21,492 research outputs found
Drift-Free Indoor Navigation Using Simultaneous Localization and Mapping of the Ambient Heterogeneous Magnetic Field
In the absence of external reference position information (e.g. GNSS) SLAM
has proven to be an effective method for indoor navigation. The positioning
drift can be reduced with regular loop-closures and global relaxation as the
backend, thus achieving a good balance between exploration and exploitation.
Although vision-based systems like laser scanners are typically deployed for
SLAM, these sensors are heavy, energy inefficient, and expensive, making them
unattractive for wearables or smartphone applications. However, the concept of
SLAM can be extended to non-optical systems such as magnetometers. Instead of
matching features such as walls and furniture using some variation of the ICP
algorithm, the local magnetic field can be matched to provide loop-closure and
global trajectory updates in a Gaussian Process (GP) SLAM framework. With a
MEMS-based inertial measurement unit providing a continuous trajectory, and the
matching of locally distinct magnetic field maps, experimental results in this
paper show that a drift-free navigation solution in an indoor environment with
millimetre-level accuracy can be achieved. The GP-SLAM approach presented can
be formulated as a maximum a posteriori estimation problem and it can naturally
perform loop-detection, feature-to-feature distance minimization, global
trajectory optimization, and magnetic field map estimation simultaneously.
Spatially continuous features (i.e. smooth magnetic field signatures) are used
instead of discrete feature correspondences (e.g. point-to-point) as in
conventional vision-based SLAM. These position updates from the ambient
magnetic field also provide enough information for calibrating the
accelerometer and gyroscope bias in-use. The only restriction for this method
is the need for magnetic disturbances (which is typically not an issue
indoors); however, no assumptions are required for the general motion of the
sensor.Comment: ISPRS Workshop Indoor 3D 201
Neuron analysis of visual perception
The receptive fields of single cells in the visual system of cat and squirrel monkey were studied investigating the vestibular input affecting the cells, and the cell's responses during visual discrimination learning process. The receptive field characteristics of the rabbit visual system, its normal development, its abnormal development following visual deprivation, and on the structural and functional re-organization of the visual system following neo-natal and prenatal surgery were also studied. The results of each individual part of each investigation are detailed
How To Attain Maximum Profit In Minority Game?
What is the physical origin of player cooperation in minority game? And how
to obtain maximum global wealth in minority game? We answer the above questions
by studying a variant of minority game from which players choose among
alternatives according to strategies picked from a restricted set of strategy
space. Our numerical experiment concludes that player cooperation is the result
of a suitable size of sampling in the available strategy space. Hence, the
overall performance of the game can be improved by suitably adjusting the
strategy space size.Comment: 4 pages in revtex 4 styl
Dyonic AdS black holes in maximal gauged supergravity
We present two new classes of dyonic anti-de Sitter black hole solutions of
4-dimensional maximal N=8, SO(8) gauged supergravity. They are: (1) static
black holes of N=2, U(1)^4 gauged supergravity with 4 electric and 4 magnetic
charges, with spherical, planar or hyperbolic horizons; and (2) rotating black
holes of N=2, U(1)^2 gauged supergravity with 2 electric and 2 magnetic
charges. We study their thermodynamics, and point out that the formulation of a
consistent thermodynamics for dyonic anti-de Sitter black holes is dependent on
the existence of boundary conditions for the gauge fields. We identify several
distinct classes of boundary conditions for gauge fields in U(1)^4
supergravity. We study a general family of metrics containing the rotating
solutions, and find Killing-Yano tensors with torsion in two conformal frames,
which underlie separability.Comment: 23 pages, 3 Mathematica files of solutions; v2: minor change
- …