• Journal of Environmental Science International
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• v.4 no.2
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• pp.151-158
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• 1995

A numerical model has been developed to predict the deposition of air pollutants considering canopy effect. In this model, the deposition velocity is calculated using the deposition resistances(aerodynamic resistance, viscosity resistance, surface resistance). Using the results, a comparative study was made between the model calculation and observation results. The calculated daily variation of deposition resistances and in daytime most of the model cases are well agreed with observation results, and a slight difference was found in nighttime. From the results, it is suggested that the present model is capable of estimating the deposition velocity of air Pollutants considering characteristics of canopy layer.

• Journal of Environmental Science International
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• v.12 no.4
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• pp.393-397
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• 2003

It has been researched the relationship between deposition velocity and factors which could affect the deposition phenomena and deposition velocity also has been estimated fer several land-use types. The typical deposition velocities are complex functions of surface types, atmospheric stabilities, friction velocities, air pollutants and so on. The canopy resistance is major contribution to the model's total resistance for O₃. Canopy wetness is also an important factor to calculate deposition velocity. We considered the canopy wetness as canopy water content(CWC) in our Model. But, it is not easy to observe CWC over each land-use types. In this study, we use CWC observed by EMEFS(CANADA Environment Service, 1988) to examine the influence of CWC in estimation of 03 dry deposition velocity(V/sub d/) in summertime. The value of O₃ V/sub d/ range 0.2 ∼ 0.7 cm s/sup -1/ on dry surface and 0.01 ∼ 0.35 cm s/sup -1/ on wet surface in daytime.

• Current Optics and Photonics
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• v.1 no.2
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• pp.113-117
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• 2017

With the increasing use of high-power laser diode bars (LDBs) and stacked LDBs, the issue of thermal control has become critical, as temperature is related to device efficiency and lifetime, as well as to beam quality. To improve the thermal resistance of an LDB set, we propose and analyze a bypass heat sink with a top canopy structure for an LDB set, instead of adopting a thick submount. The thermal bypassing in the top-canopy structure is efficient, as it avoids the cross-sectional thermal saturation that may exist in a thick submount. The efficient thickness range of the submount in a typical LDB set is guided by the thermal resistance as a function of thickness, and the simulated bypassing efficiency of a canopy is higher than a simple analytical prediction, especially for thinner canopies.

• Journal of Korean Society of Forest Science
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• v.88 no.1
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• pp.86-92
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• 1999

Evapotranspiration is one of important variables affecting ecosystem processes such as vegetation distribution and growth. It acts as a limiting factor for natural water resource management. The transpiration of vegetation is mainly determined by climatic factors. The lower slope of the study area was densely forested with Pinus densiflora S. et Z. of 8 m height, and the upper slope was covered with poorly grown Pinus densiflora S. et Z. and Quercus trees. The amount of evapotranspiration was estimated to 590.3 mm/yr by annual water budget method. The canopy resistance of Penman-Monteith model was determined as 99 s/m. Seasonal evapotranspiration can be estimated with the calculated evaporation and the canopy resistance. The amount of evapotranspiration peaked in May. That is considered from both the direct evaporation of intercepted rainfall and the transpiration of vegetation during the dry spring season.

• Journal of Environmental Science International
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• v.11 no.7
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• pp.663-667
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• 2002

The aerodynamic resistance($R_a$) to vertical transfer in the surface boundary layer can be formulated in terms of the friction velocity, height of observation, vertical heat flux and surface roughness. Unlike previous studies which focused on the role of $R_c$, present study perform additional tests using a variety of $R_a$ formulae. Several $R_a$ formulations available in the literature, suitable for unstable conditions, were tested for their influence on the dry deposition velocity. The canopy resistance($R_c$) determines the shape of the diurnal pattern, while a small amplitude diurnal cycle in $V_d$ was attributed to the aerodynamic resistance. The aerodynamic resistance is the major contributor to the formation of spikes in nighttime and $R_a$ is relatively important at night because the canopy resistance is smaller. All formulations show similar diurnal cycle and yield good agreement with the observations. Although present $V_d$ formulations are suitable for numerical air qualify models, the research must continue for further improvements in resistance parametrizations.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.60-60
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• 2017

It is important to measure the gas exchange activity of the crops in canopy scale to understand the process of biomass production and yield formation. Thermal imaging of the canopy surface temperature is a powerful tool to detect the gas exchange activity of the crop canopy. The simultaneous measurement of the canopy temperature and the meteorological data enables us to calculate the canopy diffusive conductance ($g_c$) based on the heat flux model (Monteith et al. 1973, Horie et al. 2006). It is, however, difficult to realize the long-term and continuous monitoring of $g_c$ due to the occurrence of the calculation error caused by the fluctuation of the environmental condition. This is partly because the model assumption is too simple to describe the meteorological and aerodynamic conditions of the crop canopy in the field condition. Here we report the novel method of the direct measurement of the aerodynamic resistance ($r_a$) of the crop canopy, which enables us the stable and continuous measurement of the gas exchange capacity of the crop plants. The modified heat balance model shows the improved performance to quantify $g_c$ under the fluctuating meteorological condition in the field. The relationship between $g_c$ and biomass production of rice and soybean varieties is also discussed in the presentation.

