• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.9 no.5
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• pp.445-450
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• 2016

In this paper we study the effect of chaos in nonuniform instability with optical fiber based IoT networks. The transient response of optically controlled fiber has also described. Nonlinear optical fiber effects especially fiber scattering in networks has emerged as the essential means active optical devices. The paradigm instability in fiber Internet serves as a test for fundamental study of chaos and its suppression and exploitation in practical application in optical communication. This paper attempts to present a survey and some of our research findings on the nature of chaotic effect on Internet based optical communication. The transient response in optical fiber has been evaluated theoretically by calculating the variation of the scattering function. The lines has used under open ended termination containing optically induced region. The scattered optical waves in a fiber used in optic communications are temporally unstable above certain threshold intensity.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.1
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• pp.83-91
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• 2004

Nonlinear system responses of an impact system under randomly perturbed harmonic excitations are predicted in the probability domain by adopting the semi-analytical procedure previously developed. The semi-analytical procedure is obtained by solving the Fokker-Planck equation corresponding to the stochastic differential equation of the given impact system by utilizing the path-integral solution. The evolutionary joint probability density functions are generated by using the method, and the characteristics of nonlinear dynamic response behaviors of the system are examined. Noise effects on the responses are also examined. It Is found that the semi-analytical method can provides the accurate information of the responses via the joint probability functions for the impact system. It is found that the noises weaken and eventually terminate the chaos in the responses, but it is also found that the chaotic signatures reside in the presence of the external noise with relatively high intensity. The joint probability density function shows that the ensemble of the system responses are weakly stationary.

• International Journal of Naval Architecture and Ocean Engineering
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• v.10 no.6
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• pp.692-710
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• 2018

The Three-dimensional (3-D) dynamical behaviors of a fluid-conveying pipe subjected to vortex-induced vibration are investigated with different internal flow velocity ${\nu}$. The values of the internal flow velocity are considered in both subcritical and supercritical regimes. During the study, the 3-D nonlinear equations are discretized by the Galerkin method and solved by a fourth-order Runge-Kutta method. The results indicate that for a constant internal flow velocity ${\nu}$ in the subcritical regime, the peak Cross-flow (CF) amplitude increases firstly and then decrease accompanied by amplitude jumps with the increase of the external reduced velocity. While two response bands are observed in the In-line (IL) direction. For the dynamics in the lock-in condition, 3-D periodic, quasi-periodic and chaotic vibrations are observed. A variety of CF and IL responses can be detected for different modes with the increase of ${\nu}$. For the cases studied in the supercritical regime, the dynamics shows a great diversity with that in the subcritical regime. Various dynamical responses, which include 3-D periodic, quasi-periodic as well as chaotic motions, are found while both CF and IL responses are coupled while ${\nu}$ is beyond the critical value. Besides, the responses corresponding to different couples of ${\mu}_1$ and ${\mu}_2$ are obviously distinct from each other.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.2
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• pp.168-175
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• 1999

In this paper, a modified RBF(Radial Basis Function) network structure is suggested for the prediction of a time-series with non-linear, non-stationary characteristics. Coventional RBF network predicting time series by using past outputs sense the trajectory of the time series and react when there exists strong relation between input and hidden activation function's RBF center. But this response is highly sensitive to level and trend of time serieses. In order to overcome such dependencies, hidden activation functions are modified to react to the increments of input variable and multiplied by increment(or dectement) for prediction. When the suggested structure is applied to prediction of Macyey-Glass chaotic time series, Lorenz equation, and Rossler equation, improved performances are obtained.

• Journal of Mechanical Science and Technology
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• v.18 no.7
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• pp.1246-1257
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• 2004

The objective of this paper is to characterize dynamic pressure traces measured at self-excited combustion instabilities occurring in two combustion systems of different hardware. One system is a model lean premixed gas turbine combustor and the other a fullscale bipropellant liquid rocket thrust chamber. It is commonly observed in both systems that low frequency waves at around 300㎐ are first excited at the onset of combustion instabilities and after a short duration, the instability mode becomes coupled to the resonant acoustic modes of the combustion chamber, the first longitudinal mode for the lean premixed combustor and the first tangential mode for the rocket thrust chamber. Low frequency waves seem to get excited at first since flame shows the higher heat release response on the lower frequency perturbations with the smaller phase differences between heat release and pressure fluctuations. Nonlinear time series analysis of pressure traces reveals that even stable combustion might have chaotic behavior with the positive maximum Lyapunov exponent. Also, pressure fluctuations under combustion instabilities reach a limit cycle or quasi-periodic oscillations at the very similar run conditions, which manifest that a self-excited high frequency instability has strong nonlinear characteristics.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2000.04a
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• pp.230-234
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• 2000

Thermal comfort by wearing clothes is the important element which gives influence to a clothing comfort. The thermal comfort of clothes have been evaluated by sensory test and physical property of clothes material. To evaluate a thermophysiological comfort. a new evaluation method which measures the physiological response such as electroencephalogram(EEG) is attracting the attention of many people. In the chilly environment, the EEGs in t재 kinds of thermal conditions : with and without clothes were measured. By utilizing the chaos analysis, the behavior of the obtained EEGs were quantiatively expressed in the correlation dimension. As a result, the correlation dimension of the EEGs in being thermal comfortable feeling by putting on clothes, was bigger than the correlation dimension of the EEGs in being cold and discomfort. These results suggest that chaotic analysis of EEG is effective to the quantitative evaluation of thermal esthesis.

