• Journal of The Korean Society of Agricultural Engineers
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• v.57 no.2
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• pp.37-45
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• 2015

Typically, water quality sampling takes place intermittently since sample collection and following analysis requires substantial cost and efforts. Therefore regression models (or rating curves) are often used to interpolate water quality data. LOADEST has nine regression models to estimate water quality data, and one regression model needs to be selected automatically or manually. The nine regression models in LOADEST and auto-selection by LOADEST were evaluated in the study. Suspended solids data were collected from forty-nine stations from the Water Information System of the Ministry of Environment. Suspended solid data from each station was divided into two groups for calibration and validation. Nash-Stucliffe efficiency (NSE) and coefficient of determination ($R_2$) were used to evaluate estimated suspended solid loads. The regression models numbered 1 and 3 in LOADEST provided higher NSE and $R_2$, compared to the other regression models. The regression modes numbered 2, 5, 6, 8, and 9 in LOADEST provided low NSE. In addition, the regression model selected by LOADEST did not necessarily provide better suspended solid estimations than the other regression models did.

• Journal of Environmental Health Sciences
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• v.38 no.4
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• pp.300-310
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• 2012

Objectives: Indoor air quality problems in public spaces have recently become a very important issue in South Korea, because many spend a long time every day indoors. In this study, an extensive literature review was performed on the subject of suspended bacteria and fungi in public facilities. The objective of this study was to evaluate the extent and types of suspended bacteria and fungi in indoor air in South Korea. This study will provide direction to the research in the field of indoor air. Methods: Article reviews was conducted using a search engine and the following keywords; 'bacteria', 'total suspended bacteria', 'fungi' and 'indoor air' from published articles since 2000. Results: Most of the places of measurement were schools, kindergartens, childcare centers and general hospitals. The highest concentrations of total suspended bacteria and fungi were found in schools and kindergartens. Some public facilities exceeded the standard of 800 CFU/$m^3$. There were few studies on other suspended bacteria: Gram Negative Bacteria, Staphylococcus and Klebsiella pneumoniae. Conclusions: It appears that more studies with intensive controls are needed. It was found that schools and kindergartens were most susceptible to microbial indoor air pollution. These results may be able to suggest an indoor standard for suspended bacteria and fungi in South Korea.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.24 no.1
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• pp.31-38
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• 1991

Suspended sediment budget in Gwangyang Bay was investigated using the data of suspended sediment concentration and vertical distribution of tidal currents at the mouth of the bay in the Yeosu Sound (Yeosu Haeman) . At the mouth of the bay suspended sediment concentration shows much higher value of approximately 17.80mg/l on the average near the bottom than the concentration near the surface where the average is 4.7mg/l. Tidal currents also show an asymmetry in magnitude between flood and ebb. Near the surface ebb is stronger than flood, while flood is stronger than ebb near the bottom. Due to the higher concentration and stronger flood current near the bottom, transport of suspended sediment near the bottom plays a major role to the sediment budget in the bay, and the bay is in net-depositional environment. The western part of the bay seems to gain the suspended sediment of approximately $5.66\times10^8g/day$, which corresponds to a sedimentation rate of about 1.15m/1,000years.

• Fisheries and Aquatic Sciences
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• v.13 no.2
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• pp.150-156
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• 2010

The separation performance of a low-pressure hydrocyclone (LPH) was evaluated for suspended-solids removal in a recirculating aquaculture system (RAS). The dimensions of the LPH were 335 mm cylinder diameter, 575 mm cylinder height, 60 mm overflow diameter, 50 mm underflow diameter, and $68^{\circ}$ cone angle. The inflow rate varied (400, 600, 800, and 1,000 mL $s^{-1}$) with 25%, 25%, 20%, and 10% of bypass ($R_f$), respectively. The maximum total separation efficiency (Et) and reduced separation efficiency (E't) for suspended solids from the effluent of the second settlement tank (before biofiltration) were 58.9% and 45.2%, respectively, at an inflow rate of 600 mL $s^{-1}$ and 25% of $R_f$. The maximum Et and E't for suspended solids from the water supply channel (after biofiltration) were 24.4% and 16%, respectively, at an inflow rate of 1,000 mL $s^{-1}$ and 10% of $R_f$. The maximum grade efficiency (Ei) was 51.6% for a 300 ${\mu}m$ particle size at an inflow rate of 600 mL $s^{-1}$ with 23% of $R_f$. The maximum reduced grade efficiency (E'i) was 37.6% for a 300 ${\mu}m$ particle size at an inflow rate of 1,000 mL $s^{-1}$ with 11% of $R_f$. The results indicate that the separation performance of the LPH for suspended solids removal was size selective and that maximum removal occurred at particle sizes ranging from 300 to 500 ${\mu}m$.

