• Korean Journal of Materials Research
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• v.13 no.4
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• pp.205-212
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• 2003

RF sputtering process was applied to produce thin hydroxyapatite［HA, Ca10($PO_4$)$_{6}$ $ (OH)_2$films on Ti-6Al-4V alloy substrates. To make a 101.6 mm dia.${\times}$5 mm HA target, the commercial HA powder was first calcinated for 3h at $200^{\circ}C$. A certain amount of the calcinated HA powder was pressed under a pressure of 20,000 psi by the cold isostatic press(CIP) and the pressed HA target was sintered for 6 h at $1,200^{\circ}C$. The effects of different heat treating conditions on the bonding strength between HA thin films and Ti-6Al-4V alloy substrates were studied. Before deposition, the alloy substrates were annealed for 1 h at $850^{\circ}C$ under $3.0${\times}$10^{-3}$ Xtorr, and after deposition, the hydroxyapatite/Ti-6Al-4V alloy thin films were annealed for 1 h at 400, 600 and $800^{\circ}C$ under the atmosphere, respectively. Experimental results represented that the HA thin films on the annealed substrates had higher hardness than non-heat treated substrates before the deposition.

• KSBB Journal
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• v.11 no.2
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• pp.211-217
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• 1996

Batch experiments were conducted to investigate the effect of electron donor on reductive dechlorination of 2,4,5-trichlorophenol by a methanogenic consortium. The methanogenic consortium was obtained from the anaerobic digester of a municipal wastewater treatment plant. The batch reactor containing methanogenic consortium was spiked with 2,4,6-trichlorophenol at 10 mg/$\ell$. Acetate, ethanol, glucose of methanol, each was added as an electron donor for methanogenic consortium. During the course of the experiments liquid samples were taken from the batch reactor to measure dechlorination rate and find the dechlorination pathway of 2,4,6-trichlorophenol. After incubation 2,4,6-trichlorophenol was first dechlorinated to 2,4-dichlorophenol and then to 4-chlorophenol. Phenol was not detected in the batch reactor the highest rate of dechlorination of 2,4,6-trichlorophenol was observed when ethanol was used as an electron donor.

• Journal of Ginseng Research
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• v.18 no.2
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• pp.89-94
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• 1994

The authors have already shown that 6 year old red ginseng extract or its powder has remarkable anticarcinogenic effects. In this study, we further investigated whether fresh ginseng or white ginseng has similar anticarcinogenic effects and also if their anticarcinogenic effects are related to the types and ages of ginseng using Yun's anticarcinogenicity test (9 week medium term bioassay model). Dried fresh ginseng and red ginseng at 1.5, 3, 4, 5 and 6 years, and while ginseng at 3, 4, 5 and 6 years were used. The following results were obtained: 1) In the dried fresh ginseng treated groups, the incidence of lung adenoma induced by benzo(a)pyrene was 41.39) and its incidence was reduced to 31.2%, 30.0%, 31.3%, 30.7% and 27.8% after co-treatment with 1.5, 3, 4, 5 and 6 year-dried fresh ginseng, respectively. A significant effect was observed only in 6 Year-dried fresh ginseng. 2) In the white ginseng treated groups, the incidence of lung adenoma induced by benzo(a)pyrene was 45.0% and its incidence decreased to 41.3%, 38.0%, 31.6%, and 25.3% after co-treatment with 3, 4, 5 and 6 year-white ginseng, respectively. Five and 6 year-ginsengs showed significant inhibition of lung adenoma. 3) In the red ginseng treated groups, the incidence of lung adenoma induced by benzo(a) pyrene was 48.6% and its incidence diminished to 37.9%, 41.7%, 31.7%, 28.3% and 25.5% after co-treat-melt with 1.5, 3, 4, 5 and 6 year-red ginseng, respectively. In 4, 5 and 6 year-ginsengs, the anticarcinogenic effect was prominent. From the above results, we concluded that a significant anticarcinogenic effect was observed in 6 year-dried fresh ginseng, 5 and 6 year-white ginsengs, and 4, 5 and 6 year-red ginsengs.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.59 no.2
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• pp.197-201
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• 2010

