• Title/Summary/Keyword: chaotic

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Dynamical Rolling Analysis of a Vessel in Regular Beam Seas

  • Lee, Sang-Do;You, Sam-Sang
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.24 no.3
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    • pp.325-331
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    • 2018
  • This paper deals with the dynamical analysis of a vessel that leads to capsize in regular beam seas. The complete investigation of nonlinear behaviors includes sub-harmonic motion, bifurcation, and chaos under variations of control parameters. The vessel rolling motions can exhibit various undesirable nonlinear phenomena. We have employed a linear-plus-cubic type damping term (LPCD) in a nonlinear rolling equation. Using the fourth order Runge-Kutta algorithm with the phase portraits, various dynamical behaviors (limit cycles, bifurcations, and chaos) are presented in beam seas. On increasing the value of control parameter ${\Omega}$, chaotic behavior interspersed with intermittent periodic windows are clearly observed in the numerical simulations. The chaotic region is widely spread according to system parameter ${\Omega}$ in the range of 0.1 to 0.9. When the value of the control parameter is increased beyond the chaotic region, periodic solutions are dominant in the range of frequency ratio ${\Omega}=1.01{\sim}1.6$. In addition, one more important feature is that different types of stable harmonic motions such as periodicity of 2T, 3T, 4T and 5T exist in the range of ${\Omega}=0.34{\sim}0.83$.

Hybrid CSA optimization with seasonal RVR in traffic flow forecasting

  • Shen, Zhangguo;Wang, Wanliang;Shen, Qing;Li, Zechao
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.11 no.10
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    • pp.4887-4907
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    • 2017
  • Accurate traffic flow forecasting is critical to the development and implementation of city intelligent transportation systems. Therefore, it is one of the most important components in the research of urban traffic scheduling. However, traffic flow forecasting involves a rather complex nonlinear data pattern, particularly during workday peak periods, and a lot of research has shown that traffic flow data reveals a seasonal trend. This paper proposes a new traffic flow forecasting model that combines seasonal relevance vector regression with the hybrid chaotic simulated annealing method (SRVRCSA). Additionally, a numerical example of traffic flow data from The Transportation Data Research Laboratory is used to elucidate the forecasting performance of the proposed SRVRCSA model. The forecasting results indicate that the proposed model yields more accurate forecasting results than the seasonal auto regressive integrated moving average (SARIMA), the double seasonal Holt-Winters exponential smoothing (DSHWES), and the relevance vector regression with hybrid Chaotic Simulated Annealing method (RVRCSA) models. The forecasting performance of RVRCSA with different kernel functions is also studied.

An Improved Particle Swarm Optimization Adopting Chaotic Sequences for Nonconvex Economic Dispatch Problems (개선된 PSO 기법을 적용한 전력계통의 경제급전)

  • Jeong, Yun-Won;Park, Jong-Bae;Cho, Ki-Seon;Kim, Hyeong-Jung;Shin, Joong-Rin
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.56 no.6
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    • pp.1023-1030
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    • 2007
  • This paper presents a new and efficient approach for solving the economic dispatch (ED) problems with nonconvex cost functions using particle swarm optimization (PSO). Although the PSO is easy to implement and has been empirically shown to perform well on many optimization problems, it may easily get trapped in a local optimum when solving problems with multiple local optima and heavily constrained. This paper proposes an improved PSO, which combines the conventional PSO with chaotic sequences (CPSO). The chaotic sequences combined with the linearly decreasing inertia weights in PSO are devised to improve the global searching capability and escaping from local minimum. To verify the feasibility of the proposed method, numerical studies have been performed for two different nonconvex ED test systems and its results are compared with those of previous works. The proposed CPSO algorithm outperforms other state-of-the-art algorithms in solving ED problems, which consider valve-point and multi-fuels with valve-point effects.

