• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.264.1-264.1
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• 2013

Graphene is a two-dimensional carbon material whose structure is one-atom-thick planar sheet of sp2-bonded carbon atoms densely packed in a honeycomb crystal lattice. It has drawn significant attention with its distinguished structural and electrical properties. Extremely high mobility and a tunable band gap make graphene potentially useful for innovative approaches to electronics. Although mechanical exfoliation of graphite and decomposition of SiC surfaces upon thermal treatment have been the main method for graphene, they have some limitations in quality and scalability of as-produced graphene films. Solutionphase and solvothermal syntheses of graphene achieved a major improvement for processing, however for device fabrication, a reproducible method such as chemical vapor deposition (CVD) growth yielding high quality films of controlled thickness is required. In this research, we synthesized hexagonal graphene flakes on Cu foils by CVD method and controlled its coverage, density and the size of graphene domains by changing reaction parameters. It is important to control these parameters of graphene growth during synthesis in order to achieve tunable properties and optimized device performance.

• Archives of Pharmacal Research
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• 제23권3호
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• pp.222-225
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• 2000

A series of conformationally controlled 2-PAM derivatives were prepared from 2-acetylpyridine and 2,3-pyrido[b]cycloalkenones in two steps and their reactivities towards parathion poisoned AChE were evaluated. The most planar 2,3-pyrido[b]cyclohexanone oxime methiodide showed an activity comparable to 2-PAM Implying E-syn is that the most active comformation of 2-PAM in the biological system.

• Bulletin of the Korean Chemical Society
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• 제17권8호
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• pp.688-693
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• 1996

Tetradentate Schiff base ligands derived from 2-hydroxy-1-naphthaldehyde and aliphatic diamine have been synthesized. Cu(Ⅱ) complexes of Schiff base ligands have been synthesized from the free ligands and copper acetate. The mole ratio of ligand to copper was identified to be 1:1 by the result of elemental analysis and Cu(Ⅱ) complexes were in a four-coordinated configuration. The electrochemical redox process of Cu(Ⅱ) complexes in a DMF solution has been investigated by cyclic voltammetry, chronoamperometry, differential pulse voltammetry, and controlled potential coulometry. The redox process of Cu(Ⅱ) complexes is one electron transfer process in quasi-reversible and diffusion-controlled reaction. The electrochemical redox potentials and the kinetic parameters of Cu(Ⅱ) complexes are affected by the chelate ring of Schiff base ligands.

• Smart Structures and Systems
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• 제8권3호
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• pp.303-320
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• 2011

Comparing to active damage monitoring, impact localization on composite by using time reversal focusing method has several difficulties. First, the transfer function of the actuator-sensor path is difficult to be obtained because of the limitation that no impact experiment is permitted to perform on the real structure and the difficulty to model it because the performance of real aircraft composite is much more complicated comparing to metal structure. Second, the position of impact is unknown and can not be controlled as the excitation signal used in the active monitoring. This makes it not applicable to compare the difference between the excitation and the focused signal. Another difficulty is that impact signal is frequency broadband, giving rise to the difficulty to process virtual synthesis because of the highly dispersion nature of frequency broadband Lamb wave in plate-like structure. Aiming at developing a practical method for on-line localization of impact on aircraft composite structure which can take advantage of time reversal focusing and does not rely on the transfer function, a PZT sensor array based phase synthesis time reversal impact imaging method is proposed. The complex Shannon wavelet transform is presented to extract the frequency narrow-band signals from the impact responded signals of PZT sensors. A phase synthesis process of the frequency narrow-band signals is implemented to search the time reversal focusing position on the structure which represents the impact position. Evaluation experiments on a carbon fiber composite structure show that the proposed method realizes the impact imaging and localization with an error less than 1.5 cm. Discussion of the influence of velocity errors and measurement noise is also given in detail.

