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From Pathological Bifurcations to Meaningful Planetary Change Agents
No full textInternational audienceThis chapter discusses and analyzes the phenomenon of pathological bifurcation among French engineering students. Pathological bifurcation occurs when sustainable development succeeds in inspiring student activism, but that passion expresses itself destructively. The chapter answers two questions. First, we interrogate whether pathological bifurcation is a product of lacunae with current SD education practices. Having answered affirmatively, we reflect on how to treat this diagnosis. Our suggestion is that if SDG related curricular innovations are desirable, so too is an extensive grounding in the traditional teachings of what we call planetary humanities. These are lessons drawn from around planet inculcating the very traditional moral art of controlling one's passions in such a way as to best foster collective flourishing
Monitoring of geophysical deformations on a regional scale using the low-cost GNSS collaborative network CentipedeRTK
No full textInternational audienceDeveloped since 2019, the CentipedeRTK network is a permanent collaborative GNSS network whose main objective is to make RTK positioning freely available, mainly using low-cost receivers and antennas. Since its creation, the network has grown considerably, well beyond the borders of France, and now includes more than 800 base stations. The main sector using the network is agriculture, but more and more public and private organisations and individuals are also using it. The geoscience community quickly became interested in the network, first as users of RTK positioning (for sea level monitoring, drone surveys, etc.) and then for post-processing of the raw measurements from the base stations. Since mid-2022, the RENAG network data centre has therefore been archiving the data from the base stations on a daily basis with the aim of using them for geoscience applications. A first study based on data acquired in 2023 has demonstrated the value of these data for monitoring atmospheric water vapour over continental France. Here we focus on the use of data acquired by CentipedeRTK base stations located in mainland France to monitor geophysical movements on a regional scale. To this end, the daily positions of the CentipedeRTK stations estimated in PPP using GipsyX are analysed and compared with those estimated for nearby permanent stations belonging to conventional networks. There is a slight deterioration in the repeatability of the mean positions (15 to 20% depending on the component). The time series show an increase in dispersion, but a very good consistency of the variations is still observed. The discrepancies observed can be explained by the equipment of the CentipedeRTK stations, in particular their antenna, as well as by the direct environment of the stations, which is not always as optimal as that of conventional stations. These results will be used to develop a set of recommendations for CentipedeRTK contributors and will help to increase the value of the data collected by the network's base stations for geoscience applications.
Analysis of time-harmonic electromagnetic problems with elliptic material coefficients
No full textInternational audienceWe consider time-harmonic electromagnetic problems with material coefficients represented by elliptic fields, covering a wide range of complex and anisotropic material media. The properties of elliptic fields are analyzed, with particular emphasis on scalar fields and normal tensor fields. Time-harmonic electromagnetic problems with general elliptic material fields are then studied. Well-posedness results for classical variational formulations with different boundary conditions are reviewed, and hypotheses for the coercivity of the corresponding sesquilinear forms are investigated. Finally, the proposed framework is applied to examples of media used in the literature: isotropic lossy media, geometric media, and gyrotropic media
Artificial Potential Fields-based Obstacle Avoidance for Uncrewed Sailboats (Long Version)
No full textInternational audienceTo safely navigate their environment, UncrewedSailboats must detect and avoid obstacles such as other vessels,buoys, debris, and natural formations. Although many stud-ies have proposed obstacle avoidance techniques for engine-powered autonomous vessels, such strategies cannot be directlyimplemented on sailboats due to their maneuverability con-straints. Specifically, sailboats cannot sail directly upwind andare more sensitive to ocean currents. In this study, we present anobstacle avoidance strategy based on Artificial Potential Fields,particularly tailored for autonomous sailboats without priorknowledge or memory of the surrounding environment. Sucha strategy enables handling unexpected changes in the envi-ronment or exploring unknown or poorly mapped areas wherea priori information is either unavailable or unreliable. Wemodel obstacles as Gaussian repulsive potentials, incorporatinga circular safety area proportional to detection uncertaintiesdue to errors in position, shape, and size measurements. Toaddress the issue of local minima caused by force alignmentsnear obstacles, we add two repulsive potentials along thetangent lines connecting the boundary of the safety area tothe sailboat, pointing towards the craft. Close obstacles arealso combined into a single ellipse-shaped obstacle to furtherreduce local minima. This strategy was tested in simulation,first with up to five static obstacles and then with one dynamicobstacle moving along a linear trajectory at a constant speed
Software design patterns for a STRIDE approach on an AUV fleet
