• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.5
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• pp.16-21
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• 2017

The aim of this study was to utilize ferronickel slag produced in the manufacture of stainless steel as a flowable backfill material for underground use using crushed fine powder. Experimental combinations were made using two components: Case A (sand) and Case B (soil). The optimal mixing ratio of Case A was sand (58.4%), ferronickel slag fine powder (21.6%), cement (1.8%), and water (18.2%). In the case of B, the optimal mixing ratio was determined to be soil (53.0%), ferronickel slag fine powder (20.0%), cement (1.7%), and water (25.3%). The uniaxial compressive strength of case A, which is a mixture of ordinary sand and ferronickel slag powder, was relatively larger than that of case B using soil. In addition, the strength of the specimen increased with increasing curing time. The uniaxial compressive strength tended to increase with increasing curing time. In addition, the unconfined compression strength of the fluid backfill material using common sand as the main material was relatively larger than that of the mixed material using soil as the main material. In case A, the uniaxial compressive strength ranged from 0.17-0.33 MPa, 0.21-0.39 MPa, and 0.19-0.40 MPa, respectively, at curing times of 7, 14, and 28 days. From the experimental results, it was concluded that the ratio of FNS powder and cement mixture was the most appropriate for Case A3. Case B, which used soil as the main material, showed a similar tendency to Case A. As a result of the dissolution test for evaluating the environmental harm of the FNS fine powder, there was no dissolution of substances harmful to the environment.

• Journal of Korea Foundry Society
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• v.7 no.4
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• pp.366-379
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• 1987

The influences of some factors on the variation of compression strength of $CO_2$ process were investigated with an attention given to use of high $SiO_2\;/Na_2O$ silicate, addition of organics and gassing operation. 1) Higher ratio binder offers faster rates of hardening with lower $CO_2$ consumption requiring more concentration for a good strength development. A mixture containing 4 percent of 2.7:1 ratio silicate produces the strength above $8kg\;/\;cm^2$ after 80 seconds gassing, but 5% and 6% respectively of 3.0:1 and3.3:1 ratio silicate are necessary to achieve equivalent levels of strength. 2) The correct water content in sand mixtures containing higher ratio silicates is necessary for the better strength properties to be obtained. The addition of 1% water to the sand mixtures bonded with 5%,3:1 ratio and 6%,3.3:1 ratio silicates maintains near-maximum strength on extended gassing. 3) When higher ratio silicates with 3:1 and 3.3:1 ratios are used,the addition of organic additives such as oil, sucrose and polyol results in considerable changes in strength. The presence of 1.0 to 1.5 percent of polyol produces a noticiable improvement 4) Gas diluted with air raises the efficiency of gas utilization. When gas contains 50 percent $CO_2$, the efficience is significantly increased with the best strength in the silicates having high ratios of 3:1 and 3.3:1. 5) The strength of molds is liable to change on storage with the reduction in water content. The magnitude of the strength change is determinded with the mole ratio. The presence of polyol in the mixture with 3.3:1 ratio silicate has a pronounced effect on maintaining the gassed strength.

• 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.29 no.5
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• pp.269-277
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• 2017

Recently, a submerged breakwater has been installing to prevent the erosion of shoreline everywhere. Artificially submerged breakwater is made to minimize the loss of nourishment sand beach erosion. For this reason, it has been indiscriminately constructed submerged breakwater that is planned in the country throughout. However, maintenance purposes to keep the shoreline of the beach is a method that is quite a few problems. There are also disadvantages such as expensive construction costs, ocean space utilization, water pollution and shoreline modification. In addition, person of utilizing the space of the ocean leisure does not like that because of the disconnection of ocean space. The beaches such as Gwanganri are artificially supplying nourishment sand to maintain the beach. The flexible construction method refers to a structure that is installed as a flexible material instead of submerged breakwater to prevent the loss of nourishment sand. In order to develop a new method to mitigate shoreline erosion, this study was carried out a hydraulic model experiment by installing a cell group as an example of the flexible method. Namely, in order to prevent the loss of nourishment sand, we decided to develop a new method that can mitigate the degree of beaches erosion by using cell group instead of submerged breakwater. In the two dimensional fixed hydraulic experiment, was carried out the effect reducing of wave height and the rate of low reflection due to the installation of the cell group. In movable bed experiment, the capture rate of the nourishment sand and the erosion prevention rate of the nourishment sand was performed for stability of shoreline. Therefore, according to the results of the hydraulic tests, it was possible to maintain the stable beaches due to installing the cell group on the erosion beaches, due to the effect of reducing wave height, the low reflection, the erosion prevention rate of nourishment sand, the high capture rate of nourishment sand.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.29 no.1
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• pp.14-27
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• 2024

