• Journal of Radiation Industry
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• v.4 no.4
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• pp.391-395
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• 2010

The characteristics for pollutant transport in tidal influenced area was investigated using tidal wave hydraulic scale model. Hydraulic scale model was composed of the tidal generator, attenuation area and channel. Also, wave height, current meter and conductivity meter were used with the measured instruments in hydraulic scale model. NaCl with a tracer was used to evaluate the advection phenomena under the different velocity profiles. The arrival time of the maximum concentration in the condition of the relatively fast velocity was measured about 30 seconds faster than ones in the conditions of low velocity. The measured concentrations of the tracer were shown in the detection points of the flow direction consecutively.

• Journal of the Korean GEO-environmental Society
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• v.7 no.3
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• pp.77-83
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• 2006

The purpose of this study is to analyze lateral displacement behavior of clay layers in case of the banking in soft ground through model tests. Seven model tests varying with thickness of soft clay and loading velocity are performed to correlate between ground heaving and loading velocity. In case of low loading velocity, vertical settlement below loading plate and small ground heaving are obviously observed. In case of the high loading velocity, it is shown that both soil displacement at the end of a loading plate and surface heaving are large. In addition, the calculated displacements show good agreement with three cases of field measurements in clay with high moisture contents so that we can predict the range of heaving area and the amount of heaving.

• Journal of Animal Environmental Science
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• v.8 no.2
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• pp.73-78
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• 2002

The experiment was carried out to investigate the optimal air velocity for improving the ventilation efficiency of duct ventilation system used in Korean swine building. The results are followed ; In 2.2 m height of duct, the air velocity of hole was 5.0 m/s as the over level of recommendation. In different hole interval, the air velocity was various of 4.6${\sim}$11.6 m/s in narrow hole interval, 5.4${\sim}$10.9 m/s in broad hole interval. But the air velocity was 6.6${\sim}$7.7 m/s in duct system pierced hole with equal interval, and it was equal velocity in different parts of duct in this hole interval.

• Smart Structures and Systems
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• v.7 no.4
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• pp.289-302
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• 2011

In marine clay deposits, naturally formed or artificially reclaimed, the evaluation and monitoring of the consolidation process has been a critical issue in civil engineering practices due to the time frame required for completing the consolidation process, which range from several days to several years. While complementing the conventional iconographic method suggested by Casagrande and recently developed in-situ techniques that measure the shear wave, this study suggests an alternative experimental procedure that can be used to evaluate the consolidation state of marine clay deposits using the shear wave velocity. A laboratory consolidation testing apparatus was implemented with bimorph-type piezoelectric bender elements to determine the effective stress-shear wave velocity (${\sigma}^{\prime}-V_s$) relationship with the marine clays of interest. The in-situ consolidation state was then evaluated by comparing the in-situ shear wave velocity data with the effective stress-shear wave velocity relationships obtained from laboratory experiments. The suggested methodology was applied and verified at three different sites in South Korea, i.e., a foreshore site in Incheon, a submarine deposit in Busan, and an estuary delta deposit in Busan. It is found that the shear wave-based experimental procedure presented in this paper can be effectively and reliably used to evaluate the consolidation state of marine clay deposits.

• Journal of Korean Society on Water Environment
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• v.26 no.1
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• pp.104-110
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• 2010

Eutrophication is a well-known phenomenon in lentic habitats, however it is receiving increasing attention in shallow streams of Korea due to the increase of periphyton to a nuisance level. In this study temporal and spatial variation in periphyton standing crop and nutrient concentrations were surveyed in the upper reach of the Han River (the Inbuk Stream) that used to be a pristine rural stream until 1980s. Chlorophyll-a concentration per unit surface area of bottom substrate was examined monthly for one year period at nine sites along the Inbuk Stream together with environmental factors such as phosphorus, nitrogen, and water velocity. The standing crop of periphytic algae ranged from $4{\sim}242mgChl.a/m^2$ with a median of $55mgChl.a/m^2$, often exceeding the nuisance level criterion. Along the stream periphyton increased significantly from $39{\pm}48mgChl.a/m^2$ to $94{\pm}49mgChl.a/m^2$ after merging of a tributary in an intensive agricultural basin with high phosphorus concentrations. Seasonally periphyton biomass was highest in autumn (median $171{\pm}76mgChl.a/m^2$) from October through December when water flow velocity was low (median $0.4{\pm}0.3m/s$), while it was higher in flood season (median $1.2{\pm}0.4m/s$) and freezing season (median $0.2{\pm}0.3m/s$) was lower. The result shows that this rural stream often shows characteristics of eutrophication according to periphyton standing crop and it may be regulated by phosphorus and water velocity.

