• Nuclear Engineering and Technology
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• v.53 no.10
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• pp.3217-3228
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• 2021

Flow blockage of the fuel assembly in the lead-based fast reactor (LFR) may produce critical local spots, which will result in cladding failure and threaten reactor safety. In this study, the flow blockage characteristics were analyzed with the sub-channel analysis method, and the circumferentially-varied method was employed for considering the non-uniform distribution of circumferential temperature. The developed sub-channel analysis code SACOS-PB was validated by a heat transfer experiment in a blocked 19-rod bundle cooled by lead-bismuth eutectic. The deviations between the predicted coolant temperature and experimental values are within ±5%, including small and large flow blockage scenarios. And the temperature distributions of the fuel rod could be better simulated by the circumferentially-varied method for the small blockage scenario. Based on the validated code, the analysis of blockage characteristics was conducted. It could be seen from the temperature and flow distributions that a large blockage accident is more destructive compared with a small one. The sensitivity analysis shows that the closer the blockage location is to the exit, the more dangerous the accident is. Similarly, a larger blockage length will lead to a more serious case. And a higher exit temperature will be generated resulting from a higher peak coolant temperature of the blocked region. This work could provide a reference for the future design and development of the LFR.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.24 no.2
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• pp.39-56
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• 2021

The seed zone is a map that describes the areas where plant material can be transferred with little risk for properly adapting to a new location. The seed zone study is largely divided into studies based on genetic data and studies based on climatic data. Can be. This study was conducted to establish a temporary domestic seed zone applicable to the entire Korean Peninsula and evaluate its possibility based on the US climate-based seed zone establishment methodology. The temporary seed zone was constructed in the same way as the US case by superimposing the data obtained by dividing the winter minimum temperature into 12 grades and the data obtained by dividing the annual heat: moisture index into 6 grades. As a result of the analysis, 65 temporary seed zones were formed throughout the Korean Peninsula, and the areas of the seed zones representing the smallest and largest areas were 3.0km² and 29,423.0km², respectively, and it was confirmed that they had an average size of about 5,064.9km². Temporary seed zones applied in Korea show a pattern of changes in temperature according to the relatively horizontal forest zone, and it was confirmed that the area where the Baekdu-daegan ecological axis is located has a tendency to show lower dryness than other areas. This study applied the US climate-based seed zone methodology in Korea as a pilot, and confirmed the climatic similarity across the Korean Peninsula. Furthermore, it is expected to provide an optimal seed map that improves the success rate of restoration in the future by revising the seed zone grade suitable for the domestic environment in consideration of the results of this study and the possibility of seed adaptation to the field survey and environmental space.

• Journal of Korea Port Economic Association
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• v.37 no.1
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• pp.103-119
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• 2021

Ports in Korea have been increasing in terms of volume while they have performed functions and roles such as industrial ports in promoting industries of their hinterlands as well as commercial ports supporting imports and exports. Nevertheless, specialization degree is different from port to port by cargo type and the changes in cargo volume. This study aims to analyze the structural changes and the degree of concentration and specialization by cargo type and port between 2001 and 2020. Top 10 ports were analyzed in terms of traffic volume by categorizing liquid, dry, general cargo and containers. HHI(Herfindahl-Hirschman Index), LQ(Location Coefficient), and shift-share analysis were employed in order to identify the degree of concentration, specialization and changes in cargo volume by port and cargo type. As a result of the analysis, the degree of port concentration and specialization for each cargo of 4 categories have maintained a high level, and no significant difference were found in fluctuations over the past 20 years. As a result of calculating the flucation of cargo volume through the shift-share analysis, the growth rate of liquid cargo was high in Yeosu Gwangyang Port, Pyeongtaek Dangjin Port in dry cargo, and Busan Port in general cargo and container ports. The result implies that it is not expected that the structural changes including degree of cargo concentration, specialization and relative fluctuation of cargo volume is significant in Korean ports in the future since the effects of economies of scale and clustering were achieved to the great degree.