Unlike the shelf sand ridges moribund in motion, nearshore sand ridges are highly mobile, sensitive to changes in ocean environments, thereby becoming of particular interest with respect to morphological changes. About 5 km off the Daesan port, the Jangan Sand Ridge has been undergoing severe subsea morphological change over the past two decades. Understanding the nature of sand ridges is critical to elucidate the causes of morphological changes. In this context, this study aims at understanding the characteristics and distribution patterns of surface sediments of the ridge and its vicinity. For this purpose, 227 sediment samples were acquired using a grab-sampler, the grain sizes being analysed by the sieve-pipette method. In addition, comparison of grain sizes in sediments between 1997 and 2021 was made in order to investigate the 25-years change in sediment composition. Surface sediments along the ridge axis are fine to medium sands with 2-3 phi in mean grain size, whereas, in the trough of ridge, the sediments are composed of gravels and muddy sandy gravels with mean sizes of -2 to -6 phi. Sediments in the crest of the ridge are well-sorted with normal distribution, on the other hand, the basal sediments are poorly-sorted and positively skewed. Along the ridge crest, the sediments are negatively skewed. From 1997 to 2021, the ridge sediments became largely coarser about 0.5 phi. Such coarsening trend in mean grain size can be explained either by elimination of fine sediments during high waves in winter or elimination of fines suspended during sand mining activities in the past. Spatial distribution pattern of surface sediments shows that ca. 30 m thick of the sand ridge itself overlies the thin relict gravels. The strong asymmetry of sand ridge, the exposure of ridge base, and reworked gravel lags suggest that Jangan sand ridge is probably sediment-deficit and hence erosive in nature at present.

• Advances in concrete construction
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• v.6 no.4
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• pp.375-386
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• 2018

This experimental work aims at developing and investigating a lightened concrete by the addition of treated straws. The used formulation is based on that of an ordinary concrete which is composed of sand and gravel as the main aggregates. The properties of the straws are improved by using one of two treatments before their use: the hot water and bitumen. Henceforth, the main objective of this study is to assess the mechanical characteristics of different formulations with different compositions and treatments on straws. The obtained results have shown that the addition of straws improves its lightness property. However, it decreases the compressive and flexural strengths as well as decreases the modulus of elasticity and increases the dimensional variations. Set into comparison to the concrete with untreated straws, the treatment of straws by hot water or by bitumen improves most of the characteristics.

• Korean Journal of Food Science and Technology
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• v.34 no.2
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• pp.186-193
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• 2002

This study was conducted to enhance the protein quality of wheat flour extrudates with the addition of fish sauce by-products and dried biji. The experimental design was used to determine the optimum ratio of each ingredient. The compositional and functional properties of test extrudate were measured, and these values were applied to the mathematical models. A canonical form and trace plot showed that the influence of each ingredient on the mixture final product. Protein content of extrudate was increased by the addition of the dried biji, and bending failure stress of extrudate became hardened due to interaction effects between dried biji and pacific sand lance sauce by-product. Also, the addition of dried biji decreased ash and salt contents. An optimum formulation was obtained as 15.83 : 44.17 : 40% with numerical and 15.74 : 44.26 : 26.40% with graphical method (pacific sand lance sauce by-product : dried biji : wheat flour). Based on the growth performance, feed conversion efficiency was slightly lower than control group, but the protein content in feed extrudate increased to a large extent compared to that mixed with wet biji.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.4
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• pp.438-446
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• 2006

