46,586 research outputs found

    On the origin of the deflection of light

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    Action at distance in Newtonian physics is replaced by finite propagation speeds in classical post--Newtonian physics. As a result, the differential equations of motion in Newtonian physics are replaced by functional differential equations, where the delay associated with the finite propagation speed is taken into account. Newtonian equations of motion, with post--Newtonian corrections, are often used to approximate the functional differential equations. In ``On the origin of quantum mechanics'', preprint, physics/0505181, May 2005, a simple atomic model based on a functional differential equation which reproduces the quantized Bohr atomic model was presented. The unique assumption was that the electrodynamic interaction has a finite propagation speed. In ``On the origin of the gravitational quantization: The Titius--Bode Law'', preprint, physics/0507072, Jul 2005, a simple gravitational model based on a functional differential equation which gives a gravitational quantification and an explanation of the modified Titius--Bode law is described. In ``On the origin of the anomalous precession of Mercury's perihelion'', preprint, physics/0510086, Oct 2005, an explanation of the anomalous precession of Mercury's perihelion is given in terms of a simple retarded potential, which, at first order, coincides with Gerber's potential of 1898, and which agrees with the author's previous works. In this paper, it is shown how the simple retarded potential presented in physics/0510086 also gives the correct value of the gravitational deflection of fast particles of General Relativity.Comment: 10 pages, 2 figure

    Graph Element Networks: adaptive, structured computation and memory

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    We explore the use of graph neural networks (GNNs) to model spatial processes in which there is no a priori graphical structure. Similar to finite element analysis, we assign nodes of a GNN to spatial locations and use a computational process defined on the graph to model the relationship between an initial function defined over a space and a resulting function in the same space. We use GNNs as a computational substrate, and show that the locations of the nodes in space as well as their connectivity can be optimized to focus on the most complex parts of the space. Moreover, this representational strategy allows the learned input-output relationship to generalize over the size of the underlying space and run the same model at different levels of precision, trading computation for accuracy. We demonstrate this method on a traditional PDE problem, a physical prediction problem from robotics, and learning to predict scene images from novel viewpoints.Comment: Accepted to ICML 201

    The implicit relational assessment procedure: emerging reliability and validity data

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    The Implicit Relational Assessment Procedure (IRAP) is a measure of ‘implicit cognition' developed on the basis of a contemporary behavioural analysis of language and cognition. The IRAP has now been applied to a range of foci over five years of published research. A frequently-cited caveat in publications to date is the need for further research to gauge the reliability and validity of the IRAP as an implicit measure. This review paper will provide a critical synthesis of available evidence for reliability and validity. The review applies a multifaceted test-theory approach to validity, and reliability is assessed through meta-analysis of published data. The discussion critically considers reviewed IRAP evidence with reference to the extant literature on alternative implicit measures, limitations of studies to date, and consideration of broader conceptual issues

    A particle swarm optimisation-based Grey prediction model for thermal error compensation on CNC machine tools

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    Thermal errors can have a significant effect on CNC machine tool accuracy. The thermal error compensation system has become a cost-effective method of improving machine tool accuracy in recent years. In the presented paper, the Grey relational analysis (GRA) was employed to obtain the similarity degrees between fixed temperature sensors and the thermal response of the CNC machine tool structure. Subsequently, a new Grey model with convolution integral GMC(1, N) is used to design a thermal prediction model. To improve the accuracy of the proposed model, the generation coefficients of GMC(1, N) are calibrated using an adaptive Particle Swarm Optimisation (PSO) algorithm. The results demonstrate good agreement between the experimental and predicted thermal error. Finally, the capabilities and the limitations of the model for thermal error compensation have been discussed. Keywords: CNC machine tool, Thermal error modelling, ANFIS, Fuzzy logic, Grey system theory
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