• The Korean Journal of Ceramics
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• v.5 no.4
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• pp.336-340
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• 1999

Glasses in the system $CaO-TiO_2-SiO_2-Al_2O_3-ZrO_2-B_2O_3$ were investigated to find the glass seal compositions suitable for use in the planar solid oxide fuel cell (SOFC). Glass-ceramics prepared from the glasses by one-stage heat treatment at $1,000^{\circ}C$ showed various thermal expansion coefficients (i,e., $8.6\times10^{-6^{\circ}}C^{-1}$ to $42.7\times10^{-6^{\circ}}C^{-1}$ in the range 25-$1,000^{\circ}C$) due to the viscoelastic response of glass phase. The average values of contact angles between the zirconia substrate and the glass particles heated at 1,000-$1,200^{\circ}C$ were in the range of $131^{\circ}\pm4^{\circ}$~$137^{\circ}\pm9^{\circ}$, indicating that the glass-ceramic was in partial non-wetting condition with the zirconia substrate. With increasing heat treatment time of glass samples from 0.5 to 24 h at $1,100^{\circ}C$, the DC electrical conductivity of the resultant glass-ceramics decreased from at $800^{\circ}C$. Isothermal hold of the glass sample at $1100^{\circ}C$ for 48h resulted in diffusion of Ca, Si, and Al ions from glass phase into the zirconia substrate through the glass/zirconia bonding interface. Glass phase and diffusion of the moving ion such as $Ca^{2+}$ in glass phase is responsible for the electrical conduction in the glass-ceramics.

• Korean Journal of Materials Research
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• v.9 no.5
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• pp.509-514
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• 1999

Interest in the integrated capacitors, which make it possible to reduce the size of and to obtain improved electrical performance of an electronic system, is expanding. In this study, $Ta_2$O\ulcorner thin film capacitors for MCM integrated capacitors were fabricated on a Upilex-S polymer film by DC magnetron reactive sputtering and the effects of low temperature annealing at various atmospheres and substrate surface morphology on the capacitor characteristics were discussed. The low temperature($150^{\circ}C$) annealing produced improved capacitor yield irrespective of the annealing at mosphere. But the leakage current of the $O_2$-annealed film was larger than that of any other films. This is presumably mosphere. But the leakage current of the $O_2$-annealed film was larger than that of any other films. This is presumably due to the change of the $Ta_2$O\ulcorner film surface by oxygen, which was explained by conduction mechanism study. Leakage current and breakdown field strength of the capacitors fabricated on the Upilex-S film were 7.27$\times$10\ulcornerA/$\textrm{cm}^2$ and 1.0 MV/cm respectively. These capacitor characteristics were inferior to those of the capacitors fabricated on the Si substrate but enough to be used for decoupling capacitors in multilayer package. Roughness Analysis of each layer by AFM demonstrated that the properties of the capacitors fabricated on the polymer film were affected by the surface morphology of the substrate. This substrate effect could be classified into two factors. One is the surface morphology of the polymer film and the other is the surface morphology of the metal bottom electrode determined by the deposition process. Therefore, the control of the two factors is important to obtain improved electrical of capacitors deposited on a polymer film.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.6-6
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• 2010

