• Journal of the Korean Society for Heat Treatment
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• v.35 no.6
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• pp.303-313
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• 2022

The purpose of this study was to test and analyze the effects of the mechanical properties and structural changes of the austenitized and tempered martensite STS 410 stainless steel containing 11.5~13%Cr and 0.10%C on its temper embrittlement. The STS 410 stainless steel test pieces for each 3 hours at 960℃, 1000℃ and then, tempered them for 2 hours at 300℃, 350℃, 400℃, 450℃, 500℃, 550℃, 600℃, 650℃ and 700℃ known as the intervals vulnerable to temper embrittlement to observe the changes of their structures and mechanical properties. In case autenitizing was insufficient due to lower temperature of thermal treatment for solution, unsolved carbides and ferrites remained in the structure after quenching, which meant that the parts could wear out and corrode to embrittle at the room temperature. Elongation and impact energy changes with Tempering conditions showed minimum results in range of 400~500℃. The decrease in elongation and impact energy at 400~500℃ was the hardening effect of the subgrain due to the precipitation of many M₃C or M₇C₃, M₂₃C₆. And STS 410 stainless steel corrosion tested in 10% NaCl solution at 30℃ after tempering treatment. The degree of corrosion sensitization showed increasing tendency with increase of tempering temperature and Cr carbide precipitation were observed in grain boundary.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.32 no.4
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• pp.287-294
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• 2006

The secondary correction of cleft lip nasal deformity (CLND) presents difficult surgical problems. Characteristically, nostrils are asymmetric. The present study was aimed to examine and compare the effect of Straith's alar web Z-plasty, Millard's alar web Z-plasty, alar web excision, and lateral V-Y advancement of the alar base for augmentation of the nostril with or without lengthening the columella in CLND. The subjects were 28 patients with unilateral cleft lip, who had secondary nostril correction. The nostril correction methods were Straith's alar web Z-plasty, Millard's alar web Z-plasty, alar web excision, and lateral V-Y advancement of the alar base. Facial photographs were taken before and 20 days after the operation. By using Adobe photoshop, the columella length and the nostril width were measured from the facial frontal photograph and Worm's eye view. The degree of improvement was calculated and statistically analyzed. The degree of improvement of the columella length using Straith's alar web Z-plasty was 70.20%. And then Millard's alar web Z-plasty was 55.01%, alar web excision was 39.93%, and lateral V-Y advancement of the alar base was 16.38% in order. The degree of improvement of the nostril size using lateral V-Y advancement of the alar base was 55.26%. And then alar web excision was 52.72%, Millard's alar web Z-plasty was 34.86%, and Straith's alar web Z-plasty was 16.06% in order. Straith's alar web Z-plasty and Millard's alar web Z-plasty resulted in elongation of the columella, equalization of asymmetrical nostril, and enlargement of small nostrils. Alar web excision enlarged nostrils and restored symmetry. Lateral VY advancement of the alar base increased nostril width and enlarged nostrils. These results indicate that the correction of nostrils improve the shape and the symmetry of the nostrils in CLND.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.44 no.3
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• pp.296-301
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• 1999

The concerns on the crop damage by ultraviolet (UV) radiations is increasing owing to the decrease of their absorbing stratospheric ozone in the tropospheric. Cultivar differences on early growth of UV radiation among five Korean rice cultivars, four japonica types and one Tongil type (indica-japonica cross hybrid), were studied. Pot-seeded rice plants were grown under four different radiation conditions, i.e., visible radiation only, visible radiation with supplemented with high or low dose of UV-B (280~320 nm in wavelength) and UV-C (less than 280 nm in wavelength). The inhibitory degree on plant height, shoot and root weight and length of leaf blade and leaf sheath were determined at 40 days after seeding. UV-C showed the most severe inhibitory effect on the degree of biomass gain and leaf growth in most cultivars examined, followed by high UV-B and low UV-B. Among the cultivars used, the Kuemobyeo was the most sensitive cultivar and had not repair or showed resistance ability to continued irradiation of UV radiation. However, Janganbyeo and Jaekeon showed different responses that the elongation of leaf blades was promoted on 2nd and 3rd leaves and inhibited on 4th and 5th leaves but this inhibitory degree was reduced on 6 th and 7th leaves. Such tendency on leaf growth means that both cultivars had low sensitivity and most resistant ability to continued irradiation of UV radiation. While Tongil showed different response to enhanced UV radiation, ie., low UV-B promoted leaf growth but the inhibitory was severely increased by continued irradiation of high UV-B and UV-C, which means that Tongil had high threshold of UV radiation for response as an inhibitory light of plant growth. The results of this study indicate that the differences on sensitivity or resistant to the effects of UV radiation were existed among Korean rice cultivars.

