• Progress in Superconductivity and Cryogenics
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• v.6 no.1
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• pp.28-31
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• 2004

Since the discovery of the high temperature superconductors, many researches have been performed for the practical applications of superconductivity technologies in various fields. As results. significant progress has been achieved. Especially, Superconducting Fault Current Limiter (SFCL) offers an attractive means to limit fault current in power systems. In order to verify the effectiveness of the SFCL, in this paper, the analysis of fault current and voltage stability assessment in a distribution system are performed by the PSCAD/EMTDC-based simulation method in which a component for resistive type ot SFCL is presented. Through the simulation. the advantage of SFCL application is shown, and the effective parameters of the SFCL are also recommended.

• Nuclear Engineering and Technology
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• v.56 no.5
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• pp.1874-1879
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• 2024

Owing to strict radiation safety management in Korean nuclear power plants (NPPs), most radiation workers receive very low radiation doses, even lower than the annual dose limit for the general public. However, the occupational dose distribution indicates that some Korean NPP workers receive a relatively higher dose than the average dose. This inequity in radiation exposure could be reduced by providing customized radiation protection measures, such as dose constraints, to workers receiving relatively higher doses. In this study, dose normalization was performed to identify the highest radiation exposure work in Korean pressurized water reactors (PWRs). The results show that most of the occupational exposure in Korean PWRs occurs during the planned maintenance period. Finally, the three highest radiation exposure tasks in Korean PWRs were identified: nozzle dam installation and removal, eddy current testing, and man-way opening and closing.

• Journal of Wetlands Research
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• v.10 no.2
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• pp.23-37
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• 2008

The vertical distribution of dioxins and hexachlorobenzene(HCB) in a sediment core was investigated to elucidate historical trends of dioxins and HCB deposited into Upo wetland. The total concentration of dioxin ranged from 8.7 to 66.27 pg/g-dw in Upo sediments deposited, and from 17.64 to 97.03 pg/g-dw in Mokpo. Dioxin fluxes increased from the first-1990s and then reached a maximum in the mid-1990s. The major source of dioxin by comparing the congeners pattern was pentachlorophenol(PCP) used of agrochemicals. The HCB concentration in most of samples was detected below the MDL(Method Detection Limit of 0.5ng/g), except a few samples.

• International Journal of Precision Engineering and Manufacturing
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• v.4 no.6
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• pp.12-19
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• 2003

This paper presents the effect of boundary conditions in various failure pressure models published for the estimation of failure pressure. Furthermore, this approach is extended to the failure prediction with the aid of a failure probability model. The first order Taylor series expansion of the limit state function is used in order to estimate the probability of failure associated with each corrosion defect in buried pipelines for long exposure period with unit of years. A failure probability model based on the von-Mises failure criterion is adapted. The log-normal and standard normal probability functions for varying random variables are adapted. The effects of random variables such as defect depth, pipe diameter, defect length, fluid pressure, corrosion rate, material yield stress, material ultimate tensile strength and pipe thickness on the failure probability of the buried pipelines are systematically investigated for the corrosion pipeline by using an adapted failure probability model and varying failure pressure model.

• Journal of Species Research
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• v.8 no.4
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• pp.365-372
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• 2019

We have conducted faunistic study of sea lice collected from marine plankton samples of western and southern coasts of Korea. These specimens were identified as Caligus undulatus Shen and Li, 1959, belonging to family Caligidae and order Siphonostomatoida with worldwide distribution. The range extension of C. undulatus is reported in addition to the previously known distributional range from the Northwest Pacific (China, Japan, and Korea), India, Brazil, and Mexico. This species can be distinguished from all previous reports with characteristics such as overall body proportions of both sexes, structure details of mouth appendages, armature of legs, and some variation in body size. The distributional range of C. undulatus is now given with its northern and south hemisphere limit being 40 to $10^{\circ}N$ in the Indo-Pacific and $30^{\circ}S$ in the Southwest Atlantic. This is the first record of its female occurring in Korea.

