• 한국진공학회지
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• 제5권1호
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• pp.33-38
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• 1996

The induced linewidth, frequency shift and absorption spectrum for a molecular dipole in the vicinity of a phase -conjugate mirror have been investgated within a classical phenomenological model, with particularreference to the technique of optical phase conjugation by a surface. While the shifts and the widths show similar characteristics as those obtained recently by Bochove who considered the problem within the context of four-wave mixing, the results obtained in the present model can be defined uniquely with the possibility of an infinite lifetime for the excited admolecule . Furthermore, the absorption lineshape obtained here some interesting features which depend on both the magnitude and the phase of the complex reflectivity of the mirror.

• KIEAE Journal
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• 제17권1호
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• pp.49-54
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• 2017

Purpose: Temperature in urban areas increase much more than suburban areas and it is called urban heat island (UHI) phenomenon. There are several solutions to control UHI phenomenon such as green roof system, water space construction, and cool roof system. However, application of green roof system and cool roof system to some of the buildings which compose the city has a critical limit. Therefore, in order to diminish the temperature rising and UHI phenomenon due to climate change of the city, it needs to approach from the viewpoint of site or city, rather than the viewpoint of individual buildings. This study is aims at analyzing UHI phenomenon by characteristics of surface materials and suggesting the solutions to reduce UHI phenomenon by types of complex. Method: Literature reviews were conducted to analyze the cause, mitigating plan, and recent trends of UHI phenomenon. For the simulation analysis, the type of complex was classified 3 representative complex. Based on measured reflectivity, simulation about UHI phenomenon was conducted by setting 4 strategies; albedo of roof, road pavement, green roof system, and vegetating around buildings. Result: As the results of simulating the UHI reduction factor by types of complex, it showed that the effect of temperature reduction on the building roof layer is more effective than adjusting the reflectivity of buildings such as green roof system, planting near the buildings in both the detached house complex, apartment complex, and commercial complex.

• 대한기계학회논문집A
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• 제21권5호
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• pp.835-841
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• 1997

Microscopic examination of the morphology of wear debris is an accepted method for machine condition and fault diagnosis. However wear particle analysis has not been widely accepted in industry because it is dependent on expert interpretation of particle morphology and subjective assessment criteria. This paper was undertaken to analyze the morphology of wear debris for machine condition diagnosis of the lubricated moving surfaces by image processing and analysis. The lubricating wear test was performed under different sliding conditions using a wear test device made in our laboratory and wear testing specimen of the pin-on-disk-type was rubbed in paraffine series base oil. In order to describe characteristics of debris of various shape and size, four shape parameters (50% volumetric diameter, aspect, roundness and reflectivity) have been developed and outlined in the paper. A system using such techniques promises to obviate the need for subjective, human interpretation of particle morphology in machine condition monitoring, thus to overcome many of the difficulties in current methods and to facilitate wider use of wear particle analysis in machine condition monitoring.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2007년도 공동학술대회 논문집
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• pp.157-162
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• 2007

Geophysical survey has been conducted on the continental margin off the South Shetland Islands aboard R/V Onnuri of KORDI in 1992/1993. About 800-line km of 96-channel reflection data have been acquired. On the seismic section, BSR with strong reflectivity and negative polarity has been found at 700 ms below the sea bottom. BSR is considered as the base of gas hydrates and AVO analysis was performed to study physical properties along BSR. True amplitude recovery and surface consistence amplitude were applied to seismic data and angle gathers were obtained. AVO gradient and AVO intercept are calculated on every CDP gather. Section of AVO intercept show strong reflectivity and negative polarity on BSRs and stronger continuity of BSR than stacked section. Cross plot of intercept-gradient indicates that the lower layer below BSR is filled with free gas.

• Advances in nano research
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• 제13권5호
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• pp.475-485
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• 2022

Crystalline silicon photovoltaic cells have advantages of zero pollution, large scale and high reliability. A major challenge is that sunlight wavelength with photon energy lower than semiconductor band gap is converted into heat and increase its temperature and reduce its conversion efficiency. Traditional cooling PV method is using water flowing below the modules to cool down PV temperature. In this paper, the idea is proposed to reduce the temperature of the module and improve the energy conversion efficiency of the module through the modulation of the solar spectrum. A spectrally selective nanofilm reflector located directly on the surface of PV is designed, which can reflect sunlight wavelength with low photon energy, and even enhance absorption of sunlight wavelength with high photon energy. The results indicate that nanofilm reflector can reduce spectral reflectivity integral from 9.0% to 6.93% in 400~1100 nm wavelength range, and improve spectral reflectivity integral from 23.1% to 78.34% in long wavelength range. The nanofilm reflector can reduce temperature of PV by 4.51℃ and relatively improved energy conversion efficiency of PV by 1.25% when solar irradiance is 1000 W/m². Furthermore, the nanofilm reflector is insensitive in sunlight's angle and polarization state, and be suitable for high irradiance environment.

• 한국광학회지
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• 제10권3호
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• pp.201-207
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• 1999

단일모드 광섬유와 결합기를 이용하여 간결한 구조의 광섬유 공초점 간섭 현미경을 구성하였으며, 위상 변위법을 응용한 표면 검색 방법을 제안하여 통신용의 반도체 레이저와 같이 비교적 긴 파장의 광원과, 낮은 NA의 대물렌즈를 사용하더라도 정밀한 시료 표면 검색이 가능함을 보였다. 이때 시료 표면의 높낮이는 시료로부터 반사된 빛의 위상으로부터 결정되며, 종래의 공초점 현미경에 비하여 주사시간을 크게 단축할 수 있었다. 끝으로 종래의 방법에 비해 제안된 방법은 시료의 반사율 변화에 덜 민감함을 확인할 수 있었다.

