Resistance Development in Au/YBCO Thin Film Meander Lines under High-Power Fault Conditions

김혜림,심정욱,최인지,임성우,현옥배,Kim, H.R.,Sim, J.,Choi, I.J.,Yim, S.W.,Hyun, O.B. The Korean Superconductivity Society 2006 Progress in superconductivity Vol.8 No.1

We investigated resistance development in $Au/YBa_2Cu_3O_7(YBCO)$ thin film meander lines during high-power faults. The meander lines were fabricated by patterning 300 nm thick YBCO films coated with 200 nm thick gold layers into meander lines. A gold film grown on the back side of the substrate was also patterned into a meander line. The front meander line was connected to a high-power fault-test circuit and the back line to a DC power supply. Resistance of both lines was measured during the fault. They were immersed in liquid nitrogen during the experiment. Behavior of the resistance development prior to quench completion could be understood better by comparing resistance of the front meander lines with that of the back. Quench completion point could be determined clearly. Resistance and temperature at the quench completion point were not affected by applied field strength. The experimental results were analyzed quantitatively with the concept of heat transfer within the meander lines/substrate and to the surrounding liquid nitrogen. In analysis, the fault period was divided into three regions: flux-flow region, region prior to quench completion, and region after quench completion. Resistance was calculated for each region, reflecting the observation for quench completion. The calculated resistance in three regions was joined seamlessly and agreed well with data.

3원색 분산염료를 이용한 PET 섬유의 Black 염색

김혜림,장혜경,이정진,Kim, Hae-Rim,Jang, Hae-Kyoung,Lee, Jung-Jin 한국섬유공학회 2008 한국섬유공학회지 Vol.45 No.6

In black dyeing of PET fabric, high concentrations of disperse dyes of three primary color are generally required, which leads low exhaustion level of dyes and discharge of unfixed dye into dyehouse effluent. In this study, the effect of combination ratio of dye concentration, liquor ratio, and dyeing pH on dyeing and color property of black dyed PET fabric was investigated. From the results, high K/S values and low lightness $(L^*)$ of PET fabric could be obtained with relatively small amount (1%owf) of yellow dye on condition that red and blue dye were used in high concentration. The dyeing results of red dye were consistent with those of yellow dye while blue dye did not follow the trend. Use of small amount of blue dye and large amount of yellow and red dyes resulted in PET fabric of grayish red color instead of black. Dyeing and color property of black dyed PET fabric were found to be dependent upon dyeing pH while not on liquor ratio.

나노웹으로 코팅된 네오프렌 직물의 제조 및 특성분석

김혜림,이선희,Kim, Hyelim,Lee, Sunhee 한국섬유공학회 2016 한국섬유공학회지 Vol.53 No.2

The main objective of this study was to develop improved functional textiles for marine leisure clothing. Neoprene fabrics were coated with carbon nanofibers (CNFs)/Poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) composite solution comprising 0-16 wt% CNF in 1-5 wt% PVDF-HFP via electrospinning. Electrospinning was carried out from 15 to 24 kV. Neoprene textiles coated with the CNF/PVDF-HFP composite with various applied voltages were characterized as follows: Morphology was examined using an image analyzer microscope system and a field emission scanning electron microscope (FE-SEM). The thermal storage property of these materials was also analyzed using a thermal imaging camera with a forward looking infrared (FLIR) system. The resultant samples that were laminated with a knitted fabric composed of 80% nylon and 20% polyurethane were subjected to a thermal insulation property test. The test and control specimens were irradiated for 60 min. The test specimen and the control specimen were analyzed by considering the differences in temperature between both specimens on heating. Water penetration resistance of the laminated knitted fabric with the CNF/PVDF-HFP composite nanoweb-coated neoprene fabric was measured. The water repellent property test was conducted using a drop shape analyzer (DE/DSA 100, Kruse). The results indicated that an increase in the density of nanoweb-coated neoprene fabric surface correlated with improved thermal storage, thermal insulation, water penetration resistance, and water repellent properties. In addition, increasing amounts of CNFs in the CNFs/PVDF-HFP composite solution resulted in increased thermal storage, thermal insulation, and water repellent properties.

