• Applied Chemistry for Engineering
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• v.33 no.6
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• pp.581-587
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• 2022

The leather industry generates a large amount of hazardous leather waste of various types every year. Among them, shaving scrap is difficult to recycle because it contains chromium ions. Many studies in recent years have shown that shaving scraps can be processed into various types of valuable products, such as adsorbent, filler, and poultry feed. In this study, collagen peptides were extracted from shaving scraps and structurally modified to be developed as new materials with improved physicochemical properties. First, the chromium ions contained in the shaving scraps were removed using a sodium hydroxide solution, and purified through concentration and low-temperature crystallization. The purified collagen peptide was used to prepare the powder using a spray dryer. The extracted collagen peptides were structurally modified by introducing double bonds by reacting with methacrylic anhydride (MAA), and the product was confirmed by ¹H NMR spectroscopy. Next, a copolymer was prepared by redox polymerization of the modified collagen peptide (MCP) and 2-ethylhexyl acrylate (2-EHA). The structure of the copolymer was qualitatively confirmed by FT-IR. In conclusion, this study confirmed that collagen peptides can be extracted from shaving scrap and converted into new eco-friendly materials through certain treatments.

• Korean Journal of Ecology and Environment
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• v.54 no.4
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• pp.390-397
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• 2021

The time series data of rotifer community focusing on the species number and total density were collected from 29 reservoirs located at Jeonnam Province from 2008 to 2016 quarterly. The reservoirs had similar weather condition during the study period, but their sizes and water qualities were different. To analyze the temporal dynamics of rotifer community, the medians, ranges, outliers and coefficient of variation (CV) value of rotifer species number and abundance were compared. For the temporal trend analysis, time series of each reservoir data were compared and clustered using the dynamic time warping function of the R package "dtwclust". Small-sized reservoirs showed higher variability in rotifer abundance with more frequent outliers than large-sized reservoirs. On the other hand, apparent pattern was not observed for the rotifer species number. For the temporal pattern of rotifer density, COD, phytoplankton abundance fluctuation, and cladoceran abundance fluctuation have been suggested as potential factor affecting the rotifer abundance dynamics.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.6
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• pp.880-889
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• 2021

The home meal replacement (HMR) market has attracted significant attention due to COVID-19 pandemic and products that utilize the combination of different processed ingredients are now being developed. In this study, Broughton's ribbed ark Scapharca broughtonii was soaked in seasoned soy sauce with the incorporation of mustard leaf Brassica juncea (M-BRA), which is known to have a unique texture as well as excellent functional properties such as antioxidation, to develop a regional specialty product. The optimal conditions for manufacturing M-BRA from the seasoned soy sauce (the sauce to be added [X₁] and the soaking time [X₂]), were examined using response surface methodology (RSM) to analyze the significance of the salinity (Y₁), amino-N content (Y₂), and overall acceptance (Y₃). The coefficient of determination (R²) between X₁-X₂ and Y₁-Y₃ were close to 1, thereby confirming the suitability of the RSM model. The optimal conditions were seasoned soy sauce addition of 140% and soaking time of 156 min. The M-BRA manufactured under these conditions exhibited superior overall acceptance compared to seasoned commercial soy sauce, which was used as a control. We expect that the market for M-BRA manufactured by combining marine and agricultural materials will expand owing to superior overall acceptance compared with commercial products.

• Korean Journal of Ecology and Environment
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• v.54 no.4
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• pp.374-383
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• 2021

In 2020, the diversity of benthic macroinvertebrate communities was investigated in the Sohan stream, an ecological and landscape conservation area, and the results were compared with the previous research conducted in 2011. In total, 42 species (two phyla, three classes, and seven orders) were found in the Sohan stream. Species richness and abundance sharply decreased at all sampling sites because of Typhoons Haishen and Maysak in 2020, which had a direct impact on the stream. In the functional feeding group, the ratio of collector-gatherers was the highest at all sampling sites. However, during the autumn season, the shredder ratio increased from 13.4% to 42.4% in the uppermost stream site. Compared with the diversity of benthic macroinvertebrates surveyed in 2011, a total of 53 species (two phyla, three classes, and eight orders) were found. The percentage of species richness and abundance of Ephemeroptera, Plecoptera, and Trichoptera was more than 50% both in 2011 and 2020. Only the richness of Ephemeroptera was significantly different between them (2011: 2.9 and 2020: 6.7). In this study, the abrupt changes of species richness and abundance in benthic macroinvertebrate were not observed before and after the designation of an ecological and landscape conservation area. However, it is necessary to monitor benthic macroinvertebrates in order to confirm that biodiversity is continuously maintained long after the designation of the ecological and landscape conservation area.

