• Journal of Hydrogen and New Energy
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• v.23 no.3
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• pp.219-226
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• 2012

A nuclear fusion fuel cycle plant is composed of various subsystems such as a hydrogen isotope storage and delivery system, a tokamak exhaust processing system, and a hydrogen isotope separation system. Korea shares in the construction of the International Thermonuclear Experimental Reactor fuel cycle plant with the EU, Japan and US, and is responsible for the development and supply of the storage and delivery system. We thus present details on the hydrogen isotope process safety. The main safety analysis procedure is to use a hazard and operability study. Nine segments were studied how the plant might deviate from its design purpose. We present a detailed description of the process, examine every part of it to determine how deviations from the design intent can occur and decide whether these deviations can give rise to hazards. We determine possible causes and note protective systems, evaluate the consequences of the deviation, and recommend actions to achieve our safety goal.

• Korean Journal of Environment and Ecology
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• v.21 no.3
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• pp.235-242
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• 2007

In order to find out the current situation of the fauna of the mammals which inhabit Hallasan National Park, the areas of Seongpanak, Eorimok, Gwaneumsa, Yeongsil and Donnaeko were surveyed. The survey was conducted from April 2006 to January 2007 The analysis of geographical distribution revealed that there are 15 species of mammals, which belong to eight families and five orders, in which Apodemus chejuensis, Carpreolus pygargus tianschanicns, Rhinolophus ferrumequinum and Tamias sibiriricus barberi were found to be dominant species. It was also found that there exists the fauna of mammals in Mt. Halla such as Mustela sibirica quelpartis, Crocidura dsinezmi quelpartis, Micromys minutus hertigi and Sorex caecutiens hallamontanus, showing a bio-geological attribute that territorial population of taxologically geographical subspecies class exists. The fauna of the mammals in Jeju Island is rather simpler in its species composition in comparison with the inland of the Korean Peninsula ever since Jeju Island's geographical isolation from the mainland, mainly consisting of Chiroptera and small rodents.

• Journal of Hydrogen and New Energy
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• v.24 no.1
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• pp.36-43
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• 2013

In this paper, a three-dimensional hydrogen desorption model is applied to a thin double-layered annulus ZrCo hydride bed and validated against the temperature evolution data measured by Kang et al. The present model reasonably captures the bed temperature evolution behavior and the 90% hydrogen discharging time. In addition, the performance of thin double-layered annulus bed is evaluated by comparing with a simple cylindrical bed using hydrogen desorption model. This study provides multi-dimensional contours such as temperature and H/M atomic ratio in the metal hydride region. This numerical study provides fundamental understanding during hydrogen desorption process and indicates that efficient design of the metal hydride bed is critical to achieve rapid hydrogen discharging performance. The present three-dimensional hydrogen desorption model is a useful tool for the optimization of bed design and operating conditions.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.9
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• pp.750-758
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• 2013

In this paper, we introduce the low-density parity-check (LDPC) coded orthogonal frequency division multiplexing (OFDM) subframe reordering scheme for achieving equal combined power allocation in type I hybrid automatic repeat request (H-ARQ) systems and analyze the performance improvement by using the channel capacity. Also, it is confirmed that the layered decoding for subframe reordering scheme in H-ARQ systems gives faster convergence speed. It is verified from numerical analysis that a subframe reordering pattern having larger channel capacity shows better bit error rate (BER) performance. Therefore the subframe reordering pattern achieving equal combined power allocation for each subframe maximizes the channel capacity and outperforms other subframe reordering patterns. Also, it is shown that the subframe reordering scheme for achieving equal combined power allocation gives better performance than the conventional Chase combining scheme without increasing the decoding complexity.

• Korean Journal of Ecology and Environment
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• v.42 no.1
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• pp.134-138
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• 2009

The survival rate of PIT tagged fish was investigated for five Korean Cyprindae fish species, Acheilognathus lanceolatus (n=18, total length : $92.5{\pm}13.1mm$; body weight : $9.6{\pm}4.3g$), Hemibarbus labeo (n=28, TL : $220{\pm}74.4mm$; BW : $91.8{\pm}76.2g$), Zacco koreanus (n=13, TL : $116.5{\pm}23.8mm$; BW : $13.6{\pm}10.6g$), Zacco platypus (n=108, TL : $100.6{\pm}17.8mm$; BW: $8.7{\pm}4.8g$), Opsariichthys uncirostris amurensis (n=6, TL : $161.8{\pm}26.3mm$; BW : $27.5{\pm}18.3g$) with respect to applicability and effectiveness of PIT tagging. The survival rate were daily checked for 30 days. The survival rate was the highest and lowest for Z. koreanus and Z. platypus, respectively. The survival days were greater as fish total length increased. Based on these results, PIT tagging is not effective for Z. platypus, while PIT tagging for fish>150 mm was effect for field research.

