• 대한기계학회논문집B
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• 제34권7호
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• pp.715-720
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• 2010

본 논문은 고분자전해질막 연료전지의 공기 공급을 위해 전기침투현상에 기반을 둔 공기 공급 방법을 제안하고 이를 실험적으로 평가하였다. 작동 유체의 구동을 위해서 전기침투펌프를 낮은 주파수의 교류 전기장에서 사용하였다. 작동 유체는 유연한 막에 의해 막 밀봉하였고, 막의 움직임에 의해 연료전지 내로 공기를 공급하였다. 본 연구에서는 전기침투현상 기반 공기펌프를 사용하여 연료전지의 공기 공급을 성공적으로 설명하였다. 펌프의 출력은 연료전지에서 생성되는 출력을 초과하였지만, 본 논문에서는 펌프의 출력 당 연료전지의 출력비를 줄이기 위한 몇 가지 방법들에 대해 설명하였다.

• ETRI Journal
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• 제31권6호
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• pp.717-724
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• 2009

This paper describes a 1.2 V 12 b 60 MS/s CMOS analog front-end (AFE) employing low-power and flexible design techniques for image signal processing. An op-amp preset technique and programmable capacitor array scheme are used in a variable gain amplifier to reduce the power consumption with a small area of the AFE. A pipelined analog-to-digital converter with variable resolution and a clock detector provide operation flexibility with regard to resolution and speed. The AFE is fabricated in a 0.13 ${\mu}m$ CMOS process and shows a gain error of 0.68 LSB with 0.0352 dB gain steps and a differential/integral nonlinearity of 0.64/1.58 LSB. The signal-to-noise ratio of the AFE is 59.7 dB at a 60 MHz sampling frequency. The AFE occupies 1.73 $mm^2$ and dissipates 64 mW from a 1.2 V supply. Also, the performance of the proposed AFE is demonstrated by an implementation of an image signal processing platform for digital camcorders.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2009년도 춘계학술대회
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• pp.895-898
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• 2009

본 연구에서는 임베디드 시스템, 특히 블루투스 베이스밴드에서 사용이 가능한 범용 I/O를 설계하였다. 제안하는 구조는 AMBA 버스구조의 APB 저전력 버스에 호환되도록 설계하였다. 임베디드 시스템에서 사용 가능한 범용 I/O를 인터럽트 소스로 사용될 수 있어야 한다. 본 연구에서는 에지 민감 방식과 레벨 민감 방식 모두를 고려하여 인터럽트를 수용할 수 있도록 설계하였고, 동작 폴라리티를 선택할 수 있어 임베디드 시스템에 유연하게 적용될 수 있도록 고려하였다. 설계한 범용 I/O 모듈은 자동합성하여 P&R을 수행하였다. 결과물은 Altera FPGA로 구현하였으며 25MHz에서 정상 동작하였다.

• 한국안전학회지
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• 제33권6호
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• pp.85-92
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• 2018

This study aimed to reduce of traps incident of metro train door by suggesting preventive actions throughout analyzing why railway drivers and passengers commit unsafe behaviors which are human factors making occurrence of the incidents. The incident cases were analyzed and Incident Tree was structured by brainstorming with safety experts. In addition, the questionnaire survey was conducted for comparison with the analysis results. As the result, this study suggested driver's factors, passenger's factors, and public relation plan for safe use of metro in order to reduce the frequency of the incidents. For driver's factors, implementing job-rotation systems between railway and non-railway drivers, installing Object Detection Sensors between the metro doors and PSD, and flexible operation of dwell time were suggested. For passenger's factors, placing a platform safety person, installing a safety fence in front of the stairs and the elevators, and country wide public relations through mass media were suggested.

• Nuclear Engineering and Technology
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• 제54권8호
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• pp.2883-2897
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• 2022

According to the Renewable Energy 3020 Implementation Plan announced in 2017 by the South Korean government, the electricity share of renewable energy will be expanded to 20% of the total electricity generation by 2030. Given the intermittency of electricity generation from renewable energy, realization of such a plan presents challenges to managing South Korea's isolated national electric grid and implies potentially large excess electricity generation in certain situations. The purpose of this study is: 1) to develop a model to accurately simulate the effects of excess electricity generation from renewables which would arise during the transition, and 2) to propose strategies to manage excess electricity generation through effective utilization of domestic electricity generating capabilities. Our results show that in periods of greater PV and wind power, namely the spring and fall seasons, the frequency of excess electricity generation increases, while electricity demand decreases. This being the case, flexible operation of coal and nuclear power plants along with LNG and pumped-storage hydroelectricity can be used to counterbalance the excess electricity generation from renewables. In addition, nuclear energy plays an important role in reducing CO₂ emissions and electricity costs unlike the fossil fuel-based generation sources outlined in the 8th Basic Plan.

• 대한조선학회논문집
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• 제43권5호
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• pp.560-567
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• 2006

FPSO and shuttle tanker are connected to each other by a mooring hawser and a loading hose through which cargo oil is off-loaded. Even in mild sea-state. environmental loads can cause unstable large drift motions between two vessels in tandem off-loading operations, which may result in collision incidents. Accordingly. the analysis on the relative motion between two vessels due to the environmental loads should be investigated in initial design stage. In this study, the low speed maneuvering equation is employed to simulate nonlinear motions of FPSO and shuttle tanker. Low frequency wave drift forces including hydrodynamic interactions between two vessels are evaluated by near field approaches. Current loads are determined by mathematical model of MMG and wind loads are calculated by employing the wind spectrum according to the guidelines of API-RP2A. Mooring forces produced by turret mooring lines and a flexible hawser are modeled quasi-statically by catenary equations. The effect of environmental loads that affect nonlinear motion is investigated through variation in their magnitudes and the nonlinear motions between FPSO and shuttle tanker are simulated under wave, current and wind in time domain.

