• 한국초전도ㆍ저온공학회논문지
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• 제7권3호
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• pp.29-33
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• 2005

Critical current$(I_c)$ degradation of High $T_c$ Superconducting(HTS) tapes and AC loss under mechanical load is one of the hottest issues in HTS development and application. Mechanical load reduces the critical current of superconducting wire, and the $I_c$ degradation affects the AC loss of the wire. We measured the $I_c$ degradation and AC loss under tension and bending of Bi-2223 tapes made by 'Powder-in-Tube' technique at 77K with self-field. Also, we have studied the frequency characteristics on self-field AC loss in multi-filamentary Bi-2223/Ag tape at 77K. The measurement results and discussions on the relationship between $I_c$ degradation and AC loss are presented.

• Elastomers and Composites
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• 제34권2호
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• pp.135-146
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• 1999

SBR과 타이어의 속도론적 해석을 수행하기 위하여 질소기류 상태에서 각각 5, 10, 15, $20^{\circ}C/min$으로 열분석을 수행하여 Kissinger, Friedman, Ozawa 방법에 의해 활성화 에너지와 반응차수를 계산하였다. Friedman 방법에 의해 산출된 활성화 에너지는 SBR은 247.53kJ/mol, 타이어는 230.00kJ/mol이었으며, Ozawa 방법에 의한 활성화 에너지는 SBR이 254.80kJ/mol, 타이어가 215.76kJ/mol로 나타났다. 열분석을 수행한 결과 미분법인 Friedman 방법과 적분법인 Ozawa 방법이 SBR과 타이어의 속도론적 해석에 더 적합한 것으로 나타났다. 열분해 공정을 이용하여 SBR과 타이어를 분해한 결과 온도가 증가함에 따라 액상 생성물의 수율이 전반적으로 증가하는 경향을 보였으며, 가열속도가 $20^{\circ}C/min$일 때 SBR의 경우 $700^{\circ}C$에서 액상 생성물의 수율이 86%로 최대 값을 보였으며, 타이어의 경우 $700^{\circ}C$에서 액상 생성물의 수율이 55%로 최대값을 보였다. 이로부터 SBR과 타이어 분해공정에서 열분해 온도와 가열속도가 중요한 변수로 작용함을 알 수 있으며, 본 연구에서는 $70^{\circ}C$, $20^{\circ}C/min$을 최적분해 조건으로 제시할 수 있다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.900-902
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• 2003

Critical current($I_c$) degradation of HTS tapes after bending is one of the holiest issues in HTS development and application studies. Many people are measuring $I_c$ degradations for effect of tending radius. However even if the bending radius is larger than the breaking radius a HTS tapes can be damaged by repetitive bending, which is unavoidable in the winding processes. Therefore, We studied the $I_c$ degradation after repetitive bending, at 77K with self-field, of Bi-2223 tapes processed by "Powder-in-Tube" technique, which was made by America Superconductor Corporation(AMSC), Innova Superconductor Technology(InnoST) and Korea Electro-technology Research Institute(KERI). For each specimen $I_c$ degradation was measured various bending radius as function of repetitive bending number.

• 대한기계학회논문집
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• 제18권11호
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• pp.2860-2870
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• 1994

When crack are detected in aged turbine rotors of power plants, information on fracture resistance of the aged material at operating temperature is needed for determination of critical loading condition and residual life of the turbine. In this study, fracture toughness (J$_lc$) and tearing modulus(T$_mat$) of virgin and thermally degraded 1Cr-1Mo-0.25V steel, which is one of the most widely used rotor steels, were measured at 538.deg. C according to ASTM E813 and ASTM E1152, respectively. Five kinds of specimen with different degradation levels were prepared by isothermal aging heat treatment at $630^{\circ}C.$ It was observed that J$_lc$ and T$_mat$ value decreased as the degradation level increased. Analysis of microstructures using a scanning electron microscope showed that the decrement of J$_lc$ is related to segregation of impurities at grain boundaries. It was also verified that the DC electric potential drop method is accurate and reliable for crack length monitoring at elevated temperature.

• Journal of the Korean Wood Science and Technology
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• 제44권5호
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• pp.685-694
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• 2016

본 연구에서는 반탄화 과정에서 바이오매스 열분해 거동을 열중량 분석과 발생되는 기체분석으로 확인하였다. 반응온도는 $220{\sim}300^{\circ}C$, 승온속도 $10{\sim}30^{\circ}C/min$, 반응시간은 110분으로 고정하여 분석하였다. 백합나무 중량감소율은 $220^{\circ}C$에서 8.01~8.81%, $300^{\circ}C$에서 71.86~77.38%로 나타났으며, $240^{\circ}C$ 이상에서 급격하게 증가하였다. 반면 낙엽송 중량감소율은 $300^{\circ}C$에서 49.58~54.15%로 백합나무와 비교하여 낮았다. 백합나무에 대한 활성화 에너지는 87.32~91.24 kJ/mol으로 승온속도에 따라 큰 차이를 나타내지 않았으며, 낙엽송에 대한 활성화 에너지는 83.85~91.60 kJ/mol으로 나타났다. 반탄화 과정에서 발생하는 가스성분은 대부분 헤미셀룰로오스 유래 성분이었으며 반응온도가 증가하면서 성분의 종류 및 농도도 증가하였다. 백합나무에서는 furfural, acetic acid가 고농도로 검출되었다.

