A self-mixing laser sensor design with an extended kalman filter for optimal online structure analysis and damping evaluation

We have developed a new algorithm based on the extended Kalman filter, in order to improve the resolution of an optical displacement sensor. This new non contact sensor which provides vibration measurement with a very good accuracy might be used for online quality control by measuring the damping of excited mechanical structure. This self-mixing sensor subject to weak feedback has been tested in comparison with a commercial vibrometer, to measure the frequency response function of a plate with a passive damping to be characterized, in order to show the efficiency of a damping treatment

Enabling Realistic Cross-Layer Analysis based on Satellite Physical Layer Traces

We present a solution to evaluate the performance of transport protocols as a function of link layer reliability schemes (i.e. ARQ, FEC and Hybrid ARQ) applied to satellite physical layer traces. As modelling such traces is complex and may require approximations, the use of real traces will minimise the potential for erroneous performance evaluations resulting from imperfect models. Our Trace Manager Tool (TMT) produces the corresponding link layer output, which is then used within the ns-2 network simulator via the additionally developed ns-2 interface module. We first present the analytical models for the link layer with bursty erasure packets and for the link layer reliability mechanisms with bursty erasures. Then, we present details of the TMT tool and our validation methodology, demonstrating that the selected performance metrics (recovery delay and throughput efficiency) exhibit a good match between the theoretical results and those obtained with TMT. Finally, we present results showing the impact of different link layer reliability mechanisms on the performance of TCP Cubic transport layer protocol

Conception d’un système laser de mesures de déplacements par interférométrie à rétroinjection optique dans le cas de feedbacks faible et modéré.

L'utilisation des lasers est répandue dans le domaine de l'instrumentation. Cependant, le fonctionnement de tels dispositifs peut ˆetre perturbé par le phénomène de rétroinjection optique (ou self-mixing) auquel est soumis la diode laser. Cette sensibilité du laser au faisceau optique de retour offre de nombreux avantages, notamment pour la mesure de déplacements. Les capteurs basés sur ce principe présentent l'avantage d'ˆetre compact, sans contact, et autoalignés. Après une analyse théorique, un modèle comportemental complet du self-mixing est présenté. Un capteur a été con¸cu afin de pouvoir fonctionner dans les cas les plus répandus expérimentalement, à savoir un feedback faible puis modéré. Deux algorithmes ont ensuite été développés de manière à traiter le signal pour ces différents feedbacks. Ce nouveau capteur permet également de reconstruire des déplacements aléatoires de cibles. Il a, de plus, été testé sur un montage mécanique utilisé pour l'analyse de revˆetements amortissants. ABSTRACT : Optical feedback interferometry, also known as the self-mixing effect, is similar to conventional two-beam interferometry but without any auxiliary bulk. When a small fraction of the backscattered laser beam from diffusely-reflecting surfaces re-enters the laser cavity, its spectral properties are affected. This generates a variation in the laser optical power, resulting in self-mixing which has been demonstrated to be suitable for sensing applications. A high-level behavioural model has been proposed to represent this phenomenon. A displacement sensor based on this principle has thus been designed to operate under weak and moderate feedback regimes. Two algorithms have also been developed in order to process the resulting signals, rendering the sensor capable of reconstructing random displacements. This has been verified on damped anti-vibration coatings via modal analysis

Enhancement of MARSALA Random Access with Coding Schemes, Power Distributions and Maximum Ratio Combining

Several random access (RA) techniques have been proposed recently for the satellite return link. The main objective of these techniques is to resolve packets collisions in order to enhance the limited throughput of traditional RA schemes. In this context, Multi-Replica Decoding using Correlation based Localisation(MARSALA) has been introduced and has shown good performance with DVB-RCS2 coding scheme and equi-powered transmissions. However, it has been shown in the literature that alternative coding schemes and packets power distributions can have a positive impact on RA performance. Therefore, in this paper, we investigate the behaviour of MARSALA with various coding schemes and various packet power distributions, then we propose a configuration for optimal performance. This paper also introduces the enhancement of MARSALA RA scheme by adding MRC to optimize replicas combination and study the impact on the throughput. We compare two different MRC techniques and we evaluate, via simulations, the gain achieved using MRC with different coding schemes and unbalanced packets. The simulation results demonstrate that the proposed enhancements to MARSALA show substantial performance gain, i.e. throughput achieved for a target Packet Loss Ratio (PLR)

