• Journal of Magnetics
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• v.21 no.2
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• pp.239-243
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• 2016

High temperature superconductor (HTS) magnet systems usually employ metal current leads which bridge between the cryogenic environment and room temperature. Such current leads are the dominant heat load for these magnet systems due to a combination of electrical resistance and heat conduction. HTS flux pumps enable large currents to be injected into a HTS magnet circuit without this heat load. We present results from an axial-type HTS mechanically rotating flux pump which employs a ferromagnetic circuit and a Cu-stabilized coated conductor (CC) HTS stator. We show the device can be described by a simple circuit model which was previously used to describe barrel-type flux pumps, where the model comprises an internal resistance due to dynamic resistance and a DC voltage source. Unlike previously reported devices, we show the internal resistance and DC voltage in the flux pump are not exactly proportional to frequency, and we ascribe this to the presence of eddy currents. We also show that this axial-type flux pump has superior current injection capability over barrel-type flux pumps which do not incorporate a magnetic circuit.

• Journal of Electrical Engineering and Technology
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• v.8 no.3
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• pp.603-609
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• 2013

In this paper, we describe the analysis of inkjet-printed silver (Ag) patterns on epoxy-coated substrates according to several reliability evaluation test method guidelines for conventional printed circuit boards (PCB). To prepare patterns for the reliability analysis, various regular test patterns were created by Ag inkjet printing on flame retardant 4 (FR4) and polyimide (PI) substrates coated with epoxy for each test method. We coated the substrates with an epoxy primer layer to control the surface energy during printing of the patterns. The contact angle of the ink to the coated epoxy primer was $69^{\circ}$, and its surface energy was 18.6 $mJ/m^2$. Also, the substrate temperature was set at $70^{\circ}C$. We were able to obtain continuous line patterns by inkjet printing with a droplet spacing of $60{\mu}m$. The reliability evaluation tests included the dielectric withstanding voltage, adhesive strength, thermal shock, pressure cooker, bending, uniformity of line-width and spacing, and high-frequency transmission loss tests.

• Korean Journal of Optics and Photonics
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• v.24 no.5
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• pp.251-255
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• 2013

In this paper, the characteristics of a humidity sensor implemented by Mach Zehnder Interferometer (MZI) in a Planar Lightwave Circuit (PLC) have been designed and demonstrated. The humidity outside is detected with polyvinylpyrrolidone (PVP) coated on the etched arm of the MZI. The length of the etched arm is 10 mm and the PVP was coated by dip-coating into the etched region. As the refractive index of the PVP changes with the surrounding humidity, the PVP-coated humidity sensor presented changes in the interferogram depending on RH (Relative Humidity) around the PLC. The measured results show that the proposed humidity sensor works successfully in the range of 30% to 80% of RH.

• Tribology and Lubricants
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• v.29 no.3
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• pp.143-148
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• 2013

In this study, several sensor parts used to obtain better signal stability are designed, a separate control circuit for the sensor is developed, and the results obtained using this control circuit are analyzed. The capacitances of the whole sensor system are measured using the control circuit connected to an improved flexible printed circuit board and an asymmetric dual sensor coated with a ceramic material. To realize good discrimination for a small change in the measured capacitance as the engine oil deteriorates, a commercial application-specific integrated circuit is installed on the control circuit as a capacitance-to-digital converter. The absolute error of a measured signal is found to be approximately ${\pm}4fF$.

• Korean Journal of Materials Research
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• v.26 no.2
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• pp.84-89
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• 2016

We present the rectifying and nitrogen monoxide (NO) gas sensing properties of an oxide semiconductor heterostructure composed of n-type zinc oxide (ZnO) and p-type copper oxide thin layers. A CuO thin layer was first formed on an indium-tin-oxide-coated glass substrate by sol-gel spin coating method using copper acetate monohydrate and diethanolamine as precursors; then, to form a p-n oxide heterostructure, a ZnO thin layer was spin-coated on the CuO layer using copper zinc dihydrate and diethanolamine. The crystalline structures and microstructures of the heterojunction materials were examined using X-ray diffraction and scanning electron microscopy. The observed current-voltage characteristics of the p-n oxide heterostructure showed a non-linear diode-like rectifying behavior at various temperatures ranging from room temperature to $200^{\circ}C$. When the spin-coated ZnO/CuO heterojunction was exposed to the acceptor gas NO in dry air, a significant increase in the forward diode current of the p-n junction was observed. It was found that the NO gas response of the ZnO/CuO heterostructure exhibited a maximum value at an operating temperature as low as $100^{\circ}C$ and increased gradually with increasing of the NO gas concentration up to 30 ppm. The experimental results indicate that the spin-coated ZnO/CuO heterojunction structure has significant potential applications for gas sensors and other oxide electronics.

