• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.173-178
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• 2016

When a ballast track of a high-speed train is constructed on a bridge, the displacement of the bridge decks can occur because they are not fixed to the rails. Moreover, relative displacements occur between the bridge and rails caused by temperature changes and external loads. The current longitudinal resistance criteria (UIC Code 774-3, KR C-08080) on ballast tracks with continuous welded rails (CWRs) do not take into account the longitudinal movement of the bridge and the frictional force between the ballast and slabs. In addition, the magnitude of the longitudinal resistance, k, is calculated somewhat conservatively and, (therefore?) it acts as an unfavorable element in the design of long span and continuous railway bridges. Thus, in order to replicate the actual behavior more effectively, the longitudinal resistance of CWRs should take into account the additional rigidity between the slab and track. In this study, the longitudinal resistances of the ballasted track on the bridge were analyzed by carrying out an experimental study with a test setup designed to simulate the deck and bed track. In the test results, the maximum longitudinal resistances of the tests were similar to the resistances of the current codes, however, the measured longitudinal stiffness designed to limit the displacement of the tests were much smaller in comparison with the longitudinal stiffness on the codes.

• The Korean Journal of Petroleum Geology
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• v.2 no.2 s.3
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• pp.91-99
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• 1994

In the Heunghae area, genetic relationships among sedimentary facies, lithology, stratigraphy and diagenetic mineral facies of the Yeonil Group, are discussed. Conglomerate and sandstone of lower to middle parts of the Yeonil Group contain considerable amounts of volcaniclastic sediments, which were derived from the Tertiary volcanics exposed in the western margins of the sedimentary basin. A new stratigraphic division of the Yeonil Group into the Chunbuk and Pohang Formations is proposed on the basis of sedimentary facies, lithologic characteristics including volcaniclastic feature, and the presence of a key bed of siliceous mudstone overlying the Chunbuk Formation. Diagenetic mineral facies largely depend on the lithology and composition of sediments. Heulandite, smectite, calcite, and opal-CT are commonly found as diagenetic minerals in the Yeonil Group. Among these authigenic minerals, heulandite occurs as the coarse- grained main cement in conglomerates and sandstones of the Chunbuk Formation. Formation of the zeolite cement is favored by partial volcaniclastic lithology of the Chunbuk Formation. Smectite composition and diagenetic mineral facies such as heulandite and opal-CT may reflect that the Yeoil Group has undergone a shallow rial temperature ranging $40{\~}60^{\circ}C$.

• 한국해양학회지
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• v.7 no.1
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• pp.1-14
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• 1972

Seasonal changes in nutrients and suspended organic particulates were measured in the estuary of Nak-dong River in relation to the black laver bed. Monthly measurements of water temperature, pH, dissolved oxygen, nutrients ( $NH_4$-N, $NO_2$-N, $NO_3$\-N, $PO_4$-P and $SiO_2$-Si) and organic suspended particulates (organic carbon and nitrogen) were determined at five stations from February through December, 1970. PH varied 7.6-8.4 with an average of 8.0, and percent saturation of dissolved oxygen were 71-147% with an average of 100.8%. Studies gave evidence that Nak-dong River estuary is strongly enriched with nutrients. Concentrations of nutrients were: 0.13-12.54 ${\mu}g$-atoms/${\iota}$ (averaging 1.63 ${\mu}g$-atoms/${\iota}$) for $NH_4-N$, 0.12-2.09 ${\mu}g$-atoms/${\iota}$ (averaging 0.71 ${\mu}g$-atoms/${\iota}$) for $NO_2-N$, 3.46-56.79 ${\mu}g$-atoms/${\iota}$ (averaging 21.54 ${\mu}g$-atoms/${\iota}$) for $NO_3$-N, 4.04-57.90 ${\mu}g$-atoms/${\iota}$ (averaging 23.79 ${\mu}g$-atoms/${\iota}$) for total soluble nitrogen, 0.18-5.05 ${\mu}g$-atoms/${\iota}$ (averaging 0.96 ${\mu}g$-atoms/${\iota}$) for $PO_4$-P, and 18.33-133.29 ${\mu}g$-atoms/${\iota}$ (averaging 71.57 ${\mu}g$-atoms/${\iota}$) for $SiO_2$-Si, respectively. These nutrient levels were considerably higher compare with other productive laver beds of Wan do and Pyung-il Do in Korea or Ise Bay in Japan. Concentrations of suspended organic particulates varied 55-648 ${\mu}g/{\iota}$ (averaging 392 ${\mu}g/{\iota}$) with organic carbon, 30-155 ${\mu}g/{\iota}$ (averaging 92 ${\mu}g/{\iota}$) with organic nitrogen, and its carbon-nitrogen ratios were varied within 1.5-8.4 with an average of 4.6.

