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3D-Printed Ultra-Wideband In-Band Full-Duplex Antenna System with Grating Lobes Reduction
No full text"BEST PAPER AWARD 2nd Place in the 34th International Conference on Microelectronics “IEEE ICM’22”International audienceThis article presents an ultra-wideband in-band full-duplex antenna system based on a special 3D-printed Vivaldi array. To mitigate grating lobes inherent in such arrays, the single Vivaldi element size is reduced partially at its bottom and its body is exponentially tapered. In the array, this allowsbringing the antennas closer together at their bottom parts, reducing the distance between the radiating slots, which translates to grating lobes reduction, especially at higher frequencies. The system can achieve, in simulation, a decade matching bandwidth from 2 to 20 GHz with more than 60 dB of self-interference cancellation and 12.8 dBi of average gain. The grating lobes remain at least 10 dB below the main lobe level throughout the matching bandwidth
Groupes de Lie appliqués à la localisation des robots mobiles
No full textWith the development of offshore activities, the costs of maintenance and monitoring of offshore plants in terms of crew members, boats, and money have greatly increased and are still growing dramatically. This encouraged the development of autonomous underwater vehicles (AUV). These are still very expensive because of the numerous high-end sensors they need to embark on to accomplish their missions. Thus their number is relatively low. Therefore research is made to develop low-cost AUVs that could be produced in a larger amount to perform the same missions. This thesis comes within the scope of this research field. One of the main problems when dealing with AUVs is the localisation of the vehicle which will be the one addressed throughout this work. To tackle it, we present a new guaranteed integration method, which is more robust to the uncertainties on the initial condition than the ones currently available, based on Lie symmetries. This method is first presented through different simple theoretical examples. We then apply it to a localisation problem in a robotic context.Dans le cadre du développement des énergies renouvelables, les activités offshores liées aux parcs éoliens ont grandement augmenté en nombre. Ainsi les coûts de maintenance et de surveillance de telles structures aussi bien en hommes qu'en moyens se sont accrus et cette tendance s'amplifiera sûrement au cours des prochaines années. Ceci a encouragé le développement des véhicules sous-marins autonomes (AUV). Ceux-ci sont encore très coûteux du fait des capteurs onéreux qu'ils embarquent. Ils sont donc encore rares, ce qui ne suffit pas à combler les actuels besoins. Ainsi le développement d'AUVs à bas-coût est un sujet de recherche en forte croissance. C'est dans ce champ de recherche que cette thèse vient s'inscrire. Un des problèmes principaux rencontré en robotique sous-marine est la localisation de l'engin. C'est la résolution de celui-ci qui nous servira d’objectif tout au long de ce travail. Pour ce faire, une nouvelle méthode d'intégration garantie, robuste aux incertitudes sur les conditions initiales est présentées dans ce manuscrit. Celle-ci se base sur l'utilisation des symétries de Lie appliquées aux équations différentielles. Nous la présenterons en premier lieu sur un problème théorique simple avant de l’appliquer sur le problème de localisation d’un robot sous-marin
Are All Catastrophes Now Unnatural Catastrophes? A Historical and Critical Consideration-and Defense-of an Exaggeration
No full textInternational audienc
Gouvernance et autonomie stratégique par l’innovation : Une étude exploratoire
No full textInternational audienceThe identification of ways to increase strategic autonomy, that is, a country’s ability to ensure its autonomy in strategic sectors (e.g. defense activities) has attracted increased interest recently. Such an autonomy can be perceived in terms of innovation. More precisely, this involves both having the knowledge and technologies to act alone and being able to influence technical progress at an international level. This is referred to as “innovation-led strategic autonomy”. In this paper, we study the determinants of innovation-led strategic autonomy using panel data from 33 countries worldwide, observed over the period 2000-2015. Our main focus is on governance (economic, institutional, and political), that is, to what extent differences in strategic autonomy between countries can be attributed to differentiated levels of governance. Country-level strategic autonomy scores are calculated using patent data from the European Patent Office, and relying on the economic dominance theory and structural economic methods. At the level of governance, data from the Worldwide Governance Indicators (WGI) are exploited. The estimation strategy is based on random- and fixed-effects panel regressions. Then, a Hausman test allows to highlight the model that fits the data better. It emerges that “voice and accountability” is correlated positively with innovation-led strategic autonomy. That is, countries with better participation of citizens in selecting their rulers, freedom of expression, free press, and freedom of association, exhibit greater innovation-led strategic autonomy. The greater the likelihood of terrorism, politically-motivated violence, and, more generally, destabilization or overthrow of the government, the greater a country’s level of strategic autonomy. Hence, political governance appears to be critical in explaining the differentials in strategic autonomy between countries. At the level of the control variables, military expenditures are found to be correlated positively with strategic autonomy. Results also show the association between investment and innovation-led strategic autonomy to be U-shaped. That is, there is a minimum level of investment to be achieved so that increases in investment can result in increases in strategic autonomy. We conclude by discussing