• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.397.1-397
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• 2002

For high density optical storage, there should be a high NA objective lens and a shorter wavelength laser diode. To secure the disc tilt margin related to the coma aberration, moreover, it's difficult to apply the tilt compensation mechanism into the portable PC. In this paper, we proposed the 3-axis asymmetry pickup actuator with high efficiency symmetric magnetic circuit, which consisted of the top cover type inner yoke for high magnetic flux density, the coil stack unit for the 3-axis independent operation and vertically polarized magnets. (omitted)

• 전자공학회논문지C
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• 제35C권7호
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• pp.69-77
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• 1998

In this paper, a controller is designed for efficient controlling of video data with object-oriented feature. The need of controlling video data in an object unit is on the rise for the reason of rapidly growing demand for high-quality video services. We propose a programmable architecture with stack buffers which can minimize a scheduling overhead by having separate buffes for genral data and return addresses. The buffers are veyr useful for move and copy operations for multitasking and task switching. The controller offers extended instructions that process several data types including 32bit integrer type. Operation speed of the controller is from 77MHz to 44MHz.

• 한국수소및신에너지학회논문집
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• 제15권3호
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• pp.175-186
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• 2004

In this paper, we developed the dynamic model of a fuel cell system suitable for controller design and system operation. The transient phenomena captured in the model include the flow characteristics and inertia dynamics of the compressor, the intake manifold filling dynamics, oxygen partial pressures and membrane humidity on the fuel cell voltage. In the simulations, we paid attention to the transient behavior of stack voltage and compressor pressure, stoichiometric ratio. Simulation results are presented to demonstrate the model capability. For load current following, stack voltage dynamic characteristics are plotted to understand the Electro-chemistry involved with the fuel cell system. Compressor pressure and stoichiometric ratio are strongly coupled, and independent parameters may interfere with each other, dynamic response, undershoot and overshoot.

• Journal of Power Electronics
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• 제11권4호
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• pp.551-560
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• 2011

This paper proposes a grid-tied power conditioning system for the fuel cell power generation, which consists of a 2-stage DC-DC converter and a 3-phase PWM inverter. The 2-stage DC-DC converter boosts the fuel cell stack voltage of 26-48V up to 400V, using a hard-switching boost converter and a high-frequency unregulated LLC resonant converter. The operation of the proposed power conditioning system was verified through simulations with PSCAD/EMTDC software. Based on the simulation results, a laboratory experimental set-up was built with a 1.2kW PEM fuel-cell stack to verify the feasibility of hardware implementation. The developed power conditioning system shows a high efficiency of 91%, which is a very positive result for the commercialization.

• 기술사
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• 제44권1호
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• pp.48-52
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• 2011

The KEPCO Research Institute has developed Molten Carbonate Fuel Cell(MCFC) since 1993. Recently, an 125-kW MCFC system was operated at Boryeong thermal power plant, Korea from December, 2009 to March, 2010, This system is composed of an 125-kW stack, mechanical balance of plant (MBOP), and Power Conditioning System. The stack has 200 unit cells of which effective area is 10,000 cm2. Especially, MBOP is mainly made up of ejector and catalytic combustor which help this system to be supplied with cathode inlet gas using anode tail gas and fresh air. After the pretreatment of this system was performed for about 20 days, initial load operation was performed at January. 2010. Moreover, this system had been operated for 3,270 hours.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.195-196
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• 2007

This paper shortly describe the R&D results for developing of 250 kW externally reforming MCFC (Molten Carbonate Fuel Cell) CHP proto type. Conceptual Design and basic design were alredy completed and stack which was adapted new separator and components also prepared for operation and evaluation. In parallel with stack and system development, BOP such as PCS, blower, catalytic combustor and Reformer also designed and fabricated for evaluation. The system will be fabricated by the end of 2008 and operate and evaluate in 2009.

