A minimalistic approach to appearance-based visual SLAM

This paper presents a vision-based approach to SLAM in indoor / outdoor environments with minimalistic sensing and computational requirements. The approach is based on a graph representation of robot poses, using a relaxation algorithm to obtain a globally consistent map. Each link corresponds to a relative measurement of the spatial relation between the two nodes it connects. The links describe the likelihood distribution of the relative pose as a Gaussian distribution. To estimate the covariance matrix for links obtained from an omni-directional vision sensor, a novel method is introduced based on the relative similarity of neighbouring images. This new method does not require determining distances to image features using multiple view geometry, for example. Combined indoor and outdoor experiments demonstrate that the approach can handle qualitatively different environments (without modification of the parameters), that it can cope with violations of the “flat floor assumption” to some degree, and that it scales well with increasing size of the environment, producing topologically correct and geometrically accurate maps at low computational cost. Further experiments demonstrate that the approach is also suitable for combining multiple overlapping maps, e.g. for solving the multi-robot SLAM problem with unknown initial poses

A minimalistic approach for fast computation of geodesic distances on triangular meshes

The computation of geodesic distances is an important research topic in Geometry Processing and 3D Shape Analysis as it is a basic component of many methods used in these areas. In this work, we present a minimalistic parallel algorithm based on front propagation to compute approximate geodesic distances on meshes. Our method is practical and simple to implement and does not require any heavy pre-processing. The convergence of our algorithm depends on the number of discrete level sets around the source points from which distance information propagates. To appropriately implement our method on GPUs taking into account memory coalescence problems, we take advantage of a graph representation based on a breadth-first search traversal that works harmoniously with our parallel front propagation approach. We report experiments that show how our method scales with the size of the problem. We compare the mean error and processing time obtained by our method with such measures computed using other methods. Our method produces results in competitive times with almost the same accuracy, especially for large meshes. We also demonstrate its use for solving two classical geometry processing problems: the regular sampling problem and the Voronoi tessellation on meshes.Comment: Preprint submitted to Computers & Graphic

Atmospheric and Solar Neutrinos with a Heavy Singlet

We follow a minimalistic approach to neutrino masses, by introducing a single heavy singlet $N$ into the standard model (or supersymmetric standard model) with a heavy Majorana mass $M$, which couples as a single right-handed neutrino in a Dirac fashion to leptons, and induces a single light see-saw mass $m_{\nu}\sim 5\times 10^{-2} eV$, leaving two neutrinos massless. This trivial extension to the standard model may account for the atomospheric neutrino data via $\nu_{\mu}\to \nu_{\tau}$ oscillations with near maximal mixing angle $\theta_{23}\sim \pi/4$ and $\Delta m_{\mu \tau}^2 \sim 2.5\times 10^{-3} eV^2$. In order to account for the solar neutrino data the model is extended to SUSY GUT/ string-inspired type models which can naturally yield an additional light tau neutrino mass $m_{\nu_{\tau}}\sim few \times 10^{-3} eV$ leading to $\nu_{e L}\to (\cos \theta_{23}{\nu}_{\mu L} -\sin \theta_{23}{\nu}_{\tau L})$ oscillations with $\Delta m_{e1}^2\sim 10^{-5} eV^2$ and a mixing angle $\sin^2 2 \theta_1 \approx 10^{-2}$ in the correct range for the small angle MSW solution to the solar neutrino problem. The model predicts $\nu_{e L}\to (\sin \theta_{23}{\nu}_{\mu L} +\cos \theta_{23}{\nu}_{\tau L})$ oscillations with a similar angle but a larger splitting $\Delta m_{e2}^2 \sim 2.5\times 10^{-3} eV^2$.Comment: 10 pages, Latex. Expanded discussion of mixing angles mainly in an Appendi

Virtual concrete specimens: discrete element simulations of the quasistatic and dynamic material behavior and failure mechanisms of concrete and mortar

A quite minimalistic approach is described which allows to generate differently shaped ensembles of densely packed spherical particles. The distributions of the particle diameters approximate realistic sieving distributions of concrete aggregates. An ad hoc approach is used in order to add cohesive interaction forces to the model which allows first plausibility tests

Scenarios for the future Lithuanian State forest sector

Three alternative scenarios to the much debated present organisation of the Lithuanian State forest sector are examined: (i) the integrated, where all functions are delegated to one central administrative authority – the Danish prototype, (ii) the commercialised, where State forests are managed by a commercial State company – the Irish prototype, and (iii) the minimalistic, where only negligible forest areas of special importance remain in State ownership – the Swedish prototype. The scenarios are assessed according to six imperatives: (i) sort out the ambiguity of the present structure, (ii) increase the profitability, (iii) reduce the level of public spending, (iv) accommodate changes in ownership structure, (v) rely on a holistic approach, and (vi) comply with the national forest policy. If adopted, any of the scenarios would most likely improve the various elements of State forestry, although in substantially different ways. Politicians will take the final decision that may be supported by the findings of this study

Stress in frictionless granular material: Adaptive Network Simulations

We present a minimalistic approach to simulations of force transmission through granular systems. We start from a configuration containing cohesive (tensile) contact forces and use an adaptive procedure to find the stable configuration with no tensile contact forces. The procedure works by sequentially removing and adding individual contacts between adjacent beads, while the bead positions are not modified. In a series of two-dimensional realizations, the resulting force networks are shown to satisfy a linear constraint among the three components of average stress, as anticipated by recent theories. The coefficients in the linear constraint remain nearly constant for a range of shear loadings up to about .6 of the normal loading. The spatial distribution of contact forces shows strong concentration along ``force chains". The probability of contact forces of magnitude f shows an exponential falloff with f. The response to a local perturbing force is concentrated along two characteristic rays directed downward and laterally.Comment: 8 pages, 8 figure