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극초단 펄스 레이저를 사용한 유리 내부의 필라멘테이션에 대한 실험적 연구
최원석,윤지욱,김주한,최지연,장원석,김재구,최두선,황경현,조성학,Choi, Won-Suk,Yoon, Ji-Wook,Kim, Joohan,Choi, Jiyeon,Chang, Won-Seok,Kim, Jae-Goo,Choi, Doo-Sun,Whang, Kyoung Hyun,Cho, Sung-Hak 한국레이저가공학회 2013 한국레이저가공학회지 Vol.16 No.1
We have successfully formed filament inside of a transparent soda-lime glass using a Ti:sapphire based femtosecond laser. To make filament form, keeping the laser intensity higher than critical intensity is essential. Also each of the machining parameters plays an important role for the formation of filament. In this paper, we study what parameter can possibly influence for formation of filament, and we introduce an application using filamentation by femtosecond laser for transparent material.
AMOLED 제조공정에 사용되는 Fine Metal Mask 용 얇은 Invar 합금의 진동자를 이용한 펨토초 레이저 응용 홀 드릴링
최원석,김훈영,신영관,최준하,장원석,김재구,조성학,최두선,Choi, Won-Suk,Kim, Hoon-Young,Shin, Young-Gwan,Choi, Jun-ha,Chang, Won-Seok,Kim, Jae-Gu,Cho, Sung-Hak,Choi, Doo-Sun 한국금형공학회 2020 한국금형공학회지 Vol.14 No.3
One of display trends today is development of high pixel density. To get high PPI, a small size of pixel must be developed. RGB pixel is arranged by evaporation process which determines pixel size. Normally, a fine metal mask (FMM; Invar alloy) has been used for evaporation process and it has advantages such as good strength, and low thermal expansion coefficient at low temperature. A FMM has been manufactured by chemical etching which has limitation to controlling the pattern shape and size. One of alternative method for patterning FMM is laser micromachining. Femtosecond laser is normally considered to improve those disadvantages for laser micromachining process due to such short pulse duration. In this paper, a femtosecond laser drilling for thickness of 16 ㎛ FMM is examined. Additionally, we introduce experimental results for controlling taper angle of hole by vibration module adapted in laser system. We used Ti:Sapphire based femtosecond laser with attenuating optics, co-axial illumination, vision system, 3-axis linear stage and vibration module. By controlling vibration amplitude, entrance and exit diameters are controllable. Using vibrating objective lens, we can control taper angle when femtosecond laser hole drilling by moving focusing point. The larger amplitude of vibration we control, the smaller taper angle will be carried out.
산소 분압에 따라 전자빔 증착법으로 제작된 TiO<sub>2</sub> 박막의 구조적.광학적 특성
최원석,김장섭,정종민,한성홍,김의정,이충우,주종현,Choi, Won-Seok,Kim, Jang-Seob,Jung, Jong-Min,Hahn, Sung-Hong,Kim, Eui-Jung,Lee, Chung-Woo,Joo, Jong-Hyun 한국광학회 2007 한국광학회지 Vol.18 No.2
전자빔 증착법을 이용하여 산소 분압에 따라 $TiO_2$ 박막을 제작하고, 열처리 온도에 따른 박막의 구조적 특성과 광학적 특성을 분석 하였다. $TiO_2$ 박막들의 물리적 특성은 주입된 산소량에 의존하였다. 주입된 산소량이 증가 할수록 상전이 온도가 높아지고, 가시광선 영역에서 $TiO_2$ 박막의 투과율이 증가하였다. 그리고 주입된 산소량이 작은 경우, $700^{\circ}C$에서 $1100^{\circ}C$로 열처리 후 $TiO_2$ 박막의 흡수단 이 좀더 장파장으로 이동하였다. We prepared $TiO_2$ thin films by electron-beam evaporation at various oxygen pressures, and investigated their optical and structural properties as a function of the annealing temperature. The physical properties of the $TiO_2$ thin films depend upon the injection oxygen content. With the increased injection of oxygen, the phase transformation temperature and the transmittance of $TiO_2$ thin films in the range of visible wavelength were increased. For low injection of oxygen, the absorption edges of $TiO_2$ thin films were more red-shifted when annealed at temperatures from $700^{\circ}C$ to $1100^{\circ}C$.
