• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2023년도 학술발표회
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• pp.163-163
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• 2023

Flooding has become an increasing event which is one of the major natural disasters responsible for direct economic damage in South Korea. Driven by climate change, precipitation extremes play significant role on the flood damage and its further increase is expected to exacerbate the socioeconomic impact in the country. However, the empirical evidence associating changes in precipitation extremes to the historical flood damage is limited. Thus, there is a need to assess the causal relationship between changes in precipitation extremes and flood damage, especially in agricultural region like Chungcheong region in South Korea. The spatial and temporal changes of precipitation extremes from 10 synoptic stations based on daily precipitation data were analyzed using the ClimPACT2 tool and Mann-Kendall test. The four precipitation extreme indices consisting of consecutive wet days (CWD), number of very heavy precipitation wet days (R30 mm), maximum 1-day precipitation amount (Rx1day), and simple daily precipitation intensity (SDII), which represent changes in intensity, frequency, and duration, respectively, and the time series data on flooded area and flood damage from 1985 to 2020 were used to investigate the causal relationship in the ARDL-ECM framework and pairwise Granger causality analysis. The trend results showed that majority of the precipitation indices indicated positive trends, however, CWD showed no significant changes. ARDL-ECM framework showed that there was a long-run relationship among the variables. Further analysis on the empirical results showed that flooded area and Rx1day have significant positive impacts on the flood damage in both short and long-runs while R30 mm only indicated significant positive impact in the short-run, both in the current period, which implies that an increase in flooded area, Rx1day, and R30 mm will cause an increase in the flood damage. The pairwise Granger analysis showed unidirectional causality from the flooded area, R30 mm, Rx1day, and SDII to flood damage. Thus, these precipitation indices could be useful as indicators of pluvial flood damage in Chungcheong region of South Korea.

• Journal of Korea Trade
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• 제26권3호
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• pp.45-62
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• 2022

Purpose - Using unexpected changes in geopolitical tensions on the Korean peninsula as a quasi-natural experimental setting, we examine whether and how geopolitical risks travel across borders through firm-level imports and exports linkages. We also test whether the effects are driven by either imports or exports and assess whether firms can effectively hedge themselves against geopolitical risks. Design/methodology - We focus on a series of unanticipated geopolitical events taken place in Korea in 2018. Making use of the shocks to geopolitical climate, we identify five milestone events toward peace talks. We employ the event studies methodology. We examine heterogenous firm-level stock price reactions around key event dates depending on firms' exposure to geopolitical risks. As a measure of firms' exposure to geopolitical risks in Korea, we utilize a text-based measure of firm-level trade links. When a firm announces and discusses its purchase of inputs from Korea or sales of outputs to Korea in their annual disclosure filings, we define a firm to have a trade relationship with Korea and have exposure to Korean geopolitical risks. Similarly, we use a measure of a firm's hedging policies based on a firm's textual mention of the use of foreign exchange derivatives in their annual disclosure. Findings - We find that U.S. firms that have direct trade links to Korea gained significantly more value when the intensity of geopolitical risks drops compared to firms without such trade links to Korea. The effects are pronounced for firms purchasing inputs from or selling outputs to Korea. We find that the effectiveness of foreign exchange hedging against geopolitical risks is limited. Originality/value - We document the international transmission of geopolitical uncertainty through trade linkages. Export links as well as import links serve as important nexus of transmission of geopolitical risks across borders. Hedging strategies involving foreign-exchanges derivatives do not seem to insulate firms again geopolitical risks. With the recent movements of localization and reshuffling of the global value chain, our results suggest a significant impact of geopolitical risks in Korea on the construction of the global value chain.

• Animal Bioscience
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• 제37권3호
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• pp.405-418
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• 2024

In recent years, there has been a growing argument attributing the primary cause of global climate change to livestock industry, which has led to the perception that the livestock industry is synonymous with greenhouse gas (GHG) emissions. However, a closer examination of the global GHG emission by sector reveals that the energy sector is responsible for the majority, accounting for 76.2% of the total, while agriculture contributes 11.9%. According to data from the Food and Agriculture Organization of the United Nations (FAO), the total GHG emissions associate with the livestock supply chain amount to 14.5%. Within this, emissions from direct sources, such as enteric fermentation and livestock manure treatment, which are not part of the front and rear industries, represent only 7%. Although it is true that the increase in meat consumption driven by global population growth and rising incomes, has contributed to higher methane (CH₄) emissions resulting from enteric fermentation in ruminant animals, categorizing the livestock industry as the primary source of GHG emissions oversimplifies a complex issue and disregards objective data. Therefore, it may be a misleading to solely focus on the livestock sector without addressing the significant emissions from the energy sector, which is the largest contributor to GHG emissions. The top priority should be the objective and accurate measurement of GHG emissions, followed by the development and implementation of suitable reduction policies for each industrial sector with significant GHG emissions contributions.

