• 한국항행학회논문지
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• 제22권3호
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• pp.240-245
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• 2018

전체 광 중계 구간 모두 불규칙한 분산 계수를 갖는 단일 모드 광섬유와 분산 보상 광섬유 (DCF; dispersion compensating fiber)를 이용한 융통적인 분산 제어 링크 구조를 제안하였다. 링크의 융통적 구성은 각 전송 반 구획에서 DCF의 분산 계수를 기준으로 이들을 인위적으로 분포시켜서 가능하게 하였다. 광 위상 공액기 전의 전송 반 구획에서는 DCF의 분산 계수를 점진적으로 증가시키고, 광 위상 공액기 다음의 전송 반 구획에서는 DCF의 분산 계수를 점진적으로 감소시키는 'AD' 분포에서 왜곡된 파장 분할 다중(WDM; wavelength division multiplexed) 신호가 최상으로 보상되는 것을 확인하였다. 따라서 왜곡된 WDM 채널의 보상 효과를 더욱 증가시키기 위해서는 광섬유의 길이, 중계 구간 당 잉여 분산뿐만 아니라 광섬유의 분산 계수에 상관없이 'AD' 분포를 선택할 필요가 있다는 것을 확인하였다.

• 한국대기환경학회:학술대회논문집
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• 한국대기환경학회 2002년도 춘계학술대회 논문집
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• pp.279-280
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• 2002

본 연구에서는 라그랑지안 확산모델(LDM; Lagrangian dispersion model)을 이용하여 평지 및 언덕지형에서의 연기확산을 수치모사하였다. 수치예측의 검증을 위하여 평지지형의 경우는 풍동실험 결과와 비교하고 언덕지형의 경우는 오일러리안 확산모델(EDM; Eulerian dispersion model)의 모사결과와 비교함으로써 언덕지형에서 오염물질의 확산특성을 연구하였다. (중략)

• Current Optics and Photonics
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• 제3권4호
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• pp.298-303
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• 2019

We propose a photonic quasi-crystal fiber (PQF) for supporting up to 14 orbital angular momentum (OAM) modes with low and ultra-flat dispersion characteristics over the C+L bands. The designed PQF which consists of a large hollow center and quasi structural small air holes in the clad region exhibits low confinement losses and a large effective index separation (>$10^{-4}$) between the vector modes. This proposed fiber could potentially be exploited for mode division multiplexing and other OAM mode applications in fibers.

• 무역학회지
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• 제43권2호
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• pp.69-86
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• 2018

본 연구는 1999년부터 2013년까지 300개 개별상품의 소매가격자료를 사용하여 원유가격이 가격분산에 미치는 영향을 분석한다. 실증분석 결과에 따르면 원유가격 상승은 미국내 도시 간 가격분산은 증가시키는 반면, World, OECD 등 국가 간 가격분산에는 유의미한 영향을 미치는 않는 것으로 추정된다. 이는 국내 지역 간 차익거래가 원유가격 변화에 따른 수송비용의 변화에 민감하게 반응하는 반면, 국가 간 가격분산은 소득 격차 및 소비자 선호 등 기타 요인에 의해 주로 결정된다는 것을 의미한다.

• Journal of the Korean Statistical Society
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• 제21권2호
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• pp.187-200
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• 1992

Samples are often found to be too heterogeneous to be explained by a one-parameter family of models in the sense that the implicit mean-variance relationship in such a family is violated by the data. This phenomenon is often called over-dispersion. The most frequently used method in dealing with over-dispersion is to mix a one-parameter family creating a two parameter marginal mixture family for the data. In this paper, we investigate performance of estimators such as maximum likelihood estimator, method of moment estimator, and maximum quasi-likelihood estimator in negative binomial and beta-binomial distribution. Simulations are done for various mean parameter and dispersion parameter in both distributions, and we conclude that the moment estimators are very superior in the sense of bias and asymptotic relative efficiency.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2009년도 춘계학술대회
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• pp.305-308
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• 2009

According to the returns of Housing and business cycle over the period 1992 to 2007, it is a measure of the total volatility faced by investors in Housing properties. First, it isn't a distinct difference from business cycle contrary to U.S. Second, the rise of purchase price in total apartments moves up the consumer price index. According to the cross-sectional dispersion of returns and growth in net operating income (NOI) of apartments, industrial, retail and office properties using panel data for U.S. metropolitan areas over the period 1986 to 2002, it is a measure of the total volatility faced by investors in commercial real estate. To the extent that most of that volatility is difficult to diversify, cross-sectional dispersion may be an appropriate measure of risk.

• 한국해양공학회지
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• 제22권1호
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• pp.6-12
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• 2008

The dispersion and attenuation of Lamb and Leaky Lamb waves propagating in a 1 mm-thick steel plate were investigated. For acquiring a long(or large) range inspection capability, the fundamental symmetric and anti-symmetric wave modes(S0 and A0) over law frequencies were studied. Based on the dispersion curves, as well as pitch-catch and multi-mode simulations, it was shown that the S0 mode over law frequencies is the proper mode to minimize the dispersion and attenuation. In addition, it was shown that the S0 mode couldbe easily distinguished under multi-mode simulation since it has a larger group velocity than the A0 mode.

• Journal of the Optical Society of Korea
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• 제9권4호
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• pp.140-144
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• 2005

In this paper we have investigated the guiding properties of photonic crystal fibers (PCFs) with a square-lattice of air-holes in the cladding. We have shown numerical results of PCFs with various air hole sizes and hole-to-hole spacings over a wide wavelength range. The group velocity dispersion, effective area and effective refractive index of PCF have been calculated numerically. The waveguide dispersion has greatly affected the group velocity dispersion when hole-to-hole spacing is about $1{\mu}m$. The effective area is quite flat over the wide spectral range whether the hole-to-hole spacing is large or ratio of diameter to pitch is large. From the field distribution, we found that the field is tightly confined within the core region of PCF when the pitch is $3{\mu}m$ and the air-filling fraction is 0.9.

• 반도체디스플레이기술학회지
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• 제22권4호
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• pp.1-6
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• 2023

In CO₂ laser surface machining of plastic films in modern display manufacturing, scattering of fume particles could be a major source of well-recognized film surface contamination. This computational fluid dynamics research investigates the suction air flow patterns over a film surface as well as the dispersion of micron-sized fume particles with low-Reynolds number particle drag model. The numerical results show the recirculatory flow patterns near laser machining point on film surface and also over the surface of vertical suction slot, which may hinder the efficient removal of fume particles from film surface. The dispersion characteristics of fume particles with various particle size have been tested systematically under different levels of suction flow intensity. It is found that suction removal efficiency of fume particles heavily depends on the particle size in highly nonlinear manners and a higher degree of suction does not always results in more efficient particle removal.

• Journal of Radiation Protection and Research
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• 제26권3호
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• pp.305-309
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• 2001

Site-specific atmospheric dispersion characteristics have been analyzed. The northwest and the southwest wind prevail on nuclear sites of Korea. The annual isobaric surface averaged for twenty years around Korean peninsula shows that west wind prevails. The prevailing west wind is profitable in the viewpoint of radiation protection because three of four nuclear sites are located in the east side. Large scale field tracer experiments over nuclear sites have been conducted for the purpose of analyzing the atmospheric dispersion characteristics and validating a real-time atmospheric dispersion and dose assessment system FADAS. To analyze the site-specific atmospheric dispersion characteristics is essential for making effective countermeasures against a nuclear emergency.