A lab-scale batch test was conducted to develop capping materials to reduce the sediment phosphorus in the stagnant water zone of Gyeongancheon in Paldang Lake. The mean grain size(Mz) of sediment in the investigated area was 7.7 ${\phi}$, which is very fine, and the contents of organic carbon($C_{org}$) was 2.4%, which is very high. For the phosphorous release experiment to select the optimal capping material, sand layer, powder-gypsum($CaSO_4{\cdot}2H_2O$), granule-gypsum, complex layer(gypsum+sand) and the control were compared and evaluated in the 150 L reactor for 45 days. In case of the capping with the sand, it was found that the phosphorous from the sediment could be reduced by around 50%. However, it was found that this caused the reduction of the dissolved oxygen in the water column(by less than 3 mg/L) due to the resuspension of sediment and the organic matter decomposition that comes from the generation of $CH_4$ gas in the 1 cm of the sand layer. Therefore, it is likely that the sand layer has to be thickener in case of the sand capping. Powder-gypsum and granule-Gypsum reduced phosphorous release by more than 80%. However, the concentration of ${SO_4}^{2-}$ in the water column increased, making it difficult to apply it to the drinking water protection zone. We developed Fe-Gypsum and $SiO_2$-gypsum materials to reduce the solubility of ${SO_4}^{2-}$. Powder-Gypsum creates the interception film that does not have any aperture on the sediment layer when it is combined with the water. However phosphorous release caused by the generation of $CH_4$ gas may happen at a time when the gypsum layer has the crack. Capping through the complex layer(granule-Gypsum+sand(1 cm)) found to be suitable for the drinking water protection zone because it was effective to prevent phosphorus release. Moreover, this leads to the lower solubility from the concentration of ${SO_4}^{2-}$ into the water column than the powder-Gypsum and granule-Gypsum. The addition of gypsum($CaSO_4{\cdot}2H_2O$) into the sediment can reduce the progress of methanogensis because fast early diagenesis and sufficient supply of ${SO_4}^{2-}$ to the sediment, stimulate the SRB(sulfate reducing bacteria) highly.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.11
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• pp.1180-1185
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• 2006

Lab-scale batch experiments using several 25-L transparent acrylic reactors were conducted to develop optimum capping materials that can reduce phosphorus released from polluted sediments. The sediment used in the experiment was very fine clay(8.8 $\Phi$ in mean grain size), and organic carbon($C_{org}$) content was as high as 2%. Four kinds of batches with different capping materials Brucite($Mg(OH)_2$), Sea sand($SiO_2$), Granular-gypsum($CaSO_4{\cdot}2H_2O$), Double layer(brucite+sand), and one control batch were operated for 30 days. Phosphorus fluxes released from bottom sediments in the control batch were estimated to be 14.6 $mg{\cdot}m^{-2}{\cdot}d^{-1}$, while 9.5 $mg{\cdot}m^{-2}{\cdot}d^{-1}$, 5.2 $mg{\cdot}m^{-2}{\cdot}d^{-1}$, 4.2 $mg{\cdot}m^{-2}{\cdot}d^{-1}$, and 3.1 $mg{\cdot}m^{-2}{\cdot}d^{-1}$ in the batch capped with Sea sand, Granular-gypsum, Double layer, and Brucite, respectively. The results obtained from lab-scale batch experiments show that there were 70% reduction of phosphorus for some materials such as Brucite, Double layer(brucite+sand), and whereas sea sand only about 35%. The pH range of surface sediment to which Brucite was applied showed about $8.0{\sim}9.5$ in the weak alkaline state. This effect can prevent liberation of $H_2O$. The addition of gypsum into the sediment can reduce the progress of methanogenesis because of fast early diagenesis and sufficient supply of $SO_4^{2-}$ to the sediments, stimulate the SRB highly. Therefore, the application of Brucite and Gypsum can reduce phosphorus release from the sediment as a result of formation of $Mg_5(OH)(PO_4)_3$, pyrite($FeS_x$), and apatite-mineral.

• Journal of the Korean Ceramic Society
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• v.14 no.2
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• pp.88-94
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• 1977

Zircon sand of two different particle distribution with 2 percent of ground pyrophyllite were adoted to prepare the dense specimens of the stopper nozzle for the tundish. The molding pressure of $600kg/cm^2$ brought about the superior properties to those obtained t the pressure of $300kg/cm^2$, and as the firing temperatures were increased from $1, 350^{\circ}C$ to $1, 600^{\circ}C$, the better characteristics resulted. The addition of 2 percent $MgCr_2O_4$ to zircon pyrophyllite batch was more effective in corrosion-resistance to the blast furnace-slag.