Voltage Applicable to $Au/YBa_2Cu3O_7$ Meander Lines

김혜림,임성우,유승덕,박충렬,양성은,김우석,현옥배,Kim, H.R.,Yim, S.W.,Yu, S.D.,Park, C.R.,Yang, S.E.,Kim, W.S.,Hyun, O.B. The Korean Superconductivity Society 2010 Progress in superconductivity Vol.12 No.1

We investigated the voltage applicable to $Au/YBa_2Cu3O_7$ (YBCO) meander lines. The meander line was fabricated by patterning Au/YBCO thin films grown on sapphire substrates by photolithography. It was subjected to simulated AC fault currents, and the resistance was measured and analyzed. The samples were immersed in liquid nitrogen during the experiment for effective cooling. The voltage applicable to the meander lines depended on the fault duration. Dependence was strong at short fault durations, and weak at long durations. When the voltage was plotted as a function of the fault duration on a log-log scale, data fell more or less on straight lines for all meander lines. In other words, the voltage applicable to Au/YBCO meander lines on sapphire substrates was inversely proportional to $t^b$, where t is the fault duration and b ranges from 0.4 to 0.5. The results were analyzed quantitatively with the concept of heat balance. Under adiabatic condition, the voltage is to be inversely proportional to $t^{0.5}$ for all samples. Less value of b for some samples is thought to be due to cooling of the samples by liquid nitrogen.

Quench Development in Coated Conductors

김혜림,박충렬,임성우,유승덕,오성용,현옥배,Kim, H.R.,Park, C.R.,Yim, S.W.,Yoo, S.D.,Oh, S.Y.,Hyun, O.B. The Korean Superconductivity Society 2009 Progress in superconductivity Vol.10 No.2

We measured and analyzed the quench development in coated conductor(CC) tapes. The CC was grown on hastelloy substrates and has an Ag protection layer. The tapes were subjected to simulated AC fault currents for quench development measurement. They were immersed in liquid nitrogen during the experiment. The quench resistance increased rapidly first, and the increase slowed down afterwards. It increased linearly with applied voltage at lower voltages, and depended less strongly on applied voltage at higher voltages. The resistance was compared with that of Au/YBCO films grown on sapphire substrates, and found to increase more monotonously than the latter. Data were analyzed quantitatively with the concept of heat transfer within the tape and the surrounding liquid nitrogen. A heat balance equation was derived and solved, taking into consideration temperature dependence of thermal parameters of the tapes. Solutions, together with values of thermal parameters taken from the literature, explained the data well. Cooling by liquid nitrogen affected the quench development considerably at lower applied voltages. Dependence on applied voltages could be also understood quantitatively.

Temperature Behavior of Superconducting Fault Current Limiters during Quenches

김혜림,심정욱,현옥배,Kim H.-R.,Sim J.,Hyun O.-B. The Korean Superconductivity Society 2005 Progress in superconductivity Vol.6 No.2

We investigated temperature behavior of superconducting fault current limiters (SFCLs) during quenches. Knowledge on temperature behavior during quenches is important to the design of SFCLs, because the temperature of SFCLs is related to their stability. SFCLs were fabricated by patterning $Au/YBa_2Cu_3O_7$ thin films grown on sapphire substrates into meander lines by photolithography. A gold film grown on the back side of the substrate was patterned into a meander line, and used as a temperature sensor. The front meander line was subjected to simulated AC fault currents, and the back line to DC current. They were immersed in liquid nitrogen during the experiment for effective cooling. Overall, temperature at the back side of SFCLs was close to that at the front side. It was closer at the beginning of faults, and at lower applied voltages. Temperature distribution at the back side was even except at the edge, as at the front side. These results tell that the whole SFCL was heated to similar degree during quenches, and that effective cooling of SFCLs at the back side is as important to the stability of SFCLs as at the front side. The results could be explained with the concept of heat transfer within the film.