• Structural Engineering and Mechanics
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• v.22 no.2
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• pp.197-222
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• 2006

In this paper, the non-linear time-dependent closed-form, discrete and combined solutions for the post-elastic response of a geometrically and physically non-linear suspended cable to a uniformly distributed load considering the creep effects, are presented. The time-dependent closed-form method for the particularly straightforward determination of a vertical uniformly distributed load applied over the entire span of a cable and the accompanying deflection at time t corresponding to the elastic limit and/or to the elastic region, post-elastic and failure range of a suspended cable is described. The actual stress-strain properties of steel cables as well as creep of cables and their rheological characteristics are considered. In this solution, applying the Irvine's theory, the direct use of experimental data, such as the actual stress-strain and strain-time properties of high-strength steel cables, is implemented. The results obtained by the closed-form solution, i.e., a load corresponding to the elastic limit, post-elastic and failure range at time t, enable the direct use in the discrete non-linear time-dependent post-elastic analysis of a suspended cable. This initial value of load is necessary for the non-linear time-dependent elastic and post-elastic discrete analysis, concerning incremental and iterative solution strategies with tangent modulus concept. At each time step, the suspended cable is analyzed under the applied load and imposed deformations originated due to creep. This combined time-dependent approach, based on the closed-form solution and on the FEM, allows a prediction of the required load that occurs in the post-elastic region. The application of the described methods and derived equations is illustrated by numerical examples.

• Journal of Korean Society on Water Environment
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• v.27 no.4
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• pp.542-550
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• 2011

Changes of suspended sediment concentration in the Seomjin river estuary located in south sea of the Korea peninsula were investigated during the spring tide in autumn (i.e. 25 hours in October) 2000 and winter (i.e. 25 hours in February) 2001. The changes of temperature and salinity during the spring tide in October 2000 showed larger variations than the those in February 2001. During the spring tide in October 2000, currents at bottom layer were observed to be stronger than during the spring tide in February 2001, showing that both of the two periods had ebb currents-predominant tide asymmetries. The suspended sediment concentrations in October 2000 were larger than the those in February 2001. At the time of the maximum of tide currents or after about one hour of the maximum during the autumn months, the suspended sediment turbidity was observed to be maximum. Another observation station at Hadong upstream from the Seomjin river estuary showed about one hour delay in tide phase, Thereby, the suspended sediment concentration showed high turbidity after two hours at bottom and three hours at surface layer, in particular, in October 2000. This results can be explained by the facts that river discharge increased significantly after the summer rainy season, causing also increase of erosion processes by strong current velocity at bottom layer.

• The Journal of the Acoustical Society of Korea
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• v.32 no.1
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• pp.14-21
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• 2013

The erosion, suspension, and transport of sediment frequently occur in the coastal waters and estuarine. These processes often generate the so-called fluid mud layer, which is defined as a high-concentration aqueous suspension of fine grained sediment (> 10 g/l), consisting mainly of silt and clay-size particles. Therefore the high-resolution ultrasound is mostly used to detect or monitor the fluid mud layer. Because the sound attenuation tends to increase rapidly with the suspended sediment concentration, it is necessary to consider the accurate attenuation correction to estimate the backscattering strengths from the suspended sediment layers. In this paper, the volume backscattering strengths with various suspended sediment concentrations were measured using 5-MHz ultrasound signal in a small-scale water tank. The sound attenuation due to the viscosity and scattering from suspended sediment particles was predicted by the Richard's model and applied to the sonar equation to estimate the volume backscattering strengths from the suspended sediment concentrations. For the case that the additional attenuation was not considered, the volume backscattering strengths increased to the concentration of 20 g/l, and over this point, the backscattering strengths were roughly constant. However, for the case that the attenuation due to the suspended sediment concentration was considered, the backscattering strengths increased with the concentration.

