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비휘발성 메모리 소자응용을 위한 Eu 첨가량에 따른 BET 박막의 강유전 특성
김경태,김종규,우종창,김관하,김창일,Kim, Kyoung-Tae,Kim, Jong-Gyu,Woo, Jong-Chang,Kim, Gwan-Ha,Kim, Chang-Il 한국전기전자재료학회 2007 전기전자재료학회논문지 Vol.20 No.3
The effect of Eu contents on the ferroelectric properties of $Bi_{4-x}Eu_xTi_3 O_{12}$ (BET) thin films has been investigated. Bismuth Europium titanate thin films with a Eu contents were prepared on the $Pt/Ti/SiO_2/Si$ substrate by metal-organic decomposition technique. The structure and the morphology of the films were analyzed using X-ray diffraction (XRD) and field emission scanning microscopy (FE-SEM), respectively. From the XRD analysis, it was found that BET thin films have polycrystalline structure, and the layered-perovskite phase is obtained when the Eu contents exceeds 0.2 (x > 0.2). Also, the ferroelectric characteristics of the BET thin films were found to be dependent on the Eu content. Particularly, the BET films doped with x = 0.75 show better ferroelectric properties (remanent polarization 2Pr = 60.99 C/$cm^2$ and only a little polarization fatigue up to $3.5{\times}10^9$ bipolar switching cycling) than those doped with other Eu contents.
김경태,김창일,Kim, Kyoung-Tae,Kim, Chang-Il 한국전기전자재료학회 2005 전기전자재료학회논문지 Vol.18 No.5
We investigated the structural and electrical properties of BLT films grown on Si covered with $ZrO_{2}$ buffer layer. The BLT thin film and $ZrO_{2}$ buffer layer were fabricated using a metalorganic decomposition method. The electrical properties of the MFIS structure were investigated by varying thickness of the $ZrO_{2}$ layer. AES and TEM show no interdiffusion and reaction that suppressed using the $ZrO_{2}$ film as a buffer layer The width of the memory window in the C-V curves for the MFIS structure decreased with increasing thickness of the $ZrO_{2}$ layer. It is considered that the memory window width of MFIS is not affected by remanent polarization. Leakage current density decreased by about four orders of magnitude after using $ZrO_{2}$ buffer layer. The results show that the $ZrO_{2}$ buffer layers are prospective candidates for applications in MFIS-FET memory devices.
천마(Gastrodia elate)추출물로부터 분리된 페놀성 물질의 멜라닌 생성 억제작용
김경태 ( Kyoung Tae Kim ),김진국 ( Jin Guk Kim ),박선희 ( Sun Hee Park ),이정하 ( Jeong Ha Lee ),이수희 ( Soo Hee Lee ),김기호 ( Ki Ho Kim ),박수남 ( Soo Nam Park ) 대한화장품학회 2004 대한화장품학회지 Vol.30 No.1
본 연구에서는 천마(Gastrodia elata)추출물의 분획과 butanol 분획층의 연속적인 silicagel column chromatography를 통하여 유효성 분인 4-hydroxybenzyl alcohol 1. bis(4-hydroxyphenyl) methane 2. gastrodin(4-β-D-glucopyranosyloxybenzyl alcohol) 3을 분리하였다. 4-Hydroxybenzyl alcohol 1과 gastrodin(4-β-D-glucopyranosyloxybenzyl alcohol) 3은 tyrosinase에 대한 저해작용은 없으나 B16 melanoma 세포의 melanin 새성을 억제한다는 것을 발견하였다. Bis(4-hydroxyphenyl)methane 2 (IC<sub>50</sub> = 400 ㎍/mL)은 arbutin (IC<sub>50</sub> = 400 ㎍/mL) 보다 약 1/4의 tyrosinase 활성 저해작용을 나타내었지만 B16 melanoma 세포의 melanin 생성 억제는 오히려 arbutin 보다 높게 나왔다. 또한 butanol 분획층 (IC<sub>50</sub> = 46㎍/mL)의 tyrosinase에 대한 활성 저해 작용이 arbutin (IC<sub>50</sub> = 114 ㎍/mL)보다 높은 억제 작용을 나타내었고 B16 melanoma 세포의 melanin 생성 억제도 arbutin 보다 높게 나왔다. 특히 butanol 분획층으로부터 분리된 페놀성 혼합물 (IC<sub>50</sub> = 2.37 ㎍/mL)은 arbutin 보다 약 50배 가까운 매운 높은 tyrosinase 활성 억제 작용을 나타내었다. 이러한 결과로부터 천마추출물로부터 분리된 유효성분들이 tyrosinase에 대한 저해작용 뿐만 아니라 B16 melanoma 세포의 melanin 생성을 억제하는 것을 알 수 있었다. Melanin pigmentation in human skin is a major defense mechanism against ultraviolet light of the sun, but abnormal pigmentation such as freckles, liver spot could be a serious aesthetic problem. Nearly all studies are mainly concentrated on searching for the materials that have inhibitory activities on tyrosinase. In this work, to isolate phenolic compounds from Gastrodia elata, we purified the extract through solvent fractionation, column chromatography, and recrystallization. They were identified as 4-hydroxybenzyl alcohol 1, bis(4-hydroxyphenyl)methane 