• Journal of Welding and Joining
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• v.15 no.2
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• pp.72-80
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• 1997

The spatter generation rate of GMA welding with $CO_2$ gas shielding was measured with the change of welding conditions such as wire feeding rate and welding voltage and then the results were analized with the accompanying changes in metal transfer mode and in bead geometry. The spatter generation rate (SGR) was relatively low not only wit the short circuit transfer but with the truely globular transfer mode. However, the SGR resulted with the mixed mode were consistantly high. The resultant wave pattern of mixed mode was due to the coexistance of short-circuit and globular transfer and characterized by the frequent appearance of instantaneous short circuit. Considering the result of SGR and that of bead geometry, it could be concluded that when the wire feeding rate (or welding current) was either low or high, the optimum bead shape could be obtained along with the low spatter generation. However, in the middle range of wire feeding rate, the optimum bead shape was only obtained in the mixed mode condition resulting in the high spatter generation.

• Journal of Ocean Engineering and Technology
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• v.3 no.2
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• pp.125-137
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• 1989

To check technical improvement in the soundness and strength of 12% Cr steel rotor, a 25 tons of rotor with 65 tons of ingot was made in real size and was cut to pieces to take test samples, and the various mechanical tests such as impact, tensile, creep, and fatigue were carried out. The strengths are compared with those of 1% Cr-Mo-V rotor of same size. Microstructures of the samples are examined and reviewed. The results can be summarized as follows. 1) Fracture appearance transition temperatures are 80.deg. C at the center part and 60.deg. C near surface of 12% Cr rotor, and 8.deg. C near surface of 1% Cr-Mo-V rotor. 2) Comparative rapid softening occurs at higher temperatures above 600.deg. C for 12% Cr steel and 550.deg. C for 1% Cr-Mo-V steel in tension tests. 3) Fatigue crack propagation rate of 12% Cr steel is almost same as that of 1% Cr-Mo-V steel at the same corresponding surface part of the rotors. The crack growth rate of center part of 12% Cr rotor is faster than near surface part of the rotor, and the crack growth rate at the load condition of R=0.04 is slower than that of the load condition of R=0.5 for both 12% Cr steel and 1% Cr-Mo-V steel. 4) Crack growth rate of radial direction near surface of 12% Cr rotor is faster than that of transverse direction at the same part because of the difference in residual stresses. 5) Both creep and fatigue strengths of 12% Cr steel are superior to those of 1% Cr-Mo-V steel and the difference is thought the effect of climb and glide controlled creep by solid solution of alloying elements and dispersion of carbides.

• Journal of Ocean Engineering and Technology
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• v.3 no.2
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• pp.625-625
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• 1989

To check technical improvement in the soundness and strength of 12% Cr steel rotor, a 25 tons of rotor with 65 tons of ingot was made in real size and was cut to pieces to take test samples, and the various mechanical tests such as impact, tensile, creep, and fatigue were carried out. The strengths are compared with those of 1% Cr-Mo-V rotor of same size. Microstructures of the samples are examined and reviewed. The results can be summarized as follows. 1) Fracture appearance transition temperatures are 80.deg. C at the center part and 60.deg. C near surface of 12% Cr rotor, and 8.deg. C near surface of 1% Cr-Mo-V rotor. 2) Comparative rapid softening occurs at higher temperatures above 600.deg. C for 12% Cr steel and 550.deg. C for 1% Cr-Mo-V steel in tension tests. 3) Fatigue crack propagation rate of 12% Cr steel is almost same as that of 1% Cr-Mo-V steel at the same corresponding surface part of the rotors. The crack growth rate of center part of 12% Cr rotor is faster than near surface part of the rotor, and the crack growth rate at the load condition of R=0.04 is slower than that of the load condition of R=0.5 for both 12% Cr steel and 1% Cr-Mo-V steel. 4) Crack growth rate of radial direction near surface of 12% Cr rotor is faster than that of transverse direction at the same part because of the difference in residual stresses. 5) Both creep and fatigue strengths of 12% Cr steel are superior to those of 1% Cr-Mo-V steel and the difference is thought the effect of climb and glide controlled creep by solid solution of alloying elements and dispersion of carbides.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.14 no.5
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• pp.127-136
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• 2011

This study was conducted on the field application for a method which is currently used. Although the method was performed with experimental knowledge, this study attempted to approach scientific ways through thirty sets of test-bed and three times monitoring limited by control variations for three months. The factors on previous studies are slope location, slope degree, type (roadfill vs. roadcut), aspect, vegetation cover, species, thickness, vertical length, horizontal length, soil type, elevation, erosion, soil-moisture, soil-hardness, pH, and so on. However, the factors of a suitable and significant level are slope degree, type, aspect, thickness, soil-moisture, vertical length and horizontal length in slope revegetation. the results were as follows : As a result of survey on soil types based on the status before construction, the rate of vegetation cover with non-mesh construction in soil areas was better than the rate of vegetation cover with fiber meshes and wire meshes. The rate of vegetation cover with fiber meshes in weathered rocks was better than using wire meshes. The rate of vegetation cover with the wire meshes in blasted rocks was better than using fiber meshes. Also, the factors affecting the rate of vegetation cover presented the number of appearance species, soil-moisture, thickness. this result presented the more appearance species as a positive role, and the lower soil-moisture and the thicker soil as a negative role.

