광시계

유대혁,이상경,박창용,이원규,Yu, Dae-Hyeok,Lee, Sang-Gyeong,Park, Chang-Yong,Lee, Won-Gyu 한국광학회 2014 광학과 기술 Vol.18 No.1

An Yb Optical Lattice Clock: Current Status at KRISS

유대혁,박창용,이원규,이상경,박상언,문종철,이상범,권택용 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.4

The current status of an Yb optical lattice clock at the Korea Research Institute of Standards and Science (KRISS) is reported. The systematic uncertainty of the Yb clock in the first accuracy evaluation was 1.5 × 10−14 [Park et al., Metrologia 50, 119 (2013)]. The uncertainty was dominated by the large uncertainties in the lattice ac Stark shift and the collisional shift, which were mainly limited by the large linewidth and jitter of the clock laser. Recently, a highly stable clock laser at 578 nm was developed with a short-term linewidth of 3.5 Hz and a frequency jitter of about 25Hz at 1 s and 10 s measurement times, respectively. The long-term frequency drift showed only a linear dependence on time, confirming that the temperature of the super-cavity was maintained a zero coefficient of thermal expansion. The frequency of the lattice laser at 759 nm was phase locked to the optical frequency comb and could be stabilized at the “absolute” frequency of the “magic wavelength”, to within a 1-MHz uncertainty. This improvement greatly reduced the fractional uncertainty due to the lattice ac Stark shift down to 2 × 10−16. The systematic uncertainty of the clock is currently 5.3 × 10−15 and is dominated by the collisional frequency shift.

표면 제2고조파 발생을 이용한 색소 Rd6G박막층의 손상 분석

유대혁,고춘수,임용식,이재형,장준성 한국광학회 1994 한국광학회지 Vol.5 No.2

The damage of a thin film of Rd6G dye was probed by Surface Second-Harmonic Generation(SSHG) method. A portion of the Rd6G thin film on glass substrate was damaged by 532 nm laser beam, and the damage was probed by detecting intensity variation of SSHG. The result was confirmed through direct observation with optical microscope.oscope. 색소 Rd6G박막층에서의 표면손상을 제2고조파 발생법을 응용하여 분석하였다. 유리기판 위에 스핀코팅 방법으로 Rd6G박막을 만들고 Rd6G의 강한 흡수선 근방의 Q-switched Nd:YAG 레이저의 제2고조파(532nm)를 입사시켜 손상영역을 만들었다. 여기에 기저빔 $(1.06\mu\textrm{m})$을 입사시켰을 때 손상부분에서 표면 제2고조파 신호의 세기가 감소함을 이용하여 손상부분의 모양과 범위를 측정하였다. 이 결과는 광학현미경으로 직접 관찰한 결과와 일치하였다.

