• Proceedings of the Korean Society of Marine Engineers Conference
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• 2001.11a
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• pp.80-87
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• 2001

The fatigue crack growth behavior of the SA516/60 steel which is used for pressure vessels was examined experimentally at room temperature $25^{\circ}C, -30^{\circ}C, -60^{\circ}C, -80^{\circ}C, -100^{\circ}C$ and -l2$0^{\circ}C$ with stress ratio of R=0.05, 0.1 and 0.3. Fatigue crack propagation rate da/dN related with stress intensity factor range ΔK was influenced by stress ratio in stable of fatigue crack growth (Region II) with an increase in ΔK. The resistance of fatigue crack growth at low temperature is higher compared with that at room temperature, which is attributed to the extent of plasticity-induced by compressive residual stress according to the cyclic loads. Fractographic examinations reveal that the differences of the fatigue crack growth characteristics between room and low temperatures are mainly explained by the crack closure and the strengthening due to the plasticity induced and roughness induced.

• Proceedings of the KWS Conference
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• 2001.05a
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• pp.220-223
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• 2001

In this study, CT specimens were prepared hem ASTM SA516 which was used for pressure vessel plates for room and low temperature service. And we got the following characteristics from fatigue crack growth test carried out in the environment of room and low temperature at $25^{\circ}C$, -3$0^{\circ}C$, -6$0^{\circ}C$, -8$0^{\circ}C$, -l$0^{\circ}C$ and -l2$0^{\circ}C$ and in the range of stress ratio of 0.1, 0.3 by means of opening mode displacement. At the constant stress ratio, the threshold stress intensity factor range ΔK$_{th}$ in the early stage of fatigue crack growth ( Region I ) and stress intensity factor range ΔK in the stable of fatigue crack growth ( Region II) was increased in proportion to descend temperature. It assumed that the fatigue resistance characteristics and fracture strength at low temperature is considerable higher than that of room temperature in the early stage and stable of fatigue crack growth region. The straight line slope relation of logarithm da/dN - ΔK in Region II, that is, the fatigue crack growth exponent m increased with descending temperature at the constant stress ratio. It assumed that the fatigue crack growth rate da/dN is rapid in proportion to descend temperature in Region H and the cryogenic-brittleness greatly affect a material with decreasing temperature.e.greatly affect a material with decreasing temperature.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.05a
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• pp.326-331
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• 2001

In this study. CT specimens were prepared from ASME SA5l6 which was used for pressure vessel plates for room and low temperature service. And we got the following characteristics from fatigue crack growth test carried out in the environment of room and low temperature at $25^{\circ}C$, -3$0^{\circ}C$, -6$0^{\circ}C$, -8$0^{\circ}C$, -10$0^{\circ}C$ and -12$0^{\circ}C$ in the range of stress ratio of 0.1 by means of opening mode displacement. At the constant stress ratio, the threshold stress intensity factor range ΔKsub/th/ in the early stage of fatigue crack growth ( Region I) and stress intensity factor range ΔK in the stable of fatigue crack growth ( Region II) was increased in proportion to descend temperature. It assumed that the fatigue resistance characteristics and fracture strength at low temperature is considerable higher than that of room temperature in the early stage and stable of fatigue crack growth region. The straight line slope relation of logarithm da.dN -ΔK in RegionII, that is, the fatigue crack growth exponent m increased with descending temperature at the constant stress ratio. It assumed that the fatigue crack growth rate da/dN is rapid in proportion to descend temperature in Region II and the cryogenic-brittleness greatly affect a material with decreasing temperature.

