• 한국해양공학회지
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• 제3권2호
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• pp.625-625
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• 1989

To check technical improvement in the soundness and strength of 12% Cr steel rotor, a 25 tons of rotor with 65 tons of ingot was made in real size and was cut to pieces to take test samples, and the various mechanical tests such as impact, tensile, creep, and fatigue were carried out. The strengths are compared with those of 1% Cr-Mo-V rotor of same size. Microstructures of the samples are examined and reviewed. The results can be summarized as follows. 1) Fracture appearance transition temperatures are 80.deg. C at the center part and 60.deg. C near surface of 12% Cr rotor, and 8.deg. C near surface of 1% Cr-Mo-V rotor. 2) Comparative rapid softening occurs at higher temperatures above 600.deg. C for 12% Cr steel and 550.deg. C for 1% Cr-Mo-V steel in tension tests. 3) Fatigue crack propagation rate of 12% Cr steel is almost same as that of 1% Cr-Mo-V steel at the same corresponding surface part of the rotors. The crack growth rate of center part of 12% Cr rotor is faster than near surface part of the rotor, and the crack growth rate at the load condition of R=0.04 is slower than that of the load condition of R=0.5 for both 12% Cr steel and 1% Cr-Mo-V steel. 4) Crack growth rate of radial direction near surface of 12% Cr rotor is faster than that of transverse direction at the same part because of the difference in residual stresses. 5) Both creep and fatigue strengths of 12% Cr steel are superior to those of 1% Cr-Mo-V steel and the difference is thought the effect of climb and glide controlled creep by solid solution of alloying elements and dispersion of carbides.

• 한국의류산업학회지
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• 제14권3호
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• pp.492-500
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• 2012

Cocoa is a popular drink for children and contains healthy polyphenols however; a deep brown stain is left when cocoa is spilled over clothes. The main pigments in cocoa are anthocyanins that change in washing solutions with different alkalinity and metals. The removal and color changes in a cocoa stain after washing with various pH solutions and water hardness were studied. Alkalinity and the water hardness of washing solutions were important factors for the removal of cocoa stains. The removal of cocoa things in washing solutions without detergent was low (and even became negative after removal and darker) in solutions with a pH 9 and above. The cocoa stain was not removed and only the fabric color faded, although the cocoa stained cloth was washed with Korea tap water that has a pH of 7. The cocoa stain removal in detergent solutions was conspicuously higher than for only water. Even in detergent solutions, the cocoa stain removal decreased as water hardness increased. Cocoa stain removal was more effective and the color dimmest when the stained cloth was washed in a solution without the metal cations, and the bleach added with the detergent at a temperature of $40^{\circ}C$ and for longer than 20 minutes. Effective and economical equipment for tap water softening for a washing machine should be developed and used to improve cocoa stain removal.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.49-54
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• 2000

Cr-Mo-V steel is widely used as a material for the turbine structural component in fossil power plants. It is well known that this material shows the various material degradation phenomenons such as temper embrittlement, carbide coarsening. and softening etc. or ins to the severe operation conditions as high temperature and high pressure. These deteriorative factors cause tile change of mechanical properties as reduction of fracture toughness. Therefor it is necessary to evaluate tile extent of degradation damage for Cr-Mo-V steel in life assessment of turbine structural components. In this paper. the electrochemical potentiokinetic reactivation(EPR) test in $50wt%-Ca(NO_3)_2$ solution is performed to develop the newly technique for degradation damage evaluation of Cr-Mo-V steel. The results obtained from the EPR test are compared with those in small punch(SP) tests recommended by semi-nondestructive testing method using miniaturized specimen. The evaluation parameters used in EPR test are tile reactivation current density$(I_R)$ and charge$(Q_{RC})$ reactivation rate$(I_R/I_{Crit},\;Q_R/Q_{Crit})$. The results suggest that $I_R/I_{Crit}$ in these parameters shows a good correlation with SP test results.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.223-230
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• 2001

