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Scattering in a partially open waveguide: the forward problem
No full textInternational audienceThis paper is dedicated to an acoustic scattering problem in a two-dimensional partially open waveguide, in the sense that the left part of the waveguide is closed, that is with a bounded cross-section, while the right part is bounded in the transverse direction by some Perfectly Matched Layers that mimic the situation of an open waveguide, that is with an unbounded cross-section. We prove well-posedness of such scattering problem and exhibit the asymptotic behaviour of the solution in the longitudinal direction with the help of the Kondratiev approach. Having in mind the numerical computation of the solution, we also propose some transparent boundary conditions in such longitudinal direction, based on Dirichlet-to-Neumann operators. After proving that such artificial conditions actually enable us to approximate the exact solution, some numerical experiments illustrate the quality of such approximation
Establishment of an Electro-Optical Mixing Design on a Photonic SOA-MZI Using a Differential Modulation Arrangement
No full textInternational audienceWe design and evaluate two experimental systems for a single and simultaneous electro-optical semiconductor optical amplifier Mach-Zehnder interferometer (SOA-MZI) mixing system based on the differential modulation mode. These systems and the optimization of their optical and electrical performance largely depend on characteristics of an optical pulse source (OPS), operating at a frequency of f= 39 GHz and a pulse width of 1 ps. The passive power stability of the electro-optical mixing output over one hour is better than 0.3% RMS (root mean square), which is excellent. Additionally, we generate up to 22 dBm of the total average output power with an optical conversion gain of 32 dB, while achieving a record output optical signal to noise ratio (OSNR) up to 77 dB. On the other hand, at the SOA–MZI output, the 128 quadratic amplitude modulation (128-QAM) signal at an intermediate frequency (IF), f1, is up-mixed to higher output frequencies nf ± f1. The advantages of the resulting 128-QAM mixed signal during electrical conversion gains (ECGs) and error vector magnitudes (EVMs) are also evaluated. The performed empirical SOA-MZI mixing can operate up to 118.5 GHz in its high-frequency range. The positive and almost constant conversion gains are achieved. Indeed, the obtained conversion gain values are very close across the entire range of output frequencies. The largest frequency range achieved during experimental work is 118.5 GHz, where the EVM achieves 6% at a symbol rate of 10 GSymb/s. Moreover, the peak data rate of the 128-QAM up mixed signal can reach 70 GBit/s. Finally, the study of the simultaneous electro-optical mixing system is accepted with unmatched performance improvement
Techniques for accelerating Branch-and-Bound algorithms dedicated to sparse optimization
No full textInternational audienceSparse optimization-fitting data with a low-cardinality linear model-is addressed through the minimization of a cardinality-penalized least-squares function, for which dedicated branch-and-bound algorithms clearly outperform generic mixed-integerprogramming solvers. Three acceleration techniques are proposed for such algorithms. Convex relaxation problems at each node are addressed with dual approaches, which can early prune suboptimal nodes. Screening methods are implemented, which fix variables to their optimal value during the node evaluation, reducing the subproblem size. Numerical experiments show that the efficiency of such techniques depends on the node cardinality and on the structure of the problem matrix. Last, different exploration strategies are proposed to schedule the nodes. Best-first search is shown to outperform the standard depth-first search used in the related literature. A new strategy is proposed which first explores the nodes with the lowest least-squares value, which is shown to be the best at finding the optimal solution-without proving its optimality. A C++ solver with compiling and usage instructions is made available
Taxonomy of Requirements Specification Templates
No full textInternational audienceRequirements specification is an early stage of system design. It consists of rephrasing and documenting stakeholders' explanations and needs in the form of clear and coherent requirements. However, these requirements are often expressed in natural language since it is the easiest communication method. Researchers have proposed semi-structured natural language templates or boilerplates for specifying functional and nonfunctional requirements, which consider security requirements. This seeks to enhance the quality of the requirements specifications and simplify their transformation to system models. However, it is still unknown what concepts, quality attributes, and good practices should be considered to specify requirements in a semi-structured natural language and how that information has been considered in the existing templates. In this paper, we aim to determine how templates are related among them and what are the implications (e.g., complexity, completeness, time) of using one or another. In this paper, we identify each template's concepts, quality attributes, and good practices by studying the template's aspects and then using a running example to formulate requirements using these templates. We also identify the aspects repeated or inherited from one template to another. This paper puts forward a taxonomy of requirements specification templates that categorize and specify the sources of the templates, which helps determine what template considers the aspects of another
