Distributionally robust master surgery scheduling with duration uncertainty and specialty parallelism

International audienceThis study investigates master surgery scheduling at the tactical decision-making level of operating room (OR) management, addressing uncertainty in surgeons’ surgery durations and parallelism in surgical specialties. The goal is to optimize OR time block types within the scheduling cycle, allocate them efficiently to surgical specialties and surgeons, and determine the appropriate number of surgeries to schedule. Given the limited historical data on surgery durations, we employ a distributionally robust optimization (DRO) approach to address the uncertainty in the distribution. To address the needs of different OR managers, we develop a distributionally robust chance-constrained model to manage overtime that extends beyond the designated OR time blocks. Meanwhile, we construct a distributionally robust bi-objective optimization model with the goals of minimizing the expected total duration of overtime and maximizing the number of surgeries scheduled. These optimization models are reformulated into computationally tractable forms using dual theory. We validate the proposed methods with real hospital data, finding that the DRO approach offers greater stability in scheduling solutions compared to the sample average approximation approach

Investigating general interface effects in one-dimensional phononic crystals for micro-scale sensor application

International audienceMicro-scale one-dimensional phononic crystal (PnC) sensors utilizing high-frequency acoustic waves have emerged as a prominent research focus in microfluidic detection. The large surface-to-volume ratios and unique interface properties inherent to micro-composite structures make it imperative to consider general interface effects. In this study, a general interface model is used to systematically investigate the interface effects in 1D PnCs and assess the impact on the performance of micro-scale sensors. The model incorporates interface thickness, stiffness, and inertia to provide a robust, physically realistic representation of interface behavior. Under extreme conditions, the model naturally degenerates into either the spring-layer interface model or the coherent interface model. The results indicate that general interface effects induce significant deviations in defect state PnC resonance frequencies from classical elastic theory predictions. Nevertheless, the resonance frequency remains strongly linearly correlated with the acoustic properties of the measured solution. The performance of 1D PnC sensors improves markedly as their dimensions decrease. In contrast, when the overall structure size is fixed, increases in interface thickness, reductions in stiffness, and higher inertia parameters collectively diminish sensor sensitivity

Why consumers react differently to brand transgressions: Functional vs. ethical breaches and psychological contracts

FNEGE 3, ABS 2International audienceBrand transgressions are increasingly common, but their effects on consumer behavior remain inconsistent. While some incidents lead to negative word-of-mouth without affecting sales, others cause a decline in purchasing behavior. Existing literature does not fully explain the divergence in consumer responses. This study investigates how consumers react to functional versus ethical brand transgressions through the lens of psychological contract theory. Drawing on a survey of 862 participants and using structural equation modeling, we examine the mechanisms underlying consumer reactions to breaches of brand promises. Our findings identify two mechanisms: withdrawal, primarily triggered by functional breaches, and indignation, associated with ethical breaches that generate negative word-of-mouth. This research expands psychological contract theory beyond functional failures and demonstrates its relevance in ethical contexts. The results underscore the importance of understanding how consumers interpret a transgression and of tailoring brand responses accordingly

Aborder les défis éthiques de l'IA

National audienc

Event-Triggered Controller Design for Multi-Agent Systems

International audienceThis chapter presents an event-triggered controller design for multi-agent systems, where the data transmission among agents is governed by event-triggered mechanisms. The dynamic event-triggered control with the full-state observer is introduced, with a particular concern of reducing communication frequency through designable inter-event time. An extension to directed topology, where the communication is restricted to single directions, is also discussed. The proposed methods follow the co-design principle, where the parameters of controllers, observers, and event-triggered mechanisms are synthesized simultaneously. Following a distributed design principle, only local information is required in a small range of nearby neighbors to compute the control signal and the event-triggered condition. Zeno behavior is proved to be excluded. Finally, the proposed approaches are demonstrated by a numerical example and compared with other methods to validate their effectiveness

Exponential degradation of adhesion between visco-hyperelastic materials by isogeometric analysis

