We have recently developed a chaotic gas turbine, the rotational motion of which might simulate the random reversals of large-scale circulation in turbulent Rayleigh-Bénard convection. The nondimensionalized equations of motion of the turbine are represented as a star network of many Lorenz subsystems sharing dimensionless angular velocity as the central node, referred to as augmented Lorenz equations. In this study, we investigate the dynamical nature of the augmented Lorenz model, focusing on the chaotic synchronizability of coupled augmented Lorenz oscillators with parameter mismatch.
A nonlinear portfolio model was formulated by applying a nonlinear prediction method and its prediction error to the Markowitz mean-variance portfolio model. Also, the Sharpe ratio, which is a typical evaluation function of portfolio optimization, was modified to adopt stock-trading commissions and the trading-unit system, which are inevitable for portfolio rebalancing in real investment. Then, we discussed the best rebalancing frequency from the viewpoint of the trade-off between prediction accuracy and rebalancing costs. By investment simulations based on real stock data, we confirmed that shorter-term rebalancing is more effective even if we are required to pay higher commissions because short-term nonlinear prediction works better to estimate future return rates and to reduce investment risks.
In this paper, we propose a novel control approach for some canonical forms of nonholonomic systems using networks of neural oscillators. Key features of a neural oscillator include its ability to generate stable rhythmic signals, and to tune their frequencies and patterns with the parameters and the network. Focusing on their versatile entrainment property, we adopt the network as a dynamic feedback controller for nonholonomic systems. We examined effectiveness of the proposed method by several numerical simulations.
This study investigates hybrid design by using the Takagi-Sugeno(T-S) fuzzy system modeling method and the Terminal Sliding Mode Control (TSMC) technique. The combined scheme maintains the merits of both approaches. It can alleviate the on-line computational burden by using the T-S fuzzy model to approximate original nonlinear systems since most T-S fuzzy parameters can be computed off-line. Moreover, it can preserve the advantages of TSMC, including rapid response, robustness to disturbances and/or uncertainties, and especially the guarantee of the fast finite-time convergence after the state reaching a sliding surface. The proposed method is applied to a two-link robot manipulator dynamic system. It is also compared to three other methods: 1) Conventional Sliding Mode Control (CSMC) for original nonlinear systems, 2) TSMC for original nonlinear systems, and 3) the combination of the T-S fuzzy system and CSMC design. Simulation results show the benefits of the proposed scheme.
ρ-switching is a technique whereby the topology of an injection-locked frequency divider is changed to make it divide by different values. This paper describes an experimental proof of concept whereby a CMOS LC injection-locked frequency divider with tail injection is switched between two different modes (divide-by-2 and divide-by-4) on the fly. The operation of the circuit is explained qualitatively, verified by simulation and demonstrated experimentally.
This paper presents a morphological pattern spectrum-based image manipulation detection method with a highly parallel two-dimensional cellular automata architecture (CAM2). The novel method consists of using a mathematical morphological-based algorithm to extract pictorial feature information from an original digital image and a block-cipher algorithm to protect the extracted-pictorial information. This will be useful in situations where it is important to find evidence of specific events such as in the investigations of crimes. The morphological pattern spectrum was implemented with a CAM2 instruction-set program and tested with an evaluation system. The CAM2 processor achieves highly parallel processing with low power consumption and is thus effective for mobile product applications. Analyses of manipulated-images indicated that the proposed detection method was able to clearly identify differences from the original image. The results of experiments indicated that the difference in raw integrated density and manipulated pixels was a mere 0.0015% and 0.10% (17pixels), respectively. These results show that the proposed technique has sufficient ability to distinguish the very slight manipulation. In a verification of the total power efficiencies of the CAM2 processor and three conventional mobile processors, we found that the value of Mbps/W, which is scaled to 45-nm CMOS technology for the morphological pattern spectrum and the AES cipher algorithm, drastically improved the power efficiency of the proposed image-manipulation detection with the CAM2 processor due to 16,382-way bit-serial and word-parallel operations. The CAM2 processor-based image manipulation detector achieves highly parallel processing with low power consumption; consequently, the proposed image-manipulation detection method with the CAM2 system is very effective for investigating crimes and for obtaining photographic evidence, especially in mobile products.
