1,586 research outputs found
Détection et Reconnaissance des Gestes Emblématiques
Session "Atelier IHMA"National audienceDans cette contribution, nous présentons un système de reconnaissance en ligne de gestes emblématiques et son utilisation pour le contrôle d'un robot mobile. Ce système comporte quatre sous-systèmes : un premier qui permet de détecter la personne et d'extraire les mouvements de la partie supérieure de cette personne. Un second, permet d'isoler les mouvements, une troisième permet de reconnaître un des mouvements appris a priori. Enfin le dernier module, traduit les mouvements reconnus en termes de contrôle d'un robot mobile à roues. Dans notre approche, nous avons surtout traité du problème de la généralisation : faire l'apprentissage sur une base réduite de personnes et utiliser cette connaissance pour reconnaître n'importe quelle personne, indépendamment de sa morphologie, de son âge, de son sexe et de son positionnement par rapport au capteur. Nous détaillons les résultats obtenus pour la reconnaissance ainsi que l'utilisation du système dans des scenarios de contrôle d'un robot
U(1) spin liquids and valence bond solids in a large-N three-dimensional Heisenberg model
We study possible quantum ground states of the Sp(N) generalized Heisenberg
model on a cubic lattice with nearest-neighbor and next-nearest-neighbor
exchange interactions. The phase diagram is obtained in the large-N limit and
fluctuation effects are considered via appropriate gauge theories. In
particular, we find three U(1) spin liquid phases with different short-range
magnetic correlations. These phases are characterized by deconfined gapped
spinons, gapped monopoles, and gapless ``photons''. As N becomes smaller, a
confinement transition from these phases to valence bond solids (VBS) may
occur. This transition is studied by using duality and analyzing the resulting
theory of monopoles coupled to a non-compact dual gauge field; the condensation
of the monopoles leads to VBS phases. We determine the resulting VBS phases
emerging from two of the three spin liquid states. On the other hand, the spin
liquid state near J_1 \approx J_2 appears to be more stable against monopole
condensation and could be a promising candidate for a spin liquid state in real
systems.Comment: revtex file 12 pages, 17 figure
Field emission properties of nano-composite carbon nitride films
A modified cathodic arc technique has been used to deposit carbon nitride
thin films directly on n+ Si substrates. Transmission Electron Microscopy
showed that clusters of fullerene-like nanoparticles are embedded in the
deposited material. Field emission in vacuum from as-grown films starts at an
electric field strength of 3.8 V/micron. When the films were etched in an
HF:NH4F solution for ten minutes, the threshold field decreased to 2.6
V/micron. The role of the carbon nanoparticles in the field emission process
and the influence of the chemical etching treatment are discussed.Comment: 22 pages, 8 figures, submitted to J. Vac. Sc. Techn.
Single-electron transistor made of multiwalled carbon nanotube using scanning probe manipulation
We positioned semiconducting multiwalled carbon nanotube, using an atomic force microscope, between two gold electrodes at SiO2 surface. Transport measurements exhibit single-electron effects with a charging energy of 24 K. Using the Coulomb staircase model, the capacitances and resistances between the tube and the electrodes can be characterized in detail.Peer reviewe
Effects of Genotype and Sleep on Temperament
Supported by the Canadian Institutes of Health Research
Single-Atom Resolved Fluorescence Imaging of an Atomic Mott Insulator
The reliable detection of single quantum particles has revolutionized the
field of quantum optics and quantum information processing. For several years,
researchers have aspired to extend such detection possibilities to larger scale
strongly correlated quantum systems, in order to record in-situ images of a
quantum fluid in which each underlying quantum particle is detected. Here we
report on fluorescence imaging of strongly interacting bosonic Mott insulators
in an optical lattice with single-atom and single-site resolution. From our
images, we fully reconstruct the atom distribution on the lattice and identify
individual excitations with high fidelity. A comparison of the radial density
and variance distributions with theory provides a precise in-situ temperature
and entropy measurement from single images. We observe Mott-insulating plateaus
with near zero entropy and clearly resolve the high entropy rings separating
them although their width is of the order of only a single lattice site.
Furthermore, we show how a Mott insulator melts for increasing temperatures due
to a proliferation of local defects. Our experiments open a new avenue for the
manipulation and analysis of strongly interacting quantum gases on a lattice,
as well as for quantum information processing with ultracold atoms. Using the
high spatial resolution, it is now possible to directly address individual
lattice sites. One could, e.g., introduce local perturbations or access regions
of high entropy, a crucial requirement for the implementation of novel cooling
schemes for atoms on a lattice
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