Marco Pertile

On the nucleus structure and activity of comet 67P/Churyumov-Gerasimenko

Images from the OSIRIS scientific imaging system onboard Rosetta show that the nucleus of 67P/Churyumov-Gerasimenko consists of two lobes connected by a short neck. The nucleus has a bulk density less than half that of water. Activity at a distance from the Sun of >3 astronomical units is predominantly from the neck, where jets have been seen consistently. The nucleus rotates about the principal axis of momentum. The surface morphology suggests that the removal of larger volumes of material, possibly via explosive release of subsurface pressure or via creation of overhangs by sublimation, may be a major mass loss process. The shape raises the question of whether the two lobes represent a contact binary formed 4.5 billion years ago, or a single body where a gap has evolved via mass loss.

Reduced startle reflex and aversive noise perception in patients with orbitofrontal cortex lesions

In the present study, the primary emotional response represented by the acoustic startle reflex was investigated in a group of six male patients, selected with lesions of the orbitofrontal cortex, and twenty matched healthy controls. Accurate neuropsychological assessment and lesion mapping showed relatively spared cognitive functioning in the patient group, most of the lesions being confined to the bilateral polar orbitofrontal cortex. Patients had significant inhibition of startle amplitude, together with a reduced self-evaluated perception of the unpleasantness of the acoustic probe stimulus. Results add to current literature on the circuit of the human startle reflex, by suggesting cortical-limbic down-regulation of the orbitofrontal cortex on the main startle pathway, probably at the level of the activating reticular system. The orbitofrontal cortex, together with the amygdala, is confirmed to represent the main center organizing both primary and secondary learned aspects of emotions.

Language plasticity in aphasics after recovery: Evidence from slow evoked potentials

With the present experiment we sought to investigate brain plasticity underlying language recovery in a group of seventeen patients with non-fluent aphasia mainly caused by stroke. Patients were screened along three domains of measures: analysis of linguistic components by the Aachener Aphasie Test, combined mapping of their lesion from CT/MRI scans, and functional measure of the reorganized linguistic processes by means of mapping of slow evoked potentials. The spatial dimension and temporal dynamics of word processing were measured in three tasks, Phonological, Semantic and Orthographic. Compared with the matched control group, patients showed relative inhibition (decreased negativity) of left central regions in perisylvian areas, which were damaged in most subjects. In addition, reorganization of linguistic functions occurred within the left hemisphere both at frontal and posterior sites corresponding to spared brain regions. Correlations between linguistic lateralization in the three tasks and AAT subtests point to functional reorganization of phonological processes over left frontal sites and dysfunctional reorganization of semantic processing over left posterior regions.

A Unified Framework for Uncertainty, Compatibility Analysis, and Data Fusion for Multi-Stereo 3-D Shape Estimation

This paper describes the uncertainty analysis performed for the reconstruction of a 3-D shape. Multiple stereo systems are employed to measure a 3-D surface with superimposed colored markers. The procedure comprised a detailed uncertainty analysis of all measurement phases, and the uncertainties evaluated were employed to perform a compatibility analysis of points acquired by different stereo pairs. The compatible acquired markers were statistically merged in order to obtain the measurement of a 3-D shape and an evaluation of the associated uncertainty. Both the compatibility analysis and the measurement merging are based on the evaluated uncertainty.

Uncertainty evaluation for complex propagation models by means of the theory of evidence

The present paper describes operating procedures for uncertainty expression and propagation using different approaches. Well-known methods, such as the propagation formula of the GUM (Guide to the Expression of Uncertainty in Measurement) and Monte Carlo method, are briefly described and summarized as operating procedures, while a more detailed description of the new approach based on the theory of evidence and random-fuzzy variables (RFVs) is presented. This new method based on RFV allows us to take into explicit account and to properly manage systematic effects and complete ignorance contributions to uncertainty. For all three methods, concise and schematic procedures are presented in order to give a clear comparison among them and to ease implementation. Particular attention is focused on how uncertainty can be expressed and propagated in an indirect measurement through a mathematical model. Furthermore, this paper proposes a generalized method to express and propagate uncertainty by means of RFV. This proposed method is characterized by its applicability to any type of mathematical model, even if it comprises complex numerical functions or algorithms.

