• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.05a
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• pp.154-159
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• 2001

Nakdong estuary is located at south-eastern coast of the Korea. A lot of sediment from upper river was deposited at this area. It has caused many problems such as changes in topography and tidal current. In this paper, field observation data on tidal currents and sediments were investigated as well as historical topographic changes by dredging and reclamation of the foreshore. Then, the numerical model considered the settling velocity of the suspended solids according to the particle size was applied to examine the characteristic of deposition. The results are as follows : 1. Changes of characteristics of deposition were caused by topographic changes of Nakdong estuary 2. Characteristics of deposition were influenced by river plume and tidal currents. 3. Numerical model which considers settling velocity reappeared distribution of deposition by particle-size. 4. Used model is only resonable for discussion in the quality, so, it is strongly suggested that the new model development is needed including the quatitative deposition processes.

• Journal of Korean Society for Atmospheric Environment
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• v.19 no.2
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• pp.217-229
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• 2003

The amounts of nitrogen and sulfur deposited in the region of the Yellow Sea in both dry and wet forms were estimated by using the measurement data published in tile literature during tile past 10 years. In the estimation of dry deposition, concentrations at ground stations including those at a station on the Chinese side and concentrations from shipboard and aircraft measurements were used as well as deposition velocities. Wet deposition flux was determined at ground stations on the Korean side either by taking the flux data themselves or by calculating them from precipitation data in the literature. The dry deposition flux over the Yellow Sea was much greater than those China was confirmed from the fact that the total amount summing wet and dry depositions exceeded the emission amount from Korea. Dry deposition was principally made in the gaseous form due to a larger deposition velocity. Nevertheless, since the deposition velocity over water was smaller than that over the ground, dry deposition of oxidized nitrogen was smaller than wet deposition. As a whole, wet depositions of nitrogen and sulfur were 2.3 and 1.9 times 1arger than corresponding dry depositions, respectively.

• Particle and aerosol research
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• v.5 no.1
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• pp.17-27
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• 2009

Particle deposition on a semiconductor wafer larger than 100 mm was studied experimentally and numerically. Particularly the electrostatic effect on particle deposition velocity was investigated. The experimental apparatus consisted of a particle generation system, a particle deposition chamber and a wafer surface scanner. Experimental data of particle deposition velocity were obtained for a semiconductor wafer of 200 mm diameter with the applied voltage of 5,000 V and PSL particles of the sizes between 83 and 495 nm. The experimental data of particle deposition velocity were compared with the present numerical results and the existing experimental data for a 100 mm wafer by Ye et al. (1991) and Opiolka et al. (1994). The present numerical method took into consideration the particle transport mechanisms of convection, Brownian diffusion, gravitational settling and electrostatic attraction in an Eulerian frame of reference. Based on the comparison of the present experimental and numerical results with the existing experimental results the present experimental method for a 200 mm semiconductor wafer was found to be able to present reasonable data.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.1
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• pp.159-168
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• 2008

A special field experiment has been carried out from March 2001 to June 2001 at the Changhowon in Kyunggi to investigate a better methodology for the estimation of dry deposition of pollutions applicable in Korea. In this study, dry deposition plate was used to measure of total and water soluble acidic mass fluxes, and CPRI(Coarse Particle Rotary Impactor), CI(Cascade Impactor) were also used to measure ambient concentrations in various particle size ranges. Sehmel-Hodgson model was used to estimate dry depostion velocity and Weibull probability distribution function was applied to get generalized particle size distribution for the size fractioned concentration data sampled by CPRI and CI. Atmospheric dry deposition fluxes of mass and ionic matters estimated by the various techniques(one-step, multi-step, equi-concentration, subdivision for only the coarse particle range, applying Weibull distribution function, etc.) were compared to flux data sampled by DDP. It was found out that the deposition fluxes estimation methodology calculated by the each particle size range devided by particle size distribution characteristics and the rapidly changed points of deposition velocity using Weibull probability distribution function was the most applicable.

