Cross-correlation Principle Research Articles

Reading the structure of brains

It is a fashionable philosophical tenet to consider Darwinian evolution as a process which incorporates knowledge into brains. We ask ourselves: can this knowledge about the world be recognised in the structure of brains? The present article gives a partial answer to this. Mechanisms of information handling and storage may well be related to the impressive major cortices of the vertebrate brain, the cerebral and the cerebellar cortices. The structure of the first fits the idea of an associative memory while the second strongly suggests computation of movement in terms of velocities. In some insect brains the mechanisms of visual perception can be related to detailed neuroanatomical structure, and one such network incorporates knowledge about the optics of a camera-type eye. Another one provides the wiring that would be expected in a set of velocity detectors using the principle of cross-correlation of neighbouring inputs.Knowledge acquired during a lifetime is also laid down in brains but the search for t...

ACOUSTIC FLOW INSTRUMENTS FOR SOLID/GAS FLOWS

Abstract Two nonintrusive acoustic flow sensing techniques are reported. One technique, passive in nature, simply measures the bandpassed acoustic noise level produced by particle/particle and particle/wall collisions. The noise levels, given in true root-mean-square voltages or in autocorrelations, show a linear relationship to particle velocity but increase with solid concentration. Therefore, the passive technique requires calibration and a separate measure of solid concentration before it can be used to monitor particle velocity. The second technique is based on the active cross-correlation principle. It measures particle velocity directly by correlating flow-related signatures at two sensing stations. The velocity data obtained by this technique are compared with measurements by a radioactive-particle time-of-flight (TOF) method. A multiplier of 1.53 is required to bring the acoustic data into agreement with the radioactive TOF result. The difference may originate from the difference in flow fields w...

Flame turbulence studies

Measurements of the turbulent structure of a premixed turbulent propane-air flame have been made by using a remote sensing, double-laser schlieren instrument which operates on a cross-correlation principle. Development, calibration, and improvements made for application to flames are presented and discussed. Measurements in the post flame-front region of a stoichiometric flame indicate that the front is disrupted and forms flame kernels which burn rapidly outward from their centers as they are convected downstream. The response of the laser schlieren to spherical kernels has been analyzed, and the results have been applied to the flame measurements in order to estimate the size distributions of the kernels along the flame centerline.