• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.7
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• pp.402-408
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• 2009

In this paper, the effects of ventilation and humidification on thermal comfort and indoor air quality(IAQ) were evaluated in a classroom when a heat pump system was operated in winter. Thermal comfort parameters, such as temperature, relative humidity, globe temperature and air velocity, were measured at 9 points in the classroom. The concentration of $CO_2$ and total suspended particles(TSP) in the classroom were measured in order to analyze IAQ. Temperature distribution in the classroom was decreased by $2{\sim}5^{\circ}C$ when the ventilation system and the humidifier were operated. When the relative humidity was adjusted to 60% by operating the humidifier and the ventilation system, the predicted mean vote(PMV) in the classroom was within the comfortable range of $-0.5{\sim}0.5$. When the ventilation system was operated, the average concentration of $CO_2$ and TSP were decreased by 645 ppm and 0.17 $mg/m^3$, respectively. This paper suggests the humidification and ventilation conditions to maintain the comfortable environment in the school classroom in winter experimentally.

• Journal of the Korean earth science society
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• v.40 no.4
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• pp.414-427
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• 2019

In East Asia, the long-range transport of dust storms originating from Mongolia and northern China affects airborne dust loadings over downwind areas in the southern Korean Peninsula. Since 1997, dust loading cases caused by dust storms have been observed using the thresholds of total suspended particles (TSP, ${\geq}250{\mu}g\;m^{-3}\;hr^{-1}$) and particulate matter less than $10{\mu}g$ ($PM_{10}$, ${\geq}190{\mu}g\;m^{-3}\;hr^{-1}$) in the central-southern Korean Peninsula. There were two dust loading cases that exceeded these thresholds in 2016 and three in 2017, which reflects the downward trend of the last twenty-one years in the central-southern Korean Peninsula. Furthermore, five other dust loading cases with mass concentrations lower than the thresholds were observed from 2016 to 2017. In the moderate dust loading cases exceeding the thresholds, a descending motion of cut-off lows below $45^{\circ}N$ and a southward trough at 500 hPa gpm isopleths intensified at the western ridge, and largely extended the surface high-pressure system over southeast China. Airborne dust loadings following pronounced north-westerlies in the forward side of the high-pressure system were transported to the surface of the central-southern Korean Peninsula. However, in slight dust loading cases lower than the thresholds, the restricted descending motion of cut-off lows over $45^{\circ}N$ and the southwestward trough at 500 hPa gpm isopleths intensified the zonal flow over the Korean Peninsula. Surface high- and low-pressure systems moved eastward from the source compared to moderate dust loading cases. Due to the zonal movement of dust storms traversing eastern China, slight dust loading cases were observed with relatively higher ratios of $PM_{2.5}/TSP$ and carbon monoxide (CO) in the central-southern Korean Peninsula.

• Journal of Korea Water Resources Association
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• v.54 no.8
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• pp.607-616
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• 2021

The purpose of this study is to simulate the transport of nonuniform sediment considering the hiding-exposure effect numerically. In order to calculate the transport of multi-disperse suspended sediment mixtures, the set of advection-diffusion equations for each particle class is solved. The applicability of the numerical model is examined by comparing the simulation results with experimental data. In this study, we calculate the vertical distribution of total concentration of sediment particles using two approaches: (1) by considering the mixture as represented by a single size; and (2) by combining the concentration of the sediment corresponding to several particle size classes; From the simulation results, it is shown that both approaches calculate reasonable results due to the narrow range of size distribution. Under the condition of nonuniform sediment, the critical shear stress of the sediment particle is influenced by the size-selective entrainment, i.e., hiding-exposure effect. It is shown in this study that the effect of hiding-exposure effect on the erosion rates of fine sand is negligibly small.

• Particle and aerosol research
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• v.17 no.4
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• pp.115-123
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• 2021

The emission gas from meat grilled restaurants has unpleasant odor and sticky particulate matters (PM) in form of oil mist. This affects the residents living nearby. In oder to decrease the odor and PM, electrostatic precipitators (ESP) were installed at several restaurants by support of Seoul metropolitan government and emission characteristics of PM and odor were investigated. The removal efficiency of odor and PM at before- and after-ESP was that total hydrocarbon (THC), NH₃, H₂S, acetaldehyde, butyraldehyde were not much decreased. Total suspended particles (TSP) emitted from the vent was below the value of 7 mg/m³ regardless of the concentration of before-ESP and removal efficiency was in the range of 64 ~ 86%. The ratio of PM_1.0 to PM₁₀ of emission gas was over 0.9. So it was revealed that most PM of emission gas was PM1.0. The PM concentration in the air of the street near the vent was higher than another street due to the emission gas and the PM of indoor air of restaurant grilling meats was measured very high compared to outdoor air. So it needs more powerful ventilation of indoor air.

