• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 C
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• pp.1924-1926
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• 2001

A novel wet release process ($\mu$ CARP - Micro Channel Assisted Release Process) for releasing an extreme large-area plate structure without etching hole is proposed and experimented. Etching holes in conventional process reduce a effective area and degrade an optical characteristics by a diffraction. In addition, as the area of a released structure increases, the stietion becomes more serious. The proposed process resolves these problems by the introduction of a micro fluidic channel beneath the structure which will be released. In this paper, a 5 mm${\times}$5mm-single crystal silicon plate structure was released by the proposed $\mu$CARP without etch holes on the structure. The variation in etching time with respect to the of the introduced micro channel is also examined. This process is expected to be beneficial for the actuator of a nano-scale data storage and the scanning mirror.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 D
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• pp.1367-1369
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• 1998

To achieve the ULSI goals of higher density, greater performance and operation speed have been scaled down. However, the reduction of channel length cause undesirable problems such as drop of punchthrough voltage, hot-carrier degradation and high leakage current, etc.. It is shown that the device characteristics depend on process parameters. In this Paper, we catched hold of trends of hot-carrier effects and punchthrough voltages due to variation of some process parameters such as LDD doses(P), spacer lengths, channel doses($BF_2$) and $V_T$ adjusting channel implantation energies using design trend curve (DTC). As the LDD and channel doses increased, hot-carrier phenomena became more severe, and punchthrough voltage was decreased. It were represented that punchthrough and hot carrier effects were critically depend on LDD and channel doses.

• Journal of the korean society of oceanography
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• 제34권3호
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• pp.133-143
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• 1999

We carried out simultaneous and long-time observations of currents across the western channel of the Korea Strait during the period of May, 1994 to September, 1996 in order to understand the spatial and temporal variability of tidal and nontidal currents in the Strait. Results show that currents in the Strait are quite variable in space and time, and they largely consist of mean current and diurnal and semidiurnal tidal currents of about equal magnitudes. The mean currents include the Tsushima Current and the Korea Strait Undercurrent at the center of the channel. The former occupies the upper two-thirds and the latter the lower one-third of the water column. The semidiurnal and diurnal currents are largely rectilinear in the direction of NE-SW and their amplitude variation across the channel appears to be small. However, the diurnal currents at some locations show rotational characteristics with significant nontidal effects. The station close to the Korean coast leads the phase and the phase difference of the semidiurnal current across the channel appears to be less than half an hour while that of the diurnal current is over five hours.

• 대한기계학회논문집B
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• 제32권9호
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• pp.683-694
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• 2008

The performance and durability of Polymer Electrolyte Fuel Cells (PEFCs) are strongly influenced by the uniformity of current density, temperature, species distributions inside a cell In order to obtain uniform distributions in them, the optimal design of flowfield must be a key factor. In this paper, the numerical study of land/channel flowfield optimizations is performed, using a multi-dimensional, multi-phase, non-isothermal PEFC model. Numerical simulations reveal more uniform current density and HFR(High Frequency Resistance) distributions and thus better PEFC performance with narrower land/channel width where the less severe oxygen depletion effect near the land region and more uniform contact resistance variation along the in-plane direction are achieved. The present study elucidates detailed effects of land/channel width and assist in identifying optimal flow-field design strategies for the operation of PEFCs.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.259-262
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• 2003

Superconducting flux flow transistor(SFFT) is based on a control of the Abrikosov vortex flowing along a channel. The induced voltage by moving of the Abrikosov vortex in SFFT is greatly affected by the thickness and width, of channel. In order to fabricate a reproducibility channel in SFFT, we have researched the variation of the critical characteristics of YBCO thin films with the etching time using ICP(Inductively coupled plasma) system. It was certified that the velocity of vortex decreased with increasing the width of channel and was saturated faster in low bias from a simulation. An etching mechanism of YBCO thin films by ICP system was also certified by AFM(Atomic Force Microscope) and by measuring the critical current density with etching time. As measurement result, we could analyze that we should optimize the etching thickness of channel part to construct a flux flow transistor with desired characteristics.

• 대한안전경영과학회지
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• 제20권4호
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• pp.7-13
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• 2018

This study investigates the enhancement of the oxygen diffusion rate in the cathode channel of a proton exchange membrane fuel cell (PEMFC) by pure oscillating flow, which is the same as the mechanism of human breathe. Three-dimensional numerical simulation, which has the full model of the fuel cell including electrochemical reaction, ion and electronic conduction, mass transfer and thermal variation and so on, is performed to show the phenomena in the channel at the case of a steady state. This model could analysis the oscillating flow as a moving mesh calculation coupled with electrochemical reaction on the catalyst layer, however, it needs a lot of calculation time for each case. The two dimensional numerical simulation has carried on for the study of oscillating flow effect in the cathode channel of PEMFC in order to reduce the calculation time. This study shows the diffusion rate of the oxygen increased and the emission rate of the water vapor increased in the channel by oscillating flow without any forced flow.

