• The Korean Journal of Ecology
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• 제21권4호
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• pp.345-349
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• 1998

thirteen dictyostelid cellular slime molds were isolated from forest soils, cattle dung and manure inisland Ulneungdo, South Korea. They were ten species including Dictyostelium aureo-stipes var. aureo-stipes, D. brefeldianum, D. macrocephalum, D. caudabasis, D. sphaerocephalum, D. giganteum, D. crassicaule, Polysphondylium pallidum, P. violaceum and P. tenuissimum as well as three species unidentified. D. aureo-stipes var. aureo-species of genus Polysphondylium distributed widely. It was thought that species diversi쇼 was considerabley higher.

• The Korean Journal of Ecology
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• 제21권2호
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• pp.157-161
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• 1998

Five dictyostelid cellualr slime molds were found in forests of Pinus densiflora and Quercus mongolica in Mt. Surak, uijeongbu, Kyunggi-do, South Korea. isolates were Polysphondylium pallidum, Dictystelium firibasis, D. crassicaule, P. tennuissimum and D. valenstemmum. Dominant soecies was P. pallidum. This species had occurred widely in South Korea as well as in the world. Especially, new dictyostelid, D. valenstemmum shim et Chang, was found in the fermentation layer of P. densiflora and Q. mongolica mixed-forest soils. D. firmibasis had not been described until now and found in the mountain forests.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 춘계학술대회논문집
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• pp.452-457
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• 2003

As a fundamental study on developing elements with micro shape, micro mold parts machining and experiment of injection molding using it were performed. The ultra precision micro machining system with high functionality was fabricated, and utilized in the machining of micro parts. By using this machining system and micro end-mill tool, a micro circle column structure of high aspect ratio, diameter 60 $\mu\textrm{m}$, height 500 $\mu\textrm{m}$, was fabricated. And a micro lens molds were fabricated by using ball end-mill tool of 300 $\mu\textrm{m}$ diameter and diamond fly-cut tool of 150 $\mu\textrm{m}$ radius. A micro injection molding machine, which is clamping force 1.75 ton, injection capacity 2.8cc, was fabricated for injection molding experiment using micro molds. The injection molding experiment was performed by using the injection molding machine, micro cylinder structures and lens molds. This paper introduces these micro machining system and injection molding machine and demonstrates examples of injection molding using fabricated molds.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 춘계학술대회논문집
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• pp.409-418
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• 2003

The dies & molds are a very economical production tool and a high value-added product because of its mass production capability compared to other production methods. Due to the very stiff international competitiveness, the industries meet many obstacles. At this moment, measured the status, the international trends and try to find the vision and strategy to promotion of the industry. In Korea, large portion of dies and molds are still low value-added and make large number of tools. In order to advance this industry to the high-tech area and gain competitiveness in the golbal marketplaces, effective means of resource investment and strategy should be properly provided.

• The Korean Journal of Ecology
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• 제25권1호
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• pp.51-58
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• 2002

An investigation of occurrence and distribution of dictyostelid cellular slime molds in South Korea were carried out. Thirty-one dictyostelid cellular slime molds were isolated from soils of 256 sample sites of 41 area within mountain forests, riversides, streamsides and coastal area in South Korea. The average number of species isolated at a given study area was 6.85. Based on the distribution value calculated from average frequency and site presence, four dictyostelid species distributed widely in South Korea; Polyspondylium pallidum, P violaceum, Dictyostellium mucoroides and D. minutum. Especially, P pallidum. were found in 30 area and the highest site presence. Eight dictyostelid species was described firstly in this study: D areum var. luteolum, D. delicatum, D. deminutivum, D. implicatum, D. microsporum, D. mucoroides var. stoloniferum, D septentrionalis, and P. candidum.

• Design & Manufacturing
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• 제1권1호
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• pp.33-37
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• 2007

In recent, the demand of high-productivity injection mold increases because of the growth of international packaging market. The increase of productivity leads to the large-sized injection molding machine and peripheral devices. For solving this problem, the stack mold which is based on the existing machine and device is studied in advanced countries actively. In this study, as the preliminary research of stack mold development, the stack mold which has 2 Level ${\times}4$ Cavity is designed and manufactured. Besides, the motion and structural analysis are executed to verify the stability of developed stack mold.

• 한국주조공학회지
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• 제20권6호
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• pp.407-418
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• 2000

The effect of various factors on the results of degassing of AC4C aluminum alloy melt by using rotary degasser were investigated. The difference between the effects of nitrogen gases of commercial pure and high purity grades on the degassing results was not significant. The optimum degassing condition was obtained. The effect of holding and degassing temperature was not significant, either. The result of degassing was deteriorated by the modification treatment of eutectic silicon, meanwhile improved by the grain refining. The effect of the latter was stronger than that of the former when the melt was treated simultaneously. The volume fractions of hydrogen porosity of the castings obtained from the molds with water moisture such as natural and green sand molds were much higher than those from the molds without that such as pep-set and $CO_2$ molds.

• 한국금형공학회:학술대회논문집
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• 한국금형공학회 2008년도 하계 학술대회
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• pp.175-181
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• 2008

The technologies of mold design, manufacturing, injection molding process and computer aided engineering(CAE) are developed rapidly with the growth of plastic product market. Injection molding process optimum design can not be easily determined. This study was determined factors and levels which carried out to analyze an influence of narrow pitch BGA socket warpage and performed investigating the main effect and interaction effect between factors using design of experiment. The result of this paper is injection time and packing pressure are affect on narrow pitch BGA socket warpage at injection molding.

• 아시안잔디학회지
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• 제10권3호
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• pp.231-246
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• 1996

In order to elucidate the human impact on the distribution of cellular slime molds, samples were collected from 3 types of forest ; natural forests(Mt. Deogyu and Mt. Tsukuba), semi-natural forests(Seoul Great Zoo and Tama Zoo), artificial forests(Seoul National University and Tokyo Gakugei University) .The distribution of cellular slime molds in mountains was different from that of zoo and universities. In mountains, endemic species was occurred and species diversity was higher than in zoo and universities. In zoo and universities disturbed by human, Dictyostelium sphaerocephalum was occurred with higher importance value than in mountains. 6 species were selected to investigate the effect of temperature on froctification; Polysphondylium canlidum, D. delicatum. D. firmibasis, D. sphaerocephalum P. violaceum, D. purpureum. P. violaceum and D. purpureum had an optimum temperature for fructification around 25~3O˚C but the others around 22~23˚C. The degree of sensitivity to temperature was as follows; P. candidum >D. lelicatum > D. firmibasis > D. sphaerocephalum > P. violaceum > D. purpureum. Key words: Human impact, Cellular slime molds, Occurrence and distribution, fructification, Dictylostelium delicatum. Dictyostelium sphaerocephalum.

• Journal of the Optical Society of Korea
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• 제11권3호
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• pp.85-92
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• 2007

In the past, precision optical glass lenses were produced through multiple processes such as grinding and polishing, but mass production of aspheric glass lenses requiring high accuracy and having complex profile was rather difficult. In such a background, the high-precision optical glass molding pressing (GMP) process was developed with an eye to mass production of precision optical glass parts by molding press. In this paper, as a fundamental research to develop the multi-cavity mold for higher productivity of a progressive GMP process used in the fabrication of an aspheric glass lens, an aspheric glass lens forming simulation was carried out.