• Economic and Environmental Geology
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• v.47 no.4
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• pp.317-333
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• 2014

The Pocheon iron (-copper) deposit, located at the northwestern part of the Precambrian Gyeonggi massif in South Korea, genetically remains controversial. Previous researchers advocated a metamorphosed (-exhalative) sedimentary origin for iron enrichment. In this study, we present strong evidences for skarnification and Fe mineralization, spatially associated with the Myeongseongsan granite. The Pocheon deposit is composed of diverse carbonate rocks such as dolostone and limestone which are partially overprinted by various hydrothermal skarns such as sodic-calcic, calcic and magnesian skarn. Iron (-copper) mineralization occurs mainly in the sodic-calcic skarn zone, locally superimposed by copper mineralization during retrograde stage of skarn. Age data determined on phlogopites from retrograde skarn stage by Ar-Ar and K-Ar methods range from $110.3{\pm}1.0Ma$ to $108.3{\pm}2.8Ma$, showing that skarn iron mineralization in the Pocheon is closely related to the shallow-depth Myeongseongsan granite (ca. 112 Ma). Carbon-oxygen isotopic depletions of carbonates in marbles, diverse skarns, and veins can be explained by decarbonation and interaction with an infiltrating hydrothermal fluids in open system ($XCO_2=0.1$). The results of sulfur isotope analyses indicate that both of sulfide (chalcopyrite-pyrite composite) and anhydrites in skarn have very high sulfur isotope values, suggesting the $^{34}S$ enrichment of the Pocheon sulfide and sulfate sulfur was derived from sulfate in the carbonate protolith. Shear zones with fractures in the Pocheon area channeled the saline, high $fO_2$ hydrothermal fluids, resulting in locally developed intense skarn alteration at temperature range of about $500^{\circ}$ to $400^{\circ}C$.

• Korean Journal of Ichthyology
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• v.13 no.3
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• pp.181-189
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• 2001

Spawning behavior of the Takifugu pardarlis (Temminck et Schlegel) was observed on the Jook-do coast in Tongyong from March 1997 to June 1999. The spawning ground was locted in the intertidal zone between Tongyong and Koje-do. Its bottom was mainly gravels and stones, and its depth was 0.5~1.0 m. Spawning season was from the end of the March to the middle of May. During the spawning season, the mature fishes formed school a of 10~30 individuals, then moved to the spawning ground together. When a mature female spawned eggs, the attendant males fertilized them at the same time. The fertilized eggs obtained from the parent fishes caught at the spawning ground were adhesive, opaque and spherical, measuring 1.14~1.24 mm (mean 1.19 mm, n = 50) in diameter with numerous tiny oil globules. Hatching period was about 205 hours after fertilization at water temperature of $18.0{\pm}0.5^{\circ}C$. The newly hatched larvae were 2.92~3.10 mm (mean 3.01 mm, n = 20) in total length (TL), had a large yolk, and 11~13+14~15 = 25~28 myomeres. At 5 days, the larvae had attained 3.79~3.85 mm (mean 3.82 mm, n = 20) in TL and had transformed into the postlarval stage. At 15 days, the postlarvae had attained 7.78~7.90 mm (mean 7.84 mm, n = 20) in TL. At 21 days, had larvae attained 10.15~10.27 mm (mean 10.21 mm, n = 20) in TL and had reached the juvenile stage. All fins were formed with a complete set of fin rays having the following counts: dorsal fin rays 11~12; anal fin rays 9; pectoral fin rays 14~15; caudal fin rays 11~12.

