• Journal of Korea Water Resources Association
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• v.56 no.spc1
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• pp.1049-1058
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• 2023

The flow passing through river-crossing structures such as weirs and low-fall dams is dominated by rapidly varied flow including hydraulic jump. The intense unsteadiness of flow velocity and free surface profile affects the stability of such hydraulic structures. In particular, the steady hydraulic jump generated at high Froude number conditions includes remarkably air entrainment, making the flow characteristics more complicated. In this study, a large-eddy simulation was performed for turbulence effect and the hybrid VoF technique to simulate the steady hydraulic jump at the Froude number of 7.3 and the Reynolds number of 15,700. The results of the numerical simulation showed that the instantaneous maximum pressure and time-average pressure distribution calculated on the bottom surface downstream of the structure could be reasonably well reproduced being in good agreement with the experimental values. However, the instantaneous minimum pressure distribution in the direct downstream of the structure shows the opposite pattern to the target experimental measurement value. However, the numerical simulation performed in this study is considered to reasonably predict the minimum pressure distributions observed in various experiments conducted at similar conditions. The vertical distributions of flow velocity and air concentration computed in the center of the hydraulic jump were found to be in good agreement with the experimental results measured under similar conditions, showing self-similarity. These results show that the large eddy simulation and hybrid VoF techniques applied in this study can reproduce the hydraulic jump with strong air entrainment and the resulting intense free surface and pressure fluctuations at high Froude number conditions.

• Journal of The Korean Association For Science Education
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• v.29 no.1
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• pp.90-105
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• 2009

This study analyzed current programs practiced by science-gifted education centers. This study was based on concerns of 18 science teachers on six science-gifted education centers of the Seoul Metropolitan Office of Education that had local representatives. For this study, we collected data using journals, documents, reports, survey reviews and interviews with science teachers. Science teachers were concerned about the selection and identification of gifted students, education periods, curriculum, and student evaluation. More authentic measurement for students' potential ability were needed for the identification and selection process. If the purpose of science-gifted centers was to be met, the number of students selected should be determined by local differences rather than regional equality. The curriculum and educational period could make good use of time allotted for vacation to increase lesson periods. Lessons based on strategies like contests for improving the students' creativity, free inquiry and communication skills had to be encouraged. A consistent system for science-gifted education from primary school to high school was needed.

• Journal of Korea Water Resources Association
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• v.57 no.1
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• pp.59-72
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• 2024

Agricultural reservoirs supply water for various purposes such as irrigation, maintenance, and living. Since agricultural reservoirs respond sensitively to seasonal and climate changes, it is essential to estimate supply and inflow for efficient operation, and water management should be done based on these data. However, in the case of agricultural reservoirs, the measurement of supply and inflow is relatively insufficient compared to multi-purpose dams, and inflow-supply analysis in agricultural reservoirs through water balance analysis is necessary for efficient water management. Therefore, rainfall-runoff analysis models such as ONE model and Tank model have been developed and used for reservoir water balance analysis, but the applicability analysis for ungauged watersheds is insufficient. The ONE model is designed for daily runoff calculation, and the model has one parameter, which is advantageous for calibration and ungauged watershed analysis. In this study, the water balance was analyzed through the ONE model and the Tank model for 15 watersheds upstream of dams, and R² and NSE were used to quantitatively compare the performance of the two models. The simulation results show that the ONE model is suitable for predicting the inflow of agricultural reservoirs with the ungauged watershed

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.22 no.6
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• pp.196-207
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• 2023

As part of measures to address the climate crisis, buses are also being converted to electric and hydrogen buses. Local authorities need to prioritize carbon emissions when allocating newly introduced and converted electric and hydrogen buses, and as a method, consider the introduction of Low Emission Bus Zones (LEBZ) to propose the reduction of pollution from specific links. To introduce LEBZ, it is necessary to compare the carbon emissions before and after its implementation, yet there is a shortage of studies that focus solely on buses or analyze the effects of introducing LEBZ to specific links. In this paper, we utilized bus information system data to calculate and compare the effects of introducing LEBZ to bus priority lanes in Jeju. We categorized scenarios into five groups, with scenarios 1 through 4 involving the introduction of LEBZ, and scenario 5 designating cases where LEBZ was not introduced. Comparative results confirmed that in scenarios with LEBZ introduction, the reduction per km reached a maximum of 0.097t per km, whereas in cases without LEBZ, it amounted to 0.022t per km, demonstrating higher efficiency. It underscores the significance of conducting carbon emission calculations and comparing the effects of LEBZ introduction using bus information system data, which can be directly applied by local authorities to make informed and rational decisions.

• Journal of Practical Agriculture & Fisheries Research
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• v.26 no.1
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• pp.22-29
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• 2024

In this study, we summarized the definition of smart vegetable seedling production technology, analysis of smart seedling production system, a hardware and software configuration model for smart seedling production system, research and development trends in smart seedling production system, and proposed future research and development plans for smart seedling production technology. Smart vegetable seedling production is a data-based seedling production, management, and distribution system that utilizes 4th Industrial Revolution technology to improve seedling productivity and quality. The production of vegetable seedlings using smart seedling production technology can be efficiently managed by collecting, analyzing, and managing information on seedlings, environment, and tasks at each stage of production by linking with the smart seedling integrated management system. However, there is still a lack of standardization of seedling standards and quality for each vegetable crop to establish smart seeding production technology, as well as development of smart seedling production element technology, which requires national wide R&D support.

