• Bulletin of the Korean Chemical Society
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• 제30권3호
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• pp.551-555
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• 2009

The ytterbium catalyst immobilized on the cross-linked poly(4-vinylpyridine/styrene) copolymer (P/S-Yb) was applied in the Mannich-type, three component one-pot synthesis of $\beta$-aminoketones. This catalytic system showed excellent catalytic activity and selectivity which resulted in the exclusive formation of $\beta$-aminoketone. The applicability of this immobilized catalyst system was shown by the reusability test and again highlighted by the synthesis of a $\beta$-aminoketone library using a broad range of substrates.

• Bulletin of the Korean Chemical Society
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• 제25권1호
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• pp.101-105
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• 2004

The laser ablation/ionization time-of-flight mass spectrometry is applied to the isotopic analysis of solid samples using a home-made instrument. The technique is convenient for solid sample analysis due to the onestep process of vaporization and ionization of the samples. The analyzed samples were lead, cadmium, molybdenum, and ytterbium. To optimize the analytical conditions of the technique, several parameters, such as laser energy, laser wavelength, size of the laser beam on the samples surface, and high voltages applied on the ion source electrodes were varied. Low energy of laser light was necessary to obtain the optimal mass resolution of spectra. The 532 nm light generated mass spectra with the higher signal-to-noise ratio compared with the 355 nm light. The best mass resolution obtained in the present study is ~1,500 for the ytterbium.

• 대한화학회지
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• 제39권6호
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• pp.477-480
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• 1995

• Journal of the Optical Society of Korea
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• 제17권2호
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• pp.182-187
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• 2013

We present a comparative experimental analysis of the thermal spectroscopic characteristics of a phosphosilicate (P)-based ytterbium-doped fiber (YDF) against an aluminosilicate (Al)-based YDF in the temperature range of 25 to $150^{\circ}C$. We also characterize the fibers as gain media in a cladding-pumped amplifier configuration. While both fibers exhibit comparable trends in their thermal characteristics, there are noticeable distinctions in the fluorescence lifetime reduction rate and the spectral dependence of the transition cross-sections. The P- and Al-based YDFs present thermal lifetime reduction rates of $0.012%/^{\circ}C$ and $0.026%/^{\circ}C$, respectively. In particular, in the spectral region at ~940 nm, the absorption cross-section of the P-based YDF undergoes significantly less thermal change compared to that of the Al-YDF. In the cladding-pumped amplifier configuration operating at a total gain of 10 dB, the Al-based YDF generally performs betters than the P-based YDF in the temperature range of 25 to $75^{\circ}C$. However, it is highlighted that in the high temperature range of over $75^{\circ}C$, the latter shows a less gain reduction rate than the former, thereby yielding higher relative output power by 3.3% for a 1060-nm signal, for example.

• 한국전기전자재료학회논문지
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• 제21권1호
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• pp.29-34
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• 2008

In this paper, we investigated electrical and physical characteristics of nickel silicide using rare-earth metals(Er, Yb, Tb, Dy), Incorporated Ytterbium into Ni-silicide is proposed to reduce work function of Ni-silicide for nickel silicided schottky barrier diode (Ni-silicided SBD). Nickel silicide makes ohmic-contact or low schottky barrier height with p-type silicon because of similar work function (${\phi}_M$) in comparison with p-type silicon. However, high schottky barrier height is formed between Ni-silicide and p-type substrate by depositing thin ytterbium layer prior to Ni deposition. Even though the ytterbium is deposited below nickel, ternary phase $Yb_xN_{1-x}iSi$ is formed at the top and inner region of Ni-silicide, which is believed to result in reduction of work function about 0.15 - 0.38 eV.

• 한국광학회지
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• 제24권2호
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• pp.58-63
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• 2013

본 논문에서는 능동형 Q-스위칭 광섬유 레이저에서 Q-스위치 상승 시간이 출력 펄스에 미치는 영향을 이론적으로 분석하였다. Finite Difference Time Domain (FDTD) 방법을 이용해서 비율 방정식과 전파 방정식에 대한 모델링을 수행하였다. Q-스위칭 광섬유 레이저에서 발생하는 Q-스위칭 펄스의 생성에 있어서 Q-스위치의 상승 시간이 출력 펄스 특성에 미치는 영향을 이론적으로 분석하였다. 또한, Q-스위치의 반복률에 따른 출력 펄스의 에너지 변화와 파형 변화를 확인하였다. Q-스위치 반복률이 높아지고, Q-스위치의 상승 시간이 길어질수록 출력 펄스의 멀티 피크 현상이 줄어들고 안정된 가우시안 형태의 펄스 파형이 발생함을 확인 할 수 있었다.

• 한국분말재료학회지
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• 제24권6호
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• pp.437-443
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• 2017

SiC-based composite materials with light weight, high durability, and high-temperature stability have been actively studied for use in aerospace and defense applications. Moreover, environmental barrier coating (EBC) technologies using oxide-based ceramic materials have been studied to prevent chemical deterioration at a high temperature of $1300^{\circ}C$ or higher. In this study, an ytterbium silicate material, which has recently been actively studied as an environmental barrier coating because of its high-temperature chemical stability, is fabricated on a sintered SiC substrate. $Yb_2O_3$ and $SiO_2$ are used as the raw starting materials to form ytterbium disilicate ($Yb_2Si_2O_7$). Suspension plasma spraying is applied as the coating method. The effect of the mixing method on the particle size and distribution, which affect the coating formation behavior, is investigated using a scanning electron microscope (SEM), an energy dispersive spectrometer (EDS), and X-ray diffraction (XRD) analysis. It is found that the originally designed compounds are not effectively formed because of the refinement and vaporization of the raw material particles, i.e., $SiO_2$, and the formation of a porous coating structure. By changing the coating parameters such as the deposition distance, it is found that a denser coating structure can be formed at a closer deposition distance.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.776-779
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• 2008

• Bulletin of the Korean Chemical Society
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• 제23권10호
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• pp.1367-1368
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• 2002

• 한국레이저가공학회:학술대회논문집
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• 한국레이저가공학회 2006년도 춘계학술발표대회 논문집
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• pp.108-111
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• 2006

Recently, mobile information devices, such as cellular phone, PDA(Personal Digital Assistant, PDA) are getting smaller and thinner. Accordingly, ultra precision welding technology is required to manufacture the high performance system for use in the telecommunication industry. In this study, we propose the laser micro welding process. Using ytterbium fiber laser, a wide range of experiments have been carried out for the gold wire-to-gold thin film welding.