Accumulation of microplastics in stomach, intestine, and tissue of two shrimp species (Metapenaeus moyebi and Macrobrachium rosenbergii) at the Khlong U-Taphao, southern Thailand
No full textInternational audienceThe findings revealed that fibre was the most prevalent type of microplastic found in Metapenaeus moyebi, while fragment was the most prevalent type in Macrobrachium rosenbergii. The majority of MPs found in Metapenaeus moyebi was less than 100 µm in size, whereas Macrobrachium rosenbergii are larger than 1 mm. This study discovered MPs in a variety of colours, including blue, black, deep blue, red, and green. The amount of microplastics found in the three organs of two shrimp species did not differ significantly (p > 0.05). There was no correlation between microplastic and Metapenaeus moyebi length (p > 0.05), but there was in Macrobrachium rosenbergii (p 0.5). © 2023 Association of Agricultural Technology in Southeast Asia
Renewable-based charging in green ride-sharing
No full textPaper submitted for publication consideration in Scientific ReportsInternational audienceGovernments, regulatory bodies, and manufacturers are proposing plans to accelerate the adoption of electric vehicles (EVs), with the goal of reducing the impact of greenhouse gases and pollutants from internal combustion engines on human health and climate change. In this context, the paper considers a scenario where ride-sharing enterprises utilize a 100%-electrified fleet of vehicles, and seeks responses to the following key question: How can renewable-based EV charging be maximized without disrupting the quality of the ride-sharing services? We propose a new mechanism to promote EV charging during hours of high renewable generation, and we introduce the concept of charge request, which is issued by a power utility company. Our mechanism is inspired by a game-theoretic approach where the power utility company proposes incentives and the ride-sharing platform assigns vehicles to both ride and charge requests; the bargaining mechanism leads to prices and EV assignments that are aligned with the notion of Nash equilibria. Numerical results show that it is possible to shift the EV charging during periods of high renewable generation and adapt to intermittent generation while minimizing the impact on the quality of service. The paper also investigates how the users’ willingness to ride-share affects the charging strategy and the quality of service
G∀min∃ : Exploration de la frontière entre les langages de spécification exécutables et les outils d’analyse du comportement
No full textThe formal verification community strives to prove the correctness of a specification using formal logic and mathematical proofs. The tremendous progress in computer-aided formal verification tools, along with an ever-growing number of success stories renders these methods essential in the system designer toolbox. However, with the advent of domain-specific models and languages, many formalisms are proposed for writing dynamic system specifications, each one adapted to the specific needs of the targeted domain. A new question emerges: How to bridge the gap between these domain-specific formalisms, geared toward domain experts, and the formal verification tools, geared towards mathematicians? One of the answers, ubiquitous in the literature, relies on using model transformations to syntactically translate the domain-specific model to the verification model. We argue that this approach is counterproductive leading to semantic multiplication, which requires equivalence proofs that can be hard to provide and maintain.In this dissertation, I present a new semantic-level answer developed, refined, and evaluated during the last 10 years with the help of 6 postdoctoral fellows, 8 Ph.D. candidates, and 12 collaborative projects. This approach, named G∀min∃, promises a modular, compositional, and reusable software architecture allowing the design of a wide variety of behavior exploration tools. The core building block of this approach is a language-agnostic semantic-level interface, which acts as a bridge between the dynamic semantics of a domain-specific language and the behavior analysis tools. Here we propose a formalization of the interface along with some reusable operators for creating behavior analysis tools for interactive debugging, model-checking, and runtime monitoring. Besides reviewing almost a decade of fruitful research, this document allows me to introduce some new research directions, which hopefully will ease the burden of creating novel specification-design environments and render the design process more productive.La communauté de la vérification formelle s’efforce de prouver la conformité d’une spécification par l’utilisation de la logique formelle et de preuves mathématiques. Les progrès considérables réalisés dans les outils de vérification formelle assistée par ordinateur, ainsi que le nombre croissant de réussites, rendent ces méthodes essentielles dans la boîte à outils des concepteurs de systèmes. Cependant, avec l’avènement des modèles et des langages spécifiques à un domaine, un grand nombre de formalismes ont été proposés pour écrire des spécifications de systèmes dynamiques, chacun étant adapté aux besoins spécifiques du domaine ciblé. Une nouvelle question émerge : Comment combler le fossé entre ces formalismes spécifiques au domaine, orientés vers les experts du domaine et les outils de vérification