• Clean Technology
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• v.24 no.4
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• pp.339-347
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• 2018

In order to cope with environmental problems and climate change caused by fossil fuels, renewable energy supply is increasing year by year. Currently, waste energy accounts for 60% of renewable energy production. However, waste has a lower calorific value than fossil fuels and contains various harmful substances, which causes serious problems when applied to power generation boilers. In particular, the chlorine in the waste fuel increases slagging and fouling of boiler heat exchangers, leading to a reduction in thermal efficiency and the main cause of high temperature corrosion, lowering facility operation rate and increasing operating cost. In this study, the high temperature corrosion experiments of superheater materials (ASME SA213/ASTM A213 T2, T12 and T22 alloy steel) by alkali chlorides were conducted, and their corrosion characteristics were analyzed by the weight loss method and SEM-EDS. Experiments show that the higher the temperature and chloride content, the more corrosion occurs, and KCl further corrodes the materials compared to NaCl under the same condition. In addition, the higher the chromium content of the material, the better the corrosion resistance to the alkali chlorides.

• Journal of Korea Water Resources Association
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• v.54 no.9
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• pp.657-666
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• 2021

Ecosystem biodiversity is rapidly being lost due to changes in habitat, fragmentation of habitat, climate change, and land use changes by human activities. Recently, attempts have been made to approach the watershed management level to secure the health of the watershed, but studies on how to approach biodiversity and habitat management are still in lack. The purpose of this study is to evaluate the habitat quality of Geum river basin using Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) habitat quality model. The results of habitat quality was verified to eco-natural map and ecological watershed health evaluation results. The habitat quality of watershed was evaluated from 0 to 0.86 and the results showed that habitat quality was higher in upstream than downstream. Compared the habitat quality value in each eco-natural grade, the average habitat quality of 1st, 2nd and 3rd grades were 0.80, 0.76 and 0.71 respectively. The results of the correlation analysis with ecological watershed health data, the coefficient of determination (R²) was 0.58, and the person coefficient was 0.76. The results of this study may be used as foundation data to support habitat protection and implementation of long-term biodiversity-related policies.

• Korean Journal of Environmental Biology
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• v.39 no.2
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• pp.218-224
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• 2021

This study was conducted to determine the mass-loss rates and the changes in carbon/nitrogen (C/N) ratio of dead woods, which were of following species: Dryobalanops aromatic, D. rappa, and Cratoxylum arborescens. These were dominant tree species in mixed Dipterocarp forests (MDF) and peat swamp forests (PSF) in Brunei Darussalam. In May, 2019, 48 dead wood samples (15 cm×4.8 cm×5 cm) were placed in MDF and PSF sites, and all the samples were collected after 16 months. The effects of species on mass loss were statistically significant (p<0.05); however, no difference was observed in the mass loss obtained from the two forest types (p>0.05). The initial density (g·cm^-3) of the dead woods D. aromatic, D. rappa, and C. arborescens, was 0.64±0.02, 0.60±0.00, and 0.44±0.01, respectively. Also the annual mass loss rate (%) was estimated to be 6.37, 8.17, and 18.53 for D. aromatic, D. rappa, and C. arborescens, respectively. The proportion of dead woods in decay class III was only 25% of C. arborescens samples, which were attacked by wood-feeding invertebrates, such as termites. The C/N ratio decreased significantly in D. aromatic and D. rappa, but the decreasing trend of C/N ratio was not statistically significant in C. arborescens. The results indicate that physical traits of dead woods, such as density, could be one of the main factors causing the decomposition of dead woods initially, as invertebrates such as termites are one of the key decomposers of dead wood in tropical rainforests. In the samples of C. arborescens, which was attacked by invertebrates, nitrogen immobilization occurred to lesser extent as compared to that observed in D. aromatic and D. rappa.

• Korean Journal of Environmental Biology
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• v.39 no.2
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• pp.245-257
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• 2021

