• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.156-156
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• 1999

자성박막에 존재하는 자기구역의 형상 및 동력학은, 자성박막의 학문적 연구와 응용기술 개발의 핵심을 제공하는 매우 중요한 분야의 하나로서, 최근 크게 관심이 고조되고 있다. 본 연구에서는 차세대 광자기 재질로 각광받고 있는 Co/Pd 다층박막에서의 자기구역 형상 및 자기구역 동력학을 연구하였다. 전자빔 진공증착 시스템을 사용하여, Co 층의 두께와 Pd층의 두께, 그리고 전체 층수가 변화하는 일련의 Co/Pd 다층박막 시료를 제작하였다. 제작된 모든 시료가 명목두께에 대하여 4%의 정밀도로 제작되었음을 확인하였고, 제작된 시료의 자기 및 광자기 성질은 자기이력곡선 등을 측정하였다. 또한 고성능 광자기 Kerr 현미경 시스템을 이용하여 자성박막에 존재하는 자기구역의 형상 및 자기구역 동력학을 관찰하였다. 이 장비는 1,000배의 배율에서 0.3$\mu\textrm{m}$의 공간분해능을 가지며 실시간 자기구역 영상을 CCD 카메라를 통해 컴퓨터에 저장함으로써, 자지구역 거동현상을 관찰할 수 있다. 자성다층박막에 존재하는 자기구역의 형상을 이론적으로 예측하기 위하여, 다층박막 구조에서의 정자기 에너지를 일반적으로 계산할 수 있는 이론을 유도하였다. 이 이론을 통해 다층박막의 자성층의 두께가 두꺼워짐에 따라, 자기구역의 형상이 단일 자기구역 형상에서 줄무늬 자기구역 형상으로 천이함을 예측할 수 있었고, 이러한 지구구역 천이현상을 Co-Pd 다층박막의 자화역전현상을 연구하였고, 새로운 자구동력학 정량분석기술을 개발하여 Co/Pd 다층박막에 적용함으로써 자화역전의 자구벽 이동속도와 핵형성 확률을 각각 정량적으로 구하였다. 이러한 관찰 및 분석기술을 통하여, Co/Pd 다층박막의 층구조에 따라 대조적인 자화역전현상이 존재함을 관찰하였다. 이러한 대조적인 자화역전현상을 결정짓는 요인을 연구하기 위해서 나노자성학이온을 이용한 자화역전현상을 결정짓는 요인을 연구하기 위해서 나노자성학이온을 이용한 자화역전모델을 개발하였으며, 이를 통하여 자성박막의 거시적 자기성질에 의해 이러한 대조적인 자화역전모델을 개발하였으며, 이를 통하여 자성박막의 거시적 자기성지에 의해 이러한 대조적인 자화역전현상이 결정될 수 있음을 설명하였다. 또한, 미시적 자기이력곡선 측정을 통하여 자성박막구조에 따른 국소적인 구조불균일성을 관찰하였고, 이러한 구조불균일성 또한 대조적인 자화역전현상을 결정하는 큰 요인임을 논의하였다.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2003.11a
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• pp.202-206
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• 2003

In this study, a modified bituminization technology has been developed, which needs no grinding of the granular resin waste, and enables the solid form to keep its shape stability as good as that of a cemented solid from Also, the study intended to apply the developed technology to the practical treatment of radioactive resin waste. In the experiment, the granular type resin was used and the straight-run distillation bitumen with penetration rate 60/70 was used as the solidifying agent. The PE was used as the additive. The shape stability increased remarkably with the additive of PE, which act as a binder in the solid form. The shape of the solid form was maintained without failure during the long-term exposure test when the additive content of spent PE is more than 10wt%. The proper ranges of bitumen content, PE content and operating temperature are 30-50wt%, 10-20wt% and $180^{\circ}C$ respectively. The bituminized solid form of radioactive resin waste by the technology of this study has the remarkably superior quality than the conventional solid forms, partially for the shape stability.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.4
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• pp.855-863
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• 2017

Because Li-ion battery and Li-Polymer battery have high-energy storage density, they are used for various electronic devices such as electronic cigarette, electronic bicycle, drone, second battery, even golf cart and electronic car. Recently, however, battery explosion is sometimes occurring on electronic devices using Li-ion battery and is becoming serious as bodily harm is breaking out due to explosion. For this, this paper described the Li-ion Battery's operating principles and verified the cause of explosion by overload tests caused by the high-energy storage density. According to the these experiments, we conducted a study to develope scanning techniques of fire and safety measures.

• Korean Journal of Medicinal Crop Science
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• v.7 no.1
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• pp.1-6
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• 1999

Basic informations for direct somatic embryo formation in Rehmannja glutinosa Lib. were obtained in 500ml erlenmyer flask. The ratio of ammonium to nitrate nitrogen of 825(mg/l) : 1900(mg/l) was proper condition for somatic embryo formation from stem and petiole explants and 3% sucrose was the most effective carbon source. Full strength MS medium with 2mg/l BA was better than LS medium for somatic embryogenesis. The initial pH 5.7 of medium(full strength MS with 2.0mg/l BA and 0.1mg/l NAA) was good for embryo production. Potassium ion was taken up rapidly within 2 weeks. while $Ca^{++}$ and $Mg^{++}$ ion contents were almost constant during culture period. Sucrose hydrolysis occurred throughout the culture, while glucose and fructose were absorbed simultaneously from the third week of culture.