Indium Tin Oxide (ITO)를 포함한 Transparent Conduction Oxide (TCO)는 LCD, OLED와 같은 Display, 그리고 Solar Cell 등 광신호와 전기신호간 변환이 필요한 모든 Device에 반드시 필요한 핵심 물질로, 특히 고특성 Display의 투명전극에서 요청되는 95% 이상의 투과도와 $15\;{\Omega}/{\square}$ 이하의 면저항 특성을 동시에 만족할 수 있는 기술은 현재까지 Plasma Sputtering 공정으로 $160^{\circ}C$ 이상에서 증착된 ITO 박막이 유일하다. 그러나, 최근 차세대 기술로서 Plastic Film을 기반으로 하는 Flexible Display 및 Flexible Solar Cell 구현에 대한 요구가 급증하면서, Plastic Film 기판위에 Plasma Damage이 없이 상온에 가까운 저온 ($100^{\circ}C$ 이하)에서 특성이 우수한 ITO 투명전극을 형성 할 수 있는 기술의 확보가 중요한 현안이 되고 있다. 지난 10년 동안 $100^{\circ}C$이하 저온에서 고특성의 ITO 또는 TCO 박막을 얻기위한 다양한 연구와 구체적인 공정이 활발히 연구되어 왔으나, ITO의 결정화 온도 (통상 $150{\sim}180^{\circ}C$)이하에서 증착된 ITO박막은 비정질 상태의 물성적 특성을 보여 원하는 전기적, 광학적 특성확보가 어려웠다. 본 논문에선 기본적으로 절연체 특성을 가져야 하는 산화물인 TCO가 반도체 또는 도체의 물리적 특성을 보여주는 기본원리의 고찰을 토대로, 재료학적 특성상 Crystalline 구조를 보여야 하는 ITO (Complex Cubic Bixbyte Structure)가 Plasma Sputtering 공정으로 저온에서 증착될 때 비정질 구조를 갖게 되는 원인을 규명하고, 이를 바탕으로 저온에서 증착된 ITO가 Crystalline 구조를 유지 할 수 있게 하고, Stress Control에 유리한 Nano-Crystalline 박막을 형성하면서 Crystallinity를 임의로 조절 할 수 있는 새로운 기술인 Magnetic Field Shielding Sputtering (MFSS) 공정과 최근 성과를 소개한다. 한편, 또 다른 새로운 저온 TCO 박막형성 기술로서, 유기반도체와 같은 Process Damage에 매우 취약한 유기물 위에 Plasma Damage 없이 TCO 박막을 직접 형성할 수 있는 Neutral Beam Assisted Sputtering (NBAS) 기술의 원리를 설명하고, 본 공정을 적용한 Top Emission OLED 소자의 결과를 소개한다. 또한, 고온공정이 수반되는 Solar Cell용 투명전극의 경우, 통상의 TCO박막이 고온공정을 거치면서 전기적 특성이 열화되는 원인을 규명하고, 이에 대한 근본적 해결 방법으로 ITO 박막의 Dopant인 Tin (Sn) 원자의 활성화를 증가시킨 Inductively Coupled Plasma Assisted DC Magnetron Sputtering (ICPDMS)의 원리와 박막의 물성적 특성과 내열 특성을 소개한다.

• Journal of IKEEE
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• v.18 no.2
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• pp.282-290
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• 2014

This paper presents the design of embedded electrical power control unit for Personal Electrical Vehicle(PEV). The embedded unit is designed using PIC18F8720 processor, 16Mb flash ROM, 32Mb SDRAM and signal condition circuits. The proposed PEV consists of 4KW in-wheel Brushless DC Motor(BLDCM), 3 phase voltage source inverter with the $180^{\circ}$ conduction space vector PWM method, PID speed controller and the embedded control unit. The PEV has mechanical manufacture of inverse 3 wheel system, which is applied by the in-wheel BLDCM and steering mechanism with tilting function. Also, the performances of the proposed embedded electrical power control unit are verified through the lab experiment and road driving test of PEV.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.11
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• pp.1213-1217
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• 2011

Electric stimulators are used for various treatments, such as for pain relief and to improve rehabilitation in and out of the hospital. However, if the stimulation pulse affects the patient's heart, it can cause critical cardiac disorders such as arrhythmia or ventricular fibrillation. As a result, it must be ensured that the transmission length of the stimulation pulse does not exceed the proper range in the design of an electric stimulator. Furthermore, every anticipated risk factor must be monitored in in-vitro and in-vivo experiments. A new stimulator was designed to supply continuous 0.001 J stimulation pulses at a rate of 60 pulses per second. To evaluate the safety of the new electric stimulator and to measure its energy transfer and pulse transmission length, we built a conduction model that was filled with saline and measured the electric field at various positions in response to real stimulations. In an animal experiment with two pigs, heart disorders were induced by applying electric stimulation to tissues near the heart. These heart disorders were different from the result obtained with 9 V DC stimulation.

