• Korean Journal of Plant Resources
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• v.23 no.1
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• pp.7-13
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• 2010

This experiment was conducted to establish the micropropagation of Calanthe discolor through multiple shoot formation from the culture of leaf, corm and root explants. Frequency of adventitious shoot formation from leaf explants was higher than those of corms and root explants. Frequency of adventitious shoot formation on medium with various concentrations of BA (0. 1.0, 3.0, and 5.0 mg/L) and NAA (0, 0.1, 0.5, and 1.0 mg/L) was tested. The maximun induction of adventitious shoot was obtained on half strength Murashige and Skoog (MS) medium supplemented with 3.0 mg/L BA and 1.0 mg/L NAA after 6 weeks of culture. Multiple shoots were transferred onto half strength MS medium with various concentrations of GA3 (0, 0.1, 0.5, 1.0, 3.0, and 5.0 mg/L). The number and length of multiple shoots on medium were highest on medium with 3.0 mg/L GA3. All the adventitious shoot grew well and rooted on half strength MS medium with 3.0 mg/L NAA. The plantlets were acclimatized up to 100% on sand with TKS-II or pearlite with TKS-II.

• Korean Journal of Materials Research
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• v.2 no.6
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• pp.452-460
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• 1992

Effects of the microalloyed elements, temperatures and cooling rates on the strength and toughness of the medium carbon microalloyed hot forging steels obtained by air cooling(A.C.) method and the low carbon microalloyed forging steels by direct quenching(D.Q.) method were investigated. Combined additions of V+Nb produced the optimum combination of strength and toughness with ferrite-pearlite structure of the medium carbon steel by the A.C. method. 831MPa in UTS and 52.1J in toughness were obtained for 0.40c+0.12V+0.07Nb. It was martensite structure for the low carbon steel by the D.Q. method. The highest UTS and toughness obtained by Mo additions were 855MPa and 108j by 0.12C+0.10V+0.03Nb+1.13Mo respectively. Especially, the toughness of the low carbon steel was twice better than that of the medium carbon steel. 110$0^{\circ}C$was more appropriate than 120$0^{\circ}C$ for the reheating and forging temperature and 1.$2^{\circ}C$ /s was the best cooling rate from the viewpoint of the strength and toughness. Multiple regression analysis was used to quantify the influence of the microalloyed elements, temperatures and cooling rates on the strength, toughness, austenite grain size, and the pearlite interlamellar spacing.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.1
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• pp.214-221
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• 2003

In this study, based on the effect of the interaction of fracture mechanics by graphite and fatigue limit phenomena of the microscopic observation various matrix structure, spheroidal ratio, size of graphite and distribution etc. parameters containd with Ductile Cast Iron. Therefore, in this study, different ferrite-pearlite matrix structure and spheroidal ratio of graphite of 70%, 80% and 90%, GCD40, GCD45-1 and GCD45-2 series and three different ferrite-pearlite matrix structure, GCD 45-3, GCD 50, GCD 60 series, all of which contain more than 90% spheroidal ratio of graphite, were used to obtain the correlation between mean size of spheroidal graphite and fatigue strength. (1) 73% pearlite structure had the highest fatigue limitation while 36% pearlite structure had the lowest fatigue limitation among ferrite-pearlite matrix. the increase in spheroidal ratio with increasing fatigue limitation, 90% had the highest, 14.3% increasing more then 10%, distribution range of fatigue life was small in same stress level. (2) (equation omitted) of graphite can be used to predict fatigue limit of Ductile Cast Iron. The Statistical distribution of extreme values of (equation omitted) may be used as a guideline for the control of inclusion size in the steelmaking processes.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.6
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• pp.71-77
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• 2010

Although the problems of defects and nonmetallic inclusion in metal fatigue are very complicated, it is particularly important to view these problems from the perspective that defects and inclusions are virtually equivalent to small cracks. This concept will help one to understand various fatigue phenomena caused by Ductile Cast Iron. For different ferrite-pearlite matrix structure, containing more than 90% spheroidal ratio of graphite, GCD 45-3, GCD 50, GCD 60 series and 70%, 80%, 90% spheroidal ratio of graphite, GCD 40, GCD 45-1, GCD 45-2 series, this paper has carried out image analyzer, estimated maximum and mean size of graphite, investigated correlation. It was concluded as follows. (1) A good quality of Ductile cast iron using in this experiment, the graphite was separated well. The effect of the interaction by graphite was verified by microscopic observation and by fracture mechanics investigation in surface, interior of the specimen. (2)${\sqrt{area}}_{max}$ of graphite can be used to predict fatigue limit of Ductile Cast Iron. The Statistical distribution of extreme values of ${\sqrt{area}}$ may be used as a guide line for the control of inclusion size in the steel making processes.

• Journal of Korea Foundry Society
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• v.12 no.3
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• pp.230-237
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• 1992

The purpose of present investigation is to obtain ductile cast iron with ferrite-bainite matrix by pearlite-bainite transformation treatment. Ductile cast irons having three kinds of Mn ampunt had been manufactured. Mn increased pearlite volume fraction iin as-cast ductile cast iron. Ductile cast irons of different pearlite fraction were austenitized at $875\;^{\circ}C$ for 230-350 sec or $925\;^{\circ}C$ for 130-170 sec followed by austempering at $300\;^{\circ}C$ or $400\;^{\circ}C$ for the various periods of time from 5 to 30 min. When specimen was austenitixed for 130 sec at $925\;^{\circ}C$ and for 230 sec at $875\;^{\circ}C$, pearlite was transformed into austenite. Bainite around graphite was found at $925^{\circ}C$ for 170 sec. Bainite in grain boundary of ferrite was happened at $875^{\circ}C$ for 350 sec. During the austempering process, acicular bainite was precipitated at $300^{\circ}C$ and lath bainite was precipitated at $400^{\circ}C$. Increment in manganese content restrained bainitic transformation. Retained austenie was of little quantity.