• Korean Chemical Engineering Research
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• v.59 no.3
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• pp.359-365
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• 2021

We investigated experimentally the ignition characteristic of dust and the hazard evaluating for electrostatic discharge. The ignition energy experiments were performed on sample dusts such as PE(HD), PE(LD), PMMA using the MIKE-3 apparatus. The formation of flame during the ignition of PE(HD) dust clouds occurred after the delay time of about 8 ms, and the flame kernels were not observed in center of ignition occurrence area. The voltage increased with increasing the number of dust dispersions and the increase rate of measured voltage with dust concentration was the highest in the order of PMMA, PE(LD) and PE(HD). For the effect of dispersion condition on the voltage in PE(HD) dust, the results were obtained that the voltage increased as the number of dispersions increased and as the concentration increased under the same dispersion number. The safety voltages to prevent fire and explosions by electrostatic ignition were estimated that PE(HD), PE(LD)-1, PE(LD)-2, and PMMA were 2.58, 44.72, 25.82, and 8.16 kV, respectively. We proposed the method for estimating the minimum ignition energy by using the measured voltage data for efficient investigation of electrostatic ignition hazard.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1C
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• pp.17-25
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• 2010

Electrophoresis may offer a new technique to repair in service leaking geomembrane liner of municipal solid waste (MSW) impoundment. The method involves introducing a suspended clay particles, which are charged negatively, into the leakage in geomembrane liners by electrokinetic phenomena and formation of clay cake around leakage for prevention of leachate outflows. Therefore, the 3-dimensional leakage simulation experiments are conducted to evaluate the field applicability of sealing leaks of waste impoundment. In addition, the adequateness of optimum influence factors deduced from 1-dimensional experiments is evaluated. After the test, the total size (width, length) of clay cake formation around leak is increased with enlargement of leakage diameter and distance decrease detween anode and cathode.

• Journal of Korean Society of Rural Planning
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• v.30 no.3
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• pp.1-8
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• 2024

This study focused on quantifying fugitive dust levels around rural village adjacent near a stone quarry, specifically examining the influence of quarry operations and gravel transport vehicles on road dust dispersion. For this purpose, fugitive dust concentration monitoring was conducted to understand the impact of gravel transport vehicles operating through the quarry area on the generation of road dust. Gravimetric analysis indicated substantial increases in Total Suspended Particulate (TSP) concentration (5.8 times), PM-10 (3.6 times), and PM-2.5 (2.0 times) during quarry operations on the quarry transport road. Real-time monitoring during dump truck operation revealed average dust concentrations of TSP 566.8 ㎍/m³, PM-10 174.8 ㎍/m³, and PM-2.5 55.3 ㎍/m. This indicates a significant increase compared to non-operation periods, with TSP concentration rising by 5.8 times, PM-10 concentration by 3.6 times, and PM-2.5 concentration by 2.0 times. Significantly elevated dust levels were observed at the village entrance road and quarry transport road during quarry operations, with PM-10 exceeding regulatory limits by 2.2 times and PM-2.5 exceeding limits by 1.9 times on the quarry transport road. Especially, particles with a diameter greater than 10 ㎛ exhibited a meaningful increase during dump truck transportation. Considering these findings, the study recommends implementing dust mitigation measures, including the introduction of dust barriers, screens, and wheel washing facilities for quarry-bound dump trucks.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.4
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• pp.266-274
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• 1999

