Sea glider guidance around a circle using distance measurements to a drifting acoustic source

International audienceThis paper describes a simple yet robust sea glider guidance method in a constellation of Lagrangian drifters under the polar ice cap. The glider has to perform oceanographic measurements, mainly conductivity, temperature and depth, in the area enclosed by the drifters and can not rely on GNSS (Global Navigation Satellite System) positionning data as the polar ice cap makes it impossible to surface. The originality of the presented method resides in 2 points. First, a very simple PID (Proportional, Integral and Derivative) controller based on a basic kinematic model is tuned. Second, the method does not use a localization algorithm to estimate state space model data but interval analysis methods are performed to bound the errors in range to the transponder and its derivative. Moreover, only one acoustic beacon is used. Validation is then performed through simulations

Effect of L-thyroxine treatment on peripheral blood dendritic cell subpopulations in patients with Hashimoto’s thyroiditis

Recent reports suggested dendritic cells (DCs) to be important players in the pathogenesis of autoimmune thyroid processes in humans. However, there are virtually no data addressing the influence of thyroid autoaggression-associated disturbances of thyrometabolic conditions on DCs biology. The aim of the study was to evaluate the influence of L-thyroxine supplementation on conventional and plasmacytoid peripheral blood DCs subtypes in patients with hypothyroidism due to Hashimoto’s thyroiditis (HT). Eighteen patients with newly diagnosed hypothyroidism due to HT were included into the study. All patients received L-thyroxine treatment with doses adjusted to reach euthyroidism. Peripheral blood DC subtypes structure and immunoregulatory phenotype were analyzed by flow cytometry in the same patient prospectively at two time points: (i) beforeand (ii) 3 months after beginning of L-thyroxine treatment (hypothyroidism vs. euthyroidism, respectively). Percentage of plasmacytoid DCs in peripheral blood mononuclear cells fraction was significantly decreased in the course of L-thyroxine treatment (0.27 ± 0.19 vs. 0.11 ± 0.08; p < 0.05), whereas we did not observe any changes in the number of conventional DCs. However, the phenotypic analysis showed a significant increase of conventional DCs expressing CD86 and CD91 (64.25 ± 21.6% vs. 86.3 ± 11%; p < 0.05 and 30.75 ± 11.66% vs. 44.5 ± 13.3%; p < 0.05; respectively) in euthyroid patients. Standard L-thyroxine supplementation in HT patients exerted significant immunoregulatory effects, associated with quantitative and phenotypic changes of peripheral blood DC subpopulations

Deployment of a persistent underwater acoustic sensor network: The CommsNet17 Experience

This paper presents the experimental activities performed by the NATO STO Centre for Maritime Research and Experimentation (CMRE) during the CommsNet17 trial where a persistent Underwater Acoustic Sensor Network (UASN) was deployed. The CommsNet17 trial was held from the 27th of November to the 6th of December in the Gulf of La Spezia (IT), close to the CMRE premises, using the CMRE Littoral Ocean Observatory Network (LOON) as one of its key components. A network consisting of up to eleven nodes was deployed, including static and mobile assets. Various aspects related to persistent UASNs were addressed, including autonomous and distributed network discovery and node configuration, node localisation and navigation, self-adjustment of the network topology in support to the assigned tasks, underwater docking, wireless battery recharging and data offloading. The collected results show that the employed solutions were able to successfully complete all these tasks, thus demonstrating the effective deployment of a persistent, distributed and ad-hoc UASN

Arbeitsqualität und wirtschaftlicher Erfolg: Längsschnittstudie in deutschen Betrieben ; Endbericht