• Korean Journal of Ichthyology
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• v.4 no.1
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• pp.1-13
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• 1992

The gobiid fish, Luciogobius guttalus Gill has an anguilliform with some blackish and reddish brown color in life. It grows up to 90mm in total length. The specimens have been collected from several localities in the southern parts of Korea and Hokkaido, Japan. During the ebb tide, the fish was found in high level of intertidal zone exposed to the air among pebbles in the hollows and slopes of rocks. There are also some other small gobiid fishes comprising 3 species of relative gobies and 1 species of blennioid fish. A total of 5 egg masses were collected from the coast of Haeundae in April to May 1990. Each egg mass was deposited in one layer on the underside of a stone embedded in pebbles and guarded by the male parent. The eggs are club-shaped ranging from 2.71 to 2.80mm in long axis and from 0.65 to 0.74mm in short axis. The eggs were hatched in 98 hours after incubatied at the temperature varying from 19.5 to $25.5^{\circ}C$The newly hatched larvae were from 3.85 to 4.00mm in total length with 35~36 myomeres. In eleven days after hatching, total length reached 5.50mm. The part of the fin-fold of the future dorsal and anal fins became high. In sixteen days after hatching, the lavae averaged 6.20mm in total length and the caudal notochord flex at $45^{\circ}$. The larvae reached the juvenile stage in 48~50 days after hatching and attained 12.80~14.00mm in total length, and all fin-rays was formed. Ossification of the cranium took place at 5.50mm of mean total length in parasphenoid and basioccipital. Ossification of the visceral skeleton occurred in areas where active movements of bones are required, notalbly in the parts of feeding and respiration. Vertebrae began to develop from the anterior end to ossify posteriorly. Neural and haemal spines of vertebrae ossified always prior to the corresponding centra. When larvae reached to about 6.60mm in mean total length (17~18 days after hatching), jaw bones were more repidly ossified than vertebrae and cranium. Ossification of all bones nearly completed when the larvae reached to 13.40mm in mean total length (47~50 days after hatching).

• Korean Journal of Environment and Ecology
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• v.32 no.5
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• pp.469-477
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• 2018

Hanabusaya asiatica is an endemic species whose distribution is limited in the mid-eastern part of the Korean peninsula. Due to its narrow range and small population, it is necessary to protect its habitats by identifying it as Key Biodiversity Areas (KBAs) adopted by the International Union for Conservation of Nature (IUCN). In this paper, we estimated potential natural habitats for H. asiatica using maximum entropy model (MaxEnt) and identified candidate sites for KBA based on the model results. MaxEnt is a machine learning algorithm that can predict habitats for species of interest unbiasedly with presence-only data. This property is particularly useful for the study area where data collection via a field survey is unavailable. We trained MaxEnt using 38 locations of H. asiatica and 11 environmental variables that measured climate, topography, and vegetation status of the study area which encompassed all locations of the border region between South and North Korea. Results showed that the potential habitats where the occurrence probabilities of H. asiatica exceeded 0.5 were $778km^2$, and the KBA candidate area identified by taking into account existing protected areas was $1,321km^2$. Of 11 environmental variables, elevation, annual average precipitation, average precipitation in growing seasons, and the average temperature in the coldest month had impacts on habitat selection, indicating that H. asiatica prefers cool regions at a relatively high elevation. These results can be used not only for identifying KBAs but also for the reference to a protection plan for H. asiatica in preparation of Korean reunification and climate change.

• Economic and Environmental Geology
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• v.53 no.5
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• pp.565-583
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• 2020

