• 한국해양공학회지
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• 제7권1호
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• pp.13-24
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• 1993

해양오염은 환경파괴의 주요 인자이다. 해양바닥에 가라않은 오염물질을 근본적으로 제거하는 문제와는 별도로, 파동(wave)에 의해 그것이 자동적으로확산될 수가 있다. 파문(ripple)으로 덮혀진 해저(sea bottom)에서 표면의 중력파에 의한 물의 수평방향 요동운동은 와류(vrotices)를 발생시칸다. 이런한 유동장은 해저 침전물을 부유시켜 멀리까지 화가신시키는 작용을 한다.파문주위의 유동장을 살펴보면 모서리(crest)에서 발생된 와류로 인해 정상유동성분이 존재하며 이런한 정상유동은 파문의 주기적 형상으로인해 다분히 순환적이다. 이ㅔ 파동에 의한 요동운동이 가세하면 Taylor 와류와 같은 효과를 보여 줄 것이다. 해저부근에서의 이러한 확산효과를 보기 위하여, 해양유동을 단순화하여 최근 널리 이용되고 있는 혼돈이론을 가미시켰다. 아주 단순한 유동이라도 복잡한 입자의 궤적을 나타내며 입자의 확산과 연관됨을 수치해석을 이용하여 보여준다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1850-1852
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• 2000

In this paper, new Partial Discharge (PD) detection technique using Pockels cell was proposed and considerable apparent chaotic characteristics were discussed. For this purpose, PD was generated from needle-plane electrode in air and detected by optical measuring system using Pockels cell, based on Mach-Zehnder interferometer, consisting of He-Ne laser, single mode optical fiber, 50/50 beam splitter and photo detector. A qualitative analysis was carried out by drawing Return map for the normalized time series of the detected PD signals. The results are as follows:(a) Fixed points, between 0.7 and 1.0, are appeared clearly in the right upper area of the return map as the increase in the number of obtained data.(b) Considerable periodicity have been remarked even though exact period and length can not be determined.(c) The self-similarity can be also observed inasmuch as the late paths do not follow the previous ones. Accordingly, exact quantitative analysis such as embedding dimension, fractal dimension, and Lyapunov exponents should be carried out for deducing the quantitative properties regarding PD phenomena.

• 한국정보처리학회논문지
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• 제6권5호
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• pp.1312-1322
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• 1999

The world of linearity, which is regular, predictable and irrelevant to time sequence in most natural phenomenon, is a very small part. In fact, signals generated from natural phenomenon with which we're in contact are showed only slight linearity. Therefore it is very difficult to understand and analyze natural phenomenon with only predictable and regular linear systems. Due to these reasons researches concerning non-linear signals that of analysis were excluded being regarded as noise are being actively carried out. Countless signals generated from nonlinear system have the information about itself, and analyzing those signals and get information from it, that will be able to be used effectively in so may fields. Hence, in this paper we used a higher order spectrum, especially the bispectrum. After we prove the validity applying bispectrum to logistic map, which is typical chaotic signal. Subsequently by showing the result applying for actual signal analysis of EEG according to auditory stimuli, we show that higher order spectra is a very useful parameter in analysis of non-linear signals and the result of EEG analysis according to auditory stimuli.

• 대한수학회지
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• 제56권6호
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• pp.1561-1597
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• 2019

In this paper we introduce the notions of topological entropy and topological pressure for non-autonomous iterated function systems (or NAIFSs for short) on countably infinite alphabets. NAIFSs differ from the usual (autonomous) iterated function systems, they are given [32] by a sequence of collections of continuous maps on a compact topological space, where maps are allowed to vary between iterations. Several basic properties of topological pressure and topological entropy of NAIFSs are provided. Especially, we generalize the classical Bowen's result to NAIFSs ensures that the topological entropy is concentrated on the set of nonwandering points. Then, we define the notion of specification property, under which, the NAIFSs have positive topological entropy and all points are entropy points. In particular, each NAIFS with the specification property is topologically chaotic. Additionally, the ${\ast}$-expansive property for NAIFSs is introduced. We will prove that the topological pressure of any continuous potential can be computed as a limit at a definite size scale whenever the NAIFS satisfies the ${\ast}$-expansive property. Finally, we study the NAIFSs induced by expanding maps. We prove that these NAIFSs having the specification and ${\ast}$-expansive properties.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2009년도 춘계학술대회
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• pp.171-174
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• 2009

