• Journal of the Korean Vacuum Society
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• v.16 no.5
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• pp.322-329
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• 2007

The interaction of oxygen with the ordered $Ni_3Al(111)$ alloy surface at 800 K and 1000 K has been investigated using LEED, STM, HREELS, UPS, and PAX. The clean $Ni_3Al(111)$ surface exhibits a "$2{\times}2$" LEED pattern corresponding to the ordered bulk-like terminated surface structure. For an adsorption of oxygen at 800 K, LEED shows an unrelated oxygen induced superstructure with a lattice spacing of $2.93\;{\AA}$ in addition to the ($1{\times}1$) substrate spots. The combined HREELS and the UPS data point to an oxygen chemisorption on threefold aluminum sites while PAX confirms an islands growth of the overlayer. Since such sites are not available on the $Ni_3Al(111)$ surface, we conclude the buildup of an oxygen covered aluminum overlayer. During oxygen exposure at 1000 K, however, we observe the growth of ${\gamma}'-Al_2O_3$ structure on the reordered $Ni_3Al(111)$ substrate surface. This structure has been identified by means of HREELS and STM. The HREELS data will show that at 800 K the oxidation shows a very characteristic behavior that cannot be described by the formation of an $Al_2O_3$ overlayer. Moreover, the STM image shows a "Strawberry" structure due to the oxide islands formation at 1000 K. Conclusively, from the oxygen interaction with $Ni_3Al(111)$ alloy surface at 800 K and 1000 K an islands growth of the aluminum oxide overlayer has been found.

• Korean Journal of Food Science and Technology
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• v.45 no.3
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• pp.376-381
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• 2013

In this study, we monitored total mercury and methylmercury concentrations in tuna, billfish, and deep-sea fish distributed in Seoul city. With the acquired data, we carried out statistical analysis and an exposure assessment for intake. The mean concentrations (mg/kg) of total mercury and methylmercury were $0.32{\pm}0.31/0.20{\pm}0.20$ for tuna, $0.43{\pm}0.48/0.20{\pm}0.17$ for patagonian toothfish, $0.99{\pm}0.72/0.51{\pm}0.40$ for billfish and $1.20{\pm}0.70/0.95{\pm}0.51$ for sharks, respectively. We found that sharks, billfish, patagonian toothfish, and tuna were more contaminated with total mercury and methylmercury, in sequence, and that 66% of the total mercury concentration consisted of methylmercury, on average. Although the estimated weekly intakes of methylmercury from commercial deep-sea fish were lower than the weekly intakes recommended by the Joint FAO/WHO Expert Committee on Food Additives (JECFA), we identified that the total mercury and methylmercury concentrations in tuna, billfish, and deep-sea fish continued to increase with the passage of time. Therefore, we confirmed the necessity of continuous monitoring and comprehensive analysis for general safety.

• Korean Journal of Ecology and Environment
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• v.42 no.3
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• pp.350-363
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• 2009

Inter- and intra-specific differences in removal activities, filtering rates (FR) and production of feces-and pseudo-feces (PF) between a native freshwater bivalve in Korea, Anodonta woodiana Lea and Unio douglasiae Griffith et Pidgeon, were compared using a continuous removal of organic matters (CROM) system. The CROM system comprised five steps; input of polluted water, control of water flow, mussel treatment, analysis of water quality and discharge of clean water. The study was designed to compare the removal activity of organic matters between A. woodiana and U. douglasiae, and the intra-specific differences between density and length in A. woordiana. Results clearly indicate that two kinds of mussels had obvious removal activities of seston in the eutrophic reservoir. First, if both are similar in shell length, there were no significant inter-specific differences in removal activity between A. woordiana and U. douglasiae (P>0.5), but FRs of U. douglasiae was relatively high due to low ash-fee dry weight. Second, if both are same in animal density, the smaller mussels (1$\sim$2 years old) showed a higher filtering rate and production of feces- and pseudo-feces and less release of ammonium than the larger mussels. Third, if both are same in biomass, FRs and PF of mussels were higher in the low-density tank than the high-density tank, While the Concentration of $NH_4$-N and $PO_4$-P released WRS similar to each other (P>0.5). Therefore, these results suggest that CROM system using a young bivalve A. woordiana can be applied to control the nuisance seston in eutrophic lake system, if a relevant species and density were selected. Additional pilot tests to optimize the age and density of domestic bivalves were needed for the generalization of CROM operation.

