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.

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 Laser Solutions 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.

최한기의 기학적 지리학과 지리연구방법론

최원석(Won Suk Choi) 한국지역지리학회 2009 한국지역지리학회지 Vol.15 No.1

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.

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.

백내장 수술 후 절개 방법에 따른 안압 변화 비교

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

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.

Fetal Bovine Serum을 포함한 세포 배양액에 담근 Indium Tin Oxide 전극 계면의 전기화학적 특성

최원석,조성보,Choi, Won Seok,Cho, Sungbo 대한의용생체공학회 2013 의공학회지 Vol.34 No.1

For the biocompatibility test of implantable devices or for the sensitivity evaluation of biomedical sensors, it is required to understand the mechanism of the protein adsorption and the interaction between the adsorbed proteins and cells. In this study, the adsorption of proteins in a cell culture medium with fetal bovine serum onto an indium tin-oxide electrode was characterized by using linear sweep voltammetry and impedance spectroscopy. We immersed the fabricated ITO electrodes in the culture medium for 30, 60, or 90 min, and then measured the electrochemical properties of electrodes with 10 mM $Fe(CN){_6}^{3-/4-}$ and 0.1 M KCl electrolyte. With an increase of contacting time, the anodic peak current was decreased and the charge transfer resistance was increased. However, both parameters were recovered to the values before contact with the medium after the treatment of Trypsin/Ethylenediaminetetraacetic acid hydrolyzing proteins.

심장 치료 전후의 혈압 측정 인자의 변화에 관한 연구

최원석,Choi, Wonsuk 한국융합신호처리학회 2021 융합신호처리학회 논문지 (JISPS) Vol.22 No.2

상완 수축기 혈압과 맥압은 50세 이상의 개인에서 심혈관 질환의 예측 인자이다. 강성이 증가함에 따라 수축기 후기의 반사 진폭과 압력이 증가하여 좌심실 부하와 심근 산소 요구량이 증가한다. 따라서 강성이 혈압에 미치는 영향을 연구 할 필요가 있다. 본 연구에서는 약물 복용 전후에 혈압 맥파를 측정하고, 심부전 환자에서 심근 심장 이식 전후에 혈압 맥파를 측정하였다. Windkessel 모델의 R, L 및 C 구성 요소 간의 상관관계는 혈압을 높임으로써 추정되었다. 커브 피팅 방법을 사용하여 Windkessel 모델의 매개 변수를 모델링 한 결과 혈압의 증가와 수축기 상승 시간의 감소는 RLC Windkessel 모델의 L 성분이 증가했기 때문이다. 혈관의 다양한 기계적 특성 중에 높은 BP 파형에 영향을 미치는 가장 중요한 매개 변수는 실험결과로 이너턴스인 것을 증명하였다.

열처리온도에 따른 다이아몬드상 카본박막의 구조적 특성변화

최원석,박문기,홍병유,Choi Won-Seok,Park Mun-Gi,Hong Byung-You 한국전기전자재료학회 2006 전기전자재료학회논문지 Vol.19 No.8

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 post annealing temperature on the structural variation of the DLC films. The films were annealed at temperatures ranging from 300 to $900^{\circ}C$ in steps of $200^{\circ}C$ using RTA equipment in nitrogen ambient. The thickness of the film and interface between film and substrate were observed by surface profiler, field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), respectively. Raman and X-ray photoelectron spectroscopy (XPS) analysis showed that DLC films were graphitized ($I_D/I_G$, G-peak position and $sp^2/sp^3$ increased) ratio at higher annealing temperature. The variation of surface as a function of annealing treatment was verified by a AFM and contact angle method.