• Journal of the Korean Geographical Society
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• v.46 no.3
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• pp.277-290
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• 2011

Changes of the characteristics in summer rainfall in the Republic of Korea by the regime shift and their causes were examined by analyzing long-term observational data. There has been an abrupt increase in rainfall variability since 1998, which was mainly due to the enhanced rainfall during August~September, although the gradual increase was also detected in June~July. In June~July, the enhanced rainfall developed as a band type covering the whole East Asia while in August~September, it is only found over the Republic of Korea with the greatest increase of 130 mm over Seoul and Gyeonggi area. The two intensified anticyclonic anomalies over the north-northwest/east of the Republic of Korea resulted in producing northerlies/southeasterlies, transporting cold/warm-wet air flows, respectively. The center of the convergence zone from the two separate systems located in the Republic of Korea, leading to a favorable condition for the development of the extreme rainfall. The enhanced barotropic anticyclonic anomalies also affected in warming the sea surface temperature anomalies covering from the eastern coast of East Asia to North Pacific Ocean, which in turn leaded to enhance warm air transporting back to the Republic of Korea.

• Journal of the Korean earth science society
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• v.35 no.2
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• pp.104-114
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• 2014

The variation of acidity, conductivity, and ion components in precipitation depending on the dominant wind direction was investigated from January, 2009 to December 2009 in Busan, Korea. Both southwesterly and northeasterly winds were dominant in Busan area. The volume-weighted mean acidity showed pH 7, and the high conductivity indicated 200 ${\mu}scm^{-1}$ in westerly wind. The volume-weighted mean equivalent concentration showed higher value of $K^+$ and $Cl^-$ in all wind directions. The composition ratio of $NO{_3}^-/SO{_4}^{2-}$ showed over 3 in northerly wind. The neutralization factors have been found to have higher value for potassium ion in northeasterly, easterly, southwesterly, and westerly winds compared with different wind directions, which indicated significant neutralization of acidic components over the region by potassium. Also, the concentration of sea salt has been found over 800 ${\mu}sm^{-3}$ in northeasterly and southwesterly winds. Air masses passing through Manchuria, Inner Mongolia plateau, China, and Russia in spring, autumn, and winter covered Busan, Korea in northerly, westerly, and northwesterly winds. However, air masses passing through the ocean in summer covered Busan, Korea in easterly, northeasterly, and southwesterly winds. Therefore, the variation of acidity, conductivity, and ionic components contained in precipitation shows each seasonal characteristics with prevailing wind systems between the continental and coastal area in Busan, Korea.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.11 no.1
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• pp.56-67
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• 1999

It is desired to use a domestically manufactured ocean data buoy for the long-term operational ocean monitoring. The ocean data buoy manufacturing technology was introduced through the research cooperation with the Qingkong University of Taiwan. The introduced ocean data buoy system was further expanded and improved for more efficient application for the marine environmental monitoring in Korea. The size of the ocean data buoy is 2.5 m in diameter, which is smaller compared to the NOAA's 3.0 m discus buoy to allow easy land transportation and ocean deployment as well. From the dynamic response test of the buoy carried out numerically, it was shown that the measurement of waves with period greater than 4 seconds is acceptable. The measurement and control system of the data buoy were improved to increase the number of measuring parameters, to reduce power consumption and to enhance better data analysis and management. Each component of the improved data buoy system was described in detail in this paper. Water quality sensors of water temperature, salinity, DO, pH and turbidity were added to the system in addition to the marine meteorological sensors of wind speed and direction, air temperature, humidity, air pressure and wave. Inmarsat satellite communication system is used for the real-time data telemetry from the buoy deployed offshore. A field performance test of the improved and domestically manufactured buoy was carried out for a month at the open sea off Pohang together with DatawelI's Wave-rider buoy to compare the wave data. The results of the test were satisfactory.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.2
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• pp.51-58
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• 2018

This study was a basic research for actual production of recycled aggregate concrete, and experiments were carried out on the change of water cement ratio and physical properties of recycled aggregate concrete with fixed slump. Results were as follows. Concrete using recycled aggregate were required increased water to maintain the target slump, and the recycled fine aggregate are necessary more increased water more than the recycled coarse aggregate. The replacement ratio of recycled fine aggregate be less than 60%, would be possible to obtain the air content volume that did not deviate from the concrete quality specification. The compressive strength of concrete using recycled aggregate decreased with increasing the replacement of recycled aggregate, and compressive strength decreased by 25% when 100% recycled fine aggregate were replaced. As a result of analyzing the correlation of compressive strength according to the mixing factors of concrete, it was found that replacement of recycled fine aggregate> water cement ratio> air content volume were influenced in order.

