• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.10
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• pp.2675-2685
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• 1994

A study has been conducted to provide the experimental information for the velocity and temperature profiles of steam-air mixutre and to investigate their roles on the film condensation with wavy interface. Saturated gas mixture of steam-air was made to flow through the nearly horizontal$(4.1^{\circ})$ square duct of 0.1m width and 1.56m length at atmospheric pressure, and was condensated on the bottom cold plate. The air mass fraction in the gas mixture was changed from zero(W =0, pure steam) to one(W =1, pure air), and the bulk velocity was varied from 2 to 4 m/s. Water film was injected concurrently to investigate the effect of wavy interface on the condensation. The velocity and temperature profiles were measured by LDA system and thermocouples along the three parameters ; air mass fraction, mixture velocity and film flow rate. The profiles moved toward the interface with increasing steam mass fraction, mixture velocity and film flow rate. The Prandtl and Schmidt numbers were near one in the present experimental range, however there was no complete similarity between the velocity and temperature profiles of gas mixture. And the heat transfer characteristics and interfacial structure were coupled with each other.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.23 no.4
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• pp.323-333
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• 1990

We studied the existence, form, size, variation and formation of warm lenses in the East Sea(Japan Sea) during $1979\~1988$ based on annual reports of oceanographic observations published by the National Fisheries Research and Development Agency of Korea and data of the Hydrographic Office of Republic of Korea. The warm lenses were formed in August, 1981, 1982, 1986 during study periods. The ranges of warm lenses were 50, 60, 90 km in the east-west(EW) direction and 100, 150, 120 km in the north-south(NS) direction in 1981, 1982, 1986, respectively. Because of the intrusion of cold water near 103 line, they shrink in horizontal scale in 1981. Most warm lenses were found at station 8 of 104 line in the vicinity of Ullung Island but centers of the lenses moved to the north in 1986. The form and position of warm lenses were related with the intensity of the Tsushima Warm Current and the formation of warm lenses were related with the bottom topography.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.2
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• pp.186-194
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• 2013

We compiled and analyzed long-term time-series data collected in Korea to evaluate changes in oceanographic conditions and marine ecosystems near Jeju Island ($33^{\circ}00^{\prime}-34^{\circ}00^{\prime}\;N$, $125^{\circ}30^{\prime}-127^{\circ}30^{\prime}\;E$) from 1981 to 2010. Environmental data included depth-specific time series of temperature and salinity that have been measured bimonthly since 1961 in water columns at 175 fixed stations along 22 oceanographic lines in Korean waters by the National Fisheries Research & Development Institute, and time series of estimated volume transport of the Tsushima Warm Current (TWC) and Korea Strait Bottom Cold Water (KSBCW) for the period from 1961 to 2008. We analyzed the species composition in terms of biomass of fish species caught by Korean fishing vessels in the waters near Jeju Island (1981-2010). Data were summarized and related to environmental changes using canonical correspondence analysis (CCA). The CCA detected major shifts in fish community structure between 1982 and 1983 and between 1990 and 1992; the dominant species were a filefish during 1981-1992 and chub mackerel from 1992 to 2007. CCA suggested that water temperature and salinity in the mixed layer and the volume transport of the TWC and the KSBCW were significantly related to the long-term changes in the fish community in the waters off Jeju Island. Fish community shifts seemed to be related to the well-established 1989 regime shift in the North Pacific. Further studies are required to elucidate the mechanisms driving climate change effects on the thermal windows and habitat ranges of commercial species to develop fisheries management plans based on reliable projections of long-term changes in the oceanographic conditions in waters off Jeju Island.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.23 no.3
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• pp.245-252
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• 1990

The distributions of copepods and chaetognaths in waters off the southern coast of Korea were investigated to evaluate their reliability as indicator species of different water masses. The samples for this study were collected vertically from about 5m above the bottom at 28 stations along 8 transects in three different months, February, April, and August, 1988. The sampling gear used was 0.45-meter NORPAC plankton net fitted with 0.33mm mesh. Acartia clausi, Centropages abdominalis, and Sagitta crassa were found to be reliable indicator species of neritic cold waters; Pleuromamma gracilis, Undinula darwini, Calocalanus plumulosus, Calanopia elliptica, and Sagitta enflata were of oceanic warm waters; Temora discaudata and Centropages furcatus were of neritic warm waters. According to the cluster analyses of the species found, the distinctive area in February was divisible into two regions or water masses, the coastal and off-shore regions; in April, however, it was divisible into four regions. In August, it was divisible into three areas, further indicating the strength of the Kuroshio tributaries pushing toward the coast.

