• Journal of the Korean Chemical Society
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• v.58 no.3
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• pp.277-282
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• 2014

The optical purity of 11 commercial dexibuprofens and 7 ibuprofens sold in Korea in 2013 were examined by chiral HPLC. The Chiralcel OD-H column and LUX-Cellulose-1 column were used as chiral stationary phases and the mixed eluent of hexane:isopropanol:acetic acid as 100:1:0.1 was used as a mobile phase with a flow rate of 1.0 mL/min. Each data was obtained from an average value of at least three different experiments for each sample and the average value of relative standard deviation of them appeared very small, 0.19%. Average optical purity value (97.5%) of eleven commercial dexibuprofens used in this study were smaller than those of 9 years ago (99.2%), but larger than four years ago (95.6%). Enantiomeric ratios of (R)- and (S)-isomers of seven ibuprofen samples used in this experiment were achieved at about 50:50 which was different with the result (44:56) from four years ago.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.21 no.4
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• pp.134-143
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• 2016

This study analyzed the characteristics of emergy inputs from environmental sources that are essential in maintaining ecological processes and providing ecosystems services of the tidal flat ecosystems in Korea. Environmental sources provided a total of $4.98{\times}10^{21}sej/yr$ of emergy to the tidal flats of Korea. The emergy inputs from environmental sources were worth 1,141 billion ￦/yr. This is the value of environmental conditions that are the basis of ecosystem services provided by the tidal flat ecosystems. The emergy input per hectare to regional tidal flats decreased along the coastline from northwest to southeast, with the highest input in the Incheon-Gyeonggi area in the central western part of the Korean coast and the lowest input in the Busan area in the southeastern end. This reflects the general distribution pattern of the magnitude of tidal ranges along the Korean coast. There was no a clear-cut relationship between emergy inputs per unit area and fishery production(expressed in emergy quantity) per unit area. However, tidal flats in the west coast with higher emery inputs per unit area produced more fishery products than those in the south coast with lower emergy inputs, suggesting a possibility that the emergy inputs could be used for the rapid evaluation and comparison of the potential for ecosystem service provision by individual tidal flats.

• Korean Journal of Ecology and Environment
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• v.52 no.4
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• pp.366-377
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• 2019

Paddy wetlands are a critical habitat for a variety of wild animals, and their rapid development and environmental changes pose a threat to the conservation of agrobiodiversity. The objectives of this study were to evaluate the habitat characteristics of anuran inhabiting paddy wetlands and identify major environmental variables affecting their distributions. The study was conducted in the Daeho reclaimed area in Dangjin, from March to October 2018. In this study, we found three anuran species (Pelophylax nigromaculatus, Hyla japonica and Pelophylax chosenicus). The environmental factors affecting the three species were identified as air temperature, humidity, water-depth, and micro-habitats. H. japonica were affected by water temperature, and P. chosenicus were affected by rice height and types of farming practices. All the three species richness was correlated with air temperature, humidity, and water-depth positively, and the three species used rice transplanted paddy fields the most. It was also found that paddy is the most preferred of the micro-habitats during the breeding season, so the survey area is considered to be used as the major breeding sites for the three species. P. chosenicus were more observed on environmental-friendly paddy fields than conventional paddy fields, which appears to be differences in their surroundings environment caused by predators and weeding. It will be needed to identify their relationship with predators, their preferred food resources and the richness and diversity of wild vegetation around paddy wetlands.

• Journal of Korean Society for Atmospheric Environment
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• v.21 no.6
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• pp.689-697
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• 2005

