39 research outputs found
Optimization of the Dynamic Behaviour of Complex Structures Based on a Multimodal Strategy
No full textNon
Brake Squeal Investigations Based on Acoustic Measurements Performed on the FIVE@ECL Experimental Test Bench
No full textInternational audienceRadiated noise is a major topic of interest regarding the brake squeal phenomenon as it is directly linked to the noise generated which can be potentially detrimental to user comfort and perception. However, very few studies offer in-depth and comprehensive insight into the analysis and understanding of acoustic noise during squeal events. This study is intended to provide an original contribution to this issue by investigating acoustic phenomena occurring during the squeal phenomenon via a digital antenna composed of 117 microphones. Experiments are performed on the Friction-Induced Vibration and noisE test bench at Ecole Centrale de Lyon (FIVE@ECL). The first main aim is to investigate the characteristics of the acoustic radiated field during brake squeal and more particularly to describe the evolution of the radiated field patterns per revolution of the disc system. The second major aim is to illustrate the possibility of reconstructing the radiated acoustic field everywhere in the space surrounding the brake system, leading to the construction of a robust representation of 3D acoustic patterns, providing acoustic squeal events in the physical space around the brake system. Results show that the vibratory signature remains identical during squeal event braking test. The acoustic signature of squeal noise consists mainly of a fundamental frequency and its harmonic components, with secondary lower contributions from other fundamental frequencies. The associated radiated acoustic field during squeal events are characterized by different directivities and intensities of the acoustic radiated field for each squeal frequency, with potential changes in these directivities and intensities over short times corresponding to the rotation period of the disc
MULTI-OBJECTIVE STRUCTURAL OPTIMIZATION UNDER STRESS CRITERIA BASED ON MIXED PLATE FEM AND GENETIC ALGORITHMS
No full textMulti-objective shape optimization of plate structure under stress criteria based on sub-structured mixed FEM and genetic algorithms
No full textInternational audienceThis paper presents a methodology for the multi-objective (MO) shape optimization of plate structure under stress criteria, based on a mixed Finite Element Model (FEM) enhanced with a sub-structuring method. The optimization is performed with a classical Genetic Algorithm (GA) method based on Pareto-optimal solutions and considers thickness distributions parameters and antagonist objectives among them stress criteria. We implement a displacement-stress Dynamic Mixed FEM (DM-FEM) for plate structure vibrations analysis. Such a model gives a privileged access to the stress within the plate structure compared to primal classical FEM, and features a linear dependence to the thickness parameters. A sub-structuring reduction method is also computed in order to reduce the size of the mixed FEM and split the given structure into smaller ones with their own thickness parameters. Those methods combined enable a fast and stress-wise efficient structure analysis, and improve the performance of the repetitive GA. A few cases of minimizing the mass and the maximum Von Mises stress within a plate structure under a dynamic load put forward the relevance of our method with promising results. It is able to satisfy multiple damage criteria with different thickness distributions, and use a smaller FEM. 1. Introduction The goal of this paper is to implement a DM-FEM for plate structure enhanced with a sub-structuring reduction method for MO structural optimizations with thickness repartition parameters and mass/stress criteria. This reduced model provides a fast and efficient analysis of complex plate structures vibrations and facilitates the work of the GA used for the optimization. The optimization of a structure's parameters in order to prevent damages is a major concern in mechanical engineering but can only be achieved at the expense of others essential criteria. Even though often carried out manually, MO-optimization methods also naturally appear in the litterature, such as gradient-based method [1, 7] and MO-GA-based methods [6, 8]. In this study, the optimization is performed with a classical GA-based NSGA-II method [4], as it permits to dispense with any weighting of criteria. This kind of method enables to find a set of Pareto-optimal solutions, which are all optimal compared to each other, for at least one criterion. Nevertheless, an inconvenient lies in the repetitions of the criteria's evaluation, depending on the chosen method and theory. In the literature, some of the previous works on thin structures optimization focus on laminated composites [1, 8] with thickness and orientation layer parameters, as well a
Do desamparo à dor de existir na poesia de Flobela Espanca: alguns apontamentos