• Korean Journal of Ecology and Environment
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• v.54 no.4
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• pp.327-333
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• 2021

The two main hypotheses that explain why invasive alien plants successfully colonize new environments are: 1) invasive alien plants are functionally different from native plants in a community, and 2) the plants can adapt well to new environments because they are functionally similar to native plants. The present study investigated the functional traits of naturalized alien herbaceous plants and their native neighbors in a riparian park area near the Hapcheon-Changyeong weir along the Nakdong River to determine which of the two hypotheses applied to the study area. According to the results, leaf functional traits, such as leaf area, specific leaf area, leaf thickness, leaf dry matter content, leaf nitrogen content, and leaf carbon content differed between naturalized alien and native plants, which could be attributed to the higher leaf nitrogen contents in naturalized alien plants than in native plants. The high leaf nitrogen contents are associated with high photosynthetic rates, which lead to effective resource use and rapid growth; therefore, naturalized alien plants growing in the study area were considered to have such functional traits. The results of the present study support the hypothesis that the successful establishment of invasive alien plants is attributed to the functional trait differences between invasive and native plants.

• Korean Journal of Ecology and Environment
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• v.54 no.4
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• pp.384-389
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• 2021

This study was conducted on October 23, 2020 at the Cheongpyeong Reservoir located in Seorakmyeon, Gapyeong-gun, Gyeonggi-do, and analyzed the horizontal and vertical distribution patterns of fish based on data obtained using fishfinder. The total surface area of fishfinder survey conducted was 782,853 m², and where the water depth (WD) ranges from 10 m to 12 m is widest which 31.7% of total surface area. As a result of the heat map analysis, fish density was highest at right bank under the Gapyeong-bridge, but there was no specific pattern in horizontal distribution of fish. As a result of vertical distribution of fish analysis, 86.6% of fishes are observed at below 6 m of the fish depth (FD, distance from water surface to fish). As a result of the relative height (RH, water depth-distance from bottom to fish ratio) analysis, there was a tendency that fishes are distributed in near surface area more as the WD increased. This tendency could have various reasons such as water temperature gradient along the water depth, and further studies are required for detailed explanation.

• Korean Journal of Ecology and Environment
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• v.54 no.4
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• pp.334-345
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• 2021

The present study investigated the effect of global warming on germination and initial growth across six deciduous oak species (Quercus mongolica, Q. variabilis, Q. serrata, Q. dentata, Q. aliena, and Q. acutissima), which are the dominant tree species in Korea forest ecosystems. Seeds were sown in climate change treatments, with temperatures higher than those of the control (approximately 3.0℃ higher), and CO₂ concentrations higher than those of the control (approximately 2-fold higher). Initial growth in each species was measured every two weeks. Initial growth was more rapid in all oak species at the time of root and shoot emergence under high temperature and CO₂ treatments than in the control group. Leaf emergence in Q. mongolica, Q. variabilis, and Q. serrata occurred earlier under the climate change treatments than under the control. Root length increased significantly in Q. mongolica, Q. variabilis, and Q. dentata under the climate change treatments when compared to under the control. However, Q. aliena and Q. serrata exhibited a contrasting trends, and no significant difference was observed between the species and Q. acutissima. Shoot length increased significantly in Q. aliena under climate change treatments when compared to under the control but decreased in Q. aliena. In addition, no significant difference was observed in shoot length among Q. mongolica, Q. dentata, and Q. acutissima. The results showed that climate change treatments facilitated early growth, rapid emergence from the ground, leaf development, and enhanced belowground growth in Q. mongolica. Conversely, Q. aliena exhibited the lowest aboveground and belowground growth under climate change treatments when compared to other oak species. Climate change treatments had the least impact on Q. acutissima considering the insignificant differences observed in initial growth rates under climate change treatment.

