• Korean Journal of Applied Biomechanics
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• v.31 no.1
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• pp.30-36
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• 2021

Objective: The objective of the present study was to analyze the relationship between strength of the lower extremity's joints and their local dynamic stability (LDS) of gait in elderly women. Method: Forty-five elderly women participated in this study. Average age, height, mass, and preference walking speed were 73.5±3.7 years, 153.8±4.8 cm, 56.7±6.4 kg, and 1.2±0.1 m/s, respectively. They were tested torque peak of the knee and ankle joints with a Human Norm and while they were walking on a treadmill at their preference speed for a long while, kinematic data were obtained using six 3-D motion capture cameras. LDS of the lower extremity's joints were calculated in maximum Lyapunov Exponent (LyE). Correlation coefficients between torque of the joints and LyE were obtained using Spearman rank. Level of significance was set at p<.05. Results: Knee flexion torque and its LDS was negatively associated with adduction-abduction and flexion-extension movement (p<.05). In addition, ratio of the knee flexion torque to extension and LDS was negatively related to internal-external rotation. Conclusion: In conclusion, knee flexion strength should preferentially be strengthened to increase LDS of the lower extremity's joints for preventing from small perturbations during walking in elderly women.

• Korean Journal of Applied Biomechanics
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• v.18 no.1
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• pp.21-30
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• 2008

The purpose of this study was to investigate the variability to compare local dynamic stability via a linear and nonlinear analysis during walking. Twenty four elderly males, 12 healthy elderly and 12 patients with osteoarthritise walked on a treadmill for 100 consecutive strides. Lyapunov exponent and correlation dimension and coefficient variation were calculated for the kinematic parameters to determine the dynamic stability during walking. The linear measures indicated that the healthy elderly demonstrated significantly higher variability in the ankle joint displacement. The nonlinear analysis revealed that COD for the knee joint angle were higher in patient with osteoarthritise. There were no coincidence in results between linear and nonlinear techniques over two groups. In light of nonlinear analysis, it was concluded that patients with osteoathritise showed higher local instability during walking.

• Journal of Acupuncture Research
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• v.21 no.4
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• pp.135-147
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• 2004

Objective: Moxibustion is one of major healing technique in oriental medicine. It has been widely used in many disease. There is an text which suggest moxibustion is more efficient to the situation of han(寒) and heo(虛) than yeal(熱) and sil(實) in Huangdineijing <黃帝內經>. The aim of this study is to research the effect of moxibustion at Shinmun(H7) is different according to cold or heat tendendy man by analyzing the electroencephalogram(EEG). Methods: We classified objects by their cold or heat tendency using questionnare for cold - heat patternization. (12 cold tendency man, 19 heat tendency man) Before and after moxibustion at Shinmun(H7), EEG raw data were measured during 5 minutes. The correlation dimension(D2), the correlation dimension variability rate(${\Delta}D2$), largest lyapunov exponent(L1) and largest lyapunov exponent variability rate(${\Delta}L1$) were calculated. We analyzed D2, ${\Delta}D2$, L1, ${\Delta}L1$ to see the effect of moxibustion at Shinmun(H7) was statistically different according to Cold or Heat tendendy man. Results : Paired t-test showed significant differences between before and after moxibustion at Shinmun(H7) on the Fp2 in D2(p<0.05), on the Fp2, F3 and F4 in ${\Delta}L1$(p<0.05). Student Hest showed significant differences between cold and heat tendendy man on the F3 in ${\Delta}L1$(p<0.05). Conclusion: These results suggest that moxibustion at Shinmun has an effect on stabilizing mind and it is more efficient to the cold tendendy man than the heat tendendy man.

• Proceedings of the KSME Conference
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• 2007.05a
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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.

• Proceedings of the KOSOMBE Conference
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• v.1994 no.05
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• pp.69-71
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• 1994

