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Ti-6Al-4V 합금의 내부 미소결함에 따른 초음파 신호 특성 연구
최상우,이준현,--,-- 한국비파괴검사학회 2001 한국비파괴검사학회지 Vol.21 No.6
Ti합금은 고온환경에서 고강도가 요구되는 항공기의 엔진 부품등의 소재로 적용되고 있다. Ti합금은 이와 같이 기계적 성능이 우수함에도 불구하고 α상과 β상의 조성에 의한 두 상의 띠세 구조에 의한 초음파 산란으로 초음파를 이용한 비파괴 평가에서 피로균열 검출이 어려운 단점이 있다. 합금내의 결정립에서 산란되는 초음파 신호에 의하여 결함이 존재하지 않는 경우에도 산란 신호가 검출되는 결정립 산란 잡음 신호가 존재하며, 이들 결정립 산란 잡음신호는 합금내부에 존재하는 기공 및 불순물 등의 결함 검출을 어렵게 하는 요인이다. 본 연구에서는 Ti합금의 효율적인 초음파를 이용한 비파괴 평가의 적용을 위하여 Ti합금 시험편에 대하여 초음파 전파속도 측정 및 미세 드릴 가공에 의한 인공 결함의 검출능 평가 등을 수행하였다. Ti alloy is used for essential parts of aircraft for high temperature environment. Although Ti alloy has excellent performance in regard to mechanical properties, it is difficult to find fatigue cracks by nondestructive ultrasonic inspection due to its two-phase microstructure, which consists of hard alpha and beta phases. Sound energy reflected from microstructural features in the component produces a background inspection noise which is seen even when no defects are present. This noise can inhibit the detection of critical internal defects such as pores cracks or inclusions. To obtain fundamental data on ultrasonic inspection of Ti alloy, ultrasonic testing was performed using a specimen with small drill holes and ultrasonic wave propagation velocities were measured.
SUPER LOW SPEED CONTROL FOR LIM
Y.Ogino,K.Abe,K.Ohishi,M.Nakaoka,H.Fukuda,Y.Takakado,K.Nakano,Y.Murakami 전력전자학회 1992 ICPE(ISPE)논문집 Vol.1992 No.4
This paper proposes the super low speed control method for LIM (Linear Induction Motor). The feasibly-proposed control method is based on the vector-control strategy using the current controlled VVVF inverter. Using this control implementation, both the quick speed response and the smooth thrust characteristics are realized in the super low speed range. The experimental results provide its desired operating characteristics in this system.<br/>
Changes of Serum Mineral Concentrations in Horses during Exercise
Inoue, Y.,Osawa, T.,Matsui, A.,Asai, Y.,Murakami, Y.,Matsui, T.,Yano, H. Asian Australasian Association of Animal Productio 2002 Animal Bioscience Vol.15 No.4
We investigated the exercise-induced changes in the serum concentration of several minerals in horses. Four welltrained Thoroughbred horses performed exercise for 5 d. The blood hemoglobin (Hb) concentration increased during exercise, recovered to the pre-exercise level immediately after cooling down and did not change again up till the end of experiment. The changes in serum zinc (Zn) and copper (Cu) concentrations were similar to those of blood Hb during the experiment. The serum magnesium (Mg), inorganic phosphorus (Pi) and iron (Fe) concentrations also increased during exercise. Though the serum Pi concentration recovered to the pre-exercise level immediately after the cooling down, it decreased further before the end of the experiment. The serum Mg concentration was lower immediately after cooling down than its pre-exercise level but gradually recovered from the temporal reduction. The recovery of the serum Fe concentration was delayed compared to that of other minerals and recovered 2 h after cooling down. The serum calcium (Ca) concentration did not change during exercise but rapidly decreased after cooling down. As a result, it was lower immediately after cooling down than its pre-exercise level. It recovered, however, to the pre-exercise level 2 h after cooling down. The temporal increase in the serum concentrations of all minerals except Ca is considered to result from hemoconcentration induced by exercise and the stable concentration of the serum Ca during exercise is possibly due to its strict regulation of homeostasis. These results indicate that the serum concentration of each mineral responds differently to exercise in horses, which may be due to the difference in metabolism among these minerals.
Extension of the operational regime of the LHD towards a deuterium experiment
Takeiri, Y.,Morisaki, T.,Osakabe, M.,Yokoyama, M.,Sakakibara, S.,Takahashi, H.,Nakamura, Y.,Oishi, T.,Motojima, G.,Murakami, S.,Ito, K.,Ejiri, A.,Imagawa, S.,Inagaki, S.,Isobe, M.,Kubo, S.,Masamune, S IOP 2017 Nuclear fusion. Fusion nucléaire. &n.Illiga Vol.57 No.10
<P>As the finalization of a hydrogen experiment towards the deuterium phase, the exploration of the best performance of hydrogen plasma was intensively performed in the large helical device. High ion and electron temperatures, <I>T</I> <SUB>i</SUB> and <I>T</I> <SUB>e</SUB>, of more than 6 keV were simultaneously achieved by superimposing high-power electron cyclotron resonance heating onneutral beam injection (NBI) heated plasma. Although flattening of the ion temperature profile in the core region was observed during the discharges, one could avoid degradation by increasing the electron density. Another key parameter to present plasma performance is an averaged beta value <img ALIGN='MIDDLE' ALT='$\left\langle \beta \right\rangle $ ' SRC='http://ej.iop.org/images/0029-5515/57/10/102023/nfaa7fc2ieqn001.gif'/>. The high <img ALIGN='MIDDLE' ALT='$\left\langle \beta \right\rangle $ ' SRC='http://ej.iop.org/images/0029-5515/57/10/102023/nfaa7fc2ieqn002.gif'/> regime around 4% was extended to an order of magnitude lower than the earlier collisional regime. Impurity behaviour in hydrogen discharges with NBI heating was also classified with a wide range of edge plasma parameters. The existence of a no impurity accumulation regime, where the high performance plasma is maintained with high power heating >10 MW, was identified. Wide parameter scan experiments suggest that the toroidal rotation and the turbulence are the candidates for expelling impurities from the core region.</P>