No full textInternational audienceThe use of drones has become widespread in many fields, including critical ones. It means that these devices need to be protected against cyber attacks, and more generally, against contingencies, with a view to infrastructure resilience.This study simulates the operations of a drone fleet and assesses the impact of potential attacks or threats. It leverages the STRIDE threat modeling framework, which categorizes six types of threats: impersonation, tampering, repudiation, information disclosure, denial of service, and privilege escalation. Autonomous underwater vehicles (AUVs) are available, affordable, and can play a critical role for many applications; therefore, the systems we chose as analysis targets integrate AUVs and USVs as physical components, as well as digital avatars. This work is based on a model-based systems engineering (MBSE) approach. The use of models facilitates interoperability with third-party tools, enabling hybrid simulations and flexible integration of new devices, as well as global state capture via evaluators. Moreover, the use of well-established software design patterns ensures the modularity, reusability, and maintainability of the environment.Currently, our case study is to map an area of interest using a fleet of virtual drones, prior to deploying a mixed infrastructure. The process starts with data acquisition, followed by the refinement of data into information, then into knowledge, assuming the zone has been previously covered by a hydrographic study, and finally provides mission feedback. The potential risk lies in the manipulation of data or disruption of the drones' functionalities (such as movement, communication, etc.), which could compromise the mission's success and the integrity of the infrastructure.Future work will extend this framework to advanced threat and risk assessments (TARA), taking partial failures into account, exploring complex scenarios and drawing on more comprehensive metrics to propose appropriate security enhancement measures
Efficient Quantum Circuits for Non-Unitary and Unitary Diagonal Operators with Space-Time-Accuracy trade-offs
No full textInternational audienceUnitary and non-unitary diagonal operators are fundamental building blocks in quantum algorithms with applications in the resolution of partial differential equations, Hamiltonian simulations, the loading of classical data on quantum computers (quantum state preparation) and many others. In this paper, we introduce a general approach to implement unitary and non-unitary diagonal operators with efficient-adjustable-depth quantum circuits. The depth, i.e. the number of layers of quantum gates of the quantum circuit, is reducible with respect either to the width, i.e. the number of ancilla qubits, or to the accuracy between the implemented operator and the target one. While exact methods have an optimal exponential scaling either in terms of size, i.e. the total number of primitive quantum gates, or width, approximate methods prove to be efficient for the class of diagonal operators depending on smooth, at least differentiable, functions. Our approach is general enough to allow any method for diagonal operators to become adjustable-depth or approximate, decreasing the depth of the circuit by increasing its width or its approximation level. This feature offers flexibility and can match with the hardware limitations in coherence time or cumulative gate error. We illustrate these methods by performing quantum state preparation and non-unitary-real-space simulation of the diffusion equation: an initial Gaussian function is prepared on a set of qubits before being evolved through the non-unitary evolution operator of the diffusion process
Local-scale experimental investigation of a two-phase cross-flow in a tube bundle and flow-induced vibration; Bubbly flow regime
No full textInternational audienceTwo-phase cross-flows can induce vibrations in several industrial situations. This is especially the case in nuclear power plant U-tube Steam Generator (SG) tube bundles. With the purpose of gathering high quality data for the validation of multiphase CFD simulation tools, a new experimental apparatus was designed and put in operation. The facility is instrumented for the two-phase air–water flow and tube vibration characterization. The two-phase flow was investigated starting from the bubble generation at the gas injection, to inside the tube bundle. Bubble sizes, shapes and velocities were measured by means of high speed camera image post-processing in the region comprised from the gas injection to the inlet of the tube bundle: the bubbles are generated with unstable size and shape, this results in promoting their breakup before reaching the tube bundle. The local behavior of the two-phase flow within the tube bundle was studied through an optical dual-tip probe, placed in different positions in order to obtain profiles of void fraction, bubble diameter and gas velocity. To study the flow-induced vibrations, the central tube of the bundle was designed to be flexible, and its vibrational response was studied by accelerometers. The root mean square displacements could be derived and the variation of the added mass with the void fraction could be observed. This paper represents the first part of two papers and focuses on bubbly flow experimental tests; the second part focuses on experimental tests performed at the so-called intermittent flow-regime conditions
Simulation-free Reduced-order Modeling using Invariant Manifolds
No full textInternational audienceThis chapter introduces the concept of invariant manifold as a key tool for model order reduction of dynamical systems
Energy stable and linearly well-balanced numerical schemes for the non-linear Shallow Water equations with Coriolis force
No full textInternational audienceWe analyse a class of energy-stable and linearly well-balanced numerical schemes dedicated to the nonlinearShallow Water equations with Coriolis force. The proposed algorithms rely on colocated finite-difference approx-imations formulated on cartesian geometries. They involve appropriate diffusion terms in the numerical fluxes,expressed as discrete versions of the linear geostrophic equilibrium. We show that the resulting methods ensuresemi-discrete energy estimates. Among the proposed algorithms a colocated finite-volume scheme is described.Numerical results show a very clear improvement around the nonlinear geostrophic equilibrium when comparedto those of classic Godunov-type schemes
APLOSE: A web-based annotation platform for underwater passive acoustic monitoring
No full textInternational audienceEmerging detection and classification algorithms based on deep learning models require manageable large-scale manual annotations of ground truth data. To date, the challenge of creating large and accurate annotated datasets of underwater sounds has been a major obstacle to the development of robust recognition algorithms. APLOSE (Annotation PLatform for Ocean Sound Explorers) is an open-source, web-based tool which facilitates collaborative annotation campaigns in underwater acoustics. The platform was used to carry out research projects on inter-annotator variability, to build training and testing data sets for detection algorithms and to perform bioacoustics analysis on noisy datasets. In the future, it will enable the creation of high-quality reference datasets to test and train the new detection and classification algorithms