• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.625-629
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• 1998

So far a single-axis controlled repulsive type magnetic bearing system have been designed and fabricated in our laboratory employing the repulsive forces operating between the stator and rotor permanent magnet for levitation. The radial axis is uncontrolled passive one. The higher speed of operation is limited due to the vibration along the uncontrolled axis and the increase of control current due to eddy current interference. This paper will discuss a detailed modeling of the repulsive type magnetic bearing system for five axis control including the eddy current effect and the method of reduction of eddy current effect. Simulation results using Matlab will be presented.

• 전기학회논문지
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• 제64권5호
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• pp.694-700
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• 2015

This paper deals with the design of 1-kW troidal type gyro. In general, gyro can be used as magnet bearing or flywheel energy storage device. The proposed troidal type gyro is used as a flywheel energy storage device. The gyro is capable of high-speed rotation in the air. The coriolis effect is taken into account when designing the rotor of the proposed gyro. Also the repulsive power of the permanent magnet is considered while selecting the shape and the thickness of the magnet. The neodymium is used as material of the magnets in this paper. The number of magnets are selected accordingly to reduce these torque ripples because torque ripples is an important factor while designing the gyro. The designed troidal type gyro is verified through the Finite Element Method (FEM).

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.119-124
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• 1998

This paper proposes a new repulsive-Maglev vehicle in which a vertical type PM linear synchronous motor (LSM) can levitate and propel simultaneously, independently of the vehicle speeds. A compact control method is developed which is based on the concept of controlling individually the levitation system by armature-current and the propulsion system by mechanical load-angle. The levitation-motion control experiments have carried out successfully together with positioning at standstill. The pitching motion has been compensated for very well by using the zero-phase-current control method proposed here.

• 대한전기학회논문지
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• 제45권1호
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• pp.18-23
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• 1996

This paper proposes a new levitation scheme for EDS MAGLEV vehicle with AC superconducting magnet(ACSCM). The eddy current and the levitation force are generated at all speed including stand still in this scheme, therefore, the auxiliary wheels on DCSCM can be eliminated. To reduce the ac loss of the magnet, the ACSCM also can be operated as a DCASCM at high speed because levitation force generated by DCSCM is enough at high speed. To prove the effectiveness of the proposed scheme, the repulsive force and power loss versus frequency of ACSCM is calculated. For comparison, characteristics of DCSCM of same cross section versus speed are also given. (author). 6 refs., 9 figs.

• 드라이브 ㆍ 컨트롤
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• 제18권4호
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• pp.19-27
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• 2021

A bunker bed is a type of furniture that efficiently utilizes a narrow indoor space by having a high bed and using the empty space below as a living and storage space. The demand for multi-purpose furniture is increasing due to the recent increase in single-person households and wide-spread shared accommodation. According to the consumer research, one of the major drawbacks of a bunker bed was to get on and off the bed through a ladder or stairs. In order to overcome these problems, it was confirmed that the height adjustment function that can easily adjust the minimum and maximum heights of the bed was necessary. In this study, a height adjustable bunker bed was designed by using a gas spring that generates a repulsive force by the compressed gas inside. The design process consisted of the following three steps: Firstly, the hysteresis characteristics due to a friction and spring constant of a commercial gas spring were confirmed by measuring the repulsive force vs. compressed displacement. Secondly, requirements of the vertical lifting force exerted on the bed against gravity force were derived. Finally, the height-adjustable bed using the four-bar link mechanism was designed with 4 parameters so that the bed weight of 60-70 kgf could be adjusted to 800 mm in height by an affordable initial operation force. The performance was verified through prototype production and the results of vertical displacement and force to move were nearly the same as designed. In addition, an electrically operated height-adjustable bed was also designed with linear actuators and the performance was proved with the prototype.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.554-557
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• 2002

This paper describes power potential field method for the collision-free path planning of stereo-vision based mobile robot. Area based stereo matching is performed for obstacle detection in uncertain environment. The repulsive potential is constructed by distributing source points discretely and evenly on the boundaries of obstacles and superposing the power potential which is defined so that the source potential will have more influence on the robot than the sink potential when the robot is near to source point. The mobile robot approaches the goal point by moving the robot directly in negative gradient direction of the main potential. We have investigated the possibility of power potential method for the collision-free path planning of mobile robot through various experiments.

