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The Relation Between Local Hysteresis Losses and Remanent Magnetic Fields in HTSC Films
Muyong Kim,Heeyeon Park,Chan Kim,Sang-Kook Park,Ri, H.-C Institute of Electrical and Electronics Engineers 2017 IEEE transactions on applied superconductivity Vol.27 No.4
<P>Various critical state models have been developed to understand the hysteresis loss mechanism of high-temperature superconducting (HTSC) films. The analytic relation between the hysteresis loss and the remanent field was obtained based on Bean's critical state model for thin films in the full-penetration case. Furthermore, numerical calculation of local hysteresis loops was carried out by Kim's critical state model. In this paper, we investigated local hysteresis losses for a GdBCO coated conductor by using low-temperature scanning Hall probe microscopy and reproduced the experimental results by applying the critical state model. Because of the demagnetizing effect in thin films, analysis of local hysteresis losses can be useful approach to understand of total hysteresis losses.</P>
Analysis of the local superconducting properties in YBCO coated conductors with striations
Kim, Muyong,Park, Sangkook,Park, Heeyeon,Ri, Hyeong-Cheol The Korea Institute of Applied Superconductivity a 2015 한국초전도저온공학회논문지 Vol.17 No.2
In order to realize economical applications, it is important to reduce the ac loss of 2G high-temperature superconductor coated conductors. It seems to be reasonable that a multi-filamentary wire can decrease the magnetization loss. In this study, we prepared two samples of YBCO coated conductors with striations. We measured local superconducting properties of both samples by using Low Temperature Scanning Laser and Hall Probe Microscopy (LTSLHPM). The distribution of the local critical temperature of samples was analyzed from experimental results of Low Temperature Scanning Laser Microscopy (LTSLM) near the superconducting transition temperature. According to LTSLM results, spatial distributions of the local critical temperature of both samples are homogeneous. The local current density and the local magnetization in samples were explored from measuring stray fields by using Scanning Hall Probe Microscopy (SHPM). From SHPM results, the remanent field pattern of the one bridge sample in an external magnetic field confirms the Bean's critical state model and the three bridge sample has similar remanent field pattern of the one bridge sample. The local magnetization curve in the three bridge sample was measured from external fields from -500 Oe to 500 Oe. We visualized that the distribution of local hysteresis loss are related in the distribution of the remanent field of the three bridge sample. Although the field dependence of the critical current density must be taken into account, the relation of the local hysteresis loss and the remanent field from Bean's model was useful.
Analysis of the local superconducting properties in YBCO coated conductors with striations
Muyong Kim,박상국,Hee-Yeon Park,이형철 한국초전도.저온공학회 2015 한국초전도저온공학회논문지 Vol.17 No.2
In order to realize economical applications, it is important to reduce the ac loss of 2G high-temperature superconductor coatedconductors. It seems to be reasonable that a multi-filamentary wire can decrease the magnetization loss. In this study, we preparedtwo samples of YBCO coated conductors with striations. We measured local superconducting properties of both samples by usingLow Temperature Scanning Laser and Hall Probe Microscopy (LTSLHPM). The distribution of the local critical temperature ofsamples was analyzed from experimental results of Low Temperature Scanning Laser Microscopy (LTSLM) near thesuperconducting transition temperature. According to LTSLM results, spatial distributions of the local critical temperature of bothsamples are homogeneous. The local current density and the local magnetization in samples were explored from measuring strayfields by using Scanning Hall Probe Microscopy (SHPM). From SHPM results, the remanent field pattern of the one bridge samplein an external magnetic field confirms the Bean’s critical state model and the three bridge sample has similar remanent field patternof the one bridge sample. The local magnetization curve in the three bridge sample was measured from external fields from -500 Oeto 500 Oe. We visualized that the distribution of local hysteresis loss are related in the distribution of the remanent field of the threebridge sample. Although the field dependence of the critical current density must be taken into account, the relation of the localhysteresis loss and the remanent field from Bean’s model was useful.
차실내 이산화탄소 농도 제어를 통한 A/C부하 감소 및 연비 향상
이정훈(Jeonghoon Lee),김영민(Youngmin Kim),오세원(Saewon Oh),박준규(Jungyu Park),김영길(Yeongkil Kim),김무용(Muyong Kim),구준모(Junmo Ku) 한국자동차공학회 2011 한국자동차공학회 학술대회 및 전시회 Vol.2011 No.11
Automotive air conditioning decreases approximately 25% of the vehicle fuel economy in the case of the summer and about 10% per year. A recirculation air mode, in which outside hot air influx is blocked, can improve fuel economy because a ventilation loss covers more than 10% of thermal heat load, but long time stay in this mode cause discomfort in ventilation. According to the United States air quality-related standards, CO₂ concentration, 2000 ppm and later, may induce drowsiness and can lead to the possibility of a vehicle crash, so the CO₂ concentration control is important. In this study, NDIR-Non Dispersive Infrared- CO₂ sensor measured the cabin concentrations in real time, a recirculation air rate and airflow to the cabin improved fuel economy and comfort in ventilation. This algorithm came from response surface method through a lot of vehicle experiments and computer simulation results, In ambient temperature 35℃, humidity 40%RH, vehicle speed 80 ㎞/h, sunload 850W/m2, 2 persons boarding conditions, through cabin CO₂ concentration remained constant or below 1000ppm, fuel economy increased approximately 4.5%. Also, this paper proposed the integrated recirculating air control strategies to block exhaust gas inflow into cabin by AQS (Air Quality Sensor) system and prevent fogging on windshield glass using ADS(Auto Defog Sensor) system.