• Steel and Composite Structures
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• v.30 no.3
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• pp.201-215
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• 2019

In this research, the behavior of tube-in-tube BRBs (TiTBRBs) has been investigated. In a typical TiTBRB, the yielding core tube is located inside the outer restraining one to dissipate energy through extensive plastic deformation, while the outer restraining tube remains essentially elastic. With the aid of FE analyses, the monotonic and cyclic behavior of the proposed TiTBRBs have been studied as individual brace elements. Subsequently, a detailed finite element model of a representative single span-single story frame equipped with such a TiTBRB has been constructed and both monotonic and cyclic behavior of the proposed TiTBRBs have been explored under the application of the AISC loading protocol at the braced frame level. With the aid of backbone curves derived from the FE analyses, a simplified frame model has been developed and verified through comparison with the results of the detailed FE model. It has been shown that, the simplified model is capable of predicting closely the cyclic behavior of the TiTBRB frame and hence can be used for design purposes. Considering type of connection detail used in a frame, the TiTBRB member which behave satisfactorily at the brace element level under cyclic loading conditions, may suffer global buckling due to the flexural demand exerted from the frame to the brace member at its ends. The proposed TiTBRB suit tubular members of offshore structures and the application of such TiTBRB in a typical offshore platform has been introduced and studied in a single frame level using detailed FE model.

• Korean journal of medical education
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• v.30 no.4
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• pp.339-346
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• 2018

Purpose: The purpose of this study was to examine whether non-cognitive student attributes such as learning style and personality type affected academic performance in a flipped learning classroom of a pre-dental undergraduate science course. Methods: 'Biodiversity and Global Environment,' a 15-week, 3-credit course, was designed as a flipped class in Seoul National University School of Dentistry in 2017. Second-year pre-dental students were required to enroll in the course and to engage in online learning and in-class discussion. The Kolb's Learning Style Inventory and the Myers-Briggs Type Indicator were conducted to measure non-cognitive student factors. Independent samples t-test and multivariate regression analyses were used to examine the relationships between self-rated measurements and academic achievement. Results: More than half of the students enrolled in the flipped science course had an assimilator learning style (50%), followed by convergers (24%), accommodators (16%), and divergers (10%), and their personality types were dominated by the introverted, sensing, thinking, and judging types, respectively. Examining group differences using the t-test demonstrated a significant relationship between the diverger group and higher academic success. In particular, the multivariate regression analysis indicated that both thinking types and female students performed better in discussion than feeling types and male students. Conclusion: To operate the flipped learning classroom more effectively in medical and dental education, the instructor should carefully develop and apply a more tailored facilitation and relevant assessment by considering student learning styles and personality types.

• Journal of Information Technology Applications and Management
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• v.27 no.6
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• pp.53-73
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• 2020

Many prior studies have been conducted that positive reviews increase the intention to purchase. However, there are very few papers that have studied the impact of review search on purchase satisfaction. It is meaningful to study the impact of review search on purchase satisfaction as it can lead the business successfully by inducing repurchase. There is also no study of how review search have different effects on purchase satisfaction among countries. Given the growing number of cross-border e-commerce, we believe that the need for research is high because identifying these differences between countries can have a very important impact on a company's successful overseas expansion. Therefore, in this study, the impact of positive and negative review search on purchase satisfaction and the national impact were set up as a research model. In order to verify this research model, the survey was distributed to those who experienced online purchase in Korea and China, and a total of 234 copies were collected, including 125 copies in Korea, 109 copies in China, and the research model was verified using Smart-PLS structural equation analysis tools. First, positive review search has been shown to positively affect purchase satisfaction. Second, it has been shown that negative review search also has a positive effect on purchase satisfaction. Third, the impact of positive and negative review search on purchase satisfaction was different between Korea and China. While Korea is more aggressive in review search than China due to its high tendency to avoid uncertainty, China is less likely to avoid uncertainty than Korea and is more likely to rely on brand familiarity. Therefore, according to the uncertainty avoidance moderation effect the impact of positive and negative review search on purchase satisfaction was higher in Korea than in China. In this study, Shopping mall managers need to take strategic measures to maximize shopping mall performance by recognizing positive aspects of negative review search on purchase satisfaction. Companies and managers in Korea and China can establish strategies to promote product sales when companies enter the global market.

