Influence of gust modelling on free-flight aerofoils

Gust analysis is one key task during design and certification of new aircraft. In the industrial standard, the gust is modelled as a disturbance in velocity and is superposed with the general velocity field surrounding the aircraft. The shape, typically sinusoidal or 1-cos, is uniform in vertical direction and is not changing while travelling through the computational domain. These assumptions known as the field or disturbance velocity method facilitate an efficient way of simulating gust encounter within computational fluid dynamics methods. However, how this frozen gust model effects the accuracy of loads predictions compared to more-realistic models remains an open question. A novel approach to simulate a so-called resolved gust is presented herein. An initial perturbation of the x-velocity is prescribed using a 1-cos shape in two spatial directions. Disturbances in vertical velocity as well as density and pressure are developing after some simulated time. Results are compared to the field-velocity method using the CRANK aerofoil covering subsonic and transonic flow conditions. Lift and moment responses are analysed as well as time histories of velocities at different grid locations. Furthermore, a second aerofoil is added as a horizontal tail-plane to represent a large civil aircraft. This configuration is used to include the effects of flight dynamics while analysing the responses due to the two gust models

School climate and academic performance of Italian students: the role of disciplinary behaviour and parental involvement

Educational researchers have increasingly recognised the importance of school climate as a malleable factor for improving academic performance. In this perspective, we exploit the data collected by the Italian Institute for the Evaluation of the Education System (INVALSI) to assess the effect of some school climate related factors on academic performance of tenth-grade Italian students. A Multilevel Bayesian Structural Equation Model (MBSEM) is adopted to highlight the effect of some relevant dimensions of school climate (students’ disciplinary behaviour and parents’ involvement) on academic performance and their role on the relationships between student socioeconomic status and achievement. The main findings show that disciplinary behaviour, on the one hand, directly influences the level of competence of the students, and, on the other hand, it partly mediates the effect of socioeconomic background whereas parents’ involvement does not appear to exert any significant effect on students’ performance

Model reduction for gust load analysis of free-flying aircraft

The coupling of computational fluid dynamics and rigid body dynamics promises enhanced multidisciplinary simulation capability for aircraft design and certification. Industrial application of such coupled simulations is limited however by computational cost. In this context, model reduction can retain the fidelity of the underlying model while decreasing the computational effort. A model reduction technique is presented herein based on modal decomposition and projection of the non-linear residual function. Flight dynamics eigenmodes are obtained with an operator-based identification procedure which is capable of calculating these global modes of the coupled Jacobian matrix also for an industrial use case with nearly 50 million degrees-of-freedom. Additional modes based on proper orthogonal decomposition to describe the aerodynamic response due to gust encounter are combined with the eigenmode basis. Results are presented for initial disturbance analysis using flight dynamics modes only and for gust encounter simulations using the combined modal basis. Overall, the reduced model is capable of predicting the full order results accurately

Diagnostic accuracy of transvaginal sonography for detecting parametrial involvement in women with deep endometriosis: systematic review and meta-analysis

Objective: To evaluate the accuracy of transvaginal sonography (TVS) for detecting parametrial deep endometriosis, using laparoscopy as the reference standard. Methods: A search was performed in PubMed/MEDLINE and Web of Science for studies evaluating TVS for detecting parametrial involvement in women with suspected deep endometriosis, as compared with laparoscopy, from January 2000 to December 2020. The Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool was used to evaluate the quality of the studies. Pooled sensitivity, specificity and positive and negative likelihood ratios for TVS in the detection of parametrial deep endometriosis were calculated, and the post-test probability of parametrial deep endometriosis following a positive or negative test was determined. Results: The search identified 134 citations. Four studies, comprising 560 patients, were included in the analysis. The mean prevalence of parametrial deep endometriosis at surgery was 18%. Overall, the pooled estimated sensitivity, specificity and positive and negative likelihood ratios of TVS in the detection of parametrial deep endometriosis were 31% (95% CI, 10–64%), 98% (95% CI, 95–99%), 18.5 (95% CI, 8.8–38.9) and 0.70 (95% CI, 0.46–1.06), respectively. The diagnostic odds ratio was 26 (95% CI, 10–68). Heterogeneity was high. Visualization of a lesion suspected to be parametrial deep endometriosis on TVS increased significantly the post-test probability of parametrial deep endometriosis. Conclusion: TVS has high specificity but low sensitivity for the detection of parametrial deep endometriosis. © 2021 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology

Laryngotracheal stenosis treated with multiple surgeries: experience, results and prognostic factors in 70 patients

Laryngotracheal stenosis is a complex condition that usually requires multiple procedures to restore physiological respiration. The aim of this study was to evaluate the percentage of decannulation compared to different or multiple surgical treatments. We retrospectively reviewed the charts of 70 patients treated between 1990 and 2005 for laryngotracheal stenosis of various aetiology: iatrogenic stenosis (n = 55), post-traumatic stenosis (n = 11) or other causes (autoimmune disease, n = 3; diphtheria, n = 1). In order to maintain laryngotracheal patency, a Montgomery Safe-T tube was used in all patients as a single dilation treatment or associated with endoscopic and/or open-neck surgery. Fifty-four of the 70 patients (77.1%) were eventually decannulated; 39 of these (72.2%) underwent 3 or fewer surgical procedures, showing a significant difference compared to patients who underwent more than 3 surgeries (p = 0.00002). A total of 257 surgeries were performed. Only seven of 54 patients (13%) were decannulated after more than 5 surgical procedures. Patients over 60 years of age and with a higher grade of stenosis showed a significantly lower success rate (p = 0.0017 and p = 0.007, respectively). There was no significant correlation between the rate of decannulation and gender, aetiology, site of stenosis or surgery. Patients undergoing dilation for laryngotracheal stenosis usually require multiple procedures. The T tube plays an important role in the treatment of this pathology. However, if the tracheostomy is not removed within 3 surgical interventions, the odds of decannulating the patient decrease significantly, and additional surgeries may be of questionable therapeutic benefit