• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.1
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• pp.33-44
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• 2019

Due to the recent climate change realization (timing, rainfall pattern changes), the flow regime is changing according to the watershed. The long-term change of flow regime is causing a significant change in structure and function of aquatic ecosystems. However, there is no analysis from the viewpoint of the aquatic ecosystem including flow rate alteration and ecological characteristics as well as the climate change connection in Korea yet. Therefore, We quantitatively assessed the impact of present-future flow regime alteration due to climate change on the Pseudopungtungia nigra habitat in the Mankyung river and floodplain area. As a result, it was confirmed that extreme hydrological conditions such as flood and drought are intensified in the future than the present. Especially, the changes of flow regime characteristics were clarified by comparing and analyzing the magnitude, frequency, duration, rate of change, and by linking flow regime characteristics with physical habitat analysis, it could be suggested that climate change would significantly increase the risk of future ecological changes.

• Journal of Ocean Engineering and Technology
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• v.33 no.5
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• pp.435-446
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• 2019

Because offshore structures are affected by various environmental loads, the risk of damage is high. As a result of ever-changing ocean environmental loads, damage to offshore structures is expected to differ from year to year. However, in previous studies, it was assumed that a relatively short period of load acts repeatedly during the design life of a structure. In this study, the residual life of an offshore wind turbine support structure was evaluated in consideration of the timing uncertainty of the ocean environmental load. Sampling points for the wind velocity, wave height, and wave period were generated using a central composites design, and a transfer function was constructed from the numerical analysis results. A simulation was performed using the joint probability model of ocean environmental loads. The stress time history was calculated by entering the load samples generated by the simulation into the transfer function. The damage to the structure was calculated using the rain-flow counting method, Goodman equation, Miner's rule, and S-N curve. The results confirmed that the wind speed generated at a specific time could not represent the wind speed that could occur during the design life of the structure.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.41-46
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• 2018

In this research, numerical analysis was performed to determine the effects of hydrogen on biogas combustion for homogeneous charged compression ignition (HCCI) engines. The target engine specifications were a 2300cc displacement volume, 13:1 compression ratio, 15kW of electricity, and 1.2 bar boost pressure. The engine speed was fixed to 1800rpm. By varying the excess air ratio and hydrogen contents, the cylinder pressure, nitric oxide, and carbon dioxide were measured as a function of the hydrogen contents. According to preliminary studies related to the reaction mechanism for methane combustion and oxidation, a GRI 3.0 mechanism as the base mechanism was selected for HCCI combustion calculations describing the detailed reaction mechanism. By adding hydrogen, NO was increased while $CO_2$ was decreased. The cylinder pressure was also increased, having advanced timing for the maximum cylinder pressure and pressure rise region. Furthermore, lean operation limits were extended by adding hydrogen to the HCCI engine.

• Archives of Plastic Surgery
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• v.48 no.2
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• pp.219-223
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• 2021

Background A micro-arteriovenous fistula (AVF) is a minute, short shunt between an artery and a vein that does not pass through a capillary. We investigated the association between micro-AVFs and lymphedema using computed tomography angiography (CTA) and venous blood gas analysis. Methods In 95 patients with lower limb lymphedema, the presence or absence of early venous return (EVR) was compared between patients with primary and secondary lymphedema. Furthermore, we investigated the difference in the timing of edema onset in patients with secondary lymphedema with or without EVR using CTA. In 20 patients with lower limb lymphedema with confirmed early EVR in a unilateral lower limb, the partial pressure of oxygen (PO₂) was compared between the lower limb with EVR and the contralateral lower limb. Results Secondary lymphedema with or without EVR occurred at an average of 36.0±59.3 months and 93.5±136.1 months, respectively; however, no significant difference was noted. PO₂ was 57.6±11.7 mmHg and 44.1±16.4 mmHg in the EVR and non-EVR limbs, respectively, which was a significant difference (P=0.005). Conclusions EVR and venous blood gas analysis suggested the presence of micro-AVFs in patients with lower extremity edema. Further research is warranted to examine the cause of micro-AVFs, to advance technology to facilitate the confirmation of micro-AVFs by angiography, and to improve lymphedema by ligation of micro-AVFs.

• Smart Media Journal
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• v.9 no.4
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• pp.44-51
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• 2020

Since the mid-to-late 1990s, there have obviously been many changes in the North Korean economy. Since the change has been more pronounced since Kim Jong Un took power in 2012, the purpose of the paper is to track the trend of economic policy by timing. In this paper, I use LDA Topic Modeling, a text-mining analyzer method, to analyze the economics journal "Economic Research," which is a representative literature in the economic field published in North Korea. An in-depth analysis of the "economic research," which has an unrivaled position as an economic journal produced in North Korea, can be said to be an essential task in tracking the reality, limitations facing the economy and alternatives that North Korean authorities are aware of. Through the "Economic Research," where various topics of debate on the North Korean economy are hidden, the North Korean leader's economic policy flow is examined and the contents of the "change" intended by the current Kim Jong-un regime are analyzed.

