• Journal of Korean Port Research
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• v.11 no.2
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• pp.203-214
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• 1997

Hydraulic dredgers(Hopper dredger) are the most important piece of equipment in the entire harbor engineering field, and most suitable for the removal of sand and weakly consloidated sediment such as silt. In maintenance dredging, specially confined harbor or congested passage area, Hopper dredger is user most popularly because less obstruction and danger to navigation than other mostly stationary dredgers. Investigation of the physical behave of dredged material disposal in coastal water from the Hopper dredger includes estimations of pattern as well as thickness of material on the bottom. Calculation based on vertical settling and horizontal advection of single particles ignore the effects of bulk properties of the disposed marterial, vertical and horizontal diffusion. and material dilution due to the entrainment of ambient water during descent. This paper focuses on the analysis of dredging and dumping characteristics and the spatial and temporal changes in the dumping fields for the water column and bottom at a hypothetically confined coastal water. This model accounts the behavior of material after release from the hopper dredger. It is shown that the model describes the qualitative feature of prototype dumping process and its response.

• Journal of the korean society of oceanography
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• v.38 no.1
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• pp.1-10
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• 2003

A time-series sediment trap was deployed at a depth of 1034 m in the eastern Bransfield Strait from December 25, 1998 to December 24, 1999. Particle fluxes showed large seasonal variation; about 99% of the annual total mass flux (49 g m/sup -2/) was collected during the austral summer and fall (January-March). Settling particles consisted primarily of biogenic silica, organic carbon, calcium carbonate, and lithogenic material. Biogenic silica and lithogenic material predominated settling particles, comprising 36% and 30% of the total mass flux, respectively, followed by organic carbon, 11% and calcium carbonate, merely 0.6%. The annual organic carbon flux was 5.4 g C m/sup -2/ at 1000 m in the eastern Bransfield Strait, which is greater than the central Strait flux. The relatively lower flux of organic carbon in the central Bransfield Strait may be caused by a stronger surface current in this region. Organic carbon flux estimates in the eastern Bransfield Strait are the highest in the Southern Ocean, perhaps because of the fast sinking of fecal pellets, which leads to less decomposition of organic material in the water column. Approximately 5.8% of the organic carbon produced on the surface in the eastern Bransfield Strait is exported down to 1000 m; this percentage exceeds the maximum EF/sub 1000/ values observed in the Atlantic and Southern Oceans. The eastern Bransfield Strait appears to be the most important site of organic carbon export to the deep sea in the Southern Ocean.

• Journal of Korea Water Resources Association
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• v.48 no.3
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• pp.233-243
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• 2015

The bimodal flocculation of cohesive sediments in water environments describes the aggregation and breakage process developing a bimodal floc size distribution with dense flocculi and floppy flocs. A two class population balance equation (TCPBE) was tested for simulating the bimodal flocculation by a model-data fitting analysis with two sets of experimental data (low and high turbulent flows) from 1-D flocculation-settling column tests. In contrast to the Single-Class PBE (SCPBE), the TCPBE could simulate interactions between flocculi and flocs and the flocculation mechanism by differential settling in a low turbulent flow. Also, the TCPBE could perform the same quality of simulation as the elaborate Multi-Class PBE (MCPBE), with a small number of floc size classes and differential equations. Thus, the TCPBE was proven to be the simplest model that is capable of simulating the bimodal flocculation of cohesive sediments in water environments and water, wastewater treatment systems.