비선형 동력학 시스템으로 구성된 전력 수요의 시계열 데이터를 예측하기 위해 적용된 신경망 및 퍼지 적응 알고리즘 등은 예측오차가 상대적으로 크게 나타났다. 이는 전력수요 시계열 데이터가 가지고 있는 카오스적인 성질에 기인하며 이중 초기값에 민감한 의존성은 장기적인 예측을 더욱더 어렵게 하는 요인으로 작용한다. 전력수요 시계열 데이터가 가지고 있는 카오스적인 성질을 정량 및 정성적인 방식으로 분석을 수행하고, 시스템 동력학적 특성의 정량분석에 이용되는 Lyapunov 지수를 이용하여 어트랙터 재구성, 다차원 카오스 시계열 데이터를 예측하는 방식으로 수요예측 시뮬레이션을 수행하고 결과를 비교 평가하여 기존 제안방식보다 실용적이며 효과적임을 확인한다.

• 임상간호연구
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• 제27권3호
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• pp.221-232
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• 2021

Purpose: The purpose of this study was to explore emergency room nurse's work experiences during the COVID-19 pandemic. Methods: Data were collected from 15 registered nurses working in the emergency room between October, 10th and December 15th, 2020, through focus group interviews and in depth interviews. Collected data were analyzed using Colaizzi's phenomenological method. Results: The study derived four categories and eight themes. The four categories are 'sense of cringing with fear', 'nursing in chaotic situation', 'lonely struggles', and 'career growth as a nurse'. Emergency room nurses experienced fear and confusion in the COVID-19 pandemic, but overcame the crisis and had positive experiences of professional growth as a nurse. Conclusion: To protect emergency room nurses from infectious disease and improve their professional quality of life during the COVID-19 pandemic appropriate education and healthcare resource should be provided. It is necessary to reflect clinical worker's opinions and improve the delivery system of guideline to reduce confusion in the field and develop practical infectious disease control guideline. Furthermore, better working conditions, appropriate rewards and social and mental support should be provided for nurses in emergency room.

• 한국전자통신학회논문지
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• 제9권10호
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• pp.1125-1130
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• 2014

네트워크의 속도가 향상 되면서 정보를 담고 있는 콘텐츠의 양과 질이 급격히 증가 하고 있다. 이런 정보의 급격한 변화에 맞추어 콘텐츠를 통신상에서 보호할 수 있는 혼돈신호를 이용한 새로운 통신 프로토콜을 다음과 같이 제안한다. 혼돈시스템은 초기치 민감성과 발생된 신호가 잡음과 유사하여 예측이 불가능한 특성을 가지고 있다. 우리는 이런 특성을 갖고 있는 두 개의 혼돈시스템 $F(X_n,Y_n)$와 $G(A_n,B_n)$를 구성하고 F 혼돈시스템의 신호로 G 혼돈시스템을 동기화시켜 발생되는 동일한 혼돈신호를 대칭키로 사용하고, 이렇게 구성된 암호 채널로 데이터를 송수신 하는 방법을 설계 하였다. 제안된 방법을 검증하기 위해 이미지의 암호화 및 복호화로 그 결과를 보였다. 우리가 제안한 방법은 기존의 암호화 통신과 다른 방법으로 추후 관련 분야의 연구에 초석이 될 것으로 생각된다.

