• Journal of the Korean Society of Propulsion Engineers
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• v.6 no.2
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• pp.45-52
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• 2002

An experimental investigation on the structure and dynamic behavior of two dimensional over-expanded air jets exiting into water was carried out. The hish speed digital video imaging and static pressure distribution measurement were made to characterize the structure and time-dependant behavior of the jets. Mach number at the jet exit was 2.0 and was slightly less than the value predicted by the ideal nozzle calculation. Variance of jet spreading angle at different stagnation condition was measured as a function of mass flow rate. Periodic nature of the air jet distortion in water was observed and the frequency of the repetition was approximately 5-6 Hz for all cases tested. Three characteristic length scales were defined to characterize jet structure. $L_1$, maximum width of the plume when the periodic instability occurs, $L_2$, width of the jet where secondary reverse flow entrained jet flow and $L_3$, distance from the jet exit to the location where entrainment of the secondary reverse flow occurs. The ratio of $L_1$ and $L_2$ decreased with increasing stagnation pressure, i.e. mass flow rate. $L_3$ increased with increasing stagnation pressure. The temporal behavior of static pressure measurements also showed peak around frequency of 5, which corresponds the frequency obtained by visual measurements

• FLOWER RESEARCH JOURNAL
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• v.17 no.2
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• pp.128-136
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• 2009

To obtain pure lines for breeding $F_1$ varieties of spreading surfinia and wave petunia, Petunia ${\times}$ hybrida, 20 lines of surfinia petunia and 28 lines of wave petunia that were considered uniform in growth and flowering characteristics were selected by self-pollination of the fifth($S_5$) or the seventh generation($S_7$). The 20 selected lines of surfinia petunia had the branch number ranged from 6.0 to 11.0 cm, and the internode length ranged from 2.0 to 4.2 cm. Among them, ten lines, including '$Pe99-017^7$' were above 60 cm of plant width, above 300 leaves in a plant. Fourteen lines including '$Pe99-017^7$' were more than 150 in the number of flower. In the petal color, thirteen lines, including '$Pe99-017^7$', were red-purple; three, including '$Pe99-007^7$', were purple; '$Pe04-086^7$' and '$Pe04-159^7$' were violet; and line '$Pe072-1^7$' was white. Eight lines including '$Pe02-205-2^5$' ranged from 4.0 to 5.0 cm of flowers diameter, and seven lines including '$Pe04-086^5$' ranged from 3.0 to 4.0 cm of leaf length, which is relatively low. Germination rate of the lines was more than 50%. In the wave petunia, the branch number of the 28 selected lines ranged from 8.0 to 13.0 cm, and the internode length ranged from 1.0 to 3.2 cm, which is relatively higher than surfinia petunias. Among them, ten lines, including '$Pe99-020^7$' were above 60 cm of plant width, above 200 leaves in a plant. Twelve lines including '$Pe04-034-2^5$' were more than 150 in the number of flower. In the petal color, eighteen lines, including '$Pe99-020^7$', were red-purple; three, including '$Pe04-113-4^5$', were red; three, including '$Pe04-263^5$', were white; '$Pe04-201^5$' and '$Pe04-263^5$' were violet blue; and line '$Pe04-072-5^5$' was purple. Nine lines including '$Pe04-201^5$' ranged from 4.0 to 5.0 cm of flowers diameter, and eleven lines including '$Pe04-263^5$' ranged from 3.0 to 4.0 cm of leaf length, which is relatively low. All the lines with various growth and flowering characteristics would be very promising to use as breeding materials for $F_1$ hybrids of spreading petunia, Petunia ${\times}$ hybrida.

• Mycobiology
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• v.28 no.4
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• pp.177-179
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• 2000

A soft rot of fruits caused by Rhizopus nigricans occurred on peach (Prunus persica var. vulgaris) in The Chinju City Agricultural Products Wholesale Marke during in summer season of 2000. The disease infection usually started from wounding after harvest fruits, and then moved to outside. At first, the lesions started with water soaked and rapidly softened and diseased area gradually expanded. In severely infected film house, the rate of infected fruits reached 65.2%. Numerous sporangiospores were produced on the diseased fruits. Most of the sporangiospores were appeared to be readily dispersed in the air. The mycelia grew surface of fruits and produced stolons. Colonies on potato dextrose agar at $25{\sim}30^{\circ}C$ white cottony at first becoming heavily speckled by the presence of sporangia and the browinish black at maturity, spreading rapidly by means of stolons fired at various points to the substrate by rhizoids. Sporangia were $85.3{\sim}243.5{\times}53.4{\sim}219.2\;{\mu}m$ in size and were globose or sub-globose with. somewhat flattened base. The color of sporangia was white at first and then turned black with many spores, and never over-hanging. Sporangiophores were $8.9{\sim}36.6\;{\mu}m$ in width, smooth-walled, non-septate, light brown, simple, long, arising in groups of $3{\sim}5$ from stolons opposite rhizoids. Sporangiospores was $9.7{\sim}24.8{\times}5.9{\sim}15.8\;{\mu}m$, irregular, round, oval, elongate, angular, and browinish-black streaked. Columella was $70.2{\times}149.7{\mu}m$. brownish gray, and umberella-shaped when dehisced. The causal organism was identified as. Rhizopus nigricans Lind on the basis of the morphiogical characteristics of the fungus. Rhizopus soft rot on peach (Prunus persica) caused by the fungi has not been reported in Korea. This is the first report of rhizopus soft rot on peach caused by Rhizopus nigricans in Korea.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.6
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• pp.916-922
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• 1986

This paper presents the preliminary results of an experimental study on surface crack growth under fatigue loadings. The objective of this paper is to assess the effect of the initial crack size on crack propagation behaviors. Transparent PMMA plate speciments with shallow circular arc notch were used. Crack growth behaviors were observed and measured in two directions by travelling microscopes. The fatigue crack initiated at the deepest part on the initial arc shaped notch and then propagated to depth direction as well as spreading gradually along the notch tip. A considerable number of cycles was needed until the depth crack spreaded to the surface notch tip. When the fatigue crack reached the surface notch tip the crack front became an approximate semi-ellipse, primary semi-elliptical crack. Test results suggest that the relationships between fatigue crack growth rate and stress intensity factor range in both directions can be expressed by power law (Paris) and that relationship in width direction depends upon the crack ratios a$_{1}$/b$_{1}$, of the primary semi-elliptical crack. The relationship between the nondimensional crack lengths in both directions can be represented as the formula: (a/t)$^{n}$ =B(2b/W+A) where n and A are constants and B is seems to be depended upon the crack ratio a$_{1}$/b$_{1}$.