International audienceVisco-hyperelastic materials are extensively utilized in engineering applications due to their excellent adhesive properties. However, this adhesion gradually weakens when subjected to cyclic bonding–debonding. In this paper, a modified cohesive zone model is developed by introducing an exponential degradation factor that is related to the number of bonding–debonding cycles to characterize the adhesion degradation phenomenon. This model also takes the effect of real contact area on adhesion in each bonding–debonding cycle into account. We then couple this model with the bi-potential contact algorithm to handle interfacial contact during the bonding process, because the cohesive zone model concerns the process of separation. Two-dimensional and three-dimensional numerical implementations of large deformation frictional contact and adhesion are carried out in the context of isogeometric analysis, which offers a geometrically accurate description, a continuous normal field of the contact interface, and precise determination of contact forces. Numerical examples show that the effect of material viscosity on adhesion varies depending on the boundary conditions, and the rough surface has an obvious effect on adhesion

Evolution of tribolayer in GH2132/GH4169 fretting wear at elevated temperatures

International audienceTo investigate the development of the tribolayer in the GH2132/GH4169 superalloy pair, a systematic tangential fretting wear interruption test was conducted to analyze the microstructure, chemical composition, formation mechanism, and evolutionary characteristics of the tribolayer at 600℃. The results reveal that in the early stages of fretting, severe plastic deformation of material in the contact area and dislocation accumulation within the grains promote dynamic recrystallization and crack initiation, ultimately resulting in significant adhesive wear. As the test progresses, tribo-sintering of oxidized debris and continuous grain refinement give rise to a dense nanocrystalline tribolayer with enhanced hardness. This tribolayer, which is composed of nanocrystalline metal oxides, unoxidized nanograins, and amorphous phases, forms at the contact interface and serves as a mechanically and chemically robust barrier. It suppresses metal-to-metal contact, slows oxidation, and significantly reduces the wear rate, thereby stabilizing the worn surface

Structurally defined synthetic heparin oligosaccharides reveal unique signatures for nanopore structural analysis of GAGs

International audienceEfforts to fully understand the structure-to-function relationships of glycosaminoglycans (GAGs) have beenhampered by the complexity and polydispersity of GAGs and, more importantly, by the need for sensitiveanalytical techniques to discern their subtle structural motifs. Conventional analytical methods often fail toprovide information on the sparse motifs of GAGs. Concurrently, nanopore-based analysis has shown great potentialin GAGs structural analysis. Still, until now, it has been limited by the difficulty of relating ionic currentchanges to specific motifs. To address this, the present study allowed for obtaining reference signals byemploying carefully designed synthetic sulfated tetra- to dodecasaccharides to allow precise sequence controland purity. Reference signals were obtained for specific motifs, paving the way for accurate motif recognition.The outcomes of the study demonstrated unequivocal recognition of specific GAG structures by monitoring theevolution of nanopore signals in response to the translocation of synthetic heparin (HP)-like oligosaccharideswith controlled structures, allowing extensive structural discrimination. The findings highlight the nanopore'scapability to detect subtle structural features, such as differences in sulfation patterns and epimerization ofuronic acid. These results open the way to establishing detailed heparin (HP)-specific reference signals and tonanopore fingerprinting and sequencing of GAGs

Imaginaires, technologies et enjeux éthiques à l’ère hypermoderne. Préface

International audienc

Developing and implementing business ecosystem strategies in the legal sector: current situation and prospects in France

International audienceSince the beginning of the 2000s, the concept of business ecosystem (BE), which was introduced by James F Moore in the early 1990s, has become a major topic in management (strategy, management of innovation) and economics (Daidj, 2011). BE is now a concept widely used by both the economic press and the academic world to explain why successful companies are those that collaborate with other organizations to significantly improve their performance and competitiveness (Iansiti & Levien, 2004). The application of this concept to the law thus appears promising for understanding how companies collaborate with other geographically close actors in order to develop legal ecosystems that they can, if necessary, mobilise not only to defend their own interests, but also to provide them with the information and legal know-how they need to carry out their national and international activities.From a conceptual and theoretical perspective, the interpretations of BEs may differ according to various scholars providing their own definitions and representations. Moreover, BEs also vary according to the context and the continuous changes in the business environment with digital transformation, the development and adoption of new technologies (such as artificial intelligence, blockchain, data analytics etc.) and the emergence of new players that have a significant impact on value chain and business models. As the notion of BE has been used in various and sometimes competing ways, we have made the choice here to refer mainly to Moore’s academic work in strategic management. This chapter aims at providing some theoretical insights into BEs drawing mainly from Moore’s publications in order to understand the main features and the evolution of this organizational/network form and to attempt to explain its relevance for the legal sector in France. This chapter includes a description of this sector and its main challenges today with the intensification of uberization and the competition between new entrants (technological platforms) and the various incumbent operators