Search

This paper overviews work on the use of simple chemical reactions to calculate Voronoi diagrams and undertake other related geometric calculations. This work highlights that this type of specialised chemical processor is a model example of a parallel processor. For example increasing the complexity of the input data within a given area does not increase the computation time. These processors are also able to calculate two or more Voronoi diagrams in parallel. Due to the specific chemical reactions involved and the relative strength of reaction with the substrate (and cross-reactivity with the products) these processors are also capable of calculating Voronoi diagrams sequentially from distinct chemical inputs. The chemical processors are capable of calculating a range of generalised Voronoi diagrams (either from circular drops of chemical or other geometric shapes made from adsorbent substrates soaked in reagent) , skeletonisation of planar shapes and weighted Voronoi diagrams (e.g., additively weighted Voronoi diagrams, Multiplicitavely weighted Crystal growth Voronoi diagrams). The paper will also discuss some limitations of these processors. These chemical processors constitute a class of pattern forming reactions which have parallels with those observed in natural systems. It is possible that specialised chemical processors of this general type could be useful for synthesising functional structured materials. [ABSTRACT FROM AUTHOR]

The memristor is a novel circuit element which is capable of maintaining an activity-dependent nonvolatile resistance and is therefore a candidate for use in next-generation storage and logic circuits. In this article, we present a model of the PEO-PANI memristor for use in the SPICE circuit simulation program which is especially suited to analog logic applications. Two variants are presented herein; accompanying each is a short description that explains any design decisions made, as well as elucidating on preferred simulation settings. It is shown that the model accurately replicates corresponding experimental results found in the literature. Simple simulations are used to show the suitability of each variant to specific experimental usage. Appendices contain verbatim implementations of the SPICE models. [ABSTRACT FROM AUTHOR]

In a subexcitable light-sensitive Belousov-Zhabotinsky (BZ) chemical medium an asymmetric disturbance causes the formation of localized traveling wave-fragments. Under the right conditions these wave-fragments can conserve their shape and velocity vectors for extended time periods. The size and life span of a fragment depend on the illumination level of the medium. When two or more wave-fragments collide they annihilate or merge into a new wave-fragment. In computer simulations based on the Oregonator model, we demonstrate that the outcomes of inter-fragment collisions can be controlled by varying the illumination level applied to the medium. We interpret these wave-fragments as values of Boolean variables and design collision-based polymorphic logical gates. The gate implements operation XNOR for low illumination, and it acts as NOR gate for high illumination. As a NOR gate is a universal gate, then we are able to demonstrate that a simulated light sensitive BZ medium exhibits computational universality. [ABSTRACT FROM AUTHOR]

Using the examples of an excitable chemical system (the Belousov–Zhabotinsky medium) and plasmodium of Physarum polycephalum we show that universal computation in a geometrically unconstrained medium is only possible when resources (excitability or concentration of nutrients) are limited. In situations of limited resources the systems studied develop traveling localizations. These localizations are the elementary units of dynamical logical circuits in collision-based computing architectures. [ABSTRACT FROM AUTHOR]

We discuss the experimental implementation of a chemical controller for a robotic hand. In the present case study, we have designed a closed system where a Belousov–Zhabotinsky (BZ) thin layer chemical reactor was linked to the robotic hand via an array of photo-sensors and the fingers of the hand were able to stimulate the excitation dynamics in the BZ medium via the local addition of an activator species. A principal working loop of the chemo-robotic system is that oxidation wave fronts traveling in the medium are detected by photo-sensors and cause (via a microcontroller) the fingers of the hand to bend. When a finger bends, it is set up to apply a small quantity of colloid silver to the reaction and thus causes an additional excitation wave. The traveling and interacting waves stimulate further movements of the fingers and patterns of behavior are observed. These patterns of behavior have been modeled using a cellular automaton. In the paper, we offer an experimental set-up, including algorithms and interfacing, for an experimental chemical robotic hand controller, which contributes to the fields of nonclassical computation, nonlinear physics, and unconventional robotics. [ABSTRACT FROM AUTHOR]

The work discusses the formation of Voronoi diagrams in spatially extended nonlinear systems taking experimental and theoretical results into account. Concerning experimental systems a number of chemical systems used previously as prototype chemical processors and a barrier gas-discharge system are investigated. Although the underlying microscopic processes are very different, both types of systems show self-organized Voronoi diagrams for suitable parameters. Indeed certain chemical systems exhibit Voronoi diagrams as an output state for two distinct sets of parameters one that corresponds to the interaction of stable forced trigger waves and the other that corresponds to the spontaneous initiation and interaction of waves due to point instabilities in the system. In the case of the chemical systems front initiation, propagation and interaction (annihilation) are the primary mechanisms for Voronoi diagram formation, in the case of the barrier gas-discharge system regions of vanishing electric field define the medial axes of the Voronoi diagram. On the basis of cellular automata models the general concept of the formation of Voronoi diagrams has been explained, and related mechanisms have been simulated. Another intuitive approach towards the understanding of self-organized Voronoi diagrams has been given on the basis of reaction–diffusion models explaining the formation of Voronoi diagrams as a result of the mutual interactions of trigger fronts. The variety of systems exhibiting Voronoi diagrams as stationary states indicates that Voronoi diagrams are a generic and natural pattern formation phenomenon. [ABSTRACT FROM AUTHOR]