Hydrogen peroxide is a reservoir of OH radical which is the powerful oxidant in the atmosphere. Therefore, the status of the oxidizing atmosphere could be reflected on the concentration of $H_{2}O_{2}$. In this study, the distribution of $H_{2}O_{2}$ was determined during the intensive aircraft measurements over the Yellow sea in March, December 2002, April, November 2003 and March, October 2004. Flights covered from $124^{circ}E\;to\;129^{circ}E\;and\;35^{circ}N\;to\;37^{circ}N$, and extending to 3,000 m. The flight patterns were set properly to assess the altitudinal and longitudinal distribution for $H_{2}O_{2}$. $H_{2}O_{2}$ was extracted onto aqueous solution using a continuously flowing glass coil and analyzed by a high performance liquid chromatography (HPLC) accompanied with a fluorescence detector using postcolumn enzyme derivatization. Mixing ratios of $O_{3},\;NO_{x}\;and\;SO_{2}$ were measured in real time by commercial analysis instruments. Along the heights, the maximum concentration of $H_{2}O_{2}$ appeared around 1,500 m then gradually decreased with increasing altitude. The vertical behavior of ozone showed the similar trend to $H_{2}O_{2}$. The mean mixing ratio of $NO_{x}$ was about 2 ppbv and not showed clear vertical distribution patterns. The mean value of was the same as $NO_{x}$ however $SO_{2}$ appeared extreme concentration in low altitude. $H_{2}O_{2}\;and\;O_{3}$ showed even longitudinal distribution however $NO_{x}$ mixing ratio in land ($127^{circ}E$) was much higher than over the sea. $SO_{2}$ rather decreased with increasing longitude. $H_{2}O_{2}$ was in inverse proportion to $NO_{x}$ in spring and summer and $SO_{2}$ in spring, which indicated its significant role to NO and $SO_{2}$ oxidation pathways.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.6
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• pp.68-79
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• 2018

An examination of the characteristics of the ground material in is very important in a ground investigation. Casagrande classified soil using the material properties of soils. The liquid-plastic limit test is useful for obtaining basic information of soil, and is an effective method for classifying silt and clay, as well as the material properties, such as shear strength, shrinkage, and expansion. Unlike the liquid limit test, the plasticity limit test is due to the ambiguity of the test procedure. Many geotechnical engineers and scholars have questioned the test results. In this study, a new plasticity limit method was used to compare with the thread rolling method with kaolinite, ilite and bentonite at a certain ratio, and samples were collected from the west coast of Korea. As a result of the comparison, the test value of the new test method showed high reproducibility because the error range of the test value of the conventional thread rolling test was only 10% but the error range of the new test values decreased to 2%. The difference in the slope of the existing plasticity test values was 0.1519 ~ 0.1925, and the results of the test were similar or coincided with each other. Aone - point method was proposed to make it easier to apply the new test method.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.5
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• pp.281-294
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• 2015

In order to quantitatively estimate the nonlinear destructive interaction of wave load with wind load, which is very vital for the optimal design of offshore wind energy converter, we carried out a hydraulic model test and wind tunnel test. As a substructure of offshore wind energy converter, we would deploy the monopile, which is popular due to its easiness in construction. Based on the simulation using Monte Carlo simulation using Kaimal spectrum and cross spectrum, the instantaneous maximum wind velocity is adjusted to 10 m/s. And, considering the wave conditions of the Western Sea where a pilot wind farm is planned to be constructed, $H_s=0.1m$, 0.15 m, 0.2 m is carefully chosen. It turns out that the nonlinear destructive interaction between the wind and wave loads acting on the offshore wind energy converter is more clearly visible at rough seas rather than at mild seas, which strongly support our deduction that a Large eddy, a swirling vortex developed near the bumpy water surface in the opposite direction of the wind, is the driving mechanism underlying nonlinear destructive interaction between the wind and wave loads.

• Korean Journal of Remote Sensing
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• v.34 no.2_2
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• pp.313-326
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• 2018

This paper introduces core techniques on ship detection and tracking based on a compact HF radar platform which is necessary to establish a wide-area surveillance network. Currently, most HF radar sites are primarily optimized for observing sea surface radial velocities and bearings. Therefore, many ship detection systems are vulnerable to error sources such as environmental noise and clutter when they are applied to these practical surface current observation purpose systems. In addition, due to Korea's geographical features, only compact HF radars which generates non-uniform antenna response and has no information on target information are applicable. The ship detection and tracking techniques discussed in this paper considers these practical conditions and were evaluated by real data collected from the Yellow Sea, Korea. The proposed method is composed of two parts. In the first part, ship detection, a constant false alarm rate based detector was applied and was enhanced by a PCA subspace decomposition method which reduces noise. To merge multiple detections originated from a single target due to the Doppler effect during long CPIs, a clustering method was applied. Finally, data association framework eliminates false detections by considering ship maneuvering over time. According to evaluation results, it is claimed that the proposed method produces satisfactory results within certain ranges.