• Journal of Korea Port Economic Association
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• v.37 no.3
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• pp.105-116
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• 2021

Harbor floating pier is a structure in which one or several floating vessels are connected to have a port function so that ships can be bordered regardless of tide level in places where differences between tidal rocks are severe. There are 233 harbor floating piers in Korea, and 27.5% of harbor floating pier are over 30 years old. Harbor floating piers older than 30 years are potentially at high risk of accidents. However, there is no clear standard for disposal or sale of aging harbor floating pier, and the management regulations on the timing of maintenance inspection and repair are ambiguous. In this study, the AHP model was designed by classifying the problems and improvement factors of harbor floating pier facility operation through interviews with port managers and existing literature studies. The AHP analysis showed that the relative importance of the evaluation factors of the higher class was in the order of improvement of the legal system, improvement of operational management and technical improvement. This study can be used as basic data for improving the operation of Korea harbor floating pier facilities.

• Journal of People, Plants, and Environment
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• v.24 no.5
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• pp.469-483
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• 2021

Background and objective: If the Nelumbo nucifera spreads in a wetland at a high density, it can have considerable positive and negative ecological effects on habitats. For this reason, it is necessary to precisely investigate the impacts of its rapid proliferation. This study was conducted to propose the distribution and management of N. nucifera, which can cause the degradation of wildlife habitats due to the rapid spread of internal and external environmental factors that may affect the Junam wetland ecosystem. Methods: For the investigation and analysis of physical and ecological characteristics, factors of the abiotic environment such as general weather conditions, topography and water depth structure, and soil and water quality analysis, and bioenvironment characteristics such as changes in the N. nucifera community distribution were evaluated. To assess whether the differences in the soil depth and physicochemical characteristics between the N. nucifera community and the aquatic plant community are statistically significant, a One-way ANOVA was executed. Results: N. nucifera was presumably introduced in approximately 2007 and observed at a prevalence of only 0.8% in 2009, but had expanded to 11.1% in 2014. After that, the area was increased to 19.3% in 2015 and 40.0% in 2017, about twice that of the previous survey year. The rapid diffusion of an N. nucifera colony can have adverse effects on wildlife habitats and biodiversity at Junam Wetland. To solve these problems, four management methods can be proposed; water level management, mowing management, installation of posts and removal of lotus roots. Control of the N. nucifera community using these methods was judged to be suitable for cutting and water level management when considering expansion rate, water level variation, and wildlife habitat impacts. Conclusion: As the biotic and abiotic environmental factors are different for each wetland, it is necessary to determine the timing and method of management through a detailed investigation.

• Journal of the Korea Society of Computer and Information
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• v.27 no.11
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• pp.165-172
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• 2022

This paper proposes a method to derive the time points for helpful intervention based on conclusions drawn from a previous study which collected data during barista training performed by students with developmental disabilities. To identify this intervention time, this study utilized distance information between the hand of a student and each barista tool in a virtual reality space. If the cumulative distance from a student's hand to the key barista tool is relatively longer than the cumulative distance to other barista tools, it is highly likely that the student is not using the key barista tool, which must be used to successfully complete the given task. In other words, the distance information signals the task is not being properly performed and represents the intervention time to help the student. As a result of verifying a hypothesis through statistical analysis, this study found that the relationship between the success or failure of a student's training and the cumulative distance between the student's right hand and the key barista tool was statistically significant, but not for the left hand.

• Journal of Service Research and Studies
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• v.13 no.1
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• pp.1-26
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• 2023

We analyze the effects and related factors of Smart Factory adoption. 110 and 325 samples were collected by median-size-industry matching method, respectively, of adopting and non-adopting companies. We use financial statement data (ROA, etc.) from the year before adoption to the fourth year after adoption. Abnormal operating performance and annual abnormal changes are obtained according to event study method, and analyzed by Wilcoxon signed-rank test and t-test. ROA and sales growth rate demonstrate short-term effects after adoption, but not long-term effects. As a result of regression analysis to examine if the three factors of labor intensity, R&D intensity, and prior financial performance have moderating effect, the moderating effect of R&D intensity and prior financial performance is confirmed. In addition, we perform regression analysis to confirm performance effects of early and late adoptions and whether prior financial performance and organization size have moderating effect. It is confirmed that the later the time of adoption, the greater the effect of adoption in the long term and the moderating effect of prior financial performance and organization size is confirmed.

• 한국정보교육학회:학술대회논문집
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• 2021.08a
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• pp.261-267
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• 2021

This study examines the purpose and goals of ICT education, compares them with current software and artificial intelligence-oriented information curriculum, analyzes foreign SW curriculum, extracts learning topics and elements, and analyzes whether the current information curriculum is presented effectively. As a result of the analysis, the number of information-related courses in Korea is currently lower than in other countries, which has reduced the number of basic computer applications and underlying software applications such as presentations and spreadsheets covered in ICT training in the past. In addition, compared to Korea's curriculum where information education begins in the fifth grade of elementary school, other countries are introducing information education from the first grade to the third grade of elementary school. Therefore, active discussions on the expansion of the number of information education, the timing of introduction of information education, and the utilization of basic computers are needed.