Efficient implementation of geometric integrators for separable Hamiltonian problems

We here investigate the efficient implementation of the energy-conserving methods named Hamiltonian Boundary Value Methods (HBVMs) recently introduced for the numerical solution of Hamiltonian problems. In this note, we describe an iterative procedure, based on a triangular splitting, for solving the generated discrete problems, when the problem at hand is separable.Comment: 4 page

A simple and robust method to study after-pulses in Silicon Photomultipliers

The after-pulsing probability in Silicon Photomulti- pliers and its time constant are obtained measuring the mean number of photo-electrons in a variable time window following a light pulse. The method, experimentally simple and statistically robust due to the use of the Central Limit Theorem, has been applied to an HAMAMATSU MPPC S10362-11-100C

Deep Generative Modeling of LiDAR Data

Building models capable of generating structured output is a key challenge for AI and robotics. While generative models have been explored on many types of data, little work has been done on synthesizing lidar scans, which play a key role in robot mapping and localization. In this work, we show that one can adapt deep generative models for this task by unravelling lidar scans into a 2D point map. Our approach can generate high quality samples, while simultaneously learning a meaningful latent representation of the data. We demonstrate significant improvements against state-of-the-art point cloud generation methods. Furthermore, we propose a novel data representation that augments the 2D signal with absolute positional information. We show that this helps robustness to noisy and imputed input; the learned model can recover the underlying lidar scan from seemingly uninformative dataComment: Presented at IROS 201

Stellar scintillation in short exposure regime and atmospheric coherence time evaluation

Accurately measuring the atmospheric coherence time is still an important problem despite a variety of applicable methods. The Multi-aperture scintillation sensor (MASS) designed for the vertical profiling of optical turbulence, also provides a measurements of coherence time, but its results were found to be biased. Hence there is a need for a more robust method to determine $\tau_0$. The effect of smoothing the stellar scintillation by a finite exposure of the detector is considered. The short exposure regime is described and its limits are defined. The re-analysis of previous measurements with the MASS is performed in order to test the applicability of this approach in real data processing. It is shown that most of the actual measurements satisfy the criteria of short exposures. The expressions for the mean wind speeds $\bar V_2$ in the free atmosphere from the measurement of the scintillation indices are derived for this regime. These values provide an estimate of the atmospheric coherence time $\tau_0$ without the need of empirical calibration. The verification of the method based on real measurements of the resulting $\tau_0$ are in good agreement with independent methods.Comment: Accepted for publication in Astronomy and Astrophysics, 7 pages, 6 figure