policy implications.L'identification des moyens d'accroître l'autonomie stratégique des pays a récemment suscité un intérêt accru. Une telle autonomie peut être perçue en termes d'innovation. Dans cet article, nous explorons l'association entre l'autonomie stratégique par l'innovation et la gouvernance en utilisant un panel non cylindré de 33 pays observés sur la période 2000-2015. Les résultats montrent que la dimension « voix et responsabilité » de la gouvernance est corrélée positivement avec l'autonomie stratégique par l'innovation. Plus clairement, les pays affichant un meilleur niveau de participation des citoyens dans le choix de leurs dirigeants, de liberté d'expression, de la presse et d'association, présentent une plus grande autonomie stratégique par l'innovation. Plus la probabilité de terrorisme, de violence à motivation politique et, plus généralement, de déstabilisation ou de renversement du gouvernement, est élevée, plus le niveau d'autonomie stratégique d'un pays est élevé. La gouvernance politique semble donc être importante dans l’explication des différences d'autonomie stratégique entre pays. Au niveau des variables de contrôle, les dépenses militaires sont positivement corrélées à l'autonomie stratégique par l'innovation. Les résultats montrent également une association entre l'investissement et l'autonomie stratégique par l'innovation en forme de « U ». Nous concluons en discutant des implications politiques et économiques des résultats obtenus, des limites de cette recherche, et des perspectives
Sensitivity of Shipborne GNSS Troposphere Retrieval to Processing Parameters
No full textInternational audienceWater vapor is a key variable in meteorology and climate studies. Since the late 90s, Global Navigation Satellite System (GNSS) estimates from ground antennas are commonly used for its description. Indeed, propagation delays are due to the transit of the signal through the atmosphere. The correction of these delays is a crucial step that is needed for the precise GNSS positioning. Integrated Water Vapor (IWV) contents are derived from these delays and are used to describe the distribution of water vapour in the atmosphere. However, severe meteorological phenomena often originate over the oceans and could strongly affect coastal regions. These phenomena are less well described or forecasted because of the small number of observations available in these regions. In this context, the potential of shipborne GNSS measurements has already been highlighted. This work aims at investigating the impact of some GNSS processing parameters on IWV retrieval from a shipborne antenna in PPP mode. The studied parameters are cutoff angle, random walk of the estimated delays, and observation weighting. Data were collected for 2 months in 2018 by the GNSS antenna of a vessel operating in the Bay of Brest, France. The impact of the parameters is assessed by comparing the shipborne GNSS-derived IWV to the IWV estimated from a close GNSS ground station, and those computed by the ERA5 reanalysis and operational radiosonde profiles from the nearest Météo-France station. The most satisfying parameterization is shown to have Root Mean Squared (RMS) differences of 0.5 kg m 2 , 0.9 kg m 2 , and 1.2 kg m 2 compared to GNSS ground station, ERA5, and radiosonde respectively. These conclusive results are also confirmed by comparing the GNSS height estimates to the measurements from the Brest tide gauge, with an RMS difference of 4.9 cm
Vehicle Personality alteration through independent power distribution of an electric all-wheel drive vehicle equipped with four in-wheel twin motors
No full textInternational audienc
Experimental evaluation of the main parameters influencing friction between polyamide fibers and influence of friction on the abrasion resistance
No full textInternational audienceFriction is one of the key factors in the manufacture of ropes, and has an important influence on the mechanical behavior of many fiber assemblies. For this reason, the understanding and the evaluation of the coefficients of friction between fibers is an essential step in the development of numerical rope models. This paper describes tests on a modified, upscaled version of the ASTM (American Society for Testing and Materials) standard yarn-on-yarn abrasion test device, which allows measurement of the friction coefficient between polyamide rope yarns. It is shown that the inter-fiber angle has a significant influence on the friction coefficient, and the direction of movement relative to the filament has to be considered in the determination of this coefficient. A normalized representation allows friction coefficients measured for a range of test conditions to be plotted on a single curve. The abrasion test device allows the friction coefficient to be measured throughout abrasion tests. It is concluded that lower friction leads to higher abrasion resistance and longer lifetime
Learning to Think Like a Factory
No full textInternational audienceThis paper lays out the theory and the pedagogical practice of a course on the circular economy that the authors teach at the ENSTA Bretagne. The particular focus is on how properly oriented work-based education can contribute to ecological awareness and engagement among engineering students. The text is composed in such a way as to encourage other educators to employ or adapt this course for use in their own institutions
Commissioning and first results from the new 2 × 100 TW laser at the WIS
No full textInternational audienceAt the Weizmann Institute of Science, a new high-power-laser laboratory has been established that is dedicated to the fundamental aspects of laser–matter interaction in the relativistic regime and aimed at developing compact laser-plasma accelerators for delivering high-brightness beams of electrons, ions, and x rays. The HIGGINS laser system delivers two independent 100 TW beams and an additional probe beam, and this paper describes its commissioning and presents the very first results for particle and radiation beam delivery