• Wind and Structures
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• 제9권1호
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• pp.23-35
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• 2006

The effect of buildings on flow in urban canopy is one of the most important problems in local/micro-scale meteorology. A large eddy simulation model is used to simulate the flow structure in an urban neighborhood and the bulk effect of the buildings on surrounding flows is analyzed. The results demonstrate that: (a) The inflow conditions affect the detailed flow characteristics much in the building group, including: the distortion or disappearance of the wake vortexes, the change of funneling effect area and the change of location, size of the static-wind area. (b) The bulk effect of the buildings leads to a loss of wind speed in the low layer where height is less than four times of the average building height, and this loss effect changes little when the inflow direction changes. (c) In the bulk effect to environmental fields, the change of inflow direction affects the vertical distribution of turbulence greatly. The peak value of the turbulence energy appears at the height of the average building height. The attribution of fluctuations of different components to turbulence changes greatly at different height levels, in the low levels the horizontal speed fluctuation attribute mostly, while the vertical speed fluctuation does in high levels.

• 한국환경복원기술학회지
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• 제12권3호
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• pp.98-105
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• 2009

The objective of this study is to develop numerical simulation model for analysing the wind speed reduction effect by coastal forest belts. The horizontally homogeneous turbulent flow equations, which are derived from the Reynolds-averaged Navier-Stokes method, both above the tree canopy and within the canopy were first formulated, and a first-order closure scheme with the capability of accounting the bulk momentum transport term within the canopy was employed. The averaged equations were solved numerically by finite difference method, FTCS (forward time centered space) scheme. The proposed model was also used to numerically investigate the effects of structural characteristic of forest belt on the wind speed. The effects of maximum leaf area density were evaluated, with the leaf area density of $1.0m^2/m^3$, $2.0m^2/m^3$, $3.0m^2/m^3$, and $4.0m^2/m^3$. Vertical distributions of leaf area, both uniform and varied distribution with a height, were also considered. A comparison of wind profile indicated that there was in good agreements between simulated and measured wind speed. Also, the results showed horizontal wind speed decreased under a height of the tree with increasing maximum leaf area density. In conclusion, in applications where computational efficiency and simplicity are desirable, the proposed numerical model has of great capability to determine the vertical turbulent momentum transport and wind profile in the costal forest belt.

• 대한원격탐사학회지
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• 제39권5_4호
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• pp.1155-1164
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• 2023

현재 국가산림자원조사(National Forest Inventory, NFI)는 인력에 의한 수목정보를 수집하고 있어 조사 범위와 시간의 한계가 따른다. 항공 Light Detection And Ranging (LiDAR) 및 항공 사진 등을 이용하여 넓은 지역의 수목 정보를 추출하기 위한 연구가 활발하게 진행되고 있으나 수목의 간격이 넓은 지역이거나 수목의 간격이 일정하게 배치된 지역을 대상으로 이루어지고 있어 우리나라 산림지역 특성을 반영하지 못하고 있다. 이에 본 연구에서는 항공 LiDAR를 이용하여 수치표면모델(Digital Surface Model, DSM), 수치표고모델(Digital Elevation Model, DEM), 수목높이모델(Canopy Height Model, CHM) 영상을 생성한 후 local maxima 기법을 통해 수고를 추출하고 산정식을 통해 흉고직경(Diameter at Breast Height, DBH)을 산정하는 방법론을 제안하였다. 제안한 방법론을 통해 추출한 수목의 검출 정확도는 매목지구별 각 88.46%, 86.14%, 84.31%로 나타났으며, 수고 값을 기반으로 산정한 DBH의 평균제곱근오차(Root Mean Squared Error, RMSE)가 5 cm 내외로 나타나 제안한 방법론의 활용 가능성을 확인하였다. 향후 다양한 유형의 산림에 대한 표준화 연구를 진행한다면 수작업으로 이루어지는 국가산림자원조사의 자동화 적용 범위를 확대할 수 있을 것으로 사료된다.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2009년도 춘계학술발표대회 논문집
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• pp.180-183
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• 2009

