• Korean Journal of Materials Research
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• v.10 no.1
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• pp.15-20
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• 2000

The hydrogen-storage properties of a mechanically-alloyed Mg-18wt.%Ni mixture were investigated. Among the mixtures mechanically alloyed for 1h, 3h, and 6h, the mixture mechanically alloyed for 6h(MA 6h sample) shows the best properties of activation, hydriding, and dehydriding. The $Mg_2Ni$ phase forms in the mechanically-alloyed Mg-18wt.%Ni mixture along with hydriding-dehydriding cycling. The MA 6h sample is relatively easily activated and has higher hydriding rate than the pure Mg, the Mg-10wt.%Ni alloy, and a little lower hydriding rate than the $Mg_2Ni$alloy. The MA 6h sample lower dehydriding rate than the $Mg_2$Ni alloy but higher dehydriding rate than the pure Mg and the Mg-25wt.%Ni alloy. The MA 6h sample has larger hydrogen-storage capacity than the pure Mg and the other alloys.

• Korean Journal of Ecology and Environment
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• v.45 no.1
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• pp.1-10
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• 2012

The Jinwi stream, which is located in the Gyeonggi Province, shows a large variation in water quality from the upper stream to downstream. Therefore the Jinwi stream is suitable for assessing changes to the benthic macroinvertebrate community structure according to saprobity. This study was conducted to find out the applicability of biotic indices for water quality pollution through an analysis of the correlation between water quality and benthic macroinvertebrate indices for the Jinwi stream. Along with the pollution of water, the species composition of Ephemeroptera decreased, while that of Annelida increased. The ecological score for the benthic macroinvertebrate community (ESB) showed more significant correlations than any other biotic index (H', DI, R1, J, EPT and KSI) with the water quality items.

• Korean Journal of Environmental Biology
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• v.35 no.1
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• pp.83-94
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• 2017

Benthic macroinvertebrates were investigated in thermal discharge that flows Buso stream region from December 2015 to February 2016, Korea. Study site was selected for the upstream, downstream relative to the mixing station and mixing station which thermal effluent flows, water quality analysis and benthic macroinvertebrates composition, taxa of EPT-group individuals, analysis of biological water quality. As a result, a total of 4,015 individuals including 50 species, 30 families, 11 orders, 4 classes, and 3 phyla were recognized. Taxa of species is Ephemeroptera 16 species (32.0%) including 6 families, the density composition was highest in 1,848 individuals (46.03%) Diptera. EPT-group occupied during the study period were a total of 1,876 individuals (46.72%) including 32 species and 17 family, lowest in the mixing station for study period. As a results of community analysis, mixing station in the Limnodrilus gotoi and Chironomidae sp.2, which is dominated by the analysis was Ecdyonurus levis, Cincticostella levanidovae, Nemoura KUa. The dominant species showed a difference in the upstream and downstream. In the functional feeding groups, in the upstream and mixing station Gathering-Collectors, downstream it was analyzed that the ratio of the highest Filtering-Collectors and decreased the ratio of Shredders increasing from upstream to downstream. Habitat orientation group is analyzed that accounted for most of the Clingers and Burrowers, from upstream to downstream toward the higher the ratio of Clingers. Biological water quality assessment results were analyzed the worst state in the mixing station with an average 2.73 (${\pm}0.41$). Correspondence analysis, correlation analysis results of water temperature and the cold-water species, as the water temperature increases were analyzed by reducing cold-water species and EPT-group.

• Korean Journal of Environment and Ecology
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• v.34 no.2
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• pp.121-129
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• 2020

This study investigated the change of benthic macroinvertebrates community due to erosion control dams installed in Wonju, Gangwon by comparing the data before and after a rainy season. It selected a closed-type erosion control dam (boulder stone), an open-type erosion control dam (buttress), and a control area and surveyed two upstream points and two downstream points four times between March and September 2019. The flow velocity mostly increased in the closed-type, open-type, and control areas but decreased in St. 3 after the rainy season. The number of benthic macroinvertebrates species and their populations mostly decreased after the rainy season, and the rate of decrease in the populations in the open-type and control areas were more similar than the closed-type area. Species and populations of the EPT groups mostly decreased after the rainy season. A result of the similarity analysis showed that the closed-type and open-type areas were separated by 38.4% with the control area before the rainy season, but the open-type and control areas were separated by 51.3% with the closed-type area after the rainy season. A result of the principal components analysis (PCA) based on axis 1 showed that the closed-type area had a positive value before and after the rainy season, and the open-type and control areas had a negative value before and after the rainy season. The open-type area was more correlated with the control area than the close type. The analysis of the EPT groups showed the distribution of Ephemeroptera in the closed-type area and Trichoptera in the open-type and control areas. The result of this study shows that the installation of erosion control dam can cause changes in benthic macroinvertebrates community and that the open-type area had a smaller difference community difference from the control area after the rainy season than the closed-type area.

