• Journal of Korea Water Resources Association
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• v.55 no.12
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• pp.1137-1147
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• 2022

River and groundwater stages are the main elements in the hydrologic cycle. They are spatially correlated and can be used to evaluate hydrological and agricultural drought. Stochastic simulation is often performed independently on hydrological variables that are spatiotemporally correlated. In this setting, interdependency across mutual variables may not be maintained. This study proposes the Bayesian vector autoregression model (VAR) to capture the interdependency between multiple variables over time. VAR models systematically consider the lagged stages of each variable and the lagged values of the other variables. Further, an autoregressive model (AR) was built and compared with the VAR model. It was confirmed that the VAR model was more effective in reproducing observed interdependency (or cross-correlation) between river and ground stages, while the AR generally underestimated that of the observed.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.4
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• pp.243-248
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• 2022

Weight optimization was performed for a rotorcraft shaft system using one-dimensional Euler-Bernoulli beam elements. Torsion, shaft support stiffness such as bearings, flange mass are all considered. To guarantee structural dynamic stability, eigenvalue analysis was performed to avoid critical speed and tooth mesh excitation form the gearbox. The weight optimization was performed by adjusting the thickness and radius while the length of the shaft was fixed, and the optimization process was divided into two stages. In the first, the weight is optimized with the torsional strength constraint. In the second, the difference between the primary mode of shaft and the critical speed is maximized so that the primary mode of the shaft can avoid the critical speed while the constraint on the torsional strength of the shaft is satisfied according to the standard for shaft system stability (AMC P 706-201, 1974). The proposed method was verified by comparing the results of the optimal design using the given one-dimensional beam elements with the stress results of the 3D finite element and the actual manufactured shaft.

• Journal of Aerospace System Engineering
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• v.16 no.4
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• pp.60-67
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• 2022

An Electro-Optical Tracking System (EOTS) is an electric optical system with EO/IR cameras, laser sensors, and an IMU. The EOTS calculates coordinates of targets, using attitude and acceleration measured by the IMU. In particular for an armed aircraft, the performance of the weapon system depends on how quickly and accurately it acquires the target coordinates. The IMU should be operated after alignment is complete, to meet the coordinate accuracy required by the weapon system so the initial stabilization time of the IMU should be reduced, by quickly measuring the attitude and acceleration. Alignment is the process of determining the initial attitude by resolving the attitude error of the IMU, and the IMU of mission equipment such as an airborne EOTS, uses velocity matching based on the velocity from GPS/INS for aircraft navigation. In this paper, a method is presented to improve the transfer alignment performance of the airborne EOTS, by maneuvering aircraft and the mission equipment. First, the performance factor of the alignment was identified, as a heading error through the velocity matching model and simulation results. Then acceleration maneuvers and attitude changes were necessary, to correct the error. As a result of flight tests applied to an EOTS on a OOO aircraft system, the transfer alignment performance was improved as the duration time was decreased, by more than five times when the aircraft accelerated by more than 0.2g and the EOTS was moving until 6.7deg/s.

• Journal of Korean Society of Disaster and Security
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• v.15 no.2
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• pp.13-25
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• 2022

Public consent is essential to proceed with large-scale projects such as dam and hydroelectric power plant in the Carbon Neutral Era. In general, when designing facilities such as dams and river facilities, the impact due to constructing them is analyzed through numerical simulation in advance. Those facilities are built to cope with floods and usually HEC-RAS is used for numerical simulation in this process. The numerical simulation provides accurate data, but it is very difficult to persuade the public only with the data. Therefore, this study intends to consider the utilization of metaverse in the field of urban flooding and flood response. The applicability of metaverse was confirmed by emphasizing visual effects and providing easy-to-see data, using a kind of metaverse platform called Cities: Skylines. The functions and limitations of this platform were reviewed. A virtual flood scenario was applied after implementing real cities on a metaverse. The hazard map established in Korea and the results of applying the scenario of metaverse platform were compared. On the metaverse, not only the disaster situation caused by realizing the city and society as it is, but also the spread of social disasters after the disaster can be confirmed. Through this, countermeasures can be virtually implemented. If these social and humanistic data are also verified in the future, it is expected that the overall process for responding to urban flooding can be modeled.

• The Journal of the Korea Contents Association
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• v.22 no.1
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• pp.535-544
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• 2022

This study identified the relationship between deliberate rumination of adults who experienced traumas and post-traumatic growth, and examined the mediating model of meaning of life moderated by trauma intensity on deliberate rumination and post-traumatic growth. Participants were 318 male and female adults who experienced traumas. The moderated mediating effect was analysed with PROCESS Macro 3.5 Model 7. Results revealed that deliberate rumination of adults who experienced traumas was positively correlated with trauma intensity, meaning of life, and post-traumatic growth, while meaning of life was positively correlated with post-traumatic growth. In a moderated mediating model for post-traumatic growth, there was significant interaction effect of deliberate rumination and trauma intensity; conditionally indirect effect of deliberate rumination was only significant for whose trauma intensity were high. These findings suggest that adults who did deliberate rumination are more likely to experience post-traumatic growth with finding meaning of life. And, the moderating effect suggests that this influence is only with higher levels of trauma intensity. In conclusion, deliberate rumination of severe traumatic event may lead to post-traumatic growth, and it can be helpful to experience the meaning of life in the process.