• Journal of Korea Water Resources Association
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• v.54 no.2
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• pp.135-144
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• 2021

This paper attempted to find implications for water resource management and water quality improvement by analyzing the causal relationship among discharge, water temperature and pollution index, which were expected to have a great effect on water quality with the rise of water temperature and precipitation change as the warming effect in recent years. For this purpose, the unit root test, cointegration test, and Granger causal test were carried out for 10 multi-purpose dams in Korean major water systems using time series data on discharge, water temperature, BOD, COD and DO. It was analyzed that the fluctuation of water temperature affected the pollution index more than the fluctuation of discharge volume. Also, Hapcheon dam and Chungju dam were the best water quality management dams based on the high causal relationship between water quality and discharge. The second rank was Daecheong dam. The third-ranking group were Yongdam and Andong dam, whose causal relationships between water quality and discharge were low. The last group were the remaining five dams.

• Atmosphere
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• v.32 no.4
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• pp.277-295
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• 2022

The global weather prediction model, Korean Integrated Model (KIM), has been in operation since April 2020 by the Korea Meteorological Administration. This study assessed the performance of heat waves (HWs) in Korea in 2020. Case experiments during 2018-2020 were conducted to support the reliability of assessment, and the factors which affect predictability of the HWs were analyzed. Simulated expansion and retreat of the Tibetan High and North Pacific High during the 2020 HW had a good agreement with the analysis. However, the model showed significant cold biases in the maximum surface temperature. It was found that the temperature bias was highly related to underestimation of downward shortwave radiation at surface, which was linked to cloudiness. KIM tended to overestimate nighttime clouds that delayed the dissipation of cloud in the morning, which affected the shortage of downward solar radiation. The vertical profiles of temperature and moisture showed that cold bias and trapped moisture in the lower atmosphere produce favorable conditions for cloud formation over the Yellow Sea, which affected overestimation of cloud in downwind land. Sensitivity test was performed to reduce model bias, which was done by modulating moisture mixing parameter in the boundary layer scheme. Results indicated that the daytime temperature errors were reduced by increase in surface solar irradiance with enhanced cloud dissipation. This study suggested that not only the synoptic features but also the accuracy of low-level temperature and moisture condition played an important role in predicting the maximum temperature during the HWs in medium-range forecasts.

• Earthquakes and Structures
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• v.22 no.6
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• pp.539-548
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• 2022

Steel plate shear walls (SPSWs) are one of the most important and widely used lateral load-bearing systems. The reason for this is easier execution than reinforced concrete (RC) shear walls, faster construction time, and lower final weight of the structure. However, the main drawback of SPSWs is premature buckling in low drift ratios, which affects the energy absorption capacity and global performance of the system. To address this problem, two groups of SPSWs under cyclic loading were investigated using the finite element method (FEM). In the first group, several series of circular rings have been used and in the second group, a new type of SPSW with concentric circular rings (CCRs) has been introduced. Numerous parameters include in yield stress of steel plate wall materials, steel panel thickness, and ring width were considered in nonlinear static analysis. At first, a three-dimensional (3D) numerical model was validated using three sets of laboratory SPSWs and the difference in results between numerical models and experimental specimens was less than 5% in all cases. The results of numerical models revealed that the full SPSW undergoes shear buckling at a drift ratio of 0.2% and its hysteresis behavior has a pinching in the middle part of load-drift ratio curve. Whereas, in the two categories of proposed SPSWs, the hysteresis behavior is complete and stable, and in most cases no capacity degradation of up to 6% drift ratio has been observed. Also, in most numerical models, the tangential stiffness remains almost constant in each cycle. Finally, for the innovative SPSW, a relationship was suggested to determine the shear capacity of the proposed steel wall relative to the wall slenderness coefficient.

