• Journal of the Korean Society for Heat Treatment
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• v.37 no.4
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• pp.155-162
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• 2024

SCr420H steel which is commonly utilized for automotive components requires the carburizing heat treatment process. Abnormal grain growth during this treatment significantly affects the mechanical properties of the steel parts. Consequently, a process designed to prevent abnormal grain growth at certain elevated temperatures is essential. For enhanced grain refinement, we considered the addition of Nb in SCr420H steel. The experimental condition of the carburizing heat treatment involved reheating the steel sample to temperatures between 940℃ and 1080℃. Using scanning electron microscopy, we examined the microstructure of specimens treated with the secondary solution, revealing an organization of bainite and ferrite. Transmission electron microscopy was utilized to determine the type, shape, and size of the carbonitrides, showing a high fraction of AlN at the secondary solution treatment temperature of approximately 1050℃ and of (Nb,Ti)(C,N) around 1200℃. AlN particles measured about 100 nm and (Nb,Ti)(C,N) about 50 nm. Optical microscopy was utilized to assess grain size variations at different secondary solution treatment temperatures. It is noted that the temperature at which abnormal grain coarsening occurred rose with increasing secondary solution treatment temperatures, indicating a greater influence of (Nb,Ti)(C,N) with higher heat treatment temperatures. This research provides reference data for preventing abnormal grain growth in Nb-added low alloy steels undergoing carburizing heat treatment.

• Journal of the Korean Society for Heat Treatment
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• v.37 no.4
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• pp.163-171
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• 2024

SCR420H steel is a low-carbon chromium alloy steel designed for carburizing heat treatment. Recently, research is being conducted on high-temperature carburization heat treatment to reduce costs and CO₂ emissions by shortening the carburization time to meet the international carbon neutral policy. However, this high-temperature carburization heat treatment coarsens the steel grains and causes a decrease in mechanical properties. In this study, a large amount of Ti was added to increase the grain refinement effect in the high-temperature carburizing process. We investigated the microstructure and precipitates of SCR420H steel without Ti (Al steel) and with Ti (AlTi steel). Thermodynamic calculations showed that the AlN and (Ti,Nb)(C,N) precipitated in Al steel, while (Ti,Nb)(C,N) and Ti₄C₂S₂ precipitated in AlTi steel. Addition of Ti increases the fraction of bainite after reheating process. Transmission electron microscopy analysis shows that small amounts of AlN and (Ti,Nb)(C,N) precipitates are formed in the Al steel. The addition of Ti increases the density of (Ti,Nb)(C,N) precipitates and induces the formation of Ti₄C₂S₂ precipitates, increasing the grain coarsening temperature (GCT) under all heat treatment conditions. Higher reheating temperatures also resulted in higher GCT values due to increased precipitation.

• The korean journal of orthodontics
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• v.26 no.4
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• pp.359-371
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• 1996

The purpose of this study was to investigate the changes about the cellular activity on DNA synthesis in the periodontal ligament of dog, in which experimental tooth movement was performed. A control and 5 experimental dogs, one and half year in age, were studied. Light force (50-75g) was applied by placing open-coil spring between left mandibular premolars ; heavy force (250-300g), between right mandibular premolars. Experimental dogs were sacrificed after infusion of bromodeoxyuridine(BrdU), at 12 hours, 1, 3, 7 and 14 days after force application, respectively. And the histologic and the immunohistochemical evaluation were performed on the obtained periodontal tissue around mandibular premolars, using anti-romodeoxyuridine antibody, which can indicate proliferating cells. The results were as follows: 1. The tearing of periodontal ligament and the vascular dilatation at tension side were observed in 12 hours, increasing until 3 days. After then it decreased; Such a finding was more evident in heavy force group than in light force group. 2. The hyalinization of the periodontal ligament and the activity of osteoclast at pressure side were observed in 12 hours, increasing until 3 days. But from 7 days on, it decreased; Such a finding was more evident in heavy force group than in light force group. 3. The BrdU expression in the control group was positive, mainly in the oral epithelium and the fibroblasts in the periodontal ligament, but negative in bone cells in periodontal ligament. 4. The BrdU expression in the experimental group was more positive in tension side than in pressure side; The expression was a little more positive in the periapical area than in the cervical area of tooth. 5. The BrdU expression in light force group was the highest in 1 day, after which it decreased; In heavy force group, it was the highest in 12 hours, after which it decreased. But in 14 days, there was no difference between the experimental group and control group.