• Journal of Bio-Environment Control
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• v.6 no.3
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• pp.205-215
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• 1997

An accurate transpiration model for greenhouse tomato crop, which is liable to transpiration depression and yield loss because of low solar radiation and high humidity, could be an efficient tool for the optimum control of greenhouse climate and for the optimization of Irrigation scheduling. The purpose of this study was to develop transpiration model of greenhouse tomato and to carry out the experimental verification. The formulas to calculate the canopy transpiration and temperature simultaneously were derived from the energy balance of canopy. Transpiration and microclimate variables such as net radiation, solar radiation, humidity, canopy and air temperature, etc. were simultaneously measured to estimate parameters of model equations and to verify the suggested model. Leaf boundary layer resistance was calculated as a function of Nusselt number and stomatal diffusive resistance was parameterized by solar radiation and leaf-air vapor pressure deficit. The equation for stomatal diffusive resistance could explain more than 80％ of its variation and the calculated stomatal diffusive resistance showed good agreements with the measured values in situations independent of which the constants of the equation were estimated. The canopy net radiation calculated by Stanghellini's model with slight modification agreed well with the measured values. The present transpiration model, into which afore-mentioned component equations were assembled, was found to predict the canopy temperature, instantaneous and daily transpiration with considerable accuracy in greenhouse climates.

• Journal of Environmental Science International
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• v.3 no.1
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• pp.17-29
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• 1994

An one dimensional atmosphere-vegetation interaction model is developed to discuss of the effect of vegetation on heat flux in mesoscale planetary boundary layer. The canopy model was a coupled system of three balance equations of energy, moisture at ground surface and energy state of canopy with three independent variables of $T_f$(foliage temperature), $T_g$(ground temperature) and $q_g$(ground specific humidity). The model was verified by comparative study with OSUID(Oregon State University One Dimensional Model) proved in HYPEX-MOBHLY experiment. As the result, both vegetation and soil characteristics can be emphasized as an important factor iii the analysis of heat flux in the boundary layer. From the numerical experiments, following heat flux characteristics are clearly founded simulation. The larger shielding factor(vegetation) increase of $T_f$ while decrease $T_g$. because vegetation cut solar radiation to ground. Vegetation, the increase of roughness and resistance, increase of sensible heat flux in foliage while decrease the latent heat flux in the foliage.

• Journal of Bio-Environment Control
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• v.15 no.4
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• pp.289-295
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• 2006

A computational fluid dynamics (CFD) numerical model has been developed to effectively study the ventilation efficiency of multi-span greenhouses with internal crops. As the first step of the study, the internal plants of the CFD model had to be designed as a porous media because of the complexity of its physical shapes. In this paper, the results of the wind tunnel tests were introduced to find the aerodynamic resistance of the plant canopy. The Seogun tomato was used for this study which made significant effects on thermal and mass exchanges with the adjacent air as well as internal airflow resistance. With the main factors of wind speed, static pressure, and density of plant canopy, the aerodynamic resistance factor was statically found. It was finally found to be 0.26 which will be used later as an input data of the CFD model. Moreover, the experimental procedure of how to find the aerodynamic resistance of various plants using, wind tunnel was established through this study.

• Journal of Bio-Environment Control
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• v.17 no.2
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• pp.83-89
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• 2008

A wind tunnel test was conducted at Protected Horticulture Experiment Station of National Horticultural Research Institute in Busan to find the aerodynamic resistance and quadratic resistance coefficient of chrysanthemum in greenhouse. The internal plants of the CFD model has been designed as a porous media because of the complexity of its physical shapes. Then the aerodynamic resistance value should be input for analyzing CFD model that crop is considered while the value varies by crops. In this study, the aerodynamic resistance value of chrysanthemum canopy was preliminarily found through wind tunnel test. The static pressure at windward increased as wind velocity and planting density increased. The static pressure at leeward decreased as wind velocity increased but was not significantly affected by planting density. The difference of static pressure between windward and leeward increased as wind velocity and planting density increased. The aerodynamic resistance value of chrysanthemum canopy was found to be 0.22 which will be used later as the input data of Fluent CFD model. When the planting distances were $9{\times}9\;cm$, $11{\times}11\;cm$, and $13{\times}13\;cm$, the quadratic resistance coefficients of porous media were found to be 2.22, 1.81, and 1.07, respectively. These values will be used later as the input data of CFX CFD model.