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.

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

핵의학의 세계, 생명을 살리는 소중한 방사선

최원석,Choi, Won-Seok 한국정보통신기술협회 2011 TTA저널 Vol.133 No.-

영화 속에 등장하는 방사선은 평범한 파충류를 거대한 괴물 고질라로 만들거나 사람을 녹색 괴물 헐크로 만들어 버린다. 또한 언론에 비친 방사선은 마치 '살인 광선'처럼 우리 주변에서 가장 멀리해야할 것으로 비춰지고 있다. 최근의 한 드라마에서는 국익을 위해 신형 원자로 전문가를 서로 납치하기 위해 정보기관들 끼리 치열한 첩보전을 벌이는 내용이 나오기는 했지만 여전히 방사선에 대한 이미지는 부정적이다. 하지만 알려진 것과 달리 방사선은 수많은 사람의 목숨을 살리는 '생명의 빛'이기도 하다. 그렇다면 방사선이 어떻게 생명을 살리는데 도움을 줄 수 있는 것일까?

생강의 첨가가 분쇄막창의 저장특성에 미치는 영향

최원석,최웅규,Choi, Won-Seok,Choi, Ung-Kyu 한국식품영양학회 2014 韓國食品營養學會誌 Vol.27 No.5

This study was conducted to investigate the effects of ginger addition (1%, 5% and 10%) on the quality of ground pork rectum. No significant difference in the pH was found between raw and cooked pork rectum during storage; however, the pH of cooked rectum was slightly lower than raw rectum. The TBA value of the cooked pork rectum (0.25 mg/kg) was higher than raw pork rectum (0.1 mg/kg). In addition, the TBA values of both raw and cooked pork rectum increased as storage progressed. The TBA value was found to decrease in proportion to the amount of ginger added. The volatile basic nitrogen (VBN) values also decreased with the addition of ginger. Consequently, considering that the initial stage of decomposition was 30~40%, it was determined that it would be desirable to consume the raw and cooked pork rectum within 4 and 6 days of storage at $5^{\circ}C$, respectively. Further, it was found that the addition of 10% ginger could extend the storage period beyond the 4 days at $5^{\circ}C$. 신선한 암퇘지의 막창부위에 지방을 제거하고 파쇄기로 잘게 부수어 가열하지 않은 것과 $100^{\circ}C$의 autoclave에서 10분간 가열한 것에 분쇄한 생강을 1, 5 및 10%가 되게 첨가하여 polyethylene film으로 1차 포장한 후 알루미늄 호일로 2차 포장한 다음 $5^{\circ}C$에서 보관하면서 품질의 변화를 관찰하였다. 저장 중 pH는 첨가구 사이의 유의적인 차이를 나타내지 않았으나, 가열한 막창이 다소 낮은 값을 나타내었다. TBA가는 각각 0.1 mg/kg과 0.25 mg/kg으로 가열 막창이 생막창보다 높은 값을 나타내었으며, 두 처리구에서 모두 생강의 첨가가 TBA-value의 상승을 억제시켜 저장성을 연장시키는 것을 확인할 수 있었다. 휘발성 염기질소의 함량은 생강의 첨가로 감소하였으며, 30~40 mg%의 초기부패 판정기준을 고려할 때 생막창은 $5^{\circ}C$에서 4일, 가열막창은 6일 이내에 소비하는 것이 바람직할 것으로 판단되었다. VBN 함량을 기준으로 10% 생강의 첨가는 가열막창의 저장기간을 4일 가량 연장시킬 수 있는 것으로 확인되었다.

