• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.7
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• pp.2878-2885
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• 2012

In this study, the training and sporting equipment for leg rehabilitation featuring the MR fluids is proposed. The compact MR fluid brake is designed and manufactured to apply to the rehabilitation training and sporting mechanism. The resistance characteristic of the MR fluid brake is controllable by varying the magnetic field around the fluid. Under consideration of spatial limitation, design parameters which are related with the magnetic strength are determined to maximize to a torque using finite element method. The FE analysis is performed using a commercial code, ANSYS Workbench. The proposed brake device is manufactured, and its field-dependant torque is experimentally evaluated. When the electric current is supplied, the torque of the MR fluid brake is increased and the response is very fast. Depending on the strength of the current supply, torques of the MR fluid brake also increase similar to Bingham property of MR fluid.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.6
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• pp.138-146
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• 2010

DC railway power supply system generally uses the running rails as negative-polarity return conductor for traction load current, and the induced rail potential and stay current cause serious problems to any electrified matter in the underground and also safety problems to human body. This paper presents a new algorithm for the analysis of the rail potential and the stray current in DC railway power system operated under independent/parallel power feeding mode. The effect of load current fluctuation during train operation is also calculated by using TPS(Train Performance Simulation) program to analysis the variation of the railway potential and stray current along railway track. Simulation program is developed based on the proposed algorithm and case studies are provided.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.1
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• pp.24-29
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• 2003

A 120kV/70A high voltage switch has been installed at Korea Atomic Energy Research Institute(KAERI) in Taejon to supply power with Korea Superconducting Tokamak Advanced Research(KSTAR) Neutral Beam Injection(NBI) system. NBI system requires fast cutoff of the flower supply voltage for protection of the grid when arc detected and fast turn-on the voltage for sustaining the beam current. Therefore the high voltage switch and arc current detection circuit are important part of the NBI power supply. There are much need for high voltage solid state switches in NBI system and a broad area of applications. This switch consisted of 100 series connected MOSFETs and adopted the proposed simple and reliable gate drive circuit without bias supply. Various results taken during the commissioning phase with a 100kW resistive load and NBI source arc shown. This paper presents the detailed design of 120kV/70A high voltage MOSFETs switch and simple gate drive circuit. Problems with the high voltage switch and gate driver during thefabrication and test and solutions are also presented.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.1
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• pp.30-39
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• 2003

In SRM driving, the current rate is directly related to the rate of switching device and in cost reduction, the Parallel switching operation is the alternatives because it has the smaller current rate through current division. There ire many investigations for the parallel switching operations to equaling the current division. However it remains many problems for practical usage. The reason Is that the switching characteristics are mainly relied on the different saturation voltage of each device etc. and these factors are not altered by a circuit designer. In order to compensate this problem, a proper resistance is experimently inserted to the switching device. But this method can not be the optimal solution. Therefore this paper propose a new parallel operation of SRM which uses a parallel phase winding to remove the traditional effect of switching device such as saturation voltage according to the division of current. Also the reliable and stable driving is improved through experiments and the detailed principles.

• Journal of the Korea Convergence Society
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• v.11 no.7
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• pp.151-155
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• 2020

In this study, the velocity distribution and pressure of the flow with the shape of the aircraft were analyzed to investigate its flight performance. In order to compare the flow rate and its pressure applied on the surface of airplane each other, models A and B have the blunt and sharp shapes as the distinctive shapes of airplanes. It can be inferred that the lower the maximum speed of the flow around the airplane, the less resistance the navigation produces, the less fuel consumption, which is more efficient for the sharp model B than the blunt model A. As the result of this study, the wing area and the head part of the body should be designed to withstand the pressure greater than the body. It is shown that the sharp model B can withstand more pressure due to flow than the blunt model A.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.4
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• pp.72-78
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• 2009

This paper proposes a low phase noise ring voltage controlled oscillator(VCO) with a standard $0.13{\mu}m$ CMOS process for PLL circuit using the VCO-gain-controlled Delay cell. The proposed Delay cell architecture with a active resistor using a MOS transistor. This method can reduced a VCO gain so that improve phase noise. And, Delay cell consist of Wide-Swing Cascode current mirror, Positive Latch and Symmetric load for low phase noise. The measurement results demonstrate that the phase noise is -119dBc/Hz at 1MHz offset from 1.9GHz. The VCO gain and power dissipation are 440MHz/V and 9mW, respectively.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.36C no.12
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• pp.59-68
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• 1999

The timing characteristics of an ASIC are analyzed based on the propagation delays of each gate and interconnect wire. The gate delay can be modeled using the two-dimensional delay table whose index variables are the input transition time and the output load capacitance. The AWE technique can be adopted as an algorithm to compute the interconnect delay. Since these delays are affected by the interaction to the two-dimensional delay table and the AWE technique. A method to model this effect has been proposed through the effective capacitance and the gate driver model under the assumption of single driving gate. This paper presents a new technique to handle the multiple CMOS gates driving interconnect wire by extending previous approach. This technique has been implemented in C language and applied to several interconnect circuits driven by multiple CMOS gates. In most cases, we found a few tens of speed-up and only a few percents of errors in computing both of gate and interconnect delays, compared to SPICE.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.7
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• pp.1455-1462
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• 2012