• Elastomers and Composites
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• v.42 no.4
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• pp.217-223
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• 2007

Thermomechanical and shape memory properties of dicumyl peroxide(DCP) cured semicrystalline EPDM($Nordel^{(R)}$ IP) were investigated. From gel content analysis, it can be seen that Nordel can be crosslinked by small amount of DCP and the degree of crosslinking increased with the increase of DCP content. DSC analysis revealed that the melting temperature and degree of crystallinity of the crosslinked rubber decreased with the increase of DCP. Tensile test showed that tensile modulus increased and elongation at break of the rubber decreased with an increase in the degree of cross linking. The chemically crosslinked semi-crystalline EPDM exhibited excellent shape memory behavior, i.e. the sample was easily deformed to have an arbitrary secondary shape above its melting temperature and was fixed well in its deformed state when it is cooled, and then the fixed shape was recovered to its original shape very fast upon heating above its melting temperature.

• Polymer(Korea)
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• v.36 no.2
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• pp.235-244
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• 2012

A thiazole type accelerator MBT (2-mercapto benzothiazole) was added into silica filled natural rubber (NR) compound with various concentrations (0, 1, 2, 3, 4 phr). The effects of MBT on the cure rate, mechanical property, degree of rubber-filler interaction (${\alpha}_F$), crosslinking density, and viscoelastic property ($tan{\delta}$) were investigated. As accelerator concentration increased, the $t_{s2}$ and $t_{90}$ decreased and the crosslinking density and modulus at 300% elongation increased. The tensile strength and elongation increased up to 3 phr and no further increased at 4 phr. The $tan{\delta}$ value measured at room temperature was higher than that of the $70^{\circ}C$. The ${\alpha}_F$ value was not affected by the addition of MBT. The mechanisms for the vulcanization rate were reviewed.

• Journal of Korean Society of Forest Science
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• v.78 no.2
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• pp.143-150
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• 1989

This research was performed to estimate the influence of relative light intensity and planting density on the growth of dry weight of needles and other organs growth in Korean white pine seedlings raised in the transplanting bed. 1. As treated with various light intensities, relationships between needle dry weight and growth of other organs(dry weight of shoot, root and diameter of seedlings) had significantly positive correlations and linear regressions, but regression between needle dry weight and seedling elongation was a second degree polynomial. As treated with various planting densities, the second degree regression curve was found between needle dry weight and shoot dry weight, and seedling elongation, And linear regression between needle dry weight and root dry weight, and seedling dry weight could be estimated, while any regression between needle dry weight and diameter was not recognized. 2. As treated with various light intensities, linear regression between leaf area and shoot dry weight, and seedling dry weight, exponential regression between leaf area and seedling elongation were significantly recognized, while a tendency of logarithmic regression between leaf area and diameter appeared. According to the different density treatment, logarithmic regression between leaf area and shoot dry weight, linear regression between leaf area and root dry weight, and seedling dry weight, but quadric regression between leaf area and seedling elongation and diameter were significantly found.

• Applied Chemistry for Engineering
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• v.5 no.3
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• pp.524-536
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• 1994

Chitosan is known to be a good biocompatible natural polymer. Polyethyleneglycol monomethacrylates(PEGM) were grafted onto chitosan and their reaction conditions and properties of the graft polymers obtained were estimated. Using ceric ammonium nitrate(CAN) as the initiator, the optimum condition for graft polymerization was determined amount of the initiator and monomer concentrations and reaction time. Grafting yields such as total conversion, the percentage of grafting and the efficiency of grafting were calculated and examined the optimum reaction condition for high grafting yields. The percentage of grafting and total conversion were maximum at condition that the concentration of initiator was $4{\sim}5{\times}10^{-3}M$, the concentration of monomer was 0.5~0.6M, the reaction time was 2~3 hours and the reaction temperature was about $40^{\circ}C$. Thermal characteristics, solubility for chitosan solvents and inherent viscosity of synthesized graft copolymers were investigated. In high initiator concentration, characteristics of chitosan were greatly diminshed. In case of inherent viscosities, chitosan-g-PE-90 was 2.81 dl/g, chitosan-g-PE-200, 3.01dl/g and chitosan-g-PE-350, 4.93dl/g. And a tendency of viscosity increase depending on the length of ethylene oxide residue was confirmed. Degree of swelling, tensile strength, elongation of membrane prepared from graft copolymers were determined. Properties of graft copolymers were affected by percentage of grafting and length of ethylene oxides residue in polyethylene glycol monomethacrylates. Tensile strength, elongation and degree of swelling of graft copolymers were remarkably improved than chitosan. As percentage of grafting increased, the amount of drug permeation was also increased.

