• Korean Journal of Veterinary Research
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• v.39 no.4
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• pp.673-678
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• 1999

The distribution and relative frequency of insulin-immunoreactive cells in the pancreas was studied during developmental stages (fetus, neonate, 1-month-old, 6-month-old and adult) of the Korean native goat by immunohistochemical methods. The different distribution and relative frequency of glucagon-immunoreactive cells in the pancreas of the Korean native goat was observed during development. Insulin-immunoreactive cells were detected in the exocrine and endocrine portions (pancreatic islets) of the all ages, and in the duct of the 6-month-old. The relative frequencies of these cells were increased in the pancreatic islets with ages but decreased in the exocrine portions. Generally, they were distributed in the interacinar spaces or central zone of the pancreatic islets in all ages. However, the distributions and relative frequencies in the pancreatic islets of the neonate Korean native goat were divided into three patterns : 1) located in the inner zone with numerous frequencies, 2) the peripheral zone of the pancreatic islet with moderate frequencies and 3) the peripheral zone of the pancreatic islet with a few frequencies patterns.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.2
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• pp.53-57
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• 2009

The dividing flow in an open channel has a number of distinctive characteristics. One of these is that the separation zone interacts with a secondary motion along the inner wall of a branch channel, generating sediment accumulation. To investigate this phenomenon, a two-dimensional numerical model based on the shallow-water equations, RMA2, which calculates water surface elevations and horizontal-velocity components, was used to analyze the dividing flow. The obtained numerical results fully coincide with the laboratory measurements reported by Hsu et al.(2002). For the analysis of the numerical results, a separation zone-discharge rate relationship was proposed. To reduce the size of a separation zone, the topographies of diagonal and curved edges were proposed, smoothly connecting the upstream corner to branch channel.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1243-1249
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• 2004

This study is focused on the comparison between the internal saturation temperature of the working fluid and the surface temperature of adiabatic zone of two-phase closed thermosyphons with various helical grooves. Distilled water, methanol and ethanol have been used as the working fluid. In the present work, a copper tube of the length of 1200mm and 14.28mm of inside diameter is used as the container of the thermosyphon. Each of the evaporator and the condenser section has a length of 550mm, while the remaining part of the thermosyphon tube is adiabatic section. A experimental study was carried out for analyzing the performances of having 50, 60, 70, 80, 90 helical grooves. A plain thermosyphon having the same inner and outer diameter as the grooved thermosyphons is also tested for the comparison. The results show that the numbers of grooves and the type of working fluids are very important factors for the operation of thermosyphons. A good agreement between the internal saturation temperature of working fluid and the surface temperature of adiabatic zone of two-phase closed thermosyphons with various helical grooves is obtained.

• Membrane and Water Treatment
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• v.7 no.5
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• pp.417-431
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• 2016

Poly(vinylidene fluoride) (PVDF) powder was treated with aqueous sodium hydroxide to obtain partially defluorinated fluoropolymers with expected properties such as improving hydrophilicity and fouling resistance. Raman spectrum and FT-IR results confirmed the existence of conjugated carbon double bonds after alkaline treatment. As the concentration increased, the degree of defluorination increased. The morphology and structure of membranes were examined. The permeation performance was investigated. The results showed that membrane's hydrophilicity increased with increase of the percentage of alkaline treated PVDF powder. Moreover, in terms of the water contact angle, it decreased from $92^{\circ}$ to a minimum of $68^{\circ}$; while water up take increased from 128 to 138%. Fluxof pure water and the cleaning efficiency increased with the increase of alkaline treated PVDF powder. The fouling potential also decreased with the increase of the percentage of alkaline treated PVDF powder. The reason that makes blending PVDF show different characteristics because of partial defluorination, which led the formation of conjugated C = C bonds and the inclusion of oxygen functionalities. The polyene structure followed by hydroxide attack to yield hydroxyl and carbonyl groups. Therefore, the hydrophilicity of blending membrane was improved. The SEM and porosity measurements showed that no obvious variations of the pore dimensions and structures for blend membranes were observed. Mechanical tests suggest that the high content of the alkaline treated PVDF result in membranes with less tolerance of tensile stress and higher brittleness. TGA results exhibited that the blend of alkaline treated PVDF did not change membrane thermal stability.

• Proceedings of the Korean Institute of Interior Design Conference
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• 2006.05a
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• pp.193-196
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• 2006

The storage style has changed because of diversity of family types, improvement of cost of living, and increase of leisure time. In spite of this change, storage space has still caused discomfort since it did not consider residents' convenience. Therefore, in this study, Brand Apartments were selected, furniture detail drawing was analyzed by plan of housing size and zone to calculate storage area and capacity, and finally needs of storage space were analyzed using survey. Satisfaction of storage space was generally low and $20{\sim}30%$ increase of storage space was demanded. The reasons why the storage space was not satisfied are followed. First, storage space was insufficient. Second, the inner structure of storage space was unified. According to change of life style, needs have changed. To satisfy these needs, the inner division of storage space is planned with considering various items. In addition, development of hardware, flexible division, and priority of storage space with considering user's convenience are needed.

