• Journal of the Korean Society of Radiology
• /
• v.14 no.1
• /
• pp.69-75
• /
• 2020

Multilayer mirrors have widely been used not only in the industry but also in the medical field. X-ray reflectivity was measured by X-ray diffractometer to evaluate the performance of W/C multilayer mirror with 40 layers. Genetic algorithm are used to obtain thickness, density, and interfacial roughness for each of the 40 layers. The existing uniform random selection causes a problem that the solution does not converge or the error increases even if it convergence. To reduce the time to calculate the fitness of the genetic algorithm, the genetic algorithm was written in C/C++ parallel programming. The genetic algorithm showed excellent scalability of linear time increase with increasing number of generation and population. The genetic algorithm was selected with uniform and Gaussian randomness of 1:1 to improve the convergence of solution. The improved genetic algorithm can be applied to characterize each layer of a sample with more than a few tens of layers, such as a multilayer mirror.

• Korean Journal of Optics and Photonics
• /
• v.4 no.4
• /
• pp.420-427
• /
• 1993

Dielectric thin film mirrors are embedded in multimode and single-mode fibers by a fusion splicing technique. The fibers with $45{\circ}$ angled embedded mirrors serve as ultra-compact directional couplers with low excess optical loss of 0.2 dB for multimode and 0.5 dB for single mode at 1.3 ${\mu}m$ and excellent mechanical properties. The reflectance is wavelength dependent and strongly polarization depencient. Far-field scans of the reflected output power measured with a white-light source show a pattern which is almost circularly symmetric with aspect ratio of 1.09 at 5% of the peak power. The splitting ratio in a multimode coupler measured with a diode laser source is much less dependent on input coupling conditions than in conventional fused biconical-taper couplers, indicating that these couplers are less susceptible to modal noise occuring in optical fiber communication systems. Spectral properties of multilayer internal mirrors normal to the fiber axis have been investigated experimentally, and a matrix analysis has been used to explain the results.

• Journal of the Korean Chemical Society
• /
• v.53 no.2
• /
• pp.137-143
• /
• 2009

Liquid chromatographic enantiomer separation of N-tert-butoxycarbonyl (BOC) $\alpha$-amino acids and their ethyl esters was performed on covalently immobilized chiral column (Chiralpak IC) derived from polysaccharide derivative. The solvent versatility of the covalently immobilized Chiralpak IC in enantiomer separation of N-BOC $\alpha$-amino acid ethyl ester derivatives was shown and the chromatographic parameters of their enantioselectivities and resolution factors were greatly influenced by the nature of the mobile phase. Also the effect on the dissolving solvent for these analytes on the enantiomer separation using the same mobile phase and the examples of preparative enantiomer separation on analytical column were shown.

• Journal of KIISE:Computing Practices and Letters
• /
• v.16 no.11
• /
• pp.1131-1135
• /
• 2010

This paper presents a method to capture the posture of the human lower-limbs on the 3D space by using a single camera and a planar mirror. The system estimates the pose of the camera facing the mirror by using four coplanar IR markers attached on the planar mirror. After that, the training space is set up based on the relationship between the mirror and the camera. When a patient steps on the weight board, the system obtains relative position between patients' feet. The markers are attached on the sides of both legs, so that some markers are invisible from the camera due to the self-occlusion. The reflections of the markers on the mirror can partially resolve the above problem with a single camera system. The 3D positions of the markers are estimated by using the geometric information of the camera on the training space. Finally the system estimates and visualizes the posture and motion of the both legs based on the 3D marker positions.

• Korean Journal of Optics and Photonics
• /
• v.17 no.5
• /
• pp.447-454
• /
• 2006

We obtained analytic solutions of boundary conditions to the stable region of Z-fold $Cr^{4+}$ : YAG laser cavity when the conditions are with and without thermal tensing effect. Also we investigated the influence of the thermal tensing effect on the stability of cavity, beam waist, and astigmatic compensation using aberration transformation matrices. The thermal tensing effect almost has no influence on the stable region of the cavity when the crystal is located in the middle of two concave mirrors and when the distances from the concave mirror to the reflecting mirror and the output coupler are the same. The beam waist, however, is affected more in a tangential plane than in a sagittal plane, and so it is difficult to have astigmatic compensation when the thermal tensing effect exists. This result means that the thermal tensing effect should be considered even for the Kerr-lens mode-locking.

