7,671 research outputs found
A micromechanical model for kink-band formation: Part I - Experimental study and numerical modelling
3D modeling of indoor environments for a robotic security guard
Autonomous mobile robots will play a major role in future security and surveillance tasks for large scale environments
such as shopping malls, airports, hospitals and museums. Robotic security guards will autonomously survey such environments, unless a remote human operator takes over control. In this context a 3D model can convey much more useful information than the typical 2D maps used in many robotic applications today, both for visualisation of information and as human machine interface for remote control.
This paper addresses the challenge of building such a model of a large environment (50m x 60m) using data from the robot’s own sensors: a 2D laser scanner and a panoramic camera. The data are processed in a pipeline that comprises automatic, semi-automatic and manual stages. The user can interact with the reconstruction process where necessary to ensure robustness and completeness of the model. A hybrid representation, tailored to the application, has been chosen: floors and walls are represented efficiently by textured planes. Non-planar structures like stairs
and tables, which are represented by point clouds, can be added if desired. Our methods to extract these structures include: simultaneous localization and mapping in 2D and wall extraction based on laser scanner range data, building textures from multiple omni-directional images using multi-resolution blending, and calculation of 3D geometry by a graph cut stereo technique. Various renderings illustrate the usability of the model for visualising the security guard’s position and environment
On the geometric stability of an inorganic nanowire and an organic ligand shell
The break-up of a nanowire with an organic ligand shell into discrete
droplets is analysed in terms of the Rayleigh-Plateau instability. Explicit
account is taken of the effect of the organic ligand shell upon the energetics
and kinetics of surface diffusion in the wire. Both an initial perturbation
analysis and a full numerical analysis of the evolution in wire morphology are
conducted, and the governing non-dimensional groups are identified. The
perturbation analysis is remarkably accurate in obtaining the main features of
the instability, including the pinch-off time and the resulting diameter of the
droplets. It is conjectured that the surface energy of the wire and surrounding
organic shell depends upon both the mean and deviatoric invariants of the
curvature tensor. Such a behaviour allows for the possibility of a stable
nanowire such that the Rayleigh-Plateau instability is not energetically
favourable. A stability map illustrates this. Maps are also constructed for the
final droplet size and pinch-off time as a function of two non-dimensional
groups that characterise the energetics and kinetics of diffusion in the
presence of the organic shell. These maps can guide future experimental
activity on the stabilisation of nanowires by organic ligand shells
Spectroscopy of doubly charmed baryons
We study the mass spectrum of baryons with two and three charmed quarks. For
double charm baryons the spin splitting is found to be smaller than standard
quark-model potential predictions. This splitting is not influenced either by
the particular form of the confining potential or by the regularization taken
for the contact term of the spin-spin potential. We consistently predict the
spectra for triply charmed baryons.Comment: 6 pages, 1 figure, accepted for publication in Phys. Rev.
Spectroscopy of doubly charmed baryons: and
Using the quark-diquark approximation in the framework of Buchm\" uller-Tye
potential model, we investigate the spectroscopy of doubly charmed baryons:
and . Our results include the masses, parameters
of radial wave functions of states with the different excitations of both
diquark and light quark-diquark system. We calculate the values of fine and
hyperfine splittings of these levels and discuss some new features, connected
to the identity of heavy quarks, in the dynamics of hadronic and radiative
transitions between the states of these baryons.Comment: 10 pages, Latex file, 1 fig, corrected some typo
One-dimensional metallic behavior of the stripe phase in LaSrCuO
Using an exact diagonalization method within the dynamical mean-field theory
we study stripe phases in the two-dimensional Hubbard model. We find a
crossover at doping from diagonal stripes to vertical
site-centered stripes with populated domain walls, stable in a broad range of
doping, . The calculated chemical potential shift and the doping dependence of the magnetic incommensurability are in
quantitative agreement with the experimental results for doped
LaSrCuO. The electronic structure shows one-dimensional
metallic behavior along the domain walls, and explains the suppression of
spectral weight along the Brillouin zone diagonal.Comment: 4 pages, 4 figure
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