Automatic detection and plotting of the road network from aerial images

Image analysis, in the field of cartography, is not limited only to object recognition, but also includes the precise computation of object geometric shapes . Our approach, for automatic extraction ofroad networkfor use in cartography, involves two distinct steps. Step one, recognition, extracts a topologically correct exhaustive graph of the network and step two, geometric shape extraction, computes all centerlines for the complete road network with good quality results both in accuracy and in cartographic representation . For object recognition, we have developed a road following algorithm based on the minimization of a cost function which evaluates the homogeneity . For geometric shape computation, we propose a method based on the calculation of a well balanced position of road sections with respect to a set of constraints : internal constraints - derived from a knowledge of road-shape characteristics - and external constraints-which force the connection between sets of well known points.L'analyse d'image, dans le domaine cartographique, ne se réduit pas à la reconnaissance des objets mais nécessite d'extraire leur géométrie avec une grande précision. Nous nous orientons, pour l'extraction automatique du réseau routier à des fins cartographiques, vers une approche où ces deux phases ― détection et restitution ― seraient distinctes: la phase de détection ayant pour but d'extraire un graphe exhaustif du réseau avec une topologie exacte et la phase de restitution ayant en charge le calcul de la géométrie de l'axe des routes en apportant à l'ensemble du réseau détecté une précision suffisante et une bonne représentation cartographique. Pour la détection, nous avons développé un algorithme de suivi de route basé sur l'optimisation d'un critère d'homogénéité directionnelle. Pour la phase de restitution, nous préconisons une méthode basée sur la recherche de la position d'équilibre des tronçons de route soumis à des contraintes internes ― basées sur la connaissance de la forme générale des routes ― et externes ― basées sur la connaissance de la géométrie exacte de certains points de passage de la route

Quantitative analysis of shadow X-ray Magnetic Circular Dichroism Photo-Emission Electron Microscopy

Shadow X-ray Magnetic Circular Dichroism Photo-Emission Electron Microscopy (XMCD-PEEM) is a recent technique, in which the photon intensity in the shadow of an object lying on a surface, may be used to gather information about the three-dimensional magnetization texture inside the object. Our purpose here is to lay the basis of a quantitative analysis of this technique. We first discuss the principle and implementation of a method to simulate the contrast expected from an arbitrary micromagnetic state. Text book examples and successful comparison with experiments are then given. Instrumental settings are finally discussed, having an impact on the contrast and spatial resolution : photon energy, microscope extraction voltage and plane of focus, microscope background level, electric-field related distortion of three-dimensional objects, Fresnel diffraction or photon scattering

Observation of Bloch-point domain walls in cylindrical magnetic nanowires

Topological protection is an elegant way of warranting the integrity of quantum and nanosized systems. In magnetism one example is the Bloch-point, a peculiar object implying the local vanishing of magnetization within a ferromagnet. Its existence had been postulated and described theoretically since several decades, however it has never been observed. We con rm experimentally the existence of Bloch points, imaged within domain walls in cylindrical magnetic nanowires, combining surface and transmission XMCD-PEEM magnetic microscopy. This opens the way to the experimental search for peculiar phenomena predicted during the motion of Bloch-point-based domain walls

Status of the LHCb magnet system

The LHCb experiment focuses on the precision measurement of CP violation and rare decays in the B-meson system. It plans to operate with an average luminosity of $2\times 10^{32}$~cm$^{-2}$s$~^{-1}$, which should be obtained from the beginning of the LHC operation. The LHCb detector exploits the forward region of the pp collisions at the LHC collider. It requires a single-arm spectrometer for the separation and momentum measurement of the charged particles with a large dipole magnet of a free aperture of $\pm 300$~mrad horizontally and $\pm 250$~mrad vertically. The magnet is designed for a total integrated field of 4~Tm. The pole gap is 2.2 to 3.5~m vertically (the direction of the field) and 2.6 to 4.2~m horizontally. The overall length of the magnet (in beam direction) is 5~m and its total weight about 1500~t. The power dissipation in the aluminium coils will be 4.2~MW. The magnet yoke is constructed from low carbon steel plates of 100~mm thickness. The maximum weight of one plate does not exceed 25~t. The coils are wound from large hollow aluminium conductor of $50~{\rm mm}\times 50~{\rm mm}$ cross-section with a central cooling channel of 25~mm diameter for the pressurized demineralized water. Each of the two coils is composed of 15~monolayer pancakes of 15~turns per pancake. To reach good field quality the coils are bent by 45$^\circ$ towards the gap along the horizontal aperture of $\pm 300$~mrad and the pole pieces have large shims. The underlying magnet design, its present status and milestones will be reviewed

A Model for Ferromagnetic Nanograins with Discrete Electronic States

We propose a simple phenomenological model for an ultrasmall ferromagnetic grain, formulated in terms of the grain's discrete energy levels. We compare the model's predictions with recent measurements of the discrete tunneling spectrum through such a grain. The model can qualitatively account for the observed features if we assume (i) that the anisotropy energy varies among different eigenstates of one grain, and (ii) that nonequilibrium spin accumulation occurs.Comment: 4 pages, 2 figure

Socio-Emotional Competencies and School Performance in Adolescence: What Role for School Adjustment?