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Filosofia e Ciências Humanas, Programa de Pós-Graduação em Psicologia, Florianópolis, 2014.A questão central dessa pesquisa é se a dor que Florbela descreve em seus versos poéticos tem como motivo o que Freud denominava desamparo. Trabalhamos aqui as relações do desamparo freudiano com a dor de existir na perspectiva teórica psicanalítica. A poesia de Florbela Espanca apresentada ilustra as relações do desamparo com a dor de existir. Utilizou-se do método de análise discursiva de base psicanalítica, extraindo dos trechos poéticos sentidos coerentes com essa perspectiva de análise. Realizamos uma revisão bibliográfica do tema do desamparo na teoria freudiana. Examinando os poemas escritos de 1903 a 1917, constatamos que o desamparo e a dor de existir apresentam-se na posição melancólica nas personagens da poesia de Florbela Espanca.Abstract : This text aims to discuss some effects of "Helplessness" (the Freudian idea of "Hilflosigkeit") in Florbela Espanca's poetry. Examining the author's discourse from a psychoanalytic point of view, the work tries to make the pain that the Portuguese author often describes in her verses understandable. The main conclusion is that Florbela's characters show helplessness and existential pain in a way that is typical of the melancholic position
Mass Transport-Induced Failure of Hybrid Bonding-Based Integration for Advanced Image Sensor Applications
No full textRoutes of SARS-Cov2 transmission in the Intensive Care Unit: A multicentric prospective study
No full textInternational audienceThe risk of SARS-CoV-2 transmission to health care workers in intensive care units (ICU) and the contribution of airborne and fomites to SARS-CoV-2 transmission remain unclear. To assess the rate of air and surface contamination and identify risk factors associated with this contamination in patients admitted to the ICU for acute respiratory failure due to SARS-CoV-2 pneumonia.Methods: Prospective multicentric non-interventional study conducted from June 2020 to November 2020 in 3 French ICUs. For each enrolled patient, 3 predefined surfaces were swabbed, 2 air samples at 1m and 3m from the patient’s mouth and face masks of 3 health care workers (HCW) were collected within the first 48 hours of SARS-CoV-2 positive PCR in a respiratory sample. Droplet digital PCR and quantitative PCR were performed on different samples, respectively.Results: Among 150 included patients, 5 (3.6%, 95%CI: 1.2% to 8.2%) had positive ddPCR on air samples at 1 meter or 3 meters. Seventy-one patients (53.3%, CI95%: 44.5% to 62.0%) had at least one surface positive. Face masks worn by HCW were positive in 6 patients (4.4%, CI: 1.6% to 9.4%). The threshold of RT-qPCR of the respiratory sample performed at inclusion (odds ratio, OR= 0.88, 95%CI: 0.83 to 0.93, p<0.0001) and the presence of diarrhea (OR= 3.28, 95%CI: 1.09 to 9.88, p=0.037) were significantly associated with the number of contaminated surfaces.Conclusion: In this study, including patients admitted to the ICU for acute respiratory failure « contact route » of transmission, i.e. through fomites, seems dominant. While presence of SARS-CoV-2 in the air is rare in this specific population, the presence of diarrhea is associated with surface contamination around Covid
Additional file 1: of Predictors of insufficient peak amikacin concentration in critically ill patients on extracorporeal membrane oxygenation
No full textTable S1. List of the data included into the multivariable mixed models. Table S2. Infection sites, pathogens identified and their ECOFF for Amikacin in 88 patients with documented infections. Figure S1. Distribution of amikacin Cmax concentrations in ECMO-treated patients. Table S3. Total population characteristics and univariable analyses of factors predictive of amikacin Cmax > 80 mg/L. Figure S2. Amikacin Cmax distribution within our population on ECMO with 25 mg/kg for all patients or with using potentially adapted dosing regimens based on 24-h fluid balance and BMI, as described in Table 3. (DOCX 273 kb
Predictors of insufficient peak amikacin concentration in critically ill patients on extracorporeal membrane oxygenation
No full textInternational audienceBackground: Amikacin infusion requires targeting a peak serum concentration (Cmax) 8–10 times the minimal inhibitory concentration, corresponding to a Cmax of 60–80 mg/L for the least susceptible bacteria to theoretically prevent therapeutic failure. Because drug pharmacokinetics on extracorporeal membrane oxygenation (ECMO) are challenging, we undertook this study to assess the frequency of insufficient amikacin Cmax in critically ill patients on ECMO and to identify relative risk factors.Methods: This was a prospective, observational, monocentric study in a university hospital. Patients on ECMO who received an amikacin loading dose for suspected Gram-negative infections were included. The amikacin loading dose of 25 mg/kg total body weight was administered intravenously and Cmax was measured 30 min after the end of the infusion. Independent predicators of Cmax < 60 mg/L after the first amikacin infusion were identified with mixed-model multivariable analyses. Various dosing simulations were performed to assess the probability of reaching 60 mg/L < Cmax < 80 mg/L.Results: A total of 106 patients on venoarterial ECMO (VA-ECMO) (68%) or venovenous-ECMO (32%) were included. At inclusion, their median (1st; 3rd quartile) Sequential Organ-Failure Assessment score was 15 (12; 18) and 54 patients (51%) were on renal replacement therapy. Overall ICU mortality was 54%. Cmax was < 60 mg/L in 41 patients (39%). Independent risk factors for amikacin under-dosing were body mass index (BMI) < 22 kg/m2 and a positive 24-h fluid balance. Using dosing simulation, increasing the amikacin dosing regimen to 30 mg/kg and 35 mg/kg of body weight when the 24-h fluid balance is positive and the BMI is ≥ 22 kg/m2 or < 22 kg/m2 (Table 3), respectively, would have potentially led to the therapeutic target being reached in 42% of patients while reducing under-dosing to 23% of patients.Conclusions: ECMO-treated patients were under-dosed for amikacin in one third of cases. Increasing the dose to 35 mg/kg of body weight in low-BMI patients and those with positive 24-h fluid balance on ECMO to reach adequate targeted concentrations should be investigated