• Nuclear Engineering and Technology
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• 제56권4호
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• pp.1310-1319
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• 2024

The reactor cavity cooling system (RCCS) is a passive reactor safety system commonly present in the designs of High-Temperature Gas-cooled Reactors (HTGR) that removes heat from the reactor pressure vessel by means of natural convection and radiation. It is one of the factors responsible for ensuring that the reactor does not melt down under any plausible accident scenario. For the simulation of accident scenarios, which are transient phenomena unfolding over a span of up to several days, intermediate fidelity methods and system codes must be employed to limit the models' execution time. These models can quantify radiation heat transfer well, but heat transfer caused by natural convection must be quantified with the use of correlations for the heat transfer coefficient. It is difficult to obtain reliable correlations for HTGR RCCS heat transfer coefficients experimentally due to such a system's size. They could, however, be obtained from high-fidelity steady-state simulations of RCCSs. The Rayleigh number in RCCSs is too high for using a Direct Numerical Simulation (DNS) technique; thus, a Reynolds-Averaged Navier-Stokes (RANS) approach must be employed. There are many RANS models, each performing best under different geometry and fluid flow conditions. To find the most suitable one for simulating an RCCS, the RANS models need to be validated. This work benchmarks various RANS models against three experiments performed on the HTTR RCCS Mockup by the Japanese Atomic Energy Agency (JAEA) in 1993. This facility is a 1/6 scale model of a vessel cooling system (VCS) for the High Temperature Engineering Test Reactor (HTTR), which is operated by JAEA. Multiple RANS models were evaluated on a simplified 2d-axisymmetric geometry. They were found to reproduce the experimental temperature profiles with errors of up to 22% for the lowest temperature benchmark and 15% for the higher temperature benchmarks. The results highlight that the pragmatic turbulence models need to be validated for high Rayleigh natural convection-driven flows and improved accordingly, more publicly available experimental data of RCCS resembling experiments is needed and indicate that a 2d-axisymmetric geometry approximation is likely insufficient to capture all the relevant phenomena in RCCS simulations.

• 실천공학교육논문지
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• 제16권4호
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• pp.513-520
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• 2024

본 연구는 AI의 학교교육 영향이 확대됨에 따른 교사의 직무 변화에 대한 연구이다. 전통적으로 교사는 교실 수업, 교육과정 개발, 평가 및 피드백과 같은 핵심 업무를 담당해왔다. AI는 이러한 과정을 자동화할 수 있으며, 특히 개인화된 학습을 통해 효율성을 높일 수 있으며 학생 추적, 행동 감지 및 그룹 활동 분석과 같은 복잡한 교실 관리 작업을 지원할 수 있다. 그러나 AI는 상담 및 대인 커뮤니케이션과 같은 학생 생활 지도에 중요한 측면을 자동화가 어려운 것으로 나타났다. 이와 같은 직무에서 AI가 직접적으로 상담활동을 대체 하는 것은 어렵지만, 데이터 기반의 인사이트와 사전 대화 자료를 제공함으로써 교사를 지원할 수 있다. AI시대의 교사 역량 강화 요소로는 심화 학습 운영 전문성, 데이터셋 분석 능력, 개별학습 운영 능력, 학생 및 학부모 상담역량, 그리고 AI디지털 역량이 필요하다. 교사는 AI와 협업하여 창의성과 확장적 추상능력을 강조하는 수업을 운영하고, AI시스템에서 생성된 데이터셋을 분석하고 개별화된 학습 경로를 조정하는 역량을 가져야 한다. 또한 개별화된 학습과 학생 상담에 집중하여 AI로 대체되기 어려운 부분을 수행해야 한다. 교사의 기본적인 역량으로는 AI디지털 소양 능력이 필요하며, AI시스템에 대한 이해와 학생 데이터 관리 역량이 요구된다.