2, gastrodin (4-β-D-glucopyranosyloxybenzyl alcohol) 3 on the base of spectroscopic evidences. In order to investigate their depigmentation effect, inhibitory activity against mushroom tyrosinase and inhibitory activity of melanin synthesis in B16 melanoma cells were evaluated in vitro. We have found that 4-hydroxybenzyl alcohol 1 and gastrodin (4-β-D-glucopyranosyloxybenzyl alcohol) 3 have no tyrosinase inhibitory activity, but inhibit the melanin synthesis in B16 melanoma cells. Tyrosinase inhibitory activities of bis(4-hydroxyphenyl)methane 2 (IC<sub>50</sub> = 400 ㎍/mL) and butanol fraction (IC<sub>50</sub> = 46 ㎍/mL) were lower/higher than that of arbutin (IC<sub>50</sub> = 114 ㎍/mL), but inhibitory activities of melanin synthesis in B16 melanoma cells were much higher than that of arbutin. Especially, tyrosinase inhibitory activities of isolated phenolic fraction (IC<sub>50</sub> = 2.37 ㎍/mL) from butanol fraction was very higher than that of arbutin (IC<sub>50</sub> = 114 ㎍/mL). Therefore, these results suggest that isolated phenolic compounds from Gastrodia elata have inhibitory activity against mushroom tyrosinase and inhibitory activity of melanin synthesis in 816 melanoma cells in vitro.
유기금속열분해 방법으로 제작된 NKN 박막의 강유전특성
김경태(Kyoung-Tae Kim),김창일(Chang-Il Kim),이성갑(Sung-Gap Lee) 대한전기학회 2006 대한전기학회 학술대회 논문집 Vol.2006 No.7
(Na<SUB>0.5</SUB>LaK<SUB>0.5</SUB>)NbO₃ (NKN) thin films were fabricated by the alkoxide-based MOD method. NKN stock solutions were made spin-coated onto the Pt/Ti/SiO₂/Si substrate. The structural properties of the NKN thin films examined by x-ray diffraction. The perovskite phase was obtained as a function of the annealing temperature from 550℃ to 700℃ for lh, The crystallinity and grain size of the NKN thin films increased with increasing annealing temperature. The dielectric constants and loss of the NKN thin films annealed at 650℃ (t<SUB>eq</SUB>=2.35 ㎚) showed 323 and 0.025.
김경태 ( Kyoung Tae Kim ),권정택 ( Jeong Taik Kwon ),홍현종 ( Hyun Jong Hong ),이용철 ( Yong Chul Lee ) 대한뇌종양학회·대한신경종양학회·대한소아뇌종양학회 2005 대한뇌종양학회지 Vol.4 No.1
Intracranial epidermoid tumors usually show homogeneous hypodensity on CT scans and hypointensity on T1-weighted and hyperintensity on T2-weighted MR images. Epidermoid tumors are most often located in the cerebellopontine angle and in the parasellar region. We report an unusual case of middle cranial fossa epidermoid tumor. The tumor showed inhomogeneous low density on CT scan and heterogeneous signal intensity on both T1- and T2-weighted MR images. Epidermoid tumors are usually slow growing tumor and are located in adjacent region of cranial nerve, so we must consider age and postoperative neurological defici of patient before operation.
김경태(Kyoung Tae Kim),민재홍(Jae Hong Min),이인묵(In Mook Lee) 한국철도학회 2014 한국철도학회 학술발표대회논문집 Vol.2014 No.10
수도권의 대중교통을 이용하는 승객들은 거의 대부분이 교통카드를 사용하고 있다. 수도권의 대중교통요금이 통합거리비례요금제로 운영되고 있기 때문에 정확한 승하차 정보가 필요하다. 그러나 버스 이용객들은 하차역에서 내릴 때 교통카드를 태그하는 것이 아니라 그 이전에 태그하는 현상이 많이 발생하고 있다. 본 연구에서는 교통카드 데이터를 활용하여 버스 승객들이 비정상적으로 태그하는 행태를 분석하고자 하였으며, 본 연구에서 설정한 기준에 따르면 약 40.3%에 해당하는 승객이 사전에 태그하는 것으로 분석되었다. 따라서 교통카드 데이터를 활용한 대중교통 이용객들의 평균환승거리 산정 시에는 이러한 요인을 충분히 검토하여야 한다. Transportation cards are widely used to travel by public transit in the Seoul metropolitan area. And, passengers have no resistance to transfer from one mode to the other mode because the public transportation fare is only proportional to the travel distance. Passengers have to tag when they get off the bus, but many passengers tag farther in advance. In this study, we analyzed the abnormal tag behavior of bus passengers by utilizing transport card data. It is analyzed that the ratio of tags in advance is equivalent to about 40.3% according to the suggested criteria. When you analyze average transfer distance or transfer behavior using transportation card data these factors should be considered sufficiently.