• 한국광학회지
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• 제13권3호
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• pp.209-214
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• 2002

기판의 표면거칠기가 반사경의 산란에 미치는 영향을 조사하였다. 기판의 표면거칠기가 다른 다섯 종류의 기판에 이온빔 스퍼터링 방법과 전자총 증착 방법으로 각각 반사율이 1에 가까운 고반사율 박막을 증착하고 산란을 TIS 방법으로 측정하였다. 기판의 표면거칠기가 2$\AA$ 이상인 경우의 기판의 산란에 대한 반사경 산란 비율은 표면거칠기가 2$\AA$ 미만인 경우의 산란 비율에 비하여 급격한 증가를 나타냄을 알 수 있었으며, 기판의 표면거칠기가 낮은 경우 반사경의 산란은 기판의 표면거칠기보다 반사경을 구성하는 박막의 미세구조에 의존하는 것으로 판단되었다. 한편 반사경 중에서 가장 작은 산란은 2.1 ppm이었고, 이것은 표면거칠기 0.23$\AA$인 기판에 이온빔 스퍼터링 방법으로 제작되었다.

• 한국표면공학회지
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• 제29권5호
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• pp.399-406
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• 1996

The orientational cross-over phenomena in an RF sputtering growth of TiN films were studied in an in-situ, real-time synchrotron x-ray scattering experiment. For the films grown with pure Ar sputtering gas, the cross-over from the more strained (002)-oriented grains to the less strained (111)-oriented grains occurred as the film thickness was increased. As the sputtering power was increased, the cross-over thickness, at which the growth orientation changes from the <002> to the <111> direction, was decreased. The addition of $N_2$ besides Ar as sputtering gas suppressed the cross-over, and consequently resulted in the (002) preferred orientation without exhibiting the cross-over. We attribute the observed cross-over phenomena to the competition between the surface and the strain energy. The x-ray powder diffraction, the x-ray reflectivity, and the ex-situ AFM surface topology study consistently suggest that the microscopic growth front was in fact always the (002) planes. In the initial stage of growth, the (002) planes were aligned to the substrate surface to minimize the surface energy. At later stages, however, the (002) growth front tilted away from the surface by about $60^{\circ}$ to relax the strain, which caused the cross-over of the preferred growth direction to the <111> direction.

• 지구물리
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• 제9권4호
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• pp.417-426
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• 2006

1993년 남극 하계 기간 동안 남쉐틀랜드 대륙주변부에서 한국해양연구원의 종합연구선 온누리호를 이용하여 탄성파 탐사를 실시하였으며 약 800 km의 탄성파자료를 획득하였다. 탄성파 자료에서 음의 반사계수를 보이며 상대적으로 강한 진폭을 갖는 BSR이 해저면 700 ms에서 발견되었으며 이는 가스수화물의 기저면으로 간주된다. BSR 경계면에서의 물성을 밝히기 위하여 AVO 분석을 수행하였다. 탄성파 자료에 대하여 실진폭 회수, surface consistence amplitude 보정, 입사각 변환 등을 수행하고, 각각의 CDP 자료에 대하여 AVO 절편 및 AVO 기울기를 구하였다. AVO 절편의 단면도는 BSR 경계면에서 극성이 음이고 강한 반사도를 보이며 중합단면도보다 BSR 경계면의 연속성이 뚜렷하였다. AVO 분석자료를 P-G 도면으로 표시한 결과, BSR이 뚜렷한 곳의 하부에는 가스로 채워졌음을 시사한다.

• 한국진공학회지
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• 제16권2호
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• pp.99-104
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• 2007

[ $Febry-P{\acute{e}}rot$ ] 프린지 패턴 (fringe pattern)과 광발광성 (photoluminescence, PL)의 광학적 성질을 동시에 가지고 있는 다공성 실리콘을 이용하여 가스센서를 개발하였다. 다공성 실리콘 샘플은 p-type 실리콘 웨이퍼 (boron-doped, <100> orientation, resistivity $1{\sim}10{\Omega}$)를 이용하여 전기화학적 식각을 통하여 만들어 졌다. 다공성 실리콘 샘플들은 열적 산화 방법과 hydrosilylation 방법을 통하여 그 표면이 수소로 종결된 다공성 실리콘 (Si-H)과 산화된 다공성 실리콘(Si-OH), 두 가지 각각 다른 표면 성질을 갖는 다공성 실리콘을 제작 하였다. 준비된 두 가지 다른 다공성 실리콘 칩들은 메탄올, 아세톤, 헥산, 그리고 톨루엔의 증기에 노출 시켰을 때 Febry-P rot 프린지 패턴의 변화나 PL의 변화를 관측하여 다공성 실리콘을 이용한 VOCs (volatile organic compounds) 센서로서의 응용에 대하여 연구하였다. $Febry-P{\acute{e}}rot$ 프린지 패턴은 유기 물질의 증기압이 클수록 단파장으로 이동하는 폭이 컸고, 광 발광성은 극성도가 큰 물질일수록 소강현상이 크게 일어나는 것을 알 수 있었다.