• 기술혁신학회지
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• 제19권1호
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• pp.48-79
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• 2016

최근 우리나라는 글로벌 경제의 침체를 극복하고 침체된 경제를 활성화시키기 위해서 중소기업의 혁신역량을 강화시킬 수 있는 다양한 정책을 진행해 왔다. 이 연구는 ICT 기술 기업이라는 관점에서 이러한 정부의 노력 중에서 R&D 정보 지원 사업이 가진 가능성과 한계를 실증적으로 연구해서 증거기반의 정책이 가능하도록 시사점을 제공하고자 한다. 이 연구에서는 2014년 중소기업 기술통계조사 결과를 활용해서 정부의 R&D 정보 지원 정책과 중소기업의 기술적 또는 경제적 성과가 어떤 관계가 있는지 분석했다. 이 연구의 결과에 따르면 중소기업에 제공된 R&D 지원 사업(R&D 기획 지원 및 기술정보 제공)은 기술투자에 유의한 관계가 있는 것으로 나타났다. 반면에 R&D 정보 지원 사업은 기술적 또는 경제적 성과와 직접적으로 유의한 관계는 없는 것으로 밝혀졌다. 다만, R&D 기획 지원 사업은 기업이 ICT 분야를 연구하는 경우 기술적 성과에 유의한 관계가 있는 것으로 나타났다. 이 연구의 결과는 ICT를 포함한 기술 중심의 중소기업을 지원하는 정책을 구상하는 정책입안자에게 다양한 시사점을 제공할 수 있으며, 특히 중소기업에게 정보를 지원하는 기업이나 연구자에게 여러 가지 정책적 가이드를 제공해 줄 것으로 기대한다.

• ALGAE
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• 제35권3호
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• pp.263-275
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• 2020

Water temperature is known to affect the growth and feeding of marine dinoflagellates. Each dinoflagellate species grows well at a certain optimal temperature but dies at very cold and hot temperatures. Thus, changes in water temperatures driven by global warming and extremely high or low temperatures can affect the distribution of dinoflagellates. Yihiella yeosuensis is a mixotrophic dinoflagellate that can feed on only the cryptophyte Teleaulax amphioxeia and the chlorophyte Pyramimonas sp. Furthermore, it grows fast mixotrophically but rarely grows photosynthetically. We explored the direct and indirect effects of water temperature on the growth and ingestion rates of Y. yeosuensis feeding on T. amphioxeia and the growth rates of T. amphioxeia and Pyramimonas sp. under 7 different water temperatures (5-35℃). Both the autotrophic and mixotrophic growth rates of Y. yeosuensis on T. amphioxeia were significantly affected by temperature. Under the mixotrophic and autotrophic conditions, Y. yeosuensis survived at 10-25℃, but died at 5℃ and ≥30℃. The maximum mixotrophic growth rate of Y. yeosuensis on T. amphioxeia (1.16 d^-1) was achieved at 25℃, whereas the maximum autotrophic growth rate (0.16 d^-1) was achieved at 15℃. The maximum ingestion rate of Y. yeosuensis on T. amphioxeia (0.24 ng C predator^-1 d^-1) was achieved at 25℃. The cells of T. amphioxeia survived at 10-25℃, but died at 5 and ≥30℃. The cells of Pyramimonas sp. survived at 5-25℃, but died at 30℃. The maximum growth rate of T. amphioxeia (0.72 d^-1) and Pyramimonas sp. (0.75 d^-1) was achieved at 25℃. The abundance of Y. yeosuensis is expected to be high at 25℃, at which its two prey species have their highest growth rates, whereas Y. yeosuensis is expected to be rare or absent at 5℃ or ≥30℃ at which its two prey species do not survive or grow. Therefore, temperature can directly or indirectly affect the population dynamics and distribution of Y. yeosuensis.

• 수산해양기술연구
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• 제35권1호
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• pp.25-34
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• 1999

The Steering and Sailing Rules of International Regulation for Preventing Collisions at Sea now in use direct actions to avoid collision when two power-driven vessels are meeting on reciprocal or nearly reciprocal courses so as to involve risk of collision. But these rules do not refer to the minimum relative distances and safety relative distances between two vessels when they should take such actions.In this paper the ship's collision avoiding actions being analyzed from a viewpoint of ship motions, the mathematical formulas to calculate such relative distances necessary for taking actions to avoid collision were worked out. The values of maneuvering indices being figured out through experiments of 20 actual ships of small, medium, large and mammoth size and applied to calculating formulas, the minimum relative distances and safety relative distances were calculated. The main results were as follows. 1. It was confirmed that the criterion elements for collision avoiding actions in head-on situation of two vessels shall be the minimum relative distances and safety relative distances between them. 2. On the assumption that two vessels same in size and condition were approaching each other in head-on situation, the minimum relative distance of small vessel(GT : 160~650tons) was found to be about 4.7 times her own length, and those of medium (GT:2,300~4,500tons),large(GT:15,000~62,000tons) and mommoth (GT:91,000~194,000tons) vessels were found to be about 5.2 times, about 5.2 times and about 6.1 times their own lengths respectively. 3. On the assumption that two vessels same in size and condition were approaching each other in head-on situation, the safe relative distance of small vessel (GT : 160~650tons) was found to be about 6.8 times her own length, and those of medium (GT : 2,300~4,500tons), large (GT: 15,000~62,000tons) and mammoth (GT : 91,000~194,000tons) vessels were found to be about 9.0 times, about 6.3 times, and about 8.0 times their own lengths respectively. 4. It is considered to be helpful for the safety of ship handling that the sufficient safe relative distances for every vessels shall be more than about 12~14 times which are 2 times minimum relative distance, their own length on above assumption.

