• International Journal of Aerospace System Engineering
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• 제2권2호
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• pp.79-82
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• 2015

The handicap for investigating the aero-optical effect focuses on the accurate prediction on the index refraction fluctuation or density fluctuation. In recent years, with the development of CFD techniques and optical experimental techniques, the comprehension have developed on the aero-optical transmitting effect in many kinds of complex flow. This study mainly introduces the optical aberration in compressible mixing layer. And then the debates about the mechanism of aero-optical effects and assessment of image blur also present.

• Journal of the Optical Society of Korea
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• 제7권3호
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• pp.145-149
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• 2003

The anisotropy of electron energy distribution in oxygen plasmas produced by a high intensity laser was investigated by using polarization spectroscopy. An ultra-short pulsed laser with a pulse duration of 66.5 fs and a power density of $1 {\times} 10^17/ W/$\textrm{cm}^2$$ was used. At this power density and pulse duration, the plasma was generated predominantly by optical field ionization. The degree of polarization of OVI 1s$^2$2p$^2$p2- 1s$^2$4d$^2$D$^{0}$ (J = 1/2-3/2 and 3/2-5/2) transition line at 129.92 $\AA$ was measured. O VI 1s$^2$2p$^2$P$^2$ -1s$^2$4s$^2$S$^2$ (J = 1/2-1/2 and 3/2-1/2) transition line at 132.26 $\AA$ was used to calibrate the sensitivity of the optical system. The dependencies of the degree of polarization on the initial gas density and on the laser polarization were investigated. When the laser polarization was changed from a linear to a circular polarization, the degree of polarization was decreased. When the initial gas density was increased, the degree of polarization was decreased.

• 한국멀티미디어학회논문지
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• 제12권3호
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• pp.329-334
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• 2009

광 디스크를 재생하려면 광 신호를 아날로그 전기신호로 변환하는 광 픽업을 거치고 난 뒤 신호 간 간섭을 없애기 위해 아날로그적으로 등화를 하고, 등화된 아날로그 신호를 AD 변환하여 디지털적으로 동기화된 데이터와 클록을 추출해야 한다. BD와 같은 고용량의 광 디스크를 저속으로 재생하여 동기화된 데이터와 클록을 추출하는데 었어서 추출 데이터 BER을 최소화하는 알고리즘은 다양하게 개발되어 적용되고 있다. 그러나 고용량의 광 디스크를 고속으로 재생 할 때 저속에서 적용된 알고리즘을 동일한 혼성 데이터 PLL과 PRML 하드웨어 구조에 적용하려면 800MHz 이상의 신호 처리가 이루어져야 한다. 일반적으로 사용되는 0.13-${\mu}m$ CMOS 공정에서 기존 방식의 구조를 가지고 800MHz의 이상의 신호처리를 위해서는 고속으로 동작해야하는 아날로그 코어 등이 필요하고 많은 시간과 노력의 레이아웃이 수반되어야 하는 등의 문제점이 제기된다. 본 논문에서는 고용량 광 디스크의 최고 배속인 BD 8x까지 동작 가능한 데이터 및 클록 추출 회로로서 병렬 데이터 PLL 및 PRML 구조를 제안하였다. 제안한 구조를 가지고 실험한 결과 BD 8x 에 해당하는 속도에서 오류 없이 동작함을 확인하였다.

• 한국초전도ㆍ저온공학회논문지
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• 제17권4호
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• pp.16-20
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• 2015

We investigated optical properties of an electron-doped copper oxide high temperature superconductor, $Pr_{0.85}LaCe_{0.15}CuO_4$ (PLCCO) single crystal. We obtained the optical conductivity from measured reflectance at various temperatures. We found our data contained c-axis longitudinal optical (LO) phonon modes due to miscut and intrinsic lattice distortion. We applied an extended Drude model to study the correlations between charge carriers in the system. The LO phonons appear as strong sharp peaks in the optical scattering rate. We tried to remove the LO phonon modes by using the energy loss function, which also shows the LO phonons as peaks, and could not remove them completely. We extracted the electron-boson spectral density function using a generalized Allen's formula. We observed that the resulting electron-boson density show similar temperature dependence as hole-doped cuprates.

• 정보저장시스템학회논문집
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• 제1권1호
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• pp.78-83
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• 2005

The Blu-ray disc as a next generation high density optical medium uses an objective lens of high numerical aperture(NA 0.85) and blue laser in order to increase the recording density. The double layer is also useful for doubling the density. The spherical aberration of Blu-ray disc is very sensitive to the thickness of the disk because of high numerical aperture. This paper suggests a method to compensate the spherical aberration caused by the change of disk thickness, by using the Liquid Crystal lens instead of the Liquid Crystal panel. It was possible to develop both the LC panel generating the optical phase difference and LC lens changing the optical power. In this paper, we analyzed the aberration performance and a position sensitivity of the two type LC elements when the samples deviate from the optical axis of the objective lens. The results of applying this analysis show that the LC lenses rather than the LC panels have a significant assembling tolerance. The theoretical characteristics of the two elements are calculated and compared with the measurement data.

