• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.30 no.4 s.247
• /
• pp.435-441
• /
• 2006

The anterior cruciate ligament(ACL) is an important stabilizer of knee joint. The ACL injury of knee is common and a serious ACL injury leads to ligament reconstruction surgery. Gait analysis is essential to identify knee condition of patients who display abnormal gait. The purpose of this study is to evaluate and classify knee condition of ACL deficient patients using a nonlinear dynamic method. The nonlinear method focuses on understanding how variations in the gait pattern change over time. The experiments were carried out for 17 subjects(l2 healthy subjects and five subjects with unilateral deficiency) walking on a motorized treadmill for 100 seconds. Three dimensional kinematics of the lower extremity were collected by using four cameras and KWON 3D motion analysis system. The largest Lyapunov exponent calculated from knee joint flexion-extension time series was used to quantify knee stability. The results revealed the difference between healthy subjects and patients. The deficient knee was significantly unstable compared with the contralateral knee. This study suggests an evaluation scheme of the severity of injury and the level of recovery. The proposed Lyapunov exponent can be used in rehabilitation and diagnosis of recoverable patients.

• Journal of Korea Water Resources Association
• /
• v.37 no.12
• /
• pp.993-1007
• /
• 2004

There are many different techniques for the estimation of the Hurst exponent. However, the techniques can produce different characteristics for the persistence of a time series each other. This study uses several techniques such as adjusted range, resealed range(RR) analysis, modified restated range(MRR) analysis, 1/f power spectral density analysis, Maximum Likelihood Estimation(MLE), detrended fluctuations analysis(DFA), and aggregated variance time(AVT)method for the Hurst exponent estimation. The generated time series from chaos and stochastic systems are analyzed for the comparative study of the techniques. Then this study discusses the advantages and disadvantages of the techniques and also the limitations of them.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.12 no.5
• /
• pp.977-982
• /
• 2017

Recently, the effort that converge the sport and ICT continues together with developing ICT. The game is a representative example. The digital sport is developing as mixed type that are composed with sport and digital such as screen golf and screen bowling. The addiction problem exist in the digital sport like the addiction problem exist in general sport. In this paper, we propose the addiction model in the digital sport as fractional-order. We represent time series and phase portrait for nonlinear behavior from proposed fractional-order model and we confirms the difference between them.

• Journal of Information Technology Services
• /
• v.19 no.1
• /
• pp.55-69
• /
• 2020

The Internet cyber space has become more important as it enters the intelligent information society of the 4th Industrial Revolution beyond the information age through the development of ICT, the expansion of personalized services through mobile and SNS, the development of IoT, big data, and artificial intelligence. The Internet has formed a new paradigm in human civilization, but it has focused only on the efficiency of its functions. Therefore, various side effects such as information divide, cyber terrorism, cyber violence, hacking, and personal information leakage are emerging. In this situation, facing the intelligent information society can lead to an uncontrollable chaos. Therefore, this study classifies the cyber dysfunction of intelligent information society and analyzes social cognition, suggests cyber dysfunction standard of intelligent information society, and examines the seriousness of dysfunction, and suggests technical research directions for future technologies and services. The dysfunctional classification of the intelligent information society was classified into five areas of cyber crime and terrorism, infringement of rights, intelligent information usage culture, intelligent information reliability, and social problems by FGI methodology. Based on the classification, the social perception of current and future cyber dysfunction severity was surveyed and it showed female is more sensitive than male about the dysfunction. A GAP analysis confirmed social awareness that the future society would be more serious about AI and cyber crime

• Journal of the Korean Society for Precision Engineering
• /
• v.16 no.1 s.94
• /
• pp.141-149
• /
• 1999

어느 한 계가 양수의 발산지수(Lyapunov exponent)를 가질 때 이 계는 카오스계로 분류되며 그 동특성은 예측이 불가능해 진다. 감쇠 기계계(소산계)에서는 위상공간(phase space)의 초기 부피가 시간에 따라 수축한다. 발산 지수들의 합은 음수이며 그 기계계의 감쇠와 관련되며, 따라서 발산지수들의 합은 감쇠의 변화를 감시하는데 사용되어질 수 있다. 그러나 그 감쇠변화를 감시하기 위해서는 발산지수를 계산하는데 사용하는 신호(data) 부분(segment)이 짧아야 한다. 이는 문제점을 야기시키는데 그 이유는 발산지수가 아주 많은 양의 발산률(divergence rate)의 평균으로서 구해지기 때문이다. 이 문제를 극복하기 위해서, 본 저자는 '순간발산지수(Instantaneous Lyapunov Exponent)'를 도입하였으며, 이 순간발산지수들의 합이 어떻게 기계계의 감쇠와 관련되어지는 가에 대하여 기술하였다. 미분방적식과 시계열(time series)을 이용한 컴퓨터 시뮬레이션은 '순간발산지수들의 합'의 중요성을 입증하였다. 그러나 시계열(또는 실험신호)로 부터의 정확한 순간발산지수를 측정하기는 매우 힘들기 때문에 '부분발산지수(Short term averaged Lyapunov Exponent)'를 또한 도입하였다.

