• 대한수학회논문집
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• 제37권2호
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• pp.423-443
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• 2022

We study the existence and long-time behavior of weak solutions to a class of strongly degenerate semilinear parabolic equations with exponential nonlinearities on ℝ^N. To overcome some significant difficulty caused by the lack of compactness of the embeddings, the existence of a global attractor is proved by combining the tail estimates method and the asymptotic a priori estimate method.

• 대한수학회지
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• 제58권5호
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• pp.1279-1298
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• 2021

The aim of this paper is to prove the existence of the global attractor of the Cauchy problem for a semilinear degenerate hyperbolic equation involving strongly degenerate elliptic differential operators. The attractor is characterized as the unstable manifold of the set of stationary points, due to the existence of a Lyapunov functional.

• 음성과학
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• 제10권2호
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• pp.45-55
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• 2003

Strange attractor can be used as a presentation method for signal processing. Fractal dimension is well known method that extract features from attractor. Even though the method provides powerful capabilities for speech processing, there is drawback which should be solved in advance. Normally, the size of the raw signal should be long enough for processing if we use the fractal dimension method. However, in the area of connected-digits problem, normally, syllable or semi-syllable based processing is applied. In this case, there is no evidence that we have sufficient data or not to extract characteristics of attractor. This paper discusses the relationship between the size of the signal data and the calculation result of fractal dimension, and also discusses the efficient way to be applied to connected-digit recognition.

• 한국정밀공학회지
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• 제19권1호
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• pp.158-164
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• 2002

This paper proposes the optimization of ultrasonic signal recognition in ferrite carbon steel weld zone using neural networks. For these purposes, the ultrasonic signals for defects as porosity, incomplete penetration and slag inclusion in the weld zone are acquired in the type of time series data. And then their applications evaluated feature extraction based on the time-frequency-attractor domain(peak to peak, rise time, rise slope, fall time, fall slope, pulse duration, power spectrum, and bandwidth) and attractor characteristics (fractal dimension and attractor quadrant) etc. The proposed neural networks system in this study can enhances performance of ultrasonic signal recognition.

• 음성과학
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• 제9권2호
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• pp.147-155
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• 2002

In the area of speech processing, raw signals used to be presented into 2D format. However, such kind of presentation methods have limitation to extract characteristics from the signal because of the presentation method. Generally, not much information can be detected from the 2D signal. Strange attractor in the field of chaos theory provides a 3D presentation method. In the area of recognition problem, signal presentation method is very important because good features can be detected from a good presentation. This paper discusses a new feature extraction method that extracts features from a cycle of the strange attractor. A neural network is used to check whether the method extracts suitable features or not. The result shows very good points that can be applied to some areas of signal processing.

• The Journal of the Acoustical Society of Korea
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• 제13권2E호
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• pp.26-31
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• 1994

화자인식을 위한 음성특징을 카오스의 어트랙터와 신경망를 이용해서 추출하는 방법을 제시한다. 기존의 음성신호 표현방법과 특징 추출법은 음성인식 시스템에서 별 무리가 없이 사용되었으나 2차원 표현에서 오는 한계는 아직까지 극복해야할 과제로 남아있다. 본 연구에서는 최근 각광받고있는 새로운 시그날표현기법인 카오스이론이 스트레인저 어트랙터를 이용하여 음성특징을 추출하는 화자인식시스템에 적용하고자 한다. 입력된 음성신호는 3차원 공간안에서 어트랙터라 불리우는 기하학적인 형태로 표현되는데 이 3차원 어트랙터를 이용하면 기존의 2차원적인 표현으로부터 얻는 특징보다 더 많은 정보를 추출할 수 있을 것이다. 특징추출 기법은 3가지를 제안하였고 각 기법으로 추출된 특징벡터는 신경회로망을 통해 학습되어 인식률을 실험하였다. 제시한 기법들에 따라 다르나 인식률은 약 82%부터 96%까지 나타났다.

• Korean Journal of Mathematics
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• 제9권1호
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• pp.67-73
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• 2001

For some equation related with exponential function, we seek roots and find the properties of the roots. By using the relation of the roots and attractors, we find a region in the basin of attraction of the attractor at infinity for Newton's method for solving given equation.

• 대한수학회보
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• 제37권2호
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• pp.273-283
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• 2000

In this paper we consider two delay equations with in-finite delay. We will give two sufficient conditions for the positive and zero equilibriums of these equations to be a global attractor respectively.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2001년도 춘계종합학술대회
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• pp.711-714
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• 2001

We present a detailed analysis of the behavior of a multiple-attractor cellular automata.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제6권2호
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• pp.53-62
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• 2002

In this paper we analyze the behavior of linear multiple attractor cellular automata having two-predecessors.