanorod surfaces could cause scattering of carriers, in here it was shown that the most important and dominant factor in carrier transport of nano-electronics was realization of low contact barrier between nano-channel and metal electrodes surely.

• 한국전산유체공학회:학술대회논문집
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• 2005.10a
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• pp.311-317
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• 2005

It has been the most progressive interruption technique to use the ablation gas from the surface of PTFE nozzle driven by arc plasma during switching process in $SF_6$ gas circuit breakers. This advanced interruption technique can reduce the required mechanical energy to compress and blow the gas for extinguishing the arc plasma between the electrodes due to using the ablation effect instead. In order to consider the phenomena during calculation of switching process, it is required to confirm the principles of ablation from PTFE nozzle as well as of arc plasma during switching process. In this study, we have calculated the switching process considered the ablation of PTFE nozzle driven by arc plasma using multidisciplinary simulation technique and compared the results with the data without the ablation effect. More $50\%$ difference of pressure rise inside expansion chamber has been found from the results and it should be indispensable for this type of computational work to consider and include the ablation effect of PTFE nozzle. Further study on turbulence and radiation will be followed.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.918-921
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• 1992

A basic study on the discharge phenomenum of rod-to-rod microgap in the deionized water has been investigated with emphasis on the microgap spacing. The I-V charateristics for the case of ac and dc applied voltages had 3 different regions, a low conduction ohmic region, a medium conduction corona discharge region, and a high conduction arc discharge region. The corona discharge in the deionized water for the case of ac and de applied voltages had no different from the those in the air. But the arc discharge in the water occurred pulsative with sound which, however it is not clear, would be encounted due to the influences from the low temperature of the ambient water, vast of electrolytic generated electronegative gases(e.g. $O_2$, OH, O) and water molecules($H_2O$), and the space charge effects near the rod in the microgap from the ions of $H^+$, $OH^-$, $O_2^-$, etc, whose mobilities in the water are originally very low.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.298_299
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• 2009

전력분야 응용 중, 특히 교류손실측면에서 장점을 지니고 있는 HTS-케이블 및 HTS-한류기의 경우는 선진 세계 각 국에서 배전급 전력계통에 실증시험을 하는 단계까지 와 있는 실정이다. 국내에서도 한전 주관으로 실증시험을 그 목적으로 고창시험장에 100m급, 22.9kV/50MVA HTS-케이블이 설치되어 운전되고 있다. 이와 같이 다수본의 HTS-테이프로 구성되는 HTS-케이블에서 발생되는 교류손실은 HTS-케이블의 효율을 저하시킬 뿐만 아니라 냉동기비용 증가를 초래하지만 HTS-케이블 구조의 복잡성으로 인하여 교류손실에 대한 평가가 매우 난해하다. 따라서 본 논문에서는 고창HTS-케이블의 교류손실에 대하여 실험적 이론적 조사 및 검토를 하였다. 그 주요결과를 요약하면, 측정된 Bi도체의 교류손실에 대한 손실지수 ${\kappa}$는 약 2.5로 Cu 도체에서 발생하는 Ohmic손실의 지수(~2)와 비교하여 큰 것을 볼 수 있다. 또한 전기적인 방법으로 측정한 HTS-케이블의 총손실은 열량법으로 측정한 손실과 잘 일치한다.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.415-417
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• 2009

A low temperature decal (LTD) transfer method is tried to fabricated hydrocarbon (HC) membrane based MEA. Sandwiched structures of outer ionomer/catalyst/carbon coating/substrate, which had been developed for Nafion membrane, are used for transfer of catalyst to the HC membrane. Performances of the HC MEA before and after 500hr continuous operation are compared and it is found that a severe delamination occurs at the interface between the HC membrane and the catalyst layer, which is the main reason of the low performance and its degradation. The delamination is due probably to the different nature of HC membrane to the Nafion ionomer. A substitutional method, therefore, is suggested to overcome this. In such a way, the outer ionomer process is removed and the low transfer rate of catalyst by skipping the ionomer process is compensated with optimization of other process variables such as transfer time or temperature. The resulting performance is superior to the original LTD method, which can be explained in terms of low resistive components both in ohmic and kinetic.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.479-479
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• 2013

산화물 반도체 물질을 이용한 Thin film transistor (TFT) 소자는 기존의 비정질 Si TFT와 저온 다결정 Si TFT 소자가 가지지 못하는 장점들이 보고되면서 차세대 디스플레이용 소자로 주목을 받고 있다. 그 중 TFT의 채널 물질로 a-IGZO가 많이 활용되고 있다. a-IGZO의 활용이 더 많아지고 있는 이유는 저온공정이 가능하고 3.2 eV의 큰 밴드갭으로 투명하며 높은 균일도, 캐리어 이동도를 모두 가지고 있기 때문이다. 본 연구에서는 산화물 물질인 IGZO를 채널 층으로 사용한 TFT소자에서 IGZO의 캐리어인 전자의 이동경로를 금속을 통하여 이동하게 함으로써 전기적 특성의 변화를 관찰하였다. TFT는 다수 캐리어가 게이트 전압에 의하여 박막 아래쪽에 채널을 형성하여 동작한다. 이 때 IGZO박막과 SiO2 사이의 Al을 증착하여 다수 캐리어인 전자의 이동도를 향상시켰다. 전극으로 사용되어지는 Al은 IGZO박막과 ohmic contant이기 때문에 전자의 이동이 어렵지 않기 때문이다. 소자 제작은 게이트로 도핑된 P형 기판을 사용하였고 게이트 절연체로 SiO2 200 nm를 증착하였다. 채널층로 IGZO를 증착하기 전에 게이트 절연체 위에 evaporation으로 Al을 20 nm를 증착하였다. 이때 mask는 $2.4{\times}10^{-4}cm^2$ 크기의 dot 형태를 사용하였다. Al을 증착 후 RF sputtering으로 IGZO를 30 nm 증착하였으며 $350^{\circ}C$에서 90 min 동안 열처리하였다. 소스와 드레인은 evaporation으로 Al을 100 nm 증착하였다. HB 4145B 측정기로 I-V 그래프를 통하여 전기적 특성의 변화를 관찰하였다.

• Electrical & Electronic Materials
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• v.11 no.10
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• pp.60-65
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• 1998

Deposition conditions, surface morphology, and electrical properties of polyamic acid alkylamine salts (PAAS) Langmuir-Blodgett(LB) films have been investigated through a study of surface pressure-area $\pi$-A isotherms, AFM (atomic force microscopy), and current-voltage characteristics. To obtain the optimum conditions of film deposition, the $\pi$-A isotherms were examined by varying temperature, barrier moving speed, dipping speed, spreading amount of solution etc. The Z-type LB films were made at the surface pressure of 5 mN m-1 and 25 mN m-1 for the AFM study; the former surface pressure forms the gas phase and the latter one forms the solid phase. The LB film made in the gas phase show domains with a size of about 200 A diameter and 70 A height. However, the LB films made in the solid phase show a very smooth surface with 2 A surface roughness. In the current-voltage characteristics measured along the perpendicular direction of the films, ohmic conduction has been observed below 105 V cm-1 and the calculated electrical conductivity is about 10-13 S cm-1. Nonohmic conduction has been observed above = 10-11 V cm and the conduction mechanism can be explained by the Schottky effect.