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.

최한기의 기학적 지리학과 지리연구방법론

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

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.

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.

Permeable FW-H 방법을 이용한 원형 실린더 주변의 난류유동소음해석

최원석,홍석윤,송지훈,권현웅,정철민,Choi, Woen-Sug,Hong, Suk-Yoon,Song, Jee-Hun,Kwon, Hyun-Wung,Jung, Chul-Min 해양환경안전학회 2014 海洋環境安全學會誌 Vol.20 No.6

난류유동에 의한 소음은 계산비용의 관점에서 음향 상사법을 이용하여 전산유체 기법과 결합해 다양한 해석모델이 연구되고 있다. FW-H 음향상사법을 이용한 유동소음해석의 연구가 활발히 이루어지고 있으나, 기존 문헌들의 결과에서는 계산비용의 관점에서 난류유동에 의한 소음성분을 생략하고 있다. 그러나, 최근의 연구에서 유동소음특성에 있어 난류소음의 중요성이 밝혀진바 있다. 본 논문에서는 RANS 난류모델과 투과성 경계면을 이용한 Permeable FW-H 음향상사법을 이용한 난류유동소음해석에 대해 연구하였다. 2D실린더에 대하여 직접적으로 변동압력을 추출하는 직접법과 난류성분을 고려하지 않은 FW-H 상사법, 또 난류소음의 성분을 포함하는 Permeable FW-H 방법의 경우를 비교하였다. Permeable FW-H 방법을 통해 일반적으로 적용되는 FW-H 방법에서 해석 불가능한 난류에 의한 소음의 영향을 기존의 FW-H 방법과 동일한 계산비용으로 예측할 수 있었고, 적절한 투과성 경계면 설정을 통해 높은 정확도의 해석이 가능했다. Permeable FW-H 방법을 통한 난류유동해석 절차를 확립하였으며, 그 유용성을 확인했다. Varieties of research on turbulent-induced noise is conducted with combinations of acoustic analogy methods and computational fluid dynamic methods to analyze efficiently and accurately. Application of FW-H acoustic analogy without turbulent noise is the most popular method due to its calculation cost. In this paper, turbulent-induced noise is predicted using RANS turbulence model and permeable FW-H method. For simplicity, noise from 2D cylinder is examined using three different methods, direct method of RANS, FW-H method without turbulent noise and permeable FW-H method which can take into account of turbulent-induced noise. Turbulent noise was well predicted using permeable FW-H method with same computational cost of original FW-H method. Also, ability of permeable FW-H method to predict highly accurate turbulent-induced noise by applying adequate permeable surface is presented. The procedure to predict turbulent-induced noise using permeable FW-H is established and its usability is shown.

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.

파프리카 온실에서 담배가루이의 축차표본조사법 개발

최원석,박정준,Choi, Wonseok,Park, Jung-Joon 한국응용곤충학회 2015 한국응용곤충학회지 Vol.54 No.3

파프리카(Capsicum annuum var. angulosum)의 주요해충인 담배가루이(Bemisia tabaci)의 고정 정확도 수준에서 표본조사법(Fixedprecision sampling plan)을 개발하였다. 개발된 표본 조사법은 파프리카 온실의 담배가루이 방제체계 확립을 위해 공간분포분석, 표본추출 정시선 그리고 의사결정법으로 이루어 졌다. 자료 수집은 식물체를 상단(지상으로부터 180-220 cm), 중단(지상으로부터 80-120 cm), 하단(지상으로부터 30-70 cm)로 나누어 각 위치별 3개의 파프리카 잎에서 담배가루이 성충, 번데기를 관찰하고 그 총 수를 기록하였다. 담배가루이 성충은 식물체의 상부에서 움직이고 신초에 주로 산란하며 일정부분이 하단으로 내려오기 때문에 상단과 하단에 많이 분포하였으며, 번데기의 경우 상부에 알을 낳았지만 식물체가 크면서 알을 낳은 잎이 아랫부분이 되고 부화한 유충은 잎 뒤에 고착 상태로 우화까지 움직임이 거의 없기 때문에 중단과 하단에서 많이 분포하였다. 공간분포분석은 Taylor's power law (TPL)를 이용하였으며, TPL계수의 차이를 공분산분석(ANCOVA)하여 차이가 없는 경우 자료를 통합하여 계산된 새 TPL 상수값을 이용하여 표본추출 정시선을 구하였다. 그리고 담배가루이 성충과 번데기의 방제밀도수준을 2.0마리와 10.0마리로 설정하여 방제의사를 결정하였다. 마지막으로 분석에 사용하지 않은 독립된 자료를 이용하여 개발된 표본추출법의 유효성을 Resampling Validation for Sampling Plan (RVSP) 프로그램으로 평가한 결과 적합한 정확도를 보였다. In order to establish B. tabaci control in paprika greenhouses a fixed-precision-level sampling plan was developed. The sampling plan consisted of spatial distribution analysis, a sampling stop line, and decision making. Sampling was conducted simultaneously in two independent greenhouses (GH 1, GH 2). GH 1 and 2 were surveyed every week for 22 consecutive weeks, using 19 sampling locations in GH 1 and 9 sampling locations in GH 2. The plant in both greenhouses were divided into top (180-220 cm from the ground), middle (80-120 cm from the ground) and bottom (30-70 cm from the ground) sections and B. tabaci adults and pupae were observed on three paprika leaves at each position and recorded separately. GH 2 data were used to validate the fixed-precision sampling plan, which was developed using GH 1 data. In this study, spatial distribution analysis was performed using Taylor's power law with the pooled data of the top and bottom position (B. tabaci adults), and the middle and bottom positions (B. tabaci pupae), based on a 1-leaf sampling unit. Decision making was undertaken using the maximum of action threshold in accordance with previously published method, and the value was decided by the price of the plants. Using the results obtained in the greenhouse, simulated validation of the developed sampling plan by RVSP (Resampling Validation for Sampling Plan) indicated a reasonable level of precision.

2009년 발생한 신종인플루엔자 대유행에 대한 정책적 대응 평가

최원석,김우주,정희진,Choi, Won-Suk,Kim, Woo-Joo,Cheong, Hee-Jin 대한예방의학회 2010 예방의학회지 Vol.43 No.2

Objectives: To evaluate the policies on 2009 influenza pandemic in Korea at the end of first wave. Methods: The main policies and the estimation of these were described according to the progress of 2009 influenza pandemic. Results: The public health measures for containment were estimated to be successful in the early stage. The preparedness of antiviral agents and vaccines before the pandemic, risk-communication on pandemic influenza and policies of government including vaccines, and the education of health care worker and support of health care institutions was not enough to respond to the pandemic. Conclusions: The additional evaluation should be performed at the end of the pandemic in various aspects including health and socioeconomic effects.

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

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.