• Asian-Australasian Journal of Animal Sciences
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• v.27 no.11
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• pp.1608-1614
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• 2014

The objective of this study was to investigate the different dietary ratios of n-6 to n-3 (n-6/n-3) fatty acid (FA) on performance and n-6/n-3 FA in muscles of broiler chickens. A total of 300 one-day-old Cobb chicks were randomly assigned to 3 treatments of 10 replicates in each (10 birds/replicate). Birds were fed on a corn-soybean meal-based diet containing 1% oil during starter (day 1 to 21) and 2% oil during finisher (day 22 to 39) phases, respectively. Treatments of high, medium and low dietary n-6/n-3 FA were formulated by replacing rice bran oil with linseed oil to achieve n-6/n-3 FA close to >20:1, 10:1 and 5:1, respectively. Average daily gain, average daily feed intake, and feed conversion ratio were similar (p>0.05) among the treatments. Serum glucose, cholesterol and triglycerides concentrations were not affected (p>0.05) by dietary treatments. In breast, concentration of C18:3n-3 was significantly greater (p = 0.001) for medium and low vs high n-6/n-3 FA, while concentrations of C20:5n-3, C22:6n-3, total n-3 FA, and n-6/n-3 FA were significantly higher for low vs medium, and medium vs high dietary n-6/n-3 FA. In contrast, concentrations of C18:2 and mono-unsaturated FA (MUFA) were lower for low vs high dietary n-6/n-3 FA. In thigh muscles, concentrations of C20:5n-3 were higher (p<0.05) for medium and low vs high dietary n-6/n-3 FA, and concentrations of C18:3n-3, C22:6, and n-3 FA were greater (p<0.05) for medium vs high, low vs medium dietary n-6/n-3 FA. However, concentrations of C18:1, MUFA, n-6/n-3 were lower (p<0.05) for low and medium vs high dietary n-6/n-3 FA. In conclusion, lowering the dietary n-6/n-3 FA did not affect the performance of chickens, but enhanced beneficial long-chain n-3 FA and decreased n-6/n-3 FA in chicken breast and thigh, which could be advantageous for obtaining healthy chicken products.

• Journal of Animal Environmental Science
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• v.5 no.1
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• pp.53-62
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• 1999

This study was carried out to investigate how to reuse the livestock waste and develop fly ash as a subsitution of sawdust which is used commonly to make compost. Fly ash and sawdust were mixed the ratio of 8 to 2, 7 to 3, 6, to 4, 5 to 5, 4 to 6. 3 to 7 and 2 to 8 after fermentation for 60 days the change of temperature, moisture, pH, organic matter, nitrogen content and C/N ratio were analyzed. The results are as follows; Temperature was reached to maximum (63.5$^{\circ}C$) more quickly in scraper type than in slurry type with adding large sawdust. When fly ash and sawdust were mixed same amount at scraper type and slurry type, moisture was 46.6~53.7% and maintained a good condition for fermentation. pH was showed the range of 7~10 as a mixture of fly ash. Organic matter contents were increased with increasing the added sawdust but did not show any tendency. Nitrogen content was also increased with increasing the amount of added sawdust but did not show any tendency. C/N ratio was increased to 20~60 with increasing the added sawdust, but when sawdust and fly ash were mixed 50:50, there was no significant during fermentation periods. In conclusion, supplementation of fly ash at the level of 50% of sawdust maintained a good condition for fermentation as a livestock waste composting.

• Korean Journal of Environmental Agriculture
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• v.30 no.2
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• pp.138-143
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• 2011

BACKGROUND: This study was conducted to investigate growth and yield of organically grown rice under a typhoon during a fall. The treatments included NPK chemical fertilizer, compost, oilcake, oilcake 2X, hairyvetch, and vetch+rye. METHODS AND RESULTS: Nutrient applications were made at rates equivalent to approximately 0.9 kg of actual N per acre. Oilcake and hairyvetch treatments had the lowest C:N ratio, but compost had the highest C:N ratio of 34:1. Rice treated by organic nutrient sources had great growth and development at the beginning of the growing season but had depressed growth and yield at the harvest. Oilcake 2X-treated rice in early growing season, especially, showed better growth and development than rice treated by other nutrient sources but was severely lodged at the harvest season due to the typhoon. Compost treatment with high C:N ratio slowly released inorganic N and produced poor rice growth and yield; however, it recued rice lodging. N uptake was the greatest for the oilcake 2X and vetch+rye treatments but the lowest for the compost, which was the similar pattern to the N use efficiency; the greatest and lowest N use efficiency was observed for the oilcake 2X (55%) and compost (5%), respectively. CONCLUSION(s): Rice lodging should be prevented by reducing the excessive nitrogen supplement, resulting from the lower C:N ratio of the organic materials as well as prevented by the radical midsummer drainage. Vetch+rye treatment with 25:1 of C:N had optimum vegetative growth and reduced rice lodging, which increased N use efficiency and yield.

