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        검색결과 3

        1.
        2018.08 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        MA Al alloys are examined to determine the effects of alloying of Mg and Cu and rolling on tensile deformation behavior at 748 K over a wide strain rate range(10−4-103/s). A powder metallurgy aluminum alloy produced from mechanically alloyed pure Al powder exhibits only a small elongation-to-failure(εf < ~50%) in high temperature(748 K) tensile deformation at high strain rates( = 1-102/s). εf in MA Al-0.5~4.0Mg alloys increases slightly with Mg content(εf = ~140% at 4 mass%). Combined addition of Mg and Cu(MA Al-1.5%Mg-4.0%Cu) is very effective for the occurrence of superplasticity(εf > 500%). Warm-rolling(at 393-492 K) tends to raise εf. Lowering the rolling-temperature is effective for increasing the ductility. The effect is rather weak in MA pure Al and MA Al-Mg alloys, but much larger in the MA Al-1.5%Mg-4.0%Cu alloy. Additions of Mg and Cu and warm-rolling of the alloy cause a remarkable reduction in the logarithm of the peak flow stress at low strain rates ( < ~1/s) and sharpening of microstructure and smoothening of grain boundaries. Additions of Mg and Cu make the strain rate sensitivity(the m value) larger at high strain rates, and the warm-rolling may make the grain boundary sliding easier with less cavitation. Grain boundary facets are observed on the fracture surface when εf is large, indicating the operation of grain boundary sliding to a large extent during superplastic deformation.
        4,000원
        2.
        2018.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Binary Ti-Al alloys below 51.0 mass%Al content exhibit a breakaway, transferring from parabolic to linear rate law. The second Al2O3 layer might have some protectiveness before breakaway. Ti-63.1 mass%Al oxidized at 1173 K under parabolic law. Breakaway oxidation is observed in every alloy, except for Ti-63.1 mass%Al. After breakaway, oxidation rates of the binary TiAl alloys below 34.5 mass%Al obey almost linear kinetics. The corrosion rate of Ti-63.1 mass%Al appears to be almost parabolic. As content greater than 63.0 mass% is found to be necessary to form a protective alumina film. Addition of Mo improves the oxidation resistance dramatically. No breakaway is observed at 1123 K, and breakaway is delayed by Mo addition at 1173 K. At 1123 K, no breakaway, but a parabolic increase in mass gain, are observed in the Mo-added TiAl alloys. The binary Ti-34.5 mass%Al exhibits a transfer from parabolic to linear kinetics. At 1173 K, the binary alloys show vary fast linear oxidation and even the Mo-added alloys exhibit breakaway oxidation. The 2.0 mass%Mo-added TiAl exhibits a slope between linear and parabolic. At values of 4.0 and 6.0 mass% added TiAl alloys, slightly larger rates are observed than those for the parabolic rate law, even after breakaway. On those alloys, the second Al2O3 layer appears to be persistently continuous. Oxidation resistance is considerably degraded by the addition of Mn. Mn appears to have the effect of breaking the continuity of the second Al2O3 layer.
        3,000원
        3.
        2008.05 구독 인증기관·개인회원 무료
        Murgot Looper Moth, Ascotis selenaria, is one of the worldwide pests in citrus plants. They usually damages citrus leaves and often makes young fruits injured. In Jeju, it has been discovered that A. selenaria is a pest of two major geometridae moths being occurred in citrus plant and they also had periodically occurred and damaged bean, asparagus, etc. However, physiological and ecological studies were rarely conducted on this species, which maybe resulted from the limitation of rearing method. Therefore, this study aimed on selecting the diet sources and developing mass-rearing method for A. selenaria, in order to make ease or spur a investigation related with A. selenaria. The major sources, selected among the series of semi-artificial diet, were corn and bean powder and adding yeast makes the larva developed well. Cholesterol, one of the minor sources, enhanced the development rate and lowered the mortality during 1 to 3 larva stage. Consequently the semi-artificial diet, suitable for rearing A. selenaria larva, was composed of 25g agar, 100g corn powder, 100g soybean powder, 30g yeast, 0.5g cholesterol, 2g Vanderzant's vitamin mixture, 2g Wesson's salt mixture, 2g sorbic acid, 2.5g methyl-4-hydroxybenzoate(MPH), 2g Ascorbic acid, and 1000 ml distilled water. A. selenaria larvae has 6 developmental stage and the width of head piece was 0.31 mm (1st instar) , 0.51 mm (2nd), 0.85 mm(3rd), 1.37 mm (4th), 2.14 mm (5th), and 3.19 mm (6th). The development period of A. selenaria, reared at 25℃ and 16L:8D photoperiod, was 4.7 day (egg), 3.58 day(1st instar), 1.88 day (2nd), 1.80 day (3rd), 2.46 day (4th ), 2.59 day (5th), 8.10 day (6th), 11.26 day (pupae) when citrus leaves were supplied to the larva. The larvae, fed with the artificial diet(mentioned above), showed similar developmental periods at each developmental stage as much as the case reared with citrus leaves, although the mortality was sometimes a little bit higher. The weight of pupae were 0.614g (artificial diet) and 0.427g (citrus stuff) and female adult moths lay 1094 eggs (artificial diet) and 1054 eggs (citrus stuff).