• 한국산학기술학회논문지
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• 제19권10호
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• pp.386-393
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• 2018

한국의 군수품 산업은 국내 민간 산업직접지의 전략적인 육성 정책에 맞추어, 그 개발과 생산이 특정지역에 편중되는 경향이 있다. 하지만, 최저가 입찰제, 물류의 발달 등으로 인하여 산업직접지의 거점 클러스터와 중소 클러스터의 연관성이 낮아지고 있다. 본 연구에서는 군수품의 납품에 필수적인 공인 시험성적서 관련 정보를 군수품 품질정보 시스템을 통해 수집하고, 이에 대한 사회연결망분석을 실시하였다. 사회연결망분석은 국방품질보증기관, 시험기관, 계약 및 협력업체의 관계를 UCINET의 Two-Mode Network를 통해 분석하였으며, 데이터 간 관계의 단방향성으로 인하여 근접 및 매개 중심성 등은 계산되지 않았다. 중위 기술 산업인 무기체계 분야에서는 서울지역의 시험분석 인프라에 대한 의존도가 높아 지역 산업 클러스터의 특수성능시험과 같은 시험분석 인프라 강화가 필요한 것으로 분석되었으며, 이에 대한 정부 주도의 정책적인 지원이 필요한 것으로 판단되었다. 또한, 저위 기술사업인 전력지원체계 분야에서는 상대적으로 지역적인 시험분석 인프라를 효율적으로 활용하고 있는 것으로 분석되었고, 계약 낙찰과 관련한 전략적 사유로, 지역과 관계없이 컨소시엄을 구축하고, 계약 협력업체 지위를 전략적으로 바꾸는 등 중소 클러스터의 지역적 경계를 극복하고 있는 것으로 분석되었다. 연구결과, 군수품 산업에서 거점 클러스터와 중소 클러스터의 공간적인 불일치성이 일부 확인되었으며, 이에 대한 정책적인 제언이 필요한 것으로 판단되었다.

• Ocean and Polar Research
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• 제35권2호
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• pp.157-170
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• 2013

We investigated the seasonal succession of phytoplankton assemblages in the eastern part of the South Sea of Korea in relation to surface water masses. The study areas are under the direct influence of the Tsushima Warm Current (TCW) throughout the whole year, with its strength known to be seasonally variable. The region is also influenced by coastal waters (CW) driven from the South Sea of Korea and East China Sea, particularly in summer, as indicated by low salinity in the surface water. Nutrient property of the TCW can reveals whether the origin of the TCW is the nutrient-rich Kuroshio Current or the oligotropic Taiwan Warm Current. Surface chlorophyll-a (Chl-a) concentrations displayed a large seasonal variation for all stations, with high values found in spring and autumn and low values in summer and winter. At station M (offshore) and P (intermediate location between M and R), Chl-a concentrations in October were higher than those in March, when spring bloom normally occurs. This may be related to deeper mixed layer depths in October. Diatoms dominated under conditions of high nutrient supply in which Chaetoceros spp. and Skeletonema costatum-like spp. were abundant. S. costatum-like spp. dominated at stations R (onshore station) and P in December when there was greater nutrient supply, especially of phosphate. Flagellates and dinoflagellates dominated at all three stations after diatoms blooms. Dominant species were Scrippsiella trochoid in April and Ceratium furca in October at station R, and Gyrodinium spp. and Gymnodinium spp. at station M during summer, when the effect of the oligotropic Taiwan Warm Current and the oligotropic coastal water from East China Sea were strong. Redundancy analysis showed clear seasonal successions in the phytoplankton community and environmental conditions, in which both principal components 1 and 2 accounted for 69.6% of total variance. Our results suggested that environmental conditions seemed to be determined by the origin of the TCW and the relative seasonal strength of the water masses of the TCW and CW, which may affect phytoplankton growth and compositions in the study area.