• Journal of the Korean GEO-environmental Society
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• v.10 no.6
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• pp.89-98
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• 2009

In this research, settling tests with marine clays in Korea and extensive literature review were performed to investigate the characteristics of sedimentation and consolidation so that their behaviors during dredging and reclamating could be evaluated. Design parameters related to Yano's method (1985), one of experimental approaches having been used widely in Korea to estimate sedimentation and consolidation, were analyzed and their proprieties were reassessed. For samples from four different sites of south and west coasts in Korea respectively, settling tests with 1m height of columns were carried out, changing initial water content and height of sample in order to evaluate settling and consolidation characteristics of them from analyzing test results. More reliable regression curves than values from literature review were obtained as analyzing test results of estimating coefficient of sedimentation/ consolidation and initial setting velocity with changing initial water content. Relation between height of soil solid and surface height of slurry at the stages of initiation and termination of consolidation was also assessed. Finally, for marine clays of south and west coasts of Korea, ranges and average values of these design parameters were evaluated and typical empirical equations between these design parameters were also proposed. On the other hand, comparisons of characteristics of sedimentation and consolidation between marine clays from south coast and them from west coast were also performed.

• Journal of the Korean GEO-environmental Society
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• v.15 no.6
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• pp.17-29
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• 2014

A remedial investigation was conducted at five military training ranges in northern Gyeonggi province to collect information necessary for the design of on-site treatment facilities for the abatement of explosive compounds release to the environment. These information includes (i) identification of dominant explosive compounds in each range, (ii) discharge/migration routes, and (iii) contaminant distribution in particle size fraction and settling velocity of the soils. The results of investigation showed that TNT and RDX are the major contaminants but the extent of contamination varied depending on the types of military training practices and topography of the site. RDX was also detected in the subsurface soil and in the nearby stream within the training ranges, suggesting release of contaminants to streams. The median concentrations of explosives in the surface soil were less than 20 mg/kg despite several 'hot spots' in which explosives concentrations often exceeds several hundred mg/kg. The average clay contents in the soil of target area was less than 5 % compared to 12 % in the control, indicating loss of smaller particles by surface runoff during rainfall due to lack of vegetative land cover. Analysis of explosive compounds and particle size distribution showed that the amount of explosive compounds in soil particles smaller than 0.075 mm was less than 10 % of the total. Settling column tests also revealed that the quantity of explosive compounds in the liquid phase of the effluent was greater than that in the solid phase. Therefore, pre-treatment of particulate matter in surface runoff of shooting range with a simple settling basin and subsequent effluent treatment with planted constructed wetlands as polishing stage for explosives in the aqueous phase would provide the shooting ranges with a self-standing, sustainable, green solution.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.5
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• pp.87-97
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• 2016

This work proposes a time-shared 10b DAC based on a two-step resistor string to minimize the effective area of a DAC channel for driving each AMOLED display column. The proposed DAC shows a lower effective DAC area per unit column driver and a faster conversion speed than the conventional DACs by employing a time-shared DEMUX and a ROM-based two-step decoder of 6b and 4b in the first and second resistor string. In the second-stage 4b floating resistor string, a simple current source rather than a unity-gain buffer decreases the loading effect and chip area of a DAC channel and eliminates offset mismatch between channels caused by buffer amplifiers. The proposed 1-to-24 DEMUX enables a single DAC channel to drive 24 columns sequentially with a single-phase clock and a 5b binary counter. A 0.9pF sampling capacitor and a small-sized source follower in the input stage of each column-driving buffer amplifier decrease the effect due to channel charge injection and improve the output settling accuracy of the buffer amplifier while using the top-plate sampling scheme in the proposed DAC. The proposed DAC in a $0.18{\mu}m$ CMOS shows a signal settling time of 62.5ns during code transitions from '$000_{16}$' to '$3FF_{16}$'. The prototype DAC occupies a unit channel area of $0.058mm^2$ and an effective unit channel area of $0.002mm^2$ while consuming 6.08mW with analog and digital power supplies of 3.3V and 1.8V, respectively.

