The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

Ultracapacitors: Why, How, and Where is the Technology

Nonlinear dynamic analysis of asymmetric tristable energy harvesters for enhanced energy harvesting

The structure of the edge radial electric field {ital E}{sub {ital r}} inferred from the poloidal rotation velocity is compared with that of the particle and thermal transport barrier for {ital H}-mode plasmas in JFT-2M. Both {ital E}{sub {ital r}} and its gradient {partial derivative}{ital E}{sub {ital r}}/{partial derivative}{ital r} in the thermal transport barrier are found to become more negative at the {ital L}-{ital H} transition. On the other hand, {partial derivative}{ital E}{sub {ital r}}/{partial derivative}{ital r} is more positive outside of the separatrix. The shear of the radial electric field and poloidal rotation velocity in the {ital H} mode is localized within the order of an ion poloidal gyroradius near the separatrix, in the region of ion collisionality {nu}{sub *{ital i}}{approx}20--40.

Edge electric field profiles of H-mode plasmas in JFT-2M tokamak

In this paper, a feasible feedback scheme is used to stabilize the multi-scroll attractors in the Jerk circuit, and the controller is realized using mixed Heaviside function. It is found that arbitrary number (\(n=2, 3, 4, 5,{\ldots }\)) of multi-scroll attractors can be selected from a controlled Jerk circuit, and these multi-scroll attractors can be reproduced using Pspice. The implementation of circuit and controller using Pspice is also presented. The potential mechanism could be that an external forcing in the Sine type is practical to generate a group of equilibrium points, and a linear controller composed of Heaviside function is effective to stabilize the \(n\)-scroll attractors in the chaotic systems.

Selection of multi-scroll attractors in Jerk circuits and their verification using Pspice

A theory for synchronization of dynamical systems

Homoclinic bifurcation and chaos control in MEMS resonators

The chaotic behavior of a nonlinear damped three-well Φ 6 -Van der Pol oscillator under external and parametric excitations is studied in detail by means of Melnikov's analysis. The predictions are tested against numerical simulations based on the basin of attraction of initial conditions. It is found that the threshold for the onset of chaos in the system increases as the amplitude of the parametric excitation decreases and increases as the amplitude of the external forcing increases. Additionally, the onset of chaos is studied through analysis of the Poincare map, a construction of the bifurcation diagrams and a computation of the maximal Lyapunov exponent.

Bifurcations and chaos in the triple-well Φ6-Van der Pol oscillator driven by external and parametric excitations

In this paper, we study the dynamics of a system consisting of extended Duffing–Van der Pol oscillator. Resonance and nonresonance oscillations are analyzed using the multiple scale method. From the Melnikov theorem, we obtain the condition for the existence of homoclinic bifurcation both in the case where the Φ 6 potential is a bounded or unbounded double hump. A convenient demonstration of the accuracy of the method is obtained from the fractal basin boundary.

Resonant oscillation and homoclinic bifurcation in a Φ6-Van der Pol oscillator

Secure communication via parameter modulation in a class of chaotic systems

The Rayleigh oscillator is one canonical example of self-excited systems. However, simple generalizations of such systems, such as the Rayleigh–Duffing oscillator, have not received much attention. The presence of a cubic term makes the Rayleigh–Duffing oscillator a more complex and interesting case to analyze. In this work, we use analytical techniques such as the Melnikov theory, to obtain the threshold condition for the occurrence of Smale-horseshoe type chaos in the Rayleigh–Duffing oscillator. Moreover, we examine carefully the phase space of initial conditions in order to analyze the effect of the nonlinear damping, and in particular how the basin boundaries become fractalized.

M. Siewe Siewe

Papers

Homoclinic bifurcation and chaos control in MEMS resonators

Bifurcations and chaos in the triple-well Φ6-Van der Pol oscillator driven by external and parametric excitations

Resonant oscillation and homoclinic bifurcation in a Φ6-Van der Pol oscillator

Secure communication via parameter modulation in a class of chaotic systems

Effect of nonlinear dissipation on the basin boundaries of a driven two-well Rayleigh-Duffing oscillator