There is growing evidence in the literature of positive relationships between socio-emotional competencies and school performance. Several hypotheses have been used to explain how these variables may be related to school performance. In this paper, we explored the role of various school adjustment variables in the relationship between interpersonal socio-emotional competencies and school grades, using a weighted network approach. This network approach allowed us to analyze the structure of interrelations between each variable, pointing to both central and mediatory school and socio-emotional variables within the network. Self-reported data from around 3,400 French vocational high school students were examined. This data included a set of interpersonal socio-emotional competencies (cognitive and affective empathy, socio-emotional behaviors and collective orientation), school adjustment measures (adaptation to the institution, school anxiety, self-regulation at school, and self-perceived competence at school) as well as grades in mathematics and French language. The results showed that self-regulation at school weighted the most strongly on the whole network, and was the most important mediatory pathway. More specifically, self-regulation mediated the relationships between interpersonal socio-emotional competencies and school grades

Neel probability and spin correlations in some nonmagnetic and nondegenerate states of hexanuclear antiferromagnetic ring Fe6: Application of algebraic combinatorics to finite Heisenberg spin systems

The spin correlations \omega^z_r, r=1,2,3, and the probability p_N$ of finding a system in the Neel state for the antiferromagnetic ring Fe(III)6 (the so-called `small ferric wheel') are calculated. States with magnetization M=0, total spin 0<=S<=15 and labeled by two (out of four) one-dimensional irreducible representations (irreps) of the point symmetry group D_6 are taken into account. This choice follows from importance of these irreps in analyzing low-lying states in each S-multiplet. Taking into account the Clebsch--Gordan coefficients for coupling total spins of sublattices (SA=SB=15/2) the global Neel probability p*_N can be determined. Dependencies of these quantities on state energy (per bond and in the units of exchange integral J) and the total spin S are analyzed. Providing we have determined p_N(S) etc. for other antiferromagnetic rings (Fe10, for instance) we could try to approximate results for the largest synthesized ferric wheel Fe18. Since thermodynamic properties of Fe6 have been investigated recently, in the present considerations they are not discussed, but only used to verify obtained values of eigenenergies. Numerical results re calculated with high precision using two main tools: (i) thorough analysis of symmetry properties including methods of algebraic combinatorics and (ii) multiple precision arithmetic library GMP. The system considered yields more than 45 thousands basic states (the so-called Ising configurations), but application of the method proposed reduces this problem to 20-dimensional eigenproblem for the ground state (S=0). The largest eigenproblem has to be solved for S=4; its dimension is 60. These two facts (high precision and small resultant eigenproblems) confirm efficiency and usefulness of such an approach, so it is briefly discussed here.Comment: 13 pages, 7 figs, 5 tabs, revtex

Landau model for uniaxial systems with complex order parameter

We study the Landau model for uniaxial incommensurate-commensurate systems of the I class by keeping Umklapp terms of third and fourth order in the expansion of the free energy. It applies to systems in which the soft mode minimum lies between the corresponding commensurate wave numbers. The minimization of the Landau functional leads to the sine-Gordon equation with two nonlinear terms, equivalent to the equation of motion for the well-known classical mechanical problem of two mixing resonances. We calculate the average free energies for periodic, quasiperiodic and chaotic solutions of this equation, and show that in the regime of finite strengths of Umklapp terms only periodic solutions are absolute minima of the free energy, so that the phase diagram contains only commensurate configurations. The phase transitions between neighboring configurations are of the first order, and the wave number of ordering goes through harmless staircase with a finite number of steps. These results are the basis for the interpretation of phase diagrams for some materials from the I class of incommensurate-commensurate systems, in particular of those for A$_2$BX$_4$ and BCCD compounds. Also, we argue that chaotic barriers which separate metastable periodic solutions represent an intrinsic mechanism for observed memory effects and thermal hystereses.Comment: 12 pages, 14 figures, LaTeX, to be published in Phys. Rev.