Caractérisation indirecte de défauts géométriques de forme liés au process de fabrication d'un élément d'essuie-glace

Les défauts de forme sont inévitables dans la production série de pièces mécaniques. On doit les caractériser pour quantifier leur impact sur la performance du système complet. Pour estimer les défauts locaux d'un balai d'essuie-glace, on utilise une méthode indirecte (établissement expérimental d'une courbe « caractéristique »). On montre comment identifier le défaut à partir de la courbe par un problème inverse. Le modèle de calcul utilisé étant coûteux (EF non linéaire en grands déplacements, contact), on a recours à un méta-modèle par krigeage pour résoudre le problème d'optimisation

Rare event simulation : a point process interpretation with application in probability and quantile estimation

This paper addresses the issue of estimating extreme probability and quantile on the output of complex computer codes. We introduce a new approach to solve this problem in term of a random walk in the output space, leading to two main results: (1) the number of samples required to get a realisation of a random variable in a given domain of probability measure p is drastically reduced, following a Poisson law with parameter log1/p; and (2) we get parallel algorithms for estimating probabilities and quantiles and especially the optimal parallel Multilevel Splitting algorithm where there is indeed no subset to define anymore.Non UBCUnreviewedThis collection contains the proceedings of ICASP12, the 12th International Conference on Applications of Statistics and Probability in Civil Engineering held in Vancouver, Canada on July 12-15, 2015. Abstracts were peer-reviewed and authors of accepted abstracts were invited to submit full papers. Also full papers were peer reviewed. The editor for this collection is Professor Terje Haukaas, Department of Civil Engineering, UBC Vancouver.FacultyOthe

Bayesian Calibration in a multi-output transposition context

Bayesian calibration is an effective approach for ensuring that numerical simulations accurately reflect the behavior of physical systems. However, because numerical models are never perfect, a discrepancy known as model error exists between the model outputs and the observed data, and must be quantified. Conventional methods can not be implemented in transposition situations, such as when a model has multiple outputs but only one is experimentally observed. To account for the model error in this context, we propose augmenting the calibration process by introducing additional input numerical parameters through a hierarchical Bayesian model, which includes hyperparameters for the prior distribution of the calibration variables. Importance sampling estimators are used to avoid increasing computational costs. Performance metrics are introduced to assess the proposed probabilistic model and the accuracy of its predictions. The method is applied on a computer code with three outputs that models the Taylor cylinder impact test. The outputs are considered as the observed variables one at a time, to work with three different transposition situations. The proposed method is compared with other approaches that embed model errors to demonstrate the significance of the hierarchical formulation

Bayesian Calibration in a multi-output transposition context

Bayesian calibration is an effective approach for ensuring that numerical simulations accurately reflect the behavior of physical systems. However, because numerical models are never perfect, a discrepancy known as model error exists between the model outputs and the observed data, and must be quantified. Conventional methods can not be implemented in transposition situations, such as when a model has multiple outputs but only one is experimentally observed. To account for the model error in this context, we propose augmenting the calibration process by introducing additional input numerical parameters through a hierarchical Bayesian model, which includes hyperparameters for the prior distribution of the calibration variables. Importance sampling estimators are used to avoid increasing computational costs. Performance metrics are introduced to assess the proposed probabilistic model and the accuracy of its predictions. The method is applied on a computer code with three outputs that models the Taylor cylinder impact test. The outputs are considered as the observed variables one at a time, to work with three different transposition situations. The proposed method is compared with other approaches that embed model errors to demonstrate the significance of the hierarchical formulation

Management of renal replacement therapy among adults in French intensive care units: A bedside practice evaluation

International audienceBackgroundThis study aimed to investigate renal replacement therapy (RRT) practices in a representative nationwide sample of French intensive care units (ICUs).MethodsFrom July 1 to October 5 2021, 67 French ICUs provided data regarding their ICU and RRT implementation. We used an online questionnaire to record general data about each participating ICU, including the type of hospital, number of beds, staff ratios, and RRT implementation. Each center then prospectively recorded RRT parameters from 5 consecutive acute kidney injury (AKI) patients, namely the indication, type of dialysis catheter used, type of catheter lock used, type of RRT (continuous or intermittent), the RRT parameters initially prescribed (dose, blood flow, and duration), and the anticoagulant agent used for the circuit.ResultsA total of 303 patients from 67 ICUs were analyzed. Main indications for RRT were oligo-anuria (57.4%), metabolic acidosis (52.1%), and increased plasma urea levels (47.9%). The commonest insertion site was the right internal jugular (45.2%). In 71.0% of cases, the dialysis catheter was inserted by a resident. Ultrasound guidance was used in 97.0% and isovolumic connection in 90.1%. Citrate, unfractionated heparin, and saline were used as catheter locks in 46.9%, 24.1%, and 21.1% of cases, respectively.ConclusionsPractices in French ICUs are largely compliant with current national guidelines and international literature. The findings should be interpreted in light of the limitations inherent to this type of study