Arguing with Preferences in EcoBioCap

International audienceIn this paper we present the EcoBioCap project and the modelling needs of this project in terms of argumentation based preference aggregation. The aim of the paper is to well describe the problem encountered in this context and to propose a preference logic in line with the expressivity needed by the application. We then show how to embed this logic within the ASPIC+ system. Finally, we show how argument by expert opinion could be integrated within our framework where preference aggregation needs to take into consideration the different expertise of the project stakeholders

Le Banquet de Platon : l'apologie d'Alcibiade ou les paradoxes d'Éros

Ce mémoire cherche à évaluer la culpabilité de Socrate face à l’échec et à la corruption d’Alcibiade, telle que la question se pose dans le Banquet de Platon. Il comprend quatre chapitres. Le premier démontre que le cadre dramatique lui-même fait occuper une place centrale à la vie et au déclin d’Alcibiade et au problème de la responsabilité de Socrate face aux accusations de corruption de la jeunesse qui ont pesé sur lui. Le deuxième chapitre interprète le discours d’Alcibiade comme une tentative de disculpation qui repose sur une critique acerbe du comportement de Socrate. Il se serait détourné de Socrate et de ses enseignements en raison de son ironie, de son arrogance et de son indifférence – de son hybris. Le troisième chapitre étudie le discours de Socrate sur l’accession à la beauté intelligible. Il expose la nature particulière de son éros, qui repose sur l’ironie et l’inversion des rôles comme moyens d’exhorter à la philosophie. Le quatrième chapitre pose la question de l’efficacité de ce type de pédagogie et de la responsabilité du philosophe vis-à-vis de ses disciples. L’étude conclut que l’amour et l’ironie de Socrate sont essentiellement des moyens d’inviter l’autre à se remettre lui-même en question et à prendre soin de son âme. Socrate n’est donc pas coupable d’avoir corrompu Alcibiade. La faute est entièrement celle du jeune homme. Il s’est montré incapable, par égocentrisme et fierté excessive, de réagir correctement à l’énigme posée par le comportement érotique de Socrate.This essay on Plato’s Symposium assesses to what extent Socrates could be held guilty for Alcibiades’ failure and corruption. The first of the four chapters shows that Alcibiades’ life and decline and the accusation against Socrates of youth corruption are central to the dramatic structure. The second chapter interprets Alcibiades’ speech as a sharp criticism of Socrates’ behaviour meant to exculpate himself. Alcibiades justifies his walking away from Socrates and his teachings on the basis of the philosopher’s irony, arrogance and indifference – his hybris. The third chapter looks at Socrates’ speech, which sets out the path to the highest form of Beauty. It explores the particular nature of his eros, which relies especially on irony and role inversion to induce philosophical thinking. The fourth chapter asks how effective this kind of pedagogy is, and what is the responsibility of the philosopher to his students. It is concluded that Socratic love and irony are essentially to be conceived of as means of inciting followers to put themselves into question and take greater care of their souls. Socrates is thus not guilty of corrupting the young man. The fault is entirely Alcibiades’. His pride and selfishness are what prevented him from meeting the challenge that Socrates’ erotic behavior put before him

Default Conceptual Graph Rules: Preliminary Results for an Agronomy Application

International audienceIn this paper, we extend Simple Conceptual Graphs with Reiter's default rules. The motivation for this extension came from the type of reasonings involved in an agronomy application, namely the simulation of food processing. Our contribution is many fold: rst, the expressivity of this new language corresponds to our modeling purposes. Second, we provide an effective characterization of sound and complete reasonings in this language. Third, we identify a decidable subclass of Reiter's default logics. Last we identify our language as a superset of SREC-, and provide the lacking semantics for the latter language

Supporting Argumentation Systems by Graph Representation and Computation

International audienceArgumentation is a reasoning model based on arguments and on attacks between arguments. It consists in evaluating the acceptability of arguments, according to a given semantics. Due to its generality, Dung's framework for abstract argumentation systems, proposed in 1995, is a reference in the domain. Argumentation systems are commonly represented by graph structures, where nodes and edges respectively represent arguments and attacks between arguments. However beyond this graphical support, graph operations have not been considered as reasoning tools in argumentation systems. This paper proposes a conceptual graph representation of an argumentation system and a computation of argument acceptability relying on conceptual graph default rules

Direct inscription of on-surface waveguides in polymers using a mid-ir fiber laser

A detailed study of photo-inscribed optical waveguides in PMMA and polycarbonate using a mid-IR laser is presented. The wavelength of the laser is tuned near the absorption peaks of stretching C-H molecular bonds and the focused beam is scanned onto the surface of planar polymer samples. For the first time, we report the formation of optical waveguides in both polymers through resonant absorption of the laser beam. The optical properties of the waveguides were thoroughly assessed. An elliptic Gaussian mode is guided at the surface of both polymers. Insertion losses of 3.1 dB for a 30 mm long on-surface waveguide inscribed in PMMA were recorded. Such waveguides can interact with the external medium through evanescent coupling. As a proof of concept, the surface waveguides are used as highly sensitive refractometric sensors. An attenuation dynamical range of 35 dB was obtained for a liquid that matches the index of the PMMA substrate. Our results pave the way for large scale manufacturing of low cost biocompatible photonic devices

Nonlinear increase, invisibility, and sign inversion of a localized fs-laser-induced refractive index change in crystals and glasses

