• Journal of Aerospace System Engineering
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• v.13 no.3
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• pp.1-8
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• 2019

The electromagnetic forces generate a torque on the gimbal motor, and changes in the coil current causes torque ripple. This affects the gimbals' speed and results to unstable satellite attitude. It is therefore essential to reduce the torque ripple of the gimble motor with the aim of improving the attitude control accuracy of the satellite. This paper theoretically analyzes the torque generated from the modeling of a motor for general concentrated winding and distributed winding. The prototype was designed and fabricated through selection of the winding that reduces the torque ripple through simulation results. The results of the magnetic fields' theoretical analysis and the back electromotive force of the prototype were compared with the calibrated results for verification of conformity and manufacture of the design. The low-speed test proved that the torque ripple is reduced by improving the speed stability.

• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.181-188
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• 2015

The non-contact permanent magnet gear has advantages of high efficiency and improved reliability. It has other advantages of no mechanical friction loss, very little noise and vibration, and no need for lubricant. With these advantages, the non-contact permanent magnet gear that solves the physical contact problem of the mechanical gear has drawn attention. Due to this unique non-contact characteristic, the non-contact permanent magnet gear which is capable of non-contact torque transmission has replaced mechanical gear. The mechanical gears which is in many fields of the modern industry, is used mostly for power transmitting mechanical devices. However, it also has the problem of a low torque density, which requires improvement. In this paper, a novel pole piece shape is proposed in order to improve the problem of low torque density of the non-contact permanent magnet gear. The experiment data required for predicting the relationships among them are obtained using finiteelement Operating method based on two-dimensional (2-D) numerical analysis. Therefore, this paper derived an optimal model for thenon-contact permanent magnet gear with the novel pole piece using the Box-Behnken design, and the validity of the optimal design of the proposed pole piece shape through variance analysis and regression analysis demonstrated. In this paper, we performed the thransfer torque analysis in order to improve the torque density and power density, we have performed on optimal design of proposed pole piece shape using box-behnken.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.300.1-300.1
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• 2016

최근 반도체 회로의 미세화로 인해 디자인 공정이 20 nm 이하로 내려갔다. 그 결과 회로간의 간격이 줄었으며 많은 문제가 발생 한다. 첫 번째 문제는 미세하게 여러 박막 층들을 쌓기 때문에 박막 층이 그전 50 nm 공정에 비해선 쉽게 무너질 수 있다. 따라서 하나의 박막 층은 다른 여러 박막들의 하중을 잘 견뎌야 할 것이다. 결과적으로 회로의 미세화에 따라 박막의 기계적 특성이 좋아야 될 것이다. 또 다른 문제는 너무 좁은 회로의 간격으로 인해 다른 회로에 영향을 미치는 크로스토크라는 전기적 문제이다. 크로스토크가 크다는 것은 회로간의 누설 전류가 크다는 것을 의미하며 그만큼 신호 전달 능력이 감소 한다는 것을 뜻한다. 크로스토크의 문제점을 해결하기 위해 회로 사이에 절연 막을 만들어 누설전류를 막아야 한다. 이러한 문제를 바탕으로 본 연구는 Zirconium nitride (ZrN) 박막이 이러한 문제점을 해결 할 수 있는 지연구해 보았다. 박막 제작 시 변화 요인은 질소유량 과 열처리 온도 이며 질소유량 변화는 2 sccm 과 8 sccm 두 경우로 하였다. 또한 열처리는 As-deposited state, $600^{\circ}C$ 와 $800^{\circ}C$로 열처리 하였다. 박막 증착은 RF magnetron sputtering을 이용하였으며 열처리는 질소 분위기에서 furnace를 이용하였다. 기계적 특성분석 결과 질소유량이 2 sccm 인 박막의 hardness는 as-deposited stste에서 18.8 GPa이고 $600^{\circ}C$에선 18.4 GPa로 거의 비슷하고 $800^{\circ}C$ 열처리한 경우는 15.4 GPa 으로 hardness가 감소하는 것을 알 수 있었다. 질소 유량을 8 sccm 흘려주며 증착한 박막의 경우는 as-deposited state, $600^{\circ}C$, $800^{\circ}C$에서의 hardness가 각각 17.5, 16.4, 21.1 GPa 으로 감소하다가 증가하는 경향을 보였다. 또한 zrN 박막의 전기적 특성인 누설 전류 밀도도 측정하였다. 결과적으로 본 연구는 ZrN 박막의 질소 유량 변화와 열처리에 따른 기계적, 전기적 특성변화를 확인 하였다.