• 연구논문집
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• s.29
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• pp.173-183
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• 1999

The vacuum investment casting process for a large gas turbine component, Inner Preswirl Support (IPS), was simulated by using commercial FEM package ProCAST(TM) with view factor radiation method. The solid fraction in mushy zone was directly measured by Differential thermal analysis(DTA-DSC mode). Three types gating design. considering liquid flow and heat release through it. were proposed. Solidification had begun at the ribs or thin sections of the IPS casting and advanced further through the upper and lower gates. The computed temperature gradient G and G/R values at 70% solidified temperature were used for prediction of microshrinkage formation during casting. The effect of mold preheat on the thermal history of the casting displayed minute effect on the microshrinkage formation.

• Journal of the Korean Institute of Gas
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• v.12 no.2
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• pp.18-24
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• 2008

This paper presents the stress and deformation behaviors of 9% nickel steel inner tank in a full containment LNG storage tank using a FE analysis. For an increased strength safety of an inner tank, the tension cable was fastened around the outside wall of an inner tank, which is known as a weak zone for the hydrostatic pressures, cryogenic temperature loads, and other loadings. Based on the FEM computed results between a conventional inner tank and a inner tank with tension cables around the lower part of the side wall of an inner tank, the redesigned inner tank is more safe than that of the conventional tank without a tension cable. The FEM results recommend $3{\sim}4$ steel tension cables with a diameter of 50mm for an increased strength safety of the inner tank, which may decrease the stress concentration and deformation near the lower part of the side wall. Thus the tension cable around the inner tank may be used as an alternative safety device compared to the stiffener and the top girder structures for the increased LNG storage tank, especially.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.580-585
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• 2003

The present study addresses experimental results to investigate the details of the near field flow structures produced in the under-expanded, dual, coaxial, swirling, jet. The sonic/supersonic swirling jets are emitted from the sonic inner nozzle and the outer annular nozzle produce the co-swirling and counter swirling against the primary swirling jet, respectively. The interactions between both the secondary annular swirling and primary inner supersonic swirling jets are quantified by the pitot impact and static pressure measurements and visualized by using the Schliern optical method. The experiment is performed for different swirl intensity and pressure ratio. The results obtained show that the secondary co-swirling jet significantly changes the inner under-expanded swirling jet, such as the recirculation zone, pressure distribution, through strong interactions between both the swirling jets and the effects of the secondary counter-swirling jet is similar to the secondary co-swirl jet case.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.142.2-142.2
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• 2011

Hydrodynamic simulations of gas clouds in the central hundred parsecs region of the Milky Way that is modeled with a three-dimensional bar potential are presented. Our simulations consider realistic gas cooling and heating, star formation, and supernova feedback. A ring of dense gas clouds forms as a result of $X_1-X_2$ orbit transfer, and our potential model results in a ring radius of ~200 pc, which coincides with the extraordinary reservoir of dense molecular clouds in the inner bulge, the Central Molecular Zone (CMZ). The gas clouds accumulated in the CMZ can reach high enough densities to form stars, and with an appropriate choice of simulation parameters, we successfully reproduce the observed gas mass and the star formation rate (SFR) in the CMZ, ${\sim}2{\times}10^7\;M_{\odot}$ and ${\sim}0.1\;M_{\odot}/yr$. Star formation in our simulations takes place mostly in the outermost $X_2$ orbits, and the SFR per unit surface area outside the CMZ is much lower. These facts suggest that the inner Galactic bulge may harbor a mild version of the nuclear star-forming rings seen in some external disk galaxies. We also find that the stellar population resulting from sustained star formation in the CMZ would be enlogated perpendicularly to the main bar, and this "inner bar" can migrate the gas in the CMZ further down to the central parsecs region.

• Journal of The Korean Astronomical Society
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• v.53 no.6
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• pp.117-123
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• 2020

We investigate the plausibility of mass return, from stellar mass loss processes within the central ~100 pc region of the Milky Way (the inner nuclear bulge), as a mass supply mechanism for the Circumnuclear Disk (CND). Gas in the Galactic disk migrates inward to the Galactic centre due to the asymmetric potential caused by the Galactic bar. The inward migration of gas stops and accumulates to form the central molecular zone (CMZ), at 100-200 pc from the Galactic center. It is commonly assumed that stars have formed in the CMZ throughout the lifetime of the Galaxy and have diffused inward to form a 'r-2 stellar cusp' within the inner nuclear bulge. We propose that the stars migrating inward from the CMZ supply gas to the inner nuclear bulge via stellar mass loss, resulting in the formation of a gas disk along the Galactic plane and subsequent inward migration down to the central 10 pc region (CND). We simulate the evolution of a gas distribution that initially follows the stellar distribution of the aforementioned stellar cusp, and illustrate the potential gas supply toward the CND.