• Korean Journal of Ecology and Environment
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• v.45 no.4
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• pp.444-452
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• 2012

We conducted a comprehensive monitoring for freshwater food web in a wetland system (Jangcheok Lake), from May to October, 2011. Monthly sampling for zooplankton, fish as well as organic matters, was implemented. In order to understand the food web structure and energy flow, we applied stable isotope analysis to the collected samples, based on ${\delta}^{13}C$ and ${\delta}^{15}N$ values of epiphytic particulate organic matter(EPOM) and particulate organic matter (POM), epiphytic and planktonic zooplankton, fish (Lepomis macrochirus). In the study site, epiphytic and planktonic zooplankton was 24 and 30 species, respectively, and coincidence species between epiphytic and planktonic zooplankton were 20 species. Epiphytic zooplankton were more abundant during the spring and early summer (May to July); however, planktonic zooplankton were more abundant during the autumn (September to October) season. Stable isotope analysis revealed that fish and epiphytic zooplankton had seasonal variations on their food sources. EPOM largely contributed epiphytic zooplankton in spring (May), but increasing contribution of POM in autumn (September) was detected. However, planktonic zooplankton depended on only POM in both seasons. Fish utilized both epiphytic and planktonic zooplankton, but small sized (1~3 cm), fish preferred epiphytic zooplankton, where as larger sized (4~7 cm) fish tended to consume planktonic zooplankton, and epiphytic zooplankton had important role in energy transfer. This pattern was clear when results of spring and autumn stable isotope analysis were compared. From the results of this study, we confirmed that wetlands ecosystem supported various epiphytic and planktonic zooplankton species, they depend on other food items, respectively. L. macrochirus also showed a difference of food source according to the body size, they depend on seasonal density change of zooplankton. In particular, epiphytic zooplankton was very important for growth and development of young fish in the spring.

• Journal of the Korean Vacuum Society
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• v.5 no.4
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• pp.387-390
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• 1996

The study has been performed that the high purity of platinum crystal was grown by rf floating zone refined technique. Direct electric current was also present to examine the controlling striated structure during the sample grown. It has been proved that current and orientation could affect suppression of the striation structure in Pt. Substructure in Pt was thermally unstable and was able to be removed by the annealing technique.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.2
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• pp.63-67
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• 2002

Langasite single crystal was grown by Xenon-arc floating zone method in mixutre of Af and $O_2$ gas atmosphere. Growing and rotation speed were 1.5 much and 15 rPm respectively. The grown crystal had a c-axis and color of orange. Composition of the grown crystal was $La_{3.10}Ga_{4.73}Si_{1.17}O_{14}$. Activation energy of the crystal was 0.23 eV and was PTC characteristics.

• Proceedings of the Korea Crystallographic Association Conference
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• 2000.05a
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• pp.33-33
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• 2000

• Proceedings of the Membrane Society of Korea Conference
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• 1997.10a
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• pp.33-36
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• 1997

1. 서론 : 압력-구동 막공정을 분리공정에 응용시 커다란 장해는 막표변과 내부에 용존 및 부유물질들의 성장과 침착현상이다. 지난 수년 동안에 여러 연구자들이 유체의 불안정성을 이용하여 농도분극과 오염현상을 효과적으로 제거할 수 있음을 보였다.(생략)

• Proceedings of the Korean Ceranic Society Conference
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• 2000.04a
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• pp.85.2-85.2
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• 2000

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.3
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• pp.85-88
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• 2001

High oxygen pressure has been applied for a floating zone (FZ) crystal grower in order to grow high quality $TiO_2$(rutile) single crystals suitable for optical application. The $TiO_2$ crystals, grown under 0.3, 0.4, 0.5, and 0.8MPa oxygen pressure respectively, are all transparent and dark blue. The degree of the presence of sub-grain boundary in the crystal differs from the applied oxygen pressure. In particular, $TiO_2$ single crystals grown under0.5 MPa showed sub-grain boundary-free and estimated good for optical devices.

• Korean Journal of Environmental Biology
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• v.32 no.3
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• pp.159-167
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• 2014

In this study, I examined the water quality and phytoplankton community in aquaculture laver farm in the southwest part of Aphae-do, South Korea, based on the young leaf stage, middle leaf stage, and adult leaf stage of laver thallus from October, 2013 to January, 2014. It was observed that the Aphae laver farm, as located in shallow waters, was found to have a serious resuspsension of the surface sediments due to physical disturbance caused by winds and tidal mixing. Such a resuspension of surface sediments coupled with nutrients supply obstructs light penetration into the sea for its huge amount of total suspended matters. As a result for this reason, it was viewed toimpedthe growth of phytoplankton was impeded as it also competes with laver to absorb the same kinds of nutrients as laver does during the laver growth period in winter. Such elements of the marine environment in Aphae laver farm are in contrast with the environment of Japan, where nutrients including dissolved inorganic nitrogen, in particular, are insufficient to cause the recent laver bad harvest, discoloration and quality degradation while large diatoms, with their higher nutrients absorption efficiency than laver, generate winter red tide. In other words, an important factor to maintain the high laver production in the southern parts of West Sea of Korea was found to be the marine environment of its laver farms where large diatoms are prevented from growing due to nutrients supply and dense seston weights from resuspended matters by physical disturbances.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.10
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• pp.3322-3333
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• 1996

A numerical analysis has been conducted to investigate a modified floating-zone crystal growth process in which most of the melt surface is covered with a heated ring. The crystal rod is not only pulled downward but rotated around its axisymmetric line during crystal growth process in order to produce the flat interface of crystal growth and the single crystal growth of NaNO3 is considered in 6mm diameter. The present study is made from a full-equation-based analysis considering a pulling velocity in all of solid and liquid domains and both of solid-liquid interfaces are tracked simultaneously with a governing equation in each domain. Numerical results are mainly presented for the comparison of the surface shape of rotational crystal rod with that of no-rotational crystal rod and the effects of revolution speeds of the crystal rod. Results show that the rotation of crystal rod produces more its flat surface. In addition, the shape of crystal growth near the centerline is more concaved with the increase in the revolution speed of crystal rod. The flow pattern and temperature distribution is analyzed and presented in each case. As the pulling velocity of crystal rod is increasing, the free surface of the melt below the heated ring is enlarged due to the crystal interface migrating downward.

• 한국해양학회지
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• v.21 no.2
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• pp.101-109
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• 1986

To clarify the light condition which influence phytoplankton ecology in Kyeonggi Bay, light intensity, compensation depth, extinction coefficient, transparency and suspended substances are studied from May 1981 to September 1982.Light intensities lie within adequate values for the phytoplankton growth from spring to autumn. However, in the winter season the light intensities show less than 4.8mw/$\textrm{cm}^2$ on the surface resulting lower than optimum irradiance. Light intensity could be a limiting factor for phytoplankton growth in winter. Compensation depths seasonally varied over an annual period in this study. Especially, in winter, compensation depths are confined to only 1-2m below the surface. Extinction coefficient(K) values are relatively high over an year cycle. K values is highest in winter and lowest in summer. Transparency shows seasonal variation. Tansparency is high in summer and low in winter. Thus low light intensity, low compensation depth, low transparency and high extinction coefficient in winter are due to the high turbidity and high concentrations of suspended substances. High concentrations of S.S. in winter result from the sediments and detritus resuspended by the winter turbulence induced by the strong winter winds and the convectional mixing. In summer, good light condition and low turbidity may result from the thermal stability of water mass preventing the resuspension of sediment particles.