• Magazine of the Korean Society of Agricultural Engineers
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• v.22 no.3
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• pp.37-45
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• 1980

This study was carried out to investigate the consumptive use of water for red peppers and soy beans. The correlation between the soil moisture contents and the selected meteorological factors during the growing season was analyzed. Characteristics of the drought at Jinju, Yeosu, Gwangju, and Mokpo area were figured out in view of frequency analysis. The results obtained from this study could be used as a reasonable criteria for the estimation of the duty of water in the design of upland irrigation systems. Obtained results are summarized as follows: 1. Red peppers were grown at the three levels of soil moisture contents; 75 percent, 50 percent, and 25 percent, respectively. The red pepper grown at the 75 percent of soil moisture content showed the highest yield. The total evapotranspiration during the growing season from red peppers was 471. lmm, which was 86.6mm less than the pan evaporation. 2. The soy bean grown at 75 percent soil moisture content showed the highest yield, although there was no signicant difference in yields among treatments. The total evapotranspiration during the growing season from the soy bean was 342.8 mm, which was 119.2mm less than the pan evaporation. 3. Coefficients of consumptive use(k) and meteorological data are shown on Table-9. 4. The significant correlations between the evapotranspiration and the humidity and daily temperature range were observed. Results are shown on Table-11.. Evaporanspiration can be easily estimated from the humidity and daily temperature range by using the equation...... (1) Ept=4.808-0.041H+0.207T.......(1) where, Ept; evapotranspiration(mm/day) H ; humidity(%) T ; daily temperature range ($^{\circ}C$) 5. The variations of soil moisture content during the growing season at the soil depth of 5cm, 15cm, and 45cm are shown on Fig. 4~9. The results of the correlation analysis between the evapotranspiration from the crops and the soil moisture content are shown on Table-12. The evapotranspiration can be estimated from soil moisture content at the different depth of the soil by using the equation....... (2). Ept = 3.433 - 0. 364M1 +0. 359M$_2$- 0. 055M$_3$....... (2) where, Ept; evapotranspiration (mm/day) M1 soil moisture meter reading at 5cm depth M$_2$; " 15cm " M$_2$; " 40cm " 6. The estimated probab]e successive dry days in selected areas are shown on Table 13. Gumbel-Chow method was used to calculate the probable successive dry days. Further investigation are required to obtain the more detailed and reliable results.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.1-2
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• 2012

Active process of industrialization of near-earth space assumes design and development of high effective propulsion systems with a small thrust. The specific place among propulsion systems with a small thrust is taken the propulsion systems with use of electrical propulsion thrusters (EPT).

• Proceedings of the Korean Fiber Society Conference
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• 1996.04a
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• pp.5-8
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• 1996

• Korean Journal of Environment and Ecology
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• v.24 no.5
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• pp.556-565
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• 2010

Community analysis based on functional feeding groups of benthic macro invertebrates at Wangpi-cheon was assessed with the result of four field survey from October, 2007 to May, 2008. A total 138 species of benthic macro invertebrates in 58 families, 16 orders, 6 classes, and 4 phyla were collected during the field surveys. The result of EPT index value showed high value of 61.59% and it means that the stream ecosystem of Wangpi-cheon is very clear and healthy. In this study the functional feeding groups in Wangpi-cheon were divided into two groups. First, Scrapers and Collectors-Gathering group which is normally dominant in midstream showed higher dominance in main stream than tributary. Second, shredders group showed higher dominance in tributary than main stream like as the general characteristics of upriver. With the result of cluster analysis based on the similarity index, the study areas could be grouped into a natural area(A group) and an artificial disturbance area(B group; site 8 and 11) where embankment, bank and levee had been built near by. And also, the natural area(A group) was classified into two groups which had the characteristic of main(site 1, 2, 3, 4 and 7) stream and tributary(site 5, 6, 9 and 10) respectively.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.07a
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• pp.155-155
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• 2004

• Proceedings of the Korea Society of Design Studies Conference
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• 2005.10a
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• pp.98-99
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• 2005