• Korean Journal of Ichthyology
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• v.8 no.2
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• pp.47-56
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• 1996

Hydrography of the Korea Strait was influenced by the various water masses such as Korean coastal water, East Sea cold water, and Tsushima Current. Anchovy larvae were frequently found in the area influenced by the Tsushima Current. Anchovy appeared in all seasons and were most abundant in summer. Anchovy was more abundant in the middle layer(30~70m) than the surface layer in spring and summer and was little in the deeper layer beyond the depth of 100m. It was most abundant in the surface layer in autumn, and decreased toward the deeper layer. They were more abundant in the middle layer(30~50m) than in the surface layer and the bottom layer in winter. Anchovy was most abundant in the depth of 30m to 70m during the day time, however it was more abundant in the surface layer during the night time. Although vertical distribution patterns of abundance varied seasonally and diurnally, most of the larval anchovy distributed in the upper layer within the depth of 100m and in the upper layer above the thermocline in summer and autumn.

• Journal of the Korean Wood Science and Technology
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• v.49 no.5
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• pp.416-429
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• 2021

Raru is a lesser-known plant species originating from North Sumatra, Indonesia. Information on the characteristics is still limited, especially its chemical component. Therefore, this study aims to examine the chemical composition information of Cotylelobium lanceolatum, Cotylelobium melanoxylon, and Vatica pauciflora woods based on their axial log positions (bottom, middle, and top). The wood chemical analysis was performed in terms of the Indonesian National Standard (SNI) method. Furthermore, the analysis measured holocellulose, 𝛼-cellulose, hemicellulose, lignin content, alcohol benzene extractive content, the extractive substance in hot and water, and solubility in NaOH 1%. The results indicated that the species and their log axial positions affected different chemical components, which included 𝛼-cellulose, hemicellulose, and lignin of C. lanceolatum amounting to 41.88%, 19.39%, and 28.68% respectively. Meanwhile, for C. Melanoxylon, they were 42.01%, 21.11%, and 24.76% respectively; and for V. pauciflora wood, they were 42.95%, 23.24%, and 30.11% respectively. The average values of the extractive contents including the solubility in 1: 2 ethanol benzene, NaOH, and hot water for C. lanceolatum, C. melanoxylon, and V. pauciflora wood were (10.58%, 27.62%, 8.13%), (14.54%, 28.22%, 7.82%), and (10.95%, 28.60%, 7.57%) respectively. The wood species had a significant effect on chemical components including lignin, cellulose and hemicellulose, and extractive solubility in cold water. Furthermore, the axial log position had a significant effect on all the parameters of the chemical composition of the wood being tested.

• ALGAE
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• v.23 no.2
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• pp.135-140
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• 2008

A field survey for dinoflagellate cysts was carried out from May 2000 to November 2002 for the Southwest Sea of Korea. A total dinoflagellate cysts identified were 33 species, which belonged to 17 genera, 31 species, and 2 unidentified species. A cysts density were 16-1,501 cysts-gdry$^{-1}$. The dominant species of dinoflagellate cysts in the Southwestern Sea of Korea were Spiniferites bulloideus and Scrippsiella trochoidea, which are autotrophic species. To investigate the environmental characteristics of the Southwestern Sea of Korea using the dinoflagellate cysts, a principal component analysis (PCA) was conducted using the data collected from a total of 51 stations. From the score distribution map by the PCA, the Southwestern Sea of Korea was largely divided into three regions according to the first primary component and the second primary component. In other words, Group 1 was the western sea area of Mokpo and Jindo, Group 2 was the outer sea area of the South Sea, and Group 3 was the coastal areas of the South Sea around the Archipelago. It was found that this division of sea area was influenced by effects of the sea environment of the coastal areas of Korea. The coastal areas of Mokpo and Jindo that belong to Group 1 were affected by the cold Yellow Sea water. The outer sea area of the central parts of the South Sea that belong to Group 2, which is the boundary between the Southern coastal water of Korea and the Tsushima warm water, was subject to the formation of temperature fronts throughout the year, while Group 3 was affected by the coastal waters of Korea. It was also found that this division was in close relationship with the distribution of sediment facies in the bottom layer. From the above results, the environmental factors that influence the cyst distribution in he Southwestern Sea of Korea were found to include the eutrophication status of the sea area, the physical characteristics of the sea environment such as the flow of sea current and fronts, the sediment facies in the bottom layer, and the appearance volume of motile cells.

• Applied Microscopy
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• v.38 no.4
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• pp.307-314
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• 2008

