The determination of modal parameters from experimental data of linear and nonlinear aeroelastic systems /

The determination of the modal parameters of an airplane wing, such as damping and natural frequency, as well as the determination of the aircraft's flutter speed, is an important part of aircraft design and testing. The effect that a 'defect' can have on the system, such as a loose hinge or worn fastening, is also an important part of aircraft analysis.In this study, a two-dimensional, symmetrical airfoil was mounted as part of a linear system in a wind tunnel, subject to steady, incompressible flow. Experimental data was collected using both free and forced vibrations of the airfoil, at different increments of airspeed. This data was then analyzed using conventional modal analysis techniques, extracting the damping factor and the natural frequency of the system, thus enabling a value for the flutter speed to be calculated.A structural freeplay nonlinearity was then introduced into the system, mimicking the effects a loose hinge or worn fastening can have on the airfoil modal parameters. The same tests were performed, and the modal parameters were evaluated using special nonlinear parameter extraction techniques. The behaviour of the damping and natural frequency of the nonlinear system, obtained from all three methods of data collection, were then compared to those of the linear system

Endoscopic treatment of fistula after sleeve gastrectomy: results of a multicenter retrospective study

International audienceBACKGROUND AND STUDY AIMS:Fistula is the main complication of laparoscopic sleeve gastrectomy (LSG), for which healing is difficult to achieve. The aims of the study were to evaluate the efficacy of interventional endoscopy for post-LSG fistula treatment, to evaluate various endoscopic techniques used and identify their complications, and to identify predictive factors of healing following endoscopic treatment.PATIENTS AND METHODS:This retrospective multicenter study included patients with post-LSG fistula. Therapeutic procedures were evaluated, taking into account complications and healing times. Endoscopic procedures were considered to have promoted healing if no other surgical procedure was performed. Predictive factors of healing were identified by univariate and multivariate analysis.RESULTS:A total of 110 patients were included, of whom 6 (5.5 %) healed spontaneously, 81 (73.6 %) healed following endoscopic treatment, and 19 (17.3 %) healed following surgery. Healing rates following endoscopic treatment were 84.4 % in the first 6 months of treatment (65/77), 52.4 % for treatment lasting 6 - 12 months (11/21), and 41.7 % after 12 months of treatment (5/12). A drainage procedure (surgical, endoscopic, or percutaneous) was performed in 92 patients (83.6 %). A total of 177 esogastric stents were placed in 88 patients (80.0 %). Surgical debridement, clip placement, glue sealing, and plug placement were also performed. Multivariate analysis identified four predictive factors of healing following endoscopic treatment: interval < 21 days between fistula diagnosis and first endoscopy (P = 0.003), small fistula (P = 0.01), interval between LSG and fistula ≤ 3 days (P = 0.01), no history of gastric banding (P = 0.04).CONCLUSION:Endoscopic treatment facilitated healing of post-LSG fistula in 74 % of patients. Early endoscopic treatment increased the likelihood of success, and was most effective during the first 6 months of management. After this point, surgical treatment should be considered.Fistula is the main complication of laparoscopic sleeve gastrectomy (LSG), for which healing is difficult to achieve. The aims of the study were to evaluate the efficacy of interventional endoscopy for post-LSG fistula treatment, to evaluate various endoscopic techniques used and identify their complications, and to identify predictive factors of healing following endoscopic treatment

Relationship between serotypes, disease characteristics and 30-day mortality in adults with invasive pneumococcal disease

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