• Journal of Ecology and Environment
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• v.46 no.4
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• pp.292-303
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• 2022

Background: Climate change significantly influences the geographical distribution of plant species worldwide. Selecting indicator species allows for better-informed and more effective ecosystem management in response to climate change. The Korean Peninsula is the northernmost distribution zone of warm temperate evergreen broad-leaved (WTEB) species in Northeast Asia. Considering the ecological value of these species, we evaluated the current distribution range and future suitable habitat for 13 WTEB tree species designated as climate-sensitive biological indicator species. Results: Up-to-date and accurate WTEB species distribution maps were constructed using herbarium specimens and citizen science data from the Korea Biodiversity Observation Network. Current northern limits for several species have shifted to higher latitudes compared to previous records. For example, the northern latitude limit for Stauntonia hexaphylla is higher (37° 02' N, Deokjeokdo archipelago) than that reported previously (36° 13' N). The minimum temperature of the coldest month (Bio6) is the major factor influencing species distribution. Under future climate change scenarios, suitable habitats are predicted to expand toward higher latitudes inland and along the western coastal areas. Conclusions: Our results support the suitability of WTEB trees as significant biological indicators of species' responses to warming. The findings also suggest the need for consistent monitoring of species distribution shifts. This study provides an important baseline dataset for future monitoring and management of indicator species' responses to changing climate conditions in South Korea.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.27 no.4
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• pp.296-310
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• 2023

In this paper, we derive the Γ-limit of functionals pertaining to some optimal material distribution problems that involve a variable exponent, as the exponent goes to infinity. In addition, we prove a relaxation result for supremal optimal design functionals with respect to the weak-∗ L^∞(Ω; [0, 1])× W^1,p0 (Ω;ℝ^m) weak topology.

• The Korean Journal of Ecology
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• v.6 no.3
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• pp.153-166
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• 1983

The distribution of beech species (Fagus) and beech-dominated forests along climatic gradients in the Northern Hemisphere was studied by use of taxonomic and ecological literature. The genus Fagus as a whole occurs over the range of 4.5 to 20.0。C mean annual temperature and 600 to 1000 mm in lower limit, mean annual precipitation. At the higher end of the temperature range, beech occurs in zones with relatively high growing-season precipitation. Edaphically, beech species and beech-dominated forests tend to occur on mesic, moderately fertile sites. Beech-dominated forests occur in a limited portion of the climatic range of the genus with sensitive responses to other environmental factors. The distributional range of beech-dominated forests on a global scale depends more on climatic factors and geological events than on soil conditions or other factors, summarizing the facts obtained by many researchers on beech dominated forests.

• Journal of The Korean Astronomical Society
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• v.26 no.1
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• pp.1-12
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• 1993

In order to explore the time dependence of the closure parameters of the two-fluid calculations for supernova remnants and the terminal shocks of stellar winds, we have considered a simple model in which the time evolution of the cosmic-ray distribution function was followed in the test-particle limit using the Bohm diffusion model. The particles are mostly accelerated to relativistic energy either in the free expansion phase of the SNRs or in the early phase of the stellar winds, so the evolution of the closure parameters during these early stages is substantial and should be followed correctly. We have also calculated the maximum momentum which is limited by either the age or the curvature of these spherical shocks. We found that SNRs expanding into the medium where the gas density decreases with the distance from the explosion center might be necessary to explain the observed power-law distribution of the galactic cosmic rays. The energy loss due to the escaping energetic particles has been estimated for the terminal shocks of the stellar winds.

• Journal of the Korea Safety Management & Science
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• v.21 no.4
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• pp.39-44
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• 2019

In this study, fire and evacuation safety of environmental energy facilities using fire and evacuation simulation was examined as part of performance-oriented design. The worst-case fire scenarios in which fire-fighting facilities such as sprinkler fire extinguishing and smoke control systems are not working, and the FDS analyzes the visibility, temperature distribution, and carbon monoxide concentration distribution through FDS. The safety was examined. As a result, it was proved that evacuation could limit the visibility, temperature, and carbon monoxide concentration in a smooth range, based on the safety standards set by relevant laws. In other words, it was possible to verify the safety of fire and evacuation for environmental energy facilities where a large amount of combustibles and fires coexist.