• 한국지구과학회지
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• 제32권7호
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• pp.750-760
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• 2011

본 연구에서는 신뢰성 있는 국가표준 지역기후변화 시나리오 생산을 위해 현재기후에 대한 SNURCM과 WRF의 재현성을 검증하였다. 국립기상연구소에서 생산된 HadGEM2-AO 전구자료를 지역기후모형의 경계조건으로 사용하여 CORDEX 규준 하에 28년(1978-2005)간의 장기적분을 수행하였다. 두 모형은 연평균 지표 온도 분포를 관측과의 공간상관계수가 0.98 이상으로 매우 높은 일치성을 나타내었지만, 모형 영역의 북쪽 경계를 중심으로 한랭 편차를 공통적으로 보였다. 강수의 경우 또한 육지 지역을 대상으로 한 관측과의 공간 상관 계수는 SNURCM이 0.85, WRF가 0.79로 나타나 우수한 모의 결과를 보였다. 두 모형에서 모의된 강수 분포는 적도와 중위도 지역 간에 상반되는 특성을 보였다. SNURCM은 WRF에 비교하여 중위도 동아시아 몬순 강수대의 분포를 적도 지역의 강수대보다 상대적으로 잘 모의하였으나, WRF는 그 반대의 결과를 나타내었다. 여름철(JJA) 보다 봄철(MAM)에 과다 모의되었지만 모의된 강수 분포의 일치성은 봄철에 높게 나타났다. 세부영역 별 분석에서 두 모형은 7월 강수 최대 시점과 양을 비교적 정확히 모의하였고, 특히 내륙 지역 강수량의 모의 정확도가 해양에 영향 받는 지역보다 높았다. 모의결과는 한반도 상의 높은 일평균 지표온도일수와 강한 강수일수를 표현하는데 한계를 보였다.

• Journal of the Optical Society of Korea
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• 제10권1호
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• pp.23-27
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• 2006

We are studying the application of an adaptive optics system to upgrade the beam quality of a laser. The adaptive optics (AO) system consists of a bimorph deformable mirror, a Shack-Hartmann sensor and a control system. In most AO applications, the beam aperture is considered to be circular. However, in some cases such as laser beams from unstable resonators, the beam apertures are annulus or a holed-rectangle. In this paper, we investigate how well a bimorph deformable mirror of ${\Phi}120\;mm$ clear aperture can compensate phase distortions for three different beam configurations; 1) ${\Phi}120\;mm$ circular aperture, 2) ${\Phi}100\;mm$ annulus aperture with a ${\Phi}20\;mm$ hole and 3) $70\;mm{\times}70\;mm$ square aperture with a hole of $30\;mm{\times}30\;mm$. This study concludes that the bimorph mirror, which might be considered as a modal controller, can compensate tilt, defocus, coma and astigmatism, and spherical aberration for all three beams.

• 천문학회보
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• 제37권2호
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• pp.219.2-219.2
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• 2012

We are developing Adaptive Optics (AO) system for 24 inch telescope at Seoul National University Observatory. It consists of the tip-tilt correction system and the residual wavefront error correction system with a deformable mirror and a wavefront sensor. We present the construction and performance measurements of the tip-tilt correction system. The tip-tilt component is the single largest contributor to wavefront error, especially for small telescope. The tip-tilt correction system consists of a quadrant photodiode, a tip-tilt mirror and a feed back loop. The collimated He-Ne laser beam is used for input light source and is artificially disturbed by air turbulence generated by a heat gun. Most of the turbulence is of low frequency less than 20 Hz, but extends to a few hundreds Hz. It is found that the closed loop system using proportional-integral-derivative (PID) control successfully corrects tip-tilt error at a rate as high as 300~400 Hz.