In this study, Urban Climate Simulation was performed by 3-Dimensional Urban Canopy Model. The characteristics of urban climate was analyzed combining artificial land coverage, building size, heat production from the air conditioning and topographic conditions as physical variables which affects urban climate characteristics. The results are as follows. (1)The aspects of the urban climatal change is derived to be related to the combination of the building coverage ratio, building height and shading area. (2)Whole heat generation was influenced by the convective sensible heat at the lower building height and by the artificial heat generation at the higher one over 20-story building influence to some extent of the building coverage ratio. The effect of the altitude is not more considerable than the other variables as below $1^{\circ}C$ of the air temperature.

• 한국산림과학회지
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• 제88권1호
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• pp.86-92
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• 1999

증발산량은 산원 수자원의 제한 요인이며, 한편으로는 임목의 생장, 분포에 관여하는 중요한 생태계의 요인으로 인식되고 있다. 식생에 의한 증산은 주로 기상학적 요인에 의하여 좌우된다. 조사 유역의 하부는 수고 8m의 소나무로 밀생되어 있으며, 상부는 생장이 불량한 소나무와 참나무류가 산생하고 있다. 1993년도 강수, 유출 조사 자료를 이용하여 증발산량을 구하고, Penman-Monteith 모델의 수관저항을 정하여, 이 모델에 의한 산림지역의 일 증발산량의 계절적 변이를 추정하고자 하였다. 연간 증발산량은 590.3mm이었으며 수관저항값은 99s/m로 결정되었다. 연간 증발산량 중에서 5월의 증발산량이 106.4mm로 가장 큰 값을 나타내며 이는 식생에 의한 수관차단 및 증산의 영향을 반영하고 있었다.

• 한국지형학회지
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• 제23권3호
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• pp.105-122
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• 2016

To evaluate the changes in the physical characteristics of open rainfall related to canopy effects and rainfall intensity in Korea, the terminal velocity of raindrops and drop size distributions(DSD) were continuously measured by an optical-laser disdrometer in an open site(Op) and in two forest stands(Th1: Larix leptolepis, Th2: Pinus koraiensis) during five rainfall events in 2008. The terminal velocity, DSD and two forms of kinetic energy(KE, $Jm^{-2}$ $mm^{-1}$; KER, $Jm^{-2}$ $h^{-1}$) of open rainfall drops were determined and were compared with those of throughfall drops under two different canopy heights. The effects of the canopy and rainfall intensity, together with wind speed, on the changes in drop size and kinetic energy of throughfall were evaluated. Throughfall drops were larger than open rainfall drops. The distribution of terminal velocities for the drop sizes measured at Th2 was lower than that at Op; however, at Th1 the distribution was similar to that at Op. The total kinetic energy of throughfall at Th1 and Th2 was higher than the total kinetic energy of open rainfall, and the kinetic energy distribution for the drop sizes wassimilar to the drop size distribution. The observed throughfall-KER at Th1 was lower than an estimate previously produced using a model. The overestimation from the modeled value at Th1 was likely to be due to overestimated values of a square root transformation of fall height and its coefficient in the model because the distributions of terminal velocity for the drop size measured at Th1 were similar to those of open rainfall.

• 한국태양에너지학회 논문집
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• 제29권3호
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• pp.19-27
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• 2009