• The Journal of Korean Academy of Prosthodontics
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• v.51 no.4
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• pp.300-306
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• 2013

Purpose: This study was to evaluate the accuracy of how to use the Mechanical Torque-Limiting Devices. Materials and methods: Three different implant manufacturers (Dentium, Osstem, Shinhung) were prepared for each two implant torque controllers. Divided into two groups depending on the method used for removal torque was measured. Repeated measures of ANOVA test (${\alpha}=.05$) was used as statistics to evaluate the effect of repeated loading number on the removal torque. Independent t-test was used to evaluate the difference in removal torque of two groups. Results: The removal torque significantly decreased as the number of loading repetition increased (P<.05). There was significant difference between two groups. Conclusion: Loosen the handle part of the implant torque controllers spring resilience to recover one group compared to the group that did not, showed a little more closed to the reference value.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.12
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• pp.1885-1891
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• 2010

Torque control of wind turbines is important when the wind speed is below the rated speed. The main objective of torque control is to extract the maximum power from the potential aerodynamic power of the wind. Torque control methods for wind turbines are classified as torque-mode control and speed-mode control. In torque-mode control, which is well known and traditionally used in many wind turbines, the torque demand of the generator is proportional to the square of the generator speed. In speed-mode control, a PI controller is used to generate the appropriate torque demand of the generator. In this study, the two torque control methods mentioned above are applied to a 2.75-MW wind turbine; simulation results for real turbulence wind speeds are presented, and the response properties are compared.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.7
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• pp.585-590
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• 2017

Vehicle behavior is determined by forces and a torques generated at the ground contact surface of the tire. Various tire models are used to calculate the forces and torques acting on the tire. The brush model calculates the forces and torques with fewer coefficients than other tire models. However, owing to fewer degrees of freedom in calculating the forces, this model has limitations in precisely expressing measured data. In this study, this problem was addressed by adding the least parameters to the friction coefficient and tire properties of the brush model, and the proposed model was validated.

• Proceedings of the KIEE Conference
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• 2003.07d
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• pp.2778-2780
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• 2003

본 논문에서는 모터구동밸브의 모터 토크를 전기적인 신호만으로 예측하고, 계산된 모터 토크신호를 주파수영역에서 분석하여 Motor Speed, Slip pole 주파수, WGTM(Worm Gear Tooth Mesh)과 같은 MOV의 기계적 특성 성분을 확인하였다. 또한 모의 고장 실험을 통해 MOV 기계적 고장이 이 특성성분의 변화로 나타나는 것을 확인하므로, 이 정보를 MOV의 고장 감시 기술로 적용할 수 있다. 아울러 전기 신호를 이용하여 Condition Monitoring 기법을 개발하고, MOV 고장 감시 Software를 개발하므로, MOV 주기적 확인에 대비한 규제검증 기술 및 정보를 제공하고자 한다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.11
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• pp.1239-1243
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• 2014

This paper presents the application of carbon-fiber-reinforced polymer (CFRP) for the damage absorption and optimal design of portable smart devices to close in life. CFRP specimens are subjected to a tensile test to estimate their mechanical properties in terms of the stacking angles. Further, the screw reverse torque and screw torque at each stacking angle are determined using a torque tester after tapping holes on the CFRP specimens. Two experiments are performed for comparing their results in order to determine optimal conditions. In the tensile test, a woven specimen is found to have the highest strength and stiffness. In the case of the woven specimen, no difference is observed even when it is applied to prevent loosening of the coating. And average result value was excellent.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.6
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• pp.1065-1070
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• 2017

Magnetic gears are magnetically coupled to the input side and the output side of the rotary machine to transmit power without mechanical contact. The magnetic gear consists of an inner rotor, an outer rotor and pole pieces. Torque ripple occurs due to the difference in reluctance between the two rotors and the pole pieces during power transmission. Torque ripple is a cause of the noise and vibration of the rotary machine, so it is necessary to minimize it. In this paper, we propose a shape that cuts the corner of the pole piece and apply a fillet to reduce torque ripple. We used a two-dimensional finite element analysis method to compare and analyze the torque ripple of the magnetic gears according to the change of the fillet parameters and to find the pole piece shape with excellent torque ripple.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.1
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• pp.59-65
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• 2013

In this study, the effects of the compressor for the air conditioning system on the fuel economy were experimentally investigated in an actual automobile. This study aims to analyze the level of contribution of the driving torque of the compressor to the fuel economy. A torque sensor, which is directly set on the clutch of the compressor, is developed to obtain data about the compressor load, which influences the fuel efficiency, and then, the reliability of the torque sensor is verified by comparing the results with those of a torque meter in a bench test. An actual automobile equipped with the compressor and torque sensor is operated in a climate wind tunnel in which appropriate facilities are set up to evaluate the fuel efficiency. The compressor driving torque resulting from the difference in the compressor displacement is found to influence the fuel economy, and the fuel economy is found to be worsened by up to 2~3% with an around 11% increase in the compressor displacement under the same conditions.