• Journal of the Korean Geographical Society
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• v.45 no.5
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• pp.541-552
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• 2010

Geochemical and physical investigations such as ${\delta}^{13}C$ isotope ratio, carbon/nitrogen (C/N) ratio, magnetic susceptibility (MS), and particle size analyses were carried out on the estuarine tidal flat sediments from the west coast of Korea in order to reconstruct the East Asian summer monsoon variability during the late Pleistocene and Holocene Our results indicated that the summer monsoon probably peaked around 7,700-7,800 yr BP and then started to decline about 7,400 yr BP in the Korean peninsular, and that the monsoon was relatively weak between 24,000-24,500 yr BP but relatively strong between 18,500-19,500 yr BP during the Last Glacial Maximum. Our estuarine geochemical data have proven to be valuable as a new proxy for detecting the shifts in monsoon strength. This new evidence will be helpful, especially for Korean paleoenvironmental studies with few proxy data archives.

• Journal of the Korean Ceramic Society
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• v.30 no.2
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• pp.85-92
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• 1993

Oxynitride glasses in Na-Ca-Si-O-N system were prepared by melting at 135$0^{\circ}C$ for 2 hours in N2 gas. The effects of Si/Na mole ratio and the various Si3N4 contents were investigated. Stable oxynitride glasses can be obtained up to 9wt.% Si3N4 content in case the Si/Na mole ratio was 2.12 and 1.62, but $\beta$-Si3N4 was precipitated at 9wt.% Si3N4 content in case the Si/Na mole rtio was 1.12. Density (p), chemical durability, hardness (Hv), and fracture toughness (KIC) increased with increasing Si3N4 content. In cae the Si/Na mole ratio was 1.12, the increment of properties was remarkable but hardness and fracture toughness did not increase no longer owing to precipitation of $\beta$-Si3N4.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.5
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• pp.483-491
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• 1992

Plasma silicon oxynitride film has been applied as a final passivation layer for semiconductor devices, because it has high resistance to humidity and prevents from alkali ion's penetration, and has low film stress. Structure properties of plasma silicon oxynitride film have been studied experimentally by the use of FT-IR, AES, stress gauge and ellipsometry. In this experiment,Si-N bonds increase as NS12TO/(NS12TO+NHS13T) gas ratio increases. Peaks of Si-N bond, Si-H bond and N-H bond were shifted to high wavenumber according to NS12TO/(NS12TO+NHS13T) gas ratio increase. Absorption peaks of Si-H bond were decreased by furnace anneal at 90$0^{\circ}C$. The atomic composition of film represents that oxygen atoms increase as NS12TO/(NS12TO+NHS13T) gas ratio increases, to the contrary, nitrogen atoms decrease.

• Journal of the Korean Society for Heat Treatment
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• v.8 no.4
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• pp.255-265
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• 1995

Stainless steel type 304L has been nitrided in the low pressure (600Pa) and high nitrogen (80% $N_2$+20% $H_2$) environment for 5 hours by the square-wave-pulsed-d.c. plasma as a function of temperature $400{\sim}550^{\circ}C$ and pulsation. At the lower temperature range of $400{\sim}500^{\circ}C$ and at the relatively high ratio of pulse duration to pulse period. "S-phase" has been developed in the form of thin nitrided surface layer which has many cracks, leading to be nearly impossible for the industrial anti-wear and anti-corrosion applications. At the higher temperature up to $550^{\circ}C$ with the increasing ratio of the pulse duration to pulse period up to $50{\mu}s/100{\mu}s$, the nitrided layer, whose growth rate has increased also, has been composed mainly of CrN and $Fe_4N$ phases and has become thick, uniform and nearly crack-free.