Die Studie Arbeitsqualität und wirtschaftlicher Erfolg hat zum Ziel, die Wirkung von Personalmaßnahmen und insbesondere die Zusammenhänge zwischen der Arbeitsqualität der Beschäftigten und dem wirtschaftlichen Erfolg von Betrieben zu untersuchen. Es handelt sich um eine Längsschnittstudie, in der in drei Befragungswellen seit 2012 jeweils eine Betriebs- und eine Beschäftigtenbefragung durchgeführt wurde. Der Abschlussbericht fasst die Daten aus allen Befragungswellen zusammen. Die Forschungsstudie wird vom Bundesministerium für Arbeit und Soziales (BMAS) und vom Institut für Arbeitsmarkt- und Berufsforschung (IAB) getragen und vom IAB, vom Seminar für Allgemeine Betriebswirtschaftslehre und Personalwirtschaftslehre der Universität zu Köln, dem Lehrstuhl für Managerial Accounting der Eberhard Karls Universität Tübingen und vom Zentrum für Europäische Wirtschaftsforschung (ZEW) durchgeführt. In Verlängerung des Forschungsprojekts wir derzeit eine vierte Befragungswelle vorbereitet

Méthodes ensemblistes pour une localisation robuste de robots sous-marins

For an intelligent robot to be able to properly interact with its environment, it has to know in one hand the environment and in the other hand its state in that environment. In particular, a robot must know where it is to know where it has to go. Since the appearance of GPS, the problem of localization has been practically solved on the ground. GPS doesn't work underwater since high frequency electromagnetic waves don't propagate in that environment. However, the number of undersea operations increases significantly every year. In our school, we develop an autonomous underwater vehicle to test the underwater localization systems. The main sensor we use is an imaging sonar. An imaging sonar is an acoustic sensor which detects acoustically reflective objects. For example, the sonar can be used to detect the walls of a port. The measurements from the sonar are often corrupted with outliers. An outlier may be due to an electrical failure of the sensor or a phenomenon not taken into account when modeling the environment. The number of outliers is often unknown and varies with time. The aim of this thesis was to solve the localization problem using such data. The localization problem can be formulated as a constraint satisfaction problem (CSP). A CSP is basically a system of equations (constraints). Here, the unknown is the pose of the robot. For each measurement we obtain a constraint involving the pose, a measurement and the environment (the map). The classical solution of a CSP is the set of points (poses) that satisfy all constraints. However, because of outliers, such points may not exist. The new problem is to find a solution to a CSP when only part of constraints is satisfied. We call this problem a relaxed CSP. A major contribution to the thesis was to find several representations of the solution of a relaxed CSP as well as algorithms to compute these solutions. The first representation is in the form of a polynomial with set valued coefficients also called a set polynomial. Each coefficient is the set of points that satisfy the number of constraints equal to the degree of the coefficient in the polynomial. Such representation allows the use of polynomial arithmetic to calculate the solution polynomial. A second representation is in the form of a function, called accumulator, which for each element of the search space returns the number of constraints it satisfies. One of the hurdles to overcome to solve localization problems is the representation of the map. In case of structured environments, it is possible to represent the map by a set of parameterized objects such as segments, polygons, curves. In case of unstructured maps such as seashore or lake borders, the idea is to represent the map (which actually is a set) in the form of a binary image where pixels of interest (black for example) represent the set of points of the map. Another major contribution to the thesis was to be able to use the binary image representation in CSP or relaxed CSP computer solvers in the form of a contractor called the image contractor. The usefulness of those two contributions is illustrated on a real case example of localization of an underwater robot in an abandoned marina. The thesis contains many other contributions to set membership methods and the contractor theory.Pour qu'un robot autonome puisse interagir proprement avec son milieu, ce dernier doit connaitre d'une part l'environnement dans lequel il évolue et d'autre part son état dans cet environnement. En particulier, un robot doit savoir où il est pour savoir où il doit aller. Depuis l'apparition du GPS, le problème de la localisation a été pratiquement résolu pour les robots terrestres. Le GPS ne fonctionne pas sous l'eau. Toutefois, le nombre d'opérations sous-marines augmente de manière significative chaque année. Dans notre école, nous développons un robot sous-marin pour tester des systèmes de localisation sous-marins. Le capteur principal que nous utilisons est un sonar sectoriel. Un sonar est un capteur acoustique qui positionne les objets acoustiquement réfléchissant. Par exemple, le sonar peut être utilisé pour détecter les parois d'un port. Ce capteur donne souvent des mesures aberrantes. Une telle mesure peut être due à une défaillance électrique du capteur ou d'un phénomène non pris en compte lors de la modélisation de l'environnement. Le nombre de mesures aberrantes est souvent inconnu et varie avec le temps. Le but de la thèse est de résoudre le problème de localisation avec de telles données. Un problème de localisation peut être formulé en tant que problème de satisfaction de contraintes (CSP en anglais). Un CSP est en gros un système d'équations (contraintes). Ici, l'inconnu est la pose du robot. Pour chaque mesure on obtient une contrainte reliant la pose, la mesure et l'environnement. La solution classique d'un CSP est l'ensemble des points (poses) qui satisfont toutes les contraintes. Toutefois, a cause des données aberrantes de tels points peuvent ne pas exister. Le nouveau problème consiste à trouver une solution d'un CSP lorsque une partie seulement de contraintes est satisfaite. Nous appelons ce problème un CSP relaxé. Une des contributions majeures à la thèse était de trouver plusieurs représentations de la solution d'un CSP relaxé ainsi que les algorithmes qui permettent de calculer ces solutions. La première représentation est sous la forme d'un polynôme dont les coefficients sont des ensembles que nous appelons polynômes ensemblistes. Chaque coefficient correspond à l'ensemble des points qui satisfont le nombre de contraintes égal au degré du coefficient dans le polynôme. Une telle représentation permet d'utiliser l'arithmétique des polynômes pour calculer le polynôme solution. Une deuxième représentation est sous la forme d'une fonction, qu'on appelle accumulateur, qui pour chaque élément de l'espace de recherche retourne le nombre de contraintes satisfaites. Un des obstacles à surmonter pour résoudre les problèmes de localisation est la représentation de la carte. En cas d'environnements structurés, il est possible de représenter la carte par un ensemble d'objets paramétrés tels que des segments, polygones ou des courbes. En cas d'environnements non structurées où en partie structurées tels que des cartes marines ou des cartes routières, l'idée est de représenter la carte (qui est en fait un ensemble de points) sous la forme d'une image binaire où les pixels d'intérêt (noir par exemple) représentent l'ensemble des points de la carte. Une des contributions majeures de la thèse était d'incorporer une telle représentation de la carte dans le formalisme d'un CSP ou d'un CSP relaxé sous la forme d'un contracteur appelé le contracteur sur l'image. L'utilité de ces deux contributions est montrée par un exemple de localisation d'un vrai robot dans une marina abandonnée. La thèse contient plusieurs autres contributions aux méthodes ensemblistes et la théorie des contracteurs