• Korean Journal of Materials Research
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• v.6 no.7
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• pp.700-708
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• 1996

Electroless plating technique was utilized to flip chip bonding to improve surface mount characteristics. Each step of plating procedure was studied in terms pf pH, plating temperature and plating time. Al patterned 4 inch Si wafers were used as substrstes and zincate was used as an activation solution. Heat treatment was carried out for all the specimens in the temperature range from room temperature to $400^{\circ}C$ for $30^{\circ}C$ minutes in a vacuum furnace. Homogeneous distribution of Zn particles of size was obtained by the zincate treatment with pH 13 ~ 13.5, solution concentration of 15 ~ 25% at room temperature. The plating rates for both Ni-P and Au electroless plating steps increased with increasing the plating temperature and pH. The main crystallization planes of the plated Au were found to be (111) a pH 7 and (200) and (111) at pH 9 independent of the annealing temperature.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.1
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• pp.16-25
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• 2012

To calculate the total mass flux that change in dry and flood season in the Yeomha Channel of Gyeonggi Bay, the 13 hour bottom tracking observation was performed from the southern extremity. The value of the total mass flux(Lagrange flux) was calculated as the sum of the Eulerian flux value and stroke drift value and the tidal residual flow was harmonically analyzed through the least-squares method. Moreover, the average during the tidal cycle is essential to calculate the mass flux and the tidal residual flow and there is the need to equate the grid of repeatedly observed data. Nevertheless, due to the great differences in the studied region, the number of vertical grid tends to change according to time and since the horizontal grid differs according to the transport speed of the ship as a characteristic of the bottom tracking observation, differences occur in the horizontal and vertical grid for each hour. Hence, the present study has vertically and horizontally normalized(sigma coordinate) to equate the grid per each hour. When compared to the z-level coordinate system, the Sigma coordinate system was evaluated to have no irrationalities in data analysis with 5% of error. As a result of the analysis, the tidal residual flow displayed the flow pattern of sagging in the both ends in the main waterway direction of dry season. During flood season, it was confirmed that the tidal residual flow was vertical 2-layer flow. As a result of the total mass flux, the ebb properties of 359 cm/s and 261 cm/s were observed during dry and flood season, respectively. The total mass flux was moving the intertidal region between Youngjong-do and Ganghwa-do.

• Journal of Environmental Impact Assessment
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• v.26 no.6
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• pp.538-552
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• 2017

In this study, total mercury (THg) of Black-tailed Gull (Larus crassirostris) eggs laid on Baengnyeongdo, West Sea of Korea was analyzed in order to compare the THg concentrations of eggs depending on egg-laying order. The first-laid eggs ($mean{\pm}standard$ error, $234.4{\pm}11.2ng/g\;wet$, n=18, t=8.4, p<0.01) significantly had higher THg concentrations than the second-laid eggs ($182.8{\pm}9.1ng/g\;wet$, n=18). Also, the first-laid eggs had higher values in biometrics (length $63.10{\pm}0.49mm$, t=2.4, p<0.05; width $44.51{\pm}0.19mm$, t=4.3, p<0.01; weight $65.53{\pm}0.87g$, t=4.2, p<0.01) than the second-laid eggs (length $62.37{\pm}0.40mm$, width $43.55{\pm}0.17mm$, and weight $62.48{\pm}0.72g$). These differences might be attributed to the amount of food eaten by females relating to males' courtship feeding pattern (males increase courtship feeding rate before the first eggs are laid, and decrease the rate following the laying of the first eggs). Moreover, the lower food intake of females could diminish the quantities of egg albumen that contains a protein binds to most of methylmercury during the period of egg production. Therefore, it is necessary to consistently apply one of egg selection methods (targeted selection (the first-laid egg or the second-laid egg), random selection, and etc.) in one nest for ensuring comparability of mercury concentrations among monitoring sites and monitoring years.