• Korea Real Estate Review
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• v.28 no.1
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• pp.53-63
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• 2018

This paper shows that the value of land can vary based on the future availability of the land. According to the Korean principles of land appraisal by the Ministry of Land, Infrastructure, and Transport (MOLIT), the value of a piece of land is derived mainly from the latter's fertility level or local environment. In practice, however, the values of lands may vary even though their fertility level is invariant. This paper investigates a fundamental question for many professional appraisers who argue that appraisal practices are different from the principles of appraisal. It highlights the appraisal practices for agricultural and forestry lands, which have similar agricultural productivity levels or environmental conditions. It is shown in this paper that even though the fertility level of lands is invariant, the values of lands may vary based on their locations. Therefore, this can complement the principles of land appraisal. In this paper, real cases in local areas in Gapyeong County, Kyounggi province are investigated. It can be seen from the cases in the local areas that two agricultural lands may have different values based on their locations even though they have almost similar fertility levels (e.g., their physical distance from each other is less than 0.5 km but their values differ by around 19%). This paper thus argues that the value of a piece of land can be determined by its availability.

• Journal of vocational education research
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• v.33 no.3
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• pp.105-125
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• 2014

The purposes of this study are to develop the standardized tests of career preparation behavior of career preparation behavior for college students. For these, the 'Career Preparation Behavior Scale for College Students' which was developed in 2011 was reviewed and revised. After 609 students were involved and analyzed for the pretest, 1,244 subjects were collected by taking into account gender, grade, major, and location of colleges for developing a standardized test. The Career Preparation Behavior Scale consisted of 3 subareas and 30 items: 11 items for learning area, 12 items for counseling and information collecting area, 7 items for employment action area. The levels of reliabilities, construct validity, discriminant validity, and the concurrent validity were relatively high. Also, the suitability index of the structural model was analyzed to check the structural significance. The degree of career reparation behavior among norm groups was increased in general according to the grades. Scores of students majoring in humanities and social sciences received significantly high scores compared with those of majoring in science and technology or in art and music. But the levels of satisfaction on career preparation behavior were no difference according to gender, grade, and major. 'The Standardized Career Preparation Behavior Scale for College Students' would be used for conducting career education or programs for college students in the future.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.587-593
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• 2019

The field of geospatial information is rapidly changing due to the development of sensor and data processing technology that can acquire location information. And demand is increasing in various related industries and social activities. The construction and utilization of three dimensional geospatial information that is easy to understand and easy to understand can be an essential element to improve the quality and reliability of related services. In recent years, 3D laser scanners are widely used as 3D geospatial information construction technology. However, 3D laser scanners may cause shadow areas where data acquisition is not possible when objects are large in size or complex in shape. In this study, 3D model of an object has been created by acquiring oblique images using an unmanned aerial vehicle and processing the data. The study area was selected, oblique images were acquired using an unmanned aerial vehicle, and point cloud type 3D model with 0.02 m spacing was created through data processing. The accuracy of the 3D model was 0.19m and the average was 0.11m. In the future, if accuracy is evaluated according to shooting and data processing methods, and 3D model construction and accuracy evaluation and analysis according to camera types are performed, the accuracy of the 3D model will be improved. In the point cloud type 3D model, Cross section generation, drawing of objects, and so on, it is possible to improve work efficiency of spatial information service and related work.

• Journal of the Korea Convergence Society
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• v.9 no.11
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• pp.209-216
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• 2018

This study aimed to investigate the association of the muscle activity around the neck of the operator(dental hygienists') according to the change in the patient's neck angle during a direct visual inspection on the maxillary right-side molar palatal surface. The operators were $4^{th}$ year dental hygiene students, who are future dentalhy gienists, having accurate understanding on and awareness of the location of the operation site, hand fixation, and how to use the tools. Data on the change in the muscle activity around the neck were collected by using surface electromyography and neck goniometer. SPSS statistics 20 was used for statistical analyses including Shapiro-wilk test and one-way ANOVA. As a result, the activities of the operator upper trapezius, cervical erector spinae, and levator scapulae muscles significantly decreased when the patient's head was angled compared to when it was not. For the angle of the operator head, the head bend significantly decreased when the patient's head was angled than when it was not. Based on the study results, it is expected that angling the patient's head when treating his or her teeth will decrease the excessive muscle activity around the neck of the operator, and will reduce muscle fatigue. Therefore, angling the head of the patient while treating his or her teeth is recommended. This suggests that muscle pain caused by repetitive actions in the wrong posture can be reduced.

