Impact de la pression et de la température sur la performance d'un actionneur plasma de type DBD

RÉSUMÉ Ce projet de recherche a pour objectif l’étude de performance d’un actionneur plasma de type DBD, sous de hautes pressions et de hautes températures de l’air. L’actionneur plasma est un appareil purement électrique, fonctionnant sans pièces mobiles, et permet de transformer l’électricité en quantité de mouvement par le biais des collisions entre les particules de plasma et celles du gaz neutre. Cette fonctionnalité a engendré plusieurs études sur le potentiel de l’actionneur plasma dans des applications aérodynamiques. En effet, elle paraît très intéressante pour le contrôle de mouvements sur les ailes d’avions, ou dans les turbines et les compresseurs des turbomoteurs. Ainsi, une étude de la performance de ce dispositif sous différentes conditions atmosphériques est indispensable. Ce travail représente la première étude sur l’effet couplé de la haute pression et température sur la performance d’un actionneur plasma. Une enceinte à haute pression et température, dans lequel l’actionneur opère, fut fabriquée. L’effet du dispositif sur le champ de vitesse fut mesuré via la technique de mesure PIV. Les champs de vitesse ont permis via la conservation de quantité de mouvement de calculer la poussée générée par l’actionneur. L’observation optique a aussi permis de mesurer le voltage seuil de formation du plasma. Des tests furent aussi conduits pour des pressions de 1 à 6 bar et des températures de 20°C à 200°C. Les résultats obtenus montrent de grandes variations du fonctionnement de l’actionneur plasma quand la pression et la température augmentent dans les marges étudiées. En effet, l’étude a montré que l’augmentation de la pression affecte négativement la performance, et rend le dispositif quasi-ineffectif à partir de 3 bar. L’étude du deuxième cas montre que la température affecte positivement la performance de l’actionneur, en ajoutant 80% de force d’actionnement entre 20°C et 150°C, contrairement à la pression. Finalement, les résultats ont montré que le couplage de la pression et de la température est quasi-linéaire. En effet, même à haute température, une haute pression présente un apport négatif, et inversement. Dans ce cas l’augmentation de la température jusqu’à 200°C pourrait compenser seulement une augmentation de 1 bar de la pression.----------ABSTRACT This research project aims to study the performance of a DBD type plasma actuator under high pressures and high air temperatures. The plasma actuator is a purely electric device, operating without moving parts, and transforms electricity into momentum through collisions between plasma particles and those of neutral gas. This feature has spawned several studies on the potential of the plasma actuator in aerodynamic applications. Indeed, it seems very interesting for the control of movement on the wings of planes, or in the turbines and compressors of the turboshaft engines. Thus, a study of the performance of this device under different atmospheric conditions is essential. This work represents the first study on the coupled effect of high pressure and temperature on the performance of a plasma actuator. An enclosure with high pressure and temperature, in which the actuator operates, was manufactured. The effect of the device on the velocity field was measured via the PIV measurement technique. The velocity fields allowed, via momentum conservation, to calculate the thrust generated by the actuator. Optical observation also made it possible to measure the plasma formation threshold voltage. Tests were also conducted for pressures of 1 to 6 bar and temperatures of 20 ° C to 200 ° C. The results obtained show large variations in the operation of the plasma actuator when pressure and temperature increase in the margins studied. Indeed, the study has shown that the increase in pressure adversely affects the performance, and makes the device almost ineffective from 3 bar. The study of the second case shows that the temperature positively affects the performance of the actuator, by adding 80% of actuating force between 20°C and 150°C, unlike the pressure. Finally, the results showed that the coupling of temperature and pressure is almost linear. Indeed, even at high temperature, a high pressure has a negative contribution, and vice versa. In this case the increase in temperature up to 200 ° C could compensate for only a 1 bar increase in pressure

Chemical synthesis, crystal structure, vibrational spectroscopy, non-linear optical properties and DFT calculation of bis (2,6-diaminopyridinium) sulfate monohydrate

International audienc

Intramuscular cavernous haemangioma of the triceps

A 16-year-old teenager presented himself with a swollen left elbow, with no associated vascular-nerve complications. The standard radiography was without abnormalities. The echography showed the presence of an oblong vascularized formation occupying the posterior part of the elbow. The magnetic resonance imaging (MRI) showed a hyper vascularized lesion developing at the expense of the brachial triceps muscle with an intermediate signal intensity on the sequences weighted in T1 and a hyper signal in T2. The anatomopathological study of the initial biopsy and of the tumor part concluded with a cavernous hemangioma. Although their origin is vascular, hemangiomas never metastasize and do not undergo malignant transformation. The treatment of symptomatic hemangioma consists of surgical excision