• Journal of the Korean earth science society
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• v.30 no.2
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• pp.210-222
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• 2009

Lightning data, observed from total lightning detection system (TLDS) of KMA, for the recent five years (2002-2006) have been analyzed for temporal and spatial characteristics of frequency, intensity, duration, and flash rate. Lightning frequency varies largely with years (most frequent in 2006) and the lightning during the summer accounts for 75% of total flashes and only 0.6% of lightnings strike in cold season. In rainy season (JJAS), the ratio of positive flashes to negative ones is as low as 0.15, but it increases up to 0.98 in February. The seasonal variation of lightning duration is strongly linked with lightning occurrences, whereas flashes rates show weak seasonal variability. In a daily scale, lightning, on average, occurs more often at dawn (2 am, 5-7 am) and in the mid-afternoon (15 pm), and the lightning at dawn (around 5 am) is most intense during the day. The western inland areas md the West/South Sea show high lightning density during JJAS, whereas eastern part and the East Sea exhibit a low density of lightning. Considering the low ratio of positive flashes (0.15) for the whole analysis domain during summer period, Chungnam and Jeonbuk areas have a high ratio of flashes over 0.4. However, these should be analyzed with much caution because weak positive cloud-to-cloud discharges can be regarded as cloud-to-ground flashes. The western inland also exhibits long annual flash hours (15-24). And the W3st Sea has high flash rates as a result of large density and low flash hours. The most frequent time of lightning occurrence over most inland areas lies between mid-afternoon and early-evening, whereas mountainous and coastal areas, and the northern Kyoungki and Hwanghae provinces show the maximum lightning strikes in the morning and at dawn, respectively.

• 한국해양학회지
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• v.26 no.3
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• pp.223-241
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• 1991

In order to study the formation and structure of tidal fronts and their influence on the distribution and productivity of phytoplankton in the outer of Kyonggi Bay, analyses on the water temperature data from 1977 to 1986 and 3 surveys from 1981 to 1986 were carried out in the mid0eastern coast of the Yellow Sea. Temperature gradients and dissolved oxygen gradients were implied that the tidal fronts are formed at the outer of the Kyonggi Bay along the western side of Tae-An peninsula from spring to summer. the formations of tidal fronts in this study area influence the distribution of phytoplankton and primary productivity. The standing stocks, chlorophyll concentrations and primary productivity of phytoplankton in the frontal area are higher than those of the outer stratified waters and the inner coastal mixed waters. These high production in the frontal area are resulted from good light condition and rich nutrient within the water columns. With a boundary of frontal area, there are relatively high chlorophyll concentrations and primary productivity in the coastal mixed waters while there are low chlorophyll concentrations and relatively high primary productivity in the stratified waters. These relatively high primary productivity in the outer area are resulted from the high potential production by nanoplankton in the surface layer and the high production of tychopelagic diatoms under the thermocline with the deep transparency.

• Journal of the Korean GEO-environmental Society
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• v.20 no.2
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• pp.69-79
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• 2019

The coastal area forms various sedimentary layers according to the environmental conditions such as the topography and geological features of the upper region of the river, ocean currents, and river mouth. Therefore, identifying the characteristics of the marine clay deposited in the coastal area plays a key role in the investigation of the formation of soft ground. In general, alluvial grounds are formed by a variety of factors such as changes in topography and natural environment, they have very diverse qualities depending on the deposited region or sedimentation conditions. The most important thing for the construction of social infrastructures in soft ground areas is economical and efficient treatment of soft ground. In this study, the author collected data from diverse laboratory and field tests on five areas in western and southern offshore with relatively high reliability, and then statistically analyzed them, thereby presenting standard constants for construction design. Correlation between design parameters such as over consolidation ratio, preconsolidation pressure was analyzed using linear and non-linear regression analyses. Also, proposed distribution characteristics of design parameters in consideration of each region's uncertainty through statistical analyses such as normality verification, outlier removal.