• Journal of the Korean Data and Information Science Society
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• v.28 no.1
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• pp.153-161
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• 2017

Branching processes which is used for epidemic dispersion as stochastic process model have advantages to estimate parameters by real data. We have to estimate both mean and dispersion parameter in order to use the negative binomial distribution as an offspring distribution on branching processes. In existing studies on biology and epidemiology, it is estimated using maximum-likelihood methods. However, for most of epidemic data, it is hard to get the best precision of maximum-likelihood estimator. We suggest a Bayesian inference that have good properties of statistics for small-sample. After estimating dispersion parameter we modelled the posterior distribution for 2015 Korea MERS cases. As the result, we found that the estimated dispersion parameter is relatively stable no matter how we assume prior distribution. We also computed extinction probabilities on branching processes using estimated dispersion parameters.

• Korean Journal of Plant Resources
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• v.17 no.3
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• pp.248-256
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• 2004

Dendropanax morbifera Lev.(Araliaceae), Korean endemic and evergreen small tree is a component of evergreen forest and mainly distributed in sourthern region and islands in Korea. The ecological characteristics of 4 natural stands of D. morbifera.(Sundol, Suak, Hannam, and Sangho populations in Cheju island) were studied. In most of the D. morbifera natural stands, the following tree species appeared predominantly: Castanopsis cuspidata var. sieboldii, Carpinus laxiflora, D. morbifera, Quercus glauca, Quercus myrsinaefolia, Camellia japonica, and Acer pseudo-sieboldianum. Two tree species, such as C. cuspidata var. sieboldii and C. laxiflora appeared in the all investigated stands. D. morbifera occupied 17.2% of the upper story, 12.9% of the middle story, and 10.3% of the lower story, respectively. The distribution patterns by Morisita' s Index showed that D. morbifera was distributed randomly in the three stories. The frequency distribution of DBH D. morbifera species showed reverse J-shaped, therefore it seems to remain as a dominant species.

• Korean Journal of Remote Sensing
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• v.36 no.5_4
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• pp.1255-1266
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• 2020

In this study, a complex simulation prototype was developed for rapid and accurate prediction of chemical dispersion range in order to reduce human casualties caused by chemical accidents. Complex simulation considered the leakage momentum during the near-field dispersion to take into account the leakage characteristics of the chemical. In the far-distance dispersion process, the wind distribution of the existing model, which was presented uniformly, was improved using weather and topographical information around the accident site, to realize a wind field similar to the actual one. Finally, the damage range was more precise than the existing model in line with the improved near- and far-distance dispersion process. Based on the results of damage range prediction of the complex simulation, it is expected that it will be highly utilized as a system to support policy decision-making such as evacuation and return of residents after a chemical accident.

• Journal of Korean Society of Forest Science
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• v.95 no.3
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• pp.240-249
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• 2006

Recently, dispersion of damaged forest by pine wilt disease has been regarded as a serious social issue. Damages by pine wilt disease have been spreaded by natural area expansion of the vectors in the damaged area, while the national wide damage spread has induced by human-involved carrying infected trees out of damaged area. In this study, damaged trees were detected and located on the digital map by aerial photograph and terrestrial surveys. The spatial distribution pattern of damaged trees, and the relationship of spatial distribution of damaged trees and some geomorphological factors were geostatistically analysed. Finally, we maked natural spread pattern map of pine wilt disease using geostatistical CART(Classification and Regression Trees) model. This study verified that geostatistical analysis and CART model are useful tools for understanding spatial distribution and natural spread pattern of pine wilt diseases.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.8
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• pp.1583-1594
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• 1992

A numerical calculation on the flame structure and soot particle distribution in a coannular laminar diffusion flame was performed. Flame analysis model utilized basically flame sheet concepts, Shvab-Zel'dovich assumption, and one step overall irreversible reaction. It was also considered the variation of thermodynamics and transport properties, and the stagnation enthalpy was used for solving temperature field. Radiation was taken into account, since it has been found to be important in determining the flame temperature in sooty flames. For soot particle analysis, we adopted the coagulation, suface condensation, and the oxidation model in addition to tesner's two-step formation model. Equations for primary soot particle excluding the agglomeration process were solved. Based on the results, the regions of soot generation, growth, and oxidation in the flame have been observed and radiation strongly influenced flame temperature and soot distribution.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.5
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• pp.9-17
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• 2008

Pseudo-3D spatial distribution of spray droplets is investigated by using Dual-mode Phase Doppler Anemometry (DPDA) in order to examine the disintegration and spreading behavior of spray exiting from liquid-propellant thruster injector. Spray injected from nozzle orifice with length-to-diameter ratio ($L/d_o$) of 1.67 and under the injection pressure of 27.6 bar is aligned to the vertical. Vertical and horizontal mean velocities of droplets, Sauter Mean Diameter (SMD), and volumetric flux decrease as droplets travel from center/upstream toward outer region/downstream of spray. Although the distribution of spray characteristic parameters is symmetric against the geometric axis of nozzle orifice, their absolute values are asymmetric.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.1
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• pp.62-72
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• 2008