• 대한의료기공학회지
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• 제15권1호
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• pp.44-60
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• 2015

Objective : The purpose of this study is to investigate the effect of Su-Gi therapy for Bell's palsy by using DITI. Methods : We investigated 16 patients with Bell's palsy who had visited in the H Korean medicine hospital in Gyeonggi Province from December 27th, 2010 to April 8th, 2015. The Su-Gi therapy was done by 1 times daily. We evaluated the change of them by using Digital Infrared Thermographic Imaging and Yanagihara's unweighted grading system. Results : There aren't meaningful differences in values for the meridian points in pretest and posttest which were observed by DITI of abnormal side and normal side. There are meaningful differences in values, for abnormal side and normal side of the meridian points in pretest and posttest of DITI. It was of significance that pretest Y and average ΔT of each the meridian points in the type of hyperthermia but not in the type of hypothermia. In the Correlation analysis of values of pretest and posttest, chaotic aspects of body heat distribution in the pretest change as a relatively consistent aspects in the posttest. It wasn't of significance that Correlation Analysis of Ups and downs in temperature of TE17 and Recovery speed observed by ΔY. In simple regression analysis of posttest's Y-system values against absolute ΔT by subtracting ΔTE17 from ΔST6, we didn't predict in the pretest, but could predict significantly in the posttest(Regression coefficient : -2.11) In the regression analysis result of the meridian points' ||pretest ΔT|-|posttest ΔT||, 陽白(GB14) and 頰車(ST6) are of significance (Total R-Square=0.447). But we couldn't obtain final regression analysis model. Conclusions: These results suggest that Su-Gi therapy may be effective for Bell's palsy.

• 전자공학회논문지S
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• 제35S권11호
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• pp.88-95
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• 1998

본 논문은 인공생명 기법을 이용하여 생물의 정보처리 시스템을 구현하고자 하는 것이다. 자연계의 생물은 그 자체로 훌륭한 정보처리 시스템이다. 생물체는 하나의 생식 세포로부터 발생된다. 또한 이 개체의 종은 진화의 과정을 통해 환경에 적응한다. 본 논문에서는 이와 같은 생물학적인 발생과 진화의 개념을 이용하여 신경망을 설계하는 방법을 제안한다. 생물체의 개체발생은 발생모델의 하나인 셀룰라 오토마다(CA)를 통하여 구현하였고 진화과정은 진화 알고리즘(EAs)을 사용하였다. 우리는 이와 같이 구현한 '진화하는 셀룰라 오토마타 신경망'을 줄여서 ECANS1이라 명명하였다. 셀 사이의 연결은 CA 법칙에 의하여 결정되며, 셀의 초기 패턴이 진화함으로써 유용한 신경망을 찾아낸다. 신경망의 각 셀 즉 뉴런은 생물의 발화 ${\cdot}$ 비발화의 특성을 갖는 카오스 뉴런 모델을 사용하였다. 그리고 신경마의 최종 출력값은 뉴런의 발화 빈도로서 나타내었다. 제안한 방법은 Exclusive-OR 문제 및 패리티 문제에 적용함으로써 그 유효성을 검증하였다.

• 지능정보연구
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• 제5권1호
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• pp.103-123
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• 1999

Input filtering as a preprocessing method is so much crucial to get good performance in time series forecasting. There are a few preprocessing methods (i.e. ARMA outputs as time domain filters, and Fourier transform or wavelet transform as time-frequency domain filters) for handling time series. Specially, the time-frequency domain filters describe the fractal structure of financial markets better than the time domain filters due to theoretically additional frequency information. Therefore, we, first of all, try to describe and analyze specially some issues on the effectiveness of different filtering methods from viewpoint of the performance of a neural network based forecasting. And then we discuss about neural network model architecture issues, for example, what type of neural network learning architecture is selected for our time series forecasting, and what input size should be applied to a model. In this study an input selection problem is limited to a size selection of the lagged input variables. To solve this problem, we simulate on analyzing and comparing a few neural networks having different model architecture and also use an embedding dimension measure as chaotic time series analysis or nonlinear dynamic analysis to reduce the dimensionality (i.e. the size of time delayed input variables) of the models. Throughout our study, experiments for integration methods of joint time-frequency analysis and neural network techniques are applied to a case study of daily Korean won / U. S dollar exchange returns and finally we suggest an integration framework for future research from our experimental results.