• International Journal of Fluid Machinery and Systems
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• 제3권1호
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• pp.67-79
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• 2010

Severe flexural vibration of the rotor shaft of a Francis turbine runner was experienced in the past. It was shown that the vibration was caused by the fluid forces and moments on the backshroud of the runner associated with the leakage flow through the back chamber. The aim of the present paper is to study the self-excited rotor vibration caused by the fluid force moments on the backshroud of a Francis turbine runner. The rotor vibration includes two fundamental motions, one is a whirling motion which only has a linear displacement and the other is a precession motion which only has an angular displacement. Accordingly, two types of fluid force moment are exerted on the rotor, the moment due to whirl and the moment due to precession. The main focus of the present paper is to clarify the contribution of each moment to the self-excited vibration of an overhung rotor. The runner was modeled by a disk and the whirl and the precession moments on the backshroud of the runner caused by the leakage flow were evaluated from the results of model tests conducted before. A lumped parameter model of a cantilevered rotor was used for the vibration analysis. By examining the frequency, the damping rate, the amplitude ratio of lateral and angular displacements for the cases with longer and shorter overhung rotor, it was found that the precession moment is more important for smaller overhung rotors and the whirl moment is more important for larger overhung rotors, although both types of moment due to the leakage flow can cause self-excited vibration of an overhung rotor.

• 자원환경지질
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• 제4권1호
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• pp.11-18
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• 1971

The geotectonics and geomorphic structure of Korea resulted from the Song-rim Disturbance and the Daebo orogenic movements. Afterward this mountainous peninsula underwent several geological changes on a small scale, and it was also claimed that the steady rising of the elevated peneplain of the eastern coast and the submerging of the southwestern coastal area are largely due to the tilted block movement. These views have been generally accepted good in several ways, but they are limited in range or lacking in theoretical integration. The present writer investigated the geology of the Mt. Chi-ri-san and the Honam coal mining area for a geological map in 1965, respectively. The results of these studies convinced the present writer that the conventional views, which were based upon a theory of lateral pressure should be reconsidered in many respects, and more recent studies made it clear that the morphological development in the southwestern area can be better explained by the orogenic movement and rock control. The measurement of submerging speed of the western coastal area (Pak. Y. A., 1969) and a new account on the geology and tectonics of the Mid-central region of South Korea (Kim O.J., 1970) act as an encouragement to a new explanation. The present writer's researches on the extreme southwestern portion of the peninsula show that the steady submerging of this area cannot be attributed to a simple downthrown block phenomenon caused by block movement. It is no more than the result of the differential movement of uplifting in the eastern and western coastal areas and the rising of sea-level in the post-glacial period. This phenomenon could be easily explained by the comparison of the rate of rise in sea-level and amount of heat flow between Korea and other areas in the world. The existance of the erosional planes in the Sobaik-San ranges also provide an evidence of an upheaval in the western coast area. Though the Sobaik-San ranges largely follow the direction of the Sinian system. They consist of the numerous branches, whose trends run more or less differently from their main trend because of the disharmonic folding, are converged into Mt. Sobaik-San and Chupungryung. The undulation of the land is not wholely caused by orogenic movements, where as the present writer confirmed that the diversity of morphological development is the direct reflection of geological conditions such as rocks and processes which constitute the basic elements of geomorphic structure. An east-west directed mountain range which could be named as Hansan mountain range, was claimed to be oriented by the joint control. The geological conditions such as a special erosion and weathering of agglomerate and breccia tuff usually produce pot-hole like submarine features which cause the whirling phenomenon at the southwestern coast channel.

• 한국물환경학회지
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• 제20권1호
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• pp.78-85
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• 2004

As an ozone contactor, we newly adopted HJLR (High-performance Jet Loop Reactor) for the decolorization of Reactive black 5 and the mineralization of oxalic acid, which has been applied exclusively in biological wastewater treatments and well-known for high oxygen transfer characteristics. The ozonation efficiency for organic removals and ozone utilization depending on the mass transfer rate were compared to those of Stirred bubble column reactor, which was controlled by varing energy input in the HJLR and Stirred bubble column reactor. The results were as follows; first, the decolorization rate of Reactive black 5 in the HJLR reactor was nearly proportional to the increasing $k_La$. When the $k_La$ was increased by 25 % from $13.0hr^{-1}$ to $16.4hr^{-1}$, 30 % of the k' (apparent reaction rate constant) was increased from 0.1966 to $0.2665min^{-1}$ (Stirred bubble column; from 0.1790 to $0.2564min^{-1}$). Ozone transfer was found to be a rate-determining step in decolorizing Reactive black 5, which was supported by that no residual ozone was detected in all of the experiments. Second, the mineralization of oxalic acid was not always proportional to the increasing $k_La$ in the RJLR reactor. The rate-determining step for this reaction was OH(OH radical) production with ozone transfer, because residual ozone was always detected during the ozonation of oxalic acid in contrast with Reactive black 5. This result indicates that the increase of $k_La$ in the HJLR reactor is beneficial only when there are in ozone transfer limited regions. In addition, regardless of $k_La$, the mineralization of oxalic acid was nearly accomplished within 60 minutes. It was interpreted as that the longer staying of residual ozone by whirling liquid in the HJLR reactor contributed to an high ozone utilization(83-94%), producing more OR radicals.