• Journal of the Korean Society of Food Science and Nutrition
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• v.30 no.6
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• pp.1147-1151
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• 2001

We investigated stabilities of blue pigment extracted from Gardenia jasminoides at various conditions to check its applicability for beverages. Gardenia blue pigment with maximum absorption at 587 nm was obtained from the reaction of glycine and genipin (aglycone of geniposide). The blue pigment was found to be relatively unstable at acidic pH but very stable at alkaline conditions with half-life values of 102 days and 126 days at PH 9.0 and PH 11.0, respectively. The pigment also showed high thermal stability with half-life value of 55, 18, and 2 days at 50, 70, and 9$0^{\circ}C$, respectively. The addition of inorganic ions, sugars, and amino acids to model beverage containing this blue pigment increased retention rate at room temperature while addition of vitamin C decreased the stability. The sensory evaluation of the model beverage showed that inorganic ions and amino acids increased overall acceptability, indicating that the blue pigments of Gardenia jasminoides can be used as a natural colorant for leverage.

• Journal of the Korean Electrochemical Society
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• v.22 no.1
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• pp.22-35
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• 2019

Development of low cost rechargeable batteries has been considered as a significant task for future large-scale energy storage units (i.e. electric vehicles, smart grids). Sodium-ion batteries (SIBs) have been recognized as a promising alternative to replace conventional lithium-ion batteries (LIBs) because of their abundancy and economic benign. Nevertheless, Na ions have larger ionic radius than that of Li ions, resulting in sluggish transport of Na ions in electrodes for cell operation. There have been efforts to seek suitable anode materials for the past years operated based on three different kinds of reaction mechanism (intercalation, alloy reaction, and conversion reaction). In this review, we introduce a class of conversion reaction anode materials for Na-ion batteries, which have been reported.

• Journal of the Korean Institute of Gas
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• v.24 no.6
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• pp.91-97
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• 2020

Lithium-ion batteries (LIBs) have a longer lifespan, higher energy density, and lower self-discharge rates than other batteries, therefore, they are preferred as an Energy Storage System (ESS). However, during years 2017-2019, 28 ESS fire accidents occurred in Korea, and accurate capacity estimation of LIB is essential to ensure safety and reliability during operations. In this study, data-driven modeling that predicts capacity changes according to the charging cycle of LIB was conducted, and developed models were compared their performance for the selection of the optimal machine learning model, which includes the Decision Tree, Ensemble Learning Method, Support Vector Regression, and Gaussian Process Regression (GPR). For model training, lithium battery test data provided by NASA was used, and GPR showed the best prediction performance. Based on this study, we will develop an enhanced LIB capacity prediction and remaining useful life estimation model through additional data training, and improve the performance of anomaly detection and monitoring during operations, enabling safe and stable ESS operations.

• Journal of IKEEE
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• v.27 no.4
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• pp.477-485
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• 2023

In this paper, the effect of AC ripple on the lifetime of lithium-ion batteries is experimentally analyzed. Bidirectional power conversion system(PCS) is used to increase the efficiency of energy storage systems (ESS). When connected to the grid, a current ripple with a frequency twice the grid frequency is applied to the battery due to its structure. Therefore, to analyze the effect of AC ripple on Li-ion battery aging, cycle life test are performed by applying charge/discharge profiles of DC current and DC+AC current ripple specifications. Based on the experimental results, direct current internal resistance (DCIR), incremental capacitance (IC), and surface temperature were analyzed. As a result, it is confirmed that AC ripple does not directly affect degradation and that battery degradation slows down after a certain cycle. These results can serve as a guideline for optimizing filters to reduce ripple on the battery side in applications where AC ripple occurs.

• Journal of the Korean Electrochemical Society
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• v.27 no.2
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• pp.73-79
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• 2024

As the use of fossil fuels has gradually increased, so has the emission of greenhouse gases such as carbon dioxide, leading to environmental problems. As a result, lithium-ion batteries (LiB) have emerged as the solution to this issue. To manufacture medium to large-sized lithium-ion batteries (LiB), it requires electrodes with high capacity and fast charging capabilities. Silicon (Si) is considered a next-generation anode with high-capacity properties, so, reduced graphene oxide (rGO) was compounded with Si@resorcinol-formaldehyde resin (RF) composite to prevent the volume expansion of Si. It was confirmed that the composite anode prepared exhibited improved capacity and enhanced stability.

• Food Science and Preservation
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• v.20 no.2
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• pp.182-190
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• 2013

This study investigated the quality characteristics between spring cultivars of Kimchi cabbage(Brassica rapa L. ssp. pekinesis). We measured the weight, length, width, formation index, midrib thickness and moisture contents of fresh Kimchi cabbage for characteristics of growth. And we analyzed the free sugar, amino acid, organic acid, mineral, pectin and cellulose contents of fresh Kimchi cabbage. The hardness and firmness were measured for texture of fresh Kimchi cabbage. The weight of 'K-power' cultivar was the highest than other cultivars. The 'Jeongsang' cultivars was the thinnest midrib thickness in cultivars, but it was not significantly different. The free sugar levels of spring cultivars was the highest in 'Chunkwang'. Malic acid content of 'Jeongsang' was significantly different among spring cultivars. Also amino acid content of 'K-power' and 'Chunkwang' were significantly different among spring cultivars Mineral content in 'K-power' and 'Bomaknorang' were greater than that of other cultivars. Especially Na, Ca and Mg contents of 'K-power' and 'Bomaknorang' were higher four times than that of other cultivars. Pectin content of 'Jeongsang' was higher than that of other cultivars, but it was not significantly different. Hardness and Firmness were not significantly different among spring cultivars.