Uncertainty Evaluation in Two-Dimensional Indirect Measurement by Evidence and Probability Theories

An improved method for 2-D uncertainty expression and propagation based on the theory of evidence and 2-D random-fuzzy variables (RFVs) is described. A previous 2-D RFV approach and two probability-based approaches are also introduced. The improved RFV approach exploits a new algorithm for the combination of random and systematic effects, trying to overcome a drawback of a 2-D RFV method already disclosed in a previous work. One of the two probability-based methods does not take into account any correlation among uncertainty sources and among different time instants of each source, whereas the other probability method exploits time correlation to take into account the repetitive nature of systematic uncertainty sources. All described methods are applied to the 2-D case of a vehicle position measurement on a plane. The obtained results are compared and show the compatibility of all approaches. The improved random-fuzzy method yields better uncertainty evaluation in case of narrow and elongated confidence regions than the previous method. The new 2-D RFV approach also exhibits a better behavior from a theoretical point of view. Main differences between the two probability-based methods are also presented.

An object localization and reaching method for wheeled mobile robots using laser rangefinder

This paper proposes an efficient scheme to solve the problem of identifying an object from range data and navigating to it by on line calculating and performing highly continuous paths for a precise target reaching. Our approach combines a laser range-based object localization method with the PC-sliding, a technique based upon polynomial curvature paths that are suitable for nonholonomic mobile robots and robust to measurement and model uncertainties. First the object is on-line localized using a laser rangefinder taking into account sensor and robot pose uncertainties and then a PC-path is both planned and real-time controlled with a unique strategy.

Uncertainty analysis of a stereo system performing ego-motion measurements in a simulated planetary environment

In planetary exploration space missions, motion measurement of a vehicle on the surface of a planet is a very important task. In this work, a non linear vision-based algorithm for ego-motion measurement is described and calibrated using telephoto lenses. Several motion types, including displacement, rotation and their combination, are considered and the evaluated uncertainties are compared, pointing out strengths and weaknesses of employing telephoto lenses for motion measurement.

Uncertainty analysis for multi-stereo 3d shape estimation

It is described the uncertainty analysis performed for the reconstruction of a 3D shape. Multiple stereo systems are employed to measure a 3D surface with superimposed colored markers. The described procedure comprises a detailed uncertainty analysis of all the measurement phases, and the evaluated uncertainties are employed to perform a compatibility analysis of points acquired by different stereo pairs. The compatible acquired markers are statistically merged in order to obtain a measurement of a 3D shape and an evaluation of the associated uncertainty. Both the compatibility analysis and the measurement merging is based on the evaluated uncertainty.

High-performance shutter for space applications

A new concept of electromechanical shutter has been designed and qualified for the OSIRIS imaging system to fly onboard the Rosetta Mission, whose main scientific goal are the randez-vous and the study of the Comet Wirtanen. The shutter, is composed by two blades, driven by dedicated four-bar linkages, that are moved independently by two torque motors each mounted on the same shaft of an high resolution optical encoder. A dedicate fail safe mechanism is also integrated in order to make the shutter single point failure proof. The mechanism has been designed in order to fulfil high reliability with high performance. Reliability has been verified by life testing over 100000 cycles (factor 2 on expected operative cycles). Performance verified by calibration show that the minimum exposure time with a uniformity of 1/500 is 10 ms over a large sensitive area (about 30x30 mm). The exposure time can vary from 10ms to 5s. Scope of this paper is to present the mechanism and to demonstrate that it accomplishes the sciences and interfaces requirements.