A Study on a Single Continuous Deformable Mirror for Correction of Atmospheric Disturbance

Hyun Cheol Cho(조현철),Seong Jin Kim(김성진),Jeong Min Kang(강정민),Hyun Su Jung(정현수) Korean Society for Precision Engineering 2018 한국정밀공학회지 Vol.35 No.10

The deformable mirror is the main component of the adaptive optical imaging system, which removes the atmospheric disturbance and acquires the target image without any loss and the beam transmission system, which transmits the laser beam to a long distance. The mirror transforms the optical wavefront distortion caused by atmospheric disturbance into the opposite wavefront shape thereby correcting the distorted wavefront. In order to develop the deformable mirror, it is necessary to analyze the adaptive optics system and the usage environment where the application is required. In the present work, a prototype of a deformable mirror with a single continuous mirror was developed. In order to design the deformable mirror, the main factors of the adaptive optics system and the large diameter telescope were analyzed. Subsequently, the mirror material and the actuator were selected by confirming the amount of deformation through the finite element analysis. Based on the data collected, we designed and fabricated the prototype of the deformable mirror, and the Gaussian model was derived by analyzing the influence function of the deformable mirror through the design data. It was observed that the derived Gaussian model matched with the Zernike polynomial. Apparently, the fitting ability of the deformable mirror was confirmed.

반도체 기판 위의 3차원 구조에 대한 형상 진화 모델링 연구

鄭賢洙(Hyun-Su Jung),元太映(Tae-Young Won) 大韓電子工學會 2000 電子工學會論文誌-SD (Semiconductor and devices) Vol.37 No.12

본 논문에서는 레벨셋 방법을 이용한 표면 전진기를 사용하여 반도체 공정에서 3차원 증착 프로파일을 계산하는 방법을 보고한다. 레벨셋 방법을 이용하여 효율적으로 표면의 전진, 후퇴를 모델링 하기 위하여 반복법에 의한 초기화 방법을 새로이 개발하였다. 또한, 각각의 위치에서의 증착 및 식각률을 계산하기 위하여 소스에서 표면까지의 가시도 계산 방법과 표면 반사 모델을 개발하였다. 3차원 표면 전진기로 그림자 효과와 표면 반사가 고려된 계산을 수행하였다. 흡착 계수가 1인 경우와 0.3인 경우를 비교하여 반사, 스퍼터링에 의한 증착 프로파일의 변화를 비교하였다. 그리고 종횡비에 따른 증착률의 차이를 그림자 효과에 의한 가시각의 차이로 비교하였다. This paper reports a new calculation method of three dimensional deposition rate by level set method To model an advancement of the surface efficiently, we have developed a new iteration method to re-initialize the level set function. For calculating etching and deposition rate by direct flow, we have developed a visibility test module and a refraction and re-sputtering model. Sputter deposition rate with shadow effect and surface refraction is calculated. We report that difference of profiles in cases that sticking coefficient are 1.0 and 0.3. We report that the difference of the deposition rate on bottom of the hole is caused by a difference of visible angle by the shadowing effect.

무작위 진동에 노출된 항공기 탑재 장비의 주파수영역 피로수명 평가

정현수(Hyun Su Jung),김기승(Ki Seung Kim),김준수(Jun Su Kim),이성우(Seong Woo Lee) 한국항공우주학회 2017 韓國航空宇宙學會誌 Vol.45 No.8

항공기에 탑재된 레이더 장비는 무작위진동 환경에 장기간 노출되어, 설계 시 피로수명 예측이 중요한 요소로 고려된다. 피로수명을 예측하는 방법 중 주파수영역 피로해석 방법이 지속적으로 제안되고 있다. 본 논문은 많이 사용되는 4가지의 주파수영역 피로해석 방법을 선정하여, 시편 피로시험 결과와 비교하였다. Strain gage를 이용한 시편 피로시험을 통해 시간영역 피로해석과 주파수영역 피로해석 방법을 비교한 결과, Dirlik과 Benasciutti-Tovo방법이 주파수영역 피로해석법 중 시간영역 피로해석법과 잘 일치하였다. 시편 피로시험 결과를 토대로 Dirlik과 Benasciutti-Tovo방법과 유한요소모델을 이용하여 항공기 탑재 장비의 피로해석을 수행하였으며, 요구수명이 만족함을 확인하였다. Expecting fatigue life of mounted radar in aircraft is very important when designing, because the mounted radar in aircraft is exposed to long-term external random vibration. Among the methods of predicting the fatigue life, Fatigue analysis method in frequency domain has continuously been proposed in this field. In this paper, four fatigue analysis methods in frequency domain, which are widely used, have been selected and compared with the results for Specimen fatigue test. As a result, Dirlik and Benascicutti-Tovo methods have been matched better with fatigue analysis in time domain than the method in frequency method through the comparison between the fatigue analysis method in time domain and the method in frequency domain by conducting the specimen fatigue test with strain gage. Based on the results of the specimen fatigue test, We have conducted fatigue analysis of mounted radar in aircraft with Dirlik and Benasciutti-Tovo methods in the finite element model, and confirmed that the required life was satisfying.

