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한재원(Jae Won Hahn),김용우(Yongwoo Kim),정호원(Howon Jung),김석(Seok Kim),장진희(Jinhee Jang) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
For decays, laser direct writing (LDW) is widely used for material processing of high precision engineering. The technique takes an important role in micro scale fabrication / manufacturing. In general, LDW uses beam spot focused by refractive optics and the scale of processing is mainly determined by diffraction limit. The resolution of commercially available system is about 500 ㎚. In this paper, we introduce high resolution LDW process using solid immersion lens probe or nano aperture probe which scans sample surface in contact mode assembled with LDW system. These probes are protected by diamond like carbon film for high durability. Using these contact probes, we achieved resolution up to 50 ㎚ and relatively high scan speed about 10 ㎜/s, which is several hundred times faster than conventional near-field scanning optical microscope scheme. The speed is comparable to conventional system and we expect these schemes can be practically used for fabrication system.
배연가스의 $NO_x$제거용 코로나 방전장치에서 OH 발광 스펙트럼 측정 및 관련 반응 연구
박철웅,한재원,신동남,Park, Chul-Woung,Hahn, Jae-Won,Shin, Dong-Nam 한국연소학회 1999 한국연소학회지 Vol.4 No.1
We constructed a wire-cylinder type pulsed corona discharge system for $NO_x$ removal, which was operated in room temperature. A emission spectrometer was built with a boxcar averager and monochrometer equipped with photo-multiplier tube detector. The sensitivity of the emission spectrometer was greatly improved by synchronizing the emission spectrometer with pulsed corona discharge system using a triggered spark-gap switch. $N_2$ spectrum($c^3{\Pi}_u{\rightarrow}X^1{\Sigma}_g{^+}$) was measured in the range of 300 - 450 nm and oxidizing OH radical emission($A^2{\Sigma}^+{\rightarrow}X^2{\Pi}$) was measured in case $N_2$ was supplied with water bubbling. As wet gas composition of inlet $N_2$ supplied in the discharge system increased, the intensity of OH emission was increased and saturated at wet gas composition 50%. We also investigated additive effect of $C_2H_4,\;H_2O,\;H_2O_2$ on the intensity of OR emission and $NO/NO_2/NO_x$ reduction and analysed the related reaction mechanism in corona discharge process. $H_2O_2$ additive increased the intensity of OH emission and $NO/NO_x$ reduction.
이종호,이승영,한재원,장영준,전충환,Lee, Jong-Ho,Lee, Seung-Young,Hahn, Jae-Won,Chang, Young-June,Jeon, Chung-Hwan 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.7
Co-flow axisymmetric laminar premixed flame of methane was used to study the influence of air temperature and $N_2$ addition on the flame structure, temperature field and emission characteristics. OH 2-D images and temperatures along the centerline were measured experimentally by PLIF and CARS techniques respectively to observe the influences of dilution and thermal effects of $N_2$ in the gas mixture. Also, the concentration of NOx was measured at each condition by gas analyser to see the suppression effect of N2 addition on NOx emissions. It was found that OH concentrations distribute widely as air temperature goes higher, while the effect of $N_2$ addition is not significant. But $N_2$ addition highly contributes to the flame front and NOx emissions which was argued to be due to the reduction of flame temperature. In accordance with experimental study, numerical simulation using CHEMKlN code was carried out to compare the temperature results with those acquired by CARS measurement, and we could find that there is good agreement between those results.
미량 기체의 밀도 측정을 위한 외부 공진기 반도체 레이저 광학공동 적분 투과 분광법
류훈철,유용심,이재용,한재원,Ryoo Hoon Chul,Yoo Yong Shin,Lee Jae Yong,Hahn Jae Won 한국진공학회 2006 Applied Science and Convergence Technology Vol.15 No.1
광학공동 적분 투과 분광법(integrated cavity output spectroscopy, ICOS)은 파장가변 레이저와 광학공동을 이용해 미량기체의 절대 밀도를 고감도로 측정할 수 있는 실시간 흡수 분광계측 기법이다. 이 기법은 압전 소자를 이용해 길이가 변조되는 고 피네스(high finesse) 파브리-페로 공동(Fabry-Perot cavity)을 공명 투과하는 연속파 파장 변조 레이저의 적분 출력으로 부터 공동 내부 시료의 분광 흡수량을 측정하는 원리를 이용한다. 본 연구에서는 764,7nm 파장 근처에서 파장이 변조되는 외부 공진기 반도체 레이저를 광원으로 사용하고, $99.997\%$의 높은 반사율을 갖는 거울로 구성된 파브리-페로 공동을 이용해 파장에 따른 투과 감쇠 신호를 발생시키는 실험 장치를 구성하였다. 산소 기체에 대한 측정 실험을 수행한 결과, 최소 흡수계수 $8.45\times10^{-8}cm^{-1}$에 해당하는 미량기체 밀도를 측정할 수 있는 성능을 얻었다. Integrated cavity output spectroscopy(ICOS) is a simple, non-intrusive absorption measurement technique that can detect and quantify trace-level gas species. The spectral absorbance of a gas is quantified from the integrated optical output of the modulated high-finesse cavity containing the sample which is irradiated by a wavelength-swept laser source. We constructed an experimental setup by using a tunable single mode external cavity diode laser operating at the wavelength near 765 nm and a Fabry-Perot cavity with length modulation achieved by a piezoelectric transducer where one of the cavity mirrors sat on. In the experiment performed on minute oxygen gas at the wave-length near 764.5nm, we demonstrated the minimum detectable absorption of $8.45\times10^{-8}cm^{-1}$.
레이저 유도 격자 분광장치 제작 및 C₃H8 화염에서 열 격자 측정
박철웅(Chul Woung Park),한재원(Jae Won Hahn),이중재(Joong-Jae Lee),이영우(Young-Woo Lee),고동섭(Dong-Seob Ko) 한국광학회 2001 한국광학회지 Vol.12 No.6
레이저 유도 격자 분광장치를 제작하여, C₃H_8 층류 확산화염에서 생성된 열 격자 신호를 측정하였다. 열 격자를 생성시키기 위한 여기광은 파장이 532 ㎚인 Nd:YAG 레이저를 사용하였고, 검침광은 488 ㎚의 CW Ar+ 레이저를 이용하였다. 검침광의 세기를 변화시켜 장치의 회절효율과 신호 특성을 측정하였다. 측정된 열 격자 신호의 세기를 분석하여 화염내의 매연의 농도 분포를 정성적으로 측정하였고, 신호의 주파수 변화를 측정하여 온도 분포를 구하였다. We made a laser induced grating spectrometer(LIGS) and measured the thermal grating signal generated in a C₃H_8 flame. The thermal grating was formed in the C₃H_8 flame with two second-harmonic Nd:YAG pulse laser beams, and an LIGS signal was generated by Bragg scattering of a probe laser beam Ar+ laser(488 ㎚). We found the modulation period of the signal depends linearly on the spacing of the grating set in the flame. We determined flame temperature by fitting the modulated signal and soot concentration with signal strength. Using this technique, we also obtained temperature profile and soot-particle distribution in a C₃H_8 flame.