In recent years, various social issues related to the natural radioactive elements detected in household goods and building materials are addressed, and should be solved promptly. In Korea, for more than 20 years, the Ministry of Environment has investigated the natural radioactive materials such as heavy metals, uranium, and radon in soil or groundwater. The origins of natural radioactive materials in them may have a close correlation with the geological factors including classification of rocks, petrogenetic origins, and deformation characteristics, but the exact geological correlations are not clarified because of the absence of the government policy preserved in the basement rocks, soils as well as groundwater in fault-related reservoirs. This study aims to perform a research on the correlation between the petrogeneses of the Phanerozoic plutonic rocks and natural radioactive concentrations in rocks (radon, uranium, thorium, potassium etc.) in Korea. Among the Phanerozoic plutonic rocks, alkaline plutonic rocks (syenite, monzonite and monzodiorite and alkali granite) show high U and Th concentrations by high solubilities of U, Th, Zr, REE, and Nb until the most extreme stages of magmatic fractionation (viz. crystal fractionation) due to high magma temperature and high alkalinity tendency. The highly fractionated high-K calalkaline and peraluminous granitic rocks (leucogranite, two-mica granite and leucocratic pegmatite are also U and Th concentrations compared with other less or medium fractionated granitic rocks (diorite, granodiorite and granite). The alkaline plutonic rocks are associated with intracontinental rifting and extensional environment after crustal thickening by collisional and subductional processes. In contrast, the dominant calc-alkaline granitic rocks in Korea are related to the arc environment of the subduction zone. In summary, the trends of the U, Th and K concentration from the Phanerozoic plutonic rocks in Korea are closely linked to the petrogenesis of the rocks in tectonic environment. The preliminary data for gamma-spectrometric mesurments of natural radionuclide contents (²²⁶Ra, ²³²Th and ⁴⁰K) in the Phanerozoic plutonic rocks show high values in the alkaline and highly fractionated granitic rocks.

• Journal of Life Science
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• v.26 no.5
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• pp.519-530
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• 2016

Vegetative plants in Yakutia are naturally frozen when they are covered with snow in the fall, and they function as green cryo-fodder that is a source of biologically active substances and nutrients for herbivorous animals. We observed a considerable increase in the total fatty acid content in the leaves of Avena sativa, Elytrigia rеpens, Equisetum variegatum and Equisetum scirpoides during the fall period. However, the degree of unsaturation of fatty acids was not higher in the frozen plants covered with snow than in the summer plants, with the exception of E. scirpoides, a dwarf horsetail found in the Pole of Cold in the northern hemisphere. In the internal adipose tissue of the Yakut horse (young horse meat), 18 fatty acids were found, including 10 saturated ones. Monounsaturated oleic С18:1 (n-9) acid and polyunsaturated α-linolenic С18:3 (n-3) acid were equally prevalent among the unsaturated fatty acids, accounting for 70% of the total unsaturated fatty acids. This composition of polyenoic fatty acids in the internal adipose tissue indicates that the Yakut horse actively feeds on the fall vegetation and the wintergreen sedge-grass. We believe that the high plant-specific free fatty acid content in the tissue of Yakut horses may play an important role in the regulation of their resistance to long-term low-temperature stress.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.7
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• pp.2386-2396
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• 1996

A numerical simulation has been performed for isothermal and reacting flows in an exisymmetric, bluff-body research combustor. The present formulation is based on the density-weighted averaged Navier-Stokes equations together with a k-epsilon. turbulence model and a modified eddy-breakup combustion model. The PISO algorithm is employed for solution of thel Navier-Stokes system. Comparison between measurements and predictions are made for a centerline axial velocities, location of stagnation points, strength of recirculation zone, and temperature profile. Even though the numerical simulation gives acceptable agreement with experimental data in many respects, the present model is defictient in predicting the recoveryt rate of a central near-wake region, the non-isotropic turbulence effects, and variation of turbulent Schmidt number. Several possible explanations for these discrepancies have been discussed.

• Development and Reproduction
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• v.9 no.2
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• pp.95-103
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• 2005