Multiphoton absorption via ultrafast laser focusing is the only technology that allows a three-dimensional structural modification of transparent materials. However, the magnitude of the refractive index change is rather limited, preventing the technology from being a tool of choice for the manufacture of compact photonic integrated circuits. We propose to address this issue by employing a femtosecond-laser-induced electronic band-gap shift (FLIBGS), which has an exponential impact on the refractive index change for propagating wavelengths approaching the material electronic resonance, as predicted by the Kramers–Kronig relations. Supported by theoretical calculations, based on a modified Sellmeier equation, the Tauc law, and waveguide bend loss calculations, we experimentally show that several applications could take advantage of this phenomenon. First, we demonstrate waveguide bends down to a submillimeter radius, which is of great interest for higher-density integration of fs-laser-written quantum and photonic circuits. We also demonstrate that the refractive index contrast can be switched from negative to positive, allowing direct waveguide inscription in crystals. Finally, the effect of the FLIBGS can compensate for the fs-laser-induced negative refractive index change, resulting in a zero refractive index change at specific wavelengths, paving the way for new invisibility applications

On a Discrete Element Method to simulate the mechanical behavior of heterogeneous media

The contribution is dedicated to the mechanical simulation of heterogeneous media using a cohesive discrete element method. This latter uses an equivalent continuous model based on granular packings typically composed of disks in 2D and spheres in 3D. In the present work, granular packings are generated using the efficient Lubachevsky-Stillinger algorithm and the cohesion between particles is modeled using beam elements described by Euler-Bernoulli theory. In such an approach, the local parameters related to the geometry and the mechanical behavior of the beam element does not fit the macroscopic elastic coefficients. As a result, a calibration process is set up to relate local and macroscopic parameters. Please notice that only two local parameters, namely the microscopic Young's modulus and the dimensionless thickness of the beam suffice to characterize the elastic behavior of an isotropic medium. Similarly to a finite element method, the issue of discretization is of crucial importance since this directly affects the accuracy of results. That is why, we perform preliminary tests to estimate the suitable number of particles using the discrete element code MULTICOR3D developed in our laboratory. In the context of a homogeneous medium, it turns out that a minimum number of particles of 700,000 particles has to be considered to avoid discretization effects. In a first step, several tests are carried out on 2D and 3D models composed of a single inclusion or a more complex microstructure composed of several spherical or circular inclusions. Comparisons are done with several numerical approaches such as the finite element and the fast-Fourier based methods. These highlight the ability of the proposed DE approach to yield a suitable elastic response in the context of heterogeneous media. In a second step, interfacial debonding and a failure criterion based on the hydrostatic stress are considered. The idea is to better appreciate the suitability of the discrete element method to model cracks initiation and propagation in heterogeneous media. Again, results exhibit the consistency of this approach in comparison with the finite element one. These findings are encouraging and enable us to expect thermomechanical simulations in a next future

Comportement des roches en température

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Quantum tunneling and Branly effect in granular matter

We report a study of the electrical behavior of metallic beads' assemblies and show how those behaviors are related to the Branly effect. Indeed, as first evidenced by Branly in the late 19th century, a fine metallic powder undergoes a ?transition' from an insulating to a conductive state driven by the current crossing it. The mechanism of such an electrical instability is still actively investigated. The main features of Branly effect consist of that resistive transition and the current-voltage characteristics reported in systems as simple as pairs of beads as well as larger beads assemblies. The low current ohmic I-V characteristic is associated with a very high linear resistance RL. At higher current, nonlinear effects lead to a ?flattening' of the upwards characteristic, with a systematic trend to voltage saturation. The backward I-V characteristic exhibits a clear hysteretic behavior and a modified ohmic regime associated with a strongly reduced resistance. Though not fully understood, it is believed that the non-linearity of the I-V characteristic and the saturation effect arise from enhanced thermal effects resulting in a local melting of the beads' material within the mechanical contact area. However, due to persistent grey areas regarding our poor knowledge about electrical and thermal transfer through multi-contacts interfaces, these micro-contacts nucleation alone cannot account for the whole voltage-current characteristics. The melting effect requires high local heating made possible by Holm's like constriction effects. However, the corresponding surface melting temperatures are too high to be reached at moderate current and there is no experimental evidence for such values. But this argument cannot discard this possibility which can be hidden by the high thermal conductivity of metals. In fact, the melting hypothesis proceeds from the way usually followed to assess the temperature increase at the interface: it relies on the Wiedemann-Franz law and a more questionable assumption regarding the heat transfer along current streamlines. This last assumption appears to be valid only at large distances from the interface. This raises the issue of electro-thermal coupling at metallic interfaces under mechanical load, or more generally, the crucial need for a physical model accounting properly for the Branly effect. A process which could reduce efficiently the interface resistance is electron tunneling. In situations involving two (at least) metallic solids tightly compressed, tunneling is certainly active. The influence of additional non classical ingredients, such as quantum tunneling should be investigated more deeply. Consequently, a tentative model of electron transport through a system of contacting beads influenced by mechanical stresses and electron tunneling is presented. The usually observed hysteretic features and the slow relaxation of the electrical properties of the whole assembly are obtained. The model emphasizes the competition between two major ingredients: the electron tunneling through the insulating oxide layer and the local melting effect previously stated. Considering the single contact between two adjacent beads as a simple parallel RC circuit with a capacitive element accounting for the dielectric properties of the insulating layer, the model is ruled by a kinetic equation based on quantum tunneling. Solving this equation with a homemade numerical code developed on Matlab, we computed the corresponding I-V characteristics and reproduce their observed typical shape (hysteresis loop). The model accounts properly for both the nonlinear nature of the characteristic as well as the hysteretic loop. Additional predictions regarding the influence of the mechanical conditions imposed to the interface are discussed. This work may open the way to the modeling of the electrical transport in many beads system to be associated with more complex electrical networks. Higher complexity systems can be easily handled by using appropriate probability distributions