• Journal of the Korean Ceramic Society
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• v.52 no.5
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• pp.299-303
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• 2015

The electrolyte is an important component in determining the performance of Fuel Cells. Especially, investigation of the conduction properties of electrolytes plays a key role in determining the performance of the electrolyte. The electrochemical properties of Yttrium stabilized zirconia (YSZ) were measured to allow the use of this material as an electrolyte for solid oxide fuel cells (SOFC) in the temperature range of $700-1000^{\circ}C$ and in $0.21{\leq}pO_2/atm{\leq}10^{-23}$. A Hebb-Wagner polarization experimental cell was optimally manufactured; here we discuss typical problems associated with making cells. The partial conductivities due to electrons and holes for 8YSZ, which is known as a superior oxygen conductor, were obtained using I-V characteristics based on the Hebb-Wagner polarization method. Activation energies for holes and electrons are $3.99{\pm}0.17eV$ and $1.70{\pm}0.06eV$ respectively. Further, we calculated the oxygen ion conductivity with electron, hole, and total conductivity, which was obtained by DC four probe conductivity measurements. The oxygen ion conductivity was dependent on the temperature; the activation energy was $0.80{\pm}0.10eV$. The electrolyte domain was determined from the top limit, bottom limit, and boundary (p=n) of the oxygen partial pressure. As a result, the electrolyte domain was widely presented in an extensive range of oxygen partial pressures and temperatures.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.3
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• pp.191-198
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• 2007

This paper proposes the instantaneous source voltage and phase current control for torque ripple reduction of a high speed miniature BLDC motor. As compared with general BLDC motor, a high speed miniature BLDC motor has a fast electrical time-constant. So the current and torque ripple are very serious in a conventional PWM switching during conduction period. In order to reduce the switching current ripple, instantaneously controlled source voltage is supplied to the inverter system according to the motor speed and load torque. In addition, the fast hysteresis current controller can keep the phase current In the limited band. The proposed method is verified by the computer simulation and experimental results.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.1
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• pp.89-101
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• 2001

The conventional pattern-methods for discrimination of acupoint, meridian line which is the basic object of diagnosis and medical treatment in oriental medicine is discriminated the conduction point by the stimulation in body skin with DC. But, it is not sufficient to truth in discrimination ratio, coincident ratio, body effect, reproductivity. Therefore, this paper is extracting the optimal parameter of frequency and waveform in order to improve the conventional pattern, and proposing the SPAC(Single Power Alternative Current) stimulus pattern applying that. Also, this algorithm proposes to be able to discriminate with low pressure of the electrode by displaying in the level meter both the absolution and relation value of the skin current. It is able to decrease pain and body effect by electrode pressure and discriminate acupoint regardless of skin current in difficult discrimination spot. It is compared the performance of system applying the extracted optimal parameter and algorithm, and it is confirmed that there is difference in discrimination parameter of acupoint reacted to the individual and the meridian. It is compared that discrimination, coincident ratio of the traditional acupoints as the acupoint stimulation pattern. It is confirmed truth of optimal parameter and discrimination algorithm. Keyword: Meridian, Discrimination, Coincident, Body effect, Reproductivity, SPAC, Optimal parameter.

• Korean Journal of Optics and Photonics
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• v.14 no.3
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• pp.343-348
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• 2003

Indium tin oxide (ITO) thin films (170 nm) were grown by DC magnetron sputtering deposition on Coming glass substrates without a post annealing. The electrical transport and optical properties of the films have been investigated as a function of deposition temperature $T_{s}$ (10$0^{\circ}C$$\leq$ $T_{s}$$\leq$35$0^{\circ}C$) and oxygen partial pressure $P_{o_{2}}$, (0 $P_{o_{2}}$ $\leq$ 10$^{-5}$ torr). Films were deposited from a high density (99% of theoretical density) ITO target (I $n_2$ $O_3$: Sn $O_2$= 90 wt% : 10 wt%) made of ITO nano powders. With an increase of $T_{s}$ the electrical resistivity p of ITO thin films was found to decrease, but the mobility $\mu$$_{H}$ was found to increase. The carrier density nu shows the maximum value of 6.6$\times$10$^{20}$ /㎤ at $T_{s}$ = 30$0^{\circ}C$. At fixed Is, with an increase of the oxygen partial pressure, $n_{H}$ and $\mu$$_{H}$ were found to decrease, but p was found to increase. The minimum resistivity and maximum mobility values of the ITO films were found to be 0.3 mΩ.cm and 39.3 $\textrm{cm}^2$/V.s, respectively. The visible transmittance of the ITO films was above 80%.. 80%..