Towards an Electric-Sense-Based Bioinspired Embodied Robotic Perception System: The Modelling Aspect

International audienceIn the context of the new paradigm of embodied intelligence invoked by both the roboticians and the cognitive scientists, a sensor bio-inspired from the electric fish was built. A certain geometry was pointed out for an accurate analytical prediction of the electrical measurements on the body in the presence of exterior objects. Such perception model can establish potentially a direct relation between the location of the object and the body positions measurements as well as the shape of the object and the body direction. In addition to a potential novel tomography technique and a new potential electrolocation system it o ers new insights in understanding the role of the body in perceiving the world

Momentum Dependent Vertices σγγ\sigma \gamma \gamma, σργ\sigma \rho \gamma and σρρ\sigma \rho \rho : The NJL Scalar Hidden by Chiral Symmetry

We calculate the momentum dependence of three particle vertices $\sigma \gamma \gamma$, $\sigma \rho \gamma$ and $\sigma \rho \rho$ in the context of a Nambu Jona Lasinio type model. We show how they influence the processes $\gamma \gamma \rightarrow \sigma \rightarrow \pi \pi$, $\rho \rightarrow \gamma \sigma$ and $\gamma \gamma \rightarrow \rho \rho$ and how chiral symmetry shadows the presence of the $\sigma$.Comment: 9 pages (latex), 5 figures available from the authors, preprint Coimbra 940506, IJS-TP-94/10, accepted for publication in Zeit. f. Physik

Low-energy dynamics of the γγ→ππ\gamma\gamma\to\pi\pi reaction

We calculate the one-quark-loop amplitude for the low energy $\gamma\gamma\to\pi\pi$ collision in the context of the Nambu and Jona-Lasinio model with scalar and pseudoscalar four quark couplings to all orders in the external momenta. We show that the NJL predictions for the $\gamma\gamma\to\pi^+\pi^-$ reaction are not far from the Born amplitude, which is close to the data, and is compatible with the chiral perturbation theory estimations. We determine the corrections given by the NJL model in leading order of $1/N_c$ to the chiral loop amplitude for $\gamma\gamma\to\pi^0\pi^0$. Numerical results for the $\gamma\gamma\rightarrow\pi\pi$ cross sections and for pion polarizabilities are given.Comment: 20 pages in LaTex, 3 figures in 1 Postscript fil

Lowering of ground state induced by core-shell structure in strontium titanate

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The Das-Mathur-Okubo sum rule for the charged pion polarizability in a chiral model

The Das-Mathur-Okubo (DMO) sum rule for the polarizability of charged pions is evaluated for the Nambu-Jona-Lasinio model Lagrangian in both its minimal and extended forms. A comparison is made with the results obtained using the same sum rule from chiral perturbation theory (CHPT), approximate QCD sum rule calculations, explicit calculations on the lattice by Wilcox, and using the semi-empirical Kapusta-Shuryak spectral densities. The $\chi$PT results from Compton scattering are also given. We point to a delicate cancellation between the intrinsic and recoil contributions to $\alpha_{\pi^\pm}$ in the DMO sum rule approach that can lead to calculated polarizabilities of either sign.Comment: 10 LaTeX pages plus one postscript figure, to be published in Physics Letters

Nevada Test Site Sensor Test Facility

A Sensor Test Facility (STF) was recently established at the Department of Energy`s Nevada Test Site (NTS). It has been used for a series of sensor tests that have demonstrated the usefulness of the testbed. The facility consists of a cut-and-cover bunker complex and the two square mile surrounding area. The STF was developed as a scientific testbed optimized for the development and evaluation of advanced sensor systems, including ground sensor systems designed to identify and detect hardened underground facilities. This was accomplished by identifying a facility in a remote location where seismic, acoustic, and electromagnetic interference would be minimal, establishing a testbed that would be accommodating to field testing, and conducting a thorough geophysical characterization of the area surrounding the facility in order to understand the local geology and its effects on geophysical signals emanating from the facility. The STF is representative of a number of cut-and-cover bunkers around the world that are used for the manufacture and/or storage of weapons of mass destruction. This paper provides a general description of the Nevada Test Site, the Sensor Test Facility, and the Geophysical Site Characterization

Underwater robot navigation around a sphere using electrolocation sense and Kalman filter

International audienceThe aim of this paper is to perform the navigation of an underwater robot equipped with a sensor using the electric sense. The robot navigates in an unbounded environment in presence of spheres. This sensor is inspired of some species of electric fish. A model of this sensor composed of n spherical electrodes is established. The variations of the current due to the presence of the sphere is related to the model of Rasnow [3]. Unscented Kalman Filter is used to localize the robot with respect to the sphere and to estimate the size of the sphere. We show that bio-inspired motions improve the detection of the spheres. We illustrate the efficiency of the method in two cases: a two electrodes sensor and a four electrodes sensor