• Journal of Environmental Science International
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• v.19 no.11
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• pp.1423-1436
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• 2010

The effects of meteorological and reclaiming conditions on the reduction of suspended particles are investigated using a computational fluid dynamics (CFD) model with the k-$\varepsilon$ turbulence closure scheme based on the renormalization group (RNG) theory. Twelve numerical experiments with different meteorological and reclaiming conditions are performed. For identifying the meteorological characteristics of the target area and providing the inflow conditions of the CFD model, the observed data from the automatic weather station (AWS) near the target area is analyzed. Complicated flow patterns such as flow distortion, horse-shoe vortex, recirculation zone, and channeling flow appeared due to the topography and buildings in the domain. Specially, the flow characteristics around the reclamation area are affected by the reclaiming height, reclaiming size and windbreak height. Reclaiming height affected the wind speed above the reclaiming area. Windbreak induces more complicated flow patterns around the reclaiming area as well as within the reclaiming area. In front of the windbreak, flow is distorted as it impinges on the windbreak. As a result, upward flow is generated there. Behind the windbreak, a secondary circulation, so called, a recirculation zone is generated and flow is reattached at the end of the recirculation zone (reattachment point). At the lower part of the recirculation zone, there is a reverse flow toward the windbreak. Flow passing to the reattachment point starts to be recovered. Total amounts of suspended particles are calculated using the frictional and threshold frictional velocities, erosion potential function, and the number of surface disturbance. In the case of a 10 m-reclaiming and northerly wind, the amount of suspended particles is largest. In the presence of 5 m windbreak, the friction velocity above the reclaiming area is largely reduced. As a result, the total amount of the suspended particles largely decreases, compared to the case with the same reclaiming and meteorological conditions except for the windbreak The calculated suspended particle amounts are used as the emission rate of the dispersion model simulations and the dispersion characteristics of the suspended particles are analyzed.

• Journal of the Korean GEO-environmental Society
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• v.11 no.10
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• pp.41-48
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• 2010

In this study, grain size distribution of dredged soil and suspended solid distribution of supernatant in containment area were measured and compared with design prediction for suitability evaluation on prediction of suspended solid concentration of supernatant in conventional design of containment area. In addition to that, relationship were also analyzed between current velocity and suspended solid concentration of supernatant. Evaluation results show a relatively good agreement between field measurement and design prediction. On contrast, field measurement and design prediction show a quite different value each other in the early stage of dredging or at a point that current velocity increases. It is believed that this is due to that conventional design method of containment area does not account for ponding depth and current velocity which change sensitively with dredging period. Since current velocity and distribution of suspended solid concentration measured simultaneously show a similar trend, it is observed that there exists a close relationship between current velocity and distribution of suspended solid concentration. Therefore, a new design method for containment area, which can consider sedimentation of suspended solid that changes with interface height of dredged soil, ponding depth, current speed of supernatant, is necessary in order to predict the situation change of containment area more precisely.

• Korean Journal of Ichthyology
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• v.34 no.4
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• pp.253-261
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• 2022

After exposing Olive flounder and Korean rockfish to the concentration ranges of control (0 mg/L), 100 mg/L, 250 mg/L, 500 mg/L, and 1,000 mg/L, to investigate the physiological properties of suspended load on fish AST/GOT, ALT/GPT, ALP and cortisol were analyzed. As a result of the analysis, the AST/GOT, ALT/GPT, ALP and cortisol values were higher in the suspended load concentration section than in the control group. After artificial infection with S. parauberis for Olive flounder and V. harveyi for Korean rockfish exposed to suspended load, the survival rate was higher in the control group than in the suspended load concentration section. These results are related to the previously study results of suspended load that adversely affect fish, suggesting that suspended load affects the health of fish.