• Clean Technology
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• v.27 no.4
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• pp.325-331
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• 2021

In this study, bio-carbons were produced by activation process from unused biomass (Grade 3 wood pellet and spent coffee grounds) to determine the removal performance of formaldehyde and acetaldehyde. The activation experiments were conducted in a fixed bed reactor using CO₂ as an activation agent. The temperature of the activation reactor and input of CO₂ were 900 ℃ and 1 L min^-1 for all the experiments. The maximum BET surface area of about 788 m² g^-1 was obtained for bio-carbon produced from Grade 1 wood pellet, whereas about 544 m² g^-1 was achieved with bio-carbon produced from spent coffee grounds. In all the experiments, the bio-carbons produced were mainly found to have micro-porous nature. A lower ash amount in raw material was favored for the high surface area of bio-carbons. In the removal test of formaldehyde and acetaldehyde, the bio-carbon produced from spent coffee grounds showed excellent adsorption performance compared with woody biomass (Grade 1 wood pellet and Grade 3 wood pellet). In addition, the comparative experiment of commercial impregnated activated carbon and bio-carbon produced from spent coffee grounds was conducted. In terms of formaldehyde removal performance, the commercial impregnated bio-carbon was excellent, while bio-carbon produced from spent coffee grounds was excellent in acetaldehyde removal.

• Applied Chemistry for Engineering
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• v.22 no.4
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• pp.429-432
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• 2011

The feasibility of applications of the char obtained from a gasification process of municipal-waste refuse derived fuel (RDF) as an auxiliary fuel was evaluated by combustion experiments. The higher heating value of the RDF char was 3000~4000 kcal/kg and its chlorine content was below the standard requirement demonstrating its potential as an auxiliary fuel. In the combustion exhaust gas, the maximum $NO_x$ and $SO_2$ concentrations were 240 ppm and 223 ppm, respectively. If an aftertreatment is applied, it is possible to control their concentrations low enough to meet the air pollutant emission standard. The HCl concentration was relatively high indicating that a care should be taken for HCl emission from the combustion of RDF. Based on the temperature distribution within the reactor, the concentration change of $O_2$ and $CO_2$, and the amount and the loss on ignition of solid residue, it was inferred that the combustion reaction was the most reliable when the excess air ratio of 1.3 was used.

• FLOWER RESEARCH JOURNAL
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• v.26 no.4
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• pp.187-194
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• 2018

This study was conducted to investigate the facilities, cultivation, postharvest management, and distribution status of 27 cut chrysanthemum farms in Korea. The 60% of farms have cultivated the cut chrysanthemum using soil fertigation system in the PE plastic house. In Jeonnam and Busan provinces, Standard type of chrysanthemum was cultivated mainly than spray type of chrysanthemumJeoas. Most farms have been producing the rooted cuttings by plug system using cuttings self-propagated or purchased from the company, but farms in Jeonnam have been planting cuttings directly on cultivation bed. And the 66.6% of cut chrysanthemum farms have been pretreating with dipping in hot water or tap water after harvesting. Precooling was not performed on 70.4% of the farms, and precooling farms have been mainly conducted at temperature of $2-4^{\circ}C$. After harvesting, 70.4% of the farms stored the cut flowers at $2-4^{\circ}C$ for more than 48 hours to control the distribution volume. Cut chrysanthemum was graded mainly by individuals before distribution, and some export farmers have been conducting the cooperative grading. In distribution, all farms have distributed the cut flowers to the domestic markets, and 44.4% of these farms have been also exporting. The 63.0% of farms distributed to domestic market have been trading with flower auction sites.