Surrogate models for uncertainty analysis of micro-actuator

International audienceIntelligent materials such as shape memory alloy have attracted the attention of scientists to innovate applications in micromachining technology. It is worth mentioning that the numerical study of such technology without considering uncertainties in material parameters has shown a great attention. However, material parameters show variability due to the experiment measurement of these parameters. This paper focuses on uncertainty analysis of a shape memory alloy micro actuator with taking into account uncertainties in material parameters. An uncertainty analysis approach combining the finite element method, metamodeling and Monte Carlo simulation is presented in this work. The constructed metamodels are validated and compared by errors measures and cross validation. After that, Monte Carlo simulation is conducted by the approximations provided by the metamodel. The metamodel based probabilistic method used in this paper is considered as an approach with high efficiency for uncertainty analysis in micro actuator

Pulmonary embolism in intensive care unit: Predictive factors, clinical manifestations and outcome

<b>Objective</b> :<b> </b> To determine predictive factors, clinical and demographics characteristics of patients with pulmonary embolism (PE) in ICU, and to identify factors associated with poor outcome in the hospital and in the ICU. <b> Methods</b> :<b> </b> During a four-year prospective study, a medical committee of six ICU physicians prospectively examined all available data for each patient in order to classify patients according to the level of clinical suspicion of pulmonary thromboembolism. During the study periods, all patients admitted to our ICU were classified into four groups. The first group includes all patients with confirmed PE; the second group includes some patients without clinical manifestations of PE; the third group includes patients with suspected and not confirmed PE and the fourth group includes all patients with only deep vein thromboses (DVTs) without suspicion of PE. The diagnosis of PE was confirmed either by a high-probability ventilation/perfusion (V/Q) scan or by a spiral computed tomography (CT) scan showing one or more filling defects in the pulmonary artery or in its branches. The diagnosis was also confirmed by echocardiography when a thrombus in the pulmonary artery was observed. <b> Results</b> :<b> </b> During the study periods, 4408 patients were admitted in our ICU. The diagnosis of PE was confirmed in 87 patients (1.9&#x0025;). The mean delay of development of PE was 7.8 &#177; 9.5 days.<b> </b> On the day of PE diagnosis, clinical examination showed that 50 patients (57.5&#x0025;) were hypotensive, 63 (72.4&#x0025;) have SIRS, 15 (17.2&#x0025;) have clinical manifestations of DVT and 71 (81.6&#x0025;) have respiratory distress requiring mechanical ventilation. In our study, intravenous unfractionated heparin was used in 81 cases (93.1&#x0025;) and low molecular weight heparins were used in 4 cases (4.6&#x0025;).<b> </b> The mean ICU stay was 20.2 &#177; 25.3 days and the mean hospital stay was 25.5 &#177; 25 days. The mortality rate in ICU was 47.1&#x0025; and the in-hospital mortality rate was 52.9&#x0025;.<b> </b> Multivariate analysis showed that factors associated with a poor prognosis in ICU are the use of norepinephrine and epinephrine<b> . </b> Furthermore, factors associated with in-hospital poor outcome in multivariate analysis were a number of organ failure associated with PE &#8805; 3. Moreover, comparison between patients with and without pe showed that predictive factors of pe are: acute medical illness, the presence of meningeal hemorrhage, the presence of spine fracture, hypoxemia with PaO₂ /FiO₂ ratio &#60; 300 and the absence of pharmacological prevention of venous thromboembolism. <b>Conclusion</b> :<b> </b> Despite the high frequency of DVT in critically ill patients, symptomatic PE remains not frequently observed, because systematic screening is not performed. Pulmonary embolism is associated with a high ICU and in-hospital mortality rate. Predictive factors of PE are acute medical illness, the presence of meningeal hemorrhage, the presence of spine fracture, hypoxemia with PaO₂ /FiO₂ &lt; 300 and the absence of pharmacological prevention of venous thromboembolism

