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Wide-fan-angle Flat-top Linear Laser Beam Generated by Long-pitch Diffraction Gratings
이무현,류태수,김영훈,양진규 한국광학회 2021 Current Optics and Photonics Vol.5 No.5
We demonstrated a wide-fan-angle flat-top irradiance pattern with a very narrow linewidth by using an aspheric lens and a long-pitch reflective diffraction grating. First, we numerically designed a diffraction-based linear beam homogenizer. The structure of the Al diffraction grating with an isosceles triangular shape was optimized with 0.1-mm pitch, 35.5° slope angle, and 0.02-mm radius of the rounding top. According to the numerical results, the linear uniformity of the irradiance was more sensitive to the working distance than to the shape of the Al grating. The designed Al grating reflector was fabricated by using a conventional mold injection and an Al coating process. A uniform linear irradiance of 405-nm laser diode with a 100-mm flat-top length and 0.176-mm linewidth was experimentally demonstrated at 140-mm working distance. We believe that our proposed linear beam homogenizer can be used in various potential applications at a precise inspection system such as three-dimensional morphology scanner with line lasers.
이창수,김호정,이무현,강성환,김세영,민인선,이주영,박경득,고현철,조현정,최정우 중앙대학교 의과대학 의과학연구소 2015 中央醫大誌 Vol.40 No.2
Most peptic ulcers respond to treatment with conventional therapy including antimicrobial and antisecretory agents. However, in some individuals, the ulcer recurs following successful initial treatment, which means the refractory ulcer. We report a case with a gastric ulcer at antrum, which had been treated with conventional regimen. After conventional treatment, we confirmed that the ulcer was improving through the endoscopy. However, after a short time, he came back to emergency room with acute ill-look appearance. He was pale and anemic status. Emergency endoscopy was performed and we found that the gastric ulcer had a gastroduodenal fistula without peritonitis.
이무현,허수정,박용완,Lee, Moohyun,Hur, Soojung,Park, Yongwan 대한임베디드공학회 2015 대한임베디드공학회논문지 Vol.10 No.3
We propose obstacle classification method based on 2D LIDAR(Light Detecting and Ranging) database. The existing obstacle classification method based on 2D LIDAR, has an advantage in terms of accuracy and shorter calculation time. However, it was difficult to classifier the type of obstacle and therefore accurate path planning was not possible. In order to overcome this problem, a method of classifying obstacle type based on width data of obstacle was proposed. However, width data was not sufficient to improve accuracy. In this paper, database was established by width, intensity, variance of range, variance of intensity data. The first classification was processed by the width data, and the second classification was processed by the intensity data, and the third classification was processed by the variance of range, intensity data. The classification was processed by comparing to database, and the result of obstacle classification was determined by finding the one with highest similarity values. An experiment using an actual autonomous vehicle under real environment shows that calculation time declined in comparison to 3D LIDAR and it was possible to classify obstacle using single 2D LIDAR.
초고속 플라즈마 전자 온도 측정법 개발을 통한 2㎒ 유도 결합 플라즈마의 전자 가열 및 동력학적 특성 연구
이무현,서범준,정진욱 한국진공학회 2021 한국진공학회 학술발표회초록집 Vol.2021 No.2
부유 고조화 분석법은 부유 전위에 있는 탐침에 작은 정현 전압을 인가하여 전류 파형을 얻고, 이 전류 파형의 여러 고조화 성분을 분석해 전자 온도를 구하는 방법이다. 기존의 연구들은 구동 주파수가 탐침 전압의 주파수보다 큰 조건에서 시간 평균 된 전자온도를 측정하였으나, 본 연구에서는 유도 결합 플라즈마 구동 주파수(2MHz)보다 높은 탐침 주파수(10 MHz)를 사용하여 유도 결합 플라즈마 소스의 한 주기 안에서 시변하는 전자 온도를 측정하여 전자 가열 동력학을 관찰하고자 하였다.
광산배수 내 철에 의한 하천 황화현상을 촉진하는 환경조건 연구
이무현,박형준,이종운 한국자원공학회 2016 한국자원공학회지 Vol.53 No.3
Though Fe concentration in mine drainage and treated water is lower than Korean water quality criteria (2 mg/L), the yellowboy mainly composed of Fe precipitates often occurs in lower streams. In this study, the effects of pH, temperature, dissolved major cations, stream bed materials, and Fe oxidizing bacteria on yellowboy formation were investigated. Experiments on Fe precipitation with low concentrations of Fe and washing of precipitated Fe were also conducted. Yellowboy production was accelerated under the conditions with high pH, high temperature, Ca 2+ as a dominant major ion, and the presence of stream bed materials and Fe oxidizing bacteria. Even low concentration of Fe (1 mg/L) led to formation of yellowboy. In addition, it was found that, once Fe precipitates formed by abrupt operational accidents of passive treatment systems, they might not readily be detached from stream bed. 국내 광산배수 내 철 배출허용기준(2 mg/L)을 만족하는 경우에도 수계 하류에서는 철 침전물로 구성된yellowboy가 나타난다. 이 연구에서는 철 침전물 형성에 미치는 pH, 온도, 용존 주성분 양이온, 하상물질, 철산화균의 영향을 연구하였다. 저농도 철에 의한 철 침전 및 침전된 철의 탈착 실험도 수행하였다. 철 침전은 높은pH, 고온, Ca 2+이 우세한 조건, 하상퇴적물 및 철산화균의 존재 하에서 증진되었다. 저농도(1 mg/L) 철이 함유된경우에도 철 침전이 발생함을 관찰하였으며, 자연처리시설의 돌발적인 월수 등에 의하여 하상 퇴적물에 철 침전물이 발생하면 용이하게 제거되지 않는 것으로 판단된다.