• Journal of Korean Elementary Science Education
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• v.41 no.4
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• pp.627-641
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• 2022

This study aims to help elementary school teachers increase their knowledge about the changes in the positions of the sun and moon during the day and the first time the moon observation begins in the Earth and Space section of the Earth and the Moon. The survey questions were grouped into four categories, namely, textbook explanation, inquiry activities, achievement of learning goals, and other opinions. The perception of each question differed according to advanced science majors and teaching careers and experiences of this unit. In addition, understanding the diverse views of the participants using descriptive questions was possible. The study recruited 67 teachers working at an elementary school in Gyeonggi-do. The conclusion is as follows. First, the teachers exhibited similar positive and negative perceptions about the description of the textbook on the changes in the positions of the sun and moon during the day. Second, the study found that majority of teachers used alternative methods when guiding students regarding the change in the positions. This trend was not correlated with the sun and the moon, and the study observed no difference in advanced majors and teaching careers and experience of this unit. Third, the majority of teachers responded that they could achieve their learning goals through this learning. However, many teachers complained of various difficulties in guiding students about the lesson, and the majority alternative methods. The results demonstrated the perception of teachers that students can achieve learning goals through alternative methods without direct observation.

• Journal of The Korean Association For Science Education
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• v.42 no.5
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• pp.487-499
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• 2022

This study aims to understand the trends and characteristics of elementary science textbook research. For this purpose, among the papers published in science-related journals from 2001 to 2021, 156 studies related to elementary science textbooks were analyzed to examine the research trends on textbook analysis. The analysis criteria consisted of two major categories, 'outward feature' and 'topic.' The subcategories of 'outward feature' consist of 'year of publication,' 'target curriculum,' 'target grade,' 'science content area,' 'subject of study,' and 'publishing institution.' The sub-categories of 'topic' consist of 'comparison,' 'content,' 'illustration,' 'inquiry activity,' 'perception of textbooks,' and 'others.' As a result of the analysis on 'outer feature,' textbook-related research was conducted almost every year, and the research on the 2009 revised science curriculum, on the 3-6 grades, and on the whole field of science had the most. The science textbook researches were published not only in science education-related journals but also in other areas' journals. As a result of the analysis of the 'topic,' the number of papers was higher in the order of comparative research, content analysis, illustration, inquiry activities, and perception of textbooks. Implications for accredited textbook system of elementary science were discussed based on the analyses on the elementary science textbook research trends.

• Journal of Korea Water Resources Association
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• v.55 no.12
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• pp.1065-1076
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• 2022

The purpose of this study was to investigate the effect of the expansion and withering of Salix subfragilis communities on the water quality in Namgang Dam reservoir. The distribution area of the Salix subfragilis communities was 0.12 km² in 2003 for the first time, but it was 3.58 km² in 2019, which has increased rapidly by about 30 times in 16 years. However, in 2013, the distribution area has decreased by 0.17 km² due to long-term immersion in high turbidity, and self-thinning in Salix subfragilis communities. The lake characteristics of reservoir showed a combination of lake type and river type in terms of average water depth, watershed area/lake surface area ratio, water residence time, flushing rate, and stratification. From the result of analyzing long-term changes in lake water quality, COD, TP, and chlorophyll-a in Salix subfragilis communities were significantly larger than those in the three points located in the central part of reservoir. In particular, the fact that the value of chlorophyll-a showed the maximum value in winter rather than summer, unlike the trend of the three points in the Namgang Dam water quality monitoring network, is thought to have occurred internally rather than externally. It can be estimated that one cause of this deterioration of the water quality in Namgang Dam reservoir is the huge amount of nutrients generated in the decomposition process of by-products such as fallen leaves, branches and withered trees in Salix subfragilis communities.