• Journal of the Korean Society for Precision Engineering
• /
• v.15 no.12
• /
• pp.226-235
• /
• 1998

This study proposes the analysis and evaluation of method of time series of ultrasonic signal using the chaotic feature extraction for ultrasonic pattern recognition. The features are extracted from time series data for analysis of weld defects quantitatively. For this purpose, analysis objectives in this study are fractal dimension, Lyapunov exponent, and strange attractor on hyperspace. The Lyapunov exponent is a measure of rate in which phase space diverges nearby trajectories. Chaotic trajectories have at least one positive Lyapunov exponent, and the fractal dimension appears as a metric space such as the phase space trajectory of a dynamical system. In experiment, fractal(correlation) dimensions and Lyapunov exponents show the mean value of 4.663, and 0.093 relatively in case of learning, while the mean value of 4.926, and 0.090 in case of testing in slag inclusion(weld defects) are shown. Therefore, the proposed chaotic feature extraction can be enhancement of precision rate for ultrasonic pattern recognition in defecting signals of weld zone, such as slag inclusion.

• Ocean and Polar Research
• /
• v.28 no.4
• /
• pp.459-465
• /
• 2006

Ambient noise as a background noise in the ocean has been well known for its the various and irregular signal characteristics. Generally, these signals we treated as noise and they are analyzed through stochastical level if they don't include definite sinusoidal signals. This study is to see how ocean ambient noise can be analyzed by the chaotic analysis technique. The chaotic analysis is carried out with underwater ambient noise obtained in areas near the Korean Peninsula. The calculated physical parameters of time series signal are as follows: histogram, self-correlation coefficient, delay time, frequency spectrum, sonogram, return map, embedding dimension, correlation dimension, Lyapunov exponent, etc. We investigate the chaotic pattern of noises from these parameters. From the embedding dimensions of underwater noises, the assesment of underwater noise by chaotic analysis shows similar results if they don't include a definite sinusoidal signal. However, the values of Lyapunov exponent (divergence exponent) are smaller than that of random noise signal. As a result we confirm the possibility of classification of underwater noise using Lyapunov analysis.

• Korean Institute of Interior Design Journal
• /
• v.15 no.5 s.58
• /
• pp.52-59
• /
• 2006

Since the time of Vitruvius, the sciences have impacted on the perspectives for architecture and have had a direct influence on the shaping of built space. In recent years, architects have been looking again at sciences as a source of inspiration in the production of their designs and constructions. There are various ways to look at architecture's relationship to science. It is interesting to see how many of the words of day-to-day architectural speech have been drawn from science, the abundant use of references such as topology, fractals, chaos theory, and so on. The reasons for this may be obvious, insofar as science has become the dominant discourse of our times. The numerous attempts have been made to constitute architectural practice so as to bring it into line with the methods of science. But Alberto Perez-Gomez juxtaposed architectural theory and Husserl's. The Crisis of European Science. In Husserl's 'Crisis', it is modern science itself that is laid open question. Through examining its changing relationships to architectural ideas this paper is intended to describe the problematic relationship between science and architecture, in other words, architecture's as science.

• Journal of Korea Multimedia Society
• /
• v.6 no.1
• /
• pp.89-96
• /
• 2003

This paper propose the new method witch is adopted in extracting character features and recognizing numeric characters using fractal dimension and modified Henon Attractor of the Chaos Theory. Firstly, it gets features of mesh feature, projection feature and cross distance feature from numeric character images And their feature hi converted into time series data. Then using the modified Henon system suggested in this paper, it gets last features of numeric character image after calculating Natural Measure and information bit which art meant fractal dimension. Finally, numeric character recognition is performed by statistically finding out the each information bit showing the minimum difference against the normalized pattern database. An Experimental result shows 100% character classification rates for 10 digits and 90% of recognition rates in real situation and the recognition speed was 26 characters per second.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.13 no.8
• /
• pp.1647-1652
• /
• 2009

Generally the neural network and the fuzzy compensative algorithm are applied to forecast the time series for power demand with a characteristic of non-linear dynamic system, but it has a few prediction errors relatively. It also makes long term forecast difficult for sensitivity on the initial condition. On this paper, we evaluate the chaotic characteristic of electrical power demand with analysis methods of qualitative and quantitative and perform a forecast simulation of electrical power demand in regular sequence, attractor reconstruction, time series forecast for multi dimension using Lyapunov exponent quantitatively. We compare simulated results with the previous method and verify that the purpose one being more practice and effective than it.