• Korean Journal of Environment and Ecology
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• v.36 no.4
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• pp.381-389
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• 2022

This study investigated the ecological characteristics of Microphysogobio yaluensis at Dugye Stream of Geum River basin from January to December 2021. The river bed structure of this species' habitat was rich in pebbles and gravel. The water depth ranged from 12 to 85 cm with an average of 23 cm, which was shallow. The stream velocity was rapid at 1.03±0.34(0.72-1.47) m/sec. The ratio of females to males was 1:0.86. The age according to the total length-frequency distribution as of summer (June, July) indicated that the group with less than 50 mm (30.4-49 mm) in total length was one year old, the group with 50-69 mm was two years old, and the group over 70-92 mm was three years old. Both male and female fish sexually matured at 50 mm long and two years old in June and July. The spawning season was from July to August, and the water temperature was between 25.8℃ and 28.2℃ during the period. The prosperous spawning season was July. The matured eggs were yellowish and spherical with a mean diameter of 0.52±0.16 (0.33-0.77) mm, and the average number of eggs found in the ovaries of mature female fish was 2,593 (1,343-4,672). As for the food of M. yaluensis, only attached algae, which grow by attaching to stones and gravel of the stream rapids, were identified. The feeding habit of M. yaluensis was reported to be herbivorous, ingesting Cyanophyta, Chlorophyta and Bacillariophya. Also, the species belonging to Bacillariophya and Chlorophyta were abundant in Dugye Stream.

• Clean Technology
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• v.15 no.4
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• pp.258-264
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• 2009

Thermodynamic measurements were performed to show the possibility of recovering $CO_2$ from fuel gas (the mixture of $CO_2$ and $H_2$) by forming gas hydrates with water where water was dispersed in the pores of silica gel particles having nominal 100 nm of pore diameter. The hydrate-phase equilibria for the ternary $CO_2+H_2$+water in pores were measured and $CO_2$ concentrations in vapor and hydrate phase were determined under the hydrate-vapor two phase region at constant 274.15 K. It was shown that the inhibition effect appeared due to silica gel pores, and the corresponding equilibrium dissociation pressures became higher than those of bulk water hydrates at a specific temperature. In addition, direct measurement of $CO_2$ content in the hydrate phase showed that the retrieved gas from the dissociation of hydrate contained more than 95 mol% of $CO_2$ when 42 mol% of $CO_2$ and balanced Hz mixture was applied. Compared with data obtained in case of bulk water hydrates, which showed just 83 mol% of $CO_2$ where 2-stage hydrate slurry reactor was intended to utilize this property, the hydrate formation in porous silica gel has enhanced the feasibility of $CO_2$ separation process. Hydrate formation as not for slurry but solid particle makes it possible to used fixed bed reactor, and can be a merit of well-understood technologies in the industrial field.

• Korean Journal of Ecology and Environment
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• v.56 no.4
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• pp.375-383
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• 2023

To determine the cause of the population decline in Gobiobotia naktongensis, substrate preference and burying behaviour were investigated in this study. In general, the species was shown to prefer a substrate size of 1 mm or less, depending on the flow. In addition, the burying depth varied according to the size of the fish and increased with a decrease in water temperature. Our findings showed that the main cause of the population reduction was the physical changes in the substrate structure due to the dams or barrages construction. Notably, the accumulation of silt and mud in the substrate upon the formation of an upstream lentic water region for structural construction and bed armouring caused by scouring and reduced downstream inflow of fine sediment were deterministic in the fish habitat changes, causing problems in burying. As sand substrate structure is critical for the survival and inhabitation of psammophilous species, efficient strategies should be developed with proper habitat management to reduce the anthropogenic damage

• Applied Chemistry for Engineering
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• v.34 no.5
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• pp.507-514
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• 2023

The selective catalytic reduction (SCR) of nitrogen oxides (NO_x) was investigated in a catalyst (Ag/γ-Al₂O₃) packed dielectric barrier discharge plasma reactor. The intermittent generation of plasma in the catalyst bed partially oxidized the hydrocarbon reductant for NO_x removal to several aldehydes. Compared to using the catalyst alone, higher NO_x conversion was observed with the intermittent generation of plasma due to the formation of highly reductive aldehydes. Under the same operating conditions (temperature: 250 ℃; C/N: 8), the NO_x reduction efficiencies were 47.5%, 92%, and 96% for n-heptane, propionaldehyde, and butyraldehyde, respectively, demonstrating the high NO_x reduction capability of aldehydes. To determine the optimal condition for intermittent plasma generation, the high voltage on/off cycle was adjusted from 0.5 to 3 min. The NO_x reduction performance was compared between continuous and intermittent plasma generation on the same energy density basis. The highest NO_x reduction efficiency was achieved at 2-min high voltage on/off intervals. The reason that the intermittent plasma discharge exhibited higher NO_x reduction efficiency even at the same energy density, compared to the continuous plasma generation case, is that the intermediate products, such as aldehydes generated from hydrocarbon, were more efficiently utilized for the reduction of nitrogen oxides.