In this study, Urban Climate Simulation was performed by 3-Dimensional Urban Canopy Model. The characteristics of urban climate were analyzed combining artificial land coverage, building size, heat production from the air conditioning and topographic conditions as physical variables which affects urban climate characteristics. The results are as follows. (1) The aspects of the urban climatal change is derived to be related to the combination of the building coverage ratio, building height and shading area. According to the building height, the highest temperature was increased by $2.1^{\circ}C$ from 2-story to 5-story building and the absolute humidity by 2.1g/kg maximum and the wind velocity by 1.0m/s was decreased from 2-story to 20-story building. (2) Whole heat generation was influenced by the convective sensible heat at the lower building height and by the artificial heat generation at the higher one over 20-story building influence to some extent of the building coverage ratio. The effect of the altitude is not more considerable than the other variables as below $1^{\circ}C$ of the air temperature. In the last, deriving the combination of building coverage and building height is needed to obtain effectiveness of the urban built environment planning at the point of the urban climate. These simulation results need to be constructed as DB which shows urban quantitative thermal characters by the urban physical structure. These can be quantitative base for suggesting combinations of the building and urban planning features at the point of the desirable urban thermal environment as well as analyzing urban climate phenomenon.

• 국제초고층학회논문집
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• 제1권2호
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• pp.73-80
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• 2012

In order to use sea breezes to counter the heat island phenomena, i.e. to promote urban ventilation, it is necessary to clarify the effect of building morphology and height on large-scale wind fields. In this study, the sea breeze in the vicinity of the Kanto Plain in Japan is simulated using a mesoscale meteorological model incorporating an urban canopy model, and the inland penetration of sea breezes is accurately reproduced. Additionally, a mean kinetic energy balance within a domain (Control Volume; CV) moving along the sea breeze is analysed. From the results, it is clarified that the sea breeze is interrupted by the resistance and turbulence caused by buildings at the centre of Tokyo. The interruption effect is increased in accordance with the height of these buildings. On the other hand, adverse pressure gradients interrupt in the internal region.

• 한국산림과학회지
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• 제99권2호
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• pp.204-212
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• 2010

This study was performed in 22 unthinned Larix olgensis plantations in northeast China. Data were collected on 95 sample trees of different canopy positions and the diameter at breast height ($d_{1.3}$) ranged from 5.7 cm to 40.2 cm. The individual tree models for the prediction of vertical distribution of live crown, branch and needle biomass were built. Our study showed that the crown, branch and needle biomass distributions were most in the location of 60% crown length. These results were also parallel to previous crown studies. The cumulative relative biomass of live crown, branch and needle were fitted by the sigmoid shape curve and the fitting results were quite well. Meanwhile, we developed the crown ratio and width models. Tree height was the most important predictor for crown ratio model. A negative competition factor, ccf and bas which reflected the effect of suppression on a tree, reduced the crown ratio estimates. The height-diameter ratio was a significant predictor. The higher the height-diameter ratio, the higher crown ratio is. Diameter at breast height is the strongest predictor in crown width model. The models can be used for the planning of harvesting operations, for the selection of feasible harvesting methods, and for the estimation of nutrient removals of different harvesting practices.

• 한국지리정보학회지
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• 제21권4호
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• pp.158-174
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• 2018

엽면적지수(LAI: Leaf Area Index)는 식생의 광합성, 증발산, 지표면과 대기사이의 에너지 교환 등을 설명하는 주요 인자로서, 정확하고 활용성 높은 LAI 추정 기법에 대한 연구들이 진행되었다. 본 연구에서는 UAV를 이용한 LAI 추정 방법을 모색하기 위하여 현장 실측된 LAI 자료와 UAV 영상기반의 식생지수, 수고 및 위성영상(Sentinel-2) LAI 간의 관계성을 파악하고 효과적인 UAV LAI 산정방법을 제시하고자 하였다. 그 결과 연구에 활용된 6종의 식생지수 중 Red-edge band를 포함하고 있는 NDRE ($R^2=0.496$), CIRE ($R^2=0.443$)가 LAI 추정에 효과적인 식생지수로 나타났다. 수고(Canopy Height Model) 자료를 식생지수에 적용하였을 때 LAI에 대한 설명력이 향상되었으며, NDVI의 경우에 LAI와의 선형관계에서 발생되는 포화문제(saturation problem)를 보였던 구간(0.85)이 일부 해소됨을 확인하였다.