• Korean Journal of Agricultural Science
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• v.41 no.4
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• pp.321-326
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• 2014

The aim of this study was to investigate which hydroponic system is the optimum for growth and photosynthetic characteristics of Angelica gigas during experiment. Angelica gigas 'Manchu' were sowed and managed under a growth room chamber. The environmental conditions (temperature $22^{\circ}C/18^{\circ}C$ (day/night), relative humidity 50-70%, photosynthetic photon flux density (PPFD) $120{\pm}6{\mu}mol\;m^{-2}s^{-1}$) were maintained for 3 weeks. Forty eight seedlings with 4-5 leaves were transplanted in deep flow technique (DFT), substrate, and spray culture systems [culture bed: 800 (L) ${\times}$ 800 (W) ${\times}$ 400 mm(H)] under $150{\pm}5{\mu}mol\;m^{-2}s^{-1}$ PPFD provided with fluorescence lamps and cultivated for 11 weeks. At the end of the experiment, fresh and dry weights, leaf lenghth and width, SPAD, root fresh, and dry weights, and root volume of Anglica gigas were measured. Photosynthetic rate of Anglica gigas were measured with portable photosynthesis systems to investigate optimum PPFD, $CO_2$ concentration, and air temperature conditions. Fresh and dry weights of Anglica gigas grown in substrate were significantly greater than DFT-treated, but there were not significant with spray treatment. Leaf photosynthesis of Anglica gigas showed the tendency to sharply increase as PPFD was increased from 50 to $200{\mu}mol\;m^{-2}s^{-1}$. Though $CO_2$ saturation point was around $1000-1200{\mu}mol\;mol^{-1}$, increase in air temperature from 16 to $26^{\circ}C$ did not quite affect photosynthesis of Anglica gigas. In conclusion, Anglica gigas may be optimally cultivated with a spray culture system as air temperature, PPFD, and $CO_2$ concentration for environment are controlled at $20{\pm}3^{\circ}C$, $150{\mu}mol\;m^{-2}s^{-1}$, and around $1000{\mu}mol\;mol^{-1}$ for mass production.

• Journal of Periodontal and Implant Science
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• v.29 no.1
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• pp.15-30
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• 1999