formelle, orientés vers les mathématiciens ? Une des réponses, omniprésente dans la littérature, repose sur l’utilisation de transformations de modèles pour traduire syntaxiquement le modèle spécifique au domaine vers le modèle de vérification. Nous soutenons que cette approche est contre-productive et conduit à une multiplication sémantique, qui nécessite des preuves d’équivalence qui peuvent être difficiles à fournir et à maintenir.Dans ce manuscrit, je présente une nouvelle réponse au niveau sémantique développée, raffinée et évaluée au cours des 10 dernières années avec l’aide de 6 ingénieurs postdoctoraux, 8 candidats au doctorat et 12 projets collaboratifs. Cette approche, nommée G∀min∃, promet une architecture logicielle modulaire, compositionnelle et réutilisable permettant la conception d’une grande variété d’outils d’exploration du comportement. La brique de base de cette approche est une interface de niveau sémantique agnostique au langage, qui agit comme un pont entre la sémantique dynamique d’un langage spécifique au domaine et les outils d’analyse du comportement. Nous proposons ici une formalisation de l’interface ainsi que quelques opérateurs réutilisables pour la création d’outils d’analyse du comportement pour le débogage interactif, le contrôle de modèle et la surveillance de l’exécution. En plus de passer en revue près d’une décennie de recherches fructueuses, ce document me permet de présenter quelques nouvelles directions de recherche, qui, nous l’espérons, allégeront le poids de la création de nouveaux environnements de conception de spécifications, et rendront le processus de conception plus productif
Laser emission at 428 nm in N2+: Competition between two- and three-level amplification
No full textInternational audienceLasing of N2+ at 428 nm is studied as a function of the delay dt between two 800 nm ultrashort pumping pulses from a Ti:sapphire laser. This lasing corresponds to a population-inverted transition between levels B2Σ+u(0) and X2Σ+g(1) of a singly ionized nitrogen molecule. An important erasing of laser emission is observed under pumping with two consecutive pulses separated by large delays −20 ps < dt < +20 ps. From an analysis of the quenching results, we conclude that the mechanism of lasing corresponds to a coherent two-photon amplification scheme. Our results show that a two-photon process can dominate over a population-inverted one-photon amplification
A hybrid data collection scheme to achieve load balancing for underwater sensor networks
No full textInternational audienceUnderwater wireless sensor networks possess considerable potential to monitor large and hostile underwater environments by reliably sensing, collecting, and forwarding data toward the surface sinks. Although the research community has made promising efforts, barriers such as continuous node mobility, longer delays, unavailability of location information, and energy limitations must be addressed. Taking this into account, this research aims to develop a hybrid and intelligent data collection scheme that considers node position and network characteristics during data forwarding. To accomplish the objective, the network is divided into two layers. The top layer, considered more dynamic, follows a hop-by-hop data forwarding scheme. The lower layer, experiencing stable water currents, follows a clustering-based data collection method. The proposed scheme, called Multilayer Dynamic Data Forwarding (MD2F), is suitable for large and deep underwater areas. MD2F is scalable as it uses a multi-sink architecture, while single or multiple autonomous underwater vehicles (AUVs) can be utilized depending on the area being monitored. Implementing hop-by-hop transmission and clustering-based data collection at different layers balances the network load, thereby increasing the network life. Results show that MD2F exhibits better performance when compared with Multilayer Cluster-based Energy Efficient (MLCEE) and Energy efficient and link reliable routing (E2LR) schemes, both are very close in working behavior. The results are encouraging in terms of delivery ratio, network throughput, and end-to-end delays. Alongside achieving these targets, the network also exhibits less energy consumption through load balancing
Coherence and superradiance from a plasma-based quasiparticle accelerator
No full textInternational audienceCoherent light sources, such as free electron lasers, provide bright beams for biology, chemistry, physics, and advanced technological applications. Increasing the brightness of these sources requires progressively larger devices, with the largest being several km long (e.g., LCLS). Can we reverse this trend, and bring these sources to the many thousands of labs spanning universities, hospitals, and industry? Here we address this long-standing question by rethinking basic principles of radiation physics. At the core of our work is the introduction of quasi-particle-based light sources that rely on the collective and macroscopic motion of an ensemble of light-emitting charges to evolve and radiate in ways that would be unphysical when considering single charges. The underlying concept allows for temporal coherence and superradiance in fundamentally new configurations, providing radiation with clear experimental signatures and revolutionary properties. The underlying concept is illustrated with plasma accelerators but extends well beyond this case, such as to nonlinear optical configurations. The simplicity of the quasi-particle approach makes it suitable for experimental demonstrations at existing laser and accelerator facilities