• Resources Recycling
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• v.22 no.3
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• pp.28-35
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• 2013

The recycling of the Si/SiC mixture sludge obtained from solar cell industry is very significant, environmentally and economically. The sintering characteristics of Si/SiC mixture sludge was studied for the purpose of recycling. In this study, to understand sintering behavior, SiC content in the Si/SiC mixture was controlled using an air separator. Various Si/SiC mixtures having different SiC contents were sintered using carbon black, clay and aluminum hydroxide as sintering aids. Physical properties of Si/SiC mixture and sintered bodies have been characterized using SEM, XRD, particle size analyzer and apparent density measurement. SEM and particle size analysis result confirmed that the fine particles less than 1 ${\mu}m$ decreased or removed more effectively through the air separator in the case of 95% SiC sample compared than the case of 75% SiC sample or original SiC sample. Further, with addition of the Aluminum Hydroxide, ${\beta}$-cristobalite phase gradually decreased while mullite phase gradually increased. The addition of the carbon black improved the sintering characteristics.

• Journal of the Korea Society for Simulation
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• v.30 no.3
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• pp.11-17
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• 2021

The 30mm anti-aircraft gun has been developed with various types of weapon systems such as protective, protective complex, and wheel-type anti-aircraft artillery. The role of this anti-aircraft gun is an important anti-aircraft weapon in charge of air defense. Anti-aircraft weapons are tasked with defending the airspace from aircraft attacks. In particular, anti-aircraft weapons are organized in combination with mechanized units. And anti-aircraft weapons are prone to attack by enemies because they operate on the front lines of the battlefield. The enemy is expected to attack our troops by covering up or concealing as much as possible in order to increase their viability. Therefore, this study analyzed whether our 30mm anti-aircraft bullets could subdue the enemy in cover. This study analyzed the performance of 30mm anti-aircraft bullets using the M&S technique. For this study, live shooting and simulation method by M&S were used for the experiment. In this study, steel plate and plywood were used for the live shooting experiment. In addition, in the simulation process through M&S, this study used the PRODAS model, AUTODYN model, and Split-x model to analyze the trajectory, penetration, and fragmentation capability of 30mm anti-aircraft bullets. According to the experimental results, it has been proven that 30mm anti-aircraft bullets can destroy enemy armored vehicles. 30mm anti-aircraft bullets succeeded in quickly subduing enemies concealed in general buildings or forests. In this way, it was possible to minimize damage to allies in advance.

• Journal of Environmental Science International
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• v.30 no.5
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• pp.413-424
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• 2021

In this study, we quantitatively analyze the effect of ocean emission sources on the simulated O₃ concentrations in South Korea using the community multi-scale air quality (CMAQ) model. To analyze changes in O₃ concentrations by ocean emissions, two different CMAQ simulations considering ocean emissions (OE case) and without considering ocean emissions (NE case) were conducted during the Korea-United States air quality (KORUS-AQ) campaign period (May-June 2016). The changes in the simulated O₃ concentrations due to the effect of ocean emissions (OE case-NE case) appeared mostly in the ocean areas (+1.201 ppbv). The effect of ocean emissions was positive during the daytime (+1.813 ppbv), but negative during the nighttime (-0.612 ppbv). Analysis using the integrated process rate (IPR) confirmed that the increase or decrease in O₃ concentration by ocean emissions was mainly due to chemical processes. Further analysis using the integrated reaction rate (IRR) showed that the daytime increase in O₃ concentration was mainly attributable to the increased O₃ production via O + O₂ + M → O₃ + M reaction as photolysis of NO₂ increased due to the added ocean emissions. The nighttime decrease in O₃ concentration was mainly due to the increased O₃ titration by NO (NO + O₃ → O₂ + NO₂) due to the increased NO emission. These results indicate that the changes in the concentration O₃ in the sea area by the effect of ocean emissions are mainly due to increased NO_x emissions. However, there could be a number of uncertainties in ocean emissions data used in this study, thus continuous comparative research using the most updated data will need to be carried out in the future.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.7
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• pp.841-847
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• 2018