Vertical CTDT measurement at one point near tidewater glacier of fjord-head in Marian Cove, a tributary embayment of Maxwell Bay, South Shetland Islands was performed for 24 hours during the austral summer (January 21-22, 1998) to present water-column properties and SPM (suspended particulate matter) dispersal pattern in subpolar glaciomarine setting. Marian Cove shows three distinct water layers: 1) cold, freshened, and highly turbid surface plume in the upper 2 m, 2) warm, saline, and relatively clean Maxwell Bay water between 15-35 m in water depth, and 3) cold and turbid mid plume between 40-65 m in water depth. The surface plume is composed of silt-sized clastie particles mixed with flocculated biogenic detritus, and appears to originate from either supraglacial discharge by meltwater streams along the coast or water fall of ice cliff. Freshened and turbid mid plume consists exclusively of silt-sized clastic particles, resulting from subglacial discharge beneath the tidewater glacier. The disappearance of the two turbid plumes during the earlier period of measurement seems to be largely due to the breakup of the plumes by upwelling caused by strong easterly wind (> 8 m $sec^{-1}$). Thus, wind coupling over tidal effects regionally plays a major role in dispersal pattern of SPM as well as water exchange in Marian Cove.

• Journal of the Korean Geotechnical Society
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• v.30 no.6
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• pp.23-39
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• 2014

An artificial rainwater reservoir installed in urban areas for recycling rainwater is an eco-friendly facility for reducing storm water effluence. However, in order to recycle the rainwater directly, the artificial rainwater reservoir requires an auxiliary system that can remove non-point source pollutants included in the initial rainfall of urban area. Therefore, the conventional soil filtration technology is adopted to capture non-point source pollutants in an economical and efficient way in the purification system of artificial rainwater reservoirs. In order to satisfy such a demand, clogging characteristics of the sand filter layers with different grain-size distributions were studied with real non-point source pollutants. For this, a series of lab-scale chamber tests were conducted to make a prediction model for removal of non-point source pollutants, based on the clogging theory. The laboratory chamber experiments were carried out by permeating two types of artificially contaminated water through five different types of sand filter layers with different grain-size distributions. The two artificial contaminated waters were made by fine marine-clay particles and real non-point source pollutants collected from motorcar roads of Seoul, Korea. In the laboratory chamber experiments, the concentrations of the artificial contaminated water were measured in terms of TSS (Total Suspended Solids) and COD (Chemical Oxygen Demand) and compared with each other to evaluate the performance of sand filter layers. In addition, the accumulated weight of pollutant particles clogged in the sand filter layers was estimated. This paper suggests a prediction model for removal of non-point source pollutants with theoretical consideration of the physical characteristics such as the grain-size distribution and composition, and change in the hydraulic conductivity and porosity of sand filter layers. The lumped parameter ${\theta}$ related with the clogging property was estimated by comparing the accumulated weight of pollutant particles obtained from the laboratory chamber experiments and calculated from the prediction model based on the clogging theory. It is found that the lumped parameter ${\theta}$ has a significant influence on the amount of the pollutant particles clogged in the pores of sand filter layers. In conclusion, according to the clogging prediction model, a double-sand-filter layer consisting of two separate layers: the upper sand-filter layer with the effective particle size of 1.49 mm and the lower sand-filter layer with the effective particle size of 0.93 mm, is proposed as the optimum system for removing non-point source pollutants in the field-sized artificial rainwater reservoir.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.6
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• pp.374-385
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• 2013

Sediment particle motions have been numerically simulated over a sinusoidal ripple. Turbulent boundary layer flows are generated by Large Eddy Simulation, and the sediment particle motions are simulated using Lagrangian particle tracking method. Two unsteady flow conditions are used in the experiment by employing two different wave amplitudes while keeping other conditions such as wave period same. As expected, the amount of suspended sediment particles is clearly dependent on the wave amplitude as it is increasing with increasing flow intensity. However, it is also observed that the pattern of suspension may be different as well due to the only different condition caused by wave amplitude. Specially, the time of maximum sediment suspension within the wave period is not coincident between the two cases because sediment suspension is strongly affected by the existence of turbulent eddies that are formed at different times over the ripple between the two cases as well. The role of these turbulent eddies on sediment suspension is important as it is also confirmed in previous researches. However, it is also found the time of these eddies' formation may also dependent on the wave amplitude over rippled beds. Therefore, it has been proved that various flow as well as geometric conditions under waves has to be considered in order to have better understanding on the sediment suspension process over ripples. In addition, it is found that high turbulent energy and strong upward flow velocities occur during the time of eddy formation, which also supports high suspension rate at these time steps. The results indicate that the relationship between the structure of flows and bedforms has to be carefully examined in studying sediment suspension at coastal regions.