• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.786-791
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• 2007

Statistical differences between men and women are investigated for a total of eleven joint motions during level walking. Human locomotion which exhibits nonlinear dynamical behaviors is quantified by the chaos analysis. Time series of joint motions was obtained from gait experiments with ten young males and ten young females. Body motions were captured using eight video cameras, and the corresponding angular displacements of the neck and the upper body and lower extremity were computed by motion analysis software. The maximal Lyapunov exponents for eleven joints were calculated from attractors constructed and then were analyzed statistically by one-way ANOVA test to find any difference between the genders. This study shows that sexual differences in joint motions were statistically significant at the shoulder, knee and hip joints.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.161-164
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• 1995

Nonlinear analysis of various phenomena has been developed with improvement of computer. The characteristics form nonlinear analysis are available in monitoring and diagnosis state of system. There are many nonlinear property in cutting process, but nonlinear signals have been considered as noise. In this study, nonlinear analysis technique is applied and it will be verified that cutting force is chaos by calculating Lyapunov exponents,fractal dimension and embedding dimension. The relation between characteristic parameter calculated form sensor signal and various cutting condition is investigated.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2003년도 추계종합학술대회
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• pp.589-593
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• 2003

In this paper, we propose that the chaotic behavior analysis in the mobile robot of embedding Chua's equation with obstacle. In order to analysis of chaotic behavior in the mobile robot, we apply not only qualitative analysis such as time-series, embedding phase plane, but also quantitative analysis such as Lyapunov exponent in the mobile robot with obstacle. In the obstacle, we only assume that all obstacles in the chaos trajectory surface in which robot workspace has an unstable limit cycle with Van der Pol equation.

• 한국지능시스템학회논문지
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• 제13권6호
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• pp.729-736
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• 2003

In this paper, we propose that the chaotic behavior analysis in the mobile robot of embedding some chaotic such as Chua`s equation, Arnold equation with obstacle. In order to analysis of chaotic behavior in the mobile robot, we apply not only qualitative analysis such as time-series, embedding phase plane, but also quantitative analysis such as Lyapunov exponent In the mobile robot with obstacle. We consider that there are two type of obstacle, one is fixed obstacle and the other is VDP obstacle which have an unstable limit cycle. In the VDP obstacles case, we only assume that all obstacles in the chaos trajectory surface in which robot workspace has an unstable limit cycle with Van der Pol equation.

• 한국정보통신학회논문지
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• 제8권7호
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• pp.1410-1417
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• 2004

본 논문에서는 Arnold 방정식, Chua 방정식, 하이퍼카오스 방정식을 이동 로봇에 내장한 카오스 이동 로봇에서의 카오스 거동을 해석하였다. 이동 로봇에서의 카오스 거동을 분석하기 위해서 시계열데이터, 임베딩 위상공간의 정성적인 분석뿐만 아니라 리아프노프 지수와 같은 정량적인 분석을 수행하였다.

• Journal of Welding and Joining
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• 제16권5호
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• pp.108-118
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• 1998

This study proposes th analysis and evaluation method of time series ultrasonic signal using the chaos feature extraction for ultrasonic pattern recognition. Features extracted from time series data using the chaos time series signal analyze quantitatively weld defects. For this purpose, analysis objective in this study is fractal dimension and Lyapunov exponent. Trajectory changes in the strange attractor indicated that even same type of defects carried substantial difference in chaosity resulting from distance shifts such as 0.5 and 1.0 skip distance. Such differences in chaosity enables the evaluation of unique features of defects in the weld zone. In quantitative chaos feature extraction, feature values of 4.511 and 0.091 in the case of side hole and 4.539 and 0.115 in the case of vertical hole were proposed on the basis of fractal dimension and Lyapunov exponent. Proposed chaos feature extraction in this study can enhances ultrasonic pattern recognition results from defect signals of weld zone such as side hole and vertical hole.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.109-114
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• 2002