In the present paper, we investigate the dependence on the configuration of inhibited in-coming synaptic connections in Nara & Davis chaotic neural network model related with the sensitive response of the chaotic wandering state to memory pattern fragments. It has been shown that when a memory pattern fragment was given, the chaotic wandering state in Nara & Davis chaotic neural network model suddenly converges into the target memory pattern with a high robustness. However, the potentiality depends on dynamical properties of the chaotic wandering states, which are affected with the configuration of the inhibited in-coming synaptic connections. Therefore, we investigate the sensitivity to memory pattern fragments for two types of the configuration, (i) which denotes randomly inhibited in-coming synaptic connections except for ones from memory pattern fragments referred as a partly random configuration hereafter and (ii) which defines randomly inhibited in-coming synaptic connections referred as a fully random configuration hereafter. From the computer experiments, the success ratio for the partly random configuration becomes much higher than the fully random ones, and the accessing time becomes shorter. In addition, from Lyapunov dimension, the system with the partly random configuration reveals higher developed chaos.
The authors recently published a paper on some properties of the solution curves for the last n-1 equations of F(x)+Ax=b where x=[x1,x2,...,xn]T is a variable, F(x):Rn → Rn is a nonlinear function of which the first and second derivatives are strictly positive, A ∈ Rn × n is an Ω-matrix, and b ∈ Rn is a constant vector. In that paper, the authors showed that any solution curve possesses neither maximal points nor inflection points with respect to x1, by making use of a fundamental property of Ω-matrices, which is expressed in the form of inequality. However, the proof was a little unclear as shown in Introduction. The objective of this paper is to give an explicit proof for the property of Ω-matrices, which makes the author's previous result more rigorous.
Particle Swarm Optimization (PSO) is a heuristic optimal value searching method. The method can find the better solution quickly comparing with other heuristic algorithms. The searching ability of PSO is depended on parameters. Since the parameters of PSO contain a stochastic factor, the rigorous theoretical analysis is not sufficient. In order to analyze the dynamics rigorously, a deterministic PSO has been proposed. This paper pays attention to such deterministic PSO. We derive a damping factor and a rotation angle of the trajectory from its eigenvalues. We discuss the relationship between the parameters and the searching ability. Based on the results of our numerical simulations, we clarify that the damping factor and the rotation angle influence the stability of the trajectory and the searching ability of the optimal value.
This paper presents experimental results on the characterization of dynamics and synchronization of networks of nonlinear oscillators with dynamic links. The results are obtained using a new experimental setup. Accurate evaluation of synchronization with dynamic coupling is reported, with reference to a network of Chua oscillators, each settled onto a periodic orbit. The observed synchronization levels, as function of the dynamic link parameters, give a picture of the synchronization area in parameter space which is in agreement with previous theoretical predictions.
We evaluate the performance of the chaotic code division multiple access (CDMA) on realistic communication environment. The previous researches on asynchronous chaotic CDMA systems have shown that the bit error rate (BER) can be reduced by using the chaotic sequences. It has been mathematically clarified that the cross-correlation among the chaotic sequences can be minimized by using those with negative autocorrelation in the asynchronous CDMA. For such chaotic CDMA with negative autocorrelation, it has been also clarified by numerical simulation that the sequences with the Gaussian shaped chip makes better BER performance than the general Nyquist shaped chip. In this paper, we implement the chaotic CDMA using a few software-defined radio (SDR) devices for more realistic investigation. Experimental results obtained by our implemented system on the SDR clarify that the spreading sequence with a specific negative autocorrelation and the Gaussian shaped chip sequence makes the BER lower in asynchronous CDMA system.
It is known that there exist two types of methods to derive the equations of motion for mechanical systems subject to constraints. They are called nonholonomic and vakonomic mechanics. Lewis and Murray showed some simulations for two models of a ball on a rotating table, which are modeled by nonholonomic and vakonomic mechanics, and carried out experiments using a laboratory equipment. They concluded that nonholonomic mechanics provides a good model for a ball on a rotating table. However, they did not show the details of experiments, and hence there exist some ambiguous parts in their paper. Hence, we perform additional experiments for a ball on a rotating table using a laboratory equipment of a ball on a rotating table, and compare simulation and experimental results. In this manner, we can confirm that nonholonomic mechanics shows better performances in comparison with vakonomic mechanics as Lewis and Murray asserted.