• Applied Microscopy
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• 제35권4호
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• pp.55-63
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• 2005

쥐의 뇌로부터 미세혈관에서 분리하고 배양한 내피세포의 특성을 현미경관찰, 면역염색과 전기저항을 측정해 관찰하였다. 미세혈관 내피세포는 배양 후 $5{\sim}6$일 경에 단층을 형성하였으며 특징적으로 소용돌이치는 모양을 나타냈다. 내피세포 단층의 전기저항은 배양 후 5일 경까지 따라 증가하였고 이후로는 감소하였다. 면역형광염색에서 anti-GFAP, anti-GalC, anti-neurofilament 160/200 kD antibody에 대한 면역반응을 거의 찾아볼 수 없었어 별아교세포, 희소돌기아교세포 및 신경세포에 의한 우려할 만한 오염은 배제할 수 있었다. vWF 항원에 대한 면역반응은 내피세포의 세포질에 Weibel-Palade 과립이 전반적으로 퍼져 있었다. 치밀이음부를 구성하는 occludin, ZO-1, ZO-2에 대한 면역반응은 내피세포의 접촉부위에서 매우 특징적으로 나타나고 있었다. 요약하면 쥐의 뇌 미세혈관 내피세포를 분리, 배양하여 형태학적, 조직면역 화학적 방법과 전기저항을 측정하여 내피세포의 특성을 확인하였다. 이 생체외 혈액뇌장벽 모델은 앞으로 진행될 액뇌장벽의 특징을 규명하고자 하는 시험관내 실험에 유용하게 이용될 수 있을 것이다.

• Tuberculosis and Respiratory Diseases
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• 제52권2호
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• pp.186-191
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• 2002

저자들은 53세 남자환자에서 조직학적, 면역학적으로 악성 섬유조직구종의 형태를 가진 원발성 폐육종 1예를 경험하였기에 이를 문헌고찰과 함께 보고하는 바이다.

• 공연문화연구
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• 제42호
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• pp.233-256
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• 2021

이 글은 황해도굿춤의 특성과 의미를 살핀 글이다. 먼저 황해도굿춤의 특성을 다음과 같이 정리하였다. 황해도굿춤의 모든 굿거리 등장하는 일반적인 춤은 '거상춤 - 도무 - 회전무'로 순차적으로 이어진다. 반주 장단은 거상장단, 춤장단, 연풍장단이다. 황해도굿춤 중 신령의 특성을 나타내는 무구를 손에 들고 추는 춤은 춤장단에 맞춘 도무와 연풍장단에 맞춘 회전무와 춤사위가 동일하다. 무구 이름이나 무복 이름, 신령 이름을 사용해 굿춤 명칭으로 사용할 수 있지만 춤사위의 독자성은 없다. 황해도굿춤 중 벅구춤과 삼현춤은 독자적인 장단인 벅구장단, 삼현장단을 사용하고 있어 춤사위의 독자성이 인정된다. 황해도굿춤은 장단과 긴밀한 관련성을 가진다. 황해도굿의 연행에서 장구재비와 만신의 조화는 절대적이다. 장구 연주가 만신의 굿 연행을 받쳐주지 않으면 굿의 연행이 순조롭지 않아 혼란이 발생하고, 만신의 굿 연행이 장구 연주를 따라가지 못하면 굿은 단순해진다. 황해도굿춤의 성패를 결정하는 가장 핵심적인 요소가 장구이다. 굿을 맡을 때 장구재비와 일정이 맞지 않으면 굿날을 다시 잡을 정도로 만신은 장구재비와의 호흡을 중요하게 여긴다. 그리고 황해도굿춤은 결례에 따라 차이가 있다. 하지만 결례에 따른 장단과 춤의 차이는 무형문화재로 인해 사라지게 된다. 결국 무형문화재 지정이 모든 황해도굿춤의 특성을 사라지게 한 것이다. 결례 구분이 모호해지고, 자신이 학습한 굿의 계보에 대해서도 관심을 갖지 않는다. 결례에 따른 춤의 구분이 중요한 것이 아니라 무형문화재 제도에 따른 춤의 구분이 중요해졌다.