Image Encryption by C-MLCA and 3-dimensional Chaotic Cat Map using Laplace Expansions (C-MLCA와 Laplace 전개를 이용한 3차원 카오스 캣맵에 의한 영상 암호)

  • Cho, Sung-Jin;Kim, Han-Doo;Choi, Un-Sook;Kang, Sung-Won
    • The Journal of the Korea institute of electronic communication sciences
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    • v.14 no.6
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    • pp.1187-1196
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    • 2019
  • Information security has become a major challenge with the advent of cloud and social networking sites. Conventional encryption algorithms might not be suitable for image encryption because of the large data size and high redundancy among the raw pixels of a digital image. In this paper, we generalize the encryption method for of color image proposed by Jeong et al. to color image encryption using parametric 3-dimensional chaotic cat map using Laplace expansion and C-MLCA. Through rigorous experiments, we demonstrate that the proposed new image encryption system provides high security and reliability.

Development of Matlab/Simulink Module for Voltage Flicker Simulation in Distribution Power Systems

  • Cho, Soo-Hwan;Jung, Jae-Ahn;Jang, Gil-Soo;Kwon, Sae-Hyuk;Kang, Moon-Ho
    • Journal of Electrical Engineering and Technology
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    • v.3 no.3
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    • pp.314-319
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    • 2008
  • Power quality simulation plays an important role in many practical cases, for example, when deciding the capacity of the related mitigation devices, assessing the influence of installing a nonlinear load in the distribution part, dissolving the quality issues between utilities and customers, and so on. For these purposes, many dedicated tools have been used in order to assess the level of quality distortions by various kinds of PQ indices. However, there are few modules that can accurately simulate the flicker phenomenon, that is, $P_{st}$ and the nonlinear and chaotic behavior of the electrical arc furnace, which is one of the representative nonlinear loads. This paper deals with the useful and simple modules for the voltage flicker simulation in the distribution and transmission level under the environment of Matlab/Simulink. With these modules, the various conditions of distribution systems and the capacities of arc furnaces with the chaotic characteristic can be easily taken into account.

Modeling the Selectivity of the Cod-end of a Trawl Using Chaotic Fish Behavior and Neural Networks

  • Kim, Yong-Hae;Wardle, Clement S.
    • Fisheries and Aquatic Sciences
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    • v.11 no.1
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    • pp.61-69
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    • 2008
  • Using empirical data of fish performance and physiological limits as well as physical stimuli and environmental data, a cod-end selectivity model based on a chaotic behavior model using the psycho-hydraulic wheel and neural-network approach was established to predict fish escape or herding responses in trawl and cod-end designs. Fish responses in the cod-end were categorized as escape or herding reactions based on their relative positions and reactions to the net wall. Fish movements were regulated by three factors: escape time, a visual looming effect, and an index of body girth-mesh size. The model was applied to haddock in a North Sea bottom trawl including frequencies of movement components, swimming speed, angular velocity, distance to net wall, and the caught-fish ratio; simulation results were similar to field observations. The ratio of retained fish in the cod-end was limited to 37-95% by optomotor coefficient values of 0.3-1.0 and to 13-67% by looming coefficient values of 0.1-1.0. The selectivity curves generated by this model were sensitive to changes in mesh size, towing speed, mesh type, and mesh shape.

Analysis of chaotic with lossless time-delayed chua's circuit (무손실 시간 지연을 갖는 Chua 회로에서의 카오스 해석)

  • 배영철;손영우;고윤석
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.22 no.2
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    • pp.318-324
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    • 1997
  • Chua's circuit is a simple electronic network which exhibits a variety of bifurcation and attractors. The circuit consists of two capacitors, a linear resistor, and a nonlinear resistor. In this papre we analyze a circuit obtained by replacing the parallel LC resonator in the Chua's circuit by lossless transmission line. By using the method of characteristics of this circuit we show that various periodic motions and chaotic motions can the attained according to parameter variations. From Chua's circuit with a lossless transmission line a variely of chaotic attractors which are similar to those of the normal Chua's circuit are observed.