• Korean Journal of Heritage: History & Science
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• v.57 no.1
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• pp.22-36
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• 2024

In 1993, a large number of relics was found in Cheongju Sanesa Buddhist Temple. They show superiority as bronze-based products, and are especially important in since they provide much information about the time of their creation. However, there are many opinions about the time they were hoarded: in the middle of the 13^th century, late in the 13^th century, early in the 14^th century, etc. This study estimates the time they were hoarded to be some time in April 1291 during the invasion of Kădīn (哈丹) in the Yuan Dynasty. Kădīn's troops invaded the Goryeo Dynasty, then went through Yangpyeong and Wonju in January 1291 and appeared in Yeongi-hyeon on May 1 of that year. Based on records, this study verified that the troops passed through Cheongju on their way from Chungju to Yeongi-hyeon (currently Sejong-si) and pointed out that the invasion route of the troops was the background for the hoarding of Sanesa relics. The estimation that the Sanesa relics were hoarded in 1291 when Kădīn's invasion was going on makes it possible to reasonably clear up the era of the relics in which the Heavenly Stems called gānzhī (干支) Muo (戊午), Gyeongshin (庚申), Giyu(己酉) etc. were written. That is, Giyu Geumgo is presumed to be the year 1249, Muo Hyangro 1258, Gyeongshin Hyangwan 1260, etc.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.6
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• pp.81-88
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• 2008

The purpose of this study is to improve and modify the evaluation method of load carrying capacity for simply supported PSC I Typed girder bridge. To do this, conventional ASD(Allowable Stress Design) and USD(Ultimate Strength Design) evaluation method were initially investigated and it was evaluated that the conventional USD evaluation method may perform the load carrying capacity as conservative because it do not consider the prestressing upper-force effect of simply supported PSC I Typed girder bridge. To reasonably evaluate the load carrying capacity, the upper-force effect should be considered to the PSC I Typed girder bridge. Thus, in this study, the MUSD method was Suggested and compared to the nonlinear FEM based-load carrying capacity using the live load factor and the efficiency of the evaluation method of load carrying capacity was investigated by experimental and analytical result. In the result of this study, the suggested MUSD evaluation method showed a reasonable evaluating result for the simply supported PSC bridge. For the new technique of load carrying capacity based on the nonlinear FEM analysis, it could effectively simulate the load-deflection relationship and the load carrying capacity of the PSC I Typed girder bridge.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.2 s.54
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• pp.172-180
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• 2009

Normally in order to build a semi-active control system equipped with MR damper, the dynamic modeling of the damper is required to numerically predict its dynamic damping force and also its behavioral characteristics. For the dynamic modeling of the MR damper, this paper attempts to predict and evaluate its dynamic behavior by applying specifically both a power model and a Bingham model. Dynamic loading tests were performed on the squeeze type of damper specially designed for this research, and force-displacement hysteresis loops confirmed the effectiveness of the damper as a semi-active control device. In the meantime, in order to evaluate the effectiveness of each model applied, the model parameter for each model was identified. On the basis of the parameter, we derived the error ratio of the force-velocity relationship curve and the dynamic damping force, which was contrasted and compared with the experimental results of the squeeze type of damper. Finally, the squeeze type of MR damper developed in this research was proved to be valid as a semi-active control device, and also the evaluation of the two dynamic models showed they were working fine so that they were likely to be easily utilized to numerically predict the dynamic characteristics of any dampers with MR fluid as well as the squeeze type of MR damper.

• Journal of the Korean Institute of Landscape Architecture
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• v.52 no.4
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• pp.69-85
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• 2024

The creation of open spaces has both direct and indirect impacts on the local economy, society, culture, and environment. Since the public usually finances these spaces, it is necessary to ensure procedural rationality by promoting consensus among residents and other stakeholders. This study examines the extent of public participation in the creation of open spaces and summarizes trends. By analyzing seven cases of open space development based on participation in South Korea, the study identifies the characteristics and progression of participation during four phases of the development process in the Gwanghwamun Plaza Restructuring Project (2016-2022). During the agenda-setting phase, the Gwanghwamun Forum was convened to establish agendas for the plaza's restructuring. The design and governance phase included a design competition to select a proposal for the plaza, alongside the establishment of the Gwanghwamun Citizens' Committee for governance. Despite proactive efforts in the conflict resolution phase to halt extensive restructuring and enhance communication, civic groups opposed the project by presenting five distinct agendas. In the implementation phase, multiple public participation programs were conducted before the plaza's reopening. The study found that public participation in the Gwanghwamun Plaza project faced challenges such as inadequate participation conditions, limited information sharing, and monotonous participation opportunities. Although the institutional environment for public participation is improving, practical limitations remain. Therefore, a comprehensive examination of open space creation through public participation is necessary.

• Information Systems Review
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• v.26 no.1
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• pp.289-313
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• 2024

Korean pharmaceutical and bio-health companies began applying for FDA approval in 2000. However, drug companies in South Korea are not required to obtain FDA approval to market their products on the South Korean market, and the approval process is highly resource-intensive. This study utilizes event study methodology to examine the information effect of US FDA approval announcements on the stock prices of pharmaceutical and bio-health companies listed on South Korean stock markets. The study's results show that FDA approval announcements caused abnormal increases in corporate stock prices, indicating that these announcements have a transnational information effect on South Korean companies' value. Furthermore, the results show that the impact of FDA approval announcements on stock prices is greater for small companies than mid-sized and large companies and in bio and healthcare industries than in the traditional pharmaceutical industry. This impact is also more significant on the KOSDAQ (Korea Securities Dealers Automated Quotation) companies than the KOSPI (Korean Composite Stock Price Index) companies and after the expansion of stock price limits. These findings signal that the information effect is more significant when regulatory controls are weaker. The results also indicate that obtaining FDA approval brings above-normal returns for companies and that FDA application is a high-risk, high-return investment.