Ulleungdo, a volcanic island, has different climate, soil, and topography characteristics from inland of the Korean Peninsula. Its agriculture also exhibits distinctive features. This study focused on floristic compositions and characteristics of crop lands in Ulleungdo. Flora surveys were conducted for 37 areas three times, one in May of 2016, one in July of 2020, and one in August of 2020. Results showed that vascular plants of crop lands in Ulleungdo included 186 taxa of 53 families, 132 genera, 160 species, 14 varieties, five subspecies, and five hybrids. Asteraceae had the most diverse species (33 taxa), followed by Poaceae (25 taxa), Fabaceae (12 taxa), Polygonaceae (11 taxa), and Liliaceae (nine taxa). The biological type of crop lands in Ulleungdo island was determined to be Th-R₅-D₄-e type. Rare plants were found for nine taxa: Athyrium acutipinnulum Kodama ex Nakai, Sedum takasimense Nakai, Rubus takesimensis Nakai, Dystaenia takesimana (Nakai) Kitag., Ligustrum foliosum Nakai, Aster pseudoglehni Y.Lim, Cirsium nipponicum (Maxim.) Makino, Lilium hansonii Leichtlin ex D.D.T.Moore, and Polygonatum robustum (Korsh.) Nakai. In addition, 45 taxa contained naturalized plants of 13 families, 33 genera, 44 species, and one variety. Urbanization and naturalization indices were 13.9%, and 24.2%, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.1
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• pp.257-266
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• 2021

Urban areas can often suffer flood damage because of the more frequent catastrophic rainfall events from climate change. Flood mitigation measures consist of (1) structural and (2) non-structural measures. In this study, the proposed method focused on operating an urban drainage system among non-structural measures. The combined inland-river operation technique estimates the inflow of pump stations based on the water level obtained from a preselected monitoring point, and the pump station expels the stored rainwater to the riverside based on those estimates. In this study, the proposed method was applied to the Mokgam drainage watershed, where catastrophic rainfall events occurred (i.e., 2010- and 2011-years), and severe flood damage was recorded in Seoul. Using the proposed method, the efficiency of flood reduction from the two rainfall events was reduced by 34.9 % and 54.4 %, respectively, compared to the current operation method. Thus, the proposed method can minimize the flood damage in the Mokgam drainage watershed by reserving the additional storage space of a reservoir. In addition, flooding from catastrophic rainfall can be prevented, and citizens' lives and property in urban areas can be protected.

• Korean Educational Research Journal
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• v.43 no.1
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• pp.125-152
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• 2022

The purpose of this study is to examine the differences of perceptions of teachers and students regarding teaching skills. For the analysis, data was collected by ICALT(International Comparative Analysis of Learning and Teaching) class observation tool and students survey called My Teacher Questionnaire. a student survey. The data of teachers and students can be compared because as the two tools have seven common domains(Safe and stimulating learning climate, Efficient organization, Clear and structured instructions, Intensive and activating teaching, Adjusting instructions and learner processing to inter-learner differences, Teaching learning strategies, Learner engagement). In 2016, in Daejeon, Chungbuk and Chungnam. trained teachers collected data from 106 classes, and 2,866 students responded the survey. The reliability and validity of the two tools, class observation and MTQ(My Teacher Questionnaire) are proven to be satisfactory for use in Korean schools. Students perception on teaching was high, particularly when students are in lower grades and learning major subjects like English, Korean, and math. The domain of higher teaching skills, male students show higher perceptions while female students reported higher perceptions on lower-level teaching skill domains. To compare the perceptions of teachers and students, the predictive reliability of students engagement against teaching skill domains was used. Teachers showed higher predictive reliability on lower teaching skill domains while students showed higher predictive reliability on higher teaching skill domains. It is recommended for further study to develop a professional development model using a teacher class observation tool and the My Teacher Questionnaire for pre-service teachers and school teachers.

• Journal of the Korean Society of Safety
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• v.37 no.2
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• pp.28-34
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• 2022

This study analyzes the impact that accidents and near misses have on clients' and contractors' awareness of safety culture. Due to the unique characteristic of employment structure in Korea, the occurrence of accidents differs by company size, which has relevant implications for the establishment of safety culture. Attention has been drawn to the importance of the management of accidents and near misses, with safety awareness acting as a core factor. A positive effect on the prevention of accidents could be achieved by noting the difference in safety awareness between clients and contractors and suggesting an associated suitable safety management system. In support of this study, a survey was distributed to workers in the automobile manufacturing industry (May-August 2020), and data from a total of 574 workers was collected and analyzed, including 399 clients' worksers and 175 contractors' workers. The questionnaire addressed participants' experiences of accidents and near misses as well as 50 items from the Nordic Occupational Safety Climate Questionnaire. Analysis of the responses was conducted using the methods of frequency analysis, Fisher's exact test, t-test, correlation analysis, and regression analysis. The results demonstrated that clients had more experiences with accidents and near misses compared to contractors. Additional differences between clients and contractors were noted in terms of the safety culture factors of learning, communication, and trust. A correlation was observed between the experience of accidents and safety justice management: for clients and contractors who experienced accidents, safety justice management was 9.4 times higher. Furthermore, clients' and contractors' awareness of employees' commitment to safety was determined to be 28.5 times higher in those who had experienced near misses This study concludes that, in order to improve accident prevention through the management of accidents and near misses, clients must focus on overseeing safety justice management and aspects of safety culture factors, while contractors must focus efforts on managing employees' commitment to safety. In further applications, this study could provide baseline data for health and safety activities in terms of the safety culture of clients and contractors. Further study on the establishment of safety culture as related to employment structure is proposed for future research.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.25 no.1
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• pp.57-74
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• 2022