• Korean Journal of Environmental Biology
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• v.37 no.1
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• pp.88-92
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• 2019

The objective of this study was to report the group mating of Asian Keelback snake, Hebius vibakari, in South Korea. On May 20, 2009, the group mating of H. vibakari was observed in the Maeng-gol do, Jindo-gun, Jeollanam-do, in the rocky area (107 m above sea level) on the ridge of the island. Six female and five male snakes made a form of mating behavior called "mating ball". Two couples showed "tail-wrestling" which is the copulation behavior in snake species. During the mating, the temperature and humidity were $25.7^{\circ}C$ and 59%, respectively. The result of this study was the first case report of the group mating in H. vibakari, a rare reptile.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.2
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• pp.8-13
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• 2021

The study for soil has been conducted separately by several areas such as soil mechanics and soil chemistry. Soil is important in terms of prediction of how the plant grow with nutrient requirement. Also, soil is important for machines to work on to solve labor shortage and save farmers from harsh environment during farm work. To meet diverse needs related to soil in agriculture, the soil related study needs to be conducted synthetically. Thus, we tried to obtain the data related to soil chemistry including pH and Electrical Conductivity (EC) with data related to soil mechanics including Cone Index (CI), moisture content, soil classification. Specifically, the condition of the field was set to be cultivated at least for five years continuously at a first step. The soil was taken from 30 sites. CI was obtained using the soil penetrometer and soil classification was conducted using sieve analysis with eight kinds of sieve. The soil was taken on December when is during winter in Korea. There was variation of data including moisture content and CI.

• Journal of Powder Materials
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• v.28 no.1
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• pp.51-58
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• 2021

The conversion of carbon preforms to dense SiC by liquid infiltration is a prospectively low-cost and reliable method of forming SiC-Si composites with complex shapes and high densities. Si powder was coated on top of a 2.0wt.% Y2O3-added carbon preform, and reaction bonded silicon carbide (RBSC) was prepared by infiltrating molten Si at 1,450℃ for 1-8 h. Reactive sintering of the Y2O3-free carbon preform caused Si to be pushed to one side, thereby forming cracking defects. However, when prepared from the Y2O3-added carbon preform, a SiC-Si composite in which Si is homogeneously distributed in the SiC matrix without cracking can be produced. Using the Si + C → SiC reaction at 1,450℃, 3C and 6H SiC phases, crystalline Si, and Y2O3 were generated based on XRD analysis, without the appearance of graphite. The RBSC prepared from the Y2O3-added carbon preform was densified by increasing the density and decreasing the porosity as the holding time increased at 1,450℃. Dense RBSC, which was reaction sintered at 1,450℃ for 4 h from the 2.0wt.% Y2O3-added carbon preform, had an apparent porosity of 0.11% and a relative density of 96.8%.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.1
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• pp.71-76
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• 2022

Since brightness is proportional to the operating current, a method of connecting several LEDs in series and driving with a constant current source is widely used for driving circuits of LED lights. Because several LEDs are connected in series, if some LEDs open due to a fault, the current path is broken and all other LEDs connected in series are turned off. In this paper, we designed a circuit to solve this problem by connecting a Zener diode having a breakdown voltage of about 0.4V higher than the LED operating voltage in parallel with each LED to create a current bypass in case of LED failure. Through simulations and experiments, it was confirmed that the current of the Zener diode hardly flows when the LED is operating normally, and that the Zener diode stably operates as a current bypass when the LED fails.

• Korean Journal of Materials Research
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• v.31 no.5
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• pp.301-311
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• 2021

The conversion of all carbon preforms to dense SiC by liquid infiltration can become a low-cost and reliable method to form SiC-Si composites of complex shape and high density. Reactive sintered silicon carbide (RBSC) is prepared by covering Si powder on top of 0.5-5.0 wt% Y₂O₃-added carbon preforms at 1,450 and 1,500℃ for 2 hours; samples are analyzed to determine densification. Reactive sintering from the Y₂O₃-free carbon preform causes Si to be pushed to one side and cracking defects occur. However, when prepared from the Y₂O₃-added carbon preform, an SiC-Si composite in which Si is homogeneously distributed in the SiC matrix without cracking can be produced. Using the Si + C = SiC reaction, 3C and 6H of SiC, crystalline Si, and Y₂O₃ phases are detected by XRD analysis without the appearance of graphite. As the content of Y₂O₃ in the carbon preform increases, the prepared RBSC accelerates the SiC conversion reaction, increasing the density and decreasing the pores, resulting in densification. The dense RBSC obtained by reaction sintering at 1,500 ℃ for 2 hours from a carbon preform with 2.0 wt% Y₂O₃ added has 0.20 % apparent porosity and 96.9 % relative density.