• 생명과학회지
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• 제24권5호
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• pp.485-490
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• 2014

백복령(Poria cocas)은 전통적으로 민간에서 피부미백에 효과가 있다고 보고되어 있다. 지금까지 melanin 합성에 대한 백복령의 직접적인 효과는 과학적으로 잘 연구되어 있지 않다. 따라서 멜라닌 합성에 대한 백복령 주정 추출물(PCEE)의 직접적인 효과를 밝히기 위해, 쥐의 B16F1 세포를 이용하여 DOPA synthesis assay, tyrosinase activity assay, Western blotting for melanogenic proteins [tyrosinase, tyrosinase related protein (TRP)-1 and TRP-2]를 수행하였다. 본 연구에서 PCEE가 3,4-dihydroxyindole-2-carboxylic acid (DOPA) 합성을 차단함으로써 농도 의존적으로 melanin형성을 억제한다는 것이 밝혀졌다. 비록 tyrosinase의 활성은 영향을 받지 않았지만 TRP-1 과 TRP-2의 단백질 발현 수준은 PCEE에 의해 조절되었다. 따라서 이러한 결과는 PCEE가 미백 효능을 가지고 있어 미백 화장품 개발을 위해 이용될 수 있다는 것을 시사하고 있다.

• 대한전자공학회논문지TC
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• 제39권5호
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• pp.243-250
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• 2002

임의 복사패턴을 만족시키는 배열안테나 소스 전류분포 합성시 사용하는 Woodward-Lawson 샘플링법은 우함수형 복사패턴 합성에 주로 사용되어 왔다. 본 연구에서는 이를 확장하여 기함수형 패턴도 만족시키는 비선형 소스 분포함수의 최적합성법을 제시하고, 이를 임의의 반사특성을 갖는 단일 및 결합선로의 불균일 모드 임피던스 프로필 합성에 동시에 적용하였다. 이 최적합성법은 주파수영역 반사패턴에 내재된 복소null점의 최적 섭동에 기본을 두고 있다. 제어된 반사패턴의 표본값으로부터 분산특성을 갖는 임피던스 프로필이 직접 계산되므로서 기존외 불균일선로 합성법보다 매우 간단함을 보였다. 그리고 서로 다른 임피던스간의 정합을 위한 기존이 테이퍼선로 이론에 기초한 불균일선론 합성법들을 탈피하여, 서로 같은 임피던스간의 불균일선로 합성도 가능케하므로서 본 연구에서 제시한 방법은 일반성을 가진다. 임의 통과대역을 갖는 필터 설계에 적용, 분석하므로서 타당성을 보였다.

• 대한한의학회지
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• 제23권4호
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• pp.45-54
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• 2002

Objectives: In order to investigate the relationship of Radix Trichosanthis components and the melanin synthesis, the author has analyzed the cell viability and tyrosinase activity, melanin content and morphologic changes in n-hexane, EtOAc, n-BuOH, and H2O fraction. Methods: At first, in order to determine the concentration of the Radix Trichosanthis component, the author investigated the viability of B16 melanoma cell. To measure the effects of Trichosanthes kirilowii extracts (n-BuOH, n-Hexane, EtOAc, H2O fractions) on the viability of A549 cells, A549 cells were treated with various concentrations (from 0.5 to $25{\;}\mu\textrm{g}/ml$) of components of Trichosanthes kirilowii. After 24hrs, the cell viability was measured by MTT assay. The EtOAc components of Trichosanthes kirilowii decreased the viability of A549 cells in a dose-dependent manner. H2O and n-BuOH components had no cell toxicity till $25{\;}\mu\textrm{g}/ml$, the n-hexane component showed minor cell toxicity at $25{\;}\mu\textrm{g}/ml$ and the EtOAc component cell toxicity was revealed at $5{\;}\mu\textrm{g}/ml$ concentration. Results: 1. The results of tyrosinase activity and the Radix Trichosanthis component; n-hexane and EtOAc components controlled it effectively; the n-BuOH components were less effective. 2. The results of melanin content analysis showed that the n-hexane and EtOAc components effectively inhibited, the n-BuOH fraction inhibited less, and H2O component didn't inhibit the terminal melanin formation. 3. In the n-BuOH and H2O component there were no changes, but in the n-hexane component the melanin content was effectively inhibited. 4. In the EtOAc fraction, although the melanin content was inhibited, the cell count was evidently suppressed, Of all of the Radix Trichosanthis components, the n-Hexane and EtOAc fractions inhibited the melanin synthesis best, but owing to its toxicity, the EtOAc components inhibited the cell count. Conclusion: The above results demonstrated that Radix Trichosanthis n-hexane fraction efficiently inhibited the tyrosinase activity and melanin synthesis.