픽셀이미지를 활용한 뷰티 일러스트레이션 적용에 관한 탐색적 연구

유대혁(Dae-Hyuk Yoo),윤천성(Chun-Sung Youn) 한국뷰티산업학회 2010 뷰티산업연구 Vol.4 No.2

최근 뷰티산업이 예술영역으로 확대되면서 멀티미디어의 기능이 메이크업, 바디아트 등 여러 분야에서 활용될 수 있는 방안이 모색되고 있다. 산업현장에서의 광고물 제작을 비롯해서 교육현장에서는 교육용 프로그램 개발에도 사용되고 있으며 피부나 두피관리실에서는 고객 상담에 따라 직접적인 피부나 모발 상태를 컴퓨터를 활용한 그래픽영상으로 보여준다. 이렇듯 컴퓨터를 활용한 여러 프로그램 중 픽셀이미지로써 이미지를 구현하는 대표적인 그래픽 소프트웨어는 미국 어도비사가 개발한 포토샵과 코렐사의 페인터가 있다. 두프로그램 모두 컴퓨터로 입력된 화상에 대하여 다양한 편집과 수정을 할 수 있고 나아가직접 회화작품에 버금가는 이미지를 창작할 수 있는 프로그램이다. 그래픽 아티스트가 아무리 프로그램을 능숙하게 사용한다고 하여도 포토샵을 사용하여 미용현장에서 전문적인 메이크업 아티스트의 메이크업 기술을 제대로 표현하기에는 한계가 있을 것이다. 미용인들의 창작능력과 감성의 표현이 배제된다는 뜻이다. 아트 메이크업은 인체에 표현한다는 점에서 사전 구상이 정확하지 않으면 장시간의 작업이 될 수 있다. 예컨대 물감은 굳고 모델은 힘들어지는 다양한 문제점이 발생하게 된다는 것이다. 그러나 두 프로그램을 활용하여 작업을 하면 이러한 단점들을 해소할 수 있을뿐만 아니라 아이디어를 구상하여 여러 가지 표현으로 시도해볼 수 있어서 사전 계획단계에 아이디어 스케치로서의 가치를 누릴 수 있다. 그럼에도 불구하고 미용 분야에서 컴퓨터 프로그램을 활용한 작업이 많이 소개되어 있지 않는 실정이어서 이에 대한 연구 및 작품 활동이 필요하다고 본다. 직접적으로 정확한 이미지를 빠르게 시각화 시킬 수 있다는 점에서 이 두 가지 형태의 프로그램은 미용분야에서 중요한 역할을 수행해낼 수 있을 것으로 기대한다. In recent years, large hair salons are managed through the help of internet. As the beauty industry expanded into the field of art, measures are being searched so that these multimedia functions can be directly applied in makeup, body art and various other fields. These functions are being used in creating advertisements in the industrial scene and in developing educational programs in the educational scene. Places dealing with skincare or scalp care show their customers their hair or skin conditions through graphic images. Although talented graphic artists use the programs with great competence, there are limits for them to convey through Photoshop the skills that are used by professional makeup artists in the hair salons. This means that the beautician’s expression and creativeness are excluded. Art makeup which is expressed on the human body can take a prolonged period of time unless it is perfectly planned beforehand. For example, the paint can dry or the model receiving the makeup can become fatigued. However, if the two programs are used, they can overcome such problems. Moreover, ideas could be expressed in various ways thus can act as a valuable part in the planning stage. It is expected that these two programs can act as vital pieces in the field of beauty treatment since it can promptly visualize exact images directly.

드로잉의 기법과 재료를 활용한 뷰티일러스트레이션 제작 연구

유대혁 ( Dae Hyuk Yoo ),윤천성 ( Chun Sung Youn ) 한국미용학회 2013 한국미용학회지 Vol.19 No.6

Beauty art and art have different meanings, but they are not quite distinct in that they pursue beauty from the viewpoint of art category. Likewise, to days concept of art is granted to various areas of beauty art, so many art majors and artists, as a part of contributing to the progress of industrial advancement, have converted to beauty art industry and conducted various research activities. Drawing as the mostbasic and vital factor in art has been recognized as another independent art genre in a modern society. With accelerated industrialization, cultural industry makes a progress, so drawing has been used as a tool for art as well as in many industries including art. At the beauty art scene, it has been used for pre-work in the concept of beauty illustration. But the beauty illustration used at the beauty art scene, has alot of limites unlike the reputation. To get over hteses problems, more creative and new attempt must me made. This study presented a methodology to facilitate beauty illustration to play a more proper role in beauty bart scene through various artistic views and grafting to beauty art scene.