Improved calibration procedures for the EM27/SUN spectrometers of the COllaborative Carbon Column Observing Network (COCCON)

In this study, an extension on the previously reported status of the COllaborative Carbon Column Observing Network\u27s (COCCON) calibration procedures incorporating refined methods is presented. COCCON is a global network of portable Bruker EM27/SUN FTIR spectrometers for deriving column-averaged atmospheric abundances of greenhouse gases. The original laboratory open-path lamp measurements for deriving the instrumental line shape (ILS) of the spectrometer from water vapour lines have been refined and extended to the secondary detector channel incorporated in the EM27/SUN spectrometer for detection of carbon monoxide (CO). The refinements encompass improved spectroscopic line lists for the relevant water lines and a revision of the laboratory pressure measurements used for the analysis of the spectra. The new results are found to be in good agreement with those reported by Frey et al. (2019) and discussed in detail. In addition, a new calibration cell for ILS measurements was designed, constructed and put into service. Spectrometers calibrated since January 2020 were tested using both methods for ILS characterization, open-path (OP) and cell measurements. We demonstrate that both methods can detect the small variations in ILS characteristics between different spectrometers, but the results of the cell method indicate a systematic bias of the OP method. Finally, a revision and extension of the COCCON network instrument-to-instrument calibration factors for XCO2, XCO and XCH4 is presented, incorporating 47 new spectrometers (of 83 in total by now). This calibration is based on the reference EM27/SUN spectrometer operated by the Karlsruhe Institute of Technology (KIT) and spectra collected by the collocated TCCON station Karlsruhe. Variations in the instrumental characteristics of the reference EM27/SUN from 2014 to 2017 were detected, probably arising from realignment and the dual-channel upgrade performed in early 2018. These variations are considered in the evaluation of the instrument-specific calibration factors in order to keep all tabulated calibration results consistent

Encoding and reusing linguistic information expressed by Linguistic Properties

International audienceThis paper presents a way to express linguistic knowledge independently of any algorithmic machinery and of any particular grammatical formalism. This is performed through Linguistic Properties, that will be presented. First, the status of linguistic knowledge in grammars is discussed, then the Linguistic Properties are presented and two experiments are mentioned. They illustrate the reusability of the linguistic information enclosed in these Properties

Properties in 5P

This research report presents a formalism for the description of natural languages, called Properties. Properties are an alternative to formal grammars such as GPSG, HPSG, LFG, etc. A grammar of this type has a twofold function: it is intended to be both a description of some language and the declarative source of some algorithmic machinery that can process that language. Properties, on the contrary, allow to distinguish the two aspects and are strictly limited to the descriptive aspect. They consist in formulas about the categories in the strings of the described language, specifying uniqueness and optionality characteristics, and cooccurrence, agreement or linearity relations. Properties, as a formalism, are part of a larger framework: the 5P paradigm. The 5P paradigm is conceived as a mean to effectively place linguistics within the class of empirical sciences. It is outlined in section 2 and further discussed in section 9

De la description des propriétés linguistiques à l'analyse d'une langue

International audienceUn algorithme d'analyse de texte – l'algorithme d'analyse par les feuilles – est présenté. Notre approche, inscrite dans le cadre 5P, se caractérise par:-- La source déclarative des algorithmes d'analyse est physiquement complètement séparée des descriptions linguistiques. Nous nous démarquons en cela des approches utilisant les grammaires d'unification, où la grammaire a une double fonction : exprimer les descriptions linguistiques et servir de source aux traitements. -- La possibilité de moduler la finesse de l'analyse selon les fonctionnalités que l'on souhaite assurer en extrayant des descriptions plus ou moins d'information.-- La mise en évidence de principes généraux sur le fonctionnement des langues (transition diabolique). Les idées de base de la méthodologie 5P sont rappelées, ainsi que l'appareil descriptif utilisé. On montre par la suite comment, à partir des descriptions linguistiques formalisées, dériver l'information nécessaire aux différents aspects de l'algorithme d'analyse. Enfin, les grandes lignes d'un algorithme de balisage de syntagmes nominaux dans un texte sont présentées