쌀밥의 조직감에 대한 기기적 측정값과 관능적 측정값의 상관관계 연구

최원석,Choi, Won-Seok 한국식품영양학회 2016 韓國食品營養學會誌 Vol.29 No.5

This study aimed to find the optimum instrumental test conditions for the Texture Profile Analysis (TPA) of cooked rice in order to predict the sensory texture attributes (hardness, adhesiveness, chewiness). Sensory evaluation was performed for three kinds of instant cooked rice with university students in their twenties and the results of the sensory evaluation were compared to instrumental TPA patterns. Using partial least squares regression, the instrumental TPA results at a cross-head speed of 1.0 mm/sec and a compression ratio of 70% proved to be an excellent predictor of the sensory attributes of hardness ($R^2=0.99$) and chewiness ($R^2=0.99$). The results at a cross-head speed of 0.5 mm/sec and compression ratio of 30% provided an excellent model for the prediction of sensory adhesiveness ($R^2=0.83$). In this experimental range, sensory hardness and chewiness showed a high correlation with instrumental TPA parameters (hardness, cohesiveness, adhesiveness, springiness, chewiness) with a high cross-head speed and compression ratio, while sensory adhesiveness showed a high correlation with the TPA parameters with a low cross-head speed and compression ratio.

LC 공진형 압력 센서를 이용한 돼지 경골 동맥의 실시간 혈압 측정

최원석,김진태,정연호,Choi, Won-Seok,Kim, Jin-Tae,Joung, Yeun-Ho 한국전기전자재료학회 2012 전기전자재료학회논문지 Vol.25 No.6

We have developed an implantable wireless sensor for real time pressure monitoring of blood circulation system. MEMS (micro-electro-mechanical system) technology was adopted as a sensor development method. The sensor is composed of photolithographically patterned inductors and a distributed capacitor in gap between the inductors. A resulting LC resonant system produces its resonant frequency in range of 269 to 284 MHz at 740 mmHg. To read the resonant frequency changed by blood pressure variation, we developed a custom readout system based on a network analyzer functionality. The bench-top testing of the pressure sensors showed good mechanical and electrical functionality. A sensor was implanted into tibial artery of farm pig, and interrogated wirelessly with accurate readings of blood pressure. After 45 days, the sensor's electrical response and histopathology were studied with good frequency reading and biocompatibility.

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.

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.

Thermal Aging Behavior of H-NBR/NBR Blend

최원석,김건완,도제성,유명우,류승훈,Choi, Won-Seok,Kim, Gun-Wan,Do, Je-Sung,Yoo, Myung-Ho,Ryu, Sung-Hun The Rubber Society of Korea 2011 엘라스토머 및 콤포지트 Vol. No.

본 연구는 H-NBR 함량 변화에 따른 H-NBR/NBR 블렌드의 열노화 거동에 대하여 살펴보았다. 이 때 가교제로는 dicumyl peroxide와 황 혼합물을 사용하였으며, 열노화에 따른 H-NBR/NBR 블렌드의 인장강도, 파괴신율, 경도 그리고 내마모성의 변화를 살펴보았다. H-NBR을 첨가함에 따라 인장강도는 증가하였으나 내마모성은 감소하는 현상을 나타내었다. 파괴신율과 경도는 H-NBR의 영향을 받지 않았다. 노화가 진행된 모든 시편은 초기 시편보다 낮은 인장강도, 파괴신율, 경도를 나타내었다. 그러나 H-NBR의 함량이 증가함에 따라 이러한 물성저하 속도가 감소함을 알 수 있었다. 즉 H-NBR 첨가에의해 열노화 특성이 향상됨을 알 수 있었다. 모든 NBR/H-NBR 블렌드는 노화시간이 증가함에 따라 내마모성이 감소하였으며, H-NBR을 첨가한 경우 내마모성의 저하가 상대적으로 낮음을 알 수 있었다. In the present investigation, thermal aging behavior of H-NBR/NBR blend with various H-NBR content was investigated. Mixture of dicumyl peroxide and sulfur were used as a curing agent. The influence of the thermal aging of the H-NBR/NBR blends on the solid state properties such as tensile strength, elongation at break, hardness and abrasion resistance was investigated. Tensile strength was increased with increasing H-NBR content, while abrasion resistance was decreased. Both elongation at break and hardness were not affected by the addition of H-NBR. The properties such as hardness, tensile strength and elongation at break of the aged samples were lower than unaged samples. However, the rate of deterioration of those properties was decreased by increasing the H-NBR content, which indicated that improved thermal aging behavior was obtained by the addition of H-NBR. Abrasion loss was increased with increasing aging time, but it became less by the addition of H-NBR addition.