In this paper, a BCD process based high-reliability 24-bit dual-port eFuse OTP Memory for PMICs is designed. We propose a comparison circuit at program-verify-read mode to test that the program datum is correct by using a dynamic pseudo NMOS logic circuit. The comparison result of the program datum with its read datum is outputted to PFb (pass fail bar) pin. Thus, the normal operation of the designed OTP memory can be verified easily by checking the PFb pin. Also we propose a sensing margin test circuit with a variable pull-up load out of consideration for resistance variations of programmed eFuse at program-verify-read mode. We design a 24-bit eFuse OTP memory which uses Magnachip's $0.35{\mu}m$ BCD process, and the layout size is $289.9{\mu}m{\times}163.65{\mu}m$ ($=0.0475mm^2$).

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.4
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• pp.255-262
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• 2016

There has been intense research on self-diagnosis systems in railway applications, since stability and reliability have become more and more significant issues. Wired sensors have been widely used in the railway vehicles, but because of the difficulty in their maintenance and accessibility, they ar not considered for self-diagnosis systems. To have a self-monitoring system, wireless data transmission and self-powered sensors are required. For this purpose, a thermoelectric energy harvesting module that can generate electricity from temperature gradient between the bogie axle box and ambient environment was introduced in this work. The temperature gradient was measured under actual operation conditions, and the behavior of the thermoelectric module with an external load resistance and booster circuits was studied. The proposed energy harvesting system can be applied for wireless sensor nodes in railroad vehicles with optimization of thermal management.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.249-249
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• 2010

핵융합로에서는 디버터의 열부하에 대한 안전성을 고려하기 위해 열전도도 및 열 저항성이 높은 텅스텐이 대면 물질로 고려되고 있으며, 경제적인 측면과 실용성 측면에서 텅스텐블록을 직접 제작하여 사용하는 것보다 텅스텐코팅이 효과적이라는 의견이 지배적이다. 또한 ASDEX Upgrade 에서는 탄소블럭에 텅스텐을 코팅하여 챔버 외벽 및 디버터 영역까지 구성하여 캠페인을 진행하였고, 재료적인 측면에서 안정성을 확인 하였다. 따라서 본 연구에서는 디버터 및 챔버외벽 등에 대한 대면물질을 구성하기 위해 상압 열플라즈마 제트를 이용하여 고온에서의 용융 및 냉각을 통해 모재에 텅스텐 피막을 적층하는 과정을 수행하고 있다. 기존의 연구를 통해 일부 공정 변수에 대해서는 이미 적정한 범위의 공정조건을 확보하였고, 기공도와 산화도 및 부착력 등의 물성치에 대한 추가적인 향상을 위해 주요 공정 변수에 집중하여 최적의 조건을 탐색하는 과정이 진행 중이다. 이를 위해 출력증가실험의 일환으로서 기존 36kW급 플라즈마 토치 전력을 한 단계 끌어 올려 48kW급 전력까지 단계적으로 상승시킴으로써 이에 따른 물성치 변화를 검증하고 있다. 현재 44kW 급까지 실험이 수행되었으며, 이를 통해 공극률 감소 및 미세구조 변화에 대한 결과를 얻었다. 실제로 토치의 출력을 증가시킴으로서 텅스텐 피막의 물성치가 변화하는 메커니즘은 플라즈마 제트의 중심부 온도 및 축방향 속도에 의해 결정된다. 중심부 온도가 상승하게 될수록 코팅을 위해 분사되는 분말의 용융률은 증가하지만 분말 외벽에 산화텅스텐이 형성될 가능성은 증가하게 되며, 플라즈마 제트의 모재를 향상 축방향 속도가 증가할수록 용융 된 분말이 모재에 증착 시 형성하는 형태가 원형에 가깝게 되므로 기공이 감소하는 효과가 발생한다. 특히 용융된 분말의 증착 형태는 모재의 온도 및 분말의 입사속도에 결정적이 영향을 받게 되며, 결국 모재와 분말사이의 습윤성에 의한 분말 분산속도가 분말의 입사속도에 버금갈 경우 분말은 모재 위에서 효과적으로 원형으로 전이하며 적층하게 된다. 이러한 전이 현상은 앞에서 언급한 모재의 온도 등에 의해 결정적으로 영향을 받게 되며, 모재의 온도가 전이온도 이하일 경우 폭파형태에서 원형으로 분말의 증착 형태가 전이하게 된다. 이외에 추가적으로 진행하고 있는 연구는 코팅 전처리에 해당하는 분말 효과이며, 특히 탄화텅스텐 분말을 통한 재료적 auto-shroud 효과와 미세분말을 이용한 분말 표면열속의 증가에 따른 용융률 증가효과를 연구에 포함할 계획이다. 이러한 연구는 열적, 그리고 재료적 해석을 바탕으로 해석적 접근을 통해 이루어진다.