Hydrophytes such as Spirodela polyrhiza form dormant turions to withstand cold winters. The turion is an anatomically distinct structure from which a vegetative frond arises later during germination. The turions sink to the bottom of the pond when temperatures drop and remain there throughout the winter. In the spring, they float to the surface and germinate into a new frond from the turion primordium. Unlike fronds, turions are known to possess small aerenchyma, starch grains, and relatively dense cytoplasm. These features allow the turions to survive the cold winter season at the bottom of the pond. Spirodela polyrhiza has been investigated previously to a great extent, especially in its physiological, biochemical and ecological attributes. However, a little is known about the structural features of the frond and turion during turion development. Thus, the aim of the present study was to reveal the structural characteristics of the frond and turion with regard to tissue differentiation, aerenchyma development, starch distribution, and ultrastructure, with the use of electron microscopy. A moderate degree of mesophyll tissue differentiation was found in the frond, whereas the turion did not exhibit such differentiation. Within the frond tissue, approximately $37{\sim}45%$ of the cellular volume was occupied by a large aerenchyma, but only $9{\sim}15%$ was taken up by the aerenchyma in the turion. The turion cells, especially those of the turion primordium, were derived from frond cells, and contained cytoplasm. Their cytoplasm was densely packed with plastids, mitochondria, endoplasmic reticulum, Golgi bodies, and microtubules. Plasmodesmata were also well developed within these cells. The most striking feature observed was the distribution of starch grains within the plastids of turion cells. Before the turion sank to the bottom of the pond, a considerable amount of starch accumulated in the plastid stroma. The starch grains dissolved when temperatures rose in the spring, and this promptly provided the nutrients which the primordium needed for turion germination. The turion therefore, was an appropriate dormant structure for free-floating, reduced hydrophytes like Spirodela polyhriza due to its small aerenchyma and large starch grains that aided in the purpose of sinking below the surface of the water to survive cold winters. The new fronds that arose from such turions grew rapidly in the spring, beginning the new life cycle.

• Journal of the korean society of oceanography
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• v.34 no.2
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• pp.95-112
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• 1999

To investigate a phytoplankton community structure and its biomass distribution in the Korea Strait, phytoplankton pigments were quantitatively measured by HPLC method, with hydro-graphic conditions in August and October, 1996. The measured chi. a concentrations were in the range of 7.1-1,280.7 ng/1. Horizontal distribution pattern of chi. a in summer (August) was very different from that of autumn (October). High concentration of chi. a occurred near the coast with relatively low salinity (< 33%). Vertically, the highest concentrations of pigments at most of the stations were found near the surface and above the thermocline. The maximum concentration of chi. a in October was four times higher than in August. It was notable to measure relatively high concentration of chi. b up to 190.8 ng/1 in the study area, since chi. bcontaining green algae and prochlophytes have been ignored because of their minute size and sensitivity to common preservatives. Major carotenoids detected were fucoxanthin, zeaxanthin, 19'-hexanoyloxyfucoxanthin, and prasinoxanthin. Diatoms were the dominant group with secondary important groups as pryrnnesiophytes and cyanobacteria for the biomass of phytoplankton for both cruises. The dominant species of diatoms in summer were Thalassiosira sp. and Chaetoceros peruvianus. As minor groups, prasinophytes, crysophytes, and cryptophytes were confirmed by their marker pigments and dinoflgellates by microscopical observation. Degradation products of chi. a was minor. Interestingly, at 200 m depth of St A4, the deepest station in the western channel of the Korea Strait, substantial amounts of chi. a including fucoxanthin, 19'-hexanoyloxyfucoxanthin, chi. b, and degradation products of chi. a was measured from both cruises. Higher concentration (2-3 times) of those pigments were detected from samples in summer than in autumn. Small decrease in concentration of phosphate at this depth of St. A4 was also observed. It suggested that this bottom cold water was transported from the subsurface water with biomass of active phytoplankton, which was sunk and flowed southward.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.7 no.5
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• pp.100-106
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• 2004

$NO^3$-N removal was examined from July 2002 to December 2002 of a surface-flow constructed treatment wetland cell, which was a part of a treatment wetland system composed of four wetland cells and one distribution pond. The system was established on rice paddy near the Kohung Estuarine Lake located at the southern part of the Korean Peninsula. The lake and the paddy were formed by a salt marsh reclamation project. Effluent from a secondary-level treatment plant was funneled into the system. The investigated cell was created in June 2002. Its dimensions were 87 m in length and 14 m in width. It had an open water zone at its center, which was equivalent to 10 percent of its total area. Reeds(Phragmites australis) were transplanted from natural wetlands into the cell and their stems were cut at about 40 cm height from their bottom ends. Average 25 $m^3$/day of effluent from the plant was funneled into the cell by gravity flow and average 24.2$m^3$/day of its treated effluent was discharged into the Sinyang Stream flowing into the lake. Its water depth was maintained about 0.2 m and its hydraulic detention time averaged 5.2 days. The average height of the reed stems was 45.2 cm in July 2002 and 80.5 cm in September 2002. The number of stems averaged 40.3 stems/$m^2$ in July 2002 and 74.5 stems/$m^2$ in September 2002. The reeds were established initially well. $NO_3$-N loading rate of influent and effluent averaged 173.7 and $93.5mg/m2{\cdot}day$, respectively. Removal of $NO_3$-N averaged $80.2mg/m2{\cdot}day$ and its removal rate by mass was about 50 %. Considering the initial operation of the cell and the inclusion of the cold months of November and December in the analysis period, the $NO_3$-N removal rate was good.