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In this paper, first, we investigate the CNN templates producing periodic patterns. Next, two image processing algorithms using periodic pattern formation in cellular neural networks are proposed. By applying one to a certain image, area having spatial uniformity is removed from the original image and only parts without spatial uniformity remain. Simulation results show that when this algorithm is applied to an image containing characters (texts) or a human face image, only characters or eyes and mouth are extracted. Also, by applying the other to texture image, periodicity is enhanced in area having spatial periodicity, and texture can be segmented. Simulation results show that when this algorithm is applied to image that consists of four kinds of textures, each texture area can be segmented. Index Terms--Cellular neural networks, image segmentation, pattern formation.

In this paper, we discuss the stability of the characteristic curves for nonlinear resistive circuits including parasitic elements. Although the dc solution is determined by analyzing the nonlinear resistive circuit, its equilibrium point will be stable or unstable because every resistive element has a small parasitic component in practice. We consider here two parasitic elements: a capacitor between every resistor node and ground and an inductor in series with each resistor. Of course, the stability can be decided by solving the variational equation at each equilibrium point obtained by the dc analysis; however, this is very time consuming. We show here that the stability is mainly changed at the boundary of the presence of negative differential resistance (NDR) and the bifurcation points, such as turning and pitchfork points on the dc characteristic curves. The instability regions of the solution curve are easily found by both the locations of bifurcation points and NDR regions of the nonlinear resistors. Index Terms - Bifurcation points, curve tracing method, instability regions, parasitic elements, stability of characteristic curves.

In this brief, synchronization phenomena observed from simple chaotic circuits coupled by one resistor are investigated. A simple three-dimensional autonomous circuit is considered as a chaotic subcircuit. By carrying out circuit experiments and computer calculations for two, three or four subcircuits case, various interesting synchronization phenomena of chaos, which are different types from the results reported before, are confirmed to be stably generated. Further, quasi-synchronization of asymmetric chaos are investigated with attention on the number of synchronization states.