MEMS 소자의 고체윤활박막으로 활용하기 위한 다이아몬드상 카본 박막의 트라이볼로지 특성 분석
최원석,홍병유,Choi, Won-Seok,Hong, Byung-You 한국전기전자재료학회 2006 전기전자재료학회논문지 Vol.19 No.11
Hydrogenated Diamond-like carbon (DLC) films were Prepared by the radio frequency plasma enhanced chemical vapor deposition (RF PECVD) method on silicon substrates using methane $(CH_4)$ and hydrogen $(H_2)$ gas for the application to solid lubricant of MEMS devices. We have checked the influence of varying RF power on tribological properties of DLC film. We have checked their performance as two kinds of method such as FFM (Friction Force Microscope) and BOD (Ball-on Disk) measurement. The friction coefficients and the contact number of cycles to steady state decreased as the increase of RF power with FFM and BOD measurement, respectively.
그리드 네트워크에서 종단간 전송 지연 향상을 위한 bottleneck 링크 대역폭 측정 알고리즘
최원석,안성진,정진욱,Choi, Won-Seok,Ahn, Seong-Jin,Chung, Jin-Wook 한국정보처리학회 2003 정보처리학회논문지 C : 정보통신,정보보안 Vol.10 No.7
본 논문은 그리드 네트워크의 패킷 지연시간단축을 위한 병목 링크 대역폭 측정 알고리즘을 제안하고자 한다. 병목 링크 대역폭 측정방법으로 packet pair 알고리즘과 Paced Probes가 있으나 이들은 pacer 패킷으로 cross traffic의 영향을 줄이면서 Paced probe 패킷들이 링크를 지날 때 발생하는 시간 차이를 이용하여 병목 링크 대역폭을 구한다. 그러나 경로상의 병목 링크 대역폭을 측정할 뿐이지 병목현상이 발생한 지점은 알 수 없는 문제점이 있다. 이를 hop-by-hop 측정에 기반한 병목 대역폭 측정을 제시하여 그리드 네트워크에서 전체적인 패킷 지연 개선을 이룰 수 있다. hop-by-hop의 병목 대역폭을 측정하기 위해 paced probe 패킷에 타임스탬프 옵션을 이용하며 병목현상 해소를 통하여 패킷 전송 지연의 단축을 시뮬레이션을 통해 알 수 있다. 본 논문에서 제시한 알고리즘으로 병목 링크의 대역폭과 위치를 파악하여 그리드 ETP나 실시간 QoS를 보장하는 데이터 전송에 기여할 것으로 기대된다. This paper proposes a bottleneck link bandwidth measurement algorithm for reducing packet transmission delay within the grid network. There are two methods for measuring bottleneck link bandwidth:Packet Pair algorithm and Paced Probes algorithm. They measure bottleneck link bandwidth using the difference in arrival times of two paced probe packets of the same size traveling from the same source to destination. In addition, they reduce the influences of cross traffic by pacer packet. But there are some problems on these algorithms:it's not possible to know where bottleneck link occurred because they only focus on measuring the smallest link bandwidth along the path without considering bandwidth of every link on the path. So hop-by-hop based bottleneck link bandwidth measurement algorithm can be used for reducing packet transmission delay on grid network. Timestamp option was used on the paced probe packet for the link level measurement of bottleneck bandwidth. And the reducing of packet transmission delay was simulated by the solving a bottleneck link. The algorithm suggested in this paper can contribute to data transmission ensuring FTP and realtime QoS by detecting bandwidth and the location where bottleneck link occurred.
라만 맵핑 방식을 사용한 다이아몬드상 카본박막의 미세구조변화에 관한 연구
최원석,Choi, Won-Seok 한국전기전자재료학회 2006 전기전자재료학회논문지 Vol.19 No.7
Hydrogenated Diamond-like carbon (DLC) films were prepared by the radio frequency plasma enhanced chemical vapor deposition (RF PECVD) method on silicon substrates using methane $(CH_4)$ and hydrogen $(H_2)$ gas. The wear track on the DLC films was examined after the ball-on disk (BOD) measurement with a Raman mapping method. The BOD measurement of the DLC films was performed for 1 to 3 hours with a 1-hour step time. The sliding traces on the hydrogenated DLC film after the BOD measurement were also observed using an optical microscope. The surface roughness and cross-sectional images of the wear track were obtained using an atomic force microscope (AFM). The novel Raman mapping method effectively shows the graphitization of DLC films of $300{\mu}m\times300{\mu}m$ area according to the sliding time by G-peak positions (intensities) and $I_D/I_G$ ratios.
