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Wakefield Generation in Hydrogen and Lithium Plasmas at FACET-II: Diagnostics and First Beam-Plasma Interaction Results
No full textInternational audiencePlasma Wakefield Acceleration (PWFA) provides ultrahigh acceleration gradients of 10s of GeV/m, providing a novel path towards efficient, compact, TeV-scale linear colliders and high brightness free electron lasers. Critical to the success of these applications is demonstrating simultaneously high gradient acceleration, high energy transfer efficiency, and preservation of emittance, charge, and energy spread. Experiments at the FACET-II National User Facility at SLAC National Accelerator Laboratory aim to achieve all of these milestones in a single stage plasma wakefield accelerator, providing a 10 GeV energy gain in a <1 m plasma with high energy transfer efficiency. Such a demonstration depends critically on diagnostics able to measure emittance with mm-mrad accuracy, energy spectra to determine both %-level energy spread and broadband energy gain and loss, incoming longitudinal phase space, and matching dynamics. This paper discusses the experimental setup at FACET-II, including the incoming beam parameters from the FACET-II linac, plasma sources, and diagnostics developed to meet this challenge. Initial progress on the generation of beam ionized wakes in meter-scale hydrogen gas is discussed, as well as commissioning of the plasma sources and diagnostics
Cell seeding dynamics in a porous scaffold material designed for meniscus tissue regeneration
No full textInternational audienceWe study the dynamics of a seeding experiment where a fibrous scaffold material is colonized by two types of cell populations. The specific application that we have in mind is related to the idea of meniscus tissue regeneration. In order to support the development of a promising replacement material, we discuss certain rate equations for the densities of human mesenchymal stem cells and chondrocytes and for the production of collagen‐containing extracellular matrix. For qualitative studies, we start with a system of ordinary differential equations and refine then the model to include spatial effects of the underlying nonwoven scaffold structure. Numerical experiments as well as a complete set of parameters for future benchmarking are provided
An algorithm for computing scattering poles based on dual characterization to interior eigenvalues
No full textInternational audienceWe present an algorithm for the computation of scattering poles for an impenetrable obstacle with Dirichlet or Robin boundary conditions in acoustic scattering. This paper builds upon the previous work of Cakoni et al . (2020) titled ‘A duality between scattering poles and transmission eigenvalues in scattering theory’ (Cakoni et al . 2020 Proc. A. 476 , 20200612 ( doi:10.1098/rspa.2020.0612 )), where the authors developed a conceptually unified approach for characterizing the scattering poles and interior eigenvalues corresponding to a scattering problem. This approach views scattering poles as dual to interior eigenvalues by interchanging the roles of incident and scattered fields. In this framework, both sets are linked to the kernel of the relative scattering operator that maps incident fields to scattered fields. This mapping corresponds to the exterior scattering problem for the interior eigenvalues and the interior scattering problem for scattering poles. Leveraging this dual characterization and inspired by the generalized linear sampling method for computing the interior eigenvalues, we present a novel numerical algorithm for computing scattering poles without relying on an iterative scheme. Preliminary numerical examples showcase the effectiveness of this computational approach
The impact of artificial intelligence in the evolution of innovation trajectories in agriculture
No full textInternational audienceTo what extent is Artificial Intelligence (AI) transforming ways of innovating in the agricultural sector and shaping the agricultural technological trajectory to reach Sustainable Development Goals (SDGs)? We propose a method based on network analysis to identify the technological trajectory inflections and paradigmatic shifts that innovations in AI generate in agriculture. Based on the patents’ technological contents over the period 2013-2019 and using network analysis tools, we show that AI has a driving function in the transformation of innovation processes in agriculture, in connection with the actual challenges that arise in crop management. This new General Purpose Technology is playing an increasingly active role in the technical progress of agriculture and is disrupting its invention processes and even more, help to achieve certain SDGs. For example, the technical guidance system for agricultural machinery, which involves technologies linked to control and regulation, often associated with automation and control systems, which can be crucial for optimizing industrial processes and efficient resource management, is directly impacting SDGs such as industry, innovation and infrastructure (SDG 9). Moreover, automated control systems with agricultural technologies can contribute to SDG 2 (Zero Hunger) through smart and sustainable agriculture
Impact of rotation change on the emptying of an ideal bottle of water
No full textInternational audienceWe are carrying out the experimental study of the emptying of a hermetically sealed cylindrical tank in a rotating frame. We determine the optimal rotational velocity for the tank, which minimizes the emptying time. Moreover, there exists a critical rotation velocity at which the emptying time exceeds that of the nonrotating case, depending on the relative duration of each of the three emptying regimes identified in this flow, namely, (i) a bubble regime, (ii) a vortical air jet regime, and (iii) a bathtub vortex regime. The three regimes, easily distinguished by the shape of the air-water interface, have different draining velocities. The lifetime of each regime, as well as the transitions between them, depend on both the water level and the rotating velocity of the platform
A Constraint Programming Approach for Polytopic Simulation of Ordinary Differential Equations
No full textInternational audienceThis paper presents a constraint-based approach to compute thereachable tube of nonlinear differentiable equations. A set of initialvalues for the equations is considered and defined by a polytoperepresented as intersections of zonotopes. Guaranteed numericalintegration based on zonotopic computation is used to computereachable tubes. In order to efficiently build polytopes defined bythe intersection of several zonotopes, we use a previously developedabstract domain to represent reachable tubes. The proposedcontribution allows to compute more expressive reachable tubes moreefficiently than methods based only on boxes, and therefore couldimprove verification/validation processes in robotics application forexample. The approach is evaluated on examples taken from literatureand we present two applications of this work.<br /
Dynamic analysis of 3D-printed CF-PETG composites with different infill densities
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Asymptotically minimal interval contractors based on the centered form;: Application to the stability analysis of linear time-delayed differential equations
No full textInternational audiencethe stability analysis of linear time-delayed differential equations</div
Data-centric warfare and the reshuffle of armament market
No full textInternational audienceMilitary capabilities have become increasingly technology-intensive since WWII (Bellais and Droff 2016) and it appears that this trend has been intensifying in recent years under two drivers: the comeback of Clausewitzian war (opposed to contingency operations), and the blossoming of civilian IT innovation on both software and hardware dimensions (gearing up the renewal of military resources).This evolution could jeopardised the equilibria inside the defence technological and industrial base, disrupting a quite stable landscape over more than half a century. However, can we consider that the new rules of the game are able to put this market upside down? Or, do these innovations only constitute an intensification of pre-existing trends?The question proposed in this contribution consists in analysing to what extent the growing role of data in military operations leads to question the current approach to military effectiveness and therefore how to design military capabilities in their relation to data.This contribution puts into perspective the interactions between technology, operational needs and the capability development process. It aims to identify the transformative effect of the place of data in the architecture of defence system and the possibility of developing a multilayer approach in which data and artificial intelligence play an essential place. It will put into perspective the projects for future air and land combat systems that are planned within a decade