• Journal of Korean Society on Water Environment
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• v.25 no.6
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• pp.935-942
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• 2009

During period of the rainy season of spring tide Aug. 2005, the suspended sediment transport rate from Seomjin River increased ten times as high as neap tide of low river discharge. During ebb tide of high terrestrial input, the grain size of suspended particles of both surface and bottom layer of the water column, showed a uni-modal distribution with a dominant peak at coarse fraction, which suggests a characteristic development of floc-sized particles of low mean effective density. On the contrary, the particles supplied toward upstream of Seomjin river from Gwangyang Bay during flood tide showed a bi-modal distribution with a secondary peak at finer fraction, possibly due to the resuspension and the deflocculation associated with the increased shear velocity at near bottom. Break-up of large flocs is also suggested by the increased mean effective density. However, settling velocity was lower during flood tide because of smaller grain size. Thus, net deposition of suspended sediment is expected at within Gwangyang Bay instead of upstream of Seomjin River, even though suspended sediment transport rate at near bottom water was three times higher than that at surface water during flood tide.

• Geomechanics and Engineering
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• v.33 no.3
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• pp.317-326
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• 2023

Accurately measuring the hydraulic conductivity of dredged slurry (HCODS) is a difficult task and usually requires highly developed experimental techniques. To resolve such problem, this paper presents a novel laboratory method, where a double drainage sedimentation test (DDST) is proposed to generate a downward seepage after the end of primary consolidation (EOP). Based on the established stress equilibrium equations, it is figured out that the determination of local hydraulic gradients requires the effective stress distribution to be measured. Accordingly, an additional single drainage sedimentation test (SDST) with the same initial water content is performed in the novel laboratory method, which can be utilized to establish the relationship between effective stress and water content for investigated slurry. Thus, HCODS can be determined via a pair of SDST and DDST, with the water contents after the EOP measured. The corresponding calculation procedure is given in details. With a simply-designed settling column, the hydraulic conductivity tests were performed on three types of dredged slurry. The results demonstrated the effectiveness of the novel laboratory method in measuring HCODS.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.5 no.4
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• pp.296-301
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• 1993

A hydrodynamic solution for the lateral spreading of a river plume which was developed by assuming a Gaussian distribution of density difference between a turbulent jet river plume and ambient salt water is verified by the field data in the Nakdong river plume. Effect of the river plume on the transport of fine-grained suspended sediment at the Nakdong Estuary is also examined. The analysis of fold data showed a reasonably good correspondence with the theoretical solution adopted in this work Therefore, the hydrodynamic solution can be used as a useful tool in dealing with the lateral spreading of a river plume. The density stratification due to the existence of a river plume seems to cause a retarded settling of the suspended sediments in the water column. and thus a farther transport of the fine sediment is expected than in the normal steady flow.

• Asian-Australasian Journal of Animal Sciences
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• v.6 no.4
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• pp.521-526
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• 1993

Two percent of monocalcuim phosphate (MCP) was added to control diet consisted of fish meal (18%), soybean meal (36%) and wheat flour (37%) in order to examine the effects on phosphorus (P) discharge and growth of carp (Cyprinus carpio). Growth trial, during which digestibility measurements were made over 7 days, was conducted for 4 weeks using a recirculated rearing system with a settling column for feces collection. Fishes (initial body weight of about 200 g) were fed five times a day upto satiation with tank controlled at $24-26^{\circ}C$. Fishes fed the diet containing 2% MCP (MCP-2) showed about two-fold improvement on both growth rate and feed utilization, compared to those of fishes fed the control diet; weight gain (129 g vs 62 g), feed conversion ratio (1.20 vs 2.46), protein efficiency ratio (2.09 vs 1.07) and daily growth index (3.70 vs 1.93). However, feed intakes were maintained at the same level (150 g/fish) between the two treatments. Dry matter digestibilities of two diets were relatively low, which were 58 and 60% for respective control and MCP-2 diets due to low digestibility of total carbohydrates. However, the digestibilities of both dietary protein (85%) and lipid (90%) of diets were relatively high. While all the P fed were observed to be discharged from fish fed control diet, the discharge from fish fed the MCP-2 diet was decreased up to less than the half (34.9 g/kg wt. gain) of the control. These present results revealed that the supplementation of dietary P requirement by MCP can not only promote growth performances but also reduce the level of P loading to water which is the primary water pollution indicator.