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Dy 화합물 혼합에 의한 (Nd, Dy)-Fe-B 소결자석의 자기특성 변화
남궁석,이민우,조인식,박영덕,임태환,이성래,장태석,NamKung, S.,Lee, M.W.,Cho, I.S.,Park, Y.D.,Lim, T.H.,Lee, S.R.,Jang, T.S. 한국분말야금학회 2011 한국분말재료학회지 (KPMI) Vol.18 No.1
In order to increase the coercivity of (Nd, Dy)-Fe-B sintered magnets without much reduction of remanence, small amount of Dy compounds such as $Dy_2O_3$ and $DyF_3$ was mixed with (Nd, Dy)-Fe-B powder. After mixing, the coercivity of (Nd, Dy)-Fe-B sintered magnets apparently increased with the increase of Dy compound in the mixture. Addition of $DyF_3$ was more effective than $Dy_2O_3$ for the improvement of coercivity. Reduction of the remanence by the addition of Dy compound, however, was larger than expected mostly due to unresolved coarse Dy compound in the magnet. EPMA analysis revealed that Dy was diffused throughout the grains in the magnet mixed with $DyF_3$ whereas Dy was rather concentrated around grain boundaries in the magnet mixed with $Dy_2O_3$.
베어링강의 초음파나노표면개질에 의한 초음파 가속수명 피로특성 평가
전태진(T. J. Jeon),조인식(I. S. Cho),전진우(J. W. Jeon),김경재(K. J Kim),이창순(C. S Lee),박인규(I. G. Park) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
A method of metal improvement, ultrasonic nanocrystalline surface modification (UNSM) treatment, has been applied to the SAE 52100 bearing steel which is made up of ferrite and spherodized cementite, in order to increase performances in terms of lifetime and safety. Although ultrasonic fatigue testing (UFT) is becoming more time consuming and costly with current design products, the long-time fatigue life test was performed on a piezoelectric system. It is the aim of our research to develop better understanding of fatigue properties of the untreated and UNSM-treated specimens in the gigacycle domain. The ultrasonic fatigue test results show that the gigacycle fatigue life of the UNSM-treated specimens was prolonged by spheroidal cementite particles, including increased surface microhardness in the range of 200 HV to 280 HV up to depth of 100 ㎛ from the surface. Moreover, surface structure was observed using transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) as well as fracture surface was analyzed using scanning electron microscopy (SEM).
Myo-inositol이 돼지 난모세포의 체외성숙에 미치는 영향
조인식,한효원,이상미,박효영,정영희,문승주,강승률,강만종 충남대학교 형질전환복제돼지연구센터 2004 논문집 Vol. No.8
본 연구는 미성숙 돼지 난모세포의 체외 성숙에 있어서 myo-inositol의 영향을 알아보기 위하여 실시하였다. 미성숙 돼지 난모세포을 myo-inositol을 포함하는 또는 포함하지 않은 체외 성숙배지에서 44시간 체외 성숙을 유도하였을 때 성숙율은 myo-inositol을 첨가한 성숙배지에서 성숙시킨 실험구에 유의하게 높았다(P<0.05). Myo-inositol에 의한 성숙율 향상에 있어서 난구세포의 영향을 알아보기 위하여 난추세포의 치밀도에 따라 분류하여 미성숙 난모세포을 myo-inositol을 포함하는 체외 성숙배지에서 배양하였을 때 난구세포가 치밀한 미성숙 난모세포에서가 더 높은 성숙율을 나타내었다(P<0.05). 그러나 난구세포가 치밀하지 않은 미성숙 난모세포도 myo-inositol을 포함하는 성숙배지에서 배양하면 성숙율은 대조구에 비하여 유의하게 높았다(P<0.05). 이러한 결과는 돼지 난모세포의 체외 성숙배지에 myo-inositol의 첨가는 체외 성숙율을 향상시킬 수 있음을 나타내고 있다. This study was carried out to assess whether the addition of myo-inositol to maturation medium could improve porcine oocyte maturation in vitro. Oocytes were cultured for the first 22 h in Witten's medium containing lO1U/ml PMSG, 10 IU/ml HCG supplemented with or without myo-inositol. Subsequently, they were cultured for additional 22 h in Witten's medium without hormone supplemented with or without myo-inositol. When the porcine oocytes were cultured in maturation medium containing myo-inositol, the proportion of metaphase II oocytes 44h after culture was higher in the myo-inositol group(P<O.05). To study effects of cumulus cell on the maturation induced by myo-inositol, we examined the maturation status of cumulus-enclosed or cumulus-denuded porcine follicular oocytes. The rates of maturation were significantly higher in the cumulus-enclosed oocytes(P<O.05). However, the maturation rates of cumulus-denuded oocytes cultured in medium containing myo-inositol were higher than those of control group(P<O.05). Our results suggest that myo-inositol may affect meiotic progression of porcine follicular oocytes and supplementation of myo-inositol in maturation medium may be useful for the in vitro maturation of porcine follicular oocytes.
중장비의 트랙 롤러(track roller)의 성능개선 연구
이병기,조인식,최용 선문대학교 중소기업기술지원연구소 2001 선문공대 연구/기술 논문집 Vol.6 No.1
중장비 트랙 롤러의 내식성과 내마모성을 개선하기 위하여 열처리 후 성능시험을 수행하였다. G/SEAL의 경도는 내부와 외부 층이 각각 880.1 Hv 과 1041.3 Hv 이었으나 열처리 후에는 872.2 Hv and 947.0 Hv로 변화하였으며 트랙 롤러는 665.6 Hv과 355.1 Hv이었다. NACE 표준 용액에서 부식 속도와 부식전위는 OA1-1 와 OA1-2 G/SEAL 이 1.5 A/cm2, -444.5 VSHEd와 7.5A/cm2, -428.6 VSHE이었다. OA1-1 시료의 마모면은 3층 구조미며 비교적 균일하게 마모되었으나 OA1-2 시료는 MnS와 같은 게재물이 이탈한 마모된 틈이 관찰되었다. Performance tests of track roller parts were carried to improve the corrosion and wear resistances. Microhardnesses of the inner and outer layers of G/SEAL with martensite structure were 880.1 Hv and 1041.3 Hv, respectively, which values were changed into 872.2 Hv and 947.0 Hv after a thermal treatment to get bainite structure. Those of a track roller were 665.6 Hv and 355.1 Hv, respectively Corrosion rates and potentials of the sample number OA1-1 and OA1-2 G/SEAL in NACE standard solution were 1.5 A/cm2, -444.5 VSHE and 7.5A/cm2, -428.6 VSHE. The worn surface of OA1-1 sample had triple layers which supports relatively homogeneous deformation, however, that of OA1-2 had double layers in which micro-dents due to extraction of precipitates such as MnS were observed.