$SF_6$ gas would be used in power transformer, GIS (Gas insulated switchgear) and so on because of its electrically superior insulation and chemically stable structure. Recently, the reduction of $SF_6$ is required to avoid global warming and the researches on the dilution of $SF_6$ with other gases have been carried out. $SF_6$ mixture gases with $N_2$ and $C_xF_y$ have drawn attention to the synergy effect. However, in order to understand the mechanism of the synergy effect, it is important to analyze and evaluate properties of mixture gases quantitatively. In this paper, we investigated the mechanism of synergy effect from electron collision processes and electron energy distribution by solving Boltzmann equation with propagator method. Three kinds of gases for dilution of $SF_6$ ($SF_6/N_2$, $SF_6/CF$4 and $SF_6/C_4F_8$) are considered in this simulation. On the properties of $SF_6/N_2$ mixture gas, the variation of reduced electric field was shown highly within 0%~40% mixtures of $SF_6$. And the more low-level electron energy has been distributed, the higher insulation capability has appeared.

• Korean Journal of Medicinal Crop Science
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• v.12 no.6
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• pp.483-489
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• 2004

Monthly changes of underground growth and ethanol extract content was investigated from April to September in Korean ginseng of 4, 5 and 6 year-old. Taproot's length was repeatedly reduced and recovered without increasing by growth duration, while it's diameter was gradually increased until September of harvest time. Top weight reached to the peak on July, and decreased gradually until harvest time. Root weight of 4, 5 and 6-year-old ginseng was decreased on May, but increased gradually until harvest time except 6-year-old ginseng decreased after July. Relative growth rate (RGR) of root per plant was low on May and August, but high on June, July, and September in 4, 5 and 6 year-old ginseng. RGR of 4 and 5-year-old ginseng in each lateral and fine root showed distinct changes by month, while those showed little seasonal changes in 6 year-old ginseng. Ratio of root above 60g on september was 23%, 60% and 69%, respectively, among 4, 5 and 6 year-old ginseng. Moisture content of root was gradually decreased until september without significant difference from July to september in 4, 5 and 6 year-old ginseng, and its descending order on september was 4, 5 and 6 year-old ginseng. Hardness of taproot was decreased on May, but increased until september in 4 and 5 year-old ginseng, while that of 6 year-old ginseng was gradually decreased from August to september. Extract content of 4, 5 and 6 year-old ginseng in taproot and lateral root was distinctly decreased from March to June, but gradually increased until September. Although extract content of March and May in 4 year-old ginseng on showed higher than that of 5 and 6 year-old ginseng, it of September didn't show significant difference among 4, 5 and 6 year-old ginseng.

• Journal of The Korean Society of Grassland and Forage Science
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• v.17 no.4
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• pp.407-414
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• 1997

In this study, the optimum cutting 6equency and level of mineral nitrogen fertilization were investigated for the production of Reed canarygrass in uncultivated rice paddy. The results are summarized as follows; 1. Higher relative dry matter yields were recorded in 2nd cut of plots with 3 and 5 cutting frequencies, and 3rd cut of plot with 4 cutting kquency, respectively. 2. With no nitrogen fertilization, mean dry matter yields per year were 6.2~7.6 tonsha and the highest yield appeared in plot with 4 cutting 6equency. 3. The increased fertilization of mineral nitrogen resulted in the increased dry matter yield. Significantly higher dry matter yields than that of no nitrogen fertilization were recorded in fertilization of 90 kg nitrogen per year in 3 cutting fequency, 240 kg in 4 cutting frequency and 150 kg in 5 cutting 6equency respectively. 4. Efficiency of dry matter production with nitrogen fertilization(kg DMkg N) was higher in 30kg Nhalcut in 3 and 5 cutting eequency, 60kg Nhalcut in 4 cutting 6equency respectively. In each cutting kequency, the higher efficiency of dry matter production appeared in 1st cut in 3 cutting kequency, and 2nd cut in 4 and 5 cutting 6equency respectively. 5. Economic N level(kg/ha) was 179.5~242.3kg/ha in 3 cutting 6equency, and 189.6-241.6kg/ha and 167.0 ~253.2kg/ha in 4 and 5 cutting 6equency respectively, and marginal dry matter yields were 11.4~ 12.3 tons/ ha, 11.2 ~ 11.8 tons/ha and 8.3 ~9.1 tons/ha in 3, 4 and 5 cutting 6equency respectively. 6. The limiting N fertilization level to the highest dry matter were estimated to be 569.9kg/ha, 492.4kg/ha and 654.lkg/ha in 3, 4 and 5 cutting kequency respectively.