The Monkman-Grant (M-G) and its modified parameters were estimated for modified type 316LN and $9{\sim}12Cr-1Mo$ steels with chemical variations. Several sets of creep data were obtained by constant-load creep tests in $550-650^{\circ}C$ ranges. The relation parameters, m, $m^*$, C and $C^*$ were proposed and discussed for two alloy systems. In creep fracture mode, type 316LN steel showed domination of the intergranular fracture caused by growth and coalescence of cavities. On the other hand, the Cr-Mo steel showed transgranular fracture of the ductile type caused from softening at high temperature. In spite of the basic differences in creep fracture modes as well as creep properties, the M-G and its modified relations demonstrated linearity within the $2{\sigma}$ standard deviation. The value of the m parameter of the M-G relation was 0.90 in the 316LN steel and 0.84 in the Cr-Mo steel. The value of the $m^*$ parameter of the modified relation was 0.94 in the 316LN steel and 0.89 in Cr-Mo steel. The modified relation was superior to the M-G relation because the $m^*$ slopes almost overlapped regardless of creep testing conditions and chemical variations to the two alloy systems.

• 대한기계학회논문집
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• 제13권2호
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• pp.307-315
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• 1989

본 연구에서는 단조과정을 거친후 노멀라이징(normalizing) 처리된 SF45A강종과 압연후 자연 냉각시킨 SM41B강종의 두 국산 강종에 대해 저사이클 피로시험을 행하여 저사이클 피로특성을 밝히고, 강재의 가공공정과 부하변형율변화에 따른 피로과정중의 연화 및 경화 거동을 관찰하였다. 그리고 저사이클 피로파면의 미시적 고찰을 통해서 부하변형율 크기에 따른 미시적 파면 양상의 변화를 밝혀 파괴 해석의 기초자료로 제공하였다.

• 한국식품과학회지
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• 제25권5호
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• pp.576-581
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• 1993

김치 조직의 연화에 관여하는 효소인 polygalacturonase(PG)를 배추에서 추출하여 황산암모늄 분획, 이온교환크로마토그래피 및 FPLC를 이용하여 D-PG, C-1, C-2 PG 세 분획으로 분리 정제하여 특성을 조사하였다. 분리된 세 분획의 활성 최적 온도는 $65^{\circ}C$, 최적 pH가 5.2였으며 pH$4.5{\sim}8.0$ 범위에서 안정하였다. NaCl에 의한 영향은 0.3M NaCl에서 최대의 활성을 보였으나 0.6M 이상에서는 저해를 받았으며 $CaCl_2$의 경우 $0{\sim}0.5mM$ 농도에서는 활성이 크게 영향을 받지 않았으나 0.8mM에서는 저해를 받았다. 열불활성화 특성은 isozyme간에 큰 차이가 없었으며 1차 반응을 따랐다. 이 효소 isozyme의 z값은 $8.4{\sim}9.3^{\circ}C,\;80^{\circ}C$에세 D값은 $102{\sim}126$초였다. 이 호소의 불활성화 값을 이용하여 retort pouch 김치 살균공정에 적용하고 역가의 잔존 가능성에 대하여 고찰하였다.

• 한국자동차공학회논문집
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• 제13권5호
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• pp.152-162
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• 2005

Coolant rubber hoses for automobile radiators can be degraded and thus failed due to the influence of contacting stresses of air and coolant liquid under the thermal and mechanical loadings. In this study, test analysis was carried out for evaluating the degradation and failure mechanisms of coolant hose materials. Two kinds of EPDM rubber materials applicable to the hoses were adopted: commonly-used ethylene-propylene diene monomer(EPDM) rubbers and EPDM rubbers with high resistance against electro-chemical degradation (ECD). An increase of surface hardness and a large reduction of failure strain were shown due to the formation of oxidation layer for the specimens which had been kept in a high temperature air chamber. Coolant ageing effects took place only by an amount of pure thermal degradation. The specimens degraded by ECD test showed a swelling behavior and a considerable increase in weight on account of the penetration of coolant liquid into the skin and interior of the rubber specimens. The ECD induced material softening as well as drastic reduction in strength and failure strain. However EPDM rubbers designed for high resistance against ECD revealed a large improvement in reduction of failure strain and weight. This study finally established a procedure for reliability analysis and evaluation of the degradation and failure mechanisms of EPDM rubbers used in coolant hoses for automobile radiators.

