• 한국광학회지
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• 제18권2호
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• pp.155-161
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• 2007

본 논문에서는 GaN/InGaN 다중양자우물(MQW)의 청색 발광 다이오드(LED)에서의 3차원적인 전류 및 2차원적인 광 분포를 보여 주기 위해 새롭고 간단한 3차원 회로 모델링과 해석이 처음으로 제안되었으며 이를 실험적으로 검증하였다. LED의 회로 파라미터들은 금속 및 에피 박막의 저항과 다이오드만으로 이루어져 있으며 각각의 파라미터는 전송선 모델(TLM) 및 전압-전류의 특성으로부터 얻을 수 있다. 제안된 방법과 회로 파라미터를 상부로 발광하는(top-surface emitting) LED에 적용하여 금속 및 에피 박막의 각 저항 변화에 따라 활성층을 지나가는 전류 분포의 효과를 정량적으로 해석하였다. 그리고 제작된 청색 LED 소자의 발광 분포는 p-전극 주위에서 어두운 발광 분포를 보이는 해석 결과와 유사한 경향을 보여주었다.

• 한국산림과학회지
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• 제97권6호
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• pp.661-668
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• 2008

본 연구는 임업기계화 사업을 추진함에 있어서 임업기계화 사업에 미치는 영향요인을 분석하고, 이들 요인이 사업의 결과 및 효과에 어느 정도 영향을 미치는지 그 관계를 분석하여 향후 임업기계화 사업의 성공적인 집행을 위한 유용한 정책 자료를 제공하고자 수행되었다. 연구방법은 이들 요인들 상호간의 구조관계를 공변량구조모형인 LISREL을 활용하여 분석하였으며, 자료 수집은 임업기계화 사업을 추진 운영하고 있는 사업담당자를 대상으로 설문조사를 실시하였다. 임업기계화 사업성과와 정책만족도, 교육훈련에 관한 응답결과는 보통으로 나타났으며, 정책의 일관성과 법률 및 제도 정비와 임업기계의 보급은 보통보다 낮은 것으로 나타났다. 향후 임업기계화 정책 추진에서 법률 및 제도 정비를 통한 일관성 있는 정책과 임업기계의 보급률을 높이는 정책을 추진할 필요가 있는 것으로 나타났다. 또한 임업기계화 사업에서 정책기반, 임업기계보급과 교육훈련 모두 정책성과에 정(+)의 영향을 미치는 것으로 나타났으며, 정책성과는 정책만족도에 정(+)의 영향을 미치는 것으로 나타났다. 따라서 향후 임업기계화 정책사업을 성공적으로 추진하고 정착시키기 위해서는 임업기계화 정책기반 조성도 중요하지만 더욱 많은 임업기계의 보급 및 오퍼레이터의 교육 훈련이 필요하다는 것을 알 수 있었다.

• 한국음향학회:학술대회논문집
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• 한국음향학회 2000년도 하계학술발표대회 논문집 제19권 1호
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• pp.337-338
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• 2000

The perceptual filter for speech enhancement was analytically derived where the frequency content of the input noisy signal was made the same as that of the estimated clean signal in auditory domain. However, the analytical derivation should rely on the deconvolution associated with the spreading function in the psychoacoustic model, which results in an ill-conditioned problem. In order to cope with the problem associated with the deconvolution, we propose a novel psychoacoustic model based speech enhancement filter whose principle is the same as the perceptual filter, however the filter is derived by a constrained optimization which provides solutions to the ill-conditioned problem.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.166-170
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• 1991

An advanced on-resistance model of VDMOS devices in the low voltage regime is proposed and verified by 2-D device simulations. The model considers the lateral gaussian doping profiles in the channel region and exact current spreading angles in the epitaxial layer for both linear and cellular geometries by employing the conformal mapping. It is found out that the on-resistance of low voltage VDMOS may be overestimated considerably if it is analyzed by the conventional method. The 2-D device simulation results show that the proposed model is valid for all ranges of cell spacings and breakdown voltages.

