• Macromolecular Research
• /
• v.15 no.4
• /
• pp.302-307
• /
• 2007

The living radical polymerization of methyl methacrylate (MMA) by atom transfer radical polymerization, (ATRP) employing a $Fe(II)X_2/diphenyl-2-pyridyl$ phosphine (PyP) catalytic system (X=Cl, Br), was investigated using several initiators and solvents at various temperatures. Most of the polymerizations with the PyP ligand were well controlled, with a linear increase in the number average molecular weights ($M_n$) vs. conversion, with relatively low molecular weight distributions ($M_w/M_n=1.2-1.4$) throughout the reactions. The measured weights matched those of the predicted values. The ethyl-2-bromoisobutyrate (EBriB) initiated ATRP of MMA, with the $Fe(II)X_2/diphenyl-2-pyridyl$ phosphine catalytic system (X=Cl, Br), was better controlled in p-xylene at $80^{\circ}C$ than the other solvents used in this study.

• Bulletin of the Korean Chemical Society
• /
• v.34 no.3
• /
• pp.820-822
• /
• 2013

N,N,N',N'-Tetrabromobenzene-1,3-disulfonamide (TBBDA)/$PPh_3$ and N,N,N',N'-tetrachlorobenzene-1,3-disulfonamide (TCBDA)/$PPh_3$ are two highly reactive reagent systems for the conversion of alcohols corresponding into alkyl chlorides and bromides in moderate to excellent yields in dichloromethane at room temperature under mild and neutral conditions.

• Bulletin of the Korean Chemical Society
• /
• v.35 no.3
• /
• pp.865-870
• /
• 2014

Gold nanoparticles (AuNPs) were synthesized by laser (Nd:YAG, ${\lambda}$ = 1064 nm) ablation of a gold target immersed in various aqueous electrolyte solutions (7 mM of LiCl, NaCl, KCl, NaBr, and NaI) as well as in deionized water. The surface plasmon absorption and EDX of AuNPs so produced as well as their TEM images were analyzed to investigate the effects of ambient ions on the growth and aggregation of NPs. The size of AuNPs was reduced by laser ablation in the presence of chloride and bromide ions while it increased drastically when AuNPs were formed in iodide solution. Interestingly, triangular nanoplates were synthesized only in iodide solution. Surface chemistry on AuNPs in various electrolyte solutions was explored to elucidate the role of ions on the size and stability of AuNPs.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.54 no.1
• /
• pp.47-52
• /
• 2005

This paper presents dimming control system for automotive 35W metal halide discharge(MHD) lamp electronic ballast. HID lamp demands a highly efficient ballast and very complex control circuitry that can control complex transient state in applying to automotive. Therefore, in this paper, a microcontroller-based digital control method for the HID lamp ballast is presented for optimal control that can adapt complex transient state, steady state and various environments. In developed dimming system, the system is designed to control the lamp output voltage step by step(continuous) using microcontroller according to CdS sensor. Therefore the designed dimming control system give good driving condition to diver and realize the power control effectively. The results of the proposed system is verified through various experiment results.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.58 no.8
• /
• pp.1538-1543
• /
• 2009

The electric ballast for ceramic metal halide lamp needs a protection circuit to prevent from over voltage and over current in the case that the lamp or the electric ballast are in faults. In this paper, cost-effective and high performance protection circuit is proposed for the electric ballast. The proposed protection circuit is adapted to the electric ballast with $LC_SC_P$ resonance type half bridge inverter. The experimental results demonstrate that the proposed circuit can protect effectively under open and short fault conditions.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.28 no.10
• /
• pp.394-401
• /
• 2016

The configuration of an extruded-type cooling structure was optimized for the light-emitting diode (LED) streetlights that have recently replaced convectional metal halide streetlights for energy saving. Natural convection and radiative heat transfer over the cooling structure were simulated using a numerical model with experimental verification. An improved cooling structure type was suggested to overcome the previous performance degeneration, as confirmed by analyzing the thermal flow around the existing cooling structure. A parameter study of the cooling structure geometries was also conducted and, based on the numerical results, the configuration was optimized to reduce the weight of the cooling structure. Consequently, the mass of the cooling structure was reduced by 60%, while the thermal performance was improved by 10%.

