• 한국산업보건학회지
• /
• 제1권2호
• /
• pp.144-153
• /
• 1991

This study was conducted to evaluate worker exposure to airborne asbestos fibers by industry, and to evaluate polarized-light microscopy for determining airborne asbestos fibers. A total of 11 plants including asbestos textile, brake-lining manufacturing, slate manufacturing, and automobile maintenance shops were investigated. Rsults of the study are summarized as follows. 1. Worker exposure levels to airborne asbestos fibers were the highest in asbestos textile industry, followed by brake-lining manufacturing, slate manufacturing, and automobile maintenance shops, in order. In asbestos textile industry, large variation of asbestos levels was found by plants. The worst plant indicated airborne fiber concentrations in excess of 10 fibers/cc, however, the best plant showed concentrations within 0.50 fibers/cc. 2. Characterization of airborne fibers by industry indicated that fibers from asbestos textile industry were the longest with the largest aspect ratio. Fibers from automobile maintenance shops were the shortest with the smallest aspect ratio. Based on characteristics of fibers and the highest levels of concentrations, it is concluded that workers in the asbestos textile industry are exposed to the highest risk of producing asbestosis, lung cancer, and mesothelioma. 3. Result s obtained using polarized-light microscopy were $43.7{\pm}12.3%$ of the results obtained using phase contrast microscopy. This may be resulted from the worse resolution of polarized-light microscopy than that of phase contrast microscopy. Based on the results, it is recommended that polarized-light microscopy be used for mainly bulk sample analyses and further study be performed to improve the method for determining airborne samples. However, polarized-light microscopy can be used for determining thick fibers.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2006년도 6th International Meeting on Information Display
• /
• pp.421-421
• /
• 2006

The light and energy-efficiency of classical liquid crystal displays is notoriously poor due to the use of absorption-based linear polarisers and colour filters. For instance, the light efficiency of PVAL polarisers is typically between 40 and 45 % and the colour filters have a typical efficiency below 35 % which results in a total light and energy-efficiency of the display below 10 %. In the past, a variety of polarizers were developed with an enhanced efficiency in generating linearly polarized light. Typically, these polarizers are based on the polarisationselective reflection, scattering or refraction of light i.e. one polarisation direction of light is directly transmitted to the LCD/viewer and the other polarization direction of light is depolarised and recycled which results in a typical efficiency for generating linearly polarized light of 70-85 %. Also, special colour filters have been proposed based on chiral-nematic reactive mesogens which increase the efficiency of generating colour. Despite the enormous progress in this field, a need persists for improved methods for generating polarized light and colour based on low cost optical components with a high efficiency. Here, the use of holographic phase gratings is reported for the generation of polarized light and colour. The phase grating are recorded in a photopolymer which is coated onto a backor frontlight for LCDs. Typically the recording is performed in the transmisson mode or in the waveguiding mode and slanted phase gratings are generated with their refractive index modulation at an angle between 20o and 45o with the normal of the substrate. It is shown that phase gratings with a high refractive index modulation and a high efficiency can be generated by a proper selection of the photopolymer and illumination conditions. These phase gratings coupleout linearly polarized light with a high contrast (> 100) and the light is directed directly to the LCD/viewer without the need for redirection foils. Dependent on the type of phase grating, the different colours are coupled-out at a slightly different angle which potentially increases the efficiency of classical colour filters. Moreover, the phase gratings are completely transparent in direct view which opens the possibility to use them in frontlights for LCDs. Holographic polarization gratings posses a periodic pattern in the polarization state of light (and not in the intensity of light). A periodic pattern in the polarization direction of linearly polarized light is obtained upon interference of two circularly polarized laser beams. In the second part of the lecture, it is shown that these periodic polarization patterns can be recorded in a linear photo-polymerizable polymer (LPP) and that such an alignment layer induces a period rotation in the director of (reactive and non-reactive) liquid crystals. By a proper design, optical components can be produced with only first order diffraction and with a very high efficiency (>0.98). It is shown that these diffraction gratings are potentially useful in projection displays with a high brightness and energy efficiency

• 한국광학회지
• /
• 제23권1호
• /
• pp.42-51
• /
• 2012

본 논문에서는 패브리 페롯 레이저 다이오드(FP-LD : Fabry-Perot LD)에서 활성층 구조에 따른 주입 잠금 특성을 비교하였다. 편광 및 무편광 다중양자우물 구조와 무편광 벌크 구조의 이득 스펙트럼 및 주입 캐리어 밀도에 따른 최대 이득 특성을 TE, TM 편광에 대하여 계산하였다. 계산된 이득 파라미터를 시영역 대신호 모델에 적용하여 FP-LD의 주입 잠금 특성을 확인한 결과, 무편광 FP-LD가 편광 FP-LD 에 비하여 RIN(Relative Intensity Noise) 특성 면에서 약 3 dB 정도 우수하고, 2.5 Gbps 변조시에 아이 특성이 훨씬 우수함을 알 수 있다.

• 한국전자파학회논문지
• /
• 제14권2호
• /
• pp.133-138
• /
• 2003

본 논문에서는 비가시거리(NLOS) 전파환경에서 원형편파를 송신하고 수직, 수평편파 안테나로 수신하는 원형편파 다이버시티(CV-CH)방식에 대하여 이론적 모델을 제시하고 이의 우수성을 확인하였다. 원형편파 다이버 시티에 대한 간단한 이론적 모델을 통하여 XPD에 대한 상관계수 평가식을 유도하였으며, 비가시거리 전파환경에서 원형편파다이버시티 경우 직선편파다이버시티(VV-VH) 경우보다 교차편파분리도(XPD)가 약 6~7 dB 정도 낮게 됨을 알 수 있었다. 그 결과 원형편파 다이버시티 경우의 상관계수는 기존의 직선 편파다이버시티보다 더 낮은 상관계수 값을 나타내는 이론적 모델을 제시하였고 측정된 결과로부터 이의 성능을 확인하였다.