1Hz에서 20Hz까지의 단속 주파수를 지닌 청각자극을 가해 얻은 EEG신호에서 자극에 따른 신호의 정성적이고 정량적인 특성을 카오스 분석방법을 통해 밝혔다. 먼저, 뇌전위 신호에 전반적으로 나타나는 일반적인 카오스 특징(fractal mechanism, 1/f frequency spectrum, positive lyapunov exponent등등)이 확인되어졌다. 유발전위에 대해서는 자극의 주파수에 따른 주기 배증을 경유한 카오스로 가는 길(route to chaos)과 2차원 pseudo-phase portrait의 뿌앙까레 단면에서의 기하학적 모양(topological property)의 변화가 관찰되어졌고, 자발전위가 포함된 유발전위에 대해서는 적절한 bases를 지닌 3차원 phase space에서 기이한 끌개(chaotic attractor)가, 유발전위의 정보를 지닌채 보여졌다. 끝으로 자극 주파수(단속 주파수와 반송 주파수) 변화와 측정이 이루어진 머리표면에서의 공간적 위치에 따른, lyapunov exponent값 변화가 의미있게 해석되어졌다. 이 결과는 무질서하게 보이는 뇌전위신호에서 주어진 청각자극에 대한 정보를 얻는 새로운 방법을 제시하게 된다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.10a
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• pp.459-462
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• 2000

The analysis of distribution line faults is essential to the proper protection of power system. A high impedance fault(HIF) dose not make enough current to cause conventional protective device operating. so it is well hon that undesirable operating conditions and certain types of faults on electric distribution feeders cannot be detected by using conventional protection system. In this paper, we prove that the nature of the high impedance faults is indeed a deterministic chaos, not a random motion Algorithms for estimating Lyapunov spectrum and the largest Lyapunov exponent are applied to various fault currents detections in order to evaluate the orbital instability peculiar to deterministic chaos dynamically, and fractal dimensions of fault currents which represent geometrical self-similarity are calculated. Wavelet transform analysis is applied the time-scale information to fault signal. Time-scale representation of high impedance faults can detect easily and localize correctly the fault waveform.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.2
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• pp.379-388
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• 2000

Previous studies on high impedance faults assumed that the erratic behavior of fault current would be random. In this paper, we prove that the nature of the high impedance faults is indeed a deterministic chaos, not a random motion. Algorithms for estimating Lyapunov spectrum and the largest Lyapunov exponent are applied to various fault currents in order to evaluate the orbital instability peculiar to deterministic chaos dynamically, and fractal dimensions of fault currents, which represent geometrical self-similarity are calculated. In addition, qualitative analysis such as phase planes, Poincare maps obtained from fault currents indicate that the irregular behavior is described by strange attractor.

• 한국전산유체공학회:학술대회논문집
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• 2007.10a
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• pp.49-55
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• 2007

The quality of chaotic mixing in three-dimensional micro channel flow has been numerically studied using Fractional-step method (FSM) and particle tracking techniques such as $Poincar{\acute{e}}$ section and Lyapunov exponents. The flow was driven by pressure distribution and the chaotic mixing was generated by applying alternating current to electrodes embedded on the bottom wall at a first half period and on the top wall at a second half period. The equations governing the velocity and concentration distributions were solved using FSM based on Finite Volume approach. Results showed that the mixing quality depended significantly on the modulation period. The modulation period for the best mixing performance was determined based on the mixing index for various initial conditions of concentration distribution. The optimal values of modulation period obtained by the particle tracking techniques were compared with those from the solution of concentration distribution equation using FSM and CFX software and the comparison showed their good match.

• Journal of KSNVE
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• v.8 no.3
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• pp.408-419
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• 1998

Dynamic characteristics are investigated when a nonlinear system showing periodic and chaotic responses under harmonic excitation is exposed to random perturbation. Approach for both qulitative and quantitative analysis of the noise effect in a nonlinear system under harmonic excitation is presented. For the qualitative analysis, Lyapunov exponents are calculated and Poincar map is illustrated. For the quatitative analysis. Fokker-Planck equatin is solved numerical by means of a Path-integral solution procedure. Eigenvalue problem obtained from the numerical caculation is solved and the relation of eigenvalue, eigenvector and chaotic motion is investigated.

• 한국전산유체공학회:학술대회논문집
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• 2007.04a
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• pp.53-57
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• 2007

The quality of chaotic mixing in square cavity flow was studied numerically by CFD simulation and particle tracking technique. The chaotic mixing was generated by using time-periodic electro-osmotic flow. Finite Volume Method (FVM) was employed to get the stretching and folding field in cavity domain. With adjusting the initial condition of concentration distribution, the best values of modulation period and Peclet number which gave us good mixing performance was determined precisely. From $Poicar{\acute{e}}section$and Lyapunov exponents for characteristic trajectories we find that mixing performance also depends on modulation period. The higher value of modulation period, the better mixing performance wag achieved in this case. Furthermore, the results for tracking particle trajectories were also compared between using of Bilinear Interpolation and Higher-order scheme. The values of modulation period for obtaining best mixing effect were matched between using FVM and particle tracking techniques.