• Tribology and Lubricants
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• v.35 no.2
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• pp.114-122
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• 2019

High-speed rotating machinery requires low cost and reliable bearing elements with low friction, stable rotordynamic characteristics, and a simple design. This study experimentally evaluates the effects of bearing-support elements on the vibrational characteristics of a small-sized, high-speed permanent magnetic motor. A series of coast down tests from 100 krpm characterize the vibrational behaviors, rotor displacement, and housing acceleration of motors supported by ball bearings, ball bearings with a metal mesh damper, and gas foil bearings, respectively. Two eddy-current sensors installed in the horizontal and vertical directions measure the displacement of the rotor at its front nut, and a 3-axis accelerometer attached to the motor housing measures the housing acceleration. The test results reveal that synchronous (1X) vibration components most significantly affect the rotor displacement and housing acceleration, independent of the bearing-support elements. The motor supported by the deep-groove ball bearings results in the largest rotor vibrations increasing with speed; this is due to the absence of a damping mechanism. Additionally, the metal mesh damper effectively reduces the rotor displacement, housing acceleration, and sound-pressure level in the high-speed region (i.e., above 40 krpm), thus implying its substantial damping performance when installed on the outer race of the ball bearing. Lastly, the gas foil bearing supported motor yields the smallest rotor displacement, housing acceleration, and lowest sound-pressure level because of its hydrodynamic airborne operation, which does not require rolling elements that may cause mechanical friction and vibrations.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.2
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• pp.131-143
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• 2013

Vibration condition monitoring of low-speed rotational slewing bearings is essential ever since it became necessary for a proper maintenance schedule that replaces the slewing bearings installed in massive machinery in the steel industry, among other applications. So far, acoustic emission(AE) is still the primary technique used for dealing with low-speed bearing cases. Few studies employed vibration analysis because the signal generated as a result of the impact between the rolling element and the natural defect spots at low rotational speeds is generally weak and sometimes buried in noise and other interference frequencies. In order to increase the impact energy, some researchers generate artificial defects with a predetermined length, width, and depth of crack on the inner or outer race surfaces. Consequently, the fault frequency of a particular fault is easy to identify. This paper presents the applications of empirical mode decomposition(EMD) and ensemble empirical mode decomposition(EEMD) for measuring vibration signals slewing bearings running at a low rotational speed of 15 rpm. The natural vibration damage data used in this paper are obtained from a Korean industrial company. In this study, EEMD is used to support and clarify the results of the fast Fourier transform(FFT) in identifying bearing fault frequencies.

• Journal of the Korean Society of Costume
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• v.24
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• pp.59-82
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• 1995

All kinds of art are the creatures of the daly and reflect the society and the life of the day in literary works. So, in which literary works, we can find the styles of those who lived in the specified days. And the styles of its character's costume are expressed with the day'mood and cultural backgrounds. In this study, we studied on the general meaning, which was shown in the Costume of early Ch'ing Dynasty that was forming the Costume of dress through dividing into the underwear and the outer garment in $\ulcorner$Dream of the read Chamber$\lrcorner$. During the Ch'ing Dynasty, according to the rule : Men followed it but women not" , they held on to the costume of them (both the Man and the Han) with a high pressure and a conciliatory policy. As a result, I have known that there is the Soojean clothe(수전의), which is the late Myung Dynasty's one and their is also Skirt (군), which held on the Costume of the Myung's. Hence in the Ch'ing , there are a lot of difference in the Costume , the economy and the politic because the ruler was not the han but the Ch'ing. Those characters are as follows. first, on the side of the style , it is occured in the coat and the over jacket of the round neckline. The style of the sleeves are also the tightly(고착). Second, on the side o f the material, the use of the furs are found. It seems that are influence of the north area. Third, it is involved not the traditional Costume of the Han, but the over jacket(which is waistlength), These characters had taken root into the Costume of the Ch'ing Dynasty. In case of the jacket, which are found in the novel most frequently , it was represented by the tight jacket (소오), the long jacket (대오), the short jacket(단오) and the Sam (삼). The skirt was used by women only. the Slacks were trousers only for men, so it was not foujnd in the women's wear. In the vest, the over jacket and coat, which are for putting on, its material, insiqnia and varied embroidery are very brillant and elaborate. The used materials are the silks , furs, wools and cottons. Among the dick silks are used most frequently . in case of the over jacket, the precious and varied furs are used for the collar, the sleeve or the decoration and the lining cloth. In the novel, mean followd the Costume of the Man and women followed the Costume of the Han. Especially, it is a special costume that there were women in male attire. Finally, the costume of the Ch'ing had built the unique one with holding on the advantage and the short point s of the northen race and the Han's. Also , I can find the brilliant , eleborate Customes of the aristocratic class in the novel.

• The Korean Journal of Air & Space Law and Policy
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• v.33 no.2
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• pp.443-469
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• 2018

In the sixty year since the first launch of Sputnik 1, it has become impossible to consider economic, political, or scientific human life in the communication field without reference to outer space. But, there is a growing groundswell of public opinion aimed at preventing arms race in space. Therefore it is necessary to establish some institution or mechanism such a code of conduct, international law. But every nation has a different posture on the grounds of national interest, or different levels of space development, the conditions required for the successful negotiation of a comprehensive treaty are not yet ripe. It is hoped that by beginning with soft measures (TCBM, Code of Conduct) for which it is easier to secure voluntary participation it may be possible to build up to a comprehensive treaty. The participation of the Space powers (US, Russia, China) in a dialogue of mutual exchange and shared information would contribute to international peace and give a long term benefit to humankind. It is also necessary to promote partnership through regional and bilateral cooperation. We should guide and shape opinion so that more nations ratify and sign existing international legal covenants in order to contribute to the efficency of Space law. International law needs to enforce PAROS and Space Security.

• Horticultural Science & Technology
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• v.30 no.5
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• pp.543-548
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• 2012

Morphological characters of Baemoochae, xBrassicoraphanus are mostly intermedium of the both parents, Chinese cabbage, Brassica rapa ssp. pekinensis and radish, Raphanus sativus. The upper and lower parts of the leaf resemble the shape of Chinese cabbage and radish, respectively. The midrib of the leaf is round like to that of radish, but very big more than 3 cm in diameter and white in color like that of Chinese cabbage. The root was changed from the swollen type like that of radish to the enlarged taproot like that of the land race of Chinese cabbage after attaining genetical stability. The flower is white. The seed pod is divided into 2 different parts; the upper part is radish and about 4 cm in length and holds 3-4 seeds and the lower part is Chinese cabbage and about 3 cm in length and holds 7-8 seeds. The color of seed is brown, weight per 1.000 seeds is 5.5 g and the number of seeds per mL is 120. The matured plant in the fall season is around 5 kg in weight and outer leaves are very vigorous and stiffly and inner leaves are erect and form a loose head. The leaf and the root contain a high level of sulforaphene which is well known as a functional substance for anti-cancer and anti-super-bacteria. Baemoochae is an amphidiploid and does not have the self incompatibility function. It has a high level of cross compatibility with Chinese cabbage as the female parent, but not the male parent. It is cross incompatible to cabbage, B. oleracea, black mustard, B. nigra and radish. However it is highly compatible to oil seed rape, B. napus, yellow mustard, B. carinata and partial compatible to muatard, B. juncea in the reciprocal cross.