• Korean Journal of Materials Research
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• v.10 no.7
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• pp.515-521
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• 2000

The effect of precipitates on the high temperature tensile properties of cast alloy 718 was investigated by phase extraction method and microstructural observation. The value of tensile strength and elongation gradually decreased with increasing testing temperature up to $760^{\circ}C$. Elongation of the alloy increased, while tensile strength decreased above 76$0^{\circ}C$. The amount of precipitates in the specimen that tensile tested at $760^{\circ}C$ showed maximum owing to stress assisted precipitation. Therefore, the alloy exhibited the lowest value of the elongation and the degree of decrease in yield strength at this temperature due to high flow stress of precipitates. Little amount of precipitate, especially $\gamma$' and $\gamma$＂, resulted in softening of the alloy at the temperature above $760^{\circ}C$.

• Korean Journal of Agricultural Science
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• v.27 no.2
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• pp.86-94
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• 2000

This study was carried out to determine the effectiveness of uniconazole in ameliorating low and high temperature injury in tomato plants(Lycopersicon esculentum Mill. cvs. Fireball and Patio). Plants were given a soil drench of 0, 0.001, 0.01 or $0.1mg{\cdot}pot^{-1}$ uniconazole, and after 14 days, were treated with 12-h day/12-h night cycles at $25/25^{\circ}C$, $2.5/25^{\circ}C$, $25/2.5^{\circ}C$ or $40/40^{\circ}C$ for 4 days in controlled-environment chamber. Number of damaged leaves per plant, reduction of stem elongation, and overall injury were high at $2.5/25^{\circ}C$, but more reduction of leaf elongation, delay of flowering, and abortion of floral bud were observed in plants at $40/40^{\circ}C$. There was difference in degree of injury between cultivars, thus, 'Fireball' was much affected by unfavorable temperature regimes. All concentrations of uniconazole reduced leaf and stem elongation, increased total chlorophyll concentration, delayed flowering, and significantly provided protection against low and high temperature injury in two cultivars. In general, the application of uniconazole did not inhibit flowering delay and floral bud abortion induced by high and low temperature exposure. Our results support the hypothesis that the role of uniconazole is related to defense system against oxidative stress induced by low temperature stress. Further research is required to clarifu the phytoprotective mechanism of this compound agaist high temperature stress.

• Korean Journal of Food Science and Technology
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• v.24 no.6
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• pp.574-580
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• 1992

Chitin was isolated from the residue of enzymatically hydrolyzed crab, Portunus trituberculatus, and further deacetylated by alkaline boiling to make chitosan. The physical properties of chitosan solution and its film forming properties were examined. The functional characteristics of chitosan film were compared to those of cellophane, polyvinyl chloride (PVC) and polyethylene (PE) films. The proximate chemical composition of chitin obtained from crab residue was 6.95% nitrogen, 0.3% crude ash and 4.57% moisture and the product yield was 12.8% based on a dry material basis. The degree of deacetylation of chitosan was $79{\sim}92%$ and $70{\sim}86%$ as determined by IR spectroscopy, and $70{\sim}86%$ as determined by colloid titration method each respectively. The chitosan at 1% acetic acid solution showed distinct pseudoplastic flow behavior. The flow behavior index and consistency index were 0.8886, 0.2084 $MPa{\cdot}s^n$ for 0.4% solution and 0.8498, 0.6190 $MPa{\cdot}s^n$ for 0.8% solution, respectively. The chitosan film had the highest tensile strength $(888 kg/cm^2)$ and water permeability $(100\;g/m^2{\cdot}24\;hrs)$ among the tested films, but relatively low elongation property (49%). It showed the similar tear strength (90kg/cm) and light permeability (87.7%) to other films tested in spite of the relatively high haze value (12.5%). As the thickness of chitosan film increased from 0.025 to 0.050 mm, the tensile strength of film decreased distictively, and the degree of elongation, tear strength, and water permeability of film also decreased slightly. Whereas the light permeability of film did not change and the haziness of film slightly increased by the increase of film thickness.