Application of REPAS to analyze the sump clogging issue following a LOCA and its impact on the reliability of the ECCS long-term core cooling function

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Optimal active sensing control for two-frame systems

International audienceThis paper provides a complete characterization of the trajectories that maximize the information collected by a moving vehicle, through sensors' measurements, for the recently introduced class of nonlinear "two-frame systems". The information is quantified in terms of the trace of the observability Gramian (OG) along a trajectory. In general, this quantity nontrivially depends on the control inputs and the state trajectory, resulting in a difficult optimal control problem. Herein, we leverage the property of invariant filtering that Jacobians are state-trajectory independent, that is, only depend on the control inputs, which enables us to mathematically derive optimal trajectories in closed form. We illustrate the results numerically on problems from robotics such as 3D robot localization, and 2D simultaneous localization and mapping

Hierarchical modeling of heterogeneous structures driven by a modeling error estimator

Homogenized models are widely used in multiscale analysis for their computational efficiency, but they often fail to provide sufficient accuracy in regions exhibiting high variations in the solution fields. One way to address this limitation is to adaptively couple the homogeneous model with a full field, heterogeneous one in designated zones of interest. Within the framework of finite-element based higher-order asymptotic homogenization, this work introduces a modeling error estimator in order to detect regions where refining the material model is necessary. We also analyze the competition between discretization and modeling errors. We finally propose a multiscale enhancement of the classical displacement-based submodeling technique in order to adequately couple the homogeneous and heterogeneous domains. The promise of the proposed methods and the overall associated strategy is illustrated on various numerical examples of elastic fiber-matrix composites

Understanding Creative Entrepreneurs' Work Practices: The Varying Conversation between Artistic and Economic Rationales

International audienceResearch on creative organizations often questions how artistic practices can be squared within the rational decision-making of economic thinking. This paper examines how the relational language, or conversation, between artistic and economic rationales unfolds for creative entrepreneurs. Through ethnographic work with a designer-entrepreneur, this paper presents a fine-grained analysis of the conversation the designer cultivates between artistic and economic rationales through work practices. We contribute to the literature about artistic and economic rationales at work, and more specifically to the concept of conversation. First, we show that high levels of conversing make way for low levels of conversing and vice versa. In the studio, the designer's engagement with either rationale varies as the creative process progresses. Second, on a more global dynamic, we demonstrate the conversation is continuous. It relies on its variations, which ensure the balance between rationales in the long run. We also contribute to the field of creative entrepreneurship research. We identify here one type of creative entrepreneur, with what we call a 'small is beautiful' attitude. Far from the mythical figure of the entrepreneur, this unconventional entrepreneur aims for sustainable use of creative resources rather than growth at all costs

Kinetic equations and level-set approach for simulating solid-state microstructure evolutions at the mesoscopic scale: State of the art, limitations, and prospects

International audienceFor over three decades, the front-capturing level-set method has demonstrated its prowess for the simulation, at the mesoscopic scale, of numerous mechanisms in the context of microstructure evolution occurring during complex thermomechanical paths. This review delves into the foundations of this numerical framework, charting its evolution concerning polycrystalline materials, examining its recent advancements, scrutinizing its current shortcomings, and exploring future possibilities. Special attention will be given to the context of hot metal forming processes where discontinuous/continuous dynamic recrystallization, post-dynamic recrystallization, grain growth and solid-state phase transformations are the main mechanisms of interest. In this context, this article also aims to reintroduce, as simply as possible, the kinetic equations related to the grain boundary migration

Innovation to maintain complex systems for transitions: organizing for innovative validation

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A network-based approach to improving robustness of a high-speed train by structure adjustment

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Hierarchization of social impact subcategories: towards a systematic approach for enhanced stakeholders’ representativeness

International audiencePurpose: Social life cycle assessment (S-LCA) aims to assess the potential social impacts related to stakeholders over the life cycle of a product or service. For legitimacy and meaningful results, direct consultation of stakeholders ranks among the most recommended approaches. This paper aims to provide the methodological basis for S-LCA to target potential impacts and to support decision-making using this kind of participatory approaches. In particular, the work aims to address some of the limitations of the systematization of stakeholders’ consultation. An approach to facilitate and speed up the access to stakeholders and the construction of respondent panels is proposed. Then, representativeness of the collected answers is verified using a statistical data treatment. The method is applied to hierarchize social impact subcategories in the offshore wind energy sector, a huge up-coming sector in France. This emerging sector raises a number of socio-economic issues that can be related to the development of a new industrial sector and its coexistence with local communities. Methodology: Based on the participatory approach principle, the hierarchization of social impact subcategories is carried out by stakeholders. The developed methodology includes 5 steps. In step 1, the social impact subcategories from the UNEP in Guidelines for Social Life Cycle Assessment of Products and Organizations 2020 (2020) list are adapted to the sectoral context. In step 2, the hierarchization criteria are defined. Instead of using a ranking based on an importance criterion, hierarchization is based on two quantitative criteria to target impact subcategories that are both important and perceived as potentially problematic. In step 3, the stakeholders and a sampling approach are defined. Then, in step 4, an online survey consultation methodology is used and improved for the selection of qualitative variables. Finally, in step 5, the methodology specifies the data treatment protocol. The data treatment protocol in this fifth step aims at addressing the issue of the representativeness and relevance of the responses obtained from surveys. Indeed, hierarchization approaches based on consultations typically consider responses at the aggregated level of the stakeholder category. However, it is likely that different stakeholder profiles of respondents within a large heterogeneous stakeholder category influence the perception of social impact subcategories. To verify this point, it is necessary to look at a disaggregated scale of stakeholder sub-groups. This potential bias led to the need to adjust the survey responses. Results and discussion: Large-scale sampling allowed us to collect 82 responses from value chain actors and 50 responses from local community with a respective response rate of 13% and 16%. Firstly, hierarchization of social impact subcategories was possible at the level of the whole aggregated stakeholder category. Then the disaggregated level was considered. To do so, qualitative data in the surveys allowed different profiles within a stakeholder group of the panel to be identified. Then, chi-squared tests on a representative variable were conducted and an adjustment of the responses and, therefore, on the resulting hierarchical order of social impact subcategories was applied. The study of the disaggregated responses led to the identification of a significant dispersion of the responses and the influence of certain variables of the respondents on their perception of social impacts. Conclusions: Participatory approaches were found to be useful to legitimate the selection of impact subcategories when applying S-LCA. However, considering aggregated hierarchization results at the whole stakeholder category level may mask some polarized opinions within the same stakeholder category. An adjusted hierarchization can serve to enhance the representativeness of the consulted stakeholders’ perceptions. It would be good practice for the practitioner to highlight the limitations and possible biases. For this, one recommendation is to provide transparency on the dispersion of responses and disaggregated information on the stakeholder panels involved. With the proposed method, it was possible to both adjust the hierarchization results and express the residual uncertainty for the sake of transparency. The proposed method is designed to be transferable to any sector where stakeholders are assembled in sectoral clusters. We were able to access many stakeholders with different profiles. This broad sampling supports a holistic view of the social impact subcategories. The hierarchization results allow the practitioner to target a priority order to address the impacts subcategories for next S-LCA steps and to specify the chosen scope of the study

Dynamic exploration of a 1 MW molten carbonate electrolyzer: A modeling study approach

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