• 한국재료학회지
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• 제4권7호
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• pp.741-749
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• 1994

The planar solid oxide fuel cell(SOFC) contains several ceramic materials depending on its structure and has rdfractory metal parts for manifolds, shrouds and current leads. Among ceramic materials for planar SOFC, joining of lanthanum chromite separator and yttria stabilized zirconia(YSZ) electoyte in planar SOFC stack to give strong gas tight seals is necessary for satisfactory operation and high performance. Nevertheless, for planar SOFC/sub s/, how to seal the cell stack and gas manifold remains as one of the unsolved problems. Therefore, in this study. we investigated the joining of sintered lanthanum chromite and YSZ pellets using unsintered lanthanum chromite green films as sealent. Scanning electron microscopy(SEM) and energy dispersive X-ray analysis(EDX) revealed that Ca in the sealing material diffused and dissolved into YSZ and sintered lanthanum chromite, and unsintered lanthanum chromite green films reacted with YSZ to from a new phase at the interface. Also, the densification of unsintered lanthanum chromite green films was inpeded by the Ca migration.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권7호
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• pp.2434-2454
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• 2021

This paper developed the software testing factory-cloud testing platform (STF-CTP) to address the software compatible issues in various smart devices. Software developers who only require uploading the application under test (AUT) and test script can test plenty of smart devices in STF-CTP. The challenge for the cloud test platform is how to optimize the resource and increase the performance in the limited resource. This paper proposed a new scheduling mechanism and a new process of the system operation which is based on the OpenStack platform. We decrease about 40% memory usage of OpenStack server, increase 3% to 10% Android device usage of STF-CTP, enhance about 80% test job throughput and reduces about 40% test job average waiting time.

• 항공우주기술
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• 제9권1호
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• pp.98-105
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• 2010

고속푸리에변환(Fast Fourier Transform)은 이산푸리에변환(Discrete Fourier Transform)의 주기적으로 반복되는 연산을 생략하여 그 속도를 향상시킨 연산방법이다. Radix-2 FFT는 그 정의에 따라 함수 재귀호출에 의해 구현될 수 있는데 이 방법은 스택복사 과정의 시간소모 때문에 고속동작이 어렵게 된다. 이를 극복하기 위해 신호점을 연산순서에 맞게 미리 재배열하고 배열된 신호점을 나비연산하는 방법으로 고속연산을 구현할 수 있다. 이 논문은 신호점 재배열 방법에 의한 Radix-2 FFT의 고속연산에 착안하여 Radix-3 FFT에 신호점 재배열 방식을 적용해 보고 그 타당성에 관해 고찰하였다.

• 대한기계학회논문집A
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• 제31권10호
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• pp.981-985
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• 2007

We present a MEMS-based portable Direct Methanol Fuel Cell (micro-DFMC), featured by a platinum sputtered microcolumn electrode and a built-in fuel chamber containing a limited amount of methanol fuel. Also presented is a micro-DMFC stack structure having a common electrolyte sandwiched by the microcolumn electrodes. The single cells with ME16 and PE16 electrodes show the maximum power densities of $31.04{\pm}0.29{\mu}W/cm^2$ and $9.75{\pm}0.29{\mu}W/cm^2$, respectively; thus indicating the microcolumn electrode (ME16) generates the power density (3.2 times) higher than the planar electrode (PE16). The single cell tests of ME16 and ME4 electrodes (Fig.8) show the maximum power of $31.04{\pm}0.29{\mu}W/cm^2$, and $25.23{\pm}2.7{\mu}W/cm^2$, respectively; thus demonstrating the increased window frame reduces the normalized standard power deviation (standard deviation over the average power). The normalized deviation of 0.11 in ME4 cell has been reduced to 0.01 in ME16 cell due to the increased window frames. The maximum power density of 4-cell stack is 15.7 times higher than that of the single cell. 4-cell stack produces the power capacity of 20.3mWh/g during 980min operation at the voltage of 450mV with the load resistance of $800{\Omega}$.