• 한국정보과학회논문지:시스템및이론
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• 제34권5_6호
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• pp.202-213
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• 2007

네트워크는 공학이나 자연과학은 물론이고 사회과학의 여러 분야를 연구하는데 중요하게 사용되는 모델이다. 이런 네트워크를 좀 더 쉽게 분석하기 위해서는 시각적으로 네트워크의 특징을 잘 나타내는 것이 필요하다. 이러한 그래프 레이아웃 연구는 컴퓨터 기술이 발달함에 따라 많이 연구되고 있다. 그 중에서 요즘 새롭게 부각되고 있는 척도 없는(Scale-free) 네트워크는 다양한 분야에서 복잡한 현상들을 분석하고 이해하는데 유용하게 쓰이고 있다. 이 네트워크의 특징은 링크의 수(Degree)가 멱함수(power law) 분포를 보이고, 다수의 링크를 가지는 허브가 존재함이 알려졌다. 따라서 척도 없는 네트워크에서는 허브를 시각적으로 잘 표현하는 것이 중요하지만 기존의 그래프 레이아웃 알고리즘은 클러스터를 잘 표현하는 정도이다. 그래서 본 논문에서는 척도 없는 네트워크를 잘 표현하는 그래프 레이아웃 알고리즘을 제안한다. 본 논문에서 제안한 알고리즘에서 허브들 간에 작용하는 허브성 척력이 거리에 반비례하고, 허브들의 degree가 a배 증가하면, 허브사이에 작용하는 척력의 크기는 ${\alpha}^{\gamma}({\gamma}$는 연결선 지수)배가 된다. 또한, 전체 노드수와 전체 링크수에 따라 적용되는 힘의 크기를 조정하는 계수를 두어서 네트워크의 규모에 관계없이 허브성 척력이 적용되는 특성이 있다. 제안한 알고리즘이 허브를 잘 표현하는 그래프 레이아웃 알고리즘인지를 기존의 방식과 실험을 통해서 비교하였다. 실험의 절차는 먼저 네트워크에 허브가 존재하는지를 식별한다. 허브의 존재를 식별하기 위한 방법은 연결선 지수를 확인하고, 연결선 지수의 값이 2와 3사이에 있으면 허브가 존재하는 척도 없는 네트워크로 판단한다. 다음은 이 네트워크의 레이아웃 작성에 제안한 알고리즘을 사용한다. 그 결과, 제안한 그래프 레이아웃 알고리즘이 기존의 Noack등의 클러스터중심의 알고리즘에 비해서 척도 없는 네트워크의 허브를 확실히 잘 보여주고 있음을 확인할 수 있었다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.947-951
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• 2007

This paper is concerned with a new concept for the damper without neither a coil spring nor fluid. The new damper concept consists of the permanent magnets and the cylinder of the conducting material. The opposite pole magnets produces the repulsive forces and this is substituted for the coil spring. The relative motion between the magnets and conducting cylinder produces eddy currents thus resulting in the electromagnetic force, which turns out to be the damping force thus and is substituted for a damping fluid. This damper is called the eddy current damper(ECD). The important advantage of the proposed ECD is that it does not require the damping fluid and any external power and is non-contacting and relatively insensitive to temperature. In the present study, the proposed ECD was constructed and experiments were performed to investigate its dynamic characteristics. The experiments shows that the proposed ECD has the excellent damping ability.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.147.1-147.1
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• 2016

Hydrophobic thin films are variously applicable for encapsulation of organic devices and water repulsive glass, etc. In this work, the stability of hydrophobic characteristics of plasma polymerized tetrakis (trimethylsilyloxy) silane (ppTTMSS) thin films were investigated. The films were deposited with plasma enhanced chemical vapor deposition (PECVD) on the glass. The deposition plasma power and deposition pressure was 70 W and 600 mTorr, respectively. Thereafter, deposited films were treated by 248nm KrF excimer laser. Stability of hydrophobic properties of plasma polymerized tetrakis(trimethylsilyloxy)silane film surface was tested by excimer laser irradiation, which is thought to simulate severe outdoor conditions. Excimer laser irradiation cycles changed from 10 to 200 cycles. The chemical structure and hydrophobicity of ppTTMSS films were analyzed by using Fourier transform infrared (FTIR) spectroscopy and water contact angle (WCA) measurement, respectively. Absorption spectra peaks and WCA of excimer laser treated ppTTMSS films did not change notably. These results show that our ppTTMSS films possess stable hydrophobic properties.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
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• pp.1-4
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• 2008

Fuel cells have the potential of providing several times higher energy storage densities than those possible using current state-of-the-art lithium-ion batteries, but current energy density of fuel cell system is not better than that of lithium-ion batteries. To achieve the high energy density, volume and weight of fuel cell system need to be reduced by miniaturizing system components such as stack, fuel tank, and balance-of-plant. In this paper, the thin flexible PCB (Printed circuit board) is used as a current collector to reduce the stack volume. Two end plates are made from light weight aluminum alloy plate. The plate surface is wholly oxidized through the anodizing treatment for electrical insulation. The opening rate of cathode plate hole is optimized through unit cell performance measurement of various opening rates. The performances are measured at room temperature and ambient pressure condition without any repulsive air supply. The active area of MEA is 10.08 $cm^2$ and active area per a unit cell is 1.68 $cm^2$. The peak power density is about 210 mW/$cm^2$ and the air-breathing planar stack of 2 Wis achieved as a small volume of 18 cc.