• 자원리싸이클링
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• 제18권6호
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• pp.18-23
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• 2009

염화알루미늄 수용액으로부터 알루미늄 유기화합물인 구연산알루미늄 합성실험을 수행하였다. 수용액중 알루미늄 농도와 구연산 농도비율은 몰비 2.5가 되도록 첨가해 주었으며, 합성된 구연산알루미늄은 화학분석, X-선 회절분석, 입도분석 및 SEM 분석을 통하여 시료특성을 평가하였다. 알루미늄 수용액으로부터 구연산알루미늄을 합성하기 위해서는 에탄올/알루미늄 수용액 혼합비율을 4.0이상으로 유지하여야 하는 것으로 나타났다. 또한, 97% 이상의 회수율을 얻기 위해서는 혼합액의 pH를 7.0이상으로 조절하여야 하는 것으로 나타났다. 합성반응을 통해 얻은 구연산알루미늄의 화학분석결과 $NH_4$ 17.0%, Al 4.01% 및 C 25.7%이었으며, 이의 화학식은 $(NH_4)_5Al(C_6H_4O_7)_2{\cdot}2H_2O$임을 확인할 수 있었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.30-31
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• 2006

The LSCF cathode for Solid Oxide Fuel Cell was investigated to develop high performance unit cell at intermediate temperature by modified oxalate method with different electrolyte. The LSCF precursors using oxalic acid, ethanol and $NH_4OH$ solution were prepared at $80^{\circ}C$, and pH was controlled as 2, 6, 7, 8, 9 and 10. The synthesis precursor powders were calcined at $800^{\circ}C$, $1000^{\circ}C$ and $1200^{\circ}C$ for 4hrs. Unit cells were prepared with the calcined LSCF cathode, buffer layer between cathode and each electrolyte that is the LSGM, YSZ, ScSZ and CeSZ. The synthesis LSCF powders by modified oxalate method were measured by scanning electron microscope and X-ray diffraction. The interfacial polarization resistance of cell was characterized by Solatron 1260 analyzer. The crystal of LSCF powders show single phase at pH 2, 6, 7, 8 and 9, and the average particle size was about $3{\mu}m$. The electric conductivity of synthesis LSCF cathode which was calcined at $1200^{\circ}C$ shows the highest value at pH 7. The cell consist of GDC had the lowest interfacial resistance (about 950 S/cm@650) of the cathode electrode. The polarization resistance of synthesis LSCF cathode by modified oxalate method has the value from 4.02 to 7.46ohm at $650^{\circ}C$. GDC among the electrolytes, shows the lowest polarization resistance.

• 공업화학
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• 제31권2호
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• pp.187-192
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• 2020

(2S,3R)-3-hydroxyhomoserine lactone (HSL)은 생리학적 활성을 가지는 다양한 종류의 화합물을 합성하기 위한 중간체로 활용되어 왔다. 본 논문에서는 OBO ester로 보호된 바이닐글라이신 유도체에 이중알콜화 반응을 수행하여 효율적인 HSL 합성 결과를 보고하고자 한다. 바이닐글라이신의 비고리 conformation은 크기가 큰 OBO ester에 의해 조절되었으며 N-inside conformation을 통해 이중알콜화 반응이 진행됨으로써 높은 anti 선택성(> 10 : 1)을 얻을 수 있었다. 이러한 결과를 바탕으로 N-Cbz-L-serine을 출발물질로 사용하여 총 7단계 34%의 수율로 HSL을 합성할 수 있었다. 본 연구의 결과는 amino diol 구조를 가지는 다양한 생리활성 천연물들의 입체선택적인 합성에 유용하게 활용될 수 있을 것으로 기대된다.