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CONTROL OF LASER WELD KEYHOLE DYNAMICS BY POWER MODULATION

  • Cho, Min-Hyun;Dave Farson
    • Proceedings of the KWS Conference
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    • 2002.10a
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    • pp.600-605
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    • 2002
  • The keyhole formed by high energy density laser-material interaction periodically collapses due to surface tension of the molten metal in partial penetration welds. The collapse sometimes traps a void at the bottom of the keyhole, and it remains as welding defects. This phenomenon is seen as one cause of the instability of the keyhole during laser beam welding. Thus, it seems likely that improving the stability of the keyhole can reduce voids and uniform the penetration depth. The goal of this work is to develop techniques for controlling laser weld keyhole dynamics to reduce weld defects such as voids and inconsistent penetration. Statistical analysis of the penetration depth signals in glycerin determined that keyhole dynamics are chaotic. The chaotic nature of keyhole fluctuations and the ability of laser power modulation to control them have been demonstrated by high-speed video images of laser welds in glycerin. Additionally, an incident leading beam angle is applied to enhance the stability of the keyhole. The quasi-sinusoidal laser beam power of 400Hz frequency and 15$^{\circ}$ incident leading beam angle were determined to be the optimum parameters for the reduction of voids. Finally, chaos analyses of uncontrolled signals and controlled signals were done to show the effectiveness of modulation on the keyhole dynamics. Three-dimensional phase plots for uncontrolled system and controlled system are produced to demonstrate that the chaotic keyhole dynamics is converted to regular periodic behavior by control methods: power modulation and incident leading beam angle.

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T-S Fuzzy Model-Based Adaptive Synchronization of Chaotic System with Unknown Parameters (T-S 퍼지 모델을 이용한 불확실한 카오스 시스템의 적응동기화)

  • Kim, Jae-Hun;Park, Chang-Woo;Kim, Eun-Tai;Park, Mignon
    • Journal of the Korean Institute of Intelligent Systems
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    • v.15 no.2
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    • pp.270-275
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    • 2005
  • This paper presents a fuzzy model-based adaptive approach for synchronization of chaotic systems which consist of the drive and response systems. Takagi-Sugeno (T-S) fuzzy model is employed to represent the chaotic drive and response systems. Since the parameters of the drive system are assumed unknown, we design the response system that estimates the parameters of the drive system by adaptive strategy. The adaptive law is derived to estimate the unknown parameters and its stability is guaranteed by Lyapunov stability theory. In addition, the controller in the response system contains two parts: one part that can stabilize the synchronization error dynamics and the other part that estimates the unknown parameters. Numerical examples, including Doffing oscillator and Lorenz attractor, are given to demonstrate the validity of the proposed adaptive synchronization approach.

Chaotic Responses of Curved Plate under Sinusoidal Loading

  • W.Y. Poon;C.F. Ng;Lee, Y.Y.
    • Journal of Mechanical Science and Technology
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    • v.17 no.1
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    • pp.85-96
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    • 2003
  • In the present investigation, the nonlinear dynamic buckling of a curved plate subjected to sinusoidal loading is examined. By the theoretical analyses, a highly nonlinear snap-through motion of a clamped-free-clamped-free plate and its effect on the overall vibration response are investigated. The problem is reduced to that of a single degree of freedom system with the Rayleigh-Ritz procedure. The resulting nonlinear governing equation is solved using Runge-Kutta (RK-4) numerical integration method. The snap-through boundaries, which vary with different damping coefficient and linear circular frequency of the flat plate are studied and given in terms of force and displacement. The relationships between static and dynamic responses at the start of a snap-through motion are also predicted. The analysis brings out various characteristic features of the phenomenon, i.e. 1) small oscillation about the buckled position-softening spring type motion, 2) chaotic motion of intermittent snap-through, and 3) large oscillation of continuous snap-through motion crossing the two buckled positions-hardening spring type. The responses of buckled plate were found to be greatly affected by the snap-through motion. Therefore, better understanding of the snap-through motion is needed to predict the full dynamic response of a curved plate.