Abstract: A method and apparatus are disclosed for using cellular automata to simulate systems described by partial differential equations such as those that describe the flow of fluid, diffusion or heat transfer. A two-dimensional space is tessellated into a cellular array of regular hexagons. Flow or diffusion into a cell through each of its six sides from each of its six nearest neighbor cells is represented by a value 1; and any other condition is represented by a value 0. A set of rules specifies the effect of such inward flow in terms of an outward flow through at least some of the same six sides of each cell to its nearest neighbors. Interaction of the flow with a surface or other inhomogeneity is simulated by using a different set of rules to specify the outward flow produced when an inward flow encounters a surface or other inhomogeneity in the cell. Outward flow from one cell is an inward flow into its nearest neighbors; and with the next "tick" of the clock of the mode, the cycle repeats itself.

Abstract: A random sequence generator includes a plurality of successive stages in a closed loop wherein each of the stages includes a logic circuit and an input-output circuit, the input-output circuit having an input coupled to the output of the logic circuit. The logic circuit, which has n inputs, functions as a storage element or look-up table having 2.sup.n addresses. Connection circuitry is provided for connecting one of the inputs of the logic circuit to the output of the input-output circuit of the same stage. Each of the remaining n-1 inputs of the logic circuit is connected to the output of the input-output circuit of a corresponding one of the other stages. An output signal having a plurality of sequential random values is generated at the output of each of the input-output circuits in response to an initial key signal applied to inputs of the input-output circuit.