• 한국수소및신에너지학회논문집
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• 제30권5호
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• pp.448-454
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• 2019

This paper presents a high-efficiency design technique for developing the serialized models of a single-channel pump based on the diameter, flow rate and head as the main performance parameters. The variation in pump performance by changing of the single-channel pump geometry was predicted based on computational fluid dynamics (CFD). Numerical analysis was conducted by solving three-dimensional steady Reynolds-averaged Navier-Stokes equations with the shear stress transport (SST) turbulence model. The tendencies of the hydraulic performance depending on the pump geometry scale were analyzed with the fixed rotational speed. These performances were expressed and evaluated as the functionalization for designing the serialized models of a single-channel pump in this work.

• 한국수소및신에너지학회논문집
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• 제33권5호
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• pp.550-556
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• 2022

In this study, the flow uniformity was analyzed by performing numerical analysis on the 1 kWe internal manifold type solid oxide fuel cell stack according to the channel height of the separator. Also, it was examined by varying the fuel utilization rate and oxygen utilization rate. From the calculation results, we found that as the channel height of the separator decreased, the pressure drop increased exponentially. In addition, it was found that as the channel height of the separator decreased, the gas flow resistance inside the unit cell increased, and the flow resistance increased the pressure drop, thereby improving the flow uniformity inside the stack. Finally, the calculation results showed that as the fuel and oxygen utilization increased, the flow uniformity also improved.

• 한국통신학회논문지
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• 제35권5C호
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• pp.439-444
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• 2010

본 논문에서는 대역확산 워터마킹 시스템을 무선채널 환경에서 부가데이터를 전송하기 위하여 적용할 경우 채널에 의한 영향을 분석하기 위하여 채널용량식을 정보이론적 관점에서 유도하고 분석한다. 부가데이터를 기존의 무선통신 시스템을 통하여 전송하기 위해서는 무선채널을 통과하는 워터마킹 신호가 채널에 의해서 어떻게 영향을 받고, 어느 정도의 데이터를 신뢰할 만한 수준으로 전송가능한지를 판단하는 기준으로서의 채널용량에 관한 연구가 필수적이다. 수치적 결과로부터 대역확산 워터마킹 시스템의 채널용량은 HWR, WNR, PN 길이 및 호스트 시스템의 샘플링 주파수에 의해 결정됨을 알 수 있었다. 또한 적용된 Nakagami-m 페이딩 채널과 Log-normal 새도잉 채널에서 채널 상태 변화에 따른 채널용량의 변화를 확인하였고 다이버시티를 적용했을 경우의 채널용량의 향상 또한 확인하였다. 본 논문에서 다룬 대역확산 워터마킹 시스템의 채널용량의 수식적 결과는 PN 시퀀스를 이용하는 일반적인 대역확산 워터마킹 시스템에 적용할 수 있다.

• 한국통신학회논문지
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• 제30권2A호
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• pp.51-60
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• 2005

본 논문에서는 WCDMA(Wideband Code Division Multiple Access) 단말 모뎀을 위한 개선된 SIR 측정 알고리즘을 제안한다. 제안된 알고리즘은 속도 적응형 IIR 타입의 channel estimator를 적용함으로써 DPCH(Dedicated Physical Channel)의 채널 보상으로 인한 처리 지연을 최소화하였으며, 파일럿 채널인 CPICH(Common Pilot Channel)를 사용하여 페이딩 채널 환경에서 발생하는 신호 전력 감쇄를 보상함으로써 페이딩 환경에서 SIR 측정시 발생하는 SIR 측정 오차를 대폭 감소시켰다. 또한 fading의 변화를 적절히 반영할 수 있도록 IIR 필터를 신호 전력 및 간섭 전력 측정 시에 추가함으로써 SIR 측정에 대한 안정도를 향상시켰다. 제안된 알고리즘과 기존의 SIR 측정 알고리즘과의 성능 비교를 통하여 무선 이동 채널, 특히 고속 이동체 환경에서 제안된 알고리즘의 측정된 SIR의 mean은 최대 약 8dB, jitter는 약 2dB의 향상된 우수한 성능을 보임을 입증하였다.