건식윤활코팅이 볼트 마찰계수에 미치는 영향

정현수(Hyun Su Jung),한혜선(Hye Sun Han),김준수(Jun Su Kim),김기승(Ki Seung Kim) 한국생산제조학회 2018 한국생산제조학회지 Vol.27 No.5

Dry film lubricants are used in Martian probes, artificial roller bearings, and power transmitters for infrared detectors. This study experimentally investigates the effect of a dry film lubricant on the thread, head friction coefficient, and torque-tension relationship in M5 and M6 bolts. Tests were conducted by combining the bolts with a hexagon flange nut and hexagon flange locking nut, and the test apparatus collected real-time data on the tightening torques, bolt axial forces, and corresponding reaction torques. The test data were then used to calculate the thread and head friction coefficients. The test results show the changes in friction coefficients of dry film lubricated bolts during tightening. This work will have significant influence on the reliability and safety of dry film lubricated bolt joint structures in many mechanical structural systems.

철근콘크리트 장주 교각의 시간에 따른 거동

정현수(Jung, Hyun Soo),김수만(Kim, Su Man) 한국콘크리트학회 2005 한국콘크리트학회 학술대회 논문집 Vol.2005 No.11

볼트결합 구조의 부재 강성 연구

정현수(Hyun Su Jung),한혜선(Hye Sun Han),조재욱(Jae Uk Jo),박성우(Sung Woo Park) 한국생산제조학회 2018 한국생산제조학회지 Vol.27 No.3

Bolt joints are applied especially in equipment with severe temperature change during the operating. A change in the initial axial force of the bolt due to the dissimilar material of the members causes the performance deterioration of the equipment. The variation in the bolt axial force is influenced by the member stiffness. Many have studied the method of calculating the member stiffness in a bolt–nut joint. The studies have shown the same result for calculating the member stiffness in bolt joints. Bolts of sizes M4 to M8, and the thickness and material of various members were considered in the case study. Through finite element analysis, the analytical solution of member stiffness is calculated. An equivalent pressure cone model is used to calculate the theoretical solution. The analytical result and theoretical solution were almost equal. Additionally, we proposed a formula to calculate the member stiffness relatively easily in various cases.

프레팅 피로에서 2단계 균열성장과 분지 유한요소해석

정현수(Hyun Su Jung),조성산(Sung-San Cho) 대한기계학회 2015 大韓機械學會論文集A Vol.39 No.11

프레팅 피로균열의 2단계 성장과 분지, 즉 균열이 경사방향으로 성장하다가 방향을 전환하여 수직방향으로 성장하는 과정을 유한요소법으로 해석하였다. 해석에서 A7075-T6의 프레팅 피로실험자료를 이용하였다. 균열성장방향을 결정하는 기준으로 최대 접선응력확대계수, 최대 접선응력확대계수범위, 최대 균열성장속도의 적용 가능성을 검토하였다. 하나의 기준으로는 분지 전후의 균열성장방향을 모사할 수 없고, 분지 전후에 다른 기준을 적용하면 모사가 가능하였다. 또한 분지가 발생하는 균열 길이를 결정하는 방법도 제시하였다. The stage II fretting fatigue crack growth and branching, i.e., the process of fretting fatigue crack growth starting in an inclined direction and then changing to the normal direction, is analyzed using the finite element method. The fretting fatigue experiment data of A7075-T6 are used in the analysis. The applicability of maximum tangential stress intensity factor, maximum tangential stress intensity factor range, and maximum crack growth rate as the crack growth direction criteria is examined. It is revealed that the stage II crack growth before and after the branching cannot be simulated with a single criterion, but can be done when different criteria are applied to the two stages of crack growth. Moreover, a method to determine the crack length at which the branching occurs is proposed.

Plasma Display Panel용 기판 유리용융체의 내화물 침식

김기동,정현수,김효광,Kim, Ki-Dong,Jung, Hyun-Su,Kim, Hyo-Kwang 한국세라믹학회 2007 한국세라믹학회지 Vol.44 No.1

For self-developed alkali-alkaline earth-silicate and commercial glass melts for plasma display panel substrate, the corrosion behavior of fused casting refractory consisting of $Al_2O_3-ZrO_2-SiO_2$ was examined at the temperature corresponding to $10^2\;dPa{\cdot}s$ of melt viscosity by static finger methode. The corroded refractory specimens showed a typical concave shape due to interfacial convection of melts at their flux line. However, the corrosion thickness by commercial glass melts was $6\sim10$ times comparing to that by the self?developed melts. From the view point of the glass composition and the role of alkaline earth in glass network, it was discussed the effect of alkali/alkaline earth diffusion and temperature on the refractory corrosion.

Float 공법을 고려한 Plasma Display Panel용 기판유리 용융체의 특성

김기동,정우만,정현수,권성구,최세영,Kim, Ki-Dong,Jung, Woo-Man,Jung, Hyun-Su,Kwon, Sung-Ku,Choi, Se-Young 한국세라믹학회 2006 한국세라믹학회지 Vol.43 No.7

In order to examine the working condition of melts in tin bath of float process it was investigated Sn diffusion behavior and solidification rate of melts for alkali-alkaline earth-silica PDP substrate glasses such as commercial CaO rich CS-77 glass, commercial $Al_2O_3$ rich PD-200 glass and self developed $SiO_2$ rich T-series (T-2, T-4, T-6) glasses. In the case of Sn depth and concentration created in glass surface by ion exchange between Sn and alkali, T-series showed lower value than CS-77, especially T-2 is more excellent than PD-200. The solidification rate of melts expressed by cooling time between $log{\eta}=4\;and\;7.6dPa{\cdot}s$ was low for T-series comparing with CS-77 and PD-200. Therefore, it was concluded that T-series is desirable considering forming condition in the tin bath of the float process.

대체우유 산업 현황 및 전망

권혁철(Hyuk Cheol Kwon),정현수(Hyun Su Jung),한성구(Sung Gu Han) 한국축산식품학회 2023 축산식품과학과 산업 Vol.12 No.1