• The Journal of the Korea Contents Association
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• v.22 no.2
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• pp.487-500
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• 2022

This study aims to examine visitors' usage intention of the mobile AR(Augmented reality) application for tourism in Korea. For this purpose, the study analyzed how three attributes of AR tourguide app such as interactivity, vividness, and novelty have influenced on the tourist in terms of three realms of their flow, their experience (education, entertainment, esthetics, and escapism), and their usage intention for the future. It conducted an online survey from 20 to 30 year-old 291 participants and used a structural equation modeling. Survey findings show that first, novelty has a positive influence on the state of flow in AR application after vividness; Interactivity does not any significant effect on the tourists' flow. Second, when tourists explore the flow in the AR tourguide app, it affects all realms of experience economy of education, entertainment, esthetics, and escapism. Third, when using AR tour guide app in the context of historical heritage site, the two dimensions of entertainment and education influence the usage intention but the other two of esthetics and escapism does not. This study has presented a theoretical contribution that it focuses on historical sites as one type of tourist attractions and suggests a new modeling integrating AR attributes, flow, experience, and usage intention. In addition, it can be used to become a practical reference for revising an user-oriented AR application and customer-tailored AR tourism.

• Education of Primary School Mathematics
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• v.25 no.2
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• pp.179-195
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• 2022

Mathematical communication competency, one of the six mathematical competencies emphasized in the latest mathematics curriculum, plays an important role both as a means and as a goal for students to learn mathematics. Therefore, it is meaningful to find instructional methods to improve students' mathematical communication competency and analyze their communication competency in detail. Given this background, this study analyzed 64 sixth graders' mathematical communication competency after they participated in the lessons of fraction division emphasizing mathematical communication. A written assessment for this study was developed with a focus on the four sub-elements of mathematical communication (i.e., understanding mathematical representations, developing and transforming mathematical representations, representing one's ideas, and understanding others' ideas). The results of this study showed that students could understand and represent the principle of fraction division in various mathematical representations. The students were more proficient in representing their ideas with mathematical expressions and solving them than doing with visual models. They could use appropriate mathematical terms and symbols in representing their ideas and understanding others' ideas. This paper closes with some implications on how to foster students' mathematical communication competency while teaching elementary mathematics.

• Journal of the Society of Disaster Information
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• v.18 no.3
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• pp.550-559
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• 2022

Purpose: Pipes are widely used as applied devices in many industrial fields such as machinery, electronics, electricity, and plants, and are also widely used in safety-related fields such as firefighting and chemistry. With the diversification of products, the importance of technology in the piping field is also increasing. In particular, when changing the existing copper pipe to stainless steel, it is necessary to evaluate safety and flow characteristics through structural analysis or flow analysis. Method: This study investigated the safety by flow analysis of the 6.35 inch socket model, which are integrated insert type connectors developed by a company, using CFD analysis technique. For CDF analysis, RAN model and LES model are used. Result: As results of the analysis, amplitude of the pressure fluctuation acting on the wall of the piping system is formed at a level of 3,780 Pa or less, which is a very small level of pressure compared with the operating pressure or design stress of the refrigerant piping. Conclusion: These results mean that the effect of vibration caused by turbulence on the structural safety of the pipe is negligible.

• Korean Journal of School Psychology
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• v.18 no.2
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• pp.269-290
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• 2021

This study was conducted to examine the moderated mediation effect of self-esteem through internet overdependence on the effect of academic stress on depression and anxiety. Surveys were conducted as part of the 13th wave of the Korea Welfare Panel Study. The survey included academic stress, internet overdependence, depression and anxiety, and self-esteem scales. A total of 383 middle school students completed surveys. Data was analyzed using SPSS 21.0 and SPSS PROCESS Macro. There were three major results. First, internet overdependence partially mediation the effect of academic stress on depression and anxiety. Second, self-esteem moderated the relationship between internet overdependence and depression and anxiety. Third, self-esteem also moderated the mediating effect of academic stress on depression and anxiety through internet overdependence. These results indicate that self-esteem is a protective factor against the negative effects of internet overdependence on mental health and of academic stress on depression and anxiety in middle school students. This paper discusses the implications of these results, this study's limitations, and suggestions for future studies.

• Journal of Intelligence and Information Systems
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• v.28 no.4
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• pp.135-155
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• 2022

This study analyzes patent trends by deriving sub-technical fields of Organic Light-Emitting Diodes (OLEDs) industry, and analyzing technology value, originality, and diversity for each sub-technical field. To collect patent data, a set of international patent classification(IPC) codes related to OLED technology was defined, and OLED-related patents applied from 2005 to 2017 were collected using a set of IPC codes. Then, a large number of collected patent documents were classified into 12 major technologies using the Latent Dirichlet Allocation(LDA) topic model and trends for each technology were investigated. Patents related to touch sensor, module, image processing, and circuit driving showed an increasing trend, but virtual reality and user interface recently decreased, and thin film transistor, fingerprint recognition, and optical film showed a continuous trend. To compare the technological value, the number of forward citations, originality, and diversity of patents included in each technology group were investigated. From the results, image processing, user interface(UI) and user experience(UX), module, and adhesive technology with high number of forward citations, originality and diversity showed relatively high technological value. The results provide useful information in the process of establishing a company's technology strategy.