• Journal of the Optical Society of Korea
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• 제4권1호
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• pp.1-6
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• 2000

Adaptive optics(AO) removes or compensates the distortion caused by a turbulent atmosphere or medium. A wavefront sensormeasures the distortion, on which the correction of AO is based. A new idea of pupil plane wavefront sensing, which consists of a relay lens and a pyramidal-shaped prism, was previously proposed. This paper reviews the idea of pupil wavefrontsensing and presents prism, was previously proposed. The simulation shows that pupilwavefront sensing provides full wavefront sensing when the intensity peak of PSF is located within half of the Airy radius from the apex of the sensor. Adding to this, the sensor is shown to have optimum sensor output with a finite bevel size of the pyramidal prism.

• 이베로아메리카
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• 제13권1호
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• pp.211-254
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• 2011

O presente trabalho pretende explorar a relação entre a língua nacional e a construção da idenidade nacional no Brasil, materializando os enunciados da "Casa-grande & Senzala" de Gilberto Freyre e os discursos cruzados entre Freyre e romancistas. Atualmente, o português brasileiro é uma manifestação mais extensa e mais profunda da alma multiforme da nacionalidade brasileira como a língua é um tópico essencial no processo de constituição da nacionalidade, ao lado da geografia, da história e da étnia. Junto com o português brasileiro, como o idioma oficial do Brasil, tradições, ideias nacionais se difundiam por todos os habitantes dessa comunidade imaginária. Ao invés dos temas clássicos(como a mestiçagem e a história da vida privada) de Gilberto Freyre, neste trabalho, discutimos as interpretações que Gilberto Freyre fez pelo prisma do luso-tropicalismo sobre a língua e a identidade nacional no Brasil, considerando o cruzamento da Casa-grande e da Senzala representadas na estrutura das obras dos romancistas brasileiros.

• Journal of the Optical Society of Korea
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• 제19권1호
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• pp.45-54
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• 2015

In this study, a novel parallel wavefront correction system architecture is proposed, and a model-based tabu search (MBTS) algorithm is introduced for this new system to compensate wavefront aberration caused by atmospheric turbulence in a free-space optical (FSO) communication system. The algorithm flowchart is presented, and a simple hypothetical design for the parallel correction system with multiple adaptive optical (AO) subsystems is given. The simulated performance of MBTS for an AO-FSO system is analyzed. The results indicate that the proposed algorithm offers better performance in wavefront aberration compensation, coupling efficiency, and convergence speed than a stochastic parallel gradient descent (SPGD) algorithm.

• Journal of the Optical Society of Korea
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• 제10권2호
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• pp.57-62
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• 2006

Adaptive optics (AO) has been applied in various fields including astronomy, ophthalmology and high power laser systems. An adaptive optics system for a high power laser is not significantly different from other AO systems in the point of configuration except that high energy absorbed by the deformable mirror distorts the deformable mirror surface and so degrades system performance. Currently we are researching a bimorph deformable mirror for beam cleaning of a high power class laser. The bimorph mirror was considered to have 99% reflective coating and 1% absorption. So this paper first presents the temperature profiles and corresponding thermal distortions of the bimorph mirror faceplate when the mirror is under a high power lasing for 10 seconds. The analysis was accomplished by the use of finite difference and finite element computer programs to generate the element arrays, calculate the temperature profiles, and determine the structural deformations. Then this paper proposes an 'embedded wafer' type water-cooling system with derived cooling parameters.

• 한국멀티미디어학회논문지
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• 제25권11호
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• pp.1564-1571
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• 2022

Wireless sensor network(WSN) is being used in various fields such as reconnaissance, echelon scale identification, weather observation, etc. using small sensors in an environment without a network infrastructure environment. In addition, WSN uses limited battery power, so study on routing protocols to extend the lifetime of the network is important. PEGASIS, a hierarchical routing protocol, accounts for the majority of energy-efficient routing protocol studies and is well known as a representative protocol. In this study, based on PEGASIS, we propose a protocol that constructs multiple chains rather than one chain using the AoA of nodes. The proposed protocol has the advantage of reducing the transmission distance of nodes and eliminating unnecessary transmissions, thereby increasing energy efficiency compared to the existing protocols.