• Journal of the Korean housing association
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• v.25 no.1
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• pp.1-13
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• 2014

This study analyzes the architectural characteristics of Godin's Social Palace system of ideal housing for laborers during the 19th century. Utopian socialists in the first half of the 19th century proposed different solutions to reform their chaotic capitalist society, in response to the maladies of the Industrial Revolution. Fourier designed an ideal housing referred to as the Phalanstere, in which residences coexisted in a cooperative society. His disciples tried in vain to make this ideal housing system real. The only realization of this type of ideal housing was called Godin's Social Palace, which was constructed in Guise, France. The main architectural characteristics of Godin's Social Palace are as follows: dwelling units in consideration of function and expansion are applied basically in the housing. Further, a natural ventilation system is applied between housing and courtyard, and water supply is established in the housing. In Particular, natural lighting and artificial illumination are used in the entire building appropriately. In addition, a device which promotes a community between inhabitants is established. As for such modern facilities and social devices, inhabitants were able to live a more comfortable life. Hence, it is confirmed to have been one of the important factors for sustaining the Social Palace for more than 100 years.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.10a
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• pp.185-190
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• 1995

In recent years, many researcher have been interested in the stability of a thin beam. Among them, Pai and Nayfeh[1] had investigated the nonplanar motion of the cantilever beam under lateral base excitation and chaotic motion, but this study is associated with internal resonance, i.e. one to one resonance. Also Cusumano[2] had made an experiment on a thin beam, called Elastica, under bending loads. In this experiment, he had shown that there exists out-of-plane motion, involving the bending and the torsional mode. Pak et al.[3] verified the validity of Cusumano's experimental works theoretically and defined the existence of Non-Local Mode(NLM), which is came out due to the instability of torsional mode and the corresponding aspect of motions by using the Normal Modes. Lee[4] studied on a thin beam under bending loads and investigated the routes to chaos by using forcing amplitude as a control parameter. In this paper, we are interested in the motion of a thin beam under torsional loads. Here the form of force based on the natural forcing function is used. Consequently, it is found that small torsional loads result in instability and in case that the forcing amplitude is increasing gradually, the motion appears in the form of dynamic double potential well, finally leads to complex motion. This phenomenon is investigated through the poincare map and time response. We also check that Harmonic Balance Method(H.B.M.) is a suitable tool to calculate the bifurcated modes.

• Journal of the Korea Fashion and Costume Design Association
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• v.14 no.2
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• pp.11-21
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• 2012

The purpose of this study is to understand of future image in fashion for 20C, to suggest a guideline's role in the development on fashion designs study. The methods of this study are used academic literatures as well as practical study. Futuristic image in fashion is to introduce about the future period, as fashion goes ahead times. Trends and formative characteristics of future image in 20C fashion are summarized as follows. First, futuristic images in fashion for 20C had emerged strongly futurism, space look, kinetic look, glitter look, techno look, cyber look. Second, perspectives on response for future society's changes are summarized as follows. Attitude of futuristic images of fashion, futurism, space look, kinetic look and glitter look, had been favorable about future society's changes until 1980. In 1990, techno look had been defensive and cyber look had been aggressive about future society's changes. Third, formative characteristics of future image in 20C fashion are studied shape, material, color, pattern. Shape was preferred linear and geometric form in the first half of the 20C, but body conscious type had appeared often in the second half of 20C. Material maintained the luster or the metal touch. Color was based image of colorless and preferred the gold, silver or color feels like metal. Pattern was preferred clarity with geometric type in the first half of the 20C. On the other hand in the second half of 20C pattern of future image was dominated by vague and abstract chaotic type.

• Journal of Convergence for Information Technology
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• v.11 no.11
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• pp.185-194
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• 2021

The purpose of this study is to identify the chaotic state of school education caused by COVID-19 and to seek the role of the principal in responding quickly to the national crisis. To solve this problem, 34 elementary school principals in Seoul, Busan, Daegu, Daejeon, and Jeju were surveyed with open questions through the first SNS on what leadership is needed to cope with COVID-19, and the second in-depth interview was conducted through phone calls. In the New Normal era, principal's leadership requires insightful and responsible leadership in supporting educational activities, class support, and problem prevention that can occur due to rapid response to crisis situations, rapid budgeting and input, and promotion of teacher-to-teacher communication, according to a survey. In crisis situations such as COVID-19, it is necessary to establish a role of principal for schools to cope stably and to establish an educational environment in which students learn in a safe environment. For this, national and educational policy support is needed.