• Horticultural Science & Technology
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• v.32 no.3
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• pp.318-329
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• 2014

In order to gain insight into the physiological responses of plants to high temperature stress, the effects of temperature on Chinese cabbage (Brassica campestris subsp. napus var. pekinensis cv. Detong) were investigated through analyses of photosynthesis and chlorophyll fluorescence under 3 different temperatures in the temperature gradient tunnel. Growth (leaf length and number of leaves) during the rosette stage was greater at ambient $+4^{\circ}C$ and ambient $+7^{\circ}C$ temperatures than at ambient temperature. Photosynthetic $CO_2$ fixation rates of Chinese cabbage grown under the different temperatures did not differ significantly. However, dark respiration rate was significantly higher in the cabbage that developed under ambient temperature relative to elevated temperature. Furthermore, elevated growth temperature increased transpiration rate and stomatal conductance resulting in an overall decrease of water use efficiency. The chlorophyll a fluorescence transient was also considerably affected by high temperature stress; the fluorescence yield $F_J$, $F_I$, and $F_P$ decreased considerably at ambient $+4^{\circ}C$ and ambient $+7^{\circ}C$ temperatures, with induction of $F_K$ and decrease of $F_V/F_O$. The values of RC/CS, ABS/CS, TRo/CS, and ETo/CS decreased considerably, while DIo/CS increased with increased growth temperature. The symptoms of soft-rot disease were observed in the inner part of the cabbage heads after 7, 9, and/or 10 weeks of cultivation at ambient $+4^{\circ}C$ and ambient $+7^{\circ}C$ temperatures, but not in the cabbage heads growing at ambient temperature. These results show that Chinese cabbage could be negatively affected by high temperature under a future climate change scenario. Therefore, to maintain the high productivity and quality of Chinese cabbage, it may be necessary to develop new high temperature tolerant cultivars or to markedly improve cropping systems. In addition, it would be possible to use the non-invasive fluorescence parameters $F_O$, $F_V/F_M$, and $F_V/F_O$, as well as $F_K$, $M_O$, $S_M$, RC/CS, ETo/CS, $PI_{abs}$, and $SFI_{abs}$ (which were selected in this study), to quantitatively determine the physiological status of plants in response to high temperature stresses.

• Korean Journal of Ecology and Environment
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• v.50 no.1
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• pp.29-45
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• 2017

This study explored spatiotemporal variability of water quality in correspondence with hydro-meteorological factors in the four stations of Euiam Reservoir located in the upstream region of the North-Han River from May 2012 to December 2015. Seasonal effect was apparent in the variation of water temperature, DO, electric conductivity and TSS during the study period. Stratification in the water column was observed in the near dam site every year and vanished between August and October. Increase of nitrogen nutrients was observed when inflowing discharge was low, while phosphorus increase was distinct both during the early season with increase of inflowing discharge and the period of severe draught persistent. Duration persisting high concentration of Chl-a (>$25mg\;m^{-3}$: the eutrophic status criterion, OECD, 1982) was 1~2 months of the whole year in 2014~2015, while it was almost 4 months in 2013. Water quality of Euiam Reservoir appeared to be affected basically by geomorphology and source of pollutants, such as longitudinally linked instream islands and Aggregate Island, inflowing urban stream, and wastewater treatment plant discharge. While inflowing discharge from the dams upstream and outflow pattern causing water level change seem to largely govern the variability of water quality in this particular system. In the process of spatiotemporal water quality change, factors related to climate (e.g. flood, typhoon, abruptly high rainfall, scorching heat of summer), hydrology (amount of flow and water level) might be attributed to water pulse, dilution, backflow, uptake, and sedimentation. This study showed that change of water quality in Euiam Reservoir was very dynamic and suggested that its effect could be delivered to downstream (Cheongpyeong and Paldang Reservoirs) through year-round discharge for hydropower generation.