• 한국식품과학회지
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• 제34권2호
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• pp.238-243
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• 2002

자색고구마 anthocyanin 색소 용액은 가열에 의해 1차 반응속도식에 따라 색소 함량이 감소하였으며, 이 반응은 색소용액의 농도와 가열온도에 영향을 받았다. 이 반응의 활성화 에너지 값은 색소 용액의 농도에 따라 51.29-73.02 kJ/mol이었으며, 농축하지 않은 색소 추출액을 제외하면 활성화 에너지는 색소의 농도가 증가함에 따라 직선적으로 감소하였다. 자색고구마색소를 첨가한 매실음료의 anthocyanin 색소 역시 저장 중 1차 반응에 따라 색소가 감소하였는데, 저장온도가 낮아질수록 반응속도가 낮아져 저장기간이 증가하여, $5^{\circ}C$에서 저장한 경우는 저장 8개월까지 80%이상의 색소 잔존률을 나타냈다. 매실음료에 함유된 자색고구마 anthocyanin색소 변화에 대한 활성화 에너지는 75.80 kJ/mol이었다.

• Asian-Australasian Journal of Animal Sciences
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• 제11권5호
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• pp.503-509
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• 1998

Whole faba beans (WFB) were dry roasted at different temperatures of 110, 130 and $150^{\circ}C$ for 15, 30 and 45 minutes (min) to determine the optimal heating conditions to increase bypass starch as glucose source which may be a limiting nutrient in high producing dairy cattle. Ruminant degradation characteristics of starch (St) of WFB were determined using in sacco method in 6 dairy cows fed 60% hay and 40% concentrate. Measured characteristics of St were soluble (washable) fraction (S), potentially degradation fraction (D) and the rate of degradation (Kd) of the insoluble but degradable St fraction. Based on measurement of these characteristics, percentage bypass starch (%BSt) and bypass starch (BSt) were calculated. Degradability of starch in the rumen was reduced by dry roasting at temperature of 130 and $150^{\circ}C$ and increased at $110^{\circ}C$. S varied from 50.0% in the raw whole faba beans (RWFB) and 53.7% in $110^{\circ}C$/15 min to 18.2% in $150^{\circ}C$/45 min. D varied from 49.9% in RWFB and 46.3% in $110^{\circ}C$/15 min to 81.8 % in $150^{\circ}C$/45 min. Kd varied from 9.8% in RWFB and 11.0% in the $110^{\circ}C$/30 min to 4.2 in $150^{\circ}C$/45 min. All these effects resulted in increasing %BSt from 22.1% in the $110^{\circ}C$/45 min and 23.9% in RWFB to 49.9% in the $150^{\circ}C$/45 min. Therefore BSt increased from 91.4 g/kg and 98.4 g/kg to 199.9 g/kg respectively. Dry roasting at $110^{\circ}C$ increased the starch rumen degradation. Treatment at higher temperature (130 and $150^{\circ}C$) decreased rumen degradation of starch and seemed to be linear up to highest values tested. No optimal dry roasting conditions of treatment could be determined at this stage. It may be concluded that dry roasting at temperatures of 130 and $150^{\circ}C$ was effective in shifting starch degradation from rumen to intestine to increase bypass starch.

• Journal of Welding and Joining
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• 제17권2호
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• pp.76-83
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• 1999

Fracture toughness({TEX}$J_{IC}${/TEX}) on 304 austenitic stainless steel weldments artificially degraded for long period under SCC environments were evaluated to investigate its reliability and environmental characteristics. Electro-chemical polarization tests were previously carried out to evaluate corrosion susceptiblility of weldment, and stress corrosion cracking was tested under various conditions of 3.5wt.% NaCl solution, the temperature of $25^{\circ}$C and $95^{\circ}$C, and oxygen concentration during 3000hours. From the results obtained, it was found that 304 stainless steel weldment was so susceptible under high temperature and high oxygen concentration of 3.5wt.% NaCl solution, and fracture toughness({TEX}$J_{IC}${/TEX}) was also considerably reduced by material degradation.

• 한국초전도ㆍ저온공학회논문지
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• 제11권4호
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• pp.12-15
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• 2009

The $I_c$ degradation behavior of critical current in differently processed YBCO and SmBCO CC tapes with IBAD template has been investigated. It has been known that the residual strain in the CC tape will influence the shape of the $I_c$-strain window; $I_c$ may show a peak value if there exist a residual strain induced in the tape during manufacturing. The difference of residual strain may be resulted from the adopted different deposition techniques. In this study, bending test of CC tapes has been done using the Goldacker bending test rig which can produce both compressive and tensile bending strain continuously or alternately to the sample. For SmBCO CC tapes, in continuous compressive bending test, $I_c$ showed a minimal increase and did not degrade up to the largest strain that can be applied using the bending rig equivalent to 1.15% based on the sample thickness. However, in the case of alternate application of compressive and tensile bending strain, $I_c$ showed a larger degradation and a lower reversible limit when compared with the case of continuous application of the bending strain. When $I_c$ started to degrade significantly at the tension side, the reversibility ended, also at the compression side which is resulted from the permanent deformation like delamination or cracks that was induced due to tensile bending strain.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2013년도 춘계학술대회 논문집
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• pp.1175-1176
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• 2013