건축가 이훈우에 대한 연구

김현경,유대혁,황두진 한국건축역사학회 2020 건축역사연구 Vol.29 No.3

This research focuses on the life and works of architect Yi Hunwoo, who was active in early 20th century. Yi has been previously mentioned in a few research documents, but not as a main subject of interest. Thanks to digitalized historic databases, the authors of this research were able to access more information about Yi. It was discovered that he was born in Korea in the late 19th century and then attended the Nagoya Higher Technical School in Japan. After repatriation, he participated in a few public projects in Korea as an in-house architect at the Governor-General’s office, then started his own practice and produced his individual projects. He also contributed articles on innovations in residential design to newspapers. Chronologically, his activities as an architect preceeded those of Park Gilyong, who has been conventionally regarded as the first Korean modern architect so far. This research would like to establish Yi Hunwoo as a historic figure whose professional career spanned the earlier stage of the Korean modern architecture, based on the records of his life and professional activities. The authors do not wish to present the architectural analysis nor evaluation of his works, which will be subject to future researches. 본 연구는 20세기 초반에 활동했던 건축가 이훈우의 삶과 작업에 대한 것이다. 몇몇 연구 자료에 그의 이름이 언급되기는 했지만 중요한 관심의 대상은 아니었다. 전산화된 역사 데이터베이스 덕분에 본 연구의 저자들은 그에 대한 보다 많은 정보를 접할 수 있었다. 이훈우는 19세기 말 한반도에서 태어나 일본의 나고야고등공업학교에서 수학했다. 귀국 후 총독부 건축 조직의 일원으로서 몇 개의 공공 프로젝트에 참여했고, 이어 독립하여 개인적인 작업을 시작했다. 주택 개량에 대해 언론에 기고하기도 했다. 시기적으로 보면 그의 이러한 활동은 통상 최초의 한국인 근대 건축가로 간주되어 왔던 박길룡을 앞서는 것이다. 본 연구는 이훈우의 삶과 직업적 활동에 대한 자료를 근거로 그를 한국 근대 건축의 초기 단계에서 활동했던 역사적 인물로 자리매김하고자 한다. 본 연구의 저자들은 그의 작업에 대한 건축적 분석이나 평가를 하려는 의도는 없으며 그것은 향후의 과제로 남긴다.

건축가 이훈우에 대한 추가 연구 및 관련 자료

김현경,유대혁,황두진,Kim, Hyunkyung,Yu, Dylan,Hwang, Doojin 한국건축역사학회 2021 건축역사연구 Vol.30 No.3

In 2020, Yi Hunwoo was discovered as one of the earliest modern architects in Korea. However, his personal life was yet mostly unknown, including the time of his death. The research team ('the team' hereafter) searched for the records of his personal life and professional career. First, his family genealogical chart revealed that he died in 1937. Having located and contacted Yi's direct descendents, the team was able to clarify his family background with the descendants' testimonies. They possess the photographs of him and his family members, including Yi's picture when he was a freshman at the Nagoya Higher Technical School in Japan. The team also identifies his birthplace and the location of his grave as Hadong, Gyeongsangnamdo, Korea. The team visited his project site in Jinju, Gyeonsangnamdo, Korea and obtained more detailed information about the Ilshin Girls' High School, which he designed in 1928. Gyohoan, the congregation records of Cheondogyo, one of the leading religions in Korea during Yi's times, confirmed that he was one of the congregation members. The field research also discovered the house he designed and built in his hometown of Hadong, probably the only surviving architectural project by him. This paper is to report the result of the research on Yi's life and career with the aim of providing materials for further studies in identifying and positioning him more properly in the early 20th century Korean architectural scene.

9.2 GHz 주파수 차이로 위상잠금된 두 외부 공진기 다이오드 레이저의 제작 및 특성 조사

권택용,신은주,유대혁,이호성,인민교,조혁,박상언,Kwon, Taek-Yong,Shin, Eun-Ju,Yoo, Dae-Hyuk,Lee, Ho-Sung,In, Min-Kyo,Cho, Hyuk,Park, Sang-Eon 한국광학회 2002 한국광학회지 Vol.13 No.6

9.2GHz 주파수 차이로 위상잠금(phase-locking)된 레이저 시스템을 제작하여 그 특성을 조사하였다. 외부공진기 다이오드 레이저 2대를 제작하고, 두 레이저가 9.2GHz 주파수 차이를갖도록 디지털 회로를 이용하여 위상잠금 하였다. 위상잠금된 두 레이저의 맥놀이 신호의 스펙트럼을 측정하였으며, 이로부터 신호의 반송률이 약 93%임을 알 수 있었다. 위상잠금된 두 레이서의 상대 선폭은 2Hz 이하였다. 위상잠금된 두 레이저의 맥놀이 신호의 위상잡음을 측정하였으며, 측정된 위상잡음 스펙트럼으로부터 적분시간 1s 이하에서 상대적인 주파수 안정도를 계산하였다. 적분시간 1s 이상에서는 주파수 측정방법으로 상대적인 주파수 안정도를 측정하였는데, 적분시간 20s 에서 알란편차는 $2.7{\times}10^{-19}$였다. We have constructed two extended-cavity diode lasers which are phase-locked with a 9.2 GHz frequency offset. We adopted a digital servo circuit for the phase-locking. The relative linewidth of the phase-locked lasers was less than 2 Hz. Using the measured beat spectrum, we found the carrier concentration to be about 93 %. We measured phase noise and relative frequency stability of the lasers. The Allan deviation at the gate time of 20 s was $2.7{\times}10^{-19}$.