Since global energy consumption and demand for energy have dramatically risen, a focus on environmental problems and sustainability has become more important. Clean and renewable energy sources such as offshore wind power generation have received attention among new renewable energy options as alternative energy resources. Due to maintenance and operational perspectives, offshore wind farms have been planned for installation in many coastal waters. However, development of offshore wind farms faces interference from existing maritime traffic along the planned areas. In order to safely and effectively govern marine traffic in the vicinity of wind farms and inner areas, standard criteria are suggested to allow vessels to sail the internal waters of offshore wind farm areas. Therefore, the purpose of this study is to establish allowable criteria for sailing vessels and safety zones for offshore wind farms by investigating the local regulations of various offshore wind farm cases overseas. The commended inner safety zone of wind farms is proposed to be a distance of 150 % of the rotation diameter of the wind turbine rotor and a distance of 200 m from the outer wind turbine for the outer safety zone. Besides this, the allowable criteria for sailing vessels within a wind farm is proposed to have an air draft of 14.47 m south-west wind farm sea areas for a minimum margin to avoid hull contact through evaluation of the tide and height of a wind turbine. further studies will be needed to establish vessel sailing criteria among adjacent offshore wind farms as well as vessel sailing criteria within a single offshore wind farm.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.7
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• pp.893-901
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• 2017

In order to understand the fluctuation characteristics of water temperature in August, water temperature, tide level, air temperature and wind data were analyzed using a power spectrum and coherence analysis for a region off the southern coast of Korea. Spectrum analysis showed that the water temperature and tide level in Wando, Goheung, Yeosu, Tongyeong and Masan have peaks over a semi-diurnal period. Coherence showed that water temperature was affected by tide in Wando, Goheung, Yeosu and Tongyeong where tidal range is relatively high. In Masan and Busan, where tidal range is relatively low, however, the tide did not affect water temperature significantly. In particular, wind was the most important factor in relation to water temperature in Masan. Time lags were calculated from phase. In Wando, water temperature decreased 1.5 hrs after a flood tide began. Water temperature decreased 0.3 hrs after a flood tide began in Goheung and Tongyeong. In Masan, water temperature increased 3 hrs after a south wind began. Water temperature in Yeosu was affected by tide, but air temperature, tide and wind in Busan affected water temperature very little.

• Journal of Radiation Protection and Research
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• v.44 no.3
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• pp.118-126
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• 2019

Background: Government conducts environmental radioactivity surveillance for verification purpose around nuclear facilities based on the Nuclear Safety Law and issues a surveillance report every year. This study aims to evaluate the short and the long-term fluctuation of radionuclides detected above MDC and their origins using concentration ratios between these radionuclides. Materials and Methods: Sample media for verification surveillance are air, rainwater, groundwater, soil, and milk for terrestrial samples, and seawater, marine sediment, fish, and seaweed for marine samples. Gamma-emitting radionuclides including $^{137}Cs$, $^{90}Sr$, Pu, $^3H$, and $^{14}C$ are evaluated in these samples. Results and Discussion: According to the result of the environmental radioactivity verification surveillance in the vicinity of nuclear power facilities in 2017, the anthropogenic radionuclides were not detected in most of the environmental samples except for the detection of a trace level of $^{137}Cs$, $^{90}Sr$, Pu, and $^{131}I$ in some samples. Radioactivity concentration ratios between the anthropogenic radionuclides ($^{137}Cs/^{90}Sr$, $^{137}Cs/^{239+240}Pu$, $^{90}Sr/^{239+240}Pu$) were similar to those reported in the environmental samples, which were affected by the global fallout of the past nuclear weapon test, and Pu atomic ratios ($^{240}Pu/^{239}Pu$) in the terrestrial sample and marine sample showed significant differences due to the different input pathway and the Pu source. Radioactive iodine ($^{131}I$) was detected at the range of < $5.6-190mBq{\cdot}kg-fresh^{-1}$ in the gulfweed and sea trumpet collected from the area of Kori and Wolsong intake and discharge. A high level of $^3H$ was observed in the air (Sangbong: $0.688{\pm}0.841Bq{\cdot}m^{-3}$) and the precipitation (Meteorology Post: $199{\pm}126Bq{\cdot}L^{-1}$) samples of the Wolsong nuclear power plant (NPP). $^3H$ concentration in the precipitation and pine needle samples showed typical variation pattern with the distance and the wind direction from the stack due to the gaseous release of $^3H$ in Wolsong NPP. Conclusion: Except for the detection of a trace level of $^{137}Cs$, $^{90}Sr$, Pu, and $^{131}I$ in some samples, anthropogenic radionuclides were below MDC in most of the environmental samples. Overall, no unusual radionuclides and abnormal concentration were detected in the 2017's surveillance result for verification. This research will be available in the assessment of environment around nuclear facilities in the event of radioactive material release.