• Journal of the Korean GEO-environmental Society
• /
• v.23 no.4
• /
• pp.11-20
• /
• 2022

In order to acquire hydraulic characteristics for unsaturated layers, water retention tests were performed and compared by using the evaporation method, volumetric pressure plate extractor (VPPE) and chilled-mirror dew point method. The evaporation and chilled-mirror method are currently developed experimental technology and measure the water retention curve of unsaturated soils quickly and accurately. In the evaporation and VPPE method, the water retention has been measured and compared until 100kPa matric suction and consequently the result of the evaporation method could be verified. In the chilled-mirror method, the water retention has been measured until high level of matric suction and the overall shape of water retention curves could be obtained. As a result of water retention tests, the representative water retention curves were obtained and the applicability of each test method was discussed. Using both the evaporation and chilled-mirror methods, the soil water retention curve can be acquired reasonably for the whole range of matric suction.

• ICROS
• /
• v.20 no.2
• /
• pp.31-38
• /
• 2014

인간의 행동을 통해 내재된 의도를 인식하고 그 의도에 대응하는 서비스를 제공할 수 있는 능력을 로봇에게 부여하기 위한 연구의 일환으로 모방적 동기화 및 학습에 의한 인간-로봇 상호작용(Human-Robot Interaction, HRI) 시스템의 개발이 주목받고 있다. 하지만 인간이 관찰과 모방을 통해 목적을 가진 행동을 학습하는 과정은 감각 정보를 대응하는 운동 정보로 연계하고 모방 주체와 모방 대상 간의 물리적 상태의 차이를 보정하고 관측된 행동에 내재된 의도 또는 목표를 이해하는 복잡한 메커니즘 단계의 연속이기 때문에 이를 수행하기 위한 기술개발이 필요하다. 본고에서는 실제 인간이 수행하는 모방적 동기화 및 학습에 관여하는 것으로 추정되는 거울뉴런 시스템에 대하여 소개하고 이를 HRI 시스템에 활용하기 위해 개발된 선행 기술 동향을 논하고자 한다. 또한, 본 연구실에서 관련하여 진행해온 관련 연구를 통해 현재 거울 뉴런 시스템의 발전 정도와 향후 활용 방안 및 가능성을 고찰해보도록 한다.

• Korean Journal of Optics and Photonics
• /
• v.11 no.1
• /
• pp.43-46
• /
• 2000

We generated 9-fs pulses from a Kerr-lens mode-locked Ti:sapphire laser only using commercial optical components. Two sets of prisms pair made of fused silica were used to compensate group delay dispersion inside and outside the laser oscillator respectively, and broadband mirrors were used to obtain a broad spectrum. By comparison between reflectance curves of the broadband mirrors and those of previous ones, broadband mirrors which have high reflectance bandwidth of over 180 nm were found to be essential to produce sub-IO-fs pulses. ulses.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.07a
• /
• pp.568-569
• /
• 2005

한빛 자기거울 장치는 고온 플리즈마 물성을 연구하기 위한 장치로서 플러즈마 밀도 형성을 위한 slot 형 안테나 고주파 가열 시스템이 중앙 진공용기에 설치되어 있다. 본 연구에서는 이러한 고주파 전송선로, 임피던스 정합 network. 장치 임피던스를 포함하는 한빛 장치의 고주파 가열 시스템에 대하여 기존에 정립된 고주파 가열 이론[1]을 기반으로 하여 이론적인 해석만으로 구성된 회로모델을 완성하였다. 임피던스 정합 소자 값들은 임피던스 정합 조건으로 결정함으로써 다양한 장치 및 플라즈마 변수들의 함수로 표현하여 그 의존성을 조사하였다.

• Korean Journal of Optics and Photonics
• /
• v.1 no.2
• /
• pp.178-184
• /
• 1990

The fiber laser was fabricated using Nd doped single mode fiber. The fiber was made by MCVD and solution doping method, and the Fabry-Perot resonator was composed with two dichroic mirrors. It was operated at 1.096 um with 15 nm bandwidth. When the reflectivity of the output copuling mirror was 67.5%. the maxiurn output power 1.88 mw and its slope efficiency 1.28%. was obtained.