• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.667-668
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• 2010

• Journal of Korean Society of Forest Science
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• v.111 no.4
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• pp.548-556
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• 2022

In this study, basic data were obtained to determine the optimal cultivation method to achieve stable fruiting and yield increase in "Cheonhwang" jujube trees. Accordingly, thefructification, fruit characteristics, and yield according to tree age were analyzed. The mean (and range of) tree height, crown area, stem diameter near the root, clear stem length, number of main branches, and distance between main branches were 235.6 (217.4-253.8) cm, 3.5 (3.1-4.1) m², 5.5 (4.0-7.1) cm, 70.6 (66.2-72.7) cm, 9.7 (8.6-10.5), and 10.4 (7.9-14.2) cm, respectively. Correlationanalysis results indicated that tree age was positively correlated with crown area, stem diameter near the root, and clear stem length but not with the number of main branches. The mean number (and range) of fruit per fruit-bearing mother shoot and tree were 18.3 (16.7-18.3) and 170.7 (157.9-178.3), respectively. Tree age was not significantlycorrelated with fruiting characteristics (i.e., the numbers of fruit-bearing mother shoots per main branch, fruit-bearing shoots per fruit-bearing mother shoot, fruit per fruit-bearing shoot, and fruit per tree). Given that the shape of jujube trees is constantly managed according to the growing area and greenhouse type, the tree growth characteristics were more affected by tree management techniques than by tree age. The mean (and range of) fruit weight, fruit hardness, and soluble solid content were 28.6 (27.7-30.3) g, 29.4 (28.5-30.4) N, and 20.4 (19.3-21.0) °brix, respectively, and these fruit characteristics were not significantly correlated with tree age.The average yield per tree of the 'Cheonhwang' jujube cultivar was 4.9 (4.8-5.0) kg, which was not significantly correlated with tree age.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.06a
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• pp.291-296
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• 1999

This study presents a method for determining stiffness and damping coefficients of 30% U slider-air bearings by using perturbation method, and shows that this method is more accurate than steady state method according to the comparison of those with the modal analysis method. Through a generalized lubrication equation, which based on linealized Boltzmann equation, the static and dynamic pressure distributions are calculated by finite volume method.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.04a
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• pp.159-166
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• 1998

본 연구에서는 공기포일 베어링으로 지지된 로터 베어링 시스템을 구성하고 실험을 수행함으로써 시스템의 진동을 측정하고 그 결과를 해석함으로써 로터 베어링 시스템의 안정성 검토한다. 또, 초기 구동 마찰을 고려하여 공기윤활로만 구동되는 경우와 초기에 베어링 표면에 오일이 도포된 경우를 비교한다. Transient data를 해석 함으로써 로터 베어링 시스템의 startup 및 shutdown에 대한 특성 파악이 가능해지며 시스템의 동적 특성에 대한 더욱 정확한 해석을 가능케한다.

• Journal of the KSME
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• v.16 no.2
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• pp.122-127
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• 1976

It was reported in the Journal of KSME Vol. 15, No. 3 and No. 4, 1975 that could be finished the best smooth surface by applying frictional work to the metal surface. Even if we can finish the best smooth surface of methal, it is not available when it has not anti-wear. Present study tried to investigate the anti-wear and the characteristics of frictional worked surface by using the sliding contact between plain bearing of brass and frictional worked jornal of mild steel. The results were compared with the case of ground journal.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.210-214
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• 2003

The static and dynamic characteristics of HDD slider with ulta-low flying height are analyzed using Direct Numerical method with Boundary Fitted Coordinate System. The slip flow effect is considered using the Boltzmann equation solution in a form of the flow rate database. The air film stiffness and damping are evaluated by the small perturbation method.

• 연구논문집
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• s.33
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• pp.53-65
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• 2003

Electrostatic micro-motors can be divided into three classes: (i) salient type side drive motor, (ii) radial gap type wobble motor, (iii) axial gap type wobble motor. The working mechanism, torque evaluation, fabrication, and operational characteristics of each micro motors are compared. It is proved that axial gap type wobble motor has the bigger generating torque than that of the other type. The gear ratio of wobble motors increases the driving torque at the cost of a decreasing angular speed and decreases the friction because of the rolling motion instead of sliding at the bearing. Techniques for characterizing micro-motors performance are presented.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.04a
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• pp.178-181
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• 2004

In this work, the carbon fabric reinforced phenolic composite is applied for heavy-duty journal bearings. The through thickness compressive strength (TTCS), which is one of the most important characteristics for the bearing material, is measured and analyzed with respect to the stacking sequence and composite thickness. Also, the coefficient of thermal expansion (CTE) and thermal conductivity of the composite in the thickness direction were measured with respect to stacking sequence.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2003.12a
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• pp.200-206
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• 2003

Identification method is formulated to evaluate the dynamic characteristics of air bearings under NFR (Near Field Recording) sliders. Using dynamic analysis, impulse responses and frequency response functions of NFR sliders are obtained on numerical non-linear models including rigid motion of slider and fluid motion of air bearing under the slider. System parameters are identified by modal analysis method and instrumental variable method. The identified system parameters of sliders are utilized to evaluate the dynamic characteristics of air bearings.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.236-242
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• 2001

In this paper the effect of bump compliance, load, and the number of pad on the lift-off speed is studied. When the load is greater and bump compliance lower, the shaft is lifted off at higher rotating speed. And when the load is applied near the center of pad, lift-off speed is lower. When the number of pad increases, the lift-off speed is higher. The lift-off characteristics can be used to lengthen the life time of the coating and design the rotating machinery supported by bump bearings.