The purpose of this study is to propose the general method for evaluating the equivalent damping ratios of a structure with supplemental response control dampers. We define Lyapunov function of which derivative can be expressed in autoregressive form and evaluate the equivalent damping ratios by using Lyapunov function and its derivative. This Lyapunov function may be called as generalized structural energy. In this study, it is assumed that the response of a structure is stationary random process and control dampers do not affect the modal shapes of a structure, and the structure has proportional damping. Proposed method can be used to get the equivalent damping ratios of a structure with non-linear control dampers such as friction dampers as well as linear control dampers. To show the effectiveness of the proposed method. we evaluate the equivalent damping ratios of a structure with viscous dampers. AMDs. and friction dampers. The equivalent damping ratios from proposed method are compared to those from eigenvalue analysis for linear control dampers. and those from time history analysis for non-linear control dampers. respectively.

• 한국감성과학회:학술대회논문집
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• 한국감성과학회 1997년도 한국감성과학회 연차학술대회논문집
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• pp.69-74
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• 1997

Sleep deprivation may affect the brain functions such as cognition and, consequentoy, dynamics of the EEG. we examiced the effects of sleep deprivation on chaoticity of EEG. Five volunteers were sleep-deprived over a period of 24 hours, They were checked by EEG during two days, the first day of baseline period, EEGs were reorded form 16 channels for nonlinear analysis. We dmployed a method of minimum cmbedding dimension to calculate the first positive Lyapunov exponent. For limited noisy data, this algorithm was strikingly faster and more accurate than previous ones. Our results show that the sleep deprived volunteers had lower values of the first positive Lyapunov exponent at ten channels (Fp$\_$1/, F$\_$4/, F$\_$8/, T$\_$4/, T$\_$5/, C$\_$3/, C$\_$4/, P$\_$3/, p$\_$4, O$\_$1/) compared with the values of baseline periods. These results suggested that sleep deprivation leads to decreawe of chaotic activity in brain and impairment of the information processing in the brain. We suggested that nonlinear analysis of the EEG before and after sleep deprivation may offer fruitful perspectives for understanding the role o f sleep deprivation on the brain function.

• 한국전자통신학회논문지
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• 제8권11호
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• pp.1691-1696
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• 2013

본 논문에서는 순환형 하이브리드 초소형 에너지 수확장치 장치에서 존재하는 거동해석을 수행한다. 이 거동해석은 더 많은 에너지를 생산하기 위해서 비선형 시스템이 요구되므로 비선형 시스템의 존재 유무를 확인하는 것이다. 이를 위해 먼저 타켄스의 매립법을 통한 위상 공간을 재구성한다. 또한 위상 공간을 이용하여 포엔카래 맵을 구성하고 리아프노프 지수를 구하여 분석한다.

• 감성과학
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• 제1권1호
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• pp.69-78
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• 1998

Sleep deprivation may affect the brain functions such as cognition and consequently, dynamics of the BEG. We examined the effects of sleep deprivation on chaoticity of the EEG. Five volunteers were sleep-deprived over a period of 24 hours They were checked by EEG during two days. thc first day of baseline period and the second day of total sleep deprivation period. EEGs were recorded from 16 channels for nonlinear analysis. We employed a method of minimum embedding dimension to calculate the first positive Lyapunov exponent. Fer limited noisy data, this algorithm was strikingly faster and more accurate than previous ones. Our results show that the sleep deprived volunteers had lower values of the first positive Lyapunov exponent at ten channels (Fp1, F4. F8. T4, T5. C3, C4. P3. P4. O1) compared with the values of baseline periods. These results suggested that sleep deprivation leads to decrease of chaotic activity in brain and impairment of the information processing in the brain. We suggested that nonlinear analysis of the EEG before and after sleep deprivation may offer fruitful perspectives for understanding the role if sleep and the effects of sleep deprivation on the brain function.