Seed zones were constructed using temperature and precipitation data for the Korean Peninsula and were described as 65 zones. Seed zones for South Korea were reclassified, and they were classified into 34 districts. This study was conducted to define the spread of 5 native seed species (Pinus densiflora, Quercus acutissima, Quercus variabilis, Acer pictum, Carpinus tschonoskii) by linking the seed zones with MaxEnt. The emergence point of native seeds was acquired through the 1:5,000 Forest Type Map and the 4th national natural environment survey data. Based on the MaxEnt result, regions with a habitat probability of 0.5 or more were extracted and overlapped with seed zones to identify the native seed habitat. After analyzing the climate regions with high habitat density, regions with high habitat density of native seeds for each administrative district were identified. In the case of Pinus densiflora, Quercus acutissima, and Quercus variabilis, the Winter minimum temperature(WMT) -9.4~-6.6℃, Annual Heat:Moisture(AH:M) 19~24℃/m was 37%, 43%, and 34%, respectively. occupied the largest area. In Acer pictum, WMT -6.6~-3.8℃ and AH:M 16~19℃/m accounted for 42% of the area, and Carpinus tschonoskii had WMT -3.8~-1.1℃, AH:M <16℃/m Districts accounted for the largest area at 33%. The regions with high density of Pinus densiflora, Quercus acutissima, and Quercus variabilis by administrative district were distributed in high density in Seoul, Southern Gyeonggi-do, Chungcheong-do, and Gyeongsangbuk-do. Acer pictum was distributed in high density in Jeolla-do and Gyeongsang-do, and Carpinus tschonoskii in Jeju, Jeollanam-do and Gyeongsangnam-do. Through this study, seed zones for each of the 5 native seeds were established, and it is expected to provide basic data for the management of native seeds.

• Journal of Korean Society of Disaster and Security
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• v.15 no.3
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• pp.41-46
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• 2022

Recently, the scale of flood damage occurring in urban areas is increasing due to climate change and urbanization, so various flooding analysis techniques are needed. In the Sadangcheon Stream basin, which has been continuously flooded since 2010, a basic plan for improving drainage was established using XP-SWMM and measures to prevent flooding were proposed. However, in the process of inundation analysis, the analysis considering the city's buildings was not conducted, resulting in a problem that the degree of flooding damage tends to be overestimated. Therefore, in this study, XP-SWMM was used to compare and analyze cases where buildings were not considered and designated as inactive areas. As a result of the study, it was analyzed if the building was not considered, the flood damaged area was 271,100 m² and the depth of submersion was 0.15 m, and if the building was considered inactive area, the flood damaged area was 172,900 m² and the depth of submersion was 0.32 m that it is under-estimated about 36% and an flow velocity around the building increased from 1.62 m/s to 1.83 m/s about 1.12 times.

• Journal of Korean Society of Disaster and Security
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• v.15 no.2
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• pp.37-44
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• 2022

As the frequency of torrential rains and typhoons increases due to climate change, the frequency of occurrence of debris flow is also increasing. In particular, in the case of Kangwon-do, the occurrence of damage caused by mountain disasters is increasing as it has a topographical characteristic where the mountains and the coast are in contact. In order to analyze the flow characteristics in the sedimentary part of the debris flow, input data were constructed through numerical maps and field data, and a two-dimensional model, FLO-2D, was simulated. The damaged area was divided into the inflow part of the debris flow, the village center, and the vicinity of the port, and the flow center and flow velocity of the debris flow were simulated and compared with field survey data. As a result, the maximum flow depth was found to be 2.4 m at the debris flow inlet, 2.7 m at the center of the village, and 1.4 m at the port adjacent to the port so the results were similar when compared to the field survey. And in the case of the maximum flow velocity, it was calculated as 3.6 m/s at the debris flow inlet, 4.9 m/s in the center of the village and 1.2 m/s in the vicinity of the port, so It was confirmed that the maximum flow center occurred in the section where the maximum flow rate appeared.