• Progress in Superconductivity and Cryogenics
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• v.9 no.1
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• pp.9-13
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• 2007

Coated conductor(CC) is recently in actively progress for the research and development, and its can be used various stabilizer lot the specific requirements for each application. Among various superconducting applications, coated conductor applied to superconducting fault current limiters(SFCLS) bypasses fault current to its stabilizer, where the surge is abruptly reduced ; thus, stainless steel, which has large resistivity can be a suitable stabilizer for SFCLS. Despite high n-value of the YBCO, CC stabilized with stainless steel did not effectively limit the first peak fault current. In the short circuit test results of AMSC's 344S, a half period delay was observed between the fault and the generation of resistance(60Hz). In this paper, we performed short-circuit experiments with stacked and unstacked CC and compared the test results to analyze effective fault current limiting characteristics. we compared time of the generated resistance as the fault current limiting characteristics and made the samples one is the stacked CC and the other is unstacked CC. These samples were used equal numbers of pieces of CC. In addition, comparison and analysis was made for the stacked structure by measuring fault current limiting characteristics with respect to thermal insulation by impregnating with epoxy resin.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.687-690
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• 2004

Fabrication and characterization of dye-sensitized TiO2 solar cells(DSSC) consisting of spray-coated TiO2 electrode, an electrolyte containing I-/I3- redox couple, and a Pt-coated counter electrode carried out, using mainly FE-SEM and solar simulator. Also, effect of rapid thermal annealing(RTA) temperatue on I-V curves of DSSCS consisting of approximately 10m thickness and $5{\times}5mm2$ active area. No significant difference in the apparent size of TiO2 clusters was observed with increasing RTA temperature. Also, an open circuit voltage(Voc) of approximately 0.70V and a short-circuit photocurrent(Jsc) of 8 to 12mA/cm2 were observed in the TiO2 solar cell. With increasing RTA temperature upto 550oC, photocurrent density of dye-sensitized solar cells was enhanced, leading to enhancing the efficiency of dye-sensitized solar cells having Pt-electroplated counter electrode.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.465-467
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• 1997

The oscillating properties of quartz Crystal Microbalance(QCM) were analyzed by electrical measurement. We tried to analyze the properties of quartz crystal coated with Langmuir-Bladgett(LB) films using the frequency and resistance at resonance in the electrical equivalent circuit. The resonant frequency was decreased linearly as to layers of LB films, however, there are some gap between theoretical values, Sauerbrey's equation and experimental values. The resistance was increase nonlinearly as to layers.

• Journal of Chest Surgery
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• v.33 no.12
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• pp.954-958
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• 2000

배경: 헤파린표면처리 도관(Heparin-coated circuit: HCC)이 도관과 혈액사이의 반응(Blood-marterial reaction)을 줄여주어서 보체활성화(complement activation), 백혈구활성화(leukocyte activation)와 사이토킨 분비(cytokinerelease)등을 감소시켜 준다. 그러나 HCC가 수술 후에 출혈 양을 줄여주고 헌혈 필요량을 감소시켜 준다는 임상적 효과에 대해서는 인정된 부분이 많으나 아직까지 그 기전은 대부분은 미지의 상태로 남아있는 것이 사실이다. 본 연구는 HCC를 사용한 군(Group H)과 사용하지 않은 군(Group C)간에 심폐기 사용기간(Pumptime), 활성화 응고시간(activated clotting time: ACT)과 헤파린 사용량을 비교 분석해 봄으로서 두 군간에 존재할 수 있는 헤파린 사용량을 비교 분석해 본으로서 두 군간에 존재할 수 있는 헤파린 사용량 차이에 대하여 알아보려고 하게되었다. 대상 및 방법: 본원에서 1999년 5월 1일부터 동년 12월 31일 사이에 연령이 16세 이상인 환자에서 HCC를 사용했던 16명(Group H)과 사용하지 않았던 19명(Group C)을 대상으로 하였다. 모든 환자에서 수술 전 체중, 신장, 체표면적, 심폐기 사용시간(pumptime), 수술 중 최저체온, 대동맥 차단시간(Aortic cross clamping time. ACC time), ACT, 헤파린 및 프로타민 사용 양 등을 조사하였다. 결과: 연구대상 환자의 연령, 체중, 신장, 체표면적, 대동맥차단 시간, 체온 등은 HCC를 사용한 군(H 군)과 사용하지 않은 군(C군)간에 의미 있는 차이가 없었다(p<0.05). 헤파린 공급 전, 공급 후 20분, 40분, 60분과 프로타민 공급 후 20분에 측정한 ACT는 두 군간에 의미 있는 차이가 없었다. 두 군간의 처음에 공급한 헤파린 양과 총 프로타민 사용량은 차이가 없었으나(p>0.05), 추가 공급한 헤파린 양(11$\pm$30 versus 67$\pm$49mg, p<0.05)과 총 헤파린 사용량(176$\pm$44 versus 239$\pm$70mg, p<0.05)은 H군에서 의미 있게 적게 나왔다. 두 군간에서 심폐기 사용시간에는 차이가 없었으면서 H군에서 약 38%정도의 헤파린을 적게 사용하였다. 결론: 결론적으로 HCC의 사용으로 심폐기 사용 시간과 상관없이 추가하는 헤파린 양을 줄임으로서 총 헤파린 사용량을 줄여 줄 수 있었으며 이것이 HCC의 임상적 효과를 나타나게 하는 하나의 요소로 작용할 수 있다고 생각된다.

• KIEE International Transactions on Electrophysics and Applications
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• v.5C no.2
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• pp.76-80
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• 2005

In this paper, a miniaturized ring hybrid circuit is characterized based on a thin film microstrip (TFMS) on low-resistivity silicon. In order to obtain low-loss characteristics, a polyimide layer with 50 $\mu$m thickness is spin-coated onto the silicon to be used for the substrate. First, propagation characteristics of TFMS lines consisting of the ring hybrid circuit are presented. Then, a ring hybrid circuit based on TFMS is featured by employing the triple concentric circle approach for miniaturization. Triple concentric circle lines with $\lambda$$_{g}$/4 or 3$\lambda$$_{g}$/4 line lengths are implemented on the surface of the polyimide by circularly meandering to reduce the circuit size of the designed ring hybrid. Good agreement between measured and simulated results is obtained.