Bandwidth efficient concurrent localisation and communication in underwater acoustic networks

Localisation is essential for an Autonomous Underwater Vehicle (AUV) to perform its mission and to georeference any data acquired during the dive. When the AUV is part of a heterogeneous underwater acoustic network (UAN), concurrent communications and localisation can be exploited to support AUV operations. However, since acoustic communication is low bandwidth there is the need to reduce the overhead required to exchange localisation data. This paper presents a novel method to efficiently encode and decode localisation information. This results in a lower overhead without impacting the localisation performance. Results are presented from the CommsNet17 sea trial where a network consisting of up to eleven nodes was deployed, including static and mobile nodes

Localisation using undersea wireless networks

Underwater navigation for Autonomous Underwater Vehicles (AUVs) is a challenging task, requiring a trade-off between performance, costs and operational time. The project Network Long Base Line (Net-LBL) proposes a system for acoustic-based navigation that relies on the addition of localisation services to underwater networks. The localisation capability is added on top of existing networks, without imposing constraints on their structure or operation. All the nodes can act as transponders of a network baseline, with no need for dedicated instrumentation. This paper evaluates the Net-LBL system using an interval method-based navigation solution in a number of configurations, including the use of TDMA and CSMA MAC protocols, range-only and bearing-only measurements, and with different geometries. Results collected during the NETLBL17b sea trial, held in the Gulf of La Spezia, Italy, are presented and discussed