• 대한소아치과학회지
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• 제32권4호
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• pp.611-619
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• 2005

본 연구의 목적은 초기 우식 병소에서 광원에 따른 형광효과를 비교하는 것으로 정량 분석형 laser/light 형광법(Quantitative laser/light-induced fluorescence, QLF)을 이용하여 아르곤 레이저광, 할로겐광, 발광다이오드광(LED), 플라즈마광의 형광효과를 비교하였다. 발거된 60개의 치아를 선정한 후, 인공우식용액에 노출되지 않을 부분에 nail varnish를 도포하였고 치아는 24, 48, 72시간 동안 인공우식용액에 보관되었다. 건조 후 QLF영상으로 초기 우식 부위의 광밀도 차이에 의한 탈회정도가 기록되었다. 또한 조영제를 이용하여 동일한 방법으로 실험하였고 다음과 같은 결과를 얻었다 염료를 이용하여 같은 방법으로 실험하여 또 다른 결과를 얻었다. 1. 각 군의 평균 광밀도를 볼 때, 플라즈마광이 세 군 모두에서 다른 광원들 보다 높았다(p<0.05). 2. 세 군 사이에서 평균 광밀도를 비교해 볼 때, 플라즈마광과 할로겐광이 차이를 보였다(p<0.05). 3. 조영제를 사용하였을 경우 평균 광밀도를 비교해 볼 때, 플라즈마광이 세 군 모두에서 다른 광원들보다 높았고 (p<0.05), 발광다이오드광(LED)와 아르곤 레이저광을 제외한 모든 광원이 차이를 보였다(p<0.05). 4. 조영제를 사용하지 않은 경우와 사용한 경우 평균 광밀도를 비교해 볼 때, 사용한 경우에 모든 광원의 평균 광밀도 차이가 컸다.

• Current Optics and Photonics
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• 제3권1호
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• pp.54-65
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• 2019

To develop a biomarker predicting tumor treatment efficacy is helpful to reduce time, medical expenditure, and efforts in oncology therapy. In clinics, microvessel density using immunohistochemistry has been proposed as an indicator that correlates with both tumor size and metastasis of cancer. In the preclinical study, we hypothesized that vascular morphometrics using optical coherence tomography angiography (OCTA) could be potential indicators to estimate the treatment efficacy of breast cancer. To verify this hypothesis, a 13762-MAT-B-III rat breast tumor was grown in a dorsal skinfold window chamber which was applied to a nude mouse, and the change in vascular morphology was longitudinally monitored during tumor growth and metronomic cyclophosphamide treatment. Based on the daily OCTA maximum intensity projection map, multiple vessel parameters (vessel skeleton density, vessel diameter index, fractal dimension, and lacunarity) were compared with the tumor size in no tumor, treated tumor, and untreated tumor cases. Although each case has only one animal, we found that the vessel skeleton density (VSD), vessel diameter index and fractal dimension (FD) tended to be positively correlated with tumor size while lacunarity showed a partially negative correlation. Moreover, we observed that the changes in the VSD and FD are prior to the morphological change of the tumor. This feasibility study would be helpful in evaluating the tumor vascular response to treatment in preclinical settings.

• Journal of the Optical Society of Korea
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• 제15권3호
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• pp.310-317
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• 2011

Perceptibility and acceptability are the most often used threshold units in the field of color science. The former refers to a just perceptible difference and the latter evokes a tolerable color difference. Such thresholds can be very significant to color quality control processes in the printing industry and should be defined in quality measure units. Optical density (OD) and color difference models are usually utilized as color quality measures and have been provided in a considerable number of commercial measuring devices such as spectrophotometers. However, their merits and traits are far less understood in the literature. The present study intends to evaluate performance of those color quality measures including the OD and widely known color difference models, e.g. ${\Delta}E{^*}_{ab}$, ${\Delta}E_{CMC(l:c)}$ and ${\Delta}E{^*}_{00}$. A set of psychophysical assessments were carried out in order to accumulate the perceptibility and acceptability thresholds data, and their central trend was compared with the color quality measure estimates.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.208-213
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• 2003

A note-book PC has become thinner in recent years. And optical disc drives are required to have high memory capacity. Therefore, the actuator of optical disc drives must be thinner and have disc tilt compensation function for high density memory. In this paper, the hybrid type actuator is investigated for 3-axis ultra-slim actuator. A 3-axis ultra-slim actuator is designed by using the modal analysis of the actuator and the electromagnetic analysis of magnetic circuit to achieve dynamic characteristics and magnetic flux density for high sensitivity, respectively. Also, magnetic force between tilt magnet and tilt yoke is investigated to find the influence on the DC sensitivity in the focus and track directions.

• 한국세라믹학회지
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• 제54권2호
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• pp.102-107
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• 2017

The dependence of the IR optical properties of PMMA/$Al_2O_3$ nanocomposite on the alumina content was investigated in the wavelength range of $3500-2800cm^{-1}$. The samples were prepared via emulsion polymerization technique using oleic acid as a coupling agent. Grafting density calculations were carried out by means of elemental analysis CHN to yield the best coupling agent content. FTIR analysis confirmed the existence of a chemical bond between aluminum oxide and oleic acid. The outcomes of XRD analyses showed the presence of cubic gamma aluminum oxide in the nanocomposite, in contrast to the amorphous nature of PMMA. TEM images showed the core-shell morphology of the particles other than pristine PMMA. Optical constants of the nanocomposite were calculated based on FTIR spectra and the Kramers-Kronig equations. The presence of nano alumina modified some of the optical indexes in IR region.