The purpose of this study was to evaluate the effect of mixed extracts of aralia cortex and phellodendron cortex (P55A) on activities of human gingival fibroblasts and periodontal ligament cells in vitro. First experiment was done to evaluate the effect of P55A in normal condition. In control group, the cells($4.5{\times}10^4$ cells/ml) were cultured with Dulbecco's Modified Eagle's Medium contained with 10% fetal bovine serum. In experimental groups, P55A was added to the above culture condition at the final concentrations of 0.1 ${\mu}g/ml$(Test group 1), 1 ${\mu}g/ml$(Test group 2) and 10 ${\mu}g/ml$(Test group 3). Then each group was tested for the cell proliferation rate at $\frac{1}{2}$, 2, 5 days, protein levels at 2, 5 days, and alkaline phosphatase activity at 2, 5 days. Second experiment was done to evaluate the effect of P55A in high glucose condition. 200 mg/dl glucose was added to the same culture condition of all groups in first experiment. Then each group was tested for the cell proliferation rate at $\frac{1}{2}$ , 2, 5 days, protein levels at 2, 5 days, and alkaline phoaphatase activity at 2, 5 days. The results were as follows ; 1. First experiment 1) As P55A concentration increased, cell proliferation rate increased significantly in test group 2 at 2 days, and test group 2 and 3 at 5 days in human gingival fibroblasts and periodontal ligament cells(P<0.05). 2) In human gingival fibroblasts, all test groups showed significantly increased protein levels as compared to control group at 5 days. In periodontal ligament cells, test group 2 and 3 showed significantly increased protein levels as compared to control group at 2, 5 days(P<0.05). 3) Alkaline phosphatase activity of human periodontal ligament cells increased as P55A concentration increased. The test group 2 and 3 showed significant increase as compared to control group at 5 days(P<0.05). 2. Second experiment 1) As P55A concentration increased, cell proliferation rate increased significantly in test group 2 at 2 days, and test group 2 and 3 at 5 days in human gingival fibroblasts and periodontal ligament cells(P<0.05). 2) In human gingival fibroblasts, test group 3 showed significantly increased protein levels as compared to control group at 2 days, and all test groups at 5 days. In periodontal ligament cells, test group 2 and 3 showed significantly increased protein levels as compared to control group at 2, 5 days(P<0.05). 3) Alkaline phosphatase activity of human periodontal ligament cells increased as P55A concentration increased. The test group 2 and 3 showed significant increase as compared to control group at 2 days, and all test groups at 5 days(P<0.05). From the above results, mixed extracts of aralia cortex and phellodendron cortex appeared to enhance cellular activities including cell proliferation rate, protein levels and alkaline phosphatase activity of human gingival fibroblasts and periodontal ligament cells in normal and high glucose condition. This study suggests that mixed extracts of aralia cortex and phellodendron cortex seem to be able to subside the inflammation of periodontal tissue and regenerate the destructed periodontal tissue.

• Journal of Periodontal and Implant Science
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• v.24 no.2
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• pp.219-237
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• 1994

The ultimate goal of clinical periodontal therapy is to achieve regeneration of a healthy connective tissue reattachment. Conventional therapy including scaling, root planing, gingival curettage, gingivectomy and flap procedures of various types results primarily in repair rather than regeneration of the periodontium. In order for periodontal regeneration to occur, progenitor periodontal ligament cells must migrate to the denuded root surface, attach to it, proliferate and mature into an organized and functional fibrous attachment apparatus. Polypeptide growth factors belong to a class of potent biologic mediators which regulate cell differentiation, proliferation, migration and metabolism. Insulin-like growth factor-I (IGF- I ) of these factors appear to have an important role in periodontal wound healing and bone formation. The purpose of this study is to evaluate the effects of IGF- I on the periodontal ligament cells to use as a regeneration promoting agent of periodontal tissue. Human periodontal ligament cells were obtained from periodontal tissue explants culture of the first premolar tooth extracted for the orthodontic treatment. Cells were cultured in Dulbecco's modified Eagle medium(DMEM) with 10% fetal bovine serum. Fourth to seventh passage cells were plated in 24 well tissue culture plates and medium changed to serum-free medium prior to addition of growth factors. Cell proliferation was measured by the incorporation of $[^3H]-thymidine$ into DNA, Protein synthesis was determined by measurement of $[^3H]-proline$ incorporation into collagenase-digestible protein(CDP) and noncollagenous protein(NCP) according to the method of Peterkofsky and Diegelmann (1971), And alkaline phosphatase activity was measured as one parameter of osteoblastic differentiation. The results were as follows : The DNA synthetic activity was increased in a dose-dependent manner with IGF- I except for 0.1ng/ml concentration of IGF- I At the concentration of 10, 100ng/ml, IGF- I significantly increased the DNA synthetic activity(P<0.05) The total protein, collagen and noncollagen synthesis was increased in a dose-dependent manner with IGF- I except for 0.1ng/ml concentration of IGF- I. At the concentration of 1, 10, 100ng/ml, IGF- I significantly increased the total protein, collagen and noncollagen synthesis activity(P<0.95, P<0.001). The % of collagen was not effected according to the concentration of IGF- I. The alkaline phosphatase activity was increased in a dose-, time-dependent manner with IGF- I (10, 100ng/ml). In conclusions, the present study shows that IGF- I has a potentiality to enhance the DNA synthesis of periodontal ligament cells with including the increase of the total protein and collagen synthetic activity. The use of IGF- I to mediate biological stimulation of periodontal ligament cells shows promise for future therapeutic applications.

