• 대한의용생체공학회:의공학회지
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• 제12권3호
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• pp.185-190
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• 1991

An automatized latency calculation method of an e-OAE(evoked otacoustic emission) is proposed. The e-OAE signal measured from a normal adult is averaged 1000 times to remove noises. This averaged signal is converted to digital signal and that is processed by IBM-AT computer for latency calculation. we separate the stimulated and the emitted signal on the time domain by a modified LPC (linear prediction coding) spectrum, and the latency is calculated by cross-correlation method. By proposed latency calculation method the latency is 7.9[ms] for normal adult. The performance of the proposed method is also compared with that of the auto-correlation and cross performance of the proposed method is also compared with that of the auto-correlation and cross-correlation method. The result show that the proposed method has same precision with the conventional methods and can automatically calculate latency without subjective observation.

• 한국ITS학회 논문지
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• 제4권1호
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• pp.57-62
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• 2005

본 논문에서는 OFDM 시스템에서 임펄스 신호를 이용한 채널 추정방법을 제안한다. 채널 응답을 추정하기 위해 주파수 영역에서 새로운 프리엠블을 사용하여 시간영역에서 16샘플 간격으로 4개의 구간으로 나누고, 각 구간에서 임펄스 응답이 나오도록 한다. 이 임펄스 신호들은 한 OFDM 심볼동안에 전송한다. 수신단에서, 각 구간별 임펄스 신호를 더하여 평균을 취한다. 평균된 임펄스 응답에서 최대지연 이후 데이터는 잡음이기 때문에 zero padding을 하여 제거하고 FFT를 수행하여 채널 추정 응답을 찾아낸다. 제안된 채널 추정방법을 이용한 WLAN 시스템의 BER성능은 IEEE802.11a에서 사용하는 긴 훈련신호(long preamble)를 이용한 기존의 채널 추정 방법에 비해 약 3dB 성능 향상을 보인다.

• 대한기계학회논문집B
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• 제26권8호
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• pp.1088-1094
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• 2002

A channel flow with a high Reynolds number but coarse grids is numerically studied to investigate the prediction possibility of its turbulence which is three-dimensional and time-dependent. In the present paper, a Reynolds-Averaged Navier-Stokes (RANS) model, a Large Eddy Simulation (LES) and a Navier-Stokes equation with no model are tested with a new approach of hybrid RANS/LES, which reduces to RANS model in the boundary layers and at separation, and to Smagorinsky-like LES downstream of separation, and then compared with each other. It is found that the simulations of hybrid RANS/LES method sustain turbulence like those of LES and with no model, and the results are stable and fairly accurate. This indicates strongly that gradual improvements could lead to a simple, stable, and accurate approach to predict turbulence phenomena of wall-bounded flow.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1994년도 추계학술대회
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• pp.124-127
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• 1994

A technique based on bispectrun averaging is described for generally recovering the signal waveform from a set of noisy signals with variable signal delay. The technique does not require explicit tune alignment of signals and any initial estimate of signal. The new method is suggested and is compared with other methods. This method are numerically investigated using computer generated-data and a physiological signal and noise Some experimental results for the evoked potential studios that demonstrate the technique are given. The results show the effectiveness of the technique: various potential applications of the technique might be expected.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 추계학술대회 논문집 학회본부
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• pp.394-398
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• 1988

In this paper, the time-averaged behavior of the three-phase Inductor-Converter Bridge (ICB) circuit has been analyzed by using the state-space averaging method. The results are in closed form far from the results obtained by using the Fourier series. Therefore, the computational difficulties of the infinite Fourier series can be avoided and the results derived in this paper are available especially in real time control. Unlike the SFC, $S^{4}LCL$, DFC and other circuits which have time varying switching intervals for a constant time-averaged value of coil voltage, the ICB circuits operate with a clock-driven sequence of gate pulses which have constant switching intervals.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
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• pp.237-239
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• 2003

The present study investigates on design optimization of rib-roughened two-dimensional channel to enhance turbulent heat transfer. Response surface method with Reynolds-averaged Navier-Stokes analysis is used as an optimization technique. Standard $k-{\varepsilon}$model with wall functions is adopted as a turbulence closure. The objective function is defined as a linear combination of heat transfer and friction drag coefficients with weighting factor. Computational results for overall heat transfer rate show good agreements with experimental data. Four design variables are optimized for weighting factor of 0.02.

• 한국해양공학회지
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• 제11권4호
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• pp.141-151
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• 1997

This paper deals with a numerical study of flow-guider applied to controlling current in a bay. Two dimensional numerical model for tidal currents based on the depth averaged equation is developed and standard k-.epsilon. model is adopted to determine the turbulence diffusion. Equations are described in a generalized coordinate system to be implemented by non-staggered grid system and discretized by using finite volume method. Unsteady flow is simulated by fully implicit scheme. Hybrid scheme and central differencing are used to compute the convective terms and source terms, respectively. The tidal current in a rectangular bay is simulated and it gives satisfactory results. The realistic and distinct models of a large structure placed in bay are also exemplified with or without flow-guiders. The simulation results show that the flow-guider gives the residual tidal current in the bay by the different flux with respect to the direction of tidal current.

• 한국수자원학회논문집
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• 제33권S1호
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• pp.997-1002
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• 2000

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2000년도 학술발표회 논문집
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• pp.997-1002
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• 2000

No Abstract (See Full-text)

• 한국항공우주학회지
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• 제35권2호
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• pp.124-129
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• 2007

동 연구에서는 전진비행하는 로터의 평균 유입류 예측기법 중 Drees 선형모델, 몇가지 변형된 형태의 Mangler & Squire 모델을 서로 비교하여 각 유입류 모델의 특성을 알아내고, KARI 자체 자유후류기법 코드의 해석결과를 함께 비교하여 각 유입류 예측기법의 특성을 파악하였다. 각 예측기법의 비교를 위해 유입류 실험치가 존재하는 로터에 대하여 전진비 0.15, 0.23 및 0.30의 3가지 비행조건을 적용하여 예측한 결과를 비교 분석하였다. Drees 모델의 경우 비교적 실험치에 근접하게 예측하나, 선형모델의 한계로 인해 유입류의 비균일성을 모델링하기에는 미흡하며, Mangler & Squire 모델은 끝단을 제외하고는 비교적 실험치에 근접하게 예측함을 알 수 있었으며, KARI의 자유후류기법은 유입류의 비균일성을 매우 잘 예측하나, 동체에 의한 올려흐름 효과, 후퇴부에서의 동적실속 효과 등의 추가 고려가 필요함을 알 수 있었다.