1,176 research outputs found

    Barry Smith an sich

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    Festschrift in Honor of Barry Smith on the occasion of his 65th Birthday. Published as issue 4:4 of the journal Cosmos + Taxis: Studies in Emergent Order and Organization. Includes contributions by Wolfgang Grassl, Nicola Guarino, John T. Kearns, Rudolf LĂŒthe, Luc Schneider, Peter Simons, Wojciech Ć»eƂaniec, and Jan WoleƄski

    Local Zeta Functions and Koba–Nielsen String Amplitudes

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    This article is a survey of our recent work on the connections between Koba–Nielsen amplitudes and local zeta functions (in the sense of Gel’fand, Weil, Igusa, Sato, Bernstein, Denef, Loeser, etc.). Our research program is motivated by the fact that the p-adic strings seem to be related in some interesting ways with ordinary strings. p-Adic string amplitudes share desired characteristics with their Archimedean counterparts, such as crossing symmetry and invariance under Möbius transformations. A direct connection between p-adic amplitudes and the Archimedean ones is through the limit p→1. Gerasimov and Shatashvili studied the limit p→1 of the p-adic effective action introduced by Brekke, Freund, Olson and Witten. They showed that this limit gives rise to a boundary string field theory, which was previously proposed by Witten in the context of background independent string theory. Explicit computations in the cases of 4 and 5 points show that the Feynman amplitudes at the tree level of the Gerasimov–Shatashvili Lagrangian are related to the limit p→1 of the p-adic Koba–Nielsen amplitudes. At a mathematical level, this phenomenon is deeply connected with the topological zeta functions introduced by Denef and Loeser. A Koba–Nielsen amplitude is just a new type of local zeta function, which can be studied using embedded resolution of singularities. In this way, one shows the existence of a meromorphic continuations for the Koba–Nielsen amplitudes as functions of the kinematic parameters. The Koba–Nielsen local zeta functions are algebraic-geometric integrals that can be defined over arbitrary local fields (for instance R, C, Qp, Fp((T))), and it is completely natural to expect connections between these objects. The limit p tends to one of the Koba–Nielsen amplitudes give rise to new amplitudes which we have called Denef–Loeser amplitudes. Throughout the article, we have emphasized the explicit calculations in the cases of 4 and 5 points

    Vergence control system for stereo depth recovery

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    This paper describes a vergence control algorithm for a 3D stereo recovery system. This work has been developed within framework of the project ROBTET. This project has the purpose of designing a Teleoperated Robotic System for live power lines maintenance. The tasks involved suppose the automatic calculation of path for standard tasks, collision detection to avoid electrical shocks, force feedback and accurate visual data, and the generation of collision free real paths. To accomplish these tasks the system needs an exact model of the environment that is acquired through an active stereoscopic head. A cooperative algorithm using vergence and stereo correlation is shown. The proposed system is carried out through an algorithm based on the phase correlation, trying to keep the vergence on the interest object. The sharp vergence changes produced by the variation of the interest objects are controlled through an estimation of the depth distance generated by a stereo correspondence system. In some elements of the scene, those aligned with the epipolar plane, large errors in the depth estimation as well as in the phase correlation, are produced. To minimize these errors a laser lighting system is used to help fixation, assuring an adequate vergence and depth extraction .The work presented in this paper has been supported by electric utility IBERDROLA, S.A. under project PIE No. 132.198

    El enbaxador

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    La visualizaciĂłn de esta obra se ve afectada por la mala conservaciĂłn de la obra original

    Avoiding overfitting of multilayer perceptrons by training derivatives

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    Resistance to overfitting is observed for neural networks trained with extended backpropagation algorithm. In addition to target values, its cost function uses derivatives of those up to the 4th4^{\mathrm{th}} order. For common applications of neural networks, high order derivatives are not readily available, so simpler cases are considered: training network to approximate analytical function inside 2D and 5D domains and solving Poisson equation inside a 2D circle. For function approximation, the cost is a sum of squared differences between output and target as well as their derivatives with respect to the input. Differential equations are usually solved by putting a multilayer perceptron in place of unknown function and training its weights, so that equation holds within some margin of error. Commonly used cost is the equation's residual squared. Added terms are squared derivatives of said residual with respect to the independent variables. To investigate overfitting, the cost is minimized for points of regular grids with various spacing, and its root mean is compared with its value on much denser test set. Fully connected perceptrons with six hidden layers and 2⋅1042\cdot10^{4}, 1⋅1061\cdot10^{6} and 5⋅1065\cdot10^{6} weights in total are trained with Rprop until cost changes by less than 10% for last 1000 epochs, or when the 10000th10000^{\mathrm{th}} epoch is reached. Training the network with 5⋅1065\cdot10^{6} weights to represent simple 2D function using 10 points with 8 extra derivatives in each produces cost test to train ratio of 1.51.5, whereas for classical backpropagation in comparable conditions this ratio is 2⋅1042\cdot10^{4}

    Job-shop scheduling applied to computer vision

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    This paper presents a method for minimizing the total elapsed time spent by n tasks running on m differents processors working in parallel. The developed algorithm not only minimizes the total elapsed time but also reduces the idle time and waiting time of in-process tasks. This condition is very important in some applications of computer vision in which the time to finish the total process is particularly critical -quality control in industrial inspection, real-time computer vision, guided robots, .... The scheduling algorithm is based on the use of two matrices, obtained from the precedence relationships between tasks, and the data obtained from the two matrixes. The developed scheduling algorithm has been tested in one application of quality control using computer vision. The results obtained have been satisfactory in the application of different image processing algorithms

    Copper deposition on fabrics by rf plasma sputtering for medical applications

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    https://www.scopus.com/inward/record.url?eid=2-s2.0-84938151607&partnerID=40&md5=bf2da795caced442546f442aa330773aThe present work is about preparation and characterization of RF sputtered Cu films on cotton by the usage of a Magnetron Sputter Source and 99.995% purity Cu target at room temperature. Cotton fabric samples of 1, 2 and 4 min of sputtering time at discharge pressure of 1×10-2 Torr and distance between target and sample of 8 cm were used. The main goal was to qualitatively test the antimicrobial action of copper on fabrics. For that purpose, a reference strain of Escherichia Coli ATCC 35218 that were grown in TSA plates was implemented. Results indicated a decrease in the growth of bacteria by contact with Cu; for fabric samples with longer sputtering presented lower development of E. coli colonies. The scope of this research focused on using these new textiles in health field, for example socks can be made with this textile for the treatment of athlete's foot and the use in pajamas, sheets, pillow covers and robes in hospital setting for reducing the spread of microorganisms. © Published under licence by IOP Publishing Ltd.Ad Astra Rocket Company,Instituto Tecnologico de Costa Rica,International Atomic Energy Agency (IAEA),Universidad Nacional de Costa Ric

    La Araucana, primera, Segunda y tercera parte

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    Copia digital. Madrid : Ministerio de Cultura. SubdirecciĂłn General de CoordinaciĂłn Bibliotecaria, 2009Sign.: [calderĂłn]\p6\s, 2[calderĂłn]\p2\s, A-Z\p2\s, 2A-2Z\p2\s, 3A-3E\p2\s, 3F\p1\sTexto a dos colPort. con orla tipPort. a dos tinta
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