Vitesse orbitale

thumb|Comparaisons de vitesses orbitales de différents satellites de la Terre. La vitesse orbitale d'un objet céleste, le plus souvent une planète, un satellite naturel, un satellite artificiel ou une étoile binaire, est la vitesse à laquelle il orbite autour du barycentre d'un système à deux corps, soit donc le plus souvent autour d'un corps plus massif. L'expression peut être employée pour désigner la vitesse orbitale moyenne du corps le long de son orbite ou la vitesse orbitale instantanée, en un point précis. On l'exprime en principe en , mais souvent en . Vitesse orbitale instantanée La vitesse orbitale instantanée peut être déterminée par la seconde loi de Kepler, à savoir qu'en une durée déterminée, le segment de droite reliant le barycentre au corps décrit une surface constante, quelle que soit la portion de l'orbite que le corps parcourt pendant cette durée. En conséquence, le corps va plus vite près de son périastre que de son apoastre. Cas général La

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MEMS Inertial Motion Sensing Watch for Measuring Walking and Running Activities

Kamiar Aminian, Flavien Bardyn, Pierre-André Farine, Benedikt Fasel, Sara Grassi Pauletti, Martin Savary

This paper describes the development of a sport watch, as well as the software and hardware required to design an integrated solution for getting feedback during and after walking and running activities. The developed system is autonomous, so that neither a smartphone nor a computer are necessary for configuration. The user controls the watch via a touch-screen based interface and all the relevant information is displayed on an LCD. Moreover, the watch contains all the required inertial sensors to allow giving different feedbacks to the user, such as the type of activity, the number of steps taken, the covered distance, the instantaneous speed and the average speed. Although this work is multidisciplinary, in this paper the emphasis is put on the description of the device and on the electronics and the algorithms implementation. Particular focus is on the efficiency in terms of computational time, and in achieving high autonomy on a primary cell battery.

Ieee2016

Chargement

A wrist sensor and algorithm to determine instantaneous walking cadence and speed in daily life walking

Kamiar Aminian, Flavien Bardyn, Farzin Dadashi, Cyntia Duc, Pierre-André Farine, Benedikt Fasel, Martin Savary

In daily life, a person’s gait—an important marker for his/her health status—is usually assessed using inertial sensors fixed to lower limbs or trunk. Such sensor locations are not well suited for continuous and long duration measurements. A better location would be the wrist but with the drawback of the presence of perturbative movements independent of walking. The aim of this study was to devise and validate an algorithm able to accurately estimate walking cadence and speed for daily life walking in various environments based on acceleration measured at the wrist. To this end, a cadence likelihood measure was designed, automatically filtering out perturbative movements and amplifying the periodic wrist movement characteristic of walking. Speed was estimated using a piecewise linear model. The algorithm was validated for outdoor walking in various and challenging environments (e.g., trail, uphill, downhill). Cadence and speed were successfully estimated for all conditions. Overall median (interquartile range) relative errors were −0.13% (−1.72 2.04%) for instantaneous cadence and −0.67% (−6.52 6.23%) for instantaneous speed. The performance was comparable to existing algorithms for trunk- or lower limb-fixed sensors. The algorithm’s low complexity would also allow a real-time implementation in a watch.

Springer Heidelberg2017

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Coherent Hole Transport in Selective Area Grown Ge Nanowire Networks

Anna Fontcuberta i Morral, Andrea Giunto, Nicholas Paul Morgan, Santhanu Panikar Ramanandan, Alok Rudra

Holes in germanium nanowires have emerged as a realistic platform for quantum computing based on spin qubit logic. On top of the large spin–orbit coupling that allows fast qubit operation, nanowire geometry and orientation can be tuned to cancel out charge noise and hyperfine interaction. Here, we demonstrate a scalable approach to synthesize and organize Ge nanowires on silicon (100)-oriented substrates. Germanium nanowire networks are obtained by selectively growing on nanopatterned slits in a metalorganic vapor phase epitaxy system. Low-temperature electronic transport measurements are performed on nanowire Hall bar devices revealing high hole doping of ∼1018 cm–3 and mean free path of ∼10 nm. Quantum diffusive transport phenomena, universal conductance fluctuations, and weak antilocalization are revealed through magneto transport measurements yielding a coherence and a spin–orbit length of the order of 100 and 10 nm, respectively.

2022

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Orbite

vignette|La Station spatiale internationale en orbite au-dessus de la Terre. En mécanique céleste et en mécanique spatiale, une orbite () est la courbe fermée représentant la trajectoire que dessine,

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