• Journal of the Korean Society for Heat Treatment
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• v.36 no.1
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• pp.15-21
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• 2023

Recently, ultra-high strength bolts have been developed for weight lightening of a vehicle and fuel efficiency. However, some amount of diffusible H is absorbed into the bolt during its manufacturing process so that H embrittlement (HE) often occurs particularly in high strength bolts with a tempered martensitic microstructure. This brings attention to ultra-high strength pearlitic bolts with a high resistance to HE. Therefore, in this study the HE resistance of the 1.6 GPa grade pearlitic bolt was evaluated through tightening tests and slow strain rate tests (SSRTs), and fracture surfaces of failed bolts were comparatively observed. A critical H content for the tightening test turned out to be ~0.23-0.35 mass ppm. The bolt with a diffusible H content of ~0.35 mass ppm was fractured during the tightening test, showing a quasi-cleavage fracture surface, indicating the occurrence of HE. In addition, the bolt underwent premature elastic failure during the SSRT. This implies that the HE resistance of high strength bolts can be evaluated by both tightening test and SSRT.

• Journal of agriculture & life science
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• v.50 no.2
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• pp.33-43
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• 2016

Pinellia tripartita(Blume) Schott is a herbaceous perennial plant belonging to the Araceae and distributed on Asia including of Korea, Japan, and China. P. tripartita is often used for gardening but has not been developed mass-breeding methods. In this study, we compared the tuber growth in different combinations of mixed soils used six compositions. Tubers used to study was cultured in vitro and divided into two groups. Type I was diameter more than 1cm and the group of Type II was diameter below than 1cm. Enlargement of tubers and growth of aerial parts were measuring the plant height, number of fresh leaves and dead leaves, number of bullets, tuber size, and fresh / dry weight. The size/weight and numbers of tubers from the mixed soil B (coir 68.0%, peat moss 14.7%, perlite 3.0%, vermiculite 7.0% and zeolite 7.0%) were the best grown up for eight weeks. In case of Type I, GI (Growth index) of tuber size and weight were 45% and 101%, respectively. The difference of growth was doubled compared to the bad growth treatment as the mixed soil E(Coir 14.3%, peat moss 14.3%, perlite 42.9%, vermiculite 14.3%, and zeolite 14.3%). These results could be used as the basic information for the similar experimental design for the P. ternata.

• Korean Journal of Plant Tissue Culture
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• v.21 no.4
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• pp.233-237
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• 1994

Plant regeneration system via somatic embryogenesis in leaf explant cultures of Gentiana scabra var. buergeri has been established. Leaf segments formed calli when cultured on MS medium supplemented with 0.5 mg/L 2,4-D and 2 mg/L BAP After transferred to SH medium supplemented with 0.5 mg/L 2,4-D, 2 mg/L CPA and 0.5 mg/L kinetin, the callus became embryogenic. The embryogenic callus was subcultured every 3 to 4 weeks. Upon transfer onto SH basal medium the embryogenic callus gave rise to numerous somatic embryos, which subsequently developed into plantlets. The regenerated plants were potted in an artificial soil with mixture (peatmoss : pearlite : vermiculite : 2 : 1 : 1) and transplanted to the soil after kept under a high humidity for two weeks. A total of 78 plants out of 105 regenerated plants survived in the soil. Phenotypic variations in height, number of stems and the flowering time were observed in tile regenerated plants. Cytogenetical analyses showed no chromosomal variation.

• Korean Journal of Plant Tissue Culture
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• v.24 no.1
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• pp.53-55
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• 1997

The shoot tips of Delphinium cv. Princess Caroline were cultured on the MS medium supplemented with cytokinin and auxin alone or in combination. Among cytokinins, BA was most effective in shoot multiplication, adequqte concentrations being 1.0-5.0 mg/L. Shoot multiplication was very favorable on the media with 1.0-3.0 mg/L BA and 0.1-0.5 mg/L IAA. Additions of BA and IAA did not stimulate shoot multiplication, but increased a little fresh weight. Shoots were scarcely rooted on the media with IBA or NAA, and were not done utterly on the media containing activated charcoal. Therefore, shoots were treated by Rootone and planted in the cultural media for in vivo rooting. The highest rate of rooting was 68% in the mixed cultural medium composed of Perlite 1 and Vermiculite 1.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.2 no.1
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• pp.20-28
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• 1999

Nine soil media when placed over a plastic sheet with three seeding rates were evaluated for influence on covering rate, height, growth, surface hardness, tear strength and sod establishment of Kentucky bluegrass. 1. Bark, peat and vermiculite over a plastic sheet had good effect in terms of the establishment of Kentucky bluegrass sod. 2. The good establishment of Kentucky bluegrass sod grown on bark, peat and vermiculite over a plastic sheet seemed to be caused by physical and chemical properties of each soil medium. 3. Sand, sandy loam, perlite and peatmoss caused poor effects on the covering rate, the growth, and the tear strength of Kentucky bluegrass. 4. Optimum seeding rate was $10g/m^2$ in terms of density and competition. 5. Good quality sod more depended on soil media than on seeding rates in this study.