• Proceedings of the Korean Society of Crop Science Conference
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• 2000.04a
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• pp.342-343
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• 2000

• Journal of Community Nutrition
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• v.3 no.2
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• pp.77-86
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• 2001

The purpose of this study was to investigate self-perception and practices of health and appearance, health-related lifestyles and dietary behaviors of college students(137 male, 115 female) attending web class via the Internet. This cross-sectional survey was conducted by a self-administered questionnaire and data was analyzed by SPSS program. The average height, weight and BMI of the male and female college students were 174.4cm, 67.8kg, 22.3kg/㎡ and 162.3cm, 52.1kg, 19.8kg/㎡, respectively. Male collage students perceived their health statuses significantly better compared to female students. As for self-evaluation of anemia, female college students perceived significantly more anemia symptoms compared to male college students. Female college students perceived their body image to be obese compared to male college students. Underweight college students perceived significantly less healthy statuses, more anemia symptoms, and worse hair conditions compared to other college students. The rate of male students who exercise was significantly higher compared to that of female students. Male students reported significantly more smoking and drinking of alcohol compared to female students. The rate of female college students skipping meals was significantly higher than that of male college students. Frequency of eating out in female college students was significantly higher compared to that in male students. These results may provide some basic information in developing a nutrition education program for Korean college students using Internet.

• Corrosion Science and Technology
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• v.12 no.6
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• pp.274-279
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• 2013

Flow accelerated corrosion (FAC) of the carbon steel piping in nuclear power plants (NPPs) has been major issue in nuclear industry. During the FAC, a protective oxide layer on carbon steel dissolves into flowing water leading to a thinning of the oxide layer and accelerating corrosion of base material. As a result, severe failures may occur in the piping and equipment of NPPs. Effect of alloying elements on FAC of pipe materials was studied with rotating cylinder FAC test facility at $150^{\circ}C$ and at flow velocity of 4m/s. The facility is equipped with on line monitoring of pH, conductivity, dissolved oxygen(DO) and temperature. Test solution was the demineralized water, and DO concentration was less than 1 ppb. Surface appearance of A 106 Gr. B which is used widely in secondary pipe in NPPs showed orange peel appearance, typical appearance of FAC. The materials with Cr content higher than 0.17wt.% showed pit. The pit is thought to early degradation mode of FAC. The corrosion product within the pit was enriched with Cr, Mo, Cu, Ni and S. But S was not detected in SA336 F22V with 2.25wt.% Cr. The enrichment of Cr and Mo seemed to be related with low, solubility of Cr and Mo compared to Fe. Measured FAC rate was compared with Ducreaux's relationship and showed slightly lower FAC rate than Ducreaux's relationship.

• KSBB Journal
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• v.4 no.2
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• pp.134-142
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• 1989

In exopolysaccharide fermentation by Aureobasidium pulluans, the effects culture conditions (concentration of nitrogen, potassium phosphate, dissolved oxygen, and initial pH) on the production of exopolysaccharide and the appearance of melanin pigment were investigated. The results are as follows. (1) The specific growth rate and the specific production rate of exopolysaccharide were inhibited by substrate when the carbon source concentration higher than $50g\;/\;{\ell}$ and the cell growth increased with increases of nitrogen source but exopolysaccharide production decreased with the nitrogen concentration when it become greater than $1\;g\;/\;{\ell}$. (2) The maximum cell growth and the maximum exopolysaccharide production were obtained at initial pH values of 3.0 and 7.5 respectively. As the initial pH increased, the yeast-like cells increased and the increased of dissolved oxygen increased the cell growth and exopolysaccharide production. (3) As the concentration of dissolved oxygen is increased or the concentration of nitrogen source is decreased, the period of melanin pigment appearance becomes shorter and the melanin pigment never appeared when the initial pH was less than 3.0 or the potassium phosphate was not added.

• Korean Journal of Environmental Agriculture
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• v.28 no.1
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• pp.86-91
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• 2009

The main purpose of this study is to search the water factor which influences to occurrence of the total coliforms. Occurrences rate of the total coliforms and the E coli were 57.9% 10.5% in 2007 and 47.4%, 23.7% in 2008 respectively. According to the result which examines the correlation analysis and a regression analysis, most the water factor which is effect was $Na^+$(0.497, p<0.05) in appearance of the total coliforms and was $Cl^-$(0.622, p<0.01) in appearance of the E coli. The water factor that simultaneously influences to the total coliforms and the E. coli appearances was the $Cl^-$. The predictable regression formula for appearance rate of the total coliforms was expressed as 0.462 + 0.028 [$Na^+$] - 0.644 [$COD_{Mn}$] - 8.889 [$PO_4-P$](R = 0.930, $R^2$ = 0.866, adjusted $R^2$ = 0.839, p<0.05), and that of the E coli was described as -0.012 + 0.004 [$Cl^-$](R = 0.622, $R^2$ = 0.387, adjusted $R^2$ = 0.351, p<0.05).

• Journal of The Korean Society of Grassland and Forage Science
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• v.14 no.2
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• pp.93-98
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• 1994

This experiment was canied out to investigated the effect of slope exposure on winter hardiness of grasses in mountainous pastures of Taekwalyong area The results obtained were summarized as follows; 1. Plant vigour(PV) before wintering influenced on the growth of next spring, field survival rates and winter hardiness of grasses. 2. The dry weight of plant per relative tiller appearance rates(DW/RTAR) was significantly negative correlated with plant vigour(PV) before wintering, but the weight of plant per relative tiller appearance rates(DW1 RTAR) were significantly positive correlated with the number of tiller per plant before wintering($NT_O$), number of tillers per plant of 1st cutting(NT), dry weight of plant(DW), field survival rates(SR) and relative tiller appearance rate(RTAR). 3. There ranking order of high winter hardiness of grasses, it were west(W), north-north west(NNW), eastsoutheast( ESE) and south-southwest(SSW) exposure, respectively.