• 원예과학기술지
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• 제32권5호
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• pp.614-622
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• 2014

Melons (Cucumis melo L.) are generally grafted onto Cucurbita rootstocks to manage soilborne pathogens such as Monosporascus root rot and v ine decline (MRR/VD) and Fusarium wilt. However, g rafting onto Cucurbita rootstocks reportedly results in the reduction of fruit quality. In this study, the resistance to MRR/VD, yield, and fruit quality of melons grafted onto melon rootstocks were evaluated under greenhouse conditions. Eight melon rootstocks (R1 to R8) were used and the inodorus melon 'Homerunstar' was used as scion. Melon rootstocks R1 to R6 were selected based on resistance to MRR/VD under greenhouse conditions. Non-grafted 'Homerunstar' and plants grafted onto squash interspecific hybrid 'Shintozwa' rootstock (Cucurbita maxima D. ${\times}$ C. moschata D.) served as controls. Grafted melons were cultivated in the greenhouse infested with Monosporascus cannonballus during two growing seasons (summer and autumn). The responses to MRR/VD, yield, and fruit quality differed depending on the rootstocks and growing season. The melons grafted onto 'Shintozwa' exhibited less severe disease symptoms and higher survival rates than non-grafted melons in both seasons. While the melon rootstocks in the summer cultivation did not increase the survival rate compared to non-grafted melons, the melon rootstocks R1 and R2 in the autumn cultivation led to higher survival rates. The melon rootstocks resistant to MRR/VD increased the percentage of marketable fruits and marketable yields. Grafting onto the melon rootstocks caused little or no reduction of fruit quality such as low calcium content, fruit softening, and vitrescence, especially in lower-temperature autumn season. Accordingly, these results suggest that grafting onto the melon rootstocks may increase the tolerance to MRR/VD and the marketable yield without a reduction of fruit quality.

• 대한화학회지
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• 제47권6호
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• pp.619-624
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• 2003

졸겔법을 사용하여 $Gd_{1.9-x}Li_{0.1}Eu_xO_3$(x=0.02, 0.05, 0.08, 0.12) 형광체 분말을 합성하였다. 형광체 입자의 표면을 나노 크기의 $SiO_2$(입자크기${\thickapprox}30 nm$)로 코팅한 후 스핀-코팅법으로 유리 기판에 형광체 막을 제작하였다. 유리의 연화온도인 $700^{\circ}C$ 부근에서 융착 되는 $SiO_2$ 나노 입자들에 의해 $Gd_{1.9-x}Li_{0.1}Eu_xO_3$ 입자들은 유리 기판 표면 위에 강하게 융착 되었다(>9H, 연필 경도계). 본 연구에서 채택한, 형광체 막을 제조하는 간단하고 비용이 저렴한 이 방법은 디스플레이장치의 응용 분야에 적용될 수 있을 것으로 생각한다.

• 자원리싸이클링
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• 제24권6호
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• pp.45-53
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• 2015

수명이 다하거나 용도 폐기에 의해 버려지는 PVC 스크랩은 분쇄 후 저급 제품으로 재생산되는 경우가 대부분이고 발생 원인별 물성에 관한 연구가 적은 현실이다. 본 연구에서는 의복용, 파이프 및 이음관류, 프로파일, 다양한 경질 PVC 등 수명이 다하여 발생되는 폐 PVC 스크랩을 신재 수지에 투입하되 투입되는 스크랩 함량의 변화에 따른 물성을 관찰하였다. PVC 스크랩의 기계적 물성은 스크랩의 함량이 증가함에 따라 인장강도 및 충격강도가 모두 낮아지는 결과를 나타났다. 충격강도는 Cloth insert scrap (CC) > PC (Pipe scrap) > RC (Rigid scrap), 인장강도는 PC > CC > RC, Vicat 연화온도는 경향성이 없음을 나타냈으며, CC 소재는 스크랩 함량이 50 phr일 때 신재 PVC 기계적 물성의 80 %에 이르는 물성을 나타내었고, PC 소재는 스크랩 함량이 50 phr일 때 신재 PVC 인장강도의 50 % 수준임을 알 수 있었다.