배터리 충전방식을 고려한 신재생에너지 기반 분산발전시스템의 용량선정

김혜림,김동섭,Kim, Hye Rim,Kim, Tong Seop 한국플랜트학회 2021 플랜트 저널 Vol.17 No.3

The interest in renewable energy-based distributed power generation systems is increasing due to the recognitions of the breakthrough of existing centralized power generation, energy conversion, and environmental problems. In this study, the optimal capacity was selected by simulating a distributed power generation system based on PV and WT using lead acid batteries as the energy storage system. CHP was adopted as the existing power source, and the optimal capacity of the system was derived through MOGA according to the operating modes(full load/part load) of the existing power source. In addition, it was confirmed that the battery life differs when the battery charging method is changed at the same battery capacity. Therefore, for economical and stable power supply and demand, the capacity selection of the distributed generation system considering the battery charging method should be performed. 기존의 중앙집중식 발전의 탈피와 에너지 전환 및 환경문제 인식에 의해 신재생에너지 기반의 분산발전시스템에 대한 관심이 증가하고 있다. 본 연구에서는 에너지저장장치로 납축전지를 사용하는 PV 및 WT 기반의 분산발전시스템을 모사하여 최적용량을 선정하였다. 기존 발전원으로 CHP를 채택하였으며 시스템의 최적용량은 기존발전원의 운전상황(전부하/부분부하)에 따라 MOGA를 통해 도출하였다. 또한 동일한 배터리 용량에서 배터리 충전방식이 달라지면 배터리의 수명이 달라지는 것을 확인하였다. 따라서 경제적이고 안정적인 전력수급을 위해서는 배터리 충전방식을 고려한 분산발전시스템의 용량선정이 수행되어야 한다.

Scintillation properties of the Gd3Al2Ga3O12 : Ce crystal

김혜림,김홍주,장은정,이원근,기문광,Heun-Duk Kim,전구식,Vladimir Kochurikhin 한양대학교 세라믹연구소 2015 Journal of Ceramic Processing Research Vol.16 No.1

We investigated luminescence and scintillation properties of the Gd3Al2Ga3O12 : Ce (GAGG) crystal grown in TPS(Total Polishing Solution) Co.. The GAGG crystal has the highest light yield among oxide crystal at room temperature and fast decay time for the detection of radioactivity and in nuclear and particle physics experiments and medical imaging. The scintillation properties of the GAGG crystal were studied by comparing the GAGG crystals grown by two companies. We measured an X-ray induced emission spectra, an energy resolution, an absolute light yield and a decay time. A pulse shape discrimination capability for a and g-ray was also demonstrated.

충북 제천 남천초등학교 발명공작교실

김혜림,Kim, Hye-Rim 한국발명진흥회 2006 發明特許 Vol.31 No.2

Analysis on Recovery in Au/YBCO thin Film Meander Lines

김혜림,임성우,오성용,현옥배,Kim, H.R.,Yim, S.W.,Oh, S.Y.,Hyun, O.B. The Korean Superconductivity Society 2007 Progress in superconductivity Vol.9 No.1

We investigated recovery in $Au/YBa_2Cu_3O_7$ (YBCO) thin film meander lines on sapphire substrates. The meander lines were fabricated by patterning YBCO films coated with gold layers. The lines were subjected to simulated AC fault current and then small current was applied for recovery measurements. The samples were immersed in liquid nitrogen during the experiment. After the fault, the resistance decreased linearly, first slowly and then fast to zero. The initial slow decrease was due to the decrease of the meander line temperature, whereas the fast decrease was originated from the transition from the normal state to the superconducting state. The recovery speed depended on the size of samples, and was faster in the smaller samples during the whole period of recovery. The experimental results were analyzed quantitatively with the concept of heat transfer within the sample and to the surrounding liquid nitrogen. A heat balance equation was solved for the initial phase of recovery, and an expression for the time dependence of resistance was obtained. The result agreed with data well.