Extending the limits of feature-based SLAM with B-splines

This paper describes a simultaneous localization and mapping (SLAM) algorithm for use in unstructured environments that is effective regardless of the geometric complexity of the environment. Features are described using B-splines as modeling tool, and the set of control points defining their shape is used to form a complete and compact description of the environment, thus making it feasible to use an extended Kalman-filter (EKF) based SLAM algorithm. This method is the first known EKF-SLAM implementation capable of describing general free-form features in a parametric manner. Efficient strategies for computing the relevant Jacobians, perform data association, initialization, and map enlargement are presented. The algorithms are evaluated for accuracy and consistency using computer simulations, and for effectiveness using experimental data gathered from different real environments. © 2009 IEEE

Recycled PP for 3D Printing: Material and Processing Optimization through Design of Experiment

In this work, blends that were based on first use PP added with talc (PPt) and recycled polypropylene (r-PP) were designed and formulated, aiming at producing filaments that are suitable for 3D printing fused filament fabrication (FFF) processes. A preliminary characterization of PPt/r-PP blends at different weight ratios allowed selecting two systems showing adequate rheological behavior for FFF. The selected blends were melt compounded in a twin-screw extruder, optimizing the processing conditions through a design of experiments approach, involving the use of Taguchi's method. The materials that were prepared with the optimized processing conditions, hence showing the best performance in terms of rheological behavior and thermal characteristics, were then selected for the production of the filament and for the subsequent FFF processing. Finally, the morphology of the filament and the mechanical properties of 3D-printed samples were assessed, demonstrating the achievement of satisfactory results in terms of performances. In general, the obtained results clearly demonstrated that a proper optimization of both material and processing conditions offers the possibility of using recycled PP-based formulations for additive manufacturing processes, hence allowing a remarkable valorization of a low added-value material through its utilization for an innovative and sustainable manufacturing approach

Natural history of a visceral leishmaniasis outbreak in highland Ethiopia

In May 2005, visceral leishmaniasis (VL) was recognized for the first time in Libo Kemken, Ethiopia, a highland region where only few cases had been reported before. We analyzed records of VL patients treated from May 25, 2005 to December 13, 2007 by the only VL treatment center in the area, maintained by Médecins Sans Frontières-Ethiopia, Operational Center Barcelona-Athens. The median age was 18 years; 77.6% were male. The overall case fatality rate was 4%, but adults 45 years or older were five times as likely to die as 5-29 year olds. Other factors associated with increased mortality included HIV infection, edema, severe malnutrition, pneumonia, tuberculosis, and vomiting. The VL epidemic expanded rapidly over a several-year period, culminating in an epidemic peak in the last third of 2005, spread over two districts, and transformed into a sustained endemic situation by 2007

Kinetic Theory of Collisionless Self-Gravitating Gases: II. Relativistic Corrections in Galactic Dynamics

In this paper we study the kinetic theory of many-particle astrophysical systems imposing axial symmetry and extending our previous analysis in Phys. Rev. D 83, 123007 (2011). Starting from a Newtonian model describing a collisionless self-gravitating gas, we develop a framework to include systematically the first general relativistic corrections to the matter distribution and gravitational potentials for general stationary systems. Then, we use our method to obtain particular solutions for the case of the Morgan & Morgan disks. The models obtained are fully analytical and correspond to the post-Newtonian generalizations of classical ones. We explore some properties of the models in order to estimate the importance of post-Newtonian corrections and we find that, contrary to the expectations, the main modifications appear far from the galaxy cores. As a by-product of this investigation we derive the corrected version of the tensor virial theorem. For stationary systems we recover the same result as in the Newtonian theory. However, for time dependent backgrounds we find that there is an extra piece that contributes to the variation of the inertia tensor.Comment: 30 pages, 8 figures. v2: Minor corrections and references added. Conclusions unchanged. v3: Version published in PR

Framing and Immigration Through the Trump Era

For the last decade, undocumented or illegal immigration has been one of the most contested policy issues in the United States, with significant news attention on policies affecting the undocumented population, ranging from deportations to comprehensive immigration reform, the DREAM Act, and Deferred Action for Childhood Arrivals. Despite these prominent and multifaceted policy debates, scholarship on media framing and public opinion remain more focused on the portrayal of immigrants rather than policies affecting them. In general, we find that policy frames are far more consequential to public opinion than equivalency frames (variations in how news media describe unauthorized immigrants, either as illegal or undocumented ) or episodic frames (whether news articles are heavy on human-interest stories rather than policy facts and statistics). In addition, negative frames generally have stronger effects than positive frames, and these effects sometimes vary by partisanship and family migration history. Finally, the relative infrequency of powerful frames in news stories, like time spent living in the United States, provides opportunities for advocates to move public opinion on immigration policy. These findings have important implications for future battles over immigration policy in the United States, which show no signs of abating

Charged Annular Disks and Reissner-Nordstr\"{o}m Type Black Holes from Extremal Dust

We present the first analytical superposition of a charged black hole with an annular disk of extremal dust. In order to obtain the solutions, we first solve the Einstein-Maxwell field equations for sources that represent disk-like configurations of matter in confomastatic spacetimes by assuming a functional dependence among the metric function, the electric potential and an auxiliary function,which is taken as a solution of the Laplace equation. We then employ the Lord Kelvin Inversion Method applied to models of finite extension in order to obtain annular disks. The structures obtained extend to infinity, but their total masses are finite and all the energy conditions are satisfied. Finally, we observe that the extremal Reissner-Nordstr\"{o}m black hole can be embedded into the center of the disks by adding a boundary term in the inversion.Comment: 17 revtex pages, 8 eps figure

Kinetic Theory of Collisionless Self-Gravitating Gases: Post-Newtonian Polytropes

In this paper we study the kinetic theory of many-particle astrophysical systems and we present a consistent version of the collisionless Boltzmann equation in the 1PN approximation. We argue that the equation presented by Rezania and Sobouti in A&A 354 1110 (2000) is not the correct expression to describe the evolution of a collisionless self-gravitating gas. One of the reasons that account for the previous statement is that the energy of a free-falling test particle, obeying the 1PN equations of motion for static gravitational fields, is not a static solution of the mentioned equation. The same statement holds for the angular momentum, in the case of spherical systems. We provide the necessary corrections and obtain an equation that is consistent with the corresponding equations of motion and the 1PN conserved quantities. We suggest some potential relevance for the study of high density astrophysical systems and as an application we construct the corrected version of the post-Newtonian polytropes.Comment: 23 pages, 24 figures. Accepted for publication in PR