• Journal of Environmental Science International
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• v.11 no.9
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• pp.925-931
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• 2002

Land-use types should be included in air pollutant diffusion model because a complex mixture of various land-use patterns with computational grid can make errors in calculation of several parameters. However, the air pollutant diffusion model has generally been treated with a uniform component with land-use type in each mesh because of the complexity of the simulation. This study presents a numerical simulation of the horizontal distribution of $O_3$dry deposition velocity during summertime in Busan metropolitan city. The calculation of the meteorological field was conducted using the land cover data. Simulation has been performed by the following two scenarios : (1) one with current land cover data, and (2) the other with only land and sea for the surface characteristics. The results from each scenario reveals considerable differences on the meteorological fields and these differences can cause changes in the calculation values of $O_3$deposition velocity.

• Journal of Korean Society for Atmospheric Environment
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• v.14 no.5
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• pp.421-432
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• 1998

Deposition processes limit the life time of pollutants in the atmosphere and control the distance travelled before deposition. Thus the understanding about atmospheric deposition processes is essential for a proper assessment of the environmental impacts due to the anthropogenic pollutants. The dry deposition velocities are related to surface types, atmospheric stabilities, friction velocities, air pollutants and so on. In this study we simulated the dry deposition velocities of O3 in Pusan region. The calculated deposition velocities compared to the observed O3 data obtained during the summer of 1988 over a deciduous forest in Canada. The comparison showed that the model somewhat overpredicted deposition velocities for the average diurnal variations with maxima in daytime and minima in nighttime mostly due to the turbulence intensity.

• Journal of The Korean Society of Agricultural Engineers
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• v.58 no.1
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• pp.11-17
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• 2016

Dredging and land reclamation works has actively carried out for the efficient use of land and secure of agricultural and industrial site. During the reclamation, a portion of landfills are lost from the desired location due to a variety of causes. However, these causes has been rarely studied, and water flow velocity has a great influence on the movement of landfills. For the economical and efficient reclamation, it is important to predict the movement of landfills in water. In this paper, an experimental study was carried out to investigate the deposition distance according to the flow velocity and soil grain size. We have made a large open-channel apparatus that can reproduce a laminar flow, and the deposition test was carried out on the four grain size (0.638, 1.425, 3.375, 7.125 mm) and four flow velocity (0.1, 0.3, 0.5, 0.67 m/s) with high definition video recording. As a results, average deposition distance increased with the flow velocity, and its relationship is shown linearly. For the grain size, the average deposition distance were drastically increased as the grain size becomes smaller.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.5 no.2
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• pp.130-140
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• 1993

Average particle deposition velocity toward a horizontal semiconductor wafer in vertical airflow is measured by a wafer surface scanner(PMS SAS-3600). Use of wafer surface scanner requires very short exposure time normally ranging from 10 to 30 minutes, and hence makes repetition of experiment much easier. Polystyrene latex (PSL) spheres of diameter between 0.2 and $1.0{\mu}m$ are used. The present range of particle sizes is very important in controlling particle deposition on a wafer surface in industrial applications. For the present experiment, convection, diffusion, and sedimentation comprise important agents for deposition mechanisms. To investigate confidence interval of experimental data, mean and standard deviation of average deposition velocities are obtained from more than ten data set for each PSL sphere size. It is found that the distribution of mean of average deposition velocities from the measurement agrees well with the predictions of Liu and Ahn(1987) and Emi et al.(1989).

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.5
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• pp.637-645
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• 2009

The main purpose of this study lies on the improvement of micro dilution tunnel based on the typical porous tube type chamber. The characteristics of flow and temperature fields for steady state has been obtained by numerical analysis using FLUENT. Three different geometrical variations of the porous tube; a) increase of thickness at center, b) step increase of thickness at center and downstream, c) tapered increase of thickness, have been proposed. Accordingly results are obtained and compared in terms of penetration velocity and velocity ratio to therrmophoretic velocity for improvement against particulate deposition inside the tube. The penetration velocity and velocity ratio distributions in the upstream portion and portion of impinging of dilution air are apparently shown to be improved for the case of the step and tapered change of porous tube. The tapered change of tube thickness addition are shown to be the most effective among three geometrical changes. In addition, the considerable improvement against deposition are shown that its thickness should be at least 2mm.

• 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.