• 한국자기공명학회논문지
• /
• 제7권1호
• /
• pp.62-67
• /
• 2003

MRI of laser-polarized $^{129}$ Xe under continuous flow conditions has recently been used for imaging of porous materials, however, any attempts at using a continuously circulating flow of laser-polarized $^3$He have not been made until now, presumably due to its extremely long spin exchange time (5-10 hrs). Since the inherent NMR sensitivity of $^3$He is 80 times greater than that of $^{129}$ Xe when considering the natural abundance, $^3$He can be expected to be a better nucleus for imaging than $^{129}$ Xe even under continuous flow conditions. In this report, the first MRI with continuously flowing laser-polarized $^3$He is shown for a phantom of Teflon tubing, demonstrating the feasibility of $^3$He imaging under continuous flow.

• 천문학회보
• /
• 제41권2호
• /
• pp.33.2-34
• /
• 2016

The unification model of active galactic nuclei invokes the presence of a thick molecular torus that hides the broad emission line region from a line of sight toward observers with low latitude. It is expected that the illuminated side of the molecular torus may be photodissociated by strong far UV radiation from the central AGN, forming an H I region with a high neutral column density. We propose that the Rayleigh scattering optical depth of this HI region can be significant for most broad $Ly{\alpha}$ line photons with the Doppler factor not exceeding 104 km s-1. Rayleigh scattered $Ly{\alpha}$ photons can be characterized by strong linear polarization depending on their scattering optical depth. We performed Monte Carlo simulations of polarized radiative transfer of $Ly{\alpha}$ adopting simple scattering geometries relevant to the unification model of AGN. We find that for a low torus the Rayleigh scattered $Ly{\alpha}$ is polarized in the direction parallel to the symmetry axis with the polarization degree dependent on wavelength. In the case of a high torus, the core part of $Ly{\alpha}$ is polarized in the direction perpendicular to the symmetry axis whereas the wing part is parallelly polarized. We conclude that careful spectropolarimetry around $Ly{\alpha}$ can be useful in testing the AGN unification model.

• 한국정보통신학회논문지
• /
• 제7권5호
• /
• pp.872-878
• /
• 2003

본 논문에서는 3D-Ray Tracing 기법을 이용한 옥내 무선통신용 편파발생 시뮬레이터를 개발하고, 실내 무선전파환경에서 실제 측정한 데이터와의 비교를 통하여 검증하였다. 개발된 시뮬레이터를 이용하여 Line-Of-Sight(LOS)와 Non-Line-Of-Sight(NLOS) 무선전파 환경에서 수직, 수평, 원편파에 대한 채널특성과 편파 다이버시티 수신특성을 해석하였다. 그 결과 원편파의 경우 기수회 반사파를 억제 수신하는 특성 때문에 수직 및 수평편파의 경우와 비교하여 다중경로 페이딩이 현저하게 경감됨을 알 수 있었다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2002년도 춘계학술대회 논문집 디스플레이 광소자 분야
• /
• pp.81-84
• /
• 2002

The chalcogenide glasses of thin films have the superior property of photoinduced anisotrophy(PA). In this study, we observed the linear dichroism(D) using the irradiation with polarized He-Ne laser light, in the $Ag/As_{10}Ge_{10}Se_{15}S_{35}$ multi-layer. Mutilayer structures formed by alternating metal(Ag) and chalcogenide($As_{10}Ge_{10}Se_{15}S_{35}$). The Ag polarized photodoping result in reducing time of saturation anisotrophy and increasing sensitivity of linearly anisotrophy intensity, up to maximum 220%. In the thin films of chalcogenide, the Ag polarized photodoping will be show a capability of new method that suggested more improvement of photoinduced anisotrophy property.

• 한국지구물리탐사학회:학술대회논문집
• /
• 한국지구물리탐사학회 2006년도 공동학술대회 논문집
• /
• pp.35-38
• /
• 2006

한반도 심부 지전기 구조 연구를 목적으로 실시된 MT 탐사자료의 분극 특성을 분석하였다. 대기권에서 발생하는 1Hz 이상의 전자기파들은 대부분 분극 방향이 불규칙 하지만 8Hz 부근의 슈만 공명은 $N20^{\circ}E$ - NS 방향으로 우세한 특성을 가진다. 반면, 0.1Hz 이하의 전자기파는 남북 방향으로 강하게 분극되는 특성을 나타내고 있다. 이는 자기권의 Alfv.n 파동에 의해 발생하는 지자기장 맥동이 남북방향으로 우세하게 나타나기 때문이다. 남북 방향의 강한 분극 현상은 XY 임피던스(X는 북쪽)의 추정을 불량하게하는 원인이다.

• 한국전자파학회:학술대회논문집
• /
• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
• /
• pp.478-483
• /
• 2003

In this paper, in order to fabricate the circularly polarized diversity system which will mitigate multipath fading, 5.8GHz band microstrip array antenna were designed and fabricated. These antenna were designed using Ensemble 6.0 program and the fabricated antenna were vertical and horizontal polarized antenna, left-handed circularly polarized antenna, and right-handed circularly polarized antenna. The designed antenna parameters included S11 and impedance characteristics of fabricated antenna were measured using Network Analyzer(8753ES). From the measurement results, the S11 for each polarization antenna at resonance frequency of 5.8GHz band was showed -38dB, -44dB, and -50dB respectively and it was similar to the simulation result, and also the impedance can be matched at $50{\Omega}$. In order to compare polarization characteristics, broadband measurement was also conducted in this paper.