• Journal of Environmental Science International
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• v.10 no.5
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• pp.351-358
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• 2001

The main purpose of this study was to investigate the characteristics of cylindrical electrostatic precipitator with centrifugal effect in viewpoints of pressure drip and collection efficiency, experimentally. The experiment was carried out for the analysis of current-voltage, pressure drop and collection efficiency with various experimental parameters such as the applied voltage, inlet velocity, inlet size and inlet type(upper and bottom), etc. In the results, the pressure drops were estimated as 27~54, $34~63mmH_2O$ for inlet size $15mm{\tiems}30mm$ and $30mm{\tiems}60mm$, respectively. The collection effeciencies were shown over 90% with the small inlet size($15mm{\tiems}30mm$) for the applied voltage 40kV, inlet velocity(15~21m/s), and 51~89% with the large inlet size ($30mm{\tiems}60mm$). Moreover, in the applied voltage 0kV and inlet size $15mm{\tiems}30mm$, the collection efficiency induced by centrifugal force was represented as about 35% with inlet velocity 15 - 21m/s.

• Journal of Environmental Impact Assessment
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• v.2 no.1
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• pp.57-63
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• 1993

An analysis for particle settling effects via of plume centerline tilted exponentially under the influence of panicle settling velocity is carried out for particle of $30{\mu}m$ diameter with $1g/cm^3$ density and 0.02m/s settling velocity corresponding to its particle characteristic according to various wind speeds, atmospheric stabilities. Characteristic analysis of surface concentration distribution simulated by Lagrangian model also are carried out under the influence of plume centerline tilted exponentially at 10m stack height emitted 200 particles per second. This study reveals that plume centerline at the nearby source is sharply tilted exponentially under the condition of stable, weakly wind speed, therefore the lower concentration at the nearby source, the higher concentration at the downwind distance far away from source than actual one is brought out, if not apply the effect of plume centerline tilted exponentially to diffusion Model.

• Journal of Environmental Science International
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• v.4 no.2
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• pp.245-251
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• 1995

Generally, It is Introduced to well-known other models without considering tidal current of the field. The paper presents field measurements and numerical model solving velocity field of Cheonsu Bay by two-dimensional tidal model. It was proved that this scheme is easy to handle complex topography. Computed results is represented characteristics of tidal current for Cheonsu Bay. The results of the study can be summarized as follows ; 1. Tide form number has 0.21 value. Tidal range estimated 630.3 cm on spring, 454.1 cm on mean and 277.9 cm on neap, respectively 2. Tidal current has semi-diurnal form. Distance of traveling observed 16.6 km on flood and 15.5 km on ebb. 3. Tidal velocity showed reversing current. It was found that tidal velocity above 100 cm/sec is about 20 %. 4. Computed results are in good agreement with the observed data. Applying the algorithm to Cheonsu Bay, velocity fields and dry bank phenomena are simulated well in spite of complex topography. 5. An advanced study on the effects of open boundary conditions should be continuously performed.

• 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 Environmental Science International
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• v.4 no.1
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• pp.29-40
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• 1995

Transport rate of windblown dusts such as soil, sand, snow is proportionate to $U*_^3 and U_*$, friction velocity, approximately to flow velocity of ink Therefore, through measurement and the flow velocity of wind, it turned out that, considering different velocity distributions caused by downstream distance and porosity percent, windbreaks with appropriate porosity rate to the Protection area should be chosen for the optimal fence effect. In the economic respects better are fences with gap of 20%~30%. Among the windbreaks to have the optimal fence effect.