• The Journal of the Korea Contents Association
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• v.18 no.12
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• pp.646-659
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• 2018

This study proposed "Reservoir Park", which added disaster prevention function to urban green spaces such as city parks through domestic and overseas related laws review, case studies, field trips. This is a combination of urban parks and reservoirs as urban planning facilities, which can provide both space for daily use by urban residents and disaster mitigation functions in case of emergency. In order to prevent flooding in urban areas due to climate change, facilities should be installed in the form of parks, etc., as the reservoir facility should be systematically reviewed together with urban planning facilities. However it was found that the reservoir park was not clear as a theme park. In this study, the types of storage facilities in urban areas were reclassified into five types of storage parks reflecting the characteristics of urban green spaces through domestic case studies and field trips. The classification of the reservoir parks is classified into 5 kinds such as ecological type, vegetation cover type, exercise facility type, underground burial type and hybrid type based on groundwater level, human use, and reservoir size. This classification system can be used to determine the types of facilities to be built after designating the location of future storage facilities.

• Journal of Positioning, Navigation, and Timing
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• v.7 no.4
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• pp.295-305
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• 2018

Network RTK is a highly practical technology that can provide high positioning accuracy at levels between cm~dm regardless of user location in the network by extending the available range of RTK using reference station network. In particular, unlike other carrier-based positioning techniques such as PPP, users are able to acquire high-accuracy positions within a short initialization time of a few or tens of seconds, which increases its value as a future navigation system. However, corrections must be continuously received to maintain a high level of positioning accuracy, and when a time delay of more than 30 seconds occurs, the accuracy may be reduced to the code-based positioning level of meters. In case of SSR, which is currently in the process of standardization for PPP service, the corrections by each error source are transmitted in different transmission intervals, and the rate of change of each correction is transmitted together to compensate the time delay. Using these features of SSR correction is expected to reduce the performance degradation even if users do not receive the network RTK corrections for more than 30 seconds. In this paper, the simulation data were generated from 5 domestic reference stations in Gunwi, Yeongdoek, Daegu, Gimcheon, and Yecheon, and the network RTK and SSR corrections were generated for the corresponding data and applied to the simulation data from Cheongsong reference station, assumed as the user. As a result of the experiment assuming 30 seconds of missing data, the positioning performance compensating for time delay by SSR was analyzed to be horizontal RMS (about 5 cm) and vertical RMS (about 8 cm), and the 95% error was 8.7 cm horizontal and 1cm vertical. This is a significant amount when compared to the horizontal and vertical RMS of 0.3 cm and 0.6 cm, respectively, for Network RTK without time delay for the same data, but is considerably smaller compared to the 0.5 ~ 1 m accuracy level of DGPS or SBAS. Therefore, maintaining Network RTK mode using SSR rather than switching to code-based DGPS or SBAS mode due to failure to receive the network RTK corrections for 30 seconds is considered to be favorable in terms of maintaining position accuracy and recovering performance by quickly resolving the integer ambiguity when the communication channel is recovered.

• The Journal of the Korea Contents Association
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• v.19 no.2
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• pp.340-348
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• 2019

This study analyzes the factors that influence commercial gentrification in Seoul by using both logit model analysis and machine learning with data cumulated from 2015 to 2018 regarding 158 market areas. Logit analysis indicates that log(market area average monthly rent) and the ratio of the purchasing amount by customers aged 40 and younger to total sales in the restaurant and retail business category are statistically significant at 1%; the increase in sales per female customer aged between 30 and 39 in the restaurant and retail business category is statistically significant at 5%; and the increase in number of retailers with a business history of less than two years in the franchise business category is significant at 10%. Machine learning indicates that significant factors ordered by importance are the total retail area, the existence of an industrial complex within the market area, the existence of a traditional market within the market area, the location of subway stations within the market area, the increase of entertainment facilities such as movie theaters within the market area, average monthly rent, and the growth rate of average monthly rent. The contribution of this research is threefold. First, this study analyzes the entire commercial area of Seoul, Korea. Second, this study provides a foundation for future research on predictive indicators by empirically investigating the factors that influence commercial gentrification in Seoul. Lastly, this study introduces various methods of research by utilizing a machine learning approach.