Reproductive cycle, gonadosomatic index(GSI), egg diameter composition, first sexual maturity, sexually matured length(50% of first sexual maturity), and sex ratio of Amusium japonicum japonicum, were investigated by histological observations and morphometric data. Samples were collected monthly from the subtidal zone of Sogwipo, Jejudo, Korea, for two years. The sun and moon scallop Amusium japonicum japonicum is dioecious. Monthly variation in the GSI showed similar patterns with the reproductive cycle. Ripe oocytes were about $70{\sim}90\;{\mu}m$ in diameter and had thick egg membranes. The spawning period was from November to January, and the main spawning occurred between November and December when the seawater temperature was relatively low. From monthly changes in egg diameter composition, the spawning period was once a year, although the number of spawning frequencies is assumed to occur more than twice during the spawning season. The reproductive cycle of this species could be divided into five successive stages: early active stage(April to June), late active stage(June to September), ripe stage(October to November), spawning stage(November to January), and spent/resting stage(February to April). First sexual maturities in female and male scallops ranging from 85.1 to 90.0mm in shell length were over 50% and they were 100% for scallops over 90.0mm in shell length. In this population, sexually matured shell lengths(50% of rate of group maturity) in females and males were 86.96 and 86.59mm, respectively. The female to male sex ratio among individuals over 85.1mm in shell length was not significantly different from 1:1($X^2=0.18$, p>0.05). No evidence of hermaphrodite was found in histological sections of any scallop examined.

• Journal of Food Hygiene and Safety
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• v.14 no.4
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• pp.372-379
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• 1999

A bacteriological study of sea water and oyster in Tongyeong coastal area was conducted to evaluate sanitary conditions of the bay and compliance of waters with the recommended bacteriological criteria fur the designated area of shellfish cultivation. The Samples were collected at 5 zone, 34 sampling stations(Fig. 1) established once a month from September 1997 to August 1998. During the study period, temperature ranged from 6.9 to 23.6$^{\circ}C$, transparency ranged from 2.6 to 6.2 m, chemical oxygen demand ranged from 1.35 to 1.82 mg/ι, dissolved oxy-gen ranged from 5.0 to 9.9 mg/ι, dissolved nitrogen ranged from 1.60 to 8.17 $\mu\textrm{g}$-at/ι, phosphate ranged from 0.14 to 1.21 $\mu\textrm{g}$-at/ι, Chlorophyll-a ranged from 2.03 to 69.9 mg/㎥, respectively. The coliform group and fecal coliform MPN's of sea water were ranged from <3.0~1,600 and <3.0~540, respectively. The coliform group and fecal coliform MPN's of oysters were ranged from <18~16,000 and <18~2,200, respectively. The viable cell counts in oyster ranged from $1.5\times$10$^2$to 8.2$\times$10$^3$. The coliform stoup, fecal coliform, classification of coliform group with IMViC reactions and pathogenic vibrios were analyzed. 437 strains that were obtained from Tongyeoung coastal area seawater samples represented E. coli group 47.5%, C. freundii group 14.8%, K. aerogenes 10.9%, unknown 26.8%, respectively. During the study period, infectious bacteria such as Vibrio ohoEerae, Salmonella sp. and Shigella sp. were not detected from the samples, but detection ratios of Vibrio parahaemolyticus and Vibrio vulnificus were 12~21% in summer months.

• Journal of Food Hygiene and Safety
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• v.30 no.1
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• pp.59-64
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• 2015

This study compared the content change of physiological active substances according to the extraction condition when we generally drink the extractive of Schisandra fruit with using water. Physiological active substances of the Schisandra fruit, schizandrin, gomisin A and gomisin N were analysed with HPLC. The results of extracting 1 dose of the Schisandra fruit tea, which is some as 1 g of Schisandra fruit, in 100 mL of water by differing the extraction type, extraction temperature and extraction time were of the followings. The total content of schizandrin, gomisin A and gomisin N of powder type in $26^{\circ}C$ leaching was the highest (p < 0.05) as the leaching content of 24 hours (5.54 mg/g) showed difference with different times and the contents of raw type Schisandra fruit were less than 0.1 mg/g in all of extraction time. The contents of powder type Schisandra fruit in $60^{\circ}C$ heating extraction was over 4.50 mg/g except for the 5 minute (2.94 mg/g), and the contents of raw Schisandra fruit were less than 0.3 mg/g. In case of $100^{\circ}C$ heating extraction, the contents of powder type Schisandra fruit showed over 5.10 mg/g in every time zone, and the raw type Schisandra fruit was less than 1.0 mg/g.