• Korean Journal of Ecology and Environment
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• v.50 no.1
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• pp.1-15
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• 2017

Daecheong Reservoir was made by the construction of a large dam (>15 m in height) on the middle to downstream of the Geum River and the discharge systems have the watergate-spillway (WS), a hydropower penstock (HPP), and two intake towers. The purpose of this study was to investigate the limnological anomalies of turbid water reduction, green algae phenomenon, and oligotrophic state in the lower part of reservoir dam site, and compared with hydro-meteorological factors. Field surveys were conducted in two stations of near dam and the outlet of HPP with one week intervals from January to December 2000. Rainfall was closely related to the fluctuations of inflow, outflow and water level. The rainfall pattern was depended on the storm of monsoon and typhoon, and the increase of discharge and turbidity responded more strongly to the intensity than the frequency. Water temperature and DO fluctuations within the reservoir water layer were influenced by meteorological and hydrological events, and these were mainly caused by water level fluctuation based on temperature stratification, density current and discharge types. The discharges of WS and HPP induced to the flow of water bodies and the outflows of turbid water and nutrients such as nitrogen and phosphorus, respectively. Especially, when hypoxic or low-oxygen condition was present in the bottom water, the discharge through HPP has contributed significantly to the outflow of phosphorus released from the sediment into the downstream of dam. In addition, HPP effluent which be continuously operated throughout the year, was the main factor that could change to a low trophic level in the downreservoir (lacustrine zone). And water-bloom (green-tide) occurring in the lower part of reservoir was the result that the water body of upreservoir being transported and diffused toward the downreseroir, when discharging through the WS. Finally, the hydropower effluent was included the importance and dynamics that could have a temporal and spatial impacts on the physical, chemical and biological factors of the reservoir ecosystem.

• Korean Journal of Food Science and Technology
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• v.12 no.3
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• pp.185-192
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• 1980

To study lipid components of Panax ginseng produced in Korea, the lipids of fresh ginsengs were extracted with the mixture of chloroform-methanol (2:1, v/v) and those of dried ginsengs were extracted with diethyl ether respectively. The lipid components extracted were separated and quantitated by column, thin layer and gas-liquid chromatographies. The results were summarized as follows : 1. Fresh ginseng contained 0.62% total lipid of which 45.28% were neutral lipids, 18.12% glycolipids, and 36.60% phospholipids. But dried ginseng contained 0.89% total lipids of which 86.48% were neutral lipids, 9.20% glycolipids, and 4.32% phospholipids. 2. Triglycerides (37.6 to 42.5% of the total neutral lipids) and sterol esters (16.5 to 19.6%) in all the fresh and dried ginseng were the major components among the neutral lipids. Monoglycerides, diglycerides, free fatty acids and free sterols were minor components. 3. Digalactosyl diglycerides (23.5% of the total glycolipids) in the fresh ginseng and steryl liglycosides (28.9%) in the dried ginseng were predominant components among the glycopids, respectively, Esterified steryl glycosides and monogalactosyl diglycerides were also identified, and four unknown spots in the fresh ginseng and two unknown spots in the dried ginseng were present. 4. Phosphatidyl cholines (31.3 to 31.9% of the total phospholipids) and phosphatidyl glycerols (34.8 to 36.7%) in all the fresh and dried ginseng were the major components among the phospholipids. Phosphatidyl inositols and phosphatidyl ethanolamines were also identified. 5. The major fatty acids in the fresh and dried ginseng were linoleic $(62.29{\sim}64.32%)$, palmitic $(13.16{\sim}15.63%)$, oleic $(5.73{sim}7.23%)$ and linolenic $(5.73{sim}7.23%)$. The fatty acid compositions in neutral lipid fraction was similar to the pattern in those of the total lipids. But glycolipid and phospholipid fractions contained a lower percent of linoleic acid and a higher percent of palmitic acid than the neutral lipid fraction.