유두재건을 위한 C-V피판 변법: C-U 피판법

윤인식,탁관철,유대혁 대한미용성형외과학회 2008 Archives of Aesthetic Plastic Surgery Vol.14 No.1

For ideal breast reconstruction, final nipple reconstruction with good projection, symmetrical position, shape, and texture is very important. Nowadays, C-V flap is popularly used because of its simple procedure and less donor site morbidity. But, it also has problems of maintaining good perpendicular nipple projection. Furthermore, the flap could be injured by ischemia from the overloaded tension, when it contains too much subcutaneous fat. We modified the traditional C-V flap to overcome these drawbacks and obtained satisfactory results. From April 2006 to February 2007, we applied modified C-V flap to 46 patients who underwent NAC(Nipple-Areola Complex) reconstruction for breast reconstruction. First, we modified the flap design. The tip of horizontal V-flap was changed to rectangular shape as U-flap. Secondly, we discarded the subcutaneous fat in U-flap except the base to minimize the tension after flap insetting. Thirdly, following the flap elevation, we performed donor site closure of the C-flap. Thus the donor site of U-flap could be repaired without dog ear. Finally, de-epithelization was done on the base of nipple according to the diameter of new nipple. Then a small triangular flap was made, and insetted between the junction of bilateral U-flap to minimize the contracture and inversion of new nipple. The result were followed up for an average of 8 months. There was no complication such as flap loss or infection in all 46 patients. During the follow-up periods(3-13 months), new nipple maintained symmetry and perpendicular projection to be compared with traditional C-V flap. This modification of C-U flap could overcome some drawback of traditional C-V flap and improved results were obtained.

13 km 광섬유를 통하여 원격지로 전송된 1.4 GHz RF 신호의 위상잡음 제거

이원규,박창용,문종철,유대혁,Lee, Won-Kyu,Park, Chang-Yong,Mun, Jong-Chul,Yu, Dai-Hyuk 한국광학회 2010 한국광학회지 Vol.21 No.3

13 km 광섬유를 통해 1.4 GHz의 기준 주파수를 전송할 때, 광섬유에서 발생하는 위상잡음을 제거하는 시스템을 구성하였다. 전송된 주파수의 안정도 성능은 실험장치의 온도변화폭에 의존하였다. 실험실의 온도변화폭이 $0.3^{\circ}C$ 이내로 유지되는 동안에는 광섬유의 위상잡음을 제거했을 때, 원격지에 전송된 신호가 0.8초의 평균 시간에서 $4.6{\times}10^{-14}$, 1000초의 평균 시간에서 $2.5{\times}10^{-16}$의 상대주파수 전송 안정도를 보여 만족할 만한 결과이었으나, 실험실의 온도가 $3.5^{\circ}C$ 범위로 변할 때에는, 1.2초의 평균 시간에서 $6.8{\times}10^{-14}$, 1000초의 평균 시간에서 $3.0{\times}10^{-15}$의 전송 안정도를 보였다. 이 결과로부터 1000초의 평균시간에서 $10^{-16}$ 수준의 상대주파수 안정도를 얻기 위해서 요구되는 실험장치의 온도 안정도 조건을 제시할 수 있었다. A fiber-phase-noise compensating system was constructed for a 1.4 GHz reference frequency transferred through a 13-km-long fiber spool. The transfer instability was dependent on the temperature variation of the compensating system. With the room temperature variation stabilized within $0.3^{\circ}C$, the transfer instability was $4.6{\times}10^{-14}$ at 0.8 s of average time and $2.5{\times}10^{-16}$ at 1000 s of average time with the fiber phase noise compensated. However, with the room temperature changed by $3.5^{\circ}C$, the transfer instability was $6.8{\times}10^{-14}$ at 1.2 s of average time and $3.0{\times}10^{-15}$ at 1000 s of average time. From this result, the temperature stability condition for the experimental setup could be determined to obtain a transfer instability of $10^{-16}$ at 1000 s of average time.