• Journal of the Korea Society of Computer and Information
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• v.27 no.5
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• pp.225-232
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• 2022

This study aims to empirically examine whether consumers' perceptions of Chinese e-commerce firms's CSR activities, along with psychological construct of company-consumer identification, and corporate trust affect their purchase intention based on theory of reasoned action. The study used a survey method for data collection to confirm research hypotheses with a total of 240 respondents used for final analysis. The results showed that economic responsibility, ethical responsibility, and legal responsibility have a positive effect on consumers' purchase intention. In addition, corporate trust and company-consumer identification were found to mediate the relationship between consumers' CSR perceptions and purchase intention. The result of this study is expected to provide useful theoretical as well as practical implications to advance the current understanding on the effects of consumers' CSR perception on business performance.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.58 no.1
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• pp.10-18
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• 2022

Fishery sea anchor is widely used for many fishing vessels. However, standardization of the dimension and terminology of the fishery sea anchor has not been achieved, reducing the reliability of the performance and safety of the fishery sea anchor. Therefore, this study researches the reality of usage of fishery sea anchor and then attempts to suggest the development direction of the standard draft as basic data. As a result of the survey on the reality of usage show that various terms were used for each part of the fishery sea anchor (including the incorrect form of non-standard words derived from Japanese) and that the production of this product in the fishery sea anchor market was concentrated on one specific manufacturer. In addition, the main specifications of the fishery sea anchor are set and manufactured based on conventional experience without standards. In the field, there was no standardized drawing for fishery sea anchor and users had low awareness of the main specifications of fishery sea anchor. Therefore, this study suggested the following regarding the fishery sea anchor: standard terms for each part including Korean and English names and standard drawing of sea anchor. It is hoped that this study will contribute to research for the standardization of fishery sea anchor, which will increase in reliability and lead to increased interest in standardization in the fishery field.

• Composites Research
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• v.36 no.1
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• pp.32-36
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• 2023

Recently, as global environmental issues for sustainable development, such as carbon neutrality, have emerged, disposal methods of glass fiber composites, a material of existing wind turbines, have become a problem. To solve this problem, in this study, 30kW wind turbine blades were manufactured using flax fiber-based composites, which are eco-friendly natural fiber composites that can replace existing glass fiber composites, and their suitability was evaluated. First, mechanical strength tests were conducted to verify the feasibility of using eco-friendly natural flax fiber composites as a wind turbine blade material, and as a result, better strength were confirmed compared to previous studies on the properties of flax fiber composites. In addition, the suitability was confirmed through a static strength performance evaluation test to measure the static strength of the flax fiber composite blade using the manufactured 30kW class flax fiber composite blade.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.2_2
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• pp.333-340
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• 2023

Environmental regulations are being strengthened worldwide to solve global warming. For this reason, interest in eco-friendly gas fuels such as LNG and hydrogen is continuously increasing. However, when adopting eco-friendly gas fuel, liquefying at a cryogenic temperature is essential to ensure economic feasibility in storage and transportation. Although austenitic stainless steel is typically applied to store cryogenic liquefied gas, structural steel can experience sudden heat shrinkage in the case of leakage in the loading and unloading process of LNG. In severe cases, the phase of the steel may change, so care is required. This study conducted Charpy impact tests on steel material in nine different temperature ranges, from room to cryogenic temperatures, to analyze the effects of cryogenic liquefied gas leaks. As a result of the study, it was not easy to find variations in ductile to brittle transition temperature (DBTT) due to the leakage of cryogenic liquefied gas. Still, the overall impact toughness tended to decrease, and these results were verified through fracture surface analysis. In summary, brittle fracture of the steel plate may occur when a secondary load is applied to steel for hull structural use exposed to a cryogenic environment of -40 ℃ or lower. Therefore, it needs to be considered in the ship design and operating conditions.