• 한국지구과학회지
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• 제35권4호
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• pp.249-258
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• 2014

대기 중 이산화탄소 등의 농도가 지속적으로 증가하고 있음에도 최근 10여 년 동안(2002-현재) 전지구 지표 온도는 거의 답보상태에 머물러 있다. 이처럼 온실기체 강제력에도 불구하고, 지구 온난화 경향이 사라진 듯 보이는 현상을 지구 온난화 멈춤(hiatus)이라 한다. 이 연구는 HadGEM2-AO가 모의한 RCP8.5 시나리오 실험(95년간) 자료를 분석하여, 온난화 멈춤 시기의 특징을 분석하였다. 온난화 멈춤 기간을 나타내는 시계열은 동서 평균한 연직 해수 온도 분포를 EOF 분석하여 구한 두 번째 PC (PC2)로 정의하였다. PC2를 이용하여 온난화 멈춤과 엔소와의 관련성, 기후시스템의 변화 등을 분석하였다. 라니냐 지수(NINO3지수에 -1을 곱하여 정의)가 PC2를 약 11개월 앞서는 것으로 보아 라니냐 발생이 온난화 멈춤을 유도할 수 있음을 발견하였다. 또한 기후시스템의 냉각은 해수 표층의 열이 해양 내부로 침강으로 나타남을 보였다. 이는 해양의 열흡수에 의해 전지구 온도 상승률이 약화되었음을 의미한다. 온난화 멈춤 시기에 북태평양과 북반구 극지는 양의 온도 편차가 나타났으며, 열대 해양에서는 무역풍이 강화되었다.

• 동아시아식생활학회지
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• 제24권3호
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• pp.325-334
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• 2014

The effects of aloe on liver function and lipid metabolic disorders induced by alcohol consumption were studied in rats using aloe power (0.25%, 0.5%, 1%) and 10% ethanol. 35 Sprague-Dawley (male, 4 weeks old) rats were divided into five groups and fed experimental diets for six weeks. Body weights of rats tended to be lower in all alcohol supplemented groups than in the control. Food intakes and dry feces per day were significantly lower in all alcohol supplemented groups than in the control. Atherogenic indices (AI) were highest in the alcohol group and decreased in proportion with aloe amount. Serum triglyceride level was significantly higher in the alcohol group than in the control, but tended to be lower in the aloe supplemented groups. In relation to liver function, glutamate oxaloacetate transaminase (GOT), glutamate pyruvate transaminase (GPT), and alkaline phosphatase (ALP) activities tended to be higher in the alcohol groups than in the control, but lower in the aloe groups, especially in the alcohol+0.5% AO group. The levels of liver cholesterol were significantly lower in the alcohol group than in the control and aloe supplemented groups. In the histochemical evaluation, fat droplets appeared extensively on the liver-lobule in the alcohol group, whereas they decreased slightly in the alcohol+0.25% AO group and apparently disappeared in the alcohol +0.5% AO. On the other hand, fat droplets appeared again on the liver-lobule in the alcohol+1% AO group, but were reduced compared with the alcohol group. Regarding the fatty acid composition of adipose tissue triglycerides, the level of linoleic acid (18:2) was significantly higher in the aloe supplemented group. Regarding the fatty acid composition of liver phosphatidylcholine (PC), the level of linoleic acid was higher in the alcohol group and alcohol+1% AO group than the other groups. In contrast, the level of arachidonic acid was significantly lower in the alcohol group. As a result, arachidonic / linoleic acid ratios were significantly lower in the alcohol group compared to the control group, whereas the ratios of the aloe supplemented groups were similar to that of the control group. Therefore, aloe had some beneficial effects on lipid metabolic disorders induced by alcohol and affected desaturation of fatty acids.