In this study, an analytical model has been developed to predict the build-up of heat field due to a point heat source in the presence of sharp cross-flow depth change. The model has been applied to investigate the effect of the depth change and flow pattern on the heat field. Model results show that, when there is a sharp depth change in cross-flow direction, the heat transport across the boundary of the depth change is enhanced or diminished according to the increasing or decreasing of the horizontal diffusion flux. Including residual components as well as tidal currents give rise to reduce the effect of the horizontal diffusion on the heat transport because of increasing the advection of heat.

• Korean Journal of Optics and Photonics
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• v.9 no.2
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• pp.86-91
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• 1998

Multimode planar waveguides have been fabricated by an electric-field assisted ion exchange in soda-lime glass substrates. Measurements of the mode indices have been made and the index profiles modeled on modified Fermi function are explained by a comparative analysis with the concentration profiles obtained using an electron probe X-ray micro analyzer. The analytical measurements showed that no more than 95% of sodium ions were replaced by the cesium ions. We established formulas for guide depth, mobility, and refractive index change, given the applied electric field, the diffusion temperature, and the time. We have verified the linear relations in the formulas not only between guide and root of diffusion time but also between guide depth and the applied electric filed experimentally.

• Proceedings of the Korean Information Science Society Conference
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• 2012.06c
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• pp.359-361
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• 2012

본 논문은 T2강조 MR 영상과 확산강조 MR 영상의 강체 정합을 통해 크기, 위치, 회전 변환 왜곡을 보정하여 자궁내막암의 위치를 자동으로 찾는 방법을 제안한다. 영상해상도와 밝기값 분포가 서로 다른 두 영상간 정합의 정확성을 향상시키기 위해 잡음을 제거하고 두 영상의 밝기값 신호 분포의 유사성을 강화시킨다. 유사성이 향상된 두 영상의 크기, 위치, 회전 변환 왜곡을 보정하기 위해 정규화 상호정보를 최대화 하는 강체 정합을 반복적으로 수행한다. 정합된 영상에서 악성 종양을 쉽게 판별 할 수 있도록 현상확상계수지도를 컬러맵으로 생성하여 T2강조 MR 영상에서 얻은 종양의 후보군에 매핑하여 T2강조 MR 영상과 융합한다. 실험을 위하여 최적화 반복 과정에 따른 정규화 상호정보 수치 수렴 과정을 확인하고, 융합 후 종양 영역이 매핑되는 것을 육안평가를 통해 분석하였다. 제안방법을 통하여 T2강조 MR 영상과 확산강조 MR 영상을 융합함으로써 종양의 위치를 자동으로 파악하고 자궁내막암의 병기를 확정하는 용도로 활용할 수 있다.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.296-296
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• 2011

유역의 폭 함수는 출구를 기준으로 동일한 거리에 위치한 link의 개수로 정의된다. 하천망을 구성하는 기본 성분 중의 하나인 link는 동일한 유역의 경우 유사한 평균길이와 직접배수면적을 갖는 것으로 알려져 있다. 이는 폭 함수가 흐름방향 축을 따라 정의되는 지점별 배수면적의 기여도와 동일함을 의미하는 것으로 유역의 형태학적 특성에 따라 조직되는 초기유량분포함수로 해석할 수 있다. 따라서 DEM을 기반으로 원점으로부터 동일한 거리에 위치한 pixel의 수를 계량할 경우 비교적 쉽게 유역의 폭 함수를 유도할 수 있게 된다. 또한 물 입자의 동적특성에 따라 폭 함수의 흐름방향 축을 시간 축으로 재조정할 경우 대상 유역에 대한 수문학적 응답함수로의 변환이 가능해 진다. 본 연구에서는 보청천 시험유역의 탄부수위표 지점을 출구로 하여 DEM으로부터 폭 함수를 작성하고 지면과 하천유속의 차에 따른 운동학적 확산효과만을 고려하여 재조정된 폭 함수를 다음 그림과 같이 유도하여 보았다. Figs 1, 2에서 주목되는 사항은 왜곡도의 반전으로 부왜도의 형태를 갖던 폭 함수가 정왜도의 형태를 갖는 수문학적 응답함수(순간단위도)로 변환되어 가는 과정을 시각적으로 확인할 수 있다. 이는 Mod-Clark 방법에 따른 준분포형 순간단위도의 유도과정과 유사한 것으로 이에 따라 선형저수지의 저류효과는 지면과 하천유속의 차에 따른 운동학적 확산효과와 동일한 거동을 보일 수 있음이 추론된다.