• Nuclear Engineering and Technology
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• 제48권5호
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• pp.1237-1251
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• 2016

Although the horizontal component of an earthquake response can be significantly reduced through the use of conventional seismic isolators, the vertical component of excitation is still transmitted directly into the structure. Records from instrumented structures, and some recent tests and analyses have actually seen increases in vertical responses in base isolated structures under the combined effects of horizontal and vertical ground motions. This issue becomes a great concern to facilities such as a Nuclear Power Plants (NPP), with specialized equipment and machinery that is not only expensive, but critical to safe operation. As such, there is considerable interest worldwide in vertical and three-dimensional (3D) isolation systems. This paper examines several vertical and 3D isolation systems that have been proposed and their potential application to modern nuclear facilities. In particular, a series of case study analyses of a modern NPP model are performed to examine the benefits and challenges associated with 3D isolation compared with horizontal isolation. It was found that compared with the general horizontal isolators, isolators that have vertical frequencies of no more than 3 Hz can effectively reduce the vertical in-structure responses for the studied NPP model. Among the studied cases, the case that has a vertical isolation frequency of 3 Hz is the one that can keep the horizontal period of the isolators as the first period while having the most flexible vertical isolator properties. When the vertical frequency of isolators reduces to 1 Hz, the rocking effect is obvious and rocking restraining devices are necessary.

• 대한산업공학회지
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• 제34권2호
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• pp.223-234
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• 2008

Mobile multi-hop relaying (MMR) technology is being considered as a promising solution capable to enhance coverage, user throughput, and system capacity of the current wired backbone dependent wireless access networks. Since the relaying nodes do not need a wired backbone access, MMR technology offers easy and low-cost deployment, flexible cell planning, and adaptive traffic handling performance. In this paper, we investigate performance and cost effectiveness of the MMR technology deployment in the IEEE802.16j based WiBro/WiMAX systems. We first introduce standardization activities and research issues of MMR WiBro/ WiMAX systems. Since the coverage extension problem may occur in metropolitan areas as well as suburban or rural areas where user density is relatively low or moderate, we introduce several MMR topologies and analyze cost-effectiveness of MMR based coverage extension with respect to the user traffic density. Then, we argue cost effect on MMR technology deployment and throughput performance, Finally, we introduce further study issues including sectorized base station based MMR deployment approaches and the single and multi-frame structure MMR approaches.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.311-311
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• 2013

The resistance switching memory devices have several advantages to take breakthrough for the limitation of operation speed, retention, and device scale. Especially, the metal-oxide materials such as ZnO are able to fabricate on the flexible and visible transparent plastic substrate. Also, the quantum dots (QDs) embedded in dielectric layer could be improve the ratio between the low and the high resistance becauseof their Coulomb blockade, carrier trap and induced filament path formation. In this study, we irradiated 0.2-MeV-electron beam on the ZnO/QDs/ZnO structure to control the defect and oxygen vacancy of ZnO layer. The metal-oxide QDs embedded in ZnO layer on Pt/glass substrate were fabricated for a memory device and evaluated electrical properties after 0.2-MeV-electron beam irradiations. To formation bottom electrode, the Pt layer (200 nm) was deposited on the glass substrate by direct current sputter. The ZnO layer (100 nm) was deposited by ultra-high vacuum radio frequency sputter at base pressure $1{\times}10^{-10}$ Torr. And then, the metal-oxide QDs on the ZnO layer were created by thermal annealing. Finally, the ZnO layer (100 nm) also was deposited by ultra-high vacuum sputter. Before the formation top electrode, 0.2 MeV liner accelerated electron beams with flux of $1{\times}10^{13}$ and $10^{14}$ electrons/$cm^2$ were irradiated. We will discuss the electrical properties and the physical relationships among the irradiation condition, the dislocation density and mechanism of resistive switching in the hybrid memory device.

• 조명전기설비학회논문지
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• 제16권2호
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• pp.104-112
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• 2002

본 논문에서는 FACTS 기기의 일종인 전력조류 극대화 및 제어 기능과 함께 외란에 의한 과도시의 전력계통 안정화 기능을 수행할 수 있는 TCSC용 전력시스템 안정화 장치 설계에 대하여 연구하였다. TCSC용 전력시스템 안정화 장치 설계시 파라미터 선정은 복잡한 수식이 필요 없고 계산시간을 감소시키며 적은 반복횟수로도 최적해를 찾을 수 있는 자연 생태계의 진화를 모의한 유전 알고리즘을 이용하였다. 전력 시스템의 저주파 진동에 강인성을 갖는 TCSC는 TCR(Thyristor Controlled Reactor)과 커패시터의 병렬구조에 의해 용량성과 유도성에 걸친 범위가지 연속적으로 제어할 수 있는 구조로 이루어져 있다. 이러한 제안된 방법의 강인성을 검증하기 위해 여러 가지 운전조건에 대해 전력계통 안정도 및 고유치를 해석하여 기존의 안정화 장치를 적용한 경우와 비교함 으로써 유용성을 입증하였다.