• 대한전기학회논문지
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• 제43권6호
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• pp.951-957
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• 1994

We present a new model for the series resistance of inverted-staggered amorphous silicon (a-Si) thin film transistors (TFT's) by employing the current spreading under the source and the drain contacts as well as the space charge limited current model. The calculated results based on our model have been in good agreements with the measured data over a wide range of applied voltage, gate-to-source and gate-to-drain overlap length, channel length, and operating temperature. Our model shows that the contribution of the series resistances to the current-voltage (I-V) characteristics of the a-Si TFT in the linear regime is more significant at low drain and high gate voltages, for short channel and small overlap length, and at low operating temperature, which have been verified successfully by the experimental measurements.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제13권4호
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• pp.291-297
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• 2013

Chaotic dynamics have been studied by many researchers in the fields of biology, physics, and engineering. Interest in chaos is also expanding to the social sciences such as politics, economics, and others, including the prediction of societal events. The concept of leisure has developed from a passive concept correlated with relaxation, entertainment, and ideology formation into a positive concept that assumes a more active role. As information and communications technology develops, digital leisure activity is expected to continue spreading. This expansion of digital leisure function correctly, as well as. Traditional leisure activity functions correctly more, whereas digital leisure activity is predicted to function incorrectly more often. In this paper, we propose a mathematical addiction model of digital leisure that deals with its dysfunctions such as addiction to digital leisure, including computer games, internet search, internet chatting, and social media. Herein, to solve addiction to digital leisure, we propose a model derived from a nicotine addiction.

• The Journal of the Acoustical Society of Korea
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• 제19권3E호
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• pp.12-18
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• 2000

Psychoacoustic model based methods have recently been introduced in order to enhance speech signals corrupted by ambient noise. In particular, the perceptual filter is analytically derived where the frequency content of the input noisy signal is made the same as that of the estimated clean signal in auditory domain. However, the analytical derivation should rely on the deconvolution associated with the spreading function in the psychoacoustic model, which results in an ill-conditioned problem. In order to cope with the problem associated with the deconvolution, we propose a novel psychoacoustic model based speech enhancement filter whose principle is the same as the perceptual filter, however the filter is derived by a constrained optimization which provides solutions to the ill-conditioned problem. It is demonstrated with artificially generated signals that the proposed filter operates according to the principle. It is shown that superior performance results from the proposed filter over the perceptual filter provided that a clean speech signal is separable from noise.

• The Journal of the Acoustical Society of Korea
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• 제20권2E호
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• pp.9-16
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• 2001

A psychoacoustic model based noise shaping method which shapes the noise in the frequency domain is proposed, where its presence with a host signal will not be perceptually noticeable. The derivation of imperceptible noise levels from the masking thresholds of the signal involves a deconvolution associated with the spreading function in the psychoacoustic model, which results in an ill-conditioned problem. In this paper, the problem is formulated as a constrained optimization, and it is demonstrated that the solution provides noise shaping where the noise excitation level conforms to the masking thresholds of the signal, and thus the noises embedded in the signal will not be perceived by human ear.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(1)
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• pp.25-28
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• 2000

In this paper, we assume various number of multipaths in one chip duration according to spreading bandwidth. And we take into account of the effects of autocorrelation and relative phases among multipath components within one chip duration, and analyze fading effects. We derive the average error probability for different number of users. Then, we compare the performance of W-CDMA systems with different bandwidths. From the simulation results for different band-widths, wideband CDMA systems show better performance than narrowband CDMA systems in vehicular and pedestrian environments.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(3)
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• pp.125-128
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• 2000

In this paper, we proposed the high quality digital audio watermarking algorithm in the frequency domain. The spread spectrum technique is used to encrypted a stream of information by spreading the data as much of the frequency spectrum as possible. It's technique adapt well to data hiding in audio signal. We have used the perceptual model and MDCT/IMDCT for the high qualify digital audio watermarking. The proposed watermark algorithm preserved high quality audio data from watermark signal.