• Journal of Animal Science and Technology
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• v.51 no.3
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• pp.231-240
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• 2009

Sixteen ruminally cannulated Korean native steers (Hanwoo; $626.2\pm47.72$ kg) were used to investigate the effects of polyclonal antibodies against abdominal (AAb) and subcutaneous adipocyte membrane proteins (SAb) on ruminal fermentation patterns and blood metabolites. The body weight (BW) of Hanwoo was decreased 2-weeks after AAb and SAb injection, BW reduction was also observed in control and non-immunized serum groups, indicating that stress induced by other factors (e.g. blood sampling etc.) rather than antibodies injection may affect the BW reduction. Antibodies treatment did not affect (P > 0.05) rumen pH, volatile fatty acids and ammonia-N concentration. The ranges were similar with typical ranges of those in Hanwoo. Compared with control, blood urea N concentration was decreased in AAb group and increased (P < 0.05) in SAb group before antibodies treatment. However, none of the groups were significantly (P > 0.05) affected at 2- or 4-weeks after the treatment. Concentration of plasma glucose in the non-immunized serum group was significantly higher (P < 0.05) than the other groups at 0-week after treatment. However, antibodies treatment did not affect the concentration of plasma glucose. Concentration of plasma triglyceride showed no difference (P > 0.05) between the groups and ranged from 11.4 to 19.9 mg/dl, which is the perfect range of plasma triglyceride of Hanwoo fed concentrate based diets. In conclusion, these results may indicate that the present AAb and SAb have safety in nutritional physiological metabolism in Hanwoo. Further study on in vivo fat reduction of the antibodies against abdominal and subcutaneous adipocytes PMPs of Hanwoo is required for inedible fat-reduced high quality beef production.

• Journal of The Korean Society of Grassland and Forage Science
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• v.29 no.3
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• pp.263-268
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• 2009

This study was conducted to determine application possibility of mulberry (Morus alba) silage as a functional feed in feeding management of Korean native cattle for high quality beef production by analysing active components and antioxidative activity. The chemical analysis of mulberry silage indicates that the content of dry matter, crude protein, ether extract, crude fiber and crude ash was $28.41{\pm}3.12%,\;12.43{\pm}0.28%,\;2.47{\pm}0.18%,\;20.29{\pm}0.75%\;and\;6.98{\pm}0.12%$, respectively. The content of 1-deoxynojirimycin (1-DNJ), which is representative active ingredient of mulberry and blood sugar descending component, was 0.568 mg/g and the content of $\gamma$-Aminobutyric acid (GABA), which is blood pressure descending component, was 5,936.22 pmol. Mulberry silage used in this study did not contain flavonoids but did contain total phenols for 21.69 ${\mu}g/mg$. 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity was increased with increasing the concentration of mulberry silage extracts and there was above 50% of scavenging activity at the concentration of 0.25 mg/ml. Hydroxyl radical scavenging activity was also increased with increasing the concentration of silage extracts. Alkyl radical scavenging activity was high at the low concentration of silage extracts, which was above 50% of scavenging activity at the concentration of 0.125 mg/ml. The result of this study indicated that there was high possibility of mulberry silage as a functional feed for beef cattle.