• Journal of the Korean Ceramic Society
• /
• v.44 no.4 s.299
• /
• pp.202-207
• /
• 2007

High-Quality 1-Dimensional InN single crystalline have been grown by Halide Vapor-Phase Epitaxy on the Au catalyst coated Si substrate using the vapor-liquid-solid growth mechanism. We have been grown 1-dimension InN nanowires having controlled the growth conditions for substrate temperature and gases flow rate. The grown InN nanowire of characteristics for morphologies, crystal structure, and element analysis were carried out by SEM, HR-TEM, and EDS respectively. And the defects of InN crystalline were analyzed by indexing of selective area diffraction pattern with attached HR-TEM. We have successfully obtained the defect-free 1-dimensional InN single crystalline nanowire at the atmosphere pressure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.11a
• /
• pp.344-345
• /
• 2005

본 논문에서는 홀로그래피용 감광물질로서, 앞으로 가장 발전가능성이 있다고 기대되는 photopolymer에 대해서 언급하고자 한다. 홀로그램은 물체에서 방출되는 빛의 파면에 대한 정보를 기록하는 필름을 말하며 이러한 홀로그램을 이용한 기술을 홀로그래피라고 한다. 먼저 홀로그램 및 홀로그래피의 개념과 원리에 대해 서술하고 현재 사용되고 있는 홀로그래피용 감광물질인 silver-halide나 dichromatic gelatin 등에 대해 소개한다. 이와 비교하여 photopolymer가 가지는 특성과 장점을 기술하고 photopolymer를 기반으로 한 holography의 발전에 따른 차세대 holographic applications에 대해 알아본다.

• Proceedings of the KIEE Conference
• /
• 2008.07a
• /
• pp.1003-1004
• /
• 2008

최근 메탈헬라이드 램프의 아크튜브에 석영관을 대신하여 세라믹(Ceramic)을 이용한 세라믹 메탈헬라이드 램프가 개발되어 상용화되고 있다. 이 세라믹 메탈헬라이드 램프는 탁월한 내열성 및 내식성으로 메탈헬라이드 램프로 하여금 우수한 색온도 및 연색성 유지특성을 갖는다. 본 논문에서는 PHILPS, OSRAM, GE 3사(社)의 150W 세라믹 메탈헬라이드 램프의 구동 주파수 따른 컨덕턴스 성분을 분석하였다. 또한 저주파 구동일 때와 고주파 구동일 때, 컨덕턴스 변화특성을 비교하였다.

• Proceedings of the KIEE Conference
• /
• 2008.07a
• /
• pp.1951-1952
• /
• 2008

본 논문에서는 메탈핼라이드 램프(MHL)의 원격 조도제어 및 감시 시스템을 구성하기 위하여 2.4GHz Zigbee 무선모듈로 구성된 무선모뎀을 구현하였다. MHL은 주로 가로등이나 보안등의 용도로 쓰이며, 대부분 설치되어 있는 시스템은 Group 제어 기반의 단방향 제어방식이다. 이러한 방식들은 각 등에 대한 개별적인 제어 및 감시가 이루어지지 못한다는 단점이 있으며, 이를 극복하기 위해서는 양방향 통신을 할 수 있는 통신 시스템이 필요하다. MHL은 다른 방전등들과 비교하여 비교적 방전시간이 긴 특징이 있으며, 이러한 특징은 조도제어 시스템 구성 시 고려되어야 한다. 본 논문에서는 시스템 구성을 위하여 IEEE 802.15.4 기반의 ZigBee 모듈을 이용하고, 조도제어를 위하여 Half-Bridge 방식의 전자식 안정기를 설계하여, 이를 제어하기 위한 제어회로를 구성하였으며, 램프의 특성에 맞는 프로토콜을 제안하였다.