PECVD로 합성한 다이아몬드상 카본박막의 전기적 특성
최원석,박문기,홍병유,Choi, Won-Seok,Park, Mun-Gi,Hong, Byung-You 한국전기전자재료학회 2008 전기전자재료학회논문지 Vol.21 No.11
In addition to its similarity to genuine diamond film, diamond-like carbon (DLC) film has many advantages, including its wide band gap and variable refractive index. In this study, DLC films were prepared by the RF PECVD (Plasma Enhanced Chemical Vapor Deposition) method on silicon substrates using methane ($CH_4$) and hydrogen ($H_2$) gas. We examined the effects of the RF power on the electrical properties of the DLC films. The films were deposited at several RF powers ranging from 50 to 175 W in steps of 25 W. The leakage current of DLC films increased at higher deposition RF power. And the resistivities of DLC films grown at 50 W and 175 W were $5\times10^{11}$ ${\Omega}cm$ and $2.68\times10^{10}$ ${\Omega}cm$, respectively.
Sensitiv Imago<sup>TM</sup> 측정에 의한 야뇨증 환아의 검사 결과 보고
최원석,김덕곤,이진용,Choi, Won Seok,Kim, Deog Gon,Lee, Jin Yong 대한한방소아과학회 2014 대한한방소아과학회지 Vol.28 No.4
Objectives The purpose of this study is to report the nocturnal enuresis in children using Sensitiv $Imago^{TM}$. Methods Twenty nocturnal enuresis children were tested using Sensitiv $Imago^{TM}$. Results 10 cases showed the lowest score at filter $#5^*$ and 7 cases showed the lowest score at filter $6^*$ in {Express Monitoring} of {Review of System Disorders of Homeostasis}. Conclusions Further study with more samples is necessary to establish the accuracy of Sensitiv $Imago^{TM}$.
최원석,신영주,김하경,이가영,Won Seok Choi,MD,Young Joo Shin,MD,PhD,Ha Kyoung Kim,MD,PhD,Kayoung Yi,MD,PhD 대한안과학회 2013 대한안과학회지 Vol.54 No.12
Purpose: In the present study we compared the intraocular pressure (IOP) after cataract surgery according to incisional techniques. <br /> Methods: Patients who underwent phacoemulsification with intraocular lens implantation were divided into 2 groups: clear corneal incision group (CC group), and scleral tunnel incision group (ST group). All complicated cases were excluded. IOP was measured preoperatively and at 1 week, 1, 3, 6, 12, 18 and 24 months after surgery.<br /> Results: Seventy-seven patients (100 eyes) were enrolled in the present study; CC group (28 patients, 33 eyes), ST group (49 patients 67 eyes). Preoperative IOPs in both groups were not significantly different (p = 0.908, student’s t-test). IOP in the CC group at 1 week after surgery significantly decreased 2.22 ± 2.57 mm Hg compared to preoperative IOP (p < 0.001, repeated-measures ANOVA with post hoc analysis), and the IOP of the ST group decreased 2.11 ± 2.50 mm Hg (p < 0.001, repeated-measures ANOVA with post hoc analysis). The lowered IOP was maintained for 24 months postoperatively. There was no significant difference in IOP change after surgery depending on incisional techniques (p = 0.848, repeated measures ANOVA).<br /> Conclusions: There may be no difference in IOP lowering effect after surgery depending on incisional techniques. <br /> J Korean Ophthalmol Soc 2013;54(12):1856-1861
최원석,Choi, Won-Seok 한국정보통신기술협회 2010 TTA저널 Vol.132 No.-
2003년 2월 18일 대구 지하철에서 방화로 인해 사망 192명, 부상 148명이라는 대형 참사가 발생했다. 그로부터 5년 후인 2008년 2월 11일에는 국민들이 안타까운 눈길로 지켜보는 가운데 우리나라 국보 1호인 숭례문이 방화로 인해 역사 속으로 사라져버렸다. 이렇게 화재에 대한 악몽은 잊혀질 만하면 다시 찾아오지만 아직까지 이에 대한 경각심 제고나 예방을 위한 투자에는 큰 변화가 없는 것이 현실이다. 이는 대부분이 강 건너 불구경 하듯 화재가 남의 일이라고 느끼기 때문일 것이다. 하지만 불은 항상 주변에 있기에, 언제든 우리 또한 화재의 피해자가 될 수 있다. 따라서 누구나 화재에 대해 기본적인 상식을 갖출 필요가 있다.