Post-traumatic pulmonary embolism in the intensive care unit

Objective: To determine the predictive factors, clinical manifestations, and the outcome of patients with post-traumatic pulmonary embolism (PE) admitted in the intensive care unit (ICU). Methods: During a four-year prospective study, a medical committee of six ICU physicians prospectively examined all available data for each trauma patient in order to classify patients according to the level of clinical suspicion of pulmonary thromboembolism. During the study period, all trauma patients admitted to our ICU were classified into two groups. The first group included all patients with confirmed PE; the second group included patients without clinical manifestations of PE. The diagnosis of PE was confirmed either by a high-probability ventilation/perfusion (V/Q) scan or by a spiral computed tomography (CT) scan showing one or more filling defects in the pulmonary artery or its branches. Results: During the study period, 1067 trauma patients were admitted in our ICU. The diagnosis of PE was confirmed in 34 patients (3.2%). The mean delay of development of PE was 11.3 ± 9.3 days. Eight patients (24%) developed this complication within five days of ICU admission. On the day of PE diagnosis, the clinical examination showed that 13 patients (38.2%) were hypotensive, 23 (67.7%) had systemic inflammatory response syndrome (SIRS), three (8.8%) had clinical manifestations of deep venous thrombosis (DVT), and 32 (94%) had respiratory distress requiring mechanical ventilation. In our study, intravenous unfractionated heparin was used in 32 cases (94%) and low molecular weight heparin was used in two cases (4%). The mean ICU stay was 31.6 ± 35.7 days and the mean hospital stay was 32.7 ± 35.3 days. The mortality rate in the ICU was 38.2% and the in-hospital mortality rate was 41%. The multivariate analysis showed that factors associated with poor prognosis in the ICU were the presence of circulatory failure (Shock) (Odds ratio (OR) = 9.96) and thrombocytopenia (OR = 32.5).Moreover, comparison between patients with and without PE showed that the predictive factors of PE were: Age > 40 years, a SAPS II score > 25, hypoxemia with PaO2 /FiO 2 < 200 mmHg, the presence of spine fracture, and the presence of meningeal hemorrhage. Conclusion: Despite the high frequency of DVT in post-traumatic critically ill patients, symptomatic PE remains, although not frequently observed, because systematic screening is not performed. Factors associated with poor prognosis in the ICU are the presence of circulatory failure (shock) and thrombocytopenia. Predictive factors of PE are: Age > 40 years, a SAPS II score > 25, hypoxemia with PaO2 /FiO 2 < 200, the presence of a spine fracture, and the presence of meningeal hemorrhage. Prevention is highly warranted

Isolated traumatic head injury in children: Analysis of 276 observations

<b>Background</b> : To determine predictive factors of mortality among children after isolated traumatic brain injury. <b>Materials and Methods</b> : In this retrospective study, we included all consecutive children with isolated traumatic brain injury admitted to the 22-bed intensive care unit (ICU) of Habib Bourguiba University Hospital (Sfax, Tunisia). Basic demographic, clinical, biochemical, and radiological data were recorded on admission and during ICU stay. <b>Results</b> : There were 276 patients with 196 boys (71&#x0025;) and 80 girls, with a mean age of 6.7 &#177; 3.8 years. The main cause of trauma was road traffic accident (58.3&#x0025;). Mean Glasgow Coma Scale score was 8 &#177; 2, Mean Injury Severity Score (ISS) was 23.3 &#177; 5.9, Mean Pediatric Trauma Score (PTS) was 4.8 &#177; 2.3, and Mean Pediatric Risk of Mortality (PRISM) was 10.8 &#177; 8. A total of 259 children required mechanical ventilation. Forty-eight children (17.4&#x0025;) died. Multivariate analysis showed that factors associated with a poor prognosis were PRISM &gt; 24 (OR: 10.98), neurovegetative disorder (OR: 7.1), meningeal hemorrhage (OR: 2.74), and lesion type VI according to Marshall tomographic grading (OR: 13.26). <b>Conclusion</b> : In Tunisia, head injury is a frequent cause of hospital admission and is most often due to road traffic injuries. Short-term prognosis is influenced by demographic, clinical, radiological, and biochemical factors. The need to put preventive measures in place is underscored

Isolated traumatic head injury in children: Analysis of 276 observations

BACKGROUND: To determine predictive factors of mortality among children after isolated traumatic brain injury. MATERIALS AND METHODS: In this retrospective study, we included all consecutive children with isolated traumatic brain injury admitted to the 22-bed intensive care unit (ICU) of Habib Bourguiba University Hospital (Sfax, Tunisia). Basic demographic, clinical, biochemical, and radiological data were recorded on admission and during ICU stay. RESULTS: There were 276 patients with 196 boys (71%) and 80 girls, with a mean age of 6.7 ± 3.8 years. The main cause of trauma was road traffic accident (58.3%). Mean Glasgow Coma Scale score was 8 ± 2, Mean Injury Severity Score (ISS) was 23.3 ± 5.9, Mean Pediatric Trauma Score (PTS) was 4.8 ± 2.3, and Mean Pediatric Risk of Mortality (PRISM) was 10.8 ± 8. A total of 259 children required mechanical ventilation. Forty-eight children (17.4%) died. Multivariate analysis showed that factors associated with a poor prognosis were PRISM > 24 (OR: 10.98), neurovegetative disorder (OR: 7.1), meningeal hemorrhage (OR: 2.74), and lesion type VI according to Marshall tomographic grading (OR: 13.26). CONCLUSION: In Tunisia, head injury is a frequent cause of hospital admission and is most often due to road traffic injuries. Short-term prognosis is influenced by demographic, clinical, radiological, and biochemical factors. The need to put preventive measures in place is underscored