• Journal of The Korean Society of Grassland and Forage Science
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• v.35 no.2
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• pp.112-118
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• 2015

This study was carried out to offer basic information for the promotion of the goat industry and the improvement of mountainous-pasture management by investigating seasonal changes in forage and livestock productivity according to the grazing-pasture type. The forage productivity of rangeland was the highest (p < 0.05) in summer and decreased in autumn; but that of pasture was the largest (p < 0.05) in spring and had relatively stable productivity with minor seasonal differences, although it decreased slightly in autumn. The dry matter content was not seasonally different at pasture, but it was changeable from spring to autumn at rangeland. The crude protein content increased in autumn at pasture (p < 0.05), and decreased in summer and autumn compared with spring at rangeland. The crude fiber content was lower and the ether extract was higher at pasture compared with rangeland. The average daily gain of the goats was different depending on forage productivity and pasture type; consequently, the lowered forage productivity at rangeland compared with pasture means that rangeland needs to be changed or improved to a pasture type that provides a more effective grazing system for goats.

• Journal of Society of Preventive Korean Medicine
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• v.6 no.1
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• pp.15-35
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• 2002

This study was conducted to provide basic data for policy of Oriental medicine by analyzing community resident's consciousness of taking herb medicine and its related factors. Data were collected from 1478 residents from March 2, 2001 to May 31, 2001. The results of this study are summarized as follows. 1) The rate of experience of taking herb medicine was 85.2%(88.2% of 'male'; 82.5% of 'female'). It appeared to be significantly higher in the groups of 'the married', 'housewife', and 'Buddhist'. As the age increased, so the rate of experience of taking herb medicine was significantly high. 2) In case of purpose of taking herb medicine, taking herb medicine as a restorative(66.8%) was much higher than taking it as a curative medicine. 3) 52.1% of the respondents satisfied with the effect of herb medicine. The groups of 'male', 'older age', 'residents in a big city', 'insurant in company', and 'the employed' showed significantly high rate in satisfying with herb medicine than the other groups. 4) According to the reason for preferring herb medicine, 36.7% of the respondents preferred herb medicine because the herb medicine was effective, while 27.8% preferred it because its side effect was low. 16.7% preferred it because persons around them recommended it. 5) 42.6% of the respondents did not want to take the herb medicine because the price of the herb medicine was high. Also 20.6% of the respondents did not want to take herb medicine because it is uneasy to take herb medicine. 15.8% did not want to take it because certain food should not be taken during the period of taking it. 9.4% did not want to take it because it tasted bitter. 6) In case of opinions on side effects of herb medicine, 40.8% of the respondents thinks that herb medicine is free from side effects, while 37.5% thinks that it causes side effects. There were significant difference in the opinions on side effects by sex, age, marital status, resident area, education level, occupation, and type of health insurance. 7) 60.7% of the respondents thinks the price of herb medicine is not resonable, while only 10.9% thinks it is resonable. 8) 45.2% of the respondents uses packs of decocted herbs although they think the packs of decocted herb are a little low effective because decocting herbs in home is bothersome. 45.2% uses packs of decocted herbs because they are convenient, being not related to the effect. 7.6% takes medicinal herbs after decocting them in a clay pot because they think the packs of decocted herbs have low effect. 51.9% does not know whether taking herb medicine in summer is effective or not because the effect is different according to their physical constitutions. 35.5% thinks that taking herb medicine is summer is effective because their physical stamina is weakened after sweated a lot, while 12.6% thinks that it is not effective because the effect of herb medicine disappears with sweat. 9) According to the level of satisfaction with Oriental medical care, the respondents marked $3.47{\pm}0.64$ points on the base of 5 points. It was significantly higher in the groups of 'male', 'the married, resident in a big city', 'highschool graduate', 'the unemployed', 'office clerk', 'growing up in a big city', 'insurant in region', and 'the middle class'. 10) According to the result of a regression analysis of factors influencing preference for herb medicine, the factors displayed significant difference by sex, age, education level, health status, and times of receiving Oriental medical care. As shown in the above results, the community residents satisfy with the effect of herb medicine. Therefore, the method of taking herb medicine without difficulty must be devised. The medicinal herbs in packages need to be included in health insurance coverage and resonable price of herb medicine must be set. Also, education program for community residents must be developed in order to provide right information in herb medicine. Therefore, related public authority, associations, and professionals must make efforts, forming organic cooperative system.