• Asian-Australasian Journal of Animal Sciences
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• v.13 no.11
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• pp.1518-1522
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• 2000

Since the n-6 polyunsaturated fatty acid, docosatetraenoic acid (22:4n-6), is a major functional constituent of avian spermatozoa, the effects of two dietary oils rich in fatty acids which are metabolic precursors of 22:4n-6 on the fatty acid profiles of testicular lipids were investigated during a 39 week period of supplementation from 21 to 60 weeks of age. The effects on liver lipids were determined for comparison. Dietary supplementation of male chickens with Arasco Oil, which provides a large amount of arachidonic acid (20:4n-6), increased the proportion of 20:4n-6 in liver phospholipid by almost 2.5-fold. Although liver phospholipid normally contains very little 22:4n-6, this proportion was significantly increased as a result of Arasco feeding, indicating that the conversion of 20:4n-6 to 22:4n-6 was occurring. The phospholipid of the testis contains much higher proportions of 20:4n-6 and particularly of 22:4n-6 than the liver; supplementation with Arasco Oil significantly increased the proportions of both these polyunsaturates in testis phospholipid but the magnitude of this effect was much lower than that which occurred in the liver. Dietary supplementation with Evening Primrose Oil which contains ${\gamma}-linolenic $ acid (18:3n-6) resulted in significant increases in the proportions of 20:4n-6 and 22:4n-6 in liver phospholipid, although the extent of this increase was less than that produced by the Arasco Oil. By contrast, the feeding of Evening Primrose Oil did not alter the fatty acid composition of phospholipid in the testis. The findings raise the possibility that dietary supplementation with Arasco Oil may modulate the fatty acid profile of avian spermatozoa in a way which could potentially be beneficial for fertility. Moreover, the weights of the testes were almost doubled as a result of supplementation with Arasco Oil or Evening Primrose Oil.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.57-60
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• 2003

The purpose of this study is to investigate the high temperature deformation behavior of Ti-6Al-4V alloy and to predict the final microstructure under given forming conditions. Equiaxed and widmanstatten of Ti-6Al-4V alloys were prepared as initial microstructure and the compression tests were performed to obtain the flow curves at high temperatures (700∼1100$^{\circ}C$) and various strain rates (10$\^$-4/∼10$^2$/s). Form the results of compression test various parameters such as strain rate sensitivity (m) and activation energy (Q) were calculated and used to establish constitutive equations. To predict the final microstructure after forming, finite element analysis was performed considering the microstructural parameters such as the grain size and the volume fraction of second phase.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.4
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• pp.20-28
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• 2003

The machinability of Ti-6Al-4V titanium alloy and tool wear behavior in machining of Ti-6Al-4V titanium alloy was studied to understand the machining characteristics. This material is one of the strong candidate materials in present and future aerospace or medical applications. Recently, their usage has already been broaden to everyday's commercial applications such as golf club heads, finger rings and many decorative items. To anticipate the general use of this material and development of the titanium alloys in domestic facilities, the review and the study of the machining parameters for those alloys are necessary. This study is concentrated to the machining parameters of the Ti-6Al-4V alloy due to their dominant position in the production of titanium alloys.

• Transactions of Materials Processing
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• v.12 no.4
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• pp.290-295
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• 2003

High temperature deformation behavior and prediction of final microstructure after forming of Ti-6Al-4V alloy were investigated in this study. Equiaxed and Widmanstatten microstructures of Ti-6Al-4V alloys were prepared as initial microstructures and compression tests were performed to obtain the flow curves at high temperatures (700∼110$0^{\circ}C$) and various strain rates (10$^{-4}$ ∼10$^2$/s). From the results of compression test, strain rate sensitivity (m) and activation energy (Q) were calculated and used to establish constitutive equation. To predict the final microstructure after farming, finite element analysis was performed considering the microstructural parameters such as grain size and volume fraction of second phase.